Add commit & tag signing/verification via SSH keys using ssh-keygen

From: Fabian Stelzer <[email protected]>

set gpg.format = ssh and user.signingkey to a ssh public key string (like from an authorized_keys file) and commits/tags can be signed using the private key from your ssh-agent.

Verification uses a allowed_signers_file (see ssh-keygen(1)) which defaults to .gitsigners but can be set via gpg.ssh.allowedsigners A possible gpg.ssh.revocationfile is also passed to ssh-keygen on verification.

needs openssh>8.2p1

---
RFC: Add commit & tag signing/verification via SSH keys using ssh-keygen

Support for using private keyfiles directly is still missing and i'm unsure on how to configure it or if the pubkey in the signingkey field is such a good idea. A SSH Fingerprint as signingkey would be nicer, but key lookup would be quite cumbersome. Maybe storing the fingerprint in signingkey and then have a gpg.ssh.$FINGERPRINT.publickey/privatekeyfile setting? As a default we could get the first ssh key from ssh-add and store it in the config to avoid unintentional changes of the used signing key. I've started with some tests for SSH Signing but having static private keyfiles would make this a lot easier. So still on my TODO.

This feature makes git signing much more accessible to the average user. Usually they have a SSH Key for pushing code already. Using it for signing commits allows us to verify not only the transport but the pushed code as well. The allowed_signers file could be kept in the repository if all receives are verified (allowing only useris with valid signatures to add/change them) or outside if generated/managed differently. Tools like gitolite could optionally generate and enforce them from the already existing user ssh keys for example.

In our corporate environemnt we use PIV x509 Certs on Yubikeys for email signing/encryption and ssh keys which i think is quite common (at least for the email part). This way we can establish the correct trust for the SSH Keys without setting up a separate GPG Infrastructure (which is still quite painful for users) or implementing x509 signing support for git (which lacks good forwarding mechanisms). Using ssh agent forwarding makes this feature easily usable in todays development environments where code is often checked out in remote VMs / containers.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1041%2FFStelzer%2Fsshsign-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1041/FStelzer/sshsign-v1
Pull-Request: https://github.com/git/git/pull/1041

 Documentation/config/gpg.txt  |  13 ++-
 Documentation/config/user.txt |   4 +
 gpg-interface.c               | 212 ++++++++++++++++++++++++++++++----
 gpg-interface.h               |   3 +
 4 files changed, 205 insertions(+), 27 deletions(-)

index d94025cb368..fd71bd782ec 100644
@@ -11,13 +11,13 @@ gpg.program::
 
 gpg.format::
 	Specifies which key format to use when signing with `--gpg-sign`.
-	Default is "openpgp" and another possible value is "x509".
+	Default is "openpgp". Other possible values are "x509", "ssh".
 
 gpg.<format>.program::
 	Use this to customize the program used for the signing format you
 	chose. (see `gpg.program` and `gpg.format`) `gpg.program` can still
 	be used as a legacy synonym for `gpg.openpgp.program`. The default
-	value for `gpg.x509.program` is "gpgsm".
+	value for `gpg.x509.program` is "gpgsm" and `gpg.ssh.program` is "ssh-keygen".
 
 gpg.minTrustLevel::
 	Specifies a minimum trust level for signature verification.  If

@@ -27,6 +27,15 @@ gpg.minTrustLevel::
 	with at least `undefined` trust.  Setting this option overrides
 	the required trust-level for all operations.  Supported values,
 	in increasing order of significance:
+
+gpg.ssh.allowedSigners::
+	A file containing all valid SSH signing principals. 
+	Similar to an .ssh/authorized_keys file. See ssh-keygen(1) for details.
+	Defaults to .gitsigners
+
+gpg.ssh.revocationFile::
+	Either a SSH KRL or a list of revoked public keys.
+	See ssh-keygen(1) for details.
 +
 * `undefined`
 * `never`

index 59aec7c3aed..1632e7b320f 100644
@@ -36,3 +36,7 @@ user.signingKey::
 	commit, you can override the default selection with this variable.
 	This option is passed unchanged to gpg's --local-user parameter,
 	so you may specify a key using any method that gpg supports.
+	If gpg.format is set to "ssh" this needs to contain the valid
+	ssh public key (e.g.: "ssh-rsa XXXXXX identifier") which corresponds
+	to the private key used for signing. The private key needs to be available
+	via ssh-agent. Direct private key files are not supported yet.

index 80567e48948..286c1b4167a 100644
@@ -7,6 +7,8 @@ struct strbuf;
 #define GPG_VERIFY_RAW			2
 #define GPG_VERIFY_OMIT_STATUS	4
 
+#define GPG_SSH_ALLOWED_SIGNERS ".gitsigners"
+
 enum signature_trust_level {
 	TRUST_UNDEFINED,
 	TRUST_NEVER,

@@ -64,6 +66,7 @@ int sign_buffer(struct strbuf *buffer, struct strbuf *signature,
 int git_gpg_config(const char *, const char *, void *);
 void set_signing_key(const char *);
 const char *get_signing_key(void);
+const char *get_ssh_allowed_signers(void);
 int check_signature(const char *payload, size_t plen,
 		    const char *signature, size_t slen,
 		    struct signature_check *sigc);

base-commit: 670b81a890388c60b7032a4f5b879f2ece8c4558

gitgitgadget

...

Thanks for working on this, and I support this initiative. I coincidentally have started proselytizing something similar just weeks ago.

My interest is in signing pushes rather than commits/tags, as that (in combination with SSH U2F support) provides a simple mechanism to require (forwardable!) 2-factor authentication on pushes over HTTP. I haven't looked at the signing code in detail, but I had the impression that adding SSH signatures would automatically also add support for signed pushes? (aka. push-certs) Do you know?

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Up until now i was not actually aware of the "push signing" functionality in git. I can see that the send/receive-pack use the same api function calls as commit/tag signing. So this should work just as well. Especially if using an ssh agent the whole process is identical to git. I still need to try private key files directly to see how user interaction (like entering a passphrase or touching the U2F Token) would work.

Usually we'll want to write the explanation here in full sentences with typical capitalization.

I think user.signingKey could be helpful for signing here. That could be a file name, not just a fingerprint, although we'd probably want to have support for tilde expansion. You could add an additional option, gpg.ssh.keyring, that specifies the signatures to verify. That would be named the same thing as a potential option of gpg.openpgp.keyring, which would be convenient. Also, gpg.ssh.revokedKeyring could maybe be the name for revoked keys?

I think some of this rationale would work well in the commit message, especially the part about the fact that using an SSH key may be easier for users and the fact that it can be well supported by smart cards. Those are compelling arguments about why this is a desirable change, and should be in the commit message.

I haven't looked too deeply at the intricacies of the change, but I'm in favor of it. I would, however, like to see some tests here, including for commits, tags, and push certificates. Note that you'll probably need to run the testsuite both with and without GIT_TEST_DEFAULT_HASH=sha256 to verify everything works.

brian m. carlson (he/him or they/them)
Toronto, Ontario, CA

There are probably style and coding-guideline nit people will pick in the patch, but first of all I have to say that I am uncomfortably excited to see this addition.

One thing that is unclear is how the 'allowed-signers' is expected to be maintained in the larger picture. Who decides which keys (belong to whom) are trustworthy? Does a contributor has to agree with the decision that certain keys are trustworthy made by somebody else in the project and use the same 'allowed-signers' collection of keys to effectively participate in the project? How do revoking and rotating keys work?

It was a deliberate design decision to let PGP infrastructure that is used to sign and verify signatures when we use PGP for signing without tying any of these decisions to the tracked contents, as that would reduce the attack surface for a malicious tree contents to affect the signing and verification (in other words, "we punted" ;-). Even though I am not sure exactly what you meant by "defaults to .gitsigners", I am assuming that you meant a file with the name at the top-level of the working tree, which makes me worried, as it opens us to the risk of reading from and blindly trusting whatever somebody else placed in the tree contents immediately after we "git pull" (or "git clone").

Thanks for working on it.

From: Fabian Stelzer <[email protected]>

Thanks, i was unsure about what to put in the commit and what into the cover letter. I'll fix this with the next patch update and move some of it into the commit message. In our env the commit messages are usually kept quite short.

The problem ist that looking up a key by fingerprint alone is not really possible with ssh :/
A referenced file (which could contain a public or private key) would be fine and i could return the fingerprint in the get_signing_key api which the pushcerts code uses as "pusher" info in the cert. I'll change the keyring naming to what you suggested. Makes sense to have this option for gpg as well.

I'm working on some tests but there are lots of GPG / GPGSM tests in the suite and i'm unsure of how many i should duplicate. Thanks for the info with the hash setting.

I'm not aware of a standard location. I think there are use cases to store this in the repo, but i'm of course fine not defaulting to it.

Glad to hear that :)
I tried to keep the style with the existing code but the IDE sometimes has its own idea.

I think there are two basic options for maintaining the allowed signers file:
1. Every developer has their own stored outside of the repo and adds/revokes trust manually like with gpg.
    A central repo would probably verify against a list managed by the tool (e.g. gitolite)
2. Store it in a .gitsigners file in the repo. This would only work if you only allow signed commits/pushes from this point onwards. But this way a shared understading of trusted users can be maintained easily. Only already trusted committers can add new users or change their own keys. The signers file is basically a ssh_authorized_keys file with an additional principal identifier added at the front like:
    [email protected] ssh-rsa XXXKEYXXX Comment
    [email protected] ssh-ed25519 XXXKEYXXX Comment

Where are commits usually verified at the moment? On every devs checkout or only centrally on pushes?

The signers file also supports SSH CA keys and wildcard identifiers. At the moment i look up the principal dynamically via the public key so it's just a text info of who's key is it at the moment.
The SSH CA Stuff is probably a niche use case but could be cool in a corporate setting. Thats also what the revocation file is used for. The SSH CA can generate a KRL (like crl) which you put into it or you can specify explicit public keys in it to deny them.

Thanks for explaining your thoughts (omitted). When I say "this is unclear" in my response to a patch, I expect that unclear-ness will be shared by other readers of the code, the doc and/or the log message, so please make sure an updated patch will reduce the need to ask the same question by future readers.

Documentation/CodingGuidelines and Documentation/SubmittingPatches would hopefully help (if not, please ask and/or suggest clarification on these documents).

Thanks.

Just musing here... If adding SSH CA, would not adding support for a self-signed SSL CA make sense? In such a situation, a self-signed certificate can be created at an organizational level, or even from an official root CA. Per-user self-signed certificates, or organizationally defined CAs and certificates, could be created that are more stable than SSH CAs. Then something like OpenSSL (via libcurl) could handle the signature and validation management. Signed content could propagate to Cloud-based git servers and retain their ability to be property verified. Although I can see a drawback here, which relates to expiring certificates - although the concept of an expired signed content is somewhat compelling. Imaging the use case where a company has an employee who signs a tag/commit. The employee departs/retires/terminated/etc., and with it the published certificate is also revoked - an extreme case perhaps, but if the code can no longer be trusted by virtue of the termination, maybe t
his is semantically interesting. This could be a core git function with no additional dependencies.

Regards,
Randall

Why did you choose to implement SSH-based signing as GPG interface? Why not create similar one?

If at later times we need to implement other signing methods (besides GPG and SSH), we can refactor gpg-interface into generic signing interface (say signing.h) and let each signing methods implement from it.

An old man doll... just what I always wanted! - Clara

I agree that a general purpose "signing" would be cleaner. The GPG kewords are scattered all over the codebase but all the paths i found just call the generic sign_buffer / verify_signed_buffer from gpg-interface.c in the end whose api works quite well for other signing mechanisms as well. I will rename some struct fields to be more generic and adjust a few messages printed to the user which currently say things like "gpg failed to sign the data" or "has a gpg signature" to be generic. Do we just want to call this "signature" and remove the gpg prefix or would that be too generic?

Refactoring the whole gpg part to a generic "signing" would be quite involved and should probably be a different patch even though its mostly renaming stuff. If we want to go into that direction i could add the new config keys under signing.* (signing.format = ssh|gpg, ...) and keep the compatibility for the older gpg.* keys.

From: Fabian Stelzer <[email protected]>

Openssh v8.2p1 added some new options to ssh-keygen for signature creation and verification. These allow us to use ssh keys for git signatures easily.

Set gpg.format = ssh and user.signingkey to either a ssh public key string (like from an authorized_keys file), or a ssh key file. If the key file or the config value itself contains only a public key then the private key needs to be available via ssh-agent. If no signingkey is set then git will call 'ssh-add -L' to check for available agent keys and use the first one for signing.

Verification uses the gpg.ssh.keyring file (see ssh-keygen(1) "ALLOWED SIGNERS") which contains valid public keys and an principal (usually user@domain). Depending on the environment this file can be managed by the individual developer or for example generated by the central repository server from known ssh keys with push access. If the repository only allows signed commits / pushes then the file can even be stored inside it.

To revoke a key put the public key without the principal prefix into gpg.ssh.revocationKeyring or generate a KRL (see ssh-keygen(1) "KEY REVOCATION LISTS"). The same considerations about who to trust for verification as with the keyring file apply.

This feature makes git signing much more accessible to the average user. Usually they have a SSH Key for pushing code already. Using it for signing commits allows us to verify not only the transport but the pushed code as well.

In our corporate environemnt we use PIV x509 Certs on Yubikeys for email signing/encryption and ssh keys which i think is quite common
(at least for the email part). This way we can establish the correct trust for the SSH Keys without setting up a separate GPG Infrastructure (which is still quite painful for users) or implementing x509 signing support for git (which lacks good forwarding mechanisms).
Using ssh agent forwarding makes this feature easily usable in todays development environments where code is often checked out in remote VMs / containers. In such a setup the keyring & revocationKeyring can be centrally generated from the x509 CA information and distributed to the users.

---
RFC: Add commit & tag signing/verification via SSH keys using ssh-keygen

I have added support for using keyfiles directly, lots of tests and generally cleaned up the signing & verification code a lot.

I can still rename things from being gpg specific to a more general "signing" but thats rather cosmetic. Also i'm not sure if i named the new test files correctly.

There is a patch in the pipeline for openssh by Damien Miller that will add valid-after, valid-before options to the allowed keys keyring. This allows us to pass the commit timestamp to the verification call and make key rollover possible and still be able to verify older commits. Set valid-after=NOW when adding your key to the keyring and set valid-before to make it fail if used after a certain date. Software like gitolite/github or corporate automation can do this automatically when ssh push keys are addded / removed

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1041%2FFStelzer%2Fsshsign-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1041/FStelzer/sshsign-v2
Pull-Request: https://github.com/git/git/pull/1041

Range-diff vs v1:

1: f238392bfa8 ! 1: b8b16f8e6ec Add commit & tag signing/verification via SSH keys using ssh-keygen

     @@ Metadata
      Author: Fabian Stelzer <[email protected]>
      
       ## Commit message ##
     -    Add commit & tag signing/verification via SSH keys using ssh-keygen
     +    Add commit, tag & push signing/verification via SSH keys using ssh-keygen
      
     -    set gpg.format = ssh and user.signingkey to a ssh public key string (like from an
     -    authorized_keys file) and commits/tags can be signed using the private
     -    key from your ssh-agent.
     +    Openssh v8.2p1 added some new options to ssh-keygen for signature
     +    creation and verification. These allow us to use ssh keys for git
     +    signatures easily.
      
     -    Verification uses a allowed_signers_file (see ssh-keygen(1)) which
     -    defaults to .gitsigners but can be set via gpg.ssh.allowedsigners
     -    A possible gpg.ssh.revocationfile is also passed to ssh-keygen on
     -    verification.
     +    Set gpg.format = ssh and user.signingkey to either a ssh public key
     +    string (like from an authorized_keys file), or a ssh key file.
     +    If the key file or the config value itself contains only a public key
     +    then the private key needs to be available via ssh-agent.
     +    If no signingkey is set then git will call 'ssh-add -L' to check for
     +    available agent keys and use the first one for signing.
      
     -    needs openssh>8.2p1
     +    Verification uses the gpg.ssh.keyring file (see ssh-keygen(1) "ALLOWED
     +    SIGNERS") which contains valid public keys and an principal (usually
     +    user@domain). Depending on the environment this file can be managed by
     +    the individual developer or for example generated by the central
     +    repository server from known ssh keys with push access. If the
     +    repository only allows signed commits / pushes then the file can even be
     +    stored inside it.
     +
     +    To revoke a key put the public key without the principal prefix into
     +    gpg.ssh.revocationKeyring or generate a KRL (see ssh-keygen(1)
     +    "KEY REVOCATION LISTS"). The same considerations about who to trust for
     +    verification as with the keyring file apply.
     +
     +    This feature makes git signing much more accessible to the average user.
     +    Usually they have a SSH Key for pushing code already. Using it
     +    for signing commits allows us to verify not only the transport but the
     +    pushed code as well.
     +
     +    In our corporate environemnt we use PIV x509 Certs on Yubikeys for email
     +    signing/encryption and ssh keys which i think is quite common
     +    (at least for the email part). This way we can establish the correct
     +    trust for the SSH Keys without setting up a separate GPG Infrastructure
     +    (which is still quite painful for users) or implementing x509 signing
     +    support for git (which lacks good forwarding mechanisms).
     +    Using ssh agent forwarding makes this feature easily usable in todays
     +    development environments where code is often checked out in remote VMs / containers.
     +    In such a setup the keyring & revocationKeyring can be centrally
     +    generated from the x509 CA information and distributed to the users.
      
          Signed-off-by: Fabian Stelzer <[email protected]>
      
     @@ Documentation/config/gpg.txt: gpg.program::
       gpg.minTrustLevel::
       	Specifies a minimum trust level for signature verification.  If
      @@ Documentation/config/gpg.txt: gpg.minTrustLevel::
     - 	with at least `undefined` trust.  Setting this option overrides
     - 	the required trust-level for all operations.  Supported values,
     - 	in increasing order of significance:
     + * `marginal`
     + * `fully`
     + * `ultimate`
     ++
     ++gpg.ssh.keyring::
     ++	A file containing all valid SSH public signing keys. 
     ++	Similar to an .ssh/authorized_keys file.
     ++	See ssh-keygen(1) "ALLOWED SIGNERS" for details.
     ++	If a signing key is found in this file then the trust level will
     ++	be set to "fully". Otherwise if the key is not present
     ++	but the signature is still valid then the trust level will be "undefined".
     ++
     ++	This file can be set to a location outside of the repository
     ++	and every developer maintains their own trust store.
     ++	A central repository server could generate this file automatically
     ++	from ssh keys with push	access to verify the code against.
     ++	In a corporate setting this file is probably generated at a global location
     ++	from some automation that already handles developer ssh keys. 
     ++	
     ++	A repository that is only allowing signed commits can store the file 
     ++	in the repository itself using a relative path. This way only committers
     ++	with an already valid key can add or change keys in the keyring.
      +
     -+gpg.ssh.allowedSigners::
     -+	A file containing all valid SSH signing principals. 
     -+	Similar to an .ssh/authorized_keys file. See ssh-keygen(1) for details.
     -+	Defaults to .gitsigners
     ++	Using a SSH CA key with the cert-authority option 
     ++	(see ssh-keygen(1) "CERTIFICATES") is also valid.
      +
     -+gpg.ssh.revocationFile::
     -+	Either a SSH KRL or a list of revoked public keys.
     ++	To revoke a key place the public key without the principal into the 
     ++	revocationKeyring.
     ++
     ++gpg.ssh.revocationKeyring::
     ++	Either a SSH KRL or a list of revoked public keys (without the principal prefix).
      +	See ssh-keygen(1) for details.
     - +
     - * `undefined`
     - * `never`
     ++	If a public key is found in this file then it will always be treated
     ++	as having trust level "never" and signatures will show as invalid.
      
       ## Documentation/config/user.txt ##
      @@ Documentation/config/user.txt: user.signingKey::
       	commit, you can override the default selection with this variable.
       	This option is passed unchanged to gpg's --local-user parameter,
       	so you may specify a key using any method that gpg supports.
     -+	If gpg.format is set to "ssh" this needs to contain the valid
     -+	ssh public key (e.g.: "ssh-rsa XXXXXX identifier") which corresponds
     -+	to the private key used for signing. The private key needs to be available
     -+	via ssh-agent. Direct private key files are not supported yet.
     ++	If gpg.format is set to "ssh" this can contain the literal ssh public
     ++	key (e.g.: "ssh-rsa XXXXXX identifier") or a file which contains it and 
     ++	corresponds to the private key used for signing. The private key 
     ++	needs to be available via ssh-agent. Alternatively it can be set to
     ++	a file containing a private key directly. If not set git will call 
     ++	"ssh-add -L" and try to use the first key available.
     +
     + ## builtin/receive-pack.c ##
     +@@ builtin/receive-pack.c: static int receive_pack_config(const char *var, const char *value, void *cb)
     + {
     + 	int status = parse_hide_refs_config(var, value, "receive");
     + 
     ++	git_gpg_config(var, value, NULL);
     ++
     + 	if (status)
     + 		return status;
     + 
     +@@ builtin/receive-pack.c: static void prepare_push_cert_sha1(struct child_process *proc)
     + 		bogs = parse_signed_buffer(push_cert.buf, push_cert.len);
     + 		check_signature(push_cert.buf, bogs, push_cert.buf + bogs,
     + 				push_cert.len - bogs, &sigcheck);
     +-
     ++		
     + 		nonce_status = check_nonce(push_cert.buf, bogs);
     + 	}
     + 	if (!is_null_oid(&push_cert_oid)) {
     +
     + ## fmt-merge-msg.c ##
     +@@ fmt-merge-msg.c: static void fmt_merge_msg_sigs(struct strbuf *out)
     + 			len = payload.len;
     + 			if (check_signature(payload.buf, payload.len, sig.buf,
     + 					 sig.len, &sigc) &&
     +-				!sigc.gpg_output)
     ++				!sigc.output)
     + 				strbuf_addstr(&sig, "gpg verification failed.\n");
     + 			else
     +-				strbuf_addstr(&sig, sigc.gpg_output);
     ++				strbuf_addstr(&sig, sigc.output);
     + 		}
     + 		signature_check_clear(&sigc);
     + 
      
       ## gpg-interface.c ##
      @@
     + #include "config.h"
     + #include "run-command.h"
     + #include "strbuf.h"
     ++#include "dir.h"
     + #include "gpg-interface.h"
     + #include "sigchain.h"
       #include "tempfile.h"
       
       static char *configured_signing_key;
     @@ gpg-interface.c: static struct gpg_format gpg_format[] = {
       };
       
       static struct gpg_format *use_format = &gpg_format[0];
     +@@ gpg-interface.c: static struct gpg_format *get_format_by_sig(const char *sig)
     + void signature_check_clear(struct signature_check *sigc)
     + {
     + 	FREE_AND_NULL(sigc->payload);
     ++	FREE_AND_NULL(sigc->output);
     + 	FREE_AND_NULL(sigc->gpg_output);
     + 	FREE_AND_NULL(sigc->gpg_status);
     + 	FREE_AND_NULL(sigc->signer);
      @@ gpg-interface.c: static int parse_gpg_trust_level(const char *level,
       	return 1;
       }
     @@ gpg-interface.c: static int parse_gpg_trust_level(const char *level,
      +	const char *output = NULL;
      +	char *next = NULL;
      +
     -+	// ssh-keysign output should be:
     -+	// Good "git" signature for PRINCIPAL with RSA key SHA256:FINGERPRINT
     ++	/* ssh-keysign output should be:
     ++	 * Good "git" signature for PRINCIPAL with RSA key SHA256:FINGERPRINT
     ++	 * or for valid but unknown keys:
     ++	 * Good "git" signature with RSA key SHA256:FINGERPRINT
     ++	 */
      +
     -+	output = xmemdupz(sigc->gpg_status, strcspn(sigc->gpg_status, " \n"));
     -+	if (skip_prefix(sigc->gpg_status, "Good \"git\" signature for ", &output)) {
     ++	output = xmemdupz(sigc->output, strcspn(sigc->output, " \n"));
     ++	if (skip_prefix(sigc->output, "Good \"git\" signature for ", &output)) {
     ++		// Valid signature for a trusted signer
      +		sigc->result = 'G';
     ++		sigc->trust_level = TRUST_FULLY;
      +
     -+		next = strchrnul(output, ' ');
     ++		next = strchrnul(output, ' '); // 'principal'
      +		replace_cstring(&sigc->signer, output, next);
      +		output = next + 1;
      +		next = strchrnul(output, ' '); // 'with'
     @@ gpg-interface.c: static int parse_gpg_trust_level(const char *level,
      +		output = next + 1;
      +		next = strchrnul(output, ' '); // 'key'
      +		output = next + 1;
     -+		next = strchrnul(output, ' '); // key
     ++		next = strchrnul(output, '\n'); // key
      +		replace_cstring(&sigc->fingerprint, output, next);
     ++		replace_cstring(&sigc->key, output, next);
     ++	} else if (skip_prefix(sigc->output, "Good \"git\" signature with ", &output)) {
     ++		// Valid signature, but key unknown
     ++		sigc->result = 'G';
     ++		sigc->trust_level = TRUST_UNDEFINED;
     ++
     ++		next = strchrnul(output, ' '); // KEY Type
     ++		output = next + 1;
     ++		next = strchrnul(output, ' '); // 'key'
     ++		output = next + 1;
     ++		next = strchrnul(output, '\n'); // key
     ++		replace_cstring(&sigc->fingerprint, output, next);
     ++		replace_cstring(&sigc->key, output, next);
      +	} else {
      +		sigc->result = 'B';
     ++		sigc->trust_level = TRUST_NEVER;
      +	}
     -+
     -+	// SSH-Keygen prints onto stdout instead of stderr like the output code expects - so we just copy it over
     -+	free(sigc->gpg_output);
     -+	sigc->gpg_output = xmemdupz(sigc->gpg_status, strlen(sigc->gpg_status));
      +}
      +
       static void parse_gpg_output(struct signature_check *sigc)
       {
       	const char *buf = sigc->gpg_status;
     -@@ gpg-interface.c: static int verify_signed_buffer(const char *payload, size_t payload_size,
     - 				struct strbuf *gpg_output,
     - 				struct strbuf *gpg_status)
     +@@ gpg-interface.c: error:
     + 	FREE_AND_NULL(sigc->key);
     + }
     + 
     +-static int verify_signed_buffer(const char *payload, size_t payload_size,
     +-				const char *signature, size_t signature_size,
     +-				struct strbuf *gpg_output,
     +-				struct strbuf *gpg_status)
     ++static int verify_ssh_signature(struct signature_check *sigc, struct gpg_format *fmt,
     ++	const char *payload, size_t payload_size,
     ++	const char *signature, size_t signature_size)
       {
      -	struct child_process gpg = CHILD_PROCESS_INIT;
     -+	struct child_process gpg = CHILD_PROCESS_INIT,
     -+			     ssh_keygen = CHILD_PROCESS_INIT;
     - 	struct gpg_format *fmt;
     +-	struct gpg_format *fmt;
     ++	struct child_process ssh_keygen = CHILD_PROCESS_INIT;
       	struct tempfile *temp;
       	int ret;
      -	struct strbuf buf = STRBUF_INIT;
      +	const char *line;
      +	size_t trust_size;
      +	char *principal;
     -+	struct strbuf buf = STRBUF_INIT,
     -+		      principal_out = STRBUF_INIT,
     -+		      principal_err = STRBUF_INIT;
     ++	struct strbuf ssh_keygen_out = STRBUF_INIT;
     ++	struct strbuf ssh_keygen_err = STRBUF_INIT;
       
       	temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
       	if (!temp)
      @@ gpg-interface.c: static int verify_signed_buffer(const char *payload, size_t payload_size,
     - 	if (!fmt)
     - 		BUG("bad signature '%s'", signature);
     + 		return -1;
     + 	}
       
     --	strvec_push(&gpg.args, fmt->program);
     --	strvec_pushv(&gpg.args, fmt->verify_args);
     --	strvec_pushl(&gpg.args,
     --		     "--status-fd=1",
     --		     "--verify", temp->filename.buf, "-",
     --		     NULL);
     -+	if (!strcmp(use_format->name, "ssh")) {
     -+		// Find the principal from the  signers
     -+		strvec_push(&ssh_keygen.args, fmt->program);
     -+		strvec_pushl(&ssh_keygen.args,  "-Y", "find-principals",
     -+						"-f", get_ssh_allowed_signers(),
     +-	fmt = get_format_by_sig(signature);
     +-	if (!fmt)
     +-		BUG("bad signature '%s'", signature);
     ++	// Find the principal from the  signers
     ++	strvec_pushl(&ssh_keygen.args,  fmt->program,
     ++					"-Y", "find-principals",
     ++					"-f", get_ssh_allowed_signers(),
     ++					"-s", temp->filename.buf,
     ++					NULL);
     ++	ret = pipe_command(&ssh_keygen, NULL, 0, &ssh_keygen_out, 0, &ssh_keygen_err, 0);
     ++	if (strstr(ssh_keygen_err.buf, "unknown option")) {
     ++		error(_("openssh version > 8.2p1 is needed for ssh signature verification (ssh-keygen needs -Y find-principals/verify option)"));
     ++	}
     ++	if (ret || !ssh_keygen_out.len) {
     ++		// We did not find a matching principal in the keyring - Check without validation
     ++		child_process_init(&ssh_keygen);
     ++		strvec_pushl(&ssh_keygen.args,  fmt->program,
     ++						"-Y", "check-novalidate",
     ++						"-n", "git",
      +						"-s", temp->filename.buf,
      +						NULL);
     -+		ret = pipe_command(&ssh_keygen, NULL, 0, &principal_out, 0, &principal_err, 0);
     -+		if (strstr(principal_err.buf, "unknown option")) {
     -+			error(_("openssh version > 8.2p1 is needed for ssh signature verification (ssh-keygen needs -Y find-principals/verify option)"));
     -+		}
     -+		if (ret || !principal_out.len)
     -+			goto out;
     -+
     -+		/* Iterate over all lines */
     -+		for (line = principal_out.buf; *line; line = strchrnul(line + 1, '\n')) {
     ++		ret = pipe_command(&ssh_keygen, payload, payload_size, &ssh_keygen_out, 0, &ssh_keygen_err, 0);
     ++	} else {
     ++		// Check every principal we found (one per line)
     ++		for (line = ssh_keygen_out.buf; *line; line = strchrnul(line + 1, '\n')) {
      +			while (*line == '\n')
      +				line++;
      +			if (!*line)
      +				break;
     - 
     --	if (!gpg_status)
     --		gpg_status = &buf;
     ++
      +			trust_size = strcspn(line, " \n");
      +			principal = xmemdupz(line, trust_size);
     - 
     --	sigchain_push(SIGPIPE, SIG_IGN);
     --	ret = pipe_command(&gpg, payload, payload_size,
     --			   gpg_status, 0, gpg_output, 0);
     --	sigchain_pop(SIGPIPE);
     -+			strvec_push(&gpg.args,fmt->program);
     ++
     ++			child_process_init(&ssh_keygen);
     ++			strbuf_release(&ssh_keygen_out);
     ++			strbuf_release(&ssh_keygen_err);
     ++			strvec_push(&ssh_keygen.args,fmt->program);
      +			// We found principals - Try with each until we find a match
     -+			strvec_pushl(&gpg.args, "-Y", "verify",
     -+						"-n", "git",
     -+						"-f", get_ssh_allowed_signers(),
     -+						"-I", principal,
     -+						"-s", temp->filename.buf,
     -+						 NULL);
     - 
     --	delete_tempfile(&temp);
     -+			if (ssh_revocation_file) {
     -+				strvec_pushl(&gpg.args, "-r", ssh_revocation_file, NULL);
     -+			}
     ++			strvec_pushl(&ssh_keygen.args,  "-Y", "verify",
     ++							//TODO: sprintf("-Overify-time=%s", commit->date...),
     ++							"-n", "git",
     ++							"-f", get_ssh_allowed_signers(),
     ++							"-I", principal,
     ++							"-s", temp->filename.buf,
     ++							NULL);
      +
     -+			if (!gpg_status)
     -+				gpg_status = &buf;
     ++			if (ssh_revocation_file && file_exists(ssh_revocation_file)) {
     ++				strvec_pushl(&ssh_keygen.args, "-r", ssh_revocation_file, NULL);
     ++			}
      +
      +			sigchain_push(SIGPIPE, SIG_IGN);
     -+			ret = pipe_command(&gpg, payload, payload_size,
     -+					   gpg_status, 0, gpg_output, 0);
     ++			ret = pipe_command(&ssh_keygen, payload, payload_size,
     ++					&ssh_keygen_out, 0, &ssh_keygen_err, 0);
      +			sigchain_pop(SIGPIPE);
     - 
     --	ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
     -+			ret |= !strstr(gpg_status->buf, "Good");
     ++
     ++			ret &= starts_with(ssh_keygen_out.buf, "Good");
      +			if (ret == 0)
      +				break;
      +		}
     -+	} else {
     -+		strvec_push(&gpg.args, fmt->program);
     -+		strvec_pushv(&gpg.args, fmt->verify_args);
     -+		strvec_pushl(&gpg.args,
     -+				"--status-fd=1",
     -+				"--verify", temp->filename.buf, "-",
     -+				NULL);
     ++	}
      +
     -+		if (!gpg_status)
     -+			gpg_status = &buf;
     ++	sigc->payload = xmemdupz(payload, payload_size);
     ++	strbuf_stripspace(&ssh_keygen_out, 0);
     ++	strbuf_stripspace(&ssh_keygen_err, 0);
     ++	strbuf_add(&ssh_keygen_out, ssh_keygen_err.buf, ssh_keygen_err.len);
     ++	sigc->output = strbuf_detach(&ssh_keygen_out, NULL);
      +
     -+		sigchain_push(SIGPIPE, SIG_IGN);
     -+		ret = pipe_command(&gpg, payload, payload_size, gpg_status, 0,
     -+				   gpg_output, 0);
     -+		sigchain_pop(SIGPIPE);
     -+		ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
     ++	//sigc->gpg_output = strbuf_detach(&ssh_keygen_err, NULL); // This flip around is broken...
     ++	sigc->gpg_status = strbuf_detach(&ssh_keygen_out, NULL);
     ++
     ++	parse_ssh_output(sigc);
     ++
     ++	delete_tempfile(&temp);
     ++	strbuf_release(&ssh_keygen_out);
     ++	strbuf_release(&ssh_keygen_err);
     ++
     ++	return ret;
     ++}
     ++
     ++static int verify_gpg_signature(struct signature_check *sigc, struct gpg_format *fmt, 
     ++	const char *payload, size_t payload_size,
     ++	const char *signature, size_t signature_size)
     ++{
     ++	struct child_process gpg = CHILD_PROCESS_INIT;
     ++	struct tempfile *temp;
     ++	int ret;
     ++	struct strbuf gpg_out = STRBUF_INIT;
     ++	struct strbuf gpg_err = STRBUF_INIT;
     ++
     ++	temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
     ++	if (!temp)
     ++		return error_errno(_("could not create temporary file"));
     ++	if (write_in_full(temp->fd, signature, signature_size) < 0 ||
     ++	    close_tempfile_gently(temp) < 0) {
     ++		error_errno(_("failed writing detached signature to '%s'"),
     ++			    temp->filename.buf);
     ++		delete_tempfile(&temp);
     ++		return -1;
      +	}
     + 
     + 	strvec_push(&gpg.args, fmt->program);
     + 	strvec_pushv(&gpg.args, fmt->verify_args);
     + 	strvec_pushl(&gpg.args,
     +-		     "--status-fd=1",
     +-		     "--verify", temp->filename.buf, "-",
     +-		     NULL);
     +-
     +-	if (!gpg_status)
     +-		gpg_status = &buf;
     ++			"--status-fd=1",
     ++			"--verify", temp->filename.buf, "-",
     ++			NULL);
     + 
     + 	sigchain_push(SIGPIPE, SIG_IGN);
     +-	ret = pipe_command(&gpg, payload, payload_size,
     +-			   gpg_status, 0, gpg_output, 0);
     ++	ret = pipe_command(&gpg, payload, payload_size, &gpg_out, 0,
     ++				&gpg_err, 0);
     + 	sigchain_pop(SIGPIPE);
     ++	ret |= !strstr(gpg_out.buf, "\n[GNUPG:] GOODSIG ");
     + 
     +-	delete_tempfile(&temp);
     ++	sigc->payload = xmemdupz(payload, payload_size);
     ++	sigc->output = strbuf_detach(&gpg_err, NULL);
     ++	sigc->gpg_status = strbuf_detach(&gpg_out, NULL);
     + 
     +-	ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
     +-	strbuf_release(&buf); /* no matter it was used or not */
     ++	parse_gpg_output(sigc);
      +
     -+out:
      +	delete_tempfile(&temp);
     -+	strbuf_release(&principal_out);
     -+	strbuf_release(&principal_err);
     - 	strbuf_release(&buf); /* no matter it was used or not */
     ++	strbuf_release(&gpg_out);
     ++	strbuf_release(&gpg_err);
       
       	return ret;
     -@@ gpg-interface.c: int check_signature(const char *payload, size_t plen, const char *signature,
     - 	sigc->payload = xmemdupz(payload, plen);
     - 	sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
     - 	sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
     + }
     +@@ gpg-interface.c: static int verify_signed_buffer(const char *payload, size_t payload_size,
     + int check_signature(const char *payload, size_t plen, const char *signature,
     + 	size_t slen, struct signature_check *sigc)
     + {
     +-	struct strbuf gpg_output = STRBUF_INIT;
     +-	struct strbuf gpg_status = STRBUF_INIT;
     ++	struct gpg_format *fmt;
     + 	int status;
     + 
     + 	sigc->result = 'N';
     + 	sigc->trust_level = -1;
     + 
     +-	status = verify_signed_buffer(payload, plen, signature, slen,
     +-				      &gpg_output, &gpg_status);
     +-	if (status && !gpg_output.len)
     +-		goto out;
     +-	sigc->payload = xmemdupz(payload, plen);
     +-	sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
     +-	sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
      -	parse_gpg_output(sigc);
     -+	if (!strcmp(use_format->name, "ssh")) {
     -+		parse_ssh_output(sigc);
     ++	fmt = get_format_by_sig(signature);
     ++	if (!fmt)
     ++		BUG("bad signature '%s'", signature);
     ++
     ++	if (!strcmp(fmt->name, "ssh")) {
     ++		status = verify_ssh_signature(sigc, fmt, payload, plen, signature, slen);
      +	} else {
     -+		parse_gpg_output(sigc);
     ++		status = verify_gpg_signature(sigc, fmt, payload, plen, signature, slen);
      +	}
     ++	if (status && !sigc->gpg_output)
     ++		return !!status;
     ++
       	status |= sigc->result != 'G';
       	status |= sigc->trust_level < configured_min_trust_level;
       
     +- out:
     +-	strbuf_release(&gpg_status);
     +-	strbuf_release(&gpg_output);
     +-
     + 	return !!status;
     + }
     + 
     + void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
     + {
     + 	const char *output = flags & GPG_VERIFY_RAW ?
     +-		sigc->gpg_status : sigc->gpg_output;
     ++		sigc->gpg_status : sigc->output;
     + 
     + 	if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
     + 		fputs(sigc->payload, stdout);
      @@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb)
     + 	int ret;
     + 
     + 	if (!strcmp(var, "user.signingkey")) {
     ++		/* user.signingkey can contain one of the following
     ++		 * when format = openpgp/x509
     ++		 *   - GPG KeyID
     ++		 * when format = ssh
     ++		 *   - literal ssh public key (e.g. ssh-rsa XXXKEYXXX comment)
     ++		 *   - path to a file containing a public or a private ssh key
     ++		 */
     + 		if (!value)
     + 			return config_error_nonbool(var);
     + 		set_signing_key(value);
       		return 0;
       	}
       
     -+	if (!strcmp(var, "gpg.ssh.allowedsigners")) {
     ++	if (!strcmp(var, "gpg.ssh.keyring")) {
     ++		if (!value)
     ++			return config_error_nonbool(var);
      +		return git_config_string(&ssh_allowed_signers, var, value);
      +	}
      +
     -+	if (!strcmp(var, "gpg.ssh.revocationfile")) {
     ++	if (!strcmp(var, "gpg.ssh.revocationkeyring")) {
     ++		if (!value)
     ++			return config_error_nonbool(var);
      +		return git_config_string(&ssh_revocation_file, var, value);
      +	}
      +
     @@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb
       	if (fmtname) {
       		fmt = get_format_by_name(fmtname);
       		return git_config_string(&fmt->program, var, value);
     -@@ gpg-interface.c: const char *get_signing_key(void)
     +@@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb)
     + 	return 0;
     + }
     + 
     ++static char *get_ssh_key_fingerprint(const char *signing_key) {
     ++	struct child_process ssh_keygen = CHILD_PROCESS_INIT;
     ++	int ret = -1;
     ++	struct strbuf fingerprint_stdout = STRBUF_INIT;
     ++	struct strbuf **fingerprint;
     ++
     ++	/* For SSH Signing this can contain a filename or a public key
     ++	* For textual representation we usually want a fingerprint
     ++	*/
     ++	if (istarts_with(signing_key, "ssh-")) {
     ++		strvec_pushl(&ssh_keygen.args, "ssh-keygen",
     ++					"-lf", "-",
     ++					NULL);
     ++		ret = pipe_command(&ssh_keygen, signing_key, strlen(signing_key), &fingerprint_stdout, 0,  NULL, 0);
     ++	} else {
     ++		strvec_pushl(&ssh_keygen.args, "ssh-keygen",
     ++					"-lf", configured_signing_key,
     ++					NULL);
     ++		ret = pipe_command(&ssh_keygen, NULL, 0, &fingerprint_stdout, 0, NULL, 0);
     ++		if (!!ret)
     ++			die_errno(_("failed to get the ssh fingerprint for key '%s'"), signing_key);
     ++		fingerprint = strbuf_split_max(&fingerprint_stdout, ' ', 3);
     ++		if (fingerprint[1]) {
     ++			return strbuf_detach(fingerprint[1], NULL);
     ++		}
     ++	}
     ++	die_errno(_("failed to get the ssh fingerprint for key '%s'"), signing_key);
     ++}
     ++
     ++// Returns the first public key from an ssh-agent to use for signing
     ++static char *get_default_ssh_signing_key(void) {
     ++	struct child_process ssh_add = CHILD_PROCESS_INIT;
     ++	int ret = -1;
     ++	struct strbuf key_stdout = STRBUF_INIT;
     ++	struct strbuf **keys;
     ++
     ++	strvec_pushl(&ssh_add.args, "ssh-add", "-L", NULL);
     ++	ret = pipe_command(&ssh_add, NULL, 0, &key_stdout, 0, NULL, 0);
     ++	if (!ret) { 
     ++		keys = strbuf_split_max(&key_stdout, '\n', 2);
     ++		if (keys[0])
     ++			return strbuf_detach(keys[0], NULL);
     ++	}
     ++
     ++	return "";
     ++}
     ++
     ++// Returns a textual but unique representation ot the signing key
     ++const char *get_signing_key_id(void) {
     ++	if (!strcmp(use_format->name, "ssh")) {
     ++		return get_ssh_key_fingerprint(get_signing_key());
     ++	} else {
     ++		// GPG/GPGSM only store a key id on this variable
     ++		return get_signing_key();
     ++	}
     ++}
     ++
     + const char *get_signing_key(void)
       {
       	if (configured_signing_key)
       		return configured_signing_key;
      -	return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
      +	if (!strcmp(use_format->name, "ssh")) {
     -+		// We could simply use the first key listed by ssh-add -L and risk signing with the wrong key
     -+		return "";
     ++		return get_default_ssh_signing_key();
      +	} else {
      +		return git_committer_info(IDENT_STRICT | IDENT_NO_DATE);
      +	}
     @@ gpg-interface.c: const char *get_signing_key(void)
      +{
      +	if (ssh_allowed_signers)
      +		return ssh_allowed_signers;
     -+	return GPG_SSH_ALLOWED_SIGNERS;
     ++
     ++	die("A Path to an allowed signers ssh keyring is needed for validation");
       }
       
       int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
     @@ gpg-interface.c: int sign_buffer(struct strbuf *buffer, struct strbuf *signature
       	int ret;
       	size_t i, j, bottom;
       	struct strbuf gpg_status = STRBUF_INIT;
     --
     ++	struct tempfile *temp = NULL, *buffer_file = NULL;
     ++	char *ssh_signing_key_file = NULL;
     ++	struct strbuf ssh_signature_filename = STRBUF_INIT;
     ++
     ++	if (!strcmp(use_format->name, "ssh")) {
     ++		if (!signing_key || signing_key[0] == '\0')
     ++			return error(_("user.signingkey needs to be set for ssh signing"));
     ++
     ++
     ++		if (istarts_with(signing_key, "ssh-")) {
     ++			// A literal ssh key
     ++			temp = mks_tempfile_t(".git_signing_key_tmpXXXXXX");
     ++			if (!temp)
     ++				return error_errno(_("could not create temporary file"));
     ++			if (write_in_full(temp->fd, signing_key, strlen(signing_key)) < 0 ||
     ++				close_tempfile_gently(temp) < 0) {
     ++				error_errno(_("failed writing ssh signing key to '%s'"), temp->filename.buf);
     ++				delete_tempfile(&temp);
     ++				return -1;
     ++			}
     ++			ssh_signing_key_file= temp->filename.buf;
     ++		} else {
     ++			// We assume a file
     ++			ssh_signing_key_file = expand_user_path(signing_key, 1);
     ++		}
     + 
      -	strvec_pushl(&gpg.args,
      -		     use_format->program,
      -		     "--status-fd=2",
      -		     "-bsau", signing_key,
      -		     NULL);
     -+	struct tempfile *temp = NULL;
     -+
     -+	if (!strcmp(use_format->name, "ssh")) {
     -+		if (!signing_key)
     -+			return error(_("user.signingkey needs to be set to a ssh public key for ssh signing"));
     -+
     -+		// signing_key is a public ssh key
     -+		// FIXME: Allow specifying a key file so we can use private keyfiles instead of ssh-agent
     -+		temp = mks_tempfile_t(".git_signing_key_tmpXXXXXX");
     -+		if (!temp)
     ++		buffer_file = mks_tempfile_t(".git_signing_buffer_tmpXXXXXX");
     ++		if (!buffer_file)
      +			return error_errno(_("could not create temporary file"));
     -+		if (write_in_full(temp->fd, signing_key,
     -+					strlen(signing_key)) < 0 ||
     -+			close_tempfile_gently(temp) < 0) {
     -+			error_errno(_("failed writing ssh signing key to '%s'"), temp->filename.buf);
     -+			delete_tempfile(&temp);
     ++		if (write_in_full(buffer_file->fd, buffer->buf, buffer->len) < 0 ||
     ++			close_tempfile_gently(buffer_file) < 0) {
     ++			error_errno(_("failed writing ssh signing key buffer to '%s'"), buffer_file->filename.buf);
     ++			delete_tempfile(&buffer_file);
      +			return -1;
      +		}
     ++
      +		strvec_pushl(&gpg.args, use_format->program ,
      +					"-Y", "sign",
      +					"-n", "git",
     -+					"-f", temp->filename.buf,
     ++					"-f", ssh_signing_key_file,
     ++					buffer_file->filename.buf,
      +					NULL);
     ++
     ++		sigchain_push(SIGPIPE, SIG_IGN);
     ++		ret = pipe_command(&gpg, NULL, 0, NULL, 0, &gpg_status, 0);
     ++		sigchain_pop(SIGPIPE);
     ++
     ++		strbuf_addbuf(&ssh_signature_filename, &buffer_file->filename);
     ++		strbuf_addstr(&ssh_signature_filename, ".sig");
     ++		if (strbuf_read_file(signature, ssh_signature_filename.buf, 2048) < 0) {
     ++			error_errno(_("failed reading ssh signing data buffer from '%s'"), ssh_signature_filename.buf);
     ++		}
     ++		unlink_or_warn(ssh_signature_filename.buf);
     ++		strbuf_release(&ssh_signature_filename);
     ++		delete_tempfile(&buffer_file);
      +	} else {
      +		strvec_pushl(&gpg.args, use_format->program ,
      +					"--status-fd=2",
      +					"-bsau", signing_key,
      +					NULL);
     ++
     ++		/*
     ++		* When the username signingkey is bad, program could be terminated
     ++		* because gpg exits without reading and then write gets SIGPIPE.
     ++		*/
     ++		sigchain_push(SIGPIPE, SIG_IGN);
     ++		ret = pipe_command(&gpg, buffer->buf, buffer->len, signature, 1024, &gpg_status, 0);
     ++		sigchain_pop(SIGPIPE);
      +	}
       
       	bottom = signature->len;
       
     -@@ gpg-interface.c: int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *sig
     - 			   signature, 1024, &gpg_status, 0);
     - 	sigchain_pop(SIGPIPE);
     - 
     --	ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
     +-	/*
     +-	 * When the username signingkey is bad, program could be terminated
     +-	 * because gpg exits without reading and then write gets SIGPIPE.
     +-	 */
     +-	sigchain_push(SIGPIPE, SIG_IGN);
     +-	ret = pipe_command(&gpg, buffer->buf, buffer->len,
     +-			   signature, 1024, &gpg_status, 0);
     +-	sigchain_pop(SIGPIPE);
      +	if (temp)
      +		delete_tempfile(&temp);
     -+
     + 
     +-	ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
      +	if (!strcmp(use_format->name, "ssh")) {
      +		if (strstr(gpg_status.buf, "unknown option")) {
      +			error(_("openssh version > 8.2p1 is needed for ssh signing (ssh-keygen needs -Y sign option)"));
     @@ gpg-interface.c: int sign_buffer(struct strbuf *buffer, struct strbuf *signature
       		return error(_("gpg failed to sign the data"));
      
       ## gpg-interface.h ##
     -@@ gpg-interface.h: struct strbuf;
     - #define GPG_VERIFY_RAW			2
     - #define GPG_VERIFY_OMIT_STATUS	4
     +@@ gpg-interface.h: enum signature_trust_level {
       
     -+#define GPG_SSH_ALLOWED_SIGNERS ".gitsigners"
     -+
     - enum signature_trust_level {
     - 	TRUST_UNDEFINED,
     - 	TRUST_NEVER,
     + struct signature_check {
     + 	char *payload;
     +-	char *gpg_output;
     +-	char *gpg_status;
     ++	char *output;
     ++	char *gpg_output; // This will be printed in commit logs
     ++	char *gpg_status; // Only used internally -> remove
     + 
     + 	/*
     + 	 * possible "result":
      @@ gpg-interface.h: int sign_buffer(struct strbuf *buffer, struct strbuf *signature,
       int git_gpg_config(const char *, const char *, void *);
       void set_signing_key(const char *);
       const char *get_signing_key(void);
     ++
     ++/* Returns a textual unique representation of the signing key in use
     ++ * Either a GPG KeyID or a SSH Key Fingerprint
     ++ */
     ++const char *get_signing_key_id(void);
     ++
      +const char *get_ssh_allowed_signers(void);
       int check_signature(const char *payload, size_t plen,
       		    const char *signature, size_t slen,
       		    struct signature_check *sigc);
     +
     + ## log-tree.c ##
     +@@ log-tree.c: static void show_signature(struct rev_info *opt, struct commit *commit)
     + 
     + 	status = check_signature(payload.buf, payload.len, signature.buf,
     + 				 signature.len, &sigc);
     +-	if (status && !sigc.gpg_output)
     ++	if (status && !sigc.output)
     + 		show_sig_lines(opt, status, "No signature\n");
     + 	else
     +-		show_sig_lines(opt, status, sigc.gpg_output);
     ++		show_sig_lines(opt, status, sigc.output);
     + 	signature_check_clear(&sigc);
     + 
     +  out:
     +@@ log-tree.c: static int show_one_mergetag(struct commit *commit,
     + 		/* could have a good signature */
     + 		status = check_signature(payload.buf, payload.len,
     + 					 signature.buf, signature.len, &sigc);
     +-		if (sigc.gpg_output)
     +-			strbuf_addstr(&verify_message, sigc.gpg_output);
     ++		if (sigc.output)
     ++			strbuf_addstr(&verify_message, sigc.output);
     + 		else
     + 			strbuf_addstr(&verify_message, "No signature\n");
     + 		signature_check_clear(&sigc);
     +
     + ## pretty.c ##
     +@@ pretty.c: static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
     + 			check_commit_signature(c->commit, &(c->signature_check));
     + 		switch (placeholder[1]) {
     + 		case 'G':
     +-			if (c->signature_check.gpg_output)
     +-				strbuf_addstr(sb, c->signature_check.gpg_output);
     ++			if (c->signature_check.output)
     ++				strbuf_addstr(sb, c->signature_check.output);
     + 			break;
     + 		case '?':
     + 			switch (c->signature_check.result) {
     +
     + ## send-pack.c ##
     +@@ send-pack.c: static int generate_push_cert(struct strbuf *req_buf,
     + 	const struct ref *ref;
     + 	struct string_list_item *item;
     + 	char *signing_key = xstrdup(get_signing_key());
     ++	char *signing_key_id = xstrdup(get_signing_key_id());
     + 	const char *cp, *np;
     + 	struct strbuf cert = STRBUF_INIT;
     + 	int update_seen = 0;
     +-
     ++	
     + 	strbuf_addstr(&cert, "certificate version 0.1\n");
     +-	strbuf_addf(&cert, "pusher %s ", signing_key);
     ++	strbuf_addf(&cert, "pusher %s ", signing_key_id);
     + 	datestamp(&cert);
     + 	strbuf_addch(&cert, '\n');
     + 	if (args->url && *args->url) {
     +@@ send-pack.c: static int generate_push_cert(struct strbuf *req_buf,
     + 
     + free_return:
     + 	free(signing_key);
     ++	free(signing_key_id);
     + 	strbuf_release(&cert);
     + 	return update_seen;
     + }
     +
     + ## t/lib-gpg.sh ##
     +@@ t/lib-gpg.sh: test_lazy_prereq RFC1991 '
     + 	echo | gpg --homedir "${GNUPGHOME}" -b --rfc1991 >/dev/null
     + '
     + 
     ++test_lazy_prereq GPGSSH '
     ++	ssh_version=$(ssh-keygen -Y find-principals -n "git" 2>&1)
     ++	test $? != 127 || exit 1
     ++	echo $ssh_version | grep -q "find-principals:missing signature file"
     ++	test $? = 0 || exit 1; 
     ++	mkdir -p "${GNUPGHOME}" &&
     ++	chmod 0700 "${GNUPGHOME}" &&
     ++	ssh-keygen -t ed25519 -N "" -f "${GNUPGHOME}/ed25519_ssh_signing_key" >/dev/null &&
     ++	ssh-keygen -t rsa -b 2048 -N "" -f "${GNUPGHOME}/rsa_2048_ssh_signing_key" >/dev/null &&
     ++	ssh-keygen -t ed25519 -N "super_secret" -f "${GNUPGHOME}/protected_ssh_signing_key" >/dev/null &&
     ++	find "${GNUPGHOME}" -name *ssh_signing_key.pub -exec cat {} \; | awk "{print \"principal_\" NR \" \" \$0}" > "${GNUPGHOME}/ssh.all_valid.keyring" &&
     ++	cat "${GNUPGHOME}/ssh.all_valid.keyring" &&
     ++	ssh-keygen -t ed25519 -N "" -f "${GNUPGHOME}/untrusted_ssh_signing_key" >/dev/null
     ++'
     ++
     ++SIGNING_KEY_PRIMARY="${GNUPGHOME}/ed25519_ssh_signing_key"
     ++SIGNING_KEY_SECONDARY="${GNUPGHOME}/rsa_2048_ssh_signing_key"
     ++SIGNING_KEY_UNTRUSTED="${GNUPGHOME}/untrusted_ssh_signing_key"
     ++SIGNING_KEY_WITH_PASSPHRASE="${GNUPGHOME}/protected_ssh_signing_key"
     ++SIGNING_KEY_PASSPHRASE="super_secret"
     ++SIGNING_KEYRING="${GNUPGHOME}/ssh.all_valid.keyring"
     ++
     ++GOOD_SIGNATURE_TRUSTED='Good "git" signature for'
     ++GOOD_SIGNATURE_UNTRUSTED='Good "git" signature with'
     ++KEY_NOT_TRUSTED="No principal matched"
     ++BAD_SIGNATURE="Signature verification failed"
     ++
     + sanitize_pgp() {
     + 	perl -ne '
     + 		/^-----END PGP/ and $in_pgp = 0;
     +
     + ## t/t4202-log.sh ##
     +@@ t/t4202-log.sh: test_expect_success GPGSM 'setup signed branch x509' '
     + 	git commit -S -m signed_commit
     + '
     + 
     ++test_expect_success GPGSSH 'setup sshkey signed branch' '
     ++	test_config gpg.format ssh &&
     ++	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
     ++	test_when_finished "git reset --hard && git checkout main" &&
     ++	git checkout -b signed-ssh main &&
     ++	echo foo >foo &&
     ++	git add foo &&
     ++	git commit -S -m signed_commit
     ++'
     ++
     + test_expect_success GPGSM 'log x509 fingerprint' '
     + 	echo "F8BF62E0693D0694816377099909C779FA23FD65 | " >expect &&
     + 	git log -n1 --format="%GF | %GP" signed-x509 >actual &&
     +@@ t/t4202-log.sh: test_expect_success GPGSM 'log --graph --show-signature x509' '
     + 	grep "^| gpgsm: Good signature" actual
     + '
     + 
     ++test_expect_success GPGSSH 'log ssh key fingerprint' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	ssh-keygen -lf  "${SIGNING_KEY_PRIMARY}" | awk "{print \$2\" | \"}" >expect &&
     ++	git log -n1 --format="%GF | %GP" signed-ssh >actual &&
     ++	test_cmp expect actual
     ++'
     ++
     + test_expect_success GPG 'log --graph --show-signature for merged tag' '
     + 	test_when_finished "git reset --hard && git checkout main" &&
     + 	git checkout -b plain main &&
     +
     + ## t/t5534-push-signed.sh ##
     +@@ t/t5534-push-signed.sh: test_expect_success GPG 'signed push sends push certificate' '
     + 	test_cmp expect dst/push-cert-status
     + '
     + 
     ++test_expect_success GPGSSH 'ssh signed push sends push certificate' '
     ++	prepare_dst &&
     ++	mkdir -p dst/.git/hooks &&
     ++	git -C dst config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	git -C dst config receive.certnonceseed sekrit &&
     ++	write_script dst/.git/hooks/post-receive <<-\EOF &&
     ++	# discard the update list
     ++	cat >/dev/null
     ++	# record the push certificate
     ++	if test -n "${GIT_PUSH_CERT-}"
     ++	then
     ++		git cat-file blob $GIT_PUSH_CERT >../push-cert
     ++	fi &&
     ++
     ++	cat >../push-cert-status <<E_O_F
     ++	SIGNER=${GIT_PUSH_CERT_SIGNER-nobody}
     ++	KEY=${GIT_PUSH_CERT_KEY-nokey}
     ++	STATUS=${GIT_PUSH_CERT_STATUS-nostatus}
     ++	NONCE_STATUS=${GIT_PUSH_CERT_NONCE_STATUS-nononcestatus}
     ++	NONCE=${GIT_PUSH_CERT_NONCE-nononce}
     ++	E_O_F
     ++
     ++	EOF
     ++
     ++	test_config gpg.format ssh &&
     ++	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
     ++	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_PRIMARY}" | awk "{print \$2;}") &&
     ++	git push --signed dst noop ff +noff &&
     ++
     ++	(
     ++		cat <<-\EOF &&
     ++		SIGNER=principal_1
     ++		KEY=FINGERPRINT
     ++		STATUS=G
     ++		NONCE_STATUS=OK
     ++		EOF
     ++		sed -n -e "s/^nonce /NONCE=/p" -e "/^$/q" dst/push-cert
     ++	) | sed -e "s|FINGERPRINT|$FINGERPRINT|" >expect &&
     ++
     ++	noop=$(git rev-parse noop) &&
     ++	ff=$(git rev-parse ff) &&
     ++	noff=$(git rev-parse noff) &&
     ++	grep "$noop $ff refs/heads/ff" dst/push-cert &&
     ++	grep "$noop $noff refs/heads/noff" dst/push-cert &&
     ++	test_cmp expect dst/push-cert-status
     ++'
     ++
     + test_expect_success GPG 'inconsistent push options in signed push not allowed' '
     + 	# First, invoke receive-pack with dummy input to obtain its preamble.
     + 	prepare_dst &&
     +@@ t/t5534-push-signed.sh: test_expect_success GPGSM 'fail without key and heed user.signingkey x509' '
     + 	test_cmp expect dst/push-cert-status
     + '
     + 
     ++test_expect_success GPGSSH 'fail without key and heed user.signingkey ssh' '
     ++	test_config gpg.format ssh &&
     ++	prepare_dst &&
     ++	mkdir -p dst/.git/hooks &&
     ++	git -C dst config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	git -C dst config receive.certnonceseed sekrit &&
     ++	write_script dst/.git/hooks/post-receive <<-\EOF &&
     ++	# discard the update list
     ++	cat >/dev/null
     ++	# record the push certificate
     ++	if test -n "${GIT_PUSH_CERT-}"
     ++	then
     ++		git cat-file blob $GIT_PUSH_CERT >../push-cert
     ++	fi &&
     ++
     ++	cat >../push-cert-status <<E_O_F
     ++	SIGNER=${GIT_PUSH_CERT_SIGNER-nobody}
     ++	KEY=${GIT_PUSH_CERT_KEY-nokey}
     ++	STATUS=${GIT_PUSH_CERT_STATUS-nostatus}
     ++	NONCE_STATUS=${GIT_PUSH_CERT_NONCE_STATUS-nononcestatus}
     ++	NONCE=${GIT_PUSH_CERT_NONCE-nononce}
     ++	E_O_F
     ++
     ++	EOF
     ++
     ++	test_config user.email [email protected] &&
     ++	test_config gpg.format ssh &&
     ++	
     ++	test_config user.signingkey "" &&
     ++	(
     ++		sane_unset GIT_COMMITTER_EMAIL &&
     ++		test_must_fail git push --signed dst noop ff +noff
     ++	) &&
     ++	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
     ++	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_PRIMARY}" | awk "{print \$2;}") &&
     ++	git push --signed dst noop ff +noff &&
     ++
     ++	(
     ++		cat <<-\EOF &&
     ++		SIGNER=principal_1
     ++		KEY=FINGERPRINT
     ++		STATUS=G
     ++		NONCE_STATUS=OK
     ++		EOF
     ++		sed -n -e "s/^nonce /NONCE=/p" -e "/^$/q" dst/push-cert
     ++	) | sed -e "s|FINGERPRINT|$FINGERPRINT|" >expect &&
     ++
     ++	noop=$(git rev-parse noop) &&
     ++	ff=$(git rev-parse ff) &&
     ++	noff=$(git rev-parse noff) &&
     ++	grep "$noop $ff refs/heads/ff" dst/push-cert &&
     ++	grep "$noop $noff refs/heads/noff" dst/push-cert &&
     ++	test_cmp expect dst/push-cert-status
     ++'
     ++
     + test_expect_success GPG 'failed atomic push does not execute GPG' '
     + 	prepare_dst &&
     + 	git -C dst config receive.certnonceseed sekrit &&
     +
     + ## t/t7031-verify-tag-signed-ssh.sh (new) ##
     +@@
     ++#!/bin/sh
     ++
     ++test_description='signed tag tests'
     ++GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
     ++export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
     ++
     ++. ./test-lib.sh
     ++. "$TEST_DIRECTORY/lib-gpg.sh"
     ++
     ++test_expect_success GPGSSH 'create signed tags ssh' '
     ++	test_when_finished "test_unconfig commit.gpgsign" &&
     ++	test_config gpg.format ssh &&
     ++	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
     ++
     ++	echo 1 >file && git add file &&
     ++	test_tick && git commit -m initial &&
     ++	git tag -s -m initial initial &&
     ++	git branch side &&
     ++
     ++	echo 2 >file && test_tick && git commit -a -m second &&
     ++	git tag -s -m second second &&
     ++
     ++	git checkout side &&
     ++	echo 3 >elif && git add elif &&
     ++	test_tick && git commit -m "third on side" &&
     ++
     ++	git checkout main &&
     ++	test_tick && git merge -S side &&
     ++	git tag -s -m merge merge &&
     ++
     ++	echo 4 >file && test_tick && git commit -a -S -m "fourth unsigned" &&
     ++	git tag -a -m fourth-unsigned fourth-unsigned &&
     ++
     ++	test_tick && git commit --amend -S -m "fourth signed" &&
     ++	git tag -s -m fourth fourth-signed &&
     ++
     ++	echo 5 >file && test_tick && git commit -a -m "fifth" &&
     ++	git tag fifth-unsigned &&
     ++
     ++	git config commit.gpgsign true &&
     ++	echo 6 >file && test_tick && git commit -a -m "sixth" &&
     ++	git tag -a -m sixth sixth-unsigned &&
     ++
     ++	test_tick && git rebase -f HEAD^^ && git tag -s -m 6th sixth-signed HEAD^ &&
     ++	git tag -m seventh -s seventh-signed &&
     ++
     ++	echo 8 >file && test_tick && git commit -a -m eighth &&
     ++	git tag -u"${SIGNING_KEY_UNTRUSTED}" -m eighth eighth-signed-alt
     ++'
     ++
     ++test_expect_success GPGSSH 'verify and show ssh signatures' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.mintrustlevel UNDEFINED &&
     ++	(
     ++		for tag in initial second merge fourth-signed sixth-signed seventh-signed
     ++		do
     ++			git verify-tag $tag 2>actual &&
     ++			grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
     ++			! grep "${BAD_SIGNATURE}" actual &&
     ++			echo $tag OK || exit 1
     ++		done
     ++	) &&
     ++	(
     ++		for tag in fourth-unsigned fifth-unsigned sixth-unsigned
     ++		do
     ++			test_must_fail git verify-tag $tag 2>actual &&
     ++			! grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
     ++			! grep "${BAD_SIGNATURE}" actual &&
     ++			echo $tag OK || exit 1
     ++		done
     ++	) &&
     ++	(
     ++		for tag in eighth-signed-alt
     ++		do
     ++			git verify-tag $tag 2>actual &&
     ++			grep "${GOOD_SIGNATURE_UNTRUSTED}" actual &&
     ++			! grep "${BAD_SIGNATURE}" actual &&
     ++			grep "${KEY_NOT_TRUSTED}" actual &&
     ++			echo $tag OK || exit 1
     ++		done
     ++	)
     ++'
     ++
     ++test_expect_success GPGSSH 'detect fudged ssh signature' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	git cat-file tag seventh-signed >raw &&
     ++	sed -e "/^tag / s/seventh/7th forged/" raw >forged1 &&
     ++	git hash-object -w -t tag forged1 >forged1.tag &&
     ++	test_must_fail git verify-tag $(cat forged1.tag) 2>actual1 &&
     ++	grep "${BAD_SIGNATURE}" actual1 &&
     ++	! grep "${GOOD_SIGNATURE_TRUSTED}" actual1 &&
     ++	! grep "${GOOD_SIGNATURE_UNTRUSTED}" actual1
     ++'
     ++
     ++# test_expect_success GPGSSH 'verify ssh signatures with --raw' '
     ++# 	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++# 	(
     ++# 		for tag in initial second merge fourth-signed sixth-signed seventh-signed
     ++# 		do
     ++# 			git verify-tag --raw $tag 2>actual &&
     ++# 			grep "GOODSIG" actual &&
     ++# 			! grep "BADSIG" actual &&
     ++# 			echo $tag OK || exit 1
     ++# 		done
     ++# 	) &&
     ++# 	(
     ++# 		for tag in fourth-unsigned fifth-unsigned sixth-unsigned
     ++# 		do
     ++# 			test_must_fail git verify-tag --raw $tag 2>actual &&
     ++# 			! grep "GOODSIG" actual &&
     ++# 			! grep "BADSIG" actual &&
     ++# 			echo $tag OK || exit 1
     ++# 		done
     ++# 	) &&
     ++# 	(
     ++# 		for tag in eighth-signed-alt
     ++# 		do
     ++# 			git verify-tag --raw $tag 2>actual &&
     ++# 			grep "GOODSIG" actual &&
     ++# 			! grep "BADSIG" actual &&
     ++# 			grep "TRUST_UNDEFINED" actual &&
     ++# 			echo $tag OK || exit 1
     ++# 		done
     ++# 	)
     ++# '
     ++
     ++# test_expect_success GPGSM 'verify signatures with --raw x509' '
     ++# 	git verify-tag --raw ninth-signed-x509 2>actual &&
     ++# 	grep "GOODSIG" actual &&
     ++# 	! grep "BADSIG" actual &&
     ++# 	echo ninth-signed-x509 OK
     ++# '
     ++
     ++# test_expect_success GPGSSH 'verify multiple tags' '
     ++# 	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++# 	tags="fourth-signed sixth-signed seventh-signed" &&
     ++# 	for i in $tags
     ++# 	do
     ++# 		git verify-tag -v --raw $i || return 1
     ++# 	done >expect.stdout 2>expect.stderr.1 &&
     ++# 	grep "^.GNUPG:." <expect.stderr.1 >expect.stderr &&
     ++# 	git verify-tag -v --raw $tags >actual.stdout 2>actual.stderr.1 &&
     ++# 	grep "^.GNUPG:." <actual.stderr.1 >actual.stderr &&
     ++# 	test_cmp expect.stdout actual.stdout &&
     ++# 	test_cmp expect.stderr actual.stderr
     ++# '
     ++
     ++# test_expect_success GPGSM 'verify multiple tags x509' '
     ++#	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++# 	tags="seventh-signed ninth-signed-x509" &&
     ++# 	for i in $tags
     ++# 	do
     ++# 		git verify-tag -v --raw $i || return 1
     ++# 	done >expect.stdout 2>expect.stderr.1 &&
     ++# 	grep "^.GNUPG:." <expect.stderr.1 >expect.stderr &&
     ++# 	git verify-tag -v --raw $tags >actual.stdout 2>actual.stderr.1 &&
     ++# 	grep "^.GNUPG:." <actual.stderr.1 >actual.stderr &&
     ++# 	test_cmp expect.stdout actual.stdout &&
     ++# 	test_cmp expect.stderr actual.stderr
     ++# '
     ++
     ++test_expect_success GPGSSH 'verifying tag with --format' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	cat >expect <<-\EOF &&
     ++	tagname : fourth-signed
     ++	EOF
     ++	git verify-tag --format="tagname : %(tag)" "fourth-signed" >actual &&
     ++	test_cmp expect actual
     ++'
     ++
     ++test_expect_success GPGSSH 'verifying a forged tag with --format should fail silently' '
     ++	test_must_fail git verify-tag --format="tagname : %(tag)" $(cat forged1.tag) >actual-forged &&
     ++	test_must_be_empty actual-forged
     ++'
     ++
     ++test_done
     +
     + ## t/t7527-signed-commit-ssh.sh (new) ##
     +@@
     ++#!/bin/sh
     ++
     ++test_description='ssh signed commit tests'
     ++GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
     ++export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
     ++
     ++. ./test-lib.sh
     ++GNUPGHOME_NOT_USED=$GNUPGHOME
     ++. "$TEST_DIRECTORY/lib-gpg.sh"
     ++
     ++test_expect_success GPGSSH 'create signed commits' '
     ++	test_oid_cache <<-\EOF &&
     ++	header sha1:gpgsig
     ++	header sha256:gpgsig-sha256
     ++	EOF
     ++
     ++	test_when_finished "test_unconfig commit.gpgsign" &&
     ++	test_config gpg.format ssh &&
     ++	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
     ++
     ++	echo 1 >file && git add file &&
     ++	test_tick && git commit -S -m initial &&
     ++	git tag initial &&
     ++	git branch side &&
     ++
     ++	echo 2 >file && test_tick && git commit -a -S -m second &&
     ++	git tag second &&
     ++
     ++	git checkout side &&
     ++	echo 3 >elif && git add elif &&
     ++	test_tick && git commit -m "third on side" &&
     ++
     ++	git checkout main &&
     ++	test_tick && git merge -S side &&
     ++	git tag merge &&
     ++
     ++	echo 4 >file && test_tick && git commit -a -m "fourth unsigned" &&
     ++	git tag fourth-unsigned &&
     ++
     ++	test_tick && git commit --amend -S -m "fourth signed" &&
     ++	git tag fourth-signed &&
     ++
     ++	git config commit.gpgsign true &&
     ++	echo 5 >file && test_tick && git commit -a -m "fifth signed" &&
     ++	git tag fifth-signed &&
     ++
     ++	git config commit.gpgsign false &&
     ++	echo 6 >file && test_tick && git commit -a -m "sixth" &&
     ++	git tag sixth-unsigned &&
     ++
     ++	git config commit.gpgsign true &&
     ++	echo 7 >file && test_tick && git commit -a -m "seventh" --no-gpg-sign &&
     ++	git tag seventh-unsigned &&
     ++
     ++	test_tick && git rebase -f HEAD^^ && git tag sixth-signed HEAD^ &&
     ++	git tag seventh-signed &&
     ++
     ++	echo 8 >file && test_tick && git commit -a -m eighth -S"${SIGNING_KEY_UNTRUSTED}" &&
     ++	git tag eighth-signed-alt &&
     ++
     ++	# commit.gpgsign is still on but this must not be signed
     ++	echo 9 | git commit-tree HEAD^{tree} >oid &&
     ++	test_line_count = 1 oid &&
     ++	git tag ninth-unsigned $(cat oid) &&
     ++	# explicit -S of course must sign.
     ++	echo 10 | git commit-tree -S HEAD^{tree} >oid &&
     ++	test_line_count = 1 oid &&
     ++	git tag tenth-signed $(cat oid) &&
     ++
     ++	# --gpg-sign[=<key-id>] must sign.
     ++	echo 11 | git commit-tree --gpg-sign HEAD^{tree} >oid &&
     ++	test_line_count = 1 oid &&
     ++	git tag eleventh-signed $(cat oid) &&
     ++	echo 12 | git commit-tree --gpg-sign="${SIGNING_KEY_UNTRUSTED}" HEAD^{tree} >oid &&
     ++	test_line_count = 1 oid &&
     ++	git tag twelfth-signed-alt $(cat oid)
     ++'
     ++
     ++test_expect_success GPGSSH 'verify and show signatures' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.mintrustlevel UNDEFINED &&
     ++	(
     ++		for commit in initial second merge fourth-signed \
     ++			fifth-signed sixth-signed seventh-signed tenth-signed \
     ++			eleventh-signed
     ++		do
     ++			git verify-commit $commit &&
     ++			git show --pretty=short --show-signature $commit >actual &&
     ++			grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
     ++			! grep "${BAD_SIGNATURE}" actual &&
     ++			echo $commit OK || exit 1
     ++		done
     ++	) &&
     ++	(
     ++		for commit in merge^2 fourth-unsigned sixth-unsigned \
     ++			seventh-unsigned ninth-unsigned
     ++		do
     ++			test_must_fail git verify-commit $commit &&
     ++			git show --pretty=short --show-signature $commit >actual &&
     ++			! grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
     ++			! grep "${BAD_SIGNATURE}" actual &&
     ++			echo $commit OK || exit 1
     ++		done
     ++	) &&
     ++	(
     ++		for commit in eighth-signed-alt twelfth-signed-alt
     ++		do
     ++			git show --pretty=short --show-signature $commit >actual &&
     ++			grep "${GOOD_SIGNATURE_UNTRUSTED}" actual &&
     ++			! grep "${BAD_SIGNATURE}" actual &&
     ++			grep "${KEY_NOT_TRUSTED}" actual &&
     ++			echo $commit OK || exit 1
     ++		done
     ++	)
     ++'
     ++
     ++test_expect_success GPGSSH 'verify-commit exits success on untrusted signature' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	git verify-commit eighth-signed-alt 2>actual &&
     ++	grep "${GOOD_SIGNATURE_UNTRUSTED}" actual &&
     ++	! grep "${BAD_SIGNATURE}" actual &&
     ++	grep "${KEY_NOT_TRUSTED}" actual
     ++'
     ++
     ++test_expect_success GPGSSH 'verify-commit exits success with matching minTrustLevel' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.minTrustLevel fully &&
     ++	git verify-commit sixth-signed
     ++'
     ++
     ++test_expect_success GPGSSH 'verify-commit exits success with low minTrustLevel' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.minTrustLevel marginal &&
     ++	git verify-commit sixth-signed
     ++'
     ++
     ++test_expect_success GPGSSH 'verify-commit exits failure with high minTrustLevel' '
     ++	test_config gpg.minTrustLevel ultimate &&
     ++	test_must_fail git verify-commit eighth-signed-alt
     ++'
     ++
     ++# test_expect_success GPGSSH 'verify signatures with --raw' '
     ++# 	(
     ++# 		for commit in initial second merge fourth-signed fifth-signed sixth-signed seventh-signed
     ++# 		do
     ++# 			git verify-commit --raw $commit 2>actual &&
     ++# 			grep "GOODSIG" actual &&
     ++# 			! grep "BADSIG" actual &&
     ++# 			echo $commit OK || exit 1
     ++# 		done
     ++# 	) &&
     ++# 	(
     ++# 		for commit in merge^2 fourth-unsigned sixth-unsigned seventh-unsigned
     ++# 		do
     ++# 			test_must_fail git verify-commit --raw $commit 2>actual &&
     ++# 			! grep "GOODSIG" actual &&
     ++# 			! grep "BADSIG" actual &&
     ++# 			echo $commit OK || exit 1
     ++# 		done
     ++# 	) &&
     ++# 	(
     ++# 		for commit in eighth-signed-alt
     ++# 		do
     ++# 			git verify-commit --raw $commit 2>actual &&
     ++# 			grep "GOODSIG" actual &&
     ++# 			! grep "BADSIG" actual &&
     ++# 			grep "TRUST_UNDEFINED" actual &&
     ++# 			echo $commit OK || exit 1
     ++# 		done
     ++# 	)
     ++# '
     ++
     ++test_expect_success GPGSSH 'proper header is used for hash algorithm' '
     ++	git cat-file commit fourth-signed >output &&
     ++	grep "^$(test_oid header) -----BEGIN SSH SIGNATURE-----" output
     ++'
     ++
     ++test_expect_success GPGSSH 'show signed commit with signature' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	git show -s initial >commit &&
     ++	git show -s --show-signature initial >show &&
     ++	git verify-commit -v initial >verify.1 2>verify.2 &&
     ++	git cat-file commit initial >cat &&
     ++	grep -v -e "${GOOD_SIGNATURE_TRUSTED}" -e "Warning: " show >show.commit &&
     ++	grep -e "${GOOD_SIGNATURE_TRUSTED}" -e "Warning: " show >show.gpg &&
     ++	grep -v "^ " cat | grep -v "^gpgsig.* " >cat.commit &&
     ++	test_cmp show.commit commit &&
     ++	test_cmp show.gpg verify.2 &&
     ++	test_cmp cat.commit verify.1
     ++'
     ++
     ++test_expect_success GPGSSH 'detect fudged signature' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	git cat-file commit seventh-signed >raw &&
     ++	sed -e "s/^seventh/7th forged/" raw >forged1 &&
     ++	git hash-object -w -t commit forged1 >forged1.commit &&
     ++	test_must_fail git verify-commit $(cat forged1.commit) &&
     ++	git show --pretty=short --show-signature $(cat forged1.commit) >actual1 &&
     ++	grep "${BAD_SIGNATURE}" actual1 &&
     ++	! grep "${GOOD_SIGNATURE_TRUSTED}" actual1 &&
     ++	! grep "${GOOD_SIGNATURE_UNTRUSTED}" actual1
     ++'
     ++
     ++test_expect_success GPGSSH 'detect fudged signature with NUL' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	git cat-file commit seventh-signed >raw &&
     ++	cat raw >forged2 &&
     ++	echo Qwik | tr "Q" "\000" >>forged2 &&
     ++	git hash-object -w -t commit forged2 >forged2.commit &&
     ++	test_must_fail git verify-commit $(cat forged2.commit) &&
     ++	git show --pretty=short --show-signature $(cat forged2.commit) >actual2 &&
     ++	grep "${BAD_SIGNATURE}" actual2 &&
     ++	! grep "${GOOD_SIGNATURE_TRUSTED}" actual2
     ++'
     ++
     ++test_expect_success GPGSSH 'amending already signed commit' '
     ++	test_config gpg.format ssh &&
     ++	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	git checkout fourth-signed^0 &&
     ++	git commit --amend -S --no-edit &&
     ++	git verify-commit HEAD &&
     ++	git show -s --show-signature HEAD >actual &&
     ++	grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
     ++	! grep "${BAD_SIGNATURE}" actual
     ++'
     ++
     ++test_expect_success GPGSSH 'show good signature with custom format' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_PRIMARY}" | awk "{print \$2;}") &&
     ++	cat >expect.tmpl <<-\EOF &&
     ++	G
     ++	FINGERPRINT
     ++	principal_1
     ++	FINGERPRINT
     ++	
     ++	EOF
     ++	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
     ++	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" sixth-signed >actual &&
     ++	test_cmp expect actual
     ++'
     ++
     ++test_expect_success GPGSSH 'show bad signature with custom format' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	cat >expect <<-\EOF &&
     ++	B
     ++
     ++
     ++
     ++
     ++	EOF
     ++	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" $(cat forged1.commit) >actual &&
     ++	test_cmp expect actual
     ++'
     ++
     ++test_expect_success GPGSSH 'show untrusted signature with custom format' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	cat >expect.tmpl <<-\EOF &&
     ++	U
     ++	FINGERPRINT
     ++
     ++	FINGERPRINT
     ++	
     ++	EOF
     ++	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" eighth-signed-alt >actual &&
     ++	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_UNTRUSTED}" | awk "{print \$2;}") &&
     ++	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
     ++	test_cmp expect actual
     ++'
     ++
     ++test_expect_success GPGSSH 'show untrusted signature with undefined trust level' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	cat >expect.tmpl <<-\EOF &&
     ++	undefined
     ++	FINGERPRINT
     ++
     ++	FINGERPRINT
     ++
     ++	EOF
     ++	git log -1 --format="%GT%n%GK%n%GS%n%GF%n%GP" eighth-signed-alt >actual &&
     ++	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_UNTRUSTED}" | awk "{print \$2;}") &&
     ++	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
     ++	test_cmp expect actual
     ++'
     ++
     ++test_expect_success GPGSSH 'show untrusted signature with ultimate trust level' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	cat >expect.tmpl <<-\EOF &&
     ++	fully
     ++	FINGERPRINT
     ++	principal_1
     ++	FINGERPRINT
     ++
     ++	EOF
     ++	git log -1 --format="%GT%n%GK%n%GS%n%GF%n%GP" sixth-signed >actual &&
     ++	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_PRIMARY}" | awk "{print \$2;}") &&
     ++	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
     ++	test_cmp expect actual
     ++'
     ++
     ++test_expect_success GPGSSH 'show lack of signature with custom format' '
     ++	cat >expect <<-\EOF &&
     ++	N
     ++
     ++
     ++
     ++
     ++	EOF
     ++	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" seventh-unsigned >actual &&
     ++	test_cmp expect actual
     ++'
     ++
     ++test_expect_success GPGSSH 'log.showsignature behaves like --show-signature' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config log.showsignature true &&
     ++	git show initial >actual &&
     ++	grep "${GOOD_SIGNATURE_TRUSTED}" actual
     ++'
     ++
     ++test_expect_success GPGSSH 'check config gpg.format values' '
     ++	test_config gpg.format ssh &&
     ++	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
     ++	test_config gpg.format ssh &&
     ++	git commit -S --amend -m "success" &&
     ++	test_config gpg.format OpEnPgP &&
     ++	test_must_fail git commit -S --amend -m "fail"
     ++'
     ++
     ++# test_expect_success GPGSSH 'detect fudged commit with double signature' '
     ++# 	sed -e "/gpgsig/,/END PGP/d" forged1 >double-base &&
     ++# 	sed -n -e "/gpgsig/,/END PGP/p" forged1 | \
     ++# 		sed -e "s/^$(test_oid header)//;s/^ //" | gpg --dearmor >double-sig1.sig &&
     ++# 	gpg -o double-sig2.sig -u 29472784 --detach-sign double-base &&
     ++# 	cat double-sig1.sig double-sig2.sig | gpg --enarmor >double-combined.asc &&
     ++# 	sed -e "s/^\(-.*\)ARMORED FILE/\1SIGNATURE/;1s/^/$(test_oid header) /;2,\$s/^/ /" \
     ++# 		double-combined.asc > double-gpgsig &&
     ++# 	sed -e "/committer/r double-gpgsig" double-base >double-commit &&
     ++# 	git hash-object -w -t commit double-commit >double-commit.commit &&
     ++# 	test_must_fail git verify-commit $(cat double-commit.commit) &&
     ++# 	git show --pretty=short --show-signature $(cat double-commit.commit) >double-actual &&
     ++# 	grep "BAD signature from" double-actual &&
     ++# 	grep "Good signature from" double-actual
     ++# '
     ++
     ++# test_expect_success GPGSSH 'show double signature with custom format' '
     ++# 	cat >expect <<-\EOF &&
     ++# 	E
     ++
     ++
     ++
     ++
     ++# 	EOF
     ++# 	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" $(cat double-commit.commit) >actual &&
     ++# 	test_cmp expect actual
     ++# '
     ++
     ++
     ++# test_expect_success GPGSSH 'verify-commit verifies multiply signed commits' '
     ++# 	git init multiply-signed &&
     ++# 	cd multiply-signed &&
     ++# 	test_commit first &&
     ++# 	echo 1 >second &&
     ++# 	git add second &&
     ++# 	tree=$(git write-tree) &&
     ++# 	parent=$(git rev-parse HEAD^{commit}) &&
     ++# 	git commit --gpg-sign -m second &&
     ++# 	git cat-file commit HEAD &&
     ++# 	# Avoid trailing whitespace.
     ++# 	sed -e "s/^Q//" -e "s/^Z/ /" >commit <<-EOF &&
     ++# 	Qtree $tree
     ++# 	Qparent $parent
     ++# 	Qauthor A U Thor <[email protected]> 1112912653 -0700
     ++# 	Qcommitter C O Mitter <[email protected]> 1112912653 -0700
     ++# 	Qgpgsig -----BEGIN PGP SIGNATURE-----
     ++# 	QZ
     ++# 	Q iHQEABECADQWIQRz11h0S+chaY7FTocTtvUezd5DDQUCX/uBDRYcY29tbWl0dGVy
     ++# 	Q QGV4YW1wbGUuY29tAAoJEBO29R7N3kMNd+8AoK1I8mhLHviPH+q2I5fIVgPsEtYC
     ++# 	Q AKCTqBh+VabJceXcGIZuF0Ry+udbBQ==
     ++# 	Q =tQ0N
     ++# 	Q -----END PGP SIGNATURE-----
     ++# 	Qgpgsig-sha256 -----BEGIN PGP SIGNATURE-----
     ++# 	QZ
     ++# 	Q iHQEABECADQWIQRz11h0S+chaY7FTocTtvUezd5DDQUCX/uBIBYcY29tbWl0dGVy
     ++# 	Q QGV4YW1wbGUuY29tAAoJEBO29R7N3kMN/NEAn0XO9RYSBj2dFyozi0JKSbssYMtO
     ++# 	Q AJwKCQ1BQOtuwz//IjU8TiS+6S4iUw==
     ++# 	Q =pIwP
     ++# 	Q -----END PGP SIGNATURE-----
     ++# 	Q
     ++# 	Qsecond
     ++# 	EOF
     ++# 	head=$(git hash-object -t commit -w commit) &&
     ++# 	git reset --hard $head &&
     ++# 	git verify-commit $head 2>actual &&
     ++# 	grep "Good signature from" actual &&
     ++# 	! grep "BAD signature from" actual
     ++# '
     ++
     ++test_done

 Documentation/config/gpg.txt     |  35 ++-
 Documentation/config/user.txt    |   6 +
 builtin/receive-pack.c           |   4 +-
 fmt-merge-msg.c                  |   4 +-
 gpg-interface.c                  | 414 +++++++++++++++++++++++++++----
 gpg-interface.h                  |  12 +-
 log-tree.c                       |   8 +-
 pretty.c                         |   4 +-
 send-pack.c                      |   6 +-
 t/lib-gpg.sh                     |  27 ++
 t/t4202-log.sh                   |  17 ++
 t/t5534-push-signed.sh           | 102 ++++++++
 t/t7031-verify-tag-signed-ssh.sh | 176 +++++++++++++
 t/t7527-signed-commit-ssh.sh     | 398 +++++++++++++++++++++++++++++
 14 files changed, 1147 insertions(+), 66 deletions(-)
 create mode 100755 t/t7031-verify-tag-signed-ssh.sh
 create mode 100755 t/t7527-signed-commit-ssh.sh

index d94025cb368..c2bc4d06a66 100644
@@ -11,13 +11,13 @@ gpg.program::
 
 gpg.format::
 	Specifies which key format to use when signing with `--gpg-sign`.
-	Default is "openpgp" and another possible value is "x509".
+	Default is "openpgp". Other possible values are "x509", "ssh".
 
 gpg.<format>.program::
 	Use this to customize the program used for the signing format you
 	chose. (see `gpg.program` and `gpg.format`) `gpg.program` can still
 	be used as a legacy synonym for `gpg.openpgp.program`. The default
-	value for `gpg.x509.program` is "gpgsm".
+	value for `gpg.x509.program` is "gpgsm" and `gpg.ssh.program` is "ssh-keygen".
 
 gpg.minTrustLevel::
 	Specifies a minimum trust level for signature verification.  If

@@ -33,3 +33,34 @@ gpg.minTrustLevel::
 * `marginal`
 * `fully`
 * `ultimate`
+
+gpg.ssh.keyring::
+	A file containing all valid SSH public signing keys. 
+	Similar to an .ssh/authorized_keys file.
+	See ssh-keygen(1) "ALLOWED SIGNERS" for details.
+	If a signing key is found in this file then the trust level will
+	be set to "fully". Otherwise if the key is not present
+	but the signature is still valid then the trust level will be "undefined".
+
+	This file can be set to a location outside of the repository
+	and every developer maintains their own trust store.
+	A central repository server could generate this file automatically
+	from ssh keys with push	access to verify the code against.
+	In a corporate setting this file is probably generated at a global location
+	from some automation that already handles developer ssh keys. 
+	
+	A repository that is only allowing signed commits can store the file 
+	in the repository itself using a relative path. This way only committers
+	with an already valid key can add or change keys in the keyring.
+
+	Using a SSH CA key with the cert-authority option 
+	(see ssh-keygen(1) "CERTIFICATES") is also valid.
+
+	To revoke a key place the public key without the principal into the 
+	revocationKeyring.
+
+gpg.ssh.revocationKeyring::
+	Either a SSH KRL or a list of revoked public keys (without the principal prefix).
+	See ssh-keygen(1) for details.
+	If a public key is found in this file then it will always be treated
+	as having trust level "never" and signatures will show as invalid.

index 59aec7c3aed..e71a099b8b8 100644
@@ -36,3 +36,9 @@ user.signingKey::
 	commit, you can override the default selection with this variable.
 	This option is passed unchanged to gpg's --local-user parameter,
 	so you may specify a key using any method that gpg supports.
+	If gpg.format is set to "ssh" this can contain the literal ssh public
+	key (e.g.: "ssh-rsa XXXXXX identifier") or a file which contains it and 
+	corresponds to the private key used for signing. The private key 
+	needs to be available via ssh-agent. Alternatively it can be set to
+	a file containing a private key directly. If not set git will call 
+	"ssh-add -L" and try to use the first key available.

index a34742513ac..fd790f7fd72 100644
@@ -131,6 +131,8 @@ static int receive_pack_config(const char *var, const char *value, void *cb)
 {
 	int status = parse_hide_refs_config(var, value, "receive");
 
+	git_gpg_config(var, value, NULL);
+
 	if (status)
 		return status;
 

@@ -767,7 +769,7 @@ static void prepare_push_cert_sha1(struct child_process *proc)
 		bogs = parse_signed_buffer(push_cert.buf, push_cert.len);
 		check_signature(push_cert.buf, bogs, push_cert.buf + bogs,
 				push_cert.len - bogs, &sigcheck);
-
+		
 		nonce_status = check_nonce(push_cert.buf, bogs);
 	}
 	if (!is_null_oid(&push_cert_oid)) {

index 0f66818e0f8..1d7b64fa021 100644
@@ -527,10 +527,10 @@ static void fmt_merge_msg_sigs(struct strbuf *out)
 			len = payload.len;
 			if (check_signature(payload.buf, payload.len, sig.buf,
 					 sig.len, &sigc) &&
-				!sigc.gpg_output)
+				!sigc.output)
 				strbuf_addstr(&sig, "gpg verification failed.\n");
 			else
-				strbuf_addstr(&sig, sigc.gpg_output);
+				strbuf_addstr(&sig, sigc.output);
 		}
 		signature_check_clear(&sigc);
 

index 80567e48948..03d56475b56 100644
@@ -17,8 +17,9 @@ enum signature_trust_level {
 
 struct signature_check {
 	char *payload;
-	char *gpg_output;
-	char *gpg_status;
+	char *output;
+	char *gpg_output; // This will be printed in commit logs
+	char *gpg_status; // Only used internally -> remove
 
 	/*
 	 * possible "result":

@@ -64,6 +65,13 @@ int sign_buffer(struct strbuf *buffer, struct strbuf *signature,
 int git_gpg_config(const char *, const char *, void *);
 void set_signing_key(const char *);
 const char *get_signing_key(void);
+
+/* Returns a textual unique representation of the signing key in use
+ * Either a GPG KeyID or a SSH Key Fingerprint
+ */
+const char *get_signing_key_id(void);
+
+const char *get_ssh_allowed_signers(void);
 int check_signature(const char *payload, size_t plen,
 		    const char *signature, size_t slen,
 		    struct signature_check *sigc);

index 7b823786c2c..20af9bd1c82 100644
@@ -513,10 +513,10 @@ static void show_signature(struct rev_info *opt, struct commit *commit)
 
 	status = check_signature(payload.buf, payload.len, signature.buf,
 				 signature.len, &sigc);
-	if (status && !sigc.gpg_output)
+	if (status && !sigc.output)
 		show_sig_lines(opt, status, "No signature\n");
 	else
-		show_sig_lines(opt, status, sigc.gpg_output);
+		show_sig_lines(opt, status, sigc.output);
 	signature_check_clear(&sigc);
 
  out:

@@ -583,8 +583,8 @@ static int show_one_mergetag(struct commit *commit,
 		/* could have a good signature */
 		status = check_signature(payload.buf, payload.len,
 					 signature.buf, signature.len, &sigc);
-		if (sigc.gpg_output)
-			strbuf_addstr(&verify_message, sigc.gpg_output);
+		if (sigc.output)
+			strbuf_addstr(&verify_message, sigc.output);
 		else
 			strbuf_addstr(&verify_message, "No signature\n");
 		signature_check_clear(&sigc);

index b1ecd039cef..daa71394efd 100644
@@ -1432,8 +1432,8 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 			check_commit_signature(c->commit, &(c->signature_check));
 		switch (placeholder[1]) {
 		case 'G':
-			if (c->signature_check.gpg_output)
-				strbuf_addstr(sb, c->signature_check.gpg_output);
+			if (c->signature_check.output)
+				strbuf_addstr(sb, c->signature_check.output);
 			break;
 		case '?':
 			switch (c->signature_check.result) {

index 9cb9f716509..c8fb0c30f87 100644
@@ -342,12 +342,13 @@ static int generate_push_cert(struct strbuf *req_buf,
 	const struct ref *ref;
 	struct string_list_item *item;
 	char *signing_key = xstrdup(get_signing_key());
+	char *signing_key_id = xstrdup(get_signing_key_id());
 	const char *cp, *np;
 	struct strbuf cert = STRBUF_INIT;
 	int update_seen = 0;
-
+	
 	strbuf_addstr(&cert, "certificate version 0.1\n");
-	strbuf_addf(&cert, "pusher %s ", signing_key);
+	strbuf_addf(&cert, "pusher %s ", signing_key_id);
 	datestamp(&cert);
 	strbuf_addch(&cert, '\n');
 	if (args->url && *args->url) {

@@ -387,6 +388,7 @@ static int generate_push_cert(struct strbuf *req_buf,
 
 free_return:
 	free(signing_key);
+	free(signing_key_id);
 	strbuf_release(&cert);
 	return update_seen;
 }

index 9fc5241228e..96935582262 100644
@@ -87,6 +87,33 @@ test_lazy_prereq RFC1991 '
 	echo | gpg --homedir "${GNUPGHOME}" -b --rfc1991 >/dev/null
 '
 
+test_lazy_prereq GPGSSH '
+	ssh_version=$(ssh-keygen -Y find-principals -n "git" 2>&1)
+	test $? != 127 || exit 1
+	echo $ssh_version | grep -q "find-principals:missing signature file"
+	test $? = 0 || exit 1; 
+	mkdir -p "${GNUPGHOME}" &&
+	chmod 0700 "${GNUPGHOME}" &&
+	ssh-keygen -t ed25519 -N "" -f "${GNUPGHOME}/ed25519_ssh_signing_key" >/dev/null &&
+	ssh-keygen -t rsa -b 2048 -N "" -f "${GNUPGHOME}/rsa_2048_ssh_signing_key" >/dev/null &&
+	ssh-keygen -t ed25519 -N "super_secret" -f "${GNUPGHOME}/protected_ssh_signing_key" >/dev/null &&
+	find "${GNUPGHOME}" -name *ssh_signing_key.pub -exec cat {} \; | awk "{print \"principal_\" NR \" \" \$0}" > "${GNUPGHOME}/ssh.all_valid.keyring" &&
+	cat "${GNUPGHOME}/ssh.all_valid.keyring" &&
+	ssh-keygen -t ed25519 -N "" -f "${GNUPGHOME}/untrusted_ssh_signing_key" >/dev/null
+'
+
+SIGNING_KEY_PRIMARY="${GNUPGHOME}/ed25519_ssh_signing_key"
+SIGNING_KEY_SECONDARY="${GNUPGHOME}/rsa_2048_ssh_signing_key"
+SIGNING_KEY_UNTRUSTED="${GNUPGHOME}/untrusted_ssh_signing_key"
+SIGNING_KEY_WITH_PASSPHRASE="${GNUPGHOME}/protected_ssh_signing_key"
+SIGNING_KEY_PASSPHRASE="super_secret"
+SIGNING_KEYRING="${GNUPGHOME}/ssh.all_valid.keyring"
+
+GOOD_SIGNATURE_TRUSTED='Good "git" signature for'
+GOOD_SIGNATURE_UNTRUSTED='Good "git" signature with'
+KEY_NOT_TRUSTED="No principal matched"
+BAD_SIGNATURE="Signature verification failed"
+
 sanitize_pgp() {
 	perl -ne '
 		/^-----END PGP/ and $in_pgp = 0;

index 350cfa35936..84227066685 100755
@@ -1616,6 +1616,16 @@ test_expect_success GPGSM 'setup signed branch x509' '
 	git commit -S -m signed_commit
 '
 
+test_expect_success GPGSSH 'setup sshkey signed branch' '
+	test_config gpg.format ssh &&
+	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
+	test_when_finished "git reset --hard && git checkout main" &&
+	git checkout -b signed-ssh main &&
+	echo foo >foo &&
+	git add foo &&
+	git commit -S -m signed_commit
+'
+
 test_expect_success GPGSM 'log x509 fingerprint' '
 	echo "F8BF62E0693D0694816377099909C779FA23FD65 | " >expect &&
 	git log -n1 --format="%GF | %GP" signed-x509 >actual &&

@@ -1640,6 +1650,13 @@ test_expect_success GPGSM 'log --graph --show-signature x509' '
 	grep "^| gpgsm: Good signature" actual
 '
 
+test_expect_success GPGSSH 'log ssh key fingerprint' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	ssh-keygen -lf  "${SIGNING_KEY_PRIMARY}" | awk "{print \$2\" | \"}" >expect &&
+	git log -n1 --format="%GF | %GP" signed-ssh >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success GPG 'log --graph --show-signature for merged tag' '
 	test_when_finished "git reset --hard && git checkout main" &&
 	git checkout -b plain main &&

base-commit: d486ca60a51c9cb1fe068803c3f540724e95e83a

gitgitgadget

On 12.07.21 18:55, Ævar Arnfjörð Bjarmason wrote:

I'll change all the whitespace / comments / style issues with the next commit. Thanks

I agree. This is my first patch in the git codebase so it takes a bit getting used to all the available utilities.

Sounds good. I'll give it a try.

I'll add a warning

Sorry, i should have removed it. The original code assigned gpg's stdout to gpg_status and stdout to gpg_output which can be a bit confusing.

The BUG() call is also from the original code. I agree that it should be handled differently.
Unfortunately this call is also the reason that when trying to verify a new SSH signature with a current git version you'll get a segfault from this BUG() :/
I'm not sure if i can do anything about this other than adding a completely new tag in the commit itself instead of "gpgsig" which might be quite involved. I haven't looked into that too much yet.

I'll clean up the logic. Thanks

Yes. Although this test explicitly i'm having a hard time to duplicate for ssh. I'm still trying to find out if the duplicate signature thing is actually an issue with ssh.

Sure, I can easily split the patch into seperate commits. But do i create a v3 patch from this or issue a new pull request? The diff between v2 & v3 would be quite useless otherwise wouldn't it?

And maybe another beginner contribution question:

When i make changes to a patchset do i put new changes from the review on top as new commits or do i edit the existing commits? If so what is the workflow you normally use for this? fixup commits? I know about those but haven't worked with them before.

Thanks for your help!

The interdiff might be quite useless, but not the rangediff. Either way both of those are merely tools to visualize changes between versions, ultimately what really matters is the final commits themselves.

Moreover, not all reviewers have seen every version, so for example if you properly split this patch, I might join the review process at v3, and I don't really care what was in v2, therefore I wouldn't look at the rangediff.

Edit existing commits.

git rebase --interactive is what I use, and I think that's what most people use.

This allows you to easily edit commits and add specific changes to specific commits.

Once you are familiar with this process it's easier to understand fixup commits, but I'd say rebasing comes first.

Cheers.

Felipe Contreras

From: Fabian Stelzer <[email protected]>

---
 Documentation/config/gpg.txt  | 35 +++++++++++++++++++++++++++++++++--
 Documentation/config/user.txt |  6 ++++++
 2 files changed, 39 insertions(+), 2 deletions(-)

index d94025cb368..16af0b0ada8 100644
@@ -11,13 +11,13 @@ gpg.program::
 
 gpg.format::
 	Specifies which key format to use when signing with `--gpg-sign`.
-	Default is "openpgp" and another possible value is "x509".
+	Default is "openpgp". Other possible values are "x509", "ssh".
 
 gpg.<format>.program::
 	Use this to customize the program used for the signing format you
 	chose. (see `gpg.program` and `gpg.format`) `gpg.program` can still
 	be used as a legacy synonym for `gpg.openpgp.program`. The default
-	value for `gpg.x509.program` is "gpgsm".
+	value for `gpg.x509.program` is "gpgsm" and `gpg.ssh.program` is "ssh-keygen".
 
 gpg.minTrustLevel::
 	Specifies a minimum trust level for signature verification.  If

@@ -33,3 +33,34 @@ gpg.minTrustLevel::
 * `marginal`
 * `fully`
 * `ultimate`
+
+gpg.ssh.keyring::
+	A file containing all valid SSH public signing keys.
+	Similar to an .ssh/authorized_keys file.
+	See ssh-keygen(1) "ALLOWED SIGNERS" for details.
+	If a signing key is found in this file then the trust level will
+	be set to "fully". Otherwise if the key is not present
+	but the signature is still valid then the trust level will be "undefined".
+
+	This file can be set to a location outside of the repository
+	and every developer maintains their own trust store.
+	A central repository server could generate this file automatically
+	from ssh keys with push	access to verify the code against.
+	In a corporate setting this file is probably generated at a global location
+	from some automation that already handles developer ssh keys.
+
+	A repository that is only allowing signed commits can store the file
+	in the repository itself using a relative path. This way only committers
+	with an already valid key can add or change keys in the keyring.
+
+	Using a SSH CA key with the cert-authority option
+	(see ssh-keygen(1) "CERTIFICATES") is also valid.
+
+	To revoke a key place the public key without the principal into the
+	revocationKeyring.
+
+gpg.ssh.revocationKeyring::
+	Either a SSH KRL or a list of revoked public keys (without the principal prefix).
+	See ssh-keygen(1) for details.
+	If a public key is found in this file then it will always be treated
+	as having trust level "never" and signatures will show as invalid.

index 59aec7c3aed..b3c2f2c541e 100644
@@ -36,3 +36,9 @@ user.signingKey::
 	commit, you can override the default selection with this variable.
 	This option is passed unchanged to gpg's --local-user parameter,
 	so you may specify a key using any method that gpg supports.
+	If gpg.format is set to "ssh" this can contain the literal ssh public
+	key (e.g.: "ssh-rsa XXXXXX identifier") or a file which contains it and
+	corresponds to the private key used for signing. The private key
+	needs to be available via ssh-agent. Alternatively it can be set to
+	a file containing a private key directly. If not set git will call
+	"ssh-add -L" and try to use the first key available.

gitgitgadget

From: Fabian Stelzer <[email protected]>

Openssh v8.2p1 added some new options to ssh-keygen for signature creation and verification. These allow us to use ssh keys for git signatures easily.

Start with adding the new signature format, new config options and rename some fields for consistency.

This feature makes git signing much more accessible to the average user. Usually they have a SSH Key for pushing code already. Using it for signing commits allows us to verify not only the transport but the pushed code as well.

In our corporate environemnt we use PIV x509 Certs on Yubikeys for email signing/encryption and ssh keys which i think is quite common
(at least for the email part). This way we can establish the correct trust for the SSH Keys without setting up a separate GPG Infrastructure (which is still quite painful for users) or implementing x509 signing support for git (which lacks good forwarding mechanisms).
Using ssh agent forwarding makes this feature easily usable in todays development environments where code is often checked out in remote VMs / containers. In such a setup the keyring & revocationKeyring can be centrally generated from the x509 CA information and distributed to the users.

---
 fmt-merge-msg.c |   4 +-
 gpg-interface.c | 122 +++++++++++++++++++++++++++++++++---------------
 gpg-interface.h |   5 +-
 log-tree.c      |   8 ++--
 pretty.c        |   4 +-
 5 files changed, 95 insertions(+), 48 deletions(-)

index 0f66818e0f8..1d7b64fa021 100644
@@ -527,10 +527,10 @@ static void fmt_merge_msg_sigs(struct strbuf *out)
 			len = payload.len;
 			if (check_signature(payload.buf, payload.len, sig.buf,
 					 sig.len, &sigc) &&
-				!sigc.gpg_output)
+				!sigc.output)
 				strbuf_addstr(&sig, "gpg verification failed.\n");
 			else
-				strbuf_addstr(&sig, sigc.gpg_output);
+				strbuf_addstr(&sig, sigc.output);
 		}
 		signature_check_clear(&sigc);
 

index 80567e48948..5dfd92b81f6 100644
@@ -17,8 +17,8 @@ enum signature_trust_level {
 
 struct signature_check {
 	char *payload;
-	char *gpg_output;
-	char *gpg_status;
+	char *output;
+	char *gpg_status; /* Only used internally -> remove from this public api */
 
 	/*
 	 * possible "result":

@@ -64,6 +64,7 @@ int sign_buffer(struct strbuf *buffer, struct strbuf *signature,
 int git_gpg_config(const char *, const char *, void *);
 void set_signing_key(const char *);
 const char *get_signing_key(void);
+const char *get_ssh_allowed_signers(void);
 int check_signature(const char *payload, size_t plen,
 		    const char *signature, size_t slen,
 		    struct signature_check *sigc);

index 7b823786c2c..20af9bd1c82 100644
@@ -513,10 +513,10 @@ static void show_signature(struct rev_info *opt, struct commit *commit)
 
 	status = check_signature(payload.buf, payload.len, signature.buf,
 				 signature.len, &sigc);
-	if (status && !sigc.gpg_output)
+	if (status && !sigc.output)
 		show_sig_lines(opt, status, "No signature\n");
 	else
-		show_sig_lines(opt, status, sigc.gpg_output);
+		show_sig_lines(opt, status, sigc.output);
 	signature_check_clear(&sigc);
 
  out:

@@ -583,8 +583,8 @@ static int show_one_mergetag(struct commit *commit,
 		/* could have a good signature */
 		status = check_signature(payload.buf, payload.len,
 					 signature.buf, signature.len, &sigc);
-		if (sigc.gpg_output)
-			strbuf_addstr(&verify_message, sigc.gpg_output);
+		if (sigc.output)
+			strbuf_addstr(&verify_message, sigc.output);
 		else
 			strbuf_addstr(&verify_message, "No signature\n");
 		signature_check_clear(&sigc);

index b1ecd039cef..daa71394efd 100644
@@ -1432,8 +1432,8 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 			check_commit_signature(c->commit, &(c->signature_check));
 		switch (placeholder[1]) {
 		case 'G':
-			if (c->signature_check.gpg_output)
-				strbuf_addstr(sb, c->signature_check.gpg_output);
+			if (c->signature_check.output)
+				strbuf_addstr(sb, c->signature_check.output);
 			break;
 		case '?':
 			switch (c->signature_check.result) {

gitgitgadget

I have added support for using keyfiles directly, lots of tests and generally cleaned up the signing & verification code a lot.

I can still rename things from being gpg specific to a more general "signing" but thats rather cosmetic. Also i'm not sure if i named the new test files correctly.

There is a patch in the pipeline for openssh by Damien Miller that will add valid-after, valid-before options to the allowed keys keyring. This allows us to pass the commit timestamp to the verification call and make key rollover possible and still be able to verify older commits. Set valid-after=NOW when adding your key to the keyring and set valid-before to make it fail if used after a certain date. Software like gitolite/github or corporate automation can do this automatically when ssh push keys are addded / removed

v3 addresses some issues & refactoring and splits the large commit into several smaller ones.

Fabian Stelzer (9):
Add commit, tag & push signing via SSH keys
ssh signing: add documentation
ssh signing: retrieve a default key from ssh-agent ssh signing: sign using either gpg or ssh keys
ssh signing: provide a textual representation of the signing key ssh signing: parse ssh-keygen output and verify signatures ssh signing: add test prereqs
ssh signing: duplicate t7510 tests for commits
ssh signing: add more tests for logs, tags & push certs

 Documentation/config/gpg.txt     |  35 ++-
 Documentation/config/user.txt    |   6 +
 builtin/receive-pack.c           |   2 +
 fmt-merge-msg.c                  |   4 +-
 gpg-interface.c                  | 411 +++++++++++++++++++++++++++----
 gpg-interface.h                  |  12 +-
 log-tree.c                       |   8 +-
 pretty.c                         |   4 +-
 send-pack.c                      |   8 +-
 t/lib-gpg.sh                     |  27 ++
 t/t4202-log.sh                   |  23 ++
 t/t5534-push-signed.sh           | 101 ++++++++
 t/t7031-verify-tag-signed-ssh.sh | 161 ++++++++++++
 t/t7527-signed-commit-ssh.sh     | 398 ++++++++++++++++++++++++++++++
 14 files changed, 1136 insertions(+), 64 deletions(-)
 create mode 100755 t/t7031-verify-tag-signed-ssh.sh
 create mode 100755 t/t7527-signed-commit-ssh.sh

base-commit: d486ca60a51c9cb1fe068803c3f540724e95e83a
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1041%2FFStelzer%2Fsshsign-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1041/FStelzer/sshsign-v3
Pull-Request: https://github.com/git/git/pull/1041

Range-diff vs v2:

  -:  ----------- >  1:  390a8f816cd Add commit, tag & push signing via SSH keys
  -:  ----------- >  2:  2f8452f6570 ssh signing: add documentation
  -:  ----------- >  3:  b84b2812470 ssh signing: retrieve a default key from ssh-agent
  -:  ----------- >  4:  df55b9e1d59 ssh signing: sign using either gpg or ssh keys
  -:  ----------- >  5:  0581c72634c ssh signing: provide a textual representation of the signing key
  -:  ----------- >  6:  381a950a6e1 ssh signing: parse ssh-keygen output and verify signatures
  -:  ----------- >  7:  1d292a8d7a2 ssh signing: add test prereqs
  1:  b8b16f8e6ec !  8:  338d1b976e9 Add commit, tag & push signing/verification via SSH keys using ssh-keygen
     @@ Metadata
      Author: Fabian Stelzer <[email protected]>
      
       ## Commit message ##
     -    Add commit, tag & push signing/verification via SSH keys using ssh-keygen
     -
     -    Openssh v8.2p1 added some new options to ssh-keygen for signature
     -    creation and verification. These allow us to use ssh keys for git
     -    signatures easily.
     -
     -    Set gpg.format = ssh and user.signingkey to either a ssh public key
     -    string (like from an authorized_keys file), or a ssh key file.
     -    If the key file or the config value itself contains only a public key
     -    then the private key needs to be available via ssh-agent.
     -    If no signingkey is set then git will call 'ssh-add -L' to check for
     -    available agent keys and use the first one for signing.
     -
     -    Verification uses the gpg.ssh.keyring file (see ssh-keygen(1) "ALLOWED
     -    SIGNERS") which contains valid public keys and an principal (usually
     -    user@domain). Depending on the environment this file can be managed by
     -    the individual developer or for example generated by the central
     -    repository server from known ssh keys with push access. If the
     -    repository only allows signed commits / pushes then the file can even be
     -    stored inside it.
     -
     -    To revoke a key put the public key without the principal prefix into
     -    gpg.ssh.revocationKeyring or generate a KRL (see ssh-keygen(1)
     -    "KEY REVOCATION LISTS"). The same considerations about who to trust for
     -    verification as with the keyring file apply.
     -
     -    This feature makes git signing much more accessible to the average user.
     -    Usually they have a SSH Key for pushing code already. Using it
     -    for signing commits allows us to verify not only the transport but the
     -    pushed code as well.
     -
     -    In our corporate environemnt we use PIV x509 Certs on Yubikeys for email
     -    signing/encryption and ssh keys which i think is quite common
     -    (at least for the email part). This way we can establish the correct
     -    trust for the SSH Keys without setting up a separate GPG Infrastructure
     -    (which is still quite painful for users) or implementing x509 signing
     -    support for git (which lacks good forwarding mechanisms).
     -    Using ssh agent forwarding makes this feature easily usable in todays
     -    development environments where code is often checked out in remote VMs / containers.
     -    In such a setup the keyring & revocationKeyring can be centrally
     -    generated from the x509 CA information and distributed to the users.
     +    ssh signing: duplicate t7510 tests for commits
      
          Signed-off-by: Fabian Stelzer <[email protected]>
      
     - ## Documentation/config/gpg.txt ##
     -@@ Documentation/config/gpg.txt: gpg.program::
     - 
     - gpg.format::
     - 	Specifies which key format to use when signing with `--gpg-sign`.
     --	Default is "openpgp" and another possible value is "x509".
     -+	Default is "openpgp". Other possible values are "x509", "ssh".
     - 
     - gpg.<format>.program::
     - 	Use this to customize the program used for the signing format you
     - 	chose. (see `gpg.program` and `gpg.format`) `gpg.program` can still
     - 	be used as a legacy synonym for `gpg.openpgp.program`. The default
     --	value for `gpg.x509.program` is "gpgsm".
     -+	value for `gpg.x509.program` is "gpgsm" and `gpg.ssh.program` is "ssh-keygen".
     - 
     - gpg.minTrustLevel::
     - 	Specifies a minimum trust level for signature verification.  If
     -@@ Documentation/config/gpg.txt: gpg.minTrustLevel::
     - * `marginal`
     - * `fully`
     - * `ultimate`
     -+
     -+gpg.ssh.keyring::
     -+	A file containing all valid SSH public signing keys. 
     -+	Similar to an .ssh/authorized_keys file.
     -+	See ssh-keygen(1) "ALLOWED SIGNERS" for details.
     -+	If a signing key is found in this file then the trust level will
     -+	be set to "fully". Otherwise if the key is not present
     -+	but the signature is still valid then the trust level will be "undefined".
     -+
     -+	This file can be set to a location outside of the repository
     -+	and every developer maintains their own trust store.
     -+	A central repository server could generate this file automatically
     -+	from ssh keys with push	access to verify the code against.
     -+	In a corporate setting this file is probably generated at a global location
     -+	from some automation that already handles developer ssh keys. 
     -+	
     -+	A repository that is only allowing signed commits can store the file 
     -+	in the repository itself using a relative path. This way only committers
     -+	with an already valid key can add or change keys in the keyring.
     -+
     -+	Using a SSH CA key with the cert-authority option 
     -+	(see ssh-keygen(1) "CERTIFICATES") is also valid.
     -+
     -+	To revoke a key place the public key without the principal into the 
     -+	revocationKeyring.
     -+
     -+gpg.ssh.revocationKeyring::
     -+	Either a SSH KRL or a list of revoked public keys (without the principal prefix).
     -+	See ssh-keygen(1) for details.
     -+	If a public key is found in this file then it will always be treated
     -+	as having trust level "never" and signatures will show as invalid.
     -
     - ## Documentation/config/user.txt ##
     -@@ Documentation/config/user.txt: user.signingKey::
     - 	commit, you can override the default selection with this variable.
     - 	This option is passed unchanged to gpg's --local-user parameter,
     - 	so you may specify a key using any method that gpg supports.
     -+	If gpg.format is set to "ssh" this can contain the literal ssh public
     -+	key (e.g.: "ssh-rsa XXXXXX identifier") or a file which contains it and 
     -+	corresponds to the private key used for signing. The private key 
     -+	needs to be available via ssh-agent. Alternatively it can be set to
     -+	a file containing a private key directly. If not set git will call 
     -+	"ssh-add -L" and try to use the first key available.
     -
     - ## builtin/receive-pack.c ##
     -@@ builtin/receive-pack.c: static int receive_pack_config(const char *var, const char *value, void *cb)
     - {
     - 	int status = parse_hide_refs_config(var, value, "receive");
     - 
     -+	git_gpg_config(var, value, NULL);
     -+
     - 	if (status)
     - 		return status;
     - 
     -@@ builtin/receive-pack.c: static void prepare_push_cert_sha1(struct child_process *proc)
     - 		bogs = parse_signed_buffer(push_cert.buf, push_cert.len);
     - 		check_signature(push_cert.buf, bogs, push_cert.buf + bogs,
     - 				push_cert.len - bogs, &sigcheck);
     --
     -+		
     - 		nonce_status = check_nonce(push_cert.buf, bogs);
     - 	}
     - 	if (!is_null_oid(&push_cert_oid)) {
     -
     - ## fmt-merge-msg.c ##
     -@@ fmt-merge-msg.c: static void fmt_merge_msg_sigs(struct strbuf *out)
     - 			len = payload.len;
     - 			if (check_signature(payload.buf, payload.len, sig.buf,
     - 					 sig.len, &sigc) &&
     --				!sigc.gpg_output)
     -+				!sigc.output)
     - 				strbuf_addstr(&sig, "gpg verification failed.\n");
     - 			else
     --				strbuf_addstr(&sig, sigc.gpg_output);
     -+				strbuf_addstr(&sig, sigc.output);
     - 		}
     - 		signature_check_clear(&sigc);
     - 
     -
     - ## gpg-interface.c ##
     -@@
     - #include "config.h"
     - #include "run-command.h"
     - #include "strbuf.h"
     -+#include "dir.h"
     - #include "gpg-interface.h"
     - #include "sigchain.h"
     - #include "tempfile.h"
     - 
     - static char *configured_signing_key;
     -+const char *ssh_allowed_signers, *ssh_revocation_file;
     - static enum signature_trust_level configured_min_trust_level = TRUST_UNDEFINED;
     - 
     - struct gpg_format {
     -@@ gpg-interface.c: static const char *x509_sigs[] = {
     - 	NULL
     - };
     - 
     -+static const char *ssh_verify_args[] = {
     -+	NULL
     -+};
     -+static const char *ssh_sigs[] = {
     -+	"-----BEGIN SSH SIGNATURE-----",
     -+	NULL
     -+};
     -+
     - static struct gpg_format gpg_format[] = {
     - 	{ .name = "openpgp", .program = "gpg",
     - 	  .verify_args = openpgp_verify_args,
     -@@ gpg-interface.c: static struct gpg_format gpg_format[] = {
     - 	  .verify_args = x509_verify_args,
     - 	  .sigs = x509_sigs
     - 	},
     -+	{ .name = "ssh", .program = "ssh-keygen",
     -+	  .verify_args = ssh_verify_args,
     -+	  .sigs = ssh_sigs },
     - };
     - 
     - static struct gpg_format *use_format = &gpg_format[0];
     -@@ gpg-interface.c: static struct gpg_format *get_format_by_sig(const char *sig)
     - void signature_check_clear(struct signature_check *sigc)
     - {
     - 	FREE_AND_NULL(sigc->payload);
     -+	FREE_AND_NULL(sigc->output);
     - 	FREE_AND_NULL(sigc->gpg_output);
     - 	FREE_AND_NULL(sigc->gpg_status);
     - 	FREE_AND_NULL(sigc->signer);
     -@@ gpg-interface.c: static int parse_gpg_trust_level(const char *level,
     - 	return 1;
     - }
     - 
     -+static void parse_ssh_output(struct signature_check *sigc)
     -+{
     -+	const char *output = NULL;
     -+	char *next = NULL;
     -+
     -+	/* ssh-keysign output should be:
     -+	 * Good "git" signature for PRINCIPAL with RSA key SHA256:FINGERPRINT
     -+	 * or for valid but unknown keys:
     -+	 * Good "git" signature with RSA key SHA256:FINGERPRINT
     -+	 */
     -+
     -+	output = xmemdupz(sigc->output, strcspn(sigc->output, " \n"));
     -+	if (skip_prefix(sigc->output, "Good \"git\" signature for ", &output)) {
     -+		// Valid signature for a trusted signer
     -+		sigc->result = 'G';
     -+		sigc->trust_level = TRUST_FULLY;
     -+
     -+		next = strchrnul(output, ' '); // 'principal'
     -+		replace_cstring(&sigc->signer, output, next);
     -+		output = next + 1;
     -+		next = strchrnul(output, ' '); // 'with'
     -+		output = next + 1;
     -+		next = strchrnul(output, ' '); // KEY Type
     -+		output = next + 1;
     -+		next = strchrnul(output, ' '); // 'key'
     -+		output = next + 1;
     -+		next = strchrnul(output, '\n'); // key
     -+		replace_cstring(&sigc->fingerprint, output, next);
     -+		replace_cstring(&sigc->key, output, next);
     -+	} else if (skip_prefix(sigc->output, "Good \"git\" signature with ", &output)) {
     -+		// Valid signature, but key unknown
     -+		sigc->result = 'G';
     -+		sigc->trust_level = TRUST_UNDEFINED;
     -+
     -+		next = strchrnul(output, ' '); // KEY Type
     -+		output = next + 1;
     -+		next = strchrnul(output, ' '); // 'key'
     -+		output = next + 1;
     -+		next = strchrnul(output, '\n'); // key
     -+		replace_cstring(&sigc->fingerprint, output, next);
     -+		replace_cstring(&sigc->key, output, next);
     -+	} else {
     -+		sigc->result = 'B';
     -+		sigc->trust_level = TRUST_NEVER;
     -+	}
     -+}
     -+
     - static void parse_gpg_output(struct signature_check *sigc)
     - {
     - 	const char *buf = sigc->gpg_status;
     -@@ gpg-interface.c: error:
     - 	FREE_AND_NULL(sigc->key);
     - }
     - 
     --static int verify_signed_buffer(const char *payload, size_t payload_size,
     --				const char *signature, size_t signature_size,
     --				struct strbuf *gpg_output,
     --				struct strbuf *gpg_status)
     -+static int verify_ssh_signature(struct signature_check *sigc, struct gpg_format *fmt,
     -+	const char *payload, size_t payload_size,
     -+	const char *signature, size_t signature_size)
     - {
     --	struct child_process gpg = CHILD_PROCESS_INIT;
     --	struct gpg_format *fmt;
     -+	struct child_process ssh_keygen = CHILD_PROCESS_INIT;
     - 	struct tempfile *temp;
     - 	int ret;
     --	struct strbuf buf = STRBUF_INIT;
     -+	const char *line;
     -+	size_t trust_size;
     -+	char *principal;
     -+	struct strbuf ssh_keygen_out = STRBUF_INIT;
     -+	struct strbuf ssh_keygen_err = STRBUF_INIT;
     - 
     - 	temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
     - 	if (!temp)
     -@@ gpg-interface.c: static int verify_signed_buffer(const char *payload, size_t payload_size,
     - 		return -1;
     - 	}
     - 
     --	fmt = get_format_by_sig(signature);
     --	if (!fmt)
     --		BUG("bad signature '%s'", signature);
     -+	// Find the principal from the  signers
     -+	strvec_pushl(&ssh_keygen.args,  fmt->program,
     -+					"-Y", "find-principals",
     -+					"-f", get_ssh_allowed_signers(),
     -+					"-s", temp->filename.buf,
     -+					NULL);
     -+	ret = pipe_command(&ssh_keygen, NULL, 0, &ssh_keygen_out, 0, &ssh_keygen_err, 0);
     -+	if (strstr(ssh_keygen_err.buf, "unknown option")) {
     -+		error(_("openssh version > 8.2p1 is needed for ssh signature verification (ssh-keygen needs -Y find-principals/verify option)"));
     -+	}
     -+	if (ret || !ssh_keygen_out.len) {
     -+		// We did not find a matching principal in the keyring - Check without validation
     -+		child_process_init(&ssh_keygen);
     -+		strvec_pushl(&ssh_keygen.args,  fmt->program,
     -+						"-Y", "check-novalidate",
     -+						"-n", "git",
     -+						"-s", temp->filename.buf,
     -+						NULL);
     -+		ret = pipe_command(&ssh_keygen, payload, payload_size, &ssh_keygen_out, 0, &ssh_keygen_err, 0);
     -+	} else {
     -+		// Check every principal we found (one per line)
     -+		for (line = ssh_keygen_out.buf; *line; line = strchrnul(line + 1, '\n')) {
     -+			while (*line == '\n')
     -+				line++;
     -+			if (!*line)
     -+				break;
     -+
     -+			trust_size = strcspn(line, " \n");
     -+			principal = xmemdupz(line, trust_size);
     -+
     -+			child_process_init(&ssh_keygen);
     -+			strbuf_release(&ssh_keygen_out);
     -+			strbuf_release(&ssh_keygen_err);
     -+			strvec_push(&ssh_keygen.args,fmt->program);
     -+			// We found principals - Try with each until we find a match
     -+			strvec_pushl(&ssh_keygen.args,  "-Y", "verify",
     -+							//TODO: sprintf("-Overify-time=%s", commit->date...),
     -+							"-n", "git",
     -+							"-f", get_ssh_allowed_signers(),
     -+							"-I", principal,
     -+							"-s", temp->filename.buf,
     -+							NULL);
     -+
     -+			if (ssh_revocation_file && file_exists(ssh_revocation_file)) {
     -+				strvec_pushl(&ssh_keygen.args, "-r", ssh_revocation_file, NULL);
     -+			}
     -+
     -+			sigchain_push(SIGPIPE, SIG_IGN);
     -+			ret = pipe_command(&ssh_keygen, payload, payload_size,
     -+					&ssh_keygen_out, 0, &ssh_keygen_err, 0);
     -+			sigchain_pop(SIGPIPE);
     -+
     -+			ret &= starts_with(ssh_keygen_out.buf, "Good");
     -+			if (ret == 0)
     -+				break;
     -+		}
     -+	}
     -+
     -+	sigc->payload = xmemdupz(payload, payload_size);
     -+	strbuf_stripspace(&ssh_keygen_out, 0);
     -+	strbuf_stripspace(&ssh_keygen_err, 0);
     -+	strbuf_add(&ssh_keygen_out, ssh_keygen_err.buf, ssh_keygen_err.len);
     -+	sigc->output = strbuf_detach(&ssh_keygen_out, NULL);
     -+
     -+	//sigc->gpg_output = strbuf_detach(&ssh_keygen_err, NULL); // This flip around is broken...
     -+	sigc->gpg_status = strbuf_detach(&ssh_keygen_out, NULL);
     -+
     -+	parse_ssh_output(sigc);
     -+
     -+	delete_tempfile(&temp);
     -+	strbuf_release(&ssh_keygen_out);
     -+	strbuf_release(&ssh_keygen_err);
     -+
     -+	return ret;
     -+}
     -+
     -+static int verify_gpg_signature(struct signature_check *sigc, struct gpg_format *fmt, 
     -+	const char *payload, size_t payload_size,
     -+	const char *signature, size_t signature_size)
     -+{
     -+	struct child_process gpg = CHILD_PROCESS_INIT;
     -+	struct tempfile *temp;
     -+	int ret;
     -+	struct strbuf gpg_out = STRBUF_INIT;
     -+	struct strbuf gpg_err = STRBUF_INIT;
     -+
     -+	temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
     -+	if (!temp)
     -+		return error_errno(_("could not create temporary file"));
     -+	if (write_in_full(temp->fd, signature, signature_size) < 0 ||
     -+	    close_tempfile_gently(temp) < 0) {
     -+		error_errno(_("failed writing detached signature to '%s'"),
     -+			    temp->filename.buf);
     -+		delete_tempfile(&temp);
     -+		return -1;
     -+	}
     - 
     - 	strvec_push(&gpg.args, fmt->program);
     - 	strvec_pushv(&gpg.args, fmt->verify_args);
     - 	strvec_pushl(&gpg.args,
     --		     "--status-fd=1",
     --		     "--verify", temp->filename.buf, "-",
     --		     NULL);
     --
     --	if (!gpg_status)
     --		gpg_status = &buf;
     -+			"--status-fd=1",
     -+			"--verify", temp->filename.buf, "-",
     -+			NULL);
     - 
     - 	sigchain_push(SIGPIPE, SIG_IGN);
     --	ret = pipe_command(&gpg, payload, payload_size,
     --			   gpg_status, 0, gpg_output, 0);
     -+	ret = pipe_command(&gpg, payload, payload_size, &gpg_out, 0,
     -+				&gpg_err, 0);
     - 	sigchain_pop(SIGPIPE);
     -+	ret |= !strstr(gpg_out.buf, "\n[GNUPG:] GOODSIG ");
     - 
     --	delete_tempfile(&temp);
     -+	sigc->payload = xmemdupz(payload, payload_size);
     -+	sigc->output = strbuf_detach(&gpg_err, NULL);
     -+	sigc->gpg_status = strbuf_detach(&gpg_out, NULL);
     - 
     --	ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
     --	strbuf_release(&buf); /* no matter it was used or not */
     -+	parse_gpg_output(sigc);
     -+
     -+	delete_tempfile(&temp);
     -+	strbuf_release(&gpg_out);
     -+	strbuf_release(&gpg_err);
     - 
     - 	return ret;
     - }
     -@@ gpg-interface.c: static int verify_signed_buffer(const char *payload, size_t payload_size,
     - int check_signature(const char *payload, size_t plen, const char *signature,
     - 	size_t slen, struct signature_check *sigc)
     - {
     --	struct strbuf gpg_output = STRBUF_INIT;
     --	struct strbuf gpg_status = STRBUF_INIT;
     -+	struct gpg_format *fmt;
     - 	int status;
     - 
     - 	sigc->result = 'N';
     - 	sigc->trust_level = -1;
     - 
     --	status = verify_signed_buffer(payload, plen, signature, slen,
     --				      &gpg_output, &gpg_status);
     --	if (status && !gpg_output.len)
     --		goto out;
     --	sigc->payload = xmemdupz(payload, plen);
     --	sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
     --	sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
     --	parse_gpg_output(sigc);
     -+	fmt = get_format_by_sig(signature);
     -+	if (!fmt)
     -+		BUG("bad signature '%s'", signature);
     -+
     -+	if (!strcmp(fmt->name, "ssh")) {
     -+		status = verify_ssh_signature(sigc, fmt, payload, plen, signature, slen);
     -+	} else {
     -+		status = verify_gpg_signature(sigc, fmt, payload, plen, signature, slen);
     -+	}
     -+	if (status && !sigc->gpg_output)
     -+		return !!status;
     -+
     - 	status |= sigc->result != 'G';
     - 	status |= sigc->trust_level < configured_min_trust_level;
     - 
     -- out:
     --	strbuf_release(&gpg_status);
     --	strbuf_release(&gpg_output);
     --
     - 	return !!status;
     - }
     - 
     - void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
     - {
     - 	const char *output = flags & GPG_VERIFY_RAW ?
     --		sigc->gpg_status : sigc->gpg_output;
     -+		sigc->gpg_status : sigc->output;
     - 
     - 	if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
     - 		fputs(sigc->payload, stdout);
     -@@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb)
     - 	int ret;
     - 
     - 	if (!strcmp(var, "user.signingkey")) {
     -+		/* user.signingkey can contain one of the following
     -+		 * when format = openpgp/x509
     -+		 *   - GPG KeyID
     -+		 * when format = ssh
     -+		 *   - literal ssh public key (e.g. ssh-rsa XXXKEYXXX comment)
     -+		 *   - path to a file containing a public or a private ssh key
     -+		 */
     - 		if (!value)
     - 			return config_error_nonbool(var);
     - 		set_signing_key(value);
     - 		return 0;
     - 	}
     - 
     -+	if (!strcmp(var, "gpg.ssh.keyring")) {
     -+		if (!value)
     -+			return config_error_nonbool(var);
     -+		return git_config_string(&ssh_allowed_signers, var, value);
     -+	}
     -+
     -+	if (!strcmp(var, "gpg.ssh.revocationkeyring")) {
     -+		if (!value)
     -+			return config_error_nonbool(var);
     -+		return git_config_string(&ssh_revocation_file, var, value);
     -+	}
     -+
     - 	if (!strcmp(var, "gpg.format")) {
     - 		if (!value)
     - 			return config_error_nonbool(var);
     -@@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb)
     - 	if (!strcmp(var, "gpg.x509.program"))
     - 		fmtname = "x509";
     - 
     -+	if (!strcmp(var, "gpg.ssh.program"))
     -+		fmtname = "ssh";
     -+
     - 	if (fmtname) {
     - 		fmt = get_format_by_name(fmtname);
     - 		return git_config_string(&fmt->program, var, value);
     -@@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb)
     - 	return 0;
     - }
     - 
     -+static char *get_ssh_key_fingerprint(const char *signing_key) {
     -+	struct child_process ssh_keygen = CHILD_PROCESS_INIT;
     -+	int ret = -1;
     -+	struct strbuf fingerprint_stdout = STRBUF_INIT;
     -+	struct strbuf **fingerprint;
     -+
     -+	/* For SSH Signing this can contain a filename or a public key
     -+	* For textual representation we usually want a fingerprint
     -+	*/
     -+	if (istarts_with(signing_key, "ssh-")) {
     -+		strvec_pushl(&ssh_keygen.args, "ssh-keygen",
     -+					"-lf", "-",
     -+					NULL);
     -+		ret = pipe_command(&ssh_keygen, signing_key, strlen(signing_key), &fingerprint_stdout, 0,  NULL, 0);
     -+	} else {
     -+		strvec_pushl(&ssh_keygen.args, "ssh-keygen",
     -+					"-lf", configured_signing_key,
     -+					NULL);
     -+		ret = pipe_command(&ssh_keygen, NULL, 0, &fingerprint_stdout, 0, NULL, 0);
     -+		if (!!ret)
     -+			die_errno(_("failed to get the ssh fingerprint for key '%s'"), signing_key);
     -+		fingerprint = strbuf_split_max(&fingerprint_stdout, ' ', 3);
     -+		if (fingerprint[1]) {
     -+			return strbuf_detach(fingerprint[1], NULL);
     -+		}
     -+	}
     -+	die_errno(_("failed to get the ssh fingerprint for key '%s'"), signing_key);
     -+}
     -+
     -+// Returns the first public key from an ssh-agent to use for signing
     -+static char *get_default_ssh_signing_key(void) {
     -+	struct child_process ssh_add = CHILD_PROCESS_INIT;
     -+	int ret = -1;
     -+	struct strbuf key_stdout = STRBUF_INIT;
     -+	struct strbuf **keys;
     -+
     -+	strvec_pushl(&ssh_add.args, "ssh-add", "-L", NULL);
     -+	ret = pipe_command(&ssh_add, NULL, 0, &key_stdout, 0, NULL, 0);
     -+	if (!ret) { 
     -+		keys = strbuf_split_max(&key_stdout, '\n', 2);
     -+		if (keys[0])
     -+			return strbuf_detach(keys[0], NULL);
     -+	}
     -+
     -+	return "";
     -+}
     -+
     -+// Returns a textual but unique representation ot the signing key
     -+const char *get_signing_key_id(void) {
     -+	if (!strcmp(use_format->name, "ssh")) {
     -+		return get_ssh_key_fingerprint(get_signing_key());
     -+	} else {
     -+		// GPG/GPGSM only store a key id on this variable
     -+		return get_signing_key();
     -+	}
     -+}
     -+
     - const char *get_signing_key(void)
     - {
     - 	if (configured_signing_key)
     - 		return configured_signing_key;
     --	return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
     -+	if (!strcmp(use_format->name, "ssh")) {
     -+		return get_default_ssh_signing_key();
     -+	} else {
     -+		return git_committer_info(IDENT_STRICT | IDENT_NO_DATE);
     -+	}
     -+}
     -+
     -+const char *get_ssh_allowed_signers(void)
     -+{
     -+	if (ssh_allowed_signers)
     -+		return ssh_allowed_signers;
     -+
     -+	die("A Path to an allowed signers ssh keyring is needed for validation");
     - }
     - 
     - int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
     -@@ gpg-interface.c: int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *sig
     - 	int ret;
     - 	size_t i, j, bottom;
     - 	struct strbuf gpg_status = STRBUF_INIT;
     -+	struct tempfile *temp = NULL, *buffer_file = NULL;
     -+	char *ssh_signing_key_file = NULL;
     -+	struct strbuf ssh_signature_filename = STRBUF_INIT;
     -+
     -+	if (!strcmp(use_format->name, "ssh")) {
     -+		if (!signing_key || signing_key[0] == '\0')
     -+			return error(_("user.signingkey needs to be set for ssh signing"));
     -+
     -+
     -+		if (istarts_with(signing_key, "ssh-")) {
     -+			// A literal ssh key
     -+			temp = mks_tempfile_t(".git_signing_key_tmpXXXXXX");
     -+			if (!temp)
     -+				return error_errno(_("could not create temporary file"));
     -+			if (write_in_full(temp->fd, signing_key, strlen(signing_key)) < 0 ||
     -+				close_tempfile_gently(temp) < 0) {
     -+				error_errno(_("failed writing ssh signing key to '%s'"), temp->filename.buf);
     -+				delete_tempfile(&temp);
     -+				return -1;
     -+			}
     -+			ssh_signing_key_file= temp->filename.buf;
     -+		} else {
     -+			// We assume a file
     -+			ssh_signing_key_file = expand_user_path(signing_key, 1);
     -+		}
     - 
     --	strvec_pushl(&gpg.args,
     --		     use_format->program,
     --		     "--status-fd=2",
     --		     "-bsau", signing_key,
     --		     NULL);
     -+		buffer_file = mks_tempfile_t(".git_signing_buffer_tmpXXXXXX");
     -+		if (!buffer_file)
     -+			return error_errno(_("could not create temporary file"));
     -+		if (write_in_full(buffer_file->fd, buffer->buf, buffer->len) < 0 ||
     -+			close_tempfile_gently(buffer_file) < 0) {
     -+			error_errno(_("failed writing ssh signing key buffer to '%s'"), buffer_file->filename.buf);
     -+			delete_tempfile(&buffer_file);
     -+			return -1;
     -+		}
     -+
     -+		strvec_pushl(&gpg.args, use_format->program ,
     -+					"-Y", "sign",
     -+					"-n", "git",
     -+					"-f", ssh_signing_key_file,
     -+					buffer_file->filename.buf,
     -+					NULL);
     -+
     -+		sigchain_push(SIGPIPE, SIG_IGN);
     -+		ret = pipe_command(&gpg, NULL, 0, NULL, 0, &gpg_status, 0);
     -+		sigchain_pop(SIGPIPE);
     -+
     -+		strbuf_addbuf(&ssh_signature_filename, &buffer_file->filename);
     -+		strbuf_addstr(&ssh_signature_filename, ".sig");
     -+		if (strbuf_read_file(signature, ssh_signature_filename.buf, 2048) < 0) {
     -+			error_errno(_("failed reading ssh signing data buffer from '%s'"), ssh_signature_filename.buf);
     -+		}
     -+		unlink_or_warn(ssh_signature_filename.buf);
     -+		strbuf_release(&ssh_signature_filename);
     -+		delete_tempfile(&buffer_file);
     -+	} else {
     -+		strvec_pushl(&gpg.args, use_format->program ,
     -+					"--status-fd=2",
     -+					"-bsau", signing_key,
     -+					NULL);
     -+
     -+		/*
     -+		* When the username signingkey is bad, program could be terminated
     -+		* because gpg exits without reading and then write gets SIGPIPE.
     -+		*/
     -+		sigchain_push(SIGPIPE, SIG_IGN);
     -+		ret = pipe_command(&gpg, buffer->buf, buffer->len, signature, 1024, &gpg_status, 0);
     -+		sigchain_pop(SIGPIPE);
     -+	}
     - 
     - 	bottom = signature->len;
     - 
     --	/*
     --	 * When the username signingkey is bad, program could be terminated
     --	 * because gpg exits without reading and then write gets SIGPIPE.
     --	 */
     --	sigchain_push(SIGPIPE, SIG_IGN);
     --	ret = pipe_command(&gpg, buffer->buf, buffer->len,
     --			   signature, 1024, &gpg_status, 0);
     --	sigchain_pop(SIGPIPE);
     -+	if (temp)
     -+		delete_tempfile(&temp);
     - 
     --	ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
     -+	if (!strcmp(use_format->name, "ssh")) {
     -+		if (strstr(gpg_status.buf, "unknown option")) {
     -+			error(_("openssh version > 8.2p1 is needed for ssh signing (ssh-keygen needs -Y sign option)"));
     -+		}
     -+	} else {
     -+		ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
     -+	}
     - 	strbuf_release(&gpg_status);
     - 	if (ret)
     - 		return error(_("gpg failed to sign the data"));
     -
     - ## gpg-interface.h ##
     -@@ gpg-interface.h: enum signature_trust_level {
     - 
     - struct signature_check {
     - 	char *payload;
     --	char *gpg_output;
     --	char *gpg_status;
     -+	char *output;
     -+	char *gpg_output; // This will be printed in commit logs
     -+	char *gpg_status; // Only used internally -> remove
     - 
     - 	/*
     - 	 * possible "result":
     -@@ gpg-interface.h: int sign_buffer(struct strbuf *buffer, struct strbuf *signature,
     - int git_gpg_config(const char *, const char *, void *);
     - void set_signing_key(const char *);
     - const char *get_signing_key(void);
     -+
     -+/* Returns a textual unique representation of the signing key in use
     -+ * Either a GPG KeyID or a SSH Key Fingerprint
     -+ */
     -+const char *get_signing_key_id(void);
     -+
     -+const char *get_ssh_allowed_signers(void);
     - int check_signature(const char *payload, size_t plen,
     - 		    const char *signature, size_t slen,
     - 		    struct signature_check *sigc);
     -
     - ## log-tree.c ##
     -@@ log-tree.c: static void show_signature(struct rev_info *opt, struct commit *commit)
     - 
     - 	status = check_signature(payload.buf, payload.len, signature.buf,
     - 				 signature.len, &sigc);
     --	if (status && !sigc.gpg_output)
     -+	if (status && !sigc.output)
     - 		show_sig_lines(opt, status, "No signature\n");
     - 	else
     --		show_sig_lines(opt, status, sigc.gpg_output);
     -+		show_sig_lines(opt, status, sigc.output);
     - 	signature_check_clear(&sigc);
     - 
     -  out:
     -@@ log-tree.c: static int show_one_mergetag(struct commit *commit,
     - 		/* could have a good signature */
     - 		status = check_signature(payload.buf, payload.len,
     - 					 signature.buf, signature.len, &sigc);
     --		if (sigc.gpg_output)
     --			strbuf_addstr(&verify_message, sigc.gpg_output);
     -+		if (sigc.output)
     -+			strbuf_addstr(&verify_message, sigc.output);
     - 		else
     - 			strbuf_addstr(&verify_message, "No signature\n");
     - 		signature_check_clear(&sigc);
     -
     - ## pretty.c ##
     -@@ pretty.c: static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
     - 			check_commit_signature(c->commit, &(c->signature_check));
     - 		switch (placeholder[1]) {
     - 		case 'G':
     --			if (c->signature_check.gpg_output)
     --				strbuf_addstr(sb, c->signature_check.gpg_output);
     -+			if (c->signature_check.output)
     -+				strbuf_addstr(sb, c->signature_check.output);
     - 			break;
     - 		case '?':
     - 			switch (c->signature_check.result) {
     -
     - ## send-pack.c ##
     -@@ send-pack.c: static int generate_push_cert(struct strbuf *req_buf,
     - 	const struct ref *ref;
     - 	struct string_list_item *item;
     - 	char *signing_key = xstrdup(get_signing_key());
     -+	char *signing_key_id = xstrdup(get_signing_key_id());
     - 	const char *cp, *np;
     - 	struct strbuf cert = STRBUF_INIT;
     - 	int update_seen = 0;
     --
     -+	
     - 	strbuf_addstr(&cert, "certificate version 0.1\n");
     --	strbuf_addf(&cert, "pusher %s ", signing_key);
     -+	strbuf_addf(&cert, "pusher %s ", signing_key_id);
     - 	datestamp(&cert);
     - 	strbuf_addch(&cert, '\n');
     - 	if (args->url && *args->url) {
     -@@ send-pack.c: static int generate_push_cert(struct strbuf *req_buf,
     - 
     - free_return:
     - 	free(signing_key);
     -+	free(signing_key_id);
     - 	strbuf_release(&cert);
     - 	return update_seen;
     - }
     -
     - ## t/lib-gpg.sh ##
     -@@ t/lib-gpg.sh: test_lazy_prereq RFC1991 '
     - 	echo | gpg --homedir "${GNUPGHOME}" -b --rfc1991 >/dev/null
     - '
     - 
     -+test_lazy_prereq GPGSSH '
     -+	ssh_version=$(ssh-keygen -Y find-principals -n "git" 2>&1)
     -+	test $? != 127 || exit 1
     -+	echo $ssh_version | grep -q "find-principals:missing signature file"
     -+	test $? = 0 || exit 1; 
     -+	mkdir -p "${GNUPGHOME}" &&
     -+	chmod 0700 "${GNUPGHOME}" &&
     -+	ssh-keygen -t ed25519 -N "" -f "${GNUPGHOME}/ed25519_ssh_signing_key" >/dev/null &&
     -+	ssh-keygen -t rsa -b 2048 -N "" -f "${GNUPGHOME}/rsa_2048_ssh_signing_key" >/dev/null &&
     -+	ssh-keygen -t ed25519 -N "super_secret" -f "${GNUPGHOME}/protected_ssh_signing_key" >/dev/null &&
     -+	find "${GNUPGHOME}" -name *ssh_signing_key.pub -exec cat {} \; | awk "{print \"principal_\" NR \" \" \$0}" > "${GNUPGHOME}/ssh.all_valid.keyring" &&
     -+	cat "${GNUPGHOME}/ssh.all_valid.keyring" &&
     -+	ssh-keygen -t ed25519 -N "" -f "${GNUPGHOME}/untrusted_ssh_signing_key" >/dev/null
     -+'
     -+
     -+SIGNING_KEY_PRIMARY="${GNUPGHOME}/ed25519_ssh_signing_key"
     -+SIGNING_KEY_SECONDARY="${GNUPGHOME}/rsa_2048_ssh_signing_key"
     -+SIGNING_KEY_UNTRUSTED="${GNUPGHOME}/untrusted_ssh_signing_key"
     -+SIGNING_KEY_WITH_PASSPHRASE="${GNUPGHOME}/protected_ssh_signing_key"
     -+SIGNING_KEY_PASSPHRASE="super_secret"
     -+SIGNING_KEYRING="${GNUPGHOME}/ssh.all_valid.keyring"
     -+
     -+GOOD_SIGNATURE_TRUSTED='Good "git" signature for'
     -+GOOD_SIGNATURE_UNTRUSTED='Good "git" signature with'
     -+KEY_NOT_TRUSTED="No principal matched"
     -+BAD_SIGNATURE="Signature verification failed"
     -+
     - sanitize_pgp() {
     - 	perl -ne '
     - 		/^-----END PGP/ and $in_pgp = 0;
     -
     - ## t/t4202-log.sh ##
     -@@ t/t4202-log.sh: test_expect_success GPGSM 'setup signed branch x509' '
     - 	git commit -S -m signed_commit
     - '
     - 
     -+test_expect_success GPGSSH 'setup sshkey signed branch' '
     -+	test_config gpg.format ssh &&
     -+	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
     -+	test_when_finished "git reset --hard && git checkout main" &&
     -+	git checkout -b signed-ssh main &&
     -+	echo foo >foo &&
     -+	git add foo &&
     -+	git commit -S -m signed_commit
     -+'
     -+
     - test_expect_success GPGSM 'log x509 fingerprint' '
     - 	echo "F8BF62E0693D0694816377099909C779FA23FD65 | " >expect &&
     - 	git log -n1 --format="%GF | %GP" signed-x509 >actual &&
     -@@ t/t4202-log.sh: test_expect_success GPGSM 'log --graph --show-signature x509' '
     - 	grep "^| gpgsm: Good signature" actual
     - '
     - 
     -+test_expect_success GPGSSH 'log ssh key fingerprint' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     -+	ssh-keygen -lf  "${SIGNING_KEY_PRIMARY}" | awk "{print \$2\" | \"}" >expect &&
     -+	git log -n1 --format="%GF | %GP" signed-ssh >actual &&
     -+	test_cmp expect actual
     -+'
     -+
     - test_expect_success GPG 'log --graph --show-signature for merged tag' '
     - 	test_when_finished "git reset --hard && git checkout main" &&
     - 	git checkout -b plain main &&
     -
     - ## t/t5534-push-signed.sh ##
     -@@ t/t5534-push-signed.sh: test_expect_success GPG 'signed push sends push certificate' '
     - 	test_cmp expect dst/push-cert-status
     - '
     - 
     -+test_expect_success GPGSSH 'ssh signed push sends push certificate' '
     -+	prepare_dst &&
     -+	mkdir -p dst/.git/hooks &&
     -+	git -C dst config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     -+	git -C dst config receive.certnonceseed sekrit &&
     -+	write_script dst/.git/hooks/post-receive <<-\EOF &&
     -+	# discard the update list
     -+	cat >/dev/null
     -+	# record the push certificate
     -+	if test -n "${GIT_PUSH_CERT-}"
     -+	then
     -+		git cat-file blob $GIT_PUSH_CERT >../push-cert
     -+	fi &&
     -+
     -+	cat >../push-cert-status <<E_O_F
     -+	SIGNER=${GIT_PUSH_CERT_SIGNER-nobody}
     -+	KEY=${GIT_PUSH_CERT_KEY-nokey}
     -+	STATUS=${GIT_PUSH_CERT_STATUS-nostatus}
     -+	NONCE_STATUS=${GIT_PUSH_CERT_NONCE_STATUS-nononcestatus}
     -+	NONCE=${GIT_PUSH_CERT_NONCE-nononce}
     -+	E_O_F
     -+
     -+	EOF
     -+
     -+	test_config gpg.format ssh &&
     -+	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
     -+	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_PRIMARY}" | awk "{print \$2;}") &&
     -+	git push --signed dst noop ff +noff &&
     -+
     -+	(
     -+		cat <<-\EOF &&
     -+		SIGNER=principal_1
     -+		KEY=FINGERPRINT
     -+		STATUS=G
     -+		NONCE_STATUS=OK
     -+		EOF
     -+		sed -n -e "s/^nonce /NONCE=/p" -e "/^$/q" dst/push-cert
     -+	) | sed -e "s|FINGERPRINT|$FINGERPRINT|" >expect &&
     -+
     -+	noop=$(git rev-parse noop) &&
     -+	ff=$(git rev-parse ff) &&
     -+	noff=$(git rev-parse noff) &&
     -+	grep "$noop $ff refs/heads/ff" dst/push-cert &&
     -+	grep "$noop $noff refs/heads/noff" dst/push-cert &&
     -+	test_cmp expect dst/push-cert-status
     -+'
     -+
     - test_expect_success GPG 'inconsistent push options in signed push not allowed' '
     - 	# First, invoke receive-pack with dummy input to obtain its preamble.
     - 	prepare_dst &&
     -@@ t/t5534-push-signed.sh: test_expect_success GPGSM 'fail without key and heed user.signingkey x509' '
     - 	test_cmp expect dst/push-cert-status
     - '
     - 
     -+test_expect_success GPGSSH 'fail without key and heed user.signingkey ssh' '
     -+	test_config gpg.format ssh &&
     -+	prepare_dst &&
     -+	mkdir -p dst/.git/hooks &&
     -+	git -C dst config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     -+	git -C dst config receive.certnonceseed sekrit &&
     -+	write_script dst/.git/hooks/post-receive <<-\EOF &&
     -+	# discard the update list
     -+	cat >/dev/null
     -+	# record the push certificate
     -+	if test -n "${GIT_PUSH_CERT-}"
     -+	then
     -+		git cat-file blob $GIT_PUSH_CERT >../push-cert
     -+	fi &&
     -+
     -+	cat >../push-cert-status <<E_O_F
     -+	SIGNER=${GIT_PUSH_CERT_SIGNER-nobody}
     -+	KEY=${GIT_PUSH_CERT_KEY-nokey}
     -+	STATUS=${GIT_PUSH_CERT_STATUS-nostatus}
     -+	NONCE_STATUS=${GIT_PUSH_CERT_NONCE_STATUS-nononcestatus}
     -+	NONCE=${GIT_PUSH_CERT_NONCE-nononce}
     -+	E_O_F
     -+
     -+	EOF
     -+
     -+	test_config user.email [email protected] &&
     -+	test_config gpg.format ssh &&
     -+	
     -+	test_config user.signingkey "" &&
     -+	(
     -+		sane_unset GIT_COMMITTER_EMAIL &&
     -+		test_must_fail git push --signed dst noop ff +noff
     -+	) &&
     -+	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
     -+	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_PRIMARY}" | awk "{print \$2;}") &&
     -+	git push --signed dst noop ff +noff &&
     -+
     -+	(
     -+		cat <<-\EOF &&
     -+		SIGNER=principal_1
     -+		KEY=FINGERPRINT
     -+		STATUS=G
     -+		NONCE_STATUS=OK
     -+		EOF
     -+		sed -n -e "s/^nonce /NONCE=/p" -e "/^$/q" dst/push-cert
     -+	) | sed -e "s|FINGERPRINT|$FINGERPRINT|" >expect &&
     -+
     -+	noop=$(git rev-parse noop) &&
     -+	ff=$(git rev-parse ff) &&
     -+	noff=$(git rev-parse noff) &&
     -+	grep "$noop $ff refs/heads/ff" dst/push-cert &&
     -+	grep "$noop $noff refs/heads/noff" dst/push-cert &&
     -+	test_cmp expect dst/push-cert-status
     -+'
     -+
     - test_expect_success GPG 'failed atomic push does not execute GPG' '
     - 	prepare_dst &&
     - 	git -C dst config receive.certnonceseed sekrit &&
     -
     - ## t/t7031-verify-tag-signed-ssh.sh (new) ##
     -@@
     -+#!/bin/sh
     -+
     -+test_description='signed tag tests'
     -+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
     -+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
     -+
     -+. ./test-lib.sh
     -+. "$TEST_DIRECTORY/lib-gpg.sh"
     -+
     -+test_expect_success GPGSSH 'create signed tags ssh' '
     -+	test_when_finished "test_unconfig commit.gpgsign" &&
     -+	test_config gpg.format ssh &&
     -+	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
     -+
     -+	echo 1 >file && git add file &&
     -+	test_tick && git commit -m initial &&
     -+	git tag -s -m initial initial &&
     -+	git branch side &&
     -+
     -+	echo 2 >file && test_tick && git commit -a -m second &&
     -+	git tag -s -m second second &&
     -+
     -+	git checkout side &&
     -+	echo 3 >elif && git add elif &&
     -+	test_tick && git commit -m "third on side" &&
     -+
     -+	git checkout main &&
     -+	test_tick && git merge -S side &&
     -+	git tag -s -m merge merge &&
     -+
     -+	echo 4 >file && test_tick && git commit -a -S -m "fourth unsigned" &&
     -+	git tag -a -m fourth-unsigned fourth-unsigned &&
     -+
     -+	test_tick && git commit --amend -S -m "fourth signed" &&
     -+	git tag -s -m fourth fourth-signed &&
     -+
     -+	echo 5 >file && test_tick && git commit -a -m "fifth" &&
     -+	git tag fifth-unsigned &&
     -+
     -+	git config commit.gpgsign true &&
     -+	echo 6 >file && test_tick && git commit -a -m "sixth" &&
     -+	git tag -a -m sixth sixth-unsigned &&
     -+
     -+	test_tick && git rebase -f HEAD^^ && git tag -s -m 6th sixth-signed HEAD^ &&
     -+	git tag -m seventh -s seventh-signed &&
     -+
     -+	echo 8 >file && test_tick && git commit -a -m eighth &&
     -+	git tag -u"${SIGNING_KEY_UNTRUSTED}" -m eighth eighth-signed-alt
     -+'
     -+
     -+test_expect_success GPGSSH 'verify and show ssh signatures' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     -+	test_config gpg.mintrustlevel UNDEFINED &&
     -+	(
     -+		for tag in initial second merge fourth-signed sixth-signed seventh-signed
     -+		do
     -+			git verify-tag $tag 2>actual &&
     -+			grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
     -+			! grep "${BAD_SIGNATURE}" actual &&
     -+			echo $tag OK || exit 1
     -+		done
     -+	) &&
     -+	(
     -+		for tag in fourth-unsigned fifth-unsigned sixth-unsigned
     -+		do
     -+			test_must_fail git verify-tag $tag 2>actual &&
     -+			! grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
     -+			! grep "${BAD_SIGNATURE}" actual &&
     -+			echo $tag OK || exit 1
     -+		done
     -+	) &&
     -+	(
     -+		for tag in eighth-signed-alt
     -+		do
     -+			git verify-tag $tag 2>actual &&
     -+			grep "${GOOD_SIGNATURE_UNTRUSTED}" actual &&
     -+			! grep "${BAD_SIGNATURE}" actual &&
     -+			grep "${KEY_NOT_TRUSTED}" actual &&
     -+			echo $tag OK || exit 1
     -+		done
     -+	)
     -+'
     -+
     -+test_expect_success GPGSSH 'detect fudged ssh signature' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     -+	git cat-file tag seventh-signed >raw &&
     -+	sed -e "/^tag / s/seventh/7th forged/" raw >forged1 &&
     -+	git hash-object -w -t tag forged1 >forged1.tag &&
     -+	test_must_fail git verify-tag $(cat forged1.tag) 2>actual1 &&
     -+	grep "${BAD_SIGNATURE}" actual1 &&
     -+	! grep "${GOOD_SIGNATURE_TRUSTED}" actual1 &&
     -+	! grep "${GOOD_SIGNATURE_UNTRUSTED}" actual1
     -+'
     -+
     -+# test_expect_success GPGSSH 'verify ssh signatures with --raw' '
     -+# 	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     -+# 	(
     -+# 		for tag in initial second merge fourth-signed sixth-signed seventh-signed
     -+# 		do
     -+# 			git verify-tag --raw $tag 2>actual &&
     -+# 			grep "GOODSIG" actual &&
     -+# 			! grep "BADSIG" actual &&
     -+# 			echo $tag OK || exit 1
     -+# 		done
     -+# 	) &&
     -+# 	(
     -+# 		for tag in fourth-unsigned fifth-unsigned sixth-unsigned
     -+# 		do
     -+# 			test_must_fail git verify-tag --raw $tag 2>actual &&
     -+# 			! grep "GOODSIG" actual &&
     -+# 			! grep "BADSIG" actual &&
     -+# 			echo $tag OK || exit 1
     -+# 		done
     -+# 	) &&
     -+# 	(
     -+# 		for tag in eighth-signed-alt
     -+# 		do
     -+# 			git verify-tag --raw $tag 2>actual &&
     -+# 			grep "GOODSIG" actual &&
     -+# 			! grep "BADSIG" actual &&
     -+# 			grep "TRUST_UNDEFINED" actual &&
     -+# 			echo $tag OK || exit 1
     -+# 		done
     -+# 	)
     -+# '
     -+
     -+# test_expect_success GPGSM 'verify signatures with --raw x509' '
     -+# 	git verify-tag --raw ninth-signed-x509 2>actual &&
     -+# 	grep "GOODSIG" actual &&
     -+# 	! grep "BADSIG" actual &&
     -+# 	echo ninth-signed-x509 OK
     -+# '
     -+
     -+# test_expect_success GPGSSH 'verify multiple tags' '
     -+# 	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     -+# 	tags="fourth-signed sixth-signed seventh-signed" &&
     -+# 	for i in $tags
     -+# 	do
     -+# 		git verify-tag -v --raw $i || return 1
     -+# 	done >expect.stdout 2>expect.stderr.1 &&
     -+# 	grep "^.GNUPG:." <expect.stderr.1 >expect.stderr &&
     -+# 	git verify-tag -v --raw $tags >actual.stdout 2>actual.stderr.1 &&
     -+# 	grep "^.GNUPG:." <actual.stderr.1 >actual.stderr &&
     -+# 	test_cmp expect.stdout actual.stdout &&
     -+# 	test_cmp expect.stderr actual.stderr
     -+# '
     -+
     -+# test_expect_success GPGSM 'verify multiple tags x509' '
     -+#	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     -+# 	tags="seventh-signed ninth-signed-x509" &&
     -+# 	for i in $tags
     -+# 	do
     -+# 		git verify-tag -v --raw $i || return 1
     -+# 	done >expect.stdout 2>expect.stderr.1 &&
     -+# 	grep "^.GNUPG:." <expect.stderr.1 >expect.stderr &&
     -+# 	git verify-tag -v --raw $tags >actual.stdout 2>actual.stderr.1 &&
     -+# 	grep "^.GNUPG:." <actual.stderr.1 >actual.stderr &&
     -+# 	test_cmp expect.stdout actual.stdout &&
     -+# 	test_cmp expect.stderr actual.stderr
     -+# '
     -+
     -+test_expect_success GPGSSH 'verifying tag with --format' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     -+	cat >expect <<-\EOF &&
     -+	tagname : fourth-signed
     -+	EOF
     -+	git verify-tag --format="tagname : %(tag)" "fourth-signed" >actual &&
     -+	test_cmp expect actual
     -+'
     -+
     -+test_expect_success GPGSSH 'verifying a forged tag with --format should fail silently' '
     -+	test_must_fail git verify-tag --format="tagname : %(tag)" $(cat forged1.tag) >actual-forged &&
     -+	test_must_be_empty actual-forged
     -+'
     -+
     -+test_done
     -
       ## t/t7527-signed-commit-ssh.sh (new) ##
      @@
      +#!/bin/sh
     @@ t/t7527-signed-commit-ssh.sh (new)
      +	test_must_fail git verify-commit eighth-signed-alt
      +'
      +
     -+# test_expect_success GPGSSH 'verify signatures with --raw' '
     -+# 	(
     -+# 		for commit in initial second merge fourth-signed fifth-signed sixth-signed seventh-signed
     -+# 		do
     -+# 			git verify-commit --raw $commit 2>actual &&
     -+# 			grep "GOODSIG" actual &&
     -+# 			! grep "BADSIG" actual &&
     -+# 			echo $commit OK || exit 1
     -+# 		done
     -+# 	) &&
     -+# 	(
     -+# 		for commit in merge^2 fourth-unsigned sixth-unsigned seventh-unsigned
     -+# 		do
     -+# 			test_must_fail git verify-commit --raw $commit 2>actual &&
     -+# 			! grep "GOODSIG" actual &&
     -+# 			! grep "BADSIG" actual &&
     -+# 			echo $commit OK || exit 1
     -+# 		done
     -+# 	) &&
     -+# 	(
     -+# 		for commit in eighth-signed-alt
     -+# 		do
     -+# 			git verify-commit --raw $commit 2>actual &&
     -+# 			grep "GOODSIG" actual &&
     -+# 			! grep "BADSIG" actual &&
     -+# 			grep "TRUST_UNDEFINED" actual &&
     -+# 			echo $commit OK || exit 1
     -+# 		done
     -+# 	)
     -+# '
     ++test_expect_success GPGSSH 'verify signatures with --raw' '
     ++	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	(
     ++		for commit in initial second merge fourth-signed fifth-signed sixth-signed seventh-signed
     ++		do
     ++			git verify-commit --raw $commit 2>actual &&
     ++			grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
     ++			! grep "${BAD_SIGNATURE}" actual &&
     ++			echo $commit OK || exit 1
     ++		done
     ++	) &&
     ++	(
     ++		for commit in merge^2 fourth-unsigned sixth-unsigned seventh-unsigned
     ++		do
     ++			test_must_fail git verify-commit --raw $commit 2>actual &&
     ++			! grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
     ++			! grep "${BAD_SIGNATURE}" actual &&
     ++			echo $commit OK || exit 1
     ++		done
     ++	) &&
     ++	(
     ++		for commit in eighth-signed-alt
     ++		do
     ++			git verify-commit --raw $commit 2>actual &&
     ++			grep "${GOOD_SIGNATURE_UNTRUSTED}" actual &&
     ++			! grep "${BAD_SIGNATURE}" actual &&
     ++			echo $commit OK || exit 1
     ++		done
     ++	)
     ++'
      +
      +test_expect_success GPGSSH 'proper header is used for hash algorithm' '
      +	git cat-file commit fourth-signed >output &&
     @@ t/t7527-signed-commit-ssh.sh (new)
      +	FINGERPRINT
      +	principal_1
      +	FINGERPRINT
     -+	
     ++
      +	EOF
      +	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
      +	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" sixth-signed >actual &&
     @@ t/t7527-signed-commit-ssh.sh (new)
      +	FINGERPRINT
      +
      +	FINGERPRINT
     -+	
     ++
      +	EOF
      +	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" eighth-signed-alt >actual &&
      +	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_UNTRUSTED}" | awk "{print \$2;}") &&
     @@ t/t7527-signed-commit-ssh.sh (new)
      +	test_must_fail git commit -S --amend -m "fail"
      +'
      +
     -+# test_expect_success GPGSSH 'detect fudged commit with double signature' '
     -+# 	sed -e "/gpgsig/,/END PGP/d" forged1 >double-base &&
     -+# 	sed -n -e "/gpgsig/,/END PGP/p" forged1 | \
     -+# 		sed -e "s/^$(test_oid header)//;s/^ //" | gpg --dearmor >double-sig1.sig &&
     -+# 	gpg -o double-sig2.sig -u 29472784 --detach-sign double-base &&
     -+# 	cat double-sig1.sig double-sig2.sig | gpg --enarmor >double-combined.asc &&
     -+# 	sed -e "s/^\(-.*\)ARMORED FILE/\1SIGNATURE/;1s/^/$(test_oid header) /;2,\$s/^/ /" \
     -+# 		double-combined.asc > double-gpgsig &&
     -+# 	sed -e "/committer/r double-gpgsig" double-base >double-commit &&
     -+# 	git hash-object -w -t commit double-commit >double-commit.commit &&
     -+# 	test_must_fail git verify-commit $(cat double-commit.commit) &&
     -+# 	git show --pretty=short --show-signature $(cat double-commit.commit) >double-actual &&
     -+# 	grep "BAD signature from" double-actual &&
     -+# 	grep "Good signature from" double-actual
     -+# '
     ++test_expect_failure GPGSSH 'detect fudged commit with double signature (TODO)' '
     ++	sed -e "/gpgsig/,/END PGP/d" forged1 >double-base &&
     ++	sed -n -e "/gpgsig/,/END PGP/p" forged1 | \
     ++		sed -e "s/^$(test_oid header)//;s/^ //" | gpg --dearmor >double-sig1.sig &&
     ++	gpg -o double-sig2.sig -u 29472784 --detach-sign double-base &&
     ++	cat double-sig1.sig double-sig2.sig | gpg --enarmor >double-combined.asc &&
     ++	sed -e "s/^\(-.*\)ARMORED FILE/\1SIGNATURE/;1s/^/$(test_oid header) /;2,\$s/^/ /" \
     ++		double-combined.asc > double-gpgsig &&
     ++	sed -e "/committer/r double-gpgsig" double-base >double-commit &&
     ++	git hash-object -w -t commit double-commit >double-commit.commit &&
     ++	test_must_fail git verify-commit $(cat double-commit.commit) &&
     ++	git show --pretty=short --show-signature $(cat double-commit.commit) >double-actual &&
     ++	grep "BAD signature from" double-actual &&
     ++	grep "Good signature from" double-actual
     ++'
      +
     -+# test_expect_success GPGSSH 'show double signature with custom format' '
     -+# 	cat >expect <<-\EOF &&
     -+# 	E
     ++test_expect_failure GPGSSH 'show double signature with custom format (TODO)' '
     ++	cat >expect <<-\EOF &&
     ++	E
      +
      +
      +
      +
     -+# 	EOF
     -+# 	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" $(cat double-commit.commit) >actual &&
     -+# 	test_cmp expect actual
     -+# '
     ++	EOF
     ++	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" $(cat double-commit.commit) >actual &&
     ++	test_cmp expect actual
     ++'
      +
      +
     -+# test_expect_success GPGSSH 'verify-commit verifies multiply signed commits' '
     -+# 	git init multiply-signed &&
     -+# 	cd multiply-signed &&
     -+# 	test_commit first &&
     -+# 	echo 1 >second &&
     -+# 	git add second &&
     -+# 	tree=$(git write-tree) &&
     -+# 	parent=$(git rev-parse HEAD^{commit}) &&
     -+# 	git commit --gpg-sign -m second &&
     -+# 	git cat-file commit HEAD &&
     -+# 	# Avoid trailing whitespace.
     -+# 	sed -e "s/^Q//" -e "s/^Z/ /" >commit <<-EOF &&
     -+# 	Qtree $tree
     -+# 	Qparent $parent
     -+# 	Qauthor A U Thor <[email protected]> 1112912653 -0700
     -+# 	Qcommitter C O Mitter <[email protected]> 1112912653 -0700
     -+# 	Qgpgsig -----BEGIN PGP SIGNATURE-----
     -+# 	QZ
     -+# 	Q iHQEABECADQWIQRz11h0S+chaY7FTocTtvUezd5DDQUCX/uBDRYcY29tbWl0dGVy
     -+# 	Q QGV4YW1wbGUuY29tAAoJEBO29R7N3kMNd+8AoK1I8mhLHviPH+q2I5fIVgPsEtYC
     -+# 	Q AKCTqBh+VabJceXcGIZuF0Ry+udbBQ==
     -+# 	Q =tQ0N
     -+# 	Q -----END PGP SIGNATURE-----
     -+# 	Qgpgsig-sha256 -----BEGIN PGP SIGNATURE-----
     -+# 	QZ
     -+# 	Q iHQEABECADQWIQRz11h0S+chaY7FTocTtvUezd5DDQUCX/uBIBYcY29tbWl0dGVy
     -+# 	Q QGV4YW1wbGUuY29tAAoJEBO29R7N3kMN/NEAn0XO9RYSBj2dFyozi0JKSbssYMtO
     -+# 	Q AJwKCQ1BQOtuwz//IjU8TiS+6S4iUw==
     -+# 	Q =pIwP
     -+# 	Q -----END PGP SIGNATURE-----
     -+# 	Q
     -+# 	Qsecond
     -+# 	EOF
     -+# 	head=$(git hash-object -t commit -w commit) &&
     -+# 	git reset --hard $head &&
     -+# 	git verify-commit $head 2>actual &&
     -+# 	grep "Good signature from" actual &&
     -+# 	! grep "BAD signature from" actual
     -+# '
     ++test_expect_failure GPGSSH 'verify-commit verifies multiply signed commits (TODO)' '
     ++	git init multiply-signed &&
     ++	cd multiply-signed &&
     ++	test_commit first &&
     ++	echo 1 >second &&
     ++	git add second &&
     ++	tree=$(git write-tree) &&
     ++	parent=$(git rev-parse HEAD^{commit}) &&
     ++	git commit --gpg-sign -m second &&
     ++	git cat-file commit HEAD &&
     ++	# Avoid trailing whitespace.
     ++	sed -e "s/^Q//" -e "s/^Z/ /" >commit <<-EOF &&
     ++	Qtree $tree
     ++	Qparent $parent
     ++	Qauthor A U Thor <[email protected]> 1112912653 -0700
     ++	Qcommitter C O Mitter <[email protected]> 1112912653 -0700
     ++	Qgpgsig -----BEGIN PGP SIGNATURE-----
     ++	QZ
     ++	Q iHQEABECADQWIQRz11h0S+chaY7FTocTtvUezd5DDQUCX/uBDRYcY29tbWl0dGVy
     ++	Q QGV4YW1wbGUuY29tAAoJEBO29R7N3kMNd+8AoK1I8mhLHviPH+q2I5fIVgPsEtYC
     ++	Q AKCTqBh+VabJceXcGIZuF0Ry+udbBQ==
     ++	Q =tQ0N
     ++	Q -----END PGP SIGNATURE-----
     ++	Qgpgsig-sha256 -----BEGIN PGP SIGNATURE-----
     ++	QZ
     ++	Q iHQEABECADQWIQRz11h0S+chaY7FTocTtvUezd5DDQUCX/uBIBYcY29tbWl0dGVy
     ++	Q QGV4YW1wbGUuY29tAAoJEBO29R7N3kMN/NEAn0XO9RYSBj2dFyozi0JKSbssYMtO
     ++	Q AJwKCQ1BQOtuwz//IjU8TiS+6S4iUw==
     ++	Q =pIwP
     ++	Q -----END PGP SIGNATURE-----
     ++	Q
     ++	Qsecond
     ++	EOF
     ++	head=$(git hash-object -t commit -w commit) &&
     ++	git reset --hard $head &&
     ++	git verify-commit $head 2>actual &&
     ++	grep "Good signature from" actual &&
     ++	! grep "BAD signature from" actual
     ++'
      +
      +test_done

-: ----------- > 9: 33330fda441 ssh signing: add more tests for logs, tags & push certs

gitgitgadget

From: Fabian Stelzer <[email protected]>

calls ssh-add -L and uses the first key

---
 gpg-interface.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

index 3c9a48c8e7e..c956ed87475 100644
@@ -467,6 +467,23 @@ int git_gpg_config(const char *var, const char *value, void *cb)
 	return 0;
 }
 
+/* Returns the first public key from an ssh-agent to use for signing */
+static char *get_default_ssh_signing_key(void) {
+	struct child_process ssh_add = CHILD_PROCESS_INIT;
+	int ret = -1;
+	struct strbuf key_stdout = STRBUF_INIT;
+	struct strbuf **keys;
+
+	strvec_pushl(&ssh_add.args, "ssh-add", "-L", NULL);
+	ret = pipe_command(&ssh_add, NULL, 0, &key_stdout, 0, NULL, 0);
+	if (!ret) {
+		keys = strbuf_split_max(&key_stdout, '\n', 2);
+		if (keys[0])
+			return strbuf_detach(keys[0], NULL);
+	}
+
+	return "";
+}
 const char *get_signing_key(void)
 {
 	if (configured_signing_key)

gitgitgadget

From: Fabian Stelzer <[email protected]>

implements the actual ssh-keygen -Y sign operation

Set gpg.format = ssh and user.signingkey to either a ssh public key string (like from an authorized_keys file), or a ssh key file. If the key file or the config value itself contains only a public key then the private key needs to be available via ssh-agent. If no signingkey is set then git will call 'ssh-add -L' to check for available agent keys and use the first one for signing.

---
 gpg-interface.c | 86 +++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 76 insertions(+), 10 deletions(-)

index c956ed87475..fa32a57d372 100644
@@ -505,30 +505,96 @@ const char *get_ssh_allowed_signers(void)
 
 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 {
-	struct child_process gpg = CHILD_PROCESS_INIT;
+	struct child_process signer = CHILD_PROCESS_INIT;
 	int ret;
 	size_t i, j, bottom;
-	struct strbuf gpg_status = STRBUF_INIT;
+	struct strbuf signer_stderr = STRBUF_INIT;
+	struct tempfile *temp = NULL, *buffer_file = NULL;
+	char *ssh_signing_key_file = NULL;
+	struct strbuf ssh_signature_filename = STRBUF_INIT;
 
-	strvec_pushl(&gpg.args,
-		     use_format->program,
+	if (!strcmp(use_format->name, "ssh")) {
+		if (!signing_key || signing_key[0] == '\0')
+			return error(_("user.signingkey needs to be set for ssh signing"));
+
+
+		if (istarts_with(signing_key, "ssh-")) {
+			/* A literal ssh key */
+			temp = mks_tempfile_t(".git_signing_key_tmpXXXXXX");
+			if (!temp)
+				return error_errno(_("could not create temporary file"));
+			if (write_in_full(temp->fd, signing_key, strlen(signing_key)) < 0 ||
+				close_tempfile_gently(temp) < 0) {
+				error_errno(_("failed writing ssh signing key to '%s'"),
+					temp->filename.buf);
+				delete_tempfile(&temp);
+				return -1;
+			}
+			ssh_signing_key_file= temp->filename.buf;
+		} else {
+			/* We assume a file */
+			ssh_signing_key_file = expand_user_path(signing_key, 1);
+		}
+
+		buffer_file = mks_tempfile_t(".git_signing_buffer_tmpXXXXXX");
+		if (!buffer_file)
+			return error_errno(_("could not create temporary file"));
+		if (write_in_full(buffer_file->fd, buffer->buf, buffer->len) < 0 ||
+			close_tempfile_gently(buffer_file) < 0) {
+			error_errno(_("failed writing ssh signing key buffer to '%s'"),
+				buffer_file->filename.buf);
+			delete_tempfile(&buffer_file);
+			return -1;
+		}
+
+		strvec_pushl(&signer.args, use_format->program ,
+					"-Y", "sign",
+					"-n", "git",
+					"-f", ssh_signing_key_file,
+					buffer_file->filename.buf,
+					NULL);
+
+		sigchain_push(SIGPIPE, SIG_IGN);
+		ret = pipe_command(&signer, NULL, 0, NULL, 0, &signer_stderr, 0);
+		sigchain_pop(SIGPIPE);
+
+		strbuf_addbuf(&ssh_signature_filename, &buffer_file->filename);
+		strbuf_addstr(&ssh_signature_filename, ".sig");
+		if (strbuf_read_file(signature, ssh_signature_filename.buf, 2048) < 0) {
+			error_errno(_("failed reading ssh signing data buffer from '%s'"),
+				ssh_signature_filename.buf);
+		}
+		unlink_or_warn(ssh_signature_filename.buf);
+		strbuf_release(&ssh_signature_filename);
+		delete_tempfile(&buffer_file);
+	} else {
+		strvec_pushl(&signer.args, use_format->program ,
 		     "--status-fd=2",
 		     "-bsau", signing_key,
 		     NULL);
 
-	bottom = signature->len;
-
 	/*
 	 * When the username signingkey is bad, program could be terminated
 	 * because gpg exits without reading and then write gets SIGPIPE.
 	 */
 	sigchain_push(SIGPIPE, SIG_IGN);
-	ret = pipe_command(&gpg, buffer->buf, buffer->len,
-			   signature, 1024, &gpg_status, 0);
+		ret = pipe_command(&signer, buffer->buf, buffer->len, signature, 1024, &signer_stderr, 0);
 	sigchain_pop(SIGPIPE);
+	}
+
+	bottom = signature->len;
+
+	if (temp)
+		delete_tempfile(&temp);
 
-	ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
-	strbuf_release(&gpg_status);
+	if (!strcmp(use_format->name, "ssh")) {
+		if (strstr(signer_stderr.buf, "usage:")) {
+			error(_("openssh version > 8.2p1 is needed for ssh signing (ssh-keygen needs -Y sign option)"));
+		}
+	} else {
+		ret |= !strstr(signer_stderr.buf, "\n[GNUPG:] SIG_CREATED ");
+	}
+	strbuf_release(&signer_stderr);
 	if (ret)
 		return error(_("gpg failed to sign the data"));
 

gitgitgadget

From: Fabian Stelzer <[email protected]>

for ssh the key can be a filename/path or even a literal ssh pubkey in push certs and textual output we prefer the ssh fingerprint instead

---
 gpg-interface.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 gpg-interface.h |  7 +++++++
 send-pack.c     |  8 ++++----
 3 files changed, 58 insertions(+), 4 deletions(-)

index fa32a57d372..328af86c272 100644
@@ -467,6 +467,42 @@ int git_gpg_config(const char *var, const char *value, void *cb)
 	return 0;
 }
 
+static char *get_ssh_key_fingerprint(const char *signing_key) {
+	struct child_process ssh_keygen = CHILD_PROCESS_INIT;
+	int ret = -1;
+	struct strbuf fingerprint_stdout = STRBUF_INIT;
+	struct strbuf **fingerprint;
+
+	/*
+	 * With SSH Signing this can contain a filename or a public key
+	 * For textual representation we usually want a fingerprint
+	 */
+	if (istarts_with(signing_key, "ssh-")) {
+		strvec_pushl(&ssh_keygen.args, "ssh-keygen",
+					"-lf", "-",
+					NULL);
+		ret = pipe_command(&ssh_keygen, signing_key, strlen(signing_key),
+			&fingerprint_stdout, 0,  NULL, 0);
+	} else {
+		strvec_pushl(&ssh_keygen.args, "ssh-keygen",
+					"-lf", configured_signing_key,
+					NULL);
+		ret = pipe_command(&ssh_keygen, NULL, 0, &fingerprint_stdout, 0,
+			NULL, 0);
+	}
+
+	if (!!ret)
+		die_errno(_("failed to get the ssh fingerprint for key '%s'"),
+			signing_key);
+
+	fingerprint = strbuf_split_max(&fingerprint_stdout, ' ', 3);
+	if (!fingerprint[1])
+		die_errno(_("failed to get the ssh fingerprint for key '%s'"),
+			signing_key);
+
+	return strbuf_detach(fingerprint[1], NULL);
+}
+
 /* Returns the first public key from an ssh-agent to use for signing */
 static char *get_default_ssh_signing_key(void) {
 	struct child_process ssh_add = CHILD_PROCESS_INIT;

@@ -484,6 +520,17 @@ static char *get_default_ssh_signing_key(void) {
 
 	return "";
 }
+
+/* Returns a textual but unique representation ot the signing key */
+const char *get_signing_key_id(void) {
+	if (!strcmp(use_format->name, "ssh")) {
+		return get_ssh_key_fingerprint(get_signing_key());
+	} else {
+		/* GPG/GPGSM only store a key id on this variable */
+		return get_signing_key();
+	}
+}
+
 const char *get_signing_key(void)
 {
 	if (configured_signing_key)

index 5dfd92b81f6..1e842188c26 100644
@@ -64,6 +64,13 @@ int sign_buffer(struct strbuf *buffer, struct strbuf *signature,
 int git_gpg_config(const char *, const char *, void *);
 void set_signing_key(const char *);
 const char *get_signing_key(void);
+
+/*
+ * Returns a textual unique representation of the signing key in use
+ * Either a GPG KeyID or a SSH Key Fingerprint
+ */
+const char *get_signing_key_id(void);
+
 const char *get_ssh_allowed_signers(void);
 int check_signature(const char *payload, size_t plen,
 		    const char *signature, size_t slen,

index 9cb9f716509..191fc6da544 100644
@@ -341,13 +341,13 @@ static int generate_push_cert(struct strbuf *req_buf,
 {
 	const struct ref *ref;
 	struct string_list_item *item;
-	char *signing_key = xstrdup(get_signing_key());
+	char *signing_key_id = xstrdup(get_signing_key_id());
 	const char *cp, *np;
 	struct strbuf cert = STRBUF_INIT;
 	int update_seen = 0;
 
 	strbuf_addstr(&cert, "certificate version 0.1\n");
-	strbuf_addf(&cert, "pusher %s ", signing_key);
+	strbuf_addf(&cert, "pusher %s ", signing_key_id);
 	datestamp(&cert);
 	strbuf_addch(&cert, '\n');
 	if (args->url && *args->url) {

@@ -374,7 +374,7 @@ static int generate_push_cert(struct strbuf *req_buf,
 	if (!update_seen)
 		goto free_return;
 
-	if (sign_buffer(&cert, &cert, signing_key))
+	if (sign_buffer(&cert, &cert, get_signing_key()))
 		die(_("failed to sign the push certificate"));
 
 	packet_buf_write(req_buf, "push-cert%c%s", 0, cap_string);

@@ -386,7 +386,7 @@ static int generate_push_cert(struct strbuf *req_buf,
 	packet_buf_write(req_buf, "push-cert-end\n");
 
 free_return:
-	free(signing_key);
+	free(signing_key_id);
 	strbuf_release(&cert);
 	return update_seen;
 }

gitgitgadget

From: Fabian Stelzer <[email protected]>

Verification uses the gpg.ssh.keyring file (see ssh-keygen(1) "ALLOWED SIGNERS") which contains valid public keys and a principal (usually user@domain). Depending on the environment this file can be managed by the individual developer or for example generated by the central repository server from known ssh keys with push access. If the repository only allows signed commits / pushes then the file can even be stored inside it.

To revoke a key put the public key without the principal prefix into gpg.ssh.revocationKeyring or generate a KRL (see ssh-keygen(1) "KEY REVOCATION LISTS"). The same considerations about who to trust for verification as with the keyring file apply.

Using SSH CA Keys with these files is also possible. Add "cert-authority" as key option between the principal and the key to mark it as a CA and all keys signed by it as valid for this CA.

---
 builtin/receive-pack.c |   2 +
 gpg-interface.c        | 139 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 141 insertions(+)

index a34742513ac..62b11c5f3a4 100644
@@ -131,6 +131,8 @@ static int receive_pack_config(const char *var, const char *value, void *cb)
 {
 	int status = parse_hide_refs_config(var, value, "receive");
 
+	git_gpg_config(var, value, NULL);
+
 	if (status)
 		return status;
 

gitgitgadget

From: Fabian Stelzer <[email protected]>

generate some ssh keys and a allowed keys keyring for testing

---
 t/lib-gpg.sh | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

index 9fc5241228e..c65cdde9e5f 100644
@@ -87,6 +87,33 @@ test_lazy_prereq RFC1991 '
 	echo | gpg --homedir "${GNUPGHOME}" -b --rfc1991 >/dev/null
 '
 
+test_lazy_prereq GPGSSH '
+	ssh_version=$(ssh-keygen -Y find-principals -n "git" 2>&1)
+	test $? != 127 || exit 1
+	echo $ssh_version | grep -q "find-principals:missing signature file"
+	test $? = 0 || exit 1;
+	mkdir -p "${GNUPGHOME}" &&
+	chmod 0700 "${GNUPGHOME}" &&
+	ssh-keygen -t ed25519 -N "" -f "${GNUPGHOME}/ed25519_ssh_signing_key" >/dev/null &&
+	ssh-keygen -t rsa -b 2048 -N "" -f "${GNUPGHOME}/rsa_2048_ssh_signing_key" >/dev/null &&
+	ssh-keygen -t ed25519 -N "super_secret" -f "${GNUPGHOME}/protected_ssh_signing_key" >/dev/null &&
+	find "${GNUPGHOME}" -name *ssh_signing_key.pub -exec cat {} \; | awk "{print \"principal_\" NR \" \" \$0}" > "${GNUPGHOME}/ssh.all_valid.keyring" &&
+	cat "${GNUPGHOME}/ssh.all_valid.keyring" &&
+	ssh-keygen -t ed25519 -N "" -f "${GNUPGHOME}/untrusted_ssh_signing_key" >/dev/null
+'
+
+SIGNING_KEY_PRIMARY="${GNUPGHOME}/ed25519_ssh_signing_key"
+SIGNING_KEY_SECONDARY="${GNUPGHOME}/rsa_2048_ssh_signing_key"
+SIGNING_KEY_UNTRUSTED="${GNUPGHOME}/untrusted_ssh_signing_key"
+SIGNING_KEY_WITH_PASSPHRASE="${GNUPGHOME}/protected_ssh_signing_key"
+SIGNING_KEY_PASSPHRASE="super_secret"
+SIGNING_KEYRING="${GNUPGHOME}/ssh.all_valid.keyring"
+
+GOOD_SIGNATURE_TRUSTED='Good "git" signature for'
+GOOD_SIGNATURE_UNTRUSTED='Good "git" signature with'
+KEY_NOT_TRUSTED="No principal matched"
+BAD_SIGNATURE="Signature verification failed"
+
 sanitize_pgp() {
 	perl -ne '
 		/^-----END PGP/ and $in_pgp = 0;

gitgitgadget

From: Fabian Stelzer <[email protected]>

---
 t/t7527-signed-commit-ssh.sh | 398 +++++++++++++++++++++++++++++++++++
 1 file changed, 398 insertions(+)
 create mode 100755 t/t7527-signed-commit-ssh.sh

new file mode 100755
index 00000000000..305b3b9160b
@@ -0,0 +1,398 @@
+#!/bin/sh
+
+test_description='ssh signed commit tests'
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+
+. ./test-lib.sh
+GNUPGHOME_NOT_USED=$GNUPGHOME
+. "$TEST_DIRECTORY/lib-gpg.sh"
+
+test_expect_success GPGSSH 'create signed commits' '
+	test_oid_cache <<-\EOF &&
+	header sha1:gpgsig
+	header sha256:gpgsig-sha256
+	EOF
+
+	test_when_finished "test_unconfig commit.gpgsign" &&
+	test_config gpg.format ssh &&
+	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
+
+	echo 1 >file && git add file &&
+	test_tick && git commit -S -m initial &&
+	git tag initial &&
+	git branch side &&
+
+	echo 2 >file && test_tick && git commit -a -S -m second &&
+	git tag second &&
+
+	git checkout side &&
+	echo 3 >elif && git add elif &&
+	test_tick && git commit -m "third on side" &&
+
+	git checkout main &&
+	test_tick && git merge -S side &&
+	git tag merge &&
+
+	echo 4 >file && test_tick && git commit -a -m "fourth unsigned" &&
+	git tag fourth-unsigned &&
+
+	test_tick && git commit --amend -S -m "fourth signed" &&
+	git tag fourth-signed &&
+
+	git config commit.gpgsign true &&
+	echo 5 >file && test_tick && git commit -a -m "fifth signed" &&
+	git tag fifth-signed &&
+
+	git config commit.gpgsign false &&
+	echo 6 >file && test_tick && git commit -a -m "sixth" &&
+	git tag sixth-unsigned &&
+
+	git config commit.gpgsign true &&
+	echo 7 >file && test_tick && git commit -a -m "seventh" --no-gpg-sign &&
+	git tag seventh-unsigned &&
+
+	test_tick && git rebase -f HEAD^^ && git tag sixth-signed HEAD^ &&
+	git tag seventh-signed &&
+
+	echo 8 >file && test_tick && git commit -a -m eighth -S"${SIGNING_KEY_UNTRUSTED}" &&
+	git tag eighth-signed-alt &&
+
+	# commit.gpgsign is still on but this must not be signed
+	echo 9 | git commit-tree HEAD^{tree} >oid &&
+	test_line_count = 1 oid &&
+	git tag ninth-unsigned $(cat oid) &&
+	# explicit -S of course must sign.
+	echo 10 | git commit-tree -S HEAD^{tree} >oid &&
+	test_line_count = 1 oid &&
+	git tag tenth-signed $(cat oid) &&
+
+	# --gpg-sign[=<key-id>] must sign.
+	echo 11 | git commit-tree --gpg-sign HEAD^{tree} >oid &&
+	test_line_count = 1 oid &&
+	git tag eleventh-signed $(cat oid) &&
+	echo 12 | git commit-tree --gpg-sign="${SIGNING_KEY_UNTRUSTED}" HEAD^{tree} >oid &&
+	test_line_count = 1 oid &&
+	git tag twelfth-signed-alt $(cat oid)
+'
+
+test_expect_success GPGSSH 'verify and show signatures' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	test_config gpg.mintrustlevel UNDEFINED &&
+	(
+		for commit in initial second merge fourth-signed \
+			fifth-signed sixth-signed seventh-signed tenth-signed \
+			eleventh-signed
+		do
+			git verify-commit $commit &&
+			git show --pretty=short --show-signature $commit >actual &&
+			grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
+			! grep "${BAD_SIGNATURE}" actual &&
+			echo $commit OK || exit 1
+		done
+	) &&
+	(
+		for commit in merge^2 fourth-unsigned sixth-unsigned \
+			seventh-unsigned ninth-unsigned
+		do
+			test_must_fail git verify-commit $commit &&
+			git show --pretty=short --show-signature $commit >actual &&
+			! grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
+			! grep "${BAD_SIGNATURE}" actual &&
+			echo $commit OK || exit 1
+		done
+	) &&
+	(
+		for commit in eighth-signed-alt twelfth-signed-alt
+		do
+			git show --pretty=short --show-signature $commit >actual &&
+			grep "${GOOD_SIGNATURE_UNTRUSTED}" actual &&
+			! grep "${BAD_SIGNATURE}" actual &&
+			grep "${KEY_NOT_TRUSTED}" actual &&
+			echo $commit OK || exit 1
+		done
+	)
+'
+
+test_expect_success GPGSSH 'verify-commit exits success on untrusted signature' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	git verify-commit eighth-signed-alt 2>actual &&
+	grep "${GOOD_SIGNATURE_UNTRUSTED}" actual &&
+	! grep "${BAD_SIGNATURE}" actual &&
+	grep "${KEY_NOT_TRUSTED}" actual
+'
+
+test_expect_success GPGSSH 'verify-commit exits success with matching minTrustLevel' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	test_config gpg.minTrustLevel fully &&
+	git verify-commit sixth-signed
+'
+
+test_expect_success GPGSSH 'verify-commit exits success with low minTrustLevel' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	test_config gpg.minTrustLevel marginal &&
+	git verify-commit sixth-signed
+'
+
+test_expect_success GPGSSH 'verify-commit exits failure with high minTrustLevel' '
+	test_config gpg.minTrustLevel ultimate &&
+	test_must_fail git verify-commit eighth-signed-alt
+'
+
+test_expect_success GPGSSH 'verify signatures with --raw' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	(
+		for commit in initial second merge fourth-signed fifth-signed sixth-signed seventh-signed
+		do
+			git verify-commit --raw $commit 2>actual &&
+			grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
+			! grep "${BAD_SIGNATURE}" actual &&
+			echo $commit OK || exit 1
+		done
+	) &&
+	(
+		for commit in merge^2 fourth-unsigned sixth-unsigned seventh-unsigned
+		do
+			test_must_fail git verify-commit --raw $commit 2>actual &&
+			! grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
+			! grep "${BAD_SIGNATURE}" actual &&
+			echo $commit OK || exit 1
+		done
+	) &&
+	(
+		for commit in eighth-signed-alt
+		do
+			git verify-commit --raw $commit 2>actual &&
+			grep "${GOOD_SIGNATURE_UNTRUSTED}" actual &&
+			! grep "${BAD_SIGNATURE}" actual &&
+			echo $commit OK || exit 1
+		done
+	)
+'
+
+test_expect_success GPGSSH 'proper header is used for hash algorithm' '
+	git cat-file commit fourth-signed >output &&
+	grep "^$(test_oid header) -----BEGIN SSH SIGNATURE-----" output
+'
+
+test_expect_success GPGSSH 'show signed commit with signature' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	git show -s initial >commit &&
+	git show -s --show-signature initial >show &&
+	git verify-commit -v initial >verify.1 2>verify.2 &&
+	git cat-file commit initial >cat &&
+	grep -v -e "${GOOD_SIGNATURE_TRUSTED}" -e "Warning: " show >show.commit &&
+	grep -e "${GOOD_SIGNATURE_TRUSTED}" -e "Warning: " show >show.gpg &&
+	grep -v "^ " cat | grep -v "^gpgsig.* " >cat.commit &&
+	test_cmp show.commit commit &&
+	test_cmp show.gpg verify.2 &&
+	test_cmp cat.commit verify.1
+'
+
+test_expect_success GPGSSH 'detect fudged signature' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	git cat-file commit seventh-signed >raw &&
+	sed -e "s/^seventh/7th forged/" raw >forged1 &&
+	git hash-object -w -t commit forged1 >forged1.commit &&
+	test_must_fail git verify-commit $(cat forged1.commit) &&
+	git show --pretty=short --show-signature $(cat forged1.commit) >actual1 &&
+	grep "${BAD_SIGNATURE}" actual1 &&
+	! grep "${GOOD_SIGNATURE_TRUSTED}" actual1 &&
+	! grep "${GOOD_SIGNATURE_UNTRUSTED}" actual1
+'
+
+test_expect_success GPGSSH 'detect fudged signature with NUL' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	git cat-file commit seventh-signed >raw &&
+	cat raw >forged2 &&
+	echo Qwik | tr "Q" "\000" >>forged2 &&
+	git hash-object -w -t commit forged2 >forged2.commit &&
+	test_must_fail git verify-commit $(cat forged2.commit) &&
+	git show --pretty=short --show-signature $(cat forged2.commit) >actual2 &&
+	grep "${BAD_SIGNATURE}" actual2 &&
+	! grep "${GOOD_SIGNATURE_TRUSTED}" actual2
+'
+
+test_expect_success GPGSSH 'amending already signed commit' '
+	test_config gpg.format ssh &&
+	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	git checkout fourth-signed^0 &&
+	git commit --amend -S --no-edit &&
+	git verify-commit HEAD &&
+	git show -s --show-signature HEAD >actual &&
+	grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
+	! grep "${BAD_SIGNATURE}" actual
+'
+
+test_expect_success GPGSSH 'show good signature with custom format' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_PRIMARY}" | awk "{print \$2;}") &&
+	cat >expect.tmpl <<-\EOF &&
+	G
+	FINGERPRINT
+	principal_1
+	FINGERPRINT
+
+	EOF
+	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
+	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" sixth-signed >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'show bad signature with custom format' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	cat >expect <<-\EOF &&
+	B
+
+
+
+
+	EOF
+	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" $(cat forged1.commit) >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'show untrusted signature with custom format' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	cat >expect.tmpl <<-\EOF &&
+	U
+	FINGERPRINT
+
+	FINGERPRINT
+
+	EOF
+	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" eighth-signed-alt >actual &&
+	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_UNTRUSTED}" | awk "{print \$2;}") &&
+	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'show untrusted signature with undefined trust level' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	cat >expect.tmpl <<-\EOF &&
+	undefined
+	FINGERPRINT
+
+	FINGERPRINT
+
+	EOF
+	git log -1 --format="%GT%n%GK%n%GS%n%GF%n%GP" eighth-signed-alt >actual &&
+	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_UNTRUSTED}" | awk "{print \$2;}") &&
+	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'show untrusted signature with ultimate trust level' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	cat >expect.tmpl <<-\EOF &&
+	fully
+	FINGERPRINT
+	principal_1
+	FINGERPRINT
+
+	EOF
+	git log -1 --format="%GT%n%GK%n%GS%n%GF%n%GP" sixth-signed >actual &&
+	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_PRIMARY}" | awk "{print \$2;}") &&
+	sed "s|FINGERPRINT|$FINGERPRINT|g" expect.tmpl >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'show lack of signature with custom format' '
+	cat >expect <<-\EOF &&
+	N
+
+
+
+
+	EOF
+	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" seventh-unsigned >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success GPGSSH 'log.showsignature behaves like --show-signature' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	test_config log.showsignature true &&
+	git show initial >actual &&
+	grep "${GOOD_SIGNATURE_TRUSTED}" actual
+'
+
+test_expect_success GPGSSH 'check config gpg.format values' '
+	test_config gpg.format ssh &&
+	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
+	test_config gpg.format ssh &&
+	git commit -S --amend -m "success" &&
+	test_config gpg.format OpEnPgP &&
+	test_must_fail git commit -S --amend -m "fail"
+'
+
+test_expect_failure GPGSSH 'detect fudged commit with double signature (TODO)' '
+	sed -e "/gpgsig/,/END PGP/d" forged1 >double-base &&
+	sed -n -e "/gpgsig/,/END PGP/p" forged1 | \
+		sed -e "s/^$(test_oid header)//;s/^ //" | gpg --dearmor >double-sig1.sig &&
+	gpg -o double-sig2.sig -u 29472784 --detach-sign double-base &&
+	cat double-sig1.sig double-sig2.sig | gpg --enarmor >double-combined.asc &&
+	sed -e "s/^\(-.*\)ARMORED FILE/\1SIGNATURE/;1s/^/$(test_oid header) /;2,\$s/^/ /" \
+		double-combined.asc > double-gpgsig &&
+	sed -e "/committer/r double-gpgsig" double-base >double-commit &&
+	git hash-object -w -t commit double-commit >double-commit.commit &&
+	test_must_fail git verify-commit $(cat double-commit.commit) &&
+	git show --pretty=short --show-signature $(cat double-commit.commit) >double-actual &&
+	grep "BAD signature from" double-actual &&
+	grep "Good signature from" double-actual
+'
+
+test_expect_failure GPGSSH 'show double signature with custom format (TODO)' '
+	cat >expect <<-\EOF &&
+	E
+
+
+
+
+	EOF
+	git log -1 --format="%G?%n%GK%n%GS%n%GF%n%GP" $(cat double-commit.commit) >actual &&
+	test_cmp expect actual
+'
+
+
+test_expect_failure GPGSSH 'verify-commit verifies multiply signed commits (TODO)' '
+	git init multiply-signed &&
+	cd multiply-signed &&
+	test_commit first &&
+	echo 1 >second &&
+	git add second &&
+	tree=$(git write-tree) &&
+	parent=$(git rev-parse HEAD^{commit}) &&
+	git commit --gpg-sign -m second &&
+	git cat-file commit HEAD &&
+	# Avoid trailing whitespace.
+	sed -e "s/^Q//" -e "s/^Z/ /" >commit <<-EOF &&
+	Qtree $tree
+	Qparent $parent
+	Qauthor A U Thor <[email protected]> 1112912653 -0700
+	Qcommitter C O Mitter <[email protected]> 1112912653 -0700
+	Qgpgsig -----BEGIN PGP SIGNATURE-----
+	QZ
+	Q iHQEABECADQWIQRz11h0S+chaY7FTocTtvUezd5DDQUCX/uBDRYcY29tbWl0dGVy
+	Q QGV4YW1wbGUuY29tAAoJEBO29R7N3kMNd+8AoK1I8mhLHviPH+q2I5fIVgPsEtYC
+	Q AKCTqBh+VabJceXcGIZuF0Ry+udbBQ==
+	Q =tQ0N
+	Q -----END PGP SIGNATURE-----
+	Qgpgsig-sha256 -----BEGIN PGP SIGNATURE-----
+	QZ
+	Q iHQEABECADQWIQRz11h0S+chaY7FTocTtvUezd5DDQUCX/uBIBYcY29tbWl0dGVy
+	Q QGV4YW1wbGUuY29tAAoJEBO29R7N3kMN/NEAn0XO9RYSBj2dFyozi0JKSbssYMtO
+	Q AJwKCQ1BQOtuwz//IjU8TiS+6S4iUw==
+	Q =pIwP
+	Q -----END PGP SIGNATURE-----
+	Q
+	Qsecond
+	EOF
+	head=$(git hash-object -t commit -w commit) &&
+	git reset --hard $head &&
+	git verify-commit $head 2>actual &&
+	grep "Good signature from" actual &&
+	! grep "BAD signature from" actual
+'
+
+test_done

gitgitgadget

From: Fabian Stelzer <[email protected]>

---
 t/t4202-log.sh                   |  23 +++++
 t/t5534-push-signed.sh           | 101 +++++++++++++++++++
 t/t7031-verify-tag-signed-ssh.sh | 161 +++++++++++++++++++++++++++++++
 3 files changed, 285 insertions(+)
 create mode 100755 t/t7031-verify-tag-signed-ssh.sh

index 350cfa35936..41767627ad0 100755
@@ -1616,6 +1616,16 @@ test_expect_success GPGSM 'setup signed branch x509' '
 	git commit -S -m signed_commit
 '
 
+test_expect_success GPGSSH 'setup sshkey signed branch' '
+	test_config gpg.format ssh &&
+	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
+	test_when_finished "git reset --hard && git checkout main" &&
+	git checkout -b signed-ssh main &&
+	echo foo >foo &&
+	git add foo &&
+	git commit -S -m signed_commit
+'
+
 test_expect_success GPGSM 'log x509 fingerprint' '
 	echo "F8BF62E0693D0694816377099909C779FA23FD65 | " >expect &&
 	git log -n1 --format="%GF | %GP" signed-x509 >actual &&

@@ -1628,6 +1638,13 @@ test_expect_success GPGSM 'log OpenPGP fingerprint' '
 	test_cmp expect actual
 '
 
+test_expect_success GPGSSH 'log ssh key fingerprint' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	ssh-keygen -lf  "${SIGNING_KEY_PRIMARY}" | awk "{print \$2\" | \"}" >expect &&
+	git log -n1 --format="%GF | %GP" signed-ssh >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success GPG 'log --graph --show-signature' '
 	git log --graph --show-signature -n1 signed >actual &&
 	grep "^| gpg: Signature made" actual &&

@@ -1640,6 +1657,12 @@ test_expect_success GPGSM 'log --graph --show-signature x509' '
 	grep "^| gpgsm: Good signature" actual
 '
 
+test_expect_success GPGSSH 'log --graph --show-signature ssh' '
+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
+	git log --graph --show-signature -n1 signed-ssh >actual &&
+	grep "${GOOD_SIGNATURE_TRUSTED}" actual
+'
+
 test_expect_success GPG 'log --graph --show-signature for merged tag' '
 	test_when_finished "git reset --hard && git checkout main" &&
 	git checkout -b plain main &&

gitgitgadget

If you chose "ssh signing:" as the common prefix for the series, use it consistently with this step, too.

OK.

Drop this paragraph or at least tone it down. It may hold true only around your immediate circle but it is far from clear and obvious. I'd expect more people push over https:// than ssh://.

We do not really require a new feature to make much more accessible for wide average user---making it just a bit more accessible to folks in your immediate circle is perfectly fine, as long as you are not harming other people ;-)

Upcase "I".

All of the above promises a wonderful new world, but what is left unclear is with this step alone how much of the new world we already gain. When you ask others to read and understand your code, please give them a bit more hint to guide them what to expect and where you are taking them next.

	fmt = get_format_by_sig(signature);
	if (!fmt)
		return error(_("...bad signature..."));
	fmt->verify_signature(sigc, fmt, payload, plen, signature, slen);

Documentation/SubmittingPatches::[[describe-changes]].

	eol = strchrnul(key_stdout.buf, '\n');
	strbuf_setlen(&key_stdout, eol - key_stdout.buf);

Also: s/environemnt/environment/

I recommend using clang-format (there is a config file checked into the tree) which handles most formatting conventions automatically.

Han-Wen Nienhuys - Google Munich
I work 80%. Don't expect answers from me on Fridays.
--

Google Germany GmbH, Erika-Mann-Strasse 33, 80636 Munich

Registergericht und -nummer: Hamburg, HRB 86891

Sitz der Gesellschaft: Hamburg

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado

Thanks a lot.
This should really be in the in the CodingGuidelines and the MyFirstContribution docs.

Especially the clang-format-diff line from its help
"git diff -U0 --no-color --relative HEAD^ | clang-format-diff -p1 -i" is incredibly useful. Otherwise people will reformat all the things ^^

I will make the commit message clearer. This function only provides a default key in case no key is configured in user.signingkey. If you set user.signingkey to a public key the correct private key from your agent will be used for signing.

I have changed it to what you suggested. I'm always a bit hesitant to use arithmetic with string pointers. I know its simple and efficient, but IMHO can be hard to read.

GIGACODES GmbH | Dr. Hermann-Neubauer-Ring 32 | D-63500 Seligenstadt
www.gigacodes.de | [email protected]
Phone +49 6182 8955-114 | Fax +49 6182 8955-299 |
HRB 40711 AG Offenbach a. Main
Geschäftsführer: Fabian Stelzer | Umsatzsteuer-ID DE219379936

done

i will redo the first commit with your suggestions from below only doing preperation for the upcoming change and then rewrite the commit message to reflect this as well.

true

i did put ssh first to keep the default with gpg and only needing to match the new format. But the fmt->fn variant is much better. For signing as well.

I was thinking about this one when i split up the patch. I was not sure if that was required and didn't want to add synthetic changes (that would only appear between the diffs) just for the split.

yes, i like the idea and will do that.

I can of course fix the ret logic, but i'm not happy with this check in general either :/
The problem is that ssh-keygen seems to give different error messages especially in between the versions when the command was added (8.1 -> 8.2) and mac os x has one of those by default. The check in the t/lib-gpg.sh is much safer, but requires an additional call to ssh-keygen which i wanted to avoid here.

 I will rewrite this with the fmt->fn logic.

GIGACODES GmbH | Dr. Hermann-Neubauer-Ring 32 | D-63500 Seligenstadt
www.gigacodes.de | [email protected]
Phone +49 6182 8955-114 | Fax +49 6182 8955-299 |
HRB 40711 AG Offenbach a. Main
Geschäftsführer: Fabian Stelzer | Umsatzsteuer-ID DE219379936

maybe keeeping the name "allowedSignersFile" like its called in the ssh manpage will make this clearer without needing a lot of extra explanation? The keyring name was suggested earlier to make this consistent with gpg. But it really is something different from a gpg keyring.

I meant that the format is really similar but i see the problem. I wanted to explain the format (which pretty much is just one ssh pubkey per line with a name prefixed to identify the key with) so that users don't have to look into the ssh manpage for a basic example. Maybe just provide a short example of the file contents?

SSH has nothing compared to the gpg trust levels. Your key is either in the allowed signers file or it is not. However even if it is not in the file then the signature might still be "Good" but has no matching principal to it. To be able to differentiate the two "Good" cases i used the existing gpg trust levels. This way if you set gpg.mintrustlevel = fully then the signatures with no matching key in the allowed signers file will fail to verify. Otherwise they will verify but show a message that no principal matched with this key.

I'll take a look, thanks.

GIGACODES GmbH | Dr. Hermann-Neubauer-Ring 32 | D-63500 Seligenstadt
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HRB 40711 AG Offenbach a. Main
Geschäftsführer: Fabian Stelzer | Umsatzsteuer-ID DE219379936

You can write full format description in git-allowedsigners(5) manpage, along with examples of course.

An old man doll... just what I always wanted! - Clara

Yup, that sounds like an excellent way to present this to our users.

Sounds sensible. Our task is to make sure that readers (not me, who have already been spoon-fed the answer by you just now) would reach the above understanding by just reading what we put in the documentation.

Thanks.

Oh thanks. Very nice catch. Easily fixed here but i'll have to rewrite the verification output parsing to account for this as well. I will add a testcase too.

I have added support for using keyfiles directly, lots of tests and generally cleaned up the signing & verification code a lot.

I can still rename things from being gpg specific to a more general "signing" but thats rather cosmetic. Also i'm not sure if i named the new test files correctly.

There is a patch in the pipeline for openssh by Damien Miller that will add valid-after, valid-before options to the allowed keys keyring. This allows us to pass the commit timestamp to the verification call and make key rollover possible and still be able to verify older commits. Set valid-after=NOW when adding your key to the keyring and set valid-before to make it fail if used after a certain date. Software like gitolite/github or corporate automation can do this automatically when ssh push keys are addded / removed

v3 addresses some issues & refactoring and splits the large commit into several smaller ones.

v4:

* restructures and cleans up the whole patch set - patches build on its own now and commit messages try to explain whats going on
* got rid of the if branches and used callback functions in the format struct
* fixed a bug with whitespace in principal identifiers that required a rewrite of the parse_ssh_output function
* rewrote documentation to be more clear - also renamed keyring back to allowedSignersFile

another thing we could add later (via a config switch) is to use the committer email as principal, instead of looking it up with the key that was used to sign, to allow only specific trusted keys per committer.

Fabian Stelzer (9):
ssh signing: preliminary refactoring and clean-up
ssh signing: add ssh signature format and signing using ssh keys ssh signing: retrieve a default key from ssh-agent ssh signing: provide a textual representation of the signing key ssh signing: parse ssh-keygen output and verify signatures ssh signing: add test prereqs
ssh signing: duplicate t7510 tests for commits
ssh signing: add more tests for logs, tags & push certs ssh signing: add documentation

 Documentation/config/gpg.txt     |  39 ++-
 Documentation/config/user.txt    |   6 +
 builtin/receive-pack.c           |   2 +
 fmt-merge-msg.c                  |   6 +-
 gpg-interface.c                  | 485 +++++++++++++++++++++++++++----
 gpg-interface.h                  |   8 +-
 log-tree.c                       |   8 +-
 pretty.c                         |   4 +-
 send-pack.c                      |   8 +-
 t/lib-gpg.sh                     |  27 ++
 t/t4202-log.sh                   |  23 ++
 t/t5534-push-signed.sh           | 101 +++++++
 t/t7031-verify-tag-signed-ssh.sh | 161 ++++++++++
 t/t7527-signed-commit-ssh.sh     | 398 +++++++++++++++++++++++++
 14 files changed, 1211 insertions(+), 65 deletions(-)
 create mode 100755 t/t7031-verify-tag-signed-ssh.sh
 create mode 100755 t/t7527-signed-commit-ssh.sh

base-commit: 75ae10bc75336db031ee58d13c5037b929235912
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1041%2FFStelzer%2Fsshsign-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1041/FStelzer/sshsign-v4
Pull-Request: https://github.com/git/git/pull/1041

Range-diff vs v3:

1: 390a8f816cd ! 1: b4b0e2bac1c Add commit, tag & push signing via SSH keys

     @@ Metadata
      Author: Fabian Stelzer <[email protected]>
      
       ## Commit message ##
     -    Add commit, tag & push signing via SSH keys
     +    ssh signing: preliminary refactoring and clean-up
      
          Openssh v8.2p1 added some new options to ssh-keygen for signature
          creation and verification. These allow us to use ssh keys for git
          signatures easily.
      
     -    Start with adding the new signature format, new config options and
     -    rename some fields for consistency.
     -
     -    This feature makes git signing much more accessible to the average user.
     -    Usually they have a SSH Key for pushing code already. Using it
     -    for signing commits allows us to verify not only the transport but the
     -    pushed code as well.
     -
     -    In our corporate environemnt we use PIV x509 Certs on Yubikeys for email
     -    signing/encryption and ssh keys which i think is quite common
     +    In our corporate environment we use PIV x509 Certs on Yubikeys for email
     +    signing/encryption and ssh keys which I think is quite common
          (at least for the email part). This way we can establish the correct
          trust for the SSH Keys without setting up a separate GPG Infrastructure
          (which is still quite painful for users) or implementing x509 signing
     @@ Commit message
          In such a setup the keyring & revocationKeyring can be centrally
          generated from the x509 CA information and distributed to the users.
      
     +    To be able to implement new signing formats this commit:
     +     - makes the sigc structure more generic by renaming "gpg_output" to
     +       "output"
     +     - introduces function pointers in the gpg_format structure to call
     +       format specific signing and verification functions
     +     - moves format detection from verify_signed_buffer into the check_signature
     +       api function and calls the format specific verify
     +     - renames and wraps sign_buffer to handle format specific signing logic
     +       as well
     +
          Signed-off-by: Fabian Stelzer <[email protected]>
      
       ## fmt-merge-msg.c ##
      @@ fmt-merge-msg.c: static void fmt_merge_msg_sigs(struct strbuf *out)
     + 			buf = payload.buf;
       			len = payload.len;
       			if (check_signature(payload.buf, payload.len, sig.buf,
     - 					 sig.len, &sigc) &&
     +-					 sig.len, &sigc) &&
      -				!sigc.gpg_output)
     -+				!sigc.output)
     ++					    sig.len, &sigc) &&
     ++			    !sigc.output)
       				strbuf_addstr(&sig, "gpg verification failed.\n");
       			else
      -				strbuf_addstr(&sig, sigc.gpg_output);
     @@ fmt-merge-msg.c: static void fmt_merge_msg_sigs(struct strbuf *out)
       
      
       ## gpg-interface.c ##
     -@@
     - #include "tempfile.h"
     - 
     - static char *configured_signing_key;
     -+const char *ssh_allowed_signers, *ssh_revocation_file;
     - static enum signature_trust_level configured_min_trust_level = TRUST_UNDEFINED;
     +@@ gpg-interface.c: struct gpg_format {
     + 	const char *program;
     + 	const char **verify_args;
     + 	const char **sigs;
     ++	int (*verify_signed_buffer)(struct signature_check *sigc,
     ++				    struct gpg_format *fmt, const char *payload,
     ++				    size_t payload_size, const char *signature,
     ++				    size_t signature_size);
     ++	int (*sign_buffer)(struct strbuf *buffer, struct strbuf *signature,
     ++			   const char *signing_key);
     + };
       
     - struct gpg_format {
     + static const char *openpgp_verify_args[] = {
      @@ gpg-interface.c: static const char *x509_sigs[] = {
       	NULL
       };
       
     -+static const char *ssh_verify_args[] = {
     -+	NULL
     -+};
     -+static const char *ssh_sigs[] = {
     -+	"-----BEGIN SSH SIGNATURE-----",
     -+	NULL
     -+};
     ++static int verify_gpg_signed_buffer(struct signature_check *sigc,
     ++				    struct gpg_format *fmt, const char *payload,
     ++				    size_t payload_size, const char *signature,
     ++				    size_t signature_size);
     ++static int sign_buffer_gpg(struct strbuf *buffer, struct strbuf *signature,
     ++			   const char *signing_key);
      +
       static struct gpg_format gpg_format[] = {
     - 	{ .name = "openpgp", .program = "gpg",
     - 	  .verify_args = openpgp_verify_args,
     -@@ gpg-interface.c: static struct gpg_format gpg_format[] = {
     - 	  .verify_args = x509_verify_args,
     - 	  .sigs = x509_sigs
     +-	{ .name = "openpgp", .program = "gpg",
     +-	  .verify_args = openpgp_verify_args,
     +-	  .sigs = openpgp_sigs
     ++	{
     ++		.name = "openpgp",
     ++		.program = "gpg",
     ++		.verify_args = openpgp_verify_args,
     ++		.sigs = openpgp_sigs,
     ++		.verify_signed_buffer = verify_gpg_signed_buffer,
     ++		.sign_buffer = sign_buffer_gpg,
     + 	},
     +-	{ .name = "x509", .program = "gpgsm",
     +-	  .verify_args = x509_verify_args,
     +-	  .sigs = x509_sigs
     ++	{
     ++		.name = "x509",
     ++		.program = "gpgsm",
     ++		.verify_args = x509_verify_args,
     ++		.sigs = x509_sigs,
     ++		.verify_signed_buffer = verify_gpg_signed_buffer,
     ++		.sign_buffer = sign_buffer_gpg,
       	},
     -+	{ .name = "ssh", .program = "ssh-keygen",
     -+	  .verify_args = ssh_verify_args,
     -+	  .sigs = ssh_sigs },
       };
       
     - static struct gpg_format *use_format = &gpg_format[0];
      @@ gpg-interface.c: static struct gpg_format *get_format_by_sig(const char *sig)
       void signature_check_clear(struct signature_check *sigc)
       {
     @@ gpg-interface.c: error:
      -				const char *signature, size_t signature_size,
      -				struct strbuf *gpg_output,
      -				struct strbuf *gpg_status)
     -+static int verify_gpg_signature(struct signature_check *sigc, struct gpg_format *fmt,
     -+	const char *payload, size_t payload_size,
     -+	const char *signature, size_t signature_size)
     ++static int verify_gpg_signed_buffer(struct signature_check *sigc,
     ++				    struct gpg_format *fmt, const char *payload,
     ++				    size_t payload_size, const char *signature,
     ++				    size_t signature_size)
       {
       	struct child_process gpg = CHILD_PROCESS_INIT;
      -	struct gpg_format *fmt;
       	struct tempfile *temp;
       	int ret;
      -	struct strbuf buf = STRBUF_INIT;
     -+	struct strbuf gpg_out = STRBUF_INIT;
     -+	struct strbuf gpg_err = STRBUF_INIT;
     ++	struct strbuf gpg_stdout = STRBUF_INIT;
     ++	struct strbuf gpg_stderr = STRBUF_INIT;
       
       	temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
       	if (!temp)
     @@ gpg-interface.c: static int verify_signed_buffer(const char *payload, size_t pay
       	strvec_push(&gpg.args, fmt->program);
       	strvec_pushv(&gpg.args, fmt->verify_args);
       	strvec_pushl(&gpg.args,
     --		     "--status-fd=1",
     --		     "--verify", temp->filename.buf, "-",
     --		     NULL);
     --
     +@@ gpg-interface.c: static int verify_signed_buffer(const char *payload, size_t payload_size,
     + 		     "--verify", temp->filename.buf, "-",
     + 		     NULL);
     + 
      -	if (!gpg_status)
      -		gpg_status = &buf;
     -+			"--status-fd=1",
     -+			"--verify", temp->filename.buf, "-",
     -+			NULL);
     - 
     +-
       	sigchain_push(SIGPIPE, SIG_IGN);
      -	ret = pipe_command(&gpg, payload, payload_size,
      -			   gpg_status, 0, gpg_output, 0);
     -+	ret = pipe_command(&gpg, payload, payload_size, &gpg_out, 0,
     -+				&gpg_err, 0);
     ++	ret = pipe_command(&gpg, payload, payload_size, &gpg_stdout, 0,
     ++			   &gpg_stderr, 0);
       	sigchain_pop(SIGPIPE);
     -+	ret |= !strstr(gpg_out.buf, "\n[GNUPG:] GOODSIG ");
       
     --	delete_tempfile(&temp);
     -+	sigc->payload = xmemdupz(payload, payload_size);
     -+	sigc->output = strbuf_detach(&gpg_err, NULL);
     -+	sigc->gpg_status = strbuf_detach(&gpg_out, NULL);
     + 	delete_tempfile(&temp);
       
      -	ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
      -	strbuf_release(&buf); /* no matter it was used or not */
     ++	ret |= !strstr(gpg_stdout.buf, "\n[GNUPG:] GOODSIG ");
     ++	sigc->payload = xmemdupz(payload, payload_size);
     ++	sigc->output = strbuf_detach(&gpg_stderr, NULL);
     ++	sigc->gpg_status = strbuf_detach(&gpg_stdout, NULL);
     ++
      +	parse_gpg_output(sigc);
      +
     -+	delete_tempfile(&temp);
     -+	strbuf_release(&gpg_out);
     -+	strbuf_release(&gpg_err);
     ++	strbuf_release(&gpg_stdout);
     ++	strbuf_release(&gpg_stderr);
       
       	return ret;
       }
     @@ gpg-interface.c: static int verify_signed_buffer(const char *payload, size_t pay
      -	sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
      -	parse_gpg_output(sigc);
      +	fmt = get_format_by_sig(signature);
     -+	if (!fmt) {
     -+		error(_("bad/incompatible signature '%s'"), signature);
     -+		return -1;
     -+	}
     ++	if (!fmt)
     ++		return error(_("bad/incompatible signature '%s'"), signature);
     ++
     ++	status = fmt->verify_signed_buffer(sigc, fmt, payload, plen, signature,
     ++					   slen);
      +
     -+	if (!strcmp(fmt->name, "ssh")) {
     -+		status = verify_ssh_signature(sigc, fmt, payload, plen, signature, slen);
     -+	} else {
     -+		status = verify_gpg_signature(sigc, fmt, payload, plen, signature, slen);
     -+	}
      +	if (status && !sigc->output)
      +		return !!status;
      +
     @@ gpg-interface.c: static int verify_signed_buffer(const char *payload, size_t pay
       
       void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
       {
     - 	const char *output = flags & GPG_VERIFY_RAW ?
     +-	const char *output = flags & GPG_VERIFY_RAW ?
      -		sigc->gpg_status : sigc->gpg_output;
     -+		sigc->gpg_status : sigc->output;
     ++	const char *output = flags & GPG_VERIFY_RAW ? sigc->gpg_status :
     ++							    sigc->output;
       
       	if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
       		fputs(sigc->payload, stdout);
     -@@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb)
     - 	int ret;
     - 
     - 	if (!strcmp(var, "user.signingkey")) {
     -+		/*
     -+		 * user.signingkey can contain one of the following
     -+		 * when format = openpgp/x509
     -+		 *   - GPG KeyID
     -+		 * when format = ssh
     -+		 *   - literal ssh public key (e.g. ssh-rsa XXXKEYXXX comment)
     -+		 *   - path to a file containing a public or a private ssh key
     -+		 */
     - 		if (!value)
     - 			return config_error_nonbool(var);
     - 		set_signing_key(value);
     - 		return 0;
     - 	}
     - 
     -+	if (!strcmp(var, "gpg.ssh.keyring")) {
     -+		if (!value)
     -+			return config_error_nonbool(var);
     -+		return git_config_string(&ssh_allowed_signers, var, value);
     -+	}
     -+
     -+	if (!strcmp(var, "gpg.ssh.revocationkeyring")) {
     -+		if (!value)
     -+			return config_error_nonbool(var);
     -+		return git_config_string(&ssh_revocation_file, var, value);
     -+	}
     -+
     - 	if (!strcmp(var, "gpg.format")) {
     - 		if (!value)
     - 			return config_error_nonbool(var);
     -@@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb)
     - 	if (!strcmp(var, "gpg.x509.program"))
     - 		fmtname = "x509";
     - 
     -+	if (!strcmp(var, "gpg.ssh.program"))
     -+		fmtname = "ssh";
     -+
     - 	if (fmtname) {
     - 		fmt = get_format_by_name(fmtname);
     - 		return git_config_string(&fmt->program, var, value);
      @@ gpg-interface.c: const char *get_signing_key(void)
     - {
     - 	if (configured_signing_key)
     - 		return configured_signing_key;
     --	return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
     -+	if (!strcmp(use_format->name, "ssh")) {
     -+		return get_default_ssh_signing_key();
     -+	} else {
     -+		return git_committer_info(IDENT_STRICT | IDENT_NO_DATE);
     -+	}
     -+}
     -+
     -+const char *get_ssh_allowed_signers(void)
     -+{
     -+	if (ssh_allowed_signers)
     -+		return ssh_allowed_signers;
     -+
     -+	die("A Path to an allowed signers ssh keyring is needed for validation");
       }
       
       int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
     ++{
     ++	return use_format->sign_buffer(buffer, signature, signing_key);
     ++}
     ++
     ++static int sign_buffer_gpg(struct strbuf *buffer, struct strbuf *signature,
     ++		    const char *signing_key)
     + {
     + 	struct child_process gpg = CHILD_PROCESS_INIT;
     + 	int ret;
      
       ## gpg-interface.h ##
      @@ gpg-interface.h: enum signature_trust_level {
     @@ gpg-interface.h: enum signature_trust_level {
       struct signature_check {
       	char *payload;
      -	char *gpg_output;
     --	char *gpg_status;
      +	char *output;
     -+	char *gpg_status; /* Only used internally -> remove from this public api */
     + 	char *gpg_status;
       
       	/*
     - 	 * possible "result":
     -@@ gpg-interface.h: int sign_buffer(struct strbuf *buffer, struct strbuf *signature,
     - int git_gpg_config(const char *, const char *, void *);
     - void set_signing_key(const char *);
     - const char *get_signing_key(void);
     -+const char *get_ssh_allowed_signers(void);
     - int check_signature(const char *payload, size_t plen,
     - 		    const char *signature, size_t slen,
     - 		    struct signature_check *sigc);
      
       ## log-tree.c ##
      @@ log-tree.c: static void show_signature(struct rev_info *opt, struct commit *commit)
  4:  df55b9e1d59 !  2:  2c75adee8e1 ssh signing: sign using either gpg or ssh keys
     @@ Metadata
      Author: Fabian Stelzer <[email protected]>
      
       ## Commit message ##
     -    ssh signing: sign using either gpg or ssh keys
     +    ssh signing: add ssh signature format and signing using ssh keys
      
     -    implements the actual ssh-keygen -Y sign operation
     +    implements the actual sign_buffer_ssh operation and move some shared
     +    cleanup code into a strbuf function
      
          Set gpg.format = ssh and user.signingkey to either a ssh public key
          string (like from an authorized_keys file), or a ssh key file.
          If the key file or the config value itself contains only a public key
          then the private key needs to be available via ssh-agent.
     -    If no signingkey is set then git will call 'ssh-add -L' to check for
     -    available agent keys and use the first one for signing.
     +
     +    gpg.ssh.program can be set to an alternative location of ssh-keygen.
     +    A somewhat recent openssh version (8.2p1+) of ssh-keygen is needed for
     +    this feature. Since only ssh-keygen is needed it can this way be
     +    installed seperately without upgrading your system openssh packages.
      
          Signed-off-by: Fabian Stelzer <[email protected]>
      
       ## gpg-interface.c ##
     -@@ gpg-interface.c: const char *get_ssh_allowed_signers(void)
     +@@ gpg-interface.c: static const char *x509_sigs[] = {
     + 	NULL
     + };
     + 
     ++static const char *ssh_verify_args[] = { NULL };
     ++static const char *ssh_sigs[] = {
     ++	"-----BEGIN SSH SIGNATURE-----",
     ++	NULL
     ++};
     ++
     + static int verify_gpg_signed_buffer(struct signature_check *sigc,
     + 				    struct gpg_format *fmt, const char *payload,
     + 				    size_t payload_size, const char *signature,
     + 				    size_t signature_size);
     + static int sign_buffer_gpg(struct strbuf *buffer, struct strbuf *signature,
     + 			   const char *signing_key);
     ++static int sign_buffer_ssh(struct strbuf *buffer, struct strbuf *signature,
     ++			   const char *signing_key);
     + 
     + static struct gpg_format gpg_format[] = {
     + 	{
     +@@ gpg-interface.c: static struct gpg_format gpg_format[] = {
     + 		.verify_signed_buffer = verify_gpg_signed_buffer,
     + 		.sign_buffer = sign_buffer_gpg,
     + 	},
     ++	{
     ++		.name = "ssh",
     ++		.program = "ssh-keygen",
     ++		.verify_args = ssh_verify_args,
     ++		.sigs = ssh_sigs,
     ++		.verify_signed_buffer = NULL, /* TODO */
     ++		.sign_buffer = sign_buffer_ssh
     ++	},
     + };
     + 
     + static struct gpg_format *use_format = &gpg_format[0];
     +@@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb)
     + 	if (!strcmp(var, "gpg.x509.program"))
     + 		fmtname = "x509";
     + 
     ++	if (!strcmp(var, "gpg.ssh.program"))
     ++		fmtname = "ssh";
     ++
     + 	if (fmtname) {
     + 		fmt = get_format_by_name(fmtname);
     + 		return git_config_string(&fmt->program, var, value);
     +@@ gpg-interface.c: int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *sig
     + 	return use_format->sign_buffer(buffer, signature, signing_key);
     + }
       
     - int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
     ++static void strbuf_trim_trailing_cr(struct strbuf *buffer, int offset)
     ++{
     ++	size_t i, j;
     ++
     ++	for (i = j = offset; i < buffer->len; i++) {
     ++		if (buffer->buf[i] != '\r') {
     ++			if (i != j)
     ++				buffer->buf[j] = buffer->buf[i];
     ++			j++;
     ++		}
     ++	}
     ++	strbuf_setlen(buffer, j);
     ++}
     ++
     + static int sign_buffer_gpg(struct strbuf *buffer, struct strbuf *signature,
     + 		    const char *signing_key)
       {
     --	struct child_process gpg = CHILD_PROCESS_INIT;
     -+	struct child_process signer = CHILD_PROCESS_INIT;
     + 	struct child_process gpg = CHILD_PROCESS_INIT;
       	int ret;
     - 	size_t i, j, bottom;
     --	struct strbuf gpg_status = STRBUF_INIT;
     +-	size_t i, j, bottom;
     ++	size_t bottom;
     + 	struct strbuf gpg_status = STRBUF_INIT;
     + 
     + 	strvec_pushl(&gpg.args,
     +@@ gpg-interface.c: static int sign_buffer_gpg(struct strbuf *buffer, struct strbuf *signature,
     + 		return error(_("gpg failed to sign the data"));
     + 
     + 	/* Strip CR from the line endings, in case we are on Windows. */
     +-	for (i = j = bottom; i < signature->len; i++)
     +-		if (signature->buf[i] != '\r') {
     +-			if (i != j)
     +-				signature->buf[j] = signature->buf[i];
     +-			j++;
     +-		}
     +-	strbuf_setlen(signature, j);
     ++	strbuf_trim_trailing_cr(signature, bottom);
     + 
     + 	return 0;
     + }
     ++
     ++static int sign_buffer_ssh(struct strbuf *buffer, struct strbuf *signature,
     ++			   const char *signing_key)
     ++{
     ++	struct child_process signer = CHILD_PROCESS_INIT;
     ++	int ret = -1;
     ++	size_t bottom;
      +	struct strbuf signer_stderr = STRBUF_INIT;
      +	struct tempfile *temp = NULL, *buffer_file = NULL;
      +	char *ssh_signing_key_file = NULL;
      +	struct strbuf ssh_signature_filename = STRBUF_INIT;
     - 
     --	strvec_pushl(&gpg.args,
     --		     use_format->program,
     -+	if (!strcmp(use_format->name, "ssh")) {
     -+		if (!signing_key || signing_key[0] == '\0')
     -+			return error(_("user.signingkey needs to be set for ssh signing"));
     -+
     -+
     -+		if (istarts_with(signing_key, "ssh-")) {
     -+			/* A literal ssh key */
     -+			temp = mks_tempfile_t(".git_signing_key_tmpXXXXXX");
     -+			if (!temp)
     -+				return error_errno(_("could not create temporary file"));
     -+			if (write_in_full(temp->fd, signing_key, strlen(signing_key)) < 0 ||
     -+				close_tempfile_gently(temp) < 0) {
     -+				error_errno(_("failed writing ssh signing key to '%s'"),
     -+					temp->filename.buf);
     -+				delete_tempfile(&temp);
     -+				return -1;
     -+			}
     -+			ssh_signing_key_file= temp->filename.buf;
     -+		} else {
     -+			/* We assume a file */
     -+			ssh_signing_key_file = expand_user_path(signing_key, 1);
     -+		}
      +
     -+		buffer_file = mks_tempfile_t(".git_signing_buffer_tmpXXXXXX");
     -+		if (!buffer_file)
     -+			return error_errno(_("could not create temporary file"));
     -+		if (write_in_full(buffer_file->fd, buffer->buf, buffer->len) < 0 ||
     -+			close_tempfile_gently(buffer_file) < 0) {
     -+			error_errno(_("failed writing ssh signing key buffer to '%s'"),
     -+				buffer_file->filename.buf);
     -+			delete_tempfile(&buffer_file);
     -+			return -1;
     -+		}
     ++	if (!signing_key || signing_key[0] == '\0')
     ++		return error(
     ++			_("user.signingkey needs to be set for ssh signing"));
      +
     -+		strvec_pushl(&signer.args, use_format->program ,
     -+					"-Y", "sign",
     -+					"-n", "git",
     -+					"-f", ssh_signing_key_file,
     -+					buffer_file->filename.buf,
     -+					NULL);
     -+
     -+		sigchain_push(SIGPIPE, SIG_IGN);
     -+		ret = pipe_command(&signer, NULL, 0, NULL, 0, &signer_stderr, 0);
     -+		sigchain_pop(SIGPIPE);
     -+
     -+		strbuf_addbuf(&ssh_signature_filename, &buffer_file->filename);
     -+		strbuf_addstr(&ssh_signature_filename, ".sig");
     -+		if (strbuf_read_file(signature, ssh_signature_filename.buf, 2048) < 0) {
     -+			error_errno(_("failed reading ssh signing data buffer from '%s'"),
     -+				ssh_signature_filename.buf);
     ++	if (istarts_with(signing_key, "ssh-")) {
     ++		/* A literal ssh key */
     ++		temp = mks_tempfile_t(".git_signing_key_tmpXXXXXX");
     ++		if (!temp)
     ++			return error_errno(
     ++				_("could not create temporary file"));
     ++		if (write_in_full(temp->fd, signing_key, strlen(signing_key)) <
     ++			    0 ||
     ++		    close_tempfile_gently(temp) < 0) {
     ++			error_errno(_("failed writing ssh signing key to '%s'"),
     ++				    temp->filename.buf);
     ++			goto out;
      +		}
     -+		unlink_or_warn(ssh_signature_filename.buf);
     -+		strbuf_release(&ssh_signature_filename);
     -+		delete_tempfile(&buffer_file);
     ++		ssh_signing_key_file = temp->filename.buf;
      +	} else {
     -+		strvec_pushl(&signer.args, use_format->program ,
     - 		     "--status-fd=2",
     - 		     "-bsau", signing_key,
     - 		     NULL);
     - 
     --	bottom = signature->len;
     --
     - 	/*
     - 	 * When the username signingkey is bad, program could be terminated
     - 	 * because gpg exits without reading and then write gets SIGPIPE.
     - 	 */
     - 	sigchain_push(SIGPIPE, SIG_IGN);
     --	ret = pipe_command(&gpg, buffer->buf, buffer->len,
     --			   signature, 1024, &gpg_status, 0);
     -+		ret = pipe_command(&signer, buffer->buf, buffer->len, signature, 1024, &signer_stderr, 0);
     - 	sigchain_pop(SIGPIPE);
     ++		/* We assume a file */
     ++		ssh_signing_key_file = expand_user_path(signing_key, 1);
     ++	}
     ++
     ++	buffer_file = mks_tempfile_t(".git_signing_buffer_tmpXXXXXX");
     ++	if (!buffer_file) {
     ++		error_errno(_("could not create temporary file"));
     ++		goto out;
     ++	}
     ++
     ++	if (write_in_full(buffer_file->fd, buffer->buf, buffer->len) < 0 ||
     ++	    close_tempfile_gently(buffer_file) < 0) {
     ++		error_errno(_("failed writing ssh signing key buffer to '%s'"),
     ++			    buffer_file->filename.buf);
     ++		goto out;
     ++	}
     ++
     ++	strvec_pushl(&signer.args, use_format->program, "-Y", "sign", "-n",
     ++		     "git", "-f", ssh_signing_key_file,
     ++		     buffer_file->filename.buf, NULL);
     ++
     ++	sigchain_push(SIGPIPE, SIG_IGN);
     ++	ret = pipe_command(&signer, NULL, 0, NULL, 0, &signer_stderr, 0);
     ++	sigchain_pop(SIGPIPE);
     ++
     ++	if (ret && strstr(signer_stderr.buf, "usage:")) {
     ++		error(_("ssh-keygen -Y sign is needed for ssh signing (available in openssh version 8.2p1+)"));
     ++		goto out;
     ++	}
     ++
     ++	if (ret) {
     ++		error("%s", signer_stderr.buf);
     ++		goto out;
      +	}
      +
      +	bottom = signature->len;
      +
     ++	strbuf_addbuf(&ssh_signature_filename, &buffer_file->filename);
     ++	strbuf_addstr(&ssh_signature_filename, ".sig");
     ++	if (strbuf_read_file(signature, ssh_signature_filename.buf, 2048) < 0) {
     ++		error_errno(
     ++			_("failed reading ssh signing data buffer from '%s'"),
     ++			ssh_signature_filename.buf);
     ++	}
     ++	unlink_or_warn(ssh_signature_filename.buf);
     ++
     ++	if (ret) {
     ++		error(_("ssh failed to sign the data"));
     ++		goto out;
     ++	}
     ++
     ++	/* Strip CR from the line endings, in case we are on Windows. */
     ++	strbuf_trim_trailing_cr(signature, bottom);
     ++
     ++out:
      +	if (temp)
      +		delete_tempfile(&temp);
     - 
     --	ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
     --	strbuf_release(&gpg_status);
     -+	if (!strcmp(use_format->name, "ssh")) {
     -+		if (strstr(signer_stderr.buf, "usage:")) {
     -+			error(_("openssh version > 8.2p1 is needed for ssh signing (ssh-keygen needs -Y sign option)"));
     -+		}
     -+	} else {
     -+		ret |= !strstr(signer_stderr.buf, "\n[GNUPG:] SIG_CREATED ");
     -+	}
     ++	if (buffer_file)
     ++		delete_tempfile(&buffer_file);
      +	strbuf_release(&signer_stderr);
     - 	if (ret)
     - 		return error(_("gpg failed to sign the data"));
     - 
     ++	strbuf_release(&ssh_signature_filename);
     ++	return ret;
     ++}
  3:  b84b2812470 !  3:  1ec5c06cbe9 ssh signing: retrieve a default key from ssh-agent
     @@ Metadata
       ## Commit message ##
          ssh signing: retrieve a default key from ssh-agent
      
     -    calls ssh-add -L and uses the first key
     +    if user.signingkey is not set and a ssh signature is requested we call
     +    ssh-add -L and use the first key we get
      
          Signed-off-by: Fabian Stelzer <[email protected]>
      
     @@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb
       }
       
      +/* Returns the first public key from an ssh-agent to use for signing */
     -+static char *get_default_ssh_signing_key(void) {
     ++static char *get_default_ssh_signing_key(void)
     ++{
      +	struct child_process ssh_add = CHILD_PROCESS_INIT;
      +	int ret = -1;
      +	struct strbuf key_stdout = STRBUF_INIT;
     @@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb
      +			return strbuf_detach(keys[0], NULL);
      +	}
      +
     ++	strbuf_release(&key_stdout);
      +	return "";
      +}
     ++
       const char *get_signing_key(void)
       {
       	if (configured_signing_key)
     + 		return configured_signing_key;
     +-	return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
     ++	if (!strcmp(use_format->name, "ssh")) {
     ++		return get_default_ssh_signing_key();
     ++	} else {
     ++		return git_committer_info(IDENT_STRICT | IDENT_NO_DATE);
     ++	}
     + }
     + 
     + int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
  5:  0581c72634c !  4:  ec6931082ee ssh signing: provide a textual representation of the signing key
     @@ Metadata
       ## Commit message ##
          ssh signing: provide a textual representation of the signing key
      
     -    for ssh the key can be a filename/path or even a literal ssh pubkey
     -    in push certs and textual output we prefer the ssh fingerprint instead
     +    for ssh the user.signingkey can be a filename/path or even a literal ssh pubkey.
     +    in push certs and textual output we prefer the ssh fingerprint instead.
      
          Signed-off-by: Fabian Stelzer <[email protected]>
      
     @@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb
       	return 0;
       }
       
     -+static char *get_ssh_key_fingerprint(const char *signing_key) {
     ++static char *get_ssh_key_fingerprint(const char *signing_key)
     ++{
      +	struct child_process ssh_keygen = CHILD_PROCESS_INIT;
      +	int ret = -1;
      +	struct strbuf fingerprint_stdout = STRBUF_INIT;
     @@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb
      +	 * For textual representation we usually want a fingerprint
      +	 */
      +	if (istarts_with(signing_key, "ssh-")) {
     -+		strvec_pushl(&ssh_keygen.args, "ssh-keygen",
     -+					"-lf", "-",
     -+					NULL);
     -+		ret = pipe_command(&ssh_keygen, signing_key, strlen(signing_key),
     -+			&fingerprint_stdout, 0,  NULL, 0);
     ++		strvec_pushl(&ssh_keygen.args, "ssh-keygen", "-lf", "-", NULL);
     ++		ret = pipe_command(&ssh_keygen, signing_key,
     ++				   strlen(signing_key), &fingerprint_stdout, 0,
     ++				   NULL, 0);
      +	} else {
     -+		strvec_pushl(&ssh_keygen.args, "ssh-keygen",
     -+					"-lf", configured_signing_key,
     -+					NULL);
     ++		strvec_pushl(&ssh_keygen.args, "ssh-keygen", "-lf",
     ++			     configured_signing_key, NULL);
      +		ret = pipe_command(&ssh_keygen, NULL, 0, &fingerprint_stdout, 0,
     -+			NULL, 0);
     ++				   NULL, 0);
      +	}
      +
      +	if (!!ret)
      +		die_errno(_("failed to get the ssh fingerprint for key '%s'"),
     -+			signing_key);
     ++			  signing_key);
      +
      +	fingerprint = strbuf_split_max(&fingerprint_stdout, ' ', 3);
      +	if (!fingerprint[1])
      +		die_errno(_("failed to get the ssh fingerprint for key '%s'"),
     -+			signing_key);
     ++			  signing_key);
      +
      +	return strbuf_detach(fingerprint[1], NULL);
      +}
      +
       /* Returns the first public key from an ssh-agent to use for signing */
     - static char *get_default_ssh_signing_key(void) {
     - 	struct child_process ssh_add = CHILD_PROCESS_INIT;
     -@@ gpg-interface.c: static char *get_default_ssh_signing_key(void) {
     - 
     + static char *get_default_ssh_signing_key(void)
     + {
     +@@ gpg-interface.c: static char *get_default_ssh_signing_key(void)
       	return "";
       }
     -+
     + 
      +/* Returns a textual but unique representation ot the signing key */
     -+const char *get_signing_key_id(void) {
     ++const char *get_signing_key_id(void)
     ++{
      +	if (!strcmp(use_format->name, "ssh")) {
      +		return get_ssh_key_fingerprint(get_signing_key());
      +	} else {
     @@ gpg-interface.h: int sign_buffer(struct strbuf *buffer, struct strbuf *signature
      + * Either a GPG KeyID or a SSH Key Fingerprint
      + */
      +const char *get_signing_key_id(void);
     -+
     - const char *get_ssh_allowed_signers(void);
       int check_signature(const char *payload, size_t plen,
       		    const char *signature, size_t slen,
     + 		    struct signature_check *sigc);
      
       ## send-pack.c ##
      @@ send-pack.c: static int generate_push_cert(struct strbuf *req_buf,
  6:  381a950a6e1 !  5:  4436cb3a122 ssh signing: parse ssh-keygen output and verify signatures
     @@ Metadata
       ## Commit message ##
          ssh signing: parse ssh-keygen output and verify signatures
      
     -    Verification uses the gpg.ssh.keyring file (see ssh-keygen(1) "ALLOWED
     +    to verify a ssh signature we first call ssh-keygen -Y find-principal to
     +    look up the signing principal by their public key from the
     +    allowedSignersFile. If the key is found then we do a verify. Otherwise
     +    we only validate the signature but can not verify the signers identity.
     +
     +    Verification uses the gpg.ssh.allowedSignersFile (see ssh-keygen(1) "ALLOWED
          SIGNERS") which contains valid public keys and a principal (usually
          user@domain). Depending on the environment this file can be managed by
          the individual developer or for example generated by the central
     @@ Commit message
          To revoke a key put the public key without the principal prefix into
          gpg.ssh.revocationKeyring or generate a KRL (see ssh-keygen(1)
          "KEY REVOCATION LISTS"). The same considerations about who to trust for
     -    verification as with the keyring file apply.
     +    verification as with the allowedSignersFile apply.
      
          Using SSH CA Keys with these files is also possible. Add
          "cert-authority" as key option between the principal and the key to mark
     @@ gpg-interface.c
       #include "gpg-interface.h"
       #include "sigchain.h"
       #include "tempfile.h"
     -@@ gpg-interface.c: static int parse_gpg_trust_level(const char *level,
     - 	return 1;
     + 
     + static char *configured_signing_key;
     ++static const char *ssh_allowed_signers, *ssh_revocation_file;
     + static enum signature_trust_level configured_min_trust_level = TRUST_UNDEFINED;
     + 
     + struct gpg_format {
     +@@ gpg-interface.c: static int verify_gpg_signed_buffer(struct signature_check *sigc,
     + 				    struct gpg_format *fmt, const char *payload,
     + 				    size_t payload_size, const char *signature,
     + 				    size_t signature_size);
     ++static int verify_ssh_signed_buffer(struct signature_check *sigc,
     ++				    struct gpg_format *fmt, const char *payload,
     ++				    size_t payload_size, const char *signature,
     ++				    size_t signature_size);
     + static int sign_buffer_gpg(struct strbuf *buffer, struct strbuf *signature,
     + 			   const char *signing_key);
     + static int sign_buffer_ssh(struct strbuf *buffer, struct strbuf *signature,
     +@@ gpg-interface.c: static struct gpg_format gpg_format[] = {
     + 		.program = "ssh-keygen",
     + 		.verify_args = ssh_verify_args,
     + 		.sigs = ssh_sigs,
     +-		.verify_signed_buffer = NULL, /* TODO */
     ++		.verify_signed_buffer = verify_ssh_signed_buffer,
     + 		.sign_buffer = sign_buffer_ssh
     + 	},
     + };
     +@@ gpg-interface.c: static int verify_gpg_signed_buffer(struct signature_check *sigc,
     + 	return ret;
       }
       
      +static void parse_ssh_output(struct signature_check *sigc)
      +{
     -+	struct string_list parts = STRING_LIST_INIT_DUP;
     -+	char *line = NULL;
     ++	const char *line, *principal, *search;
      +
      +	/*
      +	 * ssh-keysign output should be:
      +	 * Good "git" signature for PRINCIPAL with RSA key SHA256:FINGERPRINT
     ++	 * Good "git" signature for PRINCIPAL WITH WHITESPACE with RSA key SHA256:FINGERPRINT
      +	 * or for valid but unknown keys:
      +	 * Good "git" signature with RSA key SHA256:FINGERPRINT
      +	 */
     @@ gpg-interface.c: static int parse_gpg_trust_level(const char *level,
      +	sigc->trust_level = TRUST_NEVER;
      +
      +	line = xmemdupz(sigc->output, strcspn(sigc->output, "\n"));
     -+	string_list_split(&parts, line, ' ', 8);
     -+	if (parts.nr >= 9 && starts_with(line, "Good \"git\" signature for ")) {
     -+		/* Valid signature for a trusted signer */
     ++
     ++	if (skip_prefix(line, "Good \"git\" signature for ", &line)) {
     ++		/* Valid signature and known principal */
      +		sigc->result = 'G';
      +		sigc->trust_level = TRUST_FULLY;
     -+		sigc->signer = xstrdup(parts.items[4].string);
     -+		sigc->fingerprint = xstrdup(parts.items[8].string);
     ++
     ++		/* Search for the last "with" to get the full principal */
     ++		principal = line;
     ++		do {
     ++			search = strstr(line, " with ");
     ++			if (search)
     ++				line = search + 1;
     ++		} while (search != NULL);
     ++		sigc->signer = xmemdupz(principal, line - principal - 1);
     ++		sigc->fingerprint = xstrdup(strstr(line, "key") + 4);
      +		sigc->key = xstrdup(sigc->fingerprint);
     -+	} else if (parts.nr >= 7 && starts_with(line, "Good \"git\" signature with ")) {
     ++	} else if (skip_prefix(line, "Good \"git\" signature with ", &line)) {
      +		/* Valid signature, but key unknown */
      +		sigc->result = 'G';
      +		sigc->trust_level = TRUST_UNDEFINED;
     -+		sigc->fingerprint = xstrdup(parts.items[6].string);
     ++		sigc->fingerprint = xstrdup(strstr(line, "key") + 4);
      +		sigc->key = xstrdup(sigc->fingerprint);
      +	}
     -+	trace_printf("trace: sigc result %c/%d - %s %s %s", sigc->result, sigc->trust_level, sigc->signer, sigc->fingerprint, sigc->key);
     ++}
     ++
     ++static const char *get_ssh_allowed_signers(void)
     ++{
     ++	if (ssh_allowed_signers)
     ++		return ssh_allowed_signers;
      +
     -+	string_list_clear(&parts, 0);
     -+	FREE_AND_NULL(line);
     ++	die("gpg.ssh.allowedSignersFile needs to be configured and exist for validation");
      +}
      +
     - static void parse_gpg_output(struct signature_check *sigc)
     - {
     - 	const char *buf = sigc->gpg_status;
     -@@ gpg-interface.c: error:
     - 	FREE_AND_NULL(sigc->key);
     - }
     - 
     -+static int verify_ssh_signature(struct signature_check *sigc,
     -+	struct gpg_format *fmt,
     -+	const char *payload, size_t payload_size,
     -+	const char *signature, size_t signature_size)
     ++static int verify_ssh_signed_buffer(struct signature_check *sigc,
     ++				    struct gpg_format *fmt, const char *payload,
     ++				    size_t payload_size, const char *signature,
     ++				    size_t signature_size)
      +{
      +	struct child_process ssh_keygen = CHILD_PROCESS_INIT;
      +	struct tempfile *temp;
     @@ gpg-interface.c: error:
      +	}
      +
      +	/* Find the principal from the signers */
     -+	strvec_pushl(&ssh_keygen.args,  fmt->program,
     -+					"-Y", "find-principals",
     -+					"-f", get_ssh_allowed_signers(),
     -+					"-s", temp->filename.buf,
     -+					NULL);
     -+	ret = pipe_command(&ssh_keygen, NULL, 0, &ssh_keygen_out, 0, &ssh_keygen_err, 0);
     -+	if (strstr(ssh_keygen_err.buf, "usage:")) {
     -+		error(_("openssh version > 8.2p1 is needed for ssh signature verification (ssh-keygen needs -Y find-principals/verify option)"));
     ++	strvec_pushl(&ssh_keygen.args, fmt->program, "-Y", "find-principals",
     ++		     "-f", get_ssh_allowed_signers(), "-s", temp->filename.buf,
     ++		     NULL);
     ++	ret = pipe_command(&ssh_keygen, NULL, 0, &ssh_keygen_out, 0,
     ++			   &ssh_keygen_err, 0);
     ++	if (ret && strstr(ssh_keygen_err.buf, "usage:")) {
     ++		error(_("ssh-keygen -Y find-principals/verify is needed for ssh signature verification (available in openssh version 8.2p1+)"));
     ++		return ret;
      +	}
      +	if (ret || !ssh_keygen_out.len) {
     -+		/* We did not find a matching principal in the keyring - Check without validation */
     ++		/* We did not find a matching principal in the allowedSigners - Check
     ++		 * without validation */
      +		child_process_init(&ssh_keygen);
     -+		strvec_pushl(&ssh_keygen.args,  fmt->program,
     -+						"-Y", "check-novalidate",
     -+						"-n", "git",
     -+						"-s", temp->filename.buf,
     -+						NULL);
     -+		ret = pipe_command(&ssh_keygen, payload, payload_size, &ssh_keygen_out, 0, &ssh_keygen_err, 0);
     ++		strvec_pushl(&ssh_keygen.args, fmt->program, "-Y",
     ++			     "check-novalidate", "-n", "git", "-s",
     ++			     temp->filename.buf, NULL);
     ++		ret = pipe_command(&ssh_keygen, payload, payload_size,
     ++				   &ssh_keygen_out, 0, &ssh_keygen_err, 0);
      +	} else {
      +		/* Check every principal we found (one per line) */
     -+		for (line = ssh_keygen_out.buf; *line; line = strchrnul(line + 1, '\n')) {
     ++		for (line = ssh_keygen_out.buf; *line;
     ++		     line = strchrnul(line + 1, '\n')) {
      +			while (*line == '\n')
      +				line++;
      +			if (!*line)
      +				break;
      +
     -+			trust_size = strcspn(line, " \n");
     ++			trust_size = strcspn(line, "\n");
      +			principal = xmemdupz(line, trust_size);
      +
      +			child_process_init(&ssh_keygen);
      +			strbuf_release(&ssh_keygen_out);
      +			strbuf_release(&ssh_keygen_err);
     -+			strvec_push(&ssh_keygen.args,fmt->program);
     -+			/* We found principals - Try with each until we find a match */
     -+			strvec_pushl(&ssh_keygen.args,  "-Y", "verify",
     -+							"-n", "git",
     -+							"-f", get_ssh_allowed_signers(),
     -+							"-I", principal,
     -+							"-s", temp->filename.buf,
     -+							NULL);
     ++			strvec_push(&ssh_keygen.args, fmt->program);
     ++			/* We found principals - Try with each until we find a
     ++			 * match */
     ++			strvec_pushl(&ssh_keygen.args, "-Y", "verify", "-n",
     ++				     "git", "-f", get_ssh_allowed_signers(),
     ++				     "-I", principal, "-s", temp->filename.buf,
     ++				     NULL);
      +
      +			if (ssh_revocation_file) {
      +				if (file_exists(ssh_revocation_file)) {
     -+					strvec_pushl(&ssh_keygen.args, "-r", ssh_revocation_file, NULL);
     ++					strvec_pushl(&ssh_keygen.args, "-r",
     ++						     ssh_revocation_file, NULL);
      +				} else {
     -+					warning(_("ssh signing revocation file configured but not found: %s"), ssh_revocation_file);
     ++					warning(_("ssh signing revocation file configured but not found: %s"),
     ++						ssh_revocation_file);
      +				}
      +			}
      +
      +			sigchain_push(SIGPIPE, SIG_IGN);
      +			ret = pipe_command(&ssh_keygen, payload, payload_size,
     -+					&ssh_keygen_out, 0, &ssh_keygen_err, 0);
     ++					   &ssh_keygen_out, 0, &ssh_keygen_err, 0);
      +			sigchain_pop(SIGPIPE);
      +
     ++			FREE_AND_NULL(principal);
     ++
      +			ret &= starts_with(ssh_keygen_out.buf, "Good");
      +			if (ret == 0)
      +				break;
     @@ gpg-interface.c: error:
      +	return ret;
      +}
      +
     - static int verify_gpg_signature(struct signature_check *sigc, struct gpg_format *fmt,
     - 	const char *payload, size_t payload_size,
     - 	const char *signature, size_t signature_size)
     + int check_signature(const char *payload, size_t plen, const char *signature,
     + 	size_t slen, struct signature_check *sigc)
     + {
     +@@ gpg-interface.c: int git_gpg_config(const char *var, const char *value, void *cb)
     + 		return 0;
     + 	}
     + 
     ++	if (!strcmp(var, "gpg.ssh.allowedsignersfile")) {
     ++		if (!value)
     ++			return config_error_nonbool(var);
     ++		return git_config_string(&ssh_allowed_signers, var, value);
     ++	}
     ++
     ++	if (!strcmp(var, "gpg.ssh.revocationFile")) {
     ++		if (!value)
     ++			return config_error_nonbool(var);
     ++		return git_config_string(&ssh_revocation_file, var, value);
     ++	}
     ++
     + 	if (!strcmp(var, "gpg.program") || !strcmp(var, "gpg.openpgp.program"))
     + 		fmtname = "openpgp";
     + 
  7:  1d292a8d7a2 !  6:  06a76e64b35 ssh signing: add test prereqs
     @@ Metadata
       ## Commit message ##
          ssh signing: add test prereqs
      
     -    generate some ssh keys and a allowed keys keyring for testing
     +    generate some ssh keys and a allowedSignersFile for testing
      
          Signed-off-by: Fabian Stelzer <[email protected]>
      
     @@ t/lib-gpg.sh: test_lazy_prereq RFC1991 '
      +	ssh-keygen -t ed25519 -N "" -f "${GNUPGHOME}/ed25519_ssh_signing_key" >/dev/null &&
      +	ssh-keygen -t rsa -b 2048 -N "" -f "${GNUPGHOME}/rsa_2048_ssh_signing_key" >/dev/null &&
      +	ssh-keygen -t ed25519 -N "super_secret" -f "${GNUPGHOME}/protected_ssh_signing_key" >/dev/null &&
     -+	find "${GNUPGHOME}" -name *ssh_signing_key.pub -exec cat {} \; | awk "{print \"principal_\" NR \" \" \$0}" > "${GNUPGHOME}/ssh.all_valid.keyring" &&
     -+	cat "${GNUPGHOME}/ssh.all_valid.keyring" &&
     ++	find "${GNUPGHOME}" -name *ssh_signing_key.pub -exec cat {} \; | awk "{print \"\\\"principal with number \" NR \"\\\" \" \$0}" > "${GNUPGHOME}/ssh.all_valid.allowedSignersFile" &&
     ++	cat "${GNUPGHOME}/ssh.all_valid.allowedSignersFile" &&
      +	ssh-keygen -t ed25519 -N "" -f "${GNUPGHOME}/untrusted_ssh_signing_key" >/dev/null
      +'
      +
     @@ t/lib-gpg.sh: test_lazy_prereq RFC1991 '
      +SIGNING_KEY_UNTRUSTED="${GNUPGHOME}/untrusted_ssh_signing_key"
      +SIGNING_KEY_WITH_PASSPHRASE="${GNUPGHOME}/protected_ssh_signing_key"
      +SIGNING_KEY_PASSPHRASE="super_secret"
     -+SIGNING_KEYRING="${GNUPGHOME}/ssh.all_valid.keyring"
     ++SIGNING_ALLOWED_SIGNERS="${GNUPGHOME}/ssh.all_valid.allowedSignersFile"
      +
      +GOOD_SIGNATURE_TRUSTED='Good "git" signature for'
      +GOOD_SIGNATURE_UNTRUSTED='Good "git" signature with'
  8:  338d1b976e9 !  7:  4dc5572083b ssh signing: duplicate t7510 tests for commits
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'verify and show signatures' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	test_config gpg.mintrustlevel UNDEFINED &&
      +	(
      +		for commit in initial second merge fourth-signed \
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'verify-commit exits success on untrusted signature' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	git verify-commit eighth-signed-alt 2>actual &&
      +	grep "${GOOD_SIGNATURE_UNTRUSTED}" actual &&
      +	! grep "${BAD_SIGNATURE}" actual &&
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'verify-commit exits success with matching minTrustLevel' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	test_config gpg.minTrustLevel fully &&
      +	git verify-commit sixth-signed
      +'
      +
      +test_expect_success GPGSSH 'verify-commit exits success with low minTrustLevel' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	test_config gpg.minTrustLevel marginal &&
      +	git verify-commit sixth-signed
      +'
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'verify signatures with --raw' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	(
      +		for commit in initial second merge fourth-signed fifth-signed sixth-signed seventh-signed
      +		do
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'show signed commit with signature' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	git show -s initial >commit &&
      +	git show -s --show-signature initial >show &&
      +	git verify-commit -v initial >verify.1 2>verify.2 &&
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'detect fudged signature' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	git cat-file commit seventh-signed >raw &&
      +	sed -e "s/^seventh/7th forged/" raw >forged1 &&
      +	git hash-object -w -t commit forged1 >forged1.commit &&
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'detect fudged signature with NUL' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	git cat-file commit seventh-signed >raw &&
      +	cat raw >forged2 &&
      +	echo Qwik | tr "Q" "\000" >>forged2 &&
     @@ t/t7527-signed-commit-ssh.sh (new)
      +test_expect_success GPGSSH 'amending already signed commit' '
      +	test_config gpg.format ssh &&
      +	test_config user.signingkey "${SIGNING_KEY_PRIMARY}" &&
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	git checkout fourth-signed^0 &&
      +	git commit --amend -S --no-edit &&
      +	git verify-commit HEAD &&
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'show good signature with custom format' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	FINGERPRINT=$(ssh-keygen -lf "${SIGNING_KEY_PRIMARY}" | awk "{print \$2;}") &&
      +	cat >expect.tmpl <<-\EOF &&
      +	G
      +	FINGERPRINT
     -+	principal_1
     ++	principal with number 1
      +	FINGERPRINT
      +
      +	EOF
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'show bad signature with custom format' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	cat >expect <<-\EOF &&
      +	B
      +
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'show untrusted signature with custom format' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	cat >expect.tmpl <<-\EOF &&
      +	U
      +	FINGERPRINT
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'show untrusted signature with undefined trust level' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	cat >expect.tmpl <<-\EOF &&
      +	undefined
      +	FINGERPRINT
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'show untrusted signature with ultimate trust level' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	cat >expect.tmpl <<-\EOF &&
      +	fully
      +	FINGERPRINT
     -+	principal_1
     ++	principal with number 1
      +	FINGERPRINT
      +
      +	EOF
     @@ t/t7527-signed-commit-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'log.showsignature behaves like --show-signature' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	test_config log.showsignature true &&
      +	git show initial >actual &&
      +	grep "${GOOD_SIGNATURE_TRUSTED}" actual
  9:  33330fda441 !  8:  275dd8a1013 ssh signing: add more tests for logs, tags & push certs
     @@ t/t4202-log.sh: test_expect_success GPGSM 'log OpenPGP fingerprint' '
       '
       
      +test_expect_success GPGSSH 'log ssh key fingerprint' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	ssh-keygen -lf  "${SIGNING_KEY_PRIMARY}" | awk "{print \$2\" | \"}" >expect &&
      +	git log -n1 --format="%GF | %GP" signed-ssh >actual &&
      +	test_cmp expect actual
     @@ t/t4202-log.sh: test_expect_success GPGSM 'log --graph --show-signature x509' '
       '
       
      +test_expect_success GPGSSH 'log --graph --show-signature ssh' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	git log --graph --show-signature -n1 signed-ssh >actual &&
      +	grep "${GOOD_SIGNATURE_TRUSTED}" actual
      +'
     @@ t/t5534-push-signed.sh: test_expect_success GPG 'signed push sends push certific
      +test_expect_success GPGSSH 'ssh signed push sends push certificate' '
      +	prepare_dst &&
      +	mkdir -p dst/.git/hooks &&
     -+	git -C dst config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	git -C dst config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	git -C dst config receive.certnonceseed sekrit &&
      +	write_script dst/.git/hooks/post-receive <<-\EOF &&
      +	# discard the update list
     @@ t/t5534-push-signed.sh: test_expect_success GPG 'signed push sends push certific
      +
      +	(
      +		cat <<-\EOF &&
     -+		SIGNER=principal_1
     ++		SIGNER=principal with number 1
      +		KEY=FINGERPRINT
      +		STATUS=G
      +		NONCE_STATUS=OK
     @@ t/t5534-push-signed.sh: test_expect_success GPGSM 'fail without key and heed use
      +	test_config gpg.format ssh &&
      +	prepare_dst &&
      +	mkdir -p dst/.git/hooks &&
     -+	git -C dst config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	git -C dst config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	git -C dst config receive.certnonceseed sekrit &&
      +	write_script dst/.git/hooks/post-receive <<-\EOF &&
      +	# discard the update list
     @@ t/t5534-push-signed.sh: test_expect_success GPGSM 'fail without key and heed use
      +
      +	(
      +		cat <<-\EOF &&
     -+		SIGNER=principal_1
     ++		SIGNER=principal with number 1
      +		KEY=FINGERPRINT
      +		STATUS=G
      +		NONCE_STATUS=OK
     @@ t/t7031-verify-tag-signed-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'verify and show ssh signatures' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	(
      +		for tag in initial second merge fourth-signed sixth-signed seventh-signed
      +		do
     @@ t/t7031-verify-tag-signed-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'detect fudged ssh signature' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	git cat-file tag seventh-signed >raw &&
      +	sed -e "/^tag / s/seventh/7th forged/" raw >forged1 &&
      +	git hash-object -w -t tag forged1 >forged1.tag &&
     @@ t/t7031-verify-tag-signed-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'verify ssh signatures with --raw' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	(
      +		for tag in initial second merge fourth-signed sixth-signed seventh-signed
      +		do
     @@ t/t7031-verify-tag-signed-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'verify signatures with --raw ssh' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	git verify-tag --raw sixth-signed 2>actual &&
      +	grep "${GOOD_SIGNATURE_TRUSTED}" actual &&
      +	! grep "${BAD_SIGNATURE}" actual &&
     @@ t/t7031-verify-tag-signed-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'verify multiple tags ssh' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	tags="seventh-signed sixth-signed" &&
      +	for i in $tags
      +	do
     @@ t/t7031-verify-tag-signed-ssh.sh (new)
      +'
      +
      +test_expect_success GPGSSH 'verifying tag with --format - ssh' '
     -+	test_config gpg.ssh.keyring "${SIGNING_KEYRING}" &&
     ++	test_config gpg.ssh.allowedSignersFile "${SIGNING_ALLOWED_SIGNERS}" &&
      +	cat >expect <<-\EOF &&
      +	tagname : fourth-signed
      +	EOF

2: 2f8452f6570 ! 9: 13f6c229bd1 ssh signing: add documentation
@@ Documentation/config/gpg.txt: gpg.minTrustLevel::
* fully
* ultimate
+
-+gpg.ssh.keyring::
-+ A file containing all valid SSH public signing keys.
-+ Similar to an .ssh/authorized_keys file.
++gpg.ssh.allowedSignersFile::
++ A file containing ssh public keys which you are willing to trust.
++ The file consists of one or more lines of principals followed by an ssh
++ public key.
++ e.g.: [email protected],[email protected] ssh-rsa AAAAX1...
+ See ssh-keygen(1) "ALLOWED SIGNERS" for details.
-+ If a signing key is found in this file then the trust level will
-+ be set to "fully". Otherwise if the key is not present
-+ but the signature is still valid then the trust level will be "undefined".
++ The principal is only used to identify the key and is available when
++ verifying a signature.
+++
++SSH has no concept of trust levels like gpg does. To be able to differentiate ++between valid signatures and trusted signatures the trust level of a signature ++verification is set to fully when the public key is present in the allowedSignersFile. ++Therefore to only mark fully trusted keys as verified set gpg.minTrustLevel to fully. ++Otherwise valid but untrusted signatures will still verify but show no principal ++name of the signer.
+++
++This file can be set to a location outside of the repository and every developer ++maintains their own trust store. A central repository server could generate this ++file automatically from ssh keys with push access to verify the code against. ++In a corporate setting this file is probably generated at a global location ++from automation that already handles developer ssh keys.
+++
++A repository that only allows signed commits can store the file
++in the repository itself using a path relative to the top-level of the working tree. ++This way only committers with an already valid key can add or change keys in the keyring.
+++
++Using a SSH CA key with the cert-authority option
++(see ssh-keygen(1) "CERTIFICATES") is also valid.
+
-+ This file can be set to a location outside of the repository
-+ and every developer maintains their own trust store.
-+ A central repository server could generate this file automatically
-+ from ssh keys with push access to verify the code against.
-+ In a corporate setting this file is probably generated at a global location
-+ from some automation that already handles developer ssh keys.
-+
-+ A repository that is only allowing signed commits can store the file
-+ in the repository itself using a relative path. This way only committers
-+ with an already valid key can add or change keys in the keyring.
-+
-+ Using a SSH CA key with the cert-authority option
-+ (see ssh-keygen(1) "CERTIFICATES") is also valid.
-+
-+ To revoke a key place the public key without the principal into the
-+ revocationKeyring.
-+
-+gpg.ssh.revocationKeyring::
++gpg.ssh.revocationFile::
+ Either a SSH KRL or a list of revoked public keys (without the principal prefix).
+ See ssh-keygen(1) for details.
+ If a public key is found in this file then it will always be treated

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