docs: clarify that credential discards unrecognised attributes
PATCH 1/1 docs: clarify that credential discards unrecognised attributes
From: M Hickford <[email protected]>
It was previously unclear how unrecognised attributes are handled.
---
docs: clarify that credential discards unrecognised attributes
It was previously unclear how unrecognised attributes are handled.
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1393%2Fhickford%2Funrecognised-attributes-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1393/hickford/unrecognised-attributes-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1393
Documentation/git-credential.txt | 2 ++ Documentation/gitcredentials.txt | 1 + 2 files changed, 3 insertions(+)
Documentation/git-credential.txt +2 -0
@@ -160,6 +160,8 @@ empty string. Components which are missing from the URL (e.g., there is no username in the example above) will be left unset. +Unrecognised attributes are silently discarded. + GIT --- Part of the linkgit:git[1] suite
Documentation/gitcredentials.txt +1 -0
@@ -269,6 +269,7 @@ stdout in the same format (see linkgit:git-credential[1] for common attributes). A helper is free to produce a subset, or even no values at all if it has nothing useful to provide. Any provided attributes will overwrite those already known about by Git's credential subsystem. +Unrecognised attributes are silently discarded. While it is possible to override all attributes, well behaving helpers should refrain from doing so for any attribute other than username and
base-commit: 1fc3c0ad407008c2f71dd9ae1241d8b75f8ef886
Signature · 1 line
gitgitgadget
Quoted 1 line · M Hickford via GitGitGadget
It was previously unclear how unrecognised attributes are handled.
Yeah, this was always part of the intended behavior, but I agree we did not say it very explicitly (aside from an in-code comment!). Both the intent and content of your patch look good to me.
We did discuss patches a long time ago that would let Git carry arbitrary keys between helpers, even if Git itself didn't understand it. One of the intended uses was to let helpers talk to each other about TTLs. So if you had say:
[credential]
helper = generate-some-token
helper = cache
where the first helper generates a token, and the second caches it, the first one could shove a "ttl" or "expiration" key into the protocol, which the cache could then learn to respect.
But we never merged such a thing, and in practice I think people would just implement both parts as a single helper for simplicity. And anyway, even if we did want to do that, such a patch would want to modify the documentation to explain the new behavior. :)
-Peff
Quoted 5 lines · Jeff King
We did discuss patches a long time ago that would let Git carry arbitrary keys between helpers, even if Git itself didn't understand it. One of the intended uses was to let helpers talk to each other about TTLs. So if you had say:
Quoted 7 lines
[credential]
helper = generate-some-token
helper = cachewhere the first helper generates a token, and the second caches it, the first one could shove a "ttl" or "expiration" key into the protocol, which the cache could then learn to respect.
In case anyone is morbidly curious, it was in this thread:
https://lore.kernel.org/git/[email protected]/
-Peff
Thanks
In reply to Jeff KingThanks Jeff for your reply. This is helpful to understand the background.
(first message using git send-email, hopefully I followed the instructions correctly)
Re: Thanks
Quoted 3 lines · M Hickford
Thanks Jeff for your reply. This is helpful to understand the background.
(first message using git send-email, hopefully I followed the instructions correctly)
You messed up the thread (you broke it).
On every message showed on lore.kernel.org/git, there is reply instructions at the bottom of the message's page. Follow it closely.
If you insisted on either using git-send-email(1) or mailto: link to reply, you need to manually quote any portion of original message you wish to give the context. Make sure every line of quoted text starts with > .
Better yet, reply using "reply-all" button or key in your mail client. However, make sure your email is text/plain (not HTML) and your mail client doesn't mess up with whitespaces (convert tabs to spaces, word wrapping).
Thanks.
Signature · 1 line
An old man doll... just what I always wanted! - Clara
Re: Thanks
Quoted 3 lines
Quoted 1 line
(first message using git send-email, hopefully I followed the instructions correctly)
You messed up the thread (you broke it).
Curious. The thread overview "5+ messages" at https://lore.kernel.org/git/[email protected]/#related looks okay to me. I followed the git send-email instructions setting the In-Reply-To header. I changed the subject -- maybe that confused some clients? Thanks for the tips.
Re: Thanks
Quoted 9 lines · M Hickford
Quoted 3 lines
Quoted 1 line
(first message using git send-email, hopefully I followed the instructions correctly)
You messed up the thread (you broke it).
Curious. The thread overview "5+ messages" at
https://lore.kernel.org/git/[email protected]/#related
looks okay to me. I followed the git send-email instructions setting the In-Reply-To header. I changed the subject -- maybe that confused some clients?
Your reply looked fine to me. The in-reply-to you used is correct. It's OK to change the subject (though usually only done when the conversation drifts to a different topic).
-Peff
Re: Thanks
In reply to M HickfordQuoted 9 lines · M Hickford
Quoted 3 lines
Quoted 1 line
(first message using git send-email, hopefully I followed the instructions correctly)
You messed up the thread (you broke it).
Curious. The thread overview "5+ messages" at
https://lore.kernel.org/git/[email protected]/#related
looks okay to me. I followed the git send-email instructions setting the In-Reply-To header. I changed the subject -- maybe that confused some clients? Thanks for the tips.
Your In-Reply-To: header looked OK to me. Some webmail platforms break the thread when Subject: is edited, but that is their bug. As long as you keep the In-Reply-To: chain correct, retitling the message as necessary is indeed encouraged practice.
Quoted 8 lines · Jeff King
Quoted 1 line · M Hickford via GitGitGadget
It was previously unclear how unrecognised attributes are handled.
Yeah, this was always part of the intended behavior, but I agree we did not say it very explicitly (aside from an in-code comment!). Both the intent and content of your patch look good to me.
Thanks. What happens next? I should look for this change in the seen branch? https://git-scm.com/docs/MyFirstContribution#after-approval
Quoted 5 lines
We did discuss patches a long time ago that would let Git carry arbitrary keys between helpers, even if Git itself didn't understand it. One of the intended uses was to let helpers talk to each other about TTLs. So if you had say:
Quoted 7 lines
[credential]
helper = generate-some-token
helper = cachewhere the first helper generates a token, and the second caches it, the first one could shove a "ttl" or "expiration" key into the protocol, which the cache could then learn to respect.
Composing helpers like this is how I encourage users to configure git-credential-oauth [1][2]. Note that the storage helper should come *before* the generator, so that credential fill finds a stored credential before it generates a fresh credential.
Quoted 5 lines
the first one could shove a "ttl" or "expiration" key into the protocol, which the cache could then learn to respect.
But we never merged such a thing, and in practice I think people would just implement both parts as a single helper for simplicity.
Composing helpers has the advantage that the user can choose their preferred storage. Generated credentials aren't necessarily short lived. GitHub OAuth tokens, for example, are good for at least one year [3].
[1] https://lore.kernel.org/git/CAGJzqs=+fCQzkDX53H8Mz-DjXicVVgRmmzPjkatSiOpYO7wGGA@mail.gmail.com/
[2] https://github.com/hickford/git-credential-oauth
[3] https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/token-expiration-and-revocation#token-expired-due-to-lack-of-use
Quoted 4 lines · M Hickford
Quoted 3 lines · Jeff King
On Mon, Oct 24, 2022 at 07:57:48AM +0000, M Hickford via GitGitGadget wrote:
Quoted 8 lines
Quoted 5 lines
Quoted 1 line
It was previously unclear how unrecognised attributes are handled.
Yeah, this was always part of the intended behavior, but I agree we did not say it very explicitly (aside from an in-code comment!). Both the intent and content of your patch look good to me.
Thanks. What happens next? I should look for this change in the seen branch? https://git-scm.com/docs/MyFirstContribution#after-approval
Usually the maintainer would pick it up, it would end up in seen, then eventually 'next', and then eventually 'master'. You can check the periodic "What's Cooking" messages from the maintainer to see more discussion of various topic branches.
In this case, though, I don't see any indication that the maintainer picked saw it. It sometimes happens that a topic is simply overlooked, even if it received positive reviews.
The usual thing to do is repost it, cc-ing the maintainer. I've also cc'd the interim maintainer here, so that may get things moving. :)
Quoted 9 lines
Quoted 9 lines
We did discuss patches a long time ago that would let Git carry arbitrary keys between helpers, even if Git itself didn't understand it. One of the intended uses was to let helpers talk to each other about TTLs. So if you had say:
[credential]
helper = generate-some-token
helper = cache
Quoted 8 lines
Quoted 3 lines
where the first helper generates a token, and the second caches it, the first one could shove a "ttl" or "expiration" key into the protocol, which the cache could then learn to respect.
Composing helpers like this is how I encourage users to configure git-credential-oauth [1][2]. Note that the storage helper should come *before* the generator, so that
credential fillfinds a stored credential before it generates a fresh credential.
Right, it's been a while since I've constructed an example like this. ;)
What you're doing works fine with the code as-is; you just can't carry extra data (like a ttl) between the two.
The thread I linked earlier also discusses (in the very top-level patch) a change in behavior that would break the flow you're relying on here (because it may unexpectedly propagate credentials between helpers). But I don't think anybody is interested in pursuing that, and it has been 10 years now.
Quoted 7 lines
Quoted 2 lines
But we never merged such a thing, and in practice I think people would just implement both parts as a single helper for simplicity.
Composing helpers has the advantage that the user can choose their preferred storage. Generated credentials aren't necessarily short lived. GitHub OAuth tokens, for example, are good for at least one year [3].
Yeah, the composability was one of the goals of the system. I just think in practice that not many people use it. You can also compose outside of Git (I think the thread I linked earlier has an example of a wrapper that does so), but again, I don't think anybody really does so in practice.
I agree for GitHub's tokens that the times involved make auto-expiration not that important. The example back in that thread was something more time-limited (like minutes or hours). I don't know how often that kind of things is in the wild.
-Peff
Quoted 9 lines · Jeff King
Quoted 9 lines
Quoted 9 lines
We did discuss patches a long time ago that would let Git carry arbitrary keys between helpers, even if Git itself didn't understand it. One of the intended uses was to let helpers talk to each other about TTLs. So if you had say:
[credential]
helper = generate-some-token
helper = cache
Quoted 7 lines
Quoted 4 lines
Quoted 3 lines
where the first helper generates a token, and the second caches it, the first one could shove a "ttl" or "expiration" key into the protocol, which the cache could then learn to respect.
What you're doing works fine with the code as-is; you just can't carry extra data (like a ttl) between the two.
FWIW I have a draft patch that adds password_expiry_utc and oauth_refresh_token attributes to credential
https://github.com/gitgitgadget/git/pull/1394 introducing expiry logic in the credential layer. I'll share a RFC sometime in future.
Quoted 4 lines
I agree for GitHub's tokens that the times involved make auto-expiration not that important. The example back in that thread was something more time-limited (like minutes or hours). I don't know how often that kind of things is in the wild.
GitLab OAuth tokens expire after 2 hours (the refresh tokens are valid longer). This is a security improvement over long-lived tokens.
Quoted 20 lines · Jeff King
Quoted 4 lines · M Hickford
Quoted 3 lines · Jeff King
On Mon, Oct 24, 2022 at 07:57:48AM +0000, M Hickford via GitGitGadget wrote:
Quoted 8 lines
Quoted 5 lines
Quoted 1 line
It was previously unclear how unrecognised attributes are handled.
Yeah, this was always part of the intended behavior, but I agree we did not say it very explicitly (aside from an in-code comment!). Both the intent and content of your patch look good to me.
Thanks. What happens next? I should look for this change in the seen branch? https://git-scm.com/docs/MyFirstContribution#after-approval
Usually the maintainer would pick it up, it would end up in seen, then eventually 'next', and then eventually 'master'. You can check the periodic "What's Cooking" messages from the maintainer to see more discussion of various topic branches.
Quoted 6 lines
In this case, though, I don't see any indication that the maintainer picked saw it. It sometimes happens that a topic is simply overlooked, even if it received positive reviews.
The usual thing to do is repost it, cc-ing the maintainer. I've also cc'd the interim maintainer here, so that may get things moving. :)
I think that Junio may have missed it when picking up topics. But it happened before I start combing the list more finely, so I had already purged it from my inbox without picking it up, either.
I'll take a look now and queue it to start merging down. Thanks for the nudge.
Thanks,
Taylor
Quoted 15 lines · M Hickford
Quoted 14 lines · Jeff King
Quoted 13 lines
Quoted 12 lines
We did discuss patches a long time ago that would let Git carry arbitrary keys between helpers, even if Git itself didn't understand it. One of the intended uses was to let helpers talk to each other about TTLs. So if you had say:
[credential]
helper = generate-some-token
helper = cachewhere the first helper generates a token, and the second caches it, the first one could shove a "ttl" or "expiration" key into the protocol, which the cache could then learn to respect.
Quoted 7 lines
Quoted 2 lines
What you're doing works fine with the code as-is; you just can't carry extra data (like a ttl) between the two.
FWIW I have a draft patch that adds
password_expiry_utcandoauth_refresh_tokenattributes to credential
https://github.com/gitgitgadget/git/pull/1394 introducing expiry logic in the credential layer. I'll share a RFC sometime in future.
Neat.
I'm not _totally_ opposed to introducing these as something Git understands, but I think it makes more sense to just teach Git to relay unknown entries between helpers.
The oauth thing is going to be very helper specific, and not something I think Git would ever do anything with itself.
In theory Git might care about expiration, but in practice I think it doesn't. It's very unlikely for a token to expire in the course of Git using it. It's only much later, when we ask for it back, that a helper will notice it's expired. Git could save the helper some work by noticing this on read, but since the helper has to learn to store and report the expiration in the first place, not much is gained.
And in the case of something like credential-cache, we want to do more than just store; we'd actually drop the credential entirely (and maybe even cause the daemon to exit) if it expires before the usual timeout.
-Peff