Check codeSigning extended key usage extension
Subsystems (5)
v4 cover Check codeSigning extended key usage extension
NIAP PP_OS certification requests that the OS shall validate the CodeSigning extended key usage extension field for integrity verifiction of exectable code:
https://www.niap-ccevs.org/MMO/PP/-442-/ FIA_X509_EXT.1.1
This patchset adds the logic for parsing the codeSigning EKU extension field in X.509. And checking the CodeSigning EKU when verifying signature of kernel module or kexec PE binary in PKCS#7.
v4:
Fixed the wording in patch description.
v3:
- Add codeSigning EKU to x509.genkey key generation config.
- Add openssl command option example for generating CodeSign EKU to module-signing.rst document.
v2:
Changed the help wording in the Kconfig.
Lee, Chun-Yi (4):
X.509: Add CodeSigning extended key usage parsing PKCS#7: Check codeSigning EKU for kernel module and kexec pe
verification
modsign: Add codeSigning EKU when generating X.509 key generation
config
Documentation/admin-guide/module-signing.rst: add openssl command
option example for CodeSign EKU
Documentation/admin-guide/module-signing.rst | 6 +++++ certs/Makefile | 1 + certs/system_keyring.c | 2 +- crypto/asymmetric_keys/Kconfig | 9 +++++++ crypto/asymmetric_keys/pkcs7_trust.c | 37 +++++++++++++++++++++++++--- crypto/asymmetric_keys/x509_cert_parser.c | 24 ++++++++++++++++++ include/crypto/pkcs7.h | 3 ++- include/crypto/public_key.h | 1 + include/linux/oid_registry.h | 5 ++++ 9 files changed, 83 insertions(+), 5 deletions(-)
Signature · 1 line
2.16.4
PATCH v4 1/4 X.509: Add CodeSigning extended key usage parsing
This patch adds the logic for parsing the CodeSign extended key usage extension in X.509. The parsing result will be set to the eku flag which is carried by public key. It can be used in the PKCS#7 verification.
--- crypto/asymmetric_keys/x509_cert_parser.c | 24 ++++++++++++++++++++++++ include/crypto/public_key.h | 1 + include/linux/oid_registry.h | 5 +++++ 3 files changed, 30 insertions(+)
crypto/asymmetric_keys/x509_cert_parser.c +24 -0
@@ -497,6 +497,8 @@ int x509_process_extension(void *context, size_t hdrlen,struct x509_parse_context *ctx = context;struct asymmetric_key_id *kid;const unsigned char *v = value; +int i =0 ; +enum OID oid;pr_debug ("Extension: %u\n" , ctx->last_oid);
@@ -526,6 +528,28 @@ int x509_process_extension(void *context, size_t hdrlen,return 0 ; } +if (ctx->last_oid == OID_extKeyUsage) { +if (v[0 ] != ((ASN1_UNIV <<6 ) |ASN1_CONS_BIT |ASN1_SEQ ) || + v[1 ] != vlen -2 ) +return -EBADMSG ; + i +=2 ; + +while (i < vlen) { +/* A 10 bytes EKU OID Octet blob = +* ASN1_OID + size byte + 8 bytes OID */ +if (v[i] !=ASN1_OID || v[i +1 ] !=8 || (i +10 ) > vlen) +return -EBADMSG ; + + oid =look_up_OID (v + i +2 , v[i +1 ]); +if (oid == OID_codeSigning) { + ctx->cert->pub->eku |= EKU_codeSigning; + } + i +=10 ; + } +pr_debug ("extKeyUsage: %d\n" , ctx->cert->pub->eku); +return 0 ; + } +return 0 ; }
include/crypto/public_key.h +1 -0
@@ -29,6 +29,7 @@ struct public_key {bool key_is_private;const char *id_type;const char *pkey_algo; + unsigned int eku : 9; /* Extended Key Usage (9-bit) */ };extern void public_key_free (struct public_key *key);
include/linux/oid_registry.h +5 -0
@@ -113,9 +113,14 @@ enum OID { OID_SM2_with_SM3,/* 1.2.156.10197.1.501 */ OID_sm3WithRSAEncryption,/* 1.2.156.10197.1.504 */ +/* Extended key purpose OIDs [RFC 5280] */ + OID_codeSigning,/* 1.3.6.1.5.5.7.3.3 */ + OID__NR }; +#define EKU_codeSigning (1 << 2) +extern enum OID look_up_OID (const void *data,size_t datasize);extern int sprint_oid (const void *,size_t ,char *,size_t );extern int sprint_OID (enum OID ,char *,size_t );
Signature · 1 line
2.16.4
Jarkko Sakkinen
maintainerRe: [PATCH 1/4] X.509: Add CodeSigning extended key usage parsing
Quoted 38 lines · Chun-Yi
This patch adds the logic for parsing the CodeSign extended key usage extension in X.509. The parsing result will be set to the eku flag which is carried by public key. It can be used in the PKCS#7 verification.
Signed-off-by "Lee, Chun-Yi" <[email protected]>--- crypto/asymmetric_keys/x509_cert_parser.c | 24 ++++++++++++++++++++++++ include/crypto/public_key.h | 1 + include/linux/oid_registry.h | 5 +++++ 3 files changed, 30 insertions(+)crypto/asymmetric_keys/x509_cert_parser.c +11
-0@@ -497,6 +497,8 @@ int x509_process_extension(void *context, size_t hdrlen,struct x509_parse_context *ctx = context;struct asymmetric_key_id *kid;const unsigned char *v = value; +int i =0 ; +enum OID oid;pr_debug ("Extension: %u\n" , ctx->last_oid);@@ -526,6 +528,28 @@ int x509_process_extension(void *context, size_t hdrlen,return 0 ; } +if (ctx->last_oid == OID_extKeyUsage) { +if (v[0 ] != ((ASN1_UNIV <<6 ) |ASN1_CONS_BIT |ASN1_SEQ ) || + v[1 ] != vlen -2 ) +return -EBADMSG ; + i +=2 ; + +while (i < vlen) { +/* A 10 bytes EKU OID Octet blob = +* ASN1_OID + size byte + 8 bytes OID */
crypto/asymmetric_keys/x509_cert_parser.c int x509_process_extension(void *context, size_t hdrlen, · line 549
Quoted 10 lines
crypto/asymmetric_keys/x509_cert_parser.c +10
-0+if (v[i] !=ASN1_OID || v[i +1 ] !=8 || (i +10 ) > vlen) +return -EBADMSG ; + + oid =look_up_OID (v + i +2 , v[i +1 ]); +if (oid == OID_codeSigning) { + ctx->cert->pub->eku |= EKU_codeSigning; + } + i +=10 ; + } +pr_debug ("extKeyUsage: %d\n" , ctx->cert->pub->eku);
With eBPF around, does this make any sense?
/Jarkko
Quoted 41 lines
crypto/asymmetric_keys/x509_cert_parser.c +3
-0+return 0 ; + } +return 0 ; }include/crypto/public_key.h +1
-0@@ -29,6 +29,7 @@ struct public_key {bool key_is_private;const char *id_type;const char *pkey_algo; + unsigned int eku : 9; /* Extended Key Usage (9-bit) */ };extern void public_key_free (struct public_key *key);include/linux/oid_registry.h +5
-0@@ -113,9 +113,14 @@ enum OID { OID_SM2_with_SM3,/* 1.2.156.10197.1.501 */ OID_sm3WithRSAEncryption,/* 1.2.156.10197.1.504 */ +/* Extended key purpose OIDs [RFC 5280] */ + OID_codeSigning,/* 1.3.6.1.5.5.7.3.3 */ + OID__NR }; +#define EKU_codeSigning (1 << 2) +extern enum OID look_up_OID (const void *data,size_t datasize);extern int sprint_oid (const void *,size_t ,char *,size_t );extern int sprint_OID (enum OID ,char *,size_t );Signature · 1 line
2.16.4
Re: [PATCH 1/4] X.509: Add CodeSigning extended key usage parsing
Hi Jarkko,
Quoted 43 lines · Jarkko Sakkinen
Quoted 42 lines · Chun-Yi
This patch adds the logic for parsing the CodeSign extended key usage extension in X.509. The parsing result will be set to the eku flag which is carried by public key. It can be used in the PKCS#7 verification.
Signed-off-by "Lee, Chun-Yi" <[email protected]>--- crypto/asymmetric_keys/x509_cert_parser.c | 24 ++++++++++++++++++++++++ include/crypto/public_key.h | 1 + include/linux/oid_registry.h | 5 +++++ 3 files changed, 30 insertions(+)crypto/asymmetric_keys/x509_cert_parser.c +15
-0@@ -497,6 +497,8 @@ int x509_process_extension(void *context, size_t hdrlen,struct x509_parse_context *ctx = context;struct asymmetric_key_id *kid;const unsigned char *v = value; +int i =0 ; +enum OID oid;pr_debug ("Extension: %u\n" , ctx->last_oid);@@ -526,6 +528,28 @@ int x509_process_extension(void *context, size_t hdrlen,return 0 ; } +if (ctx->last_oid == OID_extKeyUsage) { +if (v[0 ] != ((ASN1_UNIV <<6 ) |ASN1_CONS_BIT |ASN1_SEQ ) || + v[1 ] != vlen -2 ) +return -EBADMSG ; + i +=2 ; + +while (i < vlen) { +/* A 10 bytes EKU OID Octet blob = +* ASN1_OID + size byte + 8 bytes OID */ +if (v[i] !=ASN1_OID || v[i +1 ] !=8 || (i +10 ) > vlen) +return -EBADMSG ; + + oid =look_up_OID (v + i +2 , v[i +1 ]);
Quoted 9 lines
crypto/asymmetric_keys/x509_cert_parser.c int x509_process_extension(void *context, size_t hdrlen, · line 549
Quoted 6 lines
crypto/asymmetric_keys/x509_cert_parser.c +6
-0+if (oid == OID_codeSigning) { + ctx->cert->pub->eku |= EKU_codeSigning; + } + i +=10 ; + } +pr_debug ("extKeyUsage: %d\n" , ctx->cert->pub->eku);With eBPF around, does this make any sense?
I think that the dynamic debug log is still easier for checking the EKU setting.
Thanks
Joey Lee
Jarkko Sakkinen
maintainerRe: [PATCH 1/4] X.509: Add CodeSigning extended key usage parsing
Quoted 56 lines · joeyli
Hi Jarkko,
Quoted 43 lines · Jarkko Sakkinen
Quoted 42 lines · Chun-Yi
This patch adds the logic for parsing the CodeSign extended key usage extension in X.509. The parsing result will be set to the eku flag which is carried by public key. It can be used in the PKCS#7 verification.
Signed-off-by "Lee, Chun-Yi" <[email protected]>--- crypto/asymmetric_keys/x509_cert_parser.c | 24 ++++++++++++++++++++++++ include/crypto/public_key.h | 1 + include/linux/oid_registry.h | 5 +++++ 3 files changed, 30 insertions(+)crypto/asymmetric_keys/x509_cert_parser.c +15
-0@@ -497,6 +497,8 @@ int x509_process_extension(void *context, size_t hdrlen,struct x509_parse_context *ctx = context;struct asymmetric_key_id *kid;const unsigned char *v = value; +int i =0 ; +enum OID oid;pr_debug ("Extension: %u\n" , ctx->last_oid);@@ -526,6 +528,28 @@ int x509_process_extension(void *context, size_t hdrlen,return 0 ; } +if (ctx->last_oid == OID_extKeyUsage) { +if (v[0 ] != ((ASN1_UNIV <<6 ) |ASN1_CONS_BIT |ASN1_SEQ ) || + v[1 ] != vlen -2 ) +return -EBADMSG ; + i +=2 ; + +while (i < vlen) { +/* A 10 bytes EKU OID Octet blob = +* ASN1_OID + size byte + 8 bytes OID */ +if (v[i] !=ASN1_OID || v[i +1 ] !=8 || (i +10 ) > vlen) +return -EBADMSG ; + + oid =look_up_OID (v + i +2 , v[i +1 ]);Quoted 9 lines
crypto/asymmetric_keys/x509_cert_parser.c int x509_process_extension(void *context, size_t hdrlen, · line 549
Quoted 6 lines
crypto/asymmetric_keys/x509_cert_parser.c +6
-0+if (oid == OID_codeSigning) { + ctx->cert->pub->eku |= EKU_codeSigning; + } + i +=10 ; + } +pr_debug ("extKeyUsage: %d\n" , ctx->cert->pub->eku);With eBPF around, does this make any sense?
Quoted 2 lines
I think that the dynamic debug log is still easier for checking the EKU setting.
Why?
Quoted 2 lines
Thanks
Joey Lee
/Jarkko
Re: [PATCH 1/4] X.509: Add CodeSigning extended key usage parsing
Quoted 57 lines · Jarkko Sakkinen
Quoted 56 lines · joeyli
Hi Jarkko,
Quoted 52 lines · Jarkko Sakkinen
Quoted 38 lines · Chun-Yi
This patch adds the logic for parsing the CodeSign extended key usage extension in X.509. The parsing result will be set to the eku flag which is carried by public key. It can be used in the PKCS#7 verification.
Signed-off-by "Lee, Chun-Yi" <[email protected]>--- crypto/asymmetric_keys/x509_cert_parser.c | 24 ++++++++++++++++++++++++ include/crypto/public_key.h | 1 + include/linux/oid_registry.h | 5 +++++ 3 files changed, 30 insertions(+)crypto/asymmetric_keys/x509_cert_parser.c +11
-0@@ -497,6 +497,8 @@ int x509_process_extension(void *context, size_t hdrlen,struct x509_parse_context *ctx = context;struct asymmetric_key_id *kid;const unsigned char *v = value; +int i =0 ; +enum OID oid;pr_debug ("Extension: %u\n" , ctx->last_oid);@@ -526,6 +528,28 @@ int x509_process_extension(void *context, size_t hdrlen,return 0 ; } +if (ctx->last_oid == OID_extKeyUsage) { +if (v[0 ] != ((ASN1_UNIV <<6 ) |ASN1_CONS_BIT |ASN1_SEQ ) || + v[1 ] != vlen -2 ) +return -EBADMSG ; + i +=2 ; + +while (i < vlen) { +/* A 10 bytes EKU OID Octet blob = +* ASN1_OID + size byte + 8 bytes OID */ crypto/asymmetric_keys/x509_cert_parser.c int x509_process_extension(void *context, size_t hdrlen, · line 549
Quoted 10 lines
crypto/asymmetric_keys/x509_cert_parser.c +10
-0+if (v[i] !=ASN1_OID || v[i +1 ] !=8 || (i +10 ) > vlen) +return -EBADMSG ; + + oid =look_up_OID (v + i +2 , v[i +1 ]); +if (oid == OID_codeSigning) { + ctx->cert->pub->eku |= EKU_codeSigning; + } + i +=10 ; + } +pr_debug ("extKeyUsage: %d\n" , ctx->cert->pub->eku);With eBPF around, does this make any sense?
Quoted 4 lines
Quoted 2 lines
I think that the dynamic debug log is still easier for checking the EKU setting.
Why?
There have some certificates may loaded when system boot. In booting stage, using dynamic debug log for checking EKU is easier than eBPF.
I am not good on eBPF. Correct me if I missed anything, please!
Thanks a lot!
Joey Lee
Jarkko Sakkinen
maintainerRe: [PATCH 1/4] X.509: Add CodeSigning extended key usage parsing
Quoted 61 lines · joeyli
Quoted 60 lines · Jarkko Sakkinen
Quoted 58 lines · joeyli
Hi Jarkko,
Quoted 43 lines · Jarkko Sakkinen
Quoted 42 lines · Chun-Yi
This patch adds the logic for parsing the CodeSign extended key usage extension in X.509. The parsing result will be set to the eku flag which is carried by public key. It can be used in the PKCS#7 verification.
Signed-off-by "Lee, Chun-Yi" <[email protected]>--- crypto/asymmetric_keys/x509_cert_parser.c | 24 ++++++++++++++++++++++++ include/crypto/public_key.h | 1 + include/linux/oid_registry.h | 5 +++++ 3 files changed, 30 insertions(+)crypto/asymmetric_keys/x509_cert_parser.c +15
-0@@ -497,6 +497,8 @@ int x509_process_extension(void *context, size_t hdrlen,struct x509_parse_context *ctx = context;struct asymmetric_key_id *kid;const unsigned char *v = value; +int i =0 ; +enum OID oid;pr_debug ("Extension: %u\n" , ctx->last_oid);@@ -526,6 +528,28 @@ int x509_process_extension(void *context, size_t hdrlen,return 0 ; } +if (ctx->last_oid == OID_extKeyUsage) { +if (v[0 ] != ((ASN1_UNIV <<6 ) |ASN1_CONS_BIT |ASN1_SEQ ) || + v[1 ] != vlen -2 ) +return -EBADMSG ; + i +=2 ; + +while (i < vlen) { +/* A 10 bytes EKU OID Octet blob = +* ASN1_OID + size byte + 8 bytes OID */ +if (v[i] !=ASN1_OID || v[i +1 ] !=8 || (i +10 ) > vlen) +return -EBADMSG ; + + oid =look_up_OID (v + i +2 , v[i +1 ]);Quoted 9 lines
crypto/asymmetric_keys/x509_cert_parser.c int x509_process_extension(void *context, size_t hdrlen, · line 549
Quoted 6 lines
crypto/asymmetric_keys/x509_cert_parser.c +6
-0+if (oid == OID_codeSigning) { + ctx->cert->pub->eku |= EKU_codeSigning; + } + i +=10 ; + } +pr_debug ("extKeyUsage: %d\n" , ctx->cert->pub->eku);With eBPF around, does this make any sense?
I think that the dynamic debug log is still easier for checking the EKU setting.
Quoted 6 lines
Quoted 1 line
Why?
There have some certificates may loaded when system boot. In booting stage, using dynamic debug log for checking EKU is easier than eBPF.
I am not good on eBPF. Correct me if I missed anything, please!
I think it's fine have it, thanks.
/Jarkko
David Howells
maintainerRe: [PATCH 1/4] X.509: Add CodeSigning extended key usage parsing
In reply to Jarkko SakkinenQuoted 1 line · Jarkko Sakkinen
With eBPF around, does this make any sense?
bpf/ebpf may be partially disabled if you boot in secure boot mode - not sure whether that affects this.
David
PATCH v4 2/4 PKCS#7: Check codeSigning EKU for kernel module and kexec pe verification
In reply to Lee, Chun-YiThis patch adds the logic for checking the CodeSigning extended key usage when verifying signature of kernel module or kexec PE binary in PKCS#7.
--- certs/system_keyring.c | 2 +- crypto/asymmetric_keys/Kconfig | 9 +++++++++ crypto/asymmetric_keys/pkcs7_trust.c | 37 +++++++++++++++++++++++++++++++++--- include/crypto/pkcs7.h | 3 ++- 4 files changed, 46 insertions(+), 5 deletions(-)
certs/system_keyring.c +1 -1
@@ -242,7 +242,7 @@ int verify_pkcs7_message_sig(const void *data, size_t len, goto error; } } - ret =pkcs7_validate_trust (pkcs7, trusted_keys); + ret =pkcs7_validate_trust (pkcs7, trusted_keys, usage);if (ret <0 ) {if (ret == -ENOKEY )pr_devel ("PKCS#7 signature not signed with a trusted key\n" );
crypto/asymmetric_keys/Kconfig +9 -0
@@ -96,4 +96,13 @@ config SIGNED_PE_FILE_VERIFICATION This option provides support for verifying the signature(s) on a signed PE binary. +config CHECK_CODESIGN_EKU + bool "Check codeSigning extended key usage" + depends on PKCS7_MESSAGE_PARSER=y + depends on SYSTEM_DATA_VERIFICATION + help + This option provides support for checking the codeSigning extended + key usage when verifying the signature in PKCS#7. It affects kernel + module verification and kexec PE binary verification. + endif # ASYMMETRIC_KEY_TYPE
crypto/asymmetric_keys/pkcs7_trust.c +34 -3
@@ -16,12 +16,36 @@#include <crypto/public_key.h> #include "pkcs7_parser.h" +#ifdef CONFIG_CHECK_CODESIGN_EKU +static bool check_codesign_eku (struct key *key, +enum key_being_used_for usage) +{ +struct public_key *public_key = key->payload.data[asym_crypto]; + +switch (usage) { +case VERIFYING_MODULE_SIGNATURE : +case VERIFYING_KEXEC_PE_SIGNATURE : +return !!(public_key->eku & EKU_codeSigning); +default : +break ; + } +return true; +} +#else +static bool check_codesign_eku (struct key *key, +enum key_being_used_for usage) +{ +return true; +} +#endif +/** * Check the trust on one PKCS#7 SignedInfo block. */ static int pkcs7_validate_trust_one (struct pkcs7_message *pkcs7,struct pkcs7_signed_info *sinfo, -struct key *trust_keyring) +struct key *trust_keyring, +enum key_being_used_for usage) {struct public_key_signature *sig = sinfo->sig;struct x509_certificate *x509, *last =NULL , *p;
@@ -112,6 +136,12 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,return -ENOKEY ; matched: +if (!check_codesign_eku (key, usage)) { +pr_warn ("sinfo %u: The signer %x key is not CodeSigning\n" , + sinfo->index,key_serial (key)); +key_put (key); +return -ENOKEY ; + } ret =verify_signature (key, sig);key_put (key);if (ret <0 ) {
@@ -156,7 +186,8 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,* May also return -ENOMEM. */ int pkcs7_validate_trust (struct pkcs7_message *pkcs7, -struct key *trust_keyring) +struct key *trust_keyring, +enum key_being_used_for usage) {struct pkcs7_signed_info *sinfo;struct x509_certificate *p;
@@ -167,7 +198,7 @@ int pkcs7_validate_trust(struct pkcs7_message *pkcs7, p->seen = false;for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) { - ret =pkcs7_validate_trust_one (pkcs7, sinfo, trust_keyring); + ret =pkcs7_validate_trust_one (pkcs7, sinfo, trust_keyring, usage);switch (ret) {case -ENOKEY :continue ;
include/crypto/pkcs7.h +2 -1
@@ -30,7 +30,8 @@ extern int pkcs7_get_content_data(const struct pkcs7_message *pkcs7,* pkcs7_trust.c */ extern int pkcs7_validate_trust (struct pkcs7_message *pkcs7, -struct key *trust_keyring); +struct key *trust_keyring, +enum key_being_used_for usage);/* * pkcs7_verify.c
Signature · 1 line
2.16.4
PATCH v4 3/4 modsign: Add codeSigning EKU when generating X.509 key generation config
In reply to Lee, Chun-YiAdd codeSigning EKU to the X.509 key generation config for the build time autogenerated kernel key.
--- certs/Makefile | 1 + 1 file changed, 1 insertion(+)
certs/Makefile +1 -0
@@ -88,6 +88,7 @@ $(obj)/x509.genkey: @echo >>$@ "keyUsage=digitalSignature" @echo >>$@ "subjectKeyIdentifier=hash" @echo >>$@ "authorityKeyIdentifier=keyid" + @echo >>$@ "extendedKeyUsage=codeSigning" endif # CONFIG_MODULE_SIG_KEY $(eval $(call config_filename,MODULE_SIG_KEY))
Signature · 1 line
2.16.4
PATCH v4 4/4 Documentation/admin-guide/module-signing.rst: add openssl command option example for CodeSign EKU
In reply to Lee, Chun-YiAdd an openssl command option example for generating CodeSign extended key usage in X.509 when CONFIG_CHECK_CODESIGN_EKU is enabled.
--- Documentation/admin-guide/module-signing.rst | 6 ++++++ 1 file changed, 6 insertions(+)
Documentation/admin-guide/module-signing.rst +6 -0
@@ -170,6 +170,12 @@ generate the public/private key files:: -config x509.genkey -outform PEM -out kernel_key.pem \ -keyout kernel_key.pem +When ``CONFIG_CHECK_CODESIGN_EKU`` option be enabled, the following openssl +command option should be added for generating CodeSign extended key usage in +X.509:: + + -addext "extendedKeyUsage=codeSigning" + The full pathname for the resulting kernel_key.pem file can then be specified in the ``CONFIG_MODULE_SIG_KEY`` option, and the certificate and key therein will be used instead of an autogenerated keypair.
Signature · 1 line
2.16.4