Check codeSigning extended key usage extension
Subsystems (5)
v5 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.
v5:
Fixed the wording in module-signing.rst.
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 v5 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
@@ -28,6 +28,7 @@ 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,
Quoted 26 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 +2
-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);
crypto/asymmetric_keys/x509_cert_parser.c int x509_process_extension(void *context, size_t hdrlen, · line 533
Quoted 6 lines
crypto/asymmetric_keys/x509_cert_parser.c +3
-0@@ -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 )
A bad cert might get here with vlen < 2, which would cause indexing into v to break. Please add a check for vlen >= 2 before this.
crypto/asymmetric_keys/x509_cert_parser.c int x509_process_extension(void *context, size_t hdrlen, · line 540
Quoted 7 lines
crypto/asymmetric_keys/x509_cert_parser.c +7
-0+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)
Same here, for i == (vlen - 1), v[i + 1] would fetch outside of v. Or, does the ASN.1 layout protect against this?
Quoted 47 lines
crypto/asymmetric_keys/x509_cert_parser.c +12
-0+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@@ -28,6 +28,7 @@ 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 · 7 lines
SUSE Software Solutions Germany GmbH Maxfeldstr. 5 90409 Nürnberg Germany HRB 36809, AG Nürnberg Geschäftsführer: Felix Imendörffer
Re: [PATCH 1/4] X.509: Add CodeSigning extended key usage parsing
Hi Varad,
Thanks for your review!
Quoted 32 lines · Varad Gautam
Hi,
Quoted 29 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 +2
-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 ; }
Quoted 7 lines
crypto/asymmetric_keys/x509_cert_parser.c int x509_process_extension(void *context, size_t hdrlen, · line 533
Quoted 3 lines
crypto/asymmetric_keys/x509_cert_parser.c +3
-0+if (ctx->last_oid == OID_extKeyUsage) { +if (v[0 ] != ((ASN1_UNIV <<6 ) |ASN1_CONS_BIT |ASN1_SEQ ) || + v[1 ] != vlen -2 )A bad cert might get here with vlen < 2, which would cause indexing into v to break. Please add a check for vlen >= 2 before this.
I will add the check, thanks for your suggestion!
Quoted 11 lines
crypto/asymmetric_keys/x509_cert_parser.c int x509_process_extension(void *context, size_t hdrlen, · line 540
Quoted 7 lines
crypto/asymmetric_keys/x509_cert_parser.c +7
-0+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)Same here, for i == (vlen - 1), v[i + 1] would fetch outside of v. Or, does the ASN.1 layout protect against this?
I will move the "(i + 10) > vlen" to the front of "v[i + 1] != 8". It can avoid that the last octet blob is less than 10 bytes.
Thanks!
Joey Lee
Quoted 56 lines
Quoted 47 lines
crypto/asymmetric_keys/x509_cert_parser.c +12
-0+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@@ -28,6 +28,7 @@ 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 · 7 lines
SUSE Software Solutions Germany GmbH Maxfeldstr. 5 90409 Nürnberg Germany HRB 36809, AG Nürnberg Geschäftsführer: Felix Imendörffer
PATCH v5 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
@@ -243,7 +243,7 @@ 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 v5 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 v5 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 is enabled, the following openssl +command option should be added where 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