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.
v7:
- Fixed the broken function call in is_key_on_revocation_list().
(be found by kernel test robot)
- Use a general name check_eku_by_usage() instead of check_codesign_eku().
v6:
- Add more length checking when parsing extKeyUsage and EKU's OID blob.
- Add 'usage' parameter to the comment of pkcs7_validate_trust function.
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/blacklist.c | 6 ++--
certs/system_keyring.c | 4 +--
crypto/asymmetric_keys/Kconfig | 9 ++++++
crypto/asymmetric_keys/pkcs7_trust.c | 43 ++++++++++++++++++++++++++--
crypto/asymmetric_keys/x509_cert_parser.c | 25 ++++++++++++++++
include/crypto/pkcs7.h | 4 ++-
include/crypto/public_key.h | 1 +
include/keys/system_keyring.h | 7 +++--
include/linux/oid_registry.h | 5 ++++
11 files changed, 101 insertions(+), 10 deletions(-)
--
2.16.4
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 | 25 +++++++++++++++++++++++++
include/crypto/public_key.h | 1 +
include/linux/oid_registry.h | 5 +++++
3 files changed, 31 insertions(+)
diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
index 6d003096b5bc..996db9419474 100644
--- a/crypto/asymmetric_keys/x509_cert_parser.c
+++ b/crypto/asymmetric_keys/x509_cert_parser.c
@@ -542,6 +542,8 @@ 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);
@@ -571,6 +573,29 @@ int x509_process_extension(void *context, size_t hdrlen,
return 0;
}
+ if (ctx->last_oid == OID_extKeyUsage) {
+ if (vlen < 2 ||
+ 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 ((i + 10) > vlen || v[i] != ASN1_OID || v[i + 1] != 8)
+ 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;
}
diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
index 47accec68cb0..1ccaebe2a28b 100644
--- a/include/crypto/public_key.h
+++ b/include/crypto/public_key.h
@@ -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);
diff --git a/include/linux/oid_registry.h b/include/linux/oid_registry.h
index 461b7aa587ba..8c8935f0eb73 100644
--- a/include/linux/oid_registry.h
+++ b/include/linux/oid_registry.h
@@ -125,9 +125,14 @@ enum OID {
OID_TPMImportableKey, /* 2.23.133.10.1.4 */
OID_TPMSealedData, /* 2.23.133.10.1.5 */
+ /* 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 parse_OID(const void *data, size_t datasize, enum OID *oid);
extern int sprint_oid(const void *, size_t, char *, size_t);
--
2.16.4
Add codeSigning EKU to the X.509 key generation config for the build time
autogenerated kernel key.
Signed-off-by: "Lee, Chun-Yi" <[email protected]>
---
certs/Makefile | 1 +
1 file changed, 1 insertion(+)
diff --git a/certs/Makefile b/certs/Makefile
index 359239a0ee9e..278e83d23aeb 100644
--- a/certs/Makefile
+++ b/certs/Makefile
@@ -99,6 +99,7 @@ $(obj)/x509.genkey:
@echo >>$@ "keyUsage=digitalSignature"
@echo >>$@ "subjectKeyIdentifier=hash"
@echo >>$@ "authorityKeyIdentifier=keyid"
+ @echo >>$@ "extendedKeyUsage=codeSigning"
endif # CONFIG_MODULE_SIG_KEY
$(eval $(call config_filename,MODULE_SIG_KEY))
--
2.16.4
Add an openssl command option example for generating CodeSign extended
key usage in X.509 when CONFIG_CHECK_CODESIGN_EKU is enabled.
Signed-off-by: "Lee, Chun-Yi" <[email protected]>
---
Documentation/admin-guide/module-signing.rst | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/Documentation/admin-guide/module-signing.rst b/Documentation/admin-guide/module-signing.rst
index 7d7c7c8a545c..ca3b8f19466c 100644
--- a/Documentation/admin-guide/module-signing.rst
+++ b/Documentation/admin-guide/module-signing.rst
@@ -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.
--
2.16.4