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(-)
--
2.16.4
This patch adds the logic for checking the CodeSigning extended
key usage when verifying signature of kernel module or
kexec PE binary in PKCS#7.
Signed-off-by: "Lee, Chun-Yi" <[email protected]>
---
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(-)
diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index 4b693da488f1..c9f8bca0b0d3 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -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");
diff --git a/crypto/asymmetric_keys/Kconfig b/crypto/asymmetric_keys/Kconfig
index 1f1f004dc757..1754812df989 100644
--- a/crypto/asymmetric_keys/Kconfig
+++ b/crypto/asymmetric_keys/Kconfig
@@ -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
diff --git a/crypto/asymmetric_keys/pkcs7_trust.c b/crypto/asymmetric_keys/pkcs7_trust.c
index b531df2013c4..077bfef928b6 100644
--- a/crypto/asymmetric_keys/pkcs7_trust.c
+++ b/crypto/asymmetric_keys/pkcs7_trust.c
@@ -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;
diff --git a/include/crypto/pkcs7.h b/include/crypto/pkcs7.h
index 38ec7f5f9041..b3b48240ba73 100644
--- a/include/crypto/pkcs7.h
+++ b/include/crypto/pkcs7.h
@@ -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
--
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 f4c25b67aad9..1ef4d6ca43b7 100644
--- a/certs/Makefile
+++ b/certs/Makefile
@@ -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))
--
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