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" <jlee@xxxxxxxx>
---
certs/blacklist.c | 6 +++--
certs/system_keyring.c | 4 ++--
crypto/asymmetric_keys/Kconfig | 9 ++++++++
crypto/asymmetric_keys/pkcs7_trust.c | 43 +++++++++++++++++++++++++++++++++---
include/crypto/pkcs7.h | 4 +++-
include/keys/system_keyring.h | 7 ++++--
6 files changed, 63 insertions(+), 10 deletions(-)
diff --git a/certs/blacklist.c b/certs/blacklist.c
index c9a435b15af4..a4ef26286584 100644
--- a/certs/blacklist.c
+++ b/certs/blacklist.c
@@ -16,6 +16,7 @@
#include <linux/seq_file.h>
#include <linux/uidgid.h>
#include <keys/system_keyring.h>
+#include <keys/asymmetric-type.h>
#include "blacklist.h"
#include "common.h"
@@ -181,11 +182,12 @@ int add_key_to_revocation_list(const char *data, size_t size)
* is_key_on_revocation_list - Determine if the key for a PKCS#7 message is revoked
* @pkcs7: The PKCS#7 message to check
*/
-int is_key_on_revocation_list(struct pkcs7_message *pkcs7)
+int is_key_on_revocation_list(struct pkcs7_message *pkcs7,
+ enum key_being_used_for usage)
{
int ret;
- ret = pkcs7_validate_trust(pkcs7, blacklist_keyring);
+ ret = pkcs7_validate_trust(pkcs7, blacklist_keyring, usage, false);
if (ret == 0)
return -EKEYREJECTED;
diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index 692365dee2bd..394cf4e0feed 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -221,13 +221,13 @@ int verify_pkcs7_message_sig(const void *data, size_t len,
goto error;
}
- ret = is_key_on_revocation_list(pkcs7);
+ ret = is_key_on_revocation_list(pkcs7, usage);
if (ret != -ENOKEY) {
pr_devel("PKCS#7 platform key is on revocation list\n");
goto error;
}
}
- ret = pkcs7_validate_trust(pkcs7, trusted_keys);
+ ret = pkcs7_validate_trust(pkcs7, trusted_keys, usage, true);
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..c6ebf3e6adfd 100644
--- a/crypto/asymmetric_keys/pkcs7_trust.c
+++ b/crypto/asymmetric_keys/pkcs7_trust.c
@@ -16,12 +16,40 @@
#include <crypto/public_key.h>
#include "pkcs7_parser.h"
+#ifdef CONFIG_CHECK_CODESIGN_EKU
+static bool check_eku_by_usage(struct key *key, enum key_being_used_for usage)
+{
+ struct public_key *public_key = key->payload.data[asym_crypto];
+ bool ret = true;
+
+ switch (usage) {
+ case VERIFYING_MODULE_SIGNATURE:
+ case VERIFYING_KEXEC_PE_SIGNATURE:
+ ret = !!(public_key->eku & EKU_codeSigning);
+ if (!ret)
+ pr_warn("The signer '%s' key is not CodeSigning\n",
+ key->description);
+ break;
+ default:
+ break;
+ }
+ return ret;
+}
+#else
+static bool check_eku_by_usage(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,
+ bool check_eku)
{
struct public_key_signature *sig = sinfo->sig;
struct x509_certificate *x509, *last = NULL, *p;
@@ -112,6 +140,10 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,
return -ENOKEY;
matched:
+ if (check_eku && !check_eku_by_usage(key, usage)) {
+ key_put(key);
+ return -ENOKEY;
+ }
ret = verify_signature(key, sig);
key_put(key);
if (ret < 0) {
@@ -135,6 +167,8 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,
* pkcs7_validate_trust - Validate PKCS#7 trust chain
* @pkcs7: The PKCS#7 certificate to validate
* @trust_keyring: Signing certificates to use as starting points
+ * @usage: The use to which the key is being put.
+ * @check_eku: Check EKU (Extended Key Usage)
*
* Validate that the certificate chain inside the PKCS#7 message intersects
* keys we already know and trust.
@@ -156,7 +190,9 @@ 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,
+ bool check_eku)
{
struct pkcs7_signed_info *sinfo;
struct x509_certificate *p;
@@ -167,7 +203,8 @@ 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, check_eku);
switch (ret) {
case -ENOKEY:
continue;
diff --git a/include/crypto/pkcs7.h b/include/crypto/pkcs7.h
index 38ec7f5f9041..5d87b8a02f79 100644
--- a/include/crypto/pkcs7.h
+++ b/include/crypto/pkcs7.h
@@ -30,7 +30,9 @@ 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,
+ bool check_eku);
/*
* pkcs7_verify.c
diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
index 6acd3cf13a18..3da982c3aef5 100644
--- a/include/keys/system_keyring.h
+++ b/include/keys/system_keyring.h
@@ -9,6 +9,7 @@
#define _KEYS_SYSTEM_KEYRING_H
#include <linux/key.h>
+#include <keys/asymmetric-type.h>
#ifdef CONFIG_SYSTEM_TRUSTED_KEYRING
@@ -59,13 +60,15 @@ static inline int is_binary_blacklisted(const u8 *hash, size_t hash_len)
#ifdef CONFIG_SYSTEM_REVOCATION_LIST
extern int add_key_to_revocation_list(const char *data, size_t size);
-extern int is_key_on_revocation_list(struct pkcs7_message *pkcs7);
+extern int is_key_on_revocation_list(struct pkcs7_message *pkcs7,
+ enum key_being_used_for usage);
#else
static inline int add_key_to_revocation_list(const char *data, size_t size)
{
return 0;
}
-static inline int is_key_on_revocation_list(struct pkcs7_message *pkcs7)
+static inline int is_key_on_revocation_list(struct pkcs7_message *pkcs7,
+ enum key_being_used_for usage);
{
return -ENOKEY;
}
--
2.16.4
