[PATCH 6/7] KEYS: X.509: Flag Intermediate CA certs as built in

[Eric Snowberg]

Currently X.509 Intermediate CA certs do not have the builtin root of trust
key flag set. Allow intermediate CA certs to be added.  Requirements for an
intermediate CA include: Usage extension defined as keyCertSign, Basic
Constrains for CA is false, and Intermediate CA cert is signed by a current
builtin ROT key.

Signed-off-by: Eric Snowberg <eric.snowberg@xxxxxxxxxx>
---
 crypto/asymmetric_keys/x509_public_key.c | 14 ++++++++++++--
 include/linux/ima.h                      | 16 ++++++++++++++++
 include/linux/key-type.h                 |  1 +
 security/keys/key.c                      |  5 +++++
 4 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index 7290e765f46b..9052dd761ea3 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -215,8 +215,18 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
 	prep->payload.data[asym_auth] = cert->sig;
 	prep->description = desc;
 	prep->quotalen = 100;
-	if (cert->is_kcs_set && cert->self_signed && cert->is_root_ca)
-		prep->payload_flags |= KEY_ALLOC_ROT;
+	if (cert->is_kcs_set) {
+		if (cert->self_signed && cert->is_root_ca)
+			prep->payload_flags |= KEY_ALLOC_ROT;
+		/*
+		 * In this case it could be an Intermediate CA.  Set
+		 * KEY_MAYBE_ROT for now.  If the restriction check
+		 * passes later, the key will be allocated with the
+		 * correct ROT flag.
+		 */
+		else if (!cert->self_signed && !cert->is_root_ca)
+			prep->payload_flags |= KEY_MAYBE_ROT;
+	}
 
 	/* We've finished with the certificate */
 	cert->pub = NULL;
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 426b1744215e..3f23bccf880a 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -12,6 +12,7 @@
 #include <linux/security.h>
 #include <linux/kexec.h>
 #include <crypto/hash_info.h>
+#include <keys/system_keyring.h>
 struct linux_binprm;
 
 #ifdef CONFIG_IMA
@@ -176,6 +177,21 @@ static inline void ima_post_key_create_or_update(struct key *keyring,
 						 bool create) {}
 #endif  /* CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS */
 
+#ifdef CONFIG_ASYMMETRIC_KEY_TYPE
+#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
+#define ima_validate_builtin_rot restrict_link_by_rot_builtin_and_secondary_trusted
+#else
+#define ima_validate_builtin_rot restrict_link_by_rot_builtin_trusted
+#endif
+#else
+static inline int ima_validate_builtin_rot(struct key *dest_keyring,
+					   const struct key_type *type,
+					   const union key_payload *payload,
+					   struct key *unused){
+	return -EPERM;
+}
+#endif
+
 #ifdef CONFIG_IMA_APPRAISE
 extern bool is_ima_appraise_enabled(void);
 extern void ima_inode_post_setattr(struct user_namespace *mnt_userns,
diff --git a/include/linux/key-type.h b/include/linux/key-type.h
index ed0aaad3849b..da09e68903e2 100644
--- a/include/linux/key-type.h
+++ b/include/linux/key-type.h
@@ -38,6 +38,7 @@ struct key_preparsed_payload {
 	time64_t	expiry;		/* Expiry time of key */
 	unsigned int	payload_flags;  /* Proposed payload flags */
 #define KEY_ALLOC_ROT	0x0001		/* Proposed Root of Trust (ROT) key */
+#define KEY_MAYBE_ROT	0x0002		/* Proposed possible Root of Trust key */
 } __randomize_layout;
 
 typedef int (*request_key_actor_t)(struct key *auth_key, void *aux);
diff --git a/security/keys/key.c b/security/keys/key.c
index 732bb837fc51..c553040dcc02 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -900,6 +900,11 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 		}
 	}
 
+	/* Previous restriction check passed therefore try to validate root of trust */
+	if ((prep.payload_flags & KEY_MAYBE_ROT) &&
+	   !(ima_validate_builtin_rot(keyring, index_key.type, &prep.payload, NULL)))
+		prep.payload_flags |= KEY_ALLOC_ROT;
+
 	/* if we're going to allocate a new key, we're going to have
 	 * to modify the keyring */
 	ret = key_permission(keyring_ref, KEY_NEED_WRITE);
-- 
2.27.0