linux-kernel - [PATCH v2 07/10] KEYS: X.509: Flag Intermediate CA certs as endorsed

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Message-Id: <20221207171238.2945307-8-eric.snowberg@oracle.com>
Date:   Wed,  7 Dec 2022 12:12:35 -0500
From:   Eric Snowberg <eric.snowberg@...cle.com>
To:     jarkko@...nel.org, zohar@...ux.ibm.com
Cc:     dhowells@...hat.com, dwmw2@...radead.org,
        herbert@...dor.apana.org.au, davem@...emloft.net,
        dmitry.kasatkin@...il.com, paul@...l-moore.com, jmorris@...ei.org,
        serge@...lyn.com, pvorel@...e.cz, noodles@...com, tiwai@...e.de,
        bp@...e.de, eric.snowberg@...cle.com, kanth.ghatraju@...cle.com,
        konrad.wilk@...cle.com, erpalmer@...ux.vnet.ibm.com,
        coxu@...hat.com, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: [PATCH v2 07/10] KEYS: X.509: Flag Intermediate CA certs as endorsed

Currently X.509 Intermediate CA certs do not have the endorsed CA
(KEY_FLAG_ECA) 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 endorsed CA.

Signed-off-by: Eric Snowberg <eric.snowberg@...cle.com>
---
 crypto/asymmetric_keys/x509_public_key.c | 14 ++++++++++++--
 include/linux/ima.h                      | 11 +++++++++++
 include/linux/key-type.h                 |  1 +
 security/keys/key.c                      |  5 +++++
 4 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index 64cffedc4dd0..7a87d5c0c32b 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -208,8 +208,18 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
 		goto error_free_kids;
 	}
 
-	if (cert->kcs_set && cert->self_signed && cert->root_ca)
-		prep->payload_flags |= KEY_ALLOC_PECA;
+	if (cert->kcs_set) {
+		if (cert->self_signed && cert->root_ca)
+			prep->payload_flags |= KEY_ALLOC_PECA;
+		/*
+		 * In this case it could be an Intermediate CA.  Set
+		 * KEY_MAYBE_PECA for now.  If the restriction check
+		 * passes later, the key will be allocated with the
+		 * correct CA flag
+		 */
+		else if (!cert->self_signed && !cert->root_ca)
+			prep->payload_flags |= KEY_MAYBE_PECA;
+	}
 
 	/* We're pinning the module by being linked against it */
 	__module_get(public_key_subtype.owner);
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 81708ca0ebc7..6597081b6b1a 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
@@ -181,6 +182,16 @@ 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_ca restrict_link_by_ca_builtin_and_secondary_trusted
+#else
+#define ima_validate_builtin_ca restrict_link_by_ca_builtin_trusted
+#endif
+#else
+#define ima_validate_builtin_ca restrict_link_reject
+#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 0b500578441c..0d2f95f6b8a1 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_PECA	0x0001		/* Proposed Endorsed CA (ECA) key */
+#define KEY_MAYBE_PECA	0x0002		/* Proposed possible ECA 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 e6b4946aca70..69d5f143683f 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 endorsed ca */
+	if ((prep.payload_flags & KEY_MAYBE_PECA) &&
+	   !(ima_validate_builtin_ca(keyring, index_key.type, &prep.payload, NULL)))
+		prep.payload_flags |= KEY_ALLOC_PECA;
+
 	/* 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