Merge branch 'keys-sig' into keys-next

These commits do the following:

 (1) Retain a signature in an asymmetric-type key and associate with it the
     identifiers that will match a key that can be used to verify it.

 (2) Differentiate an X.509 cert that cannot be used versus one that cannot
     be verified due to unavailable crypto.  This is noted in the
     structures involved.

 (3) Determination of the self-signedness of an X.509 cert is improved to
     include checks on the subject/issuer names and the key
     algorithm/signature algorithm types.

 (4) Self-signed X.509 certificates are consistency checked early on if the
     appropriate crypto is available.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 119 insertions, 63 deletions

diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index 733c046aacc6..fc77a2bd70ba 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -88,7 +88,7 @@ struct key *x509_request_asymmetric_key(struct key *keyring,
 		lookup = skid->data;
 		len = skid->len;
 	}
-	
+
 	/* Construct an identifier "id:<keyid>". */
 	p = req = kmalloc(2 + 1 + len * 2 + 1, GFP_KERNEL);
 	if (!req)
@@ -137,7 +137,7 @@ struct key *x509_request_asymmetric_key(struct key *keyring,
 			goto reject;
 		}
 	}
-	
+
 	pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key));
 	return key;
 
@@ -153,90 +153,128 @@ EXPORT_SYMBOL_GPL(x509_request_asymmetric_key);
  */
 int x509_get_sig_params(struct x509_certificate *cert)
 {
+	struct public_key_signature *sig = cert->sig;
 	struct crypto_shash *tfm;
 	struct shash_desc *desc;
-	size_t digest_size, desc_size;
-	void *digest;
+	size_t desc_size;
 	int ret;
 
 	pr_devel("==>%s()\n", __func__);
 
-	if (cert->unsupported_crypto)
-		return -ENOPKG;
-	if (cert->sig.s)
+	if (!cert->pub->pkey_algo)
+		cert->unsupported_key = true;
+
+	if (!sig->pkey_algo)
+		cert->unsupported_sig = true;
+
+	/* We check the hash if we can - even if we can't then verify it */
+	if (!sig->hash_algo) {
+		cert->unsupported_sig = true;
 		return 0;
+	}
 
-	cert->sig.s = kmemdup(cert->raw_sig, cert->raw_sig_size,
-			      GFP_KERNEL);
-	if (!cert->sig.s)
+	sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
+	if (!sig->s)
 		return -ENOMEM;
 
-	cert->sig.s_size = cert->raw_sig_size;
+	sig->s_size = cert->raw_sig_size;
 
 	/* Allocate the hashing algorithm we're going to need and find out how
 	 * big the hash operational data will be.
 	 */
-	tfm = crypto_alloc_shash(cert->sig.hash_algo, 0, 0);
+	tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
 	if (IS_ERR(tfm)) {
 		if (PTR_ERR(tfm) == -ENOENT) {
-			cert->unsupported_crypto = true;
-			return -ENOPKG;
+			cert->unsupported_sig = true;
+			return 0;
 		}
 		return PTR_ERR(tfm);
 	}
 
 	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
-	digest_size = crypto_shash_digestsize(tfm);
+	sig->digest_size = crypto_shash_digestsize(tfm);
 
-	/* We allocate the hash operational data storage on the end of the
-	 * digest storage space.
-	 */
 	ret = -ENOMEM;
-	digest = kzalloc(ALIGN(digest_size, __alignof__(*desc)) + desc_size,
-			 GFP_KERNEL);
-	if (!digest)
+	sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
+	if (!sig->digest)
 		goto error;
 
-	cert->sig.digest = digest;
-	cert->sig.digest_size = digest_size;
+	desc = kzalloc(desc_size, GFP_KERNEL);
+	if (!desc)
+		goto error;
 
-	desc = PTR_ALIGN(digest + digest_size, __alignof__(*desc));
 	desc->tfm = tfm;
 	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 
 	ret = crypto_shash_init(desc);
 	if (ret < 0)
-		goto error;
+		goto error_2;
 	might_sleep();
-	ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
+	ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, sig->digest);
+
+error_2:
+	kfree(desc);
 error:
 	crypto_free_shash(tfm);
 	pr_devel("<==%s() = %d\n", __func__, ret);
 	return ret;
 }
-EXPORT_SYMBOL_GPL(x509_get_sig_params);
 
 /*
- * Check the signature on a certificate using the provided public key
+ * Check for self-signedness in an X.509 cert and if found, check the signature
+ * immediately if we can.
  */
-int x509_check_signature(const struct public_key *pub,
-			 struct x509_certificate *cert)
+int x509_check_for_self_signed(struct x509_certificate *cert)
 {
-	int ret;
+	int ret = 0;
 
 	pr_devel("==>%s()\n", __func__);
 
-	ret = x509_get_sig_params(cert);
-	if (ret < 0)
-		return ret;
+	if (cert->raw_subject_size != cert->raw_issuer_size ||
+	    memcmp(cert->raw_subject, cert->raw_issuer,
+		   cert->raw_issuer_size) != 0)
+		goto not_self_signed;
+
+	if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
+		/* If the AKID is present it may have one or two parts.  If
+		 * both are supplied, both must match.
+		 */
+		bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
+		bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);
+
+		if (!a && !b)
+			goto not_self_signed;
+
+		ret = -EKEYREJECTED;
+		if (((a && !b) || (b && !a)) &&
+		    cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
+			goto out;
+	}
 
-	ret = public_key_verify_signature(pub, &cert->sig);
-	if (ret == -ENOPKG)
-		cert->unsupported_crypto = true;
-	pr_debug("Cert Verification: %d\n", ret);
+	ret = -EKEYREJECTED;
+	if (cert->pub->pkey_algo != cert->sig->pkey_algo)
+		goto out;
+
+	ret = public_key_verify_signature(cert->pub, cert->sig);
+	if (ret < 0) {
+		if (ret == -ENOPKG) {
+			cert->unsupported_sig = true;
+			ret = 0;
+		}
+		goto out;
+	}
+
+	pr_devel("Cert Self-signature verified");
+	cert->self_signed = true;
+
+out:
+	pr_devel("<==%s() = %d\n", __func__, ret);
 	return ret;
+
+not_self_signed:
+	pr_devel("<==%s() = 0 [not]\n", __func__);
+	return 0;
 }
-EXPORT_SYMBOL_GPL(x509_check_signature);
 
 /*
  * Check the new certificate against the ones in the trust keyring.  If one of
@@ -250,25 +288,34 @@ EXPORT_SYMBOL_GPL(x509_check_signature);
 static int x509_validate_trust(struct x509_certificate *cert,
 			       struct key *trust_keyring)
 {
+	struct public_key_signature *sig = cert->sig;
 	struct key *key;
 	int ret = 1;
 
+	if (!sig->auth_ids[0] && !sig->auth_ids[1])
+		return 1;
+
 	if (!trust_keyring)
 		return -EOPNOTSUPP;
-
-	if (ca_keyid && !asymmetric_key_id_partial(cert->akid_skid, ca_keyid))
+	if (ca_keyid && !asymmetric_key_id_partial(sig->auth_ids[1], ca_keyid))
 		return -EPERM;
+	if (cert->unsupported_sig)
+		return -ENOPKG;
 
 	key = x509_request_asymmetric_key(trust_keyring,
-					  cert->akid_id, cert->akid_skid,
+					  sig->auth_ids[0], sig->auth_ids[1],
 					  false);
-	if (!IS_ERR(key))  {
-		if (!use_builtin_keys
-		    || test_bit(KEY_FLAG_BUILTIN, &key->flags))
-			ret = x509_check_signature(key->payload.data[asym_crypto],
-						   cert);
-		key_put(key);
+	if (IS_ERR(key))
+		return PTR_ERR(key);
+
+	if (!use_builtin_keys ||
+	    test_bit(KEY_FLAG_BUILTIN, &key->flags)) {
+		ret = public_key_verify_signature(
+			key->payload.data[asym_crypto], cert->sig);
+		if (ret == -ENOPKG)
+			cert->unsupported_sig = true;
 	}
+	key_put(key);
 	return ret;
 }
 
@@ -291,34 +338,41 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
 	pr_devel("Cert Issuer: %s\n", cert->issuer);
 	pr_devel("Cert Subject: %s\n", cert->subject);
 
-	if (!cert->pub->pkey_algo ||
-	    !cert->sig.pkey_algo ||
-	    !cert->sig.hash_algo) {
+	if (cert->unsupported_key) {
 		ret = -ENOPKG;
 		goto error_free_cert;
 	}
 
 	pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
 	pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
-	pr_devel("Cert Signature: %s + %s\n",
-		 cert->sig.pkey_algo,
-		 cert->sig.hash_algo);
 
 	cert->pub->id_type = "X509";
 
-	/* Check the signature on the key if it appears to be self-signed */
-	if ((!cert->akid_skid && !cert->akid_id) ||
-	    asymmetric_key_id_same(cert->skid, cert->akid_skid) ||
-	    asymmetric_key_id_same(cert->id, cert->akid_id)) {
-		ret = x509_check_signature(cert->pub, cert); /* self-signed */
-		if (ret < 0)
-			goto error_free_cert;
-	} else if (!prep->trusted) {
+	/* See if we can derive the trustability of this certificate.
+	 *
+	 * When it comes to self-signed certificates, we cannot evaluate
+	 * trustedness except by the fact that we obtained it from a trusted
+	 * location.  So we just rely on x509_validate_trust() failing in this
+	 * case.
+	 *
+	 * Note that there's a possibility of a self-signed cert matching a
+	 * cert that we have (most likely a duplicate that we already trust) -
+	 * in which case it will be marked trusted.
+	 */
+	if (cert->unsupported_sig || cert->self_signed) {
+		public_key_signature_free(cert->sig);
+		cert->sig = NULL;
+	} else {
+		pr_devel("Cert Signature: %s + %s\n",
+			 cert->sig->pkey_algo, cert->sig->hash_algo);
+
 		ret = x509_validate_trust(cert, get_system_trusted_keyring());
 		if (ret)
 			ret = x509_validate_trust(cert, get_ima_mok_keyring());
+		if (ret == -EKEYREJECTED)
+			goto error_free_cert;
 		if (!ret)
-			prep->trusted = 1;
+			prep->trusted = true;
 	}
 
 	/* Propose a description */
@@ -353,6 +407,7 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
 	prep->payload.data[asym_subtype] = &public_key_subtype;
 	prep->payload.data[asym_key_ids] = kids;
 	prep->payload.data[asym_crypto] = cert->pub;
+	prep->payload.data[asym_auth] = cert->sig;
 	prep->description = desc;
 	prep->quotalen = 100;
 
@@ -360,6 +415,7 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
 	cert->pub = NULL;
 	cert->id = NULL;
 	cert->skid = NULL;
+	cert->sig = NULL;
 	desc = NULL;
 	ret = 0;