KEYS: Restore partial ID matching functionality for asymmetric keys

Bring back the functionality whereby an asymmetric key can be matched with a
partial match on one of its IDs.

Whilst we're at it, allow for the possibility of having an increased number of
IDs.

Reported-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: David Howells <dhowells@redhat.com>

6 files changed, 81 insertions, 25 deletions

diff --git a/crypto/asymmetric_keys/asymmetric_keys.h b/crypto/asymmetric_keys/asymmetric_keys.h
index fd21ac2..f973308 100644
--- a/crypto/asymmetric_keys/asymmetric_keys.h
+++ b/crypto/asymmetric_keys/asymmetric_keys.h
@@ -9,9 +9,6 @@
  * 2 of the Licence, or (at your option) any later version.
  */
 
-extern bool asymmetric_match_key_ids(const struct asymmetric_key_ids *kids,
-				     const struct asymmetric_key_id *match_id);
-
 extern struct asymmetric_key_id *asymmetric_key_hex_to_key_id(const char *id);
 
 static inline
diff --git a/crypto/asymmetric_keys/asymmetric_type.c b/crypto/asymmetric_keys/asymmetric_type.c
index 29983cbb..052e944 100644
--- a/crypto/asymmetric_keys/asymmetric_type.c
+++ b/crypto/asymmetric_keys/asymmetric_type.c
@@ -66,22 +66,43 @@ bool asymmetric_key_id_same(const struct asymmetric_key_id *kid1,
 EXPORT_SYMBOL_GPL(asymmetric_key_id_same);
 
 /**
+ * asymmetric_key_id_partial - Return true if two asymmetric keys IDs
+ * partially match
+ * @kid_1, @kid_2: The key IDs to compare
+ */
+bool asymmetric_key_id_partial(const struct asymmetric_key_id *kid1,
+			       const struct asymmetric_key_id *kid2)
+{
+	if (!kid1 || !kid2)
+		return false;
+	if (kid1->len < kid2->len)
+		return false;
+	return memcmp(kid1->data + (kid1->len - kid2->len),
+		      kid2->data, kid2->len) == 0;
+}
+EXPORT_SYMBOL_GPL(asymmetric_key_id_partial);
+
+/**
  * asymmetric_match_key_ids - Search asymmetric key IDs
  * @kids: The list of key IDs to check
  * @match_id: The key ID we're looking for
+ * @match: The match function to use
  */
-bool asymmetric_match_key_ids(const struct asymmetric_key_ids *kids,
-			      const struct asymmetric_key_id *match_id)
+static bool asymmetric_match_key_ids(
+	const struct asymmetric_key_ids *kids,
+	const struct asymmetric_key_id *match_id,
+	bool (*match)(const struct asymmetric_key_id *kid1,
+		      const struct asymmetric_key_id *kid2))
 {
+	int i;
+
 	if (!kids || !match_id)
 		return false;
-	if (asymmetric_key_id_same(kids->id[0], match_id))
-		return true;
-	if (asymmetric_key_id_same(kids->id[1], match_id))
-		return true;
+	for (i = 0; i < ARRAY_SIZE(kids->id); i++)
+		if (match(kids->id[i], match_id))
+			return true;
 	return false;
 }
-EXPORT_SYMBOL_GPL(asymmetric_match_key_ids);
 
 /**
  * asymmetric_key_hex_to_key_id - Convert a hex string into a key ID.
@@ -113,7 +134,7 @@ struct asymmetric_key_id *asymmetric_key_hex_to_key_id(const char *id)
 }
 
 /*
- * Match asymmetric keys by ID.
+ * Match asymmetric keys by an exact match on an ID.
  */
 static bool asymmetric_key_cmp(const struct key *key,
 			       const struct key_match_data *match_data)
@@ -121,7 +142,21 @@ static bool asymmetric_key_cmp(const struct key *key,
 	const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
 	const struct asymmetric_key_id *match_id = match_data->preparsed;
 
-	return asymmetric_match_key_ids(kids, match_id);
+	return asymmetric_match_key_ids(kids, match_id,
+					asymmetric_key_id_same);
+}
+
+/*
+ * Match asymmetric keys by a partial match on an IDs.
+ */
+static bool asymmetric_key_cmp_partial(const struct key *key,
+				       const struct key_match_data *match_data)
+{
+	const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
+	const struct asymmetric_key_id *match_id = match_data->preparsed;
+
+	return asymmetric_match_key_ids(kids, match_id,
+					asymmetric_key_id_partial);
 }
 
 /*
@@ -131,7 +166,8 @@ static bool asymmetric_key_cmp(const struct key *key,
  * There are some specifiers for matching key IDs rather than by the key
  * description:
  *
- *	"id:<id>" - request a key by any available ID
+ *	"id:<id>" - find a key by partial match on any available ID
+ *	"ex:<id>" - find a key by exact match on any available ID
  *
  * These have to be searched by iteration rather than by direct lookup because
  * the key is hashed according to its description.
@@ -141,6 +177,8 @@ static int asymmetric_key_match_preparse(struct key_match_data *match_data)
 	struct asymmetric_key_id *match_id;
 	const char *spec = match_data->raw_data;
 	const char *id;
+	bool (*cmp)(const struct key *, const struct key_match_data *) =
+		asymmetric_key_cmp;
 
 	if (!spec || !*spec)
 		return -EINVAL;
@@ -148,6 +186,11 @@ static int asymmetric_key_match_preparse(struct key_match_data *match_data)
 	    spec[1] == 'd' &&
 	    spec[2] == ':') {
 		id = spec + 3;
+		cmp = asymmetric_key_cmp_partial;
+	} else if (spec[0] == 'e' &&
+		   spec[1] == 'x' &&
+		   spec[2] == ':') {
+		id = spec + 3;
 	} else {
 		goto default_match;
 	}
@@ -157,7 +200,7 @@ static int asymmetric_key_match_preparse(struct key_match_data *match_data)
 		return PTR_ERR(match_id);
 
 	match_data->preparsed = match_id;
-	match_data->cmp = asymmetric_key_cmp;
+	match_data->cmp = cmp;
 	match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE;
 	return 0;
 
@@ -251,6 +294,7 @@ static void asymmetric_key_free_preparse(struct key_preparsed_payload *prep)
 {
 	struct asymmetric_key_subtype *subtype = prep->type_data[0];
 	struct asymmetric_key_ids *kids = prep->type_data[1];
+	int i;
 
 	pr_devel("==>%s()\n", __func__);
 
@@ -259,8 +303,8 @@ static void asymmetric_key_free_preparse(struct key_preparsed_payload *prep)
 		module_put(subtype->owner);
 	}
 	if (kids) {
-		kfree(kids->id[0]);
-		kfree(kids->id[1]);
+		for (i = 0; i < ARRAY_SIZE(kids->id); i++)
+			kfree(kids->id[i]);
 		kfree(kids);
 	}
 	kfree(prep->description);
diff --git a/crypto/asymmetric_keys/pkcs7_trust.c b/crypto/asymmetric_keys/pkcs7_trust.c
index ae47be6..1d29376 100644
--- a/crypto/asymmetric_keys/pkcs7_trust.c
+++ b/crypto/asymmetric_keys/pkcs7_trust.c
@@ -54,7 +54,8 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,
 		/* Look to see if this certificate is present in the trusted
 		 * keys.
 		 */
-		key = x509_request_asymmetric_key(trust_keyring, x509->id);
+		key = x509_request_asymmetric_key(trust_keyring, x509->id,
+						  false);
 		if (!IS_ERR(key)) {
 			/* One of the X.509 certificates in the PKCS#7 message
 			 * is apparently the same as one we already trust.
@@ -85,7 +86,8 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,
 	 * trusted keys.
 	 */
 	if (last && last->authority) {
-		key = x509_request_asymmetric_key(trust_keyring, last->authority);
+		key = x509_request_asymmetric_key(trust_keyring, last->authority,
+						  false);
 		if (!IS_ERR(key)) {
 			x509 = last;
 			pr_devel("sinfo %u: Root cert %u signer is key %x\n",
@@ -100,7 +102,8 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,
 	 * the signed info directly.
 	 */
 	key = x509_request_asymmetric_key(trust_keyring,
-					  sinfo->signing_cert_id);
+					  sinfo->signing_cert_id,
+					  false);
 	if (!IS_ERR(key)) {
 		pr_devel("sinfo %u: Direct signer is key %x\n",
 			 sinfo->index, key_serial(key));
diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index 8bffb06..6ef5449 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -53,13 +53,15 @@ __setup("ca_keys=", ca_keys_setup);
  * x509_request_asymmetric_key - Request a key by X.509 certificate params.
  * @keyring: The keys to search.
  * @kid: The key ID.
+ * @partial: Use partial match if true, exact if false.
  *
  * Find a key in the given keyring by subject name and key ID.  These might,
  * for instance, be the issuer name and the authority key ID of an X.509
  * certificate that needs to be verified.
  */
 struct key *x509_request_asymmetric_key(struct key *keyring,
-					const struct asymmetric_key_id *kid)
+					const struct asymmetric_key_id *kid,
+					bool partial)
 {
 	key_ref_t key;
 	char *id, *p;
@@ -69,8 +71,13 @@ struct key *x509_request_asymmetric_key(struct key *keyring,
 	if (!id)
 		return ERR_PTR(-ENOMEM);
 
-	*p++ = 'i';
-	*p++ = 'd';
+	if (partial) {
+		*p++ = 'i';
+		*p++ = 'd';
+	} else {
+		*p++ = 'e';
+		*p++ = 'x';
+	}
 	*p++ = ':';
 	p = bin2hex(p, kid->data, kid->len);
 	*p = 0;
@@ -207,10 +214,11 @@ static int x509_validate_trust(struct x509_certificate *cert,
 	if (!trust_keyring)
 		return -EOPNOTSUPP;
 
-	if (ca_keyid && !asymmetric_key_id_same(cert->authority, ca_keyid))
+	if (ca_keyid && !asymmetric_key_id_partial(cert->authority, ca_keyid))
 		return -EPERM;
 
-	key = x509_request_asymmetric_key(trust_keyring, cert->authority);
+	key = x509_request_asymmetric_key(trust_keyring, cert->authority,
+					  false);
 	if (!IS_ERR(key))  {
 		if (!use_builtin_keys
 		    || test_bit(KEY_FLAG_BUILTIN, &key->flags))
diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
index fa73a6f..54add20 100644
--- a/include/crypto/public_key.h
+++ b/include/crypto/public_key.h
@@ -101,6 +101,7 @@ extern int verify_signature(const struct key *key,
 
 struct asymmetric_key_id;
 extern struct key *x509_request_asymmetric_key(struct key *keyring,
-					       const struct asymmetric_key_id *kid);
+					       const struct asymmetric_key_id *kid,
+					       bool partial);
 
 #endif /* _LINUX_PUBLIC_KEY_H */
diff --git a/include/keys/asymmetric-type.h b/include/keys/asymmetric-type.h
index 044ab0d..c0754ab 100644
--- a/include/keys/asymmetric-type.h
+++ b/include/keys/asymmetric-type.h
@@ -51,6 +51,9 @@ struct asymmetric_key_ids {
 extern bool asymmetric_key_id_same(const struct asymmetric_key_id *kid1,
 				   const struct asymmetric_key_id *kid2);
 
+extern bool asymmetric_key_id_partial(const struct asymmetric_key_id *kid1,
+				      const struct asymmetric_key_id *kid2);
+
 extern struct asymmetric_key_id *asymmetric_key_generate_id(const void *val_1,
 							    size_t len_1,
 							    const void *val_2,