KEYS: validate certificate trust with selected owner or builtin key

Key id matching will also be used in the following patch. To avoid code duplication this patch moves functionality to a separate function.

Signed-off-by Dmitry Kasatkin <[email protected]>

---
 crypto/asymmetric_keys/asymmetric_keys.h |  2 ++
 crypto/asymmetric_keys/asymmetric_type.c | 50 ++++++++++++++++++++------------
 2 files changed, 33 insertions(+), 19 deletions(-)

crypto/asymmetric_keys/asymmetric_keys.h +2 -0

index 515b634..a63c551 100644
@@ -9,6 +9,8 @@
  * 2 of the Licence, or (at your option) any later version.
  */
 
+int asymmetric_keyid_match(const char *kid, const char *id);
+
 static inline const char *asymmetric_key_id(const struct key *key)
 {
 	return key->type_data.p[1];

crypto/asymmetric_keys/asymmetric_type.c +31 -19

index b77eb53..1fd1d30 100644
@@ -23,6 +23,34 @@ static LIST_HEAD(asymmetric_key_parsers);
 static DECLARE_RWSEM(asymmetric_key_parsers_sem);
 
 /*
+ * Match asymmetric key id with partial match
+ * @id:		key id to match in a form "id:<id>"
+ */
+int asymmetric_keyid_match(const char *kid, const char *id)
+{
+	size_t idlen, kidlen;
+
+	if (!kid || !id)
+		return 0;
+
+	/* make it possible to use id as in the request: "id:<id>" */
+	if (strncmp(id, "id:", 3) == 0)
+		id += 3;
+
+	/* Anything after here requires a partial match on the ID string */
+	idlen = strlen(id);
+	kidlen = strlen(kid);
+	if (idlen > kidlen)
+		return 0;
+
+	kid += kidlen - idlen;
+	if (strcasecmp(id, kid) != 0)
+		return 0;
+
+	return 1;
+}
+
+/*
  * Match asymmetric keys on (part of) their name
  * We have some shorthand methods for matching keys.  We allow:
  *

@@ -34,9 +62,8 @@ static int asymmetric_key_match(const struct key *key, const void *description)
 {
 	const struct asymmetric_key_subtype *subtype = asymmetric_key_subtype(key);
 	const char *spec = description;
-	const char *id, *kid;
+	const char *id;
 	ptrdiff_t speclen;
-	size_t idlen, kidlen;
 
 	if (!subtype || !spec || !*spec)
 		return 0;

@@ -55,23 +82,8 @@ static int asymmetric_key_match(const struct key *key, const void *description)
 	speclen = id - spec;
 	id++;
 
-	/* Anything after here requires a partial match on the ID string */
-	kid = asymmetric_key_id(key);
-	if (!kid)
-		return 0;
-
-	idlen = strlen(id);
-	kidlen = strlen(kid);
-	if (idlen > kidlen)
-		return 0;
-
-	kid += kidlen - idlen;
-	if (strcasecmp(id, kid) != 0)
-		return 0;
-
-	if (speclen == 2 &&
-	    memcmp(spec, "id", 2) == 0)
-		return 1;
+	if (speclen == 2 && memcmp(spec, "id", 2) == 0)
+		return asymmetric_keyid_match(asymmetric_key_id(key), id);
 
 	if (speclen == subtype->name_len &&
 	    memcmp(spec, subtype->name, speclen) == 0)

Instead of allowing public keys, with certificates signed by any key on the system trusted keyring, to be added to a trusted keyring, this patch set further restricts the certificates to those signed by a particular key or builtin keys on the system keyring.

This patch defines a new kernel parameter 'keys_ownerid={id: | builtin}' to use specific key or any builtin key.

Changes to v1:
* key id matching code from asymmetric_type.c is reused in the patch