KEYS: make partial key id matching as a dedicated function

To avoid code duplication this patch refactors asymmetric_key_match(),
making partial ID string match a separate function.

This patch also implicitly fixes a bug in the code.  asymmetric_key_match()
allows to match the key by its subtype. But subtype matching could be
undone if asymmetric_key_id(key) would return NULL. This patch first
checks for matching spec and then for its value.

Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

2 files changed, 33 insertions, 19 deletions

diff --git a/crypto/asymmetric_keys/asymmetric_keys.h b/crypto/asymmetric_keys/asymmetric_keys.h
index 515b63430812..a63c551c6557 100644
--- a/crypto/asymmetric_keys/asymmetric_keys.h
+++ b/crypto/asymmetric_keys/asymmetric_keys.h
@@ -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];
diff --git a/crypto/asymmetric_keys/asymmetric_type.c b/crypto/asymmetric_keys/asymmetric_type.c
index b77eb5304788..1fd1d304a15a 100644
--- a/crypto/asymmetric_keys/asymmetric_type.c
+++ b/crypto/asymmetric_keys/asymmetric_type.c
@@ -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)