KEYS: Improve /proc/keys

Improve /proc/keys by:

 (1) Don't attempt to summarise the payload of a negated key.  It won't have
     one.  To this end, a helper function - key_is_instantiated() has been
     added that allows the caller to find out whether the key is positively
     instantiated (as opposed to being uninstantiated or negatively
     instantiated).

 (2) Do show keys that are negative, expired or revoked rather than hiding
     them.  This requires an override flag (no_state_check) to be passed to
     search_my_process_keyrings() and keyring_search_aux() to suppress this
     check.

     Without this, keys that are possessed by the caller, but only grant
     permissions to the caller if possessed are skipped as the possession check
     fails.

     Keys that are visible due to user, group or other checks are visible with
     or without this patch.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 24 insertions, 13 deletions

diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index cdd2f3f88c88..a06ffab38568 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -176,13 +176,15 @@ static void keyring_describe(const struct key *keyring, struct seq_file *m)
 	else
 		seq_puts(m, "[anon]");
 
-	rcu_read_lock();
-	klist = rcu_dereference(keyring->payload.subscriptions);
-	if (klist)
-		seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
-	else
-		seq_puts(m, ": empty");
-	rcu_read_unlock();
+	if (key_is_instantiated(keyring)) {
+		rcu_read_lock();
+		klist = rcu_dereference(keyring->payload.subscriptions);
+		if (klist)
+			seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
+		else
+			seq_puts(m, ": empty");
+		rcu_read_unlock();
+	}
 }
 
 /*
@@ -271,6 +273,7 @@ struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
  * @type: The type of key to search for.
  * @description: Parameter for @match.
  * @match: Function to rule on whether or not a key is the one required.
+ * @no_state_check: Don't check if a matching key is bad
  *
  * Search the supplied keyring tree for a key that matches the criteria given.
  * The root keyring and any linked keyrings must grant Search permission to the
@@ -303,7 +306,8 @@ key_ref_t keyring_search_aux(key_ref_t keyring_ref,
 			     const struct cred *cred,
 			     struct key_type *type,
 			     const void *description,
-			     key_match_func_t match)
+			     key_match_func_t match,
+			     bool no_state_check)
 {
 	struct {
 		struct keyring_list *keylist;
@@ -345,6 +349,8 @@ key_ref_t keyring_search_aux(key_ref_t keyring_ref,
 	kflags = keyring->flags;
 	if (keyring->type == type && match(keyring, description)) {
 		key = keyring;
+		if (no_state_check)
+			goto found;
 
 		/* check it isn't negative and hasn't expired or been
 		 * revoked */
@@ -384,11 +390,13 @@ descend:
 			continue;
 
 		/* skip revoked keys and expired keys */
-		if (kflags & (1 << KEY_FLAG_REVOKED))
-			continue;
+		if (!no_state_check) {
+			if (kflags & (1 << KEY_FLAG_REVOKED))
+				continue;
 
-		if (key->expiry && now.tv_sec >= key->expiry)
-			continue;
+			if (key->expiry && now.tv_sec >= key->expiry)
+				continue;
+		}
 
 		/* keys that don't match */
 		if (!match(key, description))
@@ -399,6 +407,9 @@ descend:
 					cred, KEY_SEARCH) < 0)
 			continue;
 
+		if (no_state_check)
+			goto found;
+
 		/* we set a different error code if we pass a negative key */
 		if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
 			err = key->type_data.reject_error;
@@ -478,7 +489,7 @@ key_ref_t keyring_search(key_ref_t keyring,
 		return ERR_PTR(-ENOKEY);
 
 	return keyring_search_aux(keyring, current->cred,
-				  type, description, type->match);
+				  type, description, type->match, false);
 }
 EXPORT_SYMBOL(keyring_search);