stun: check identifier before using it

By default, 'candidate_identifier == NULL' only happens for 'compatibility
== NICE_COMPATIBILITY_GOOGLE'. However, keepalive=true will also trigger
the same code path so candidate_identifier must be checked to avoid a
segfault.

diff --git a/stun/usages/ice.c b/stun/usages/ice.c
index 47d998b..2d76ff0 100644 (file)
--- a/stun/usages/ice.c
+++ b/stun/usages/ice.c
@@ -100,7 +100,8 @@ stun_usage_ice_conncheck_create (StunAgent *agent, StunMessage *msg,
       return 0;
   }
 
-  if (compatibility == STUN_USAGE_ICE_COMPATIBILITY_MSICE2) {
+  if (compatibility == STUN_USAGE_ICE_COMPATIBILITY_MSICE2 &&
+      candidate_identifier) {
     size_t identifier_len = strlen(candidate_identifier);
     size_t attribute_len = identifier_len;
     int modulo4 = identifier_len % 4;