AST-2012-009: Fix crash in chan_skinny due to Key Pad Button Message handling

AST-2012-008 (r367844) fixed a denial of service attack exploitable in the
Skinny channel driver that occurred when certain messages are sent after a
previously registered station sends an Off Hook message.  Unresolved in that
patch is an issue in the Asterisk 10 releases, wherein, if a Station Key
Pad Button Message is processed after an Off Hook message, the channel driver
will inappropriately dereference a NULL pointer.

This patch fixes those places where the message handling or the channel
callback functions would attempt to dereference the line's pointer to the
device.

(issue ASTERISK-19905)
Reported by: Christoph Hebeisen
Tested by: mjordan, Christoph Hebeisen
Patches:
  AST-2012-009-10.diff uploaded by mjordan (license 6283)

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@368947 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/channels/chan_skinny.c b/channels/chan_skinny.c
index ecd017cd15eda54f83e1fb65a830844f3e160db7..0107e2ce987636499ea1ed35987941183d3924e5 100644 (file)
--- a/channels/chan_skinny.c
+++ b/channels/chan_skinny.c
@@ -4976,6 +4976,11 @@ static void setsubstate(struct skinny_subchannel *sub, int state)
        pthread_t t;
        int actualstate = state;
 
+       if (!l->device) {
+               ast_log(LOG_WARNING, "Device for line %s is not registered.\n", l->name);
+               return;
+       }
+
        if (sub->substate == SUBSTATE_ONHOOK) {
                return;
        }
@@ -5365,15 +5370,20 @@ static void dumpsub(struct skinny_subchannel *sub, int forcehangup)
        struct skinny_subchannel *activatesub = NULL;
        struct skinny_subchannel *tsub;
 
+       if (!l->device) {
+               ast_log(LOG_WARNING, "Device for line %s is not registered.\n", l->name);
+               return;
+       }
+
        if (skinnydebug) {
                ast_verb(3, "Sub %d - Dumping\n", sub->callid);
        }
-       
+
        if (!forcehangup && sub->substate == SUBSTATE_HOLD) {
                l->activesub = NULL;
                return;
        }
-       
+
        if (sub == l->activesub) {
                d->hookstate = SKINNY_ONHOOK;
                transmit_speaker_mode(d, SKINNY_SPEAKEROFF);