AST-2019-004 - res_pjsip_t38.c: Add NULL checks before using session media

After receiving a 200 OK with a declined stream in response to a T.38
initiated re-invite Asterisk would crash when attempting to dereference
a NULL session media object.

This patch checks to make sure the session media object is not NULL before
attempting to use it.

ASTERISK-28495
patches:
  ast-2019-004.patch submitted by Alexei Gradinari (license 5691)

Change-Id: I168f45f4da29cfe739acf87e597baa2aae7aa572

diff --git a/res/res_pjsip_t38.c b/res/res_pjsip_t38.c
index 11804e2c2994af8e675a03ad528696bd0ba40ee2..e5c609050db1cdfe532a7106017d6f430eb54730 100644 (file)
--- a/res/res_pjsip_t38.c
+++ b/res/res_pjsip_t38.c
@@ -203,7 +203,6 @@ static int t38_automatic_reject(void *obj)
 {
        RAII_VAR(struct ast_sip_session *, session, obj, ao2_cleanup);
        RAII_VAR(struct ast_datastore *, datastore, ast_sip_session_get_datastore(session, "t38"), ao2_cleanup);
-       struct ast_sip_session_media *session_media;
 
        if (!datastore) {
                return 0;
@@ -212,8 +211,7 @@ static int t38_automatic_reject(void *obj)
        ast_debug(2, "Automatically rejecting T.38 request on channel '%s'\n",
                session->channel ? ast_channel_name(session->channel) : "<gone>");
 
-       session_media = session->pending_media_state->default_session[AST_MEDIA_TYPE_IMAGE];
-       t38_change_state(session, session_media, datastore->data, T38_REJECTED);
+       t38_change_state(session, NULL, datastore->data, T38_REJECTED);
        ast_sip_session_resume_reinvite(session);
 
        return 0;
@@ -322,28 +320,37 @@ static int t38_reinvite_response_cb(struct ast_sip_session *session, pjsip_rx_da
                int index;
 
                session_media = session->active_media_state->default_session[AST_MEDIA_TYPE_IMAGE];
-               t38_change_state(session, session_media, state, T38_ENABLED);
+               if (!session_media) {
+                       ast_log(LOG_WARNING, "Received %d response to T.38 re-invite on '%s' but no active session media\n",
+                                       status.code, session->channel ? ast_channel_name(session->channel) : "unknown channel");
+               } else {
+                       t38_change_state(session, session_media, state, T38_ENABLED);
 
-               /* Stop all the streams in the stored away active state, they'll go back to being active once
-                * we reinvite back.
-                */
-               for (index = 0; index < AST_VECTOR_SIZE(&state->media_state->sessions); ++index) {
-                       struct ast_sip_session_media *session_media = AST_VECTOR_GET(&state->media_state->sessions, index);
+                       /* Stop all the streams in the stored away active state, they'll go back to being active once
+                        * we reinvite back.
+                        */
+                       for (index = 0; index < AST_VECTOR_SIZE(&state->media_state->sessions); ++index) {
+                               struct ast_sip_session_media *session_media = AST_VECTOR_GET(&state->media_state->sessions, index);
 
-                       if (session_media && session_media->handler && session_media->handler->stream_stop) {
-                               session_media->handler->stream_stop(session_media);
+                               if (session_media && session_media->handler && session_media->handler->stream_stop) {
+                                       session_media->handler->stream_stop(session_media);
+                               }
                        }
+
+                       return 0;
                }
        } else {
                session_media = session->pending_media_state->default_session[AST_MEDIA_TYPE_IMAGE];
-               t38_change_state(session, session_media, state, T38_REJECTED);
-
-               /* Abort this attempt at switching to T.38 by resetting the pending state and freeing our stored away active state */
-               ast_sip_session_media_state_free(state->media_state);
-               state->media_state = NULL;
-               ast_sip_session_media_state_reset(session->pending_media_state);
        }
 
+       /* If no session_media then response contained a declined stream, so disable */
+       t38_change_state(session, NULL, state, session_media ? T38_REJECTED : T38_DISABLED);
+
+       /* Abort this attempt at switching to T.38 by resetting the pending state and freeing our stored away active state */
+       ast_sip_session_media_state_free(state->media_state);
+       state->media_state = NULL;
+       ast_sip_session_media_state_reset(session->pending_media_state);
+
        return 0;
 }
 
@@ -426,12 +433,10 @@ static int t38_interpret_parameters(void *obj)
                /* Negotiation can not take place without a valid max_ifp value. */
                if (!parameters->max_ifp) {
                        if (data->session->t38state == T38_PEER_REINVITE) {
-                               session_media = data->session->pending_media_state->default_session[AST_MEDIA_TYPE_IMAGE];
-                               t38_change_state(data->session, session_media, state, T38_REJECTED);
+                               t38_change_state(data->session, NULL, state, T38_REJECTED);
                                ast_sip_session_resume_reinvite(data->session);
                        } else if (data->session->t38state == T38_ENABLED) {
-                               session_media = data->session->active_media_state->default_session[AST_MEDIA_TYPE_IMAGE];
-                               t38_change_state(data->session, session_media, state, T38_DISABLED);
+                               t38_change_state(data->session, NULL, state, T38_DISABLED);
                                ast_sip_session_refresh(data->session, NULL, NULL, NULL,
                                        AST_SIP_SESSION_REFRESH_METHOD_INVITE, 1, state->media_state);
                                state->media_state = NULL;
@@ -454,6 +459,11 @@ static int t38_interpret_parameters(void *obj)
                        state->our_parms.version = MIN(state->our_parms.version, state->their_parms.version);
                        state->our_parms.rate_management = state->their_parms.rate_management;
                        session_media = data->session->pending_media_state->default_session[AST_MEDIA_TYPE_IMAGE];
+                       if (!session_media) {
+                               ast_log(LOG_ERROR, "Failed to negotiate parameters for reinvite on channel '%s' (No pending session media).\n",
+                                       data->session->channel ? ast_channel_name(data->session->channel) : "unknown channel");
+                               break;
+                       }
                        ast_udptl_set_local_max_ifp(session_media->udptl, state->our_parms.max_ifp);
                        t38_change_state(data->session, session_media, state, T38_ENABLED);
                        ast_sip_session_resume_reinvite(data->session);
@@ -468,8 +478,13 @@ static int t38_interpret_parameters(void *obj)
                        }
                        state->our_parms = *parameters;
                        session_media = media_state->default_session[AST_MEDIA_TYPE_IMAGE];
+                       if (!session_media) {
+                               ast_log(LOG_ERROR, "Failed to negotiate parameters on channel '%s' (No default session media).\n",
+                                       data->session->channel ? ast_channel_name(data->session->channel) : "unknown channel");
+                               break;
+                       }
                        ast_udptl_set_local_max_ifp(session_media->udptl, state->our_parms.max_ifp);
-                       t38_change_state(data->session, session_media, state, T38_LOCAL_REINVITE);
+                       t38_change_state(data->session, NULL, state, T38_LOCAL_REINVITE);
                        ast_sip_session_refresh(data->session, NULL, t38_reinvite_sdp_cb, t38_reinvite_response_cb,
                                AST_SIP_SESSION_REFRESH_METHOD_INVITE, 1, media_state);
                }
@@ -478,12 +493,10 @@ static int t38_interpret_parameters(void *obj)
        case AST_T38_REFUSED:
        case AST_T38_REQUEST_TERMINATE:         /* Shutdown T38 */
                if (data->session->t38state == T38_PEER_REINVITE) {
-                       session_media = data->session->pending_media_state->default_session[AST_MEDIA_TYPE_IMAGE];
-                       t38_change_state(data->session, session_media, state, T38_REJECTED);
+                       t38_change_state(data->session, NULL, state, T38_REJECTED);
                        ast_sip_session_resume_reinvite(data->session);
                } else if (data->session->t38state == T38_ENABLED) {
-                       session_media = data->session->active_media_state->default_session[AST_MEDIA_TYPE_IMAGE];
-                       t38_change_state(data->session, session_media, state, T38_DISABLED);
+                       t38_change_state(data->session, NULL, state, T38_DISABLED);
                        ast_sip_session_refresh(data->session, NULL, NULL, NULL, AST_SIP_SESSION_REFRESH_METHOD_INVITE, 1, state->media_state);
                        state->media_state = NULL;
                }
@@ -493,6 +506,11 @@ static int t38_interpret_parameters(void *obj)
 
                if (data->session->t38state == T38_PEER_REINVITE) {
                        session_media = data->session->pending_media_state->default_session[AST_MEDIA_TYPE_IMAGE];
+                       if (!session_media) {
+                               ast_log(LOG_ERROR, "Failed to request parameters for reinvite on channel '%s' (No pending session media).\n",
+                                       data->session->channel ? ast_channel_name(data->session->channel) : "unknown channel");
+                               break;
+                       }
                        parameters.max_ifp = ast_udptl_get_far_max_ifp(session_media->udptl);
                        parameters.request_response = AST_T38_REQUEST_NEGOTIATE;
                        ast_queue_control_data(data->session->channel, AST_CONTROL_T38_PARAMETERS, &parameters, sizeof(parameters));
@@ -788,7 +806,7 @@ static int negotiate_incoming_sdp_stream(struct ast_sip_session *session,
 
        if ((session->t38state == T38_REJECTED) || (session->t38state == T38_DISABLED)) {
                ast_debug(3, "Declining; T.38 state is rejected or declined\n");
-               t38_change_state(session, session_media, state, T38_DISABLED);
+               t38_change_state(session, NULL, state, T38_DISABLED);
                return 0;
        }