Fix crash on fdopen failure

See security advisory AST-2011-004

(closes issue #18845)
Reported by: cmaj
Patches: 
      patch-main-tcptls-1.8.3-rc2-open-session-crash-take2.diff.txt uploaded by cmaj (license 830)
      patch-main-tcptls-1.8.3-rc2-open-session-crash-take3.diff.txt uploaded by cmaj (license 830)
Tested by: cmaj, twilson


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.1@310995 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/tcptls.c

@@ -139,8 +139,12 @@ static void *handle_tcptls_connection(void *data)
 	* open a FILE * as appropriate.
 	*/
 	if (!tcptls_session->parent->tls_cfg) {
-		tcptls_session->f = fdopen(tcptls_session->fd, "w+");
-		setvbuf(tcptls_session->f, NULL, _IONBF, 0);
+		if ((tcptls_session->f = fdopen(tcptls_session->fd, "w+"))) {
+			if(setvbuf(tcptls_session->f, NULL, _IONBF, 0)) {
+				fclose(tcptls_session->f);
+				tcptls_session->f = NULL;
+			}
+		}
 	}
 #ifdef DO_SSL
 	else if ( (tcptls_session->ssl = SSL_new(tcptls_session->parent->tls_cfg->ssl_ctx)) ) {