Cleaning up chan_sip/tcptls file descriptor closing.

This patch attempts to eliminate various possible instances of undefined behavior caused
by invoking close/fclose in situations where fclose may have already been issued on a
tcptls_session_instance and/or closing file descriptors that don't have a valid index
for fd (-1). Thanks for more than a little help from wdoekes.

(closes issue ASTERISK-18700)
Reported by: Erik Wallin

(issue ASTERISK-18345)
Reported by: Stephane Cazelas

(issue ASTERISK-18342)
Reported by: Stephane Chazelas

Review: https://reviewboard.asterisk.org/r/1576/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@346525 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -2813,14 +2813,7 @@ cleanup:
 
 	if (tcptls_session) {
 		ast_mutex_lock(&tcptls_session->lock);
-		if (tcptls_session->f) {
-			fclose(tcptls_session->f);
-			tcptls_session->f = NULL;
-		}
-		if (tcptls_session->fd != -1) {
-			close(tcptls_session->fd);
-			tcptls_session->fd = -1;
-		}
+		ast_tcptls_close_session_file(tcptls_session);
 		tcptls_session->parent = NULL;
 		ast_mutex_unlock(&tcptls_session->lock);
 
@@ -26019,8 +26012,8 @@ create_tcptls_session_fail:
 		ao2_t_ref(ca, -1, "failed to create client, getting rid of client tcptls_session arguments");
 	}
 	if (s->tcptls_session) {
-		close(tcptls_session->fd);
-		s->fd = tcptls_session->fd = -1;
+		ast_tcptls_close_session_file(tcptls_session);
+		s->fd = -1;
 		ao2_ref(s->tcptls_session, -1);
 		s->tcptls_session = NULL;
 	}

include/asterisk/tcptls.h

@@ -176,6 +176,13 @@ struct ast_tcptls_session_instance *ast_tcptls_client_create(struct ast_tcptls_s
 
 void *ast_tcptls_server_root(void *);
 
+/*!
+ * \brief Closes a tcptls session instance's file and/or file descriptor.
+ * The tcptls_session will be set to NULL and it's file descriptor will be set to -1
+ * by this function.
+ */
+void ast_tcptls_close_session_file(struct ast_tcptls_session_instance *tcptls_session);
+
 /*!
  * \brief This is a generic (re)start routine for a TCP server,
  * which does the socket/bind/listen and starts a thread for handling

main/tcptls.c

@@ -78,9 +78,23 @@ static HOOK_T ssl_write(void *cookie, const char *buf, LEN_T len)
 
 static int ssl_close(void *cookie)
 {
-	close(SSL_get_fd(cookie));
-	SSL_shutdown(cookie);
-	SSL_free(cookie);
+	int cookie_fd = SSL_get_fd(cookie);
+	int ret;
+	if (cookie_fd > -1) {
+		/*
+		 * According to the TLS standard, it is acceptable for an application to only send its shutdown
+		 * alert and then close the underlying connection without waiting for the peer's response (this
+		 * way resources can be saved, as the process can already terminate or serve another connection).
+		 */
+		if ((ret = SSL_shutdown(cookie)) < 0) {
+			ast_log(LOG_ERROR, "SSL_shutdown() failed: %d\n", SSL_get_error(cookie, ret));
+		}
+		SSL_free(cookie);
+		/* adding shutdown(2) here has no added benefit */
+		if (close(cookie_fd)) {
+			ast_log(LOG_ERROR, "close() failed: %s\n", strerror(errno));
+		}
+	}
 	return 0;
 }
 #endif	/* DO_SSL */
@@ -145,8 +159,7 @@ static void *handle_tcptls_connection(void *data)
 	if (!tcptls_session->parent->tls_cfg) {
 		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;
+				ast_tcptls_close_session_file(tcptls_session);
 			}
 		}
 	}
@@ -212,8 +225,7 @@ static void *handle_tcptls_connection(void *data)
 						if (peer) {
 							X509_free(peer);
 						}
-						close(tcptls_session->fd);
-						fclose(tcptls_session->f);
+						ast_tcptls_close_session_file(tcptls_session);
 						ao2_ref(tcptls_session, -1);
 						return NULL;
 					}
@@ -230,7 +242,7 @@ static void *handle_tcptls_connection(void *data)
 #endif /* DO_SSL */
 
 	if (!tcptls_session->f) {
-		close(tcptls_session->fd);
+		ast_tcptls_close_session_file(tcptls_session);
 		ast_log(LOG_WARNING, "FILE * open failed!\n");
 #ifndef DO_SSL
 		if (tcptls_session->parent->tls_cfg) {
@@ -276,7 +288,9 @@ void *ast_tcptls_server_root(void *data)
 		tcptls_session = ao2_alloc(sizeof(*tcptls_session), session_instance_destructor);
 		if (!tcptls_session) {
 			ast_log(LOG_WARNING, "No memory for new session: %s\n", strerror(errno));
-			close(fd);
+			if (close(fd)) {
+				ast_log(LOG_ERROR, "close() failed: %s\n", strerror(errno));
+			}
 			continue;
 		}
 
@@ -293,7 +307,7 @@ void *ast_tcptls_server_root(void *data)
 		/* This thread is now the only place that controls the single ref to tcptls_session */
 		if (ast_pthread_create_detached_background(&launched, NULL, handle_tcptls_connection, tcptls_session)) {
 			ast_log(LOG_WARNING, "Unable to launch helper thread: %s\n", strerror(errno));
-			close(tcptls_session->fd);
+			ast_tcptls_close_session_file(tcptls_session);
 			ao2_ref(tcptls_session, -1);
 		}
 	}
@@ -558,6 +572,24 @@ error:
 	desc->accept_fd = -1;
 }
 
+void ast_tcptls_close_session_file(struct ast_tcptls_session_instance *tcptls_session)
+{
+	if (tcptls_session->f) {
+		if (fclose(tcptls_session->f)) {
+			ast_log(LOG_ERROR, "fclose() failed: %s\n", strerror(errno));
+		}
+		tcptls_session->f = NULL;
+		tcptls_session->fd = -1;
+	} else if (tcptls_session->fd != -1) {
+		if (close(tcptls_session->fd)) {
+			ast_log(LOG_ERROR, "close() failed: %s\n", strerror(errno));
+		}
+		tcptls_session->fd = -1;
+	} else {
+		ast_log(LOG_ERROR, "ast_tcptls_close_session_file invoked on session instance without file or file descriptor\n");
+	}
+}
+
 void ast_tcptls_server_stop(struct ast_tcptls_session_args *desc)
 {
 	if (desc->master != AST_PTHREADT_NULL) {