res_http_websocket: Fix crash due to double freeing memory when receiving a payload...

Frames with a payload length of 0 were incorrectly handled in res_http_websocket.
Provided a frame with a payload had been received prior it was possible for a double
free to occur. The realloc operation would succeed (thus freeing the payload) but be
treated as an error. When the session was then torn down the payload would be
freed again causing a crash. The read function now takes this into account.

This change also fixes assumptions made by users of res_http_websocket. There is no
guarantee that a frame received from it will be NULL terminated.

ASTERISK-24472 #close
Reported by: Badalian Vyacheslav

Review: https://reviewboard.asterisk.org/r/4220/
Review: https://reviewboard.asterisk.org/r/4219/

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@429270 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index 8ac9aaeacb699d1f48abc46ebda4b0bb7d904ac4..5c6a843794b73028f8aa9ffc2d998db5e69209e4 100644 (file)
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -2596,12 +2596,16 @@ static void sip_websocket_callback(struct ast_websocket *session, struct ast_var
 
                if (opcode == AST_WEBSOCKET_OPCODE_TEXT || opcode == AST_WEBSOCKET_OPCODE_BINARY) {
                        struct sip_request req = { 0, };
+                       char data[payload_len + 1];
 
                        if (!(req.data = ast_str_create(payload_len + 1))) {
                                goto end;
                        }
 
-                       if (ast_str_set(&req.data, -1, "%s", payload) == AST_DYNSTR_BUILD_FAILED) {
+                       strncpy(data, payload, payload_len);
+                       data[payload_len] = '\0';
+
+                       if (ast_str_set(&req.data, -1, "%s", data) == AST_DYNSTR_BUILD_FAILED) {
                                deinit_req(&req);
                                goto end;
                        }

diff --git a/res/res_http_websocket.c b/res/res_http_websocket.c
index 5258a5f556b3759237cb681e6f3760112e30fbaf..81fa83d1e8db5d9e038bf052d7168afeae352060 100644 (file)
--- a/res/res_http_websocket.c
+++ b/res/res_http_websocket.c
@@ -462,14 +462,6 @@ int AST_OPTIONAL_API_NAME(ast_websocket_read)(struct ast_websocket *session, cha
                        }
                }
 
-               if (!(new_payload = ast_realloc(session->payload, (session->payload_len + *payload_len)))) {
-                       ast_log(LOG_WARNING, "Failed allocation: %p, %zu, %"PRIu64"\n",
-                               session->payload, session->payload_len, *payload_len);
-                       *payload_len = 0;
-                       ast_websocket_close(session, 1009);
-                       return 0;
-               }
-
                /* Per the RFC for PING we need to send back an opcode with the application data as received */
                if ((*opcode == AST_WEBSOCKET_OPCODE_PING) && (ast_websocket_write(session, AST_WEBSOCKET_OPCODE_PONG, *payload, *payload_len))) {
                        *payload_len = 0;
@@ -477,9 +469,22 @@ int AST_OPTIONAL_API_NAME(ast_websocket_read)(struct ast_websocket *session, cha
                        return 0;
                }
 
-               session->payload = new_payload;
-               memcpy((session->payload + session->payload_len), (*payload), (*payload_len));
-               session->payload_len += *payload_len;
+               if (*payload_len) {
+                       if (!(new_payload = ast_realloc(session->payload, (session->payload_len + *payload_len)))) {
+                               ast_log(LOG_WARNING, "Failed allocation: %p, %zu, %"PRIu64"\n",
+                                       session->payload, session->payload_len, *payload_len);
+                               *payload_len = 0;
+                               ast_websocket_close(session, 1009);
+                               return 0;
+                       }
+
+                       session->payload = new_payload;
+                       memcpy((session->payload + session->payload_len), (*payload), (*payload_len));
+                       session->payload_len += *payload_len;
+               } else if (!session->payload_len && session->payload) {
+                       ast_free(session->payload);
+                       session->payload = NULL;
+               }
 
                if (!fin && session->reconstruct && (session->payload_len < session->reconstruct)) {
                        /* If this is not a final message we need to defer returning it until later */