Fix receive amf checking

[Fahnenfluchtige]

The Svace static analysis tool identified a potential issue in the function ngx_rtmp_relay_on_status(), where the return value of ngx_rtmp_receive_amf() is not checked (line 1292):

ngx_rtmp_receive_amf(s, in, in_elts_meta,
        sizeof(in_elts_meta) / sizeof(in_elts_meta[0]));

The function ngx_rtmp_receive_amf() calls ngx_rtmp_amf_read(), which can return NGX_ERROR in case of a parsing failure. However, no error handling is performed, and the function ngx_rtmp_relay_on_status() always returns NGX_OK, even if parsing fails.

So, the solution is to add error checking:

@@ -1289,11 +1289,23 @@ ngx_rtmp_relay_on_status(ngx_rtmp_session_t *s, ngx_rtmp_header_t *h,

    ngx_memzero(&v, sizeof(v));
    if (h->type == NGX_RTMP_MSG_AMF_META) {
-        ngx_rtmp_receive_amf(s, in, in_elts_meta,
-                sizeof(in_elts_meta) / sizeof(in_elts_meta[0]));
+        if (ngx_rtmp_receive_amf(s, in, in_elts_meta,
+                             sizeof(in_elts_meta) / sizeof(in_elts_meta[0])) != NGX_OK)
+        {
+            ngx_log_error(NGX_LOG_ERR, s->connection->log, 0,
+                      "relay: failed to parse AMF metadata");
+
+            return NGX_ERROR;
+        }
    } else {
-        ngx_rtmp_receive_amf(s, in, in_elts,
-                sizeof(in_elts) / sizeof(in_elts[0]));
+        if (ngx_rtmp_receive_amf(s, in, in_elts,
+                                 sizeof(in_elts) / sizeof(in_elts[0])) != NGX_OK)
+        {
+            ngx_log_error(NGX_LOG_ERR, s->connection->log, 0,
+                      "relay: failed to parse AMF message");
+
+            return NGX_ERROR;
+        }
    }

    ngx_log_debug3(NGX_LOG_DEBUG_RTMP, s->connection->log, 0,