Prevent JS from bypassing RTP data channel bandwidth limitation.

talk/app/webrtc/webrtcsdp.cc

 /*
  * libjingle
  * Copyright 2011 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 1256 matching lines @@
       transport_info->description.identity_fingerprint.get() : NULL;
 
   // Add the m and c lines.
   InitLine(kLineTypeMedia, type, &os);
   os << " " << port << " " << media_desc->protocol() << fmt;
   std::string mline = os.str();
   UpdateMediaDefaultDestination(candidates, mline, message);
 
   // RFC 4566
   // b=AS:<bandwidth>
-  // We should always use the default bandwidth for RTP-based data
-  // channels.  Don't allow SDP to set the bandwidth, because that
-  // would give JS the opportunity to "break the Internet".
-  // TODO(pthatcher): But we need to temporarily allow the SDP to control
-  // this for backwards-compatibility.  Once we don't need that any
-  // more, remove this.
-  bool support_dc_sdp_bandwidth_temporarily = true;
-  if (media_desc->bandwidth() >= 1000 &&
-      (media_type != cricket::MEDIA_TYPE_DATA ||
-       support_dc_sdp_bandwidth_temporarily)) {
+  if (media_desc->bandwidth() >= 1000) {
     InitLine(kLineTypeSessionBandwidth, kApplicationSpecificMaximum, &os);
     os << kSdpDelimiterColon << (media_desc->bandwidth() / 1000);
     AddLine(os.str(), message);
   }
 
   // Add the a=rtcp line.
   if (IsRtp(media_desc->protocol())) {
     std::string rtcp_line = GetRtcpLine(candidates);
     if (!rtcp_line.empty()) {
       AddLine(rtcp_line, message);
@@ skipping 945 matching lines @@
                     message, cricket::MEDIA_TYPE_DATA, mline_index, protocol,
                     codec_preference, pos, &content_name,
                     &transport, candidates, error);
       content.reset(data_desc);
 
       int p;
       if (data_desc && IsDtlsSctp(protocol) && rtc::FromString(fields[3], &p)) {
         if (!AddSctpDataCodec(data_desc, p))
           return false;
       }
-
-      // We should always use the default bandwidth for RTP-based data
-      // channels.  Don't allow SDP to set the bandwidth, because that
-      // would give JS the opportunity to "break the Internet".
-      // TODO(pthatcher): But we need to temporarily allow the SDP to control
-      // this for backwards-compatibility.  Once we don't need that any
-      // more, remove this.
-      bool support_dc_sdp_bandwidth_temporarily = true;
-      if (content.get() && !support_dc_sdp_bandwidth_temporarily) {
-        content->set_bandwidth(cricket::kAutoBandwidth);
-      }
     } else {
       LOG(LS_WARNING) << "Unsupported media type: " << line;
       continue;
     }
     if (!content.get()) {
       // ParseContentDescription returns NULL if failed.
       return false;
     }
 
     if (IsRtp(protocol)) {
@@ skipping 237 matching lines @@
     if (IsLineType(line, kLineTypeSessionBandwidth)) {
       std::string bandwidth;
       if (HasAttribute(line, kApplicationSpecificMaximum)) {
         if (!GetValue(line, kApplicationSpecificMaximum, &bandwidth, error)) {
           return false;
         } else {
           int b = 0;
           if (!GetValueFromString(line, bandwidth, &b, error)) {
             return false;
           }
+          // We should never use more than the default bandwidth for RTP-based
+          // data channels. Don't allow SDP to set the bandwidth, because
+          // that would give JS the opportunity to "break the Internet".

[pthatcher1, 2015/06/24 20:01:56]

Please reference the bug URL here.

Just say "See $URL".

[Taylor Brandstetter, 2015/06/24 21:41:24]

Done.

+          if (media_type == cricket::MEDIA_TYPE_DATA &&
+              b > cricket::kDataMaxBandwidth / 1000) {

[pthatcher1, 2015/06/24 20:01:56]

&& IsRtp(media_desc->protocol())

[Taylor Brandstetter, 2015/06/24 21:41:24]

Done.

+            std::ostringstream description;
+            description << "SDP data bandwidth must not exceed "

[pthatcher1, 2015/06/24 20:01:57]

A more accurate message would be "RTP-based data channels may not send more than
30kbps".

[Taylor Brandstetter, 2015/06/24 21:41:24]

Done.

+                        << cricket::kDataMaxBandwidth / 1000 << "kbps.";
+            return ParseFailed(line, description.str(), error);
+          }
           media_desc->set_bandwidth(b * 1000);
         }
       }
       continue;
     }
 
     if (!IsLineType(line, kLineTypeAttributes)) {
       // TODO: Handle other lines if needed.
       LOG(LS_INFO) << "Ignored line: " << line;
       continue;
@@ skipping 577 matching lines @@
     UpdateCodec<AudioContentDescription, cricket::AudioCodec>(
         media_desc, payload_type, feedback_param);
   } else if (media_type == cricket::MEDIA_TYPE_VIDEO) {
     UpdateCodec<VideoContentDescription, cricket::VideoCodec>(
         media_desc, payload_type, feedback_param);
   }
   return true;
 }
 
 }  // namespace webrtc