Fix out of bound reads in ParseIceServerUrl() for various input.

webrtc/api/peerconnection.cc

Index: webrtc/api/peerconnection.cc
diff --git a/webrtc/api/peerconnection.cc b/webrtc/api/peerconnection.cc
index 46bdec594a9c90fcd1630db748921237807902d2..7731c0f4f3e660c4b4c974a526d117dd3ffdf7da 100644
--- a/webrtc/api/peerconnection.cc
+++ b/webrtc/api/peerconnection.cc
@@ -231,21 +231,24 @@ bool ParseIceServerUrl(const PeerConnectionInterface::IceServer& server,
   std::vector<std::string> tokens;
   cricket::ProtocolType turn_transport_type = cricket::PROTO_UDP;
   RTC_DCHECK(!url.empty());
-  rtc::tokenize(url, '?', &tokens);
+  rtc::tokenize_with_empty_tokens(url, '?', &tokens);
   std::string uri_without_transport = tokens[0];
   // Let's look into transport= param, if it exists.
   if (tokens.size() == kTurnTransportTokensNum) {  // ?transport= is present.
     std::string uri_transport_param = tokens[1];
-    rtc::tokenize(uri_transport_param, '=', &tokens);
-    if (tokens[0] == kTransport) {
-      // As per above grammar transport param will be consist of lower case
-      // letters.
-      if (!cricket::StringToProto(tokens[1].c_str(), &turn_transport_type) ||
-          (turn_transport_type != cricket::PROTO_UDP &&
-           turn_transport_type != cricket::PROTO_TCP)) {
-        LOG(LS_WARNING) << "Transport param should always be udp or tcp.";
-        return false;
-      }
+    rtc::tokenize_with_empty_tokens(uri_transport_param, '=', &tokens);
+    if (tokens[0] != kTransport) {
+      LOG(LS_WARNING) << "Invalid transport parameter key.";
+      return false;
+    }
+    // As per above grammar transport param will be consist of lower case

[hta-webrtc, 2016/12/09 12:02:09]

Drive-by comment:
While you're here, can you fix the grammar of the comment?

"As per the above grammar, the transport param will consist of lower case
letters."

Or delete it - I can't see that it aids readability of the code.

[hnsl1, 2016/12/12 09:28:20]

I have a branch where I refactored the whole parser to make it actually
readable. In this patch I opted to just fix this specific bug with as little
change as possible. But sure, I'll delete this comment.

+    // letters.
+    if (tokens.size() < 2 ||
+        !cricket::StringToProto(tokens[1].c_str(), &turn_transport_type) ||
+        (turn_transport_type != cricket::PROTO_UDP &&
+         turn_transport_type != cricket::PROTO_TCP)) {
+      LOG(LS_WARNING) << "Transport param should always be udp or tcp.";
+      return false;
     }
   }