GetDefaultLocalAddress should return the bestIP

webrtc/base/network.cc

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 339 matching lines @@
     default_local_ipv6_address_ = ipv6;
   }
 }
 
 bool NetworkManagerBase::GetDefaultLocalAddress(int family,
                                                 IPAddress* ipaddr) const {
   if (family == AF_INET && !default_local_ipv4_address_.IsNil()) {
     *ipaddr = default_local_ipv4_address_;
     return true;
   } else if (family == AF_INET6 && !default_local_ipv6_address_.IsNil()) {
-    *ipaddr = default_local_ipv6_address_;
+    Network* ipv6_network = GetNetworkFromAddress(default_local_ipv6_address_);
+    if (ipv6_network) {
+      // If the default ipv6 network's BestIP is different than
+      // default_local_ipv6_address_, use it instead.
+      // This is to prevent potential IP address leakage. See WebRTC bug 5376.
+      *ipaddr = ipv6_network->GetBestIP();
+    } else {
+      *ipaddr = default_local_ipv6_address_;
+    }
     return true;
   }
   return false;
 }
 
+Network* NetworkManagerBase::GetNetworkFromAddress(
+    const rtc::IPAddress& ip) const {
+  for (Network* network : networks_) {
+    const auto& ips = network->GetIPs();
+    if (std::find_if(ips.begin(), ips.end(),
+                     [ip](const InterfaceAddress& existing_ip) {
+                       return ip == static_cast<rtc::IPAddress>(existing_ip);
+                     }) != ips.end()) {
+      return network;
+    }
+  }
+  return nullptr;
+}
+
 BasicNetworkManager::BasicNetworkManager()
     : thread_(NULL), sent_first_update_(false), start_count_(0),
       ignore_non_default_routes_(false) {
 }
 
 BasicNetworkManager::~BasicNetworkManager() {
 }
 
 void BasicNetworkManager::OnNetworksChanged() {
   LOG(LS_VERBOSE) << "Network change was observed at the network manager";
@@ skipping 540 matching lines @@
   std::stringstream ss;
   // Print out the first space-terminated token of the network desc, plus
   // the IP address.
   ss << "Net[" << description_.substr(0, description_.find(' '))
      << ":" << prefix_.ToSensitiveString() << "/" << prefix_length_
      << ":" << AdapterTypeToString(type_) << "]";
   return ss.str();
 }
 
 }  // namespace rtc