Delay a QUIC server's use of the FORWARD_SECURE encrypter until the

net/quic/quic_connection.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_connection.h"
 
 #include <string.h>
 #include <sys/types.h>
 
 #include <algorithm>
@@ skipping 178 matching lines @@
                                const PacketWriterFactory& writer_factory,
                                bool owns_writer,
                                bool is_server,
                                const QuicVersionVector& supported_versions)
     : framer_(supported_versions, helper->GetClock()->ApproximateNow(),
               is_server),
       helper_(helper),
       writer_(writer_factory.Create(this)),
       owns_writer_(owns_writer),
       encryption_level_(ENCRYPTION_NONE),
+      has_forward_secure_encrypter_(false),
+      first_required_forward_secure_packet_(0),
       clock_(helper->GetClock()),
       random_generator_(helper->GetRandomGenerator()),
       connection_id_(connection_id),
       peer_address_(address),
       migrating_peer_port_(0),
       last_packet_decrypted_(false),
       last_packet_revived_(false),
       last_size_(0),
       last_decrypted_packet_level_(ENCRYPTION_NONE),
       largest_seen_packet_with_ack_(0),
@@ skipping 241 matching lines @@
   return true;
 }
 
 bool QuicConnection::OnUnauthenticatedHeader(const QuicPacketHeader& header) {
   return true;
 }
 
 void QuicConnection::OnDecryptedPacket(EncryptionLevel level) {
   last_decrypted_packet_level_ = level;
   last_packet_decrypted_ = true;
+  // If this packet was foward-secure encrypted and the forward-secure encrypter
+  // is not being used, start using it.
+  if (FLAGS_enable_quic_delay_forward_security &&
+      encryption_level_ != ENCRYPTION_FORWARD_SECURE &&
+      has_forward_secure_encrypter_ &&
+      level == ENCRYPTION_FORWARD_SECURE) {
+    SetDefaultEncryptionLevel(ENCRYPTION_FORWARD_SECURE);
+  }
 }
 
 bool QuicConnection::OnPacketHeader(const QuicPacketHeader& header) {
   if (debug_visitor_.get() != nullptr) {
     debug_visitor_->OnPacketHeader(header);
   }
 
   if (!ProcessValidatedPacket()) {
     return false;
   }
@@ skipping 1076 matching lines @@
 
 void QuicConnection::OnWriteError(int error_code) {
   DVLOG(1) << ENDPOINT << "Write failed with error: " << error_code
            << " (" << ErrorToString(error_code) << ")";
   // We can't send an error as the socket is presumably borked.
   CloseConnection(QUIC_PACKET_WRITE_ERROR, false);
 }
 
 void QuicConnection::OnSerializedPacket(
     const SerializedPacket& serialized_packet) {
+  // If a forward-secure encrypter is available but is not being used and this
+  // packet's sequence number is after the first packet which requires
+  // forward security, start using the forward-secure encrypter.
+  if (FLAGS_enable_quic_delay_forward_security &&
+      encryption_level_ != ENCRYPTION_FORWARD_SECURE &&
+      has_forward_secure_encrypter_ &&
+      serialized_packet.sequence_number >=
+          first_required_forward_secure_packet_) {
+    SetDefaultEncryptionLevel(ENCRYPTION_FORWARD_SECURE);
+  }
   if (serialized_packet.retransmittable_frames) {
     serialized_packet.retransmittable_frames->
         set_encryption_level(encryption_level_);
   }
   SendOrQueuePacket(QueuedPacket(serialized_packet, encryption_level_));
 }
 
 void QuicConnection::OnCongestionWindowChange(QuicByteCount congestion_window) {
   packet_generator_.OnCongestionWindowChange(congestion_window);
   visitor_->OnCongestionWindowChange(clock_->ApproximateNow());
@@ skipping 80 matching lines @@
     QuicTime rto_timeout = sent_packet_manager_.GetRetransmissionTime();
     if (rto_timeout.IsInitialized()) {
       retransmission_alarm_->Set(rto_timeout);
     }
   }
 }
 
 void QuicConnection::SetEncrypter(EncryptionLevel level,
                                   QuicEncrypter* encrypter) {
   framer_.SetEncrypter(level, encrypter);
+  if (FLAGS_enable_quic_delay_forward_security &&
+      level == ENCRYPTION_FORWARD_SECURE) {
+    has_forward_secure_encrypter_ = true;
+    first_required_forward_secure_packet_ =
+        sequence_number_of_last_sent_packet_ +
+        // 3 times the current congestion window (in slow start) should cover
+        // about two full round trips worth of packets, which should be
+        // sufficient.
+        3 * sent_packet_manager_.GetCongestionWindow() / max_packet_length();
+  }
 }
 
 const QuicEncrypter* QuicConnection::encrypter(EncryptionLevel level) const {
   return framer_.encrypter(level);
 }
 
 void QuicConnection::SetDefaultEncryptionLevel(EncryptionLevel level) {
   encryption_level_ = level;
   packet_generator_.set_encryption_level(level);
 }
@@ skipping 407 matching lines @@
   }
   for (size_t i = 0; i < retransmittable_frames->frames().size(); ++i) {
     if (retransmittable_frames->frames()[i].type == CONNECTION_CLOSE_FRAME) {
       return true;
     }
   }
   return false;
 }
 
 }  // namespace net