Land Recent QUIC changes

net/quic/crypto/cert_compressor.cc

+// Copyright (c) 2013 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/crypto/cert_compressor.h"
+
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "net/quic/quic_utils.h"
+#include "third_party/zlib/zlib.h"
+
+using base::StringPiece;
+using std::string;
+using std::vector;
+
+namespace net {
+
+namespace {
+
+// kCommonCertSubstrings contains ~1500 bytes of common certificate substrings
+// in order to help zlib.
+static unsigned char kCommonCertSubstrings[] = {
+  0x04, 0x02, 0x30, 0x00, 0x30, 0x1d, 0x06, 0x03, 0x55, 0x1d, 0x25, 0x04,
+  0x16, 0x30, 0x14, 0x06, 0x08, 0x2b, 0x06, 0x01, 0x05, 0x05, 0x07, 0x03,
+  0x01, 0x06, 0x08, 0x2b, 0x06, 0x01, 0x05, 0x05, 0x07, 0x03, 0x02, 0x30,
+  0x5f, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x86, 0xf8, 0x42, 0x04, 0x01,
+  0x06, 0x06, 0x0b, 0x60, 0x86, 0x48, 0x01, 0x86, 0xfd, 0x6d, 0x01, 0x07,
+  0x17, 0x01, 0x30, 0x33, 0x20, 0x45, 0x78, 0x74, 0x65, 0x6e, 0x64, 0x65,
+  0x64, 0x20, 0x56, 0x61, 0x6c, 0x69, 0x64, 0x61, 0x74, 0x69, 0x6f, 0x6e,
+  0x20, 0x53, 0x20, 0x4c, 0x69, 0x6d, 0x69, 0x74, 0x65, 0x64, 0x31, 0x34,
+  0x20, 0x53, 0x53, 0x4c, 0x20, 0x43, 0x41, 0x30, 0x1e, 0x17, 0x0d, 0x31,
+  0x32, 0x20, 0x53, 0x65, 0x63, 0x75, 0x72, 0x65, 0x20, 0x53, 0x65, 0x72,
+  0x76, 0x65, 0x72, 0x20, 0x43, 0x41, 0x30, 0x2d, 0x61, 0x69, 0x61, 0x2e,
+  0x76, 0x65, 0x72, 0x69, 0x73, 0x69, 0x67, 0x6e, 0x2e, 0x63, 0x6f, 0x6d,
+  0x2f, 0x45, 0x2d, 0x63, 0x72, 0x6c, 0x2e, 0x76, 0x65, 0x72, 0x69, 0x73,
+  0x69, 0x67, 0x6e, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x45, 0x2e, 0x63, 0x65,
+  0x72, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01,
+  0x01, 0x05, 0x05, 0x00, 0x03, 0x82, 0x01, 0x01, 0x00, 0x4a, 0x2e, 0x63,
+  0x6f, 0x6d, 0x2f, 0x72, 0x65, 0x73, 0x6f, 0x75, 0x72, 0x63, 0x65, 0x73,
+  0x2f, 0x63, 0x70, 0x73, 0x20, 0x28, 0x63, 0x29, 0x30, 0x30, 0x09, 0x06,
+  0x03, 0x55, 0x1d, 0x13, 0x04, 0x02, 0x30, 0x00, 0x30, 0x1d, 0x30, 0x0d,
+  0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x05, 0x05,
+  0x00, 0x03, 0x82, 0x01, 0x01, 0x00, 0x7b, 0x30, 0x1d, 0x06, 0x03, 0x55,
+  0x1d, 0x0e, 0x30, 0x82, 0x01, 0x22, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86,
+  0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00, 0x03, 0x82, 0x01,
+  0x0f, 0x00, 0x30, 0x82, 0x01, 0x0a, 0x02, 0x82, 0x01, 0x01, 0x00, 0xd2,
+  0x6f, 0x64, 0x6f, 0x63, 0x61, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x43, 0x2e,
+  0x63, 0x72, 0x6c, 0x30, 0x1d, 0x06, 0x03, 0x55, 0x1d, 0x0e, 0x04, 0x16,
+  0x04, 0x14, 0xb4, 0x2e, 0x67, 0x6c, 0x6f, 0x62, 0x61, 0x6c, 0x73, 0x69,
+  0x67, 0x6e, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x72, 0x30, 0x0b, 0x06, 0x03,
+  0x55, 0x1d, 0x0f, 0x04, 0x04, 0x03, 0x02, 0x01, 0x30, 0x0d, 0x06, 0x09,
+  0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x05, 0x05, 0x00, 0x30,
+  0x81, 0xca, 0x31, 0x0b, 0x30, 0x09, 0x06, 0x03, 0x55, 0x04, 0x06, 0x13,
+  0x02, 0x55, 0x53, 0x31, 0x10, 0x30, 0x0e, 0x06, 0x03, 0x55, 0x04, 0x08,
+  0x13, 0x07, 0x41, 0x72, 0x69, 0x7a, 0x6f, 0x6e, 0x61, 0x31, 0x13, 0x30,
+  0x11, 0x06, 0x03, 0x55, 0x04, 0x07, 0x13, 0x0a, 0x53, 0x63, 0x6f, 0x74,
+  0x74, 0x73, 0x64, 0x61, 0x6c, 0x65, 0x31, 0x1a, 0x30, 0x18, 0x06, 0x03,
+  0x55, 0x04, 0x0a, 0x13, 0x11, 0x47, 0x6f, 0x44, 0x61, 0x64, 0x64, 0x79,
+  0x2e, 0x63, 0x6f, 0x6d, 0x2c, 0x20, 0x49, 0x6e, 0x63, 0x2e, 0x31, 0x33,
+  0x30, 0x31, 0x06, 0x03, 0x55, 0x04, 0x0b, 0x13, 0x2a, 0x68, 0x74, 0x74,
+  0x70, 0x3a, 0x2f, 0x2f, 0x63, 0x65, 0x72, 0x74, 0x69, 0x66, 0x69, 0x63,
+  0x61, 0x74, 0x65, 0x73, 0x2e, 0x67, 0x6f, 0x64, 0x61, 0x64, 0x64, 0x79,
+  0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x72, 0x65, 0x70, 0x6f, 0x73, 0x69, 0x74,
+  0x6f, 0x72, 0x79, 0x31, 0x30, 0x30, 0x2e, 0x06, 0x03, 0x55, 0x04, 0x03,
+  0x13, 0x27, 0x47, 0x6f, 0x20, 0x44, 0x61, 0x64, 0x64, 0x79, 0x20, 0x53,
+  0x65, 0x63, 0x75, 0x72, 0x65, 0x20, 0x43, 0x65, 0x72, 0x74, 0x69, 0x66,
+  0x69, 0x63, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x20, 0x41, 0x75, 0x74, 0x68,
+  0x6f, 0x72, 0x69, 0x74, 0x79, 0x31, 0x11, 0x30, 0x0f, 0x06, 0x03, 0x55,
+  0x04, 0x05, 0x13, 0x08, 0x30, 0x37, 0x39, 0x36, 0x39, 0x32, 0x38, 0x37,
+  0x30, 0x1e, 0x17, 0x0d, 0x31, 0x31, 0x30, 0x0e, 0x06, 0x03, 0x55, 0x1d,
+  0x0f, 0x01, 0x01, 0xff, 0x04, 0x04, 0x03, 0x02, 0x05, 0xa0, 0x30, 0x0c,
+  0x06, 0x03, 0x55, 0x1d, 0x13, 0x01, 0x01, 0xff, 0x04, 0x02, 0x30, 0x00,
+  0x30, 0x1d, 0x30, 0x0f, 0x06, 0x03, 0x55, 0x1d, 0x13, 0x01, 0x01, 0xff,
+  0x04, 0x05, 0x30, 0x03, 0x01, 0x01, 0x00, 0x30, 0x1d, 0x06, 0x03, 0x55,
+  0x1d, 0x25, 0x04, 0x16, 0x30, 0x14, 0x06, 0x08, 0x2b, 0x06, 0x01, 0x05,
+  0x05, 0x07, 0x03, 0x01, 0x06, 0x08, 0x2b, 0x06, 0x01, 0x05, 0x05, 0x07,
+  0x03, 0x02, 0x30, 0x0e, 0x06, 0x03, 0x55, 0x1d, 0x0f, 0x01, 0x01, 0xff,
+  0x04, 0x04, 0x03, 0x02, 0x05, 0xa0, 0x30, 0x33, 0x06, 0x03, 0x55, 0x1d,
+  0x1f, 0x04, 0x2c, 0x30, 0x2a, 0x30, 0x28, 0xa0, 0x26, 0xa0, 0x24, 0x86,
+  0x22, 0x68, 0x74, 0x74, 0x70, 0x3a, 0x2f, 0x2f, 0x63, 0x72, 0x6c, 0x2e,
+  0x67, 0x6f, 0x64, 0x61, 0x64, 0x64, 0x79, 0x2e, 0x63, 0x6f, 0x6d, 0x2f,
+  0x67, 0x64, 0x73, 0x31, 0x2d, 0x32, 0x30, 0x2a, 0x30, 0x28, 0x06, 0x08,
+  0x2b, 0x06, 0x01, 0x05, 0x05, 0x07, 0x02, 0x01, 0x16, 0x1c, 0x68, 0x74,
+  0x74, 0x70, 0x73, 0x3a, 0x2f, 0x2f, 0x77, 0x77, 0x77, 0x2e, 0x76, 0x65,
+  0x72, 0x69, 0x73, 0x69, 0x67, 0x6e, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x63,
+  0x70, 0x73, 0x30, 0x34, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x5a, 0x17,
+  0x0d, 0x31, 0x33, 0x30, 0x35, 0x30, 0x39, 0x06, 0x08, 0x2b, 0x06, 0x01,
+  0x05, 0x05, 0x07, 0x30, 0x02, 0x86, 0x2d, 0x68, 0x74, 0x74, 0x70, 0x3a,
+  0x2f, 0x2f, 0x73, 0x30, 0x39, 0x30, 0x37, 0x06, 0x08, 0x2b, 0x06, 0x01,
+  0x05, 0x05, 0x07, 0x02, 0x30, 0x44, 0x06, 0x03, 0x55, 0x1d, 0x20, 0x04,
+  0x3d, 0x30, 0x3b, 0x30, 0x39, 0x06, 0x0b, 0x60, 0x86, 0x48, 0x01, 0x86,
+  0xf8, 0x45, 0x01, 0x07, 0x17, 0x06, 0x31, 0x0b, 0x30, 0x09, 0x06, 0x03,
+  0x55, 0x04, 0x06, 0x13, 0x02, 0x47, 0x42, 0x31, 0x1b, 0x53, 0x31, 0x17,
+  0x30, 0x15, 0x06, 0x03, 0x55, 0x04, 0x0a, 0x13, 0x0e, 0x56, 0x65, 0x72,
+  0x69, 0x53, 0x69, 0x67, 0x6e, 0x2c, 0x20, 0x49, 0x6e, 0x63, 0x2e, 0x31,
+  0x1f, 0x30, 0x1d, 0x06, 0x03, 0x55, 0x04, 0x0b, 0x13, 0x16, 0x56, 0x65,
+  0x72, 0x69, 0x53, 0x69, 0x67, 0x6e, 0x20, 0x54, 0x72, 0x75, 0x73, 0x74,
+  0x20, 0x4e, 0x65, 0x74, 0x77, 0x6f, 0x72, 0x6b, 0x31, 0x3b, 0x30, 0x39,
+  0x06, 0x03, 0x55, 0x04, 0x0b, 0x13, 0x32, 0x54, 0x65, 0x72, 0x6d, 0x73,
+  0x20, 0x6f, 0x66, 0x20, 0x75, 0x73, 0x65, 0x20, 0x61, 0x74, 0x20, 0x68,
+  0x74, 0x74, 0x70, 0x73, 0x3a, 0x2f, 0x2f, 0x77, 0x77, 0x77, 0x2e, 0x76,
+  0x65, 0x72, 0x69, 0x73, 0x69, 0x67, 0x6e, 0x2e, 0x63, 0x6f, 0x6d, 0x2f,
+  0x72, 0x70, 0x61, 0x20, 0x28, 0x63, 0x29, 0x30, 0x31, 0x10, 0x30, 0x0e,
+  0x06, 0x03, 0x55, 0x04, 0x07, 0x13, 0x07, 0x53, 0x31, 0x13, 0x30, 0x11,
+  0x06, 0x03, 0x55, 0x04, 0x0b, 0x13, 0x0a, 0x47, 0x31, 0x13, 0x30, 0x11,
+  0x06, 0x0b, 0x2b, 0x06, 0x01, 0x04, 0x01, 0x82, 0x37, 0x3c, 0x02, 0x01,
+  0x03, 0x13, 0x02, 0x55, 0x31, 0x16, 0x30, 0x14, 0x06, 0x03, 0x55, 0x04,
+  0x03, 0x14, 0x31, 0x19, 0x30, 0x17, 0x06, 0x03, 0x55, 0x04, 0x03, 0x13,
+  0x31, 0x1d, 0x30, 0x1b, 0x06, 0x03, 0x55, 0x04, 0x0f, 0x13, 0x14, 0x50,
+  0x72, 0x69, 0x76, 0x61, 0x74, 0x65, 0x20, 0x4f, 0x72, 0x67, 0x61, 0x6e,
+  0x69, 0x7a, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x31, 0x12, 0x31, 0x21, 0x30,
+  0x1f, 0x06, 0x03, 0x55, 0x04, 0x0b, 0x13, 0x18, 0x44, 0x6f, 0x6d, 0x61,
+  0x69, 0x6e, 0x20, 0x43, 0x6f, 0x6e, 0x74, 0x72, 0x6f, 0x6c, 0x20, 0x56,
+  0x61, 0x6c, 0x69, 0x64, 0x61, 0x74, 0x65, 0x64, 0x31, 0x14, 0x31, 0x31,
+  0x30, 0x2f, 0x06, 0x03, 0x55, 0x04, 0x0b, 0x13, 0x28, 0x53, 0x65, 0x65,
+  0x20, 0x77, 0x77, 0x77, 0x2e, 0x72, 0x3a, 0x2f, 0x2f, 0x73, 0x65, 0x63,
+  0x75, 0x72, 0x65, 0x2e, 0x67, 0x47, 0x6c, 0x6f, 0x62, 0x61, 0x6c, 0x53,
+  0x69, 0x67, 0x6e, 0x31, 0x53, 0x65, 0x72, 0x76, 0x65, 0x72, 0x43, 0x41,
+  0x2e, 0x63, 0x72, 0x6c, 0x56, 0x65, 0x72, 0x69, 0x53, 0x69, 0x67, 0x6e,
+  0x20, 0x43, 0x6c, 0x61, 0x73, 0x73, 0x20, 0x33, 0x20, 0x45, 0x63, 0x72,
+  0x6c, 0x2e, 0x67, 0x65, 0x6f, 0x74, 0x72, 0x75, 0x73, 0x74, 0x2e, 0x63,
+  0x6f, 0x6d, 0x2f, 0x63, 0x72, 0x6c, 0x73, 0x2f, 0x73, 0x64, 0x31, 0x1a,
+  0x30, 0x18, 0x06, 0x03, 0x55, 0x04, 0x0a, 0x68, 0x74, 0x74, 0x70, 0x3a,
+  0x2f, 0x2f, 0x45, 0x56, 0x49, 0x6e, 0x74, 0x6c, 0x2d, 0x63, 0x63, 0x72,
+  0x74, 0x2e, 0x67, 0x77, 0x77, 0x77, 0x2e, 0x67, 0x69, 0x63, 0x65, 0x72,
+  0x74, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x31, 0x6f, 0x63, 0x73, 0x70, 0x2e,
+  0x76, 0x65, 0x72, 0x69, 0x73, 0x69, 0x67, 0x6e, 0x2e, 0x63, 0x6f, 0x6d,
+  0x30, 0x39, 0x72, 0x61, 0x70, 0x69, 0x64, 0x73, 0x73, 0x6c, 0x2e, 0x63,
+  0x6f, 0x73, 0x2e, 0x67, 0x6f, 0x64, 0x61, 0x64, 0x64, 0x79, 0x2e, 0x63,
+  0x6f, 0x6d, 0x2f, 0x72, 0x65, 0x70, 0x6f, 0x73, 0x69, 0x74, 0x6f, 0x72,
+  0x79, 0x2f, 0x30, 0x81, 0x80, 0x06, 0x08, 0x2b, 0x06, 0x01, 0x05, 0x05,
+  0x07, 0x01, 0x01, 0x04, 0x74, 0x30, 0x72, 0x30, 0x24, 0x06, 0x08, 0x2b,
+  0x06, 0x01, 0x05, 0x05, 0x07, 0x30, 0x01, 0x86, 0x18, 0x68, 0x74, 0x74,
+  0x70, 0x3a, 0x2f, 0x2f, 0x6f, 0x63, 0x73, 0x70, 0x2e, 0x67, 0x6f, 0x64,
+  0x61, 0x64, 0x64, 0x79, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x30, 0x4a, 0x06,
+  0x08, 0x2b, 0x06, 0x01, 0x05, 0x05, 0x07, 0x30, 0x02, 0x86, 0x3e, 0x68,
+  0x74, 0x74, 0x70, 0x3a, 0x2f, 0x2f, 0x63, 0x65, 0x72, 0x74, 0x69, 0x66,
+  0x69, 0x63, 0x61, 0x74, 0x65, 0x73, 0x2e, 0x67, 0x6f, 0x64, 0x61, 0x64,
+  0x64, 0x79, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x72, 0x65, 0x70, 0x6f, 0x73,
+  0x69, 0x74, 0x6f, 0x72, 0x79, 0x2f, 0x67, 0x64, 0x5f, 0x69, 0x6e, 0x74,
+  0x65, 0x72, 0x6d, 0x65, 0x64, 0x69, 0x61, 0x74, 0x65, 0x2e, 0x63, 0x72,
+  0x74, 0x30, 0x1f, 0x06, 0x03, 0x55, 0x1d, 0x23, 0x04, 0x18, 0x30, 0x16,
+  0x80, 0x14, 0xfd, 0xac, 0x61, 0x32, 0x93, 0x6c, 0x45, 0xd6, 0xe2, 0xee,
+  0x85, 0x5f, 0x9a, 0xba, 0xe7, 0x76, 0x99, 0x68, 0xcc, 0xe7, 0x30, 0x27,
+  0x86, 0x29, 0x68, 0x74, 0x74, 0x70, 0x3a, 0x2f, 0x2f, 0x63, 0x86, 0x30,
+  0x68, 0x74, 0x74, 0x70, 0x3a, 0x2f, 0x2f, 0x73,
+};
+
+// CertEntry represents a certificate in compressed form. Each entry is one of
+// the three types enumerated in |Type|.
+struct CertEntry {
+ public:
+  enum Type {
+    // COMPRESSED means that the certificate is included in the trailing zlib
+    // data.
+    COMPRESSED = 1,
+    // CACHED means that the certificate is already known to the peer and will
+    // be replaced by its 64-bit hash (in |hash|).
+    CACHED = 2,
+    // COMMON means that the certificate is in a common certificate set known
+    // to the peer with hash |set_hash| and index |index|.
+    COMMON = 3,
+  };
+
+  Type type;
+  uint64 hash;
+  uint64 set_hash;
+  uint32 index;
+};
+
+// MatchCerts returns a vector of CertEntries describing how to most
+// efficiently represent |certs| to a peer who has the common sets identified
+// by |client_common_set_hashes| and who has cached the certificates with the
+// 64-bit, FNV-1a hashes in |client_cached|.
+vector<CertEntry> MatchCerts(const vector<string>& certs,
+                             StringPiece client_common_set_hashes,
+                             StringPiece client_cached,
+                             CommonCertSet* common_set) {
+  vector<CertEntry> entries;
+  entries.reserve(certs.size());
+
+  const bool cached_valid = client_cached.size() % sizeof(uint64) == 0 &&
+                            !client_cached.empty();
+
+  for (vector<string>::const_iterator i = certs.begin();
+       i != certs.end(); ++i) {
+    CertEntry entry;
+
+    if (cached_valid) {
+      bool cached = false;
+
+      uint64 hash = QuicUtils::FNV1a_64_Hash(i->data(), i->size());
+      // This assumes that the machine is little-endian.
+      for (size_t i = 0; i < client_cached.size(); i += sizeof(uint64)) {
+        uint64 cached_hash;
+        memcpy(&cached_hash, client_cached.data() + i, sizeof(uint64));
+        if (hash != cached_hash) {
+          continue;
+        }
+
+        entry.type = CertEntry::CACHED;
+        entry.hash = hash;
+        entries.push_back(entry);
+        cached = true;
+        break;
+      }
+
+      if (cached) {
+        continue;
+      }
+    }
+
+    if (common_set &&
+        common_set->MatchCert(*i, client_common_set_hashes, &entry.set_hash,
+                              &entry.index)) {
+      entry.type = CertEntry::COMMON;
+      entries.push_back(entry);
+      continue;
+    }
+
+    entry.type = CertEntry::COMPRESSED;
+    entries.push_back(entry);
+  }
+
+  return entries;
+}
+
+// CertEntriesSize returns the size, in bytes, of the serialised form of
+// |entries|.
+size_t CertEntriesSize(const vector<CertEntry>& entries) {
+  size_t entries_size = 0;
+
+  for (vector<CertEntry>::const_iterator i = entries.begin();
+       i != entries.end(); ++i) {
+    switch (i->type) {
+      case CertEntry::COMPRESSED:
+        entries_size++;
+        break;
+      case CertEntry::CACHED:
+        entries_size += 1 + sizeof(uint64);
+        break;
+      case CertEntry::COMMON:
+        entries_size += 1 + sizeof(uint64) + sizeof(uint32);
+        break;
+    }
+  }
+
+  entries_size++;  // for end marker
+
+  return entries_size;
+}
+
+// SerializeCertEntries serialises |entries| to |out|, which must have enough
+// space to contain them.
+void SerializeCertEntries(uint8* out, const vector<CertEntry>& entries) {
+  for (vector<CertEntry>::const_iterator i = entries.begin();
+       i != entries.end(); ++i) {
+    *out++ = i->type;
+    switch (i->type) {
+      case CertEntry::COMPRESSED:
+        break;
+      case CertEntry::CACHED:
+        memcpy(out, &i->hash, sizeof(i->hash));
+        out += sizeof(uint64);
+        break;
+      case CertEntry::COMMON:
+        // Assumes a little-endian machine.
+        memcpy(out, &i->set_hash, sizeof(i->set_hash));
+        out += sizeof(i->set_hash);
+        memcpy(out, &i->index, sizeof(uint32));
+        out += sizeof(uint32);
+        break;
+    }
+  }
+
+  *out++ = 0;  // end marker
+}
+
+// ZlibDictForEntries returns a string that contains the zlib pre-shared
+// dictionary to use in order to decompress a zlib block following |entries|.
+// |certs| is one-to-one with |entries| and contains the certificates for those
+// entries that are CACHED or COMMON.
+string ZlibDictForEntries(const vector<CertEntry>& entries,
+                          const vector<string>& certs) {
+  string zlib_dict;
+
+  // The dictionary starts with the common and cached certs in reverse order.
+  size_t zlib_dict_size = 0;
+  for (size_t i = certs.size() - 1; i < certs.size(); i--) {
+    if (entries[i].type != CertEntry::COMPRESSED) {
+      zlib_dict_size += certs[i].size();
+    }
+  }
+
+  // At the end of the dictionary is a block of common certificate substrings.
+  zlib_dict_size += sizeof(kCommonCertSubstrings);
+
+  zlib_dict.reserve(zlib_dict_size);
+
+  for (size_t i = certs.size() - 1; i < certs.size(); i--) {
+    if (entries[i].type != CertEntry::COMPRESSED) {
+      zlib_dict += certs[i];
+    }
+  }
+
+  zlib_dict += string(reinterpret_cast<const char*>(kCommonCertSubstrings),
+                      sizeof(kCommonCertSubstrings));
+
+  DCHECK_EQ(zlib_dict.size(), zlib_dict_size);
+
+  return zlib_dict;
+}
+
+// HashCerts returns the FNV-1a hashes of |certs|.
+vector<uint64> HashCerts(const vector<string>& certs) {
+  vector<uint64> ret;
+
+  for (vector<string>::const_iterator i = certs.begin();
+       i != certs.end(); ++i) {
+    ret.push_back(QuicUtils::FNV1a_64_Hash(i->data(), i->size()));
+  }
+
+  return ret;
+}
+
+// ParseEntries parses the serialised form of a vector of CertEntries from
+// |in_out| and writes them to |out_entries|. CACHED and COMMON entries are
+// resolved using |cached_certs| and |common_set| and written to |out_certs|.
+// |in_out| is updated to contain the trailing data.
+bool ParseEntries(StringPiece* in_out,
+                  const vector<string>& cached_certs,
+                  CommonCertSet* common_set,
+                  vector<CertEntry>* out_entries,
+                  vector<string>* out_certs) {
+  StringPiece in = *in_out;
+  vector<uint64> cached_hashes;
+
+  out_entries->clear();
+  out_certs->clear();
+
+  for (;;) {
+    if (in.empty()) {
+      return false;
+    }
+    CertEntry entry;
+    const uint8 type_byte = in[0];
+    in.remove_prefix(1);
+
+    if (type_byte == 0) {
+      break;
+    }
+
+    entry.type = static_cast<CertEntry::Type>(type_byte);
+
+    switch (entry.type) {
+      case CertEntry::COMPRESSED:
+        out_certs->push_back(string());
+        break;
+      case CertEntry::CACHED: {
+        if (in.size() < sizeof(uint64)) {
+          return false;
+        }
+        memcpy(&entry.hash, in.data(), sizeof(uint64));
+        in.remove_prefix(sizeof(uint64));
+
+        if (cached_hashes.size() != cached_certs.size()) {
+          cached_hashes = HashCerts(cached_certs);
+        }
+        bool found = false;
+        for (size_t i = 0; i < cached_hashes.size(); i++) {
+          if (cached_hashes[i] == entry.hash) {
+            out_certs->push_back(cached_certs[i]);
+            found = true;
+            break;
+          }
+        }
+        if (!found) {
+          return false;
+        }
+        break;
+      }
+      case CertEntry::COMMON: {
+        if (!common_set) {
+          return false;
+        }
+        if (in.size() < sizeof(uint64)) {
+          return false;
+        }
+        memcpy(&entry.set_hash, in.data(), sizeof(uint64));
+        in.remove_prefix(sizeof(uint64));
+
+        if (in.size() < sizeof(uint32)) {
+          return false;
+        }
+        memcpy(&entry.index, in.data(), sizeof(uint32));
+        in.remove_prefix(sizeof(uint32));
+
+        StringPiece cert = common_set->GetCert(entry.set_hash, entry.index);
+        if (cert.empty()) {
+          return false;
+        }
+        out_certs->push_back(cert.as_string());
+        break;
+      }
+      default:
+        return false;
+    }
+    out_entries->push_back(entry);
+  }
+
+  *in_out = in;
+  return true;
+}
+
+class ScopedZLib {
+ public:
+  enum Type {
+    INFLATE,
+    DEFLATE,
+  };
+
+  explicit ScopedZLib(Type type)
+      : z_(NULL),
+        type_(type) {
+  }
+
+  void reset(z_stream* z) {
+    z_ = z;
+  }
+
+  ~ScopedZLib() {
+    if (z_) {
+      if (type_ == DEFLATE) {
+        deflateEnd(z_);
+      } else {
+        inflateEnd(z_);
+      }
+      z_ = NULL;
+    }
+  }
+
+ private:
+  z_stream* z_;
+  const Type type_;
+};
+
+}  // anonymous namespace
+
+
+// static
+string CertCompressor::CompressChain(const vector<string>& certs,
+                                     StringPiece client_common_set_hashes,
+                                     StringPiece client_cached,
+                                     CommonCertSet* common_set) {
+  const vector<CertEntry> entries = MatchCerts(
+      certs, client_common_set_hashes, client_cached, common_set);
+  DCHECK_EQ(entries.size(), certs.size());
+
+  size_t uncompressed_size = 0;
+  for (size_t i = 0; i < entries.size(); i++) {
+    if (entries[i].type == CertEntry::COMPRESSED) {
+      uncompressed_size += 4 /* uint32 length */ + certs[i].size();
+    }
+  }
+
+  size_t compressed_size = 0;
+  z_stream z;
+  ScopedZLib scoped_z(ScopedZLib::DEFLATE);
+
+  if (uncompressed_size > 0) {
+    memset(&z, 0, sizeof(z));
+    int rv = deflateInit(&z, Z_DEFAULT_COMPRESSION);
+    DCHECK_EQ(Z_OK, rv);
+    if (rv != Z_OK) {
+      return "";
+    }
+    scoped_z.reset(&z);
+
+    string zlib_dict = ZlibDictForEntries(entries, certs);
+
+    rv = deflateSetDictionary(&z, reinterpret_cast<const uint8*>(&zlib_dict[0]),
+                              zlib_dict.size());
+    DCHECK_EQ(Z_OK, rv);
+    if (rv != Z_OK) {
+      return "";
+    }
+
+    compressed_size = deflateBound(&z, uncompressed_size);
+  }
+
+  const size_t entries_size = CertEntriesSize(entries);
+
+  string result;
+  result.resize(entries_size + (uncompressed_size > 0 ? 4 : 0) +
+                compressed_size);
+
+  uint8* j = reinterpret_cast<uint8*>(&result[0]);
+  SerializeCertEntries(j, entries);
+  j += entries_size;
+
+  if (uncompressed_size == 0) {
+    return result;
+  }
+
+  uint32 uncompressed_size_32 = uncompressed_size;
+  memcpy(j, &uncompressed_size_32, sizeof(uint32));
+  j += sizeof(uint32);
+
+  int rv;
+
+  z.next_out = j;
+  z.avail_out = compressed_size;
+
+  for (size_t i = 0; i < certs.size(); i++) {
+    if (entries[i].type != CertEntry::COMPRESSED) {
+      continue;
+    }
+
+    uint32 length = certs[i].size();
+    z.next_in = reinterpret_cast<uint8*>(&length);
+    z.avail_in = sizeof(length);
+    rv = deflate(&z, Z_NO_FLUSH);
+    DCHECK_EQ(Z_OK, rv);
+    DCHECK_EQ(0u, z.avail_in);
+    if (rv != Z_OK || z.avail_in) {
+      return "";
+    }
+
+    z.next_in =
+        const_cast<uint8*>(reinterpret_cast<const uint8*>(certs[i].data()));
+    z.avail_in = certs[i].size();
+    rv = deflate(&z, Z_NO_FLUSH);
+    DCHECK_EQ(Z_OK, rv);
+    DCHECK_EQ(0u, z.avail_in);
+    if (rv != Z_OK || z.avail_in) {
+      return "";
+    }
+  }
+
+  z.avail_in = 0;
+  rv = deflate(&z, Z_FINISH);
+  DCHECK_EQ(Z_STREAM_END, rv);
+  if (rv != Z_STREAM_END) {
+    return "";
+  }
+
+  result.resize(result.size() - z.avail_out);
+  return result;
+}
+
+// static
+bool CertCompressor::DecompressChain(StringPiece in,
+                                     const vector<string>& cached_certs,
+                                     CommonCertSet* common_set,
+                                     vector<string>* out_certs) {
+  vector<CertEntry> entries;
+  if (!ParseEntries(&in, cached_certs, common_set, &entries, out_certs)) {
+    return false;
+  }
+  DCHECK_EQ(entries.size(), out_certs->size());
+
+  scoped_ptr<uint8[]> uncompressed_data;
+  StringPiece uncompressed;
+
+  if (!in.empty()) {
+    if (in.size() < sizeof(uint32)) {
+      return false;
+    }
+
+    uint32 uncompressed_size;
+    memcpy(&uncompressed_size, in.data(), sizeof(uncompressed_size));
+    in.remove_prefix(sizeof(uint32));
+
+    if (uncompressed_size > 128 * 1024) {
+      return false;
+    }
+
+    uncompressed_data.reset(new uint8[uncompressed_size]);
+    z_stream z;
+    ScopedZLib scoped_z(ScopedZLib::INFLATE);
+
+    memset(&z, 0, sizeof(z));
+    z.next_out = uncompressed_data.get();
+    z.avail_out = uncompressed_size;
+    z.next_in = const_cast<uint8*>(reinterpret_cast<const uint8*>(in.data()));
+    z.avail_in = in.size();
+
+    if (Z_OK != inflateInit(&z)) {
+      return false;
+    }
+    scoped_z.reset(&z);
+
+    int rv = inflate(&z, Z_FINISH);
+    if (rv == Z_NEED_DICT) {
+      string zlib_dict = ZlibDictForEntries(entries, *out_certs);
+      const uint8* dict = reinterpret_cast<const uint8*>(zlib_dict.data());
+      if (Z_OK != inflateSetDictionary(&z, dict, zlib_dict.size())) {
+        return false;
+      }
+      rv = inflate(&z, Z_FINISH);
+    }
+
+    if (Z_STREAM_END != rv ||
+        z.avail_out > 0 ||
+        z.avail_in > 0) {
+      return false;
+    }
+
+    uncompressed = StringPiece(reinterpret_cast<char*>(uncompressed_data.get()),
+                               uncompressed_size);
+  }
+
+  for (size_t i = 0; i < entries.size(); i++) {
+    switch (entries[i].type) {
+      case CertEntry::COMPRESSED:
+        if (uncompressed.size() < sizeof(uint32)) {
+          return false;
+        }
+        uint32 cert_len;
+        memcpy(&cert_len, uncompressed.data(), sizeof(cert_len));
+        uncompressed.remove_prefix(sizeof(uint32));
+        if (uncompressed.size() < cert_len) {
+          return false;
+        }
+        (*out_certs)[i] = uncompressed.substr(0, cert_len).as_string();
+        uncompressed.remove_prefix(cert_len);
+        break;
+      case CertEntry::CACHED:
+      case CertEntry::COMMON:
+        break;
+    }
+  }
+
+  if (!uncompressed.empty()) {
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace net