// 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. This was generated via a fairly dumb algorithm from
// the Alexa Top 5000 set - we could probably do better.
static const 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,
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};
// CertEntry represents a certificate in compressed form. Each entry is one of
// the three types enumerated in |Type|.
struct CertEntry {
public:
enum Type {
// Type 0 is reserved to mean "end of list" in the wire format.
// 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 certificate 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_cert_hashes|.
vector<CertEntry> MatchCerts(const vector<string>& certs,
StringPiece client_common_set_hashes,
StringPiece client_cached_cert_hashes,
const CommonCertSets* common_sets) {
vector<CertEntry> entries;
entries.reserve(certs.size());
const bool cached_valid =
client_cached_cert_hashes.size() % sizeof(uint64) == 0 &&
!client_cached_cert_hashes.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_cert_hashes.size();
i += sizeof(uint64)) {
uint64 cached_hash;
memcpy(&cached_hash, client_cached_cert_hashes.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_sets && common_sets->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) {
entries_size++;
switch (i->type) {
case CertEntry::COMPRESSED:
break;
case CertEntry::CACHED:
entries_size += sizeof(uint64);
break;
case CertEntry::COMMON:
entries_size += 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;
ret.reserve(certs.size());
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_sets| and written to |out_certs|.
// |in_out| is updated to contain the trailing data.
bool ParseEntries(StringPiece* in_out,
const vector<string>& cached_certs,
const CommonCertSets* common_sets,
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_sets) {
return false;
}
if (in.size() < sizeof(uint64) + sizeof(uint32)) {
return false;
}
memcpy(&entry.set_hash, in.data(), sizeof(uint64));
in.remove_prefix(sizeof(uint64));
memcpy(&entry.index, in.data(), sizeof(uint32));
in.remove_prefix(sizeof(uint32));
StringPiece cert = common_sets->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;
}
// ScopedZLib deals with the automatic destruction of a zlib context.
class ScopedZLib {
public:
enum Type {
INFLATE,
DEFLATE,
};
explicit ScopedZLib(Type type) : z_(NULL), type_(type) {}
void reset(z_stream* z) {
Clear();
z_ = z;
}
~ScopedZLib() {
Clear();
}
private:
void Clear() {
if (!z_) {
return;
}
if (type_ == DEFLATE) {
deflateEnd(z_);
} else {
inflateEnd(z_);
}
z_ = NULL;
}
z_stream* z_;
const Type type_;
};
} // anonymous namespace
// static
string CertCompressor::CompressChain(const vector<string>& certs,
StringPiece client_common_set_hashes,
StringPiece client_cached_cert_hashes,
const CommonCertSets* common_sets) {
const vector<CertEntry> entries = MatchCerts(
certs, client_common_set_hashes, client_cached_cert_hashes, common_sets);
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 length32 = certs[i].size();
z.next_in = reinterpret_cast<uint8*>(&length32);
z.avail_in = sizeof(length32);
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,
const CommonCertSets* common_sets,
vector<string>* out_certs) {
vector<CertEntry> entries;
if (!ParseEntries(&in, cached_certs, common_sets, &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