blob: 1f523a7f6e600403381672acef2fd16733a75d6d [file] [log] [blame]
// Copyright 2017 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 "components/crx_file/crx_verifier.h"
#include <cstring>
#include <iterator>
#include <memory>
#include <set>
#include <utility>
#include "base/base64.h"
#include "base/bind.h"
#include "base/callback.h"
#include "base/files/file.h"
#include "base/files/file_path.h"
#include "base/stl_util.h"
#include "base/strings/string_number_conversions.h"
#include "components/crx_file/crx3.pb.h"
#include "components/crx_file/crx_file.h"
#include "components/crx_file/id_util.h"
#include "crypto/secure_hash.h"
#include "crypto/secure_util.h"
#include "crypto/sha2.h"
#include "crypto/signature_verifier.h"
namespace crx_file {
namespace {
// The maximum size the Crx3 parser will tolerate for a header.
constexpr uint32_t kMaxHeaderSize = 1 << 18;
// The SHA256 hash of the DER SPKI "ecdsa_2017_public" Crx3 key.
constexpr uint8_t kPublisherKeyHash[] = {
0x61, 0xf7, 0xf2, 0xa6, 0xbf, 0xcf, 0x74, 0xcd, 0x0b, 0xc1, 0xfe,
0x24, 0x97, 0xcc, 0x9b, 0x04, 0x25, 0x4c, 0x65, 0x8f, 0x79, 0xf2,
0x14, 0x53, 0x92, 0x86, 0x7e, 0xa8, 0x36, 0x63, 0x67, 0xcf};
// The SHA256 hash of the DER SPKI "ecdsa_2017_public" Crx3 test key.
constexpr uint8_t kPublisherTestKeyHash[] = {
0x6c, 0x46, 0x41, 0x3b, 0x00, 0xd0, 0xfa, 0x0e, 0x72, 0xc8, 0xd2,
0x5f, 0x64, 0xf3, 0xa6, 0x17, 0x03, 0x0d, 0xde, 0x21, 0x61, 0xbe,
0xb7, 0x95, 0x91, 0x95, 0x83, 0x68, 0x12, 0xe9, 0x78, 0x1e};
using VerifierCollection =
using RepeatedProof = google::protobuf::RepeatedPtrField<AsymmetricKeyProof>;
int ReadAndHashBuffer(uint8_t* buffer,
int length,
base::File* file,
crypto::SecureHash* hash) {
static_assert(sizeof(char) == sizeof(uint8_t), "Unsupported char size.");
int read = file->ReadAtCurrentPos(reinterpret_cast<char*>(buffer), length);
if (read > 0)
hash->Update(buffer, read);
return read;
// Returns UINT32_MAX in the case of an unexpected EOF or read error, else
// returns the read uint32.
uint32_t ReadAndHashLittleEndianUInt32(base::File* file,
crypto::SecureHash* hash) {
uint8_t buffer[4] = {};
if (ReadAndHashBuffer(buffer, 4, file, hash) != 4)
return UINT32_MAX;
return buffer[3] << 24 | buffer[2] << 16 | buffer[1] << 8 | buffer[0];
// Read to the end of the file, updating the hash and all verifiers.
bool ReadHashAndVerifyArchive(base::File* file,
crypto::SecureHash* hash,
const VerifierCollection& verifiers) {
uint8_t buffer[1 << 12] = {};
size_t len = 0;
while ((len = ReadAndHashBuffer(buffer, base::size(buffer), file, hash)) >
0) {
for (auto& verifier : verifiers)
verifier->VerifyUpdate(base::make_span(buffer, len));
for (auto& verifier : verifiers) {
if (!verifier->VerifyFinal())
return false;
return len == 0;
// The remaining contents of a Crx3 file are [header-size][header][archive].
// [header] is an encoded protocol buffer and contains both a signed and
// unsigned section. The unsigned section contains a set of key/signature pairs,
// and the signed section is the encoding of another protocol buffer. All
// signatures cover [prefix][signed-header-size][signed-header][archive].
VerifierResult VerifyCrx3(
base::File* file,
crypto::SecureHash* hash,
const std::vector<std::vector<uint8_t>>& required_key_hashes,
std::string* public_key,
std::string* crx_id,
bool require_publisher_key,
bool accept_publisher_test_key) {
// Parse [header-size] and [header].
const uint32_t header_size = ReadAndHashLittleEndianUInt32(file, hash);
if (header_size > kMaxHeaderSize)
return VerifierResult::ERROR_HEADER_INVALID;
std::vector<uint8_t> header_bytes(header_size);
// Assuming kMaxHeaderSize can fit in an int, the following cast is safe.
if (ReadAndHashBuffer(, header_size, file, hash) !=
return VerifierResult::ERROR_HEADER_INVALID;
CrxFileHeader header;
if (!header.ParseFromArray(, header_size))
return VerifierResult::ERROR_HEADER_INVALID;
// Parse [signed-header].
const std::string& signed_header_data_str = header.signed_header_data();
SignedData signed_header_data;
if (!signed_header_data.ParseFromString(signed_header_data_str))
return VerifierResult::ERROR_HEADER_INVALID;
const std::string& crx_id_encoded = signed_header_data.crx_id();
const std::string declared_crx_id = id_util::GenerateIdFromHex(
base::HexEncode(, crx_id_encoded.size()));
// Create a little-endian representation of [signed-header-size].
const int signed_header_size = signed_header_data_str.size();
const uint8_t header_size_octets[] = {
signed_header_size, signed_header_size >> 8, signed_header_size >> 16,
signed_header_size >> 24};
// Create a set of all required key hashes.
std::set<std::vector<uint8_t>> required_key_set(required_key_hashes.begin(),
using ProofFetcher = const RepeatedProof& (CrxFileHeader::*)() const;
ProofFetcher rsa = &CrxFileHeader::sha256_with_rsa;
ProofFetcher ecdsa = &CrxFileHeader::sha256_with_ecdsa;
std::string public_key_bytes;
VerifierCollection verifiers;
verifiers.reserve(header.sha256_with_rsa_size() +
const std::vector<
std::pair<ProofFetcher, crypto::SignatureVerifier::SignatureAlgorithm>>
proof_types = {
std::make_pair(rsa, crypto::SignatureVerifier::RSA_PKCS1_SHA256),
std::make_pair(ecdsa, crypto::SignatureVerifier::ECDSA_SHA256)};
std::vector<uint8_t> publisher_key(std::begin(kPublisherKeyHash),
base::Optional<std::vector<uint8_t>> publisher_test_key;
if (accept_publisher_test_key) {
bool found_publisher_key = false;
// Initialize all verifiers and update them with
// [prefix][signed-header-size][signed-header].
// Clear any elements of required_key_set that are encountered, and watch for
// the developer key.
for (const auto& proof_type : proof_types) {
for (const auto& proof : (header.*proof_type.first)()) {
const std::string& key = proof.public_key();
const std::string& sig = proof.signature();
if (id_util::GenerateId(key) == declared_crx_id)
public_key_bytes = key;
std::vector<uint8_t> key_hash(crypto::kSHA256Length);
crypto::SHA256HashString(key,, key_hash.size());
DCHECK_EQ(accept_publisher_test_key, publisher_test_key.has_value());
found_publisher_key =
found_publisher_key || key_hash == publisher_key ||
(accept_publisher_test_key && key_hash == *publisher_test_key);
auto v = std::make_unique<crypto::SignatureVerifier>();
static_assert(sizeof(unsigned char) == sizeof(uint8_t),
"Unsupported char size.");
if (!v->VerifyInit(proof_type.second,
if (public_key_bytes.empty() || !required_key_set.empty())
if (require_publisher_key && !found_publisher_key)
// Update and finalize the verifiers with [archive].
if (!ReadHashAndVerifyArchive(file, hash, verifiers))
base::Base64Encode(public_key_bytes, public_key);
*crx_id = declared_crx_id;
return VerifierResult::OK_FULL;
} // namespace
VerifierResult Verify(
const base::FilePath& crx_path,
const VerifierFormat& format,
const std::vector<std::vector<uint8_t>>& required_key_hashes,
const std::vector<uint8_t>& required_file_hash,
std::string* public_key,
std::string* crx_id) {
std::string public_key_local;
std::string crx_id_local;
base::File file(crx_path, base::File::FLAG_OPEN | base::File::FLAG_READ);
if (!file.IsValid())
return VerifierResult::ERROR_FILE_NOT_READABLE;
std::unique_ptr<crypto::SecureHash> file_hash =
// Magic number.
bool diff = false;
char buffer[kCrxFileHeaderMagicSize] = {};
if (file.ReadAtCurrentPos(buffer, kCrxFileHeaderMagicSize) !=
return VerifierResult::ERROR_HEADER_INVALID;
if (!strncmp(buffer, kCrxDiffFileHeaderMagic, kCrxFileHeaderMagicSize))
diff = true;
else if (strncmp(buffer, kCrxFileHeaderMagic, kCrxFileHeaderMagicSize))
return VerifierResult::ERROR_HEADER_INVALID;
file_hash->Update(buffer, sizeof(buffer));
// Version number.
const uint32_t version =
ReadAndHashLittleEndianUInt32(&file, file_hash.get());
VerifierResult result;
if (version == 3) {
bool require_publisher_key =
format == VerifierFormat::CRX3_WITH_PUBLISHER_PROOF ||
format == VerifierFormat::CRX3_WITH_TEST_PUBLISHER_PROOF;
result =
VerifyCrx3(&file, file_hash.get(), required_key_hashes,
&public_key_local, &crx_id_local, require_publisher_key,
format == VerifierFormat::CRX3_WITH_TEST_PUBLISHER_PROOF);
} else {
result = VerifierResult::ERROR_HEADER_INVALID;
if (result != VerifierResult::OK_FULL)
return result;
// Finalize file hash.
uint8_t final_hash[crypto::kSHA256Length] = {};
file_hash->Finish(final_hash, sizeof(final_hash));
if (!required_file_hash.empty()) {
if (required_file_hash.size() != crypto::kSHA256Length)
if (!crypto::SecureMemEqual(final_hash,,
return VerifierResult::ERROR_FILE_HASH_FAILED;
// All is well. Set the out-params and return.
if (public_key)
*public_key = public_key_local;
if (crx_id)
*crx_id = crx_id_local;
return diff ? VerifierResult::OK_DELTA : VerifierResult::OK_FULL;
} // namespace crx_file