blob: 3ceeb70548434bb473776fc638fa0897ac7ce0e2 [file] [log] [blame]
// Copyright 2016 The Chromium OS 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 "imageloader/component.h"
#include <fcntl.h>
#include <algorithm>
#include <string>
#include <utility>
#include <vector>
#include <base/files/file.h>
#include <base/files/file_enumerator.h>
#include <base/files/file_path.h>
#include <base/files/file_util.h>
#include <base/files/scoped_file.h>
#include <base/json/json_string_value_serializer.h>
#include <base/logging.h>
#include <base/numerics/safe_conversions.h>
#include <base/posix/eintr_wrapper.h>
#include <base/strings/string_number_conversions.h>
#include <base/strings/string_util.h>
#include <crypto/secure_hash.h>
#include <crypto/sha2.h>
#include <crypto/signature_verifier.h>
#include "imageloader/helper_process_proxy.h"
namespace imageloader {
namespace {
// The name of the imageloader manifest file.
constexpr char kManifestName[] = "imageloader.json";
// The name of the fingerprint file.
constexpr char kFingerprintName[] = "manifest.fingerprint";
// The manifest signature.
constexpr char kManifestSignatureNamePattern[] = "imageloader.sig.[1-2]";
// The name of the image file (squashfs).
constexpr char kImageFileNameSquashFS[] = "image.squash";
// The name of the image file (ext4).
constexpr char kImageFileNameExt4[] = "image.ext4";
// The name of the table file.
constexpr char kTableFileName[] = "table";
base::FilePath GetManifestPath(const base::FilePath& component_dir) {
return component_dir.Append(kManifestName);
bool GetSignaturePath(const base::FilePath& component_dir,
base::FilePath* signature_path,
size_t* key_number) {
base::FileEnumerator files(component_dir, false,
for (base::FilePath path = files.Next(); !path.empty(); path = files.Next()) {
// Extract the key number.
std::string key_ext = path.FinalExtension();
if (key_ext.empty())
size_t ext_number;
if (!base::StringToSizeT(key_ext.substr(1), &ext_number))
*signature_path = path;
*key_number = ext_number;
return true;
return false;
base::FilePath GetSignaturePathForKey(const base::FilePath& component_dir,
size_t key_number) {
std::string signature_name(kManifestSignatureNamePattern);
signature_name =
signature_name.substr(0, signature_name.find_last_of('.') + 1);
return component_dir.Append(signature_name +
base::FilePath GetFingerprintPath(const base::FilePath& component_dir) {
return component_dir.Append(kFingerprintName);
base::FilePath GetTablePath(const base::FilePath& component_dir) {
return component_dir.Append(kTableFileName);
base::FilePath GetImagePath(const base::FilePath& component_dir,
FileSystem fs_type) {
if (fs_type == FileSystem::kExt4) {
return component_dir.Append(kImageFileNameExt4);
} else if (fs_type == FileSystem::kSquashFS) {
return component_dir.Append(kImageFileNameSquashFS);
} else {
return base::FilePath();
bool WriteFileToDisk(const base::FilePath& path, const std::string& contents) {
base::ScopedFD fd(HANDLE_EINTR(open(
path.value().c_str(), O_CREAT | O_WRONLY | O_EXCL, kComponentFilePerms)));
if (!fd.is_valid()) {
PLOG(ERROR) << "Error creating file for " << path.value();
return false;
base::File file(fd.release());
int size = base::checked_cast<int>(contents.size());
return file.Write(0,, contents.size()) == size;
bool GetAndVerifyTable(const base::FilePath& path,
const std::vector<uint8_t>& hash,
std::string* out_table) {
std::string table;
if (!base::ReadFileToStringWithMaxSize(path, &table, kMaximumFilesize)) {
return false;
std::vector<uint8_t> table_hash(crypto::kSHA256Length);
crypto::SHA256HashString(table,, table_hash.size());
if (table_hash != hash) {
LOG(ERROR) << "dm-verity table file has the wrong hash.";
return false;
return true;
} // namespace
Component::Component(const base::FilePath& component_dir, int key_number)
: component_dir_(component_dir), key_number_(key_number) {}
std::unique_ptr<Component> Component::Create(
const base::FilePath& component_dir, const Keys& public_keys) {
base::FilePath signature_path;
size_t key_number;
if (!GetSignaturePath(component_dir, &signature_path, &key_number)) {
LOG(ERROR) << "Could not find manifest signature";
return nullptr;
if (key_number < 1 || key_number > public_keys.size()) {
LOG(ERROR) << "Invalid key number";
return nullptr;
std::unique_ptr<Component> component(
new Component(component_dir, key_number));
if (!component->LoadManifest(public_keys[key_number - 1]))
return nullptr;
return component;
const Manifest& Component::manifest() {
return manifest_;
bool Component::Mount(HelperProcessProxy* mounter,
const base::FilePath& dest_dir) {
// Read the table in and verify the hash.
std::string table;
if (!GetAndVerifyTable(GetTablePath(component_dir_), manifest_.table_sha256(),
&table)) {
LOG(ERROR) << "Could not read and verify dm-verity table.";
return false;
base::FilePath image_path(GetImagePath(component_dir_, manifest_.fs_type()));
base::File image(image_path, base::File::FLAG_OPEN | base::File::FLAG_READ);
if (!image.IsValid()) {
LOG(ERROR) << "Could not open image file.";
return false;
base::ScopedFD image_fd(image.TakePlatformFile());
return mounter->SendMountCommand(image_fd.get(), dest_dir.value(),
manifest_.fs_type(), table);
bool Component::LoadManifest(const std::vector<uint8_t>& public_key) {
if (!base::ReadFileToStringWithMaxSize(GetManifestPath(component_dir_),
&manifest_raw_, kMaximumFilesize)) {
LOG(ERROR) << "Could not read manifest file.";
return false;
if (!base::ReadFileToStringWithMaxSize(
GetSignaturePathForKey(component_dir_, key_number_), &manifest_sig_,
kMaximumFilesize)) {
LOG(ERROR) << "Could not read signature file.";
return false;
crypto::SignatureVerifier verifier;
if (!verifier.VerifyInit(
reinterpret_cast<const uint8_t*>(,
base::checked_cast<int>(public_key.size()))) {
LOG(ERROR) << "Failed to initialize signature verification.";
return false;
verifier.VerifyUpdate(reinterpret_cast<const uint8_t*>(,
if (!verifier.VerifyFinal()) {
LOG(ERROR) << "Manifest failed signature verification.";
return false;
return manifest_.ParseManifest(manifest_raw_);
bool Component::CopyTo(const base::FilePath& dest_dir) {
if (!WriteFileToDisk(GetManifestPath(dest_dir), manifest_raw_) ||
!WriteFileToDisk(GetSignaturePathForKey(dest_dir, key_number_),
manifest_sig_)) {
LOG(ERROR) << "Could not write manifest and signature to disk.";
return false;
base::FilePath table_src(GetTablePath(component_dir_));
base::FilePath table_dest(GetTablePath(dest_dir));
if (!CopyComponentFile(table_src, table_dest, manifest_.table_sha256())) {
LOG(ERROR) << "Could not copy table file.";
return false;
base::FilePath image_src(GetImagePath(component_dir_, manifest_.fs_type()));
base::FilePath image_dest(GetImagePath(dest_dir, manifest_.fs_type()));
if (!CopyComponentFile(image_src, image_dest, manifest_.image_sha256())) {
LOG(ERROR) << "Could not copy image file.";
return false;
if (!CopyFingerprintFile(component_dir_, dest_dir)) {
LOG(ERROR) << "Could not copy manifest.fingerprint file.";
return false;
return true;
bool Component::CopyComponentFile(const base::FilePath& src,
const base::FilePath& dest_path,
const std::vector<uint8_t>& expected_hash) {
base::File file(src, base::File::FLAG_OPEN | base::File::FLAG_READ);
if (!file.IsValid())
return false;
base::ScopedFD dest(
HANDLE_EINTR(open(dest_path.value().c_str(), O_CREAT | O_WRONLY | O_EXCL,
if (!dest.is_valid())
return false;
base::File out_file(dest.release());
std::unique_ptr<crypto::SecureHash> sha256(
std::vector<uint8_t> file_hash(crypto::kSHA256Length);
if (!ReadHashAndCopyFile(&file, &file_hash, &out_file)) {
LOG(ERROR) << "Failed to read image file.";
return false;
if (expected_hash != file_hash) {
LOG(ERROR) << "Image is corrupt or modified.";
return false;
return true;
bool Component::ReadHashAndCopyFile(base::File* file,
std::vector<uint8_t>* file_hash,
base::File* out_file) {
std::unique_ptr<crypto::SecureHash> sha256(
int size = file->GetLength();
if (size <= 0)
return false;
int rv = 0, bytes_read = 0;
char buf[4096];
do {
int remaining = size - bytes_read;
int bytes_to_read =
std::min(remaining, base::checked_cast<int>(sizeof(buf)));
rv = file->ReadAtCurrentPos(buf, bytes_to_read);
if (rv <= 0)
bytes_read += rv;
sha256->Update(buf, rv);
if (out_file) {
out_file->WriteAtCurrentPos(buf, rv);
} while (bytes_read <= size);
sha256->Finish(file_hash->data(), file_hash->size());
return bytes_read == size;
bool Component::CopyFingerprintFile(const base::FilePath& src,
const base::FilePath& dest) {
base::FilePath fingerprint_path(GetFingerprintPath(src));
if (base::PathExists(fingerprint_path)) {
std::string fingerprint_contents;
if (!base::ReadFileToStringWithMaxSize(
fingerprint_path, &fingerprint_contents, kMaximumFilesize)) {
return false;
if (!IsValidFingerprintFile(fingerprint_contents))
return false;
if (!WriteFileToDisk(GetFingerprintPath(dest), fingerprint_contents)) {
return false;
return true;
// The client inserts manifest.fingerprint into components after unpacking the
// CRX. The file is used for delta updates. Since Chrome OS doesn't rely on it
// for security of the disk image, we are fine with validating the contents
// and then preserving the unsigned file.
bool Component::IsValidFingerprintFile(const std::string& contents) {
return contents.size() <= 256 &&
std::find_if_not(contents.begin(), contents.end(), [](char ch) {
return base::IsAsciiAlpha(ch) || base::IsAsciiDigit(ch) || ch == '.';
}) == contents.end();
} // namespace imageloader