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// Copyright 2014 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 "extensions/browser/content_hash_reader.h"
#include "base/files/file_util.h"
#include "base/memory/ptr_util.h"
#include "base/metrics/histogram_macros.h"
#include "base/stl_util.h"
#include "base/strings/string_util.h"
#include "base/timer/elapsed_timer.h"
#include "base/values.h"
#include "crypto/sha2.h"
#include "extensions/browser/computed_hashes.h"
#include "extensions/browser/content_hash_tree.h"
#include "extensions/browser/content_verifier/content_hash.h"
#include "extensions/browser/verified_contents.h"
namespace extensions {
ContentHashReader::ContentHashReader(InitStatus status) : status_(status) {}
ContentHashReader::~ContentHashReader() = default;
// static
std::unique_ptr<const ContentHashReader> ContentHashReader::Create(
const base::FilePath& relative_path,
const scoped_refptr<const ContentHash>& content_hash) {
base::ElapsedTimer timer;
ComputedHashes::Status hashes_status = content_hash->computed_hashes_status();
if (hashes_status == ComputedHashes::Status::UNKNOWN ||
hashes_status == ComputedHashes::Status::READ_FAILED) {
// Failure: no hashes at all.
return base::WrapUnique(new ContentHashReader(InitStatus::HASHES_MISSING));
}
if (hashes_status == ComputedHashes::Status::PARSE_FAILED) {
// Failure: hashes are unreadable.
return base::WrapUnique(new ContentHashReader(InitStatus::HASHES_DAMAGED));
}
DCHECK_EQ(ComputedHashes::Status::SUCCESS, hashes_status);
const ComputedHashes& computed_hashes = content_hash->computed_hashes();
base::Optional<std::string> root;
int block_size;
std::vector<std::string> block_hashes;
if (computed_hashes.GetHashes(relative_path, &block_size, &block_hashes) &&
block_size % crypto::kSHA256Length == 0) {
root =
ComputeTreeHashRoot(block_hashes, block_size / crypto::kSHA256Length);
}
ContentHash::TreeHashVerificationResult verification =
content_hash->VerifyTreeHashRoot(relative_path,
base::OptionalOrNullptr(root));
// Extensions sometimes request resources that do not have an entry in
// computed_hashes.json or verified_content.json. This can happen, for
// example, when an extension sends an XHR to a resource. This should not be
// considered as a failure.
if (verification != ContentHash::TreeHashVerificationResult::SUCCESS) {
base::FilePath full_path =
content_hash->extension_root().Append(relative_path);
// Making a request to a non-existent file or to a directory should not
// result in content verification failure.
// TODO(proberge): This logic could be simplified if |content_verify_job|
// kept track of whether the file being verified was successfully read.
// A content verification failure should be triggered if there is a mismatch
// between the file read state and the existence of verification hashes.
if (verification == ContentHash::TreeHashVerificationResult::NO_ENTRY &&
(!base::PathExists(full_path) || base::DirectoryExists(full_path))) {
// Expected failure: no hashes for non-existing resource.
return base::WrapUnique(new ContentHashReader(
InitStatus::NO_HASHES_FOR_NON_EXISTING_RESOURCE));
}
// Failure: no hashes when resource need them.
return base::WrapUnique(
new ContentHashReader(InitStatus::NO_HASHES_FOR_RESOURCE));
}
auto hash_reader =
base::WrapUnique(new ContentHashReader(InitStatus::SUCCESS));
hash_reader->block_size_ = block_size;
hash_reader->hashes_ = std::move(block_hashes);
UMA_HISTOGRAM_TIMES("ExtensionContentHashReader.InitLatency",
timer.Elapsed());
return hash_reader; // Success.
}
int ContentHashReader::block_count() const {
return hashes_.size();
}
int ContentHashReader::block_size() const {
return block_size_;
}
bool ContentHashReader::GetHashForBlock(int block_index,
const std::string** result) const {
if (status_ != InitStatus::SUCCESS)
return false;
DCHECK(block_index >= 0);
if (static_cast<unsigned>(block_index) >= hashes_.size())
return false;
*result = &hashes_[block_index];
return true;
}
} // namespace extensions
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