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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/computed_hashes.h"
#include "base/base64.h"
#include "base/files/file_path.h"
#include "base/files/file_util.h"
#include "base/json/json_reader.h"
#include "base/json/json_writer.h"
#include "base/stl_util.h"
#include "base/values.h"
#include "crypto/secure_hash.h"
#include "crypto/sha2.h"
namespace {
const char kBlockHashesKey[] = "block_hashes";
const char kBlockSizeKey[] = "block_size";
const char kFileHashesKey[] = "file_hashes";
const char kPathKey[] = "path";
const char kVersionKey[] = "version";
const int kVersion = 2;
} // namespace
namespace extensions {
ComputedHashes::Reader::Reader() {
}
ComputedHashes::Reader::~Reader() {
}
bool ComputedHashes::Reader::InitFromFile(const base::FilePath& path) {
std::string contents;
if (!base::ReadFileToString(path, &contents))
return false;
base::DictionaryValue* top_dictionary = NULL;
scoped_ptr<base::Value> value(base::JSONReader::Read(contents));
if (!value.get() || !value->GetAsDictionary(&top_dictionary))
return false;
// For now we don't support forwards or backwards compatability in the
// format, so we return false on version mismatch.
int version = 0;
if (!top_dictionary->GetInteger(kVersionKey, &version) || version != kVersion)
return false;
base::ListValue* all_hashes = NULL;
if (!top_dictionary->GetList(kFileHashesKey, &all_hashes))
return false;
for (size_t i = 0; i < all_hashes->GetSize(); i++) {
base::DictionaryValue* dictionary = NULL;
if (!all_hashes->GetDictionary(i, &dictionary))
return false;
std::string relative_path_utf8;
if (!dictionary->GetString(kPathKey, &relative_path_utf8))
return false;
int block_size;
if (!dictionary->GetInteger(kBlockSizeKey, &block_size))
return false;
if (block_size <= 0 || ((block_size % 1024) != 0)) {
LOG(ERROR) << "Invalid block size: " << block_size;
block_size = 0;
return false;
}
base::ListValue* hashes_list = NULL;
if (!dictionary->GetList(kBlockHashesKey, &hashes_list))
return false;
base::FilePath relative_path =
base::FilePath::FromUTF8Unsafe(relative_path_utf8);
relative_path = relative_path.NormalizePathSeparatorsTo('/');
data_[relative_path] = HashInfo(block_size, std::vector<std::string>());
std::vector<std::string>* hashes = &(data_[relative_path].second);
for (size_t j = 0; j < hashes_list->GetSize(); j++) {
std::string encoded;
if (!hashes_list->GetString(j, &encoded))
return false;
hashes->push_back(std::string());
std::string* decoded = &hashes->back();
if (!base::Base64Decode(encoded, decoded)) {
hashes->clear();
return false;
}
}
}
return true;
}
bool ComputedHashes::Reader::GetHashes(const base::FilePath& relative_path,
int* block_size,
std::vector<std::string>* hashes) {
base::FilePath path = relative_path.NormalizePathSeparatorsTo('/');
std::map<base::FilePath, HashInfo>::iterator i = data_.find(path);
if (i == data_.end()) {
// If we didn't find the entry using exact match, it's possible the
// developer is using a path with some letters in the incorrect case, which
// happens to work on windows/osx. So try doing a linear scan to look for a
// case-insensitive match. In practice most extensions don't have that big
// a list of files so the performance penalty is probably not too big
// here. Also for crbug.com/29941 we plan to start warning developers when
// they are making this mistake, since their extension will be broken on
// linux/chromeos.
for (i = data_.begin(); i != data_.end(); ++i) {
const base::FilePath& entry = i->first;
if (base::FilePath::CompareEqualIgnoreCase(entry.value(), path.value()))
break;
}
if (i == data_.end())
return false;
}
HashInfo& info = i->second;
*block_size = info.first;
*hashes = info.second;
return true;
}
ComputedHashes::Writer::Writer() : file_list_(new base::ListValue) {
}
ComputedHashes::Writer::~Writer() {
}
void ComputedHashes::Writer::AddHashes(const base::FilePath& relative_path,
int block_size,
const std::vector<std::string>& hashes) {
base::DictionaryValue* dict = new base::DictionaryValue();
base::ListValue* block_hashes = new base::ListValue();
file_list_->Append(dict);
dict->SetString(kPathKey,
relative_path.NormalizePathSeparatorsTo('/').AsUTF8Unsafe());
dict->SetInteger(kBlockSizeKey, block_size);
dict->Set(kBlockHashesKey, block_hashes);
for (std::vector<std::string>::const_iterator i = hashes.begin();
i != hashes.end();
++i) {
std::string encoded;
base::Base64Encode(*i, &encoded);
block_hashes->AppendString(encoded);
}
}
bool ComputedHashes::Writer::WriteToFile(const base::FilePath& path) {
std::string json;
base::DictionaryValue top_dictionary;
top_dictionary.SetInteger(kVersionKey, kVersion);
top_dictionary.Set(kFileHashesKey, file_list_.release());
if (!base::JSONWriter::Write(top_dictionary, &json))
return false;
int written = base::WriteFile(path, json.data(), json.size());
if (static_cast<unsigned>(written) != json.size()) {
LOG(ERROR) << "Error writing " << path.AsUTF8Unsafe()
<< " ; write result:" << written << " expected:" << json.size();
return false;
}
return true;
}
void ComputedHashes::ComputeHashesForContent(const std::string& contents,
size_t block_size,
std::vector<std::string>* hashes) {
size_t offset = 0;
// Even when the contents is empty, we want to output at least one hash
// block (the hash of the empty string).
do {
const char* block_start = contents.data() + offset;
DCHECK(offset <= contents.size());
size_t bytes_to_read = std::min(contents.size() - offset, block_size);
scoped_ptr<crypto::SecureHash> hash(
crypto::SecureHash::Create(crypto::SecureHash::SHA256));
hash->Update(block_start, bytes_to_read);
hashes->push_back(std::string());
std::string* buffer = &(hashes->back());
buffer->resize(crypto::kSHA256Length);
hash->Finish(string_as_array(buffer), buffer->size());
// If |contents| is empty, then we want to just exit here.
if (bytes_to_read == 0)
break;
offset += bytes_to_read;
} while (offset < contents.size());
}
} // namespace extensions
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