src/storage/encrypted_string_storage.cc

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#include "storage/encrypted_string_storage.h"

#ifdef OS_WIN
#include <Windows.h>
#endif

#include <cstring>
#include <string>

#include "base/encryptor.h"
#include "base/file_stream.h"
#include "base/file_util.h"
#include "base/logging.h"
#include "base/mmap.h"
#include "base/password_manager.h"
#include "base/util.h"

namespace mozc {
namespace storage {

namespace {
// Salt size for encryption
const size_t kSaltSize = 32;

// Maximum file size (64Mbyte)
const size_t kMaxFileSize = 64 * 1024 * 1024;
}  // namespace

EncryptedStringStorage::EncryptedStringStorage(const string &filename)
    : filename_(filename) {}

EncryptedStringStorage::~EncryptedStringStorage() {}

bool EncryptedStringStorage::Load(string *output) const {
  DCHECK(output);

  string salt;

  // Reads encrypted message and salt from local file
  {
    Mmap mmap;
    if (!mmap.Open(filename_.c_str(), "r")) {
      LOG(ERROR) << "cannot open user history file";
      return false;
    }

    if (mmap.size() < kSaltSize) {
      LOG(ERROR) << "file size is too small";
      return false;
    }

    if (mmap.size() > kMaxFileSize) {
      LOG(ERROR) << "file size is too big.";
      return false;
    }

    // copy salt
    salt.assign(mmap.begin(), kSaltSize);

    // copy body
    output->assign(mmap.begin() + kSaltSize, mmap.size() - kSaltSize);
  }

  return Decrypt(salt, output);
}

bool EncryptedStringStorage::Decrypt(const string &salt, string *data) const {
  DCHECK(data);

  string password;
  if (!PasswordManager::GetPassword(&password)) {
    LOG(ERROR) << "PasswordManager::GetPassword() failed";
    return false;
  }

  if (password.empty()) {
    LOG(ERROR) << "password is empty";
    return false;
  }

  // Decrypt message
  Encryptor::Key key;
  if (!key.DeriveFromPassword(password, salt)) {
    LOG(ERROR) << "Encryptor::Key::DeriveFromPassword failed";
    return false;
  }

  if (!Encryptor::DecryptString(key, data)) {
    LOG(ERROR) << "Encryptor::DecryptString() failed";
    return false;
  }

  return true;
}

bool EncryptedStringStorage::Save(const string &input) const {
  string output, salt;
  // Generate salt.
  salt.resize(kSaltSize);
  Util::GetRandomSequence(&salt[0], kSaltSize);

  output.assign(input);
  if (!Encrypt(salt, &output)) {
    return false;
  }

  // Even if histoy is empty, save to them into a file to
  // make the file empty
  const string tmp_filename = filename_ + ".tmp";
  {
    OutputFileStream ofs(tmp_filename.c_str(), ios::out | ios::binary);
    if (!ofs) {
      LOG(ERROR) << "failed to write: " << tmp_filename;
      return false;
    }

    VLOG(1) << "Syncing user history to: " << filename_;
    ofs.write(salt.data(), salt.size());
    ofs.write(output.data(), output.size());
  }

  if (!FileUtil::AtomicRename(tmp_filename, filename_)) {
    LOG(ERROR) << "AtomicRename failed";
    return false;
  }

#ifdef OS_WIN
  if (!FileUtil::HideFile(filename_)) {
    LOG(ERROR) << "Cannot make hidden: " << filename_
               << " " << ::GetLastError();
  }
#endif

  return true;
}

bool EncryptedStringStorage::Encrypt(const string &salt, string *data) const {
  DCHECK(data);

  string password;
  if (!PasswordManager::GetPassword(&password)) {
    LOG(ERROR) << "PasswordManager::GetPassword() failed";
    return false;
  }

  if (password.empty()) {
    LOG(ERROR) << "password is empty";
    return false;
  }

  Encryptor::Key key;
  if (!key.DeriveFromPassword(password, salt)) {
    LOG(ERROR) << "Encryptor::Key::DeriveFromPassword() failed";
    return false;
  }

  if (!Encryptor::EncryptString(key, data)) {
    LOG(ERROR) << "Encryptor::EncryptString() failed";
    return false;
  }

  return true;
}

}  // namespace storage
}  // namespace mozc