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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 "components/os_crypt/os_crypt.h"
#include <CommonCrypto/CommonCryptor.h> // for kCCBlockSizeAES128
#include <stddef.h>
#include "base/command_line.h"
#include "base/debug/leak_annotations.h"
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/strings/utf_string_conversions.h"
#include "base/synchronization/lock.h"
#include "components/os_crypt/keychain_password_mac.h"
#include "components/os_crypt/os_crypt_switches.h"
#include "crypto/apple_keychain.h"
#include "crypto/encryptor.h"
#include "crypto/mock_apple_keychain.h"
#include "crypto/symmetric_key.h"
using crypto::AppleKeychain;
namespace {
// Salt for Symmetric key derivation.
const char kSalt[] = "saltysalt";
// Key size required for 128 bit AES.
const size_t kDerivedKeySizeInBits = 128;
// Constant for Symmetic key derivation.
const size_t kEncryptionIterations = 1003;
// TODO(dhollowa): Refactor to allow dependency injection of Keychain.
static bool use_mock_keychain = false;
// Prefix for cypher text returned by current encryption version. We prefix
// the cypher text with this string so that future data migration can detect
// this and migrate to different encryption without data loss.
const char kEncryptionVersionPrefix[] = "v10";
// Generates a newly allocated SymmetricKey object based on the password found
// in the Keychain. The generated key is for AES encryption. Returns NULL key
// in the case password access is denied or key generation error occurs.
crypto::SymmetricKey* GetEncryptionKey() {
static crypto::SymmetricKey* cached_encryption_key = NULL;
static bool key_is_cached = false;
static base::Lock lock;
base::AutoLock auto_lock(lock);
if (key_is_cached)
return cached_encryption_key;
static bool mock_keychain_command_line_flag =
base::CommandLine::ForCurrentProcess()->HasSwitch(
os_crypt::switches::kUseMockKeychain);
std::string password;
if (use_mock_keychain || mock_keychain_command_line_flag) {
crypto::MockAppleKeychain keychain;
password = keychain.GetEncryptionPassword();
} else {
AppleKeychain keychain;
KeychainPassword encryptor_password(keychain);
password = encryptor_password.GetPassword();
}
// Subsequent code must guarantee that the correct key is cached before
// returning.
key_is_cached = true;
if (password.empty())
return cached_encryption_key;
std::string salt(kSalt);
// Create an encryption key from our password and salt. The key is
// intentionally leaked.
cached_encryption_key =
crypto::SymmetricKey::DeriveKeyFromPassword(crypto::SymmetricKey::AES,
password,
salt,
kEncryptionIterations,
kDerivedKeySizeInBits);
ANNOTATE_LEAKING_OBJECT_PTR(cached_encryption_key);
DCHECK(cached_encryption_key);
return cached_encryption_key;
}
} // namespace
bool OSCrypt::EncryptString16(const base::string16& plaintext,
std::string* ciphertext) {
return EncryptString(base::UTF16ToUTF8(plaintext), ciphertext);
}
bool OSCrypt::DecryptString16(const std::string& ciphertext,
base::string16* plaintext) {
std::string utf8;
if (!DecryptString(ciphertext, &utf8))
return false;
*plaintext = base::UTF8ToUTF16(utf8);
return true;
}
bool OSCrypt::EncryptString(const std::string& plaintext,
std::string* ciphertext) {
if (plaintext.empty()) {
*ciphertext = std::string();
return true;
}
crypto::SymmetricKey* encryption_key = GetEncryptionKey();
if (!encryption_key)
return false;
std::string iv(kCCBlockSizeAES128, ' ');
crypto::Encryptor encryptor;
if (!encryptor.Init(encryption_key, crypto::Encryptor::CBC, iv))
return false;
if (!encryptor.Encrypt(plaintext, ciphertext))
return false;
// Prefix the cypher text with version information.
ciphertext->insert(0, kEncryptionVersionPrefix);
return true;
}
bool OSCrypt::DecryptString(const std::string& ciphertext,
std::string* plaintext) {
if (ciphertext.empty()) {
*plaintext = std::string();
return true;
}
// Check that the incoming cyphertext was indeed encrypted with the expected
// version. If the prefix is not found then we'll assume we're dealing with
// old data saved as clear text and we'll return it directly.
// Credit card numbers are current legacy data, so false match with prefix
// won't happen.
if (ciphertext.find(kEncryptionVersionPrefix) != 0) {
*plaintext = ciphertext;
return true;
}
// Strip off the versioning prefix before decrypting.
std::string raw_ciphertext =
ciphertext.substr(strlen(kEncryptionVersionPrefix));
crypto::SymmetricKey* encryption_key = GetEncryptionKey();
if (!encryption_key)
return false;
std::string iv(kCCBlockSizeAES128, ' ');
crypto::Encryptor encryptor;
if (!encryptor.Init(encryption_key, crypto::Encryptor::CBC, iv))
return false;
if (!encryptor.Decrypt(raw_ciphertext, plaintext))
return false;
return true;
}
void OSCrypt::UseMockKeychain(bool use_mock) {
use_mock_keychain = use_mock;
}
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