components/os_crypt/os_crypt_posix.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "components/os_crypt/os_crypt.h"
   6
   7 #include "base/logging.h"
   8 #include "base/memory/scoped_ptr.h"
   9 #include "base/strings/utf_string_conversions.h"
  10 #include "crypto/encryptor.h"
  11 #include "crypto/symmetric_key.h"
  12
  13 namespace {
  14
  15 // Salt for Symmetric key derivation.
  16 const char kSalt[] = "saltysalt";
  17
  18 // Key size required for 128 bit AES.
  19 const size_t kDerivedKeySizeInBits = 128;
  20
  21 // Constant for Symmetic key derivation.
  22 const size_t kEncryptionIterations = 1;
  23
  24 // Size of initialization vector for AES 128-bit.
  25 const size_t kIVBlockSizeAES128 = 16;
  26
  27 // Prefix for cypher text returned by obfuscation version.  We prefix the
  28 // cyphertext with this string so that future data migration can detect
  29 // this and migrate to full encryption without data loss.
  30 const char kObfuscationPrefix[] = "v10";
  31
  32 // Generates a newly allocated SymmetricKey object based a hard-coded password.
  33 // Ownership of the key is passed to the caller.  Returns NULL key if a key
  34 // generation error occurs.
  35 crypto::SymmetricKey* GetEncryptionKey() {
  36   // We currently "obfuscate" by encrypting and decrypting with hard-coded
  37   // password.  We need to improve this password situation by moving a secure
  38   // password into a system-level key store.
  39   // http://crbug.com/25404 and http://crbug.com/49115
  40   std::string password = "peanuts";
  41   std::string salt(kSalt);
  42
  43   // Create an encryption key from our password and salt.
  44   scoped_ptr<crypto::SymmetricKey> encryption_key(
  45       crypto::SymmetricKey::DeriveKeyFromPassword(crypto::SymmetricKey::AES,
  46                                                   password,
  47                                                   salt,
  48                                                   kEncryptionIterations,
  49                                                   kDerivedKeySizeInBits));
  50   DCHECK(encryption_key.get());
  51
  52   return encryption_key.release();
  53 }
  54
  55 }  // namespace
  56
  57 bool OSCrypt::EncryptString16(const base::string16& plaintext,
  58                               std::string* ciphertext) {
  59   return EncryptString(base::UTF16ToUTF8(plaintext), ciphertext);
  60 }
  61
  62 bool OSCrypt::DecryptString16(const std::string& ciphertext,
  63                               base::string16* plaintext) {
  64   std::string utf8;
  65   if (!DecryptString(ciphertext, &utf8))
  66     return false;
  67
  68   *plaintext = base::UTF8ToUTF16(utf8);
  69   return true;
  70 }
  71
  72 bool OSCrypt::EncryptString(const std::string& plaintext,
  73                             std::string* ciphertext) {
  74   // This currently "obfuscates" by encrypting with hard-coded password.
  75   // We need to improve this password situation by moving a secure password
  76   // into a system-level key store.
  77   // http://crbug.com/25404 and http://crbug.com/49115
  78
  79   if (plaintext.empty()) {
  80     *ciphertext = std::string();
  81     return true;
  82   }
  83
  84   scoped_ptr<crypto::SymmetricKey> encryption_key(GetEncryptionKey());
  85   if (!encryption_key.get())
  86     return false;
  87
  88   std::string iv(kIVBlockSizeAES128, ' ');
  89   crypto::Encryptor encryptor;
  90   if (!encryptor.Init(encryption_key.get(), crypto::Encryptor::CBC, iv))
  91     return false;
  92
  93   if (!encryptor.Encrypt(plaintext, ciphertext))
  94     return false;
  95
  96   // Prefix the cypher text with version information.
  97   ciphertext->insert(0, kObfuscationPrefix);
  98   return true;
  99 }
 100
 101 bool OSCrypt::DecryptString(const std::string& ciphertext,
 102                             std::string* plaintext) {
 103   // This currently "obfuscates" by encrypting with hard-coded password.
 104   // We need to improve this password situation by moving a secure password
 105   // into a system-level key store.
 106   // http://crbug.com/25404 and http://crbug.com/49115
 107
 108   if (ciphertext.empty()) {
 109     *plaintext = std::string();
 110     return true;
 111   }
 112
 113   // Check that the incoming cyphertext was indeed encrypted with the expected
 114   // version.  If the prefix is not found then we'll assume we're dealing with
 115   // old data saved as clear text and we'll return it directly.
 116   // Credit card numbers are current legacy data, so false match with prefix
 117   // won't happen.
 118   if (ciphertext.find(kObfuscationPrefix) != 0) {
 119     *plaintext = ciphertext;
 120     return true;
 121   }
 122
 123   // Strip off the versioning prefix before decrypting.
 124   std::string raw_ciphertext = ciphertext.substr(strlen(kObfuscationPrefix));
 125
 126   scoped_ptr<crypto::SymmetricKey> encryption_key(GetEncryptionKey());
 127   if (!encryption_key.get())
 128     return false;
 129
 130   std::string iv(kIVBlockSizeAES128, ' ');
 131   crypto::Encryptor encryptor;
 132   if (!encryptor.Init(encryption_key.get(), crypto::Encryptor::CBC, iv))
 133     return false;
 134
 135   if (!encryptor.Decrypt(raw_ciphertext, plaintext))
 136     return false;
 137
 138   return true;
 139 }