chromeos/login/auth/key.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 "chromeos/login/auth/key.h"
   6
   7 #include "base/base64.h"
   8 #include "base/logging.h"
   9 #include "base/memory/scoped_ptr.h"
  10 #include "base/strings/string_number_conversions.h"
  11 #include "base/strings/string_util.h"
  12 #include "crypto/sha2.h"
  13 #include "crypto/symmetric_key.h"
  14
  15 namespace chromeos {
  16
  17 namespace {
  18
  19 // Parameters for the transformation to KEY_TYPE_SALTED_AES256_1234.
  20 const int kNumIterations = 1234;
  21 const int kKeySizeInBits = 256;
  22
  23 }  // namespace
  24
  25 Key::Key() : key_type_(KEY_TYPE_PASSWORD_PLAIN) {
  26 }
  27
  28 Key::Key(const Key& other)
  29     : key_type_(other.key_type_),
  30       salt_(other.salt_),
  31       secret_(other.secret_),
  32       label_(other.label_) {
  33 }
  34
  35 Key::Key(const std::string& plain_text_password)
  36     : key_type_(KEY_TYPE_PASSWORD_PLAIN), secret_(plain_text_password) {
  37 }
  38
  39 Key::Key(KeyType key_type, const std::string& salt, const std::string& secret)
  40     : key_type_(key_type), salt_(salt), secret_(secret) {
  41 }
  42
  43 Key::~Key() {
  44 }
  45
  46 bool Key::operator==(const Key& other) const {
  47   return other.key_type_ == key_type_ && other.salt_ == salt_ &&
  48          other.secret_ == secret_ && other.label_ == label_;
  49 }
  50
  51 Key::KeyType Key::GetKeyType() const {
  52   return key_type_;
  53 }
  54
  55 const std::string& Key::GetSecret() const {
  56   return secret_;
  57 }
  58
  59 const std::string& Key::GetLabel() const {
  60   return label_;
  61 }
  62
  63 void Key::SetLabel(const std::string& label) {
  64   label_ = label;
  65 }
  66
  67 void Key::ClearSecret() {
  68   secret_.clear();
  69 }
  70
  71 void Key::Transform(KeyType target_key_type, const std::string& salt) {
  72   if (key_type_ != KEY_TYPE_PASSWORD_PLAIN) {
  73     NOTREACHED();
  74     return;
  75   }
  76
  77   switch (target_key_type) {
  78     case KEY_TYPE_SALTED_SHA256_TOP_HALF: {
  79       // TODO(stevenjb/nkostylev): Handle empty salt gracefully.
  80       CHECK(!salt.empty());
  81       char hash[crypto::kSHA256Length];
  82       crypto::SHA256HashString(salt + secret_, &hash, sizeof(hash));
  83
  84       // Keep only the first half of the hash for 'weak' hashing so that the
  85       // plain text secret cannot be reconstructed even if the hashing is
  86       // reversed.
  87       secret_ = base::ToLowerASCII(base::HexEncode(
  88           reinterpret_cast<const void*>(hash), sizeof(hash) / 2));
  89       break;
  90     }
  91     case KEY_TYPE_SALTED_PBKDF2_AES256_1234: {
  92       scoped_ptr<crypto::SymmetricKey> key(
  93           crypto::SymmetricKey::DeriveKeyFromPassword(crypto::SymmetricKey::AES,
  94                                                       secret_,
  95                                                       salt,
  96                                                       kNumIterations,
  97                                                       kKeySizeInBits));
  98       std::string raw_secret;
  99       key->GetRawKey(&raw_secret);
 100       base::Base64Encode(raw_secret, &secret_);
 101       break;
 102     }
 103     case KEY_TYPE_SALTED_SHA256:
 104       base::Base64Encode(crypto::SHA256HashString(salt + secret_), &secret_);
 105       break;
 106
 107     default:
 108       // The resulting key will be sent to cryptohomed. It should always be
 109       // hashed. If hashing fails, crash instead of sending a plain-text key.
 110       CHECK(false);
 111       return;
 112   }
 113
 114   key_type_ = target_key_type;
 115   salt_ = salt;
 116 }
 117
 118 }  // namespace chromeos