sync/util/nigori.cc

   1 // Copyright (c) 2012 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 "sync/util/nigori.h"
   6
   7 #include <sstream>
   8 #include <vector>
   9
  10 #include "base/base64.h"
  11 #include "base/logging.h"
  12 #include "base/string_util.h"
  13 #include "base/sys_byteorder.h"
  14 #include "crypto/encryptor.h"
  15 #include "crypto/hmac.h"
  16 #include "crypto/random.h"
  17 #include "crypto/symmetric_key.h"
  18
  19 using base::Base64Encode;
  20 using base::Base64Decode;
  21 using crypto::Encryptor;
  22 using crypto::HMAC;
  23 using crypto::SymmetricKey;
  24
  25 namespace syncer {
  26
  27 // NigoriStream simplifies the concatenation operation of the Nigori protocol.
  28 class NigoriStream {
  29  public:
  30   // Append the big-endian representation of the length of |value| with 32 bits,
  31   // followed by |value| itself to the stream.
  32   NigoriStream& operator<<(const std::string& value) {
  33     uint32 size = base::HostToNet32(value.size());
  34     stream_.write((char *) &size, sizeof(uint32));
  35     stream_ << value;
  36     return *this;
  37   }
  38
  39   // Append the big-endian representation of the length of |type| with 32 bits,
  40   // followed by the big-endian representation of the value of |type|, with 32
  41   // bits, to the stream.
  42   NigoriStream& operator<<(const Nigori::Type type) {
  43     uint32 size = base::HostToNet32(sizeof(uint32));
  44     stream_.write((char *) &size, sizeof(uint32));
  45     uint32 value = base::HostToNet32(type);
  46     stream_.write((char *) &value, sizeof(uint32));
  47     return *this;
  48   }
  49
  50   std::string str() {
  51     return stream_.str();
  52   }
  53
  54  private:
  55   std::ostringstream stream_;
  56 };
  57
  58 // static
  59 const char Nigori::kSaltSalt[] = "saltsalt";
  60
  61 Nigori::Nigori() {
  62 }
  63
  64 Nigori::~Nigori() {
  65 }
  66
  67 bool Nigori::InitByDerivation(const std::string& hostname,
  68                               const std::string& username,
  69                               const std::string& password) {
  70   NigoriStream salt_password;
  71   salt_password << username << hostname;
  72
  73   // Suser = PBKDF2(Username || Servername, "saltsalt", Nsalt, 8)
  74   scoped_ptr<SymmetricKey> user_salt(SymmetricKey::DeriveKeyFromPassword(
  75       SymmetricKey::HMAC_SHA1, salt_password.str(),
  76       kSaltSalt,
  77       kSaltIterations,
  78       kSaltKeySizeInBits));
  79   DCHECK(user_salt.get());
  80
  81   std::string raw_user_salt;
  82   if (!user_salt->GetRawKey(&raw_user_salt))
  83     return false;
  84
  85   // Kuser = PBKDF2(P, Suser, Nuser, 16)
  86   user_key_.reset(SymmetricKey::DeriveKeyFromPassword(SymmetricKey::AES,
  87       password, raw_user_salt, kUserIterations, kDerivedKeySizeInBits));
  88   DCHECK(user_key_.get());
  89
  90   // Kenc = PBKDF2(P, Suser, Nenc, 16)
  91   encryption_key_.reset(SymmetricKey::DeriveKeyFromPassword(SymmetricKey::AES,
  92       password, raw_user_salt, kEncryptionIterations, kDerivedKeySizeInBits));
  93   DCHECK(encryption_key_.get());
  94
  95   // Kmac = PBKDF2(P, Suser, Nmac, 16)
  96   mac_key_.reset(SymmetricKey::DeriveKeyFromPassword(
  97       SymmetricKey::HMAC_SHA1, password, raw_user_salt, kSigningIterations,
  98       kDerivedKeySizeInBits));
  99   DCHECK(mac_key_.get());
 100
 101   return user_key_.get() && encryption_key_.get() && mac_key_.get();
 102 }
 103
 104 bool Nigori::InitByImport(const std::string& user_key,
 105                           const std::string& encryption_key,
 106                           const std::string& mac_key) {
 107   user_key_.reset(SymmetricKey::Import(SymmetricKey::AES, user_key));
 108   DCHECK(user_key_.get());
 109
 110   encryption_key_.reset(SymmetricKey::Import(SymmetricKey::AES,
 111                                              encryption_key));
 112   DCHECK(encryption_key_.get());
 113
 114   mac_key_.reset(SymmetricKey::Import(SymmetricKey::HMAC_SHA1, mac_key));
 115   DCHECK(mac_key_.get());
 116
 117   return user_key_.get() && encryption_key_.get() && mac_key_.get();
 118 }
 119
 120 // Permute[Kenc,Kmac](type || name)
 121 bool Nigori::Permute(Type type, const std::string& name,
 122                      std::string* permuted) const {
 123   DCHECK_LT(0U, name.size());
 124
 125   NigoriStream plaintext;
 126   plaintext << type << name;
 127
 128   Encryptor encryptor;
 129   if (!encryptor.Init(encryption_key_.get(), Encryptor::CBC,
 130                       std::string(kIvSize, 0)))
 131     return false;
 132
 133   std::string ciphertext;
 134   if (!encryptor.Encrypt(plaintext.str(), &ciphertext))
 135     return false;
 136
 137   std::string raw_mac_key;
 138   if (!mac_key_->GetRawKey(&raw_mac_key))
 139     return false;
 140
 141   HMAC hmac(HMAC::SHA256);
 142   if (!hmac.Init(raw_mac_key))
 143     return false;
 144
 145   std::vector<unsigned char> hash(kHashSize);
 146   if (!hmac.Sign(ciphertext, &hash[0], hash.size()))
 147     return false;
 148
 149   std::string output;
 150   output.assign(ciphertext);
 151   output.append(hash.begin(), hash.end());
 152
 153   return Base64Encode(output, permuted);
 154 }
 155
 156 // Enc[Kenc,Kmac](value)
 157 bool Nigori::Encrypt(const std::string& value, std::string* encrypted) const {
 158   if (0U >= value.size())
 159     return false;
 160
 161   std::string iv;
 162   crypto::RandBytes(WriteInto(&iv, kIvSize + 1), kIvSize);
 163
 164   Encryptor encryptor;
 165   if (!encryptor.Init(encryption_key_.get(), Encryptor::CBC, iv))
 166     return false;
 167
 168   std::string ciphertext;
 169   if (!encryptor.Encrypt(value, &ciphertext))
 170     return false;
 171
 172   std::string raw_mac_key;
 173   if (!mac_key_->GetRawKey(&raw_mac_key))
 174     return false;
 175
 176   HMAC hmac(HMAC::SHA256);
 177   if (!hmac.Init(raw_mac_key))
 178     return false;
 179
 180   std::vector<unsigned char> hash(kHashSize);
 181   if (!hmac.Sign(ciphertext, &hash[0], hash.size()))
 182     return false;
 183
 184   std::string output;
 185   output.assign(iv);
 186   output.append(ciphertext);
 187   output.append(hash.begin(), hash.end());
 188
 189   return Base64Encode(output, encrypted);
 190 }
 191
 192 bool Nigori::Decrypt(const std::string& encrypted, std::string* value) const {
 193   std::string input;
 194   if (!Base64Decode(encrypted, &input))
 195     return false;
 196
 197   if (input.size() < kIvSize * 2 + kHashSize)
 198     return false;
 199
 200   // The input is:
 201   // * iv (16 bytes)
 202   // * ciphertext (multiple of 16 bytes)
 203   // * hash (32 bytes)
 204   std::string iv(input.substr(0, kIvSize));
 205   std::string ciphertext(input.substr(kIvSize,
 206                                       input.size() - (kIvSize + kHashSize)));
 207   std::string hash(input.substr(input.size() - kHashSize, kHashSize));
 208
 209   std::string raw_mac_key;
 210   if (!mac_key_->GetRawKey(&raw_mac_key))
 211     return false;
 212
 213   HMAC hmac(HMAC::SHA256);
 214   if (!hmac.Init(raw_mac_key))
 215     return false;
 216
 217   std::vector<unsigned char> expected(kHashSize);
 218   if (!hmac.Sign(ciphertext, &expected[0], expected.size()))
 219     return false;
 220
 221   if (hash.compare(0, hash.size(),
 222                    reinterpret_cast<char *>(&expected[0]),
 223                    expected.size()))
 224     return false;
 225
 226   Encryptor encryptor;
 227   if (!encryptor.Init(encryption_key_.get(), Encryptor::CBC, iv))
 228     return false;
 229
 230   std::string plaintext;
 231   if (!encryptor.Decrypt(ciphertext, value))
 232     return false;
 233
 234   return true;
 235 }
 236
 237 bool Nigori::ExportKeys(std::string* user_key,
 238                         std::string* encryption_key,
 239                         std::string* mac_key) const {
 240   DCHECK(user_key);
 241   DCHECK(encryption_key);
 242   DCHECK(mac_key);
 243
 244   return user_key_->GetRawKey(user_key) &&
 245       encryption_key_->GetRawKey(encryption_key) &&
 246       mac_key_->GetRawKey(mac_key);
 247 }
 248
 249 }  // namespace syncer