sync/util/cryptographer.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/cryptographer.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/base64.h"
  10 #include "base/basictypes.h"
  11 #include "base/logging.h"
  12 #include "sync/protocol/nigori_specifics.pb.h"
  13 #include "sync/util/encryptor.h"
  14
  15 namespace syncer {
  16
  17 const char kNigoriTag[] = "google_chrome_nigori";
  18
  19 // We name a particular Nigori instance (ie. a triplet consisting of a hostname,
  20 // a username, and a password) by calling Permute on this string. Since the
  21 // output of Permute is always the same for a given triplet, clients will always
  22 // assign the same name to a particular triplet.
  23 const char kNigoriKeyName[] = "nigori-key";
  24
  25 Cryptographer::Cryptographer(Encryptor* encryptor)
  26     : encryptor_(encryptor) {
  27   DCHECK(encryptor);
  28 }
  29
  30 Cryptographer::~Cryptographer() {}
  31
  32
  33 void Cryptographer::Bootstrap(const std::string& restored_bootstrap_token) {
  34   if (is_initialized()) {
  35     NOTREACHED();
  36     return;
  37   }
  38
  39   std::string serialized_nigori_key =
  40       UnpackBootstrapToken(restored_bootstrap_token);
  41   if (serialized_nigori_key.empty())
  42     return;
  43   ImportNigoriKey(serialized_nigori_key);
  44 }
  45
  46 bool Cryptographer::CanDecrypt(const sync_pb::EncryptedData& data) const {
  47   return nigoris_.end() != nigoris_.find(data.key_name());
  48 }
  49
  50 bool Cryptographer::CanDecryptUsingDefaultKey(
  51     const sync_pb::EncryptedData& data) const {
  52   return !default_nigori_name_.empty() &&
  53          data.key_name() == default_nigori_name_;
  54 }
  55
  56 bool Cryptographer::Encrypt(
  57     const ::google::protobuf::MessageLite& message,
  58     sync_pb::EncryptedData* encrypted) const {
  59   DCHECK(encrypted);
  60   if (default_nigori_name_.empty()) {
  61     LOG(ERROR) << "Cryptographer not ready, failed to encrypt.";
  62     return false;
  63   }
  64
  65   std::string serialized;
  66   if (!message.SerializeToString(&serialized)) {
  67     LOG(ERROR) << "Message is invalid/missing a required field.";
  68     return false;
  69   }
  70
  71   return EncryptString(serialized, encrypted);
  72 }
  73
  74 bool Cryptographer::EncryptString(
  75     const std::string& serialized,
  76     sync_pb::EncryptedData* encrypted) const {
  77   if (CanDecryptUsingDefaultKey(*encrypted)) {
  78     const std::string& original_serialized = DecryptToString(*encrypted);
  79     if (original_serialized == serialized) {
  80       DVLOG(2) << "Re-encryption unnecessary, encrypted data already matches.";
  81       return true;
  82     }
  83   }
  84
  85   NigoriMap::const_iterator default_nigori =
  86       nigoris_.find(default_nigori_name_);
  87   if (default_nigori == nigoris_.end()) {
  88     LOG(ERROR) << "Corrupt default key.";
  89     return false;
  90   }
  91
  92   encrypted->set_key_name(default_nigori_name_);
  93   if (!default_nigori->second->Encrypt(serialized,
  94                                        encrypted->mutable_blob())) {
  95     LOG(ERROR) << "Failed to encrypt data.";
  96     return false;
  97   }
  98   return true;
  99 }
 100
 101 bool Cryptographer::Decrypt(const sync_pb::EncryptedData& encrypted,
 102                             ::google::protobuf::MessageLite* message) const {
 103   DCHECK(message);
 104   std::string plaintext = DecryptToString(encrypted);
 105   return message->ParseFromString(plaintext);
 106 }
 107
 108 std::string Cryptographer::DecryptToString(
 109     const sync_pb::EncryptedData& encrypted) const {
 110   NigoriMap::const_iterator it = nigoris_.find(encrypted.key_name());
 111   if (nigoris_.end() == it) {
 112     NOTREACHED() << "Cannot decrypt message";
 113     return std::string();  // Caller should have called CanDecrypt(encrypt).
 114   }
 115
 116   std::string plaintext;
 117   if (!it->second->Decrypt(encrypted.blob(), &plaintext)) {
 118     return std::string();
 119   }
 120
 121   return plaintext;
 122 }
 123
 124 bool Cryptographer::GetKeys(sync_pb::EncryptedData* encrypted) const {
 125   DCHECK(encrypted);
 126   DCHECK(!nigoris_.empty());
 127
 128   // Create a bag of all the Nigori parameters we know about.
 129   sync_pb::NigoriKeyBag bag;
 130   for (NigoriMap::const_iterator it = nigoris_.begin(); it != nigoris_.end();
 131        ++it) {
 132     const Nigori& nigori = *it->second;
 133     sync_pb::NigoriKey* key = bag.add_key();
 134     key->set_name(it->first);
 135     nigori.ExportKeys(key->mutable_user_key(),
 136                       key->mutable_encryption_key(),
 137                       key->mutable_mac_key());
 138   }
 139
 140   // Encrypt the bag with the default Nigori.
 141   return Encrypt(bag, encrypted);
 142 }
 143
 144 bool Cryptographer::AddKey(const KeyParams& params) {
 145   // Create the new Nigori and make it the default encryptor.
 146   scoped_ptr<Nigori> nigori(new Nigori);
 147   if (!nigori->InitByDerivation(params.hostname,
 148                                 params.username,
 149                                 params.password)) {
 150     NOTREACHED();  // Invalid username or password.
 151     return false;
 152   }
 153   return AddKeyImpl(nigori.Pass(), true);
 154 }
 155
 156 bool Cryptographer::AddNonDefaultKey(const KeyParams& params) {
 157   DCHECK(is_initialized());
 158   // Create the new Nigori and add it to the keybag.
 159   scoped_ptr<Nigori> nigori(new Nigori);
 160   if (!nigori->InitByDerivation(params.hostname,
 161                                 params.username,
 162                                 params.password)) {
 163     NOTREACHED();  // Invalid username or password.
 164     return false;
 165   }
 166   return AddKeyImpl(nigori.Pass(), false);
 167 }
 168
 169 bool Cryptographer::AddKeyFromBootstrapToken(
 170     const std::string restored_bootstrap_token) {
 171   // Create the new Nigori and make it the default encryptor.
 172   std::string serialized_nigori_key = UnpackBootstrapToken(
 173       restored_bootstrap_token);
 174   return ImportNigoriKey(serialized_nigori_key);
 175 }
 176
 177 bool Cryptographer::AddKeyImpl(scoped_ptr<Nigori> initialized_nigori,
 178                                bool set_as_default) {
 179   std::string name;
 180   if (!initialized_nigori->Permute(Nigori::Password, kNigoriKeyName, &name)) {
 181     NOTREACHED();
 182     return false;
 183   }
 184
 185   nigoris_[name] = make_linked_ptr(initialized_nigori.release());
 186
 187   // Check if the key we just added can decrypt the pending keys and add them
 188   // too if so.
 189   if (pending_keys_.get() && CanDecrypt(*pending_keys_)) {
 190     sync_pb::NigoriKeyBag pending_bag;
 191     Decrypt(*pending_keys_, &pending_bag);
 192     InstallKeyBag(pending_bag);
 193     SetDefaultKey(pending_keys_->key_name());
 194     pending_keys_.reset();
 195   }
 196
 197   // The just-added key takes priority over the pending keys as default.
 198   if (set_as_default) SetDefaultKey(name);
 199   return true;
 200 }
 201
 202 void Cryptographer::InstallKeys(const sync_pb::EncryptedData& encrypted) {
 203   DCHECK(CanDecrypt(encrypted));
 204
 205   sync_pb::NigoriKeyBag bag;
 206   if (!Decrypt(encrypted, &bag))
 207     return;
 208   InstallKeyBag(bag);
 209 }
 210
 211 void Cryptographer::SetDefaultKey(const std::string& key_name) {
 212   DCHECK(nigoris_.end() != nigoris_.find(key_name));
 213   default_nigori_name_ = key_name;
 214 }
 215
 216 void Cryptographer::SetPendingKeys(const sync_pb::EncryptedData& encrypted) {
 217   DCHECK(!CanDecrypt(encrypted));
 218   DCHECK(!encrypted.blob().empty());
 219   pending_keys_.reset(new sync_pb::EncryptedData(encrypted));
 220 }
 221
 222 const sync_pb::EncryptedData& Cryptographer::GetPendingKeys() const {
 223   DCHECK(has_pending_keys());
 224   return *(pending_keys_.get());
 225 }
 226
 227 bool Cryptographer::DecryptPendingKeys(const KeyParams& params) {
 228   Nigori nigori;
 229   if (!nigori.InitByDerivation(params.hostname,
 230                                params.username,
 231                                params.password)) {
 232     NOTREACHED();
 233     return false;
 234   }
 235
 236   std::string plaintext;
 237   if (!nigori.Decrypt(pending_keys_->blob(), &plaintext))
 238     return false;
 239
 240   sync_pb::NigoriKeyBag bag;
 241   if (!bag.ParseFromString(plaintext)) {
 242     NOTREACHED();
 243     return false;
 244   }
 245   InstallKeyBag(bag);
 246   const std::string& new_default_key_name = pending_keys_->key_name();
 247   SetDefaultKey(new_default_key_name);
 248   pending_keys_.reset();
 249   return true;
 250 }
 251
 252 bool Cryptographer::GetBootstrapToken(std::string* token) const {
 253   DCHECK(token);
 254   std::string unencrypted_token = GetDefaultNigoriKey();
 255   if (unencrypted_token.empty())
 256     return false;
 257
 258   std::string encrypted_token;
 259   if (!encryptor_->EncryptString(unencrypted_token, &encrypted_token)) {
 260     NOTREACHED();
 261     return false;
 262   }
 263
 264   base::Base64Encode(encrypted_token, token);
 265
 266   return true;
 267 }
 268
 269 std::string Cryptographer::UnpackBootstrapToken(
 270     const std::string& token) const {
 271   if (token.empty())
 272     return std::string();
 273
 274   std::string encrypted_data;
 275   if (!base::Base64Decode(token, &encrypted_data)) {
 276     DLOG(WARNING) << "Could not decode token.";
 277     return std::string();
 278   }
 279
 280   std::string unencrypted_token;
 281   if (!encryptor_->DecryptString(encrypted_data, &unencrypted_token)) {
 282     DLOG(WARNING) << "Decryption of bootstrap token failed.";
 283     return std::string();
 284   }
 285   return unencrypted_token;
 286 }
 287
 288 void Cryptographer::InstallKeyBag(const sync_pb::NigoriKeyBag& bag) {
 289   int key_size = bag.key_size();
 290   for (int i = 0; i < key_size; ++i) {
 291     const sync_pb::NigoriKey key = bag.key(i);
 292     // Only use this key if we don't already know about it.
 293     if (nigoris_.end() == nigoris_.find(key.name())) {
 294       scoped_ptr<Nigori> new_nigori(new Nigori);
 295       if (!new_nigori->InitByImport(key.user_key(),
 296                                     key.encryption_key(),
 297                                     key.mac_key())) {
 298         NOTREACHED();
 299         continue;
 300       }
 301       nigoris_[key.name()] = make_linked_ptr(new_nigori.release());
 302     }
 303   }
 304 }
 305
 306 bool Cryptographer::KeybagIsStale(
 307     const sync_pb::EncryptedData& encrypted_bag) const {
 308   if (!is_ready())
 309     return false;
 310   if (encrypted_bag.blob().empty())
 311     return true;
 312   if (!CanDecrypt(encrypted_bag))
 313     return false;
 314   if (!CanDecryptUsingDefaultKey(encrypted_bag))
 315     return true;
 316   sync_pb::NigoriKeyBag bag;
 317   if (!Decrypt(encrypted_bag, &bag)) {
 318     LOG(ERROR) << "Failed to decrypt keybag for stale check. "
 319                << "Assuming keybag is corrupted.";
 320     return true;
 321   }
 322   if (static_cast<size_t>(bag.key_size()) < nigoris_.size())
 323     return true;
 324   return false;
 325 }
 326
 327 std::string Cryptographer::GetDefaultNigoriKey() const {
 328   if (!is_initialized())
 329     return std::string();
 330   NigoriMap::const_iterator iter = nigoris_.find(default_nigori_name_);
 331   if (iter == nigoris_.end())
 332     return std::string();
 333   sync_pb::NigoriKey key;
 334   if (!iter->second->ExportKeys(key.mutable_user_key(),
 335                                 key.mutable_encryption_key(),
 336                                 key.mutable_mac_key()))
 337     return std::string();
 338   return key.SerializeAsString();
 339 }
 340
 341 bool Cryptographer::ImportNigoriKey(const std::string serialized_nigori_key) {
 342   if (serialized_nigori_key.empty())
 343     return false;
 344
 345   sync_pb::NigoriKey key;
 346   if (!key.ParseFromString(serialized_nigori_key))
 347     return false;
 348
 349   scoped_ptr<Nigori> nigori(new Nigori);
 350   if (!nigori->InitByImport(key.user_key(), key.encryption_key(),
 351                             key.mac_key())) {
 352     NOTREACHED();
 353     return false;
 354   }
 355
 356   if (!AddKeyImpl(nigori.Pass(), true))
 357     return false;
 358   return true;
 359 }
 360
 361 }  // namespace syncer