chrome/browser/prefs/pref_hash_store_impl.cc

   1 // Copyright 2013 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 "chrome/browser/prefs/pref_hash_store_impl.h"
   6
   7 #include "base/logging.h"
   8 #include "base/metrics/histogram.h"
   9 #include "base/values.h"
  10 #include "chrome/browser/prefs/pref_hash_store_transaction.h"
  11 #include "chrome/browser/prefs/tracked/hash_store_contents.h"
  12
  13 namespace {
  14
  15 // Returns true if the dictionary of hashes stored in |contents| is trusted
  16 // (which implies unknown values can be trusted as newly tracked values).
  17 bool IsHashDictionaryTrusted(const PrefHashCalculator& calculator,
  18                              const HashStoreContents& contents) {
  19   const base::DictionaryValue* store_contents = contents.GetContents();
  20   std::string super_mac = contents.GetSuperMac();
  21   // The store must be initialized and have a valid super MAC to be trusted.
  22   return store_contents && !super_mac.empty() &&
  23          calculator.Validate(contents.hash_store_id(),
  24                              store_contents,
  25                              super_mac) == PrefHashCalculator::VALID;
  26 }
  27
  28 }  // namespace
  29
  30 class PrefHashStoreImpl::PrefHashStoreTransactionImpl
  31     : public PrefHashStoreTransaction {
  32  public:
  33   // Constructs a PrefHashStoreTransactionImpl which can use the private
  34   // members of its |outer| PrefHashStoreImpl.
  35   explicit PrefHashStoreTransactionImpl(PrefHashStoreImpl* outer);
  36   virtual ~PrefHashStoreTransactionImpl();
  37
  38   // PrefHashStoreTransaction implementation.
  39   virtual ValueState CheckValue(const std::string& path,
  40                                 const base::Value* value) const OVERRIDE;
  41   virtual void StoreHash(const std::string& path,
  42                          const base::Value* value) OVERRIDE;
  43   virtual ValueState CheckSplitValue(
  44       const std::string& path,
  45       const base::DictionaryValue* initial_split_value,
  46       std::vector<std::string>* invalid_keys) const OVERRIDE;
  47   virtual void StoreSplitHash(
  48       const std::string& path,
  49       const base::DictionaryValue* split_value) OVERRIDE;
  50
  51  private:
  52   bool GetSplitMacs(const std::string& path,
  53                     std::map<std::string, std::string>* split_macs) const;
  54   PrefHashStoreImpl* outer_;
  55   bool has_changed_;
  56
  57   DISALLOW_COPY_AND_ASSIGN(PrefHashStoreTransactionImpl);
  58 };
  59
  60 PrefHashStoreImpl::PrefHashStoreImpl(const std::string& seed,
  61                                      const std::string& device_id,
  62                                      scoped_ptr<HashStoreContents> contents)
  63     : pref_hash_calculator_(seed, device_id),
  64       contents_(contents.Pass()),
  65       initial_hashes_dictionary_trusted_(
  66           IsHashDictionaryTrusted(pref_hash_calculator_, *contents_)),
  67       has_pending_write_(false) {
  68   DCHECK(contents_);
  69   UMA_HISTOGRAM_BOOLEAN("Settings.HashesDictionaryTrusted",
  70                         initial_hashes_dictionary_trusted_);
  71 }
  72
  73 PrefHashStoreImpl::~PrefHashStoreImpl() {}
  74
  75 void PrefHashStoreImpl::Reset() {
  76   contents_->Reset();
  77 }
  78
  79 scoped_ptr<PrefHashStoreTransaction> PrefHashStoreImpl::BeginTransaction() {
  80   return scoped_ptr<PrefHashStoreTransaction>(
  81       new PrefHashStoreTransactionImpl(this));
  82 }
  83
  84 PrefHashStoreImpl::StoreVersion PrefHashStoreImpl::GetCurrentVersion() const {
  85   if (!contents_->IsInitialized())
  86     return VERSION_UNINITIALIZED;
  87
  88   int current_version;
  89   if (!contents_->GetVersion(&current_version)) {
  90     return VERSION_PRE_MIGRATION;
  91   }
  92
  93   DCHECK_GT(current_version, VERSION_PRE_MIGRATION);
  94   return static_cast<StoreVersion>(current_version);
  95 }
  96
  97 void PrefHashStoreImpl::CommitPendingWrite() {
  98   if (has_pending_write_) {
  99     contents_->CommitPendingWrite();
 100     has_pending_write_ = false;
 101   }
 102 }
 103
 104 PrefHashStoreImpl::PrefHashStoreTransactionImpl::PrefHashStoreTransactionImpl(
 105     PrefHashStoreImpl* outer) : outer_(outer), has_changed_(false) {
 106 }
 107
 108 PrefHashStoreImpl::PrefHashStoreTransactionImpl::
 109     ~PrefHashStoreTransactionImpl() {
 110   // Update the super MAC if and only if the hashes dictionary has been
 111   // modified in this transaction.
 112   if (has_changed_) {
 113     // Get the dictionary of hashes (or NULL if it doesn't exist).
 114     const base::DictionaryValue* hashes_dict = outer_->contents_->GetContents();
 115     outer_->contents_->SetSuperMac(outer_->pref_hash_calculator_.Calculate(
 116         outer_->contents_->hash_store_id(), hashes_dict));
 117
 118     outer_->has_pending_write_ = true;
 119   }
 120
 121   // Mark this hash store has having been updated to the latest version (in
 122   // practice only initialization transactions will actually do this, but
 123   // since they always occur before minor update transaction it's okay
 124   // to unconditionally do this here). Only do this if this store's version
 125   // isn't already at VERSION_LATEST (to avoid scheduling a write when
 126   // unecessary). Note, this is outside of |if (has_changed)| to also seed
 127   // version number of otherwise unchanged profiles.
 128   int current_version;
 129   if (!outer_->contents_->GetVersion(&current_version) ||
 130       current_version != VERSION_LATEST) {
 131     outer_->contents_->SetVersion(VERSION_LATEST);
 132     outer_->has_pending_write_ = true;
 133   }
 134 }
 135
 136 PrefHashStoreTransaction::ValueState
 137 PrefHashStoreImpl::PrefHashStoreTransactionImpl::CheckValue(
 138     const std::string& path, const base::Value* initial_value) const {
 139   const base::DictionaryValue* hashed_prefs = outer_->contents_->GetContents();
 140
 141   std::string last_hash;
 142   if (hashed_prefs)
 143     hashed_prefs->GetString(path, &last_hash);
 144
 145   if (last_hash.empty()) {
 146     // In the absence of a hash for this pref, always trust a NULL value, but
 147     // only trust an existing value if the initial hashes dictionary is trusted.
 148     return (!initial_value || outer_->initial_hashes_dictionary_trusted_) ?
 149                TRUSTED_UNKNOWN_VALUE : UNTRUSTED_UNKNOWN_VALUE;
 150   }
 151
 152   PrefHashCalculator::ValidationResult validation_result =
 153       outer_->pref_hash_calculator_.Validate(path, initial_value, last_hash);
 154   switch (validation_result) {
 155     case PrefHashCalculator::VALID:
 156       return UNCHANGED;
 157     case PrefHashCalculator::VALID_WEAK_LEGACY:
 158       return WEAK_LEGACY;
 159     case PrefHashCalculator::VALID_SECURE_LEGACY:
 160       return SECURE_LEGACY;
 161     case PrefHashCalculator::INVALID:
 162       return initial_value ? CHANGED : CLEARED;
 163   }
 164   NOTREACHED() << "Unexpected PrefHashCalculator::ValidationResult: "
 165                << validation_result;
 166   return UNTRUSTED_UNKNOWN_VALUE;
 167 }
 168
 169 void PrefHashStoreImpl::PrefHashStoreTransactionImpl::StoreHash(
 170     const std::string& path, const base::Value* new_value) {
 171   const std::string mac =
 172       outer_->pref_hash_calculator_.Calculate(path, new_value);
 173   (*outer_->contents_->GetMutableContents())->SetString(path, mac);
 174   has_changed_ = true;
 175 }
 176
 177 PrefHashStoreTransaction::ValueState
 178 PrefHashStoreImpl::PrefHashStoreTransactionImpl::CheckSplitValue(
 179     const std::string& path,
 180     const base::DictionaryValue* initial_split_value,
 181     std::vector<std::string>* invalid_keys) const {
 182   DCHECK(invalid_keys && invalid_keys->empty());
 183
 184   std::map<std::string, std::string> split_macs;
 185   const bool has_hashes = GetSplitMacs(path, &split_macs);
 186
 187   // Treat NULL and empty the same; otherwise we would need to store a hash
 188   // for the entire dictionary (or some other special beacon) to
 189   // differentiate these two cases which are really the same for
 190   // dictionaries.
 191   if (!initial_split_value || initial_split_value->empty())
 192     return has_hashes ? CLEARED : UNCHANGED;
 193
 194   if (!has_hashes) {
 195     return outer_->initial_hashes_dictionary_trusted_ ?
 196         TRUSTED_UNKNOWN_VALUE : UNTRUSTED_UNKNOWN_VALUE;
 197   }
 198
 199   bool has_secure_legacy_id_hashes = false;
 200   std::string keyed_path(path);
 201   keyed_path.push_back('.');
 202   const size_t common_part_length = keyed_path.length();
 203   for (base::DictionaryValue::Iterator it(*initial_split_value); !it.IsAtEnd();
 204        it.Advance()) {
 205     std::map<std::string, std::string>::iterator entry =
 206         split_macs.find(it.key());
 207     if (entry == split_macs.end()) {
 208       invalid_keys->push_back(it.key());
 209     } else {
 210       // Keep the common part from the old |keyed_path| and replace the key to
 211       // get the new |keyed_path|.
 212       keyed_path.replace(common_part_length, std::string::npos, it.key());
 213       switch (outer_->pref_hash_calculator_.Validate(
 214           keyed_path, &it.value(), entry->second)) {
 215         case PrefHashCalculator::VALID:
 216           break;
 217         case WEAK_LEGACY:
 218           // Split tracked preferences were introduced after the migration from
 219           // the weaker legacy algorithm started so no migration is expected,
 220           // but declare it invalid in Release builds anyways.
 221           NOTREACHED();
 222           invalid_keys->push_back(it.key());
 223           break;
 224         case SECURE_LEGACY:
 225           // Secure legacy device IDs based hashes are still accepted, but we
 226           // should make sure to notify the caller for him to update the legacy
 227           // hashes.
 228           has_secure_legacy_id_hashes = true;
 229           break;
 230         case PrefHashCalculator::INVALID:
 231           invalid_keys->push_back(it.key());
 232           break;
 233       }
 234       // Remove processed MACs, remaining MACs at the end will also be
 235       // considered invalid.
 236       split_macs.erase(entry);
 237     }
 238   }
 239
 240   // Anything left in the map is missing from the data.
 241   for (std::map<std::string, std::string>::const_iterator it =
 242            split_macs.begin();
 243        it != split_macs.end();
 244        ++it) {
 245     invalid_keys->push_back(it->first);
 246   }
 247
 248   return invalid_keys->empty()
 249       ? (has_secure_legacy_id_hashes ? SECURE_LEGACY : UNCHANGED)
 250       : CHANGED;
 251 }
 252
 253 void PrefHashStoreImpl::PrefHashStoreTransactionImpl::StoreSplitHash(
 254     const std::string& path,
 255     const base::DictionaryValue* split_value) {
 256   scoped_ptr<HashStoreContents::MutableDictionary> mutable_dictionary =
 257       outer_->contents_->GetMutableContents();
 258   (*mutable_dictionary)->Remove(path, NULL);
 259
 260   if (split_value) {
 261     std::string keyed_path(path);
 262     keyed_path.push_back('.');
 263     const size_t common_part_length = keyed_path.length();
 264     for (base::DictionaryValue::Iterator it(*split_value); !it.IsAtEnd();
 265          it.Advance()) {
 266       // Keep the common part from the old |keyed_path| and replace the key to
 267       // get the new |keyed_path|.
 268       keyed_path.replace(common_part_length, std::string::npos, it.key());
 269       (*mutable_dictionary)->SetString(
 270           keyed_path,
 271           outer_->pref_hash_calculator_.Calculate(keyed_path, &it.value()));
 272     }
 273   }
 274   has_changed_ = true;
 275 }
 276
 277 bool PrefHashStoreImpl::PrefHashStoreTransactionImpl::GetSplitMacs(
 278     const std::string& key,
 279     std::map<std::string, std::string>* split_macs) const {
 280   DCHECK(split_macs);
 281   DCHECK(split_macs->empty());
 282
 283   const base::DictionaryValue* hashed_prefs = outer_->contents_->GetContents();
 284   const base::DictionaryValue* split_mac_dictionary = NULL;
 285   if (!hashed_prefs || !hashed_prefs->GetDictionary(key, &split_mac_dictionary))
 286     return false;
 287   for (base::DictionaryValue::Iterator it(*split_mac_dictionary); !it.IsAtEnd();
 288        it.Advance()) {
 289     std::string mac_string;
 290     if (!it.value().GetAsString(&mac_string)) {
 291       NOTREACHED();
 292       continue;
 293     }
 294     split_macs->insert(make_pair(it.key(), mac_string));
 295   }
 296   return true;
 297 }