chrome/browser/metrics/variations/variations_seed_store.h

   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 #ifndef CHROME_BROWSER_METRICS_VARIATIONS_VARIATIONS_SEED_STORE_H_
   6 #define CHROME_BROWSER_METRICS_VARIATIONS_VARIATIONS_SEED_STORE_H_
   7
   8 #include <string>
   9
  10 #include "base/compiler_specific.h"
  11 #include "base/gtest_prod_util.h"
  12 #include "base/time/time.h"
  13
  14 class PrefService;
  15 class PrefRegistrySimple;
  16
  17 namespace variations {
  18 class VariationsSeed;
  19 }
  20
  21 namespace chrome_variations {
  22
  23 // VariationsSeedStore is a helper class for reading and writing the variations
  24 // seed from Local State.
  25 class VariationsSeedStore {
  26  public:
  27   explicit VariationsSeedStore(PrefService* local_state);
  28   virtual ~VariationsSeedStore();
  29
  30   // Loads the variations seed data from local state into |seed|. If there is a
  31   // problem with loading, the pref value is cleared and false is returned. If
  32   // successful, |seed| will contain the loaded data and true is returned.
  33   bool LoadSeed(variations::VariationsSeed* seed);
  34
  35   // Stores the given seed |data| (serialized protobuf) to local state, along
  36   // with a base64-encoded digital signature for seed and the date when it was
  37   // fetched. If |is_delta_compressed| is true, treats |data| as being delta
  38   // compressed and attempts to decode it first using the store's seed data.
  39   // The actual seed data will be base64 encoded for storage. If the string
  40   // is invalid, the existing prefs are untouched and false is returned.
  41   // Additionally, stores the |country_code| that was received with the seed in
  42   // a separate pref. On success and if |parsed_seed| is not NULL, |parsed_seed|
  43   // will be filled with the de-serialized decoded protobuf.
  44   bool StoreSeedData(const std::string& data,
  45                      const std::string& base64_seed_signature,
  46                      const std::string& country_code,
  47                      const base::Time& date_fetched,
  48                      bool is_delta_compressed,
  49                      variations::VariationsSeed* parsed_seed);
  50
  51   // Updates |kVariationsSeedDate| and logs when previous date was from a
  52   // different day.
  53   void UpdateSeedDateAndLogDayChange(const base::Time& server_date_fetched);
  54
  55   // Returns the serial number of the last loaded or stored seed.
  56   const std::string& variations_serial_number() const {
  57     return variations_serial_number_;
  58   }
  59
  60   // Returns whether the last loaded or stored seed has the country field set.
  61   bool seed_has_country_code() const {
  62     return seed_has_country_code_;
  63   }
  64
  65   // Returns the invalid signature in base64 format, or an empty string if the
  66   // signature was valid, missing, or if signature verification is disabled.
  67   std::string GetInvalidSignature() const;
  68
  69   // Registers Local State prefs used by this class.
  70   static void RegisterPrefs(PrefRegistrySimple* registry);
  71
  72  protected:
  73   // Note: UMA histogram enum - don't re-order or remove entries.
  74   enum VerifySignatureResult {
  75     VARIATIONS_SEED_SIGNATURE_MISSING,
  76     VARIATIONS_SEED_SIGNATURE_DECODE_FAILED,
  77     VARIATIONS_SEED_SIGNATURE_INVALID_SIGNATURE,
  78     VARIATIONS_SEED_SIGNATURE_INVALID_SEED,
  79     VARIATIONS_SEED_SIGNATURE_VALID,
  80     VARIATIONS_SEED_SIGNATURE_ENUM_SIZE,
  81   };
  82
  83   // Verifies a variations seed (the serialized proto bytes) with the specified
  84   // base-64 encoded signature that was received from the server and returns the
  85   // result. The signature is assumed to be an "ECDSA with SHA-256" signature
  86   // (see kECDSAWithSHA256AlgorithmID in the .cc file). Returns the result of
  87   // signature verification or VARIATIONS_SEED_SIGNATURE_ENUM_SIZE if signature
  88   // verification is not enabled.
  89   virtual VariationsSeedStore::VerifySignatureResult VerifySeedSignature(
  90       const std::string& seed_bytes,
  91       const std::string& base64_seed_signature);
  92
  93  private:
  94   FRIEND_TEST_ALL_PREFIXES(VariationsSeedStoreTest, VerifySeedSignature);
  95   FRIEND_TEST_ALL_PREFIXES(VariationsSeedStoreTest, ApplyDeltaPatch);
  96
  97   // Clears all prefs related to variations seed storage.
  98   void ClearPrefs();
  99
 100   // Reads the variations seed data from prefs; returns true on success.
 101   bool ReadSeedData(std::string* seed_data);
 102
 103   // Internal version of |StoreSeedData()| that assumes |seed_data| is not delta
 104   // compressed.
 105   bool StoreSeedDataNoDelta(
 106       const std::string& seed_data,
 107       const std::string& base64_seed_signature,
 108       const std::string& country_code,
 109       const base::Time& date_fetched,
 110       variations::VariationsSeed* parsed_seed);
 111
 112   // Applies a delta-compressed |patch| to |existing_data|, producing the result
 113   // in |output|. Returns whether the operation was successful.
 114   static bool ApplyDeltaPatch(const std::string& existing_data,
 115                               const std::string& patch,
 116                               std::string* output);
 117
 118   // The pref service used to persist the variations seed.
 119   PrefService* local_state_;
 120
 121   // Cached serial number from the most recently fetched variations seed.
 122   std::string variations_serial_number_;
 123
 124   // Whether the most recently fetched variations seed has the country code
 125   // field set.
 126   bool seed_has_country_code_;
 127
 128   // Keeps track of an invalid signature.
 129   std::string invalid_base64_signature_;
 130
 131   DISALLOW_COPY_AND_ASSIGN(VariationsSeedStore);
 132 };
 133
 134 }  // namespace chrome_variations
 135
 136 #endif  // CHROME_BROWSER_METRICS_VARIATIONS_VARIATIONS_SEED_STORE_H_