components/rappor/rappor_prefs.cc

   1 // Copyright 2015 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 "components/rappor/rappor_prefs.h"
   6
   7 #include "base/base64.h"
   8 #include "base/metrics/histogram.h"
   9 #include "base/prefs/pref_registry_simple.h"
  10 #include "base/prefs/pref_service.h"
  11 #include "base/rand_util.h"
  12 #include "components/metrics/daily_event.h"
  13 #include "components/rappor/byte_vector_utils.h"
  14 #include "components/rappor/rappor_parameters.h"
  15 #include "components/rappor/rappor_pref_names.h"
  16
  17 namespace rappor {
  18
  19 namespace internal {
  20
  21 const char kLoadCohortHistogramName[] = "Rappor.LoadCohortResult";
  22 const char kLoadSecretHistogramName[] = "Rappor.LoadSecretResult";
  23
  24 namespace {
  25
  26 void RecordLoadCohortResult(LoadResult reason) {
  27   UMA_HISTOGRAM_ENUMERATION(kLoadCohortHistogramName,
  28                             reason,
  29                             NUM_LOAD_RESULTS);
  30 }
  31
  32 void RecordLoadSecretResult(LoadResult reason) {
  33   UMA_HISTOGRAM_ENUMERATION(kLoadSecretHistogramName,
  34                             reason,
  35                             NUM_LOAD_RESULTS);
  36 }
  37
  38 } // namespace
  39
  40 void RegisterPrefs(PrefRegistrySimple* registry) {
  41   registry->RegisterStringPref(prefs::kRapporSecret, std::string());
  42   registry->RegisterIntegerPref(prefs::kRapporCohortDeprecated, -1);
  43   registry->RegisterIntegerPref(prefs::kRapporCohortSeed, -1);
  44   metrics::DailyEvent::RegisterPref(registry, prefs::kRapporLastDailySample);
  45 }
  46
  47 int32_t LoadCohort(PrefService* pref_service) {
  48   // Ignore and delete old cohort parameter.
  49   pref_service->ClearPref(prefs::kRapporCohortDeprecated);
  50
  51   int32_t cohort = pref_service->GetInteger(prefs::kRapporCohortSeed);
  52   // If the user is already assigned to a valid cohort, we're done.
  53   if (cohort >= 0 && cohort < RapporParameters::kMaxCohorts) {
  54     RecordLoadCohortResult(LOAD_SUCCESS);
  55     DVLOG(2) << "Rappor cohort loaded.";
  56     return cohort;
  57   }
  58
  59   // This is the first time the client has started the service (or their
  60   // preferences were corrupted).  Randomly assign them to a cohort.
  61   RecordLoadCohortResult(cohort == -1 ? LOAD_EMPTY_VALUE : LOAD_CORRUPT_VALUE);
  62   cohort = base::RandGenerator(RapporParameters::kMaxCohorts);
  63   DVLOG(2) << "Selected a new Rappor cohort: " << cohort;
  64   pref_service->SetInteger(prefs::kRapporCohortSeed, cohort);
  65   return cohort;
  66 }
  67
  68 std::string LoadSecret(PrefService* pref_service) {
  69   std::string secret;
  70   std::string secret_base64 = pref_service->GetString(prefs::kRapporSecret);
  71   if (!secret_base64.empty()) {
  72     bool decoded = base::Base64Decode(secret_base64, &secret);
  73     if (decoded &&
  74         secret.size() == HmacByteVectorGenerator::kEntropyInputSize) {
  75       DVLOG(2) << "Rappor secret loaded.";
  76       RecordLoadSecretResult(LOAD_SUCCESS);
  77       return secret;
  78     }
  79     // If the preference fails to decode, or is the wrong size, it must be
  80     // corrupt, so continue as though it didn't exist yet and generate a new
  81     // one.
  82     DVLOG(2) << "Corrupt Rappor secret found.";
  83     RecordLoadSecretResult(LOAD_CORRUPT_VALUE);
  84   } else {
  85     DVLOG(2) << "No Rappor secret found.";
  86     RecordLoadSecretResult(LOAD_EMPTY_VALUE);
  87   }
  88
  89   DVLOG(2) << "Generated a new Rappor secret.";
  90   secret = HmacByteVectorGenerator::GenerateEntropyInput();
  91   base::Base64Encode(secret, &secret_base64);
  92   pref_service->SetString(prefs::kRapporSecret, secret_base64);
  93   return secret;
  94 }
  95
  96 }  // namespace internal
  97
  98 }  // namespace rappor