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->RegisterBooleanPref(prefs::kRapporEnabled, true);
  42   registry->RegisterStringPref(prefs::kRapporSecret, std::string());
  43   registry->RegisterIntegerPref(prefs::kRapporCohortDeprecated, -1);
  44   registry->RegisterIntegerPref(prefs::kRapporCohortSeed, -1);
  45   metrics::DailyEvent::RegisterPref(registry, prefs::kRapporLastDailySample);
  46 }
  47
  48 int32_t LoadCohort(PrefService* pref_service) {
  49   // Ignore and delete old cohort parameter.
  50   pref_service->ClearPref(prefs::kRapporCohortDeprecated);
  51
  52   int32_t cohort = pref_service->GetInteger(prefs::kRapporCohortSeed);
  53   // If the user is already assigned to a valid cohort, we're done.
  54   if (cohort >= 0 && cohort < RapporParameters::kMaxCohorts) {
  55     RecordLoadCohortResult(LOAD_SUCCESS);
  56     DVLOG(2) << "Rappor cohort loaded.";
  57     return cohort;
  58   }
  59
  60   // This is the first time the client has started the service (or their
  61   // preferences were corrupted).  Randomly assign them to a cohort.
  62   RecordLoadCohortResult(cohort == -1 ? LOAD_EMPTY_VALUE : LOAD_CORRUPT_VALUE);
  63   cohort = base::RandGenerator(RapporParameters::kMaxCohorts);
  64   DVLOG(2) << "Selected a new Rappor cohort: " << cohort;
  65   pref_service->SetInteger(prefs::kRapporCohortSeed, cohort);
  66   return cohort;
  67 }
  68
  69 std::string LoadSecret(PrefService* pref_service) {
  70   std::string secret;
  71   std::string secret_base64 = pref_service->GetString(prefs::kRapporSecret);
  72   if (!secret_base64.empty()) {
  73     bool decoded = base::Base64Decode(secret_base64, &secret);
  74     if (decoded &&
  75         secret.size() == HmacByteVectorGenerator::kEntropyInputSize) {
  76       DVLOG(2) << "Rappor secret loaded.";
  77       RecordLoadSecretResult(LOAD_SUCCESS);
  78       return secret;
  79     }
  80     // If the preference fails to decode, or is the wrong size, it must be
  81     // corrupt, so continue as though it didn't exist yet and generate a new
  82     // one.
  83     DVLOG(2) << "Corrupt Rappor secret found.";
  84     RecordLoadSecretResult(LOAD_CORRUPT_VALUE);
  85   } else {
  86     DVLOG(2) << "No Rappor secret found.";
  87     RecordLoadSecretResult(LOAD_EMPTY_VALUE);
  88   }
  89
  90   DVLOG(2) << "Generated a new Rappor secret.";
  91   secret = HmacByteVectorGenerator::GenerateEntropyInput();
  92   base::Base64Encode(secret, &secret_base64);
  93   pref_service->SetString(prefs::kRapporSecret, secret_base64);
  94   return secret;
  95 }
  96
  97 }  // namespace internal
  98
  99 }  // namespace rappor