Add stricter tests for RapporService::LoadSecret

components/rappor/rappor_prefs.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/rappor/rappor_prefs.h"
+
+#include "base/base64.h"
+#include "base/metrics/histogram.h"
+#include "base/prefs/pref_registry_simple.h"
+#include "base/prefs/pref_service.h"
+#include "base/rand_util.h"
+#include "components/metrics/daily_event.h"
+#include "components/rappor/byte_vector_utils.h"
+#include "components/rappor/rappor_parameters.h"
+#include "components/rappor/rappor_pref_names.h"
+
+namespace rappor {
+
+const char kLoadCohortHistogramName[] = "Rappor.LoadCohortResult";
+const char kLoadSecretHistogramName[] = "Rappor.LoadSecretResult";
+
+namespace {
+
+void RecordLoadCohortResult(LoadResult reason) {
+  UMA_HISTOGRAM_ENUMERATION(kLoadCohortHistogramName,
+                            reason,
+                            NUM_LOAD_RESULTS);
+}
+
+void RecordLoadSecretResult(LoadResult reason) {
+  UMA_HISTOGRAM_ENUMERATION(kLoadSecretHistogramName,
+                            reason,
+                            NUM_LOAD_RESULTS);
+}
+
+} // namespace
+
+void RegisterPrefs(PrefRegistrySimple* registry) {
+  registry->RegisterStringPref(prefs::kRapporSecret, std::string());
+  registry->RegisterIntegerPref(prefs::kRapporCohortDeprecated, -1);
+  registry->RegisterIntegerPref(prefs::kRapporCohortSeed, -1);
+  metrics::DailyEvent::RegisterPref(registry, prefs::kRapporLastDailySample);
+}
+
+int32_t LoadCohort(PrefService* pref_service) {
+  // Ignore and delete old cohort parameter.
+  pref_service->ClearPref(prefs::kRapporCohortDeprecated);
+
+  int32_t cohort = pref_service->GetInteger(prefs::kRapporCohortSeed);
+  // If the user is already assigned to a valid cohort, we're done.
+  if (cohort >= 0 && cohort < RapporParameters::kMaxCohorts) {
+    RecordLoadCohortResult(LOAD_SUCCESS);
+    DVLOG(2) << "Rappor cohort loaded.";
+    return cohort;
+  }
+
+  // This is the first time the client has started the service (or their
+  // preferences were corrupted).  Randomly assign them to a cohort.
+  RecordLoadCohortResult(cohort == -1 ? LOAD_EMPTY_VALUE : LOAD_CORRUPT_VALUE);
+  cohort = base::RandGenerator(RapporParameters::kMaxCohorts);
+  DVLOG(2) << "Selected a new Rappor cohort: " << cohort;
+  pref_service->SetInteger(prefs::kRapporCohortSeed, cohort);
+  return cohort;
+}
+
+std::string LoadSecret(PrefService* pref_service) {
+  std::string secret;
+  std::string secret_base64 = pref_service->GetString(prefs::kRapporSecret);
+  if (!secret_base64.empty()) {
+    bool decoded = base::Base64Decode(secret_base64, &secret);
+    if (decoded &&
+        secret.size() == HmacByteVectorGenerator::kEntropyInputSize) {
+      DVLOG(2) << "Rappor secret loaded.";
+      RecordLoadSecretResult(LOAD_SUCCESS);
+      return secret;
+    }
+    // If the preference fails to decode, or is the wrong size, it must be
+    // corrupt, so continue as though it didn't exist yet and generate a new
+    // one.
+    DVLOG(2) << "Corrupt Rappor secret found.";
+    RecordLoadSecretResult(LOAD_CORRUPT_VALUE);
+  } else {
+    DVLOG(2) << "No Rappor secret found.";
+    RecordLoadSecretResult(LOAD_EMPTY_VALUE);
+  }
+
+  DVLOG(2) << "Generated a new Rappor secret.";
+  secret = HmacByteVectorGenerator::GenerateEntropyInput();
+  base::Base64Encode(secret, &secret_base64);
+  pref_service->SetString(prefs::kRapporSecret, secret_base64);
+  return secret;
+}
+
+}  // namespace rappor