Certificate Transparency: Notify STH Observers of known STHs

net/cert/sth_distributor_unittest.cc

+// Copyright 2016 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 "net/cert/sth_distributor.h"
+
+#include <map>
+#include <string>
+
+#include "base/test/histogram_tester.h"
+#include "crypto/sha2.h"
+#include "net/cert/signed_tree_head.h"
+#include "net/cert/sth_observer.h"
+#include "net/test/ct_test_util.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace net {
+
+namespace ct {
+
+namespace {
+
+// An STHObserver implementation that simply stores all
+// observed STHs, keyed by log ID.
+class StoringSTHObserver : public STHObserver {
+ public:
+  void NewSTHObserved(const SignedTreeHead& sth) override {
+    sths[sth.log_id] = sth;
+  }
+
+  std::map<std::string, SignedTreeHead> sths;
+};
+
+class STHDistributorTest : public ::testing::Test {
+ public:
+  STHDistributorTest() {}
+
+  void SetUp() override {
+    ASSERT_TRUE(GetSampleSignedTreeHead(&sample_sth_));
+    sample_sth_.log_id = GetTestPublicKeyId();
+  }
+
+ protected:
+  STHDistributor distributor_;
+  SignedTreeHead sample_sth_;
+};
+
+// Test that when a new observer is registered, the STHDistributor notifies it
+// of all the observed STHs it received so far.
+// This test makes sure that all observed STHs are reported to the observer.
+TEST_F(STHDistributorTest, NotifiesOfExistingSTHs) {
+  // Create an STH that differs from the |sample_sth_| by belonging to a
+  // different log.
+  const std::string other_log = "another log";
+  SignedTreeHead second_sth(sample_sth_);
+  second_sth.log_id = other_log;
+
+  // Notify |distributor_| of both STHs.
+  distributor_.NewSTHObserved(sample_sth_);
+  distributor_.NewSTHObserved(second_sth);
+
+  StoringSTHObserver observer;
+  distributor_.RegisterObserver(&observer);
+
+  // Check that two STHs from different logs received prior to observer
+  // registration were reported to the observer once registered.
+  EXPECT_EQ(2u, observer.sths.size());
+  EXPECT_EQ(1u, observer.sths.count(other_log));
+}
+
+// Test that histograms are properly recorded for the STH age when an STH
+// from Google's Pilot log is observed.
+TEST_F(STHDistributorTest, LogsUMAForPilotSTH) {
+  const char kPilotSTHAgeHistogram[] =
+      "Net.CertificateTransparency.PilotSTHAge";
+  base::HistogramTester histograms;
+  histograms.ExpectTotalCount(kPilotSTHAgeHistogram, 0);
+
+  const uint8_t kPilotLogID[] = {
+      0xa4, 0xb9, 0x09, 0x90, 0xb4, 0x18, 0x58, 0x14, 0x87, 0xbb, 0x13,
+      0xa2, 0xcc, 0x67, 0x70, 0x0a, 0x3c, 0x35, 0x98, 0x04, 0xf9, 0x1b,
+      0xdf, 0xb8, 0xe3, 0x77, 0xcd, 0x0e, 0xc8, 0x0d, 0xdc, 0x10};
+  sample_sth_.log_id = std::string(reinterpret_cast<const char*>(kPilotLogID),
+                                   crypto::kSHA256Length);
+
+  distributor_.NewSTHObserved(sample_sth_);
+  histograms.ExpectTotalCount(kPilotSTHAgeHistogram, 1);
+}
+
+// Test that the STHDistributor updates, rather than accumulates, STHs
+// coming from the same log.
+// This is tested by notifying the STHDistributor of an STH, modifying that
+// STH, notifying the STHDistributor of the modified STH, then registering
+// an observer which should get notified only once, with the modified STH.
+TEST_F(STHDistributorTest, UpdatesObservedSTHData) {
+  // Observe an initial STH
+  StoringSTHObserver observer;
+  distributor_.RegisterObserver(&observer);
+
+  distributor_.NewSTHObserved(sample_sth_);
+
+  EXPECT_EQ(1u, observer.sths.size());
+  EXPECT_EQ(sample_sth_, observer.sths[GetTestPublicKeyId()]);
+
+  // Observe a new STH. "new" simply means that it is a more recently observed
+  // SignedTreeHead for the given log ID, not necessarily that it's newer
+  // chronologically (the timestamp) or the log state (the tree size).
+  // To make sure the more recently observed SignedTreeHead is returned, just
+  // modify some fields.
+  SignedTreeHead new_sth = sample_sth_;
+  new_sth.tree_size++;
+  new_sth.timestamp -= base::TimeDelta::FromSeconds(3);
+
+  distributor_.NewSTHObserved(new_sth);
+  // The STH should have been broadcast to existing observers.
+  EXPECT_EQ(1u, observer.sths.size());
+  EXPECT_NE(sample_sth_, observer.sths[GetTestPublicKeyId()]);
+  EXPECT_EQ(new_sth, observer.sths[GetTestPublicKeyId()]);
+
+  // Registering a new observer should only receive the most recently observed
+  // STH.
+  StoringSTHObserver new_observer;
+  distributor_.RegisterObserver(&new_observer);
+  EXPECT_EQ(1u, new_observer.sths.size());
+  EXPECT_NE(sample_sth_, new_observer.sths[GetTestPublicKeyId()]);
+  EXPECT_EQ(new_sth, new_observer.sths[GetTestPublicKeyId()]);
+}
+
+}  // namespace
+
+}  // namespace ct
+
+}  // namespace net