Certificate Transparency: Start tracking logs' state

components/certificate_transparency/single_tree_tracker.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 "components/certificate_transparency/single_tree_tracker.h"
+
+#include <utility>
+
+#include "net/cert/ct_log_verifier.h"
+#include "net/cert/signed_certificate_timestamp.h"
+#include "net/cert/x509_certificate.h"
+
+using net::ct::SignedTreeHead;
+
+namespace certificate_transparency {
+
+SingleTreeTracker::SingleTreeTracker(
+    scoped_refptr<const net::CTLogVerifier> ct_log)
+    : ct_log_(std::move(ct_log)) {}
+
+SingleTreeTracker::~SingleTreeTracker() {}
+
+void SingleTreeTracker::OnSCTVerified(
+    net::X509Certificate* cert,
+    const net::ct::SignedCertificateTimestamp* sct) {
+  DCHECK_EQ(ct_log_->key_id(), sct->log_id);
+
+  // SCT was previously observed, so its status should not be changed.
+  if (entries_status_.find(sct->timestamp) != entries_status_.end())
+    return;
+
+  // If there isn't a valid STH or the STH is not fresh enough to check
+  // inclusion against, store the SCT for future checking and return.
+  if (verified_sth_.timestamp.is_null() ||
+      (verified_sth_.timestamp <
+       (sct->timestamp + base::TimeDelta::FromHours(24)))) {
+    // TODO(eranm): UMA - how often SCTs have to wait for a newer STH for
+    // inclusion check.
+    entries_status_.insert(
+        std::make_pair(sct->timestamp, SCT_PENDING_NEWER_STH));
+    return;
+  }
+
+  // TODO(eranm): Check inclusion here.
+  // TODO(eranm): UMA - how often inclusion can be checked immediately.
+  entries_status_.insert(
+      std::make_pair(sct->timestamp, SCT_PENDING_INCLUSION_CHECK));
+}
+
+void SingleTreeTracker::NewSTHObserved(const SignedTreeHead& sth) {
+  DCHECK_EQ(ct_log_->key_id(), sth.log_id);
+
+  if (!ct_log_->VerifySignedTreeHead(sth)) {
+    // Sanity check the STH; the caller should have done this
+    // already, but being paranoid here.
+    // NOTE(eranm): Right now there's no way to get rid of this check here
+    // as this is the first object in the chain that has an instance of
+    // a CTLogVerifier to verify the STH.
+    return;
+  }
+
+  // In order to avoid updating |verified_sth_| to an older STH in case
+  // an older STH is observed, check that either the observed STH is for
+  // a larger tree size or that it is for the same tree size but has
+  // a newer timestamp.
+  const bool sths_for_same_tree = verified_sth_.tree_size == sth.tree_size;
+  const bool received_sth_is_for_larger_tree =
+      (verified_sth_.tree_size > sth.tree_size);
+  const bool received_sth_is_newer = (sth.timestamp > verified_sth_.timestamp);
+
+  if (verified_sth_.timestamp.is_null() || received_sth_is_for_larger_tree ||
+      (sths_for_same_tree && received_sth_is_newer)) {
+    verified_sth_ = sth;
+  }
+
+  // Find out which SCTs can now be checked for inclusion.
+  // TODO(eranm): Keep two maps of MerkleTreeLeaf instances, one for leaves
+  // pending inclusion checks and one for leaves pending a new STH.
+  // The comparison function between MerkleTreeLeaf instances should use the
+  // timestamp to determine sorting order, so that bulk moving from one
+  // map to the other can happen.
+  auto entry = entries_status_.begin();
+  while (entry != entries_status_.end() &&
+         entry->first < verified_sth_.timestamp) {
+    entry->second = SCT_PENDING_INCLUSION_CHECK;
+    ++entry;
+    // TODO(eranm): Check inclusion here.
+  }
+}
+
+SingleTreeTracker::SCTInclusionStatus
+SingleTreeTracker::GetLogEntryInclusionStatus(
+    net::X509Certificate* cert,
+    const net::ct::SignedCertificateTimestamp* sct) {
+  auto it = entries_status_.find(sct->timestamp);
+
+  return it == entries_status_.end() ? SCT_NOT_OBSERVED : it->second;
+}
+
+}  // namespace certificate_transparency