Certificate Transparency: Notify STH Observers of known STHs

net/cert/sth_distributor.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 "base/metrics/histogram_macros.h"
 #include "base/time/time.h"
 #include "net/cert/signed_tree_head.h"
 
 namespace {
 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};
 }
 
 namespace net {
 
 namespace ct {
 
 STHDistributor::STHDistributor()
     : observer_list_(base::ObserverList<STHObserver>::NOTIFY_EXISTING_ONLY) {}
 
 STHDistributor::~STHDistributor() {}
 
 void STHDistributor::NewSTHObserved(const SignedTreeHead& sth) {
+  auto it = std::find_if(observed_sths_.begin(), observed_sths_.end(),
+                         [&sth](const SignedTreeHead& other) {
+                           return sth.log_id == other.log_id;
+                         });
+
+  if (it == observed_sths_.end())
+    observed_sths_.push_back(sth);
+  else
+    *it = sth;
+
   FOR_EACH_OBSERVER(STHObserver, observer_list_, NewSTHObserved(sth));
 
   if (sth.log_id.compare(0, sth.log_id.size(),
                          reinterpret_cast<const char*>(kPilotLogID),
                          sizeof(kPilotLogID)) != 0)
     return;
 
   const base::TimeDelta sth_age = base::Time::Now() - sth.timestamp;
   UMA_HISTOGRAM_CUSTOM_TIMES("Net.CertificateTransparency.PilotSTHAge", sth_age,
                              base::TimeDelta::FromHours(1),
                              base::TimeDelta::FromDays(4), 100);
 }
 
 void STHDistributor::RegisterObserver(STHObserver* observer) {
   observer_list_.AddObserver(observer);
+  // Make a local copy, because notifying the |observer| of a
+  // new STH may result in this class being notified of a
+  // (different) new STH, thus invalidating the iterator.
+  std::vector<SignedTreeHead> local_sths(observed_sths_);
+
+  for (const auto& sth : local_sths)
+    observer->NewSTHObserved(sth);
 }
 
 void STHDistributor::UnregisterObserver(STHObserver* observer) {
   observer_list_.RemoveObserver(observer);
 }
 
 }  // namespace ct
 
 }  // namespace net