net/cert/multi_log_ct_verifier.cc

   1 // Copyright 2013 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 "net/cert/multi_log_ct_verifier.h"
   6
   7 #include <vector>
   8
   9 #include "base/bind.h"
  10 #include "base/callback_helpers.h"
  11 #include "base/metrics/histogram.h"
  12 #include "net/base/net_errors.h"
  13 #include "net/base/net_log.h"
  14 #include "net/cert/ct_log_verifier.h"
  15 #include "net/cert/ct_objects_extractor.h"
  16 #include "net/cert/ct_serialization.h"
  17 #include "net/cert/ct_signed_certificate_timestamp_log_param.h"
  18 #include "net/cert/ct_verify_result.h"
  19 #include "net/cert/sct_status_flags.h"
  20 #include "net/cert/x509_certificate.h"
  21
  22 namespace net {
  23
  24 namespace {
  25
  26 // Record SCT verification status. This metric would help detecting presence
  27 // of unknown CT logs as well as bad deployments (invalid SCTs).
  28 void LogSCTStatusToUMA(ct::SCTVerifyStatus status) {
  29   UMA_HISTOGRAM_ENUMERATION(
  30       "Net.CertificateTransparency.SCTStatus", status, ct::SCT_STATUS_MAX);
  31 }
  32
  33 // Record SCT origin enum. This metric measure the popularity
  34 // of the various channels of providing SCTs for a certificate.
  35 void LogSCTOriginToUMA(ct::SignedCertificateTimestamp::Origin origin) {
  36   UMA_HISTOGRAM_ENUMERATION("Net.CertificateTransparency.SCTOrigin",
  37                             origin,
  38                             ct::SignedCertificateTimestamp::SCT_ORIGIN_MAX);
  39 }
  40
  41 // Count the number of SCTs that were available for each SSL connection
  42 // (including SCTs embedded in the certificate).
  43 // This metric would allow measuring:
  44 // * Of all SSL connections, how many had SCTs available for validation.
  45 // * When SCTs are available, how many are available per connection.
  46 void LogNumSCTsToUMA(const ct::CTVerifyResult& result) {
  47   UMA_HISTOGRAM_CUSTOM_COUNTS("Net.CertificateTransparency.SCTsPerConnection",
  48                               result.invalid_scts.size() +
  49                                   result.verified_scts.size() +
  50                                   result.unknown_logs_scts.size(),
  51                               1,
  52                               10,
  53                               11);
  54 }
  55
  56 }  // namespace
  57
  58 MultiLogCTVerifier::MultiLogCTVerifier() { }
  59
  60 MultiLogCTVerifier::~MultiLogCTVerifier() { }
  61
  62 void MultiLogCTVerifier::AddLog(scoped_ptr<CTLogVerifier> log_verifier) {
  63   DCHECK(log_verifier);
  64   if (!log_verifier)
  65     return;
  66
  67   linked_ptr<CTLogVerifier> log(log_verifier.release());
  68   logs_[log->key_id()] = log;
  69 }
  70
  71 void MultiLogCTVerifier::AddLogs(
  72     ScopedVector<CTLogVerifier> log_verifiers) {
  73   for (ScopedVector<CTLogVerifier>::iterator it =
  74        log_verifiers.begin(); it != log_verifiers.end(); ++it) {
  75     linked_ptr<CTLogVerifier> log(*it);
  76     VLOG(1) << "Adding CT log: " << log->description();
  77     logs_[log->key_id()] = log;
  78   }
  79
  80   // Ownership of the pointers in |log_verifiers| is transferred to |logs_|
  81   log_verifiers.weak_clear();
  82 }
  83
  84 int MultiLogCTVerifier::Verify(
  85     X509Certificate* cert,
  86     const std::string& stapled_ocsp_response,
  87     const std::string& sct_list_from_tls_extension,
  88     ct::CTVerifyResult* result,
  89     const BoundNetLog& net_log)  {
  90   DCHECK(cert);
  91   DCHECK(result);
  92
  93   result->verified_scts.clear();
  94   result->invalid_scts.clear();
  95   result->unknown_logs_scts.clear();
  96
  97   bool has_verified_scts = false;
  98
  99   std::string embedded_scts;
 100   if (!cert->GetIntermediateCertificates().empty() &&
 101       ct::ExtractEmbeddedSCTList(
 102           cert->os_cert_handle(),
 103           &embedded_scts)) {
 104     ct::LogEntry precert_entry;
 105
 106     has_verified_scts =
 107         ct::GetPrecertLogEntry(
 108             cert->os_cert_handle(),
 109             cert->GetIntermediateCertificates().front(),
 110             &precert_entry) &&
 111         VerifySCTs(
 112             embedded_scts,
 113             precert_entry,
 114             ct::SignedCertificateTimestamp::SCT_EMBEDDED,
 115             result);
 116   }
 117
 118   std::string sct_list_from_ocsp;
 119   if (!stapled_ocsp_response.empty() &&
 120       !cert->GetIntermediateCertificates().empty()) {
 121     ct::ExtractSCTListFromOCSPResponse(
 122         cert->GetIntermediateCertificates().front(), cert->serial_number(),
 123         stapled_ocsp_response, &sct_list_from_ocsp);
 124   }
 125
 126   // Log to Net Log, after extracting SCTs but before possibly failing on
 127   // X.509 entry creation.
 128   NetLog::ParametersCallback net_log_callback =
 129       base::Bind(&NetLogRawSignedCertificateTimestampCallback,
 130           &embedded_scts, &sct_list_from_ocsp, &sct_list_from_tls_extension);
 131
 132   net_log.AddEvent(
 133       NetLog::TYPE_SIGNED_CERTIFICATE_TIMESTAMPS_RECEIVED,
 134       net_log_callback);
 135
 136   ct::LogEntry x509_entry;
 137   if (ct::GetX509LogEntry(cert->os_cert_handle(), &x509_entry)) {
 138     has_verified_scts |= VerifySCTs(
 139         sct_list_from_ocsp,
 140         x509_entry,
 141         ct::SignedCertificateTimestamp::SCT_FROM_OCSP_RESPONSE,
 142         result);
 143
 144     has_verified_scts |= VerifySCTs(
 145         sct_list_from_tls_extension,
 146         x509_entry,
 147         ct::SignedCertificateTimestamp::SCT_FROM_TLS_EXTENSION,
 148         result);
 149   }
 150
 151   NetLog::ParametersCallback net_log_checked_callback =
 152       base::Bind(&NetLogSignedCertificateTimestampCallback, result);
 153
 154   net_log.AddEvent(
 155       NetLog::TYPE_SIGNED_CERTIFICATE_TIMESTAMPS_CHECKED,
 156       net_log_checked_callback);
 157
 158   LogNumSCTsToUMA(*result);
 159
 160   if (has_verified_scts)
 161     return OK;
 162
 163   return ERR_CT_NO_SCTS_VERIFIED_OK;
 164 }
 165
 166 bool MultiLogCTVerifier::VerifySCTs(
 167     const std::string& encoded_sct_list,
 168     const ct::LogEntry& expected_entry,
 169     ct::SignedCertificateTimestamp::Origin origin,
 170     ct::CTVerifyResult* result) {
 171   if (logs_.empty())
 172     return false;
 173
 174   base::StringPiece temp(encoded_sct_list);
 175   std::vector<base::StringPiece> sct_list;
 176
 177   if (!ct::DecodeSCTList(&temp, &sct_list))
 178     return false;
 179
 180   bool verified = false;
 181   for (std::vector<base::StringPiece>::const_iterator it = sct_list.begin();
 182        it != sct_list.end(); ++it) {
 183     base::StringPiece encoded_sct(*it);
 184     LogSCTOriginToUMA(origin);
 185
 186     scoped_refptr<ct::SignedCertificateTimestamp> decoded_sct;
 187     if (!DecodeSignedCertificateTimestamp(&encoded_sct, &decoded_sct)) {
 188       LogSCTStatusToUMA(ct::SCT_STATUS_NONE);
 189       // XXX(rsleevi): Should we really just skip over bad SCTs?
 190       continue;
 191     }
 192     decoded_sct->origin = origin;
 193
 194     verified |= VerifySingleSCT(decoded_sct, expected_entry, result);
 195   }
 196
 197   return verified;
 198 }
 199
 200 bool MultiLogCTVerifier::VerifySingleSCT(
 201     scoped_refptr<ct::SignedCertificateTimestamp> sct,
 202     const ct::LogEntry& expected_entry,
 203     ct::CTVerifyResult* result) {
 204
 205   // Assume this SCT is untrusted until proven otherwise.
 206   IDToLogMap::iterator it = logs_.find(sct->log_id);
 207   if (it == logs_.end()) {
 208     DVLOG(1) << "SCT does not match any known log.";
 209     result->unknown_logs_scts.push_back(sct);
 210     LogSCTStatusToUMA(ct::SCT_STATUS_LOG_UNKNOWN);
 211     return false;
 212   }
 213
 214   sct->log_description = it->second->description();
 215
 216   if (!it->second->Verify(expected_entry, *sct.get())) {
 217     DVLOG(1) << "Unable to verify SCT signature.";
 218     result->invalid_scts.push_back(sct);
 219     LogSCTStatusToUMA(ct::SCT_STATUS_INVALID);
 220     return false;
 221   }
 222
 223   // SCT verified ok, just make sure the timestamp is legitimate.
 224   if (sct->timestamp > base::Time::Now()) {
 225     DVLOG(1) << "SCT is from the future!";
 226     result->invalid_scts.push_back(sct);
 227     LogSCTStatusToUMA(ct::SCT_STATUS_INVALID);
 228     return false;
 229   }
 230
 231   LogSCTStatusToUMA(ct::SCT_STATUS_OK);
 232   result->verified_scts.push_back(sct);
 233   return true;
 234 }
 235
 236 } // namespace net