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// Copyright 2013 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/multi_log_ct_verifier.h"
#include <vector>
#include "base/bind.h"
#include "base/callback_helpers.h"
#include "base/metrics/histogram_macros.h"
#include "base/values.h"
#include "net/base/net_errors.h"
#include "net/cert/ct_log_verifier.h"
#include "net/cert/ct_objects_extractor.h"
#include "net/cert/ct_serialization.h"
#include "net/cert/ct_signed_certificate_timestamp_log_param.h"
#include "net/cert/sct_status_flags.h"
#include "net/cert/signed_certificate_timestamp_and_status.h"
#include "net/cert/x509_certificate.h"
#include "net/log/net_log_event_type.h"
#include "net/log/net_log_parameters_callback.h"
#include "net/log/net_log_with_source.h"
namespace net {
namespace {
// Record SCT verification status. This metric would help detecting presence
// of unknown CT logs as well as bad deployments (invalid SCTs).
void LogSCTStatusToUMA(ct::SCTVerifyStatus status) {
// Note SCT_STATUS_MAX + 1 is passed to the UMA_HISTOGRAM_ENUMERATION as that
// macro requires the values to be strictly less than the boundary value,
// and SCT_STATUS_MAX is the last valid value of the SCTVerifyStatus enum
// (since that enum is used for IPC as well).
UMA_HISTOGRAM_ENUMERATION("Net.CertificateTransparency.SCTStatus", status,
ct::SCT_STATUS_MAX + 1);
}
// Record SCT origin enum. This metric measure the popularity
// of the various channels of providing SCTs for a certificate.
void LogSCTOriginToUMA(ct::SignedCertificateTimestamp::Origin origin) {
UMA_HISTOGRAM_ENUMERATION("Net.CertificateTransparency.SCTOrigin",
origin,
ct::SignedCertificateTimestamp::SCT_ORIGIN_MAX);
}
// Count the number of SCTs that were available for each SSL connection
// (including SCTs embedded in the certificate).
// This metric would allow measuring:
// * Of all SSL connections, how many had SCTs available for validation.
// * When SCTs are available, how many are available per connection.
void LogNumSCTsToUMA(const SignedCertificateTimestampAndStatusList& scts) {
UMA_HISTOGRAM_CUSTOM_COUNTS("Net.CertificateTransparency.SCTsPerConnection",
scts.size(), 1, 10, 11);
}
void AddSCTAndLogStatus(scoped_refptr<ct::SignedCertificateTimestamp> sct,
ct::SCTVerifyStatus status,
SignedCertificateTimestampAndStatusList* sct_list) {
LogSCTStatusToUMA(status);
sct_list->push_back(SignedCertificateTimestampAndStatus(sct, status));
}
} // namespace
MultiLogCTVerifier::MultiLogCTVerifier() : observer_(nullptr) {
}
MultiLogCTVerifier::~MultiLogCTVerifier() { }
void MultiLogCTVerifier::AddLogs(
const std::vector<scoped_refptr<const CTLogVerifier>>& log_verifiers) {
for (const auto& log_verifier : log_verifiers) {
VLOG(1) << "Adding CT log: " << log_verifier->description();
logs_[log_verifier->key_id()] = log_verifier;
}
}
void MultiLogCTVerifier::SetObserver(Observer* observer) {
observer_ = observer;
}
void MultiLogCTVerifier::Verify(
X509Certificate* cert,
base::StringPiece stapled_ocsp_response,
base::StringPiece sct_list_from_tls_extension,
SignedCertificateTimestampAndStatusList* output_scts,
const NetLogWithSource& net_log) {
DCHECK(cert);
DCHECK(output_scts);
output_scts->clear();
std::string embedded_scts;
if (!cert->GetIntermediateCertificates().empty() &&
ct::ExtractEmbeddedSCTList(
cert->os_cert_handle(),
&embedded_scts)) {
ct::SignedEntryData precert_entry;
if (ct::GetPrecertSignedEntry(cert->os_cert_handle(),
cert->GetIntermediateCertificates().front(),
&precert_entry)) {
VerifySCTs(embedded_scts, precert_entry,
ct::SignedCertificateTimestamp::SCT_EMBEDDED, cert,
output_scts);
}
}
std::string sct_list_from_ocsp;
if (!stapled_ocsp_response.empty() &&
!cert->GetIntermediateCertificates().empty()) {
ct::ExtractSCTListFromOCSPResponse(
cert->GetIntermediateCertificates().front(), cert->serial_number(),
stapled_ocsp_response, &sct_list_from_ocsp);
}
// Log to Net Log, after extracting SCTs but before possibly failing on
// X.509 entry creation.
NetLogParametersCallback net_log_callback =
base::Bind(&NetLogRawSignedCertificateTimestampCallback, embedded_scts,
sct_list_from_ocsp, sct_list_from_tls_extension);
net_log.AddEvent(NetLogEventType::SIGNED_CERTIFICATE_TIMESTAMPS_RECEIVED,
net_log_callback);
ct::SignedEntryData x509_entry;
if (ct::GetX509SignedEntry(cert->os_cert_handle(), &x509_entry)) {
VerifySCTs(sct_list_from_ocsp, x509_entry,
ct::SignedCertificateTimestamp::SCT_FROM_OCSP_RESPONSE, cert,
output_scts);
VerifySCTs(sct_list_from_tls_extension, x509_entry,
ct::SignedCertificateTimestamp::SCT_FROM_TLS_EXTENSION, cert,
output_scts);
}
NetLogParametersCallback net_log_checked_callback =
base::Bind(&NetLogSignedCertificateTimestampCallback, output_scts);
net_log.AddEvent(NetLogEventType::SIGNED_CERTIFICATE_TIMESTAMPS_CHECKED,
net_log_checked_callback);
LogNumSCTsToUMA(*output_scts);
}
void MultiLogCTVerifier::VerifySCTs(
base::StringPiece encoded_sct_list,
const ct::SignedEntryData& expected_entry,
ct::SignedCertificateTimestamp::Origin origin,
X509Certificate* cert,
SignedCertificateTimestampAndStatusList* output_scts) {
if (logs_.empty())
return;
std::vector<base::StringPiece> sct_list;
if (!ct::DecodeSCTList(encoded_sct_list, &sct_list))
return;
for (std::vector<base::StringPiece>::const_iterator it = sct_list.begin();
it != sct_list.end(); ++it) {
base::StringPiece encoded_sct(*it);
LogSCTOriginToUMA(origin);
scoped_refptr<ct::SignedCertificateTimestamp> decoded_sct;
if (!DecodeSignedCertificateTimestamp(&encoded_sct, &decoded_sct)) {
LogSCTStatusToUMA(ct::SCT_STATUS_NONE);
continue;
}
decoded_sct->origin = origin;
VerifySingleSCT(decoded_sct, expected_entry, cert, output_scts);
}
}
bool MultiLogCTVerifier::VerifySingleSCT(
scoped_refptr<ct::SignedCertificateTimestamp> sct,
const ct::SignedEntryData& expected_entry,
X509Certificate* cert,
SignedCertificateTimestampAndStatusList* output_scts) {
// Assume this SCT is untrusted until proven otherwise.
const auto& it = logs_.find(sct->log_id);
if (it == logs_.end()) {
DVLOG(1) << "SCT does not match any known log.";
AddSCTAndLogStatus(sct, ct::SCT_STATUS_LOG_UNKNOWN, output_scts);
return false;
}
sct->log_description = it->second->description();
if (!it->second->Verify(expected_entry, *sct.get())) {
DVLOG(1) << "Unable to verify SCT signature.";
AddSCTAndLogStatus(sct, ct::SCT_STATUS_INVALID_SIGNATURE, output_scts);
return false;
}
// SCT verified ok, just make sure the timestamp is legitimate.
if (sct->timestamp > base::Time::Now()) {
DVLOG(1) << "SCT is from the future!";
AddSCTAndLogStatus(sct, ct::SCT_STATUS_INVALID_TIMESTAMP, output_scts);
return false;
}
AddSCTAndLogStatus(sct, ct::SCT_STATUS_OK, output_scts);
if (observer_)
observer_->OnSCTVerified(cert, sct.get());
return true;
}
} // namespace net