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// Copyright 2013 The Chromium Authors
// 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 <string_view>
#include <vector>
#include "base/logging.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_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);
}
void AddSCTAndLogStatus(scoped_refptr<ct::SignedCertificateTimestamp> sct,
ct::SCTVerifyStatus status,
SignedCertificateTimestampAndStatusList* sct_list) {
LogSCTStatusToUMA(status);
sct_list->push_back(SignedCertificateTimestampAndStatus(sct, status));
}
std::map<std::string, scoped_refptr<const CTLogVerifier>> CreateLogsMap(
const std::vector<scoped_refptr<const CTLogVerifier>>& log_verifiers) {
std::map<std::string, scoped_refptr<const CTLogVerifier>> logs;
for (const auto& log_verifier : log_verifiers) {
logs[log_verifier->key_id()] = log_verifier;
}
return logs;
}
} // namespace
MultiLogCTVerifier::MultiLogCTVerifier(
const std::vector<scoped_refptr<const CTLogVerifier>>& log_verifiers)
: logs_(CreateLogsMap(log_verifiers)) {}
MultiLogCTVerifier::~MultiLogCTVerifier() = default;
void MultiLogCTVerifier::Verify(
X509Certificate* cert,
std::string_view stapled_ocsp_response,
std::string_view sct_list_from_tls_extension,
base::Time current_time,
SignedCertificateTimestampAndStatusList* output_scts,
const NetLogWithSource& net_log) const {
DCHECK(cert);
DCHECK(output_scts);
output_scts->clear();
std::string embedded_scts;
if (!cert->intermediate_buffers().empty() &&
ct::ExtractEmbeddedSCTList(cert->cert_buffer(), &embedded_scts)) {
ct::SignedEntryData precert_entry;
if (ct::GetPrecertSignedEntry(cert->cert_buffer(),
cert->intermediate_buffers().front().get(),
&precert_entry)) {
VerifySCTs(embedded_scts, precert_entry,
ct::SignedCertificateTimestamp::SCT_EMBEDDED, current_time,
cert, output_scts);
}
}
std::string sct_list_from_ocsp;
if (!stapled_ocsp_response.empty() && !cert->intermediate_buffers().empty()) {
ct::ExtractSCTListFromOCSPResponse(
cert->intermediate_buffers().front().get(), 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.
net_log.AddEvent(
NetLogEventType::SIGNED_CERTIFICATE_TIMESTAMPS_RECEIVED, [&] {
return NetLogRawSignedCertificateTimestampParams(
embedded_scts, sct_list_from_ocsp, sct_list_from_tls_extension);
});
ct::SignedEntryData x509_entry;
if (ct::GetX509SignedEntry(cert->cert_buffer(), &x509_entry)) {
VerifySCTs(sct_list_from_ocsp, x509_entry,
ct::SignedCertificateTimestamp::SCT_FROM_OCSP_RESPONSE,
current_time, cert, output_scts);
VerifySCTs(sct_list_from_tls_extension, x509_entry,
ct::SignedCertificateTimestamp::SCT_FROM_TLS_EXTENSION,
current_time, cert, output_scts);
}
net_log.AddEvent(NetLogEventType::SIGNED_CERTIFICATE_TIMESTAMPS_CHECKED, [&] {
return NetLogSignedCertificateTimestampParams(output_scts);
});
}
void MultiLogCTVerifier::VerifySCTs(
std::string_view encoded_sct_list,
const ct::SignedEntryData& expected_entry,
ct::SignedCertificateTimestamp::Origin origin,
base::Time current_time,
X509Certificate* cert,
SignedCertificateTimestampAndStatusList* output_scts) const {
if (logs_.empty())
return;
std::vector<std::string_view> sct_list;
if (!ct::DecodeSCTList(encoded_sct_list, &sct_list))
return;
for (std::vector<std::string_view>::const_iterator it = sct_list.begin();
it != sct_list.end(); ++it) {
std::string_view 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, current_time, cert,
output_scts);
}
}
bool MultiLogCTVerifier::VerifySingleSCT(
scoped_refptr<ct::SignedCertificateTimestamp> sct,
const ct::SignedEntryData& expected_entry,
base::Time current_time,
X509Certificate* cert,
SignedCertificateTimestampAndStatusList* output_scts) const {
// Assume this SCT is untrusted until proven otherwise.
const auto& it = logs_.find(sct->log_id);
if (it == logs_.end()) {
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())) {
AddSCTAndLogStatus(sct, ct::SCT_STATUS_INVALID_SIGNATURE, output_scts);
return false;
}
// SCT verified ok, just make sure the timestamp is legitimate.
if (sct->timestamp > current_time) {
AddSCTAndLogStatus(sct, ct::SCT_STATUS_INVALID_TIMESTAMP, output_scts);
return false;
}
AddSCTAndLogStatus(sct, ct::SCT_STATUS_OK, output_scts);
return true;
}
} // namespace net
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