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// Copyright 2024 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/ssl/client_cert_matcher.h"
#include <algorithm>
#include "base/containers/span.h"
#include "base/logging.h"
#include "net/cert/asn1_util.h"
#include "net/cert/x509_certificate.h"
#include "net/cert/x509_util.h"
#include "third_party/boringssl/src/include/openssl/pool.h"
namespace net {
namespace {
bool MatchClientCertificateIssuers(
X509Certificate* cert,
const std::vector<std::string>& cert_authorities,
const ClientCertIssuerSourceCollection& sources,
std::vector<bssl::UniquePtr<CRYPTO_BUFFER>>* intermediates) {
constexpr size_t kMaxDepth = 20;
intermediates->clear();
// If the request didn't supply `cert_authorities`, all client certs are
// returned.
if (cert_authorities.empty()) {
return true;
}
base::span<const uint8_t> current_issuer;
base::span<const uint8_t> current_subject;
if (!asn1::ExtractIssuerAndSubjectFromDERCert(
cert->cert_span(), ¤t_issuer, ¤t_subject)) {
return false;
}
while (intermediates->size() < kMaxDepth) {
// If the current cert in the chain is issued by one of the names in
// `cert_authorities`, this chain matches the request.
for (const std::string& authority : cert_authorities) {
if (base::as_byte_span(authority) == current_issuer) {
return true;
}
}
// If the chain reached a self-issued cert before matching the requested
// `cert_authorities`, give up.
if (current_issuer == current_subject) {
return false;
}
// Look for an issuer of the current cert.
bool found_issuer = false;
for (const auto& source : sources) {
std::vector<bssl::UniquePtr<CRYPTO_BUFFER>> issuers =
source->GetCertsByName(current_issuer);
for (auto& issuer : issuers) {
if (asn1::ExtractIssuerAndSubjectFromDERCert(
x509_util::CryptoBufferAsSpan(issuer.get()), ¤t_issuer,
¤t_subject)) {
// The first issuer found at each step is used. This algorithm doesn't
// do a full graph exploration.
found_issuer = true;
intermediates->push_back(std::move(issuer));
break;
}
}
}
if (!found_issuer) {
// No issuers were found, give up.
return false;
}
}
return false;
}
} // namespace
ClientCertIssuerSourceInMemory::ClientCertIssuerSourceInMemory(
std::vector<bssl::UniquePtr<CRYPTO_BUFFER>> certs)
: certs_(std::move(certs)) {
for (const auto& cert : certs_) {
std::string_view subject;
if (asn1::ExtractSubjectFromDERCert(
x509_util::CryptoBufferAsStringPiece(cert.get()), &subject)) {
cert_map_.emplace(base::as_byte_span(subject), cert.get());
}
}
}
ClientCertIssuerSourceInMemory::~ClientCertIssuerSourceInMemory() = default;
std::vector<bssl::UniquePtr<CRYPTO_BUFFER>>
ClientCertIssuerSourceInMemory::GetCertsByName(base::span<const uint8_t> name) {
std::vector<bssl::UniquePtr<CRYPTO_BUFFER>> result;
auto range = cert_map_.equal_range(name);
for (auto it = range.first; it != range.second; ++it) {
result.push_back(bssl::UpRef(it->second));
}
return result;
}
void FilterMatchingClientCertIdentities(
ClientCertIdentityList* identities,
const SSLCertRequestInfo& request,
const ClientCertIssuerSourceCollection& sources) {
size_t num_raw = 0;
auto keep_iter = identities->begin();
base::Time now = base::Time::Now();
for (auto examine_iter = identities->begin();
examine_iter != identities->end(); ++examine_iter) {
++num_raw;
X509Certificate* cert = (*examine_iter)->certificate();
// Only offer unexpired certificates.
// TODO(https://crbug.com/379943126): If the client system time is
// incorrect this may prune certificates that the server would have
// accepted (and we may still successfully validate the server certificate
// by using secure time). Consider removing.
if (now < cert->valid_start()) {
DVLOG(2) << "is not yet valid: " << cert->subject().GetDisplayName();
continue;
}
if (now > cert->valid_expiry()) {
DVLOG(2) << "is expired: " << cert->subject().GetDisplayName();
continue;
}
std::vector<bssl::UniquePtr<CRYPTO_BUFFER>> intermediates;
if (!MatchClientCertificateIssuers(cert, request.cert_authorities, sources,
&intermediates)) {
DVLOG(2) << "doesn't match: " << cert->subject().GetDisplayName();
continue;
} else {
DVLOG(2) << "found a match: " << cert->subject().GetDisplayName();
}
// Retain a copy of the intermediates. Some deployments expect the client to
// supply intermediates out of the local store. See
// https://crbug.com/548631.
(*examine_iter)->SetIntermediates(std::move(intermediates));
if (examine_iter == keep_iter) {
++keep_iter;
} else {
*keep_iter++ = std::move(*examine_iter);
}
}
identities->erase(keep_iter, identities->end());
DVLOG(2) << "num_raw:" << num_raw << " num_filtered:" << identities->size();
std::ranges::sort(*identities, ClientCertIdentitySorter());
}
} // namespace net
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