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* Copyright 2020 The WebRTC Project Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#include "rtc_base/boringssl_certificate.h"
#include "absl/strings/string_view.h"
#if defined(WEBRTC_WIN)
// Must be included first before openssl headers.
#include "rtc_base/win32.h" // NOLINT
#endif // WEBRTC_WIN
#include <openssl/asn1.h>
#include <openssl/bytestring.h>
#include <openssl/digest.h>
#include <openssl/evp.h>
#include <openssl/mem.h>
#include <openssl/pool.h>
#include <openssl/rand.h>
#include <time.h>
#include <cstring>
#include <memory>
#include <utility>
#include <vector>
#include "rtc_base/checks.h"
#include "rtc_base/helpers.h"
#include "rtc_base/logging.h"
#include "rtc_base/message_digest.h"
#include "rtc_base/openssl_digest.h"
#include "rtc_base/openssl_key_pair.h"
#include "rtc_base/openssl_utility.h"
namespace rtc {
namespace {
// List of OIDs of signature algorithms accepted by WebRTC.
// Taken from openssl/nid.h.
static const uint8_t kMD5WithRSA[] = {0x2b, 0x0e, 0x03, 0x02, 0x03};
static const uint8_t kMD5WithRSAEncryption[] = {0x2a, 0x86, 0x48, 0x86, 0xf7,
0x0d, 0x01, 0x01, 0x04};
static const uint8_t kECDSAWithSHA1[] = {0x2a, 0x86, 0x48, 0xce,
0x3d, 0x04, 0x01};
static const uint8_t kDSAWithSHA1[] = {0x2a, 0x86, 0x48, 0xce,
0x38, 0x04, 0x03};
static const uint8_t kDSAWithSHA1_2[] = {0x2b, 0x0e, 0x03, 0x02, 0x1b};
static const uint8_t kSHA1WithRSA[] = {0x2b, 0x0e, 0x03, 0x02, 0x1d};
static const uint8_t kSHA1WithRSAEncryption[] = {0x2a, 0x86, 0x48, 0x86, 0xf7,
0x0d, 0x01, 0x01, 0x05};
static const uint8_t kECDSAWithSHA224[] = {0x2a, 0x86, 0x48, 0xce,
0x3d, 0x04, 0x03, 0x01};
static const uint8_t kSHA224WithRSAEncryption[] = {0x2a, 0x86, 0x48, 0x86, 0xf7,
0x0d, 0x01, 0x01, 0x0e};
static const uint8_t kDSAWithSHA224[] = {0x60, 0x86, 0x48, 0x01, 0x65,
0x03, 0x04, 0x03, 0x01};
static const uint8_t kECDSAWithSHA256[] = {0x2a, 0x86, 0x48, 0xce,
0x3d, 0x04, 0x03, 0x02};
static const uint8_t kSHA256WithRSAEncryption[] = {0x2a, 0x86, 0x48, 0x86, 0xf7,
0x0d, 0x01, 0x01, 0x0b};
static const uint8_t kDSAWithSHA256[] = {0x60, 0x86, 0x48, 0x01, 0x65,
0x03, 0x04, 0x03, 0x02};
static const uint8_t kECDSAWithSHA384[] = {0x2a, 0x86, 0x48, 0xce,
0x3d, 0x04, 0x03, 0x03};
static const uint8_t kSHA384WithRSAEncryption[] = {0x2a, 0x86, 0x48, 0x86, 0xf7,
0x0d, 0x01, 0x01, 0x0c};
static const uint8_t kECDSAWithSHA512[] = {0x2a, 0x86, 0x48, 0xce,
0x3d, 0x04, 0x03, 0x04};
static const uint8_t kSHA512WithRSAEncryption[] = {0x2a, 0x86, 0x48, 0x86, 0xf7,
0x0d, 0x01, 0x01, 0x0d};
#if !defined(NDEBUG)
// Print a certificate to the log, for debugging.
static void PrintCert(BoringSSLCertificate* cert) {
// Since we're using CRYPTO_BUFFER, we can't use X509_print_ex, so we'll just
// print the PEM string.
RTC_DLOG(LS_VERBOSE) << "PEM representation of certificate:\n"
<< cert->ToPEMString();
bool AddSHA256SignatureAlgorithm(CBB* cbb, KeyType key_type) {
// An AlgorithmIdentifier is described in RFC 5280,
CBB sequence, oid, params;
if (!CBB_add_asn1(cbb, &sequence, CBS_ASN1_SEQUENCE) ||
!CBB_add_asn1(&sequence, &oid, CBS_ASN1_OBJECT)) {
return false;
switch (key_type) {
case KT_RSA:
if (!CBB_add_bytes(&oid, kSHA256WithRSAEncryption,
sizeof(kSHA256WithRSAEncryption)) ||
!CBB_add_asn1(&sequence, &params, CBS_ASN1_NULL)) {
return false;
case KT_ECDSA:
if (!CBB_add_bytes(&oid, kECDSAWithSHA256, sizeof(kECDSAWithSHA256))) {
return false;
return false;
if (!CBB_flush(cbb)) {
return false;
return true;
// Adds an X.509 Common Name to `cbb`.
bool AddCommonName(CBB* cbb, absl::string_view common_name) {
// See RFC 4519.
static const uint8_t kCommonName[] = {0x55, 0x04, 0x03};
if (common_name.empty()) {
RTC_LOG(LS_ERROR) << "Common name cannot be empty.";
return false;
// See RFC 5280, section
CBB rdns;
if (!CBB_add_asn1(cbb, &rdns, CBS_ASN1_SEQUENCE)) {
return false;
CBB rdn, attr, type, value;
if (!CBB_add_asn1(&rdns, &rdn, CBS_ASN1_SET) ||
!CBB_add_asn1(&rdn, &attr, CBS_ASN1_SEQUENCE) ||
!CBB_add_asn1(&attr, &type, CBS_ASN1_OBJECT) ||
!CBB_add_bytes(&type, kCommonName, sizeof(kCommonName)) ||
!CBB_add_asn1(&attr, &value, CBS_ASN1_UTF8STRING) ||
reinterpret_cast<const uint8_t*>(,
common_name.size()) ||
!CBB_flush(cbb)) {
return false;
return true;
bool AddTime(CBB* cbb, time_t time) {
bssl::UniquePtr<ASN1_TIME> asn1_time(ASN1_TIME_new());
if (!asn1_time) {
return false;
if (!ASN1_TIME_set(asn1_time.get(), time)) {
return false;
unsigned tag;
switch (asn1_time->type) {
return false;
CBB child;
if (!CBB_add_asn1(cbb, &child, tag) ||
!CBB_add_bytes(&child, asn1_time->data, asn1_time->length) ||
!CBB_flush(cbb)) {
return false;
return true;
// Generate a self-signed certificate, with the public key from the
// given key pair. Caller is responsible for freeing the returned object.
static bssl::UniquePtr<CRYPTO_BUFFER> MakeCertificate(
EVP_PKEY* pkey,
const SSLIdentityParams& params) {
RTC_LOG(LS_INFO) << "Making certificate for " << params.common_name;
// See RFC 5280, section 4.1. First, construct the TBSCertificate.
bssl::ScopedCBB cbb;
CBB tbs_cert, version, validity;
uint8_t* tbs_cert_bytes;
size_t tbs_cert_len;
uint64_t serial_number;
if (!CBB_init(cbb.get(), 64) ||
!CBB_add_asn1(cbb.get(), &tbs_cert, CBS_ASN1_SEQUENCE) ||
!CBB_add_asn1(&tbs_cert, &version,
!CBB_add_asn1_uint64(&version, 2) ||
sizeof(serial_number)) ||
!CBB_add_asn1_uint64(&tbs_cert, serial_number) ||
!AddSHA256SignatureAlgorithm(&tbs_cert, params.key_params.type()) ||
!AddCommonName(&tbs_cert, params.common_name) || // issuer
!CBB_add_asn1(&tbs_cert, &validity, CBS_ASN1_SEQUENCE) ||
!AddTime(&validity, params.not_before) ||
!AddTime(&validity, params.not_after) ||
!AddCommonName(&tbs_cert, params.common_name) || // subject
!EVP_marshal_public_key(&tbs_cert, pkey) || // subjectPublicKeyInfo
!CBB_finish(cbb.get(), &tbs_cert_bytes, &tbs_cert_len)) {
return nullptr;
bssl::UniquePtr<uint8_t> delete_tbs_cert_bytes(tbs_cert_bytes);
// Sign the TBSCertificate and write the entire certificate.
CBB cert, signature;
bssl::ScopedEVP_MD_CTX ctx;
uint8_t* sig_out;
size_t sig_len;
uint8_t* cert_bytes;
size_t cert_len;
if (!CBB_init(cbb.get(), tbs_cert_len) ||
!CBB_add_asn1(cbb.get(), &cert, CBS_ASN1_SEQUENCE) ||
!CBB_add_bytes(&cert, tbs_cert_bytes, tbs_cert_len) ||
!AddSHA256SignatureAlgorithm(&cert, params.key_params.type()) ||
!CBB_add_asn1(&cert, &signature, CBS_ASN1_BITSTRING) ||
!CBB_add_u8(&signature, 0 /* no unused bits */) ||
!EVP_DigestSignInit(ctx.get(), nullptr, EVP_sha256(), nullptr, pkey) ||
// Compute the maximum signature length.
!EVP_DigestSign(ctx.get(), nullptr, &sig_len, tbs_cert_bytes,
tbs_cert_len) ||
!CBB_reserve(&signature, &sig_out, sig_len) ||
// Actually sign the TBSCertificate.
!EVP_DigestSign(ctx.get(), sig_out, &sig_len, tbs_cert_bytes,
tbs_cert_len) ||
!CBB_did_write(&signature, sig_len) ||
!CBB_finish(cbb.get(), &cert_bytes, &cert_len)) {
return nullptr;
bssl::UniquePtr<uint8_t> delete_cert_bytes(cert_bytes);
RTC_LOG(LS_INFO) << "Returning certificate";
return bssl::UniquePtr<CRYPTO_BUFFER>(
CRYPTO_BUFFER_new(cert_bytes, cert_len, openssl::GetBufferPool()));
} // namespace
bssl::UniquePtr<CRYPTO_BUFFER> cert_buffer)
: cert_buffer_(std::move(cert_buffer)) {
RTC_DCHECK(cert_buffer_ != nullptr);
std::unique_ptr<BoringSSLCertificate> BoringSSLCertificate::Generate(
OpenSSLKeyPair* key_pair,
const SSLIdentityParams& params) {
SSLIdentityParams actual_params(params);
if (actual_params.common_name.empty()) {
// Use a random string, arbitrarily 8 chars long.
actual_params.common_name = CreateRandomString(8);
bssl::UniquePtr<CRYPTO_BUFFER> cert_buffer =
MakeCertificate(key_pair->pkey(), actual_params);
if (!cert_buffer) {
openssl::LogSSLErrors("Generating certificate");
return nullptr;
auto ret = std::make_unique<BoringSSLCertificate>(std::move(cert_buffer));
#if !defined(NDEBUG)
return ret;
std::unique_ptr<BoringSSLCertificate> BoringSSLCertificate::FromPEMString(
absl::string_view pem_string) {
std::string der;
if (!SSLIdentity::PemToDer(kPemTypeCertificate, pem_string, &der)) {
return nullptr;
bssl::UniquePtr<CRYPTO_BUFFER> cert_buffer(
CRYPTO_BUFFER_new(reinterpret_cast<const uint8_t*>(der.c_str()),
der.length(), openssl::GetBufferPool()));
if (!cert_buffer) {
return nullptr;
return std::make_unique<BoringSSLCertificate>(std::move(cert_buffer));
#define OID_MATCHES(oid, oid_other) \
(CBS_len(&oid) == sizeof(oid_other) && \
0 == memcmp(CBS_data(&oid), oid_other, sizeof(oid_other)))
bool BoringSSLCertificate::GetSignatureDigestAlgorithm(
std::string* algorithm) const {
CBS oid;
if (!openssl::ParseCertificate(cert_buffer_.get(), &oid, nullptr)) {
RTC_LOG(LS_ERROR) << "Failed to parse certificate.";
return false;
if (OID_MATCHES(oid, kMD5WithRSA) ||
OID_MATCHES(oid, kMD5WithRSAEncryption)) {
*algorithm = DIGEST_MD5;
return true;
if (OID_MATCHES(oid, kECDSAWithSHA1) || OID_MATCHES(oid, kDSAWithSHA1) ||
OID_MATCHES(oid, kDSAWithSHA1_2) || OID_MATCHES(oid, kSHA1WithRSA) ||
OID_MATCHES(oid, kSHA1WithRSAEncryption)) {
*algorithm = DIGEST_SHA_1;
return true;
if (OID_MATCHES(oid, kECDSAWithSHA224) ||
OID_MATCHES(oid, kSHA224WithRSAEncryption) ||
OID_MATCHES(oid, kDSAWithSHA224)) {
*algorithm = DIGEST_SHA_224;
return true;
if (OID_MATCHES(oid, kECDSAWithSHA256) ||
OID_MATCHES(oid, kSHA256WithRSAEncryption) ||
OID_MATCHES(oid, kDSAWithSHA256)) {
*algorithm = DIGEST_SHA_256;
return true;
if (OID_MATCHES(oid, kECDSAWithSHA384) ||
OID_MATCHES(oid, kSHA384WithRSAEncryption)) {
*algorithm = DIGEST_SHA_384;
return true;
if (OID_MATCHES(oid, kECDSAWithSHA512) ||
OID_MATCHES(oid, kSHA512WithRSAEncryption)) {
*algorithm = DIGEST_SHA_512;
return true;
// Unknown algorithm. There are several unhandled options that are less
// common and more complex.
RTC_LOG(LS_ERROR) << "Unknown signature algorithm.";
return false;
bool BoringSSLCertificate::ComputeDigest(absl::string_view algorithm,
unsigned char* digest,
size_t size,
size_t* length) const {
return ComputeDigest(cert_buffer_.get(), algorithm, digest, size, length);
bool BoringSSLCertificate::ComputeDigest(const CRYPTO_BUFFER* cert_buffer,
absl::string_view algorithm,
unsigned char* digest,
size_t size,
size_t* length) {
const EVP_MD* md = nullptr;
unsigned int n = 0;
if (!OpenSSLDigest::GetDigestEVP(algorithm, &md)) {
return false;
if (size < static_cast<size_t>(EVP_MD_size(md))) {
return false;
if (!EVP_Digest(CRYPTO_BUFFER_data(cert_buffer),
CRYPTO_BUFFER_len(cert_buffer), digest, &n, md, nullptr)) {
return false;
*length = n;
return true;
BoringSSLCertificate::~BoringSSLCertificate() {}
std::unique_ptr<SSLCertificate> BoringSSLCertificate::Clone() const {
return std::make_unique<BoringSSLCertificate>(
std::string BoringSSLCertificate::ToPEMString() const {
return SSLIdentity::DerToPem(kPemTypeCertificate,
void BoringSSLCertificate::ToDER(Buffer* der_buffer) const {
bool BoringSSLCertificate::operator==(const BoringSSLCertificate& other) const {
return CRYPTO_BUFFER_len(cert_buffer_.get()) ==
CRYPTO_BUFFER_len(other.cert_buffer_.get()) &&
0 == memcmp(CRYPTO_BUFFER_data(cert_buffer_.get()),
bool BoringSSLCertificate::operator!=(const BoringSSLCertificate& other) const {
return !(*this == other);
int64_t BoringSSLCertificate::CertificateExpirationTime() const {
int64_t ret;
if (!openssl::ParseCertificate(cert_buffer_.get(), nullptr, &ret)) {
RTC_LOG(LS_ERROR) << "Failed to parse certificate.";
return -1;
return ret;
} // namespace rtc