// 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/ct_objects_extractor.h"
#include <string.h>
#include <openssl/bytestring.h>
#include <openssl/obj.h>
#include <openssl/x509.h>
#include "base/logging.h"
#include "base/sha1.h"
#include "base/strings/string_util.h"
#include "crypto/scoped_openssl_types.h"
#include "crypto/sha2.h"
#include "net/cert/asn1_util.h"
#include "net/cert/signed_certificate_timestamp.h"
namespace net {
namespace ct {
namespace {
typedef crypto::ScopedOpenSSL<X509, X509_free>::Type ScopedX509;
void FreeX509_EXTENSIONS(X509_EXTENSIONS* ptr) {
sk_X509_EXTENSION_pop_free(ptr, X509_EXTENSION_free);
}
typedef crypto::ScopedOpenSSL<X509_EXTENSIONS, FreeX509_EXTENSIONS>::Type
ScopedX509_EXTENSIONS;
// The wire form of the OID 1.3.6.1.4.1.11129.2.4.2. See Section 3.3 of
// RFC6962.
const uint8_t kEmbeddedSCTOid[] = {0x2B, 0x06, 0x01, 0x04, 0x01, 0xD6, 0x79,
0x02, 0x04, 0x02};
// The wire form of the OID 1.3.6.1.4.1.11129.2.4.5 - OCSP SingleExtension for
// X.509v3 Certificate Transparency Signed Certificate Timestamp List, see
// Section 3.3 of RFC6962.
const uint8_t kOCSPExtensionOid[] = {0x2B, 0x06, 0x01, 0x04, 0x01, 0xD6, 0x79,
0x02, 0x04, 0x05};
bool StringEqualToCBS(const std::string& value1, const CBS* value2) {
if (CBS_len(value2) != value1.size())
return false;
return memcmp(value1.data(), CBS_data(value2), CBS_len(value2)) == 0;
}
ScopedX509 OSCertHandleToOpenSSL(X509Certificate::OSCertHandle os_handle) {
#if defined(USE_OPENSSL_CERTS)
return ScopedX509(X509Certificate::DupOSCertHandle(os_handle));
#else
std::string der_encoded;
if (!X509Certificate::GetDEREncoded(os_handle, &der_encoded))
return ScopedX509();
const uint8_t* bytes = reinterpret_cast<const uint8_t*>(der_encoded.data());
return ScopedX509(d2i_X509(NULL, &bytes, der_encoded.size()));
#endif
}
// Finds the SignedCertificateTimestampList in an extension with OID |oid| in
// |x509_exts|. If found, returns true and sets |*out_sct_list| to the encoded
// SCT list. |out_sct_list| may be NULL.
bool GetSCTListFromX509_EXTENSIONS(const X509_EXTENSIONS* x509_exts,
const uint8_t* oid,
size_t oid_len,
std::string* out_sct_list) {
for (size_t i = 0; i < sk_X509_EXTENSION_num(x509_exts); i++) {
X509_EXTENSION* x509_ext = sk_X509_EXTENSION_value(x509_exts, i);
if (static_cast<size_t>(x509_ext->object->length) == oid_len &&
memcmp(x509_ext->object->data, oid, oid_len) == 0) {
// The SCT list is an OCTET STRING inside the extension.
CBS ext_value, sct_list;
CBS_init(&ext_value, x509_ext->value->data, x509_ext->value->length);
if (!CBS_get_asn1(&ext_value, &sct_list, CBS_ASN1_OCTETSTRING) ||
CBS_len(&ext_value) != 0) {
return false;
}
if (out_sct_list) {
*out_sct_list = std::string(
reinterpret_cast<const char*>(CBS_data(&sct_list)),
CBS_len(&sct_list));
}
return true;
}
}
return false;
}
// Finds the SingleResponse in |responses| which matches |issuer| and
// |cert_serial_number|. On success, returns true and sets
// |*out_single_response| to the body of the SingleResponse starting at the
// |certStatus| field.
bool FindMatchingSingleResponse(CBS* responses,
X509Certificate::OSCertHandle issuer,
const std::string& cert_serial_number,
CBS* out_single_response) {
std::string issuer_der;
if (!X509Certificate::GetDEREncoded(issuer, &issuer_der))
return false;
base::StringPiece issuer_spki;
if (!asn1::ExtractSPKIFromDERCert(issuer_der, &issuer_spki))
return false;
// In OCSP, only the key itself is under hash.
base::StringPiece issuer_spk;
if (!asn1::ExtractSubjectPublicKeyFromSPKI(issuer_spki, &issuer_spk))
return false;
// ExtractSubjectPublicKey... does not remove the initial octet encoding the
// number of unused bits in the ASN.1 BIT STRING so we do it here. For public
// keys, the bitstring is in practice always byte-aligned.
if (issuer_spk.empty() || issuer_spk[0] != 0)
return false;
issuer_spk.remove_prefix(1);
// TODO(ekasper): add SHA-384 to crypto/sha2.h and here if it proves
// necessary.
// TODO(ekasper): only compute the hashes on demand.
std::string issuer_key_sha256_hash = crypto::SHA256HashString(issuer_spk);
std::string issuer_key_sha1_hash = base::SHA1HashString(
issuer_spk.as_string());
while (CBS_len(responses) > 0) {
CBS single_response, cert_id;
if (!CBS_get_asn1(responses, &single_response, CBS_ASN1_SEQUENCE) ||
!CBS_get_asn1(&single_response, &cert_id, CBS_ASN1_SEQUENCE)) {
return false;
}
CBS hash_algorithm, hash, serial_number, issuer_name_hash, issuer_key_hash;
if (!CBS_get_asn1(&cert_id, &hash_algorithm, CBS_ASN1_SEQUENCE) ||
!CBS_get_asn1(&hash_algorithm, &hash, CBS_ASN1_OBJECT) ||
!CBS_get_asn1(&cert_id, &issuer_name_hash, CBS_ASN1_OCTETSTRING) ||
!CBS_get_asn1(&cert_id, &issuer_key_hash, CBS_ASN1_OCTETSTRING) ||
!CBS_get_asn1(&cert_id, &serial_number, CBS_ASN1_INTEGER) ||
CBS_len(&cert_id) != 0) {
return false;
}
// Check the serial number matches.
if (!StringEqualToCBS(cert_serial_number, &serial_number))
continue;
// Check if the issuer_key_hash matches.
// TODO(ekasper): also use the issuer name hash in matching.
switch (OBJ_cbs2nid(&hash)) {
case NID_sha1:
if (StringEqualToCBS(issuer_key_sha1_hash, &issuer_key_hash)) {
*out_single_response = single_response;
return true;
}
break;
case NID_sha256:
if (StringEqualToCBS(issuer_key_sha256_hash, &issuer_key_hash)) {
*out_single_response = single_response;
return true;
}
break;
}
}
return false;
}
} // namespace
bool ExtractEmbeddedSCTList(X509Certificate::OSCertHandle cert,
std::string* sct_list) {
ScopedX509 x509(OSCertHandleToOpenSSL(cert));
if (!x509)
return false;
X509_EXTENSIONS* x509_exts = x509->cert_info->extensions;
if (!x509_exts)
return false;
return GetSCTListFromX509_EXTENSIONS(
x509->cert_info->extensions, kEmbeddedSCTOid, sizeof(kEmbeddedSCTOid),
sct_list);
}
bool GetPrecertLogEntry(X509Certificate::OSCertHandle leaf,
X509Certificate::OSCertHandle issuer,
LogEntry* result) {
result->Reset();
ScopedX509 leaf_x509(OSCertHandleToOpenSSL(leaf));
if (!leaf_x509)
return false;
// XXX(rsleevi): This check may be overkill, since we should be able to
// generate precerts for certs without the extension. For now, just a sanity
// check to match the reference implementation.
if (!leaf_x509->cert_info->extensions ||
!GetSCTListFromX509_EXTENSIONS(leaf_x509->cert_info->extensions,
kEmbeddedSCTOid, sizeof(kEmbeddedSCTOid),
NULL)) {
return false;
}
// The Precertificate log entry is the final certificate's TBSCertificate
// without the SCT extension (RFC6962, section 3.2).
ScopedX509 leaf_copy(X509_dup(leaf_x509.get()));
if (!leaf_copy || !leaf_copy->cert_info->extensions) {
NOTREACHED();
return false;
}
X509_EXTENSIONS* leaf_copy_exts = leaf_copy->cert_info->extensions;
for (size_t i = 0; i < sk_X509_EXTENSION_num(leaf_copy_exts); i++) {
X509_EXTENSION* ext = sk_X509_EXTENSION_value(leaf_copy_exts, i);
if (static_cast<size_t>(ext->object->length) == sizeof(kEmbeddedSCTOid) &&
memcmp(ext->object->data,
kEmbeddedSCTOid, sizeof(kEmbeddedSCTOid)) == 0) {
X509_EXTENSION_free(sk_X509_EXTENSION_delete(leaf_copy_exts, i));
X509_CINF_set_modified(leaf_copy->cert_info);
break;
}
}
std::string to_be_signed;
int len = i2d_X509_CINF(leaf_copy->cert_info, NULL);
if (len < 0)
return false;
uint8_t* ptr = reinterpret_cast<uint8_t*>(WriteInto(&to_be_signed, len + 1));
if (i2d_X509_CINF(leaf_copy->cert_info, &ptr) < 0)
return false;
// Extract the issuer's public key.
std::string issuer_der;
if (!X509Certificate::GetDEREncoded(issuer, &issuer_der))
return ScopedX509();
base::StringPiece issuer_key;
if (!asn1::ExtractSPKIFromDERCert(issuer_der, &issuer_key))
return false;
// Fill in the LogEntry.
result->type = ct::LogEntry::LOG_ENTRY_TYPE_PRECERT;
result->tbs_certificate.swap(to_be_signed);
crypto::SHA256HashString(issuer_key,
result->issuer_key_hash.data,
sizeof(result->issuer_key_hash.data));
return true;
}
bool GetX509LogEntry(X509Certificate::OSCertHandle leaf, LogEntry* result) {
DCHECK(leaf);
std::string encoded;
if (!X509Certificate::GetDEREncoded(leaf, &encoded))
return false;
result->Reset();
result->type = ct::LogEntry::LOG_ENTRY_TYPE_X509;
result->leaf_certificate.swap(encoded);
return true;
}
bool ExtractSCTListFromOCSPResponse(X509Certificate::OSCertHandle issuer,
const std::string& cert_serial_number,
const std::string& ocsp_response,
std::string* sct_list) {
// The input is an OCSPResponse. See RFC2560, section 4.2.1. The SCT list is
// in the extensions field of the SingleResponse which matches the input
// certificate.
CBS cbs;
CBS_init(&cbs,
reinterpret_cast<const uint8_t*>(ocsp_response.data()),
ocsp_response.size());
// Parse down to the ResponseBytes. The ResponseBytes is optional, but if it's
// missing, this can't include an SCT list.
CBS sequence, response_status, tagged_response_bytes, response_bytes;
CBS response_type, response;
if (!CBS_get_asn1(&cbs, &sequence, CBS_ASN1_SEQUENCE) ||
CBS_len(&cbs) != 0 ||
!CBS_get_asn1(&sequence, &response_status, CBS_ASN1_ENUMERATED) ||
!CBS_get_asn1(&sequence, &tagged_response_bytes,
CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0) ||
CBS_len(&sequence) != 0 ||
!CBS_get_asn1(&tagged_response_bytes, &response_bytes,
CBS_ASN1_SEQUENCE) ||
CBS_len(&tagged_response_bytes) != 0 ||
!CBS_get_asn1(&response_bytes, &response_type, CBS_ASN1_OBJECT) ||
!CBS_get_asn1(&response_bytes, &response, CBS_ASN1_OCTETSTRING) ||
CBS_len(&response_bytes) != 0) {
return false;
}
// The only relevant ResponseType is id-pkix-ocsp-basic.
if (OBJ_cbs2nid(&response_type) != NID_id_pkix_OCSP_basic)
return false;
// Parse the ResponseData out of the BasicOCSPResponse. Ignore the rest.
CBS basic_response, response_data, responses;
if (!CBS_get_asn1(&response, &basic_response, CBS_ASN1_SEQUENCE) ||
CBS_len(&response) != 0 ||
!CBS_get_asn1(&basic_response, &response_data, CBS_ASN1_SEQUENCE)) {
}
// Skip the optional version.
const int kVersionTag =
CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0;
if (CBS_len(&response_data) > 0 &&
CBS_data(&response_data)[0] == kVersionTag &&
!CBS_get_asn1(&response_data, NULL /* version */, kVersionTag)) {
return false;
}
// Extract the list of SingleResponses.
if (!CBS_get_any_asn1_element(&response_data,
NULL /* responderID */, NULL, NULL) ||
!CBS_get_any_asn1_element(&response_data,
NULL /* producedAt */, NULL, NULL) ||
!CBS_get_asn1(&response_data, &responses, CBS_ASN1_SEQUENCE)) {
return false;
}
CBS single_response;
if (!FindMatchingSingleResponse(&responses, issuer, cert_serial_number,
&single_response)) {
return false;
}
// Skip the certStatus and thisUpdate fields.
if (!CBS_get_any_asn1_element(&single_response,
NULL /* certStatus */, NULL, NULL) ||
!CBS_get_any_asn1_element(&single_response,
NULL /* thisUpdate */, NULL, NULL)) {
return false;
}
const int kNextUpdateTag =
CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0;
const int kSingleExtensionsTag =
CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 1;
// Skip the optional nextUpdate field.
if (CBS_len(&single_response) > 0 &&
CBS_data(&single_response)[0] == kNextUpdateTag &&
!CBS_get_asn1(&single_response, NULL /* nextUpdate */, kNextUpdateTag)) {
return false;
}
CBS extensions;
if (!CBS_get_asn1(&single_response, &extensions, kSingleExtensionsTag))
return false;
const uint8_t* ptr = CBS_data(&extensions);
ScopedX509_EXTENSIONS x509_exts(
d2i_X509_EXTENSIONS(NULL, &ptr, CBS_len(&extensions)));
if (!x509_exts || ptr != CBS_data(&extensions) + CBS_len(&extensions))
return false;
return GetSCTListFromX509_EXTENSIONS(
x509_exts.get(), kOCSPExtensionOid, sizeof(kOCSPExtensionOid), sct_list);
}
} // namespace ct
} // namespace net