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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/ct_objects_extractor.h"
- #include <string.h>
- #include "base/hash/sha1.h"
- #include "base/logging.h"
- #include "base/strings/string_piece.h"
- #include "base/strings/string_util.h"
- #include "crypto/sha2.h"
- #include "net/cert/asn1_util.h"
- #include "net/cert/signed_certificate_timestamp.h"
- #include "net/cert/x509_util.h"
- #include "third_party/boringssl/src/include/openssl/bytestring.h"
- #include "third_party/boringssl/src/include/openssl/mem.h"
- namespace net::ct {
- namespace {
- // 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};
- // The wire form of the OID 1.3.6.1.5.5.7.48.1.1. See RFC 6960.
- const uint8_t kOCSPBasicResponseOid[] = {0x2b, 0x06, 0x01, 0x05, 0x05,
- 0x07, 0x30, 0x01, 0x01};
- // The wire form of the OID 1.3.14.3.2.26.
- const uint8_t kSHA1Oid[] = {0x2b, 0x0e, 0x03, 0x02, 0x1a};
- // The wire form of the OID 2.16.840.1.101.3.4.2.1.
- const uint8_t kSHA256Oid[] = {0x60, 0x86, 0x48, 0x01, 0x65,
- 0x03, 0x04, 0x02, 0x01};
- 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;
- }
- bool SkipElements(CBS* cbs, int count) {
- for (int i = 0; i < count; i++) {
- if (!CBS_get_any_asn1_element(cbs, nullptr, nullptr, nullptr))
- return false;
- }
- return true;
- }
- bool SkipOptionalElement(CBS* cbs, unsigned tag) {
- CBS unused;
- return !CBS_peek_asn1_tag(cbs, tag) || CBS_get_asn1(cbs, &unused, tag);
- }
- // Copies all the bytes in |outer| which are before |inner| to |out|. |inner|
- // must be a subset of |outer|.
- bool CopyBefore(const CBS& outer, const CBS& inner, CBB* out) {
- CHECK_LE(CBS_data(&outer), CBS_data(&inner));
- CHECK_LE(CBS_data(&inner) + CBS_len(&inner),
- CBS_data(&outer) + CBS_len(&outer));
- return !!CBB_add_bytes(out, CBS_data(&outer),
- CBS_data(&inner) - CBS_data(&outer));
- }
- // Copies all the bytes in |outer| which are after |inner| to |out|. |inner|
- // must be a subset of |outer|.
- bool CopyAfter(const CBS& outer, const CBS& inner, CBB* out) {
- CHECK_LE(CBS_data(&outer), CBS_data(&inner));
- CHECK_LE(CBS_data(&inner) + CBS_len(&inner),
- CBS_data(&outer) + CBS_len(&outer));
- return !!CBB_add_bytes(
- out, CBS_data(&inner) + CBS_len(&inner),
- CBS_data(&outer) + CBS_len(&outer) - CBS_data(&inner) - CBS_len(&inner));
- }
- // Skips |tbs_cert|, which must be a TBSCertificate body, to just before the
- // extensions element.
- bool SkipTBSCertificateToExtensions(CBS* tbs_cert) {
- constexpr unsigned kVersionTag =
- CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0;
- constexpr unsigned kIssuerUniqueIDTag = CBS_ASN1_CONTEXT_SPECIFIC | 1;
- constexpr unsigned kSubjectUniqueIDTag = CBS_ASN1_CONTEXT_SPECIFIC | 2;
- return SkipOptionalElement(tbs_cert, kVersionTag) &&
- SkipElements(tbs_cert,
- 6 /* serialNumber through subjectPublicKeyInfo */) &&
- SkipOptionalElement(tbs_cert, kIssuerUniqueIDTag) &&
- SkipOptionalElement(tbs_cert, kSubjectUniqueIDTag);
- }
- // Looks for the extension with the specified OID in |extensions|, which must
- // contain the contents of a SEQUENCE of X.509 extension structures. If found,
- // returns true and sets |*out| to the full extension element.
- bool FindExtensionElement(const CBS& extensions,
- const uint8_t* oid,
- size_t oid_len,
- CBS* out) {
- CBS extensions_copy = extensions;
- CBS result;
- CBS_init(&result, nullptr, 0);
- bool found = false;
- while (CBS_len(&extensions_copy) > 0) {
- CBS extension_element;
- if (!CBS_get_asn1_element(&extensions_copy, &extension_element,
- CBS_ASN1_SEQUENCE)) {
- return false;
- }
- CBS copy = extension_element;
- CBS extension, extension_oid;
- if (!CBS_get_asn1(©, &extension, CBS_ASN1_SEQUENCE) ||
- !CBS_get_asn1(&extension, &extension_oid, CBS_ASN1_OBJECT)) {
- return false;
- }
- if (CBS_mem_equal(&extension_oid, oid, oid_len)) {
- if (found)
- return false;
- found = true;
- result = extension_element;
- }
- }
- if (!found)
- return false;
- *out = result;
- return true;
- }
- // 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.
- bool ParseSCTListFromExtensions(const CBS& extensions,
- const uint8_t* oid,
- size_t oid_len,
- std::string* out_sct_list) {
- CBS extension_element, extension, extension_oid, value, sct_list;
- if (!FindExtensionElement(extensions, oid, oid_len, &extension_element) ||
- !CBS_get_asn1(&extension_element, &extension, CBS_ASN1_SEQUENCE) ||
- !CBS_get_asn1(&extension, &extension_oid, CBS_ASN1_OBJECT) ||
- // Skip the optional critical element.
- !SkipOptionalElement(&extension, CBS_ASN1_BOOLEAN) ||
- // The extension value is stored in an OCTET STRING.
- !CBS_get_asn1(&extension, &value, CBS_ASN1_OCTETSTRING) ||
- CBS_len(&extension) != 0 ||
- // The extension value itself is an OCTET STRING containing the
- // serialized SCT list.
- !CBS_get_asn1(&value, &sct_list, CBS_ASN1_OCTETSTRING) ||
- CBS_len(&value) != 0) {
- return false;
- }
- DCHECK(CBS_mem_equal(&extension_oid, oid, oid_len));
- *out_sct_list = std::string(
- reinterpret_cast<const char*>(CBS_data(&sct_list)), CBS_len(&sct_list));
- return true;
- }
- // 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,
- const CRYPTO_BUFFER* issuer,
- const std::string& cert_serial_number,
- CBS* out_single_response) {
- base::StringPiece issuer_spki;
- if (!asn1::ExtractSPKIFromDERCert(
- x509_util::CryptoBufferAsStringPiece(issuer), &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;
- // ExtractSubjectPublicKeyFromSPKI 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(std::string(issuer_spk));
- 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.
- if (CBS_mem_equal(&hash, kSHA1Oid, sizeof(kSHA1Oid))) {
- if (StringEqualToCBS(issuer_key_sha1_hash, &issuer_key_hash)) {
- *out_single_response = single_response;
- return true;
- }
- } else if (CBS_mem_equal(&hash, kSHA256Oid, sizeof(kSHA256Oid))) {
- if (StringEqualToCBS(issuer_key_sha256_hash, &issuer_key_hash)) {
- *out_single_response = single_response;
- return true;
- }
- }
- }
- return false;
- }
- } // namespace
- bool ExtractEmbeddedSCTList(const CRYPTO_BUFFER* cert, std::string* sct_list) {
- CBS cert_cbs;
- CBS_init(&cert_cbs, CRYPTO_BUFFER_data(cert), CRYPTO_BUFFER_len(cert));
- CBS cert_body, tbs_cert, extensions_wrap, extensions;
- if (!CBS_get_asn1(&cert_cbs, &cert_body, CBS_ASN1_SEQUENCE) ||
- CBS_len(&cert_cbs) != 0 ||
- !CBS_get_asn1(&cert_body, &tbs_cert, CBS_ASN1_SEQUENCE) ||
- !SkipTBSCertificateToExtensions(&tbs_cert) ||
- // Extract the extensions list.
- !CBS_get_asn1(&tbs_cert, &extensions_wrap,
- CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 3) ||
- !CBS_get_asn1(&extensions_wrap, &extensions, CBS_ASN1_SEQUENCE) ||
- CBS_len(&extensions_wrap) != 0 || CBS_len(&tbs_cert) != 0) {
- return false;
- }
- return ParseSCTListFromExtensions(extensions, kEmbeddedSCTOid,
- sizeof(kEmbeddedSCTOid), sct_list);
- }
- bool GetPrecertSignedEntry(const CRYPTO_BUFFER* leaf,
- const CRYPTO_BUFFER* issuer,
- SignedEntryData* result) {
- result->Reset();
- // Parse the TBSCertificate.
- CBS cert_cbs;
- CBS_init(&cert_cbs, CRYPTO_BUFFER_data(leaf), CRYPTO_BUFFER_len(leaf));
- CBS cert_body, tbs_cert;
- if (!CBS_get_asn1(&cert_cbs, &cert_body, CBS_ASN1_SEQUENCE) ||
- CBS_len(&cert_cbs) != 0 ||
- !CBS_get_asn1(&cert_body, &tbs_cert, CBS_ASN1_SEQUENCE)) {
- return false;
- }
- CBS tbs_cert_copy = tbs_cert;
- if (!SkipTBSCertificateToExtensions(&tbs_cert))
- return false;
- // Start filling in a new TBSCertificate. Copy everything parsed or skipped
- // so far to the |new_tbs_cert|.
- bssl::ScopedCBB cbb;
- CBB new_tbs_cert;
- if (!CBB_init(cbb.get(), CBS_len(&tbs_cert_copy)) ||
- !CBB_add_asn1(cbb.get(), &new_tbs_cert, CBS_ASN1_SEQUENCE) ||
- !CopyBefore(tbs_cert_copy, tbs_cert, &new_tbs_cert)) {
- return false;
- }
- // Parse the extensions list and find the SCT extension.
- //
- // XXX(rsleevi): We could generate precerts for certs without the extension
- // by leaving the TBSCertificate as-is. The reference implementation does not
- // do this.
- constexpr unsigned kExtensionsTag =
- CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 3;
- CBS extensions_wrap, extensions, sct_extension;
- if (!CBS_get_asn1(&tbs_cert, &extensions_wrap, kExtensionsTag) ||
- !CBS_get_asn1(&extensions_wrap, &extensions, CBS_ASN1_SEQUENCE) ||
- CBS_len(&extensions_wrap) != 0 || CBS_len(&tbs_cert) != 0 ||
- !FindExtensionElement(extensions, kEmbeddedSCTOid,
- sizeof(kEmbeddedSCTOid), &sct_extension)) {
- return false;
- }
- // Add extensions to the TBSCertificate. Copy all extensions except the
- // embedded SCT extension.
- CBB new_extensions_wrap, new_extensions;
- if (!CBB_add_asn1(&new_tbs_cert, &new_extensions_wrap, kExtensionsTag) ||
- !CBB_add_asn1(&new_extensions_wrap, &new_extensions, CBS_ASN1_SEQUENCE) ||
- !CopyBefore(extensions, sct_extension, &new_extensions) ||
- !CopyAfter(extensions, sct_extension, &new_extensions)) {
- return false;
- }
- uint8_t* new_tbs_cert_der;
- size_t new_tbs_cert_len;
- if (!CBB_finish(cbb.get(), &new_tbs_cert_der, &new_tbs_cert_len))
- return false;
- bssl::UniquePtr<uint8_t> scoped_new_tbs_cert_der(new_tbs_cert_der);
- // Extract the issuer's public key.
- base::StringPiece issuer_key;
- if (!asn1::ExtractSPKIFromDERCert(
- x509_util::CryptoBufferAsStringPiece(issuer), &issuer_key)) {
- return false;
- }
- // Fill in the SignedEntryData.
- result->type = ct::SignedEntryData::LOG_ENTRY_TYPE_PRECERT;
- result->tbs_certificate.assign(
- reinterpret_cast<const char*>(new_tbs_cert_der), new_tbs_cert_len);
- crypto::SHA256HashString(issuer_key, result->issuer_key_hash.data,
- sizeof(result->issuer_key_hash.data));
- return true;
- }
- bool GetX509SignedEntry(const CRYPTO_BUFFER* leaf, SignedEntryData* result) {
- DCHECK(leaf);
- result->Reset();
- result->type = ct::SignedEntryData::LOG_ENTRY_TYPE_X509;
- result->leaf_certificate =
- std::string(x509_util::CryptoBufferAsStringPiece(leaf));
- return true;
- }
- bool ExtractSCTListFromOCSPResponse(const CRYPTO_BUFFER* issuer,
- const std::string& cert_serial_number,
- base::StringPiece 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, tagged_response_bytes, response_bytes, response_type, response;
- if (!CBS_get_asn1(&cbs, &sequence, CBS_ASN1_SEQUENCE) || CBS_len(&cbs) != 0 ||
- !SkipElements(&sequence, 1 /* responseStatus */) ||
- !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 (!CBS_mem_equal(&response_type, kOCSPBasicResponseOid,
- sizeof(kOCSPBasicResponseOid))) {
- return false;
- }
- // Parse the ResponseData out of the BasicOCSPResponse. Ignore the rest.
- constexpr unsigned kVersionTag =
- CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0;
- 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)) {
- return false;
- }
- // Extract the list of SingleResponses from the ResponseData.
- if (!SkipOptionalElement(&response_data, kVersionTag) ||
- !SkipElements(&response_data, 2 /* responderID, producedAt */) ||
- !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;
- }
- // Parse the extensions out of the SingleResponse.
- constexpr unsigned kNextUpdateTag =
- CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0;
- constexpr unsigned kSingleExtensionsTag =
- CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 1;
- CBS extensions_wrap, extensions;
- if (!SkipElements(&single_response, 2 /* certStatus, thisUpdate */) ||
- !SkipOptionalElement(&single_response, kNextUpdateTag) ||
- !CBS_get_asn1(&single_response, &extensions_wrap, kSingleExtensionsTag) ||
- !CBS_get_asn1(&extensions_wrap, &extensions, CBS_ASN1_SEQUENCE) ||
- CBS_len(&extensions_wrap) != 0) {
- return false;
- }
- return ParseSCTListFromExtensions(extensions, kOCSPExtensionOid,
- sizeof(kOCSPExtensionOid), sct_list);
- }
- } // namespace net::ct
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