net/cert/ct_objects_extractor_openssl.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "net/cert/ct_objects_extractor.h"
   6
   7 #include <string.h>
   8
   9 #include <openssl/bytestring.h>
  10 #include <openssl/obj.h>
  11 #include <openssl/x509.h>
  12
  13 #include "base/logging.h"
  14 #include "base/sha1.h"
  15 #include "base/strings/string_util.h"
  16 #include "crypto/scoped_openssl_types.h"
  17 #include "crypto/sha2.h"
  18 #include "net/cert/asn1_util.h"
  19 #include "net/cert/signed_certificate_timestamp.h"
  20 #include "net/ssl/scoped_openssl_types.h"
  21
  22 namespace net {
  23
  24 namespace ct {
  25
  26 namespace {
  27
  28 void FreeX509_EXTENSIONS(X509_EXTENSIONS* ptr) {
  29   sk_X509_EXTENSION_pop_free(ptr, X509_EXTENSION_free);
  30 }
  31
  32 using ScopedX509_EXTENSIONS =
  33     crypto::ScopedOpenSSL<X509_EXTENSIONS, FreeX509_EXTENSIONS>;
  34
  35 // The wire form of the OID 1.3.6.1.4.1.11129.2.4.2. See Section 3.3 of
  36 // RFC6962.
  37 const uint8_t kEmbeddedSCTOid[] = {0x2B, 0x06, 0x01, 0x04, 0x01, 0xD6, 0x79,
  38                                    0x02, 0x04, 0x02};
  39
  40 // The wire form of the OID 1.3.6.1.4.1.11129.2.4.5 - OCSP SingleExtension for
  41 // X.509v3 Certificate Transparency Signed Certificate Timestamp List, see
  42 // Section 3.3 of RFC6962.
  43 const uint8_t kOCSPExtensionOid[] = {0x2B, 0x06, 0x01, 0x04, 0x01, 0xD6, 0x79,
  44                                      0x02, 0x04, 0x05};
  45
  46 bool StringEqualToCBS(const std::string& value1, const CBS* value2) {
  47   if (CBS_len(value2) != value1.size())
  48     return false;
  49   return memcmp(value1.data(), CBS_data(value2), CBS_len(value2)) == 0;
  50 }
  51
  52 ScopedX509 OSCertHandleToOpenSSL(X509Certificate::OSCertHandle os_handle) {
  53 #if defined(USE_OPENSSL_CERTS)
  54   return ScopedX509(X509Certificate::DupOSCertHandle(os_handle));
  55 #else
  56   std::string der_encoded;
  57   if (!X509Certificate::GetDEREncoded(os_handle, &der_encoded))
  58     return ScopedX509();
  59   const uint8_t* bytes = reinterpret_cast<const uint8_t*>(der_encoded.data());
  60   return ScopedX509(d2i_X509(NULL, &bytes, der_encoded.size()));
  61 #endif
  62 }
  63
  64 // Finds the SignedCertificateTimestampList in an extension with OID |oid| in
  65 // |x509_exts|. If found, returns true and sets |*out_sct_list| to the encoded
  66 // SCT list. |out_sct_list| may be NULL.
  67 bool GetSCTListFromX509_EXTENSIONS(const X509_EXTENSIONS* x509_exts,
  68                                    const uint8_t* oid,
  69                                    size_t oid_len,
  70                                    std::string* out_sct_list) {
  71   for (size_t i = 0; i < sk_X509_EXTENSION_num(x509_exts); i++) {
  72     X509_EXTENSION* x509_ext = sk_X509_EXTENSION_value(x509_exts, i);
  73     if (static_cast<size_t>(x509_ext->object->length) == oid_len &&
  74         memcmp(x509_ext->object->data, oid, oid_len) == 0) {
  75       // The SCT list is an OCTET STRING inside the extension.
  76       CBS ext_value, sct_list;
  77       CBS_init(&ext_value, x509_ext->value->data, x509_ext->value->length);
  78       if (!CBS_get_asn1(&ext_value, &sct_list, CBS_ASN1_OCTETSTRING) ||
  79           CBS_len(&ext_value) != 0) {
  80         return false;
  81       }
  82       if (out_sct_list) {
  83         *out_sct_list = std::string(
  84             reinterpret_cast<const char*>(CBS_data(&sct_list)),
  85             CBS_len(&sct_list));
  86       }
  87       return true;
  88     }
  89   }
  90   return false;
  91 }
  92
  93 // Finds the SingleResponse in |responses| which matches |issuer| and
  94 // |cert_serial_number|. On success, returns true and sets
  95 // |*out_single_response| to the body of the SingleResponse starting at the
  96 // |certStatus| field.
  97 bool FindMatchingSingleResponse(CBS* responses,
  98                                 X509Certificate::OSCertHandle issuer,
  99                                 const std::string& cert_serial_number,
 100                                 CBS* out_single_response) {
 101   std::string issuer_der;
 102   if (!X509Certificate::GetDEREncoded(issuer, &issuer_der))
 103     return false;
 104
 105   base::StringPiece issuer_spki;
 106   if (!asn1::ExtractSPKIFromDERCert(issuer_der, &issuer_spki))
 107     return false;
 108
 109   // In OCSP, only the key itself is under hash.
 110   base::StringPiece issuer_spk;
 111   if (!asn1::ExtractSubjectPublicKeyFromSPKI(issuer_spki, &issuer_spk))
 112     return false;
 113
 114   // ExtractSubjectPublicKey... does not remove the initial octet encoding the
 115   // number of unused bits in the ASN.1 BIT STRING so we do it here. For public
 116   // keys, the bitstring is in practice always byte-aligned.
 117   if (issuer_spk.empty() || issuer_spk[0] != 0)
 118     return false;
 119   issuer_spk.remove_prefix(1);
 120
 121   // TODO(ekasper): add SHA-384 to crypto/sha2.h and here if it proves
 122   // necessary.
 123   // TODO(ekasper): only compute the hashes on demand.
 124   std::string issuer_key_sha256_hash = crypto::SHA256HashString(issuer_spk);
 125   std::string issuer_key_sha1_hash = base::SHA1HashString(
 126       issuer_spk.as_string());
 127
 128   while (CBS_len(responses) > 0) {
 129     CBS single_response, cert_id;
 130     if (!CBS_get_asn1(responses, &single_response, CBS_ASN1_SEQUENCE) ||
 131         !CBS_get_asn1(&single_response, &cert_id, CBS_ASN1_SEQUENCE)) {
 132       return false;
 133     }
 134
 135     CBS hash_algorithm, hash, serial_number, issuer_name_hash, issuer_key_hash;
 136     if (!CBS_get_asn1(&cert_id, &hash_algorithm, CBS_ASN1_SEQUENCE) ||
 137         !CBS_get_asn1(&hash_algorithm, &hash, CBS_ASN1_OBJECT) ||
 138         !CBS_get_asn1(&cert_id, &issuer_name_hash, CBS_ASN1_OCTETSTRING) ||
 139         !CBS_get_asn1(&cert_id, &issuer_key_hash, CBS_ASN1_OCTETSTRING) ||
 140         !CBS_get_asn1(&cert_id, &serial_number, CBS_ASN1_INTEGER) ||
 141         CBS_len(&cert_id) != 0) {
 142       return false;
 143     }
 144
 145     // Check the serial number matches.
 146     if (!StringEqualToCBS(cert_serial_number, &serial_number))
 147       continue;
 148
 149     // Check if the issuer_key_hash matches.
 150     // TODO(ekasper): also use the issuer name hash in matching.
 151     switch (OBJ_cbs2nid(&hash)) {
 152       case NID_sha1:
 153         if (StringEqualToCBS(issuer_key_sha1_hash, &issuer_key_hash)) {
 154           *out_single_response = single_response;
 155           return true;
 156         }
 157         break;
 158       case NID_sha256:
 159         if (StringEqualToCBS(issuer_key_sha256_hash, &issuer_key_hash)) {
 160           *out_single_response = single_response;
 161           return true;
 162         }
 163         break;
 164     }
 165   }
 166
 167   return false;
 168 }
 169
 170 }  // namespace
 171
 172 bool ExtractEmbeddedSCTList(X509Certificate::OSCertHandle cert,
 173                             std::string* sct_list) {
 174   ScopedX509 x509(OSCertHandleToOpenSSL(cert));
 175   if (!x509)
 176     return false;
 177   X509_EXTENSIONS* x509_exts = x509->cert_info->extensions;
 178   if (!x509_exts)
 179     return false;
 180   return GetSCTListFromX509_EXTENSIONS(
 181       x509->cert_info->extensions, kEmbeddedSCTOid, sizeof(kEmbeddedSCTOid),
 182       sct_list);
 183 }
 184
 185 bool GetPrecertLogEntry(X509Certificate::OSCertHandle leaf,
 186                         X509Certificate::OSCertHandle issuer,
 187                         LogEntry* result) {
 188   result->Reset();
 189
 190   ScopedX509 leaf_x509(OSCertHandleToOpenSSL(leaf));
 191   if (!leaf_x509)
 192     return false;
 193
 194   // XXX(rsleevi): This check may be overkill, since we should be able to
 195   // generate precerts for certs without the extension. For now, just a sanity
 196   // check to match the reference implementation.
 197   if (!leaf_x509->cert_info->extensions ||
 198       !GetSCTListFromX509_EXTENSIONS(leaf_x509->cert_info->extensions,
 199                                      kEmbeddedSCTOid, sizeof(kEmbeddedSCTOid),
 200                                      NULL)) {
 201     return false;
 202   }
 203
 204   // The Precertificate log entry is the final certificate's TBSCertificate
 205   // without the SCT extension (RFC6962, section 3.2).
 206   ScopedX509 leaf_copy(X509_dup(leaf_x509.get()));
 207   if (!leaf_copy || !leaf_copy->cert_info->extensions) {
 208     NOTREACHED();
 209     return false;
 210   }
 211   X509_EXTENSIONS* leaf_copy_exts = leaf_copy->cert_info->extensions;
 212   for (size_t i = 0; i < sk_X509_EXTENSION_num(leaf_copy_exts); i++) {
 213     X509_EXTENSION* ext = sk_X509_EXTENSION_value(leaf_copy_exts, i);
 214     if (static_cast<size_t>(ext->object->length) == sizeof(kEmbeddedSCTOid) &&
 215         memcmp(ext->object->data,
 216                kEmbeddedSCTOid, sizeof(kEmbeddedSCTOid)) == 0) {
 217       X509_EXTENSION_free(sk_X509_EXTENSION_delete(leaf_copy_exts, i));
 218       X509_CINF_set_modified(leaf_copy->cert_info);
 219       break;
 220     }
 221   }
 222
 223   std::string to_be_signed;
 224   int len = i2d_X509_CINF(leaf_copy->cert_info, NULL);
 225   if (len < 0)
 226     return false;
 227   uint8_t* ptr = reinterpret_cast<uint8_t*>(WriteInto(&to_be_signed, len + 1));
 228   if (i2d_X509_CINF(leaf_copy->cert_info, &ptr) < 0)
 229     return false;
 230
 231   // Extract the issuer's public key.
 232   std::string issuer_der;
 233   if (!X509Certificate::GetDEREncoded(issuer, &issuer_der))
 234     return ScopedX509();
 235   base::StringPiece issuer_key;
 236   if (!asn1::ExtractSPKIFromDERCert(issuer_der, &issuer_key))
 237     return false;
 238
 239   // Fill in the LogEntry.
 240   result->type = ct::LogEntry::LOG_ENTRY_TYPE_PRECERT;
 241   result->tbs_certificate.swap(to_be_signed);
 242   crypto::SHA256HashString(issuer_key,
 243                            result->issuer_key_hash.data,
 244                            sizeof(result->issuer_key_hash.data));
 245
 246   return true;
 247 }
 248
 249 bool GetX509LogEntry(X509Certificate::OSCertHandle leaf, LogEntry* result) {
 250   DCHECK(leaf);
 251
 252   std::string encoded;
 253   if (!X509Certificate::GetDEREncoded(leaf, &encoded))
 254     return false;
 255
 256   result->Reset();
 257   result->type = ct::LogEntry::LOG_ENTRY_TYPE_X509;
 258   result->leaf_certificate.swap(encoded);
 259   return true;
 260 }
 261
 262 bool ExtractSCTListFromOCSPResponse(X509Certificate::OSCertHandle issuer,
 263                                     const std::string& cert_serial_number,
 264                                     const std::string& ocsp_response,
 265                                     std::string* sct_list) {
 266   // The input is an OCSPResponse. See RFC2560, section 4.2.1. The SCT list is
 267   // in the extensions field of the SingleResponse which matches the input
 268   // certificate.
 269   CBS cbs;
 270   CBS_init(&cbs,
 271            reinterpret_cast<const uint8_t*>(ocsp_response.data()),
 272            ocsp_response.size());
 273
 274   // Parse down to the ResponseBytes. The ResponseBytes is optional, but if it's
 275   // missing, this can't include an SCT list.
 276   CBS sequence, response_status, tagged_response_bytes, response_bytes;
 277   CBS response_type, response;
 278   if (!CBS_get_asn1(&cbs, &sequence, CBS_ASN1_SEQUENCE) ||
 279       CBS_len(&cbs) != 0 ||
 280       !CBS_get_asn1(&sequence, &response_status, CBS_ASN1_ENUMERATED) ||
 281       !CBS_get_asn1(&sequence, &tagged_response_bytes,
 282                     CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0) ||
 283       CBS_len(&sequence) != 0 ||
 284       !CBS_get_asn1(&tagged_response_bytes, &response_bytes,
 285                     CBS_ASN1_SEQUENCE) ||
 286       CBS_len(&tagged_response_bytes) != 0 ||
 287       !CBS_get_asn1(&response_bytes, &response_type, CBS_ASN1_OBJECT) ||
 288       !CBS_get_asn1(&response_bytes, &response, CBS_ASN1_OCTETSTRING) ||
 289       CBS_len(&response_bytes) != 0) {
 290     return false;
 291   }
 292
 293   // The only relevant ResponseType is id-pkix-ocsp-basic.
 294   if (OBJ_cbs2nid(&response_type) != NID_id_pkix_OCSP_basic)
 295     return false;
 296
 297   // Parse the ResponseData out of the BasicOCSPResponse. Ignore the rest.
 298   CBS basic_response, response_data, responses;
 299   if (!CBS_get_asn1(&response, &basic_response, CBS_ASN1_SEQUENCE) ||
 300       CBS_len(&response) != 0 ||
 301       !CBS_get_asn1(&basic_response, &response_data, CBS_ASN1_SEQUENCE)) {
 302   }
 303
 304   // Skip the optional version.
 305   const int kVersionTag =
 306       CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0;
 307   if (CBS_len(&response_data) > 0 &&
 308       CBS_data(&response_data)[0] == kVersionTag &&
 309       !CBS_get_asn1(&response_data, NULL /* version */, kVersionTag)) {
 310     return false;
 311   }
 312
 313   // Extract the list of SingleResponses.
 314   if (!CBS_get_any_asn1_element(&response_data,
 315                                 NULL /* responderID */, NULL, NULL) ||
 316       !CBS_get_any_asn1_element(&response_data,
 317                                 NULL /* producedAt */, NULL, NULL) ||
 318       !CBS_get_asn1(&response_data, &responses, CBS_ASN1_SEQUENCE)) {
 319     return false;
 320   }
 321
 322   CBS single_response;
 323   if (!FindMatchingSingleResponse(&responses, issuer, cert_serial_number,
 324                                   &single_response)) {
 325     return false;
 326   }
 327
 328   // Skip the certStatus and thisUpdate fields.
 329   if (!CBS_get_any_asn1_element(&single_response,
 330                                 NULL /* certStatus */, NULL, NULL) ||
 331       !CBS_get_any_asn1_element(&single_response,
 332                                 NULL /* thisUpdate */, NULL, NULL)) {
 333     return false;
 334   }
 335
 336   const int kNextUpdateTag =
 337       CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0;
 338   const int kSingleExtensionsTag =
 339       CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 1;
 340
 341   // Skip the optional nextUpdate field.
 342   if (CBS_len(&single_response) > 0 &&
 343       CBS_data(&single_response)[0] == kNextUpdateTag &&
 344       !CBS_get_asn1(&single_response, NULL /* nextUpdate */, kNextUpdateTag)) {
 345     return false;
 346   }
 347
 348   CBS extensions;
 349   if (!CBS_get_asn1(&single_response, &extensions, kSingleExtensionsTag))
 350     return false;
 351   const uint8_t* ptr = CBS_data(&extensions);
 352   ScopedX509_EXTENSIONS x509_exts(
 353       d2i_X509_EXTENSIONS(NULL, &ptr, CBS_len(&extensions)));
 354   if (!x509_exts || ptr != CBS_data(&extensions) + CBS_len(&extensions))
 355     return false;
 356
 357   return GetSCTListFromX509_EXTENSIONS(
 358       x509_exts.get(), kOCSPExtensionOid, sizeof(kOCSPExtensionOid), sct_list);
 359 }
 360
 361 }  // namespace ct
 362
 363 }  // namespace net