net/cert/ct_serialization.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_serialization.h"
   6
   7 #include "base/basictypes.h"
   8 #include "base/logging.h"
   9
  10 namespace net {
  11
  12 namespace ct {
  13
  14 namespace {
  15
  16 // Note: length is always specified in bytes.
  17 // Signed Certificate Timestamp (SCT) Version length
  18 const size_t kVersionLength = 1;
  19
  20 // Members of a V1 SCT
  21 const size_t kLogIdLength = 32;
  22 const size_t kTimestampLength = 8;
  23 const size_t kExtensionsLengthBytes = 2;
  24 const size_t kHashAlgorithmLength = 1;
  25 const size_t kSigAlgorithmLength = 1;
  26 const size_t kSignatureLengthBytes = 2;
  27
  28 // Members of the digitally-signed struct of a V1 SCT
  29 const size_t kSignatureTypeLength = 1;
  30 const size_t kLogEntryTypeLength = 2;
  31 const size_t kAsn1CertificateLengthBytes = 3;
  32 const size_t kTbsCertificateLengthBytes = 3;
  33
  34 const size_t kSCTListLengthBytes = 2;
  35 const size_t kSerializedSCTLengthBytes = 2;
  36
  37 enum SignatureType {
  38   SIGNATURE_TYPE_CERTIFICATE_TIMESTAMP = 0,
  39   TREE_HASH = 1,
  40 };
  41
  42 // Reads a TLS-encoded variable length unsigned integer from |in|.
  43 // The integer is expected to be in big-endian order, which is used by TLS.
  44 // The bytes read from |in| are discarded (i.e. |in|'s prefix removed)
  45 // |length| indicates the size (in bytes) of the integer. On success, returns
  46 // true and stores the result in |*out|.
  47 template <typename T>
  48 bool ReadUint(size_t length, base::StringPiece* in, T* out) {
  49   if (in->size() < length)
  50     return false;
  51   DCHECK_LE(length, sizeof(T));
  52
  53   T result = 0;
  54   for (size_t i = 0; i < length; ++i) {
  55     result = (result << 8) | static_cast<unsigned char>((*in)[i]);
  56   }
  57   in->remove_prefix(length);
  58   *out = result;
  59   return true;
  60 }
  61
  62 // Reads a TLS-encoded field length from |in|.
  63 // The bytes read from |in| are discarded (i.e. |in|'s prefix removed)
  64 // |prefix_length| indicates the bytes needed to represent the length (e.g. 3)
  65 // success, returns true and stores the result in |*out|.
  66 bool ReadLength(size_t prefix_length, base::StringPiece* in, size_t* out) {
  67   size_t length;
  68   if (!ReadUint(prefix_length, in, &length))
  69     return false;
  70   *out = length;
  71   return true;
  72 }
  73
  74 // Reads |length| bytes from |*in|. If |*in| is too small, returns false.
  75 // The bytes read from |in| are discarded (i.e. |in|'s prefix removed)
  76 bool ReadFixedBytes(size_t length,
  77                     base::StringPiece* in,
  78                     base::StringPiece* out) {
  79   if (in->length() < length)
  80     return false;
  81   out->set(in->data(), length);
  82   in->remove_prefix(length);
  83   return true;
  84 }
  85
  86 // Reads a length-prefixed variable amount of bytes from |in|, updating |out|
  87 // on success. |prefix_length| indicates the number of bytes needed to represent
  88 // the length.
  89 // The bytes read from |in| are discarded (i.e. |in|'s prefix removed)
  90 bool ReadVariableBytes(size_t prefix_length,
  91                        base::StringPiece* in,
  92                        base::StringPiece* out) {
  93   size_t length;
  94   if (!ReadLength(prefix_length, in, &length))
  95     return false;
  96   return ReadFixedBytes(length, in, out);
  97 }
  98
  99 // Reads a variable-length list that has been TLS encoded.
 100 // The bytes read from |in| are discarded (i.e. |in|'s prefix removed)
 101 // |max_list_length| contains the overall length of the encoded list.
 102 // |max_item_length| contains the maximum length of a single item.
 103 // On success, returns true and updates |*out| with the encoded list.
 104 bool ReadList(size_t max_list_length,
 105               size_t max_item_length,
 106               base::StringPiece* in,
 107               std::vector<base::StringPiece>* out) {
 108   std::vector<base::StringPiece> result;
 109
 110   base::StringPiece list_data;
 111   if (!ReadVariableBytes(max_list_length, in, &list_data))
 112     return false;
 113
 114   while (!list_data.empty()) {
 115     base::StringPiece list_item;
 116     if (!ReadVariableBytes(max_item_length, &list_data, &list_item)) {
 117       DVLOG(1) << "Failed to read item in list.";
 118       return false;
 119     }
 120     if (list_item.empty()) {
 121       DVLOG(1) << "Empty item in list";
 122       return false;
 123     }
 124     result.push_back(list_item);
 125   }
 126
 127   result.swap(*out);
 128   return true;
 129 }
 130
 131 // Checks and converts a hash algorithm.
 132 // |in| is the numeric representation of the algorithm.
 133 // If the hash algorithm value is in a set of known values, fills in |out| and
 134 // returns true. Otherwise, returns false.
 135 bool ConvertHashAlgorithm(unsigned in, DigitallySigned::HashAlgorithm* out) {
 136   switch (in) {
 137     case DigitallySigned::HASH_ALGO_NONE:
 138     case DigitallySigned::HASH_ALGO_MD5:
 139     case DigitallySigned::HASH_ALGO_SHA1:
 140     case DigitallySigned::HASH_ALGO_SHA224:
 141     case DigitallySigned::HASH_ALGO_SHA256:
 142     case DigitallySigned::HASH_ALGO_SHA384:
 143     case DigitallySigned::HASH_ALGO_SHA512:
 144       break;
 145     default:
 146       return false;
 147   }
 148   *out = static_cast<DigitallySigned::HashAlgorithm>(in);
 149   return true;
 150 }
 151
 152 // Checks and converts a signing algorithm.
 153 // |in| is the numeric representation of the algorithm.
 154 // If the signing algorithm value is in a set of known values, fills in |out|
 155 // and returns true. Otherwise, returns false.
 156 bool ConvertSignatureAlgorithm(
 157     unsigned in,
 158     DigitallySigned::SignatureAlgorithm* out) {
 159   switch (in) {
 160     case DigitallySigned::SIG_ALGO_ANONYMOUS:
 161     case DigitallySigned::SIG_ALGO_RSA:
 162     case DigitallySigned::SIG_ALGO_DSA:
 163     case DigitallySigned::SIG_ALGO_ECDSA:
 164       break;
 165     default:
 166       return false;
 167   }
 168   *out = static_cast<DigitallySigned::SignatureAlgorithm>(in);
 169   return true;
 170 }
 171
 172 // Writes a TLS-encoded variable length unsigned integer to |output|.
 173 // |length| indicates the size (in bytes) of the integer.
 174 // |value| the value itself to be written.
 175 template <typename T>
 176 void WriteUint(size_t length, T value, std::string* output) {
 177   DCHECK_LE(length, sizeof(T));
 178   DCHECK(length == sizeof(T) || value >> (length * 8) == 0);
 179
 180   for (; length > 0; --length) {
 181     output->push_back((value >> ((length - 1)* 8)) & 0xFF);
 182   }
 183 }
 184
 185 // Writes an array to |output| from |input|.
 186 // Should be used in one of two cases:
 187 // * The length of |input| has already been encoded into the |output| stream.
 188 // * The length of |input| is fixed and the reader is expected to specify that
 189 // length when reading.
 190 // If the length of |input| is dynamic and data is expected to follow it,
 191 // WriteVariableBytes must be used.
 192 void WriteEncodedBytes(const base::StringPiece& input, std::string* output) {
 193   input.AppendToString(output);
 194 }
 195
 196 // Writes a variable-length array to |output|.
 197 // |prefix_length| indicates the number of bytes needed to represnt the length.
 198 // |input| is the array itself.
 199 // If the size of |input| is less than 2^|prefix_length| - 1, encode the
 200 // length and data and return true. Otherwise, return false.
 201 bool WriteVariableBytes(size_t prefix_length,
 202                         const base::StringPiece& input,
 203                         std::string* output) {
 204   size_t input_size = input.size();
 205   size_t max_allowed_input_size =
 206       static_cast<size_t>(((1 << (prefix_length * 8)) - 1));
 207   if (input_size > max_allowed_input_size)
 208     return false;
 209
 210   WriteUint(prefix_length, input.size(), output);
 211   WriteEncodedBytes(input, output);
 212
 213   return true;
 214 }
 215
 216 // Writes a LogEntry of type X.509 cert to |output|.
 217 // |input| is the LogEntry containing the certificate.
 218 // Returns true if the leaf_certificate in the LogEntry does not exceed
 219 // kMaxAsn1CertificateLength and so can be written to |output|.
 220 bool EncodeAsn1CertLogEntry(const LogEntry& input, std::string* output) {
 221   return WriteVariableBytes(kAsn1CertificateLengthBytes,
 222                             input.leaf_certificate, output);
 223 }
 224
 225 // Writes a LogEntry of type PreCertificate to |output|.
 226 // |input| is the LogEntry containing the TBSCertificate and issuer key hash.
 227 // Returns true if the TBSCertificate component in the LogEntry does not
 228 // exceed kMaxTbsCertificateLength and so can be written to |output|.
 229 bool EncodePrecertLogEntry(const LogEntry& input, std::string* output) {
 230   WriteEncodedBytes(
 231       base::StringPiece(
 232           reinterpret_cast<const char*>(input.issuer_key_hash.data),
 233           kLogIdLength),
 234       output);
 235   return WriteVariableBytes(kTbsCertificateLengthBytes,
 236                             input.tbs_certificate, output);
 237 }
 238
 239 }  // namespace
 240
 241 bool EncodeDigitallySigned(const DigitallySigned& input,
 242                            std::string* output) {
 243   WriteUint(kHashAlgorithmLength, input.hash_algorithm, output);
 244   WriteUint(kSigAlgorithmLength, input.signature_algorithm,
 245             output);
 246   return WriteVariableBytes(kSignatureLengthBytes, input.signature_data,
 247                             output);
 248 }
 249
 250 bool DecodeDigitallySigned(base::StringPiece* input,
 251                            DigitallySigned* output) {
 252   unsigned hash_algo;
 253   unsigned sig_algo;
 254   base::StringPiece sig_data;
 255
 256   if (!ReadUint(kHashAlgorithmLength, input, &hash_algo) ||
 257       !ReadUint(kSigAlgorithmLength, input, &sig_algo) ||
 258       !ReadVariableBytes(kSignatureLengthBytes, input, &sig_data)) {
 259     return false;
 260   }
 261
 262   DigitallySigned result;
 263   if (!ConvertHashAlgorithm(hash_algo, &result.hash_algorithm)) {
 264     DVLOG(1) << "Invalid hash algorithm " << hash_algo;
 265     return false;
 266   }
 267   if (!ConvertSignatureAlgorithm(sig_algo, &result.signature_algorithm)) {
 268     DVLOG(1) << "Invalid signature algorithm " << sig_algo;
 269     return false;
 270   }
 271   sig_data.CopyToString(&result.signature_data);
 272
 273   *output = result;
 274   return true;
 275 }
 276
 277 bool EncodeLogEntry(const LogEntry& input, std::string* output) {
 278   WriteUint(kLogEntryTypeLength, input.type, output);
 279   switch (input.type) {
 280     case LogEntry::LOG_ENTRY_TYPE_X509:
 281       return EncodeAsn1CertLogEntry(input, output);
 282     case LogEntry::LOG_ENTRY_TYPE_PRECERT:
 283       return EncodePrecertLogEntry(input, output);
 284   }
 285   return false;
 286 }
 287
 288 bool EncodeV1SCTSignedData(const base::Time& timestamp,
 289                            const std::string& serialized_log_entry,
 290                            const std::string& extensions,
 291                            std::string* output) {
 292   WriteUint(kVersionLength, SignedCertificateTimestamp::SCT_VERSION_1,
 293             output);
 294   WriteUint(kSignatureTypeLength, SIGNATURE_TYPE_CERTIFICATE_TIMESTAMP,
 295             output);
 296   base::TimeDelta time_since_epoch = timestamp - base::Time::UnixEpoch();
 297   WriteUint(kTimestampLength, time_since_epoch.InMilliseconds(),
 298             output);
 299   // NOTE: serialized_log_entry must already be serialized and contain the
 300   // length as the prefix.
 301   WriteEncodedBytes(serialized_log_entry, output);
 302   return WriteVariableBytes(kExtensionsLengthBytes, extensions, output);
 303 }
 304
 305 bool DecodeSCTList(base::StringPiece* input,
 306                    std::vector<base::StringPiece>* output) {
 307   std::vector<base::StringPiece> result;
 308   if (!ReadList(kSCTListLengthBytes, kSerializedSCTLengthBytes,
 309                 input, &result)) {
 310     return false;
 311   }
 312
 313   if (!input->empty() || result.empty())
 314     return false;
 315   output->swap(result);
 316   return true;
 317 }
 318
 319 bool DecodeSignedCertificateTimestamp(
 320     base::StringPiece* input,
 321     scoped_refptr<SignedCertificateTimestamp>* output) {
 322   scoped_refptr<SignedCertificateTimestamp> result(
 323       new SignedCertificateTimestamp());
 324   unsigned version;
 325   if (!ReadUint(kVersionLength, input, &version))
 326     return false;
 327   if (version != SignedCertificateTimestamp::SCT_VERSION_1) {
 328     DVLOG(1) << "Unsupported/invalid version " << version;
 329     return false;
 330   }
 331
 332   result->version = SignedCertificateTimestamp::SCT_VERSION_1;
 333   uint64 timestamp;
 334   base::StringPiece log_id;
 335   base::StringPiece extensions;
 336   if (!ReadFixedBytes(kLogIdLength, input, &log_id) ||
 337       !ReadUint(kTimestampLength, input, &timestamp) ||
 338       !ReadVariableBytes(kExtensionsLengthBytes, input,
 339                          &extensions) ||
 340       !DecodeDigitallySigned(input, &result->signature)) {
 341     return false;
 342   }
 343
 344   if (timestamp > static_cast<uint64>(kint64max)) {
 345     DVLOG(1) << "Timestamp value too big to cast to int64: " << timestamp;
 346     return false;
 347   }
 348
 349   log_id.CopyToString(&result->log_id);
 350   extensions.CopyToString(&result->extensions);
 351   result->timestamp =
 352       base::Time::UnixEpoch() +
 353       base::TimeDelta::FromMilliseconds(static_cast<int64>(timestamp));
 354
 355   output->swap(result);
 356   return true;
 357 }
 358
 359 bool EncodeSCTListForTesting(const base::StringPiece& sct,
 360                              std::string* output) {
 361   std::string encoded_sct;
 362   return WriteVariableBytes(kSerializedSCTLengthBytes, sct, &encoded_sct) &&
 363       WriteVariableBytes(kSCTListLengthBytes, encoded_sct, output);
 364 }
 365
 366 }  // namespace ct
 367
 368 }  // namespace net