Quelle CTSerialization.cpp Sprache: C

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "CTSerialization.h"
#include "CTUtils.h"

#include <stdint.h>
#include <type_traits>

namespace mozilla {
namespace ct {

using namespace mozilla::pkix;

typedef mozilla::pkix::Result Result;

// Note: length is always specified in bytes.
// Signed Certificate Timestamp (SCT) Version length
static const size_t kVersionLength = 1;

// Members of a V1 SCT
static const size_t kLogIdLength = 32;
static const size_t kTimestampLength = 8;
static const size_t kExtensionsLengthBytes = 2;
static const size_t kHashAlgorithmLength = 1;
static const size_t kSigAlgorithmLength = 1;
static const size_t kSignatureLengthBytes = 2;

// Members of the digitally-signed struct of a V1 SCT
static const size_t kSignatureTypeLength = 1;
static const size_t kLogEntryTypeLength = 2;
static const size_t kAsn1CertificateLengthBytes = 3;
static const size_t kTbsCertificateLengthBytes = 3;

static const size_t kSCTListLengthBytes = 2;
static const size_t kSerializedSCTLengthBytes = 2;

enum class SignatureType {
  CertificateTimestamp = 0,
  TreeHash = 1,
};

// Reads a serialized hash algorithm.
static Result ReadHashAlgorithm(Reader& in,
                                DigitallySigned::HashAlgorithm& out) {
  unsigned int value;
  Result rv = ReadUint<kHashAlgorithmLength>(in, value);
  if (rv != Success) {
    return rv;
  }
  DigitallySigned::HashAlgorithm algo =
      static_cast<DigitallySigned::HashAlgorithm>(value);
  switch (algo) {
    case DigitallySigned::HashAlgorithm::None:
    case DigitallySigned::HashAlgorithm::MD5:
    case DigitallySigned::HashAlgorithm::SHA1:
    case DigitallySigned::HashAlgorithm::SHA224:
    case DigitallySigned::HashAlgorithm::SHA256:
    case DigitallySigned::HashAlgorithm::SHA384:
    case DigitallySigned::HashAlgorithm::SHA512:
      out = algo;
      return Success;
  }
  return Result::ERROR_BAD_DER;
}

// Reads a serialized signature algorithm.
static Result ReadSignatureAlgorithm(Reader& in,
                                     DigitallySigned::SignatureAlgorithm& out) {
  unsigned int value;
  Result rv = ReadUint<kSigAlgorithmLength>(in, value);
  if (rv != Success) {
    return rv;
  }
  DigitallySigned::SignatureAlgorithm algo =
      static_cast<DigitallySigned::SignatureAlgorithm>(value);
  switch (algo) {
    case DigitallySigned::SignatureAlgorithm::Anonymous:
    case DigitallySigned::SignatureAlgorithm::RSA:
    case DigitallySigned::SignatureAlgorithm::DSA:
    case DigitallySigned::SignatureAlgorithm::ECDSA:
      out = algo;
      return Success;
  }
  return Result::ERROR_BAD_DER;
}

// Reads a serialized version enum.
static Result ReadVersion(Reader& in,
                          SignedCertificateTimestamp::Version& out) {
  unsigned int value;
  Result rv = ReadUint<kVersionLength>(in, value);
  if (rv != Success) {
    return rv;
  }
  SignedCertificateTimestamp::Version version =
      static_cast<SignedCertificateTimestamp::Version>(value);
  switch (version) {
    case SignedCertificateTimestamp::Version::V1:
      out = version;
      return Success;
  }
  return Result::ERROR_BAD_DER;
}

// Writes a TLS-encoded variable length unsigned integer to |output|.
// Note: range/overflow checks are not performed on the input parameters.
// |length| indicates the size (in bytes) of the integer to be written.
// |value| the value itself to be written.
static Result UncheckedWriteUint(size_t length, uint64_t value,
                                 Buffer& output) {
  output.reserve(length + output.size());
  for (; length > 0; --length) {
    uint8_t nextByte = (value >> ((length - 1) * 8)) & 0xFF;
    output.push_back(nextByte);
  }
  return Success;
}

// Performs sanity checks on T and calls UncheckedWriteUint.
template <size_t length, typename T>
static inline Result WriteUint(T value, Buffer& output) {
  static_assert(length <= 8, "At most 8 byte integers can be written");
  static_assert(sizeof(T) >= length, "T must be able to hold bytes");
  if (std::is_signed<T>::value) {
    // We accept signed integer types assuming the actual value is non-negative.
    if (value < 0) {
      return Result::FATAL_ERROR_INVALID_ARGS;
    }
  }
  if (sizeof(T) > length) {
    // We allow the value variable to take more bytes than is written,
    // but the unwritten bytes must be zero.
    // Note: when "sizeof(T) == length" holds, "value >> (length * 8)" is
    // undefined since the shift is too big. On some compilers, this would
    // produce a warning even though the actual code is unreachable.
    if (value >> (length * 8 - 1) > 1) {
      return Result::FATAL_ERROR_INVALID_ARGS;
    }
  }
  return UncheckedWriteUint(length, static_cast<uint64_t>(value), output);
}

// Writes an array to |output| from |input|.
// Should be used in one of two cases:
// * The length of |input| has already been encoded into the |output| stream.
// * The length of |input| is fixed and the reader is expected to specify that
// length when reading.
// If the length of |input| is dynamic and data is expected to follow it,
// WriteVariableBytes must be used.
static void WriteEncodedBytes(Input input, Buffer& output) {
  output.insert(output.end(), input.UnsafeGetData(),
                input.UnsafeGetData() + input.GetLength());
}

// Same as above, but the source data is in a Buffer.
static void WriteEncodedBytes(const Buffer& source, Buffer& output) {
  output.insert(output.end(), source.begin(), source.end());
}

// A variable-length byte array is prefixed by its length when serialized.
// This writes the length prefix.
// |prefixLength| indicates the number of bytes needed to represent the length.
// |dataLength| is the length of the byte array following the prefix.
// Fails if |dataLength| is more than 2^|prefixLength| - 1.
template <size_t prefixLength>
static Result WriteVariableBytesPrefix(size_t dataLength, Buffer& output) {
  const size_t maxAllowedInputSize =
      static_cast<size_t>(((1 << (prefixLength * 8)) - 1));
  if (dataLength > maxAllowedInputSize) {
    return Result::FATAL_ERROR_INVALID_ARGS;
  }

  return WriteUint<prefixLength>(dataLength, output);
}

// Writes a variable-length array to |output|.
// |prefixLength| indicates the number of bytes needed to represent the length.
// |input| is the array itself.
// Fails if the size of |input| is more than 2^|prefixLength| - 1.
template <size_t prefixLength>
static Result WriteVariableBytes(Input input, Buffer& output) {
  Result rv = WriteVariableBytesPrefix<prefixLength>(input.GetLength(), output);
  if (rv != Success) {
    return rv;
  }
  WriteEncodedBytes(input, output);
  return Success;
}

// Same as above, but the source data is in a Buffer.
template <size_t prefixLength>
static Result WriteVariableBytes(const Buffer& source, Buffer& output) {
  Input input;
  Result rv = BufferToInput(source, input);
  if (rv != Success) {
    return rv;
  }
  return WriteVariableBytes<prefixLength>(input, output);
}

// Writes a LogEntry of type X.509 cert to |output|.
// |input| is the LogEntry containing the certificate.
static Result EncodeAsn1CertLogEntry(const LogEntry& entry, Buffer& output) {
  return WriteVariableBytes<kAsn1CertificateLengthBytes>(entry.leafCertificate,
                                                         output);
}

// Writes a LogEntry of type PreCertificate to |output|.
// |input| is the LogEntry containing the TBSCertificate and issuer key hash.
static Result EncodePrecertLogEntry(const LogEntry& entry, Buffer& output) {
  if (entry.issuerKeyHash.size() != kLogIdLength) {
    return Result::FATAL_ERROR_INVALID_ARGS;
  }
  WriteEncodedBytes(entry.issuerKeyHash, output);
  return WriteVariableBytes<kTbsCertificateLengthBytes>(entry.tbsCertificate,
                                                        output);
}

Result EncodeDigitallySigned(const DigitallySigned& data, Buffer& output) {
  Result rv = WriteUint<kHashAlgorithmLength>(
      static_cast<unsigned int>(data.hashAlgorithm), output);
  if (rv != Success) {
    return rv;
  }
  rv = WriteUint<kSigAlgorithmLength>(
      static_cast<unsigned int>(data.signatureAlgorithm), output);
  if (rv != Success) {
    return rv;
  }
  return WriteVariableBytes<kSignatureLengthBytes>(data.signatureData, output);
}

Result DecodeDigitallySigned(Reader& reader, DigitallySigned& output) {
  DigitallySigned result;

  Result rv = ReadHashAlgorithm(reader, result.hashAlgorithm);
  if (rv != Success) {
    return rv;
  }
  rv = ReadSignatureAlgorithm(reader, result.signatureAlgorithm);
  if (rv != Success) {
    return rv;
  }

  Input signatureData;
  rv = ReadVariableBytes<kSignatureLengthBytes>(reader, signatureData);
  if (rv != Success) {
    return rv;
  }
  InputToBuffer(signatureData, result.signatureData);

  output = std::move(result);
  return Success;
}

Result EncodeLogEntry(const LogEntry& entry, Buffer& output) {
  Result rv = WriteUint<kLogEntryTypeLength>(
      static_cast<unsigned int>(entry.type), output);
  if (rv != Success) {
    return rv;
  }
  switch (entry.type) {
    case LogEntry::Type::X509:
      return EncodeAsn1CertLogEntry(entry, output);
    case LogEntry::Type::Precert:
      return EncodePrecertLogEntry(entry, output);
    default:
      assert(false);
  }
  return Result::ERROR_BAD_DER;
}

static Result WriteTimeSinceEpoch(uint64_t timestamp, Buffer& output) {
  return WriteUint<kTimestampLength>(timestamp, output);
}

Result EncodeV1SCTSignedData(uint64_t timestamp, Input serializedLogEntry,
                             Input extensions, Buffer& output) {
  Result rv = WriteUint<kVersionLength>(
      static_cast<unsigned int>(SignedCertificateTimestamp::Version::V1),
      output);
  if (rv != Success) {
    return rv;
  }
  rv = WriteUint<kSignatureTypeLength>(
      static_cast<unsigned int>(SignatureType::CertificateTimestamp), output);
  if (rv != Success) {
    return rv;
  }
  rv = WriteTimeSinceEpoch(timestamp, output);
  if (rv != Success) {
    return rv;
  }
  // NOTE: serializedLogEntry must already be serialized and contain the
  // length as the prefix.
  WriteEncodedBytes(serializedLogEntry, output);
  return WriteVariableBytes<kExtensionsLengthBytes>(extensions, output);
}

Result DecodeSCTList(Input input, Reader& listReader) {
  Reader inputReader(input);
  Input listData;
  Result rv = ReadVariableBytes<kSCTListLengthBytes>(inputReader, listData);
  if (rv != Success) {
    return rv;
  }
  return listReader.Init(listData);
}

Result ReadSCTListItem(Reader& listReader, Input& output) {
  if (listReader.AtEnd()) {
    return Result::FATAL_ERROR_INVALID_ARGS;
  }

  Result rv = ReadVariableBytes<kSerializedSCTLengthBytes>(listReader, output);
  if (rv != Success) {
    return rv;
  }
  if (output.GetLength() == 0) {
    return Result::ERROR_BAD_DER;
  }
  return Success;
}

Result DecodeSignedCertificateTimestamp(Reader& reader,
                                        SignedCertificateTimestamp& output) {
  SignedCertificateTimestamp result;

  Result rv = ReadVersion(reader, result.version);
  if (rv != Success) {
    return rv;
  }

  uint64_t timestamp;
  Input logId;
  Input extensions;

  rv = ReadFixedBytes(kLogIdLength, reader, logId);
  if (rv != Success) {
    return rv;
  }
  rv = ReadUint<kTimestampLength>(reader, timestamp);
  if (rv != Success) {
    return rv;
  }
  rv = ReadVariableBytes<kExtensionsLengthBytes>(reader, extensions);
  if (rv != Success) {
    return rv;
  }
  rv = DecodeDigitallySigned(reader, result.signature);
  if (rv != Success) {
    return rv;
  }

  InputToBuffer(logId, result.logId);
  InputToBuffer(extensions, result.extensions);
  result.timestamp = timestamp;

  output = std::move(result);
  return Success;
}

Result EncodeSCTList(const std::vector<pkix::Input>& scts, Buffer& output) {
  // Find out the total size of the SCT list to be written so we can
  // write the prefix for the list before writing its contents.
  size_t sctListLength = 0;
  for (auto& sct : scts) {
    sctListLength +=
        /* data size */ sct.GetLength() +
        /* length prefix size */ kSerializedSCTLengthBytes;
  }

  output.reserve(kSCTListLengthBytes + sctListLength);

  // Write the prefix for the SCT list.
  Result rv =
      WriteVariableBytesPrefix<kSCTListLengthBytes>(sctListLength, output);
  if (rv != Success) {
    return rv;
  }
  // Now write each SCT from the list.
  for (auto& sct : scts) {
    rv = WriteVariableBytes<kSerializedSCTLengthBytes>(sct, output);
    if (rv != Success) {
      return rv;
    }
  }
  return Success;
}

}  // namespace ct
}  // namespace mozilla

quality97%

¤ Dauer der Verarbeitung: 0.17 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.