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/* -*- 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
#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 <length> 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