constant_time.hh

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/*
 * libkeepass - KeePass key database importer/exporter
 * Copyright (C) 2014 Christian Kindahl
 * Copyright (C) 2024 Dominik Krümpelmann
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#pragma once
#include <array>
#include <cstddef>
#include <cstdint>
 
#include <openssl/crypto.h>
 
namespace keepass {
namespace detail {
 
 
inline bool constant_time_eq(const void* a, std::size_t a_size, const void* b,
                             std::size_t b_size) noexcept {
  if (a_size != b_size)
    return false;
  if (a_size == 0)
    return true;
  return CRYPTO_memcmp(a, b, a_size) == 0;
}
 
 
template <std::size_t N>
inline bool constant_time_eq(const std::array<uint8_t, N>& a,
                             const std::array<uint8_t, N>& b) noexcept {
  return constant_time_eq(a.data(), N, b.data(), N);
}
 
} // namespace detail
} // namespace keepass