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/************************************************************************
*
* Copyright (C) 2021-2025 IRCAD France
*
* This file is part of Sight.
*
* Sight is free software: you can redistribute it and/or modify it under
* the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Sight 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with Sight. If not, see <https://www.gnu.org/licenses/>.
*
***********************************************************************/
#include "aes256.hpp"
#include "sha256.hpp"
#include <openssl/err.h>
#include <openssl/evp.h>
#include <array>
#include <cstring>
#include <stdexcept>
namespace sight::core::crypto
{
//------------------------------------------------------------------------------
static constexpr auto check_aes(const auto& _expr)
{
const auto result = _expr();
if(result == 0)
{
throw std::runtime_error(std::string(ERR_error_string(ERR_get_error(), nullptr)));
}
return result;
}
// Load the necessary cipher
static struct openssl_initializer final
{
openssl_initializer()
{
ERR_load_crypto_strings();
check_aes([&]{return EVP_add_cipher(EVP_aes_256_cbc());});
}
~openssl_initializer()
{
ERR_free_strings();
EVP_cleanup();
}
} s_openssl_initializer;
// en/decrypt a message using the given password.
// Uses function pointers to minimize code duplication
template<typename T>
inline static T xx_crypt(
decltype(&::EVP_DecryptInit_ex) _xx_crypt_init,
decltype(&::EVP_DecryptUpdate) _xx_crypt_update,
decltype(&::EVP_DecryptFinal_ex) _xx_crypt_final,
const T& _message,
const secure_string& _password
)
{
static_assert(
std::is_same_v<secure_string, T>|| std::is_same_v<std::string, T>,
"T must be a string"
);
// Initialize key (265 bits) and iv(128 bits)
std::array<unsigned char, HASH_SIZE> key {};
std::array<unsigned char, EVP_MAX_IV_LENGTH> iv = {0};
// Compute password hash and randomize initialization vector
hash(_password, key);
// Initialize the output with size of the original message expanded to block size
T output;
output.resize(_message.size() + iv.size());
int processed_size = static_cast<int>(output.size());
// Initialize context
EVP_CIPHER_CTX* ctx = EVP_CIPHER_CTX_new();
// Initialize en/decryption
check_aes([&]{return _xx_crypt_init(ctx, EVP_aes_256_cbc(), nullptr, key.data(), iv.data());});
// Update en/decryption
check_aes(
[&]
{
return _xx_crypt_update(
ctx,
reinterpret_cast<unsigned char*>(output.data()),
&processed_size,
reinterpret_cast<const unsigned char*>(_message.data()),
static_cast<int>(_message.size())
);
});
// Compute remaining size
int remaining_size = static_cast<int>(output.size()) - processed_size;
// Finalize en/decryption
check_aes(
[&]
{
return _xx_crypt_final(
ctx,
reinterpret_cast<unsigned char*>(output.data()) + processed_size,
&remaining_size
);
});
// Adjust output to the real size
output.resize(static_cast<std::size_t>(processed_size) + static_cast<std::size_t>(remaining_size));
output.shrink_to_fit();
// Cleaning
EVP_CIPHER_CTX_free(ctx);
OPENSSL_cleanse(key.data(), key.size());
OPENSSL_cleanse(iv.data(), iv.size());
return output;
}
//------------------------------------------------------------------------------
std::string decrypt(const std::string& _message, const secure_string& _password)
{
return xx_crypt<std::string>(
&::EVP_DecryptInit_ex,
&::EVP_DecryptUpdate,
&::EVP_DecryptFinal_ex,
_message,
_password
);
}
//------------------------------------------------------------------------------
secure_string decrypt(const secure_string& _message, const secure_string& _password)
{
return xx_crypt<secure_string>(
&::EVP_DecryptInit_ex,
&::EVP_DecryptUpdate,
&::EVP_DecryptFinal_ex,
_message,
_password
);
}
//------------------------------------------------------------------------------
secure_string decrypt(const char* const _message, const secure_string& _password)
{
return decrypt(secure_string(_message), _password);
}
//------------------------------------------------------------------------------
std::string encrypt(const std::string& _message, const secure_string& _password)
{
return xx_crypt<std::string>(
&::EVP_EncryptInit_ex,
&::EVP_EncryptUpdate,
&::EVP_EncryptFinal_ex,
_message,
_password
);
}
//------------------------------------------------------------------------------
secure_string encrypt(const secure_string& _message, const secure_string& _password)
{
return xx_crypt<secure_string>(
&::EVP_EncryptInit_ex,
&::EVP_EncryptUpdate,
&::EVP_EncryptFinal_ex,
_message,
_password
);
}
//------------------------------------------------------------------------------
secure_string encrypt(const char* const _message, const secure_string& _password)
{
return encrypt(secure_string(_message), _password);
}
} // namespace sight::core::crypto
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