AES.cpp

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/*
 This file is part of cpp-ethereum.
 
 cpp-ethereum 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.
 
 cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
 */
#include "AES.h"
#include <cryptopp/aes.h>
#include <cryptopp/filters.h>
#include <cryptopp/pwdbased.h>
#include <cryptopp/modes.h>
#include <cryptopp/sha.h>

using namespace dev;
using namespace dev::crypto;

bytes dev::aesDecrypt(bytesConstRef _ivCipher, std::string const& _password, unsigned _rounds, bytesConstRef _salt)
{
    bytes pw = asBytes(_password);

    if (!_salt.size())
        _salt = &pw;

    bytes target(64);
    CryptoPP::PKCS5_PBKDF2_HMAC<CryptoPP::SHA256>().DeriveKey(target.data(), target.size(), 0, pw.data(), pw.size(), _salt.data(), _salt.size(), _rounds);

    try
    {
        CryptoPP::AES::Decryption aesDecryption(target.data(), 16);
        auto cipher = _ivCipher.cropped(16);
        auto iv = _ivCipher.cropped(0, 16);
        CryptoPP::CBC_Mode_ExternalCipher::Decryption cbcDecryption(aesDecryption, iv.data());
        std::string decrypted;
        CryptoPP::StreamTransformationFilter stfDecryptor(cbcDecryption, new CryptoPP::StringSink(decrypted));
        stfDecryptor.Put(cipher.data(), cipher.size());
        stfDecryptor.MessageEnd();
        return asBytes(decrypted);
    }
    catch (std::exception const& e)
    {
        // FIXME: Handle this error better.
        std::cerr << e.what() << '\n';
        return bytes();
    }
}