bitcoin/src/crypter.cpp

// Copyright (c) 2011 The Bitcoin Developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <openssl/aes.h>
#include <openssl/evp.h>
#include <vector>
#include <string>
#include "headers.h"
#ifdef WIN32
#include <windows.h>
#endif

#include "crypter.h"
#include "main.h"
#include "util.h"

bool CCrypter::SetKeyFromPassphrase(const SecureString& strKeyData, const std::vector<unsigned char>& chSalt, const unsigned int nRounds, const unsigned int nDerivationMethod)
{
    if (nRounds < 1 || chSalt.size() != WALLET_CRYPTO_SALT_SIZE)
        return false;

    // Try to keep the keydata out of swap (and be a bit over-careful to keep the IV that we don't even use out of swap)
    // Note that this does nothing about suspend-to-disk (which will put all our key data on disk)
    // Note as well that at no point in this program is any attempt made to prevent stealing of keys by reading the memory of the running process.  
    mlock(&chKey[0], sizeof chKey);
    mlock(&chIV[0], sizeof chIV);

    int i = 0;
    if (nDerivationMethod == 0)
        i = EVP_BytesToKey(EVP_aes_256_cbc(), EVP_sha512(), &chSalt[0],
                          (unsigned char *)&strKeyData[0], strKeyData.size(), nRounds, chKey, chIV);

    if (i != WALLET_CRYPTO_KEY_SIZE)
    {
        memset(&chKey, 0, sizeof chKey);
        memset(&chIV, 0, sizeof chIV);
        return false;
    }

    fKeySet = true;
    return true;
}

bool CCrypter::SetKey(const CKeyingMaterial& chNewKey, const std::vector<unsigned char>& chNewIV)
{
    if (chNewKey.size() != WALLET_CRYPTO_KEY_SIZE || chNewIV.size() != WALLET_CRYPTO_KEY_SIZE)
        return false;

    // Try to keep the keydata out of swap
    // Note that this does nothing about suspend-to-disk (which will put all our key data on disk)
    // Note as well that at no point in this program is any attempt made to prevent stealing of keys by reading the memory of the running process.  
    mlock(&chKey[0], sizeof chKey);
    mlock(&chIV[0], sizeof chIV);

    memcpy(&chKey[0], &chNewKey[0], sizeof chKey);
    memcpy(&chIV[0], &chNewIV[0], sizeof chIV);

    fKeySet = true;
    return true;
}

bool CCrypter::Encrypt(const CKeyingMaterial& vchPlaintext, std::vector<unsigned char> &vchCiphertext)
{
    if (!fKeySet)
        return false;

    // max ciphertext len for a n bytes of plaintext is
    // n + AES_BLOCK_SIZE - 1 bytes
    int nLen = vchPlaintext.size();
    int nCLen = nLen + AES_BLOCK_SIZE, nFLen = 0;
    vchCiphertext = std::vector<unsigned char> (nCLen);

    EVP_CIPHER_CTX ctx;

    EVP_CIPHER_CTX_init(&ctx);
    EVP_EncryptInit_ex(&ctx, EVP_aes_256_cbc(), NULL, chKey, chIV);

    EVP_EncryptUpdate(&ctx, &vchCiphertext[0], &nCLen, &vchPlaintext[0], nLen);
    EVP_EncryptFinal_ex(&ctx, (&vchCiphertext[0])+nCLen, &nFLen);

    EVP_CIPHER_CTX_cleanup(&ctx);

    vchCiphertext.resize(nCLen + nFLen);
    return true;
}

bool CCrypter::Decrypt(const std::vector<unsigned char>& vchCiphertext, CKeyingMaterial& vchPlaintext)
{
    if (!fKeySet)
        return false;

    // plaintext will always be equal to or lesser than length of ciphertext
    int nLen = vchCiphertext.size();
    int nPLen = nLen, nFLen = 0;

    vchPlaintext = CKeyingMaterial(nPLen);

    EVP_CIPHER_CTX ctx;

    EVP_CIPHER_CTX_init(&ctx);
    EVP_DecryptInit_ex(&ctx, EVP_aes_256_cbc(), NULL, chKey, chIV);

    EVP_DecryptUpdate(&ctx, &vchPlaintext[0], &nPLen, &vchCiphertext[0], nLen);
    EVP_DecryptFinal_ex(&ctx, (&vchPlaintext[0])+nPLen, &nFLen);

    EVP_CIPHER_CTX_cleanup(&ctx);

    vchPlaintext.resize(nPLen + nFLen);
    return true;
}


bool EncryptSecret(CKeyingMaterial& vMasterKey, const CSecret &vchPlaintext, const uint256& nIV, std::vector<unsigned char> &vchCiphertext)
{
    CCrypter cKeyCrypter;
    std::vector<unsigned char> chIV(WALLET_CRYPTO_KEY_SIZE);
    memcpy(&chIV[0], &nIV, WALLET_CRYPTO_KEY_SIZE);
    if(!cKeyCrypter.SetKey(vMasterKey, chIV))
        return false;
    return cKeyCrypter.Encrypt((CKeyingMaterial)vchPlaintext, vchCiphertext);
}

bool DecryptSecret(const CKeyingMaterial& vMasterKey, const std::vector<unsigned char>& vchCiphertext, const uint256& nIV, CSecret& vchPlaintext)
{
    CCrypter cKeyCrypter;
    std::vector<unsigned char> chIV(WALLET_CRYPTO_KEY_SIZE);
    memcpy(&chIV[0], &nIV, WALLET_CRYPTO_KEY_SIZE);
    if(!cKeyCrypter.SetKey(vMasterKey, chIV))
        return false;
    return cKeyCrypter.Decrypt(vchCiphertext, *((CKeyingMaterial*)&vchPlaintext));
}