crypter.h

// Copyright (c) 2009-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_WALLET_CRYPTER_H
#define BITCOIN_WALLET_CRYPTER_H

#include <serialize.h>
#include <support/allocators/secure.h>
#include <script/signingprovider.h>


const unsigned int WALLET_CRYPTO_KEY_SIZE = 32;
const unsigned int WALLET_CRYPTO_SALT_SIZE = 8;
const unsigned int WALLET_CRYPTO_IV_SIZE = 16;

/**
 * Private key encryption is done based on a CMasterKey,
 * which holds a salt and random encryption key.
 *
 * CMasterKeys are encrypted using AES-256-CBC using a key
 * derived using derivation method nDerivationMethod
 * (0 == EVP_sha512()) and derivation iterations nDeriveIterations.
 * vchOtherDerivationParameters is provided for alternative algorithms
 * which may require more parameters (such as scrypt).
 *
 * Wallet Private Keys are then encrypted using AES-256-CBC
 * with the double-sha256 of the public key as the IV, and the
 * master key's key as the encryption key (see keystore.[ch]).
 */

/** Master key for wallet encryption */
class CMasterKey
{
public:
    std::vector<unsigned char> vchCryptedKey;
    std::vector<unsigned char> vchSalt;
    //! 0 = EVP_sha512()
    //! 1 = scrypt()
    unsigned int nDerivationMethod;
    unsigned int nDeriveIterations;
    //! Use this for more parameters to key derivation,
    //! such as the various parameters to scrypt
    std::vector<unsigned char> vchOtherDerivationParameters;

    SERIALIZE_METHODS(CMasterKey, obj)
    {
        READWRITE(obj.vchCryptedKey, obj.vchSalt, obj.nDerivationMethod, obj.nDeriveIterations, obj.vchOtherDerivationParameters);
    }

    CMasterKey()
    {
        // 25000 rounds is just under 0.1 seconds on a 1.86 GHz Pentium M
        // ie slightly lower than the lowest hardware we need bother supporting
        nDeriveIterations = 25000;
        nDerivationMethod = 0;
        vchOtherDerivationParameters = std::vector<unsigned char>(0);
    }
};

typedef std::vector<unsigned char, secure_allocator<unsigned char> > CKeyingMaterial;

namespace wallet_crypto_tests
{
    class TestCrypter;
}

/** Encryption/decryption context with key information */
class CCrypter
{
friend class wallet_crypto_tests::TestCrypter; // for test access to chKey/chIV
private:
    std::vector<unsigned char, secure_allocator<unsigned char>> vchKey;
    std::vector<unsigned char, secure_allocator<unsigned char>> vchIV;
    bool fKeySet;

    int BytesToKeySHA512AES(const std::vector<unsigned char>& chSalt, const SecureString& strKeyData, int count, unsigned char *key,unsigned char *iv) const;

public:
    bool SetKeyFromPassphrase(const SecureString &strKeyData, const std::vector<unsigned char>& chSalt, const unsigned int nRounds, const unsigned int nDerivationMethod);
    bool Encrypt(const CKeyingMaterial& vchPlaintext, std::vector<unsigned char> &vchCiphertext) const;
    bool Decrypt(const std::vector<unsigned char>& vchCiphertext, CKeyingMaterial& vchPlaintext) const;
    bool SetKey(const CKeyingMaterial& chNewKey, const std::vector<unsigned char>& chNewIV);

    void CleanKey()
    {
        memory_cleanse(vchKey.data(), vchKey.size());
        memory_cleanse(vchIV.data(), vchIV.size());
        fKeySet = false;
    }

    CCrypter()
    {
        fKeySet = false;
        vchKey.resize(WALLET_CRYPTO_KEY_SIZE);
        vchIV.resize(WALLET_CRYPTO_IV_SIZE);
    }

    ~CCrypter()
    {
        CleanKey();
    }
};

bool EncryptSecret(const CKeyingMaterial& vMasterKey, const CKeyingMaterial &vchPlaintext, const uint256& nIV, std::vector<unsigned char> &vchCiphertext);
bool DecryptSecret(const CKeyingMaterial& vMasterKey, const std::vector<unsigned char>& vchCiphertext, const uint256& nIV, CKeyingMaterial& vchPlaintext);
bool DecryptKey(const CKeyingMaterial& vMasterKey, const std::vector<unsigned char>& vchCryptedSecret, const CPubKey& vchPubKey, CKey& key);

#endif // BITCOIN_WALLET_CRYPTER_H