src/crypter.h

   1 // Copyright (c) 2009-2012 The Bitcoin Developers
   2 // Distributed under the MIT/X11 software license, see the accompanying
   3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4 #ifndef __CRYPTER_H__
   5 #define __CRYPTER_H__
   6
   7 #include "allocators.h" /* for SecureString */
   8 #include "key.h"
   9 #include "serialize.h"
  10
  11 const unsigned int WALLET_CRYPTO_KEY_SIZE = 32;
  12 const unsigned int WALLET_CRYPTO_SALT_SIZE = 8;
  13
  14 /*
  15 Private key encryption is done based on a CMasterKey,
  16 which holds a salt and random encryption key.
  17
  18 CMasterKeys are encrypted using AES-256-CBC using a key
  19 derived using derivation method nDerivationMethod
  20 (0 == EVP_sha512()) and derivation iterations nDeriveIterations.
  21 vchOtherDerivationParameters is provided for alternative algorithms
  22 which may require more parameters (such as scrypt).
  23
  24 Wallet Private Keys are then encrypted using AES-256-CBC
  25 with the double-sha256 of the public key as the IV, and the
  26 master key's key as the encryption key (see keystore.[ch]).
  27 */
  28
  29 /** Master key for wallet encryption */
  30 class CMasterKey
  31 {
  32 public:
  33     std::vector<unsigned char> vchCryptedKey;
  34     std::vector<unsigned char> vchSalt;
  35     // 0 = EVP_sha512()
  36     // 1 = scrypt()
  37     unsigned int nDerivationMethod;
  38     unsigned int nDeriveIterations;
  39     // Use this for more parameters to key derivation,
  40     // such as the various parameters to scrypt
  41     std::vector<unsigned char> vchOtherDerivationParameters;
  42
  43     IMPLEMENT_SERIALIZE
  44     (
  45         READWRITE(vchCryptedKey);
  46         READWRITE(vchSalt);
  47         READWRITE(nDerivationMethod);
  48         READWRITE(nDeriveIterations);
  49         READWRITE(vchOtherDerivationParameters);
  50     )
  51     CMasterKey()
  52     {
  53         // 25000 rounds is just under 0.1 seconds on a 1.86 GHz Pentium M
  54         // ie slightly lower than the lowest hardware we need bother supporting
  55         nDeriveIterations = 25000;
  56         nDerivationMethod = 0;
  57         vchOtherDerivationParameters = std::vector<unsigned char>(0);
  58     }
  59 };
  60
  61 typedef std::vector<unsigned char, secure_allocator<unsigned char> > CKeyingMaterial;
  62
  63 /** Encryption/decryption context with key information */
  64 class CCrypter
  65 {
  66 private:
  67     unsigned char chKey[WALLET_CRYPTO_KEY_SIZE];
  68     unsigned char chIV[WALLET_CRYPTO_KEY_SIZE];
  69     bool fKeySet;
  70
  71 public:
  72     bool SetKeyFromPassphrase(const SecureString &strKeyData, const std::vector<unsigned char>& chSalt, const unsigned int nRounds, const unsigned int nDerivationMethod);
  73     bool Encrypt(const CKeyingMaterial& vchPlaintext, std::vector<unsigned char> &vchCiphertext);
  74     bool Decrypt(const std::vector<unsigned char>& vchCiphertext, CKeyingMaterial& vchPlaintext);
  75     bool SetKey(const CKeyingMaterial& chNewKey, const std::vector<unsigned char>& chNewIV);
  76
  77     void CleanKey()
  78     {
  79         OPENSSL_cleanse(chKey, sizeof(chKey));
  80         OPENSSL_cleanse(chIV, sizeof(chIV));
  81         fKeySet = false;
  82     }
  83
  84     CCrypter()
  85     {
  86         fKeySet = false;
  87
  88         // Try to keep the key data out of swap (and be a bit over-careful to keep the IV that we don't even use out of swap)
  89         // Note that this does nothing about suspend-to-disk (which will put all our key data on disk)
  90         // 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.
  91         LockedPageManager::instance.LockRange(&chKey[0], sizeof chKey);
  92         LockedPageManager::instance.LockRange(&chIV[0], sizeof chIV);
  93     }
  94
  95     ~CCrypter()
  96     {
  97         CleanKey();
  98
  99         LockedPageManager::instance.UnlockRange(&chKey[0], sizeof chKey);
 100         LockedPageManager::instance.UnlockRange(&chIV[0], sizeof chIV);
 101     }
 102 };
 103
 104 bool EncryptSecret(CKeyingMaterial& vMasterKey, const CSecret &vchPlaintext, const uint256& nIV, std::vector<unsigned char> &vchCiphertext);
 105 bool DecryptSecret(const CKeyingMaterial& vMasterKey, const std::vector<unsigned char> &vchCiphertext, const uint256& nIV, CSecret &vchPlaintext);
 106
 107 #endif