src/crypter.h

   1 // Copyright (c) 2009-2013 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
   5 #ifndef __CRYPTER_H__
   6 #define __CRYPTER_H__
   7
   8 #include "allocators.h"
   9 #include "serialize.h"
  10 #include "keystore.h"
  11
  12 class uint256;
  13
  14 const unsigned int WALLET_CRYPTO_KEY_SIZE = 32;
  15 const unsigned int WALLET_CRYPTO_SALT_SIZE = 8;
  16
  17 /*
  18 Private key encryption is done based on a CMasterKey,
  19 which holds a salt and random encryption key.
  20
  21 CMasterKeys are encrypted using AES-256-CBC using a key
  22 derived using derivation method nDerivationMethod
  23 (0 == EVP_sha512()) and derivation iterations nDeriveIterations.
  24 vchOtherDerivationParameters is provided for alternative algorithms
  25 which may require more parameters (such as scrypt).
  26
  27 Wallet Private Keys are then encrypted using AES-256-CBC
  28 with the double-sha256 of the public key as the IV, and the
  29 master key's key as the encryption key (see keystore.[ch]).
  30 */
  31
  32 /** Master key for wallet encryption */
  33 class CMasterKey
  34 {
  35 public:
  36     std::vector<unsigned char> vchCryptedKey;
  37     std::vector<unsigned char> vchSalt;
  38     // 0 = EVP_sha512()
  39     // 1 = scrypt()
  40     unsigned int nDerivationMethod;
  41     unsigned int nDeriveIterations;
  42     // Use this for more parameters to key derivation,
  43     // such as the various parameters to scrypt
  44     std::vector<unsigned char> vchOtherDerivationParameters;
  45
  46     IMPLEMENT_SERIALIZE
  47     (
  48         READWRITE(vchCryptedKey);
  49         READWRITE(vchSalt);
  50         READWRITE(nDerivationMethod);
  51         READWRITE(nDeriveIterations);
  52         READWRITE(vchOtherDerivationParameters);
  53     )
  54     CMasterKey()
  55     {
  56         // 25000 rounds is just under 0.1 seconds on a 1.86 GHz Pentium M
  57         // ie slightly lower than the lowest hardware we need bother supporting
  58         nDeriveIterations = 25000;
  59         nDerivationMethod = 0;
  60         vchOtherDerivationParameters = std::vector<unsigned char>(0);
  61     }
  62 };
  63
  64 typedef std::vector<unsigned char, secure_allocator<unsigned char> > CKeyingMaterial;
  65
  66 /** Encryption/decryption context with key information */
  67 class CCrypter
  68 {
  69 private:
  70     unsigned char chKey[WALLET_CRYPTO_KEY_SIZE];
  71     unsigned char chIV[WALLET_CRYPTO_KEY_SIZE];
  72     bool fKeySet;
  73
  74 public:
  75     bool SetKeyFromPassphrase(const SecureString &strKeyData, const std::vector<unsigned char>& chSalt, const unsigned int nRounds, const unsigned int nDerivationMethod);
  76     bool Encrypt(const CKeyingMaterial& vchPlaintext, std::vector<unsigned char> &vchCiphertext);
  77     bool Decrypt(const std::vector<unsigned char>& vchCiphertext, CKeyingMaterial& vchPlaintext);
  78     bool SetKey(const CKeyingMaterial& chNewKey, const std::vector<unsigned char>& chNewIV);
  79
  80     void CleanKey()
  81     {
  82         OPENSSL_cleanse(chKey, sizeof(chKey));
  83         OPENSSL_cleanse(chIV, sizeof(chIV));
  84         fKeySet = false;
  85     }
  86
  87     CCrypter()
  88     {
  89         fKeySet = false;
  90
  91         // 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)
  92         // Note that this does nothing about suspend-to-disk (which will put all our key data on disk)
  93         // 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.
  94         LockedPageManager::Instance().LockRange(&chKey[0], sizeof chKey);
  95         LockedPageManager::Instance().LockRange(&chIV[0], sizeof chIV);
  96     }
  97
  98     ~CCrypter()
  99     {
 100         CleanKey();
 101
 102         LockedPageManager::Instance().UnlockRange(&chKey[0], sizeof chKey);
 103         LockedPageManager::Instance().UnlockRange(&chIV[0], sizeof chIV);
 104     }
 105 };
 106
 107 bool EncryptSecret(const CKeyingMaterial& vMasterKey, const CKeyingMaterial &vchPlaintext, const uint256& nIV, std::vector<unsigned char> &vchCiphertext);
 108 bool DecryptSecret(const CKeyingMaterial& vMasterKey, const std::vector<unsigned char>& vchCiphertext, const uint256& nIV, CKeyingMaterial& vchPlaintext);
 109
 110 /** Keystore which keeps the private keys encrypted.
 111  * It derives from the basic key store, which is used if no encryption is active.
 112  */
 113 class CCryptoKeyStore : public CBasicKeyStore
 114 {
 115 private:
 116     CryptedKeyMap mapCryptedKeys;
 117
 118     CKeyingMaterial vMasterKey;
 119
 120     // if fUseCrypto is true, mapKeys must be empty
 121     // if fUseCrypto is false, vMasterKey must be empty
 122     bool fUseCrypto;
 123
 124     // keeps track of whether Unlock has run a thourough check before
 125     bool fDecryptionThoroughlyChecked;
 126
 127 protected:
 128     bool SetCrypted();
 129
 130     // will encrypt previously unencrypted keys
 131     bool EncryptKeys(CKeyingMaterial& vMasterKeyIn);
 132
 133     bool Unlock(const CKeyingMaterial& vMasterKeyIn);
 134
 135 public:
 136     CCryptoKeyStore() : fUseCrypto(false), fDecryptionThoroughlyChecked(false)
 137     {
 138     }
 139
 140     bool IsCrypted() const
 141     {
 142         return fUseCrypto;
 143     }
 144
 145     bool IsLocked() const
 146     {
 147         if (!IsCrypted())
 148             return false;
 149         bool result;
 150         {
 151             LOCK(cs_KeyStore);
 152             result = vMasterKey.empty();
 153         }
 154         return result;
 155     }
 156
 157     bool Lock();
 158
 159     virtual bool AddCryptedKey(const CPubKey &vchPubKey, const std::vector<unsigned char> &vchCryptedSecret);
 160     bool AddKeyPubKey(const CKey& key, const CPubKey &pubkey);
 161     bool HaveKey(const CKeyID &address) const
 162     {
 163         {
 164             LOCK(cs_KeyStore);
 165             if (!IsCrypted())
 166                 return CBasicKeyStore::HaveKey(address);
 167             return mapCryptedKeys.count(address) > 0;
 168         }
 169         return false;
 170     }
 171     bool GetKey(const CKeyID &address, CKey& keyOut) const;
 172     bool GetPubKey(const CKeyID &address, CPubKey& vchPubKeyOut) const;
 173     void GetKeys(std::set<CKeyID> &setAddress) const
 174     {
 175         if (!IsCrypted())
 176         {
 177             CBasicKeyStore::GetKeys(setAddress);
 178             return;
 179         }
 180         setAddress.clear();
 181         CryptedKeyMap::const_iterator mi = mapCryptedKeys.begin();
 182         while (mi != mapCryptedKeys.end())
 183         {
 184             setAddress.insert((*mi).first);
 185             mi++;
 186         }
 187     }
 188
 189     /* Wallet status (encrypted, locked) changed.
 190      * Note: Called without locks held.
 191      */
 192     boost::signals2::signal<void (CCryptoKeyStore* wallet)> NotifyStatusChanged;
 193 };
 194
 195 #endif