src/key.cpp

   1 // Copyright (c) 2009-2016 The Bitcoin Core developers
   2 // Distributed under the MIT software license, see the accompanying
   3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4
   5 #include <key.h>
   6
   7 #include <arith_uint256.h>
   8 #include <crypto/common.h>
   9 #include <crypto/hmac_sha512.h>
  10 #include <random.h>
  11
  12 #include <secp256k1.h>
  13 #include <secp256k1_recovery.h>
  14
  15 static secp256k1_context* secp256k1_context_sign = nullptr;
  16
  17 /** These functions are taken from the libsecp256k1 distribution and are very ugly. */
  18 static int ec_privkey_import_der(const secp256k1_context* ctx, unsigned char *out32, const unsigned char *privkey, size_t privkeylen) {
  19     const unsigned char *end = privkey + privkeylen;
  20     int lenb = 0;
  21     int len = 0;
  22     memset(out32, 0, 32);
  23     /* sequence header */
  24     if (end < privkey+1 || *privkey != 0x30) {
  25         return 0;
  26     }
  27     privkey++;
  28     /* sequence length constructor */
  29     if (end < privkey+1 || !(*privkey & 0x80)) {
  30         return 0;
  31     }
  32     lenb = *privkey & ~0x80; privkey++;
  33     if (lenb < 1 || lenb > 2) {
  34         return 0;
  35     }
  36     if (end < privkey+lenb) {
  37         return 0;
  38     }
  39     /* sequence length */
  40     len = privkey[lenb-1] | (lenb > 1 ? privkey[lenb-2] << 8 : 0);
  41     privkey += lenb;
  42     if (end < privkey+len) {
  43         return 0;
  44     }
  45     /* sequence element 0: version number (=1) */
  46     if (end < privkey+3 || privkey[0] != 0x02 || privkey[1] != 0x01 || privkey[2] != 0x01) {
  47         return 0;
  48     }
  49     privkey += 3;
  50     /* sequence element 1: octet string, up to 32 bytes */
  51     if (end < privkey+2 || privkey[0] != 0x04 || privkey[1] > 0x20 || end < privkey+2+privkey[1]) {
  52         return 0;
  53     }
  54     memcpy(out32 + 32 - privkey[1], privkey + 2, privkey[1]);
  55     if (!secp256k1_ec_seckey_verify(ctx, out32)) {
  56         memset(out32, 0, 32);
  57         return 0;
  58     }
  59     return 1;
  60 }
  61
  62 static int ec_privkey_export_der(const secp256k1_context *ctx, unsigned char *privkey, size_t *privkeylen, const unsigned char *key32, int compressed) {
  63     secp256k1_pubkey pubkey;
  64     size_t pubkeylen = 0;
  65     if (!secp256k1_ec_pubkey_create(ctx, &pubkey, key32)) {
  66         *privkeylen = 0;
  67         return 0;
  68     }
  69     if (compressed) {
  70         static const unsigned char begin[] = {
  71             0x30,0x81,0xD3,0x02,0x01,0x01,0x04,0x20
  72         };
  73         static const unsigned char middle[] = {
  74             0xA0,0x81,0x85,0x30,0x81,0x82,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
  75             0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
  76             0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
  77             0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
  78             0x21,0x02,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
  79             0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
  80             0x17,0x98,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
  81             0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
  82             0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x24,0x03,0x22,0x00
  83         };
  84         unsigned char *ptr = privkey;
  85         memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
  86         memcpy(ptr, key32, 32); ptr += 32;
  87         memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
  88         pubkeylen = 33;
  89         secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_COMPRESSED);
  90         ptr += pubkeylen;
  91         *privkeylen = ptr - privkey;
  92     } else {
  93         static const unsigned char begin[] = {
  94             0x30,0x82,0x01,0x13,0x02,0x01,0x01,0x04,0x20
  95         };
  96         static const unsigned char middle[] = {
  97             0xA0,0x81,0xA5,0x30,0x81,0xA2,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
  98             0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
  99             0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
 100             0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
 101             0x41,0x04,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
 102             0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
 103             0x17,0x98,0x48,0x3A,0xDA,0x77,0x26,0xA3,0xC4,0x65,0x5D,0xA4,0xFB,0xFC,0x0E,0x11,
 104             0x08,0xA8,0xFD,0x17,0xB4,0x48,0xA6,0x85,0x54,0x19,0x9C,0x47,0xD0,0x8F,0xFB,0x10,
 105             0xD4,0xB8,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
 106             0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
 107             0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x44,0x03,0x42,0x00
 108         };
 109         unsigned char *ptr = privkey;
 110         memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
 111         memcpy(ptr, key32, 32); ptr += 32;
 112         memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
 113         pubkeylen = 65;
 114         secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
 115         ptr += pubkeylen;
 116         *privkeylen = ptr - privkey;
 117     }
 118     return 1;
 119 }
 120
 121 bool CKey::Check(const unsigned char *vch) {
 122     return secp256k1_ec_seckey_verify(secp256k1_context_sign, vch);
 123 }
 124
 125 void CKey::MakeNewKey(bool fCompressedIn) {
 126     do {
 127         GetStrongRandBytes(keydata.data(), keydata.size());
 128     } while (!Check(keydata.data()));
 129     fValid = true;
 130     fCompressed = fCompressedIn;
 131 }
 132
 133 CPrivKey CKey::GetPrivKey() const {
 134     assert(fValid);
 135     CPrivKey privkey;
 136     int ret;
 137     size_t privkeylen;
 138     privkey.resize(279);
 139     privkeylen = 279;
 140     ret = ec_privkey_export_der(secp256k1_context_sign, (unsigned char*) privkey.data(), &privkeylen, begin(), fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
 141     assert(ret);
 142     privkey.resize(privkeylen);
 143     return privkey;
 144 }
 145
 146 CPubKey CKey::GetPubKey() const {
 147     assert(fValid);
 148     secp256k1_pubkey pubkey;
 149     size_t clen = 65;
 150     CPubKey result;
 151     int ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &pubkey, begin());
 152     assert(ret);
 153     secp256k1_ec_pubkey_serialize(secp256k1_context_sign, (unsigned char*)result.begin(), &clen, &pubkey, fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
 154     assert(result.size() == clen);
 155     assert(result.IsValid());
 156     return result;
 157 }
 158
 159 bool CKey::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig, uint32_t test_case) const {
 160     if (!fValid)
 161         return false;
 162     vchSig.resize(72);
 163     size_t nSigLen = 72;
 164     unsigned char extra_entropy[32] = {0};
 165     WriteLE32(extra_entropy, test_case);
 166     secp256k1_ecdsa_signature sig;
 167     int ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, test_case ? extra_entropy : nullptr);
 168     assert(ret);
 169     secp256k1_ecdsa_signature_serialize_der(secp256k1_context_sign, (unsigned char*)vchSig.data(), &nSigLen, &sig);
 170     vchSig.resize(nSigLen);
 171     return true;
 172 }
 173
 174 bool CKey::VerifyPubKey(const CPubKey& pubkey) const {
 175     if (pubkey.IsCompressed() != fCompressed) {
 176         return false;
 177     }
 178     unsigned char rnd[8];
 179     std::string str = "Bitcoin key verification\n";
 180     GetRandBytes(rnd, sizeof(rnd));
 181     uint256 hash;
 182     CHash256().Write((unsigned char*)str.data(), str.size()).Write(rnd, sizeof(rnd)).Finalize(hash.begin());
 183     std::vector<unsigned char> vchSig;
 184     Sign(hash, vchSig);
 185     return pubkey.Verify(hash, vchSig);
 186 }
 187
 188 bool CKey::SignCompact(const uint256 &hash, std::vector<unsigned char>& vchSig) const {
 189     if (!fValid)
 190         return false;
 191     vchSig.resize(65);
 192     int rec = -1;
 193     secp256k1_ecdsa_recoverable_signature sig;
 194     int ret = secp256k1_ecdsa_sign_recoverable(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, nullptr);
 195     assert(ret);
 196     secp256k1_ecdsa_recoverable_signature_serialize_compact(secp256k1_context_sign, (unsigned char*)&vchSig[1], &rec, &sig);
 197     assert(ret);
 198     assert(rec != -1);
 199     vchSig[0] = 27 + rec + (fCompressed ? 4 : 0);
 200     return true;
 201 }
 202
 203 bool CKey::Load(CPrivKey &privkey, CPubKey &vchPubKey, bool fSkipCheck=false) {
 204     if (!ec_privkey_import_der(secp256k1_context_sign, (unsigned char*)begin(), privkey.data(), privkey.size()))
 205         return false;
 206     fCompressed = vchPubKey.IsCompressed();
 207     fValid = true;
 208
 209     if (fSkipCheck)
 210         return true;
 211
 212     return VerifyPubKey(vchPubKey);
 213 }
 214
 215 bool CKey::Derive(CKey& keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {
 216     assert(IsValid());
 217     assert(IsCompressed());
 218     std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
 219     if ((nChild >> 31) == 0) {
 220         CPubKey pubkey = GetPubKey();
 221         assert(pubkey.begin() + 33 == pubkey.end());
 222         BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin()+1, vout.data());
 223     } else {
 224         assert(begin() + 32 == end());
 225         BIP32Hash(cc, nChild, 0, begin(), vout.data());
 226     }
 227     memcpy(ccChild.begin(), vout.data()+32, 32);
 228     memcpy((unsigned char*)keyChild.begin(), begin(), 32);
 229     bool ret = secp256k1_ec_privkey_tweak_add(secp256k1_context_sign, (unsigned char*)keyChild.begin(), vout.data());
 230     keyChild.fCompressed = true;
 231     keyChild.fValid = ret;
 232     return ret;
 233 }
 234
 235 bool CExtKey::Derive(CExtKey &out, unsigned int _nChild) const {
 236     out.nDepth = nDepth + 1;
 237     CKeyID id = key.GetPubKey().GetID();
 238     memcpy(&out.vchFingerprint[0], &id, 4);
 239     out.nChild = _nChild;
 240     return key.Derive(out.key, out.chaincode, _nChild, chaincode);
 241 }
 242
 243 void CExtKey::SetMaster(const unsigned char *seed, unsigned int nSeedLen) {
 244     static const unsigned char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'};
 245     std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
 246     CHMAC_SHA512(hashkey, sizeof(hashkey)).Write(seed, nSeedLen).Finalize(vout.data());
 247     key.Set(vout.data(), vout.data() + 32, true);
 248     memcpy(chaincode.begin(), vout.data() + 32, 32);
 249     nDepth = 0;
 250     nChild = 0;
 251     memset(vchFingerprint, 0, sizeof(vchFingerprint));
 252 }
 253
 254 CExtPubKey CExtKey::Neuter() const {
 255     CExtPubKey ret;
 256     ret.nDepth = nDepth;
 257     memcpy(&ret.vchFingerprint[0], &vchFingerprint[0], 4);
 258     ret.nChild = nChild;
 259     ret.pubkey = key.GetPubKey();
 260     ret.chaincode = chaincode;
 261     return ret;
 262 }
 263
 264 void CExtKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
 265     code[0] = nDepth;
 266     memcpy(code+1, vchFingerprint, 4);
 267     code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF;
 268     code[7] = (nChild >>  8) & 0xFF; code[8] = (nChild >>  0) & 0xFF;
 269     memcpy(code+9, chaincode.begin(), 32);
 270     code[41] = 0;
 271     assert(key.size() == 32);
 272     memcpy(code+42, key.begin(), 32);
 273 }
 274
 275 void CExtKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
 276     nDepth = code[0];
 277     memcpy(vchFingerprint, code+1, 4);
 278     nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
 279     memcpy(chaincode.begin(), code+9, 32);
 280     key.Set(code+42, code+BIP32_EXTKEY_SIZE, true);
 281 }
 282
 283 bool ECC_InitSanityCheck() {
 284     CKey key;
 285     key.MakeNewKey(true);
 286     CPubKey pubkey = key.GetPubKey();
 287     return key.VerifyPubKey(pubkey);
 288 }
 289
 290 void ECC_Start() {
 291     assert(secp256k1_context_sign == nullptr);
 292
 293     secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
 294     assert(ctx != nullptr);
 295
 296     {
 297         // Pass in a random blinding seed to the secp256k1 context.
 298         std::vector<unsigned char, secure_allocator<unsigned char>> vseed(32);
 299         GetRandBytes(vseed.data(), 32);
 300         bool ret = secp256k1_context_randomize(ctx, vseed.data());
 301         assert(ret);
 302     }
 303
 304     secp256k1_context_sign = ctx;
 305 }
 306
 307 void ECC_Stop() {
 308     secp256k1_context *ctx = secp256k1_context_sign;
 309     secp256k1_context_sign = nullptr;
 310
 311     if (ctx) {
 312         secp256k1_context_destroy(ctx);
 313     }
 314 }