src/key.cpp

   1 // Copyright (c) 2009-2017 The Bitcoin Core developers
   2 // Copyright (c) 2017 The Zcash developers
   3 // Distributed under the MIT software license, see the accompanying
   4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #include <key.h>
   7
   8 #include <arith_uint256.h>
   9 #include <crypto/common.h>
  10 #include <crypto/hmac_sha512.h>
  11 #include <random.h>
  12
  13 #include <secp256k1.h>
  14 #include <secp256k1_recovery.h>
  15
  16 static secp256k1_context* secp256k1_context_sign = nullptr;
  17
  18 /** These functions are taken from the libsecp256k1 distribution and are very ugly. */
  19
  20 /**
  21  * This parses a format loosely based on a DER encoding of the ECPrivateKey type from
  22  * section C.4 of SEC 1 <http://www.secg.org/sec1-v2.pdf>, with the following caveats:
  23  *
  24  * * The octet-length of the SEQUENCE must be encoded as 1 or 2 octets. It is not
  25  *   required to be encoded as one octet if it is less than 256, as DER would require.
  26  * * The octet-length of the SEQUENCE must not be greater than the remaining
  27  *   length of the key encoding, but need not match it (i.e. the encoding may contain
  28  *   junk after the encoded SEQUENCE).
  29  * * The privateKey OCTET STRING is zero-filled on the left to 32 octets.
  30  * * Anything after the encoding of the privateKey OCTET STRING is ignored, whether
  31  *   or not it is validly encoded DER.
  32  *
  33  * out32 must point to an output buffer of length at least 32 bytes.
  34  */
  35 static int ec_privkey_import_der(const secp256k1_context* ctx, unsigned char *out32, const unsigned char *privkey, size_t privkeylen) {
  36     const unsigned char *end = privkey + privkeylen;
  37     memset(out32, 0, 32);
  38     /* sequence header */
  39     if (end - privkey < 1 || *privkey != 0x30u) {
  40         return 0;
  41     }
  42     privkey++;
  43     /* sequence length constructor */
  44     if (end - privkey < 1 || !(*privkey & 0x80u)) {
  45         return 0;
  46     }
  47     size_t lenb = *privkey & ~0x80u; privkey++;
  48     if (lenb < 1 || lenb > 2) {
  49         return 0;
  50     }
  51     if (end - privkey < lenb) {
  52         return 0;
  53     }
  54     /* sequence length */
  55     size_t len = privkey[lenb-1] | (lenb > 1 ? privkey[lenb-2] << 8 : 0u);
  56     privkey += lenb;
  57     if (end - privkey < len) {
  58         return 0;
  59     }
  60     /* sequence element 0: version number (=1) */
  61     if (end - privkey < 3 || privkey[0] != 0x02u || privkey[1] != 0x01u || privkey[2] != 0x01u) {
  62         return 0;
  63     }
  64     privkey += 3;
  65     /* sequence element 1: octet string, up to 32 bytes */
  66     if (end - privkey < 2 || privkey[0] != 0x04u) {
  67         return 0;
  68     }
  69     size_t oslen = privkey[1];
  70     privkey += 2;
  71     if (oslen > 32 || end - privkey < oslen) {
  72         return 0;
  73     }
  74     memcpy(out32 + (32 - oslen), privkey, oslen);
  75     if (!secp256k1_ec_seckey_verify(ctx, out32)) {
  76         memset(out32, 0, 32);
  77         return 0;
  78     }
  79     return 1;
  80 }
  81
  82 /**
  83  * This serializes to a DER encoding of the ECPrivateKey type from section C.4 of SEC 1
  84  * <http://www.secg.org/sec1-v2.pdf>. The optional parameters and publicKey fields are
  85  * included.
  86  *
  87  * privkey must point to an output buffer of length at least CKey::PRIVATE_KEY_SIZE bytes.
  88  * privkeylen must initially be set to the size of the privkey buffer. Upon return it
  89  * will be set to the number of bytes used in the buffer.
  90  * key32 must point to a 32-byte raw private key.
  91  */
  92 static int ec_privkey_export_der(const secp256k1_context *ctx, unsigned char *privkey, size_t *privkeylen, const unsigned char *key32, int compressed) {
  93     assert(*privkeylen >= CKey::PRIVATE_KEY_SIZE);
  94     secp256k1_pubkey pubkey;
  95     size_t pubkeylen = 0;
  96     if (!secp256k1_ec_pubkey_create(ctx, &pubkey, key32)) {
  97         *privkeylen = 0;
  98         return 0;
  99     }
 100     if (compressed) {
 101         static const unsigned char begin[] = {
 102             0x30,0x81,0xD3,0x02,0x01,0x01,0x04,0x20
 103         };
 104         static const unsigned char middle[] = {
 105             0xA0,0x81,0x85,0x30,0x81,0x82,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
 106             0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
 107             0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
 108             0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
 109             0x21,0x02,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
 110             0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
 111             0x17,0x98,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
 112             0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
 113             0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x24,0x03,0x22,0x00
 114         };
 115         unsigned char *ptr = privkey;
 116         memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
 117         memcpy(ptr, key32, 32); ptr += 32;
 118         memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
 119         pubkeylen = CPubKey::COMPRESSED_PUBLIC_KEY_SIZE;
 120         secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_COMPRESSED);
 121         ptr += pubkeylen;
 122         *privkeylen = ptr - privkey;
 123         assert(*privkeylen == CKey::COMPRESSED_PRIVATE_KEY_SIZE);
 124     } else {
 125         static const unsigned char begin[] = {
 126             0x30,0x82,0x01,0x13,0x02,0x01,0x01,0x04,0x20
 127         };
 128         static const unsigned char middle[] = {
 129             0xA0,0x81,0xA5,0x30,0x81,0xA2,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
 130             0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
 131             0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
 132             0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
 133             0x41,0x04,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
 134             0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
 135             0x17,0x98,0x48,0x3A,0xDA,0x77,0x26,0xA3,0xC4,0x65,0x5D,0xA4,0xFB,0xFC,0x0E,0x11,
 136             0x08,0xA8,0xFD,0x17,0xB4,0x48,0xA6,0x85,0x54,0x19,0x9C,0x47,0xD0,0x8F,0xFB,0x10,
 137             0xD4,0xB8,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
 138             0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
 139             0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x44,0x03,0x42,0x00
 140         };
 141         unsigned char *ptr = privkey;
 142         memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
 143         memcpy(ptr, key32, 32); ptr += 32;
 144         memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
 145         pubkeylen = CPubKey::PUBLIC_KEY_SIZE;
 146         secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
 147         ptr += pubkeylen;
 148         *privkeylen = ptr - privkey;
 149         assert(*privkeylen == CKey::PRIVATE_KEY_SIZE);
 150     }
 151     return 1;
 152 }
 153
 154 bool CKey::Check(const unsigned char *vch) {
 155     return secp256k1_ec_seckey_verify(secp256k1_context_sign, vch);
 156 }
 157
 158 void CKey::MakeNewKey(bool fCompressedIn) {
 159     do {
 160         GetStrongRandBytes(keydata.data(), keydata.size());
 161     } while (!Check(keydata.data()));
 162     fValid = true;
 163     fCompressed = fCompressedIn;
 164 }
 165
 166 CPrivKey CKey::GetPrivKey() const {
 167     assert(fValid);
 168     CPrivKey privkey;
 169     int ret;
 170     size_t privkeylen;
 171     privkey.resize(PRIVATE_KEY_SIZE);
 172     privkeylen = PRIVATE_KEY_SIZE;
 173     ret = ec_privkey_export_der(secp256k1_context_sign, (unsigned char*) privkey.data(), &privkeylen, begin(), fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
 174     assert(ret);
 175     privkey.resize(privkeylen);
 176     return privkey;
 177 }
 178
 179 CPubKey CKey::GetPubKey() const {
 180     assert(fValid);
 181     secp256k1_pubkey pubkey;
 182     size_t clen = CPubKey::PUBLIC_KEY_SIZE;
 183     CPubKey result;
 184     int ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &pubkey, begin());
 185     assert(ret);
 186     secp256k1_ec_pubkey_serialize(secp256k1_context_sign, (unsigned char*)result.begin(), &clen, &pubkey, fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
 187     assert(result.size() == clen);
 188     assert(result.IsValid());
 189     return result;
 190 }
 191
 192 bool CKey::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig, uint32_t test_case) const {
 193     if (!fValid)
 194         return false;
 195     vchSig.resize(CPubKey::SIGNATURE_SIZE);
 196     size_t nSigLen = CPubKey::SIGNATURE_SIZE;
 197     unsigned char extra_entropy[32] = {0};
 198     WriteLE32(extra_entropy, test_case);
 199     secp256k1_ecdsa_signature sig;
 200     int ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, test_case ? extra_entropy : nullptr);
 201     assert(ret);
 202     secp256k1_ecdsa_signature_serialize_der(secp256k1_context_sign, (unsigned char*)vchSig.data(), &nSigLen, &sig);
 203     vchSig.resize(nSigLen);
 204     return true;
 205 }
 206
 207 bool CKey::VerifyPubKey(const CPubKey& pubkey) const {
 208     if (pubkey.IsCompressed() != fCompressed) {
 209         return false;
 210     }
 211     unsigned char rnd[8];
 212     std::string str = "Bitcoin key verification\n";
 213     GetRandBytes(rnd, sizeof(rnd));
 214     uint256 hash;
 215     CHash256().Write((unsigned char*)str.data(), str.size()).Write(rnd, sizeof(rnd)).Finalize(hash.begin());
 216     std::vector<unsigned char> vchSig;
 217     Sign(hash, vchSig);
 218     return pubkey.Verify(hash, vchSig);
 219 }
 220
 221 bool CKey::SignCompact(const uint256 &hash, std::vector<unsigned char>& vchSig) const {
 222     if (!fValid)
 223         return false;
 224     vchSig.resize(CPubKey::COMPACT_SIGNATURE_SIZE);
 225     int rec = -1;
 226     secp256k1_ecdsa_recoverable_signature sig;
 227     int ret = secp256k1_ecdsa_sign_recoverable(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, nullptr);
 228     assert(ret);
 229     secp256k1_ecdsa_recoverable_signature_serialize_compact(secp256k1_context_sign, (unsigned char*)&vchSig[1], &rec, &sig);
 230     assert(ret);
 231     assert(rec != -1);
 232     vchSig[0] = 27 + rec + (fCompressed ? 4 : 0);
 233     return true;
 234 }
 235
 236 bool CKey::Load(CPrivKey &privkey, CPubKey &vchPubKey, bool fSkipCheck=false) {
 237     if (!ec_privkey_import_der(secp256k1_context_sign, (unsigned char*)begin(), privkey.data(), privkey.size()))
 238         return false;
 239     fCompressed = vchPubKey.IsCompressed();
 240     fValid = true;
 241
 242     if (fSkipCheck)
 243         return true;
 244
 245     return VerifyPubKey(vchPubKey);
 246 }
 247
 248 bool CKey::Derive(CKey& keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {
 249     assert(IsValid());
 250     assert(IsCompressed());
 251     std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
 252     if ((nChild >> 31) == 0) {
 253         CPubKey pubkey = GetPubKey();
 254         assert(pubkey.size() == CPubKey::COMPRESSED_PUBLIC_KEY_SIZE);
 255         BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin()+1, vout.data());
 256     } else {
 257         assert(size() == 32);
 258         BIP32Hash(cc, nChild, 0, begin(), vout.data());
 259     }
 260     memcpy(ccChild.begin(), vout.data()+32, 32);
 261     memcpy((unsigned char*)keyChild.begin(), begin(), 32);
 262     bool ret = secp256k1_ec_privkey_tweak_add(secp256k1_context_sign, (unsigned char*)keyChild.begin(), vout.data());
 263     keyChild.fCompressed = true;
 264     keyChild.fValid = ret;
 265     return ret;
 266 }
 267
 268 bool CExtKey::Derive(CExtKey &out, unsigned int _nChild) const {
 269     out.nDepth = nDepth + 1;
 270     CKeyID id = key.GetPubKey().GetID();
 271     memcpy(&out.vchFingerprint[0], &id, 4);
 272     out.nChild = _nChild;
 273     return key.Derive(out.key, out.chaincode, _nChild, chaincode);
 274 }
 275
 276 void CExtKey::SetMaster(const unsigned char *seed, unsigned int nSeedLen) {
 277     static const unsigned char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'};
 278     std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
 279     CHMAC_SHA512(hashkey, sizeof(hashkey)).Write(seed, nSeedLen).Finalize(vout.data());
 280     key.Set(vout.data(), vout.data() + 32, true);
 281     memcpy(chaincode.begin(), vout.data() + 32, 32);
 282     nDepth = 0;
 283     nChild = 0;
 284     memset(vchFingerprint, 0, sizeof(vchFingerprint));
 285 }
 286
 287 CExtPubKey CExtKey::Neuter() const {
 288     CExtPubKey ret;
 289     ret.nDepth = nDepth;
 290     memcpy(&ret.vchFingerprint[0], &vchFingerprint[0], 4);
 291     ret.nChild = nChild;
 292     ret.pubkey = key.GetPubKey();
 293     ret.chaincode = chaincode;
 294     return ret;
 295 }
 296
 297 void CExtKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
 298     code[0] = nDepth;
 299     memcpy(code+1, vchFingerprint, 4);
 300     code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF;
 301     code[7] = (nChild >>  8) & 0xFF; code[8] = (nChild >>  0) & 0xFF;
 302     memcpy(code+9, chaincode.begin(), 32);
 303     code[41] = 0;
 304     assert(key.size() == 32);
 305     memcpy(code+42, key.begin(), 32);
 306 }
 307
 308 void CExtKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
 309     nDepth = code[0];
 310     memcpy(vchFingerprint, code+1, 4);
 311     nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
 312     memcpy(chaincode.begin(), code+9, 32);
 313     key.Set(code+42, code+BIP32_EXTKEY_SIZE, true);
 314 }
 315
 316 bool ECC_InitSanityCheck() {
 317     CKey key;
 318     key.MakeNewKey(true);
 319     CPubKey pubkey = key.GetPubKey();
 320     return key.VerifyPubKey(pubkey);
 321 }
 322
 323 void ECC_Start() {
 324     assert(secp256k1_context_sign == nullptr);
 325
 326     secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
 327     assert(ctx != nullptr);
 328
 329     {
 330         // Pass in a random blinding seed to the secp256k1 context.
 331         std::vector<unsigned char, secure_allocator<unsigned char>> vseed(32);
 332         GetRandBytes(vseed.data(), 32);
 333         bool ret = secp256k1_context_randomize(ctx, vseed.data());
 334         assert(ret);
 335     }
 336
 337     secp256k1_context_sign = ctx;
 338 }
 339
 340 void ECC_Stop() {
 341     secp256k1_context *ctx = secp256k1_context_sign;
 342     secp256k1_context_sign = nullptr;
 343
 344     if (ctx) {
 345         secp256k1_context_destroy(ctx);
 346     }
 347 }