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 "pubkey.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 static int ec_privkey_import_der(const secp256k1_context* ctx, unsigned char *out32, const unsigned char *privkey, size_t privkeylen) {
  20     const unsigned char *end = privkey + privkeylen;
  21     int lenb = 0;
  22     int len = 0;
  23     memset(out32, 0, 32);
  24     /* sequence header */
  25     if (end < privkey+1 || *privkey != 0x30) {
  26         return 0;
  27     }
  28     privkey++;
  29     /* sequence length constructor */
  30     if (end < privkey+1 || !(*privkey & 0x80)) {
  31         return 0;
  32     }
  33     lenb = *privkey & ~0x80; privkey++;
  34     if (lenb < 1 || lenb > 2) {
  35         return 0;
  36     }
  37     if (end < privkey+lenb) {
  38         return 0;
  39     }
  40     /* sequence length */
  41     len = privkey[lenb-1] | (lenb > 1 ? privkey[lenb-2] << 8 : 0);
  42     privkey += lenb;
  43     if (end < privkey+len) {
  44         return 0;
  45     }
  46     /* sequence element 0: version number (=1) */
  47     if (end < privkey+3 || privkey[0] != 0x02 || privkey[1] != 0x01 || privkey[2] != 0x01) {
  48         return 0;
  49     }
  50     privkey += 3;
  51     /* sequence element 1: octet string, up to 32 bytes */
  52     if (end < privkey+2 || privkey[0] != 0x04 || privkey[1] > 0x20 || end < privkey+2+privkey[1]) {
  53         return 0;
  54     }
  55     memcpy(out32 + 32 - privkey[1], privkey + 2, privkey[1]);
  56     if (!secp256k1_ec_seckey_verify(ctx, out32)) {
  57         memset(out32, 0, 32);
  58         return 0;
  59     }
  60     return 1;
  61 }
  62
  63 static int ec_privkey_export_der(const secp256k1_context *ctx, unsigned char *privkey, size_t *privkeylen, const unsigned char *key32, int compressed) {
  64     secp256k1_pubkey pubkey;
  65     size_t pubkeylen = 0;
  66     if (!secp256k1_ec_pubkey_create(ctx, &pubkey, key32)) {
  67         *privkeylen = 0;
  68         return 0;
  69     }
  70     if (compressed) {
  71         static const unsigned char begin[] = {
  72             0x30,0x81,0xD3,0x02,0x01,0x01,0x04,0x20
  73         };
  74         static const unsigned char middle[] = {
  75             0xA0,0x81,0x85,0x30,0x81,0x82,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
  76             0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
  77             0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
  78             0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
  79             0x21,0x02,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
  80             0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
  81             0x17,0x98,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
  82             0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
  83             0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x24,0x03,0x22,0x00
  84         };
  85         unsigned char *ptr = privkey;
  86         memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
  87         memcpy(ptr, key32, 32); ptr += 32;
  88         memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
  89         pubkeylen = 33;
  90         secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_COMPRESSED);
  91         ptr += pubkeylen;
  92         *privkeylen = ptr - privkey;
  93     } else {
  94         static const unsigned char begin[] = {
  95             0x30,0x82,0x01,0x13,0x02,0x01,0x01,0x04,0x20
  96         };
  97         static const unsigned char middle[] = {
  98             0xA0,0x81,0xA5,0x30,0x81,0xA2,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
  99             0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
 100             0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
 101             0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
 102             0x41,0x04,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
 103             0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
 104             0x17,0x98,0x48,0x3A,0xDA,0x77,0x26,0xA3,0xC4,0x65,0x5D,0xA4,0xFB,0xFC,0x0E,0x11,
 105             0x08,0xA8,0xFD,0x17,0xB4,0x48,0xA6,0x85,0x54,0x19,0x9C,0x47,0xD0,0x8F,0xFB,0x10,
 106             0xD4,0xB8,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
 107             0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
 108             0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x44,0x03,0x42,0x00
 109         };
 110         unsigned char *ptr = privkey;
 111         memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
 112         memcpy(ptr, key32, 32); ptr += 32;
 113         memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
 114         pubkeylen = 65;
 115         secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
 116         ptr += pubkeylen;
 117         *privkeylen = ptr - privkey;
 118     }
 119     return 1;
 120 }
 121
 122 bool CKey::Check(const unsigned char *vch) {
 123     return secp256k1_ec_seckey_verify(secp256k1_context_sign, vch);
 124 }
 125
 126 void CKey::MakeNewKey(bool fCompressedIn) {
 127     do {
 128         GetStrongRandBytes(keydata.data(), keydata.size());
 129     } while (!Check(keydata.data()));
 130     fValid = true;
 131     fCompressed = fCompressedIn;
 132 }
 133
 134 CPrivKey CKey::GetPrivKey() const {
 135     assert(fValid);
 136     CPrivKey privkey;
 137     int ret;
 138     size_t privkeylen;
 139     privkey.resize(279);
 140     privkeylen = 279;
 141     ret = ec_privkey_export_der(secp256k1_context_sign, (unsigned char*) privkey.data(), &privkeylen, begin(), fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
 142     assert(ret);
 143     privkey.resize(privkeylen);
 144     return privkey;
 145 }
 146
 147 CPubKey CKey::GetPubKey() const {
 148     assert(fValid);
 149     secp256k1_pubkey pubkey;
 150     size_t clen = 65;
 151     CPubKey result;
 152     int ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &pubkey, begin());
 153     assert(ret);
 154     secp256k1_ec_pubkey_serialize(secp256k1_context_sign, (unsigned char*)result.begin(), &clen, &pubkey, fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
 155     assert(result.size() == clen);
 156     assert(result.IsValid());
 157     return result;
 158 }
 159
 160 bool CKey::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig, uint32_t test_case) const {
 161     if (!fValid)
 162         return false;
 163     vchSig.resize(72);
 164     size_t nSigLen = 72;
 165     unsigned char extra_entropy[32] = {0};
 166     WriteLE32(extra_entropy, test_case);
 167     secp256k1_ecdsa_signature sig;
 168     int ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, test_case ? extra_entropy : nullptr);
 169     assert(ret);
 170     secp256k1_ecdsa_signature_serialize_der(secp256k1_context_sign, (unsigned char*)vchSig.data(), &nSigLen, &sig);
 171     vchSig.resize(nSigLen);
 172     return true;
 173 }
 174
 175 bool CKey::VerifyPubKey(const CPubKey& pubkey) const {
 176     if (pubkey.IsCompressed() != fCompressed) {
 177         return false;
 178     }
 179     unsigned char rnd[8];
 180     std::string str = "Bitcoin key verification\n";
 181     GetRandBytes(rnd, sizeof(rnd));
 182     uint256 hash;
 183     CHash256().Write((unsigned char*)str.data(), str.size()).Write(rnd, sizeof(rnd)).Finalize(hash.begin());
 184     std::vector<unsigned char> vchSig;
 185     Sign(hash, vchSig);
 186     return pubkey.Verify(hash, vchSig);
 187 }
 188
 189 bool CKey::SignCompact(const uint256 &hash, std::vector<unsigned char>& vchSig) const {
 190     if (!fValid)
 191         return false;
 192     vchSig.resize(65);
 193     int rec = -1;
 194     secp256k1_ecdsa_recoverable_signature sig;
 195     int ret = secp256k1_ecdsa_sign_recoverable(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, nullptr);
 196     assert(ret);
 197     secp256k1_ecdsa_recoverable_signature_serialize_compact(secp256k1_context_sign, (unsigned char*)&vchSig[1], &rec, &sig);
 198     assert(ret);
 199     assert(rec != -1);
 200     vchSig[0] = 27 + rec + (fCompressed ? 4 : 0);
 201     return true;
 202 }
 203
 204 bool CKey::Load(CPrivKey &privkey, CPubKey &vchPubKey, bool fSkipCheck=false) {
 205     if (!ec_privkey_import_der(secp256k1_context_sign, (unsigned char*)begin(), privkey.data(), privkey.size()))
 206         return false;
 207     fCompressed = vchPubKey.IsCompressed();
 208     fValid = true;
 209
 210     if (fSkipCheck)
 211         return true;
 212
 213     return VerifyPubKey(vchPubKey);
 214 }
 215
 216 bool CKey::Derive(CKey& keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {
 217     assert(IsValid());
 218     assert(IsCompressed());
 219     std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
 220     if ((nChild >> 31) == 0) {
 221         CPubKey pubkey = GetPubKey();
 222         assert(pubkey.begin() + 33 == pubkey.end());
 223         BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin()+1, vout.data());
 224     } else {
 225         assert(begin() + 32 == end());
 226         BIP32Hash(cc, nChild, 0, begin(), vout.data());
 227     }
 228     memcpy(ccChild.begin(), vout.data()+32, 32);
 229     memcpy((unsigned char*)keyChild.begin(), begin(), 32);
 230     bool ret = secp256k1_ec_privkey_tweak_add(secp256k1_context_sign, (unsigned char*)keyChild.begin(), vout.data());
 231     keyChild.fCompressed = true;
 232     keyChild.fValid = ret;
 233     return ret;
 234 }
 235
 236 bool CExtKey::Derive(CExtKey &out, unsigned int _nChild) const {
 237     out.nDepth = nDepth + 1;
 238     CKeyID id = key.GetPubKey().GetID();
 239     memcpy(&out.vchFingerprint[0], &id, 4);
 240     out.nChild = _nChild;
 241     return key.Derive(out.key, out.chaincode, _nChild, chaincode);
 242 }
 243
 244 void CExtKey::SetMaster(const unsigned char *seed, unsigned int nSeedLen) {
 245     static const unsigned char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'};
 246     std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
 247     CHMAC_SHA512(hashkey, sizeof(hashkey)).Write(seed, nSeedLen).Finalize(vout.data());
 248     key.Set(vout.data(), vout.data() + 32, true);
 249     memcpy(chaincode.begin(), vout.data() + 32, 32);
 250     nDepth = 0;
 251     nChild = 0;
 252     memset(vchFingerprint, 0, sizeof(vchFingerprint));
 253 }
 254
 255 CExtPubKey CExtKey::Neuter() const {
 256     CExtPubKey ret;
 257     ret.nDepth = nDepth;
 258     memcpy(&ret.vchFingerprint[0], &vchFingerprint[0], 4);
 259     ret.nChild = nChild;
 260     ret.pubkey = key.GetPubKey();
 261     ret.chaincode = chaincode;
 262     return ret;
 263 }
 264
 265 void CExtKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
 266     code[0] = nDepth;
 267     memcpy(code+1, vchFingerprint, 4);
 268     code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF;
 269     code[7] = (nChild >>  8) & 0xFF; code[8] = (nChild >>  0) & 0xFF;
 270     memcpy(code+9, chaincode.begin(), 32);
 271     code[41] = 0;
 272     assert(key.size() == 32);
 273     memcpy(code+42, key.begin(), 32);
 274 }
 275
 276 void CExtKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
 277     nDepth = code[0];
 278     memcpy(vchFingerprint, code+1, 4);
 279     nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
 280     memcpy(chaincode.begin(), code+9, 32);
 281     key.Set(code+42, code+BIP32_EXTKEY_SIZE, true);
 282 }
 283
 284 bool ECC_InitSanityCheck() {
 285     CKey key;
 286     key.MakeNewKey(true);
 287     CPubKey pubkey = key.GetPubKey();
 288     return key.VerifyPubKey(pubkey);
 289 }
 290
 291 void ECC_Start() {
 292     assert(secp256k1_context_sign == nullptr);
 293
 294     secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
 295     assert(ctx != nullptr);
 296
 297     {
 298         // Pass in a random blinding seed to the secp256k1 context.
 299         std::vector<unsigned char, secure_allocator<unsigned char>> vseed(32);
 300         GetRandBytes(vseed.data(), 32);
 301         bool ret = secp256k1_context_randomize(ctx, vseed.data());
 302         assert(ret);
 303     }
 304
 305     secp256k1_context_sign = ctx;
 306 }
 307
 308 void ECC_Stop() {
 309     secp256k1_context *ctx = secp256k1_context_sign;
 310     secp256k1_context_sign = nullptr;
 311
 312     if (ctx) {
 313         secp256k1_context_destroy(ctx);
 314     }
 315 }