// Copyright (c) 2009-2020 The Bitcoin Core developers // Copyright (c) 2017 The Zcash developers // Distributed under the MIT software license, see the accompanying // file COPYING or http://www.opensource.org/licenses/mit-license.php. #include #include #include #include #include #include #include static secp256k1_context* secp256k1_context_sign = nullptr; /** These functions are taken from the libsecp256k1 distribution and are very ugly. */ /** * This parses a format loosely based on a DER encoding of the ECPrivateKey type from * section C.4 of SEC 1 , with the following caveats: * * * The octet-length of the SEQUENCE must be encoded as 1 or 2 octets. It is not * required to be encoded as one octet if it is less than 256, as DER would require. * * The octet-length of the SEQUENCE must not be greater than the remaining * length of the key encoding, but need not match it (i.e. the encoding may contain * junk after the encoded SEQUENCE). * * The privateKey OCTET STRING is zero-filled on the left to 32 octets. * * Anything after the encoding of the privateKey OCTET STRING is ignored, whether * or not it is validly encoded DER. * * out32 must point to an output buffer of length at least 32 bytes. */ int ec_seckey_import_der(const secp256k1_context* ctx, unsigned char *out32, const unsigned char *seckey, size_t seckeylen) { const unsigned char *end = seckey + seckeylen; memset(out32, 0, 32); /* sequence header */ if (end - seckey < 1 || *seckey != 0x30u) { return 0; } seckey++; /* sequence length constructor */ if (end - seckey < 1 || !(*seckey & 0x80u)) { return 0; } ptrdiff_t lenb = *seckey & ~0x80u; seckey++; if (lenb < 1 || lenb > 2) { return 0; } if (end - seckey < lenb) { return 0; } /* sequence length */ ptrdiff_t len = seckey[lenb-1] | (lenb > 1 ? seckey[lenb-2] << 8 : 0u); seckey += lenb; if (end - seckey < len) { return 0; } /* sequence element 0: version number (=1) */ if (end - seckey < 3 || seckey[0] != 0x02u || seckey[1] != 0x01u || seckey[2] != 0x01u) { return 0; } seckey += 3; /* sequence element 1: octet string, up to 32 bytes */ if (end - seckey < 2 || seckey[0] != 0x04u) { return 0; } ptrdiff_t oslen = seckey[1]; seckey += 2; if (oslen > 32 || end - seckey < oslen) { return 0; } memcpy(out32 + (32 - oslen), seckey, oslen); if (!secp256k1_ec_seckey_verify(ctx, out32)) { memset(out32, 0, 32); return 0; } return 1; } /** * This serializes to a DER encoding of the ECPrivateKey type from section C.4 of SEC 1 * . The optional parameters and publicKey fields are * included. * * seckey must point to an output buffer of length at least CKey::SIZE bytes. * seckeylen must initially be set to the size of the seckey buffer. Upon return it * will be set to the number of bytes used in the buffer. * key32 must point to a 32-byte raw private key. */ int ec_seckey_export_der(const secp256k1_context *ctx, unsigned char *seckey, size_t *seckeylen, const unsigned char *key32, bool compressed) { assert(*seckeylen >= CKey::SIZE); secp256k1_pubkey pubkey; size_t pubkeylen = 0; if (!secp256k1_ec_pubkey_create(ctx, &pubkey, key32)) { *seckeylen = 0; return 0; } if (compressed) { static const unsigned char begin[] = { 0x30,0x81,0xD3,0x02,0x01,0x01,0x04,0x20 }; static const unsigned char middle[] = { 0xA0,0x81,0x85,0x30,0x81,0x82,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48, 0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, 0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04, 0x21,0x02,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87, 0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8, 0x17,0x98,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, 0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E, 0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x24,0x03,0x22,0x00 }; unsigned char *ptr = seckey; memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin); memcpy(ptr, key32, 32); ptr += 32; memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle); pubkeylen = CPubKey::COMPRESSED_SIZE; secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_COMPRESSED); ptr += pubkeylen; *seckeylen = ptr - seckey; assert(*seckeylen == CKey::COMPRESSED_SIZE); } else { static const unsigned char begin[] = { 0x30,0x82,0x01,0x13,0x02,0x01,0x01,0x04,0x20 }; static const unsigned char middle[] = { 0xA0,0x81,0xA5,0x30,0x81,0xA2,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48, 0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, 0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04, 0x41,0x04,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87, 0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8, 0x17,0x98,0x48,0x3A,0xDA,0x77,0x26,0xA3,0xC4,0x65,0x5D,0xA4,0xFB,0xFC,0x0E,0x11, 0x08,0xA8,0xFD,0x17,0xB4,0x48,0xA6,0x85,0x54,0x19,0x9C,0x47,0xD0,0x8F,0xFB,0x10, 0xD4,0xB8,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, 0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E, 0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x44,0x03,0x42,0x00 }; unsigned char *ptr = seckey; memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin); memcpy(ptr, key32, 32); ptr += 32; memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle); pubkeylen = CPubKey::SIZE; secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_UNCOMPRESSED); ptr += pubkeylen; *seckeylen = ptr - seckey; assert(*seckeylen == CKey::SIZE); } return 1; } bool CKey::Check(const unsigned char *vch) { return secp256k1_ec_seckey_verify(secp256k1_context_sign, vch); } void CKey::MakeNewKey(bool fCompressedIn) { do { GetStrongRandBytes(keydata); } while (!Check(keydata.data())); fValid = true; fCompressed = fCompressedIn; } bool CKey::Negate() { assert(fValid); return secp256k1_ec_seckey_negate(secp256k1_context_sign, keydata.data()); } CPrivKey CKey::GetPrivKey() const { assert(fValid); CPrivKey seckey; int ret; size_t seckeylen; seckey.resize(SIZE); seckeylen = SIZE; ret = ec_seckey_export_der(secp256k1_context_sign, seckey.data(), &seckeylen, begin(), fCompressed); assert(ret); seckey.resize(seckeylen); return seckey; } CPubKey CKey::GetPubKey() const { assert(fValid); secp256k1_pubkey pubkey; size_t clen = CPubKey::SIZE; CPubKey result; int ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &pubkey, begin()); assert(ret); secp256k1_ec_pubkey_serialize(secp256k1_context_sign, (unsigned char*)result.begin(), &clen, &pubkey, fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED); assert(result.size() == clen); assert(result.IsValid()); return result; } // Check that the sig has a low R value and will be less than 71 bytes bool SigHasLowR(const secp256k1_ecdsa_signature* sig) { unsigned char compact_sig[64]; secp256k1_ecdsa_signature_serialize_compact(secp256k1_context_sign, compact_sig, sig); // In DER serialization, all values are interpreted as big-endian, signed integers. The highest bit in the integer indicates // its signed-ness; 0 is positive, 1 is negative. When the value is interpreted as a negative integer, it must be converted // to a positive value by prepending a 0x00 byte so that the highest bit is 0. We can avoid this prepending by ensuring that // our highest bit is always 0, and thus we must check that the first byte is less than 0x80. return compact_sig[0] < 0x80; } bool CKey::Sign(const uint256 &hash, std::vector& vchSig, bool grind, uint32_t test_case) const { if (!fValid) return false; vchSig.resize(CPubKey::SIGNATURE_SIZE); size_t nSigLen = CPubKey::SIGNATURE_SIZE; unsigned char extra_entropy[32] = {0}; WriteLE32(extra_entropy, test_case); secp256k1_ecdsa_signature sig; uint32_t counter = 0; int ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, (!grind && test_case) ? extra_entropy : nullptr); // Grind for low R while (ret && !SigHasLowR(&sig) && grind) { WriteLE32(extra_entropy, ++counter); ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, extra_entropy); } assert(ret); secp256k1_ecdsa_signature_serialize_der(secp256k1_context_sign, vchSig.data(), &nSigLen, &sig); vchSig.resize(nSigLen); // Additional verification step to prevent using a potentially corrupted signature secp256k1_pubkey pk; ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &pk, begin()); assert(ret); ret = secp256k1_ecdsa_verify(secp256k1_context_static, &sig, hash.begin(), &pk); assert(ret); return true; } bool CKey::VerifyPubKey(const CPubKey& pubkey) const { if (pubkey.IsCompressed() != fCompressed) { return false; } unsigned char rnd[8]; std::string str = "Bitcoin key verification\n"; GetRandBytes(rnd); uint256 hash; CHash256().Write(MakeUCharSpan(str)).Write(rnd).Finalize(hash); std::vector vchSig; Sign(hash, vchSig); return pubkey.Verify(hash, vchSig); } bool CKey::SignCompact(const uint256 &hash, std::vector& vchSig) const { if (!fValid) return false; vchSig.resize(CPubKey::COMPACT_SIGNATURE_SIZE); int rec = -1; secp256k1_ecdsa_recoverable_signature rsig; int ret = secp256k1_ecdsa_sign_recoverable(secp256k1_context_sign, &rsig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, nullptr); assert(ret); ret = secp256k1_ecdsa_recoverable_signature_serialize_compact(secp256k1_context_sign, &vchSig[1], &rec, &rsig); assert(ret); assert(rec != -1); vchSig[0] = 27 + rec + (fCompressed ? 4 : 0); // Additional verification step to prevent using a potentially corrupted signature secp256k1_pubkey epk, rpk; ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &epk, begin()); assert(ret); ret = secp256k1_ecdsa_recover(secp256k1_context_static, &rpk, &rsig, hash.begin()); assert(ret); ret = secp256k1_ec_pubkey_cmp(secp256k1_context_static, &epk, &rpk); assert(ret == 0); return true; } bool CKey::Load(const CPrivKey &seckey, const CPubKey &vchPubKey, bool fSkipCheck=false) { if (!ec_seckey_import_der(secp256k1_context_sign, (unsigned char*)begin(), seckey.data(), seckey.size())) return false; fCompressed = vchPubKey.IsCompressed(); fValid = true; if (fSkipCheck) return true; return VerifyPubKey(vchPubKey); } bool CKey::Derive(CKey& keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const { assert(IsValid()); assert(IsCompressed()); std::vector> vout(64); if ((nChild >> 31) == 0) { CPubKey pubkey = GetPubKey(); assert(pubkey.size() == CPubKey::COMPRESSED_SIZE); BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin()+1, vout.data()); } else { assert(size() == 32); BIP32Hash(cc, nChild, 0, begin(), vout.data()); } memcpy(ccChild.begin(), vout.data()+32, 32); memcpy((unsigned char*)keyChild.begin(), begin(), 32); bool ret = secp256k1_ec_seckey_tweak_add(secp256k1_context_sign, (unsigned char*)keyChild.begin(), vout.data()); keyChild.fCompressed = true; keyChild.fValid = ret; return ret; } EllSwiftPubKey CKey::EllSwiftCreate(Span ent32) const { assert(fValid); assert(ent32.size() == 32); std::array encoded_pubkey; auto success = secp256k1_ellswift_create(secp256k1_context_sign, UCharCast(encoded_pubkey.data()), keydata.data(), UCharCast(ent32.data())); // Should always succeed for valid keys (asserted above). assert(success); return {encoded_pubkey}; } ECDHSecret CKey::ComputeBIP324ECDHSecret(const EllSwiftPubKey& their_ellswift, const EllSwiftPubKey& our_ellswift, bool initiating) const { assert(fValid); ECDHSecret output; // BIP324 uses the initiator as party A, and the responder as party B. Remap the inputs // accordingly: bool success = secp256k1_ellswift_xdh(secp256k1_context_sign, UCharCast(output.data()), UCharCast(initiating ? our_ellswift.data() : their_ellswift.data()), UCharCast(initiating ? their_ellswift.data() : our_ellswift.data()), keydata.data(), initiating ? 0 : 1, secp256k1_ellswift_xdh_hash_function_bip324, nullptr); // Should always succeed for valid keys (assert above). assert(success); return output; } bool CExtKey::Derive(CExtKey &out, unsigned int _nChild) const { out.nDepth = nDepth + 1; CKeyID id = key.GetPubKey().GetID(); memcpy(out.vchFingerprint, &id, 4); out.nChild = _nChild; return key.Derive(out.key, out.chaincode, _nChild, chaincode); } void CExtKey::SetSeed(Span seed) { static const unsigned char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'}; std::vector> vout(64); CHMAC_SHA512{hashkey, sizeof(hashkey)}.Write(seed.data(), seed.size()).Finalize(vout.data()); key.Set(vout.data(), vout.data() + 32, true); memcpy(chaincode.begin(), vout.data() + 32, 32); nDepth = 0; nChild = 0; memset(vchFingerprint, 0, sizeof(vchFingerprint)); } CExtPubKey CExtKey::Neuter() const { CExtPubKey ret; ret.nDepth = nDepth; memcpy(ret.vchFingerprint, vchFingerprint, 4); ret.nChild = nChild; ret.pubkey = key.GetPubKey(); ret.chaincode = chaincode; return ret; } void CExtKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const { code[0] = nDepth; memcpy(code+1, vchFingerprint, 4); WriteBE32(code+5, nChild); memcpy(code+9, chaincode.begin(), 32); code[41] = 0; assert(key.size() == 32); memcpy(code+42, key.begin(), 32); } void CExtKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) { nDepth = code[0]; memcpy(vchFingerprint, code+1, 4); nChild = ReadBE32(code+5); memcpy(chaincode.begin(), code+9, 32); key.Set(code+42, code+BIP32_EXTKEY_SIZE, true); if ((nDepth == 0 && (nChild != 0 || ReadLE32(vchFingerprint) != 0)) || code[41] != 0) key = CKey(); } bool ECC_InitSanityCheck() { CKey key; key.MakeNewKey(true); CPubKey pubkey = key.GetPubKey(); return key.VerifyPubKey(pubkey); } void ECC_Start() { assert(secp256k1_context_sign == nullptr); secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_NONE); assert(ctx != nullptr); { // Pass in a random blinding seed to the secp256k1 context. std::vector> vseed(32); GetRandBytes(vseed); bool ret = secp256k1_context_randomize(ctx, vseed.data()); assert(ret); } secp256k1_context_sign = ctx; } void ECC_Stop() { secp256k1_context *ctx = secp256k1_context_sign; secp256k1_context_sign = nullptr; if (ctx) { secp256k1_context_destroy(ctx); } }