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Diffstat (limited to 'src/key.cpp')
| -rw-r--r-- | src/key.cpp | 393 |
1 files changed, 393 insertions, 0 deletions
diff --git a/src/key.cpp b/src/key.cpp new file mode 100644 index 0000000000..7bef3d529b --- /dev/null +++ b/src/key.cpp @@ -0,0 +1,393 @@ +// 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 <key.h> + +#include <crypto/common.h> +#include <crypto/hmac_sha512.h> +#include <hash.h> +#include <random.h> + +#include <secp256k1.h> +#include <secp256k1_extrakeys.h> +#include <secp256k1_recovery.h> +#include <secp256k1_schnorrsig.h> + +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 <https://www.secg.org/sec1-v2.pdf>, 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 + * <https://www.secg.org/sec1-v2.pdf>. 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.data(), keydata.size()); + } 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<unsigned char>& 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); + 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, sizeof(rnd)); + uint256 hash; + CHash256().Write(MakeUCharSpan(str)).Write(rnd).Finalize(hash); + std::vector<unsigned char> vchSig; + Sign(hash, vchSig); + return pubkey.Verify(hash, vchSig); +} + +bool CKey::SignCompact(const uint256 &hash, std::vector<unsigned char>& vchSig) const { + if (!fValid) + return false; + vchSig.resize(CPubKey::COMPACT_SIGNATURE_SIZE); + int rec = -1; + secp256k1_ecdsa_recoverable_signature sig; + int ret = secp256k1_ecdsa_sign_recoverable(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, nullptr); + assert(ret); + ret = secp256k1_ecdsa_recoverable_signature_serialize_compact(secp256k1_context_sign, &vchSig[1], &rec, &sig); + assert(ret); + assert(rec != -1); + vchSig[0] = 27 + rec + (fCompressed ? 4 : 0); + return true; +} + +bool CKey::SignSchnorr(const uint256& hash, Span<unsigned char> sig, const uint256* merkle_root, const uint256* aux) const +{ + assert(sig.size() == 64); + secp256k1_keypair keypair; + if (!secp256k1_keypair_create(secp256k1_context_sign, &keypair, begin())) return false; + if (merkle_root) { + secp256k1_xonly_pubkey pubkey; + if (!secp256k1_keypair_xonly_pub(secp256k1_context_sign, &pubkey, nullptr, &keypair)) return false; + unsigned char pubkey_bytes[32]; + if (!secp256k1_xonly_pubkey_serialize(secp256k1_context_sign, pubkey_bytes, &pubkey)) return false; + uint256 tweak = XOnlyPubKey(pubkey_bytes).ComputeTapTweakHash(merkle_root->IsNull() ? nullptr : merkle_root); + if (!secp256k1_keypair_xonly_tweak_add(GetVerifyContext(), &keypair, tweak.data())) return false; + } + bool ret = secp256k1_schnorrsig_sign(secp256k1_context_sign, sig.data(), hash.data(), &keypair, aux ? (unsigned char*)aux->data() : nullptr); + memory_cleanse(&keypair, sizeof(keypair)); + return ret; +} + +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<unsigned char, secure_allocator<unsigned char>> 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; +} + +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(const unsigned char *seed, unsigned int nSeedLen) { + static const unsigned char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'}; + std::vector<unsigned char, secure_allocator<unsigned char>> vout(64); + CHMAC_SHA512(hashkey, sizeof(hashkey)).Write(seed, nSeedLen).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); + code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF; + code[7] = (nChild >> 8) & 0xFF; code[8] = (nChild >> 0) & 0xFF; + 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 = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8]; + memcpy(chaincode.begin(), code+9, 32); + key.Set(code+42, code+BIP32_EXTKEY_SIZE, true); +} + +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_SIGN); + assert(ctx != nullptr); + + { + // Pass in a random blinding seed to the secp256k1 context. + std::vector<unsigned char, secure_allocator<unsigned char>> vseed(32); + GetRandBytes(vseed.data(), 32); + 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); + } +} |