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372 lines
14 KiB
C++
372 lines
14 KiB
C++
// Copyright (c) 2009-2015 The Bitcoin Core developers
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// Copyright (c) 2017 The Zcash developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#include <key.h>
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#include <crypto/common.h>
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#include <crypto/hmac_sha512.h>
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#include <random.h>
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#include <secp256k1.h>
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#include <secp256k1_recovery.h>
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static secp256k1_context* secp256k1_context_sign = nullptr;
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/** These functions are taken from the libsecp256k1 distribution and are very ugly. */
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/**
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* This parses a format loosely based on a DER encoding of the ECPrivateKey type from
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* section C.4 of SEC 1 <http://www.secg.org/sec1-v2.pdf>, with the following caveats:
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*
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* * The octet-length of the SEQUENCE must be encoded as 1 or 2 octets. It is not
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* required to be encoded as one octet if it is less than 256, as DER would require.
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* * The octet-length of the SEQUENCE must not be greater than the remaining
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* length of the key encoding, but need not match it (i.e. the encoding may contain
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* junk after the encoded SEQUENCE).
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* * The privateKey OCTET STRING is zero-filled on the left to 32 octets.
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* * Anything after the encoding of the privateKey OCTET STRING is ignored, whether
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* or not it is validly encoded DER.
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*
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* out32 must point to an output buffer of length at least 32 bytes.
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*/
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int ec_seckey_import_der(const secp256k1_context* ctx, unsigned char *out32, const unsigned char *seckey, size_t seckeylen) {
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const unsigned char *end = seckey + seckeylen;
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memset(out32, 0, 32);
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/* sequence header */
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if (end - seckey < 1 || *seckey != 0x30u) {
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return 0;
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}
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seckey++;
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/* sequence length constructor */
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if (end - seckey < 1 || !(*seckey & 0x80u)) {
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return 0;
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}
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ptrdiff_t lenb = *seckey & ~0x80u; seckey++;
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if (lenb < 1 || lenb > 2) {
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return 0;
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}
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if (end - seckey < lenb) {
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return 0;
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}
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/* sequence length */
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ptrdiff_t len = seckey[lenb-1] | (lenb > 1 ? seckey[lenb-2] << 8 : 0u);
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seckey += lenb;
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if (end - seckey < len) {
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return 0;
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}
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/* sequence element 0: version number (=1) */
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if (end - seckey < 3 || seckey[0] != 0x02u || seckey[1] != 0x01u || seckey[2] != 0x01u) {
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return 0;
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}
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seckey += 3;
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/* sequence element 1: octet string, up to 32 bytes */
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if (end - seckey < 2 || seckey[0] != 0x04u) {
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return 0;
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}
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ptrdiff_t oslen = seckey[1];
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seckey += 2;
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if (oslen > 32 || end - seckey < oslen) {
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return 0;
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}
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memcpy(out32 + (32 - oslen), seckey, oslen);
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if (!secp256k1_ec_seckey_verify(ctx, out32)) {
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memset(out32, 0, 32);
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return 0;
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}
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return 1;
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}
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/**
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* This serializes to a DER encoding of the ECPrivateKey type from section C.4 of SEC 1
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* <http://www.secg.org/sec1-v2.pdf>. The optional parameters and publicKey fields are
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* included.
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*
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* seckey must point to an output buffer of length at least CKey::SIZE bytes.
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* seckeylen must initially be set to the size of the seckey buffer. Upon return it
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* will be set to the number of bytes used in the buffer.
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* key32 must point to a 32-byte raw private key.
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*/
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int ec_seckey_export_der(const secp256k1_context *ctx, unsigned char *seckey, size_t *seckeylen, const unsigned char *key32, bool compressed) {
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assert(*seckeylen >= CKey::SIZE);
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secp256k1_pubkey pubkey;
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size_t pubkeylen = 0;
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if (!secp256k1_ec_pubkey_create(ctx, &pubkey, key32)) {
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*seckeylen = 0;
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return 0;
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}
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if (compressed) {
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static const unsigned char begin[] = {
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0x30,0x81,0xD3,0x02,0x01,0x01,0x04,0x20
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};
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static const unsigned char middle[] = {
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0xA0,0x81,0x85,0x30,0x81,0x82,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
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0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
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0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
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0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
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0x21,0x02,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
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0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
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0x17,0x98,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
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0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
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0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x24,0x03,0x22,0x00
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};
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unsigned char *ptr = seckey;
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memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
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memcpy(ptr, key32, 32); ptr += 32;
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memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
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pubkeylen = CPubKey::COMPRESSED_SIZE;
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secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_COMPRESSED);
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ptr += pubkeylen;
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*seckeylen = ptr - seckey;
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assert(*seckeylen == CKey::COMPRESSED_SIZE);
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} else {
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static const unsigned char begin[] = {
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0x30,0x82,0x01,0x13,0x02,0x01,0x01,0x04,0x20
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};
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static const unsigned char middle[] = {
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0xA0,0x81,0xA5,0x30,0x81,0xA2,0x02,0x01,0x01,0x30,0x2C,0x06,0x07,0x2A,0x86,0x48,
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0xCE,0x3D,0x01,0x01,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
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0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
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0xFF,0xFF,0xFE,0xFF,0xFF,0xFC,0x2F,0x30,0x06,0x04,0x01,0x00,0x04,0x01,0x07,0x04,
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0x41,0x04,0x79,0xBE,0x66,0x7E,0xF9,0xDC,0xBB,0xAC,0x55,0xA0,0x62,0x95,0xCE,0x87,
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0x0B,0x07,0x02,0x9B,0xFC,0xDB,0x2D,0xCE,0x28,0xD9,0x59,0xF2,0x81,0x5B,0x16,0xF8,
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0x17,0x98,0x48,0x3A,0xDA,0x77,0x26,0xA3,0xC4,0x65,0x5D,0xA4,0xFB,0xFC,0x0E,0x11,
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0x08,0xA8,0xFD,0x17,0xB4,0x48,0xA6,0x85,0x54,0x19,0x9C,0x47,0xD0,0x8F,0xFB,0x10,
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0xD4,0xB8,0x02,0x21,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
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0xFF,0xFF,0xFF,0xFF,0xFE,0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,0xBF,0xD2,0x5E,
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0x8C,0xD0,0x36,0x41,0x41,0x02,0x01,0x01,0xA1,0x44,0x03,0x42,0x00
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};
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unsigned char *ptr = seckey;
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memcpy(ptr, begin, sizeof(begin)); ptr += sizeof(begin);
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memcpy(ptr, key32, 32); ptr += 32;
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memcpy(ptr, middle, sizeof(middle)); ptr += sizeof(middle);
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pubkeylen = CPubKey::SIZE;
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secp256k1_ec_pubkey_serialize(ctx, ptr, &pubkeylen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
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ptr += pubkeylen;
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*seckeylen = ptr - seckey;
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assert(*seckeylen == CKey::SIZE);
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}
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return 1;
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}
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bool CKey::Check(const unsigned char *vch) {
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return secp256k1_ec_seckey_verify(secp256k1_context_sign, vch);
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}
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void CKey::MakeNewKey(bool fCompressedIn) {
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do {
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GetStrongRandBytes(keydata.data(), keydata.size());
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} while (!Check(keydata.data()));
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fValid = true;
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fCompressed = fCompressedIn;
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}
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bool CKey::Negate()
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{
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assert(fValid);
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return secp256k1_ec_seckey_negate(secp256k1_context_sign, keydata.data());
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}
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CPrivKey CKey::GetPrivKey() const {
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assert(fValid);
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CPrivKey seckey;
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int ret;
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size_t seckeylen;
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seckey.resize(SIZE);
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seckeylen = SIZE;
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ret = ec_seckey_export_der(secp256k1_context_sign, seckey.data(), &seckeylen, begin(), fCompressed);
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assert(ret);
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seckey.resize(seckeylen);
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return seckey;
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}
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CPubKey CKey::GetPubKey() const {
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assert(fValid);
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secp256k1_pubkey pubkey;
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size_t clen = CPubKey::SIZE;
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CPubKey result;
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int ret = secp256k1_ec_pubkey_create(secp256k1_context_sign, &pubkey, begin());
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assert(ret);
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secp256k1_ec_pubkey_serialize(secp256k1_context_sign, (unsigned char*)result.begin(), &clen, &pubkey, fCompressed ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
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assert(result.size() == clen);
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assert(result.IsValid());
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return result;
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}
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// Check that the sig has a low R value and will be less than 71 bytes
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bool SigHasLowR(const secp256k1_ecdsa_signature* sig)
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{
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unsigned char compact_sig[64];
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secp256k1_ecdsa_signature_serialize_compact(secp256k1_context_sign, compact_sig, sig);
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// In DER serialization, all values are interpreted as big-endian, signed integers. The highest bit in the integer indicates
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// its signed-ness; 0 is positive, 1 is negative. When the value is interpreted as a negative integer, it must be converted
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// to a positive value by prepending a 0x00 byte so that the highest bit is 0. We can avoid this prepending by ensuring that
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// our highest bit is always 0, and thus we must check that the first byte is less than 0x80.
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return compact_sig[0] < 0x80;
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}
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bool CKey::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig, bool grind, uint32_t test_case) const {
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if (!fValid)
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return false;
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vchSig.resize(CPubKey::SIGNATURE_SIZE);
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size_t nSigLen = CPubKey::SIGNATURE_SIZE;
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unsigned char extra_entropy[32] = {0};
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WriteLE32(extra_entropy, test_case);
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secp256k1_ecdsa_signature sig;
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uint32_t counter = 0;
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int ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, (!grind && test_case) ? extra_entropy : nullptr);
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// Grind for low R
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while (ret && !SigHasLowR(&sig) && grind) {
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WriteLE32(extra_entropy, ++counter);
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ret = secp256k1_ecdsa_sign(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, extra_entropy);
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}
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assert(ret);
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secp256k1_ecdsa_signature_serialize_der(secp256k1_context_sign, vchSig.data(), &nSigLen, &sig);
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vchSig.resize(nSigLen);
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return true;
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}
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bool CKey::VerifyPubKey(const CPubKey& pubkey) const {
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if (pubkey.IsCompressed() != fCompressed) {
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return false;
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}
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unsigned char rnd[8];
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std::string str = "Bitcoin key verification\n";
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GetRandBytes(rnd, sizeof(rnd));
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uint256 hash;
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CHash256().Write(MakeUCharSpan(str)).Write(rnd).Finalize(hash);
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std::vector<unsigned char> vchSig;
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Sign(hash, vchSig);
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return pubkey.Verify(hash, vchSig);
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}
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bool CKey::SignCompact(const uint256 &hash, std::vector<unsigned char>& vchSig) const {
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if (!fValid)
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return false;
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vchSig.resize(CPubKey::COMPACT_SIGNATURE_SIZE);
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int rec = -1;
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secp256k1_ecdsa_recoverable_signature sig;
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int ret = secp256k1_ecdsa_sign_recoverable(secp256k1_context_sign, &sig, hash.begin(), begin(), secp256k1_nonce_function_rfc6979, nullptr);
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assert(ret);
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ret = secp256k1_ecdsa_recoverable_signature_serialize_compact(secp256k1_context_sign, &vchSig[1], &rec, &sig);
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assert(ret);
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assert(rec != -1);
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vchSig[0] = 27 + rec + (fCompressed ? 4 : 0);
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return true;
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}
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bool CKey::Load(const CPrivKey &seckey, const CPubKey &vchPubKey, bool fSkipCheck=false) {
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if (!ec_seckey_import_der(secp256k1_context_sign, (unsigned char*)begin(), seckey.data(), seckey.size()))
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return false;
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fCompressed = vchPubKey.IsCompressed();
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fValid = true;
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if (fSkipCheck)
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return true;
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return VerifyPubKey(vchPubKey);
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}
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bool CKey::Derive(CKey& keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {
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assert(IsValid());
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assert(IsCompressed());
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std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
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if ((nChild >> 31) == 0) {
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CPubKey pubkey = GetPubKey();
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assert(pubkey.size() == CPubKey::COMPRESSED_SIZE);
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BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin()+1, vout.data());
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} else {
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assert(size() == 32);
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BIP32Hash(cc, nChild, 0, begin(), vout.data());
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}
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memcpy(ccChild.begin(), vout.data()+32, 32);
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memcpy((unsigned char*)keyChild.begin(), begin(), 32);
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bool ret = secp256k1_ec_seckey_tweak_add(secp256k1_context_sign, (unsigned char*)keyChild.begin(), vout.data());
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keyChild.fCompressed = true;
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keyChild.fValid = ret;
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return ret;
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}
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bool CExtKey::Derive(CExtKey &out, unsigned int _nChild) const {
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out.nDepth = nDepth + 1;
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CKeyID id = key.GetPubKey().GetID();
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memcpy(&out.vchFingerprint[0], &id, 4);
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out.nChild = _nChild;
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return key.Derive(out.key, out.chaincode, _nChild, chaincode);
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}
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void CExtKey::SetSeed(const unsigned char *seed, unsigned int nSeedLen) {
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static const unsigned char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'};
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std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
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CHMAC_SHA512(hashkey, sizeof(hashkey)).Write(seed, nSeedLen).Finalize(vout.data());
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key.Set(vout.data(), vout.data() + 32, true);
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memcpy(chaincode.begin(), vout.data() + 32, 32);
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nDepth = 0;
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nChild = 0;
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memset(vchFingerprint, 0, sizeof(vchFingerprint));
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}
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CExtPubKey CExtKey::Neuter() const {
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CExtPubKey ret;
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ret.nDepth = nDepth;
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memcpy(&ret.vchFingerprint[0], &vchFingerprint[0], 4);
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ret.nChild = nChild;
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ret.pubkey = key.GetPubKey();
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ret.chaincode = chaincode;
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return ret;
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}
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void CExtKey::Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const {
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code[0] = nDepth;
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memcpy(code+1, vchFingerprint, 4);
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WriteBE32(code+5, nChild);
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memcpy(code+9, chaincode.begin(), 32);
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code[41] = 0;
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assert(key.size() == 32);
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memcpy(code+42, key.begin(), 32);
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}
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void CExtKey::Decode(const unsigned char code[BIP32_EXTKEY_SIZE]) {
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nDepth = code[0];
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memcpy(vchFingerprint, code+1, 4);
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nChild = ReadBE32(code+5);
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memcpy(chaincode.begin(), code+9, 32);
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key.Set(code+42, code+BIP32_EXTKEY_SIZE, true);
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}
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bool ECC_InitSanityCheck() {
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CKey key;
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key.MakeNewKey(true);
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CPubKey pubkey = key.GetPubKey();
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return key.VerifyPubKey(pubkey);
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}
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void ECC_Start() {
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assert(secp256k1_context_sign == nullptr);
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secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
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assert(ctx != nullptr);
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{
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// Pass in a random blinding seed to the secp256k1 context.
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std::vector<unsigned char, secure_allocator<unsigned char>> vseed(32);
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GetRandBytes(vseed.data(), 32);
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bool ret = secp256k1_context_randomize(ctx, vseed.data());
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assert(ret);
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}
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secp256k1_context_sign = ctx;
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}
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void ECC_Stop() {
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secp256k1_context *ctx = secp256k1_context_sign;
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secp256k1_context_sign = nullptr;
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if (ctx) {
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secp256k1_context_destroy(ctx);
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}
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}
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