libzcash_script 0.1.0

// Copyright (c) 2009-2014 The Bitcoin Core developers
// Copyright (c) 2017-2023 The Zcash developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or https://www.opensource.org/licenses/mit-license.php .

#include "pubkey.h"

#include <secp256k1.h>
#include <secp256k1_recovery.h>

namespace {

struct Secp256k1SelfTester
{
    Secp256k1SelfTester() {
        /* Run libsecp256k1 self-test before using the secp256k1_context_static. */
        secp256k1_selftest();
    }
} SECP256K1_SELFTESTER;

} // namespace

bool CPubKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchSig) const {
    if (!IsValid())
        return false;
    secp256k1_pubkey pubkey;
    secp256k1_ecdsa_signature sig;
    if (!secp256k1_ec_pubkey_parse(secp256k1_context_static, &pubkey, &(*this)[0], size())) {
        return false;
    }
    if (vchSig.size() == 0) {
        return false;
    }
    /* Zcash, unlike Bitcoin, has always enforced strict DER signatures. */
    if (!secp256k1_ecdsa_signature_parse_der(secp256k1_context_static, &sig, &vchSig[0], vchSig.size())) {
        return false;
    }
    /* libsecp256k1's ECDSA verification requires lower-S signatures, which have
     * not historically been enforced in Bitcoin or Zcash, so normalize them first. */
    secp256k1_ecdsa_signature_normalize(secp256k1_context_static, &sig, &sig);
    return secp256k1_ecdsa_verify(secp256k1_context_static, &sig, hash.begin(), &pubkey);
}

#if 0

bool CPubKey::RecoverCompact(const uint256 &hash, const std::vector<unsigned char>& vchSig) {
    if (vchSig.size() != COMPACT_SIGNATURE_SIZE)
        return false;
    int recid = (vchSig[0] - 27) & 3;
    bool fComp = ((vchSig[0] - 27) & 4) != 0;
    secp256k1_pubkey pubkey;
    secp256k1_ecdsa_recoverable_signature sig;
    if (!secp256k1_ecdsa_recoverable_signature_parse_compact(secp256k1_context_static, &sig, &vchSig[1], recid)) {
        return false;
    }
    if (!secp256k1_ecdsa_recover(secp256k1_context_static, &pubkey, &sig, hash.begin())) {
        return false;
    }
    unsigned char pub[PUBLIC_KEY_SIZE];
    size_t publen = PUBLIC_KEY_SIZE;
    secp256k1_ec_pubkey_serialize(secp256k1_context_static, pub, &publen, &pubkey, fComp ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED);
    Set(pub, pub + publen);
    return true;
}

bool CPubKey::IsFullyValid() const {
    if (!IsValid())
        return false;
    secp256k1_pubkey pubkey;
    return secp256k1_ec_pubkey_parse(secp256k1_context_static, &pubkey, &(*this)[0], size());
}

bool CPubKey::Decompress() {
    if (!IsValid())
        return false;
    secp256k1_pubkey pubkey;
    if (!secp256k1_ec_pubkey_parse(secp256k1_context_static, &pubkey, &(*this)[0], size())) {
        return false;
    }
    unsigned char pub[PUBLIC_KEY_SIZE];
    size_t publen = PUBLIC_KEY_SIZE;
    secp256k1_ec_pubkey_serialize(secp256k1_context_static, pub, &publen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
    Set(pub, pub + publen);
    return true;
}

bool CPubKey::Derive(CPubKey& pubkeyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode& cc) const {
    assert(IsValid());
    assert((nChild >> 31) == 0);
    assert(size() == COMPRESSED_PUBLIC_KEY_SIZE);
    unsigned char out[64];
    BIP32Hash(cc, nChild, *begin(), begin()+1, out);
    memcpy(ccChild.begin(), out+32, 32);
    secp256k1_pubkey pubkey;
    if (!secp256k1_ec_pubkey_parse(secp256k1_context_static, &pubkey, &(*this)[0], size())) {
        return false;
    }
    if (!secp256k1_ec_pubkey_tweak_add(secp256k1_context_static, &pubkey, out)) {
        return false;
    }
    unsigned char pub[COMPRESSED_PUBLIC_KEY_SIZE];
    size_t publen = COMPRESSED_PUBLIC_KEY_SIZE;
    secp256k1_ec_pubkey_serialize(secp256k1_context_static, pub, &publen, &pubkey, SECP256K1_EC_COMPRESSED);
    pubkeyChild.Set(pub, pub + publen);
    return true;
}

std::optional<CChainablePubKey> CChainablePubKey::Derive(unsigned int nChild) const {
    CPubKey pubkeyChild;
    ChainCode ccChild;
    if (pubkey.Derive(pubkeyChild, ccChild, nChild, chaincode)) {
        return CChainablePubKey::FromParts(ccChild, pubkeyChild);
    } else {
        return std::nullopt;
    }
}

void CExtPubKey::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);
    assert(pubkey.size() == CPubKey::COMPRESSED_PUBLIC_KEY_SIZE);
    memcpy(code+41, pubkey.begin(), CPubKey::COMPRESSED_PUBLIC_KEY_SIZE);
}

void CExtPubKey::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);
    pubkey.Set(code+41, code+BIP32_EXTKEY_SIZE);
}

bool CExtPubKey::Derive(CExtPubKey &out, unsigned int _nChild) const {
    out.nDepth = nDepth + 1;
    CKeyID id = pubkey.GetID();
    memcpy(&out.vchFingerprint[0], &id, 4);
    out.nChild = _nChild;
    return pubkey.Derive(out.pubkey, out.chaincode, _nChild, chaincode);
}
#endif

/* static */ bool CPubKey::CheckLowS(const std::vector<unsigned char>& vchSig) {
    secp256k1_ecdsa_signature sig;

    /* Zcash, unlike Bitcoin, has always enforced strict DER signatures. */
    if (!secp256k1_ecdsa_signature_parse_der(secp256k1_context_static, &sig, &vchSig[0], vchSig.size())) {
        return false;
    }
    return (!secp256k1_ecdsa_signature_normalize(secp256k1_context_static, NULL, &sig));
}

#if 0
/* static */ std::optional<CChainablePubKey> CChainablePubKey::FromParts(ChainCode chaincode, CPubKey pubkey) {
    if (pubkey.IsCompressed()) {
        return CChainablePubKey(chaincode, pubkey);
    } else {
        return std::nullopt;
    }
}

#endif