Function check_tx_sig

bitcoin/signature.c:202–229

}

bool check_tx_sig(const struct bitcoin_tx *tx, size_t input_num,
		  const u8 *redeemscript,
		  const u8 *witness_script,
		  const struct pubkey *key,
		  const struct bitcoin_signature *sig)
{
	struct sha256_double hash;
	bool use_segwit = witness_script != NULL;
	const u8 *script = use_segwit ? witness_script : redeemscript;
	bool ret;

	/* We only support a limited subset of sighash types. */
	if (sig->sighash_type != SIGHASH_ALL) {
		if (!witness_script)
			return false;
		if (sig->sighash_type != (SIGHASH_SINGLE|SIGHASH_ANYONECANPAY))
			return false;
	}
	assert(input_num < tx->wtx->num_inputs);

	bitcoin_tx_hash_for_sig(tx, input_num, script, sig->sighash_type, &hash);
	dump_tx("check_tx_sig", tx, input_num, script, key, &hash);

	ret = check_signed_hash(&hash, &sig->s, key);
	if (!ret)
		dump_tx("Sig failed", tx, input_num, redeemscript, key, &hash);
	return ret;
}

/* Stolen direct from bitcoin/src/script/sign.cpp:
// Copyright (c) 2009-2010 Satoshi Nakamoto