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Hedera Services API Utilities
There is a newer version: 0.56.6
/*
 * Copyright (C) 2020-2024 Hedera Hashgraph, LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.hedera.node.app.hapi.utils;

import static com.swirlds.common.crypto.SignatureType.ECDSA_SECP256K1;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.Provider;
import java.security.Signature;
import java.security.SignatureException;
import java.security.interfaces.ECPrivateKey;
import net.i2p.crypto.eddsa.EdDSAEngine;
import net.i2p.crypto.eddsa.EdDSAPrivateKey;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

public final class SignatureGenerator {
    private SignatureGenerator() {
        throw new UnsupportedOperationException("Utility Class");
    }

    public static final Provider BOUNCYCASTLE_PROVIDER = new BouncyCastleProvider();

    /**
     * Signs a message with a private key.
     *
     * @param msg to be signed
     * @param privateKey private key
     * @return signature in hex format
     * @throws InvalidKeyException if the key is invalid
     * @throws SignatureException if there is an error in the signature
     * @throws NoSuchAlgorithmException if an expected signing algorithm is unavailable
     */
    public static byte[] signBytes(final byte[] msg, final PrivateKey privateKey)
            throws InvalidKeyException, SignatureException, NoSuchAlgorithmException {
        if (privateKey instanceof EdDSAPrivateKey) {
            final var engine = new EdDSAEngine();
            engine.initSign(privateKey);
            return engine.signOneShot(msg);
        } else if (privateKey instanceof ECPrivateKey) {
            final Signature ecdsaSign =
                    Signature.getInstance(ECDSA_SECP256K1.signingAlgorithm(), BOUNCYCASTLE_PROVIDER);
            ecdsaSign.initSign(privateKey);
            ecdsaSign.update(msg);
            final var asn1Sig = ecdsaSign.sign();
            return rawEcdsaSigFromAsn1Der(asn1Sig);
        } else {
            throw new IllegalArgumentException("Unusable private key " + privateKey);
        }
    }

    private static byte[] rawEcdsaSigFromAsn1Der(final byte[] derSig) {
        final var rLenIndex = 3;
        final var rawBytes = new byte[64];

        final var origRLen = derSig[rLenIndex] & 0xff;
        int finalRLen = origRLen;
        int rStart = rLenIndex + 1;
        while (finalRLen > 32) {
            rStart++;
            finalRLen--;
        }
        System.arraycopy(derSig, rStart, rawBytes, 32 - finalRLen, Math.min(32, origRLen));

        final var sLenPos = rLenIndex + (derSig[rLenIndex] & 0xff) + 2;

        final var origSLen = derSig[sLenPos] & 0xff;
        int finalSLen = origSLen;
        int sStart = sLenPos + 1;
        while (finalSLen > 32) {
            sStart++;
            finalSLen--;
        }
        System.arraycopy(derSig, sStart, rawBytes, 32 + (32 - finalSLen), Math.min(32, origSLen));

        return rawBytes;
    }
}