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SSHv2 library for Java
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/*
 * Copyright 2010 Shikhar Bhushan
 *
 * 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.
 *
 * This file may incorporate work covered by the following copyright and
 * permission notice:
 *
 *     Licensed to the Apache Software Foundation (ASF) under one
 *     or more contributor license agreements.  See the NOTICE file
 *     distributed with this work for additional information
 *     regarding copyright ownership.  The ASF licenses this file
 *     to you 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 net.schmizz.sshj.signature;

import net.schmizz.sshj.common.SSHRuntimeException;
import net.schmizz.sshj.common.SecurityUtils;

import java.security.GeneralSecurityException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SignatureException;

/** An abstract class for {@link Signature} that implements common functionality. */
public abstract class AbstractSignature
        implements Signature {

    protected java.security.Signature signature;
    protected String algorithm;

    protected AbstractSignature(String algorithm) {
        this.algorithm = algorithm;
    }

    public void init(PublicKey pubkey, PrivateKey prvkey) {
        try {
            signature = SecurityUtils.getSignature(algorithm);
            if (pubkey != null)
                signature.initVerify(pubkey);
            if (prvkey != null)
                signature.initSign(prvkey);
        } catch (GeneralSecurityException e) {
            throw new SSHRuntimeException(e);
        }
    }

    public void update(byte[] foo) {
        update(foo, 0, foo.length);
    }

    public void update(byte[] foo, int off, int len) {
        try {
            signature.update(foo, off, len);
        } catch (SignatureException e) {
            throw new SSHRuntimeException(e);
        }
    }

    protected byte[] extractSig(byte[] sig) {
        if (sig[0] == 0 && sig[1] == 0 && sig[2] == 0) {
            int i = 0;
            int j;
            j = sig[i++] << 24 & 0xff000000 //
                | sig[i++] << 16 & 0x00ff0000 //
                | sig[i++] << 8 & 0x0000ff00 //
                | sig[i++] & 0x000000ff;
            i += j;
            j = sig[i++] << 24 & 0xff000000 //
                | sig[i++] << 16 & 0x00ff0000 //
                | sig[i++] << 8 & 0x0000ff00 //
                | sig[i++] & 0x000000ff;
            byte[] tmp = new byte[j];
            System.arraycopy(sig, i, tmp, 0, j);
            sig = tmp;
        }
        return sig;
    }

}