dsawithsha1.java

一个非常好的ssh客户端实现

/******************************************************************************
 *
 * Copyright (c) 1999-2003 AppGate Network Security AB. All Rights Reserved.
 * 
 * This file contains Original Code and/or Modifications of Original Code as
 * defined in and that are subject to the MindTerm Public Source License,
 * Version 2.0, (the 'License'). You may not use this file except in compliance
 * with the License.
 * 
 * You should have received a copy of the MindTerm Public Source License
 * along with this software; see the file LICENSE.  If not, write to
 * AppGate Network Security AB, Otterhallegatan 2, SE-41118 Goteborg, SWEDEN
 *
 *****************************************************************************/

package com.mindbright.security.publickey;

import java.math.BigInteger;

import java.io.IOException;
import java.io.ByteArrayOutputStream;

import com.mindbright.asn1.ASN1Sequence;
import com.mindbright.asn1.ASN1Integer;
import com.mindbright.asn1.ASN1DER;

public final class DSAWithSHA1 extends RawDSAWithSHA1 {

    /**
     * DSA_SIG ::= SEQUENCE {
     *   r        INTEGER,
     *   s        INTEGER,
     * }
     */
    public static final class DSASIG extends ASN1Sequence {

	public ASN1Integer r;
	public ASN1Integer s;

	public DSASIG() {
	    r       = new ASN1Integer();
	    s       = new ASN1Integer();
	    addComponent(r);
	    addComponent(s);
	}

	public DSASIG(BigInteger r, BigInteger s) {
	    this();
	    this.r.setValue(r);
	    this.s.setValue(s);
	}

    }


    public static byte[] toDer(byte[] sig) {
        // Extract integers
	int        dataSz = sig.length / 2;
	byte[]     ra     = new byte[dataSz];
	byte[]     sa     = new byte[dataSz];
        
	System.arraycopy(sig, 0, ra, 0, dataSz);
	System.arraycopy(sig, dataSz, sa, 0, dataSz);
        
	BigInteger r  = new BigInteger(1, ra);
	BigInteger s  = new BigInteger(1, sa);
        
        //  Encode
        DSASIG dsasig= new DSASIG(r, s);
	ByteArrayOutputStream enc = new ByteArrayOutputStream(128);
	ASN1DER               der = new ASN1DER();
        
	try {
	    der.encode(enc, dsasig);
	} catch (IOException e) {
	    // This should not happen
	}
        
	return enc.toByteArray();
    }
    
    //
    // The RawDSAWithSHA1.sign function leaves two 160 bits long integers
    // in its output buffer. We must recode this into a suitable DER structure.
    //
    protected byte[] sign(byte[] data) {
        return toDer(super.sign(data));
    }
}