package ch.ethz.ssh2.signature;
import java.io.IOException;
import java.math.BigInteger;
import java.security.SecureRandom;
import ch.ethz.ssh2.crypto.digest.SHA1;
import ch.ethz.ssh2.log.Logger;
import ch.ethz.ssh2.packets.TypesReader;
import ch.ethz.ssh2.packets.TypesWriter;
/**
* DSASHA1Verify.
*
* @author Christian Plattner, plattner@inf.ethz.ch
* @version $Id: DSASHA1Verify.java,v 1.5 2006/02/14 19:43:16 cplattne Exp $
*/
public class DSASHA1Verify
{
private static final Logger log = Logger.getLogger(DSASHA1Verify.class);
public static DSAPublicKey decodeSSHDSAPublicKey(byte[] key) throws IOException
{
TypesReader tr = new TypesReader(key);
String key_format = tr.readString();
if (key_format.equals("ssh-dss") == false)
throw new IllegalArgumentException("This is not a ssh-dss public key!");
BigInteger p = tr.readMPINT();
BigInteger q = tr.readMPINT();
BigInteger g = tr.readMPINT();
BigInteger y = tr.readMPINT();
if (tr.remain() != 0)
throw new IOException("Padding in DSA public key!");
return new DSAPublicKey(p, q, g, y);
}
public static byte[] encodeSSHDSAPublicKey(DSAPublicKey pk) throws IOException
{
TypesWriter tw = new TypesWriter();
tw.writeString("ssh-dss");
tw.writeMPInt(pk.getP());
tw.writeMPInt(pk.getQ());
tw.writeMPInt(pk.getG());
tw.writeMPInt(pk.getY());
return tw.getBytes();
}
public static byte[] encodeSSHDSASignature(DSASignature ds)
{
TypesWriter tw = new TypesWriter();
tw.writeString("ssh-dss");
byte[] r = ds.getR().toByteArray();
byte[] s = ds.getS().toByteArray();
byte[] a40 = new byte[40];
/* Patch (unsigned) r and s into the target array. */
int r_copylen = (r.length < 20) ? r.length : 20;
int s_copylen = (s.length < 20) ? s.length : 20;
System.arraycopy(r, r.length - r_copylen, a40, 20 - r_copylen, r_copylen);
System.arraycopy(s, s.length - s_copylen, a40, 40 - s_copylen, s_copylen);
tw.writeString(a40, 0, 40);
return tw.getBytes();
}
public static DSASignature decodeSSHDSASignature(byte[] sig) throws IOException
{
TypesReader tr = new TypesReader(sig);
String sig_format = tr.readString();
if (sig_format.equals("ssh-dss") == false)
throw new IOException("Peer sent wrong signature format");
byte[] rsArray = tr.readByteString();
if (rsArray.length != 40)
throw new IOException("Peer sent corrupt signature");
if (tr.remain() != 0)
throw new IOException("Padding in DSA signature!");
/* Remember, s and r are unsigned ints. */
byte[] tmp = new byte[20];
System.arraycopy(rsArray, 0, tmp, 0, 20);
BigInteger r = new BigInteger(1, tmp);
System.arraycopy(rsArray, 20, tmp, 0, 20);
BigInteger s = new BigInteger(1, tmp);
if (log.isEnabled())
{
log.log(30, "decoded ssh-dss signature: first bytes r(" + ((rsArray[0]) & 0xff) + "), s("
+ ((rsArray[20]) & 0xff) + ")");
}
return new DSASignature(r, s);
}
public static boolean verifySignature(byte[] message, DSASignature ds, DSAPublicKey dpk) throws IOException
{
/* Inspired by Bouncycastle's DSASigner class */
SHA1 md = new SHA1();
md.update(message);
byte[] sha_message = new byte[md.getDigestLength()];
md.digest(sha_message);
BigInteger m = new BigInteger(1, sha_message);
BigInteger r = ds.getR();
BigInteger s = ds.getS();
BigInteger g = dpk.getG();
BigInteger p = dpk.getP();
BigInteger q = dpk.getQ();
BigInteger y = dpk.getY();
BigInteger zero = BigInteger.ZERO;
if (log.isEnabled())
{
log.log(60, "ssh-dss signature: m: " + m.toString(16));
log.log(60, "ssh-dss signature: r: " + r.toString(16));
log.log(60, "ssh-dss signature: s: " + s.toString(16));
log.log(60, "ssh-dss signature: g: " + g.toString(16));
log.log(60, "ssh-dss signature: p: " + p.toString(16));
log.log(60, "ssh-dss signature: q: " + q.toString(16));
log.log(60, "ssh-dss signature: y: " + y.toString(16));
}
if (zero.compareTo(r) >= 0 || q.compareTo(r) <= 0)
{
log.log(20, "ssh-dss signature: zero.compareTo(r) >= 0 || q.compareTo(r) <= 0");
return false;
}
if (zero.compareTo(s) >= 0 || q.compareTo(s) <= 0)
{
log.log(20, "ssh-dss signature: zero.compareTo(s) >= 0 || q.compareTo(s) <= 0");
return false;
}
BigInteger w = s.modInverse(q);
BigInteger u1 = m.multiply(w).mod(q);
BigInteger u2 = r.multiply(w).mod(q);
u1 = g.modPow(u1, p);
u2 = y.modPow(u2, p);
BigInteger v = u1.multiply(u2).mod(p).mod(q);
return v.equals(r);
}
public static DSASignature generateSignature(byte[] message, DSAPrivateKey pk, SecureRandom rnd)
{
SHA1 md = new SHA1();
md.update(message);
byte[] sha_message = new byte[md.getDigestLength()];
md.digest(sha_message);
BigInteger m = new BigInteger(1, sha_message);
BigInteger k;
int qBitLength = pk.getQ().bitLength();
do
{
k = new BigInteger(qBitLength, rnd);
}
while (k.compareTo(pk.getQ()) >= 0);
BigInteger r = pk.getG().modPow(k, pk.getP()).mod(pk.getQ());
k = k.modInverse(pk.getQ()).multiply(m.add((pk).getX().multiply(r)));
BigInteger s = k.mod(pk.getQ());
return new DSASignature(r, s);
}
}