--- a/src/ch/ethz/ssh2/signature/DSASHA1Verify.java	Fri Jul 18 11:59:52 2014 -0700
+++ b/src/ch/ethz/ssh2/signature/DSASHA1Verify.java	Fri Jul 18 16:45:43 2014 -0700
@@ -1,213 +1,230 @@
-/*
- * Copyright (c) 2006-2011 Christian Plattner. All rights reserved.
- * Please refer to the LICENSE.txt for licensing details.
- */
-package ch.ethz.ssh2.signature;
+
+package com.trilead.ssh2.signature;
 
 import java.io.IOException;
 import java.math.BigInteger;
-import java.security.DigestException;
+import java.security.InvalidKeyException;
+import java.security.KeyFactory;
+import java.security.NoSuchAlgorithmException;
 import java.security.SecureRandom;
+import java.security.Signature;
+import java.security.SignatureException;
+import java.security.interfaces.DSAParams;
+import java.security.interfaces.DSAPrivateKey;
+import java.security.interfaces.DSAPublicKey;
+import java.security.spec.DSAPublicKeySpec;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.KeySpec;
 
-import ch.ethz.ssh2.PacketFormatException;
-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;
+import com.trilead.ssh2.log.Logger;
+import com.trilead.ssh2.packets.TypesReader;
+import com.trilead.ssh2.packets.TypesWriter;
+
 
 /**
  * DSASHA1Verify.
  *
- * @author Christian Plattner
- * @version $Id: DSASHA1Verify.java 154 2014-04-28 11:45:02Z dkocher@sudo.ch $
+ * @author Christian Plattner, plattner@trilead.com
+ * @version $Id: DSASHA1Verify.java,v 1.2 2008/04/01 12:38:09 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")) {
-            throw new IllegalArgumentException("Not a ssh-dss public key");
-        }
+        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 PacketFormatException("Padding in DSA public key");
+        if (tr.remain() != 0)
+            throw new IOException("Padding in DSA public key!");
+
+        try {
+            KeyFactory kf = KeyFactory.getInstance("DSA");
+            KeySpec ks = new DSAPublicKeySpec(y, p, q, g);
+            return (DSAPublicKey) kf.generatePublic(ks);
         }
-
-        return new DSAPublicKey(p, q, g, y);
+        catch (NoSuchAlgorithmException e) {
+            IOException ex = new IOException();
+            ex.initCause(e);
+            throw ex;
+        }
+        catch (InvalidKeySpecException e) {
+            IOException ex = new IOException();
+            ex.initCause(e);
+            throw ex;
+        }
     }
 
     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());
+        DSAParams params = pk.getParams();
+        tw.writeMPInt(params.getP());
+        tw.writeMPInt(params.getQ());
+        tw.writeMPInt(params.getG());
         tw.writeMPInt(pk.getY());
-
         return tw.getBytes();
     }
 
-    public static byte[] encodeSSHDSASignature(DSASignature ds) {
+    /**
+     * Convert from Java's signature ASN.1 encoding to the SSH spec.
+     * <p>
+     * Java ASN.1 encoding:
+     * <pre>
+     * SEQUENCE ::= {
+     *    r INTEGER,
+     *    s INTEGER
+     * }
+     * </pre>
+     */
+    public static byte[] encodeSSHDSASignature(byte[] ds) {
         TypesWriter tw = new TypesWriter();
-
         tw.writeString("ssh-dss");
-
-        byte[] r = ds.getR().toByteArray();
-        byte[] s = ds.getS().toByteArray();
-
+        int len, index;
+        index = 3;
+        len = ds[index++] & 0xff;
+        byte[] r = new byte[len];
+        System.arraycopy(ds, index, r, 0, r.length);
+        index = index + len + 1;
+        len = ds[index++] & 0xff;
+        byte[] s = new byte[len];
+        System.arraycopy(ds, index, s, 0, s.length);
         byte[] a40 = new byte[40];
-
-		/* Patch (unsigned) r and s into the target array. */
-
+        /* 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 {
-        byte[] rsArray;
+    public static byte[] decodeSSHDSASignature(byte[] sig) throws IOException {
+        byte[] rsArray = null;
 
-        if(sig.length == 40) {
+        if (sig.length == 40) {
+            /* OK, another broken SSH server. */
             rsArray = sig;
         }
         else {
+            /* Hopefully a server obeying the standard... */
             TypesReader tr = new TypesReader(sig);
-
             String sig_format = tr.readString();
 
-            if(sig_format.equals("ssh-dss") == false) {
-                throw new PacketFormatException("Peer sent wrong signature format");
-            }
+            if (sig_format.equals("ssh-dss") == false)
+                throw new IOException("Peer sent wrong signature format");
 
             rsArray = tr.readByteString();
 
-            if(rsArray.length != 40) {
-                throw new PacketFormatException("Peer sent corrupt signature");
-            }
+            if (rsArray.length != 40)
+                throw new IOException("Peer sent corrupt signature");
 
-            if(tr.remain() != 0) {
-                throw new PacketFormatException("Padding in DSA 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.isDebugEnabled()) {
-            log.debug("decoded ssh-dss signature: first bytes r(" + ((rsArray[0]) & 0xff) + "), s("
-                    + ((rsArray[20]) & 0xff) + ")");
-        }
+        int i = 0;
+        int j = 0;
+        byte[] tmp;
 
-        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()];
-        try {
-            md.digest(sha_message);
-        }
-        catch(DigestException e) {
-            throw new IOException(e);
+        if (rsArray[0] == 0 && rsArray[1] == 0 && rsArray[2] == 0) {
+            j = ((rsArray[i++] << 24) & 0xff000000) | ((rsArray[i++] << 16) & 0x00ff0000)
+                | ((rsArray[i++] << 8) & 0x0000ff00) | ((rsArray[i++]) & 0x000000ff);
+            i += j;
+            j = ((rsArray[i++] << 24) & 0xff000000) | ((rsArray[i++] << 16) & 0x00ff0000)
+                | ((rsArray[i++] << 8) & 0x0000ff00) | ((rsArray[i++]) & 0x000000ff);
+            tmp = new byte[j];
+            System.arraycopy(rsArray, i, tmp, 0, j);
+            rsArray = tmp;
         }
 
-        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();
+        /* ASN.1 */
+        int frst = ((rsArray[0] & 0x80) != 0 ? 1 : 0);
+        int scnd = ((rsArray[20] & 0x80) != 0 ? 1 : 0);
+        /* Calculate output length */
+        int length = rsArray.length + 6 + frst + scnd;
+        tmp = new byte[length];
+        /* DER-encoding to match Java */
+        tmp[0] = (byte) 0x30;
 
-        BigInteger zero = BigInteger.ZERO;
-
-        if(log.isDebugEnabled()) {
-            log.debug("ssh-dss signature: m: " + m.toString(16));
-            log.debug("ssh-dss signature: r: " + r.toString(16));
-            log.debug("ssh-dss signature: s: " + s.toString(16));
-            log.debug("ssh-dss signature: g: " + g.toString(16));
-            log.debug("ssh-dss signature: p: " + p.toString(16));
-            log.debug("ssh-dss signature: q: " + q.toString(16));
-            log.debug("ssh-dss signature: y: " + y.toString(16));
-        }
+        if (rsArray.length != 40)
+            throw new IOException("Peer sent corrupt signature");
 
-        if(zero.compareTo(r) >= 0 || q.compareTo(r) <= 0) {
-            log.warning("ssh-dss signature: zero.compareTo(r) >= 0 || q.compareTo(r) <= 0");
-            return false;
-        }
-
-        if(zero.compareTo(s) >= 0 || q.compareTo(s) <= 0) {
-            log.warning("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);
+        /* Calculate length */
+        tmp[1] = (byte) 0x2c;
+        tmp[1] += frst;
+        tmp[1] += scnd;
+        /* First item */
+        tmp[2] = (byte) 0x02;
+        /* First item length */
+        tmp[3] = (byte) 0x14;
+        tmp[3] += frst;
+        /* Copy in the data for first item */
+        System.arraycopy(rsArray, 0, tmp, 4 + frst, 20);
+        /* Second item */
+        tmp[4 + tmp[3]] = (byte) 0x02;
+        /* Second item length */
+        tmp[5 + tmp[3]] = (byte) 0x14;
+        tmp[5 + tmp[3]] += scnd;
+        /* Copy in the data for the second item */
+        System.arraycopy(rsArray, 20, tmp, 6 + tmp[3] + scnd, 20);
+        /* Swap buffers */
+        rsArray = tmp;
+        return rsArray;
     }
 
-    public static DSASignature generateSignature(byte[] message, DSAPrivateKey pk, SecureRandom rnd) throws IOException {
-        SHA1 md = new SHA1();
-        md.update(message);
-        byte[] sha_message = new byte[md.getDigestLength()];
+    public static boolean verifySignature(byte[] message, byte[] ds, DSAPublicKey dpk) throws IOException {
         try {
-            md.digest(sha_message);
+            Signature s = Signature.getInstance("SHA1withDSA");
+            s.initVerify(dpk);
+            s.update(message);
+            return s.verify(ds);
+        }
+        catch (NoSuchAlgorithmException e) {
+            IOException ex = new IOException("No such algorithm");
+            ex.initCause(e);
+            throw ex;
         }
-        catch(DigestException e) {
-            throw new IOException(e);
+        catch (InvalidKeyException e) {
+            IOException ex = new IOException("No such algorithm");
+            ex.initCause(e);
+            throw ex;
         }
+        catch (SignatureException e) {
+            IOException ex = new IOException();
+            ex.initCause(e);
+            throw ex;
+        }
+    }
 
-        BigInteger m = new BigInteger(1, sha_message);
-        BigInteger k;
-        int qBitLength = pk.getQ().bitLength();
-
-        do {
-            k = new BigInteger(qBitLength, rnd);
+    public static byte[] generateSignature(byte[] message, DSAPrivateKey pk, SecureRandom rnd) throws IOException {
+        try {
+            Signature s = Signature.getInstance("SHA1withDSA");
+            s.initSign(pk);
+            s.update(message);
+            return s.sign();
         }
-        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);
+        catch (NoSuchAlgorithmException e) {
+            IOException ex = new IOException();
+            ex.initCause(e);
+            throw ex;
+        }
+        catch (InvalidKeyException e) {
+            IOException ex = new IOException();
+            ex.initCause(e);
+            throw ex;
+        }
+        catch (SignatureException e) {
+            IOException ex = new IOException();
+            ex.initCause(e);
+            throw ex;
+        }
     }
 }