1 files changed, 115 insertions, 0 deletions
diff --git a/src/main/java/ch/ethz/ssh2/crypto/dh/DhGroupExchange.java b/src/main/java/ch/ethz/ssh2/crypto/dh/DhGroupExchange.java
new file mode 100644
index 0000000..c2defda
--- /dev/null
+++ b/src/main/java/ch/ethz/ssh2/crypto/dh/DhGroupExchange.java
@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) 2006-2011 Christian Plattner. All rights reserved.
+ * Please refer to the LICENSE.txt for licensing details.
+ */
+package ch.ethz.ssh2.crypto.dh;
+
+import java.math.BigInteger;
+import java.security.SecureRandom;
+
+import ch.ethz.ssh2.DHGexParameters;
+import ch.ethz.ssh2.crypto.digest.HashForSSH2Types;
+
+/**
+ * DhGroupExchange.
+ * 
+ * @author Christian Plattner
+ * @version 2.50, 03/15/10
+ */
+public class DhGroupExchange
+{
+	/* Given by the standard */
+
+	private BigInteger p;
+	private BigInteger g;
+
+	/* Client public and private */
+
+	private BigInteger e;
+	private BigInteger x;
+
+	/* Server public */
+
+	private BigInteger f;
+
+	/* Shared secret */
+
+	private BigInteger k;
+
+	public DhGroupExchange(BigInteger p, BigInteger g)
+	{
+		this.p = p;
+		this.g = g;
+	}
+
+	public void init(SecureRandom rnd)
+	{
+		k = null;
+
+		x = new BigInteger(p.bitLength() - 1, rnd);
+		e = g.modPow(x, p);
+	}
+
+	/**
+	 * @return Returns the e.
+	 */
+	public BigInteger getE()
+	{
+		if (e == null)
+			throw new IllegalStateException("Not initialized!");
+
+		return e;
+	}
+
+	/**
+	 * @return Returns the shared secret k.
+	 */
+	public BigInteger getK()
+	{
+		if (k == null)
+			throw new IllegalStateException("Shared secret not yet known, need f first!");
+
+		return k;
+	}
+
+	/**
+	 * Sets f and calculates the shared secret.
+	 */
+	public void setF(BigInteger f)
+	{
+		if (e == null)
+			throw new IllegalStateException("Not initialized!");
+
+		BigInteger zero = BigInteger.valueOf(0);
+
+		if (zero.compareTo(f) >= 0 || p.compareTo(f) <= 0)
+			throw new IllegalArgumentException("Invalid f specified!");
+
+		this.f = f;
+		this.k = f.modPow(x, p);
+	}
+
+	public byte[] calculateH(byte[] clientversion, byte[] serverversion, byte[] clientKexPayload,
+			byte[] serverKexPayload, byte[] hostKey, DHGexParameters para)
+	{
+		HashForSSH2Types hash = new HashForSSH2Types("SHA1");
+
+		hash.updateByteString(clientversion);
+		hash.updateByteString(serverversion);
+		hash.updateByteString(clientKexPayload);
+		hash.updateByteString(serverKexPayload);
+		hash.updateByteString(hostKey);
+		if (para.getMin_group_len() > 0)
+			hash.updateUINT32(para.getMin_group_len());
+		hash.updateUINT32(para.getPref_group_len());
+		if (para.getMax_group_len() > 0)
+			hash.updateUINT32(para.getMax_group_len());
+		hash.updateBigInt(p);
+		hash.updateBigInt(g);
+		hash.updateBigInt(e);
+		hash.updateBigInt(f);
+		hash.updateBigInt(k);
+
+		return hash.getDigest();
+	}
+}