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/*
 * Copyright (c) 2006-2013 Christian Plattner. All rights reserved.
 * Please refer to the LICENSE.txt for licensing details.
 */
package ch.ethz.ssh2.transport;

import java.io.IOException;

import ch.ethz.ssh2.ConnectionInfo;
import ch.ethz.ssh2.auth.ServerAuthenticationManager;
import ch.ethz.ssh2.crypto.cipher.BlockCipher;
import ch.ethz.ssh2.crypto.cipher.BlockCipherFactory;
import ch.ethz.ssh2.crypto.dh.DhExchange;
import ch.ethz.ssh2.crypto.digest.MAC;
import ch.ethz.ssh2.packets.PacketKexDHInit;
import ch.ethz.ssh2.packets.PacketKexDHReply;
import ch.ethz.ssh2.packets.PacketKexInit;
import ch.ethz.ssh2.packets.Packets;
import ch.ethz.ssh2.server.ServerConnectionState;
import ch.ethz.ssh2.signature.DSASHA1Verify;
import ch.ethz.ssh2.signature.DSASignature;
import ch.ethz.ssh2.signature.RSASHA1Verify;
import ch.ethz.ssh2.signature.RSASignature;

public class ServerKexManager extends KexManager
{
	private final ServerConnectionState state;
	private boolean authenticationStarted = false;

	public ServerKexManager(ServerConnectionState state)
	{
		super(state.tm, state.csh, state.next_cryptoWishList, state.generator);
		this.state = state;
	}

	public void handleMessage(byte[] msg, int msglen) throws IOException
	{
		PacketKexInit kip;

		if (msg == null)
		{
			synchronized (accessLock)
			{
				connectionClosed = true;
				accessLock.notifyAll();
				return;
			}
		}

		if ((kxs == null) && (msg[0] != Packets.SSH_MSG_KEXINIT))
			throw new IOException("Unexpected KEX message (type " + msg[0] + ")");

		if (ignore_next_kex_packet)
		{
			ignore_next_kex_packet = false;
			return;
		}

		if (msg[0] == Packets.SSH_MSG_KEXINIT)
		{
			if ((kxs != null) && (kxs.state != 0))
				throw new IOException("Unexpected SSH_MSG_KEXINIT message during on-going kex exchange!");
			
			if (kxs == null)
			{
				/*
				 * Ah, OK, peer wants to do KEX. Let's be nice and play
				 * together.
				 */
				kxs = new KexState();
				kxs.local_dsa_key = nextKEXdsakey;
				kxs.local_rsa_key = nextKEXrsakey;
				kxs.dhgexParameters = nextKEXdhgexParameters;
				kip = new PacketKexInit(nextKEXcryptoWishList, rnd);
				kxs.localKEX = kip;
				tm.sendKexMessage(kip.getPayload());
			}

			kip = new PacketKexInit(msg, 0, msglen);
			kxs.remoteKEX = kip;

			kxs.np = mergeKexParameters(kxs.remoteKEX.getKexParameters(), kxs.localKEX.getKexParameters());

			if (kxs.np == null)
				throw new IOException("Cannot negotiate, proposals do not match.");

			if (kxs.remoteKEX.isFirst_kex_packet_follows() && (kxs.np.guessOK == false))
			{
				/*
				 * Guess was wrong, we need to ignore the next kex packet.
				 */

				ignore_next_kex_packet = true;
			}

			if (kxs.np.kex_algo.equals("diffie-hellman-group1-sha1")
					|| kxs.np.kex_algo.equals("diffie-hellman-group14-sha1"))
			{
				kxs.dhx = new DhExchange();

				if (kxs.np.kex_algo.equals("diffie-hellman-group1-sha1"))
					kxs.dhx.serverInit(1, rnd);
				else
					kxs.dhx.serverInit(14, rnd);

				kxs.state = 1;
				return;
			}

			throw new IllegalStateException("Unkown KEX method!");
		}

		if (msg[0] == Packets.SSH_MSG_NEWKEYS)
		{
			if (km == null)
				throw new IOException("Peer sent SSH_MSG_NEWKEYS, but I have no key material ready!");

			BlockCipher cbc;
			MAC mac;

			try
			{
				cbc = BlockCipherFactory.createCipher(kxs.np.enc_algo_client_to_server, false,
						km.enc_key_client_to_server, km.initial_iv_client_to_server);

				mac = new MAC(kxs.np.mac_algo_client_to_server, km.integrity_key_client_to_server);

			}
			catch (IllegalArgumentException e1)
			{
				throw new IOException("Fatal error during MAC startup!");
			}

			tm.changeRecvCipher(cbc, mac);

			ConnectionInfo sci = new ConnectionInfo();

			kexCount++;

			sci.keyExchangeAlgorithm = kxs.np.kex_algo;
			sci.keyExchangeCounter = kexCount;
			sci.clientToServerCryptoAlgorithm = kxs.np.enc_algo_client_to_server;
			sci.serverToClientCryptoAlgorithm = kxs.np.enc_algo_server_to_client;
			sci.clientToServerMACAlgorithm = kxs.np.mac_algo_client_to_server;
			sci.serverToClientMACAlgorithm = kxs.np.mac_algo_server_to_client;
			sci.serverHostKeyAlgorithm = kxs.np.server_host_key_algo;
			sci.serverHostKey = kxs.remote_hostkey;

			synchronized (accessLock)
			{
				lastConnInfo = sci;
				accessLock.notifyAll();
			}

			kxs = null;
			return;
		}

		if ((kxs == null) || (kxs.state == 0))
			throw new IOException("Unexpected Kex submessage!");

		if (kxs.np.kex_algo.equals("diffie-hellman-group1-sha1")
				|| kxs.np.kex_algo.equals("diffie-hellman-group14-sha1"))
		{
			if (kxs.state == 1)
			{
				PacketKexDHInit dhi = new PacketKexDHInit(msg, 0, msglen);

				kxs.dhx.setE(dhi.getE());

				byte[] hostKey = null;

				if (kxs.np.server_host_key_algo.equals("ssh-rsa"))
				{
					hostKey = RSASHA1Verify.encodeSSHRSAPublicKey(kxs.local_rsa_key.getPublicKey());
				}

				if (kxs.np.server_host_key_algo.equals("ssh-dss"))
				{
					hostKey = DSASHA1Verify.encodeSSHDSAPublicKey(kxs.local_dsa_key.getPublicKey());
				}

				try
				{
					kxs.H = kxs.dhx.calculateH(csh.getClientString(), csh.getServerString(),
							kxs.remoteKEX.getPayload(), kxs.localKEX.getPayload(), hostKey);
				}
				catch (IllegalArgumentException e)
				{
					throw new IOException("KEX error.", e);
				}

				kxs.K = kxs.dhx.getK();

				byte[] signature = null;

				if (kxs.np.server_host_key_algo.equals("ssh-rsa"))
				{
					RSASignature rs = RSASHA1Verify.generateSignature(kxs.H, kxs.local_rsa_key);
					signature = RSASHA1Verify.encodeSSHRSASignature(rs);
				}

				if (kxs.np.server_host_key_algo.equals("ssh-dss"))
				{
					DSASignature ds = DSASHA1Verify.generateSignature(kxs.H, kxs.local_dsa_key, rnd);
					signature = DSASHA1Verify.encodeSSHDSASignature(ds);
				}

				PacketKexDHReply dhr = new PacketKexDHReply(hostKey, kxs.dhx.getF(), signature);
				tm.sendKexMessage(dhr.getPayload());

				finishKex(false);
				kxs.state = -1;

				if (authenticationStarted == false)
				{
					authenticationStarted = true;
					state.am = new ServerAuthenticationManager(state);
				}

				return;
			}
		}

		throw new IllegalStateException("Unkown KEX method! (" + kxs.np.kex_algo + ")");
	}
}