/*
 * 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 java.security.DigestException;
import java.security.SecureRandom;
import java.security.interfaces.DSAPublicKey;
import java.security.interfaces.ECPublicKey;
import java.security.interfaces.RSAPublicKey;

import ch.ethz.ssh2.ConnectionInfo;
import ch.ethz.ssh2.PacketTypeException;
import ch.ethz.ssh2.ServerHostKeyVerifier;
import ch.ethz.ssh2.compression.CompressionFactory;
import ch.ethz.ssh2.compression.Compressor;
import ch.ethz.ssh2.crypto.CryptoWishList;
import ch.ethz.ssh2.crypto.cipher.BlockCipher;
import ch.ethz.ssh2.crypto.cipher.BlockCipherFactory;
import ch.ethz.ssh2.crypto.dh.GenericDhExchange;
import ch.ethz.ssh2.crypto.dh.DhGroupExchange;
import ch.ethz.ssh2.crypto.digest.MAC;
import ch.ethz.ssh2.packets.PacketKexDHInit;
import ch.ethz.ssh2.packets.PacketKexDHReply;
import ch.ethz.ssh2.packets.PacketKexDhGexGroup;
import ch.ethz.ssh2.packets.PacketKexDhGexInit;
import ch.ethz.ssh2.packets.PacketKexDhGexReply;
import ch.ethz.ssh2.packets.PacketKexDhGexRequest;
import ch.ethz.ssh2.packets.PacketKexDhGexRequestOld;
import ch.ethz.ssh2.packets.PacketKexInit;
import ch.ethz.ssh2.packets.Packets;
import ch.ethz.ssh2.signature.DSASHA1Verify;
import ch.ethz.ssh2.signature.ECDSASHA2Verify;
import ch.ethz.ssh2.signature.RSASHA1Verify;

/**
 * @version $Id: ClientKexManager.java 160 2014-05-01 14:30:26Z dkocher@sudo.ch $
 */
public class ClientKexManager extends KexManager {

    private final ServerHostKeyVerifier verifier;

    private final String hostname;

    private final int port;

    public ClientKexManager(TransportManager tm, ClientServerHello csh, CryptoWishList initialCwl, String hostname, int port,
                            ServerHostKeyVerifier keyVerifier, SecureRandom rnd) {
        super(tm, csh, initialCwl, rnd);
        this.hostname = hostname;
        this.port = port;
        this.verifier = keyVerifier;
    }

    protected boolean verifySignature(byte[] sig, byte[] hostkey) throws IOException {
        if (kxs.np.server_host_key_algo.startsWith("ecdsa-sha2-")) {
            byte[] rs = ECDSASHA2Verify.decodeSSHECDSASignature(sig);
            ECPublicKey epk = ECDSASHA2Verify.decodeSSHECDSAPublicKey(hostkey);
            log.debug("Verifying ecdsa signature");
            return ECDSASHA2Verify.verifySignature(kxs.H, rs, epk);
        }

        if (kxs.np.server_host_key_algo.equals("ssh-rsa")) {
            byte[] rs = RSASHA1Verify.decodeSSHRSASignature(sig);
            RSAPublicKey rpk = RSASHA1Verify.decodeSSHRSAPublicKey(hostkey);
            log.debug("Verifying ssh-rsa signature");
            return RSASHA1Verify.verifySignature(kxs.H, rs, rpk);
        }

        if (kxs.np.server_host_key_algo.equals("ssh-dss")) {
            byte[] ds = DSASHA1Verify.decodeSSHDSASignature(sig);
            DSAPublicKey dpk = DSASHA1Verify.decodeSSHDSAPublicKey(hostkey);
            log.debug("Verifying ssh-dss signature");
            return DSASHA1Verify.verifySignature(kxs.H, ds, dpk);
        }

        throw new IOException("Unknown server host key algorithm '" + kxs.np.server_host_key_algo + "'");
    }

    public void handleFailure(final IOException failure) {
        synchronized(accessLock) {
            connectionClosed = true;
            accessLock.notifyAll();
        }
    }

    public synchronized void handleMessage(byte[] msg) 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 PacketTypeException(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 PacketTypeException(msg[0]);
            }

            if(kxs == null) {
                /*
                 * Ah, OK, peer wants to do KEX. Let's be nice and play
				 * together.
				 */
                kxs = new KexState();
                kxs.dhgexParameters = nextKEXdhgexParameters;
                kip = new PacketKexInit(nextKEXcryptoWishList, rnd);
                kxs.localKEX = kip;
                tm.sendKexMessage(kip.getPayload());
            }

            kip = new PacketKexInit(msg);
            kxs.remoteKEX = kip;

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

            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-group-exchange-sha1") ||
                kxs.np.kex_algo.equals("diffie-hellman-group-exchange-sha256")) {
                if(kxs.dhgexParameters.getMin_group_len() == 0) {
                    PacketKexDhGexRequestOld dhgexreq = new PacketKexDhGexRequestOld(kxs.dhgexParameters);
                    tm.sendKexMessage(dhgexreq.getPayload());

                }
                else {
                    PacketKexDhGexRequest dhgexreq = new PacketKexDhGexRequest(kxs.dhgexParameters);
                    tm.sendKexMessage(dhgexreq.getPayload());
                }
                if (kxs.np.kex_algo.endsWith("sha1")) {
                    kxs.hashAlgo = "SHA1";
                }
                else {
                    kxs.hashAlgo = "SHA-256";
                }
                kxs.state = 1;
                return;
            }

            if (kxs.np.kex_algo.equals("diffie-hellman-group1-sha1")  ||
                kxs.np.kex_algo.equals("diffie-hellman-group14-sha1") ||
                kxs.np.kex_algo.equals("ecdh-sha2-nistp256")          ||
                kxs.np.kex_algo.equals("ecdh-sha2-nistp384")          ||
                kxs.np.kex_algo.equals("ecdh-sha2-nistp521")) {
                kxs.dhx = GenericDhExchange.getInstance(kxs.np.kex_algo);
                kxs.dhx.init(kxs.np.kex_algo);
                PacketKexDHInit kp = new PacketKexDHInit(kxs.dhx.getE());
                tm.sendKexMessage(kp.getPayload());
                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;
            Compressor comp;

            try {
                cbc = BlockCipherFactory.createCipher(kxs.np.enc_algo_server_to_client, false,
                        km.enc_key_server_to_client, km.initial_iv_server_to_client);

                try {
                    mac = new MAC(kxs.np.mac_algo_server_to_client, km.integrity_key_server_to_client);
                }
                catch(DigestException e) {
                    throw new IOException(e);
                }

                comp = CompressionFactory.createCompressor(kxs.np.comp_algo_server_to_client);
            }
            catch(IllegalArgumentException e) {
                throw new IOException(e.getMessage());
            }

            tm.changeRecvCipher(cbc, mac);
            tm.changeRecvCompression(comp);

            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-group-exchange-sha1") ||
            kxs.np.kex_algo.equals("diffie-hellman-group-exchange-sha256")) {
            if(kxs.state == 1) {
                PacketKexDhGexGroup dhgexgrp = new PacketKexDhGexGroup(msg);
                kxs.dhgx = new DhGroupExchange(dhgexgrp.getP(), dhgexgrp.getG());
                kxs.dhgx.init(rnd);
                PacketKexDhGexInit dhgexinit = new PacketKexDhGexInit(kxs.dhgx.getE());
                tm.sendKexMessage(dhgexinit.getPayload());
                kxs.state = 2;
                return;
            }

            if(kxs.state == 2) {
                PacketKexDhGexReply dhgexrpl = new PacketKexDhGexReply(msg);

                kxs.remote_hostkey = dhgexrpl.getHostKey();

                if(verifier != null) {
                    try {
                        if(!verifier.verifyServerHostKey(hostname, port, kxs.np.server_host_key_algo, kxs.remote_hostkey)) {
                            throw new IOException("The server host key was not accepted by the verifier callback");
                        }
                    }
                    catch(Exception e) {
                        throw new IOException(
                                "The server host key was not accepted by the verifier callback.", e);
                    }
                }

                kxs.dhgx.setF(dhgexrpl.getF());

                try {
                    kxs.H = kxs.dhgx.calculateH(csh.getClientString(), csh.getServerString(),
                            kxs.localKEX.getPayload(), kxs.remoteKEX.getPayload(), dhgexrpl.getHostKey(),
                            kxs.dhgexParameters);
                }
                catch(IllegalArgumentException e) {
                    throw new IOException("KEX error.", e);
                }
                if(!verifySignature(dhgexrpl.getSignature(), kxs.remote_hostkey)) {
                    throw new IOException("Invalid remote host key signature");
                }
                kxs.K = kxs.dhgx.getK();
                finishKex(true);
                kxs.state = -1;
                return;
            }

            throw new IllegalStateException("Illegal State in KEX Exchange!");
        }

        if (kxs.np.kex_algo.equals("diffie-hellman-group1-sha1")  ||
            kxs.np.kex_algo.equals("diffie-hellman-group14-sha1") ||
            kxs.np.kex_algo.equals("ecdh-sha2-nistp256")          ||
            kxs.np.kex_algo.equals("ecdh-sha2-nistp384")          ||
            kxs.np.kex_algo.equals("ecdh-sha2-nistp521")) {
            if(kxs.state == 1) {
                PacketKexDHReply dhr = new PacketKexDHReply(msg);
                kxs.remote_hostkey = dhr.getHostKey();

                if(verifier != null) {
                    try {
                        if(!verifier.verifyServerHostKey(hostname, port, kxs.np.server_host_key_algo, kxs.remote_hostkey)) {
                            throw new IOException("The server host key was not accepted by the verifier callback");
                        }
                    }
                    catch(Exception e) {
                        throw new IOException("The server host key was not accepted by the verifier callback", e);
                    }
                }
                kxs.dhx.setF(dhr.getF());
                try {
                    kxs.H = kxs.dhx.calculateH(csh.getClientString(), csh.getServerString(), kxs.localKEX.getPayload(),
                            kxs.remoteKEX.getPayload(), dhr.getHostKey());
                }
                catch(IllegalArgumentException e) {
                    throw new IOException("KEX error.", e);
                }
                if(!verifySignature(dhr.getSignature(), kxs.remote_hostkey)) {
                    throw new IOException("Invalid remote host key signature");
                }
                kxs.K = kxs.dhx.getK();
                finishKex(true);
                kxs.state = -1;
                return;
            }
        }
        throw new IllegalStateException(String.format("Unknown KEX method %s", kxs.np.kex_algo));
    }
}