/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.sshd.server.kex;
import java.security.KeyPair;
import java.security.PublicKey;
import org.apache.sshd.common.Digest;
import org.apache.sshd.common.KeyExchange;
import org.apache.sshd.common.NamedFactory;
import org.apache.sshd.common.Signature;
import org.apache.sshd.common.SshConstants;
import org.apache.sshd.common.SshException;
import org.apache.sshd.common.kex.AbstractDH;
import org.apache.sshd.common.session.AbstractSession;
import org.apache.sshd.common.util.Buffer;
import org.apache.sshd.common.util.BufferUtils;
import org.apache.sshd.server.session.ServerSession;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* TODO Add javadoc
*
* @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
*/
public abstract class AbstractDHGServer implements KeyExchange {
private final Logger log = LoggerFactory.getLogger(getClass());
private ServerSession session;
private byte[] V_S;
private byte[] V_C;
private byte[] I_S;
private byte[] I_C;
private Digest hash;
private AbstractDH dh;
private byte[] e;
private byte[] f;
private byte[] K;
private byte[] H;
public void init(AbstractSession s, byte[] V_S, byte[] V_C, byte[] I_S, byte[] I_C) throws Exception {
if (!(s instanceof ServerSession)) {
throw new IllegalStateException("Using a server side KeyExchange on a client");
}
session = (ServerSession) s;
this.V_S = V_S;
this.V_C = V_C;
this.I_S = I_S;
this.I_C = I_C;
dh = getDH();
hash = dh.getHash();
hash.init();
f = dh.getE();
}
protected abstract AbstractDH getDH() throws Exception;
public boolean next(Buffer buffer) throws Exception {
byte cmd = buffer.getByte();
if (cmd != SshConstants.SSH_MSG_KEXDH_INIT) {
throw new SshException(SshConstants.SSH2_DISCONNECT_KEY_EXCHANGE_FAILED,
"Protocol error: expected packet " + SshConstants.SSH_MSG_KEXDH_INIT + ", got " + cmd);
}
log.debug("Received SSH_MSG_KEXDH_INIT");
e = buffer.getMPIntAsBytes();
dh.setF(e);
K = dh.getK();
byte[] K_S;
KeyPair kp = session.getHostKey();
String algo = session.getNegotiated(SshConstants.PROPOSAL_SERVER_HOST_KEY_ALGS);
Signature sig = NamedFactory.Utils.create(session.getFactoryManager().getSignatureFactories(), algo);
sig.init(kp.getPublic(), kp.getPrivate());
buffer = new Buffer();
buffer.putRawPublicKey(kp.getPublic());
K_S = buffer.getCompactData();
buffer.clear();
buffer.putString(V_C);
buffer.putString(V_S);
buffer.putString(I_C);
buffer.putString(I_S);
buffer.putString(K_S);
buffer.putMPInt(e);
buffer.putMPInt(f);
buffer.putMPInt(K);
hash.update(buffer.array(), 0, buffer.available());
H = hash.digest();
byte[] sigH;
buffer.clear();
sig.update(H, 0, H.length);
buffer.putString(algo);
buffer.putString(sig.sign());
sigH = buffer.getCompactData();
if (log.isDebugEnabled()) {
log.debug("K_S: {}", BufferUtils.printHex(K_S));
log.debug("f: {}", BufferUtils.printHex(f));
log.debug("sigH: {}", BufferUtils.printHex(sigH));
}
// Send response
log.debug("Send SSH_MSG_KEXDH_REPLY");
buffer.clear();
buffer.rpos(5);
buffer.wpos(5);
buffer.putByte(SshConstants.SSH_MSG_KEXDH_REPLY);
buffer.putString(K_S);
buffer.putString(f);
buffer.putString(sigH);
session.writePacket(buffer);
return true;
}
public Digest getHash() {
return hash;
}
public byte[] getH() {
return H;
}
public byte[] getK() {
return K;
}
public PublicKey getServerKey() {
return session.getHostKey().getPublic();
}
}