/*
* Copyright 2010, 2011 sshj contributors
*
* Licensed 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.
*
* This file may incorporate work covered by the following copyright and
* permission notice:
*
* 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 net.schmizz.sshj.transport.kex;
import net.schmizz.sshj.common.Buffer;
import net.schmizz.sshj.common.DisconnectReason;
import net.schmizz.sshj.common.Factory;
import net.schmizz.sshj.common.KeyType;
import net.schmizz.sshj.common.Message;
import net.schmizz.sshj.common.SSHPacket;
import net.schmizz.sshj.signature.Signature;
import net.schmizz.sshj.transport.Transport;
import net.schmizz.sshj.transport.TransportException;
import net.schmizz.sshj.transport.digest.Digest;
import net.schmizz.sshj.transport.digest.SHA1;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.math.BigInteger;
import java.security.GeneralSecurityException;
import java.security.PublicKey;
import java.util.Arrays;
/**
* Base class for DHG key exchange algorithms. Implementations will only have to configure the required data on the
* {@link DH} class in the
*/
public abstract class AbstractDHG
implements KeyExchange {
private final Logger log = LoggerFactory.getLogger(getClass());
private Transport trans;
private final Digest sha1 = new SHA1();
private final DH dh = new DH();
private String V_S;
private String V_C;
private byte[] I_S;
private byte[] I_C;
private byte[] H;
private PublicKey hostKey;
@Override
public byte[] getH() {
return Arrays.copyOf(H, H.length);
}
@Override
public BigInteger getK() {
return dh.getK();
}
@Override
public Digest getHash() {
return sha1;
}
@Override
public PublicKey getHostKey() {
return hostKey;
}
@Override
public void init(Transport trans, String V_S, String V_C, byte[] I_S, byte[] I_C)
throws GeneralSecurityException, TransportException {
this.trans = trans;
this.V_S = V_S;
this.V_C = V_C;
this.I_S = Arrays.copyOf(I_S, I_S.length);
this.I_C = Arrays.copyOf(I_C, I_C.length);
sha1.init();
initDH(dh);
log.info("Sending SSH_MSG_KEXDH_INIT");
trans.write(new SSHPacket(Message.KEXDH_INIT).putMPInt(dh.getE()));
}
@Override
public boolean next(Message msg, SSHPacket packet)
throws GeneralSecurityException, TransportException {
if (msg != Message.KEXDH_31)
throw new TransportException(DisconnectReason.KEY_EXCHANGE_FAILED, "Unexpected packet: " + msg);
log.info("Received SSH_MSG_KEXDH_REPLY");
final byte[] K_S;
final BigInteger f;
final byte[] sig; // signature sent by server
try {
K_S = packet.readBytes();
f = packet.readMPInt();
sig = packet.readBytes();
hostKey = new Buffer.PlainBuffer(K_S).readPublicKey();
} catch (Buffer.BufferException be) {
throw new TransportException(be);
}
dh.computeK(f);
final Buffer.PlainBuffer buf = new Buffer.PlainBuffer()
.putString(V_C)
.putString(V_S)
.putString(I_C)
.putString(I_S)
.putString(K_S)
.putMPInt(dh.getE())
.putMPInt(f)
.putMPInt(dh.getK());
sha1.update(buf.array(), buf.rpos(), buf.available());
H = sha1.digest();
Signature signature = Factory.Named.Util.create(trans.getConfig().getSignatureFactories(),
KeyType.fromKey(hostKey).toString());
signature.init(hostKey, null);
signature.update(H, 0, H.length);
if (!signature.verify(sig))
throw new TransportException(DisconnectReason.KEY_EXCHANGE_FAILED,
"KeyExchange signature verification failed");
return true;
}
protected abstract void initDH(DH dh)
throws GeneralSecurityException;
}