/*
* 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.client.kex;
import java.util.Objects;
import org.apache.sshd.common.NamedFactory;
import org.apache.sshd.common.SshConstants;
import org.apache.sshd.common.SshException;
import org.apache.sshd.common.config.keys.KeyUtils;
import org.apache.sshd.common.kex.AbstractDH;
import org.apache.sshd.common.kex.DHFactory;
import org.apache.sshd.common.kex.KeyExchange;
import org.apache.sshd.common.kex.KeyExchangeFactory;
import org.apache.sshd.common.session.Session;
import org.apache.sshd.common.signature.Signature;
import org.apache.sshd.common.util.GenericUtils;
import org.apache.sshd.common.util.ValidateUtils;
import org.apache.sshd.common.util.buffer.Buffer;
import org.apache.sshd.common.util.buffer.ByteArrayBuffer;
/**
* Base class for DHG key exchange algorithms.
* Implementations will only have to configure the required data on the
* {@link org.apache.sshd.common.kex.DHG} class in the {@link #getDH()} method.
*
* @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
*/
public class DHGClient extends AbstractDHClientKeyExchange {
protected final DHFactory factory;
protected AbstractDH dh;
protected DHGClient(DHFactory factory) {
this.factory = Objects.requireNonNull(factory, "No factory");
}
@Override
public final String getName() {
return factory.getName();
}
public static KeyExchangeFactory newFactory(final DHFactory delegate) {
return new KeyExchangeFactory() {
@Override
public String getName() {
return delegate.getName();
}
@Override
public KeyExchange create() {
return new DHGClient(delegate);
}
@Override
public String toString() {
return NamedFactory.class.getSimpleName()
+ "<" + KeyExchange.class.getSimpleName() + ">"
+ "[" + getName() + "]";
}
};
}
@Override
public void init(Session s, byte[] v_s, byte[] v_c, byte[] i_s, byte[] i_c) throws Exception {
super.init(s, v_s, v_c, i_s, i_c);
dh = getDH();
hash = dh.getHash();
hash.init();
e = dh.getE();
if (log.isDebugEnabled()) {
log.debug("init({})[{}] Send SSH_MSG_KEXDH_INIT", this, s);
}
Buffer buffer = s.createBuffer(SshConstants.SSH_MSG_KEXDH_INIT, e.length + Integer.SIZE);
buffer.putMPInt(e);
s.writePacket(buffer);
}
protected AbstractDH getDH() throws Exception {
return factory.create();
}
@Override
public boolean next(int cmd, Buffer buffer) throws Exception {
Session session = getSession();
if (log.isDebugEnabled()) {
log.debug("next({})[{}] process command={}", this, session, KeyExchange.getSimpleKexOpcodeName(cmd));
}
if (cmd != SshConstants.SSH_MSG_KEXDH_REPLY) {
throw new SshException(SshConstants.SSH2_DISCONNECT_KEY_EXCHANGE_FAILED,
"Protocol error: expected packet SSH_MSG_KEXDH_REPLY, got " + KeyExchange.getSimpleKexOpcodeName(cmd));
}
byte[] k_s = buffer.getBytes();
f = buffer.getMPIntAsBytes();
byte[] sig = buffer.getBytes();
dh.setF(f);
k = dh.getK();
buffer = new ByteArrayBuffer(k_s);
serverKey = buffer.getRawPublicKey();
final String keyAlg = KeyUtils.getKeyType(serverKey);
if (GenericUtils.isEmpty(keyAlg)) {
throw new SshException("Unsupported server key type");
}
buffer = new ByteArrayBuffer();
buffer.putBytes(v_c);
buffer.putBytes(v_s);
buffer.putBytes(i_c);
buffer.putBytes(i_s);
buffer.putBytes(k_s);
buffer.putMPInt(e);
buffer.putMPInt(f);
buffer.putMPInt(k);
hash.update(buffer.array(), 0, buffer.available());
h = hash.digest();
Signature verif = ValidateUtils.checkNotNull(NamedFactory.create(session.getSignatureFactories(), keyAlg),
"No verifier located for algorithm=%s",
keyAlg);
verif.initVerifier(serverKey);
verif.update(h);
if (!verif.verify(sig)) {
throw new SshException(SshConstants.SSH2_DISCONNECT_KEY_EXCHANGE_FAILED, "KeyExchange signature verification failed for key type=" + keyAlg);
}
return true;
}
}