org.apache.sshd.client.kex.DHGEXClient Maven / Gradle / Ivy
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* 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
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* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
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package org.apache.sshd.client.kex;
import java.math.BigInteger;
import java.security.PublicKey;
import java.util.Objects;
import org.apache.sshd.client.session.AbstractClientSession;
import org.apache.sshd.common.NamedFactory;
import org.apache.sshd.common.SshConstants;
import org.apache.sshd.common.SshException;
import org.apache.sshd.common.kex.AbstractDH;
import org.apache.sshd.common.kex.DHFactory;
import org.apache.sshd.common.kex.KexProposalOption;
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.BufferUtils;
import org.apache.sshd.common.util.buffer.ByteArrayBuffer;
import org.apache.sshd.common.util.security.SecurityUtils;
import org.apache.sshd.core.CoreModuleProperties;
/**
* @author Apache MINA SSHD Project
*/
public class DHGEXClient extends AbstractDHClientKeyExchange {
protected final DHFactory factory;
protected byte expected;
protected int min;
protected int prf;
protected int max;
protected AbstractDH dh;
protected byte[] g;
private byte[] p;
private BigInteger pValue;
protected DHGEXClient(DHFactory factory, Session session) {
super(session);
this.factory = Objects.requireNonNull(factory, "No factory");
// SSHD-941 give the user a chance to intervene in the choice
min = CoreModuleProperties.PROP_DHGEX_CLIENT_MIN_KEY.get(session)
.orElse(SecurityUtils.getMinDHGroupExchangeKeySize());
max = CoreModuleProperties.PROP_DHGEX_CLIENT_MAX_KEY.get(session)
.orElse(SecurityUtils.getMaxDHGroupExchangeKeySize());
prf = CoreModuleProperties.PROP_DHGEX_CLIENT_PRF_KEY.get(session)
.orElse(Math.min(SecurityUtils.PREFERRED_DHGEX_KEY_SIZE, max));
}
@Override
public final String getName() {
return factory.getName();
}
protected byte[] getP() {
return p;
}
protected BigInteger getPValue() {
if (pValue == null) {
pValue = BufferUtils.fromMPIntBytes(getP());
}
return pValue;
}
protected void setP(byte[] p) {
this.p = p;
if (pValue != null) {
pValue = null; // force lazy re-initialization
}
}
protected void validateEValue() throws Exception {
validateEValue(getPValue());
}
protected void validateFValue() throws Exception {
validateFValue(getPValue());
}
public static KeyExchangeFactory newFactory(DHFactory delegate) {
return new KeyExchangeFactory() {
@Override
public String getName() {
return delegate.getName();
}
@Override
public KeyExchange createKeyExchange(Session session) throws Exception {
return new DHGEXClient(delegate, session);
}
@Override
public String toString() {
return NamedFactory.class.getSimpleName()
+ "<" + KeyExchange.class.getSimpleName() + ">"
+ "[" + getName() + "]";
}
};
}
@Override
public void init(byte[] v_s, byte[] v_c, byte[] i_s, byte[] i_c) throws Exception {
super.init(v_s, v_c, i_s, i_c);
Session s = getSession();
if (log.isDebugEnabled()) {
log.debug("init({})[{}] Send SSH_MSG_KEX_DH_GEX_REQUEST - min={}, prf={}, max={}",
this, s, min, prf, max);
}
if ((max < min) || (prf < min) || (max < prf)) {
throw new SshException(SshConstants.SSH2_DISCONNECT_KEY_EXCHANGE_FAILED,
"Protocol error: bad parameters " + min + " !< " + prf + " !< " + max);
}
Buffer buffer = s.createBuffer(SshConstants.SSH_MSG_KEX_DH_GEX_REQUEST, Integer.SIZE);
buffer.putInt(min);
buffer.putInt(prf);
buffer.putInt(max);
s.writePacket(buffer);
expected = SshConstants.SSH_MSG_KEX_DH_GEX_GROUP;
}
@Override
@SuppressWarnings("checkstyle:VariableDeclarationUsageDistance")
public boolean next(int cmd, Buffer buffer) throws Exception {
AbstractClientSession session = getClientSession();
boolean debugEnabled = log.isDebugEnabled();
if (debugEnabled) {
log.debug("next({})[{}] process command={} (expected={})",
this, session, KeyExchange.getGroupKexOpcodeName(cmd),
KeyExchange.getGroupKexOpcodeName(expected));
}
if (cmd != expected) {
throw new SshException(SshConstants.SSH2_DISCONNECT_KEY_EXCHANGE_FAILED,
"Protocol error: expected packet " + KeyExchange.getGroupKexOpcodeName(expected)
+ ", got "
+ KeyExchange.getGroupKexOpcodeName(cmd));
}
if (cmd == SshConstants.SSH_MSG_KEX_DH_GEX_GROUP) {
setP(buffer.getMPIntAsBytes());
g = buffer.getMPIntAsBytes();
dh = getDH(getPValue(), new BigInteger(g));
hash = dh.getHash();
hash.init();
byte[] e = updateE(dh.getE());
validateEValue();
if (debugEnabled) {
log.debug("next({})[{}] Send SSH_MSG_KEX_DH_GEX_INIT", this, session);
}
buffer = session.createBuffer(
SshConstants.SSH_MSG_KEX_DH_GEX_INIT, e.length + Byte.SIZE);
buffer.putMPInt(e);
session.writePacket(buffer);
expected = SshConstants.SSH_MSG_KEX_DH_GEX_REPLY;
return false;
}
if (cmd == SshConstants.SSH_MSG_KEX_DH_GEX_REPLY) {
if (debugEnabled) {
log.debug("next({})[{}] validate SSH_MSG_KEX_DH_GEX_REPLY - min={}, prf={}, max={}",
this, session, min, prf, max);
}
byte[] k_s = buffer.getBytes();
byte[] f = updateF(buffer);
byte[] sig = buffer.getBytes();
validateFValue();
dh.setF(f);
k = normalize(dh.getK());
buffer = new ByteArrayBuffer(k_s);
PublicKey serverKey = buffer.getRawPublicKey();
String keyAlg = session.getNegotiatedKexParameter(KexProposalOption.SERVERKEYS);
if (GenericUtils.isEmpty(keyAlg)) {
throw new SshException("Unsupported server key type: " + serverKey.getAlgorithm()
+ " [" + serverKey.getFormat() + "]");
}
buffer = new ByteArrayBuffer();
buffer.putBytes(v_c);
buffer.putBytes(v_s);
buffer.putBytes(i_c);
buffer.putBytes(i_s);
buffer.putBytes(k_s);
buffer.putInt(min);
buffer.putInt(prf);
buffer.putInt(max);
buffer.putMPInt(getP());
buffer.putMPInt(g);
buffer.putMPInt(getE());
buffer.putMPInt(f);
buffer.putBytes(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(session, serverKey);
verif.update(session, h);
if (!verif.verify(session, sig)) {
throw new SshException(SshConstants.SSH2_DISCONNECT_KEY_EXCHANGE_FAILED,
"KeyExchange signature verification failed for key type=" + keyAlg);
}
session.setServerKey(serverKey);
return true;
}
throw new IllegalStateException("Unknown command value: " + KeyExchange.getGroupKexOpcodeName(cmd));
}
protected AbstractDH getDH(BigInteger p, BigInteger g) throws Exception {
return factory.create(p, g);
}
}
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