org.apache.sshd.server.kex.DHGEXServer Maven / Gradle / Ivy
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* 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
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* 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.io.FileNotFoundException;
import java.io.IOException;
import java.math.BigInteger;
import java.net.URL;
import java.security.KeyPair;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import org.apache.sshd.common.Factory;
import org.apache.sshd.common.FactoryManager;
import org.apache.sshd.common.NamedFactory;
import org.apache.sshd.common.SshConstants;
import org.apache.sshd.common.SshException;
import org.apache.sshd.common.kex.DHFactory;
import org.apache.sshd.common.kex.DHG;
import org.apache.sshd.common.kex.DHGroupData;
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.random.Random;
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;
import org.apache.sshd.server.session.ServerSession;
/**
* @author Apache MINA SSHD Project
*/
public class DHGEXServer extends AbstractDHServerKeyExchange {
protected final DHFactory factory;
protected DHG dh;
protected int min;
protected int prf;
protected int max;
protected byte expected;
protected boolean oldRequest;
protected DHGEXServer(DHFactory factory, Session session) {
super(session);
this.factory = Objects.requireNonNull(factory, "No factory");
}
@Override
public final String getName() {
return factory.getName();
}
public static KeyExchangeFactory newFactory(DHFactory factory) {
return new KeyExchangeFactory() {
@Override
public KeyExchange createKeyExchange(Session session) throws Exception {
return new DHGEXServer(factory, session);
}
@Override
public String getName() {
return factory.getName();
}
@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);
expected = SshConstants.SSH_MSG_KEX_DH_GEX_REQUEST;
}
@Override
public boolean next(int cmd, Buffer buffer) throws Exception {
ServerSession session = getServerSession();
boolean debugEnabled = log.isDebugEnabled();
if (debugEnabled) {
log.debug("next({})[{}] process command={} (expected={})",
this, session, KeyExchange.getGroupKexOpcodeName(cmd),
KeyExchange.getGroupKexOpcodeName(expected));
}
if ((cmd == SshConstants.SSH_MSG_KEX_DH_GEX_REQUEST_OLD)
&& (expected == SshConstants.SSH_MSG_KEX_DH_GEX_REQUEST)) {
oldRequest = true;
min = CoreModuleProperties.PROP_DHGEX_SERVER_MIN_KEY.get(session)
.orElse(SecurityUtils.getMinDHGroupExchangeKeySize());
prf = buffer.getInt();
max = CoreModuleProperties.PROP_DHGEX_SERVER_MAX_KEY.get(session)
.orElse(SecurityUtils.getMaxDHGroupExchangeKeySize());
if ((max < min) || (prf < min) || (max < prf)) {
throw new SshException(
SshConstants.SSH2_DISCONNECT_KEY_EXCHANGE_FAILED,
"Protocol error: bad parameters " + min + " !< " + prf + " !< " + max);
}
dh = chooseDH(min, prf, max);
setF(dh.getE());
BigInteger pValue = dh.getP();
validateFValue(pValue);
hash = dh.getHash();
hash.init();
if (debugEnabled) {
log.debug("next({})[{}] send (old request) SSH_MSG_KEX_DH_GEX_GROUP - min={}, prf={}, max={}",
this, session, min, prf, max);
}
buffer = session.createBuffer(SshConstants.SSH_MSG_KEX_DH_GEX_GROUP);
buffer.putMPInt(pValue);
buffer.putMPInt(dh.getG());
session.writePacket(buffer);
expected = SshConstants.SSH_MSG_KEX_DH_GEX_INIT;
return false;
}
if ((cmd == SshConstants.SSH_MSG_KEX_DH_GEX_REQUEST)
&& (expected == SshConstants.SSH_MSG_KEX_DH_GEX_REQUEST)) {
min = buffer.getInt();
prf = buffer.getInt();
max = buffer.getInt();
if ((prf < min) || (max < prf)) {
throw new SshException(
SshConstants.SSH2_DISCONNECT_KEY_EXCHANGE_FAILED,
"Protocol error: bad parameters " + min + " !< " + prf + " !< " + max);
}
dh = chooseDH(min, prf, max);
setF(dh.getE());
BigInteger pValue = dh.getP();
validateFValue(pValue);
hash = dh.getHash();
hash.init();
if (debugEnabled) {
log.debug("next({})[{}] Send SSH_MSG_KEX_DH_GEX_GROUP - min={}, prf={}, max={}",
this, session, min, prf, max);
}
buffer = session.createBuffer(SshConstants.SSH_MSG_KEX_DH_GEX_GROUP);
buffer.putMPInt(pValue);
buffer.putMPInt(dh.getG());
session.writePacket(buffer);
expected = SshConstants.SSH_MSG_KEX_DH_GEX_INIT;
return false;
}
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_INIT) {
byte[] e = updateE(buffer.getMPIntAsBytes());
BigInteger pValue = dh.getP();
validateEValue(pValue);
dh.setF(e);
k = dh.getK();
KeyPair kp = Objects.requireNonNull(session.getHostKey(), "No server key pair available");
String algo = session.getNegotiatedKexParameter(KexProposalOption.SERVERKEYS);
Signature sig = ValidateUtils.checkNotNull(
NamedFactory.create(session.getSignatureFactories(), algo),
"Unknown negotiated server keys: %s", algo);
sig.initSigner(session, kp.getPrivate());
buffer = new ByteArrayBuffer();
buffer.putRawPublicKey(kp.getPublic());
byte[] k_s = buffer.getCompactData();
buffer.clear();
buffer.putBytes(v_c);
buffer.putBytes(v_s);
buffer.putBytes(i_c);
buffer.putBytes(i_s);
buffer.putBytes(k_s);
if (oldRequest) {
buffer.putInt(prf);
} else {
buffer.putInt(min);
buffer.putInt(prf);
buffer.putInt(max);
}
buffer.putMPInt(pValue);
buffer.putMPInt(dh.getG());
buffer.putMPInt(e);
byte[] f = getF();
buffer.putMPInt(f);
buffer.putMPInt(k);
hash.update(buffer.array(), 0, buffer.available());
h = hash.digest();
sig.update(session, h);
buffer.clear();
buffer.putString(algo);
byte[] sigBytes = sig.sign(session);
buffer.putBytes(sigBytes);
byte[] sigH = buffer.getCompactData();
if (log.isTraceEnabled()) {
log.trace("next({})[{}][K_S]: {}", this, session, BufferUtils.toHex(k_s));
log.trace("next({})[{}][f]: {}", this, session, BufferUtils.toHex(f));
log.trace("next({})[{}][sigH]: {}", this, session, BufferUtils.toHex(sigH));
}
// Send response
if (debugEnabled) {
log.debug("next({})[{}] Send SSH_MSG_KEX_DH_GEX_REPLY - old={}, min={}, prf={}, max={}",
this, session, oldRequest, min, prf, max);
}
buffer = session.prepareBuffer(
SshConstants.SSH_MSG_KEX_DH_GEX_REPLY, BufferUtils.clear(buffer));
buffer.putBytes(k_s);
buffer.putBytes(f);
buffer.putBytes(sigH);
session.writePacket(buffer);
return true;
}
return false;
}
protected DHG chooseDH(int min, int prf, int max) throws Exception {
ServerSession session = getServerSession();
List groups = loadModuliGroups(session);
List selected = selectModuliGroups(session, min, prf, max, groups);
if (GenericUtils.isEmpty(selected)) {
if (!CoreModuleProperties.ALLOW_DHG1_KEX_FALLBACK.getRequired(session)) {
log.error("chooseDH({})[{}][prf={}, min={}, max={}] No suitable primes found - failing",
this, session, prf, min, max);
throw new SshException(
SshConstants.SSH2_DISCONNECT_KEY_EXCHANGE_FAILED,
"No suitable primes found for DH group exchange");
}
log.warn("chooseDH({})[{}][prf={}, min={}, max={}] No suitable primes found - defaulting to DHG1",
this, session, prf, min, max);
return getDH(new BigInteger(DHGroupData.getP1()), new BigInteger(DHGroupData.getG()));
}
FactoryManager manager = Objects.requireNonNull(session.getFactoryManager(), "No factory manager");
Factory factory = Objects.requireNonNull(manager.getRandomFactory(), "No random factory");
Random random = Objects.requireNonNull(factory.create(), "No random generator");
int which = random.random(selected.size());
Moduli.DhGroup group = selected.get(which);
if (log.isTraceEnabled()) {
log.trace("chooseDH({})[{}][prf={}, min={}, max={}] selected {}",
this, session, prf, min, max, group);
}
return getDH(group.getP(), group.getG());
}
protected List selectModuliGroups(
ServerSession session, int min, int prf, int max, List groups)
throws Exception {
int maxDHGroupExchangeKeySize = SecurityUtils.getMaxDHGroupExchangeKeySize();
int minDHGroupExchangeKeySize = SecurityUtils.getMinDHGroupExchangeKeySize();
min = Math.max(min, minDHGroupExchangeKeySize);
prf = Math.max(prf, minDHGroupExchangeKeySize);
prf = Math.min(prf, maxDHGroupExchangeKeySize);
max = Math.min(max, maxDHGroupExchangeKeySize);
List selected = new ArrayList<>();
int bestSize = 0;
boolean traceEnabled = log.isTraceEnabled();
for (Moduli.DhGroup group : groups) {
int size = group.getSize();
if ((size < min) || (size > max)) {
if (traceEnabled) {
log.trace("selectModuliGroups({})[{}] - skip group={} - size not in range [{}-{}]",
this, session, group, min, max);
}
continue;
}
if (((size > prf) && (size < bestSize)) || ((size > bestSize) && (bestSize < prf))) {
bestSize = size;
if (traceEnabled) {
log.trace("selectModuliGroups({})[{}][prf={}, min={}, max={}] new best size={} from group={}",
this, session, prf, min, max, bestSize, group);
}
selected.clear();
}
if (size == bestSize) {
if (traceEnabled) {
log.trace("selectModuliGroups({})[{}][prf={}, min={}, max={}] selected {}",
this, session, prf, min, max, group);
}
selected.add(group);
}
}
return selected;
}
protected List loadModuliGroups(ServerSession session) throws IOException {
String moduliStr = CoreModuleProperties.MODULI_URL.getOrNull(session);
List groups = null;
if (!GenericUtils.isEmpty(moduliStr)) {
try {
URL moduli = new URL(moduliStr);
groups = Moduli.parseModuli(moduli);
} catch (IOException e) { // OK - use internal moduli
log.warn("loadModuliGroups({})[{}] Error ({}) loading external moduli from {}: {}",
this, session, e.getClass().getSimpleName(), moduliStr, e.getMessage());
}
}
if (groups == null) {
moduliStr = Moduli.INTERNAL_MODULI_RESPATH;
try {
URL moduli = getClass().getResource(moduliStr);
if (moduli == null) {
throw new FileNotFoundException("Missing internal moduli file");
}
moduliStr = moduli.toExternalForm();
groups = Moduli.loadInternalModuli(moduli);
} catch (IOException e) {
log.warn("loadModuliGroups({})[{}] Error ({}) loading internal moduli from {}: {}",
this, session, e.getClass().getSimpleName(), moduliStr, e.getMessage());
throw e; // this time we MUST throw the exception
}
}
if (log.isDebugEnabled()) {
log.debug("loadModuliGroups({})[{}] Loaded {} moduli groups from {}",
this, session, GenericUtils.size(groups), moduliStr);
}
return groups;
}
protected DHG getDH(BigInteger p, BigInteger g) throws Exception {
return (DHG) factory.create(p, g);
}
}
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