| /* |
| * 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.common.kex; |
| |
| import java.security.KeyPair; |
| import java.util.Objects; |
| |
| import org.apache.sshd.common.util.buffer.Buffer; |
| |
| /** |
| * Provides Diffie-Hellman SSH key exchange algorithms for the Montgomery curves specified in RFC 8731. |
| * |
| * @see <a href="https://www.rfc-editor.org/info/rfc8731">RFC 8731</a> |
| */ |
| public abstract class XDH extends AbstractDH { |
| |
| protected MontgomeryCurve curve; |
| protected byte[] f; |
| |
| public XDH(MontgomeryCurve curve) throws Exception { |
| this.curve = Objects.requireNonNull(curve, "No MontgomeryCurve provided"); |
| myKeyAgree = curve.createKeyAgreement(); |
| } |
| |
| public int getKeySize() { |
| return curve.getKeySize(); |
| } |
| |
| @Override |
| protected byte[] calculateE() throws Exception { |
| KeyPair keyPair = curve.generateKeyPair(); |
| myKeyAgree.init(keyPair.getPrivate()); |
| return curve.encode(keyPair.getPublic()); |
| } |
| |
| @Override |
| public void setF(byte[] f) { |
| this.f = Objects.requireNonNull(f, "No 'f' value provided"); |
| } |
| |
| @Override |
| public void putE(Buffer buffer, byte[] e) { |
| // RFC 5656, section 4: Q_C and Q_S, which take the place of e and f, are written as "strings", i.e., byte |
| // arrays. |
| // RFC 8731, section 3: Public ephemeral keys are encoded for transmission as standard SSH strings. (Q_C and Q_S |
| // are the client's and server's ephemeral public keys.) |
| buffer.putBytes(e); |
| } |
| |
| @Override |
| public void putF(Buffer buffer, byte[] f) { |
| // RFC 5656, section 4: Q_C and Q_S, which take the place of e and f, are written as "strings", i.e., byte |
| // arrays. |
| // RFC 8731, section 3: Public ephemeral keys are encoded for transmission as standard SSH strings. (Q_C and Q_S |
| // are the client's and server's ephemeral public keys.) |
| buffer.putBytes(f); |
| } |
| |
| @Override |
| protected byte[] calculateK() throws Exception { |
| Objects.requireNonNull(f, "Missing 'f' value"); |
| myKeyAgree.doPhase(curve.decode(f), true); |
| return stripLeadingZeroes(myKeyAgree.generateSecret()); |
| } |
| } |