| /* |
| * Copyright (C) 2021 Thomas Wolf <thomas.wolf@paranor.ch> and others |
| * |
| * This program and the accompanying materials are made available under the |
| * terms of the Eclipse Distribution License v. 1.0 which is available at |
| * https://www.eclipse.org/org/documents/edl-v10.php. |
| * |
| * SPDX-License-Identifier: BSD-3-Clause |
| */ |
| package org.eclipse.jgit.internal.transport.sshd; |
| |
| import java.io.IOException; |
| import java.util.ArrayList; |
| import java.util.Collection; |
| import java.util.Iterator; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.Set; |
| import java.util.TreeSet; |
| |
| import org.apache.sshd.common.AttributeRepository.AttributeKey; |
| import org.apache.sshd.common.NamedFactory; |
| import org.apache.sshd.common.kex.KexProposalOption; |
| import org.apache.sshd.common.kex.extension.KexExtensionHandler; |
| import org.apache.sshd.common.kex.extension.KexExtensions; |
| import org.apache.sshd.common.kex.extension.parser.ServerSignatureAlgorithms; |
| import org.apache.sshd.common.session.Session; |
| import org.apache.sshd.common.signature.Signature; |
| import org.apache.sshd.common.util.logging.AbstractLoggingBean; |
| import org.eclipse.jgit.util.StringUtils; |
| |
| /** |
| * Do not use the DefaultClientKexExtensionHandler from sshd; it doesn't work |
| * properly because of misconceptions. See SSHD-1141. |
| * |
| * @see <a href="https://issues.apache.org/jira/browse/SSHD-1141">SSHD-1141</a> |
| */ |
| public class JGitKexExtensionHandler extends AbstractLoggingBean |
| implements KexExtensionHandler { |
| |
| /** Singleton instance. */ |
| public static final JGitKexExtensionHandler INSTANCE = new JGitKexExtensionHandler(); |
| |
| /** |
| * Session {@link AttributeKey} used to store whether the extension |
| * indicator was already sent. |
| */ |
| private static final AttributeKey<Boolean> CLIENT_PROPOSAL_MADE = new AttributeKey<>(); |
| |
| /** |
| * Session {@link AttributeKey} storing the algorithms announced by the |
| * server as known. |
| */ |
| public static final AttributeKey<Set<String>> SERVER_ALGORITHMS = new AttributeKey<>(); |
| |
| private JGitKexExtensionHandler() { |
| // No public instantiation for singleton |
| } |
| |
| @Override |
| public boolean isKexExtensionsAvailable(Session session, |
| AvailabilityPhase phase) throws IOException { |
| return !AvailabilityPhase.PREKEX.equals(phase); |
| } |
| |
| @Override |
| public void handleKexInitProposal(Session session, boolean initiator, |
| Map<KexProposalOption, String> proposal) throws IOException { |
| // If it's the very first time, we may add the marker telling the server |
| // that we are ready to handle SSH_MSG_EXT_INFO |
| if (session == null || session.isServerSession() || !initiator) { |
| return; |
| } |
| if (session.getAttribute(CLIENT_PROPOSAL_MADE) != null) { |
| return; |
| } |
| String kexAlgorithms = proposal.get(KexProposalOption.SERVERKEYS); |
| if (StringUtils.isEmptyOrNull(kexAlgorithms)) { |
| return; |
| } |
| List<String> algorithms = new ArrayList<>(); |
| // We're a client. We mustn't send the server extension, and we should |
| // send the client extension only once. |
| for (String algo : kexAlgorithms.split(",")) { //$NON-NLS-1$ |
| if (KexExtensions.CLIENT_KEX_EXTENSION.equalsIgnoreCase(algo) |
| || KexExtensions.SERVER_KEX_EXTENSION |
| .equalsIgnoreCase(algo)) { |
| continue; |
| } |
| algorithms.add(algo); |
| } |
| // Tell the server that we want to receive SSH2_MSG_EXT_INFO |
| algorithms.add(KexExtensions.CLIENT_KEX_EXTENSION); |
| if (log.isDebugEnabled()) { |
| log.debug( |
| "handleKexInitProposal({}): proposing HostKeyAlgorithms {}", //$NON-NLS-1$ |
| session, algorithms); |
| } |
| proposal.put(KexProposalOption.SERVERKEYS, |
| String.join(",", algorithms)); //$NON-NLS-1$ |
| session.setAttribute(CLIENT_PROPOSAL_MADE, Boolean.TRUE); |
| } |
| |
| @Override |
| public boolean handleKexExtensionRequest(Session session, int index, |
| int count, String name, byte[] data) throws IOException { |
| if (ServerSignatureAlgorithms.NAME.equals(name)) { |
| handleServerSignatureAlgorithms(session, |
| ServerSignatureAlgorithms.INSTANCE.parseExtension(data)); |
| } |
| return true; |
| } |
| |
| /** |
| * Perform updates after a server-sig-algs extension has been received. |
| * |
| * @param session |
| * the message was received for |
| * @param serverAlgorithms |
| * signature algorithm names announced by the server |
| */ |
| protected void handleServerSignatureAlgorithms(Session session, |
| Collection<String> serverAlgorithms) { |
| if (log.isDebugEnabled()) { |
| log.debug("handleServerSignatureAlgorithms({}): {}", session, //$NON-NLS-1$ |
| serverAlgorithms); |
| } |
| // Client determines order; server says what it supports. Re-order |
| // such that supported ones are at the front, in client order, |
| // followed by unsupported ones, also in client order. |
| if (serverAlgorithms != null && !serverAlgorithms.isEmpty()) { |
| List<NamedFactory<Signature>> clientAlgorithms = new ArrayList<>( |
| session.getSignatureFactories()); |
| if (log.isDebugEnabled()) { |
| log.debug( |
| "handleServerSignatureAlgorithms({}): PubkeyAcceptedAlgorithms before: {}", //$NON-NLS-1$ |
| session, clientAlgorithms); |
| } |
| List<NamedFactory<Signature>> unknown = new ArrayList<>(); |
| Set<String> known = new TreeSet<>(String.CASE_INSENSITIVE_ORDER); |
| known.addAll(serverAlgorithms); |
| for (Iterator<NamedFactory<Signature>> iter = clientAlgorithms |
| .iterator(); iter.hasNext();) { |
| NamedFactory<Signature> algo = iter.next(); |
| if (!known.contains(algo.getName())) { |
| unknown.add(algo); |
| iter.remove(); |
| } |
| } |
| // Re-add the unknown ones at the end. Per RFC 8308, some |
| // servers may not announce _all_ their supported algorithms, |
| // and a client may use unknown algorithms. |
| clientAlgorithms.addAll(unknown); |
| if (log.isDebugEnabled()) { |
| log.debug( |
| "handleServerSignatureAlgorithms({}): PubkeyAcceptedAlgorithms after: {}", //$NON-NLS-1$ |
| session, clientAlgorithms); |
| } |
| session.setAttribute(SERVER_ALGORITHMS, known); |
| session.setSignatureFactories(clientAlgorithms); |
| } |
| } |
| } |