org.apache.sshd.common.kex.extension.KexExtensions Maven / Gradle / Ivy
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* 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.extension;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.AbstractMap.SimpleImmutableEntry;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.NavigableMap;
import java.util.NavigableSet;
import java.util.Objects;
import java.util.TreeMap;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import org.apache.sshd.common.NamedResource;
import org.apache.sshd.common.kex.extension.parser.DelayCompression;
import org.apache.sshd.common.kex.extension.parser.Elevation;
import org.apache.sshd.common.kex.extension.parser.NoFlowControl;
import org.apache.sshd.common.kex.extension.parser.ServerSignatureAlgorithms;
import org.apache.sshd.common.util.GenericUtils;
import org.apache.sshd.common.util.MapEntryUtils;
import org.apache.sshd.common.util.Readable;
import org.apache.sshd.common.util.ValidateUtils;
import org.apache.sshd.common.util.buffer.Buffer;
/**
* Provides some helpers for RFC 8308
*
* @author Apache MINA SSHD Project
*/
public final class KexExtensions {
public static final byte SSH_MSG_EXT_INFO = 7;
public static final byte SSH_MSG_NEWCOMPRESS = 8;
public static final String CLIENT_KEX_EXTENSION = "ext-info-c";
public static final String SERVER_KEX_EXTENSION = "ext-info-s";
public static final Predicate IS_KEX_EXTENSION_SIGNAL = //
n -> CLIENT_KEX_EXTENSION.equalsIgnoreCase(n) || SERVER_KEX_EXTENSION.equalsIgnoreCase(n);
/**
* Reminder:
*
* These pseudo-algorithms are only valid in the initial SSH2_MSG_KEXINIT and MUST be ignored if they are present in
* subsequent SSH2_MSG_KEXINIT packets.
*
* Note: these values are appended to the initial proposals and removed if received before proceeding
* with the standard KEX proposals negotiation.
*
* @see OpenSSH PROTOCOL - 1.9 transport:
* strict key exchange extension
*/
public static final String STRICT_KEX_CLIENT_EXTENSION = "[email protected]";
public static final String STRICT_KEX_SERVER_EXTENSION = "[email protected]";
/**
* A case insensitive map of all the default known {@link KexExtensionParser} where key=the extension name
*/
private static final NavigableMap> EXTENSION_PARSERS = Stream.of(
ServerSignatureAlgorithms.INSTANCE,
NoFlowControl.INSTANCE,
Elevation.INSTANCE,
DelayCompression.INSTANCE)
.collect(Collectors.toMap(
NamedResource::getName, Function.identity(),
MapEntryUtils.throwingMerger(), () -> new TreeMap<>(String.CASE_INSENSITIVE_ORDER)));
private KexExtensions() {
throw new UnsupportedOperationException("No instance allowed");
}
/**
* @return A case insensitive copy of the currently registered {@link KexExtensionParser}s names
*/
public static NavigableSet getRegisteredExtensionParserNames() {
synchronized (EXTENSION_PARSERS) {
return EXTENSION_PARSERS.isEmpty()
? Collections.emptyNavigableSet()
: GenericUtils.asSortedSet(String.CASE_INSENSITIVE_ORDER, EXTENSION_PARSERS.keySet());
}
}
/**
* @param name The (never {@code null}/empty) extension name
* @return The registered {@code KexExtensionParser} for the (case insensitive) extension name -
* {@code null} if no match found
*/
public static KexExtensionParser getRegisteredExtensionParser(String name) {
ValidateUtils.checkNotNullAndNotEmpty(name, "No extension name provided");
synchronized (EXTENSION_PARSERS) {
return EXTENSION_PARSERS.get(name);
}
}
/**
* Registers a {@link KexExtensionParser} for a named extension
*
* @param parser The (never {@code null}) parser to register
* @return The replaced parser for the named extension (case insensitive) - {@code null} if no
* previous parser registered for this extension
*/
public static KexExtensionParser registerExtensionParser(KexExtensionParser parser) {
Objects.requireNonNull(parser, "No parser provided");
String name = ValidateUtils.checkNotNullAndNotEmpty(parser.getName(), "No extension name provided");
synchronized (EXTENSION_PARSERS) {
return EXTENSION_PARSERS.put(name, parser);
}
}
/**
* Registers {@link KexExtensionParser} for a named extension
*
* @param name The (never {@code null}/empty) extension name
* @return The removed {@code KexExtensionParser} for the (case insensitive) extension name -
* {@code null} if no match found
*/
public static KexExtensionParser unregisterExtensionParser(String name) {
ValidateUtils.checkNotNullAndNotEmpty(name, "No extension name provided");
synchronized (EXTENSION_PARSERS) {
return EXTENSION_PARSERS.remove(name);
}
}
/**
* Attempts to parse an {@code SSH_MSG_EXT_INFO} message
*
* @param buffer The {@link Buffer} containing the message
* @return A {@link List} of key/value "pairs" where key=the extension name, value=the parsed
* value using the matching registered {@link KexExtensionParser}. If no such parser found then
* the raw value bytes are set as the extension value.
* @throws IOException If failed to parse one of the extensions
* @see RFC-8308 - section 2.3
*/
public static List> parseExtensions(Buffer buffer) throws IOException {
int count = buffer.getInt();
// Protect agains malicious packets
ValidateUtils.checkTrue(count >= 0, "Invalid extensions count: %d", count);
if (count == 0) {
return Collections.emptyList();
}
List> entries = new ArrayList<>(count);
for (int index = 0; index < count; index++) {
String name = buffer.getString();
byte[] data = buffer.getBytes();
KexExtensionParser parser = getRegisteredExtensionParser(name);
Object value = (parser == null) ? data : parser.parseExtension(data);
entries.add(new SimpleImmutableEntry<>(name, value));
}
return entries;
}
/**
* Creates an {@code SSH_MSG_EXT_INFO} message using the provided extensions.
*
* @param exts A {@link Collection} of key/value "pairs" where key=the extension name, value=the
* extension value. Note: if a registered {@link KexExtensionParser} exists for the name,
* then it is assumed that the value is of the correct type. If no registered parser found the
* value is assumed to be either the encoded value as an array of bytes or as another
* {@link Readable} (e.g., another {@link Buffer}) or a {@link ByteBuffer}.
* @param buffer The target {@link Buffer} - assumed to already contain the {@code SSH_MSG_EXT_INFO} opcode
* @throws IOException If failed to encode
*/
public static void putExtensions(Collection> exts, Buffer buffer) throws IOException {
int count = GenericUtils.size(exts);
buffer.putUInt(count);
if (count <= 0) {
return;
}
for (Map.Entry ee : exts) {
String name = ee.getKey();
Object value = ee.getValue();
@SuppressWarnings("unchecked")
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