1a53df1031
Motivation: It is possible that the user uses a too big EDNS0 setting for the MTU and so we may receive a truncated datagram packet. In this case we should try to detect this and retry via TCP if possible Modifications: - Fix detecting of incomplete records - Mark response as truncated if we did not consume the whole packet - Add unit test Result: Fixes https://github.com/netty/netty/issues/9365
105 lines
3.8 KiB
Java
105 lines
3.8 KiB
Java
/*
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* Copyright 2019 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.handler.codec.dns;
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import io.netty.buffer.ByteBuf;
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import io.netty.handler.codec.CorruptedFrameException;
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import java.net.SocketAddress;
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import java.util.Objects;
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abstract class DnsResponseDecoder<A extends SocketAddress> {
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private final DnsRecordDecoder recordDecoder;
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/**
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* Creates a new decoder with the specified {@code recordDecoder}.
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*/
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DnsResponseDecoder(DnsRecordDecoder recordDecoder) {
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this.recordDecoder = Objects.requireNonNull(recordDecoder, "recordDecoder");
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}
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final DnsResponse decode(A sender, A recipient, ByteBuf buffer) throws Exception {
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final int id = buffer.readUnsignedShort();
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final int flags = buffer.readUnsignedShort();
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if (flags >> 15 == 0) {
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throw new CorruptedFrameException("not a response");
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}
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final DnsResponse response = newResponse(
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sender,
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recipient,
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id,
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DnsOpCode.valueOf((byte) (flags >> 11 & 0xf)), DnsResponseCode.valueOf((byte) (flags & 0xf)));
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response.setRecursionDesired((flags >> 8 & 1) == 1);
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response.setAuthoritativeAnswer((flags >> 10 & 1) == 1);
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response.setTruncated((flags >> 9 & 1) == 1);
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response.setRecursionAvailable((flags >> 7 & 1) == 1);
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response.setZ(flags >> 4 & 0x7);
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boolean success = false;
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try {
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final int questionCount = buffer.readUnsignedShort();
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final int answerCount = buffer.readUnsignedShort();
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final int authorityRecordCount = buffer.readUnsignedShort();
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final int additionalRecordCount = buffer.readUnsignedShort();
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decodeQuestions(response, buffer, questionCount);
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if (!decodeRecords(response, DnsSection.ANSWER, buffer, answerCount)) {
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success = true;
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return response;
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}
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if (!decodeRecords(response, DnsSection.AUTHORITY, buffer, authorityRecordCount)) {
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success = true;
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return response;
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}
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decodeRecords(response, DnsSection.ADDITIONAL, buffer, additionalRecordCount);
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success = true;
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return response;
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} finally {
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if (!success) {
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response.release();
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}
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}
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}
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protected abstract DnsResponse newResponse(A sender, A recipient, int id,
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DnsOpCode opCode, DnsResponseCode responseCode) throws Exception;
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private void decodeQuestions(DnsResponse response, ByteBuf buf, int questionCount) throws Exception {
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for (int i = questionCount; i > 0; i --) {
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response.addRecord(DnsSection.QUESTION, recordDecoder.decodeQuestion(buf));
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}
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}
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private boolean decodeRecords(
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DnsResponse response, DnsSection section, ByteBuf buf, int count) throws Exception {
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for (int i = count; i > 0; i --) {
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final DnsRecord r = recordDecoder.decodeRecord(buf);
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if (r == null) {
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// Truncated response
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return false;
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}
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response.addRecord(section, r);
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}
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return true;
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}
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}
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