133 lines
4.2 KiB
Java
133 lines
4.2 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.buffer.ByteBufUtil;
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import io.netty.buffer.Unpooled;
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import io.netty.handler.codec.CorruptedFrameException;
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import io.netty.util.CharsetUtil;
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import static io.netty.handler.codec.dns.DefaultDnsRecordDecoder.*;
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final class DnsCodecUtil {
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private DnsCodecUtil() {
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// Util class
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}
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static void encodeDomainName(String name, ByteBuf buf) {
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if (ROOT.equals(name)) {
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// Root domain
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buf.writeByte(0);
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return;
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}
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final String[] labels = name.split("\\.");
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for (String label : labels) {
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final int labelLen = label.length();
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if (labelLen == 0) {
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// zero-length label means the end of the name.
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break;
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}
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buf.writeByte(labelLen);
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ByteBufUtil.writeAscii(buf, label);
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}
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buf.writeByte(0); // marks end of name field
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}
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static String decodeDomainName(ByteBuf in) {
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int position = -1;
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int checked = 0;
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final int end = in.writerIndex();
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final int readable = in.readableBytes();
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// Looking at the spec we should always have at least enough readable bytes to read a byte here but it seems
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// some servers do not respect this for empty names. So just workaround this and return an empty name in this
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// case.
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//
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// See:
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// - https://github.com/netty/netty/issues/5014
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// - https://www.ietf.org/rfc/rfc1035.txt , Section 3.1
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if (readable == 0) {
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return ROOT;
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}
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final StringBuilder name = new StringBuilder(readable << 1);
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while (in.isReadable()) {
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final int len = in.readUnsignedByte();
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final boolean pointer = (len & 0xc0) == 0xc0;
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if (pointer) {
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if (position == -1) {
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position = in.readerIndex() + 1;
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}
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if (!in.isReadable()) {
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throw new CorruptedFrameException("truncated pointer in a name");
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}
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final int next = (len & 0x3f) << 8 | in.readUnsignedByte();
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if (next >= end) {
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throw new CorruptedFrameException("name has an out-of-range pointer");
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}
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in.readerIndex(next);
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// check for loops
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checked += 2;
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if (checked >= end) {
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throw new CorruptedFrameException("name contains a loop.");
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}
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} else if (len != 0) {
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if (!in.isReadable(len)) {
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throw new CorruptedFrameException("truncated label in a name");
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}
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name.append(in.toString(in.readerIndex(), len, CharsetUtil.UTF_8)).append('.');
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in.skipBytes(len);
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} else { // len == 0
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break;
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}
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}
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if (position != -1) {
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in.readerIndex(position);
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}
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if (name.length() == 0) {
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return ROOT;
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}
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if (name.charAt(name.length() - 1) != '.') {
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name.append('.');
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}
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return name.toString();
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}
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/**
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* Decompress pointer data.
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* @param compression comporession data
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* @return decompressed data
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*/
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static ByteBuf decompressDomainName(ByteBuf compression) {
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String domainName = decodeDomainName(compression);
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ByteBuf result = compression.alloc().buffer(domainName.length() << 1);
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encodeDomainName(domainName, result);
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return result;
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}
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}
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