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Pre-decompressed DNS record RData that may contain compression pointers #9311
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132 changes: 132 additions & 0 deletions
132
codec-dns/src/main/java/io/netty/handler/codec/dns/DnsCodecUtil.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,132 @@ | ||
| /* | ||
| * Copyright 2019 The Netty Project | ||
| * | ||
| * The Netty Project 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. | ||
| */ | ||
|
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| package io.netty.handler.codec.dns; | ||
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| import io.netty.buffer.ByteBuf; | ||
| import io.netty.buffer.ByteBufUtil; | ||
| import io.netty.buffer.Unpooled; | ||
| import io.netty.handler.codec.CorruptedFrameException; | ||
| import io.netty.util.CharsetUtil; | ||
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| import static io.netty.handler.codec.dns.DefaultDnsRecordDecoder.*; | ||
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| final class DnsCodecUtil { | ||
| private DnsCodecUtil() { | ||
| // Util class | ||
| } | ||
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| static void encodeDomainName(String name, ByteBuf buf) { | ||
| if (ROOT.equals(name)) { | ||
| // Root domain | ||
| buf.writeByte(0); | ||
| return; | ||
| } | ||
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| final String[] labels = name.split("\\."); | ||
| for (String label : labels) { | ||
| final int labelLen = label.length(); | ||
| if (labelLen == 0) { | ||
| // zero-length label means the end of the name. | ||
| break; | ||
| } | ||
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| buf.writeByte(labelLen); | ||
| ByteBufUtil.writeAscii(buf, label); | ||
| } | ||
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| buf.writeByte(0); // marks end of name field | ||
| } | ||
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| static String decodeDomainName(ByteBuf in) { | ||
| int position = -1; | ||
| int checked = 0; | ||
| final int end = in.writerIndex(); | ||
| 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 | ||
| // some servers do not respect this for empty names. So just workaround this and return an empty name in this | ||
| // case. | ||
| // | ||
| // See: | ||
| // - https://github.com/netty/netty/issues/5014 | ||
| // - https://www.ietf.org/rfc/rfc1035.txt , Section 3.1 | ||
| if (readable == 0) { | ||
| return ROOT; | ||
| } | ||
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| final StringBuilder name = new StringBuilder(readable << 1); | ||
| while (in.isReadable()) { | ||
| final int len = in.readUnsignedByte(); | ||
| final boolean pointer = (len & 0xc0) == 0xc0; | ||
| if (pointer) { | ||
| if (position == -1) { | ||
| position = in.readerIndex() + 1; | ||
| } | ||
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| if (!in.isReadable()) { | ||
| throw new CorruptedFrameException("truncated pointer in a name"); | ||
| } | ||
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| final int next = (len & 0x3f) << 8 | in.readUnsignedByte(); | ||
| if (next >= end) { | ||
| throw new CorruptedFrameException("name has an out-of-range pointer"); | ||
| } | ||
| in.readerIndex(next); | ||
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| // check for loops | ||
| checked += 2; | ||
| if (checked >= end) { | ||
| throw new CorruptedFrameException("name contains a loop."); | ||
| } | ||
| } else if (len != 0) { | ||
| if (!in.isReadable(len)) { | ||
| throw new CorruptedFrameException("truncated label in a name"); | ||
| } | ||
| name.append(in.toString(in.readerIndex(), len, CharsetUtil.UTF_8)).append('.'); | ||
| in.skipBytes(len); | ||
| } else { // len == 0 | ||
| break; | ||
| } | ||
| } | ||
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| if (position != -1) { | ||
| in.readerIndex(position); | ||
| } | ||
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| if (name.length() == 0) { | ||
| return ROOT; | ||
| } | ||
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| if (name.charAt(name.length() - 1) != '.') { | ||
| name.append('.'); | ||
| } | ||
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| return name.toString(); | ||
| } | ||
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| /** | ||
| * Decompress pointer data. | ||
| * @param compression comporession data | ||
| * @return decompressed data | ||
| */ | ||
| static ByteBuf decompressDomainName(ByteBuf compression) { | ||
| String domainName = decodeDomainName(compression); | ||
| ByteBuf result = compression.alloc().buffer(domainName.length() << 1); | ||
| encodeDomainName(domainName, result); | ||
| return result; | ||
| } | ||
| } |
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nit: typo... should be "uncompressed"
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Done