io.netty.handler.codec.dns.DnsCodecUtil Maven / Gradle / Ivy
/*
* 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.
*/
package io.netty.handler.codec.dns;
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;
import static io.netty.handler.codec.dns.DefaultDnsRecordDecoder.*;
final class DnsCodecUtil {
private DnsCodecUtil() {
// Util class
}
static void encodeDomainName(String name, ByteBuf buf) {
if (ROOT.equals(name)) {
// Root domain
buf.writeByte(0);
return;
}
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;
}
buf.writeByte(labelLen);
ByteBufUtil.writeAscii(buf, label);
}
buf.writeByte(0); // marks end of name field
}
static String decodeDomainName(ByteBuf in) {
int position = -1;
int checked = 0;
final int end = in.writerIndex();
final int readable = in.readableBytes();
// 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;
}
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;
}
if (!in.isReadable()) {
throw new CorruptedFrameException("truncated pointer in a name");
}
final int next = (len & 0x3f) << 8 | in.readUnsignedByte();
if (next >= end) {
throw new CorruptedFrameException("name has an out-of-range pointer");
}
in.readerIndex(next);
// 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;
}
}
if (position != -1) {
in.readerIndex(position);
}
if (name.length() == 0) {
return ROOT;
}
if (name.charAt(name.length() - 1) != '.') {
name.append('.');
}
return name.toString();
}
/**
* 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;
}
}