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1   /*
2    * Copyright 2014 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   https://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  
17  package io.netty.handler.codec.socksx.v5;
18  
19  import io.netty.buffer.ByteBuf;
20  import io.netty.buffer.ByteBufUtil;
21  import io.netty.channel.ChannelHandlerContext;
22  import io.netty.handler.codec.DecoderException;
23  import io.netty.handler.codec.DecoderResult;
24  import io.netty.handler.codec.ReplayingDecoder;
25  import io.netty.handler.codec.socksx.SocksVersion;
26  import io.netty.handler.codec.socksx.v5.Socks5CommandRequestDecoder.State;
27  import io.netty.util.internal.ObjectUtil;
28  import io.netty.util.internal.UnstableApi;
29  
30  import java.util.List;
31  
32  /**
33   * Decodes a single {@link Socks5CommandRequest} from the inbound {@link ByteBuf}s.
34   * On successful decode, this decoder will forward the received data to the next handler, so that
35   * other handler can remove or replace this decoder later.  On failed decode, this decoder will
36   * discard the received data, so that other handler closes the connection later.
37   */
38  public class Socks5CommandRequestDecoder extends ReplayingDecoder<State> {
39  
40      @UnstableApi
41      public enum State {
42          INIT,
43          SUCCESS,
44          FAILURE
45      }
46  
47      private final Socks5AddressDecoder addressDecoder;
48  
49      public Socks5CommandRequestDecoder() {
50          this(Socks5AddressDecoder.DEFAULT);
51      }
52  
53      public Socks5CommandRequestDecoder(Socks5AddressDecoder addressDecoder) {
54          super(State.INIT);
55          this.addressDecoder = ObjectUtil.checkNotNull(addressDecoder, "addressDecoder");
56      }
57  
58      @Override
59      protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
60          try {
61              switch (state()) {
62              case INIT: {
63                  final byte version = in.readByte();
64                  if (version != SocksVersion.SOCKS5.byteValue()) {
65                      throw new DecoderException(
66                              "unsupported version: " + version + " (expected: " + SocksVersion.SOCKS5.byteValue() + ')');
67                  }
68  
69                  final Socks5CommandType type = Socks5CommandType.valueOf(in.readByte());
70                  in.skipBytes(1); // RSV
71                  final Socks5AddressType dstAddrType = Socks5AddressType.valueOf(in.readByte());
72                  final String dstAddr = addressDecoder.decodeAddress(dstAddrType, in);
73                  final int dstPort = ByteBufUtil.readUnsignedShortBE(in);
74  
75                  out.add(new DefaultSocks5CommandRequest(type, dstAddrType, dstAddr, dstPort));
76                  checkpoint(State.SUCCESS);
77              }
78              case SUCCESS: {
79                  int readableBytes = actualReadableBytes();
80                  if (readableBytes > 0) {
81                      out.add(in.readRetainedSlice(readableBytes));
82                  }
83                  break;
84              }
85              case FAILURE: {
86                  in.skipBytes(actualReadableBytes());
87                  break;
88              }
89              }
90          } catch (Exception e) {
91              fail(out, e);
92          }
93      }
94  
95      private void fail(List<Object> out, Exception cause) {
96          if (!(cause instanceof DecoderException)) {
97              cause = new DecoderException(cause);
98          }
99  
100         checkpoint(State.FAILURE);
101 
102         Socks5Message m = new DefaultSocks5CommandRequest(
103                 Socks5CommandType.CONNECT, Socks5AddressType.IPv4, "0.0.0.0", 1);
104         m.setDecoderResult(DecoderResult.failure(cause));
105         out.add(m);
106     }
107 }