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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    *   http://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.channel.ChannelHandlerContext;
21  import io.netty.handler.codec.DecoderException;
22  import io.netty.handler.codec.DecoderResult;
23  import io.netty.handler.codec.ReplayingDecoder;
24  import io.netty.handler.codec.socksx.SocksVersion;
25  import io.netty.handler.codec.socksx.v5.Socks5CommandRequestDecoder.State;
26  
27  import java.util.List;
28  
29  /**
30   * Decodes a single {@link Socks5CommandRequest} from the inbound {@link ByteBuf}s.
31   * On successful decode, this decoder will forward the received data to the next handler, so that
32   * other handler can remove or replace this decoder later.  On failed decode, this decoder will
33   * discard the received data, so that other handler closes the connection later.
34   */
35  public class Socks5CommandRequestDecoder extends ReplayingDecoder<State> {
36  
37      enum State {
38          INIT,
39          SUCCESS,
40          FAILURE
41      }
42  
43      private final Socks5AddressDecoder addressDecoder;
44  
45      public Socks5CommandRequestDecoder() {
46          this(Socks5AddressDecoder.DEFAULT);
47      }
48  
49      public Socks5CommandRequestDecoder(Socks5AddressDecoder addressDecoder) {
50          super(State.INIT);
51          if (addressDecoder == null) {
52              throw new NullPointerException("addressDecoder");
53          }
54  
55          this.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 = in.readUnsignedShort();
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.readSlice(readableBytes).retain());
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, Throwable 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 }