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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.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.Socks5CommandResponseDecoder.State;
26  import io.netty.util.internal.ObjectUtil;
27  import io.netty.util.internal.UnstableApi;
28  
29  import java.util.List;
30  
31  /**
32   * Decodes a single {@link Socks5CommandResponse} from the inbound {@link ByteBuf}s.
33   * On successful decode, this decoder will forward the received data to the next handler, so that
34   * other handler can remove or replace this decoder later.  On failed decode, this decoder will
35   * discard the received data, so that other handler closes the connection later.
36   */
37  public class Socks5CommandResponseDecoder extends ReplayingDecoder<State> {
38  
39      @UnstableApi
40      public enum State {
41          INIT,
42          SUCCESS,
43          FAILURE
44      }
45  
46      private final Socks5AddressDecoder addressDecoder;
47  
48      public Socks5CommandResponseDecoder() {
49          this(Socks5AddressDecoder.DEFAULT);
50      }
51  
52      public Socks5CommandResponseDecoder(Socks5AddressDecoder addressDecoder) {
53          super(State.INIT);
54          this.addressDecoder = ObjectUtil.checkNotNull(addressDecoder, "addressDecoder");
55      }
56  
57      @Override
58      protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
59          try {
60              switch (state()) {
61              case INIT: {
62                  final byte version = in.readByte();
63                  if (version != SocksVersion.SOCKS5.byteValue()) {
64                      throw new DecoderException(
65                              "unsupported version: " + version + " (expected: " + SocksVersion.SOCKS5.byteValue() + ')');
66                  }
67                  final Socks5CommandStatus status = Socks5CommandStatus.valueOf(in.readByte());
68                  in.skipBytes(1); // Reserved
69                  final Socks5AddressType addrType = Socks5AddressType.valueOf(in.readByte());
70                  final String addr = addressDecoder.decodeAddress(addrType, in);
71                  final int port = in.readUnsignedShort();
72  
73                  out.add(new DefaultSocks5CommandResponse(status, addrType, addr, port));
74                  checkpoint(State.SUCCESS);
75              }
76              case SUCCESS: {
77                  int readableBytes = actualReadableBytes();
78                  if (readableBytes > 0) {
79                      out.add(in.readRetainedSlice(readableBytes));
80                  }
81                  break;
82              }
83              case FAILURE: {
84                  in.skipBytes(actualReadableBytes());
85                  break;
86              }
87              }
88          } catch (Exception e) {
89              fail(out, e);
90          }
91      }
92  
93      private void fail(List<Object> out, Exception cause) {
94          if (!(cause instanceof DecoderException)) {
95              cause = new DecoderException(cause);
96          }
97  
98          checkpoint(State.FAILURE);
99  
100         Socks5Message m = new DefaultSocks5CommandResponse(
101                 Socks5CommandStatus.FAILURE, Socks5AddressType.IPv4, null, 0);
102         m.setDecoderResult(DecoderResult.failure(cause));
103         out.add(m);
104     }
105 }