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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.Socks5InitialResponseDecoder.State;
26  
27  import java.util.List;
28  
29  /**
30   * Decodes a single {@link Socks5InitialResponse} 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 Socks5InitialResponseDecoder extends ReplayingDecoder<State> {
36  
37      enum State {
38          INIT,
39          SUCCESS,
40          FAILURE
41      }
42  
43      public Socks5InitialResponseDecoder() {
44          super(State.INIT);
45      }
46  
47      @Override
48      protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
49          try {
50              switch (state()) {
51              case INIT: {
52                  final byte version = in.readByte();
53                  if (version != SocksVersion.SOCKS5.byteValue()) {
54                      throw new DecoderException(
55                              "unsupported version: " + version + " (expected: " + SocksVersion.SOCKS5.byteValue() + ')');
56                  }
57  
58                  final Socks5AuthMethod authMethod = Socks5AuthMethod.valueOf(in.readByte());
59                  out.add(new DefaultSocks5InitialResponse(authMethod));
60                  checkpoint(State.SUCCESS);
61              }
62              case SUCCESS: {
63                  int readableBytes = actualReadableBytes();
64                  if (readableBytes > 0) {
65                      out.add(in.readRetainedSlice(readableBytes));
66                  }
67                  break;
68              }
69              case FAILURE: {
70                  in.skipBytes(actualReadableBytes());
71                  break;
72              }
73              }
74          } catch (Exception e) {
75              fail(out, e);
76          }
77      }
78  
79      private void fail(List<Object> out, Exception cause) {
80          if (!(cause instanceof DecoderException)) {
81              cause = new DecoderException(cause);
82          }
83  
84          checkpoint(State.FAILURE);
85  
86          Socks5Message m = new DefaultSocks5InitialResponse(Socks5AuthMethod.UNACCEPTED);
87          m.setDecoderResult(DecoderResult.failure(cause));
88          out.add(m);
89      }
90  }