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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.Socks5InitialRequestDecoder.State;
26  
27  import java.util.List;
28  
29  /**
30   * Decodes a single {@link Socks5InitialRequest} 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 Socks5InitialRequestDecoder extends ReplayingDecoder<State> {
36  
37      enum State {
38          INIT,
39          SUCCESS,
40          FAILURE
41      }
42  
43      public Socks5InitialRequestDecoder() {
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 int authMethodCnt = in.readUnsignedByte();
59                  if (actualReadableBytes() < authMethodCnt) {
60                      break;
61                  }
62  
63                  final Socks5AuthMethod[] authMethods = new Socks5AuthMethod[authMethodCnt];
64                  for (int i = 0; i < authMethodCnt; i++) {
65                      authMethods[i] = Socks5AuthMethod.valueOf(in.readByte());
66                  }
67  
68                  out.add(new DefaultSocks5InitialRequest(authMethods));
69                  checkpoint(State.SUCCESS);
70              }
71              case SUCCESS: {
72                  int readableBytes = actualReadableBytes();
73                  if (readableBytes > 0) {
74                      out.add(in.readSlice(readableBytes).retain());
75                  }
76                  break;
77              }
78              case FAILURE: {
79                  in.skipBytes(actualReadableBytes());
80                  break;
81              }
82              }
83          } catch (Exception e) {
84              fail(out, e);
85          }
86      }
87  
88      private void fail(List<Object> out, Throwable cause) {
89          if (!(cause instanceof DecoderException)) {
90              cause = new DecoderException(cause);
91          }
92  
93          checkpoint(State.FAILURE);
94  
95          Socks5Message m = new DefaultSocks5InitialRequest(Socks5AuthMethod.NO_AUTH);
96          m.setDecoderResult(DecoderResult.failure(cause));
97          out.add(m);
98      }
99  }