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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  package io.netty.handler.ssl;
17  
18  import java.util.Collections;
19  import java.util.List;
20  
21  import javax.net.ssl.SSLEngine;
22  
23  import static io.netty.handler.ssl.ApplicationProtocolUtil.toList;
24  import static io.netty.util.internal.ObjectUtil.checkNotNull;
25  
26  /**
27   * Provides an {@link SSLEngine} agnostic way to configure a {@link ApplicationProtocolNegotiator}.
28   */
29  public final class ApplicationProtocolConfig {
30  
31      /**
32       * The configuration that disables application protocol negotiation.
33       */
34      public static final ApplicationProtocolConfig DISABLED = new ApplicationProtocolConfig();
35  
36      private final List<String> supportedProtocols;
37      private final Protocol protocol;
38      private final SelectorFailureBehavior selectorBehavior;
39      private final SelectedListenerFailureBehavior selectedBehavior;
40  
41      /**
42       * Create a new instance.
43       * @param protocol The application protocol functionality to use.
44       * @param selectorBehavior How the peer selecting the protocol should behave.
45       * @param selectedBehavior How the peer being notified of the selected protocol should behave.
46       * @param supportedProtocols The order of iteration determines the preference of support for protocols.
47       */
48      public ApplicationProtocolConfig(Protocol protocol, SelectorFailureBehavior selectorBehavior,
49              SelectedListenerFailureBehavior selectedBehavior, Iterable<String> supportedProtocols) {
50          this(protocol, selectorBehavior, selectedBehavior, toList(supportedProtocols));
51      }
52  
53      /**
54       * Create a new instance.
55       * @param protocol The application protocol functionality to use.
56       * @param selectorBehavior How the peer selecting the protocol should behave.
57       * @param selectedBehavior How the peer being notified of the selected protocol should behave.
58       * @param supportedProtocols The order of iteration determines the preference of support for protocols.
59       */
60      public ApplicationProtocolConfig(Protocol protocol, SelectorFailureBehavior selectorBehavior,
61              SelectedListenerFailureBehavior selectedBehavior, String... supportedProtocols) {
62          this(protocol, selectorBehavior, selectedBehavior, toList(supportedProtocols));
63      }
64  
65      /**
66       * Create a new instance.
67       * @param protocol The application protocol functionality to use.
68       * @param selectorBehavior How the peer selecting the protocol should behave.
69       * @param selectedBehavior How the peer being notified of the selected protocol should behave.
70       * @param supportedProtocols The order of iteration determines the preference of support for protocols.
71       */
72      private ApplicationProtocolConfig(
73              Protocol protocol, SelectorFailureBehavior selectorBehavior,
74              SelectedListenerFailureBehavior selectedBehavior, List<String> supportedProtocols) {
75          this.supportedProtocols = Collections.unmodifiableList(checkNotNull(supportedProtocols, "supportedProtocols"));
76          this.protocol = checkNotNull(protocol, "protocol");
77          this.selectorBehavior = checkNotNull(selectorBehavior, "selectorBehavior");
78          this.selectedBehavior = checkNotNull(selectedBehavior, "selectedBehavior");
79  
80          if (protocol == Protocol.NONE) {
81              throw new IllegalArgumentException("protocol (" + Protocol.NONE + ") must not be " + Protocol.NONE + '.');
82          }
83          if (supportedProtocols.isEmpty()) {
84              throw new IllegalArgumentException("supportedProtocols must be not empty");
85          }
86      }
87  
88      /**
89       * A special constructor that is used to instantiate {@link #DISABLED}.
90       */
91      private ApplicationProtocolConfig() {
92          supportedProtocols = Collections.emptyList();
93          protocol = Protocol.NONE;
94          selectorBehavior = SelectorFailureBehavior.CHOOSE_MY_LAST_PROTOCOL;
95          selectedBehavior = SelectedListenerFailureBehavior.ACCEPT;
96      }
97  
98      /**
99       * Defines which application level protocol negotiation to use.
100      */
101     public enum Protocol {
102         NONE, NPN, ALPN, NPN_AND_ALPN
103     }
104 
105     /**
106      * Defines the most common behaviors for the peer that selects the application protocol.
107      */
108     public enum SelectorFailureBehavior {
109         /**
110          * If the peer who selects the application protocol doesn't find a match this will result in the failing the
111          * handshake with a fatal alert.
112          * <p>
113          * For example in the case of ALPN this will result in a
114          * <a herf="https://tools.ietf.org/html/rfc7301#section-3.2">no_application_protocol(120)</a> alert.
115          */
116         FATAL_ALERT,
117         /**
118          * If the peer who selects the application protocol doesn't find a match it will pretend no to support
119          * the TLS extension by not advertising support for the TLS extension in the handshake. This is used in cases
120          * where a "best effort" is desired to talk even if there is no matching protocol.
121          */
122         NO_ADVERTISE,
123         /**
124          * If the peer who selects the application protocol doesn't find a match it will just select the last protocol
125          * it advertised support for. This is used in cases where a "best effort" is desired to talk even if there
126          * is no matching protocol, and the assumption is the "most general" fallback protocol is typically listed last.
127          * <p>
128          * This may be <a href="https://tools.ietf.org/html/rfc7301#section-3.2">illegal for some RFCs</a> but was
129          * observed behavior by some SSL implementations, and is supported for flexibility/compatibility.
130          */
131         CHOOSE_MY_LAST_PROTOCOL
132     }
133 
134     /**
135      * Defines the most common behaviors for the peer which is notified of the selected protocol.
136      */
137     public enum SelectedListenerFailureBehavior {
138         /**
139          * If the peer who is notified what protocol was selected determines the selection was not matched, or the peer
140          * didn't advertise support for the TLS extension then the handshake will continue and the application protocol
141          * is assumed to be accepted.
142          */
143         ACCEPT,
144         /**
145          * If the peer who is notified what protocol was selected determines the selection was not matched, or the peer
146          * didn't advertise support for the TLS extension then the handshake will be failed with a fatal alert.
147          */
148         FATAL_ALERT,
149         /**
150          * If the peer who is notified what protocol was selected determines the selection was not matched, or the peer
151          * didn't advertise support for the TLS extension then the handshake will continue assuming the last protocol
152          * supported by this peer is used. This is used in cases where a "best effort" is desired to talk even if there
153          * is no matching protocol, and the assumption is the "most general" fallback protocol is typically listed last.
154          */
155         CHOOSE_MY_LAST_PROTOCOL
156     }
157 
158     /**
159      * The application level protocols supported.
160      */
161     public List<String> supportedProtocols() {
162         return supportedProtocols;
163     }
164 
165     /**
166      * Get which application level protocol negotiation to use.
167      */
168     public Protocol protocol() {
169         return protocol;
170     }
171 
172     /**
173      * Get the desired behavior for the peer who selects the application protocol.
174      */
175     public SelectorFailureBehavior selectorFailureBehavior() {
176         return selectorBehavior;
177     }
178 
179     /**
180      * Get the desired behavior for the peer who is notified of the selected protocol.
181      */
182     public SelectedListenerFailureBehavior selectedListenerFailureBehavior() {
183         return selectedBehavior;
184     }
185 }