Improve PerMessageDeflateClientExtensionHandler (#11413)

Motivation:

The `PerMessageDeflateClientExtensionHandler` has the following strange behaviors currently:

* The `requestedServerNoContext` parameter doesn't actually add the `server_no_context_takeover` parameter to the client offer; instead it depends on the requested server window size.
* The handshake will fail if the server responds with a `server_no_context_takeover` parameter and `requestedServerNoContext` is false. According to RFC 7692 (7.1.1.1) the server may do this, and this means that to cover both cases one needs to use two handshakers in the channel pipeline: one with `requestedServerNoContext = true` and one with `requestedServerNoContext = false`.
* The value of the `server_max_window_bits` parameter in the server response is never checked (should be between 8 and 15). And the value of `client_max_window_bits` is checked only in the branch handling the server window parameter.

Modification:

* Add the `server_no_context_takeover` parameter if `requestedServerNoContext` is true.
* Accept a server handshake response which includes the server no context takeover parameter even if we did not request it.
* Check the values of the client and server window size in their respective branches and fail the handshake if they are out of bounds.

Result:

There will be no need to use two handshakers in the pipeline to be lenient in what handshakes are accepted.

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/extensions/compression/PerMessageDeflateClientExtensionHandshaker.java

@@ -117,7 +117,7 @@ public final class PerMessageDeflateClientExtensionHandshaker implements WebSock
     @Override
     public WebSocketExtensionData newRequestData() {
         HashMap<String, String> parameters = new HashMap<String, String>(4);
-        if (requestedServerWindowSize != MAX_WINDOW_SIZE) {
+        if (requestedServerNoContext) {
             parameters.put(SERVER_NO_CONTEXT, null);
         }
         if (allowClientNoContext) {
@@ -153,13 +153,16 @@ public final class PerMessageDeflateClientExtensionHandshaker implements WebSock
                 // allowed client_window_size_bits
                 if (allowClientWindowSize) {
                     clientWindowSize = Integer.parseInt(parameter.getValue());
+                    if (clientWindowSize > MAX_WINDOW_SIZE || clientWindowSize < MIN_WINDOW_SIZE) {
+                        succeed = false;
+                    }
                 } else {
                     succeed = false;
                 }
             } else if (SERVER_MAX_WINDOW.equalsIgnoreCase(parameter.getKey())) {
                 // acknowledged server_window_size_bits
                 serverWindowSize = Integer.parseInt(parameter.getValue());
-                if (clientWindowSize > MAX_WINDOW_SIZE || clientWindowSize < MIN_WINDOW_SIZE) {
+                if (serverWindowSize > MAX_WINDOW_SIZE || serverWindowSize < MIN_WINDOW_SIZE) {
                     succeed = false;
                 }
             } else if (CLIENT_NO_CONTEXT.equalsIgnoreCase(parameter.getKey())) {
@@ -171,11 +174,7 @@ public final class PerMessageDeflateClientExtensionHandshaker implements WebSock
                 }
             } else if (SERVER_NO_CONTEXT.equalsIgnoreCase(parameter.getKey())) {
                 // acknowledged server_no_context_takeover
-                if (requestedServerNoContext) {
+                serverNoContext = true;
-                    serverNoContext = true;
-                } else {
-                    succeed = false;
-                }
             } else {
                 // unknown parameter
                 succeed = false;

codec-http/src/test/java/io/netty/handler/codec/http/websocketx/extensions/compression/PerMessageDeflateClientExtensionHandshakerTest.java

@@ -130,6 +130,63 @@ public class PerMessageDeflateClientExtensionHandshakerTest {
         assertNull(extension);
     }
 
+    @Test
+    public void testParameterValidation() {
+        WebSocketClientExtension extension;
+        Map<String, String> parameters;
+
+        PerMessageDeflateClientExtensionHandshaker handshaker =
+                new PerMessageDeflateClientExtensionHandshaker(6, true, 15, true, false);
+
+        parameters = new HashMap<String, String>();
+        parameters.put(CLIENT_MAX_WINDOW, "15");
+        parameters.put(SERVER_MAX_WINDOW, "8");
+        extension = handshaker.handshakeExtension(new WebSocketExtensionData(PERMESSAGE_DEFLATE_EXTENSION, parameters));
+
+        // Test that handshake succeeds when parameters are valid
+        assertNotNull(extension);
+        assertEquals(RSV1, extension.rsv());
+        assertTrue(extension.newExtensionDecoder() instanceof PerMessageDeflateDecoder);
+        assertTrue(extension.newExtensionEncoder() instanceof PerMessageDeflateEncoder);
+
+        parameters = new HashMap<String, String>();
+        parameters.put(CLIENT_MAX_WINDOW, "15");
+        parameters.put(SERVER_MAX_WINDOW, "7");
+
+        extension = handshaker.handshakeExtension(new WebSocketExtensionData(PERMESSAGE_DEFLATE_EXTENSION, parameters));
+
+        // Test that handshake fails when parameters are invalid
+        assertNull(extension);
+    }
+
+    @Test
+    public void testServerNoContextTakeover() {
+        WebSocketClientExtension extension;
+        Map<String, String> parameters;
+
+        PerMessageDeflateClientExtensionHandshaker handshaker =
+                new PerMessageDeflateClientExtensionHandshaker(6, true, 15, true, false);
+
+        parameters = new HashMap<String, String>();
+        parameters.put(SERVER_NO_CONTEXT, null);
+        extension = handshaker.handshakeExtension(new WebSocketExtensionData(PERMESSAGE_DEFLATE_EXTENSION, parameters));
+
+        // Test that handshake succeeds when server responds with `server_no_context_takeover` that we didn't offer
+        assertNotNull(extension);
+        assertEquals(RSV1, extension.rsv());
+        assertTrue(extension.newExtensionDecoder() instanceof PerMessageDeflateDecoder);
+        assertTrue(extension.newExtensionEncoder() instanceof PerMessageDeflateEncoder);
+
+        // initialize
+        handshaker = new PerMessageDeflateClientExtensionHandshaker(6, true, 15, true, true);
+
+        parameters = new HashMap<String, String>();
+        extension = handshaker.handshakeExtension(new WebSocketExtensionData(PERMESSAGE_DEFLATE_EXTENSION, parameters));
+
+        // Test that handshake fails when client offers `server_no_context_takeover` but server doesn't support it
+        assertNull(extension);
+    }
+
     @Test
     public void testDecoderNoClientContext() {
         PerMessageDeflateClientExtensionHandshaker handshaker =