Give a choice for app to extend the length limitation of clientId even in mqtt v3.1 on the server side (#11205)

Motivation:

In the mqtt v3.1 protocol, the default maximum Client Identifier length is 23.However, in (#11114), there are many cases, the server may still receive a client ID with a length greater than 23. Perhaps should consider letting the user decide whether accept client id greater than 23 on the server side

Modification:

- Allow to specify max length.

Result:

Give a choice for app to extend the length limitation of clientId even in mqtt v3.1 on the server side.

Signed-off-by: xingrufei <xingrufei@sogou-inc.com>

Co-authored-by: xingrufei <xingrufei@sogou-inc.com>

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttCodecUtil.java

@@ -21,11 +21,11 @@ import io.netty.handler.codec.DecoderException;
 import io.netty.util.Attribute;
 import io.netty.util.AttributeKey;
 
+import static io.netty.handler.codec.mqtt.MqttConstant.MIN_CLIENT_ID_LENGTH;
+
 final class MqttCodecUtil {
 
     private static final char[] TOPIC_WILDCARDS = {'#', '+'};
-    private static final int MIN_CLIENT_ID_LENGTH = 1;
-    private static final int MAX_CLIENT_ID_LENGTH = 23;
 
     static final AttributeKey<MqttVersion> MQTT_VERSION_KEY = AttributeKey.valueOf("NETTY_CODEC_MQTT_VERSION");
 
@@ -57,10 +57,10 @@ final class MqttCodecUtil {
         return messageId != 0;
     }
 
-    static boolean isValidClientId(MqttVersion mqttVersion, String clientId) {
+    static boolean isValidClientId(MqttVersion mqttVersion, int maxClientIdLength, String clientId) {
         if (mqttVersion == MqttVersion.MQTT_3_1) {
             return clientId != null && clientId.length() >= MIN_CLIENT_ID_LENGTH &&
-                clientId.length() <= MAX_CLIENT_ID_LENGTH;
+                clientId.length() <= maxClientIdLength;
         }
         if (mqttVersion == MqttVersion.MQTT_3_1_1 || mqttVersion == MqttVersion.MQTT_5) {
             // In 3.1.3.1 Client Identifier of MQTT 3.1.1 and 5.0 specifications, The Server MAY allow ClientId’s

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttConstant.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2021 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.handler.codec.mqtt;
+
+public final class MqttConstant {
+
+    private MqttConstant() {
+    }
+
+    /**
+     * Default max bytes in message
+     */
+    public static final int DEFAULT_MAX_BYTES_IN_MESSAGE = 8092;
+
+    /**
+     * min client id length
+     */
+    public static final int MIN_CLIENT_ID_LENGTH = 1;
+
+    /**
+     * Default max client id length,In the mqtt3.1 protocol,
+     * the default maximum Client Identifier length is 23
+     */
+    public static final int DEFAULT_MAX_CLIENT_ID_LENGTH = 23;
+
+}

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttDecoder.java

@@ -24,6 +24,7 @@ import io.netty.handler.codec.TooLongFrameException;
 import io.netty.handler.codec.mqtt.MqttDecoder.DecoderState;
 import io.netty.handler.codec.mqtt.MqttProperties.IntegerProperty;
 import io.netty.util.CharsetUtil;
+import io.netty.util.internal.ObjectUtil;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -33,6 +34,8 @@ import static io.netty.handler.codec.mqtt.MqttCodecUtil.isValidMessageId;
 import static io.netty.handler.codec.mqtt.MqttCodecUtil.isValidPublishTopicName;
 import static io.netty.handler.codec.mqtt.MqttCodecUtil.resetUnusedFields;
 import static io.netty.handler.codec.mqtt.MqttCodecUtil.validateFixedHeader;
+import static io.netty.handler.codec.mqtt.MqttConstant.DEFAULT_MAX_BYTES_IN_MESSAGE;
+import static io.netty.handler.codec.mqtt.MqttConstant.DEFAULT_MAX_CLIENT_ID_LENGTH;
 import static io.netty.handler.codec.mqtt.MqttSubscriptionOption.RetainedHandlingPolicy;
 
 /**
@@ -45,8 +48,6 @@ import static io.netty.handler.codec.mqtt.MqttSubscriptionOption.RetainedHandlin
  */
 public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
 
-    private static final int DEFAULT_MAX_BYTES_IN_MESSAGE = 8092;
-
     /**
      * States of the decoder.
      * We start at READ_FIXED_HEADER, followed by
@@ -64,14 +65,20 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
     private int bytesRemainingInVariablePart;
 
     private final int maxBytesInMessage;
+    private final int maxClientIdLength;
 
     public MqttDecoder() {
-      this(DEFAULT_MAX_BYTES_IN_MESSAGE);
+      this(DEFAULT_MAX_BYTES_IN_MESSAGE, DEFAULT_MAX_CLIENT_ID_LENGTH);
     }
 
     public MqttDecoder(int maxBytesInMessage) {
+        this(maxBytesInMessage, DEFAULT_MAX_CLIENT_ID_LENGTH);
+    }
+
+    public MqttDecoder(int maxBytesInMessage, int maxClientIdLength) {
         super(DecoderState.READ_FIXED_HEADER);
-        this.maxBytesInMessage = maxBytesInMessage;
+        this.maxBytesInMessage = ObjectUtil.checkPositive(maxBytesInMessage, "maxBytesInMessage");
+        this.maxClientIdLength = ObjectUtil.checkPositive(maxClientIdLength, "maxClientIdLength");
     }
 
     @Override
@@ -108,6 +115,7 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
                                 buffer,
                                 mqttFixedHeader.messageType(),
                                 bytesRemainingInVariablePart,
+                                maxClientIdLength,
                                 variableHeader);
                 bytesRemainingInVariablePart -= decodedPayload.numberOfBytesConsumed;
                 if (bytesRemainingInVariablePart != 0) {
@@ -434,10 +442,11 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
             ByteBuf buffer,
             MqttMessageType messageType,
             int bytesRemainingInVariablePart,
+            int maxClientIdLength,
             Object variableHeader) {
         switch (messageType) {
             case CONNECT:
-                return decodeConnectionPayload(buffer, (MqttConnectVariableHeader) variableHeader);
+                return decodeConnectionPayload(buffer, maxClientIdLength, (MqttConnectVariableHeader) variableHeader);
 
             case SUBSCRIBE:
                 return decodeSubscribePayload(buffer, bytesRemainingInVariablePart);
@@ -462,12 +471,13 @@ public final class MqttDecoder extends ReplayingDecoder<DecoderState> {
 
     private static Result<MqttConnectPayload> decodeConnectionPayload(
             ByteBuf buffer,
+            int maxClientIdLength,
             MqttConnectVariableHeader mqttConnectVariableHeader) {
         final Result<String> decodedClientId = decodeString(buffer);
         final String decodedClientIdValue = decodedClientId.value;
         final MqttVersion mqttVersion = MqttVersion.fromProtocolNameAndLevel(mqttConnectVariableHeader.name(),
                 (byte) mqttConnectVariableHeader.version());
-        if (!isValidClientId(mqttVersion, decodedClientIdValue)) {
+        if (!isValidClientId(mqttVersion, maxClientIdLength, decodedClientIdValue)) {
             throw new MqttIdentifierRejectedException("invalid clientIdentifier: " + decodedClientIdValue);
         }
         int numberOfBytesConsumed = decodedClientId.numberOfBytesConsumed;

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttEncoder.java

@@ -31,6 +31,7 @@ import static io.netty.buffer.ByteBufUtil.*;
 import static io.netty.handler.codec.mqtt.MqttCodecUtil.getMqttVersion;
 import static io.netty.handler.codec.mqtt.MqttCodecUtil.isValidClientId;
 import static io.netty.handler.codec.mqtt.MqttCodecUtil.setMqttVersion;
+import static io.netty.handler.codec.mqtt.MqttConstant.DEFAULT_MAX_CLIENT_ID_LENGTH;
 
 /**
  * Encodes Mqtt messages into bytes following the protocol specification v3.1
@@ -124,7 +125,7 @@ public final class MqttEncoder extends MessageToMessageEncoder<MqttMessage> {
 
         // Client id
         String clientIdentifier = payload.clientIdentifier();
-        if (!isValidClientId(mqttVersion, clientIdentifier)) {
+        if (!isValidClientId(mqttVersion, DEFAULT_MAX_CLIENT_ID_LENGTH, clientIdentifier)) {
             throw new MqttIdentifierRejectedException("invalid clientIdentifier: " + clientIdentifier);
         }
         int clientIdentifierBytes = utf8Bytes(clientIdentifier);