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io.netty.handler.codec.mqtt.MqttDecoder Maven / Gradle / Ivy
/*
* Copyright 2014 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:
*
* http://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;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.DecoderException;
import io.netty.handler.codec.ReplayingDecoder;
import io.netty.handler.codec.mqtt.MqttDecoder.DecoderState;
import io.netty.util.CharsetUtil;
import java.util.ArrayList;
import java.util.List;
import static io.netty.handler.codec.mqtt.MqttCodecUtil.*;
/**
* Decodes Mqtt messages from bytes, following
*
* the MQTT protocl specification v3.1
*/
public class MqttDecoder extends ReplayingDecoder {
private static final int DEFAULT_MAX_BYTES_IN_MESSAGE = 8092;
/**
* States of the decoder.
* We start at READ_FIXED_HEADER, followed by
* READ_VARIABLE_HEADER and finally READ_PAYLOAD.
*/
enum DecoderState {
READ_FIXED_HEADER,
READ_VARIABLE_HEADER,
READ_PAYLOAD,
BAD_MESSAGE,
}
private MqttFixedHeader mqttFixedHeader;
private Object variableHeader;
private Object payload;
private int bytesRemainingInVariablePart;
private final int maxBytesInMessage;
public MqttDecoder() {
this(DEFAULT_MAX_BYTES_IN_MESSAGE);
}
public MqttDecoder(int maxBytesInMessage) {
super(DecoderState.READ_FIXED_HEADER);
this.maxBytesInMessage = maxBytesInMessage;
}
@Override
protected void decode(ChannelHandlerContext ctx, ByteBuf buffer, List out) throws Exception {
switch (state()) {
case READ_FIXED_HEADER:
mqttFixedHeader = decodeFixedHeader(buffer);
bytesRemainingInVariablePart = mqttFixedHeader.remainingLength();
checkpoint(DecoderState.READ_VARIABLE_HEADER);
// fall through
case READ_VARIABLE_HEADER: try {
if (bytesRemainingInVariablePart > maxBytesInMessage) {
throw new DecoderException("too large message: " + bytesRemainingInVariablePart + " bytes");
}
final Result decodedVariableHeader = decodeVariableHeader(buffer, mqttFixedHeader);
variableHeader = decodedVariableHeader.value;
bytesRemainingInVariablePart -= decodedVariableHeader.numberOfBytesConsumed;
checkpoint(DecoderState.READ_PAYLOAD);
// fall through
} catch (Exception cause) {
out.add(invalidMessage(cause));
return;
}
case READ_PAYLOAD: try {
final Result decodedPayload =
decodePayload(
buffer,
mqttFixedHeader.messageType(),
bytesRemainingInVariablePart,
variableHeader);
payload = decodedPayload.value;
bytesRemainingInVariablePart -= decodedPayload.numberOfBytesConsumed;
if (bytesRemainingInVariablePart != 0) {
throw new DecoderException(
"non-zero remaining payload bytes: " +
bytesRemainingInVariablePart + " (" + mqttFixedHeader.messageType() + ')');
}
checkpoint(DecoderState.READ_FIXED_HEADER);
MqttMessage message = MqttMessageFactory.newMessage(mqttFixedHeader, variableHeader, payload);
mqttFixedHeader = null;
variableHeader = null;
payload = null;
out.add(message);
break;
} catch (Exception cause) {
out.add(invalidMessage(cause));
return;
}
case BAD_MESSAGE:
// Keep discarding until disconnection.
buffer.skipBytes(actualReadableBytes());
break;
default:
// Shouldn't reach here.
throw new Error();
}
}
private MqttMessage invalidMessage(Throwable cause) {
checkpoint(DecoderState.BAD_MESSAGE);
return MqttMessageFactory.newInvalidMessage(cause);
}
/**
* Decodes the fixed header. It's one byte for the flags and then variable bytes for the remaining length.
*
* @param buffer the buffer to decode from
* @return the fixed header
*/
private static MqttFixedHeader decodeFixedHeader(ByteBuf buffer) {
short b1 = buffer.readUnsignedByte();
MqttMessageType messageType = MqttMessageType.valueOf(b1 >> 4);
boolean dupFlag = (b1 & 0x08) == 0x08;
int qosLevel = (b1 & 0x06) >> 1;
boolean retain = (b1 & 0x01) != 0;
int remainingLength = 0;
int multiplier = 1;
short digit;
int loops = 0;
do {
digit = buffer.readUnsignedByte();
remainingLength += (digit & 127) * multiplier;
multiplier *= 128;
loops++;
} while ((digit & 128) != 0 && loops < 4);
// MQTT protocol limits Remaining Length to 4 bytes
if (loops == 4 && (digit & 128) != 0) {
throw new DecoderException("remaining length exceeds 4 digits (" + messageType + ')');
}
MqttFixedHeader decodedFixedHeader =
new MqttFixedHeader(messageType, dupFlag, MqttQoS.valueOf(qosLevel), retain, remainingLength);
return validateFixedHeader(resetUnusedFields(decodedFixedHeader));
}
/**
* Decodes the variable header (if any)
* @param buffer the buffer to decode from
* @param mqttFixedHeader MqttFixedHeader of the same message
* @return the variable header
*/
private static Result decodeVariableHeader(ByteBuf buffer, MqttFixedHeader mqttFixedHeader) {
switch (mqttFixedHeader.messageType()) {
case CONNECT:
return decodeConnectionVariableHeader(buffer);
case CONNACK:
return decodeConnAckVariableHeader(buffer);
case SUBSCRIBE:
case UNSUBSCRIBE:
case SUBACK:
case UNSUBACK:
case PUBACK:
case PUBREC:
case PUBCOMP:
case PUBREL:
return decodeMessageIdVariableHeader(buffer);
case PUBLISH:
return decodePublishVariableHeader(buffer, mqttFixedHeader);
case PINGREQ:
case PINGRESP:
case DISCONNECT:
// Empty variable header
return new Result(null, 0);
}
return new Result(null, 0); //should never reach here
}
private static Result decodeConnectionVariableHeader(ByteBuf buffer) {
final Result protoString = decodeString(buffer);
int numberOfBytesConsumed = protoString.numberOfBytesConsumed;
final byte protocolLevel = buffer.readByte();
numberOfBytesConsumed += 1;
final MqttVersion mqttVersion = MqttVersion.fromProtocolNameAndLevel(protoString.value, protocolLevel);
final int b1 = buffer.readUnsignedByte();
numberOfBytesConsumed += 1;
final Result keepAlive = decodeMsbLsb(buffer);
numberOfBytesConsumed += keepAlive.numberOfBytesConsumed;
final boolean hasUserName = (b1 & 0x80) == 0x80;
final boolean hasPassword = (b1 & 0x40) == 0x40;
final boolean willRetain = (b1 & 0x20) == 0x20;
final int willQos = (b1 & 0x18) >> 3;
final boolean willFlag = (b1 & 0x04) == 0x04;
final boolean cleanSession = (b1 & 0x02) == 0x02;
final MqttConnectVariableHeader mqttConnectVariableHeader = new MqttConnectVariableHeader(
mqttVersion.protocolName(),
mqttVersion.protocolLevel(),
hasUserName,
hasPassword,
willRetain,
willQos,
willFlag,
cleanSession,
keepAlive.value);
return new Result(mqttConnectVariableHeader, numberOfBytesConsumed);
}
private static Result decodeConnAckVariableHeader(ByteBuf buffer) {
final boolean sessionPresent = (buffer.readUnsignedByte() & 0x01) == 0x01;
byte returnCode = buffer.readByte();
final int numberOfBytesConsumed = 2;
final MqttConnAckVariableHeader mqttConnAckVariableHeader =
new MqttConnAckVariableHeader(MqttConnectReturnCode.valueOf(returnCode), sessionPresent);
return new Result(mqttConnAckVariableHeader, numberOfBytesConsumed);
}
private static Result decodeMessageIdVariableHeader(ByteBuf buffer) {
final Result messageId = decodeMessageId(buffer);
return new Result(
MqttMessageIdVariableHeader.from(messageId.value),
messageId.numberOfBytesConsumed);
}
private static Result decodePublishVariableHeader(
ByteBuf buffer,
MqttFixedHeader mqttFixedHeader) {
final Result decodedTopic = decodeString(buffer);
if (!isValidPublishTopicName(decodedTopic.value)) {
throw new DecoderException("invalid publish topic name: " + decodedTopic.value + " (contains wildcards)");
}
int numberOfBytesConsumed = decodedTopic.numberOfBytesConsumed;
int messageId = -1;
if (mqttFixedHeader.qosLevel().value() > 0) {
final Result decodedMessageId = decodeMessageId(buffer);
messageId = decodedMessageId.value;
numberOfBytesConsumed += decodedMessageId.numberOfBytesConsumed;
}
final MqttPublishVariableHeader mqttPublishVariableHeader =
new MqttPublishVariableHeader(decodedTopic.value, messageId);
return new Result(mqttPublishVariableHeader, numberOfBytesConsumed);
}
private static Result decodeMessageId(ByteBuf buffer) {
final Result messageId = decodeMsbLsb(buffer);
if (!isValidMessageId(messageId.value)) {
throw new DecoderException("invalid messageId: " + messageId.value);
}
return messageId;
}
/**
* Decodes the payload.
*
* @param buffer the buffer to decode from
* @param messageType type of the message being decoded
* @param bytesRemainingInVariablePart bytes remaining
* @param variableHeader variable header of the same message
* @return the payload
*/
private static Result decodePayload(
ByteBuf buffer,
MqttMessageType messageType,
int bytesRemainingInVariablePart,
Object variableHeader) {
switch (messageType) {
case CONNECT:
return decodeConnectionPayload(buffer, (MqttConnectVariableHeader) variableHeader);
case SUBSCRIBE:
return decodeSubscribePayload(buffer, bytesRemainingInVariablePart);
case SUBACK:
return decodeSubackPayload(buffer, bytesRemainingInVariablePart);
case UNSUBSCRIBE:
return decodeUnsubscribePayload(buffer, bytesRemainingInVariablePart);
case PUBLISH:
return decodePublishPayload(buffer, bytesRemainingInVariablePart);
default:
// unknown payload , no byte consumed
return new Result(null, 0);
}
}
private static Result decodeConnectionPayload(
ByteBuf buffer,
MqttConnectVariableHeader mqttConnectVariableHeader) {
final Result decodedClientId = decodeString(buffer);
final String decodedClientIdValue = decodedClientId.value;
final MqttVersion mqttVersion = MqttVersion.fromProtocolNameAndLevel(mqttConnectVariableHeader.name(),
(byte) mqttConnectVariableHeader.version());
if (!isValidClientId(mqttVersion, decodedClientIdValue)) {
throw new MqttIdentifierRejectedException("invalid clientIdentifier: " + decodedClientIdValue);
}
int numberOfBytesConsumed = decodedClientId.numberOfBytesConsumed;
Result decodedWillTopic = null;
Result decodedWillMessage = null;
if (mqttConnectVariableHeader.isWillFlag()) {
decodedWillTopic = decodeString(buffer, 0, 32767);
numberOfBytesConsumed += decodedWillTopic.numberOfBytesConsumed;
decodedWillMessage = decodeAsciiString(buffer);
numberOfBytesConsumed += decodedWillMessage.numberOfBytesConsumed;
}
Result decodedUserName = null;
Result decodedPassword = null;
if (mqttConnectVariableHeader.hasUserName()) {
decodedUserName = decodeString(buffer);
numberOfBytesConsumed += decodedUserName.numberOfBytesConsumed;
}
if (mqttConnectVariableHeader.hasPassword()) {
decodedPassword = decodeString(buffer);
numberOfBytesConsumed += decodedPassword.numberOfBytesConsumed;
}
final MqttConnectPayload mqttConnectPayload =
new MqttConnectPayload(
decodedClientId.value,
decodedWillTopic != null ? decodedWillTopic.value : null,
decodedWillMessage != null ? decodedWillMessage.value : null,
decodedUserName != null ? decodedUserName.value : null,
decodedPassword != null ? decodedPassword.value : null);
return new Result(mqttConnectPayload, numberOfBytesConsumed);
}
private static Result decodeSubscribePayload(
ByteBuf buffer,
int bytesRemainingInVariablePart) {
final List subscribeTopics = new ArrayList();
int numberOfBytesConsumed = 0;
while (numberOfBytesConsumed < bytesRemainingInVariablePart) {
final Result decodedTopicName = decodeString(buffer);
numberOfBytesConsumed += decodedTopicName.numberOfBytesConsumed;
int qos = buffer.readUnsignedByte() & 0x03;
numberOfBytesConsumed++;
subscribeTopics.add(new MqttTopicSubscription(decodedTopicName.value, MqttQoS.valueOf(qos)));
}
return new Result(new MqttSubscribePayload(subscribeTopics), numberOfBytesConsumed);
}
private static Result decodeSubackPayload(
ByteBuf buffer,
int bytesRemainingInVariablePart) {
final List grantedQos = new ArrayList();
int numberOfBytesConsumed = 0;
while (numberOfBytesConsumed < bytesRemainingInVariablePart) {
int qos = buffer.readUnsignedByte() & 0x03;
numberOfBytesConsumed++;
grantedQos.add(qos);
}
return new Result(new MqttSubAckPayload(grantedQos), numberOfBytesConsumed);
}
private static Result decodeUnsubscribePayload(
ByteBuf buffer,
int bytesRemainingInVariablePart) {
final List unsubscribeTopics = new ArrayList();
int numberOfBytesConsumed = 0;
while (numberOfBytesConsumed < bytesRemainingInVariablePart) {
final Result decodedTopicName = decodeString(buffer);
numberOfBytesConsumed += decodedTopicName.numberOfBytesConsumed;
unsubscribeTopics.add(decodedTopicName.value);
}
return new Result(
new MqttUnsubscribePayload(unsubscribeTopics),
numberOfBytesConsumed);
}
private static Result decodePublishPayload(ByteBuf buffer, int bytesRemainingInVariablePart) {
ByteBuf b = buffer.readSlice(bytesRemainingInVariablePart).retain();
return new Result(b, bytesRemainingInVariablePart);
}
private static Result decodeString(ByteBuf buffer) {
return decodeString(buffer, 0, Integer.MAX_VALUE);
}
private static Result decodeAsciiString(ByteBuf buffer) {
Result result = decodeString(buffer, 0, Integer.MAX_VALUE);
final String s = result.value;
for (int i = 0; i < s.length(); i++) {
if (s.charAt(i) > 127) {
return new Result(null, result.numberOfBytesConsumed);
}
}
return new Result(s, result.numberOfBytesConsumed);
}
private static Result decodeString(ByteBuf buffer, int minBytes, int maxBytes) {
final Result decodedSize = decodeMsbLsb(buffer);
int size = decodedSize.value;
int numberOfBytesConsumed = decodedSize.numberOfBytesConsumed;
if (size < minBytes || size > maxBytes) {
buffer.skipBytes(size);
numberOfBytesConsumed += size;
return new Result(null, numberOfBytesConsumed);
}
ByteBuf buf = buffer.readBytes(size);
numberOfBytesConsumed += size;
return new Result(buf.toString(CharsetUtil.UTF_8), numberOfBytesConsumed);
}
private static Result decodeMsbLsb(ByteBuf buffer) {
return decodeMsbLsb(buffer, 0, 65535);
}
private static Result decodeMsbLsb(ByteBuf buffer, int min, int max) {
short msbSize = buffer.readUnsignedByte();
short lsbSize = buffer.readUnsignedByte();
final int numberOfBytesConsumed = 2;
int result = msbSize << 8 | lsbSize;
if (result < min || result > max) {
result = -1;
}
return new Result(result, numberOfBytesConsumed);
}
private static final class Result {
private final T value;
private final int numberOfBytesConsumed;
Result(T value, int numberOfBytesConsumed) {
this.value = value;
this.numberOfBytesConsumed = numberOfBytesConsumed;
}
}
}
