Fix parsing error of AUTH packet with empty body (#2070)

* Reformat code

* Fix issue

* Fix AUTH packet serialization

Source/MQTTnet.Tests/Formatter/MqttPacketSerialization_V5_Tests.cs

@@ -4,32 +4,36 @@
 
 using System;
 using System.Buffers;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Formatter;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Tests.Formatter
+namespace MQTTnet.Tests.Formatter;
-{
+
 [TestClass]
 public sealed class MqttPacketSerialization_V5_Tests
 {
+    [TestMethod]
+    public void Empty_Auth_Packet_Is_Success()
+    {
+        var buffer = MqttPacketSerializationHelper.EncodePacket(new MqttAuthPacket(), MqttProtocolVersion.V500);
+        var packet = MqttPacketSerializationHelper.DecodePacket(buffer, MqttProtocolVersion.V500);
+
+        Assert.IsNotNull(packet);
+        Assert.IsInstanceOfType<MqttAuthPacket>(packet);
+    }
+
     [TestMethod]
     public void Serialize_Full_MqttAuthPacket_V500()
     {
         var authPacket = new MqttAuthPacket
         {
-                AuthenticationData = Encoding.UTF8.GetBytes("AuthenticationData"),
+            AuthenticationData = "AuthenticationData"u8.ToArray(),
             AuthenticationMethod = "AuthenticationMethod",
             ReasonCode = MqttAuthenticateReasonCode.ContinueAuthentication,
             ReasonString = "ReasonString",
-                UserProperties = new List<MqttUserProperty>
+            UserProperties = [new MqttUserProperty("Foo", "Bar")]
-                {
-                    new MqttUserProperty("Foo", "Bar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(authPacket, MqttProtocolVersion.V500);
@@ -46,7 +50,7 @@ namespace MQTTnet.Tests.Formatter
     {
         var connAckPacket = new MqttConnAckPacket
         {
-                AuthenticationData = Encoding.UTF8.GetBytes("AuthenticationData"),
+            AuthenticationData = "AuthenticationData"u8.ToArray(),
             AuthenticationMethod = "AuthenticationMethod",
             ReasonCode = MqttConnectReasonCode.ServerUnavailable,
             ReasonString = "ReasonString",
@@ -65,10 +69,7 @@ namespace MQTTnet.Tests.Formatter
             SubscriptionIdentifiersAvailable = true,
             TopicAliasMaximum = 963,
             WildcardSubscriptionAvailable = true,
-                UserProperties = new List<MqttUserProperty>
+            UserProperties = [new MqttUserProperty("Foo", "Bar")]
-                {
-                    new MqttUserProperty("Foo", "Bar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(connAckPacket, MqttProtocolVersion.V500);
@@ -101,15 +102,15 @@ namespace MQTTnet.Tests.Formatter
         var connectPacket = new MqttConnectPacket
         {
             Username = "Username",
-                Password = Encoding.UTF8.GetBytes("Password"),
+            Password = "Password"u8.ToArray(),
             ClientId = "ClientId",
-                AuthenticationData = Encoding.UTF8.GetBytes("AuthenticationData"),
+            AuthenticationData = "AuthenticationData"u8.ToArray(),
             AuthenticationMethod = "AuthenticationMethod",
             CleanSession = true,
             ReceiveMaximum = 123,
             WillFlag = true,
             WillTopic = "WillTopic",
-                WillMessage = Encoding.UTF8.GetBytes("WillMessage"),
+            WillMessage = "WillMessage"u8.ToArray(),
             WillRetain = true,
             KeepAlivePeriod = 456,
             MaximumPacketSize = 789,
@@ -118,20 +119,14 @@ namespace MQTTnet.Tests.Formatter
             SessionExpiryInterval = 27,
             TopicAliasMaximum = 67,
             WillContentType = "WillContentType",
-                WillCorrelationData = Encoding.UTF8.GetBytes("WillCorrelationData"),
+            WillCorrelationData = "WillCorrelationData"u8.ToArray(),
             WillDelayInterval = 782,
             WillQoS = MqttQualityOfServiceLevel.ExactlyOnce,
             WillResponseTopic = "WillResponseTopic",
             WillMessageExpiryInterval = 542,
             WillPayloadFormatIndicator = MqttPayloadFormatIndicator.CharacterData,
-                UserProperties = new List<MqttUserProperty>
+            UserProperties = [new MqttUserProperty("Foo", "Bar")],
-                {
+            WillUserProperties = [new MqttUserProperty("WillFoo", "WillBar")]
-                    new MqttUserProperty("Foo", "Bar")
-                },
-                WillUserProperties = new List<MqttUserProperty>
-                {
-                    new MqttUserProperty("WillFoo", "WillBar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(connectPacket, MqttProtocolVersion.V500);
@@ -173,10 +168,7 @@ namespace MQTTnet.Tests.Formatter
             ReasonString = "ReasonString",
             ServerReference = "ServerReference",
             SessionExpiryInterval = 234,
-                UserProperties = new List<MqttUserProperty>
+            UserProperties = [new MqttUserProperty("Foo", "Bar")]
-                {
-                    new MqttUserProperty("Foo", "Bar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(disconnectPacket, MqttProtocolVersion.V500);
@@ -216,10 +208,7 @@ namespace MQTTnet.Tests.Formatter
             PacketIdentifier = 123,
             ReasonCode = MqttPubAckReasonCode.NoMatchingSubscribers,
             ReasonString = "ReasonString",
-                UserProperties = new List<MqttUserProperty>
+            UserProperties = [new MqttUserProperty("Foo", "Bar")]
-                {
-                    new MqttUserProperty("Foo", "Bar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(pubAckPacket, MqttProtocolVersion.V500);
@@ -238,10 +227,7 @@ namespace MQTTnet.Tests.Formatter
             PacketIdentifier = 123,
             ReasonCode = MqttPubCompReasonCode.PacketIdentifierNotFound,
             ReasonString = "ReasonString",
-                UserProperties = new List<MqttUserProperty>
+            UserProperties = [new MqttUserProperty("Foo", "Bar")]
-                {
-                    new MqttUserProperty("Foo", "Bar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(pubCompPacket, MqttProtocolVersion.V500);
@@ -260,23 +246,17 @@ namespace MQTTnet.Tests.Formatter
             PacketIdentifier = 123,
             Dup = true,
             Retain = true,
-                PayloadSegment = new ArraySegment<byte>(Encoding.ASCII.GetBytes("Payload")),
+            PayloadSegment = new ArraySegment<byte>("Payload"u8.ToArray()),
             QualityOfServiceLevel = MqttQualityOfServiceLevel.AtLeastOnce,
             Topic = "Topic",
             ResponseTopic = "/Response",
             ContentType = "Content-Type",
-                CorrelationData = Encoding.UTF8.GetBytes("CorrelationData"),
+            CorrelationData = "CorrelationData"u8.ToArray(),
             TopicAlias = 27,
-                SubscriptionIdentifiers = new List<uint>
+            SubscriptionIdentifiers = [123],
-                {
-                    123
-                },
             MessageExpiryInterval = 38,
             PayloadFormatIndicator = MqttPayloadFormatIndicator.CharacterData,
-                UserProperties = new List<MqttUserProperty>
+            UserProperties = [new MqttUserProperty("Foo", "Bar")]
-                {
-                    new MqttUserProperty("Foo", "Bar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(publishPacket, MqttProtocolVersion.V500);
@@ -305,10 +285,7 @@ namespace MQTTnet.Tests.Formatter
             PacketIdentifier = 123,
             ReasonCode = MqttPubRecReasonCode.UnspecifiedError,
             ReasonString = "ReasonString",
-                UserProperties = new List<MqttUserProperty>
+            UserProperties = [new MqttUserProperty("Foo", "Bar")]
-                {
-                    new MqttUserProperty("Foo", "Bar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(pubRecPacket, MqttProtocolVersion.V500);
@@ -327,10 +304,7 @@ namespace MQTTnet.Tests.Formatter
             PacketIdentifier = 123,
             ReasonCode = MqttPubRelReasonCode.PacketIdentifierNotFound,
             ReasonString = "ReasonString",
-                UserProperties = new List<MqttUserProperty>
+            UserProperties = [new MqttUserProperty("Foo", "Bar")]
-                {
-                    new MqttUserProperty("Foo", "Bar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(pubRelPacket, MqttProtocolVersion.V500);
@@ -348,14 +322,8 @@ namespace MQTTnet.Tests.Formatter
         {
             PacketIdentifier = 123,
             ReasonString = "ReasonString",
-                ReasonCodes = new List<MqttSubscribeReasonCode>
+            ReasonCodes = [MqttSubscribeReasonCode.GrantedQoS1],
-                {
+            UserProperties = [new MqttUserProperty("Foo", "Bar")]
-                    MqttSubscribeReasonCode.GrantedQoS1
-                },
-                UserProperties = new List<MqttUserProperty>
-                {
-                    new MqttUserProperty("Foo", "Bar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(subAckPacket, MqttProtocolVersion.V500);
@@ -374,8 +342,8 @@ namespace MQTTnet.Tests.Formatter
         {
             PacketIdentifier = 123,
             SubscriptionIdentifier = 456,
-                TopicFilters = new List<MqttTopicFilter>
+            TopicFilters =
-                {
+            [
                 new MqttTopicFilter
                 {
                     Topic = "Topic",
@@ -384,11 +352,8 @@ namespace MQTTnet.Tests.Formatter
                     RetainAsPublished = true,
                     QualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce
                 }
-                },
+            ],
-                UserProperties = new List<MqttUserProperty>
+            UserProperties = [new MqttUserProperty("Foo", "Bar")]
-                {
-                    new MqttUserProperty("Foo", "Bar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(subscribePacket, MqttProtocolVersion.V500);
@@ -410,15 +375,9 @@ namespace MQTTnet.Tests.Formatter
         var unsubAckPacket = new MqttUnsubAckPacket
         {
             PacketIdentifier = 123,
-                ReasonCodes = new List<MqttUnsubscribeReasonCode>
+            ReasonCodes = [MqttUnsubscribeReasonCode.ImplementationSpecificError],
-                {
-                    MqttUnsubscribeReasonCode.ImplementationSpecificError
-                },
             ReasonString = "ReasonString",
-                UserProperties = new List<MqttUserProperty>
+            UserProperties = [new MqttUserProperty("Foo", "Bar")]
-                {
-                    new MqttUserProperty("Foo", "Bar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(unsubAckPacket, MqttProtocolVersion.V500);
@@ -436,14 +395,8 @@ namespace MQTTnet.Tests.Formatter
         var unsubscribePacket = new MqttUnsubscribePacket
         {
             PacketIdentifier = 123,
-                TopicFilters = new List<string>
+            TopicFilters = ["TopicFilter1"],
-                {
+            UserProperties = [new MqttUserProperty("Foo", "Bar")]
-                    "TopicFilter1"
-                },
-                UserProperties = new List<MqttUserProperty>
-                {
-                    new MqttUserProperty("Foo", "Bar")
-                }
         };
 
         var deserialized = MqttPacketSerializationHelper.EncodeAndDecodePacket(unsubscribePacket, MqttProtocolVersion.V500);
@@ -454,4 +407,3 @@ namespace MQTTnet.Tests.Formatter
         CollectionAssert.AreEqual(unsubscribePacket.UserProperties, deserialized.UserProperties);
     }
 }
-}

Source/MQTTnet.Tests/MqttPacketSerializationHelper.cs

@@ -6,8 +6,8 @@ using MQTTnet.Formatter;
 using MQTTnet.Packets;
 using MQTTnet.Tests.Mockups;
 
-namespace MQTTnet.Tests
+namespace MQTTnet.Tests;
-{
+
 public sealed class MqttPacketSerializationHelper : IDisposable
 {
     readonly IMqttPacketFormatter _packetFormatter;
@@ -27,13 +27,17 @@ namespace MQTTnet.Tests
 
     public MqttPacket Decode(MqttPacketBuffer buffer)
     {
-            using (var channel = new MemoryMqttChannel(buffer.ToArray()))
+        using var channel = new MemoryMqttChannel(buffer.ToArray());
-            {
         var formatterAdapter = new MqttPacketFormatterAdapter(_protocolVersion, new MqttBufferWriter(4096, 65535));
 
         var adapter = new MqttChannelAdapter(channel, formatterAdapter, MqttNetNullLogger.Instance);
         return adapter.ReceivePacketAsync(CancellationToken.None).GetAwaiter().GetResult();
     }
+
+    public static MqttPacket DecodePacket(byte[] buffer, MqttProtocolVersion protocolVersion)
+    {
+        using var helper = new MqttPacketSerializationHelper(protocolVersion);
+        return helper.Decode(new MqttPacketBuffer(buffer));
     }
 
     public void Dispose()
@@ -47,19 +51,14 @@ namespace MQTTnet.Tests
 
     public static TPacket EncodeAndDecodePacket<TPacket>(TPacket packet, MqttProtocolVersion protocolVersion) where TPacket : MqttPacket
     {
-            using (var helper = new MqttPacketSerializationHelper(protocolVersion))
+        using var helper = new MqttPacketSerializationHelper(protocolVersion);
-            {
         var buffer = helper.Encode(packet);
         return (TPacket)helper.Decode(buffer);
     }
-        }
 
-        public static byte[] EncodePacket(MqttPacket packet)
+    public static byte[] EncodePacket(MqttPacket packet, MqttProtocolVersion protocolVersion)
-        {
-            using (var helper = new MqttPacketSerializationHelper())
     {
+        using var helper = new MqttPacketSerializationHelper(protocolVersion);
         return helper.Encode(packet).ToArray();
     }
 }
-    }
-}

Source/MQTTnet/Formatter/V5/MqttV5PacketDecoder.cs

@@ -68,12 +68,12 @@ namespace MQTTnet.Formatter.V5
 
         MqttPacket DecodeAuthPacket(ArraySegment<byte> body)
         {
-            ThrowIfBodyIsEmpty(body);
-
             _bufferReader.SetBuffer(body.Array, body.Offset, body.Count);
 
             var packet = new MqttAuthPacket();
 
+            // MQTT spec: The Reason Code and Property Length can be omitted if the Reason Code is 0x00 (Success) and there are no Properties.
+            // In this case the AUTH has a Remaining Length of 0.
             if (_bufferReader.EndOfStream)
             {
                 packet.ReasonCode = MqttAuthenticateReasonCode.Success;

Source/MQTTnet/Formatter/V5/MqttV5PacketEncoder.cs

@@ -9,14 +9,14 @@ using MQTTnet.Exceptions;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 
-namespace MQTTnet.Formatter.V5
+namespace MQTTnet.Formatter.V5;
-{
+
 public sealed class MqttV5PacketEncoder
 {
     const int FixedHeaderSize = 1;
 
     readonly MqttBufferWriter _bufferWriter;
-        readonly MqttV5PropertiesWriter _propertiesWriter = new MqttV5PropertiesWriter(new MqttBufferWriter(1024, 4096));
+    readonly MqttV5PropertiesWriter _propertiesWriter = new(new MqttBufferWriter(1024, 4096));
 
     public MqttV5PacketEncoder(MqttBufferWriter bufferWriter)
     {
@@ -36,7 +36,7 @@ namespace MQTTnet.Formatter.V5
         _bufferWriter.Seek(ReservedHeaderSize);
 
         var fixedHeader = EncodePacket(packet);
-            uint remainingLength = (uint)_bufferWriter.Length - ReservedHeaderSize;
+        var remainingLength = (uint)_bufferWriter.Length - ReservedHeaderSize;
 
         ReadOnlySequence<byte> payload = default;
         if (packet is MqttPublishPacket publishPacket)
@@ -62,20 +62,25 @@ namespace MQTTnet.Formatter.V5
         var buffer = _bufferWriter.GetBuffer();
         var firstSegment = new ArraySegment<byte>(buffer, headerOffset, _bufferWriter.Length - headerOffset);
 
-            return publishPacket == null
+        return publishPacket == null ? new MqttPacketBuffer(firstSegment) : new MqttPacketBuffer(firstSegment, publishPacket.Payload);
-               ? new MqttPacketBuffer(firstSegment)
-               : new MqttPacketBuffer(firstSegment, publishPacket.Payload);
     }
 
     byte EncodeAuthPacket(MqttAuthPacket packet)
     {
-            _bufferWriter.WriteByte((byte)packet.ReasonCode);
-
         _propertiesWriter.WriteAuthenticationMethod(packet.AuthenticationMethod);
         _propertiesWriter.WriteAuthenticationData(packet.AuthenticationData);
         _propertiesWriter.WriteReasonString(packet.ReasonString);
         _propertiesWriter.WriteUserProperties(packet.UserProperties);
 
+        // MQTT spec: The Reason Code and Property Length can be omitted if the Reason Code is 0x00 (Success) and there are no Properties.
+        // In this case the AUTH has a Remaining Length of 0.
+        if (packet.ReasonCode == MqttAuthenticateReasonCode.Success && _propertiesWriter.Length == 0)
+        {
+            return MqttBufferWriter.BuildFixedHeader(MqttControlPacketType.Auth);
+        }
+
+        _bufferWriter.WriteByte((byte)packet.ReasonCode);
+
         _propertiesWriter.WriteTo(_bufferWriter);
         _propertiesWriter.Reset();
 
@@ -539,4 +544,3 @@ namespace MQTTnet.Formatter.V5
         }
     }
 }
-}