improving network resiliency

ACEmulator · Dec 25, 2023 · b7216d0 · b7216d0
1 parent c0a1793
commit b7216d0
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Showing 3 changed files with 18 additions and 5 deletions.
diff --git a/Source/ACE.Server/Network/ClientMessage.cs b/Source/ACE.Server/Network/ClientMessage.cs
@@ -4,19 +4,21 @@ namespace ACE.Server.Network
 {
     public class ClientMessage
     {
-        public BinaryReader Payload { get; }
-
         public MemoryStream Data { get; }
 
+        public BinaryReader Payload { get; }
+
         public uint Opcode { get; }
 
+        /// <exception cref="EndOfStreamException">stream must be at least 4 bytes in length remaining to read</exception>
         public ClientMessage(MemoryStream stream)
         {
             Data = stream;
             Payload = new BinaryReader(Data);
             Opcode = Payload.ReadUInt32();
         }
 
+        /// <exception cref="EndOfStreamException">data must be at least 4 bytes in length</exception>
         public ClientMessage(byte[] data)
         {
             Data = new MemoryStream(data);

diff --git a/Source/ACE.Server/Network/MessageBuffer.cs b/Source/ACE.Server/Network/MessageBuffer.cs
@@ -30,16 +30,25 @@ public void AddFragment(ClientPacketFragment fragment)
             }
         }
 
-        public ClientMessage GetMessage()
+        /// <summary>
+        /// This will return null if not enough data exists to create a valid ClientMessage (4 bytes minimum are required)
+        /// </summary>
+        public ClientMessage TryGetMessage()
         {
             fragments.Sort(delegate (ClientPacketFragment x, ClientPacketFragment y) { return x.Header.Index - y.Header.Index; });
+
             MemoryStream stream = new MemoryStream();
             BinaryWriter writer = new BinaryWriter(stream);
             foreach (ClientPacketFragment fragment in fragments)
             {
                 writer.Write(fragment.Data);
             }
+
             stream.Seek(0, SeekOrigin.Begin);
+
+            if (stream.Length < 4) // ClientMessage must be a minimum of 4 bytes in length
+                return null;
+
             return new ClientMessage(stream);
         }
     }

diff --git a/Source/ACE.Server/Network/NetworkSession.cs b/Source/ACE.Server/Network/NetworkSession.cs
@@ -475,7 +475,7 @@ private void ProcessFragment(ClientPacketFragment fragment)
                     {
                         // The buffer is complete, so we can go ahead and handle
                         packetLog.DebugFormat("[{0}] Buffer {1} is complete", session.LoggingIdentifier, buffer.Sequence);
-                        message = buffer.GetMessage();
+                        message = buffer.TryGetMessage();
                         MessageBuffer removed = null;
                         partialFragments.TryRemove(fragment.Header.Sequence, out removed);
                     }
@@ -495,7 +495,9 @@ private void ProcessFragment(ClientPacketFragment fragment)
             {
                 // Packet is not split, proceed with handling it.
                 packetLog.DebugFormat("[{0}] Fragment {1} is not split", session.LoggingIdentifier, fragment.Header.Sequence);
-                message = new ClientMessage(fragment.Data);
+
+                if (fragment.Data.Length >= 4) // ClientMessage must be a minimum of 4 bytes in length
+                    message = new ClientMessage(fragment.Data);
             }
 
             // If message is not null, we have a complete message to handle