Throw CoapOptionException when deserialising unsupported critical opt…

…ions
NZSmartie · Aug 23, 2017 · 330ade3 · 330ade3
1 parent 98e879f
commit 330ade3
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Showing 3 changed files with 45 additions and 9 deletions.
diff --git a/CoAPNet/Message.cs b/CoAPNet/Message.cs
@@ -84,7 +84,7 @@ public static bool IsServerError(this CoapMessageCode code)
         }
     }
 
-    public class CoapMessageFormatException : Exception {
+    public class CoapMessageFormatException : CoapException {
         public CoapMessageFormatException() :base() { }
 
         public CoapMessageFormatException(string message) : base(message) { }
@@ -285,11 +285,11 @@ public byte[] Serialise()
         public void Deserialise(byte[] data)
         {
             if (data == null)
-                throw new ArgumentNullException("data");
+                throw new ArgumentNullException(nameof(data));
             if (data.Length < 4)
                 throw new CoapMessageFormatException("Message must be at least 4 bytes long");
             if ((data[0] & 0xC0) != 0x40)
-                throw new CoapMessageFormatException("Only verison 1 of CoAP protocol is supported");
+                throw new CoapMessageFormatException($"Unexpected CoAP version ({data[0] & 0xC0:D}). Only verison 1 is supported");
 
             var offset = 4;
 
@@ -305,13 +305,12 @@ public void Deserialise(byte[] data)
             if (Code == CoapMessageCode.None && data.Length > 4)
                 throw new CoapMessageFormatException("Empty message must be 4 bytes long");
 
-            if (new int[] { 1, 6, 7 }.Contains(code / 100))
-                throw new CoapMessageFormatException("Message.Code can not use reserved classes");
-
             offset += data[0] & 0x0F;
             if ((data[0] & 0x0F) > 0)
                 _token = data.Skip(4).Take(data[0] & 0x0F).ToArray();
 
+            // Catch all the CoapOptionExceptions and throw them after all the options have been parsed.
+            var badOptions = new List<int>();
             var optionDelta = 0;
             for(var i = offset; i<data.Length; i++)
             {
@@ -340,12 +339,29 @@ public void Deserialise(byte[] data)
                     dataLen = data[i++ + 1] << 8;
                     dataLen |= data[i++ + 1] + 269;
                 }
-                Options.Add(CoAPNet.Options.Factory.Create(optCode + optionDelta, data.Skip(i+1).Take(dataLen).ToArray()));
+
+                try
+                {
+                    var option = CoAPNet.Options.Factory.Create(optCode + optionDelta,
+                        data.Skip(i + 1).Take(dataLen).ToArray());
+                    if (option != null)
+                        Options.Add(option);
+                }
+                catch (CoapOptionException)
+                {
+                    badOptions.Add(optCode + optionDelta);
+                }
+
                 i += dataLen;
                 optionDelta += optCode;
             }
 
+            // Performing this check after parsing the options to allow the chance of reading the message token
+            if (new int[] {1, 6, 7}.Contains(code / 100))
+                throw new CoapMessageFormatException("Message.Code can not use reserved classes");
 
+            if (badOptions.Count > 0)
+                throw new CoapOptionException($"Unsupported critical option ({string.Join(", ", badOptions)})");
         }
 
         /// <summary>

diff --git a/CoAPNet/Options.cs b/CoAPNet/Options.cs
@@ -5,6 +5,15 @@
 
 namespace CoAPNet
 {
+    public class CoapOptionException : CoapException
+    {
+        public CoapOptionException() : base() { }
+
+        public CoapOptionException(string message) : base(message) { }
+
+        public CoapOptionException(string message, Exception innerException) : base(message, innerException) { }
+    }
+
     public enum OptionType
     {
         /// <summary>

diff --git a/CoAPNet/Options/Factory.cs b/CoAPNet/Options/Factory.cs
@@ -40,18 +40,29 @@ public static void Register<T>() where T : CoapOption
         public static void Register(Type type)
         {
             if(!type.GetTypeInfo().IsSubclassOf(typeof(CoapOption)))
-                throw new ArgumentException(string.Format("Type must be a subclass of {0}", typeof(CoapOption).FullName));
+                throw new ArgumentException($"Type must be a subclass of {nameof(CoapOption)}");
 
             var option = (CoapOption)Activator.CreateInstance(type);
             _options.Add(option.OptionNumber, type);
         }
 
+        /// <summary>
+        /// Try to create an <see cref="CoapOption"/> from the option number and data. 
+        /// </summary>
+        /// <param name="number"></param>
+        /// <param name="data"></param>
+        /// <returns><value>null</value> if the option is unsupported.</returns>
+        /// <exception cref="CoapOptionException">If the option number is unsuppported and is critical (See RFC 7252 Section 5.4.1)</exception>
         public static CoapOption Create(int number, byte[] data = null)
         {
             // Let the exception get thrown if index is out of range
             Type type = null;
             if (!_options.TryGetValue(number, out type))
-                throw new ArgumentException(string.Format("Unsupported option number {0}", number));
+            {
+                if (number % 2 == 1)
+                    throw new CoapOptionException($"Unsupported critical option ({number})", new ArgumentOutOfRangeException(nameof(number)));
+                return null;
+            }
 
             var option = (CoapOption)Activator.CreateInstance(type);
             if (data != null)