src: Fix tag parameter validation.

Author: samuel-lucas6

src/MultiMAC/MultiMac.cs

@@ -43,7 +43,7 @@ public static byte[] Compute(byte[] key1, byte[] key2, TagLength tagLength, para
 
     public static bool Verify(byte[] tag, byte[] key1, byte[] key2, params byte[][] inputs)
     {
-        ParameterValidation.Tag(tag, tag?.Length ?? 0);
+        ParameterValidation.Tag(tag);
         byte[] computedTag = Compute(key1, key2, (TagLength)tag.Length, inputs);
         return Utilities.Compare(tag, computedTag);
     }

src/MultiMAC/ParameterValidation.cs

@@ -40,9 +40,9 @@ internal static void Inputs(params byte[][] inputs)
         }
     }
 
-    internal static void Tag(byte[] tag, int validTagLength)
+    internal static void Tag(byte[] tag)
     {
         if (tag == null) { throw new ArgumentNullException(nameof(tag), "The tag cannot be null."); }
-        if (tag.Length != validTagLength) { throw new ArgumentOutOfRangeException(nameof(tag), tag.Length, $"The tag must be {validTagLength} bytes in length."); }
+        if (tag.Length != (int)TagLength.BLAKE2b256 & tag.Length != (int)TagLength.BLAKE2b384 & tag.Length != (int)TagLength.BLAKE2b512) { throw new ArgumentOutOfRangeException(nameof(tag), tag.Length, $"The tag must be {(int)TagLength.BLAKE2b256}, {(int)TagLength.BLAKE2b384}, or {(int)TagLength.BLAKE2b512} bytes in length."); }
     }
 }