Sunlighter.TypeTraitsLib 1.0.1

TypeTraitsLib

This is a type traits library that allows for comparison, hashing, and serialization of a wide variety of C# types, including immutable collections. The central interface is ITypeTraits<T>. There are many extension methods, singleton classes which implement the traits for various values of T, and some classes for tuples and immutable collections. There are also classes for union types, record types, and types which might be self-referential (see RecursiveTypeTraits<T>.) It is also possible to implement ITypeTraits<T> directly.

Although generally designed for immutable types, the library also supports StrongBox<T> and user-defined mutable box types. Mutable boxes can be used to create circular references, which are serialized correctly but verbosely: the library may serialize a second copy before detecting a circular reference.

There is also code to send serialized objects as blobs over TCP, and to set up servers and clients.

This implementation of the traits library has traits for System.Type and System.Assembly which are generally intended to allow types to be used, for example, as keys in immutable sorted dictionaries. However, the traits would allow instances of these types to be serialized and deserialized, and it might be dangerous to deserialize a file where an attacker could have specified an arbitrary type or assembly to deserialize. It should be noted that I do not have any code that loads assemblies as a result of deserialization. You can only deserialize an assembly if it is already loaded. If the deserialized data specifies an assembly which is not loaded, an exception will be thrown during deserialization. But I do not know if this is sufficient to ensure security.

I have seen some cases where the same assembly seems to be loaded twice, but types from one loading do not seem to be equivalent to types from the other loading. (This seems to only happen when running tests, and it only affects certain test-related assemblies which are probably used internally by the test framework but would probably not be used by normal tests or by the code being tested — but even if they are used, you probably wouldn’t want to create traits for these types and try to serialize instances of these types, etc.) The traits classes, as currently written, will not be able to work with types where the assembly cannot be uniquely identified.