Allow SecretBox.easy to also accept user Uint8List key instead of only generated ones

[gabrielpacheco23]

The problem is that I can't pass my secret key array (Uint8List type) inside the function because it only accepts SecureKey instances and SecureKey objects are only created by this library key generation.

[Skycoder42]

Hi @gabrielpacheco23 - thanks for trying out the library in it's early stages.

This is actually something I had on my list for quite a while. I just pushed a commit that adds a Sodium.secureCopy method, which allows you to create a SecureKey by copying a Uint8List.

However, I am still unsure about how the API should work with the keys. In other languages, I would just overload the methods to accept both, a SecureKey and a Uint8Array, but I can't do that in dart. So, I though about the following alternative approaches. I would like to hear your opinion, if you have one:

1. Keep the API as is
2. Add an additional Uint8List plainKey parameter and make the normal key optional - this API-consumers can decide, which type of key the want to add - however, at the cost of runtime checks, if a key was actually provided.
3. Add factory constructors to SecureKey, to make it easier to use, as well as a SecureKey.unsafe constructor, which just wraps a Uint8List for easy consumption.

[gabrielpacheco23]

Thanks for the quick reply! Before seeing your answer I used a workaround with an extension method in the SecretBox class. That's how I made it:

extension KeyExt on SecretBox {
  SecureKey keyFromBytes(Uint8List rawBytes, DynamicLibrary dylib) {
    final sodiumPtr = sodiumffi.SodiumPointer<Uint8>.alloc(
      sodiumffi.LibSodiumFFI(dylib),
      count: rawBytes.length,
    );

    sodiumPtr.fill(rawBytes);
    return SecureKeyFFI(sodiumPtr);
  }
}

I dont know if that's a efficient way to fill the memory with the raw bytes but seems to work.

For your question, I think that making factory constructors to SecureKey would be a nicer approach, since it's more similar to constructor method overloading from other languages, but I don't know it would affect your implementation.

Anyways, great work on making this library! I was just in need of a libsodium wrapper so this came in handy.

[Skycoder42]

You are actually quite on point with your implementation, it's basically the same thing the SecureKey classes do internally.
I decided to add factory constructors, and I think I like the outcome. Thanks for your input!

I will close this now as the original problem was solved. If you have any other feedback, feel free to create a new one. :)