use native API for AES

[totaam]

Switch from forge to W3C: SubtleCrypto interface

forge has problems and doesn't handle Uint8Array natively, which makes it slow - also it looks abandoned.
The new API supports BufferSource.

We can remove huge libraries and rely on the browser implemenation!
even Safari supports it: caniuse: SubtleCrypto

Some examples here: aes-cbc

[totaam]

Some useful links:

• Mozilla Web Crypto API
• diafygi : webcrypto-examples
• PeculiarVentures: webcrypto-docs
• pedrouid: Web Cryptography API Examples

[totaam]

The key (!) problem is that the xpra python code wrongly used 258 bits of padding with AES-CBC, which manifested itself half the time! See: Xpra-org/xpra#4372 (comment)

[totaam]

Now working for AES-CBC (which is the default mode).

The other modes need more work.

[totaam]

As per the Xpra-org/xpra#4372 (comment), the browser's implementation of AES is inadequate for our use case.
What we really want is Web Crypto Streams instead - which is only at the draft stage 😞

So the options to make this work without making it completely unsafe are:

• send new IV with each new encrypted packet - would make sense to use a counter for some of the bits rather than just random input, to avoid the birthday paradox: 3 common mistakes when implementing encryption : IV generation: It's always better to generate AES-GCM, AES-CTR and ChaCha20 nonces deterministically with a counter rather than randomly, or worse, hardcoded.
• does this make any sense to use any other modes at all?

[totaam]

This will do for now.

It's likely that more updates will be needed for Xpra-org/xpra#4375