Don't hardcode the signature length to RSA-2048

[cgutman]

Description

This PR fixes the hardcoded assumption that signatures will always be 256 bytes long (corresponding to RSA-2048). With this change, we can support larger 3072 or 4096 bit RSA keys or other algorithms like ECDSA. Moonlight clients also need to be running updated code that corrects this assumption on their side too.

Interestingly, GFE has the same bug and won't tolerate anything but RSA-2048 keys.

Screenshot

Issues Fixed or Closed

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Dependency update (updates to dependencies)
• Documentation update (changes to documentation)
• Repository update (changes to repository files, e.g. .github/...)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the in code docstring/documentation-blocks for new or existing methods/components

Branch Updates

LizardByte requires that branches be up-to-date before merging. This means that after any PR is merged, this branch
must be updated before it can be merged. You must also
Allow edits from maintainers.

• I want maintainers to keep my branch updated

[ReenigneArcher]

I approved it before I realized there are mentions in the docs about the length being 2048.

https://docs.lizardbyte.dev/projects/sunshine/en/latest/about/advanced_usage.html#pkey

https://docs.lizardbyte.dev/projects/sunshine/en/latest/about/advanced_usage.html#cert

[cgutman]

Good catch, I didn't realize we documented that limitation. I pushed an update to those docs.

[ReenigneArcher]

Thanks! Feel free to merge whenever.