[8.x] Keep backward compatibility with custom ciphers

[AdrianPop]

• Laravel Version: 8.56.0
• PHP Version: 8.0.0
• Database Driver & Version:

Description:

Laravel 8.56 was released a few days ago and these changes in the Encryption library break custom ciphers - illuminate/encryption@v8.55.0...v8.56.0#diff-4f830444085dd7aded928d1f4c746b2b2a3ced0c12e2788d4474e777e4b9113dL73

php artisan key:generate doesn't work if the usec cipher is XSalsa20

Steps To Reproduce:

• change in config/app this line to 'cipher' => 'XSalsa20',
• run php artisan key:generate
• (libsodium must be installed)

Fixes #38555

[Krisell]

I'm trying to understand exactly what the problem was here @AdrianPop. How are you using the XSalsa20 cipher? Are you extending the Encrypter class to add support for XSalsa20, or using the encryption key in a completely different place?

Using the default Encrypter class throws an unsupported cipher error since XSalsa20 is not in the list of Laravel's supported ciphers, and this change doesn't affect that.

This change hardcodes a key-size of 256 bits if the cipher is unknown. This might be a reasonable default, but it will certainly not be correct in all cases.