I own a Brother printer and was curious how the upload worked. Apparently, it is just screenscraping the CSRF token[0], and submitting the cert upload form[1] in the printer's admin web interface. It needs the printer's admin credentials for the upload to work.

[0]: https://github.com/gregtwallace/brother-cert/blob/main/pkg/p...

[1]: https://github.com/gregtwallace/brother-cert/blob/main/pkg/p...