I need to create a certificate which I can use on whatever I want using lots of domains as SAN.
Is it possible to generate one from a .txt or so and will this be usable on any device that supports ssl certificates ? I’m not sure if a client is that needed on a device where the cert is used.
Yes; I’m building a tool that lets you issue domains in bulk from a text file: https://github.com/mholt/certs (note that this is still incomplete, but I’ve already used it with success to generate certificates).
It’s not production-ready yet, but basically you have a CSV file with one certificate per line, and up to 100 names per line. Each line is thus a SAN certificate.
Right now it has to be run on the machine that the domains point to, but as soon as DNS challenge is implemented you can run from anywhere as long as you have credentials for a supported DNS provider and the domains are served by that DNS provider.