Be up-front about security: OpenSSL is known to have issues,
you can't trust what comes down the pipe, and your private key's integrity
is a hard requirement. Not a situation where you can be careless.
acme-client is a client for Let's Encrypt users, but one designed for security.
No Python. No Ruby. No Bash.
A straightforward, open source implementation in C that isolates each step of the sequence.

TODO: build lib libseccomp.

1. build dependencies:
   1. libbsd-devel
   2. libtls-devel