Lightweight client for the RFC8555 ACMEv2 protocol, written in plain
C with minimal dependencies (libcurl and one of GnuTLS, OpenSSL or
mbedTLS).  The ACMEv2 protocol allows a Certificate Authority (Let's
Encrypt is a popular one) and an applicant to automate the process
of verification and certificate issuance.  The protocol also provides
facilities for other certificate management functions, such as
certificate revocation.

WWW: https://github.com/ndilieto/uacme