Wildcard Certificates with acme.sh

acme.sh is a lightweight shell script based tool to handle Let's Encrypt certificates, etc.

Install the bash script

wget https://get.acme.sh 

As root:

sh acme.sh

This will install the script to /root/.acme and add it to path by sourcing a script from root's .bashrc

Request a wildcard cert for lurk.org

We use wildcard certificates with DNS authentification, and we use the DNS server of our registrar, porkbun. It's not great (terrible UI for DNS editing), but it's cheap. Porkbun DNS support was added in recent versions of acme.sh. To make it work, we first need to find our Porkbun API keys and use them to set the following environment variables in root's .bashrc:

export PORKBUN_API_KEY="..."
export PORKBUN_SECRET_API_KEY="..."

When ready and reloaded:

acme.sh --issue --dns dns_porkbun -d lurk.org -d *.lurk.org

result:

• cert is in: /root/.acme.sh/lurk.org_ecc/lurk.org.cer
• cert key is in: /root/.acme.sh/lurk.org_ecc/lurk.org.key
• intermediate CA cert is in: /root/.acme.sh/lurk.org_ecc/ca.cer
• full-chain cert is in: /root/.acme.sh/lurk.org_ecc/fullchain.cer

Install the certs for nginx

The following command will install the certs for nginx, assuming there is a /etc/nginx/certs/ directory. Should be set and forget.

acme.sh --install-cert -d lurk.org -d *.lurk.org --key-file /etc/nginx/certs/key.pem --fullchain-file /etc/nginx/certs/cert.pem --reloadcmd "systemctl force-reload nginx"

Deployment for other services

acme.sh can also support custom installs of the certificates. They call this deployment, and all the scripts provided by the project can be found in /root/.acme.sh/deploy.

It's possible to make new deploy scripts quite easily, here is an example for cooldaemon.sh:

# this makes accessible as variables all the necessary paths and files
cooldaemon_deploy() {
_cdomain="$1"
_ckey="$2"
_ccert="$3"
_cca="$4"
_cfullchain="$5"

_debug _cdomain "$_cdomain"
_debug _ckey "$_ckey"
_debug _ccert "$_ccert"
_debug _cca "$_cca"
_debug _cfullchain "$_cfullchain"

# make a var for the target location
_ssl_path="/etc/cooldaemon/certs/"

# cooldaemon only needs the fullchain perm and the key so
# we only copy these
cp $_ckey $_ssl_path
cp $_cfullchain $_ssl_path

# any extra commands can be added here for instance
# maybe cooldaemon is picky about cert ownership
chown -R cooldaemon:cooldaemon $_ssl_path

# last but not least we reload cool daemon
# please note that some other daemons may need a restart instead
systemctl reload mumble-server

return 0
}

To enable the deployment at every cert renewal:

acme.sh --deploy -d lurk.org -d *.lurk.org --deploy-hook cooldaemon

set up a cron job

24 3 * * * "/root/.acme.sh"/acme.sh --cron --home "/root/.acme.sh" --reloadcmd "systemctl force-reload nginx" --renew-hook "/root/icecast_certs.sh"

To be fully modern and cool, we should probably switch from cron to a systemd timer but that's for another day. There's also a deploy script for icecast so this could theoretically all be done in one run but there are no docs for --cron so it's not clear how to set this up. For now we use a post renewal hook that smooshes the certs together for icecast:

#!/bin/sh
# turn the acme certs in to a certificate chain for icecast streaming
cat /root/.acme.sh/\*.lurk.org/fullchain.cer > /usr/local/share/icecast/icecast.pem
cat /root/.acme.sh/\*.lurk.org/\*.lurk.org.key >> /usr/local/share/icecast/icecast.pem
systemctl restart icecast