Let's Encrypt worked well for me the other day, except that I hit a firewall problem. I firewall all "new connection" outbound traffic, so that if a web app gets compromised, it can't start sending spam or try to spread a compromise to other sites.
This caused Let's Encrypt to fail.
I worked around this by temporarily allowing outbound connections, but I wonder whether this needs to be fixed more generally? It seems reasonable to me to block all outbound connections on a web server that isn't expected to need any. But Let's Encrypt's (perfectly reasonable) need to renew certificates breaks this assumption. Unfortunately, it doesn't seem easy to set up an exception on an IP-based firewall to allow Let's Encrypt outbound connections only. This makes automated renewals hard.
This caused Let's Encrypt to fail.
I worked around this by temporarily allowing outbound connections, but I wonder whether this needs to be fixed more generally? It seems reasonable to me to block all outbound connections on a web server that isn't expected to need any. But Let's Encrypt's (perfectly reasonable) need to renew certificates breaks this assumption. Unfortunately, it doesn't seem easy to set up an exception on an IP-based firewall to allow Let's Encrypt outbound connections only. This makes automated renewals hard.