• BernardSpil
• LetsEncrypt.sh

Some notes on the configuration of my setup

1. All services accessible from the internet run in jails (all jails reside in /usr/jails by default on FreeBSD)

2. I use LibreSSL (LibreSSL port)

3. I use The Z Shell (zsh port)

Things that don't need to run as root will be running as an unprivileged user. I will use the user _letsencrypt with group _letsencrypt as the unprivileged user that will perform the certificate renewal process. Deployment of the keys and certificates will have to be executed with a privileged user, this guide uses root.

Install Letsencrypt.sh

The port is available in the ports tree. Install it using the official pkg repository using

pkg install letsencrypt.sh

or alternatively (e.g. when you want to use ZSH) build your own using Poudriere or any of the other building-from-source options and install it. The port works with either zsh or bash.

This will install the actual script into /usr/local/bin. Configuration will land in /usr/local/etc/letsencrypt.sh as will the keys, certificates and certificate-chains. You should want to check that the configuration directory is not world-writable.

Prepare user & directories

To make life easier all of the challenges (LetsEncrypt as well as keybase etc) will be hosted in a shared dir /usr/local/www/.well-known on the jail running my Apache server. The LetsEncrypt bits will land in /usr/local/etc/letsencrypt.sh on the host system. There's no requirement to run the interaction with the LetsEncrypt servers as root, so these will run as a non-privileged user. This unprivileged user will have to write to the acme-challenge and the directory that will contain the keys and certificates.

pw groupadd -n _letsencrypt -g 443
pw useradd  -n _letsencrypt -u 443 -g 443 -d /usr/local/etc/letsencrypt.sh -w no -s /nonexistent
chown root:_letsencrypt /usr/local/etc/letsencrypt.sh
chmod 770               /usr/local/etc/letsencrypt.sh
mkdir -p -m 775    /usr/jails/http/usr/local/www/.well-known/acme-challenge
chgrp _letsencrypt /usr/jails/http/usr/local/www/.well-known/acme-challenge

Adapt the .well-known/acme-challenge directory to your situation.

Modify Apache configuration

The acme validation will GET a uniquely named file from http://<example.org>/.well-known/acme-challenge/

Access to the .well-known directory is granted in my main Apache config file /usr/local/etc/apache24/httpd.conf

<Directory "/usr/local/www/.well-known/">
   Options None
   AllowOverride None
   Require all granted
   Header add Content-Type text/plain
</Directory>

The Content-Type header was in my configs somewhere, shouldn't hurt.
If you want to only share the ACME challenges you can suffix .well-known/ with acme-challenge/

Now every (non-ssl) Virtual Host that I have gets a on-line addition

   Alias /.well-known/ /usr/local/www/.well-known/

Letsencrypt configuration

Domains to sign

The script requires a list of domain names you want to have a SAN cert for in the following format:

example.com www.example.com
example.net www.example.net wiki.example.net

Domains and sub-domains that are listed on the same line will result in SAN-certificates (Subject-Alternative-Name).
Store this as /usr/local/etc/letsencrypt.sh/domains.txt

The default configuration file requires some changes, these are stored in /usr/local/etc/letsencrypt.sh/config.sh

BASEDIR="/usr/local/etc/letsencrypt.sh"
WELLKNOWN="/usr/jails/http/usr/local/www/.well-known/acme-challenge"
alias openssl='/usr/local/bin/openssl'

To make use of LibreSSL (or OpenSSL from ports) you must add the alias openssl to the config script.

Configure periodic job

The security/letsencrypt.sh port includes a periodic job that makes automation very simple. To automatically renew certificates, add the following to your /etc/periodic.conf

weekly_letsencrypt_enable="YES"
weekly_letsencrypt_user="_letsencrypt"
weekly_letsencrypt_deployscript="/usr/local/etc/letsencrypt.sh/deploy.sh"

First run

You will probably want to run LetsEncrypt manually the first time

cd /usr/local/etc/letsencrypt.sh
su -m _letsencrypt -c 'zsh /usr/local/bin/letsencrypt.sh --cron'

(Replace zsh with bash if that's the shell you have installed)

You will end up with a sub-directory certs that contains your domains as directories with the Subject-Alternative-Names certs and the corresponding private keys. The symbolic links are useful for deployment.

example.com/
   cert-1453573903.csr
   cert-1453573903.pem
   cert.csr -> cert-1453573903.csr
   cert.pem -> cert-1453573903.pem
   chain-1453573903.pem
   chain.pem -> chain-1453573903.pem
   fullchain-1453573903.pem
   fullchain.pem -> fullchain-1453573903.pem
   privkey-1453573903.pem
   privkey.pem -> privkey-1453573903.pem
example.net/
   cert-1453576309.csr
   cert-1453576309.pem
   cert.csr -> cert-1453576309.csr
   cert.pem -> cert-1453576309.pem
   chain-1453576309.pem
   chain.pem -> chain-1453576309.pem
   fullchain-1453576309.pem
   fullchain.pem -> fullchain-1453576309.pem
   privkey-1453576309.pem
   privkey.pem -> privkey-1453576309.pem

Deploy new certs

We've run the certificate request process as a restricted user but you'll need to run the deploy script as root.

Here you'll probably need to get creative with scripting. In the host environment, your now have

/usr/local/etc/letsencrypt.sh/certs/example.net/privkey.pem
/usr/local/etc/letsencrypt.sh/certs/example.net/fullchain.pem

NB: These are symlinks!!!

Example (jailed) applications

Your Apache server may (should?) run in the http jail and you've setup an Apache Virtual Host with

SSLCertificateFile /etc/ssl/certs/example.net.pem
SSLCertificateKeyFile /etc/ssl/priv/example.net.pem

and your OpenSMTPd mailserver for example.net in the mail jail

pki example.net certificate "/etc/ssl/certs/example.net.pem"
pki example.net key         "/etc/ssl/priv/example.net.pem"
listen on $lan_addr port 587 tls-require \
       pki example.net hostname example.net auth

Seen from the host environment your certificates actually need to end up in

/usr/jails/```http```/etc/ssl
/usr/jails/```mail```/etc/ssl

Example deployment script

You could use the following script to deploy new certs

#!/bin/sh
domain="example.net"
letsencryptdir="/usr/local/etc/letsencrypt.sh"
targets="mail http"
for jail in ${targets}; do
  targetdir="/usr/jails/${jail}/etc/ssl"
  # Check if the certificate has changed
  [ -z "`diff -rq ${letsencryptdir}/certs/${domain}/fullchain.pem ${targetdir}/certs/${domain}.pem`" ] && continue
  cp -L "${letsencryptdir}/certs/${domain}/privkey.pem"   "${targetdir}/priv/${domain}.pem"
  cp -L "${letsencryptdir}/certs/${domain}/fullchain.pem" "${targetdir}/certs/${domain}.pem"
  chmod 400 "${targetdir}/priv/${domain}.pem"
  chmod 644 "${targetdir}/certs/${domain}.pem"
  # Restart/-load relevant services
  [ "${jail}" = "http" ] && jexec ${jail} service apache24 restart
  [ "${jail}" = "mail" ] && jexec ${jail} service smtpd    restart
done
# Clean up old keys and certs
/usr/local/bin/letsencrypt.sh --cleanup

Store this as /usr/local/etc/letsencrypt.sh/deploy.sh and make sure the execute bit is set.
NB: Some applications want a private key, certificate and separate chain instead. If this is the case you'll need to copy cert.pem and chain.pem to the appropriate location in stead.