Getting started with LetsEncrypt

Obtaining the cert

I wanted a central location to manage my certificate lifecycle as well as having a single repository to handle the orchestration of the deployment of such certificates. As such, the default mechanism of dropping a challenge file in a webroot wouldn’t work, as well as a few of the things I run don’t lend itself to such an auth mechanism. In favor of this, I decided to leverage dns-01 instead.

I like things tidy, so I keep everything inside of a directory structure as follows in /opt/:

lego
├── ansible // Where I keep the installation automation playbooks
│   └── roles
│       ├── host1
│       │   ├── files
│       │   ├── handlers
│       │   └── tasks
│       ├── host2
│       │   ├── files
│       │   ├── handlers
│       │   └── tasks
│       └── host3
│           ├── files
│           ├── handlers
│           └── tasks
├── bin // Lego bin lives here and misc scripts
└── data // Where Lego writes its goods
    ├── accounts
        │   └── acme-v01.api.letsencrypt.org
            │       └── email@example.com
                │           └── keys
                    └── certificates // Here be certs

Since I am using the dns-01 challenge with AWS Route53, the following environment variables must be defined: AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY. Ensure there is a proper IAM role defined for this task, as well a corresponding policy. The Lego README provides an example policy which will get you going:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "route53:GetChange",
                "route53:ListHostedZonesByName"
            ],
            "Resource": [
                "*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "route53:ChangeResourceRecordSets"
            ],
            "Resource": [
                "arn:aws:route53:::hostedzone/<INSERT_YOUR_HOSTED_ZONE_ID_HERE>"
            ]
        }
    ]
}

If you have multiple domains, in the second resource block just add a second ARN in a comma separated list. Or if you are less particular in doing things right and want to be looser on security, add arn:aws:route53:::hostedzone/* to allow modifications to all domains.

With that done, we can finally get our certs! This is as simple as:

AWS_ACCESS_KEY_ID="<accessid>" AWS_SECRET_ACCESS_KEY="<secretkey>" /opt/lego/bin/lego -a --path="/opt/lego/data/" --email="email@example.com" --domain="domain.com" --dns route53 run

Arguments are:

-a	Acknowledges that you agree to the current LetsEncrypt terms of service
--path	Where to stick the certs and account information
--email	The identity you want to use to register the cert with, they send you things like expiration notices
--domain	The domain you want to get the cert for
--dns	Specifies the DNS challenge, in this case route 53

You will notice that it both creates the DNS resource record to satisfy the challenge, and if everything went swimmingly will cleanup said record leaving things nice and tidy.

Renewing the certs

With the cert obtained, we need to ensure that the certs get renewed with the standard 90 day life of a LetsEncrypt certificate. This is as simple as changing run to renew and adding --days 30 to renew it within 30 days of expiration.

But since we want to automate this, lets make a little script to do this for us:

#!/bin/bash

DOMAINS="example.com example.org example.net""
AWS_ACCESS_KEY_ID="<access_key>"
AWS_SECRET_ACCESS_KEY="<secret_key>"

for domain in $DOMAINS; do
    /opt/lego/bin/lego -a --path="/opt/lego/data/" --email="email@example.com" --domains="$domain" --dns route53 renew --days 30
    done

This will iterate through the list of $DOMAINS and will renew each one. I threw this in a cronjob to run every night, but a systemd timer is nice too if you swing that way.

Installing the certs

There probably is a more elegant way of approaching this, but Ansible seemed perfect for what is being done here. It will ensure the certs are placed on the remote servers, and will execute actions if an update has happened and will noop otherwise. A basic boilerplate requires your inventory defined, I call mine hosts.ini. In my playbook I define each host as a role to customize how each server needs to be handled. My playbook certificates.yaml looks as follows:

- hosts: host1
  sudo: yes
  roles:
      - {role: 'roles/host1'}

Inside of each role’s files directory I then symlink the cert and key in /opt/lego/data/certificates/ and define the specific installation plays in tasks.

Once your playbook looks and acts reasonably, cron it out:

ansible-playbook -i /opt/lego/ansible/hosts.ini /opt/lego/ansible/certificates.yaml > /dev/null

---
- name: Install certs
  copy: src={{ item }} dest=/opt/subsonic/ssl/{{ item }} mode=0600
  with_items:
      - subsonic.example.com.crt
      - subsonic.example.com.key
  notify:
      - generate keystore
      - restart subsonic

- name: generate keystore
  shell: /opt/subsonic/ssl/keytool.sh

- name: restart subsonic
  service: name=subsonic state=restarted

#!/bin/bash

/usr/bin/openssl pkcs12 -in /opt/subsonic/ssl/subsonic.example.com.crt -inkey /opt/subsonic/ssl/subsonic.example.com.key key -export -out /opt/subsonic/ssl/subsonic.pkcs12 -password pass:subsonic

/usr/bin/keytool -importkeystore -srckeystore /opt/subsonic/ssl/subsonic.pkcs12 -destkeystore /opt/subsonic/ssl/subsonic.keystore -srcstoretype PKCS12 -srcstorepass subsonic -deststorepass subsonic -srcalias 1 -destalias subsonic

/usr/bin/zip -j /opt/subsonic/subsonic-booter-jar-with-dependencies.jar /opt/subsonic/ssl/subsonic.keystore

/bin/rm /opt/subsonic/ssl/subsonic.keystore /opt/subsonic/ssl/subsonic.pkcs12

- name: Install certs for weechat
  copy: src={{ item }} dest=/home/taco/.weechat/certs/{{ item }} mode=600
  with_items:
      - weechat.example.com.crt
      - weechat.example.com.key
  notify:
      - reload weechat certs

- name: reload weechat certs
  shell: /home/taco/.weechat/reloadcert.sh

#!/bin/bash

cat /home/taco/.weechat/certs/weechat.example.com.key /home/taco/.weechat/certs/weechat.example.com.crt > /home/taco/.weechat/certs/relay.pem
for fifo in /home/taco/.weechat/weechat_fifo_*
do
    printf '%b' '*/relay sslcertkey\n' > "$fifo"
done