acme-nginx 0.2.0

A simple client/tool for Let's Encrypt or any ACME server that issues SSL certificates.

acme-nginx

Simple way to get SSL certificates for free.

Table of Contents

• Features
• Description
• ACME v2
• ACME v1
• Installation
• Usage
  • Wildcard certificates
  • Debug
  • Renewal

Features

• Supports both Python 2 and Python 3
• Works with both ACMEv1 and ACMEv2 protocols
• Can issue wildcard certificates!
• Easy to use and extend

Description

This is ACME client implementation in Python originally based on https://github.com/diafygi/acme-tiny code. Now completely different. It's written in pure Python depends on pyOpenSSL and pycrypto and the only binary it calls is ps to determine nginx master process id to send SIGHUP to it during challenge completion.

As you may not trust this script feel free to check source code, it's under 700 lines of code.

Script should be run as root on host with running nginx server. Domain for which you request certificate should point to that host's IP and port 80 should be available from outside if you use HTTP challenge. Script can generate all keys for you if you don't set them with command line arguments. Keys are RSA with length of 2048 bytes. You can specify as many alternative domain names as you wish. The result PEM file is a certificate chain containing your signed certificate and letsencrypt signed chain. You can use it with nginx.

Should work with Python >= 2.6

ACME v2

ACME v2 requires more logic so it's not as small as acme v1 script.

ACME v2 is supported partially: only http-01 and dns-01 challenges. Check https://tools.ietf.org/html/draft-ietf-acme-acme-07#section-9.7.6

New protocol is used by default.

http-01 challenge is passed exactly as in v1 protocol realisation.

dns-01 currently supports only DigitalOcean, AWS Route53 DNS providers.

Technically nginx is not needed for this type of challenge but script still calls nginx reload by default because it assumes that you store certificates on the same server where you issue them. To disable that behavior please specify --no-reload-nginx parameter.

AWS Route53 uses default profile in session, specifying profile works with environment variables only. Please check https://boto3.amazonaws.com/v1/documentation/api/latest/guide/configuration.html#environment-variable-configuration

In case you want to add support of different DNS providers your contribution is highly apprectiated.

Wildcard certificates can not be issued with non-wildcard for the same domain. I.e. it's not possible to issue certificates for *.example.com and www.example.com at the same time.

ACME v1

Still supported with flag --acme-v1. Only HTTP challenge is supported at the moment.

Installation

Please be informed that the quickiest and easiest way of installation is to use your OS installation way because Python way includes compilation of dependencies that may take much time and CPU resources and may require you to install all build dependencies.

Fastest way

Just download executable compiled with pyinstaller.

wget https://github.com/kshcherban/acme-nginx/releases/download/v0.1.2/acme-nginx
chmod +x acme-nginx

Python way

Automatically

pip install acme-nginx

or manually

git clone https://github.com/kshcherban/acme-nginx
cd acme-nginx
python setup.py install

Debian/Ubuntu way

sudo apt-get install -y python-openssl python-crypto python-setuptools
sudo python setup.py install

CentOS/RedHat/Fedora way

sudo yum install -y pyOpenSSL python-crypto python-setuptools
sudo yum groupinstall -y "Development tools"
sudo python setup.py install

Usage

Simplest scenario: you have neither letsencrypt account key nor domain key and want to generate certificate for example.com and www.example.com

sudo acme-nginx -d example.com -d www.example.com

You will see output similar to this:

Oct 12 23:42:17 Can not open key /etc/ssl/private/letsencrypt-account.key, generating new
Oct 12 23:42:17 Can not open key /etc/ssl/private/letsencrypt-domain.key, generating new
Oct 12 23:42:17 Trying to register account key
Oct 12 23:42:18 Registered!
Oct 12 23:42:18 Requesting challenge
Oct 12 23:42:19 Adding nginx virtual host and completing challenge
Oct 12 23:42:19 Creating file /etc/nginx/sites-enabled/letsencrypt
Oct 12 23:42:21 example.com verified!
Oct 12 23:42:21 Requesting challenge
Oct 12 23:42:21 Adding nginx virtual host and completing challenge
Oct 12 23:42:21 Creating file /etc/nginx/sites-enabled/letsencrypt
Oct 12 23:42:23 www.example.com verified!
Oct 12 23:42:23 Signing certificate
Oct 12 23:42:23 Certificate signed!
Oct 12 23:42:23 Writing result file in /etc/ssl/private/letsencrypt-domain.pem
Oct 12 23:42:23 Removing /etc/nginx/sites-enabled/letsencrypt and sending HUP to nginx

Certificate was generated into /etc/ssl/private/letsencrypt-domain.pem

You can now configure nginx to use it:

server {
  listen 443;
  ssl on;
  ssl_certificate /etc/ssl/private/letsencrypt-domain.pem;
  ssl_certificate_key /etc/ssl/private/letsencrypt-domain.key;
  ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
  ...

To renew it simply rerun the command! You can put it in cron, but don't forget about letsencrypt rate limits.

More complicated scenario: you have both account, domain keys and custom virtual host

sudo acme-nginx \
    -k /path/to/account.key \
    --domain-private-key /path/to/domain.key \
    --virtual-host /etc/nginx/sites-enabled/customvhost \
    -o /path/to/signed_certificate.pem \
    -d example.com -d www.example.com

Wildcard certificates

For wildcard certificate you need to have your domain managed by DNS provider with API. Currently only DigitalOcean DNS and AWS Route53 are supported.

Example how to get wildcard certificate without nginx

sudo acme-nginx --no-reload-nginx --dns-provider route53 -d "*.example.com"

DigitalOcean

Please create and export your DO API token as API_TOKEN env variable. Now you can generate wildcard certificate

sudo su -
export API_TOKEN=yourDigitalOceanApiToken
acme-nginx --dns digitalocean -d '*.example.com'

Debug

To debug please use --debug flag. With debug enabled all intermediate files will not be removed, so you can check /etc/nginx/sites-enabled for temporary virtual host configuration, by default it's /etc/nginx/sites-enabled/0-letsencrypt.conf.

Execute acme-nginx --help to see all available flags and their default values.

Renewal

Personally i use following cronjob to renew certificates of my blog. Here's contents of /etc/cron.d/renew-cert

MAILTO=[e-mail]
12 11 10 * * root timeout -k 600 -s 9 3600 /usr/local/bin/acme-nginx -d prolinux.org -d www.prolinux.org >> /var/log/letsencrypt.log 2>&1 || echo "Failed to renew certificate"