acme-nginx 0.5.0

Python library/program to create LetsEncrypt 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

• Simply works with running nginx or without it (DNS validation only)
• 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 cryptography 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 small, under 1000 lines of code in total.

Script should be run as root on host with running nginx server if you use http verification or if you use DNS verification as a regular user. 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 >= 3.9.2

ACME v2

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

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

dns-01 currently supports following providers:

• DigitalOcean
• AWS Route53
• Cloudflare

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 appreciated.

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

Is deprecated and not supported by LetsEncrypt anymore, so it was removed from that project too.

Installation

Preferred way

Using uv.

1. First install uv:

   curl -LsSf https://astral.sh/uv/install.sh | sh
   

2. Clone acme-nginx:

   git clone https://github.com/kshcherban/acme-nginx
   

3. Install it:

   cd acme-nginx
   uv run acme-nginx
   

Python pip way

Automatically

pip3 install acme-nginx

Docker way

You can build docker image with acme-nginx inside:

docker build -t acme-nginx .
docker run --rm -v /etc/nginx:/etc/nginx --pid=host \
	-d example.com -d www.example.com

Generate requirements

You can generate requirements.txt file with uv like: uv export --no-hashes --no-emit-workspace > requirements.txt

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/conf.d/0-letsencrypt.conf
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/conf.d/0-letsencrypt.conf
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/conf.d/0-letsencrypt.conf 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;
  ...

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/conf.d/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, Cloudflare 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-provider digitalocean -d '*.example.com'

Cloudflare

Create API token first. Then export it as API_TOKEN environment variable and use like this:

sudo su -
export API_TOKEN=yourCloudflareApiToken
acme-nginx --dns-provider cloudflare -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/conf.d for temporary virtual host configuration, by default it's /etc/nginx/conf.d/0-letsencrypt.conf.

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

Renewal

Personally I used the following cronjob to renew certificates of my blog. Here's content 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 --renew-days 33 >> /var/log/letsencrypt.log 2>&1 || echo "Failed to renew certificate"