Python module to integrate automated Let's Encrypt `certbot certonly` certificate creation into Python projects.
Current Status: Very Alpha, Proof of Concept
Use at your own peril, until there’s some shakedown.
This library is a wrapper around the certbot/certbot-auto command line tool operating certonly in manual, non-interactive mode. It does this via Python’s subprocess.Popen().
This allows Python developers to automate the creation of certificates in a web app (ie. Flask or Django). Let’s Encrypt’s certificate generation process, simplified:
- certbot sends a certificate request for a domain (or multiple domains in the case of SAN/UCC)
- Let’s Encrypt responds with validation instructions for each requested domain
- For each set of validation instructions, << developer/operations team member needs to manually perform some action - DNS record addition or web server file creation >>
- Let’s Encrypt attempts to validate each domain
- Upon successful validation, a certificate is provided (either single domain or SAN/UCC)
Step 3 is where this library allows the developer to customize and automate their process of setting up validation (see auth_script below). This library currently only supports web server validation (ie http-01).
An example scenario where this library becomes useful: > You have a blogging platform (ie. blog-platform.io) where your customers can sign up and create their own blog (ie. customer1.blog-platform.io). > >The Customer would like to host their new blog on their own sub-domain (ie. blog.customer-site.com) for SEO purposes - obviously they want to make sure it’s HTTPS enabled. They can easily do this by adding a CNAME from blog.customer-site.com to customer1.blog-platform.io. > > So your blogging platform needs to automatically provision HTTPS certificates as your customers create new blogs and set up CNAMEs for them. certbot_py to the rescue.
Please note that there is NO mechanism for renewal included; using ``certbot renew` via a cron job is the recommended way <https://certbot.eff.org/docs/using.html#renewing-certificates>`__.
- You must install certbot or certbot-auto as you will need to specify the full path to it. It does all the heavy lifting.
- The user running your Python project code must have access to run
sudo certbot or sudo certbot-auto without a password, which
is largely dependent on how you configure your gunicorn,
uwsgi, etc to run (if in a web environment).
- This likely means running sudo visudo or adding an entry to /etc/sudoers.d/.
- For security, it is highly recommended to only allow ``sudo`` access to just the one command (``certbot`` or ``certbot-auto``).
- Register an account with Let’s Encrypt’s servers (if you haven’t already). Note that certbot_py (this library) defaults to using Let’s Encrypt staging servers, while certbot and certbot-auto default to production servers. An example of registration for staging servers: certbot register --staging # OR certbot-auto register --staging
- In your Python project’s virtual environment, install certbot_py: pip install certbot_py
Ensure you register an account with Let’s Encrypt, as mentioned above.
There is a single generate_certificate method which requires 3 parameters: domains, certbot_command, and auth_script. There are many other optional parameters which mostly map to corresponding certbot arguments.
from certbot_py import client command = '/my/path/to/certbot' script = '/my/other/path/to/auth-hook-script.sh' my_domains = ['example1.com', 'example2.com', 'example3.com'] results = client.generate_certificate( domains=my_domains, certbot_command=command, auth_script=script )
If you wanted to generate a SAN (ie. UCC) certificate instead, use san_ucc=True. As with certbot, the first domain in domains will be the common name listed on the resulting cert.
results = client.generate_certificate( domains=my_domains, certbot_command=command, auth_script=script, san_ucc=True )
There are many more options, most of the pertinent ones are listed below. Skip further down for more information on auth_script.
Full list of generate_certificate parameters (order is unimportant as they must be passed as keyword arguments):
account = None allow_domain_subset = False allow_self_upgrade = False auth_script = None certbot_command = None domains = None hsts = False must_staple = False production = False redirect = False rsa_key_size = None san_ucc = False staple_ocsp = False uir = False
These mostly map to corresponding ``certbot` arguments <https://certbot.eff.org/docs/using.html#certbot-command-line-options>`__, with a few exceptions:
- production will enable the live generation of certificates from Let’s Encrypt’s production servers. By default (and safely), certbot_py uses staging servers.
- san_ucc indicates that a SAN/UCC certificate is wanted, otherwise an individual cert will be requested for each domain passed in.
- certbot_command is the full path the the installed certbot or certbot-auto command line executable.
- auth_script is the full path to a script which will use the certbot-provided $CERTBOT_DOMAIN, $CERTBOT_VALIDATION, and $CERTBOT_TOKEN environment variables to perform some developer-specific action (ie. add $CERTBOT_VALIDATION and $CERTBOT_TOKEN to a database) so that the subsequent validation request from Let’s Encrypt’s servers can succeed.
- allow_self_upgrade would allow auto-upgrading (certbot-auto only), which has been disabled by default to prevent breakage due to tool upgrades
Example auth_script (Django example), just a single bash script:
#~/bin/bash /home/webuser/.virtualenvs/bin/python /home/webuser/my_project/manage.py set_domain_validation "$CERTBOT_DOMAIN" "$CERTBOT_VALIDATION" "$CERTBOT_TOKEN"
There is a command line alias configured upon pip install that you can use to test with. Simply use certbot_py on the command line, full help is available.
- certbot version 0.10.0 is the first version to expose the necessary command line arguments - prior versions will fail.
- This library should be updated for security and bug fixes (obviously) but also may require updating if the underlying arguments to certbot change or features are added.
Gee, I should mock in some tests…
Longer term, I look forward to having this library change (and improve!) so that it no longer needs Python’s subprocess.Popen() or a certbot installation. This is technically possible using Let’s Encrypt’s `acme library <https://github.com/certbot/certbot/tree/master/acme>`__; however creating a client around acme involves much more than something simple like acme.generate_certificate(...). Much in this ACME/Let’s Encrypt world seems in flux at the moment, so implementing this wrapper felt like the easiest path forward for the time being - and retains full compatibility with the standard Let’s Encrypt command line tools.
Feedback is encouraged and appreciated. File issues on Github. Feel free to fork and suggest improvements.
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