certbot/docs/contributing.rst

Contributing

Hacking

In order to start hacking, you will first have to create a development environment. Start by installing dependencies and setting up Let's Encrypt <using>.

Now you can install the development packages:

./venv/bin/pip install -r requirements.txt -e .[dev,docs,testing]

The code base, including your pull requests, must have 100% test statement coverage and be compliant with the coding style <coding-style>.

The following tools are there to help you:

• ./venv/bin/tox starts a full set of tests. Please make sure you run it before submitting a new pull request.
• ./venv/bin/tox -e cover checks the test coverage only.
• ./venv/bin/tox -e lint checks the style of the whole project, while ./venv/bin/pylint --rcfile=.pylintrc file will check a single file only.

Vagrant

If you are a Vagrant user, Let's Encrypt comes with a Vagrantfile that automates setting up a development environment in an Ubuntu 14.04 LTS VM. To set it up, simply run vagrant up. The repository is synced to /vagrant, so you can get started with:

vagrant ssh
cd /vagrant
./venv/bin/pip install -r requirements.txt
sudo ./venv/bin/letsencrypt

Support for other Linux distributions coming soon.

Note

Unfortunately, Python distutils and, by extension, setup.py and tox, use hard linking quite extensively. Hard linking is not supported by the default sync filesystem in Vagrant. As a result, all actions with these commands are significantly slower in Vagrant. One potential fix is to use NFS (related issue).

Code components and layout

acme

contains all protocol specific code

letsencrypt

all client code

Plugin-architecture

Let's Encrypt has a plugin architecture to facilitate support for different webservers, other TLS servers, and operating systems. The interfaces available for plugins to implement are defined in interfaces.py.

The most common kind of plugin is a "Configurator", which is likely to implement the ~letsencrypt.interfaces.IAuthenticator and ~letsencrypt.interfaces.IInstaller interfaces (though some Configurators may implement just one of those).

There are also ~letsencrypt.interfaces.IDisplay plugins, which implement bindings to alternative UI libraries.

Authenticators

Authenticators are plugins designed to solve challenges received from the ACME server. From the protocol, there are essentially two different types of challenges. Challenges that must be solved by individual plugins in order to satisfy domain validation (subclasses of ~.DVChallenge, i.e. ~.challenges.DVSNI, ~.challenges.SimpleHTTPS, ~.challenges.DNS) and continuity specific challenges (subclasses of ~.ContinuityChallenge, i.e. ~.challenges.RecoveryToken, ~.challenges.RecoveryContact, ~.challenges.ProofOfPossession). Continuity challenges are always handled by the ~.ContinuityAuthenticator, while plugins are expected to handle ~.DVChallenge types. Right now, we have two authenticator plugins, the ~.ApacheConfigurator and the ~.StandaloneAuthenticator. The Standalone and Apache authenticators only solve the ~.challenges.DVSNI challenge currently. (You can set which challenges your authenticator can handle through the ~.IAuthenticator.get_chall_pref.

(FYI: We also have a partial implementation for a ~.DNSAuthenticator in a separate branch).

Installer

Installers classes exist to actually setup the certificate and be able to enhance the configuration. (Turn on HSTS, redirect to HTTPS, etc). You can indicate your abilities through the ~.IInstaller.supported_enhancements call. We currently only have one Installer written (still developing), ~.ApacheConfigurator.

Installers and Authenticators will oftentimes be the same class/object. Installers and Authenticators are kept separate because it should be possible to use the ~.StandaloneAuthenticator (it sets up its own Python server to perform challenges) with a program that cannot solve challenges itself. (Imagine MTA installers).

Installer Development

There are a few existing classes that may be beneficial while developing a new ~letsencrypt.interfaces.IInstaller. Installers aimed to reconfigure UNIX servers may use Augeas for configuration parsing and can inherit from ~.AugeasConfigurator class to handle much of the interface. Installers that are unable to use Augeas may still find the ~.Reverter class helpful in handling configuration checkpoints and rollback.

Display

We currently offer a pythondialog and "text" mode for displays. Display plugins implement the ~letsencrypt.interfaces.IDisplay interface.

Coding style

Please:

1. Be consistent with the rest of the code.

2. Read PEP 8 - Style Guide for Python Code.

3. Follow the Google Python Style Guide, with the exception that we use Sphinx-style documentation:

   def foo(arg):
       """Short description.
   
       :param int arg: Some number.
   
       :returns: Argument
       :rtype: int
   
       """
       return arg

4. Remember to use ./venv/bin/pylint.

Updating the documentation

In order to generate the Sphinx documentation, run the following commands:

cd docs
make clean html SPHINXBUILD=../venv/bin/sphinx-build

This should generate documentation in the docs/_build/html directory.