certbot/docs/contributing.rst

Contributing

Hacking

Start by installing dependencies and setting up Let's Encrypt <using>.

When you're done activate the virtualenv:

source ./venv/bin/activate

This step should prepend you prompt with (venv) and save you from typing ./venv/bin/.... It is also required to run some of the testing tools. Virtualenv can be disabled at any time by typing deactivate. More information can be found in virtualenv documentation.

Install the development packages:

pip install -r requirements.txt -e acme -e .[dev,docs,testing] -e letsencrypt-apache -e letsencrypt-nginx -e letshelp-letsencrypt

Note

-e (short for --editable) turns on editable mode in which any source code changes in the current working directory are "live" and no further pip install ... invocations are necessary while developing.

This is roughly equivalent to python setup.py develop. For more info see man pip.

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

Testing

The following tools are there to help you:

• tox starts a full set of tests. Please make sure you run it before submitting a new pull request.
• tox -e cover checks the test coverage only. Calling the ./tox.cover.sh script directly (or even ./tox.cover.sh $pkg1 $pkg2 ... for any subpackages) might be a bit quicker, though.
• tox -e lint checks the style of the whole project, while pylint --rcfile=.pylintrc path will check a single file or specific directory only.
• For debugging, we recommend pip install ipdb and putting import ipdb; ipdb.set_trace() statement inside the source code. Alternatively, you can use Python'd standard library pdb, but you won't get TAB completion...

Integration

First, install Go 1.5 and start Boulder, an ACME CA server:

./tests/boulder-start.sh

The script will download, compile and run the executable; please be patient - it will take some time... Once its ready, you will see Server running, listening on 127.0.0.1:4000.... You may now run (in a separate terminal):

./tests/boulder-integration.sh && echo OK || echo FAIL

If you would like to test letsencrypt_nginx plugin (highly encouraged) make sure to install prerequisites as listed in tests/integration/nginx.sh:

and rerun the integration tests suite.

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 .[dev,docs,testing]
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).

Docker

OSX users will probably find it easiest to set up a Docker container for development. Let's Encrypt comes with a Dockerfile (Dockerfile-dev) for doing so. To use Docker on OSX, install boot2docker using the instructions at https://docs.docker.com/installation/mac/ and start it from the command line (boot2docker init).

To build the development Docker image:

docker build -t letsencrypt -f Dockerfile-dev .

Now run tests inside the Docker image:

docker run -it letsencrypt bash
cd src
tox -e py27

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 pylint.

Updating the documentation

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

make -C docs clean html

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