uw-saml

A UW-specific adapter to the python3-saml package. This package was built to federate with other IdPs, but the default case is to use the UW Identity Provider. It can be used against any framework. For a django-specific package, also consider uw-django-saml2.

Installation

pip install uw-saml[python3-saml]

The extra [python3-saml] is because the SAML package can be cumbersome to install in a workstation environment, on account of needing the libxmlsec1-dev library. Therefore, it's an optional requirement, causing a runtime error instead of an install-time error. Alternatively, you can use a mock interface by setting uw_saml2.python3_saml.MOCK = True.

If you are able to run your app as a Docker container, you can base your image on ghcr.io/uwit-iam/uw-saml-poetry:latest which comes with all dependencies pre-installed. Here is an example. Note that you don't have to use poetry in your install process to use this image.

FROM ghcr.io/uwit-iam/uw-saml-poetry:latest AS dependencies
RUN pip install flask uw-saml  # uw-saml and python3-saml are already installed!
COPY app.py ./
CMD flask run app

Example login endpoint using flask

In this example you've gone to SP Registry and registered an Entity ID of https://samldemo.iamdev.s.uw.edu/saml, with an ACS endpoint of https://samldemo.iamdev.s.uw.edu/saml/login. GETs will return a redirect to the IdP for authentication, and POSTs will try to process a SAML Response.

from flask import request, session, redirect
import uw_saml2

app = Flask(__name__)

@app.route('/saml/login', methods=['GET', 'POST'])
def login():
    session.clear()
    args = {
        'entity_id': 'https://samldemo.iamdev.s.uw.edu/saml',
        'acs_url': 'https://samldemo.iamdev.s.uw.edu/saml/login'
    }
    if request.method == 'GET':
        args['return_to'] = request.args.get('url', None)
        return redirect(uw_saml2.login_redirect(**args))

    attributes = uw_saml2.process_response(request.form, **args)
    session['userid'] = attributes['uwnetid']
    session['groups'] = attributes.get('groups', [])

    relay_state = request.form.get('RelayState')
    if relay_state and relay_state.startswith('/'):
        return redirect(urljoin(request.url_root, request.form['RelayState']))

    return 'Welcome ' + session['userid']

Considerations

Sessions

Give some consideration to session lifetime. The session in this example lives as a signed cookie. Ideally the cookie would expire at browser close, along with some time limit appropriate for your application. An example again with flask for a ten minute limit...

from datetime import timedelta

app.config.update(
    PERMANENT_SESSION_LIFETIME=timedelta(minutes=10)
)

Replay attack prevention

By default this package uses an in-memory cache to check for replay attacks. To use a distributed cache such as redis or memcached you would inject a cache object into uw_saml2.auth.CACHE. Here's an example of how to do it...

import werkzeug.contrib.cache
import uw_saml2.auth

uw_saml2.auth.CACHE = werkzeug.contrib.cache.RedisCache()

Django's cache backend uses the same methods so that could be injected as well.

Developers

Maintenance

People who are developing this package should have either [poetry] or a docker daemon installed. This is so that you can run validations before pushing your code.

Using docker (recommended)

This is recommended because this is the script the CI pipeline uses, so if this works for you, it ought to work in the pipeline, too!

./scripts/pre-push.sh

Using poetry

Running directly is helpful when you want to attach debuggers, etc.

poetry install
poetry run pytest
poetry run black uw_saml2 tests

Pull Requests

When creating a pull request for this repository, a semver-guidance label must be applied to the PR. If you do not have write access, a reviewer must do this for you.

Use the following guidelines to select a version level for your change:

no-bump if the change is only for documentation, CI workflow, etc.
patch if the change is a simple update or bugfix (e.g., idp metadata update, certificate renewal, etc.), or if dependencies are updated (poetry.lock changes)
minor if new features are added or deprecated but the change is backwards-compatible
major if the change is not backwards compatible and will break consumers

Casecommons/uw-saml-python