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zulip/docs/prod-authentication-methods.md

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Authentication methods

Zulip supports several different authentications methods:

  • EmailAuthBackend - Email/password authentication.
  • ZulipLDAPAuthBackend - LDAP username/password authentication.
  • GoogleMobileOauth2Backend - Google authentication.
  • GitHubAuthBackend - GitHub authentication.
  • ZulipRemoteUserBackend - Authentication using an existing Single-Sign-On (SSO) system that can set REMOTE_USER in Apache.
  • DevAuthBackend - Only for development, passwordless login as any user.

It's easy to add more, see the docs on python-social-auth below.

The setup documentation for most of these is simple enough that we've included it inline in /etc/zulip/settings.py, right above to the settings used to configure them. The remote user authentication backend is more complex since it requires interfacing with a generic third-party authentication system, and so we've documented it in detail below.

Adding additional methods using python-social-auth

The implementation for GitHubAuthBackend is a small wrapper around the popular python-social-auth library. So if you'd like to integrate Zulip with another authentication provider (e.g. Facebook, Twitter, etc.), you can do this by writing a class similar to GitHubAuthBackend in zproject/backends.py and adding a few settings. Pull requests to add new backends are welcome; they should be tested using the framework in test_auth_backends.py.

Remote User SSO Authentication

Zulip supports integrating with a Single-Sign-On solution. There are a few ways to do it, but this section documents how to configure Zulip to use an SSO solution that best supports Apache and will set the REMOTE_USER variable:

(0) Check that /etc/zulip/settings.py has zproject.backends.ZulipRemoteUserBackend as the only enabled value in the AUTHENTICATION_BACKENDS list, and that SSO_APPEND_DOMAIN is correct set depending on whether your SSO system uses email addresses or just usernames in REMOTE_USER.

Make sure that you've restarted the Zulip server since making this configuration change.

(1) Edit /etc/zulip/zulip.conf and change the puppet_classes line to read:

puppet_classes = zulip::voyager, zulip::apache_sso

(2) As root, run /home/zulip/deployments/current/scripts/zulip-puppet-apply to install our SSO integration.

(3) To configure our SSO integration, edit /etc/apache2/sites-available/zulip-sso.example and fill in the configuration required for your SSO service to set REMOTE_USER and place your completed configuration file at /etc/apache2/sites-available/zulip-sso.conf

zulip-sso.example is correct configuration for using an htpasswd file for REMOTE_USER authentication, which is useful for testing quickly. You can set it up by doing the following:

/home/zulip/deployments/current/scripts/restart-server
cd /etc/apache2/sites-available/
cp zulip-sso.example zulip-sso.conf
htpasswd -c /home/zulip/zpasswd username@example.com # prompts for a password

and then continuing with the steps below.

(4) Run a2ensite zulip-sso to enable the Apache integration site.

(5) Run service apache2 reload to use your new configuration. If Apache isn't already running, you may need to run service apache2 start instead.

Now you should be able to visit https://zulip.example.com/ and login via the SSO solution.

Troubleshooting Remote User SSO

This system is a little finicky to networking setup (e.g. common issues have to do with /etc/hosts not mapping settings.EXTERNAL_HOST to the Apache listening on 127.0.0.1/localhost, for example). It can often help while debugging to temporarily change the Apache config in /etc/apache2/sites-available/zulip-sso to listen on all interfaces rather than just 127.0.0.1 as you debug this. It can also be helpful to change /etc/nginx/zulip-include/app.d/external-sso.conf to proxy_pass to a more explicit URL possibly not over HTTPS when debugging. The following log files can be helpful when debugging this setup:

  • /var/log/zulip/{errors.log,server.log} (the usual places)
  • /var/log/nginx/access.log (nginx access logs)
  • /var/log/apache2/zulip_auth_access.log (you may want to change LogLevel to "debug" in the apache config file to make this more verbose)

Here's a summary of how the remote user SSO system works assuming you're using HTTP basic auth; this summary should help with understanding what's going on as you try to debug:

  • Since you've configured /etc/zulip/settings.py to only define the zproject.backends.ZulipRemoteUserBackend, zproject/settings.py configures /accounts/login/sso as HOME_NOT_LOGGED_IN, which makes https://zulip.example.com/ aka the homepage for the main Zulip Django app running behind nginx redirect to /accounts/login/sso if you're not logged in.

  • nginx proxies requests to /accounts/login/sso/ to an Apache instance listening on localhost:8888 apache via the config in /etc/nginx/zulip-include/app.d/external-sso.conf (using the upstream localhost:8888 defined in /etc/nginx/zulip-include/upstreams).

  • The Apache zulip-sso site which you've enabled listens on localhost:8888 and presents the htpasswd dialogue; you provide correct login information and the request reaches a second Zulip Django app instance that is running behind Apache with with REMOTE_USER set. That request is served by zerver.views.remote_user_sso, which just checks the REMOTE_USER variable and either logs in (sets a cookie) or registers the new user (depending whether they have an account).

  • After succeeding, that redirects the user back to / on port 443 (hosted by nginx); the main Zulip Django app sees the cookie and proceeds to load the site homepage with them logged in (just as if they'd logged in normally via username/password).

Again, most issues with this setup tend to be subtle issues with the hostname/DNS side of the configuration. Suggestions for how to improve this SSO setup documentation are very welcome!