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Web application authentication developer setup

Web applications that get deployed in large organizations typically need to be able to work with user identities provided by external identity sources like FreeIPA/IdM (IPA), Active Directory domains, SAML Identity Providers (IdP), or OpenID Providers (OP).

To support additional identity provider in Web application, using front-end HTTP server for authentication and top-level authorization with existing HTTP server modules might be preferred over implementing every new protocol in every application or Web framework. The applications then consume the authentication result as REMOTE_USER environment variable or other means (for example X-Remote-User HTTP header in case of HTTP proxy setup), as well as additional user attributes and user group membership information that can be used to control access within the application. More details about the approach can be found at

Even if consuming external authentication results might seem straightforward, it is still useful to verify the interaction, especially when HTTP status 401 for Kerberos or 30x redirects for SAML or OpenID Connect are involved.

This repository aims to help with that task, providing multi-container developer setup that can be used for development and testing of external authentication methods for Web applications. By default, the setup contains IPA server in container (service) ipa, Ipsilon SAML Identity Provider and OpenID Provider (idp), Firefox browser already configured to use the server for Kerberos authentication (client), Apache HTTP server with modules for GSS-API (Kerberos) and SAML and OpenID Connect (www), as well as an example Django application that shows the effect of propagating authentication result and the user information to an application (app).

                                               HTTP with auth
╔══════════╗     HTTP    ╔══════════════════╗  result      ╔═════════════╗
║ Browser  ║ ──────────▶ ║ Web server       ║ ───────────▶ ║ Application ║
║ "client" ║ ◀────────── ║ with authn/authz ║ ◀─────────── ║ "app"       ║
╚══════════╝  Negotiate  ║ setup            ║  application ╚═════════════╝
      │      or redirect ║ "www"            ║  content
      │                  ╚══════════════════╝
      │
      │             ╔═════════╗
      │  Kerberos   ║ FreeIPA ║
      ├───────────▶ ║ "ipa"   ║
      │             ╚═════════╝
      │ or SAML
      │ or OpenID Connect
      │ redirects   ╔═════════════════╗
      └───────────▶ ║ SAML IdP or     ║
                    ║ OpenID Provider ║
                    ║ "idp"           ║
                    ╚═════════════════╝

By changing the configuration of the Web server, it is possible to switch from Kerberos to SAML or OpenID Connect and see the effects in action. It is also possible to rebuild the setup to run the application directly in the Web server container -- the example application would then be deployed there via mod_wsgi.

This default setup can serve as demonstration of the concepts all by itself but its primary goal is to help developers get infrastructure for external authentication and plug in applications they develop or test. Instead of the provided example application, developers can instead put their application to the app or www containers, or configure the Web server to proxy the requests to completely different backend location where the application resides.

Instead of using the provided client container for browser testing, it is possible to access the IPA, IdP/OP, and the authentication HTTP server from a Web client (browser) outside of the setup. However, DNS or manual hosts records will likely need to be set up manually, as well a local Kerberos configuration, so starting with the provided client with Firefox might be easier.

Prerequisites

The setup uses docker and docker-compose, so they should be available.

When started, the containers will store their configuration and data in *-data/ sub-directories, and their ownership will change to root and their SELinux labels will likely change as well. You might want to pick location for the local copy/clone of the repository where this will not cause problems.

On SELinux enabled systems,

setsebool -P container_manage_cgroup 1

might be needed to enable running systemd in the containers.

Building the setup

With the freeipa-server image available, running

docker-compose build

in the directory of this repo will build create five container images. Depending on the machine where you run the build, it might take minutes to dozens of minutes to build.

Running the setup

The setup can be started with

docker-compose up

It will provide long output starting with

Creating webauthinfra_ipa_1 ... done
Creating webauthinfra_app_1 ... done
Creating webauthinfra_idp_1 ... done
Creating webauthinfra_www_1 ... done
Creating webauthinfra_client_1 ... done
Attaching to webauthinfra_app_1, webauthinfra_ipa_1, webauthinfra_idp_1, webauthinfra_www_1, webauthinfra_client_1
ipa_1     | Configuring ipa.example.test ...
ipa_1     | Mon Dec 10 18:42:42 UTC 2018 /usr/sbin/ipa-server-configure-first
ipa_1     |
ipa_1     | The log file for this installation can be found in /var/log/ipaserver-install.log
ipa_1     | ==============================================================================
ipa_1     | This program will set up the FreeIPA Server.
idp_1     | Waiting for FreeIPA server (HTTP Server) ...
www_1     | Waiting for FreeIPA server (HTTP Server) ...

and you can watch IPA server and Ipsilon IdP/OP being configured, and then the client container with Firefox IPA-enrolled and www container with the Apache HTTP server IPA-enrolled and configured as SAML Service Provider and OpenID Provider, as well as the example Django application configured and started.

After all the containers have initialized, you can use ssh -X to log in to the container where Firefox is configured, and run the browser:

ssh -X -i client-data/id_rsa -p 55022 developer@localhost firefox -no-remote

(When running ssh as root, chmod 600 client-data/id_rsa might be needed.)

It will open four tabs -- the example application, IPA and IdP/OP logon pages, and a page that allows you to obtain Kerberos Ticket Granting Ticket (kinit) or change IPA user passwords in the client container. There will be one admin user in the IPA server -- the password for that account can be found with

cat ipa-data/admin-password

You can log in to the IPA server WebUI, either by kinit-ing first or with login and password and create more users and groups. Then you can to log in into the example application via www.example.test (again, Kerberos or login and password should work). The application aims at easily presenting authentication-related information, so it will show the list of last logged-in users, and for authenticated access, it will display information about the user.

If you want to drive permissions of users in the example application, log in as admin to its Admin interface and create groups there, with names matching user groups in IPA with ext: prefix. For example, if you created group webapp-admin in IPA, the counterpart in the example application would be ext:webapp-admin. You can attach the application-level permissions to the group. Upon logon, users will have their user attributes and group membership synced into the example Django database.

Note that the Admin part of the application is only accessible to users with a Staff flag which the example application sets to members of IPA's admins group. Due to the Django Admin internals, the Staff flag cannot be linked to group membership to be populated with more flexibility.

Explore https://github.com/adelton/django-identity-external to see the approach used.

To switch the Kerberos-based authentication to SAML-based, copy the example src/www-proxy-saml.conf to www's data directory:

cp src/www-proxy-saml.conf www-data/www.conf

or

docker cp src/www-proxy-saml.conf webauthinfra_www_1:/data/www.conf

and restart the Apache HTTP server:

docker exec -ti webauthinfra_www_1 systemctl restart httpd

When you try to log in to the example application now, instead of Kerberos authentication used, you should see HTTP redirection to the IdP at idp.example.test/idp where you will authenticate and be redirected back.

For OpenID Connect, use src/www-proxy-openidc.conf in similar manner.

To switch back to Kerberos, use src/www-proxy-gssapi.conf which was the default /data/www.conf configuration in the www container.

The tests/test.sh can be used for testing the basic operation.

Developing with the setup

There are multiple ways to use the setup with application that you develop:

  • Deploy application in the HTTP server (www) container.
  • Run application in the existing app container instead of the default example application, using the www container as authentication HTTP proxy.
  • Point the setup to an external location (container, host) where the application runs, again, using the www container as authentication HTTP proxy.

Each method is described in more detail below.

Deploy application in the HTTP server (www) container

Amend src/Dockerfile.www to install additional Apache modules like mod_wsgi, and either install the application into the image in build time or make it available in the container via www-data/ or some other bind mount location. This way you will test the application on the same "machine" as the front-end authentication HTTP server.

Check the src/Dockerfile.www-with-app for an example of turning the HTTP proxy based setup into mod_wsgi-based one, running the application in the www container directly, instead of in the app container. In fact, if you edit the docker-compose.yml file and use the commented-out dockerfile: line instead of the original one and rebuild the setup, you will get the example application running locally in the HTTP server (www) container. Explore the diff of src/Dockerfile.www and src/Dockerfile.www-with-app to get an inspiration for putting your application into the www container.

Replace example application with your application in app container

Change src/Dockerfile.app to include and run your application instead of the example one in the separate container. Chances are your application has different layout of the logon URLs, so the Apache HTTP server configuration in the www container will need to be tweaked a bit as well, either by changing the src/www*.conf files or by putting the configuration to www-data/www.conf directly.

This will turn the HTTP server container into authentication HTTP proxy for your application, instead of the default example one.

It is important that in production, the communication between the authentication proxy and the application is protected as the authentication and authorization result is passed via HTTP headers of the HTTP request. If users are able to connect to the backend application directly, they'd be able to provide any HTTP header content they'd like, sidestepping the authentication setup. Depending on the network and system infrastructure, iptables, mutual TLS authentication, or other means might be appropriate.

Use existing application location

Change www-data/www.conf to proxy the requests to whatever location your application runs on, potentially on the host machine directly. With this setup, you will use the authentication HTTP proxy approach, without forcing the application to be run in container.

The note from the previous item about securing the communication in production setups applies here as well.

The defaults of the setup

The services

  • ipa -- IPA server

    • Hostname: ipa.example.test
    • Persistent storage in ipa-data/

  • idp -- Ipsilon IdP server

    • Hostname: idp.example.test
    • Persistent storage in idp-data/

  • www -- Apache HTTP server with authn/authz modules

    • Hostname: www.example.test
    • Configuration stored in www-data/; namely Apache HTTP server loads www-data/www.conf.
    • IPA-enrolled during the first run.

  • app Back-end server with example application

    • Hostname: app.example.test
    • Database stored in app-data/

  • client -- SSH server and Firefox

    • Hostname: client.example.test
    • Accessible on host's port 55022.
    • IPA-enrolled during the first run.

Precreated accounts

  • admin (IPA)

    • password in ipa-data/admin-password

  • admin (the example application)

    • password in the docker-compose output (but access with IPA's admin password will also work)

PAM services and host-based access access control (HBAC) rules:

  • webapp

  • idp

    • used for HBAC idp.example.test/idp
    • HBAC rule: allow_idp

Both HBAC rules are set up to allow access for any user but the HBAC rules can be changed in IPA. The allow_all is disabled by default for HBAC to work.

Set of applications and authentication modules was used to demonstrate the external authentication concepts. In future versions, different versions or different applications might be used to achieve the same goal.

Automated testing

The client container has Selenium with Python bindings installed, so it can be directly used for automated testing of the setup or developed application. Examples of simple tests can be found in src/test-kerberos.py, src/test-saml.py, and src/test-openidc.py -- they are invoked from tests/test.sh.

Licence

Copyright 2016--2022 Jan Pazdziora

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at https://www.apache.org/licenses/LICENSE-2.0.

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.