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Touchstone Integration with Django

These notes are from trying to set up a Django application to work with MIT's Touchstone system, which is an implementation of Shibboleth. This is a long, involved process, so strap in and get ready to learn a lot of devops! This assumes that you are running on a vanilla Debian server -- my test box has a DNS entry of django-shibboleth-demo.odl.mit.edu.

Here are the steps at a high level:

  1. Compile & install nginx with Shibboleth integration
  2. Create a vanilla Django project
  3. Run Django project with nginx through uWSGI
  4. Set up HTTPS with Let's Encrypt
  5. Install Shibboleth SP and run as daemon through Supervisor
  6. Configure routes in Shibboleth
  7. Customize Django project to pick up Shibboleth headers

NGINX

It would be great if we could install nginx from the APT package repository, but unfortunately it's not that simple. We need to add the nginx-http-shibboleth module to nginx, and the documentation for that module suggests adding the headers-more-nginx-module as well, so that we can avoid having malicious users spoof headers to Shibboleth. Nginx does have limited support for dynamic modules, but for various reasons we can't go this route, so we'll have to compile nginx from source and add these modules into the mix.

sudo apt-get install git build-essential libpcre3-dev zlib1g-dev libssl-dev libgeoip-dev
mkdir nginx-compile && cd nginx-compile
git clone https://github.com/nginx/nginx.git -b release-1.11.12
git clone https://github.com/nginx-shib/nginx-http-shibboleth.git
git clone https://github.com/openresty/headers-more-nginx-module.git
cd nginx
./auto/configure --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --conf-path=/etc/nginx/nginx.conf --pid-path=/run/nginx.pid --add-module=../nginx-http-shibboleth/ --add-module=../headers-more-nginx-module/ --with-pcre --with-http_ssl_module --with-http_stub_status_module --with-http_geoip_module --with-http_auth_request_module --with-http_gzip_static_module --with-http_v2_module --with-http_realip_module --with-http_sub_module
make
sudo make install
sudo cp ../nginx-http-shibboleth/includes/* /etc/nginx/

Note that this will install nginx at version 1.11.12. If a more recent version of nginx is available, you should modify the git clone line to grab that release.

Nginx is now installed, but we're not done. When you install nginx via APT, it also takes care of some additional housekeeping to make it play nicely with the rest of the computer. Since we're installing it from source, we need to do that housekeeping ourselves.

First, create a new user for nginx to run under, and make a few new directories:

sudo useradd --home-dir /etc/nginx nginx
sudo mkdir /var/log/nginx
sudo mkdir /etc/nginx/conf.d

Next, edit nginx's config file at /etc/nginx/nginx.conf. Set these lines at the top of the file:

user       nginx;
error_log  /var/log/nginx/error.log;
pid        /run/nginx.pid;

In the same config file, there is an http section. At the bottom of that file, just before the closing brace of this section, add the line include conf.d/*.conf;.

It would also be nice to integrate nginx with systemd, so that nginx would be automatically launched when the computer boots up. At a coworker's suggestion, I've copied over the file that APT's packaged nginx uses to integrate it with systemd. Create a new file at /etc/systemd/system/multi-user.target.wants/nginx.service with this content:

[Unit]
Description=A high performance web server and a reverse proxy server
After=network.target

[Service]
Type=forking
PIDFile=/run/nginx.pid
ExecStartPre=/usr/sbin/nginx -t -q -g 'daemon on; master_process on;'
ExecStart=/usr/sbin/nginx -g 'daemon on; master_process on;'
ExecReload=/usr/sbin/nginx -g 'daemon on; master_process on;' -s reload
ExecStop=-/sbin/start-stop-daemon --quiet --stop --retry QUIT/5 --pidfile /run/nginx.pid
TimeoutStopSec=5
KillMode=mixed

[Install]
WantedBy=multi-user.target

Then run:

sudo systemctl daemon-reload
sudo systemctl enable nginx

Theoretically, this should work. In practice, it doesn't, for some reason. I ended up starting and stopping nginx by running the ExecStart command manually.

Django

Next, we need a Django application. For now, this is pretty vanilla.

sudo apt-get install python3-venv
python3 -m venv venv
source venv/bin/activate
pip install django
django-admin startproject testproject
cd testproject
django-admin startapp testapp

Then, install the app into the settings.py file, create a view in the app's views.py file, hook it up to the project urls.py file, and try running the project with manage.py runserver. Also add the correct host URL to the ALLOWED_HOSTS list in settings.py.

uWSGI

To make nginx run your Django application, we need to use uwsgi. There is a uwsgi package available from the apt-get system, but it doesn't seem to work the way we want, and the official docs recommend installing with pip, instead. Activate the virtualenv, then:

sudo apt-get install python3-dev
pip install uwsgi
uwsgi --module=testproject.wsgi:application --env DJANGO_SETTINGS_MODULE=testproject.settings --socket=127.0.0.1:29000 --daemonize=uwsgi.log --pidfile=uwsgi.pid

Port 29000 is arbitrary; use whatever port you want. To test that it's working, you can do this:

pip install uwsgi-tools
uwsgi_curl 127.0.0.1:29000

and verify that you get the output you expect from your site.

Next, make sure that the nginx.conf is reading files in the conf.d directory, and create this file at /etc/nginx/conf.d/django.conf:

upstream django {
    server 127.0.0.1:29000;
}

server {
    listen 80;
    server_name django-shibboleth-demo.odl.mit.edu;
    root /var/www/shibdemo;

    location / {
        uwsgi_pass django;
        include /etc/nginx/uwsgi_params;
    }

    location /static/  {
        alias /var/www/shibdemo/static/;
    }

    location /.well-known/  {
        alias /var/www/shibdemo/.well-known/;
    }
}

Also edit the file /etc/nginx/uwsgi_params and add the following lines to it:

uwsgi_param Host $host;
uwsgi_param X-Real-IP $remote_addr;
uwsgi_param X-Forwarded-For $proxy_add_x_forwarded_for;
uwsgi_param X-Forwarded-Proto $http_x_forwarded_proto;

Make sure that /var/www/shibdemo exists, and then tell nginx to reload its configuration. You can run this command to test that everything is working:

curl localhost -H "Host: django-shibboleth-demo.odl.mit.edu"

Let's Encrypt

Shibboleth needs HTTPS to work, and the best way to get that is with Let's Encrypt.

sudo apt-get install certbot -t jessie-backports
sudo certbot certonly --webroot -w /var/www/shibdemo -d django-shibboleth-demo.odl.mit.edu

You should now have a certificate in the /etc/letsencrypt/live/django-shibboleth-demo.odl.mit.edu/ directory. Next, we need to tell nginx about it. Add another server block to the /etc/nginx/conf.d/django.conf file that looks like this:

server {
    listen 443 ssl;
    server_name django-shibboleth-demo.odl.mit.edu;
    root /var/www/shibdemo;
    ssl_certificate /etc/letsencrypt/live/django-shibboleth-demo.odl.mit.edu/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/django-shibboleth-demo.odl.mit.edu/privkey.pem;

    location / {
        uwsgi_pass django;
        include /etc/nginx/uwsgi_params;
    }

    location /static/  {
        alias /var/www/shibdemo/static/;
    }

    location /.well-known/  {
        alias /var/www/shibdemo/.well-known/;
    }
}

The only difference is the listen line, and adding the ssl_certificate and ssl_certificate_key lines. Reload nginx again, and your site should be working over HTTPS!

Last, we need to disable insecure HTTP and redirect all requests to HTTPS. To do that, replace the first server block in the /etc/nginx/conf.d/django.conf file (the one that configures it for insecure HTTP) with this server block, instead:

server {
    listen 80;
    server_name django-shibboleth-demo.odl.mit.edu;
    return 301 https://$server_name$request_uri;
}

Reload nginx again, and test that HTTP requests are redirected to HTTPS.

Shibboleth SP

sudo apt-get install shibboleth-sp2-common shibboleth-sp2-utils supervisor
cd /etc/shibboleth
sudo wget -N http://web.mit.edu/touchstone/config/shibboleth2-sp/2.5/gen-shib2.sh
sudo sh gen-shib2.sh

Next, we need to set up Shibboleth SP as a backend for a FastCGI process. Create the following file at /etc/supervisor/conf.d/shibboleth-fastcgi.conf:

[fcgi-program:shibauthorizer]
command=/usr/lib/x86_64-linux-gnu/shibboleth/shibauthorizer
socket=unix:///run/shibboleth/shibauthorizer.sock
socket_owner=_shibd:nginx
socket_mode=0660
user=_shibd
stdout_logfile=/var/log/supervisor/shibauthorizer.log
stderr_logfile=/var/log/supervisor/shibauthorizer.error.log

[fcgi-program:shibresponder]
command=/usr/lib/x86_64-linux-gnu/shibboleth/shibresponder
socket=unix:///run/shibboleth/shibresponder.sock
socket_owner=_shibd:nginx
socket_mode=0660
user=_shibd
stdout_logfile=/var/log/supervisor/shibresponder.log
stderr_logfile=/var/log/supervisor/shibresponder.error.log

The socket locations (/run/shibboleth/shibauthorizer.sock and /run/shibboleth/shibresponder.sock) are arbitrary; use whatever locations you want.

The restart Supervisor with this command: sudo systemctl restart supervisor.service. If it doesn't work, try running sudo unlink /var/run/supervisor.sock first. Verify that it's working by checking to see if the /run/shibboleth/shibauthorizer.sock and /run/shibboleth/shibresponder.sock sockets exist.

Next, we need to connect nginx to Shibboleth via these sockets. First, create the file /etc/nginx/shib_mit_params with the following contents:

shib_request_set $shib_remote_user $upstream_http_variable_remote_user;
uwsgi_param REMOTE_USER $shib_remote_user;
shib_request_set $shib_eppn $upstream_http_variable_eppn;
uwsgi_param EPPN $shib_eppn;
shib_request_set $shib_mail $upstream_http_variable_mail;
uwsgi_param MAIL $shib_mail;
shib_request_set $shib_displayname $upstream_http_variable_displayname;
uwsgi_param DISPLAY_NAME $shib_displayname;

This instructs nginx to grab headers from the Shibboleth authorizer response and send them to Django, so that Django knows who the user is. Then add the following sections to your /etc/nginx/conf.d/django.conf file, inside of the server block:

# FastCGI authorizer for Auth Request module
location = /shibauthorizer {
    internal;
    include fastcgi_params;
    fastcgi_pass unix:/run/shibboleth/shibauthorizer.sock;
}

# FastCGI responder
location /Shibboleth.sso {
    include fastcgi_params;
    fastcgi_pass unix:/run/shibboleth/shibresponder.sock;
}

# A secured location.  Here all incoming requests query the
# FastCGI authorizer.  Watch out for performance issues and spoofing.
location /secure {
    include shib_clear_headers;
    shib_request /shibauthorizer;
    shib_request_use_headers on;
    include shib_mit_params;
    uwsgi_pass django;
    include /etc/nginx/uwsgi_params;
}

Reload nginx again, and verify that you can visit https://django-shibboleth-demo.odl.mit.edu/Shibboleth.sso/Metadata and get content from Shibboleth SP.

Next, you'll need to send an email to [email protected] to get your client registered in MIT's Touchstone identity provider (IdP). Include the contents of /etc/shibboleth/sp-cert.pem in your email.

Configure routes in Shibboleth

We've now configured nginx to know which routes are secured by Shibboleth, but Shibboleth needs to know that information, too. We're gonna edit some XML files by hand!

Open the /etc/shibboleth/shibboleth2.xml file that was generated by MIT's gen-shib2.sh script. The top-level element should be <SPConfig>, with an <ApplicationDefaults> element nested underneath it. Create a new <RequestMapper> element that is a child of <SPConfig> and a sibling of <ApplicationDefaults>. The element should look like this:

<RequestMapper type="Native">
  <RequestMap>
    <Host name="django-shibboleth-demo.odl.mit.edu">
      <Path name="secure" authType="shibboleth" requireSession="true" />
    </Host>
  </RequestMap>
</RequestMapper>

This RequestMapper is documented on the Shibboleth wiki.

Installing Shibboleth from APT also set up the shibd daemon, which now needs to be restarted to pick up the new configuration. We'll also need to restart Supervisor, so that the shibauthorizer and shibresponder processes pick up the new configuration, as well. After you've edited the shibboleth2.xml file, run these commands:

sudo service shibd restart
sudo service supervisor restart

Configure Django with Shibboleth headers

We need to enable authentication using the REMOTE_USER enviornment variable from nginx. Django's docs for how to do so are here: https://docs.djangoproject.com/en/1.10/howto/auth-remote-user/ But we can go through it here, as well.

Activate your virtualenv, and install the django-shibboleth-remoteuser library:

pip install git+https://github.com/Brown-University-Library/django-shibboleth-remoteuser.git

Next, open the settings.py file, and add the following variables to it:

SHIBBOLETH_ATTRIBUTE_MAP = {
    "EPPN": (True, "username"),
    "MAIL": (True, "email"),
    # full name is in the "DISPLAY_NAME" header,
    # but no way to parse that into first_name and last_name...
}
AUTHENTICATION_BACKENDS = [
    'shibboleth.backends.ShibbolethRemoteUserBackend',
]

Also, add the ShibbolethRemoteUserMiddleware to the MIDDLEWARE list, after the Django's AuthenticationMiddleware:

MIDDLEWARE = [
    ...
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'shibboleth.middleware.ShibbolethRemoteUserMiddleware',
    ...
]

You might want to use the following template for testing purposes:

<h1>Touchstone test</h1>
{% if user.is_authenticated %}
  <p>You are logged in as {{ user.username }}, ID {{ user.id }}</p>
{% else %}
  <p><a href="/Shibboleth.sso/Login">Login with Touchstone</a></p>
{% endif %}
<p><a href="/Shibboleth.sso/Session">Shibboleth session info</a></p>

In order to see your changes, you'll need to restart uWSGI:

# activate your virtualenv, then
uwsgi --reload=uwsgi.pid
uwsgi --module=testproject.wsgi:application --env DJANGO_SETTINGS_MODULE=testproject.settings --socket=127.0.0.1:29000 --daemonize=uwsgi.log --pidfile=uwsgi.pid

Finished

You now have a Django project running behind nginx that works with Shibboleth. Congratulations!