Set Up SSO in Apache with ModAuthMellon and AzureAD on Ubuntu 22.04

This guide will walk you through the steps to set up authentication, authorization and Single sign-on in Apache web server with Azure Active Directory as an identity provider on an Ubuntu 22.04. These instructions can also be applied if you are running an earlier release of Ubuntu 18.04 or 20.04.

• ModAuthMellon is an authentication module for Apache. It authenticates the user against a SAML 2.0 IdP, and grants access to resources depending on attributes received from the identity provider (IdP).
  
• Apache is the most widely-used web server in the world. It provides many powerful features including dynamically loadable modules, robust media support, and extensive integration with other popular software.
• Azure Active Directory (AzureAD) is Microsoft's enterprise cloud-based identity and access management (IAM) solution. It can sync with on-premise Active Directory and provide authentication to other cloud-based systems, and applications via authentication protocols like OAuth2, SAML, and WS-Security.
• Single sign-on (SSO) is a property of access control of multiple related, yet independent, software systems. With this property, a user logs in with a single ID and password to gain access to a connected system or systems without using different usernames or passwords, or in some configurations seamlessly sign on at each system. 
  

Security Assertion Markup Language (SAML 2.0) enables web applications to delegate user authentication to a SAML identity provider. For this guide, we will use Azure Active Directory (AzureAD) as a SAML Identity Provider. 

To follow this tutorial along, you will need a (physical or virtual) machine installed with Ubuntu 22.04.

 

Install Prerequisites

Log in to your Ubuntu 22.04 using a non-root user with sudo privileges, and perform the following steps. 

Type following command on your Ubuntu to set correct timezone:

sudo timedatectl set-timezone Asia/Karachi

Make sure you replace highlighted text with yours.

Type following command on your Ubuntu to install Apache, ModAuthMellon and their required dependencies:

sudo apt install -y openssl apache2 libapache2-mod-auth-mellon ntpdate php php-fpm

 

Configure ModAuthMellon

In SAML, identity providers are referred to by the acronym IdP. Application using an IdP is called a service provider, usually referred to by the acronym SP.

IdP's and SP's learn about each other by exchanging metadata. SAML metadata is XML. The schema for the metadata is a standard thus assuring participating SAML entities can consume each others metadata. SAML IdP's and SP's identify themselves via a unique name known as an EntityID.

It is recommended to keep all the configuration files related to ModAuthMellon in one location. For that, we will create a new directory mellon located under the Apache configuration root directory /etc/apache2.

sudo mkdir -p /etc/apache2/mellon

cd /etc/apache2/mellon

Create a few helper shell variables to be used with mellon metadata creation tool:

fqdn="myapp.stepstoperform.com"
mellon_endpoint_url="https://${fqdn}/mellon"
mellon_entity_id="https://${fqdn}"

Make sure you replace the highlighted text with yours.

Execute the Mellon metadata creation script:

sudo /usr/sbin/mellon_create_metadata $mellon_entity_id $mellon_endpoint_url

This will create .key .cert and .xml files in /etc/apache2/mellon directory. You should rename these files to keep the name short and appropriate:

sudo mv *.key mellon.key
sudo mv *.cert mellon.cert
sudo mv *.xml mellon_metadata.xml

If the "mellon_create_metadata" fails to generate the XML metadata file, you should edit it and comment out the "set -e" line:

sudo nano /usr/sbin/mellon_create_metadata

Comment out the set -e line:

# set -e

Save and close the editor when you are finished.

Execute the "mellon_create_metadata" script again as described above to generate XML metadata file.

Configuration for Apache add-on modules are located in the directory /etc/apache2/conf-available with file name extension of .conf. We will create a mellon.conf file in /etc/apache2/conf-available directory and place Mellon's configuration directives in it:

sudo nano /etc/apache2/conf-available/mellon.conf

Add following configuration directives:

<Location / >
    MellonEnable info
    MellonEndpointPath /mellon/
    MellonSPMetadataFile /etc/apache2/mellon/mellon_metadata.xml
    MellonSPPrivateKeyFile /etc/apache2/mellon/mellon.key
    MellonSPCertFile /etc/apache2/mellon/mellon.cert
    MellonIdPMetadataFile /etc/apache2/mellon/idp_metadata.xml
</Location>

We will place idp_metadata.xml file in /etc/apache2/mellon directory later because we need to obtain idp metadata from our Azure Active Directory and for that we need to perform few configuration steps at AzureAD as well.

 

Save and close the editor when you are finished.

Create Self-signed SSL Certificate

You can obtain SSL certificate from any of the SSL certificates provider i.e. DigiCert, VeriSign, etc. Since this is our test environment, we will create a self-signed SSL certificate to be used with https://myapp.stepstoperform.com/ url: 

sudo nano /etc/apache2/mellon/myapp.cnf

Add following directives:

[req]
default_bits       = 2048
default_keyfile    = private.key
distinguished_name = req_distinguished_name
prompt             = no
[req_distinguished_name]
commonName         = myapp.stepstoperform.com

Make sure you replace the highlighted text with yours. Save and close the editor when you are finished.

Execute following command to generate self-signed SSL certificate:

cd /etc/apache2/mellon

sudo openssl req -utf8 -batch -config "myapp.cnf" -new -x509 -days 3652 -nodes -out "myapp.crt" -keyout "myapp.key"

 

Create Apache VirtualHost

We will create myapp.conf file in /etc/apache2/sites-available/ directory to declear https://myapp.stepstoperform.com/ url and to host protected contents in /var/www/html/private directory.

sudo nano /etc/apache2/sites-available/myapp.conf

Add following configuration directives:

<IfModule mod_ssl.c>
<VirtualHost *:443>
ServerName myapp.stepstoperform.com
DocumentRoot /var/www/html

ErrorLog /var/log/apache2/error.log
CustomLog /var/log/apache2/access.log combined
LogLevel info ssl:warn

SSLCertificateFile /etc/apache2/mellon/myapp.crt
SSLCertificateKeyFile /etc/apache2/mellon/myapp.key
</VirtualHost>

<Location /private>
AuthType "Mellon"
MellonEnable "auth"
Require valid-user
MellonUser "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name"
</Location>
</IfModule>

Make sure you replace the highlighted text with yours. Save and close the editor when you are finished.

Create a private directory under /var/www/html to host your web contents:

sudo mkdir -p /var/www/html/private

We do not have any application to host but for demonstration purpose, we will create a simple index page in /var/www/html/private location:

sudo nano /var/www/html/private/index.html

Add simple html code in your index.html page:

<html>
        <head>
                <title>Index Page</title>
        </head>
        <body>
                <h2>This is to test Apache and Azure Active Directory authentication configuration!</h2>
                <p>If you see this on your web browser once you logged in, your Apache and AzureAD authentication configuration working perfectly
fine</p>
        </body>
</html>

Save and close the editor when you are finished.

Type following command to verify Apache configuration:

sudo apache2ctl configtest

If everything configured correctly as described, you will see Syntax OK in the output. If there is any error in the configuration file, fix them first and then test the apache configuration again.

Type following command to activate your Apache configuration:

sudo a2enmod ssl
sudo a2enconf mellon.conf
sudo a2ensite myapp.conf

Do not start or restart Apache at this stage as we still need to perform few more steps on Azure AD to obtain idp metadata file.

 

Configure SAML Authentication on AzureAD

First obtain mellon_metadata.xml file from your Ubuntu machine located under /etc/apache2/mellon directory as you need it to upload to your AzureAD.

Log in to your Azure portal and perform the following steps to configure SAML authentication for your browser based application.

Navigate to Azure Active Directory > Enterprise application

 

Click New application 

 

Click Create your own application

 

Enter your application URL (myapp.stepstoperform.com) for example, in the name box.

Select Integrate any other application you don’t find in the gallery (Non-gallery) from the option.

Click Create

Click on Set up single sign on

 

Click on SAML

 

Click on Upload metadata file

 

Click Browse icon.

 

Select your mellon_metadata.xml file you obtained from your Ubuntu.

 

Click on Add

 

Click Save, then Click X sign to close Basic SAML Configuration screen.

 

Click on No. I’ll test later 

 

Scroll down to download Federation Metadata XML file from the SAML Signing Certificate section.

Save this federation metadata file and rename it as idp_metadata.xml.

Next, navigate to Properties

 

Change User assignment required from Yes to No 

Click Save

At this stage, your Azure Active Directory is ready to serve SAML authentication to your browser based application. You need to transfer idp_metadata.xml file to your Ubuntu in /etc/apache2/mellon directory.

Log in to your Ubuntu, and restart Apache to make the changes effect:

sudo systemctl restart apache2

 

Test Apache and AzureAD SAML Authentication

From a web browser, enter https://myapp.stepstoperform.com/private url in the address bar.

This will take you to your Azure Active Directory authentication page where you need to enter your credentials to log in. 

When you are logged in using your Azure Active Directory credentials, you will be redirected to your simple index.html page as shown in screenshot below:

You can verify logged in user from Apache logs using tail -f /var/log/apache2/access.log command.

As you can see in Apache logs that we are logged in using webappuser1@techsupportpk.com and that is our Azure Active Directory user.

At this stage, you have successfully implemented Authentication, authorization, and Single sign-on in your Apache using ModAuthMellon as SAML service provider and Azure Active Directory as an SAML identity provider.

 

Conclusion

I hope this guide was helpful to integrate Azure Active Directory authentication in Apache on your Ubuntu 22.04. We highly appreciate if you leave few words of your thoughts about this tutorial in the comment section below.