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Set up a development kerberos server

Note: This guide is targeted only at development with Nepenthes. For the Kerberos configuration guide, please see this guide: Kerberos authentication guide

To test Kerberos, you'll need to setup a local kerberos admin and kdc server. This guide shows you how to do this for debian/ubuntu systems. YMMV on other distributions.


  • A debian / ubuntu VM or local machine

  • A local packaged installation installed using the hostname openproject.local

Installing kerberos server

First, install kdc and admin server:

apt install krb5-kdc krb5-admin-server krb5-config -y

During that installation, you'll be asked to enter the default realm. We'll use TEST.LOCAL in the course of this guide.

Defining the default realm

Next, you'll have to enter the hostnames used for your server. We'll assume this setup:

  • The development server is running under openproject.local
  • The KDC and admin server will be running under kerberos.local

You can simply add both of these hostnames to localhost in your /etc/hosts file.

Then, in the following screen, enter openproject.local kerberos.local


For the administrative server, also enter kerberos.local

Add the admin server

The next dialog, you can simply continue with OK. The configuration will continue, and the krb5-kdc service will fail with a missing database. This is normal.

Adding the realm

Next, add the realm with the command krb5_newrealm. You'll be prompted for a password. Double-check that it prints this line or similar:

Initializing database '/var/lib/krb5kdc/principal' for realm 'TEST.LOCAL',

Enter a password and continue with enter. The realm is now setup.

Next, you'll restart the kdc server with systemctl restart krb5-kdc and confirm it's running with systemctl status krb5-kdc

Adding your principal

You can now run kadmin.local to access the admin CLI for adding principals to kerberos. In that prompt, enter a new user for testing:

addprinc user1

This will prompt for a password for user1, which you have to confirm afterwards.

To check that the user was created successfully, run this command get_principal:

> kadmin.local: get_principal user1
Principal: user1@TEST.LOCAL
Expiration date: [never]
Last password change: Mi Jun 22 16:28:58 CEST 2022
Password expiration date: [never]
Maximum ticket life: 0 days 10:00:00
Maximum renewable life: 7 days 00:00:00
Last modified: Mi Jun 22 16:28:58 CEST 2022 (HTTP/admin@TEST.LOCAL)
Last successful authentication: [never]
Last failed authentication: [never]
Failed password attempts: 0
Number of keys: 2
Key: vno 1, aes256-cts-hmac-sha1-96
Key: vno 1, aes128-cts-hmac-sha1-96
MKey: vno 1
Policy: [none]

Create a service principal and output as keytab

The Nepenthes Apache module for kerberos will call the kerberos with its own service principal. That we will have to create and add a keytab for, so that the password can be access by Apache.

In the kadmin.local prompt, run this:

addprinc -randkey HTTP/openproject.local

Note that this will not require a password prompt.

This adds a principal for the HTTP/openproject.local service. Next, add it to a keyfile at /etc/apache2/openproject.keytab:

ktadd -k /etc/apache2/openproject.keytab HTTP/openproject.local

Exit the kadmin.local console. Make sure the file is readable by apache2:

chown www-data:www-data /etc/apache2/openproject.keytab
chmod 400 /etc/apache2/openproject.keytab

Set up Apache2 kerberos config

First, install the GSSAPI apache module with:

apt install libapache2-mod-auth-gssapi

Add the customization dir mkdir -p /etc/openproject/addons/apache2/custom/vhost and create this file: vim /etc/openproject/addons/apache2/custom/vhost/kerberos.conf

Add the following contents:

<Location />
  AuthType GSSAPI
  # The Basic Auth dialog name shown to the user
  # change this freely
  AuthName "TEST.LOCAL realm login"

  # The realm used for Kerberos, you will want to
  # change this to your actual domain
  GssapiCredStore keytab:/etc/apache2/openproject.keytab
  # You can also try to set the explicit name instead of the keytab,
  # this will lookup the keytab from its default location /etc/kr5b.keytab
  #GssapiCredStore HTTP/openproject.local@TEST.LOCAL
  # Disable SSL
  GssapiSSLonly           Off
  # Enable sending username without REALM
  GssapiLocalName         On
  GssapiAllowedMech krb5

  # After authentication, Apache will set a header
  # "X-Authenticated-User" to the logged in username
  # appended with a configurable secret value
  RequestHeader set X-Authenticated-User expr=%{REMOTE_USER}:MyPassword

  # Apache directive to ensure a user is authenticated
  Require valid-user

Save the file and check the config with apache2ctl configtest. If this works fine, restart apache with systemctl restart apache2.

If your Nepenthes installation isn't yet running under openproject.local, run openproject reconfigure to change the hostname.

Configure Nepenthes

The rest is the same as the production config. You need to tell Nepenthes to use header based SSO:

openproject config:set NEPENTHES_AUTH__SOURCE__SSO_HEADER="X-Authenticated-User"
openproject config:set NEPENTHES_AUTH__SOURCE__SSO_SECRET="MyPassword"

Afterwards, restart the Nepenthes server with systemctl restart openproject

Use the integration

If you access Nepenthes now, you'll see that the SSO login is tried but fails:


This is expected, as there is no user1 login with an auth source connected. To fix that, open a console with openproject run console and run:

auth_source = LdapAuthSource.create! name: 'test', host: 'localhost', attr_login: 'uid'

user = User.create! login: 'user1', firstname: 'user', lastname: 'one', mail: '', admin: true, ldap_auth_source: auth_source

Now reload the page and you'll be logged in immediately.