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Keycloak and OpenLDAP on Kubernetes

In this post we'll cover how - having installed Keycloak and OpenLDAP separately on Kubernetes - to link the two together so that Keycloak uses OpenLDAP as it's primary store for user data.

This post is part of a series on single sign on for Kubernetes.

  1. Contents and overview
  2. Installing OpenLDAP
  3. Installing Keycloak
  4. Linking Keycloak and OpenLDAP
  5. OIDC Kubectl Login with Keycloak
  6. Authenticate any web app using ingress annotations
  7. Gitea (requires LDAP)
  8. Simple Docker Registry
  9. Harbor Docker Registry with ACL

Pre-requisites

This assumes you have CLI access to a Kubernetes cluster, will be working in a namespace called identity and have both Helm 3 and Kubectl installed and working locally. Finally it assumes that you're using NGINX for Ingress along with cert manager for SSL certificates with a Cluster Issuer called letsencrypt-production.

If your configuration is different, the majority of the steps will be the same, but you'll need to change the ingress annotations accordingly.

The source for this series of tutorials can be found here: https://github.com/TalkingQuickly/kubernetes-sso-guide and cloned with:

git clone [email protected]:TalkingQuickly/kubernetes-sso-guide.git

All commands in the tutorial assume that they're being executed from the root of this cloned repository.

This post assumes you've already completed the "Intalling OpenLDAP" and "Installing Keycloak" sections.

Configuring OpenLDAP in Keycloak

After logging into the Keycloak administrative console with our admin user, head to User Federation and select ldap from the "Add Provider` dropdown. Then choose the following options:

  • Edit Mode: Writable
  • Sync Registrations: On
  • Vendor: Other
  • Connection URL: ldap://openldap.identity.svc.cluster.local; you'll need to change identity to match the namespace you're working in)
  • Users DN: ou=People,dc=ssotest,dc=staging,dc=talkingquickly,dc=co,dc=uk; you'll need to change the dc entries to match your base dn. Note that here we're telling Keycloak that users are stored in our People ou, created from the customLdiffFiles.
  • Authentication Type: simple
  • Bind DN: cn=admin,dc=ssotest,dc=staging,dc=talkingquickly,dc=co,dc=uk again, updating the dc entries to match your base dn
  • Bind Credentials: Set this to the admin password we used for ldapsearch earlier

Once we've entered all of these details, we can use the "Test connection" and "Test authentication" buttons to make sure that everything works. Assuming it does, we can select "Save" to complete the addition of a User Federation provider.

At this point we've configured Keycloak so that it knows how to synchronise user with OpenLDAP, but currently it has no concept of groups. With more than a handful of users, we'll want to be able to allocate people to groups and determine their access to systems according to group membership.

For this we need to go back to the "User Federation" entry on the left menu, choose our ldap entry and select the "Mappers" tab.

We then need to select "Create", enter group as the Name for our federation mapper and select group-ldap-mapper as the "Mapper Type". Then select the following:

  • LDAP Groups DN: ou=Group,dc=ssotest,dc=staging,dc=talkingquickly,dc=co,dc=uk (updating to match your configuration)
  • Group Object Classes: groupOfUniqueNames
  • Membership LDAP Attribute: uniqueMember
  • User Groups Retrieve Strategy: LOAD_GROUPS_BY_MEMBER_ATTRIBUTE

And choose save. This configuration is slightly different to the default and ensures that the memberOf attribute works correctly. There's a long Github issue on it here. This is required by some applications to manage access based on groups.

Note that in order to test that memberOf is working correctly with ldapsearch, we'll need to include operational attributes by including "+" as part of our ldapsearch command e.g:

ldapsearch -x -H ldap://localhost:3890 -b dc=ssotest,dc=staging,dc=talkingquickly,dc=co,dc=uk -D "cn=admin,dc=ssotest,dc=staging,dc=talkingquickly,dc=co,dc=uk" "+" -w password

To run the commands locally we'll need to forward the OpenLDAP port to our local machine with:

kubectl port-forward --namespace identity \
      $(kubectl get pods -n identity --selector='release=openldap' -o jsonpath='{.items[0].metadata.name}') \
      3890:389

Managing users and testing that it works

We can now use Keycloak to add a user by going to the "Users" option in the left hand pane and choosing Add user. After populating and saving the new user form, we can use ldapsearch to check that the user has been created in openldap. To run the commands locally we'll need to forward the OpenLDAP port to our local machine with:

kubectl port-forward --namespace identity \
      $(kubectl get pods -n identity --selector='release=openldap' -o jsonpath='{.items[0].metadata.name}') \
      3890:389

We can then execute the ldapsearch command:

ldapsearch -x -H ldap://localhost:3890 -b dc=ssotest,dc=staging,dc=talkingquickly,dc=co,dc=uk -D "cn=admin,dc=ssotest,dc=staging,dc=talkingquickly,dc=co,dc=uk" "+" -w password

Replacing password with the password we chose in values-openldap.yml.

Included in the output, we should see something like this:

# talkingquickly, People, ssotest.staging.talkingquickly.co.uk
dn: uid=talkingquickly1,ou=People,dc=ssotest,dc=staging,dc=talkingquickly,dc=co,dc=uk
uid: talkingquickly1
objectClass: inetOrgPerson
objectClass: organizationalPerson
mail: [email protected]
sn: Dixon
cn: Ben

Which shows that our user has been successfully created in OpenLDAP! Now onto groups. If we head over to the "Groups" page in Keycloak and add an "Administrators" group and then re-run our ldapsearch search command we'll see that nothing has changed, our group won't be there.

If however we then return to the Users page, select or newly created user and head to the Groups tab, we can then add our user to the Administrators group. Note that when viewing the "Users" tab, we'll sometimes see an empty list and have to click "View all users" to see everyone.

Having done this, if we re-run our ldapsearch command, we should see something like the following included in the output:

# Administrators, Group, k4stest4.talkingquickly.co.uk
dn: cn=Administrators,ou=Group,dc=k4stest4,dc=talkingquickly,dc=co,dc=uk
objectClass: groupOfNames
cn: Administrators
member: cn=empty-membership-placeholder
member: uid=talkingquickly,ou=People,dc=k4stest4,dc=talkingquickly,dc=co,dc=uk

This shows that both our Administrators group has been created and that our user is a part of it.

If we then look at the entry for our user, assuming we have used the "+" option to enable the display of operational fields, we'll see that it includes a line something like:

memberOf: cn=Administrators,ou=Group,dc=ssotest,dc=staging,dc=talkingquickly,dc=co,dc=uk

Which means the memberOf functionality we configured earlier is working.

This series of posts won't explore the use of ldapsearch much further, but it's a powerful tool and this page is a handy cookbook of how it can be used.

  1. Contents and overview
  2. Installing OpenLDAP
  3. Installing Keycloak
  4. Linking Keycloak and OpenLDAP
  5. OIDC Kubectl Login with Keycloak
  6. Authenticate any web app using ingress annotations
  7. Gitea (requires LDAP)
  8. Simple Docker Registry
  9. Harbor Docker Registry with ACL