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OpenShift - Sync LDAP Groups

OpenShift offers the capability to leverage a Directory Service as an authentication source for user lookup. However, it lacks native functionality for automatic group synchronization into its Identity Management system. To achieve group syncing, we will implement a workaround solution. This involves deploying a cronjob that synchronizes groups from the source LDAP (FreeIPA in this instance) to OpenShift's OAuth service.

Start by creating a dedicated namespace to encapsulate all the resources required for the automated synchronization of LDAP groups with OpenShift.

 $ cat << EOF > 0-namespace.yml  
 ---  
 apiVersion: v1  
 kind: Namespace  
 metadata:  
  name: ldap-group-sync  
 ...  
 EOF  
 $ oc apply -f 0-namespace.yml

Given the use of LDAPS with certificates signed by a custom Certificate Authority (CA), it is necessary to create:

  • A ConfigMap to store the CA certificate.
  • A Secret to securely store the password for the service account used for LDAP lookups."

 $ oc -n ldap-group-sync create configmap ldap-cacert --from-file ca.crt=/etc/ipa/ca.crt  
 $ oc -n ldap-group-sync create secret generic ldap-bindpw --from-literal bindPassword='super-secure-password-for-ldap-bind-user'

The jobs executed by the CronJob will require elevated privileges to manage group configurations and memberships. To address this requirement, we will create:

  • A ServiceAccount
  • A ClusterRole to define the necessary permissions
  • A RoleBinding to associate the ClusterRole with the ServiceAccount.
Here's the manifest for the Serviceaccount:

 $ cat << EOF > 1-serviceaccount.yml  
 ---  
 apiVersion: v1  
 kind: ServiceAccount  
 metadata:  
   name: ldap-group-syncer  
   namespace: ldap-group-sync  
 ...  
 EOF  
 $ oc apply -f 1-serviceaccount.yml

The Clusterrole adds privileges to manage group objects:

 $ cat << EOF > 2-clusterrole.yml  
 ---  
 apiVersion: rbac.authorization.k8s.io/v1  
 kind: ClusterRole  
 metadata:  
   namespace: ldap-group-sync  
   name: ldap-group-syncer  
 rules:  
   - apiGroups:  
       - user.openshift.io  
     resources:  
       - groups  
     verbs:  
       - get  
       - list  
       - create  
       - update  
 ...  
 EOF  
 $ oc apply -f 2-clusterrole.yml

Definition for the Clusterrolebinding tying it all together:

 $ cat << EOF > 3-clusterrolebinding.yml  
 ---  
 apiVersion: rbac.authorization.k8s.io/v1  
 kind: ClusterRoleBinding  
 metadata:  
   name: ldap-group-syncer  
 subjects:  
   - kind: ServiceAccount  
     name: ldap-group-syncer  
     namespace: ldap-group-sync  
 roleRef:  
   apiGroup: rbac.authorization.k8s.io  
   kind: ClusterRole  
   name: ldap-group-syncer  
 ...  
 EOF  
 $ oc apply -f 3-clusterrolebinding.yml

The subsequent step involves creating a ConfigMap. This ConfigMap will encapsulate the LDAP Sync Configuration. This configuration encompasses details such as attribute mappings, base search parameters, filters, and the bind account credential references:

 $ cat << EOF > 4-configmap.yml  
 ---  
 apiVersion: v1  
 kind: ConfigMap  
 metadata:  
   namespace: ldap-group-sync  
   name: ldap-group-syncer  
 data:  
   sync.yaml: |  
     ---  
     apiVersion: v1  
     kind: LDAPSyncConfig  
     url: ldaps://ipa03.archyslife.lan:636  
     insecure: false  
     ca: /etc/ldap-ca/ca.crt  
     bindDN: uid=openshift-bind,cn=users,cn=accounts,dc=archyslife,dc=lan  
     bindPassword:  
       file: /etc/secrets/bindPassword  
     rfc2307:  
       groupsQuery:  
         baseDN: 'cn=groups,cn=accounts,dc=archyslife,dc=lan'  
         scope: sub  
         derefAliases: never  
         pageSize: 0  
         filter: (cn=ocpadmins)  
       groupUIDAttribute: dn  
       groupNameAttributes: [ cn ]  
       groupMembershipAttributes: [ member ]  
       usersQuery:  
         baseDN: 'cn=users,cn=accounts,dc=archyslife,dc=lan'  
         scope: sub  
         derefAliases: never  
         pageSize: 0  
       userUIDAttribute: dn  
       userNameAttributes: [ uid ]  
       tolerateMemberNotFoundErrors: false  
       tolerateMemberOutOfScopeErrors: false  
     ...  
 ...  
 EOF  
 $ oc apply -f 4-configmap.yml

The last piece of the puzzle is the CronJob configuration:

 $ cat << EOF > 5-cronjob.yml  
 ---  
 apiVersion: batch/v1  
 kind: CronJob  
 metadata:  
   name: ldap-group-syncer  
   namespace: ldap-group-sync  
 spec:  
   timeZone: "Europe/Prague"  
   schedule: "*/30 * * * *"  
   concurrencyPolicy: Forbid  
   jobTemplate:  
     spec:  
       backoffLimit: 0  
       ttlSecondsAfterFinished: 1800  
       template:  
         spec:  
           restartPolicy: Never  
           terminationGracePeriodSeconds: 30  
           activeDeadlineSeconds: 500  
           dnsPolicy: ClusterFirst  
           serviceAccountName: ldap-group-syncer  
           containers:  
             - name: ldap-group-sync  
               image: registry.redhat.io/openshift4/ose-cli@sha256:a0fc3e52059468c0176d917e026310d91230f276913086ba678635179373a11a  
               command:  
                 - "/bin/bash"  
                 - "-c"  
                 - "oc adm groups sync --sync-config=/etc/config/sync.yaml --confirm"  
               volumeMounts:  
                 - mountPath: /etc/config  
                   name: ldap-sync-volume  
                 - mountPath: /etc/secrets  
                   name: ldap-bind-password  
                 - mountPath: /etc/ldap-ca  
                   name: ldap-ca-cert  
           volumes:  
             - name: ldap-sync-volume  
               configMap:  
                 name: ldap-group-syncer  
             - name: ldap-bind-password  
               secret:  
                 secretName: ldap-bindpw  
             - name: ldap-ca-cert  
               configMap:  
                 name: ldap-cacert  
 ...  
 EOF  
 $ oc apply -f 5-cronjob.yml

This CronJob will trigger the execution of jobs. These jobs will subsequently spawn pods. These pods will then facilitate the synchronization of groups from the source LDAP directory, as defined within the ConfigMap, into the OpenShift environment.

While technically optional, this next step is highly recommended. It involves binding ClusterRoles to groups, which will be automatically synchronized from the CronJob previously configured.

 $ cat << EOF > 6-clusterrolebinding.yml  
 ---  
 apiVersion: rbac.authorization.k8s.io/v1  
 kind: ClusterRoleBinding  
 metadata:  
   name: ocpadmins-cluster-admin  
 subjects:  
   - apiGroup: rbac.authorization.k8s.io  
     kind: Group  
     name: ocpadmins  
 roleRef:  
   apiGroup: rbac.authorization.k8s.io  
   kind: ClusterRole  
   name: cluster-admin  
 ...  
 EOF  
 $ oc apply -f 6-clusterrolebinding.yml
This Clusterrolebinding will automatically provide all members of the 'ocpadmins' with the 'cluster-admin' clusterrole.

Upon completion of this final step, the scheduled synchronization jobs will dynamically adjust group configurations within the OpenShift environment to accurately reflect the current state of group memberships as defined in the underlying LDAP Directory Service.

Feel free to comment and / or suggest a topic.

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