Managing SELinux profiles

To control what namespaced workloads can access on RHCOS nodes, use the Security Profiles Operator to create SELinux profiles, bind them to pods, and record policies from running applications.

Warning

The Security Profiles Operator supports only Red Hat Enterprise Linux CoreOS (RHCOS) worker nodes. Red Hat Enterprise Linux (RHEL) nodes are not supported.

Create SELinux profiles

Use the SelinuxProfile object to create SELinux profiles.

The SelinuxProfile object has several features that allow for better security hardening and readability:

• Restricts the profiles to inherit from to the current namespace or a system-wide profile. Because there are typically many profiles installed on the system, but only a subset should be used by cluster workloads, the inheritable system profiles are listed in the spod instance in spec.selinuxOptions.allowedSystemProfiles.
• Performs basic validation of the permissions, classes and labels.
• Adds a new keyword @self that describes the process using the policy. This allows reusing a policy between workloads and namespaces easily, as the usage of the policy is based on the name and namespace.
• Adds features for better security hardening and readability compared to writing a profile directly in the SELinux CIL language.

Procedure

1. Create a project by running the following command:

   $ oc new-project nginx-deploy
   

2. Create a policy that can be used with a non-privileged workload by creating the following SelinuxProfile object:

   apiVersion: security-profiles-operator.x-k8s.io/v1alpha2
   kind: SelinuxProfile
   metadata:
     name: nginx-secure
   spec:
     allow:
       '@self':
         tcp_socket:
         - listen
       http_cache_port_t:
         tcp_socket:
         - name_bind
       node_t:
         tcp_socket:
         - node_bind
     inherit:
     - kind: System
       name: container
   

3. Wait for selinuxd to install the policy by running the following command:

   $ oc wait --for=condition=ready selinuxprofile nginx-secure
   

   Example output

   selinuxprofile.security-profiles-operator.x-k8s.io/nginx-secure condition met
   

   The policies are placed into an emptyDir in the container owned by the Security Profiles Operator. The policies are saved in Common Intermediate Language (CIL) format in /etc/selinux.d/<name>_<namespace>.cil.

4. Access the pod by running the following command:

   $ oc -n openshift-security-profiles rsh -c selinuxd ds/spod
   

Verification

1. View the file contents with cat by running the following command:

   $ cat /etc/selinux.d/nginx-secure.cil
   

   Example output

   (block nginx-secure
   (blockinherit container)
   (allow process nginx-secure.process ( tcp_socket ( listen )))
   (allow process http_cache_port_t ( tcp_socket ( name_bind )))
   (allow process node_t ( tcp_socket ( node_bind )))
   )
   

2. Verify that a policy has been installed by running the following command:

   $ semodule -l | grep nginx-secure
   

   Example output

   nginx-secure
   

Apply SELinux profiles to a pod

To enforce a recorded or custom SELinux profile on a workload, create a pod that references the profile in its security context.

For SELinux profiles, the namespace must be labeled to allow privileged workloads.

Procedure

1. Apply the scc.podSecurityLabelSync=false label to the nginx-deploy namespace by running the following command:

   $ oc label ns nginx-deploy security.openshift.io/scc.podSecurityLabelSync=false
   

2. Apply the privileged label to the nginx-deploy namespace by running the following command:

   $ oc label ns nginx-deploy --overwrite=true pod-security.kubernetes.io/enforce=privileged
   

3. Obtain the SELinux profile usage string by running the following command:

   $ oc get selinuxprofile.security-profiles-operator.x-k8s.io/nginx-secure -ojsonpath='{.status.usage}'
   

   Example output

   nginx-secure.process
   

4. Apply the output string in the workload manifest in the .spec.containers[].securityContext.seLinuxOptions attribute:

   apiVersion: v1
   kind: Pod
   metadata:
     name: nginx-secure
     namespace: nginx-deploy
   spec:
     securityContext:
       runAsNonRoot: true
       seccompProfile:
         type: RuntimeDefault
     containers:
       - image: nginxinc/nginx-unprivileged:1.21
         name: nginx
         securityContext:
           allowPrivilegeEscalation: false
           capabilities:
             drop: [ALL]
           seLinuxOptions:
             # NOTE: This uses an appropriate SELinux type
             type: nginx-secure.process
   

   Warning

   The SELinux type must exist before creating the workload.

Apply SELinux log policies

To log policy violations or AVC denials, set the SElinuxProfile profile to permissive.

Warning

This procedure defines logging policies. It does not set enforcement policies.

Procedure

• Add permissive: true to an SElinuxProfile:

  apiVersion: security-profiles-operator.x-k8s.io/v1alpha2
  kind: SelinuxProfile
  metadata:
    name: nginx-secure
  spec:
    permissive: true
  

Bind workloads to profiles with ProfileBindings

You can use the ProfileBinding resource to bind a security profile to the SecurityContext of a container.

Procedure

1. To bind a pod that uses a quay.io/security-profiles-operator/test-nginx-unprivileged:1.21 image to the example SelinuxProfile profile, create a ProfileBinding object in the same namespace with the pod and the SelinuxProfile objects:

   apiVersion: security-profiles-operator.x-k8s.io/v1alpha1
   kind: ProfileBinding
   metadata:
     namespace: my-namespace
     name: nginx-binding
   spec:
     profileRef:
       kind: SelinuxProfile
       name: profile
     image: quay.io/security-profiles-operator/test-nginx-unprivileged:1.21
   

   where:

   spec.profileRef.kind

   Specifies the kind of the profile.

   spec.profileRef.name

   Specifies the name of the profile.

   spec.image

   Allows you to enable a default security profile by using a wildcard in the image attribute: image: "*"

   Warning

   Using the image: "*" wildcard attribute binds all new pods with a default security profile in a given namespace.

2. Label the namespace with enable-binding=true by running the following command:

   $ oc label ns my-namespace spo.x-k8s.io/enable-binding=true
   

3. Define a pod named test-pod.yaml:

   apiVersion: v1
   kind: Pod
   metadata:
     name: test-pod
   spec:
     containers:
     - name: test-container
       image: quay.io/security-profiles-operator/test-nginx-unprivileged:1.21
   

4. Create the pod:

   $ oc create -f test-pod.yaml
   

   Note

   If the pod already exists, you must re-create the pod for the binding to work properly.

Verification

• Confirm the pod inherits the ProfileBinding by running the following command:

  $ oc get pod test-pod -o jsonpath='{.spec.containers[*].securityContext.seLinuxOptions.type}'
  

  Example output

  profile.process
  

Replicate controllers and SecurityContextConstraints

Deploy SELinux policies for replicating controllers such as deployments or daemon sets so the pods those controllers create can use custom SELinux policies.

Pods that the controllers create do not run with the identity of the user who creates the workload. Unless you select a ServiceAccount, the pods might use a restricted SecurityContextConstraints (SCC) object that does not allow custom security policies.

Procedure

1. Create a project by running the following command:

   $ oc new-project nginx-secure
   

2. Create the following RoleBinding object to allow SELinux policies to be used in the nginx-secure namespace:

   kind: RoleBinding
   apiVersion: rbac.authorization.k8s.io/v1
   metadata:
     name: spo-nginx
     namespace: nginx-secure
   subjects:
   - kind: ServiceAccount
     name: spo-deploy-test
   roleRef:
     kind: Role
     name: spo-nginx
     apiGroup: rbac.authorization.k8s.io
   

3. Create the Role object:

   apiVersion: rbac.authorization.k8s.io/v1
   kind: Role
   metadata:
     creationTimestamp: null
     name: spo-nginx
     namespace: nginx-secure
   rules:
   - apiGroups:
     - security.openshift.io
     resources:
     - securitycontextconstraints
     resourceNames:
     - privileged
     verbs:
     - use
   

4. Create the ServiceAccount object:

   apiVersion: v1
   kind: ServiceAccount
   metadata:
     creationTimestamp: null
     name: spo-deploy-test
     namespace: nginx-secure
   

5. Create the Deployment object:

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: selinux-test
     namespace: nginx-secure
     metadata:
       labels:
         app: selinux-test
   spec:
     replicas: 3
     selector:
       matchLabels:
         app: selinux-test
     template:
       metadata:
         labels:
           app: selinux-test
       spec:
         serviceAccountName: spo-deploy-test
         securityContext:
           seLinuxOptions:
             type: nginx-secure.process
         containers:
         - name: nginx-unpriv
           image: quay.io/security-profiles-operator/test-nginx-unprivileged:1.21
           ports:
           - containerPort: 8080
   

   The spec.template.spec.securityContext.seLinuxOptions.type must exist before the Deployment is created.

   Note

   The SELinux type is not specified in the workload and is handled by the SCC. When the pods are created by the deployment and the ReplicaSet, the pods will run with the appropriate profile.

   Ensure that your SCC is usable by only the correct service account. Refer to Additional resources for more information.

Record profiles from workloads

The Security Profiles Operator can record system calls with ProfileRecording objects to create baseline profiles for applications.

When using the log enricher for recording SELinux profiles, verify the log enricher feature is enabled. See Additional resources for more information.

Note

A container with privileged: true security context restraints prevents log-based recording. Privileged containers are not subject to SELinux policies, and log-based recording makes use of a special SELinux profile to record events.

Procedure

1. Create a project by running the following command:

   $ oc new-project my-namespace
   

2. Label the namespace with enable-recording=true by running the following command:

   $ oc label ns my-namespace spo.x-k8s.io/enable-recording=true
   

3. Create a ProfileRecording object containing a recorder: logs variable:

   apiVersion: security-profiles-operator.x-k8s.io/v1alpha1
   kind: ProfileRecording
   metadata:
     namespace: my-namespace
     name: test-recording
   spec:
     kind: SelinuxProfile
     recorder: logs
     podSelector:
       matchLabels:
         app: my-app
   

4. Create a workload to record:

   apiVersion: v1
   kind: Pod
   metadata:
     namespace: my-namespace
     name: my-pod
     labels:
       app: my-app
   spec:
     securityContext:
       runAsNonRoot: true
       seccompProfile:
         type: RuntimeDefault
     containers:
       - name: nginx
         image: quay.io/security-profiles-operator/test-nginx-unprivileged:1.21
         ports:
           - containerPort: 8080
         securityContext:
           allowPrivilegeEscalation: false
           capabilities:
             drop: [ALL]
       - name: redis
         image: quay.io/security-profiles-operator/redis:6.2.1
         securityContext:
           allowPrivilegeEscalation: false
           capabilities:
             drop: [ALL]
   

5. Confirm the pod is in a Running state by entering the following command:

   $ oc -n my-namespace get pods
   

   Example output

   NAME     READY   STATUS    RESTARTS   AGE
   my-pod   2/2     Running   0          18s
   

6. Confirm the enricher indicates that it receives audit logs for those containers:

   $ oc -n openshift-security-profiles logs --since=1m --selector name=spod -c log-enricher
   

   Example output

   I0517 13:55:36.383187  348295 enricher.go:376] log-enricher "msg"="audit" "container"="redis" "namespace"="my-namespace" "node"="ip-10-0-189-53.us-east-2.compute.internal" "perm"="name_bind" "pod"="my-pod" "profile"="test-recording_redis_6kmrb_1684331729" "scontext"="system_u:system_r:selinuxrecording.process:s0:c4,c27" "tclass"="tcp_socket" "tcontext"="system_u:object_r:redis_port_t:s0" "timestamp"="1684331735.105:273965" "type"="selinux"
   

Verification

1. Remove the pod:

   $ oc -n my-namespace delete pod my-pod
   

2. Confirm the Security Profiles Operator reconciles the two SELinux profiles:

   $ oc get selinuxprofiles -lspo.x-k8s.io/recording-id=test-recording
   

   Example output for SELinux profile

   NAME                   USAGE                                 STATE
   test-recording-nginx   test-recording-nginx.process   Installed
   test-recording-redis   test-recording-redis.process   Installed
   

Merge per-container profile instances

To reuse one recorded profile when deploying applications with a ReplicaSet or Deployment, configure the Security Profiles Operator to merge per-container profile instances into a single profile instead of keeping a separate profile for each container.

Procedure

1. Edit a ProfileRecording object to include a mergeStrategy: containers variable:

   apiVersion: security-profiles-operator.x-k8s.io/v1alpha1
   kind: ProfileRecording
   metadata:
     # The name of the Recording is the same as the resulting SelinuxProfile CRD
     # after reconciliation.
     name: test-recording
     namespace: my-namespace
   spec:
     kind: SelinuxProfile
     recorder: logs
     mergeStrategy: containers
     podSelector:
       matchLabels:
         app: sp-record
   

2. Label the namespace by running the following command:

   $ oc label ns my-namespace security.openshift.io/scc.podSecurityLabelSync=false pod-security.kubernetes.io/enforce=privileged pod-security.kubernetes.io/audit=privileged pod-security.kubernetes.io/warn=privileged --overwrite=true
   

3. Create the workload with the following YAML:

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: nginx-deploy
     namespace: my-namespace
   spec:
     replicas: 3
     selector:
       matchLabels:
         app: sp-record
     template:
       metadata:
         labels:
           app: sp-record
       spec:
         serviceAccountName: spo-record-sa
         containers:
         - name: nginx-record
           image: quay.io/security-profiles-operator/test-nginx-unprivileged:1.21
           ports:
           - containerPort: 8080
   

4. To record the individual profiles, delete the deployment by running the following command:

   $ oc delete deployment nginx-deploy -n my-namespace
   

5. To merge the profiles, delete the profile recording by running the following command:

   $ oc delete profilerecording test-recording -n my-namespace
   

6. To start the merge operation and generate the results profile, run the following command:

   $ oc get selinuxprofiles -lspo.x-k8s.io/recording-id=test-recording -n my-namespace
   

   Example output for SELinux profile

   NAME                          USAGE                            STATE
   test-recording-nginx-record   test-recording-nginx-record.process   Installed
   

7. To view the permissions used by any of the containers, run the following command:

   $ oc get selinuxprofiles test-recording-nginx-record -o yaml
   

About seLinuxContext: RunAsAny

To record SELinux policies, a webhook injects a permissive SELinux type so the pod logs AVC denials while recording.

The SELinux type makes the pod run in permissive mode, logging all the AVC denials into audit.log. By default, a workload is not allowed to run with a custom SELinux policy, but uses an automatically generated type.

To record a workload, the workload must use a service account that has permissions to use an SCC that allows the webhook to inject the permissive SELinux type. The privileged SCC contains seLinuxContext: RunAsAny.

In addition, the namespace must be labeled with pod-security.kubernetes.io/enforce: privileged if your cluster enables Pod Security Admission, because only the privileged Pod Security Standard allows using a custom SELinux policy.

Additional resources

• Managing security context constraints
• Managing SCCs in OpenShift
• About security profiles
• Use the log enricher
• Pod Security Admission
• Pod Security Standard