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Creating SELinux profiles

Use the SelinuxProfile object to create 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 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
      namespace: nginx-deploy
    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
  2. Wait for selinuxd to install the policy by running the following command:

    $ oc wait --for=condition=ready -n nginx-deploy 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.

  3. 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_nginx-deploy.cil
    Example output
    (block nginx-secure_nginx-deploy
    (blockinherit container)
    (allow process nginx-secure_nginx-deploy.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_nginx-deploy

Applying SELinux profiles to a pod

Create a pod to apply one of the created profiles.

For SELinux profiles, the namespace must be labelled 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 -n nginx-deploy -ojsonpath='{.status.usage}'
    Example output
    nginx-secure_nginx-deploy.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:
      containers:
        - image: nginxinc/nginx-unprivileged:1.21
          name: nginx
          securityContext:
            seLinuxOptions:
              # NOTE: This uses an appropriate SELinux type
              type: nginx-secure_nginx-deploy.process

    The SELinux type must exist before creating the workload.

Applying SELinux log policies

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

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
      namespace: nginx-deploy
    spec:
      permissive: true

Binding 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 (1)
        name: profile (2)
      image: quay.io/security-profiles-operator/test-nginx-unprivileged:1.21
    1 The kind: variable refers to the name of the profile.
    2 The name: variable refers to the name of the profile.
  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. Delete and re-create the pod to use the ProfileBinding object:

    $ oc delete pods test-pod && oc create -f pod01.yaml
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_nginx-binding.process

Replicating controllers and SecurityContextConstraints

When deploying SELinux policies for replicating controllers, such as deployments or daemon sets, note that the Pod objects spawned by the controllers are not running with the identity of the user who creates the workload. Unless a ServiceAccount is selected, the pods might revert to using a restricted SecurityContextConstraints (SCC) which does not allow use of custom security policies.

Procedure
  1. 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-use-seccomp-scc
      namespace: nginx-secure
    subjects:
    - kind: ServiceAccount
      name: spo-deploy-test
    roleRef:
      kind: Role
      name: spo-use-seccomp-scc
      apiGroup: rbac.authorization.k8s.io
  2. Create the Role object:

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

    apiVersion: v1
    kind: ServiceAccount
    metadata:
      creationTimestamp: null
      name: spo-deploy-test
      namespace: nginx-secure
  4. 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_nginx-secure.process (1)
          containers:
          - name: nginx-unpriv
            image: quay.io/security-profiles-operator/test-nginx-unprivileged:1.21
            ports:
            - containerPort: 8080
    1 The .seLinuxOptions.type must exist before the Deployment is created.

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

Recording profiles from workloads

The Security Profiles Operator can record system calls with ProfileRecording objects, making it easier 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.

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

    $ oc label ns my-namespace spo.x-k8s.io/enable-recording=true
  2. Create a ProfileRecording object containing a recorder: logs variable:

    apiVersion: security-profiles-operator.x-k8s.io/v1alpha1
    kind: ProfileRecording
    metadata:
      name: test-recording
    spec:
      kind: SelinuxProfile
      recorder: logs
      podSelector:
        matchLabels:
          app: my-app
  3. Create a workload to record:

    apiVersion: v1
    kind: Pod
    metadata:
      name: my-pod
      labels:
        app: my-app
    spec:
      containers:
        - name: nginx
          image: quay.io/security-profiles-operator/test-nginx-unprivileged:1.21
          ports:
            - containerPort: 8080
        - name: redis
          image: quay.io/security-profiles-operator/redis:6.2.1
  4. Confirm the pod is in a Running state by entering the following command:

    $ oc -n openshift-security-profiles get pods
    Example output
    NAME     READY   STATUS    RESTARTS   AGE
    my-pod   2/2     Running   0          18s
  5. 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
    …
    I0705 12:08:18.729660 1843190 enricher.go:136] log-enricher "msg"="audit"  "container"="redis" "executable"="/usr/local/bin/redis-server" "namespace"="default" "node"="127.0.0.1" "pid"=1847839 "pod"="my-pod" "syscallID"=232 "syscallName"="epoll_wait" "timestamp"="1625486870.273:187492" "type"="{type}"
Verification
  1. Remove the pod:

    $ oc -n openshift-security-profiles delete pod my-pod
  2. Confirm the Security Profiles Operator reconciles the two SELinux profiles:

    $ oc -n openshift-security-profiles get sp
    Example output
    NAME                   STATUS      AGE
    test-recording-nginx   Installed   15s
    test-recording-redis   Installed   15s

Merging per-container profile instances

By default, each container instance records into a separate profile. The Security Profiles Operator can merge the per-container profiles into a single profile. Merging profiles is useful when deploying applications using ReplicaSet or Deployment objects.

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
    spec:
      kind: SelinuxProfile
      recorder: logs
      mergeStrategy: containers
      podSelector:
        matchLabels:
          app: sp-record
  2. Create the workload:

    apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: nginx-deploy
    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
  3. To record the individual profiles, delete the deployment by running the following command:

    $ oc delete deployment nginx-deploy
  4. To merge the profiles, delete the profile recording by running the following command:

    $ oc delete profilerecording test-recording
  5. To start the merge operation and generate the results profile, run the following command:

    $ oc get sp -lspo.x-k8s.io/recording-id=test-recording
    Example output
    NAME                          STATUS      AGE
    test-recording-nginx-record   Installed   17m
  6. To view the syscalls used by any of the containers, run the following command:

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

About seLinuxContext: RunAsAny

Recording of SELinux policies is implemented with a webhook that injects a special SELinux type to the pods being recorded. 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 auto-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 the Pod Security Admission because only the privileged Pod Security Standard allows using a custom SELinux policy.

Additional resources