Managing SELinux profiles - Security Profiles Operator | Security and compliance

Creating SELinux profiles
Applying SELinux profiles to a pod
Recording profiles from workloads
- Merging per-container profile instances
- About seLinuxContext: RunAsAny

Create and manage SELinux profiles and bind them to workloads.

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

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

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.

Access the pod by running the following command:

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

Verification

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 )))
)

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

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
```

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

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%

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

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.
Label the namespace with enable-binding=true by running the following command:
```
$ oc label ns my-namespace spo.x-k8s.io/enable-binding=true
```
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

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

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

Create the ServiceAccount object:

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

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

Label the namespace with enable-recording=true by running the following command:
```
$ oc label ns my-namespace spo.x-k8s.io/enable-recording=true
```

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

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

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

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

Remove the pod:

$ oc -n openshift-security-profiles delete pod my-pod

Confirm the Security Profiles Operator reconciles the two SELinux profiles:

$ oc get selinuxprofiles -n my-namespace

Example output

NAME                   USAGE                                       STATE
test-recording-nginx   test-recording-nginx_my-namespace.process   Installed
test-recording-redis   test-recording-redis_my-namespace.process   Installed

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

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

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

To record the individual profiles, delete the deployment by running the following command:
```
$ oc delete deployment nginx-deploy
```
To merge the profiles, delete the profile recording by running the following command:
```
$ oc delete profilerecording test-recording
```

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

Example output

NAME                          USAGE                                         STATE
test-recording-nginx-record   test-recording-nginx-record_mytest1.process   Installed

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

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.

1	The `kind:` variable refers to the name of the profile.
2	The `name:` variable refers to the name of the profile.