Add SELinux support

Security-Enhanced Linux (SELinux) is a Linux kernel security module that provides a mechanism for supporting access control security policies, including mandatory access controls (MAC).

To add SELinux support, perform the following procedures:

Install a custom SELinux policy

Distribute the SELinux policy package to all Kubernetes nodes using one of the following options:
- Clone WEKA CSI Plugin Github repository:
  git clone https://github.com/weka/csi-wekafs.git
- Copy the content of the selinux directory directly to Kubernetes nodes
Apply the policy package directly:
```
$ semodule -i csi-wekafs.pp
```
Verify that the policy is applied correctly:
```
$ getsebool -a | grep wekafs
container_use_wekafs --> off
```
If the output matches mentioned above, skip to step 4. Otherwise, proceed to step 3 to build the policy from the sources.
In certain circumstances, the pre-compiled policy installation could fail. For example, in a different Kernel version or Linux distribution. In this case, build the policy and install it from the source using the following steps:
```
$ checkmodule -M -m -o csi-wekafs.mod csi-wekafs.te
$ semodule_package -o csi-wekafs.pp -m csi-wekafs.mod
$ make -f /usr/share/selinux/devel/Makefile csi-wekafs.pp
$ semodule -i csi-wekafs.pp
```
For this purpose, the policycoreutils-devel package (or its alternative in case of Linux distribution different from the Red Hat family) is required.
Verify that the policy is applied correctly:
```
$ getsebool -a | grep wekafs
container_use_wekafs --> off
```
The policy provides a boolean setting that allows on-demand enablement of relevant permissions. To enable WekaFS CSI volumes access from pods, run the command:
```
$ setsebool container_use_wekafs=on
```
To disable access, perform the command:
```
$ setsebool container_use_wekafs=off
```
The configuration changes are applied immediately.

Install and configure the WEKA CSI Plugin

To label volumes correctly, install the WEKA CSI Plugin in an SELinux-compatible mode. To do that, set the selinuxSupport value to "enforced" or "mixed” by editing the file values.yaml or passing the parameter directly in the helm installation command.

Example:

$ helm install --upgrade csi-wekafsplugin csi-wekafs/csi-wekafsplugin --namespace csi-wekafsplugin --create-namespace --set selinuxSupport=enforced

Follow these considerations:

WEKA CSI Plugin supports both the enforced and mixed modes of selinuxSupport. The installation depends on the following mode settings:
- When selinuxSupport is enforced, only SELinux-enabled CSI plugin node components are installed.
- When selinuxSupport is mixed, both non-SELinux and SELinux-enabled components are installed.
- When selinuxSupport is off, only non-SELinux CSI plugin node components are installed.
The SELinux status cannot be known from within the CSI plugin pod. Therefore, a way of distinguishing between SELinux-enabled and non-SELinux nodes is required. WEKA CSI Plugin relies on the node affinity mechanism by matching the value of a certain node label in a mutually exclusive way. Only when the label exists and is set to true, an SELinux-enabled node component will start on that node. Otherwise, the non-SELinux node component will start.
To ensure that the plugin starts in compatibility mode, set the following label on each SELinux-enabled Kubernetes node:
If a node label is modified after installing the WEKA CSI Plugin node component on that node, terminate the csi-wekafs-node-XXXX component on the affected node. As a result, a replacement pod is automatically scheduled on the node but with the correct SELinux configuration.

csi.weka.io/selinux_enabled="true"

If another label stating SELinux support is already maintained on nodes, you can modify the expected label name in the selinuxNodeLabel parameter by editing the file values.yaml or by setting it directly during the WEKA CSI Plugin installation.
Example:

$ helm install --upgrade csi-wekafsplugin csi-wekafs/csi-wekafsplugin --namespace csi-wekafsplugin --create-namespace --set selinuxSupport=mixed --set selinuxNodeLabel="selinux_enabled"

Test the WEKA CSI plugin operation

Make sure you have configured a valid CSI API secret. Create a valid WEKA CSI Plugin storageClass.
Provision a PersistentVolumeClaim.
Provision a DaemonSet to enable access to all pods on all nodes.
Monitor the pod logs using the following command (expect no printing in the log files):
```
$ kubectl logs -f -lapp=csi-daemonset-app-on-dir-api
```
If the command returns a repeating message like the following one, it is most likely that the node on which the relevant pod is running is misconfigured:
```
/bin/sh: can't create /data/csi-wekafs-test-api-gldmk.txt: Permission denied
```

Obtain the node name from the pod:

$ kubectl get pod csi-wekafs-test-api-gldmk -o wide
NAME                        READY   STATUS    RESTARTS   AGE   IP            NODE         NOMINATED NODE   READINESS GATES
csi-wekafs-test-api-gldmk   1/1     Running   0          98m   10.244.15.2   don-kube-8   <none>           <none>

Connect to the relevant node and check if the WEKA CSI SELinux policy is installed and enabled:
```
$ getsebool -a | grep wekafs
container_use_wekafs --> on
```
- If the result matches the example, proceed to the next step.
- If there is no result, the policy is not installed. Perform the Install a custom SELinux policy procedure.
- If the policy is off, enable it and check the pod output again by running:
  $ setsebool container_use_wekafs=on
Check if the node is labeled with the plugin is operating in SELinux-compatible mode by running the following command:
```
$ kubectl describe node don-kube-8 | grep csi.weka.io/selinux_enabled
             csi.weka.io/selinux_enabled=true
```
- If the output is empty, Perform the Install and configure the Weka CSI Plugin procedure.
  If the label was missing and added by you during troubleshooting, the CSI node server component must be restarted on the node. Perform the following command to terminate the relevant pod, and another instance will start automatically:

$ POD=$(kubectl get pod -n csi-wekafs -lcomponent=csi-wekafs-node -o wide | grep -w don-kube-8 | cut -d" " -f1)
$ kubectl delete pod -n csi-wekafs $POD

Collect CSI node server logs from the matching Kubernetes nodes and contact the Customer Success Team.

$ POD=$(kubectl get pod -n csi-wekafs -lcomponent=csi-wekafs-node -o wide | grep -w don-kube-8 | cut -d" " -f1)
$ kubectl logs -n csi-wekafs -c wekafs $POD > log.txt

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