feat: avoid setting privileged flag if seLinuxOptions is not null

[backjo]

This PR sets the privileged flag to false if SELinuxOptions are present/defined. This is needed because containerd treats SELinux and Privileged controls as mutually exclusive - see https://github.com/containerd/cri/blob/aa2d5a97c/pkg/server/container_create.go#L164 .

This allows users who use SELinux for managing privileged processes to use GH Actions - otherwise, based on the SELinux policy, the Docker in Docker container might not be privileged enough.

Signed-off-by: Jonah Back jonah@jonahback.com

[mumoshu]

@backjo Hey! Thanks for your contribution. A bit hesitant to ask, but would you mind adding a short description and example to explain how you would use this feature in practice?

I have literally no experience using seLinux thing with containers.

Probably one would start with a "allow all" selinux policy(is there the term "policy" really?) that contains a full list of allowed operations, and gradually trim it down so that you can only allow specific operations. But I don't even know what a "allow all" selinux policies would look like and therefore no idea how I could test or maintain this feature.

[mumoshu]

a short description and example to explain how you would use this feature in practice?

Whatever place or whatever style is okay. As long as it is written somewhere in the README, I can move or edit it appropriately later. The hardest part for me is about how I could start testing this.

[backjo]

Yeah - I can try, but SELinux is pretty complicated, even for me :/ . We leverage AWS BottleRocket OS, which comes with a built-in set of policies. I imagine most folks who are using SELinuxOptions will be somewhat familiar already - maybe just a link to something like https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux_atomic_host/7/html/container_security_guide/docker_selinux_security_policy ?

[mumoshu]

@backjo Thanks for clarifying! I see. Yes, the redhat doc seems great so a snippet of Runner/RunnerDeployment manifest and a short description and a link to the redhat doc seems to do the job.

[mumoshu]

LGTM. Thanks a lot for your contribution @backjo ☺️

[peimanja]

@backjo I appreciate if you can help me with this issue that I'm facing since we are also running github action runners on AWS BottleRocket OS. So I've been seeing this error on runners startup:

mv: setting attribute 'security.selinux' for 'security.selinux': Permission denied
mv: setting attribute 'security.selinux' for 'security.selinux': Permission denied
mv: setting attribute 'security.selinux' for 'security.selinux': Permission denied
mv: setting attribute 'security.selinux' for 'security.selinux': Permission denied
mv: setting attribute 'security.selinux' for 'security.selinux': Permission denied

but runners working fine and get started without any issue.
the we've started seeing errors like this on some actions:

Status: Downloaded newer image for mysql:5.7
docker: Error response from daemon: failed to copy xattrs: failed to set xattr "security.selinux" on /var/lib/docker/volumes/ac04276306bcdac9522a2e785260017fe7fceed01382998b528f684aac5b0150/_data: permission denied.

I've looked around and noticed we can set the SELinuxOptions on runners. So I set it like this:

      securityContext:
        seLinuxOptions:
          level: "s0"
          role: "system_r"
          type: "super_t"
          user: "system_u"

When I set these the startup errors go away and runners come up without any issue. However now looks like docker having issue

time="2021-09-27T07:50:08.623439127Z" level=error msg="failed to mount overlay: operation not permitted" storage-driver=overlay2
time="2021-09-27T07:50:08.623481986Z" level=error msg="exec: \"fuse-overlayfs\": executable file not found in $PATH" storage-driver=fuse-overlayfs
time="2021-09-27T07:50:08.625989494Z" level=error msg="AUFS was not found in /proc/filesystems" storage-driver=aufs
time="2021-09-27T07:50:08.626346406Z" level=error msg="failed to mount overlay: operation not permitted" storage-driver=overlay
time="2021-09-27T07:50:08.626360291Z" level=error msg="Failed to built-in GetDriver graph devicemapper /var/lib/docker"
time="2021-09-27T07:50:08.630144575Z" level=warning msg="Running iptables --wait -t nat -L -n failed with message: `iptables v1.8.4 (legacy): can't initialize iptables table `nat': Permission denied (you must be root)\nPerhaps iptables or your kernel needs to be upgraded.`, error: exit status 3"

I'm running latest version of the controller + using runner docker in docker latest image and have Bottlerocket OS 1.2.0 and also can test on Bottlerocket OS 1.0.5

I also noticed that RunnerDeployment crd does not support all the configuration https://github.com/actions-runner-controller/actions-runner-controller/blob/3f331e9a3965f38fc98f452571735e0469de8c6d/charts/actions-runner-controller/crds/actions.summerwind.dev_runnerdeployments.yaml#L3052 such as allowPrivilegeEscalation or capabilities since I wanted to play around with those as I saw this issue bottlerocket-os/bottlerocket#1569 (comment).

So not sure what's the issue and how you got around it?

I'm also watching this PR to see if that can help bottlerocket-os/bottlerocket#1733

[backjo]

Hey @peimanja - here's the resource we define, hope it helps

apiVersion: actions.summerwind.dev/v1alpha1
kind: RunnerDeployment
metadata:
  name: devops-runners
  namespace: actions-runner-system
spec:
  replicas: 1
  template:
    spec:
      volumes:
      - name: cgroupfs
        hostPath:
          path: /sys/fs/cgroup
      securityContext:
        seLinuxOptions:
          level: s0
          role: system_r
          type: super_t
          user: system_u
      labels:
        - runner-devops
        - ubuntu-latest
      organization: devops
      nodeSelector:
        kubernetes.io/os: linux
        kubernetes.io/arch: amd64
      #image: ubuntu:focal
      #imagePullPolicy: Always
      #dockerdWithinRunnerContainer: false
      dockerVolumeMounts:
      - mountPath: /sys/fs/cgroup
        name: cgroupfs
      resources:
        limits:
          cpu: "2"
          memory: "2Gi"
        requests:
          cpu: "2"
          memory: "2Gi"
      # Timeout after a node crashed or became unreachable to evict your pods somewhere else (default 5mins)
      tolerations:
        - key: "node.kubernetes.io/unreachable"
          operator: "Exists"
          effect: "NoExecute"
          tolerationSeconds: 30