Examples of Host Security Policy

Here, we demonstrate how to define host security policies.

• Process Execution Restriction

  • Block a specific executable (hsp-kubearmor-dev-proc-path-block.yaml)

    apiVersion: security.kubearmor.com/v1
    kind: KubeArmorHostPolicy
    metadata:
      name: hsp-kubearmor-dev-proc-path-block
    spec:
      nodeSelector:
        matchLabels:
          kubernetes.io/hostname: kubearmor-dev
      severity: 5
      process:
        matchPaths:
        - path: /usr/bin/diff
      action:
        Block

    • Explanation: The purpose of this policy is to block the execution of '/usr/bin/diff' in a host whose host name is 'kubearmor-dev'. For this, we define 'kubernetes.io/hostname: kubearmor-dev' in nodeSelector -> matchLabels and the specific path ('/usr/bin/diff') in process -> matchPaths. Also, we put 'Block' as the action of this policy.

    • Verification: After applying this policy, please open a new terminal (or connect to the host with a new session) and run '/usr/bin/diff'. You will see that /usr/bin/diff is blocked.

    ---

    NOTE

    The given policy works with almost every linux distribution. If it is not working in your case, check the process location. The following location shows location of sleep binary in different ubuntu distributions:

    • In case of Ubuntu 20.04 : /usr/bin/sleep
    • In case of Ubuntu 18.04 : /bin/sleep

    ---

• File Access Restriction

  • Audit a critical file access (hsp-kubearmor-dev-file-path-audit.yaml)

    apiVersion: security.kubearmor.com/v1
    kind: KubeArmorHostPolicy
    metadata:
      name: hsp-kubearmor-dev-file-path-audit
    spec:
      nodeSelector:
        matchLabels:
          kubernetes.io/hostname: kubearmor-dev
      severity: 5
      file:
        matchPaths:
        - path: /etc/passwd
      action:
        Audit

    • Explanation: The purpose of this policy is to audit any accesses to a critical file (i.e., '/etc/passwd'). Since we want to audit one critical file, we use matchPaths to specify the path of '/etc/passwd'.

    • Verification: After applying this policy, please open a new terminal (or connect to the host with a new session) and run 'sudo cat /etc/passwd'. Then, check the alert logs of KubeArmor.

• System calls alerting

  • Alert for all unlink syscalls

  apiVersion: security.kubearmor.com/v1
  kind: KubeArmorHostPolicy
  metadata:
    name: audit-all-unlink
  spec:
    severity: 3
    nodeSelector:
          matchLabels:
            kubernetes.io/hostname: vagrant
    syscalls:
      matchSyscalls:
      - syscall:
        - unlink
    action:
      Audit

{
  "Timestamp": 1661937152,
  "UpdatedTime": "2022-08-31T09:12:32.967304Z",
  "ClusterName": "default",
  "HostName": "vagrant",
  "HostPPID": 8563,
  "HostPID": 310459,
  "PPID": 8563,
  "PID": 310459,
  "UID": 1000,
  "ProcessName": "/usr/bin/unlink",
  "PolicyName": "audit-all-unlink",
  "Severity": "3",
  "Type": "MatchedHostPolicy",
  "Source": "/usr/bin/unlink /home/vagrant/secret.txt",
  "Operation": "Syscall",
  "Resource": "/home/vagrant/secret.txt",
  "Data": "syscall=SYS_UNLINK",
  "Action": "Audit",
  "Result": "Passed"
}

• Alert on all rmdir syscalls targeting anything in /home/ directory and sub-directories

apiVersion: security.kubearmor.com/v1
kind: KubeArmorHostPolicy
metadata:
  name: audit-home-rmdir
spec:
  severity: 3
  nodeSelector:
        matchLabels:
          kubernetes.io/hostname: vagrant
  syscalls:
    matchPaths:
    - syscall:
      - rmdir
      path: /home/
      recursive: true
  action:
    Audit

{
  "Timestamp": 1661936983,
  "UpdatedTime": "2022-08-31T09:09:43.894787Z",
  "ClusterName": "default",
  "HostName": "vagrant",
  "HostPPID": 308001,
  "HostPID": 308002,
  "PPID": 308001,
  "PID": 308002,
  "ProcessName": "/usr/bin/rmdir",
  "PolicyName": "audit-home-rmdir",
  "Severity": "3",
  "Type": "MatchedHostPolicy",
  "Source": "/usr/bin/rmdir jane-doe",
  "Operation": "Syscall",
  "Resource": "/home/jane-doe",
  "Data": "syscall=SYS_RMDIR",
  "Action": "Audit",
  "Result": "Passed"
}