Merge pull request #17 from sibi361/master

Add hack.lu 2023 misc: Bat Kube

hack.lu-ctf-2023/misc/Bat_Kube.md

@@ -0,0 +1,158 @@
+Challenge name: Bat Kube
+
+Category: misc
+
+Points: 94
+
+Solves: 76
+
+
+### Given information
+
+> Unlucky, the flag is in Kubernetes and im not joking :/
+
+> nc k8s.0xf.eu 8888
+
+### Solution
+
+Upon `netcat`-ing to the given host we receive a YAML response which is in fact a Kubernetes config:
+
+```
+Creating Cluster
+Waiting for control plane............................................
+Here is your Kubeconfig:
+
+apiVersion: v1
+clusters:
+- cluster:
+    server: https://flux-cluster-c92f12b8c63a464590e418baff193e78.0xf.eu
+  name: ctf-cluster
+contexts:
+- context:
+    cluster: ctf-cluster
+    user: ctf-player
+  name: ctf-cluster
+[...]
+users:
+- name: ctf-player
+  user:
+    token: ey[...]mdQ
+
+Leave this open until you solved the challenge, otherwise your cluster will be deleted. Please save it to a file and use it with kubectl --kubeconfig or use the KUBECONFIG env.
+```
+
+The obtained token appears to be an API key sort of thing assigned to the user `ctf-player`. Visiting the `server` url given in the response returns `403 Forbidden` with the note: anonymous access disallowed. We save token in a variable `token` for further use.
+
+Let's begin the recon by listing all permissions granted to our token:
+```
+kubectl auth can-i --list --token=$token
+```
+
+```
+deployments.*                                   []                                     []               [get list watch]
+flags.*                                         []                                     []               [get list watch]
+ingress.*                                       []                                     []               [get list watch]
+namespaces.*                                    []                                     []               [get list watch]
+pods.*                                          []                                     []               [get list watch]
+services.*                                      []                                     []               [get list watch]
+pods.*/log                                      []                                     []               [get]
+```
+
+---
+
+After going through [this](https://ctftime.org/writeup/30561) writeup we proceed to list secrets, following which we obtain one secret named `kube-baby-flag-part1-of-3`, upon fetching which we get the fist part of the flag.
+
+```
+kubectl get secrets --token=$token
+```
+
+```
+kubectl get secret kube-baby-flag-part1-of-3 -o jsonpath="{.data} --token=$token"
+```
+
+Returns `{"flag":"ZmxhZ3trOHNfMXNf","hint":"RG8geW91IGtub3cgbmFtZXNwYWNlcz8="}`
+
+The given hint on `base64` decoding says "Do you know namespaces?"
+Flag decodes to `flag{k8s_1s_`
+
+The command by itself wasn't returning anything useful until the output format was specified as JSON with `-o jsonpath="{.data}`.
+
+---
+
+Listing all namespaces returns one namespace named `secret-namespace`. Querying that namespace for pods returns two pods.
+
+```
+kubectl get namespaces --all-namespaces --token=$token
+```
+
+```
+kubectl get pods --namespace secret-namespace --output=custom-columns="NAME:.metadata.name,IMAGE:.spec.containers[*].image" --token=$token
+```
+
+```
+kube-baby-flag-part2-of-3-6b97f47974-8vfbj   nginx
+kube-baby-flag-part2-of-3-6b97f47974-cgxst   nginx
+```
+
+Reading the logs of one of the pods gives us the second part of the flag.
+
+```
+kubectl logs pod kube-baby-flag-part2-of-3-6b97f47974-cgxst
+```
+
+```
+r34lly_fun_but
+What about Flags in the Kubernetes API?
+[...]
+```
+
+---
+
+We proceed to save the namespace for convenience and then look for Kubernetes Flags.
+
+```
+kubectl config set-context --current --namespace=secret-namespace
+```
+
+Pro-tip: Append `-A` / `--all-namespaces` to `kubectl` command to query all namespaces at once.
+
+```
+kubectl get flags
+```
+
+Returns one Kubernetes flag. Trying to output it as JSON returns nothing but changing the output format to YAML gets us the last part of the flag.
+
+```
+kube-baby-flag-part3-of-3   You are on the right track, look more in detail!
+```
+
+```
+kubectl get flag kube-baby-flag-part3-of-3 -o jsonpath="{.data}" # No output
+```
+
+```
+kubectl get flag kube-baby-flag-part3-of-3 -o yaml
+```
+
+```
+apiVersion: ctf.fluxfingers.hack.lu/v1
+kind: Flag
+metadata:
+  creationTimestamp: "2023-10-15T16:56:11Z"
+  name: kube-baby-flag-part3-of-3
+  namespace: secret-namespace
+  [...]
+spec:
+  flag: XzF0c18zdjNuX2IzdHQzcl8xbl9DVEZTfQ==
+  hint: You are on the right track, look more in detail!
+```
+
+`flag{k8s_1s_r34lly_fun_but_1ts_3v3n_b3tt3r_1n_CTFS}`
+
+---
+
+### References
+
+https://kubernetes.io/docs/reference/kubectl/
+
+https://kubernetes.io/docs/reference/kubectl/cheatsheet/