kCTF Learnings

When to use kCTF

For PWN challenges and Crypto challenges which require TCP connection. Web challenges that use HTTPS can use GCloud Run.

Local Setup (Ubuntu 20.04)

First it is recommended to get used to kctf by running it locally. Follow the instructions here: https://google.github.io/kctf/local-testing.html

Then install the gcloud SDK. On Ubuntu 20.04 I was able to do:

sudo apt-get install apt-transport-https ca-certificates gnupg
echo "deb [signed-by=/usr/share/keyrings/cloud.google.gpg] https://packages.cloud.google.com/apt cloud-sdk main" | sudo tee -a /etc/apt/sources.list.d/google-cloud-sdk.list
curl https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key --keyring /usr/share/keyrings/cloud.google.gpg add -
sudo apt-get update && sudo apt-get install google-cloud-cli google-cloud-sdk-gke-gcloud-auth-plugin kubectl

GCloud Setup

Follow the guide here: https://google.github.io/kctf/google-cloud.html

It is smart to use an account when has the free $300 in credits to start. You must also set up billing to start using all of the features necessary to run kCTF. It may be smart to set up a budget with alerts to make sure you don't go over during testing.

Useful Commands

kctf cluster stop Shuts down the current cluster. This takes a while on GCloud.

kctf chal start Use when you are in a challenge directory (e.g. there is a challenge.yaml present) to build the Docker containers and roll out a new version.

kctf chal stop Use when you are in a challenge directory to stop a challenge.

kctf chal list Lists all challenges. It finds them by looking for directories with challenge.yaml

kctf cluster create local-cluster --start --type kind Create a local cluster for testing (fast).

kctf cluster create --project <GCloud project ID> --domain-name <name>-codelab.kctf.cloud --start remote-cluster

Challenge URLs and Ports

https://google.github.io/kctf/custom-domains.html

Make sure to use different ports for each challenge!