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Installation & Usage Guide

TLDR

If you never deployed a CTFd instance before:

curl -fsSL https://get.docker.com -o get-docker.sh
sh get-docker.sh
docker swarm init
docker node update --label-add='name=linux-1' $(docker node ls -q)

git clone https://github.com/CTFd/CTFd --depth=1
git clone https://github.com/frankli0324/ctfd-whale CTFd/CTFd/plugins/ctfd-whale --depth=1
curl -fsSL https://cdn.jsdelivr.net/gh/frankli0324/ctfd-whale/docker-compose.example.yml -o CTFd/docker-compose.yml

# make sure you have pip3 installed on your rig
pip3 install docker-compose
docker-compose -f CTFd/docker-compose.yml up -d
# wait till the containers are ready
docker-compose -f CTFd/docker-compose.yml exec ctfd python manage.py set_config whale:auto_connect_network

The commands above tries to install docker-ce，python3-pip and docker-compose. Make sure the following requirements are satisfied before you execute them:

  • have curl, git, python3 and pip installed
  • GitHub is reachable
  • Docker Registry is reachable

Installation

Start from scratch

First of all, you should initialize a docker swarm and label the nodes

names of nodes running linux/windows should begin with linux/windows-*

docker swarm init
docker node update --label-add "name=linux-1" $(docker node ls -q)

Taken advantage of the orchestration ability of docker swarm, ctfd-whale is able to distribute challenge containers to different nodes(machines). Each time a user request for a challenge container, ctfd-whale will randomly pick a suitable node for running the container.

After initializing a swarm, make sure that CTFd runs as expected on your PC/server

Note that the included compose file in CTFd 2.5.0+ starts an nginx container by default, which takes the http/80 port. make sure there's no conflicts.

git clone https://github.com/CTFd/CTFd --depth=1
cd CTFd  # the cwd will not change throughout this guide from this line on

Change the first line of docker-compose.yml to support attachable property

version '2' -> version '3'

docker-compose up -d

take a look at http://localhost(or port 8000) and setup CTFd

Configure frps

frps could be started by docker-compose along with CTFd

define a network for communication between frpc and frps, and create a frps service block

services:
    ...
    frps:
        image: glzjin/frp
        restart: always
        volumes:
            - ./conf/frp:/conf
        entrypoint:
            - /usr/local/bin/frps
            - -c
            - /conf/frps.ini
        ports:
            - 10000-10100:10000-10100  # for "direct" challenges
            - 8001:8001  # for "http" challenges
        networks:
            default:  # frps ports should be mapped to host
            frp_connect:

networks:
    ...
    frp_connect:
        driver: overlay
        internal: true
        ipam:
            config:
                - subnet: 172.1.0.0/16

Create a folder in conf/ called frp

mkdir ./conf/frp

then create a configuration file for frps ./conf/frp/frps.ini, and fill it with:

[common]
# following ports must not overlap with "direct" port range defined in the compose file
bind_port = 7987  # port for frpc to connect to
vhost_http_port = 8001  # port for mapping http challenges
token = your_token
subdomain_host = node3.buuoj.cn
# hostname that's mapped to frps by some reverse proxy (or IS frps itself)

Configure frpc

Likewise, create a network and a service for frpc

the network allows challenges to be accessed by frpc

services:
    ...
    frpc:
        image: glzjin/frp:latest
        restart: always
        volumes:
          - ./conf/frp:/conf/
        entrypoint:
          - /usr/local/bin/frpc
          - -c
          - /conf/frpc.ini
        depends_on:
          - frps #need frps to run first
        networks:
            frp_containers:
            frp_connect:
                ipv4_address: 172.1.0.3

networks:
    ...
    frp_containers:  # challenge containers are attached to this network
        driver: overlay
        internal: true
        # if challenge containers are allowed to access the internet, remove this line
        attachable: true
        ipam:
            config:
                - subnet: 172.2.0.0/16

Likewise, create an frpc config file ./conf/frp/frpc.ini

[common]
token = your_token
server_addr = frps
server_port = 7897  # == frps.bind_port
admin_addr = 172.1.0.3  # refer to "Security"
admin_port = 7400

Verify frp configurations

update compose stack with docker-compose up -d

by executing docker-compose logs frpc, you should see that frpc produced following logs:

[service.go:224] login to server success, get run id [******], server udp port [******]
[service.go:109] admin server listen on ******

by seeing this, you can confirm that frpc/frps is set up correctly.

Note: folder layout in this guide:

CTFd/
    conf/
        nginx/  # included in CTFd 2.5.0+
        frp/
            frpc.ini
            frps.ini
    serve.py <- this is just an anchor

Configure CTFd

After finishing everything above:

  • map docker socket into CTFd container
  • Attach CTFd container to frp_connect
services:
    ctfd:
        ...
        volumes:
            - /var/run/docker.sock:/var/run/docker.sock
        depends_on:
            - frpc #need frpc to run ahead
        networks:
            ...
            frp_connect:

and then clone Whale into CTFd plugins directory (yes, finally)

git clone https://github.com/frankli0324/CTFd-Whale CTFd/plugins/ctfd-whale --depth=1
docker-compose build # for pip to find requirements.txt
docker-compose up -d

go to the Whale Configuration page (/plugins/ctfd-whale/admin/settings)

Docker related configs

Auto Connect Network, if you strictly followed the guide, should be ctfd_frp_containers

If you're not sure about that, this command lists all networks in the current stack

docker network ls -f "label=com.docker.compose.project=ctfd" --format "{{.Name}}"

frp related configs

  • HTTP Domain Suffix should be consistent with subdomain_host in frps
  • HTTP Port with vhost_http_port in frps
  • Direct IP Address should be a hostname/ip address that can be used to access frps
  • Direct Minimum Port and Direct Maximum Port, you know what to do
  • as long as API URL is filled in correctly, Whale will read the config of the connected frpc into Frpc config template
  • setting Frpc config template will override contents in frpc.ini

Whale should be kinda usable at this moment.

Configure nginx

If you are using CTFd 2.5.0+, you can utilize the included nginx.

remove the port mapping rule for frps vhost http port(8001) in the compose file

If you wnat to go deeper:

  • add nginx to default and internal network
  • remove CTFd from default and remove the mapped 8000 port

add following server block to ./conf/nginx/nginx.conf:

server {
  listen 80;
  server_name *.node3.buuoj.cn;
  location / {
    proxy_pass http://frps:8001;
    proxy_redirect off;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Host $server_name;
  }
}

Challenge Deployment

Standalone Containers

Take a look at https://github.com/CTFTraining

In one word, a FLAG variable will be passed into the container when it's started. You should write your own startup script (usually with bash and sed) to:

  • replace your flag with the generated flag
  • remove or override the FLAG variable

PLEASE create challenge images with care.

Grouped Containers

"name" the challenge image with a json object, for example:

{
    "hostname": "image",
}

Whale will keep the order of the keys in the json object, and take the first image as the "main container" of a challenge. The "main container" will be mapped to frp with same rules from standalone containers

see how grouped containers are created in the code

Security

  • Please do not allow untrusted people to access the admin account. Theoretically there's an SSTI vulnerability in the config page.
  • Do not set bind_addr of the frpc to 0.0.0.0 if you are following this guide. This may enable contestants to override frpc configurations.
  • If you are annoyed by the complicated configuration, and you just want to set bind_addr = 0.0.0.0, remember to enable Basic Auth included in frpc, and set API URL accordingly, for example, http://username:password@frpc:7400

Advanced Deployment

To separate the target server (for lunching instance) and CTFd web server with TLS secured docker API, please refer to this document