enochecker3

A FastAPI based checker library for writing async checkers in python. It is called enochecker3 even though enochecker2 never existed, because it is intended to be the reference implementation for version 3 of the enochecker API specification which is yet to come.

Quick Start

Getting started is really easy. Simply install enochecker3 using

pip3 install enochecker3

Create an example.py file with the following content:

import secrets
from typing import Optional

from httpx import AsyncClient

from enochecker3 import (
    ChainDB,
    Enochecker,
    GetflagCheckerTaskMessage,
    MumbleException,
    PutflagCheckerTaskMessage,
)
from enochecker3.utils import FlagSearcher, assert_equals, assert_in

checker = Enochecker("ExampleService", 1337)


@checker.putflag(0)
async def putflag_test(
    task: PutflagCheckerTaskMessage,
    client: AsyncClient,
    db: ChainDB,
) -> None:
    token = secrets.token_hex(32)
    r = await client.post("/note", json={"token": token, "flag": task.flag})
    assert_equals(r.status_code, 200, "storing note with flag failed")

    await db.set("token", token)


@checker.getflag(0)
async def getflag_test(
    task: GetflagCheckerTaskMessage, client: AsyncClient, db: ChainDB
) -> None:
    try:
        token = await db.get("token")
    except KeyError:
        raise MumbleException("Missing database entry from putflag")

    r = await client.get(f"/note/{token}")
    assert_equals(r.status_code, 200, "getting note with flag failed")
    assert_in(task.flag, r.text, "flag missing from note")


@checker.exploit(0)
async def exploit_test(searcher: FlagSearcher, client: AsyncClient) -> Optional[str]:
    r = await client.get(
        "/note/*",
    )
    assert not r.is_error

    if flag := searcher.search_flag(r.text):
        return flag

Start the checker using

uvicorn --reload example:checker.app

And browse to (http://localhost:8000/docs) to explore the web interface, which allows you to send requests to the checker.

Documentation

You can check out the full tutorial at (https://enowars.github.io/docs)