the-guard-captcha-plugin

captcha.ts

import { getUser, verifyCaptcha } from '../stores/user';
import { Composer } from 'telegraf';
import type { ExtendedContext } from '../typings/context';
import { logError } from '../utils/log';
import { lrm } from '../utils/html';
import { telegram } from '../bot';

// Time to answer the math question, in seconds
const TIME_TO_ANSWER = 60;

// How long should the user stay banned, in seconds
const BAN_DURATION = 60;

// How long after join the bot is allowed to show captcha, in seconds
// e.g. when set to 30, if bot gets the join message after 1 minute, it would ignore and not show captcha
// useful for when the bot is down and you don't want to take old joins into affect
const AFFECTIVE_JOIN_TIME = Infinity;

const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];
const calc = {
	'+': (a: number, b: number) => a + b,
	'-': (a: number, b: number) => a - b,
	'*': (a: number, b: number) => a * b,
};

const pick = <T>(list: T[]) => list[Math.floor(Math.random() * list.length)];

const catchError = (err) => logError('[captcha] ' + err.message);

type Challenge = {
	userId: number;
	mathQuestion: string;
	mathAnswer: number;
	timeout: number;
	groups: { id?: number; messageId: number }[];
};

const kickOutMember = (
	challenges: Challenge[],
	curerntChallenge: Challenge
): number => {
	return (setTimeout(() => {
		// Delete from active challenges
		const foundChallengeIndex = challenges.indexOf(curerntChallenge);
		if (foundChallengeIndex >= 0) {
			challenges.splice(foundChallengeIndex, 1);
		}

		// Check if user is banned already
		const user = getUser({ id: curerntChallenge.userId });

		// For each group:
		curerntChallenge.groups.forEach((group) => {
			// Kick user
			if (group.id && !user.banned) {
				telegram
					.kickChatMember(
						group.id,
						curerntChallenge.userId,
						Date.now() / 1000 + BAN_DURATION
					)
					.catch(catchError);
			}

			// Delete message
			if (group.id && group.messageId) {
				telegram.deleteMessage(group.id, group.messageId).catch(catchError);
			}
		});
	}, TIME_TO_ANSWER * 1000) as unknown) as number;
};

const createMath = (): { answer: number; question: string } => {
	let a: number;
	let b: number;
	let op: keyof typeof calc;
	let result: number;

	do {
		a = pick(numbers);
		b = pick(numbers);
		op = pick(Object.keys(calc)) as keyof typeof calc;
		result = calc[op](a, b);
	} while (result === 0);

	return {
		answer: result,
		question: `${a} ${op} ${b}`,
	};
};

const activeChallenges: Challenge[] = [];

export = Composer.mount('message', async (ctx: ExtendedContext, next) => {
	// If chat is private ignore
	if (ctx.chat?.type === 'private') {
		return next();
	}

	const members = ctx.message?.new_chat_members?.filter(
		(user) => user.username !== ctx.me
	);

	// If a text message
	if (!members || members.length === 0) {
		// Check if there's a challenge for this user
		const foundChallenge = activeChallenges.find(
			(activeChallenge) => activeChallenge.userId === ctx.from?.id
		);
		if (!foundChallenge) {
			return next();
		}

		// If answer is right
		const isAnswerRight =
			Number(ctx.message?.text) === foundChallenge.mathAnswer;
		if (isAnswerRight) {
			// For each challange
			// 1. Clear timeout
			clearTimeout(foundChallenge.timeout);

			// 2. Delete question
			foundChallenge.groups.forEach((group) => {
				if (group.id && group.messageId) {
					telegram.deleteMessage(group.id, group.messageId).catch(catchError);
				}
			});

			// 3. Remove user and challange from active challenges
			activeChallenges.splice(activeChallenges.indexOf(foundChallenge), 1);

			// 4. Verify user
			await verifyCaptcha({ id: ctx.from?.id }).catch(catchError);
		}

		// Delete answer
		if (ctx.message?.message_id) {
			ctx.deleteMessage(ctx.message?.message_id).catch(catchError);
		}

		return next();
	}

	// If new member
	await Promise.all(
		members.map(async (member) => {
			// If join time is old, ignore
			const shouldIgnoreJoin =
				Math.abs((ctx.message?.date || 0) - Date.now() / 1000) >
				AFFECTIVE_JOIN_TIME;

			if (shouldIgnoreJoin) return;

			// Get user and check if already is verified
			const user = getUser({ id: member.id });
			if (user.captcha) return;

			// Check if already has shown
			const challenge = activeChallenges.find(
				(activeChallenge) => activeChallenge.userId === member.id
			) as Challenge;

			// Create or use already created math
			const math = createMath();
			const mathAnswer = challenge ? challenge.mathAnswer : math.answer;
			const mathQuestion = challenge ? challenge.mathQuestion : math.question;

			// Send message
			const message = await ctx.replyWithHTML(
				`${lrm}<a href="tg://user?id=${member.id}">${member.first_name}</a> [<code>${member.id}</code>] ` +
					'please solve the following arithmetic operation in ' +
					`${TIME_TO_ANSWER} seconds and read our rules(!) right after:\n` +
					`<b>${mathQuestion} = ?</b>`,
				{ disable_notification: true }
			);

			const challengeGroup = {
				id: ctx.chat?.id,
				messageId: message.message_id,
			};

			// Create a channel to use when there's none
			const newChallenge: Challenge = {
				groups: [challengeGroup],
				mathAnswer,
				mathQuestion,
				userId: member.id,
				timeout: 0,
			};

			// Clear previous timeouts
			if (challenge) {
				clearTimeout(challenge.timeout);
			}

			// Create kick out timeout
			const timeout = kickOutMember(
				activeChallenges,
				challenge || newChallenge
			);

			if (challenge) {
				challenge.groups.push(challengeGroup);
				challenge.timeout = timeout;
			} else {
				newChallenge.timeout = timeout;
				activeChallenges.push(newChallenge);
			}
		})
	).catch(catchError);

	return next();
});

This plugin adds a simple captcha to The Guard bot.

It is synced across groups and kicks the user if they don't answer within the specified time.

Preview:

Is there a way to send the captcha without a notification? It's a nuisance, especially in the "Devs Share" chat where notifications are welcome.

I'm familiar with the Telegram API but not the Javascipt library used here, so I'm unable to make a patch.

https://core.telegram.org/bots/api#sendmessage "disable_notification"

@torresjrjr Thanks for the suggestion, added.

this seems to be the only working plugin at the moment after the bot was updated and the plugin page doesn't seem to be updated either as it still shows the old way and the api gives errors. i'm not 100% familiar with typescript and i realize this would be a big ask, but would it be possible for you to upload a plugin script that simply responds to a phrase? it would show basic API functionality and would help a lot in getting started setting up my own plugins. just something that sees a certain specific message and replies to it. that way i could figure out how to do different types of stuff from other non-bot related scripts.. in responce to events, messages, or various commands. it would be extremely helpful in learning.. and i feel like something like that might help other people than just myself

This is now part of https://github.com/thedevs-network/the-guard-bot-plugins