Very lightweight Telegram captcha bot written in Go

Caution

This repository is deprecated in favor of captcha. It's hard to maintain two separate repositories at once, while both requires intensive security updates. We decided to streamline everything on the upstream captcha repository instead. Please do not use this repository at all cost.

Some captcha bot on Telegram requires you to pay to be used on groups with 1000+ members. Some is just so bad, bots can bypass through them.

We made something that's can't be bypassed by bots and free of cost.

The full-version one has more dependencies, database connections (CockroachDB, MongoDB, and Redis), and a constant worker that logs the group. Yet, it only runs on a free VM on fly.io which only has 1 shared vCPU, 3GB volume storage, and 256 MB of RAM.

Well, the point is: if the full-blown version is running on a very low-end VM and still be able to handle lots and lots of traffic (yes, we had an encounter of spam bots joining our server before), this one should use even less resources!

Late 2022 update: The bot now runs on a Linux VM on Docker, only using 10 MB of RAM with 1 shared vCPU.

Deployment

Before you deploy the bot, you'll need to setup some environment variables to make everything works. See Environment Variables section.

The easiest way to deploy the bot is through Docker.

docker run -e BOT_TOKEN="<telegram bot token>" -e ENVIRONMENT=production ghcr.io/teknologi-umum/captcha-lite:latest

# Or if you prefer the bleeding edge version
docker run -e BOT_TOKEN="<telegram bot token>" -e ENVIRONMENT=production ghcr.io/teknologi-umum/captcha-lite:edge

You can use Heroku or Fly.io to deploy the app. We've provided the corresponding configuration file.

Or if you prefer to build everything from source.

# We assume you've installed Go 1.18 or higher (https://go.dev/dl)
go build .
./captcha-lite

Or run the captcha-lite binary file through systemd or supervisord.

Environment Variables

• ENVIRONMENT: denotes the environment stage. Available options: "development" / "production"
• BOT_TOKEN: Your Telegram bot token that is acquired from BotFather
• LANGUAGE: The language of the bot. Available options: "ID" (for Indonesian) / "EN" (for English) Defaults to "EN"
• LOG_PROVIDER: Error log provider. Available options:
  • "noop" -- stands for no-operation. It literally do nothing.
  • "sentry" -- See https://sentry.io/
  • "rollbar" -- See https://rollbar.com/
• SENTRY_DSN: Sentry's DSN URL. Required if using "sentry" as the LOG_RPOVIDER
• ROLLBAR_TOKEN: Rollbar's token. Required if using "rollbar" as the LOG_PROVIDER
• ROLLBAR_SERVERHOST: Rollbar's server host. Required if using "rollbar" as the LOG_PROVIDER
• ROLLBAR_SERVERROOT: Rollbar's server root. Required if using "rollbar" as the LOG_PROVIDER

License

MIT License

Copyright © 2022 Teknologi Umum <opensource@teknologiumum.com>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.