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Bashbot - A Telegram bot written in bash.

Written by Drew (@topkecleon) and Kay M (@gnadelwartz).

Contributions by Daniil Gentili (@danog), JuanPotato, BigNerd95, TiagoDanin, iicc1 and dcoomber.

Released to the public domain wherever applicable. Elsewhere, consider it released under the WTFPLv2.

Linted by #ShellCheck

Bashbot is created by old-fashioned shell hackers to show that it's possible to write a bot in Bash.

It is designed for simple use cases and easily integrates with Linux tasks. For bots that serve a lot of users or a heavy workload, I strongly recommend using a dedicated bot framework.

Prerequisites

Uses JSON.sh/JSON.awk and the magic of sed.

Bashbot is written in bash. It depends on commands typically available in a Linux/Unix Environment. For more information on commands provided by recent versions of coreutils, busybox or toybox, see Developer Notes.

Note for MacOS and BSD Users: Bashbot will not run without installing additional software as it uses modern bash and (gnu) grep/sed features. See Install Bashbot.

Note for embedded systems: You need to install a "real" bash as the vanilla installation of busybox or toybox is not sufficient. See Install Bashbot.

Bashbot Documentation and Downloads are available on www.github.com.

Documentation

Your very first bashbot in a nutshell

To install and run bashbot you need access to a Linux/Unix command line with bash, a Telegram client and a mobile phone with a Telegram account.

First you need to create a new Telegram Bot token for your bot and write it down.

Now open a Linux/Unix terminal with bash, create a new directory, change to it and install telegram-bot-bash:

# create bot dir
mkdir mybot
cd mybot

# download latest release with wget or from https://github.com/topkecleon/telegram-bot-bash/releases/latest
wget "https://github.com/$(wget -q "https://github.com/topkecleon/telegram-bot-bash/releases/latest" -O - | egrep '/.*/download/.*/.*tar.gz' -o)"

# Extract the tar archive and go into bot dir
tar -xzf *.tar.gz
cd telegram-bot-bash

# initialize your bot
# Enter your bot token when asked, all other questions can be answered by hitting the \<Return\> key.
./bashbot.sh init

# Now start your bot
./bashbot.sh start

Bottoken is valid ...
Bot Name: yourbotname_bot
Session Name: yourbotname_bot-startbot
Bot started successfully.

Now open the Telegram App on your mobile phone and start a chat with your bot (your bot's username is shown after 'Bot Name:'):

/start

You are Botadmin
Available commands:
  /start: _Start bot and get this message_.
  /help: _Get this message_.
  /info: _Get shorter info message about this bot_....

/info

This is bashbot, the Telegram bot written entirely in bash.
It features background tasks and interactive chats, and can serve as an interface for CLI programs.

For more Information on how to install, customize and use your new bot, read the Documentation.

Log files

Bashbot actions are logged to BASHBOT.log. Telegram send/receive errors are logged to ERROR.log. Start bashbot in debug mode to see all messages sent to / received from Telegram, as well as bash command error messages.

To enable debug mode, start bashbot with debug as third argument: bashbot start debug

|__ logs
|     |__ BASHBOT.log  # log what your bot is doing ...
|     |__ ERROR.log    # connection errors from / to Telegram API
|     |
|     |__ DEBUG.log    # stdout/stderr of you bot (debug mode enabled)
|     |__ MESSAGE.log  # full text of all message send/received (debug mode enabled)

Security Considerations

Running a Telegram Bot means it is connected to the public and you never know what's send to your Bot.

Bash scripts in general are not designed to be bulletproof, so consider this Bot as a proof of concept. Bash programmers often struggle with 'quoting hell' and globbing, see Implications of wrong quoting.

Whenever you are processing input from untrusted sources (messages, files, network) you must be as careful as possible (e.g. set IFS appropriately, disable globbing with set -f and quote everything). In addition remove unused scripts and examples from your Bot (e.g. everything in example/) and disable/remove all unused bot commands.

It's important to escape or remove $ and ` in input from user, files or network (as bashbot does). One of the powerful features of Unix shells is variable and command substitution using ${var}, $(cmd) and `cmd` can lead to remote code execution (RCE) or remote information disclosure (RID) bugs if unescaped $ or ` is included in untrusted input (e.g. $$ or $(rm -rf /*)).

A powerful tool to improve your scripts is shellcheck. You can use it online or install shellcheck locally. Shellcheck is used extensively in bashbot development to ensure a high code quality (e.g. it's not allowed to push changes without passing all shellcheck tests). In addition bashbot has a test suite to check if important functionality is working as expected.

Use printf whenever possible

If you're writing a script that accepts external input (e.g. from the user as arguments or the file system), you shouldn't use echo to display it. Use printf whenever possible.

Run your Bot as a restricted user

I recommend running your bot as a user with almost no access rights. All files your Bot has write access to are in danger of being overwritten/deleted if your bot is hacked. For the same reason every file your Bot can read is in danger of being disclosed. Restrict your Bots access rights to the absolute minimum.

Never run your Bot as root, this is the most dangerous you can do! Usually the user 'nobody' has almost no rights on Linux/Unix systems. See Expert use on how to run your Bot as an other user.

Secure your Bot installation

Your Bot configuration must not be readable by other users. Everyone who can read your Bots token is able to act as your Bot and has access to all chats the Bot is in!

Everyone with read access to your Bot files can extract your Bots data. Especially your Bot config in config.jssh must be protected against other users. No one except you should have write access to the Bot files. The Bot should be restricted to have write access to count.jssh, data-bot-bash/ and logs/ only, all other files must be write protected.

To set access rights for your bashbot installation to a reasonable default run sudo ./bashbot.sh init after every update or change to your installation directory.

Note: Keep old log files in a safe place or even better delete them, they are GDPR relevant and may contain information you don't want to be public.

FAQ

Is this Bot insecure?

Bashbot is not more (in)secure than a Bot written in another language. We have done our best to make it as secure as possible. But YOU are responsible for the bot commands you wrote and you should know about the risks ...

Note: Up to version 0.941 (mai/22/2020) telegram-bot-bash had a remote code execution bug, please update if you use an older version!

Why Bash and not the much better xyz?

Well, that's a damn good question... maybe because I'm a Unix admin from the stone age. Nevertheless there are more reasons from my side:

  • bashbot will run wherever bash and (gnu) sed is available, from embedded Linux to mainframe
  • easy to integrate with other shell scripts, e.g. for sending system message / health status
  • no need to install or learn a new programming language, library or framework
  • no database, not event driven, not object oriented ...

Can I have the single bashbot.sh file back?

At the beginning bashbot was simply the file bashbot.sh that you could copy everywhere and run the bot. Now we have 'commands.sh', 'mycommands.sh', 'modules/*.sh' and much more.

Hey no problem, if you are finished with your cool bot, run dev/make-standalone.sh to create a stripped down version of your bot containing only 'bashbot.sh' and 'commands.sh'! For more information see Create a stripped down version of your Bot.

Can I send messages from CLI and scripts?

Of course you can send messages from command line and scripts! Simply install bashbot as described here, send the message '/start' to set yourself as botadmin and then stop the bot with ./bashbot.sh stop.

Bashbot provides some ready to use scripts for sending messages from command line in bin/ dir, e.g. send_message.sh.

bin/send_message.sh BOTADMIN "This is my first message send from CLI"

bin/send_message.sh --help

You can also source bashbot for use in your scripts, for more information see Expert Use.

Blocked by telegram?

This may happen if too many or wrong requests are sent to api.telegram.org, e.g. using a invalid token or invalid API calls. If the block stay for longer time you can ask telegram service to unblock your IP-Address.

You can check with curl or wget if you are blocked by Telegram:

curl -m 10  https://api.telegram.org/bot
#curl: (28) Connection timed out after 10001 milliseconds

wget -t 1 -T 10 https://api.telegram.org/bot
#Connecting to api.telegram.org (api.telegram.org)|46.38.243.234|:443... failed: Connection timed out.

nc -w 2 api.telegram.org 443 || echo "your IP seems blocked by telegram"
#your IP seems blocked by telegram

Bashbot offers the option to recover from broken connections (blocked). Therefore you can provide a function named bashbotBlockRecover() in mycommands.sh, the function is called every time when a broken connection is detected.

Possible actions are: Check if network is working, change IP-Address or simply wait some time. See mycommnds.sh.dist for an example.

@Gnadelwartz

That's it all guys!

If you feel that there's something missing or if you found a bug, feel free to submit a pull request!

$$VERSION$$ v1.52-1-g0dae2db

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