Bashbot README

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

Prerequisites

Even bashbot is written in bash, it depends on commands typically availible in a Unix/Linux Environment. More concret on the common commands provided by recent versions of coreutils, busybox or toybox, see Developer Notes

Note for MacOS and BSD Users: As bashbot heavily uses modern bash and (gnu) grep/sed features, bashbot will not run without installing additional software, see Install Bashbot

Documentation

Your really first bashbot in a nutshell

To install and run bashbot you need acess to a linux/unix command line. If you don't know how to get accces to a linux/unix/bsd like command line you should stop reading here :-(

In addition you need a Telegram client and a mobile phone to register an account. If you don't want to register for Telegram you should stop reading here ;-)

Now open a linux/unix/bsd terminal and check if bash is installed: which bash && echo "bash installed!". If you get an error message bash is not installed.

wget -q https://github.com/$(wget -q https://github.com/topkecleon/telegram-bot-bash/releases/latest -O - | egrep '/.*/.*/.*tar.gz' -o)

Extract the '*.tar.gz' file and change to bashbot directory: tar -xzf *.tar.gz; cd telegram-bot-bash, install bashbot: ./bashbot.sh init and enter your bot token when asked. All other questions can be answered by hitting the <Return> key.

Thats all, now you can start your bot with ./bashbot.sh start and send him messages:

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

Security Considerations

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

Bash scripts in general are not designed to be bullet proof, 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 from untrusted sources (messages, files, network) you must be as carefull as possible, e.g. set IFS appropriate, disable globbing (set -f) and quote everthing. In addition delete unused scripts and examples from your Bot, e.g. scripts 'notify', 'calc', 'question', and disable all not used commands.

Note: Until v0.941 (mai/22/2020) telegram-bot-bash has a remote code execution bug, pls update if you use an older version! One of the most powerful features of unix shells like bash is variable and command substitution, this can lead to RCE and information disclosing bugs if you do not escape '$' porperly, see Issue #125

A powerful tool to improve your scripts is shellcheck. You can use it online or install shellcheck locally. Shellcheck is used extensive in bashbot development to enshure 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 and it is taking external input (from the user as arguments, or file names from the file system...), you shouldn't use echo to display it. Use printf whenever possible

  # very simple
  echo "text with variables. PWD=$PWD"
  printf '%s\n' "text with variables. PWD=$PWD"
  -> text with variables. PWD=/home/xxx

  # more advanced
  FLOAT="1.2346777892864" INTEGER="12345.123"
  echo "text with variabeles. float=$FLOAT, integer=$INTEGER, PWD=$PWD"
  ->text with variables. float=1.2346777892864, integer=12345.123, PWD=/home/xxx

  printf "text with variables. float=%.2f, integer=%d, PWD=%s\n" "" "$INTEGER" "$PWD"
  ->text with variables. float=1.23, integer=12345, PWD=/home/xxx

Do not use #!/usr/bin/env bash

We stay with /bin/bash shebang, because it's more save from security perspective.

Using a fixed path to the system provided bash makes it harder for attackers or users to place alternative versions of bash and avoids using a possibly broken, mangled or compromised bash executable.

If you are a BSD / MacOS user or must to use an other bash location, see Install Bashbot

Run your Bot as a restricted user

I recommend to run your bot as a user, with almost no access rights. All files your Bot have write access to are in danger to be overwritten/deleted if your bot is hacked. For the same reason ervery file your Bot can read is in danger to be disclosed. Restict your Bots access rigths 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 Unix/Linux systems. See Expert use on how to run your Bot as an other user.

Secure your Bot installation

Your Bot configuration must no be readable from other users. Everyone who can read your Bots token can act as your Bot and has access to all chats your Bot is in!

Everyone with read access to your Bot files can extract your Bots data. Especially your Bot Token in token must be protected against other users. No one exept you must have write access to the Bot files. The Bot must be restricted to have write access to count and tmp-bot-bash 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.

FAQ

Is this Bot insecure?

Bashbot is not more (in)secure as any other Bot written in any other 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: Until v0.941 (mai/22/2020) telegram-bot-bash has a remote code execution bug, pls update if you use an older version!

Why Bash and not the much better xyz?

Well, thats a damn good question ... may be because I'm an Unix/Linux admin from stone age. Nevertheless there are more reasons from my side:

Can I have the single bashbot.sh file back?

At the beginning bashbot was simply the file bashbot.sh you can 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 CLI and scripts, simply install bashbot as described here, send the messsage '/start' to set yourself as botadmin and stop the bot with ./bashbot.sh kill.

Run the following commands in your bash shell or script while you are in the installation directory:

# prepare bash / script to send commands
export BASHBOT_HOME="$(pwd)"
source ./bashbot.sh source

# send me a test message
send_message "$(cat "$BOTADMIN")" "test"

# send me output of a system command
send_message "$(<"$BOTADMIN")" "$(df -h)"

Why do I get "EXPECTED value GOT EOF" on start?

May be your IP is blocked by telegram. You can test this by running curl or wget manually:

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.

This may happen if to many wrong requests are sent to api.telegram.org, e.g. using a wrong token or not existing API calls. If you have a fixed IP you can ask telegram service to unblock your ip or change your IP. If you are running a socks or tor proxy on your server look for the BASHBOT_CURL_ARGS lines in 'mycommands.sh' as example.

That's it!

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