Bashbot README

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

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 available in a Unix/Linux Environment. More concrete 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

Note for embedded systems: busybox or toybox ONLY is not sufficient, you need a to install a "real" bash, see also Install Bashbot

Documentation

Your really first bashbot in a nutshell

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 chatting with your bot (your bot's username is shown after 'Bot Name:'):

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

Log files

Since version 0.96 bashbot log commands received/send and connection errors. If you start bashbot in debug mode bash stdout, stderr and all send/received telegram message are logged also.

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

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 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 untrusted sources (messages, files, network) you must be as careful as possible, e.g. set IFS appropriate, disable globbing (set -f) and quote everything. In addition delete unused scripts and examples from your Bot, e.g. scripts 'notify', 'calc', 'question', and disable all not used commands.

Note: Up to version v0.941 (mai/22/2020) telegram-bot-bash had a remote code execution (RCE) bug, please update if you use an older version! see Issue #125

One of the most powerful features of unix shells is variable and command substitution using ${} and $(), but as they are expanded in double quotes, this can lead to RCE and information disclosing bugs in complex scripts like bashbot. So it's more secure to escape or remove '$' in input from user, files or network.

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 and it is taking external input (from the user as arguments or 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"
  printf 'text with variables. PWD=%s\n' "$PWD"
  -> text with variables. PWD=/home/xxx

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

  printf "text with variables. float=%.2f, integer=%d, PWD=%s\n" "$FLOAT" "$INTEGER" "$PWD"
  -> 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.

Use of 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 every file your Bot can read is in danger to be 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 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 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 and data-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 Bot written in an 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: 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 ... may be because I'm an unix 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 message '/start' to set yourself as botadmin and stop the bot with ./bashbot.sh stop.

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 "$(getConfigKey "botadmin")" "test"

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

Blocked by telegram?

This may happen if to many or wrong requests are sent to api.telegram.org, e.g. using a invalid token or not existing API calls. If the block stay for longer time you can ask telegram service to unblock your IP-Adress.

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

Since Version 0.96 bashbot offers the option to recover from broken connections (aka blocked). Therefore you can provide a function named bashbotBlockRecover() in mycommands.sh. If the function exists it is called every time when a broken connection is detected.

Possible actions are: Check if network is working, change IP-Adress or simply wait some time.

# called when bashbot sedn command failed because we can not connect to telegram
# return 0 to retry, return non 0 to give up
bashbotBlockRecover() {
    # place your commands to unblock here, e.g. change IP-Adess or simply wait
    sleep 60 && return 0 # may be temporary
    return 1 
    }

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!