Server login notifications (SSH / TERMINAL) cheap and cheerful

Greetings to the community. This is the first publication, far from being a pro administrator, but I just wanted to share a short and simple experience that may be useful for a newbie like myself.

It so happened that it was necessary to control about 30 VDS-oks on Debian, which I safely “transferred” to supervision (and I’m more like a programmer than a * nix-administrator). And the first thought that came to my mind after the basic operations of changing and checking accesses was “If I missed something, I want to quickly know about the connections.” There are recipes (including on Habré) for binding SSH authorization events and email notifications, which I used as a base, but I still wanted to be responsive and some informative. In general, I eventually got this kind of "system", which for quite a month works quite successfully and informs me of any fact of authorization.

1. Using manuals on API telegrams, a token and chat-id were received for the notification bot (I won’t distribute here, it's all easily and simply located in the 1-2 line of the search engine).
2. Two scripts were created, the code from which will be posted below. In principle, you can put everything in one file, but because I wanted modularity, then I put in a separate script the function of sending notifications to the telegram bot.
3. In two settings files, he added a call to the script for registering the server login event and restarted the SSH service.

Everything about everything takes about 5-10 minutes, no more. Well, now actually the technicals.

PS. Everything was running on Debian9 x64 (if that matters).

/ sbin / onlogged

#!/bin/sh
if [ "$1" = "ssh" ] && [ -z "$TERM" ] ; then
    MESS="USER USE SSH AUTH [not console]"
elif [ "$1" = "bash" ] && [ ! -z "$TERM" ] ; then
    if [ ! -z "$SUDO_USER" ] && [ "$TERM" = "linux" ] ; then
	MESS="USER USE SUDO DISPLAY CONSOLE [terminal]"
    elif [ ! -z "$SUDO_USER" ] && [ ! "$TERM" = "linux" ] ; then
	MESS="USER USE SUDO SSH CONSOLE [ssh session]"
    elif [ "$TERM" = "linux" ] ; then
	MESS="USER USE DISPLAY CONSOLE [terminal]"
    elif [ ! -z "$SSH_TTY" ] ; then
	MESS="USER USE SSH CONSOLE [ssh session]"
    else
	MESS="USER LOGGED [unknown]"
    fi
fi
if [ ! -z "$MESS" ] ; then
    if [ ! -z "$SSH_TTY" ] ; then
	M_TTY=" TTY = $SSH_TTY |"
    fi
    if [ ! -z "$SUDO_USER" ] ; then
	M_SUDO=" SUDO = $SUDO_USER |"
    fi
    if [ ! -z "$TERM" ] ; then
	M_TERM=" TERM = $TERM |"
    fi
    SEND="$MESS | USER = $USER |$M_TTY$M_SUDO$M_TERM"
    /sbin/telegram "$SEND" "ALERT" > /dev/null
fi

/ sbin / telegram

#!/bin/sh
if [ $# -gt 0 ]
then
	text="[$2] `cat /etc/hostname` : $1"
	url="https://api.telegram.org/bot{TOKEN}/sendMessage"
	curl \
		--data-urlencode "chat_id={CHAT_ID}" \
		--data-urlencode "text=$text" \
		--connect-timeout 10 \
		--max-time 10 \
		$url > /dev/null 2>&1
else
	echo "Text is empty"
fi

/ etc / ssh / sshrc

/sbin/onlogged ssh

/etc/bash.bashrc

... тут весь текущий код ...
/sbin/onlogged bash

Perhaps this is all banal and simple, but someone will be interested or just the basis for creating something of their own.