#!/bin/bash

# Script to safely provide access to tech-support over-the-network.
# Uses 'ssh' for connection
# 'screen' for terminal screen-sharing
# The COMMAND a few lines below limits tech-support's access,
# so they can't have absolute control over your system without supervision

# For developers: change SSH public key and name ('pritam') before sending this out to customers
# Dev. usage: ssh -t user@hostname. -t (force create pty) is compulsory.

# Author: Chhatoi Pritam Baral <pritam@pritambaral.com>

pushd $(dirname $0) &> /dev/null
SCRIPTPATH=$(pwd)"/"$(basename $0)
popd &> /dev/null

COMMAND='command="/usr/bin/screen -rx techsupport",no-port-forwarding,no-X11-forwarding,no-agent-forwarding ssh-dss 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 pritam@Pritam-ArchVaio'

which ssh &> /dev/null

if [ $? -ne 0 ]
then
    echo "You need to install ssh"
    echo "Typically, that is done by running this:"
    echo '"sudo apt-get install ssh"'
    exit
fi

if [ ! -d "~/.ssh/" ]
then
    mkdir -p ~/.ssh
    chmod 700 ~/.ssh
fi

grep 'pritam@Pritam-ArchVaio' ~/.ssh/authorized_keys &> /dev/null

if [ $? -ne 0 ]
then
    echo $COMMAND >> ~/.ssh/authorized_keys
fi

which screen &> /dev/null

if [ $? -ne 0 ]
then
    echo "You need to install screen"
    echo "Typically, that is done by running this:"
    echo '"sudo apt-get install screen"'
    exit
fi

# Check to see if a session is already active
screen -ls | grep -c techsupport &> /dev/null
if [ $? -ne 0 ]
then
    screen -S techsupport sh -c "$SCRIPTPATH; bash -i "&> /dev/null 
    sed -i "/techsupport/d" ~/.ssh/authorized_keys
    exit
fi

echo -e "\nAll set. Tell pritam to connect\n"
echo "He'll need the following info"
echo "username:" $(whoami)
echo "IP addresses" $(ip addr show | grep -o 'inet [0-9.]*' | grep -o '[0-9.]*')
echo

# Alert user if session is active, but this is not the session
echo $STY | grep techsupport &> /dev/null
if [ $? -ne 0 ]
then
    echo "Screen is already running, but elsewhere."
    echo "If you know where, switch to it."
    echo "If you don't, run the following to see the screen"
    echo
    echo "screen -rx techsupport"
    echo
fi