#!/bin/bash
###
# adduser.sh
# Add user to system with random pass, add user to groups, create directories and fix permission
#
# Copyright (c) 2016 thomas.zink _at_ uni-konstanz _dot_ de (tz)
# Usage of the works is permitted provided that this instrument is retained with the works, so that any entity that uses the works is notified of this instrument.
# DISCLAIMER: THE WORKS ARE WITHOUT WARRANTY.
#
# This scripts performs the following actions:
# 1. add a new user with random password
# 2. add user to specified groups
# 3. create .ssh, authorized_keys, and set permissions correctly
# 4. set age of user to 0 to force password change at next login
#
# version:
# - 2016-04-06-01 | tz | pwgen with 8 chars, touch create instead of created
# - 2016-03-17-02 | tz | added history; group arguments; better output
# - 2016-03-17-01 | tz | initial version
###

set -eu -o pipefail
shopt -s failglob

# check if we got a username
user="$1"
[[ -z "$user" ]] && echo "usage: `basename $0` USERNAME [GROUPS..]" && exit 0;

# check if we got any groups
if [ ! -z "$2" ]; then
	shift
	groups=( "$@" )
fi

# add a new user with name $user, create home (-m), use bash as shell (-s /bin/bash)
echo "useradd: Add user ${user}"
pass=$(pwgen 8 1)
sudo useradd -m -s /bin/bash -p $(openssl passwd -1 ${pass}) $user

# add to groups
for grp in "${groups[@]}"; do
	sudo usermod -aG $grp $user
	echo "usermod: Add user ${user} to group ${grp}"
done

# create .ssh, authorized_keys
sudo mkdir -p -v /home/$user/.ssh
sudo touch /home/$user/.ssh/authorized_keys
echo "touch: create /home/${user}/.ssh/authorized_keys"

# set user:group and permissions
sudo chown -R $user:$user /home/$user/.ssh
echo "chown: set ${user}:${user} for /home/${user}/.ssh"
sudo chmod 700 /home/$user/.ssh
echo "chmod: set 700 for /home/${user}/.ssh"
sudo chmod 600 /home/$user/.ssh/authorized_keys
echo "chmod: set 600 for /home/${user}/.ssh/authorized_keys"

# change age to force user to change pass
sudo chage -d 0 $user
echo "chage: force ${user} to change pass at first login"

# give feedback
echo ""
echo -e "INFO: Created user \e[1m${user}\e[0m with pass \e[1m${pass}\e[0m"
echo ""
echo -e "WARN: User \e[4mmust\e[0m change pass at first login"
echo ""
echo "NEXT:"
echo "If user $user does not have an SSH key yet, on ${user}'s machine, create SSH key."
echo "Use a keysize of at least 2048."
echo ""
echo "Linux: ssh-keygen -t rsa -b 2048 -C "${user}" -f ~/.ssh/id_rsa"
echo "Windows: Use PuTTYgen, SSH-2 RSA, 2048"
echo ""
echo "Paste content of public key (id_rsa.pub) into server:/home/${user}/.ssh/authorized_keys"
echo ""
echo "Bye."