SSH • Meaningful configuration

Posted on by DomainRooster

Description

Sets a meaningful configuration for :

  • enables key authentication
  • disables password authentication
  • sets a custom banner
  • keeps only meaningful MOTDs

Important

  • create yourself an ASCII Banner and replace the default one
  • run as root user
#!/bin/bash
#
# Description:
# This script sets certain parameters in /etc/ssh/sshd_config.
#
# What should it do?
# * Check whether a /etc/ssh/sshd_config file exists
# * Create a backup of this file
# * Edit the file to set certain parameters
# * Reload the sshd configuration
# To enable debugging mode remove '#' from the following line
#set -x

# Variables
file="$1"
param[1]="PermitRootLogin"
param[2]="PubkeyAuthentication"
param[3]="ChallengeResponseAuthentication"
param[4]="PasswordAuthentication"
param[5]="Banner"

# Functions
usage(){
  cat << EOF
    usage: $0 ARG1
    ARG1 Name of the sshd_config file to edit.
    In case ARG1 is empty, /etc/ssh/sshd_config will be used as default.

    Description:
    This script sets certain parameters in /etc/ssh/sshd_config.

    What should it do?
    * Check whether a /etc/ssh/sshd_config file exists
    * Create a backup of this file
    * Edit the file to set certain parameters
EOF
}

backup_sshd_config(){
  if [ -f ${file} ]
  then
    /usr/bin/cp ${file} ${file}.1
  else
    /usr/bin/echo "File ${file} not found."
    exit 1
  fi
}

edit_sshd_config(){
  for PARAM in ${param[@]}
  do
    /usr/bin/sed -i '/^'"${PARAM}"'/d' ${file}
    /usr/bin/echo "All lines beginning with '${PARAM}' were deleted from ${file}."
  done
  /usr/bin/echo "${param[1]} yes" >> ${file}
  /usr/bin/echo "'${param[1]} yes' was added to ${file}."
  /usr/bin/echo "${param[2]} yes" >> ${file}
  /usr/bin/echo "'${param[2]} yes' was added to ${file}."
  /usr/bin/echo "${param[3]} no" >> ${file}
  /usr/bin/echo "'${param[3]} no' was added to ${file}"
  /usr/bin/echo "${param[4]} no" >> ${file}
  /usr/bin/echo "'${param[4]} no' was added to ${file}"
  /usr/bin/echo "${param[5]} /etc/ssh/banner" >> ${file}
  /usr/bin/echo "'${param[5]} /etc/ssh/banner' was added to ${file}"
}

reload_sshd(){
  /usr/bin/systemctl reload sshd.service
}

add_banner() {
  sudo echo "

" > /etc/ssh/banner
}

remove_spam_motd() {
  sudo rm -rf /etc/update-motd.d/10-help-text
  sudo rm -rf /etc/update-motd.d/50-motd-news
  sudo sed -i 's/Welcome to //' /etc/update-motd.d/00-header
}

# main
while getopts .h. OPTION
do
  case $OPTION in
    h)
    usage
    exit;;
    ?)
    usage
    exit;;
  esac
done

if [ -z "${file}" ]
then

file="/etc/ssh/sshd_config"
fi
backup_sshd_config
edit_sshd_config
add_banner
remove_spam_motd
reload_sshd

echo "👍 Meaningful SSH configuration has been set!"

 

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Published by DomainRooster