Tag: symmetric key cryptography

Backup shell script to backup selected directories and upload securely (gpg) to FTP server

in Categories Backup last updated April 9, 2008

This script requires GNU Privacy Guard – cryptographic software on Linux / UNIX systems. GnuPG encrypts messages using asymmetric keypairs individually generated by GnuPG users. The resulting public keys can be exchanged with other users in a variety of ways, such as Internet key servers. They must always be exchanged carefully to prevent identity spoofing by corrupting public key ↔ ‘owner’ identity correspondences. It is also possible to add a cryptographic digital signature to a message, so the message integrity and sender can be verified, if a particular correspondence relied upon has not been corrupted.

GnuPG does not use patented or otherwise restricted software or algorithms, including the IDEA encryption algorithm which has been present in PGP almost from the beginning. Instead, it uses a variety of other, non-patented algorithms such as CAST5, Triple DES, AES, Blowfish and Twofish. It is still possible to use IDEA in GnuPG by downloading a plugin for it, however this may require getting a license for some uses in some countries in which IDEA is patented.

GnuPG is a hybrid encryption software program in that it uses a combination of conventional symmetric-key cryptography for speed, and public-key cryptography for ease of secure key exchange, typically by using the recipient’s public key to encrypt a session key which is only used once. This mode of operation is part of the OpenPGP standard and has been part of PGP from its first version.

Shell Script

#!/bin/bash
# Shell script (BASH) to backup the selected directory on server and upload to 
# another ftp server securely. This script uses the gpg command to 
# encrypt the .tar.gz file before upload take place. 
#
# In order to run this script you must have following tools installed:
# - /usr/bin/ncftpput
# - /bin/tar
# - /usr/bin/mail
# - /usr/bin/gpg
#
# Script also mails back the ftp operation failed or not
#
# Installation:
# Customize the script according to your need. You need to setup ftp 
# server, password etc. Next, you need to setup gpg user name and 
# import public key so that you can encrypt the files. Usually following two 
# commands needed for gpg:
# gpg --import userkey
# gpg --edit-key KEY_ID|USER_ID
# Command>trust
# 
# --------------------------------------------------------------------
# This is a free shell script under GNU GPL version 2.0 or above
# Copyright (C) 2005 nixCraft project.
# Feedback/comment/suggestions : http://cyberciti.biz/fb/
# -------------------------------------------------------------------------
# This script is part of nixCraft shell script collection (NSSC)
# Visit http://bash.cyberciti.biz/ for more information.
# -------------------------------------------------------------------------
 
# Dirs to backup, Separate multiple directories using space 
# for example /home /www /data2
BACKUP="/home"
 
# Remote ftp server
FTPH="ftp.backup.com"
 
# Remote ftp user name
FTPU="ftpusername"
 
# Remote ftp user password
FTPP="secret"
 
# Local gpg user_id 
GPGU="nixcraft"
 
# Remote directory, blank for default remote dir
# If dir does not exist it will be created automatically by ncftpput :)
FTPD="backup/"
 
# Temporary directory to store tar.gz file and process it
TMPD="/tmp"
 
# Mail message
# Admin email me@mycorp.com or pager@yourmobile.com
MTO="support@mycorp.com"
# Mail subject
MSUB="Backup $(hostname) report"
# Admin info, URL email id; change it according to your need :)
ADMIN_INFO="For support visit http://cyberciti.biz/fb/ or write an email to nobody@cyberciti.biz"
 
# Only change if your UNIX stores bin in diffrent location
NCFTP="/usr/bin/ncftpput"
TAR="/bin/tar"  # must be gnu tar
MAILC="/usr/bin/mail"
GPG="/usr/bin/gpg"
 
#######################################################################
# Do not change anything below
#######################################################################
FILE="$(hostname).$(date +"%d-%m-%Y").tar.gz"
OUT="$TMPD/$FILE"
FOUT="$OUT.gpg"
MFILE="/tmp/ftpout.$$.txt"
MESS=""
 
if [ ! -x $TAR ]; then
  echo "$TAR command not found, contact $ADMIN_INFO" 
  exit 1
fi
 
if [ ! -x $NCFTP ]; then
  echo "$NCFTP command not found, contact $ADMIN_INFO" 
  exit 1
fi
 
if [ ! -x $GPG ] ; then
  echo "$GPG command not found, contact $ADMIN_INFO" 
  exit 1
fi
 
$TAR -zcf $OUT $BACKUP
if [ $? -ne 0 ]; 
then
   MESS="$TAR failed to create backup. Nothing uploaded to remote FTP $FTPH server"
else
   # Encrypt the .tar.gz file before upload
   $GPG -e -r $GPGU -o $FOUT $OUT
   $NCFTP -m -u "$FTPU" -p "$FTPP" "$FTPH" "$FTPD" "$FOUT"
   OSTAT="$?"
   case $OSTAT in
	0) MESS="Success.";;
	1) MESS="Could not connect to remote host $FTPH.";;
        2) MESS="Could not connect to remote host $FTPH - timed out.";;
        3) MESS="Transfer failed.";;
        4) MESS="Transfer failed - timed out.";;
        5) MESS="Directory change failed.";;
        6) MESS="Directory change failed - timed out.";;
        7) MESS="Malformed URL.";;
        8) MESS="Usage error. May be your version of ncftpput ($NCFTP) is old";;
        9) MESS="Error in login configuration file.";;
        10)MESS="Library initialization failed.";;
        11) MESS="Session initialization failed.";;
	*) MESS="Unknown error, contact admin $ADMIN_INFO";;
   esac
fi
 
>$MFILE
echo "Backup status for $(hostname) as on $(date):" >>$MFILE
echo "" >>$MFILE
echo "Backup File : $FOUT" >>$MFILE
echo "Backup ftp server : $FTPH" >>$MFILE
echo "Backup status message : $MESS" >>$MFILE
echo "" >>$MFILE
echo "-- Automatically generated by $(basename $0)" >>$MFILE
 
# send an email to admin
$MAILC -s "$MSUB" $MTO <$MFILE
# remove the files 
[ -f $MFILE ] && rm -f $MFILE || :
[ -f $FOUT ] && rm -f $FOUT || :
[ -f $OUT ] && rm -f $OUT || :