openSSHTool.sh

gistfile1.txt

#!/bin/bash

ACTION=$1
KEY=$2
SRCFILE=$3
OUTFILE=$4

function usage(){
	echo $0 '[encrypt|decrypt] KEYFILE SRCFILE OUTFILE'
	echo for decrypt KEYFILE is private Key file
	echo for encrypt KEYFILE is public Key file
	echo example 
	echo $0 encrypt publicKey.pem ~/tmp/clearFile.png /tmp/encrypted.png
	echo $0 decrypt privateKey.pem /tmp/encrypted.png ~/tmp/decrypted.png
	echo To generate key files use something like this:
	echo 
	echo 'echo -n secret123 > passphrase.txt'
	echo 'openssl genrsa -aes128 -passout file:passphrase.txt 4096 > privateKey.pem'
	echo 'openssl rsa -in privateKey.pem -passin file:passphrase.txt -pubout > publicKey.pem'
	echo 
}	

function encrypt(){
PUBKEY=$KEY
cat /dev/random | dd bs=1 count=32 > tmpPass.txt
openssl rsautl -in tmpPass.txt -out tmpPass.enc -pubin -inkey ${PUBKEY} -encrypt
openssl bf -pbkdf2 -in ${SRCFILE} -out tmpFile.enc -pass file:tmpPass.txt -e
cat tmpPass.enc tmpFile.enc > ${OUTFILE}
}

function decrypt(){
PVTKEY=$KEY
cat ${SRCFILE} | dd bs=1 count=512 > tmpPass1.enc
cat ${SRCFILE} | dd bs=1 skip=512  > tmpFile1.enc
openssl rsautl -passin file:passphrase.txt -in tmpPass1.enc -out tmpPass1.txt -inkey ${PVTKEY} -decrypt
openssl bf -pbkdf2 -in tmpFile1.enc -out ${OUTFILE} -pass file:tmpPass1.txt -d
}

if [ $# -lt 4 ];
then
	usage 
	exit
fi

if [ "x${ACTION}" = "xencrypt" ];
then
   encrypt
fi

if [ "x${ACTION}" = "xdecrypt" ];
then
   decrypt
fi

### How to use?
### Use case: A wants to send some sensitive file (clearFile.png) to B. 
### Assuming that A and B both have this wonderful script.
### Step 1: B generates key pair as mentioned in usage example
### Step 2: B sends the publicKey.pem to A using email. Only publicKey.pem not privateKey.pem.
### Step 3: A uses this script to encrypt the file.
###       ./openSSLTool.sh encrypt publicKey.pem ~/tmp/clearFile.png /tmp/encrypted.png
### Step 4: A sends /tmp/encrypted.png to B using email
### Step 5: B saved the file as /tmp/encrypted.png uses this script to decrypt the file
###       ./openSSLTool.sh decrypt privateKey.pem /tmp/encrypted.png ~/tmp/decrypted.png