Encrypt bash script on Linux using shc

Download and install shc source.

wget http://www.datsi.fi.upm.es/~frosal/sources/shc-3.8.7.tgz

tar xzvf shc-3.8.7.tgz

cd shc-3.8.7

make

make install

Create simple script file with following codes

#!/bin/bash

echo -e -n "Enter the first value \t:"

read a

echo -e -n "Enter the second value \t:"

read b

sum=$(expr $a + $b)

echo "Result is $sum"

Encrypt the test.sh script file with shc as below.

$ ./shc -f test.sh

List the files with ls command Now we have 2 more files with .sh.x and .sh.x.c extensions

[root@core scripts]# ls

test.sh  test.sh.x  test.sh.x.c

Execute the Encrypted script file with following command

 ./test.sh.x

Additional parameter that can be used with shc are below

 Setting expiration date on the script file with the message.

 shc -e '28/09/2015' -m "This script file is expired" -f test.sh

 

Execute the script before expiration date.

 ./test.sh.x 

 Change date and time with following command

  sudo date +%Y%m%d -s '20150928'

  

Execute the script after expiration date.  

  [dilli@core scripts]$ ./test.sh.x 

./test.sh.x: has expired!

This script file is expired

ulimit -c

If output is zero means that core file is not created.

Now we set core file size limit to 70000 byte

ulimit -c 70000

Now we start binary & segfault it right away.I used IP-Digger binary to get plain text from it.

./IP-Digger4.sh.x&  ( sleep 0.02 && kill -SIGSEGV $! )

 sleep 0.02 will give the binary enough time to start up and decrypt the original script. The variable $! contains the pid of the last background process started, so we can easily kill it with the segmentation fault signal SIGSEGV (same as kill -11 $!). 

+ segmentation fault (core dumped)  ./IP-Digger4.sh.x

cat core | strings >plain_text