Control and protect shell scripts
Shell scripts are simple to create, but if a user has permission to
execute the script, they also have permission to read it. There are
ways to prevent that:
shc - shell script compiler
Shc is available from Francisco Javier Rosales Garcia and compiles
with a simple "make".
It's function really isn't a compiler: instead, it encrypts the
shell script, and puts a C wrapper around it that, when run, decrypts the script
and calls the requested shell for execution. Therefore, you must have
a shebang line (#!/bin/sh or whatever). That also means it isn't limited
to shell scripts: you can "compile" a Perl script just as easily.
You can optionally specify an expiration date with a message to display
if the program is used after that date, and it also allows passing other
arguments to the shell. In its simplest form "shc -f script" will
produce "script.x" and "script.x.c"; the "script.x" is your executable
and the ".c" is the source code.
In the October 2005 Linux Journal, Nalneesh Guar reports that
he was able to break the encryption very easily. The man page seems to
You can use it if you wish to distribute your scripts
but don't want them to be easily readable by other people.
Note 'easily'. As the old saying goes, locks keep out honest people. In
a typical office, this might be all you need to prevent casual observation or modification of scripts, and could be useful for that.
If all you want to do is password protect a script, there is a simple way to that:
The script you want to protect is /usr/bin/yourscript
(Article continues after the break)
Create a user "runme" and set your script tobe exaeutable only by that user:
# useradd -m runme
# passwd runme
Enter new UNIX password:
Retype new UNIX password:
# chown runme /usr/bin/yourscript
# chmod 700 /usr/bin/yourscript
Create the script "/usr/bin/doit" to contain:
su - runme /usr/bin/yourscript
Make "doit" executable
# chmod 755 /usr/bin/doit
An ordinary user can't run or read "yourscript", but when they run "doit", they'll be asked for "runme"'s password. If they enter it correctly. "yourscript" will run.
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