[CentOS] bash - safely pass untrusted strings?
Benjamin Smith
lists at benjamindsmith.com
Tue Feb 26 16:25:54 UTC 2008
On Tuesday 26 February 2008, Ralph Angenendt wrote:
> > There is no mechanism for escaping untrusted input?
>
> Correct. At least there's no magic quoting function.
Ok. So I'm going to have to pull up my sleeves and do this with sed/awk pipes.
Got it. I'll quit looking for a simply solution to this (I thought) simple
problem.
Now for a more philosophical question....
WHY THE @!#! NOT?!?!?
Bash is used, extensively in many cases, to deal with untrusted data. This can
include random file names in user home directories, parameters on various
scripts, etc. It's highly sensitive to being passed characters that have,
over the past NN years, resulted in quite a number of security holes and
problems.
Yet there exists NO MECHANISM for simply ensuring that a given argument is an
escaped string?
How many "homebrew" ISP or hosting administration scripts could be compromised
by simply putting a file in your home directory called ";rm -rf /" ?
This doesn't strike you as fundamentally borkeD? Why would we accept a work
environment that is effectively laden with randomly placed, loaded rat traps?
Not trying to bash (ahem) bash needlessly, but this is a problem that so
smacks of 1977...
I guess I just hadn't noticed how bad this was, since I started using PHP as
shell scripts years ago to run everything, despite the mild performance hit.
escapeshallarg() and addslashes() combined with a few backticks provides easy
access to the power of the shell, and excellent "don't need to worry about
it" security.
This just blows my mind....
-Ben
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