Re: Potential Bash Script Vulnerability

[Jon Seymour]

You do realise that if you allow an untrusted script to run at root, having
it modify itself is the least of your concerns. There are *so* many ways an
untrusted script can cause a problem that do not require your
self-modifying script and for which your proposed mitigation will do
nothing. What's the point in protecting against the 0.000001% case if you
have done nothing to protect yourself against system
administrators executing untrusted scripts as root?

On Sun, 7 Apr 2024 at 14:18, <admin@osrc.rip> wrote:

> Hello everyone!
>
> I've attached a minimal script which shows the issue, and my recommended
> solution.
>
> Affected for sure:
> System1: 64 bit Ubuntu 22.04.4 LTS - Bash: 5.1.16(1)-release - Hardware:
> HP Pavilion 14-ec0013nq (Ryzen 5 5500u, 32GB RAM, Radeon grapics, nvme
> SSD.)
> System2: 64 bit Ubuntu 20.10 (No longer supported.) - Bash:
> 5.0.17(1)-release - Hardware: DIY (AMD A10-5800k, 32GB RAM, Radeon
> graphics, several SATA drives)
> and probably a lot more...
>
> Not sure whether or not this is a know issue, truth be told I discovered
> it years ago (back around 2016) as I was learning bash scripting, and
> accidentally appended a command to the running script, which got
> executed immediately after the script but back then I didn't find it
> important to report since I considered myself a noob. I figured someone
> more experienced will probably find and fix it, or there must be a
> reason for it. I forgotű it. Now watching a video about clever use of
> shell in XZ stuff I remembered, tested it again and found it still
> unpatched. :S So now I'm reporting it and hope it helps!
>
> Read the code, test it, fix it. More explanation in the comments.
>
> Since it's very old I'd recommend a silent fix before announcement,
> especially since I also found a potentially easy fix.
>
> Kind regards
> Tibor