full-disclosure - Local suid files and buffer overflows

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Date: Sun Oct  9 17:41:44 2005
From: fosforo at gmail.com (Fósforo)
Subject: Local suid files and buffer overflows

try copying /bin/bash to /tmp/ directory, setting suid for all

t+

2005/10/9, Joachim Schipper <j.schipper@...h.uu.nl>:
> On Sun, Oct 09, 2005 at 01:17:39AM +0200, Werner Schalk wrote:
> > Hi,
> >
> > first of all apologies for asking such a newbie question but I am trying
> > to learn how to exploit buffer overflows and therefore wrote a little
> > program to exploit. This little program has the following permissions:
> >
> > $ ls -la test1
> > -rwsr-sr-x  1 root root 17164 Oct  8 01:25 test1
> >
> > Now I exploited it using Aleph One's shellcode (see
> > http://shellcode.org/shellcode/linux/null-free/) but I won't get a SUID
> > shell afterwards (I know the exploit did work but I still have my normal
> > user privleges). Why? I have tried a different shellcode to write a file
> > and this file was root:root. Any ideas, hints, rtfm?
> >
> > Thank you.
> >
> > Best regards,
> > Werner.
>
> Try the following:
>
> # mount
> <snippity>
> /dev/hdb2 on /home type ext3 (rw,nosuid,nodev)
> <snippity>
>
> nosuid means that suid binaries lose their special properties here.
> See mount(8). As you just proved, it's not completely useless.
>
> As an additional exercise, bypass the nosuid mount option. Or just copy
> it somewhere without nosuid.
>
> (There are many, many other ways this behaviour could have happened, but
> this one sounds most likely...)
>
>                 Joachim
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