Re: Why SUID Binary exploit does not yield root shell?

> I've managed to find a buffer overflow and exploit it to exeve a /bin/sh

Some /bin/sh's will drop privs if uid != euid. Bash is one of these. Instead of using /bin/sh during your test, try /usr/bin/id just to see what uid and euid are. If euid is root yet /bin/sh is not yielding root, that's the cause. You can always compile your own sh frontend to fix uid too:

...
main () {

	setuid(0); seteuid(0); setgid(0);
	execve("/bin/sh",...)

Compile, install, and call that instead. You should probably just include setuid(0) instructions into your shellcode to avoid the middle man. Or you could call /bin/csh which usually doesn't drop privs (but leaves folks stuck in the unpleasant world of C shell) or any pretty much other shell-like program.

> What is the magic here (if any)?

Bash is being "smarter" than you want it to be.

--
Brian Hatch                  Is a book on
   Systems and                voyeurism a
   Security Engineer          peeping tome.
http://www.ifokr.org/bri/

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