Re: No-Exec Stack Smashing 101

[woloszyn () IPARTNERS PL (M.C.Mar)]

> Thought I'd try to liven the discussion up here a bit...
>
> Okay, so I'm setting off to exploit the /usr/bin/man MANPATH exploit on
> RH6.1 (actually my system is RH6.2 i686 with man-1.5g-6 installed on it).
> And I'm looking for a little help here.  What I've been playing with so
> far is things like the following trying to sort out the parameters of the
> buffer overflow:
>
> setenv MANPAGER `perl -e 'print "A" x 4057; print "\xe0\xca\x05\x40";
> /usr/bin/man man
> gdb /usr/bin/man core
>
> Now the goal is to make man do a system("/bin/echo i 0wn y3w") call via
> returning into system() with the string being a parameter to the call with
> no code being excuted on the stack.

I'm affraid you made wrong aproach...
If you have nonexeck stack patch installed you cannot jump into libc, cos
libc is mmaped undex 0x00XXXXXX address!
The best idea is to jump into PLT. To find system() PLT entry do the
following:

(gdb) p system
$2 = {<text variable, no debug info>} 0x8048d38 <system>

0x8048d38 is a PLT addr of system() call.

As the system() call takes only one argument try to fing correct offset
in the bufer where is the value that overwrites the RET. Put there
0x8048d38 and after that any value (fo saved %ebp, which should be there :)
and then addr where is your string to execute via system();

If anyone need I can write full working explot that uses system() or
strcpy() functions to execute anything you want! :)

--
Mariusz Wo³oszyn
Internet Security Specialist, IT -- Internet Partners
E-mail: Mariusz.Woloszyn () it pl, woloszyn () it pl