Vulnerability Development mailing list archives
Re: No-Exec Stack Smashing 101
From: lamont () ICOPYRIGHT COM (Granquist, Lamont)
Date: Thu, 20 Apr 2000 10:36:13 -0700
Well, its not an inherant feature of non-executable stacks that libc is mapped to an address with a zero in it. That's just a feature of Solar Designer's patch for Linux. My next question would have been, of course, how to get around that. And it is still useful to discuss the return-into-libc approach just for educational benefit. And also because in addition to getting around no-exec stacks it also lets you bypass writing shellcode and means that your exploits will not have NOPs in them that IDSes could trigger off of (for remote exploits). And then there's exploits which don't just copy a null-terminated string and for those it doesn't matter if libc has a zero in it. Of course it sounds like what you're talking about below works as well and more generally. What is a PLT, if i might ask? Also, I'm still trying to figure out what you need to make the stack look like in order to do a return-into-libc exploit. I've got Solar Designer's lpr -C exploit, but I don't quite understand his comments (I mean I understand what he's making the stack look like, but I don't understand why). On Thu, 20 Apr 2000, M.C.Mar wrote:
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
Current thread:
- No-Exec Stack Smashing 101 Granquist, Lamont (Apr 19)
- Re: No-Exec Stack Smashing 101 Crispin Cowan (Apr 19)
- Re: No-Exec Stack Smashing 101 M.C.Mar (Apr 20)
- Re: No-Exec Stack Smashing 101 M.C.Mar (Apr 20)
- Re: No-Exec Stack Smashing 101 Granquist, Lamont (Apr 20)
- Re: No-Exec Stack Smashing 101 M.C.Mar (Apr 20)
- Re: No-Exec Stack Smashing 101 Granquist, Lamont (Apr 20)
- Re: No-Exec Stack Smashing 101 Mariusz Woloszyn (Apr 21)
- Securax Security Advisory: Windows98 contains a serious buffer overflow with long filenameextensions. Zoa_Chien (Apr 21)
- Re: Securax Security Advisory: Windows98 contains a serious buffer overflow with long filenameextensions. Bob Fiero (Apr 21)
- Re: Securax Security Advisory: Windows98 contains a serious buffer overflow with long filenameextensions. Ron DuFresne (Apr 21)
- Re: Securax Security Advisory: Windows98 contains a serious buffer overflow with long filenameextensions. Zoa_Chien (Apr 21)
- Re: Securax Security Advisory: Windows98 contains a seriousbuffer overflow with long filenameextensions. Markus Kern (Apr 22)
- Re: Securax Security Advisory: Windows98 contains a seriousbuffer overflow with long filenameextensions. Zoa_Chien (Apr 23)
- Re: No-Exec Stack Smashing 101 M.C.Mar (Apr 20)
- Re: No-Exec Stack Smashing 101 Crispin Cowan (Apr 19)
- koules again Kotz (Apr 21)