HP-> "... oh you say you found a bunch of overflows... that does not matter... there is no way you will bypass our non-executable stack.. we are not going to fix any of them... we are gonna let em fester... our non-exec stack is Hack proof"
(time elapse... 2 months)
SNO-> "...oh yeah we bypassed your non-exec stack and have successfully exploited several of those overflows we told you about a few months ago...
bash-2.05a$ id
uid=201(dotslash) gid=15(users) groups=0(system)
bash-2.05a$ ./TRU64_su
# id
uid=0(root) gid=15(users) groups=15(users),0(system)
# sysconfig -q proc executable_stack
proc:
executable_stack = 0
(hrmm your stack REALLY helped out)
HP-> "ok thanks we will procede to sue you now"
-KF
It's been proved many times that non-executable stack adds NO security at all. Every single class of vulnerabilities exploitable with executable stack can be also exploited with non-executable stack. See for example our article (http://www.phrack.org/show.php?p=56&a=5) which shows how to bypass a stack protector even with a non-executable stack.
What we're discussing here is an internal structures and data protecting. IMHO the ProPolice (http://www.research.ibm.com/trl/projects/security/ssp/), is the best protection in this kind, even comparing to "two stack" approach. Beside that it's an existing, well tested and wide used (for example OpenBSD uses it by default now). I see no real reason why the major Linux companies are not using it for its products.
Best regards,
-- Mariusz Woloszyn Internet Security Specialist, GTS - Internet Partners _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html
