Bugtraq mailing list archives
Re: Security Problem in MH 6.8.4
From: cschuber () uumail gov bc ca (Cy Schubert - ITSD Open Systems Group)
Date: Tue, 20 Jan 1998 00:20:44 -0800
Description: Due to lack of security checks there is a standard stack smashing probl
em.
Local user can execute code as root. Let's see. [tascon@archivald]$ id uid=500(tascon) gid=500(tascon) groups=500(tascon),100(users) [tascon@archivald]$ cat /etc/redhat-release release 5.0 (Hurricane) [tascon@archivald]$ ls -l /usr/bin/mh/inc -rwsr-sr-x 1 root mail 82972 Oct 15 18:06 /usr/bin/mh/inc [tascon@archivald]$ /usr/bin/mh/inc inc: no mail to incorporate [tascon@archivald]$ /usr/bin/mh/inc -host XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXX[...]
XXXXX <---- (2000 X's here) Segmentation fault ^^^^^^^^^^^^^^^^^^ Dangerous isn't it?
Under FreeBSD (while using NIS), specifying an argument greater than 1024 bytes causes an infinite loop with the following message being printed; yp_match: clnt_call: RPC: Can't encode arguments Under FreeBSD (while not using NIS) and DEC UNIX (using MH 6.8.4 instead of the MH 6.7 that is supplied with DUNIX), specifying an argument greater than 4600 bytes, the error is handled properly and the the following message is produced; inc: no servers available Without having a chance to recompile MH with -g and testing it under gdb, I suspect that the Linux segmentation violation and the FreeBSD NIS loop are occuring within the gethostbyname() call or some libc call made by gethostbyname(). One may argue that the FreeBSD NIS loop may constitue a DoS attack as it chews up a fair amount of CPU time, however there are probably better ways to bring a system to its knees. I'd characterize the FreeBSD NIS bug as more of an annoyance. The Linux bug is definitely a security issue. I suspect it to be in RedHat's implementation of libc.
Local exploit exists for that option. Note that MH isn't even configured. It's as the installation of RedHat 5.0 left it. Note also that MH is intalled by deffect with RedHat 5.0. Solution: Uninstall this package or remove the suid-bit until patch becomes available.
Another solution might be to recompile MH without POP support, however that is just a band-aid solution and doesn't really fix the problem with RedHat's libc.
MH also installs another suid-program: msgchk. It's also posible to get a Segmentation fault whith the same option, but I haven't been able to exploit it. I have worked on it quite a few. Could someone probe it a little deeper?? Greetings ----o-------------------------------o-------------------------------------o--
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Space reserved to describe / Cesar Tascon Alvarez my job when I got one. / University of Valladolid (SPAIN) Yes, I'm just a student ;) / tascon () gui uva es ----o-----------------------o---------------------------------------------o--
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Regards, Phone: (250)387-8437 Cy Schubert Fax: (250)387-5766 UNIX Support OV/VM: BCSC02(CSCHUBER) ITSD BITNET: CSCHUBER@BCSC02.BITNET Government of BC Internet: cschuber () uumail gov bc ca Cy.Schubert () gems8 gov bc ca "Quit spooling around, JES do it."
Current thread:
- Java reboots win95 Joe Lindstr?m (Jan 17)
- Re: Java reboots win95 David LeBlanc (Jan 17)
- GCC Exploit Phillip R. Jaenke (Jan 17)
- Security Problem in MH 6.8.4 Cesar Tascon Alvarez (Jan 19)
- Re: Security Problem in MH 6.8.4 mparson () SMARTNAP COM (Jan 19)
- Re: Security Problem in MH 6.8.4 Philip Guenther (Jan 20)
- Re: Security Problem in MH 6.8.4 Cy Schubert - ITSD Open Systems Group (Jan 20)
- Re: Security Problem in MH 6.8.4 Alan Cox (Jan 20)
- L0pht Security Advisory mattw (Jan 20)
- Re: Security Problem in MH 6.8.4 mparson () SMARTNAP COM (Jan 19)