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Home » Hacking News » Caldera - CSSA-2001-SCO.35.2 - OpenServer: setcontext and sysi86 vulnerabilities

Caldera - CSSA-2001-SCO.35.2 - OpenServer: setcontext and sysi86 vulnerabilities

by Nikola Strahija on January 26th, 2002 This patch closes a family of security holes present in SCO OpenServer 5.0.6 and previous releases, which stem from the ability of regular user processes to reprogram segment descriptors and certain other CPU registers.


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Caldera International, Inc. Security Advisory

Subject: REVISED: OpenServer: setcontext and sysi86 vulnerabilities
Advisory number: CSSA-2001-SCO.35.2
Issue date: 2002 January 21
Cross reference: CSSA-2001-SCO-35 CSSA-2001-SCO.35.1
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1. Problem Description

[ The previous release of this fix was flawed, and required a
recut. If CSSA-2001-SCO-35 or CSSA-2001-SCO-35.1 has already
been applied, Caldera stongly recommends that you install the
updated fix. NB: Before installing CSSA-2001-SCO.35.2, any
previously installed version of CSSA-2001-SCO.35 must be
removed. ]

This patch closes a family of security holes present in SCO
OpenServer 5.0.6 and previous releases, which stem from the
ability of regular user processes to reprogram segment
descriptors and certain other CPU registers.

This patch can be applied on SCO OpenServer 5.0.4, 5.0.4c,
5.0.5, 5.0.5a, 5.0.6, or 5.0.6a. This fix will be included in
releases subsequent to 5.0.6a.

Closing this family of security holes does, however, result in
a functionality change which may prevent certain applications
from running -- they will exit with an error, or dump core,
instead of running properly. For example, the i286emul and
x286emul emulators will not work, so any '286 executables
which require those emulators will not work. It is our
intention to enhance this patch in the future, such that it
enables full functionality of such applications while still
closing the security holes.

If this patch breaks any crucial applications, the system
administrator may choose to disable the patch, by editing the
file /etc/conf/pack.d/kernel/space.c and setting the value of
the allow_dscr_remap parameter to 1. This will return the
kernel to the old (non-secure) behavior.


2. Vulnerable Versions

Operating System Version Affected Files
------------------------------------------------------------------
OpenServer All /etc/conf/pack.d/kernel/os.a(machdep.o)
/etc/conf/pack.d/kernel/os.a(sysi86.o)


3. Workaround

None.


4. OpenServer

4.1 Location of Fixed Binaries

ftp://stage.caldera.com/pub/security/openserver/CSSA-2001-SCO.35.2/


4.2 Verification

md5 checksums:

MD5 (CSSA-2001-SCO.35.2.tar) = 08a06921bfc5050020a459595f05a146


md5 is available for download from

ftp://stage.caldera.com/pub/security/tools/


4.3 Installing Fixed Binaries

*** Before installing CSSA-2001-SCO.35.2, any previously ***
*** installed version of CSSA-2001-SCO.35 must be removed. ***

Upgrade the affected binaries with the following commands:

Download the CSSA-2001-SCO.35.2.tar file to /tmp.

# cd /tmp
# tar xvf CSSA-2001-SCO.35.2.tar
# custom

Instruct custom to install from images, and supply /tmp as the
directory of the VOL image.


5. References

ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2001-002.txt.asc

This and other advisories are located at
http://stage.caldera.com/support/security

This advisory addresses Caldera Security internal incidents
sr855993, sr855994, SCO-559-1328, SCO-559-1329, erg711906 and
erg711905.


6. Disclaimer

Caldera International, Inc. is not responsible for the misuse
of any of the information we provide on our website and/or
through our security advisories. Our advisories are a service
to our customers intended to promote secure installation and
use of Caldera International products.


7. Acknowledgements

Caldera wishes to thank the Last Stage of Delirium Research
Group ([email protected]) for their discovering of, and
research into, these issues.


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