The SCO Group Information for VU#314963

SCO Security Advisory:

UnixWare 7.1.1 Open UNIX 8.0.0 : closed file descriptor race vulnerability

Detail
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SCO Security Advisory

Subject: UnixWare 7.1.1 Open UNIX 8.0.0 : closed file descriptor race vulnerability
Advisory number: CSSA-2002-SCO.43
Issue date: 2002 December 09
Cross reference:
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1. Problem Description

On current OpenBSD systems, any local user (being or not in
the wheel group) can fill the kernel file descriptors table,
leading to a denial of service. Because of a flaw in the way
the kernel checks closed file descriptors 0-2 when running a
setuid program, it is possible to combine these bugs and earn
root access by winning a race condition.

Since UnixWare does not have a global kernel file descriptors
table (it has per-process dynamic file descriptors table), it
is not prone to the denial of service attack and the race
condition resulting in root exploit.

The second problem, however, does exist - closing file
descriptors 0, 1 and/or 2 before exec'ing a setuid program
can make this program open files under these fds, which have
special meanings for libc (stdin/out/err). Reading or writing
to root-owned files can be made possible, since
stdXX==opened_file.

The fix done for BSD is to check (in the kernel) before
exec'ing a set[ug]id program if fd 0, 1 and 2 are closed, and
if so redirect them to /dev/null. We have done the same fix
for UnixWare.

This fix will only kick in when an unprivileged process
execs a set[ug]id program.


2. Vulnerable Supported Versions

System Binaries
----------------------------------------------------------------------
UnixWare 7.1.1 /etc/conf/pack.d/proc/Driver_atup.o
/etc/conf/pack.d/proc/Driver_mp.o

Open UNIX 8.0.0 /etc/conf/pack.d/proc/Driver_atup.o
/etc/conf/pack.d/proc/Driver_mp.o


3. Solution

The proper solution is to install the latest packages.


4. UnixWare 7.1.1

4.1 Location of Fixed Binaries

ftp://ftp.sco.com/pub/updates/OpenUNIX/CSSA-2002-SCO.43


4.2 Verification

MD5 (erg712059.711.pkg.Z) = 1545beb0d12890de701e129de54bf7b6

md5 is available for download from
ftp://ftp.sco.com/pub/security/tools


4.3 Installing Fixed Binaries

*** NOTE: THE UW711M2 SUPPLEMENT MUST BE INSTALLED PRIOR TO
         APPLYING THIS UPDATE.

Upgrade the affected binaries with the following sequence:

Download erg712059.711.pkg.Z to the /var/spool/pkg directory

# uncompress /var/spool/pkg/erg712059.711.pkg.Z
# pkgadd -d /var/spool/pkg/erg712059.711.pkg


5. Open UNIX 8.0.0

5.1 Location of Fixed Binaries

ftp://ftp.sco.com/pub/updates/OpenUNIX/CSSA-2002-SCO.43


5.2 Verification

MD5 (erg712059.ou8.pkg.Z) = 9291ab96576e48b55e981190480855ca

md5 is available for download from
ftp://ftp.sco.com/pub/security/tools


5.3 Installing Fixed Binaries

*** NOTE: THE OU800PK4 SUPPLEMENT MUST BE INSTALLED PRIOR TO
         APPLYING THIS UPDATE.

Upgrade the affected binaries with the following sequence:

Download erg712059.ou8.pkg.Z to the /var/spool/pkg directory

# uncompress /var/spool/pkg/erg712059.ou8.pkg.Z
# pkgadd -d /var/spool/pkg/erg712059.ou8.pkg


6. References

Specific references for this advisory:

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-0766

SCO security resources:

http://www.sco.com/support/security/index.html

This security fix closes SCO incidents sr865063, fz526562,
erg712059.


7. Disclaimer

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


8. Acknowledgements

FozZy <fozzy@dmpfrance.com>, et al. discovered and researched
this vulnerability.

If you have feedback, comments, or additional information about this vulnerability, please send us email.