To: bugtraqat_private announceat_private scoannmodat_private full-disclosureat_private ______________________________________________________________________________ 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: ______________________________________________________________________________ 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 <fozzyat_private>, et al. discovered and researched this vulnerability. ______________________________________________________________________________
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