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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 <fozzydmpfrance.com>, et al. discovered and researched
        this vulnerability.

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