FreeBSD Security Advisory: FreeBSD-SA-96:18.lpr

[security-officer () FreeBSD org (FreeBSD Security Officer)]

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=============================================================================
FreeBSD-SA-96:18                                            Security Advisory
                                                                FreeBSD, Inc.

Topic:          Buffer overflow in lpr

Category:       core
Module:         lpr
Announced:      1996-11-25
Affects:        FreeBSD 2.*
Corrected:      FreeBSD-current as of 1996/10/27
                FreeBSD-stable as of 1996/11/01
FreeBSD only:   no

Patches:        ftp://freebsd.org/pub/CERT/patches/SA-96:18/

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I.   Background

     The lpr program is used to print files. It is standard software
     in the FreeBSD operating system.

     This advisory is based on AUSCERT's advisory AA-96.12. The FreeBSD
     security-officers would like to thank AUSCERT for their efforts.


II.  Problem Description

     Due to its nature, the lpr program is setuid root. Unfortunately,
     the program does not do sufficient bounds checking on arguments which
     are supplied by users..  As a result it is possible to overwrite the
     internal stack space of the program while it's executing.  This can
     allow an intruder to execute arbitrary code by crafting a carefully
     designed argument to lpr.  As lpr runs as root this allows intruders
     to run arbitrary commands as root.


III. Impact
     Local users can gain root privileges.


IV. Workaround

     AUSCERT has developed a wrapper to help prevent lpr being exploited
     using this vulnerability.  This wrapper, including installation
     instructions, can be found in
                ftp://ftp.auscert.org.au/pub/auscert/advisory/
                        AA-96.12.lpr.buffer.overrun.vul

V. Solution

     Apply one of the following patches. Patches are provided for
     FreeBSD-current (before 1996/10/27) (SA-96:18-solution.current)
     FreeBSD-2.0.5, FreeBSD-2.1.0, FreeBSD-2.1.5 and
        FreeBSd-stable (before 1996/11/01) (SA-96:18-solution.2xx)

     Patches can be found on ftp://freebsd.org/pub/CERT/patches/SA-96:18

=============================================================================
FreeBSD, Inc.

Web Site:                       http://www.freebsd.org/
Confidential contacts:          security-officer () freebsd org
PGP Key:                        ftp://freebsd.org/pub/CERT/public_key.asc
Security notifications:         security-notifications () freebsd org
Security public discussion:     security () freebsd org

Notice: Any patches in this document may not apply cleanly due to
        modifications caused by digital signature or mailer software.
        Please reference the URL listed at the top of this document
        for original copies of all patches if necessary.
=============================================================================


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