TUCoPS :: HP/UX :: ciach032.txt

HP-UX Ppl Core Dump Vulnerability



                       The U.S. Department of Energy
                    Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___

                             INFORMATION BULLETIN

                       HP-UX ppl Core Dump Vulnerability

February 18, 1997 22:00 GMT                                        Number H-32
PROBLEM:       A vulnerability exists in the ppl(1) program.
PLATFORM:      HP-UX 9.x and 10.x
DAMAGE:        This vulnerability may allow local users to gain root
SOLUTION:      Until patches are available, take the steps outlined in section
               3 as soon as possible.
VULNERABILITY  Exploit details involving this vulnerability have been made
ASSESSMENT:    publicly available.

[ Start AUSCERT Advisory ]

AA-97.07                        AUSCERT Advisory
                         HP-UX ppl core dump vulnerability
                                18 February 1997

Last Revised: --

- ----------------------------------------------------------------------------
AUSCERT has received information that a vulnerability exists in the
ppl(1) program under HP-UX 9.x and 10.x.

This vulnerability may allow local users to gain root privileges.

Exploit information involving this vulnerability has been made publicly

The patches listed in HP security bulletin #00053, 13 February 1997,
"Security Vulnerability in the ppl executable", do not correct this

Currently there are no vendor patches available that address this
vulnerability.  AUSCERT recommends that sites take the steps outlined in
section 3 as soon as possible.

This advisory will be updated as more information becomes available.
- ----------------------------------------------------------------------------

1.  Description

    AUSCERT has received information that a vulnerability exists in the
    HP-UX ppl(1) program used to perform point-to-point serial networking
    using SLIP or CSLIP.

    ppl is a setuid root program.  While ppl is executing with root
    privileges, it is possible for local users to force ppl to core dump.
    As users have the ability to manipulate the location of the core, this
    vulnerability may be used to create or overwrite any file on the

    This vulnerability is known to exist in HP-UX 9.x and 10.x.

    The patches listed in HP security bulletin #00053, 13 February 1997,
    "Security Vulnerability in the ppl executable", do not correct this
    problem.  They address other security vulnerabilities.

    Exploit information involving this vulnerability has been made publicly

    The default location for ppl under HP-UX 9.x and 10.x is /usr/bin.

2.  Impact

    Local users may be able to create or overwrite arbitrary files on
    the system.  This can be leveraged to gain root privileges.

3.  Workarounds/Solution

    AUSCERT recommends that sites prevent the exploitation of the
    vulnerability in ppl by immediately applying the workaround given in
    Section 3.1.

    If the ppl functionality is required for non privileged users, AUSCERT
    recommends that access be restricted to a trusted set of users as
    given in Section 3.2.

    Currently there are no vendor patches available that address this
    vulnerability.  AUSCERT recommends that official vendor patches be
    installed when they are made available.

3.1 Remove setuid and execute permissions

    Until official vendor patches are made available, sites should remove
    the setuid root and execute permissions from ppl.  To do this,
    the following command should be run as root:

        # chmod 400 /usr/bin/ppl
        # ls -l /usr/bin/ppl
        -r--------   1 root bin        98304 Jan 24 08:13 /usr/bin/ppl

    Note that this will remove the ability for any user to run this

3.2 Restrict ppl access

    If the ppl functionality is required by a small set of trusted users,
    sites may wish to restrict the execution of ppl to that group of users.
    For example, if the Unix group "trusted" exists and contains only
    those users allowed to use the ppl functionality, the following
    commands will restrict its use:

        # chgrp trusted /usr/bin/ppl
        # chmod 4550 /usr/bin/ppl
        # ls -l /usr/bin/ppl
        -r-sr-x---   1 root trusted    98304 Jan 24 08:13 /usr/bin/ppl

    Note access to any account in the "trusted" group will allow the ppl
    package to be exploited.

4.  Previous patches

    During the installation of HP-UX patches, copies of files being
    replaced are saved in case the patches need to be backed out of.  The
    original versions of patched files are stored in the following

        HP-UX 9.x:      /system/<PATCH-NAME>/orig/
        HP-UX 10.x:     /var/adm/sw/patch/<PATCH_NAME>/

    If patches for vulnerable programs have been previously installed,
    copies of the vulnerable programs may be available in the above
    locations.  Sites should ensure the directories have permissions
    which restrict access to the patch areas.

5.  Additional measures

    Most Unix systems ship with numerous programs which have setuid or
    setgid privileges.  Often the functionality supplied by these
    privileged programs is not required by many sites.  The large number
    of privileged programs that are shipped by default are to cater for
    all possible uses of the system.

    AUSCERT encourages sites to examine all the setuid/setgid programs
    and determine the necessity of each program.  If a program does not
    absolutely require the setuid/setgid privileges to operate (for
    example, it is only run by the root user),  the setuid/setgid
    privileges should be removed.  Furthermore, if a program is not
    required at your site, then all execute permissions should be removed.

    A sample command to find all setuid/setgid programs is (run as root):

       # find / \( -perm -4000 -o -perm -2000 \) -type f -exec ls -l {} \;

    It is AUSCERT's experience that many vulnerability are being discovered
    in setuid/setgid programs which are not necessary for the correct
    operation of most systems.  Sites can increase their security
    by removing unnecessary setuid/setgid programs.

    For example, the functionality provided by the ppl program is
    not needed by many sites.  If sites had previously disabled this
    program, they would not have been susceptible to this latest

- ----------------------------------------------------------------------------

[ End AUSCERT Advisory ]


CIAC wishes to acknowledge the contributions of AUSCERT & Hewlett-Packard for
the information contained in this bulletin.

CIAC, the Computer Incident Advisory Capability, is the computer
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