TUCoPS :: SunOS/Solaris :: ciach044.txt

Solaris2x Fdformat Buffer Overflow

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             __________________________________________________________

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

                             INFORMATION BULLETIN

               Solaris 2.x fdformat Buffer Overflow Vulnerability

March 24, 1997 18:00 GMT                                           Number H-44
______________________________________________________________________________
PROBLEM:       A vulnerability exists in fdformat (1).
PLATFORM:      All platforms running Solaris 2.4, 2.5, 2.5.1. Earlier versions
               may also be vulnerable.
DAMAGE:        This vulnerability may allow local users to gain root
               privileges.
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-97.11                        AUSCERT Advisory
                   Solaris 2.x fdformat Buffer Overflow Vulnerability
                                24 March 1997

Last Revised:
- ------------------------------------------------------------------------------

AUSCERT has received information that a vulnerability exists in
fdformat(1), distributed under Solaris 2.4, 2.5 and 2.5.1. Earlier versions
may be vulnerable.

This vulnerability may allow local users to gain root privileges.

Exploit information involving this vulnerability has been made publicly
available.

At this stage, AUSCERT is unaware of any official vendor patches.  AUSCERT
recommends that sites apply the workaround given in Section 3 until vendor
patches are made available.

This advisory will be updated as more information becomes available.

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

1.  Description

    fdformat(1) is a utility for formatting both diskettes and PCMCIA
    memory cards.

    Due to insufficient bounds checking on arguments which are supplied
    by users, it is possible to overwrite the internal stack space of the
    fdformat program while it is executing.  By supplying a carefully
    designed argument to the fdformat program, intruders may be able to
    force fdformat to execute arbitrary commands.  As fdformat is setuid
    root, this may allow intruders to run arbitrary commands with root
    privileges.

    Sites can determine if this program is installed by using:

        % ls -l /usr/bin/fdformat

    fdformat is installed by default in /usr/bin.  Sites are encouraged
    to check for the presence of this program regardless of the version
    of Solaris installed.

    Exploit information involving this vulnerability has been made publicly
    available.

    Sun Microsystems has informed AUSCERT that they are currently working
    on this vulnerability.

2.  Impact

    Local users may gain root privileges.

3.  Workarounds/Solution

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

    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 execute permissions

    To prevent the exploitation of the vulnerability described in this
    advisory, AUSCERT recommends that the setuid permissions be removed
    from the fdformat program immediately.

        # ls -l /usr/bin/fdformat
        -r-sr-xr-x   1 root   bin     26284 Oct 25  1995 /usr/bin/fdformat

        # chmod 555 /usr/bin/fdformat
        # ls -l /usr/bin/fdformat
        -r-xr-xr-x   1 root   bin     26284 Oct 25  1995 /usr/bin/fdformat

4.  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 fdformat program is
    not needed by many sites.  If sites had previously disabled this
    program, they would not have been susceptible to this latest
    vulnerability.

[ End AUSCERT Advisory ]

______________________________________________________________________________

CIAC wishes to acknowledge the contributions of AUSCERT & Sun Microsystems for
the information contained in this bulletin.
______________________________________________________________________________


CIAC, the Computer Incident Advisory Capability, is the computer
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