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TUCoPS :: Linux :: Apps A-M :: ciacg029.txt

Dip Program Vulnerability





             __________________________________________________________

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

                             INFORMATION BULLETIN

                           dip Program Vulnerability

July 9, 1996 17:00 GMT                                             Number G-29
______________________________________________________________________________
PROBLEM:       A vulnerability in the dip program makes it possible to
               overflow an internal buffer whose value is under the control of
               the user of the dip program. The dip program manages the 
               connections needed for dial-up links such as SLIP and PPP.
PLATFORM:      Linux systems for X86 hardware.
DAMAGE:        On systems that have dip installed as set-user-id root, anyone
               with access to an account on that system can gain root access.
SOLUTION:      Disable the present installed version and install the new
               version of dip.
______________________________________________________________________________
VULNERABILITY  Exploitation scripts for dip have been found running on Linux
ASSESSMENT:    systems for X86 hardware. However, exploitation scripts for
               other architectures and operating systems have not been found,
               but could be easily developed.
______________________________________________________________________________

[ Start of CERT Advisory ]

=============================================================================
CERT(sm) Advisory CA-96.13
July 9, 1996

Topic: Vulnerability in the dip program

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

The CERT Coordination Center has received several reports of exploitations of
a vulnerability in the dip program on Linux systems. The dip program is
shipped with most versions of the Linux system; and versions up to and
including version 3.3.7n are vulnerable. An exploitation script for Linux
running on X86-based hardware is publicly available. Although exploitation
scripts for other architectures and operating systems have not yet been found,
we believe that they could be easily developed.

The CERT Coordination Center recommends that you disable dip and re-enable it
only after you have installed a new version. Section III below describes how
to do that.

As we receive additional information relating to this advisory, we
will place it in

        ftp://info.cert.org/pub/cert_advisories/CA-96.13.README

We encourage you to check our README files regularly for updates on
advisories that relate to your site.

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

I.   Description

     dip is a freely available program that is included in most distributions
     of Linux. It is possible to build it for and use it on other UNIX systems.

     The dip program manages the connections needed for dial-up links such
     as SLIP and PPP. It can handle both incoming and outgoing connections.
     To gain access to resources it needs to establish these IP connections,
     the dip program must be installed as set-user-id root.

     A vulnerability in dip makes it possible to overflow an internal buffer
     whose value is under the control of the user of the dip program. If this
     buffer is overflowed with the appropriate data, a program such as a
     shell can be started. This program then runs with root permissions on the
     local machine.

     Exploitation scripts for dip have been found running on Linux systems for
     X86 hardware. Although exploitation scripts for other architectures
     and operating systems have not yet been found, we believe that they could
     be easily developed.

II.  Impact

     On a system that has dip installed as set-user-id root, anyone with
     access to an account on that system can gain root access.

III. Solution

     Follow the steps in Section A to disable your currently installed version
     of dip. Then, if you need the functionality that dip provides, follow the
     steps given in Section B.

     A.  Disable the presently installed version of dip.
         As root,
                chmod 0755 /usr/sbin/dip

         By default, dip is installed in the /usr/sbin directory. Note that it
         may be installed elsewhere on your system.


     B.  Install a new version of dip.
         If you need the functionality that dip provides, retrieve and install
         the following version of the source code for dip, which fixes this
         vulnerability. dip is available from 

ftp://sunsite.unc.edu/pub/Linux/system/Network/serial/dip/dip337o-uri.tgz
ftp://sunsite.unc.edu/pub/Linux/system/Network/serial/dip/dip337o-uri.tgz.sig

         MD5   (dip337o-uri.tgz) = 45fc2a9abbcb3892648933cadf7ba090
         SHash (dip337o-uri.tgz) = 6e3848b9b5f9d5b308bbac104eaf858be4dc51dc

----------------------------------------------------------------------------
The CERT Coordination Center staff thanks Uri Blumenthal for his solution to
the problem and Linux for their support in the development of this advisory.
----------------------------------------------------------------------------

[ End of CERT Advisory ]

_______________________________________________________________________________

CIAC wishes to acknowledge the contributions of CERT for the information 
contained in this bulletin.
_______________________________________________________________________________

CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.

CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
    Voice:    +1 510-422-8193
    FAX:      +1 510-423-8002
    STU-III:  +1 510-423-2604
    E-mail:   ciac@llnl.gov

For emergencies and off-hour assistance, DOE, DOE contractor sites,
and the NIH may contact CIAC 24-hours a day. During off hours (5PM -
8AM PST), call the CIAC voice number 510-422-8193 and leave a message,
or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two
Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC
duty person, and the secondary PIN number, 8550074 is for the CIAC
Project Leader.

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

   World Wide Web:      http://ciac.llnl.gov/
   Anonymous FTP:       ciac.llnl.gov (128.115.19.53)
   Modem access:        +1 (510) 423-4753 (28.8K baud)
                        +1 (510) 423-3331 (28.8K baud)

CIAC has several self-subscribing mailing lists for electronic
publications:
1. CIAC-BULLETIN for Advisories, highest priority - time critical
   information and Bulletins, important computer security information;
2. CIAC-NOTES for Notes, a collection of computer security articles;
3. SPI-ANNOUNCE for official news about Security Profile Inspector
   (SPI) software updates, new features, distribution and
   availability;
4. SPI-NOTES, for discussion of problems and solutions regarding the
   use of SPI products.

Our mailing lists are managed by a public domain software package
called ListProcessor, which ignores E-mail header subject lines. To
subscribe (add yourself) to one of our mailing lists, send the
following request as the E-mail message body, substituting
CIAC-BULLETIN, CIAC-NOTES, SPI-ANNOUNCE or SPI-NOTES for list-name and
valid information for LastName FirstName and PhoneNumber when sending

E-mail to       ciac-listproc@llnl.gov:
        subscribe list-name LastName, FirstName PhoneNumber
  e.g., subscribe ciac-notes OHara, Scarlett W. 404-555-1212 x36

You will receive an acknowledgment containing address, initial PIN,
and information on how to change either of them, cancel your
subscription, or get help.

PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained by sending email to
docserver@first.org with an empty subject line and a message body
containing the line: send first-contacts.

This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
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otherwise, does not necessarily constitute or imply its endorsement,
recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the United States
Government or the University of California, and shall not be used for
advertising or product endorsement purposes.

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