TUCoPS :: BSD :: ciaci051.txt

FreeBSD TTCP Vulnerability



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

                             INFORMATION BULLETIN

                          FreeBSD T/TCP Vulnerability

May 19, 1998 21:00 GMT                                            Number I-051
PROBLEM:       FreeBSD had identified a vulnerability in the T/TCP, extension
               for transactions to TCP
PLATFORM:      FreeBSD 2.1.* FreeBSD 2.2.*, FreeBSD-2.2-stable before
               1998/05/14 and FreeBSD-3.0-current before 1998/05/05.Any other
               system incorporating TTCP extentions may be affected.
DAMAGE:        If exploited, the hole may be used to obtain unauthorized
               access to the system by spoofing connections to the
SOLUTION:      Apply patch or workaround
VULNERABILITY  CIAC recommends that action to correct this problem be takes as
ASSESSMENT:    soon as possible if your systems is vulnerable.

[  Start FreeBSD Advisory  ]

WARNING: The patch given in the original advisory had an error. You should
apply the patch in this advisory. In order to do so, you should have the
original file. If you do no longer have the original, look at
It contains the original patch. You should then apply it first using patch
with the -R option.
We're sorry for any inconvenience this may cause.

This advisory also contains a valid patch for FreeBSD 2.1.* versions.

FreeBSD-SA-98:03                                            Security Advisory
                                                                FreeBSD, Inc.

Topic:          Problems with TTCP

Category:       core
Module:         kernel
Announced:      1998-05-14, revised at 1998-05-18
Affects:        FreeBSD 2.1.*
                FreeBSD 2.2.*,
                FreeBSD-2.2-stable before 1998/05/14 and
                FreeBSD-3.0-current before 1998/05/05 suffer from this problem.
Corrected:      FreeBSD-3.0-current as of 1998/05/14
                FreeBSD-2.2-stable as of 1998/05/05
                FreeBSD-2.1-stable as of 1998/05/18
FreeBSD only:   No. Any other system incorporating TTCP extentions may be

Patches:        ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-98:03/

I.   Background   

     RFC 1644 provides an extension to TCP called TCP Extensions for
     Transactions, or shortly T/TCP. It provides a way of bypassing
     the standard three-way handshake found in TCP, thus speeding up
     T/TCP has been incorporated in FreeBSD since FreeBSD 2.0.5.

II.  Problem Description

     An accelerated open is initiated by a client by sending a new
     TCP option, called CC, to the server.  The kernel keeps a
     special cache for each host it communicated with, among others
     containing the value of the last CC option used by the client.
     A new accelerated open is allowed when the CC sent is larger
     than the one in the per-host cache. Thus one can spoof complete
III. Impact
     The hole can be used to obtain unauthorized acces to the system
     by spoofing connections to the r*-services. This can only be
     done in the case where an .rhost file and/or a host.equiv file
     is used as the sole method of authentication.

IV.  Workaround

     Disable all r-* services. Note that setting the kernel variable
     net.inet.tcp.rfc1644 to 0 does not solve the problem. This
     variable controls whether the system will initiate rfc1644
     based connections and does not affect the ability to receive
     such connections.

V.   Solution

     Apply the following patch, rebuild your kernel, install it
     and reboot your system. The patch is valid for 2.1.* systems,
     for 2.1-stable, for 2.2.* systems, for 2.2-stable and for 3.0-current.

     The patch below can be found on

  Index: tcp_input.c
  RCS file: /home/ncvs/src/sys/netinet/tcp_input.c,v
  retrieving revision 1.74
  retrieving revision 1.77
  diff -u -r1.74 -r1.77
  --- tcp_input.c       1998/04/24 10:08:57     1.74
  +++ tcp_input.c       1998/05/18 17:11:24     1.77
  @@ -680,7 +680,9 @@
                 * - otherwise do a normal 3-way handshake.
                if ((to.to_flag & TOF_CC) != 0) {
  -                 if (taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) {
  +                 if (((tp->t_flags & TF_NOPUSH) != 0) &&
  +                     taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) {
                        taop->tao_cc = to.to_cc;
                        tp->t_state = TCPS_ESTABLISHED;
FreeBSD, Inc.

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

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.

[  End FreeBSD Advisory  ]

CIAC wishes to acknowledge the contributions of FreeBSD, Inc. 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:    +1 925-422-8193
    FAX:      +1 925-423-8002
    STU-III:  +1 925-423-2604
    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 925-422-8193 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://www.ciac.org/
                        (or http://ciac.llnl.gov -- they're the same machine)
   Anonymous FTP:       ftp.ciac.org
                        (or ciac.llnl.gov -- they're the same machine)
   Modem access:        +1 (925) 423-4753 (28.8K baud)
                        +1 (925) 423-3331 (28.8K baud)

CIAC has several self-subscribing mailing lists for electronic
1. CIAC-BULLETIN for Advisories, highest priority - time critical
   information and Bulletins, important computer security information;
2. SPI-ANNOUNCE for official news about Security Profile Inspector
   (SPI) software updates, new features, distribution and
3. 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 Majordomo, 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, spi-announce OR spi-notes for list-name:

E-mail to       ciac-listproc@llnl.gov or majordomo@tholia.llnl.gov:
        subscribe list-name
  e.g., subscribe ciac-bulletin

You will receive an acknowledgment email immediately with a confirmation
that you will need to mail back to the addresses above, as per the
instructions in the email.  This is a partial protection to make sure
you are really the one who asked to be signed up for the list in question.

If you include the word 'help' in the body of an email to the above address,
it will also send back an information file on how to subscribe/unsubscribe,
get past issues of CIAC bulletins via email, etc.

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 via WWW at http://www.first.org/.

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
owned rights. Reference herein to any specific commercial products,
process, or service by trade name, trademark, manufacturer, or
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.

LAST 10 CIAC BULLETINS ISSUED (Previous bulletins available from CIAC)

I-041: Performer API Search Tool 2.2 pfdispaly.cgi Vulnerability
I-042: SGI IRIX lp(1) Security Vulnerability
I-043: SGI IRIX mailcap Vulnerability
I-044: BIND Vulnerabilities
I-045: SGI IRIX LicenseManager(1M) Vulnerabilities
I-046: Open Group xterm and Xaw Library Vulnerabilities
I-047: HP-UX OpenMail Vulnerability
I-048: SunOS mountd Vulnerability
I-049: SunOS ufsrestore Vulnerability
I-050: Digital UNIX Softlinks - advfs Vulnerability

Version: 4.0 Business Edition


TUCoPS is optimized to look best in Firefox® on a widescreen monitor (1440x900 or better).
Site design & layout copyright © 1986-2024 AOH