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===========================================================================
             AUSCERT External Security Bulletin Redistribution

                 ESB-2001.193 -- FreeBSD Security Advisory
                Changes to FreeBSD security support policy
                                14 May 2001

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:                FreeBSD
Vendor:                 FreeBSD
Operating System:       FreeBSD

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This announcement describes a change in the security support status of
the FreeBSD 3.x branch, as well as the introduction of two new methods
for tracking security fixes to FreeBSD 4.3-RELEASE: a FreeBSD CVS
branch based on 4.3-RELEASE which will contain security fixes only,
and the intention to trial binary security update packages for users
of FreeBSD 4.3-RELEASE on the i386 platform.

1) CHANGE IN SUPPORT FOR THE FREEBSD 3.x BRANCH
   --------------------------------------------

As of this point, the Security Officer Team will provide full
vulnerability response (assessment, correction, notification) for the
FreeBSD 4.x branch only; the FreeBSD 3.x branch will continue to see
vulnerability response only for remotely exploitable vulnerabilities.
This eliminates support for the class of vulnerabilities exploitable
by users with accounts on the system.  This is necessary due to
substantial divergence of the supported 4.x branch from the 3.x
branch, and the increasing age of userland library infrastructure in
the 3.x branch.  Details on unresolved vulnerabilities in the 3.x
branch may be found later in this document.

FreeBSD Branch Support Status
- - -----------------------------

  Branch/Release    Support Status
  --------------    --------------
  3.5.1-RELEASE  | 
  3.5-STABLE     |  Support for remotely exploitable vulnerabilities.

  4.3-STABLE     |  Support for all local and remote security
  4.2-RELEASE    |  vulnerabilities.
  4.3-RELEASE    |

  5.0-CURRENT    |  This development branch is not yet supported by
                 |  the Security Officer Team

Recommendation to Users of the FreeBSD 3.x Branch
- - -------------------------------------------------

The FreeBSD Security Officer recommends that all systems currently
running a version of FreeBSD 3.x be upgraded to 4.3-RELEASE or higher.
Use of FreeBSD 3.5.1-RELEASE or FreeBSD 3.5-STABLE as a sealed-box
network appliance without untrusted local user access will continue to
be supported until at least the release of FreeBSD 5.0-RELEASE.  This
change in policy will allow the Security Officer Team to devote
greater energy to addressing in a timely manner any security issues
that may evolve on the 4.x branch, as well as to provide more support
to the FreeBSD developer community to improve development practices.

Outstanding Local Vulnerabilities in the 3.x Branch
- - ---------------------------------------------------

Currently, FreeBSD Security Advisory SA-00:68, ``ncurses allows local
privilege escalation,'' is unresolved in the 3.x branch, as noted in
that advisory at time of release.  Upgrading the necessary libraries
in the 3.x branch would require introducing binary incompatibilities
in 3.5.1-RELEASE systems comparable to an upgrade to the 4.x branch.
Such disruption is against the policy of FreeBSD regarding ``-STABLE''
branches, and would cause significant disruption to users of that
branch for whom local security vulnerabilities may not be of concern.

As the code in question is more than 5 years old, and substantially
different from the corresponding code in the 4.x branch, developing an
equivalent fix has proven very difficult.  It may be feasible for
individual installations to manually upgrade their ncurses libraries
to a non-vulnerable version, but this is not a strategy supported by
the FreeBSD Security Officer.

As an interim strategy prior to upgrading to FreeBSD 4.3-RELEASE or
later, see the workarounds contained in the advisory referenced above.

2) INTRODUCTION OF THE RELENG_4_3 SECURITY BRANCH
   ----------------------------------------------

As of FreeBSD 4.3-RELEASE, the security officer will be providing
support for a new CVS branch consisting of 4.3-RELEASE plus all
released security patches from FreeBSD Security Advisories.  This
branch carries the CVS branch tag of ``RELENG_4_3'', and can be
tracked using the usual source distribution methods such as cvsup
using this branch tag.

In contrast to 4.3-STABLE (``RELENG_4''), which carries security
updates as well as general bugfixes and feature enhancements, the
RELENG_4_3 release branch will carry ONLY security fixes: it is
intended for users of FreeBSD who do not wish to track the full
4.3-STABLE branch but who wish to keep their system up-to-date with
security fixes in a semi-automated manner (i.e. without applying
patches by hand).

This practise of using a release branch to hold security fixes is
likely to be continued for future releases of FreeBSD.

3) PROVISION OF BINARY UPDATE PACKAGES FOR SECURITY FIXES
   ------------------------------------------------------

In response to many user requests, the Security Officer Team will
trial the production of binary packages for correcting security
vulnerabilities in the FreeBSD base system.  At this stage only
support for userland (as opposed to kernel) vulnerabilities is planned
due to the difficulty of providing a single update for
locally-customized kernel versions, although we may be able to provide
an updated version of the GENERIC kernel for users who wish to use it
to avoid patching and recompiling their own GENERIC kernel from
source.

The correct operation of binary patches relies heavily on a known
common base to which the update is applied.  Therefore binary patches
will only be supported for users of FreeBSD 4.3-RELEASE on the i386.
Users of older supported releases of FreeBSD, users of FreeBSD
4.3-STABLE, or users who choose to follow the RELENG_4_3 branch
(described above) are expected to use traditional methods of applying
security fixes to their FreeBSD installations, such as applying
patches by hand, or using cvsup to update the source collection.

For questions regarding the matters discussed in this announcement,
please contact the FreeBSD Security Officer
<security-officer@FreeBSD.org>.
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