copyright | disclaimer | privacy | contact  
Australia's Leading Computer Emergency Response Team
 
Search this site

 
On this site

 > HOME
 > About AusCERT
 > Membership
 > Contact Us
 > PKI Services
 > Publications
 > Sec. Bulletins
 > Conferences
 > News & Media
 > Services
 > Web Log
 > Site Map
 > Site Help
 > Member login





 

ESB-2016.0710.2 - UPDATE [FreeBSD] sysarch: Denial of service - Existing account

Date: 26 October 2016

Click here for printable version
Click here for PGP verifiable version
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

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

                              ESB-2016.0710.2
                Incorrect argument validation in sysarch(2)
                              26 October 2016

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

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

Product:           sysarch
Publisher:         FreeBSD
Operating System:  FreeBSD
Impact/Access:     Denial of Service -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2016-1885  

Original Bulletin: 
   https://security.freebsd.org/advisories/FreeBSD-SA-16:15.sysarch.asc

Revision History:  October 26 2016: Revised patch from publisher
                   March   17 2016: Initial Release

- --------------------------BEGIN INCLUDED TEXT--------------------

- -----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

=============================================================================
FreeBSD-SA-16:15.sysarch [REVISED]                          Security Advisory
                                                          The FreeBSD Project

Topic:          Incorrect argument validation in sysarch(2)

Category:       core
Module:         kernel
Announced:      2016-10-25
Credits:        Core Security, ahaha from Chaitin Tech
Affects:        All supported versions of FreeBSD.
Corrected:      2016-10-25 17:14:50 UTC (stable/11, 11.0-STABLE)
                2016-10-25 17:11:20 UTC (releng/11.0, 11.0-RELEASE-p2)
                2016-10-25 17:16:08 UTC (stable/10, 10.3-STABLE)
                2016-10-25 17:11:15 UTC (releng/10.3, 10.3-RELEASE-p11)
                2016-10-25 17:11:11 UTC (releng/10.2, 10.2-RELEASE-p24)
                2016-10-25 17:11:07 UTC (releng/10.1, 10.1-RELEASE-p41)
                2016-10-25 17:16:58 UTC (stable/9, 9.3-STABLE)
                2016-10-25 17:11:02 UTC (releng/9.3, 9.3-RELEASE-p49)
CVE Name:       CVE-2016-1885

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

0.   Revision history

v1.0  2016-03-16 Initial release.
v1.1  2016-10-25 Revised patch to address a problem pointed out by
                 ahaha from Chaitin Tech.

I.   Background

The IA-32 architecture allows programs to define segments, which provides
based and size-limited view into the program address space.  The
memory-resident processor structure, called Local Descriptor Table,
usually abbreviated LDT, contains definitions of the segments.  Since
incorrect or malicious segments would breach system integrity, operating
systems do not provide processes direct access to the LDT, instead
they provide system calls which allow controlled installation and removal 
of segments.

II.  Problem Description

A special combination of sysarch(2) arguments, specify a request to
uninstall a set of descriptors from the LDT.  The start descriptor
is cleared and the number of descriptors are provided.  Due to lack
of sufficient bounds checking during argument validity verification,
unbound zero'ing of the process LDT and adjacent memory can be initiated
from usermode.

III. Impact

This vulnerability could cause the kernel to panic. In addition it is
possible to perform a local Denial of Service against the system by
unprivileged processes. 

IV.  Workaround

No workaround is available, but only the amd64 architecture is affected.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.

Reboot is required.

2) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD platforms can be updated
via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

Reboot is required.

3) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

[*** v1.1 NOTE ***] If your sources are not yet patched using the initially
published advisory patches, then you need to apply both sysarch.patch and
sysarch-01.patch.  If your sources are already updated, or patched with
patches from the initial advisory, then you need to apply sysarch-01.patch
only.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

[ FreeBSD system not patched with original SA-16:15 patch]
# fetch https://security.FreeBSD.org/patches/SA-16:15/sysarch.patch
# fetch https://security.FreeBSD.org/patches/SA-16:15/sysarch.patch.asc
# gpg --verify sysarch.patch.asc

[ FreeBSD system that has been patched with original SA-16:15 patch]
# fetch https://security.FreeBSD.org/patches/SA-16:15/sysarch-01.patch
# fetch https://security.FreeBSD.org/patches/SA-16:15/sysarch-01.patch.asc
# gpg --verify sysarch-01.patch.asc

b) Apply the patch(es).  Execute the following commands as root for
every patch file downloaded:

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- - -------------------------------------------------------------------------
stable/9/                                                         r307941
releng/9.3/                                                       r307931
stable/10/                                                        r307940
releng/10.1/                                                      r307932
releng/10.2/                                                      r307933
releng/10.3/                                                      r307934
stable/11/                                                        r307938
releng/11.0/                                                      r307935
- - -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-1885>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-16:15.sysarch.asc>
- -----BEGIN PGP SIGNATURE-----
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=NWuL
- -----END PGP SIGNATURE-----

- --------------------------END INCLUDED TEXT--------------------

You have received this e-mail bulletin as a result of your organisation's
registration with AusCERT. The mailing list you are subscribed to is
maintained within your organisation, so if you do not wish to continue
receiving these bulletins you should contact your local IT manager. If
you do not know who that is, please send an email to auscert@auscert.org.au
and we will forward your request to the appropriate person.

NOTE: Third Party Rights
This security bulletin is provided as a service to AusCERT's members.  As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to follow or act on information or advice
contained in this security bulletin is the responsibility of each user or
organisation, and should be considered in accordance with your organisation's
site policies and procedures. AusCERT takes no responsibility for consequences
which may arise from following or acting on information or advice contained in
this security bulletin.

NOTE: This is only the original release of the security bulletin.  It may
not be updated when updates to the original are made.  If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author's website to ensure that the information is still current.

Contact information for the authors of the original document is included
in the Security Bulletin above.  If you have any questions or need further
information, please contact them directly.

Previous advisories and external security bulletins can be retrieved from:

        http://www.auscert.org.au/render.html?cid=1980

===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
                AusCERT personnel answer during Queensland business hours
                which are GMT+10:00 (AEST).
                On call after hours for member emergencies only.
===========================================================================
-----BEGIN PGP SIGNATURE-----
Comment: http://www.auscert.org.au/render.html?it=1967
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=DCBd
-----END PGP SIGNATURE-----