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ESB-2014.0868 - [UNIX/Linux][FreeBSD] sendmail: Reduced security - Existing account

Date: 04 June 2014

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

                               ESB-2014.0868
               sendmail improper close-on-exec flag handling
                                4 June 2014

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

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

Product:           sendmail
Publisher:         FreeBSD
Operating System:  FreeBSD
                   UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Reduced Security -- Existing Account
Resolution:        Patch/Upgrade

Original Bulletin: 
   ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-14:11.sendmail.asc

Comment: This advisory references vulnerabilities in products which run on 
         platforms other than FreeBSD. It is recommended that administrators
         running sendmail check for an updated version of the software for 
         their operating system.

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=============================================================================
FreeBSD-SA-14:11.sendmail                                   Security Advisory
                                                          The FreeBSD Project

Topic:          sendmail improper close-on-exec flag handling

Category:       contrib
Module:         sendmail
Announced:      2014-06-03
Affects:        All supported versions of FreeBSD.
Corrected:      2014-05-26 15:35:11 UTC (stable/10, 10.0-STABLE)
                2014-06-03 19:02:52 UTC (releng/10.0, 10.0-RELEASE-p4)
                2014-05-26 20:10:00 UTC (stable/9, 9.3-PRERELEASE)
                2014-06-03 19:03:11 UTC (releng/9.2, 9.2-RELEASE-p7)
                2014-06-03 19:03:11 UTC (releng/9.1, 9.1-RELEASE-p14)
                2014-05-26 15:30:27 UTC (stable/8, 8.4-STABLE)
                2014-06-03 19:03:23 UTC (releng/8.4, 8.4-RELEASE-p11)

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

I.   Background

FreeBSD includes sendmail(8), a general purpose internetwork mail
routing facility, as the default Mail Transfer Agent (MTA).

FreeBSD uses file descriptor as an abstract indicator for accessing a file.
Upon execve(2), file descriptors open in the calling process image remain
open in the new process image, except for those for which the close-on-exec
flag is set.

II.  Problem Description

There is a programming error in sendmail(8) that prevented open file
descriptors have close-on-exec properly set.  Consequently a subprocess
will be able to access all open files that the parent process have open.

III. Impact

A local user who can execute their own program for mail delivery will be
able to interfere with an open SMTP connection.

IV.  Workaround

Do not allow untrusted users to specify programs for mail delivery, for
instance, procmail.

Systems that do not use sendmail(8) MTA are not 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.

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

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

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

# fetch http://security.FreeBSD.org/patches/SA-14:11/sendmail.patch
# fetch http://security.FreeBSD.org/patches/SA-14:11/sendmail.patch.asc
# gpg --verify sendmail.patch.asc

b) Apply the patch.  Execute the following commands as root:

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

c) Recompile the operating system using buildworld and installworld as
described in <URL:http://www.FreeBSD.org/handbook/makeworld.html>.

Restart the applicable daemons, or reboot the system.

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

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

VI.  Correction details

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

Branch/path                                                      Revision
- - -------------------------------------------------------------------------
stable/8/                                                         r266693
releng/8.4/                                                       r267019
stable/9/                                                         r266711
releng/9.1/                                                       r267018
releng/9.2/                                                       r267018
stable/10/                                                        r266692
releng/10.0/                                                      r267017
- - -------------------------------------------------------------------------

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:http://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

The latest revision of this advisory is available at
<URL:http://security.FreeBSD.org/advisories/FreeBSD-SA-14:11.sendmail.asc>
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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.
===========================================================================
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