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FreeBSD-SA-96:03:*suggested action only* sendmail smrsh now available Print E-mail
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Posted by LinuxSecurity.com Team   
FreeBSD Sendmail has the ability to deliver mail to a program on the local system via a pipe. This feature is often used to support automatic mail filtering and vacation programs. This provides a very flexible way to deliver information to an automated task running on a mailserver. Unfortunately, this allows unprivileged users to write tasks that may not properly check for common attacks via the program delivery system. The next release of FreeBSD will now install the sendmail restricted shell utility, smrsh in /usr/libexec and create the directory /usr/libexec/sm.bin to hold programs that may be executed by sendmail to deliver mail to pipes.
-----BEGIN PGP SIGNED MESSAGE-----

=============================================================================
FreeBSD-SA-96:03                                            Security Advisory
                                                                FreeBSD, Inc.

Topic:          *suggested action only* sendmail smrsh now available

Category:       core
Module:         sendmail
Announced:      1996-04-20
Affects:        FreeBSD 2.1.0 and earlier distributions
Corrected:      1996-04-21 2.2-current and 2.1-stable sources
FreeBSD only:   no

Patches:        ftp://freebsd.org/pub/CERT/patches/SA-96:03/

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

I.   Background    

     The sendmail mail transfer agent has a rather poor reputation
     for security related problems.  FreeBSD ships a version of
     sendmail that has all known security problems fixed, but this
     doesn't mean there won't be more found in the future.

     The author of sendmail recognized this posibility and has
     included a new utility called "smrsh".  The FreeBSD Project
     would like to encourage system administrators to use this
     utility as a hedge against future possible security holes.


II.  Problem Description

     Sendmail has the ability to deliver mail to a program on the
     local system via a pipe.  This feature is often used to
     support automatic mail filtering and vacation programs.

     This provides a very flexible way to deliver information to
     an automated task running on a mailserver.  Unfortunately,
     this allows unprivileged users to write tasks that may not
     properly check for common attacks via the program delivery
     system.

     The next release of FreeBSD will now install the sendmail
     restricted shell utility, smrsh in /usr/libexec and create
     the directory /usr/libexec/sm.bin to hold programs that
     may be executed by sendmail to deliver mail to pipes.


III. Impact

     There is no known security impact on FreeBSD systems at the
     of this document's publication.  There is no direct requirement
     to install the smrsh utility.

     The FreeBSD Project suggests using smrsh in conjunction with
     sendmail in environments where the local system administrator
     believes there is a need to protect against as-of-yet undiscovered
     security holes in sendmail.

     Use of this utility is /not/ enabled by default in standard
     sendmail configuration files distributed by FreeBSD to retain
     backwards compatibility with previous sendmail operation.  Use
     of this utility may break functionality that users expect.
     Please read the smrsh(8) manual page and/or the README file in
     /usr/src/usr.sbin/sendmail/smrsh BEFORE attempting to use smrsh.


IV. Solution(s)

     This program is available in the 2.1-stable and 2.2-current
     source code distributions.  It is not compiled, installed,
     or enabled in FreeBSD 2.1.0 by default.

     The Apache Group released version 1.05 of the daemon which fixes
     this vulnerability.  The FreeBSD Project updated the ports and
     packages system to use this new daemon.

     Interested parties may obtain an updated pre-compiled FreeBSD
     package from:

     ftp://ftp.freebsd.org/pub/FreeBSD/packages-current/www/apache-1.0.5.tgz

     and an updated "automatic port" from the directory hierarchy:

     ftp://ftp.freebsd.org/pub/FreeBSD/ports-current/www/apache.tar.gz


=============================================================================
FreeBSD, Inc.

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

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.
=============================================================================

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