[UNIX] /usr/bin/mail OpenBSD Local Root Compromise (Escaping Tilde)

From: support@securiteam.com
Date: 04/14/02 

From: support@securiteam.com
To: list@securiteam.com
Date: Sun, 14 Apr 2002 22:15:05 +0200 (CEST)

The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
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  /usr/bin/mail OpenBSD Local Root Compromise (Escaping Tilde)
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SUMMARY

Program /usr/bin/mail is a simple mail user agent which can be used also
in the batch mode, for example to send mail to the administrator when
running cron tasks. There is a local root compromise in all versions of
OpenBSD including OpenBSD Current prior to April 9, 2002 due to a bug in
program /usr/bin/mail.

DETAILS

The program /usr/bin/mail accepts escape sequences while running in the
non-interactive mode. When an attacker inserts an escape sequence into the
stream that is used as an input to the mail command this escape sequence
is interpreted by the mail command this in turn will allow execution of
arbitrary commands or read/write any file in the system with the
privileges of the user running /usr/bin/mail.

Impact:
Users can gain superuser privileges because the output of the /etc/daily
script is piped to the /usr/bin/mail command while running regular cron
tasks. There exists a method developed by Przemyslav Frasunek that allows
performing a local attack by creating a file with a specially designed
filename and permissions. Method of performing remote exploitation of this
bug is currently unknown.

Contact Status:
Vendor was contacted on 2002-04-08. Problem report related to the security
advisory was sent on 2002-04-10. A security patch has been made available.
    
Available Fixes:
A patch is available at: <http://www.openbsd.org/errata29.html>
http://www.openbsd.org/errata29.html

ADDITIONAL INFORMATION

The information has been provided by <mailto:urbanek@zoom-int.cz> Milos
Urbanek and <mailto:gwyllion@ace.ulyssis.org> Dries Schellekens.

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