Slackware: utempter Insecure symlink vulnerability
Posted by LinuxSecurity.com Team   
Slackware Steve Grubb has identified an issue with utempter-0.5.2 where under certain circumstances an attacker could cause it to overwrite files through a symlink.

[slackware-security]  utempter security update (SSA:2004-110-01)

New utempter packages are available for Slackware 9.1 and -current to
fix a security issue.  (Slackware 9.1 was the first version of Slackware
to use the libutempter library, and earlier versions of Slackware are
not affected by this issue)

The utempter package provides a utility and shared library that
allows terminal applications such as xterm and screen to update
/var/run/utmp and /var/log/wtmp without requiring root privileges.
Steve Grubb has identified an issue with utempter-0.5.2 where
under certain circumstances an attacker could cause it to
overwrite files through a symlink.  This has been addressed by
upgrading the utempter package to use Dmitry V. Levin's new
implementation of libutempter that does not have this bug.

More details about this issue may be found in the Common
Vulnerabilities and Exposures (CVE) database:

   http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0233

Here are the details from the Slackware 9.1 ChangeLog:
+--------------------------+
Mon Apr 19 13:51:01 PDT 2004
patches/packages/utempter-1.1.1-i486-1.tgz:  Upgraded to libutempter-1.1.1
  (this is a new version written by Dmitry V. Levin of ALT Linux).
  This upgrade fixes a low-level security issue in utempter-0.5.2 where
  utempter could possibly be tricked into writing through a symlink, and is
  a cleaner implementation all-around.
  For more details, see:
     http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0233
  (* Security fix *)
+--------------------------+


WHERE TO FIND THE NEW PACKAGE:
+-----------------------------+

Updated package for Slackware 9.1: 
ftp://ftp.slackware.com/pub/slackware/slackware-9.1/patches/packages/utempter-1.1.1-i486-1.tgz

Updated package for Slackware -current: 
ftp://ftp.slackware.com/pub/slackware/slackware-current/slackware/l/utempter-1.1.1-i486-1.tgz


MD5 SIGNATURES:
+-------------+

Slackware 9.1 package:
839cd39cb90f31253d5bc4c028c28fe1  utempter-1.1.1-i486-1.tgz

Slackware -current package:
97ce776901ca9b20ffe916228a487729  utempter-1.1.1-i486-1.tgz


INSTALLATION INSTRUCTIONS:
+------------------------+

Upgrade the package as root:
# upgradepkg utempter-1.1.1-i486-1.tgz


+-----+

Slackware Linux Security Team 
http://slackware.com/gpg-key
security@slackware.com