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Category:   Application (Security)  >   Util-linux Vendors:   [Multiple Authors/Vendors]
(Red Hat Issues Additional Fix) Util-linux With PAM Group Limits May Let Remote Users Gain Privileges of a Previous Login Users
SecurityTracker Alert ID:  1002608
SecurityTracker URL:  http://securitytracker.com/id/1002608
CVE Reference:   GENERIC-MAP-NOMATCH   (Links to External Site)
Date:  Oct 22 2001
Impact:   Root access via local system, Root access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): util-linux-2.11l and prior
Description:   A vulnerability was reported in Util-linux that could allow an authorized remote user to login and obtain the privileges of the last user that logged in.

It is reported that if there are any limits set for a group of users, then the users in that group can login by any method that uses /bin/login (e.g., console, telnet) to obtain the privileges of the last user that logged in.

The following steps will apparently trigger the vulnerability:

# groupadd testgroup
# useradd testuser -g testgroup
# echo '@testgroup - maxlogins 2'

Then, use ssh to login as root into the target host and then telnet into the host as testuser to obtain root privileges.

[Editor's Note: This was previously reported as a PAM vulnerability but has been reclassified as a Util-linux vulnerability.]

Impact:   A remote authorized user that is part of the specified group with a PAM limit can login to obtain the privileges of the last user that logged in using a login function (such as SSH).
Solution:   The vendor has released a fix:

Red Hat Linux 7.1:

SRPMS:
ftp://updates.redhat.com/7.1/en/os/SRPMS/util-linux-2.11f-11.7.1.src.rpm

alpha:
ftp://updates.redhat.com/7.1/en/os/alpha/util-linux-2.11f-11.7.1.alpha.rpm

i386:
ftp://updates.redhat.com/7.1/en/os/i386/util-linux-2.11f-11.7.1.i386.rpm

ia64:
ftp://updates.redhat.com/7.1/en/os/ia64/util-linux-2.11f-11.7.1.ia64.rpm

Red Hat Linux 7.2:

SRPMS:
ftp://updates.redhat.com/7.2/en/os/SRPMS/util-linux-2.11f-12.src.rpm

i386:
ftp://updates.redhat.com/7.2/en/os/i386/util-linux-2.11f-12.i386.rpm

Vendor URL:  freshmeat.net/projects/util-linux/ (Links to External Site)
Cause:   State error
Underlying OS:  Linux (Red Hat Linux)
Underlying OS Comments:  Tested on RedHat Linux using OpenSSH

Message History:   This archive entry is a follow-up to the message listed below.
Sep 11 2001 Util-linux With PAM Group Limits May Let Remote Users Gain Privileges of a Previous Login Users



 Source Message Contents

Subject:  [RHSA-2001:132-04] New util-linux packages available to fix /bin/login pam problem


---------------------------------------------------------------------
                   Red Hat, Inc. Red Hat Security Advisory

Synopsis:          New util-linux packages available to fix /bin/login pam problem
Advisory ID:       RHSA-2001:132-04
Issue date:        2001-10-11
Updated on:        2001-10-16
Product:           Red Hat Linux
Keywords:          login pam pam_limits
Cross references:  
Obsoletes:         RHSA-2001:095-04
---------------------------------------------------------------------

1. Topic:

New util-linux packages are available that fix a problem with /bin/login's
PAM implementation. This could, in some non-default setups, cause users to
receive credentials of other users. It is recommended that all users
update to the fixed packages.

2001-10-22: Packages are now available for Red Hat Linux 7.2. Notably,
these packages also fix the problem noted in RHSA-2001:095-04 (vipw
incorrectly setting permissions on some files) - this bug was accidentally
reintroduced in Red Hat Linux 7.2.

2. Relevant releases/architectures:

Red Hat Linux 7.1 - alpha, i386, ia64

Red Hat Linux 7.2 - i386

3. Problem description:

A problem existed in /bin/login's PAM implementation; it stored the value
of a static pwent buffer across PAM calls; when used with some PAM modules
in non-default configuration (such as pam_limits), it would overwrite the
buffer, causing a user to get credentials of another user.

Thanks go to Tarhon-Onu Victor <mituc@ac.tuiasi.ro> for bringing the
problem to our attention, and to Olaf Kirch <okir@caldera.de> for providing
the patch.

4. Solution:

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

To update all RPMs for your particular architecture, run:

rpm -Fvh [filenames]

where [filenames] is a list of the RPMs you wish to upgrade.  Only those
RPMs which are currently installed will be updated.  Those RPMs which are
not installed but included in the list will not be updated.  Note that you
can also use wildcards (*.rpm) if your current directory *only* contains
the
desired RPMs.

Please note that this update is also available via Red Hat Network.  Many
people find this an easier way to apply updates.  To use Red Hat Network,
launch the Red Hat Update Agent with the following command:

up2date

This will start an interactive process that will result in the appropriate
RPMs being upgraded on your system.

5. Bug IDs fixed (http://bugzilla.redhat.com/bugzilla for more info):

51646 - pam limits drops other user privileges

6. RPMs required:

Red Hat Linux 7.1:

SRPMS:
ftp://updates.redhat.com/7.1/en/os/SRPMS/util-linux-2.11f-11.7.1.src.rpm

alpha:
ftp://updates.redhat.com/7.1/en/os/alpha/util-linux-2.11f-11.7.1.alpha.rpm

i386:
ftp://updates.redhat.com/7.1/en/os/i386/util-linux-2.11f-11.7.1.i386.rpm

ia64:
ftp://updates.redhat.com/7.1/en/os/ia64/util-linux-2.11f-11.7.1.ia64.rpm

Red Hat Linux 7.2:

SRPMS:
ftp://updates.redhat.com/7.2/en/os/SRPMS/util-linux-2.11f-12.src.rpm

i386:
ftp://updates.redhat.com/7.2/en/os/i386/util-linux-2.11f-12.i386.rpm



7. Verification:

MD5 sum                           Package Name
--------------------------------------------------------------------------
db33b22f50978471a25fd5cc973f8f54 7.1/en/os/SRPMS/util-linux-2.11f-11.7.1.src.rpm
d55f6ec42e3c0268f2ab4decb24deb53 7.1/en/os/alpha/util-linux-2.11f-11.7.1.alpha.rpm
2bf1db1cadc50f783220f70aa2b7a09c 7.1/en/os/i386/util-linux-2.11f-11.7.1.i386.rpm
568c4ec61cb9cc0ebd6313fb14d0419c 7.1/en/os/ia64/util-linux-2.11f-11.7.1.ia64.rpm
3b5448a60fa6cb5580eb690a303827a5 7.2/en/os/SRPMS/util-linux-2.11f-12.src.rpm
c0f329c070e416fbb20c97670199d3fe 7.2/en/os/i386/util-linux-2.11f-12.i386.rpm

These packages are GPG signed by Red Hat, Inc. for security.  Our key
is available at:
    http://www.redhat.com/about/contact/pgpkey.html

You can verify each package with the following command:
    rpm --checksig  <filename>

If you only wish to verify that each package has not been corrupted or
tampered with, examine only the md5sum with the following command:
    rpm --checksig --nogpg <filename>

8. References:




Copyright(c) 2000, 2001 Red Hat, Inc.



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