RHSA-2012:0902 - Security Advisory

Topic

An updated cifs-utils package that fixes one security issue, multiple bugs,
and adds various enhancements is now available for Red Hat
Enterprise Linux 6.

The Red Hat Security Response Team has rated this update as having low
security impact. A Common Vulnerability Scoring System (CVSS) base score,
which gives a detailed severity rating, is available from the CVE link in
the References section.

Description

The cifs-utils package contains tools for mounting and managing shares on
Linux using the SMB/CIFS protocol. The CIFS shares can be used as standard
Linux file systems.

A file existence disclosure flaw was found in mount.cifs. If the tool was
installed with the setuid bit set, a local attacker could use this flaw to
determine the existence of files or directories in directories not
accessible to the attacker. (CVE-2012-1586)

Note: mount.cifs from the cifs-utils package distributed by Red Hat does
not have the setuid bit set. We recommend that administrators do not
manually set the setuid bit for mount.cifs.

This update also fixes the following bugs:

• The cifs.mount(8) manual page was previously missing documentation for

several mount options. With this update, the missing entries have been
added to the manual page. (BZ#769923)

• Previously, the mount.cifs utility did not properly update the

"/etc/mtab" system information file when remounting an existing CIFS
mount. Consequently, mount.cifs created a duplicate entry of the existing
mount entry. This update adds the del_mtab() function to cifs.mount, which
ensures that the old mount entry is removed from "/etc/mtab" before adding
the updated mount entry. (BZ#770004)

• The mount.cifs utility did not properly convert user and group names to

numeric UIDs and GIDs. Therefore, when the "uid", "gid" or "cruid" mount
options were specified with user or group names, CIFS shares were mounted
with default values. This caused shares to be inaccessible to the intended
users because UID and GID is set to "0" by default. With this update, user
and group names are properly converted so that CIFS shares are now mounted
with specified user and group ownership as expected. (BZ#796463)

• The cifs.upcall utility did not respect the "domain_realm" section in

the "krb5.conf" file and worked only with the default domain.
Consequently, an attempt to mount a CIFS share from a different than the
default domain failed with the following error message:

mount error(126): Required key not available

This update modifies the underlying code so that cifs.upcall handles
multiple Kerberos domains correctly and CIFS shares can now be mounted as
expected in a multi-domain environment. (BZ#805490)

In addition, this update adds the following enhancements:

• The cifs.upcall utility previously always used the "/etc/krb5.conf" file

regardless of whether the user had specified a custom Kerberos
configuration file. This update adds the "--krb5conf" option to
cifs.upcall allowing the administrator to specify an alternate
krb5.conf file. For more information on this option, refer to the
cifs.upcall(8) manual page. (BZ#748756)

• The cifs.upcall utility did not optimally determine the correct service

principal name (SPN) used for Kerberos authentication, which occasionally
caused krb5 authentication to fail when mounting a server's unqualified
domain name. This update improves cifs.upcall so that the method used to
determine the SPN is now more versatile. (BZ#748757)

• This update adds the "backupuid" and "backupgid" mount options to the

mount.cifs utility. When specified, these options grant a user or a group
the right to access files with the backup intent. For more information on
these options, refer to the mount.cifs(8) manual page. (BZ#806337)

All users of cifs-utils are advised to upgrade to this updated package,
which contains backported patches to fix these issues and add these
enhancements.

Solution

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

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
https://access.redhat.com/knowledge/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension (for IBM z Systems) 6 s390x

Fixes

• BZ - 748756 - mount.cifs does not use KRB5_CONFIG
• BZ - 748757 - RFE: Improve selection of SPNs with cifs.upcall
• BZ - 807252 - CVE-2012-1586 samba / cifs-utils: mount.cifs file existence disclosure vulnerability

CVEs

• CVE-2012-1586

References

• https://access.redhat.com/security/updates/classification/#low