(RHSA-2012:0902) Low: cifs-utils security, bug fix, and enhancement update

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.