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Ubuntu Security Notice USN-1188-1
August 09, 2011

ecryptfs-utils vulnerabilities

A security issue affects these releases of Ubuntu and its derivatives:

• Ubuntu 11.04
• Ubuntu 10.10
• Ubuntu 10.04 LTS

Summary:

eCryptfs could be tricked into mounting and unmounting arbitrary locations,
and possibly disclose confidential information.

Software Description:

• ecryptfs-utils: ecryptfs cryptographic filesystem (utilities)

Details:

Vasiliy Kulikov and Dan Rosenberg discovered that eCryptfs incorrectly
validated permissions on the requested mountpoint. A local attacker could
use this flaw to mount to arbitrary locations, leading to privilege
escalation. (CVE-2011-1831)

Vasiliy Kulikov and Dan Rosenberg discovered that eCryptfs incorrectly
validated permissions on the requested mountpoint. A local attacker could
use this flaw to unmount to arbitrary locations, leading to a denial of
service. (CVE-2011-1832)

Vasiliy Kulikov and Dan Rosenberg discovered that eCryptfs incorrectly
validated permissions on the requested source directory. A local attacker
could use this flaw to mount an arbitrary directory, possibly leading to
information disclosure. A pending kernel update will provide the other
half of the fix for this issue. (CVE-2011-1833)

Dan Rosenberg and Marc Deslauriers discovered that eCryptfs incorrectly
handled modifications to the mtab file when an error occurs. A local
attacker could use this flaw to corrupt the mtab file, and possibly unmount
arbitrary locations, leading to a denial of service. (CVE-2011-1834)

Marc Deslauriers discovered that eCryptfs incorrectly handled keys when
setting up an encrypted private directory. A local attacker could use this
flaw to manipulate keys during creation of a new user. (CVE-2011-1835)

Marc Deslauriers discovered that eCryptfs incorrectly handled permissions
during recovery. A local attacker could use this flaw to possibly access
another user's data during the recovery process. This issue only applied to
Ubuntu 11.04. (CVE-2011-1836)

Vasiliy Kulikov discovered that eCryptfs incorrectly handled lock counters.
A local attacker could use this flaw to possibly overwrite arbitrary files.
The default symlink restrictions in Ubuntu 10.10 and 11.04 should protect
against this issue. (CVE-2011-1837)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 11.04:
ecryptfs-utils 87-0ubuntu1.1

Ubuntu 10.10:
ecryptfs-utils 83-0ubuntu3.2.10.10.1

Ubuntu 10.04 LTS:
ecryptfs-utils 83-0ubuntu3.2.10.04.1

In general, a standard system update will make all the necessary changes.

References:
http://www.ubuntu.com/usn/usn-1188-1
CVE-2011-1831, CVE-2011-1832, CVE-2011-1833, CVE-2011-1834,
CVE-2011-1835, CVE-2011-1836, CVE-2011-1837

Package Information:
https://launchpad.net/ubuntu/+source/ecryptfs-utils/87-0ubuntu1.1
https://launchpad.net/ubuntu/+source/ecryptfs-utils/83-0ubuntu3.2.10.10.1
https://launchpad.net/ubuntu/+source/ecryptfs-utils/83-0ubuntu3.2.10.04.1