Home page logo
/

oss-sec logo oss-sec mailing list archives

Re: CVE request: sudo authentication bypass when clock is reset
From: Kurt Seifried <kseifried () redhat com>
Date: Wed, 27 Feb 2013 11:04:47 -0700

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 02/27/2013 09:23 AM, Todd C. Miller wrote:
Sudo 1.8.6p7 and 1.7.10p7 are now available which include a fix
for the following bug:

Sudo authentication bypass when clock is reset

Summary:
    When a user successfully authenticates with sudo, a time stamp
    file is updated to allow that user to continue running sudo
    without requiring a password for a preset time period (five
    minutes by default).  The user's time stamp file can be reset
    using "sudo -k" or removed altogether via "sudo -K".

    A user who has sudo access and is able to control the local
    clock (common in desktop environments) can run a command via
    sudo without authenticating as long as they have previously
    authenticated themselves at least once by running "sudo -k" and
    then setting the clock to the epoch (1970-01-01 01:00:00).

    The vulnerability does not permit a user to run commands other
    than those allowed by the sudoers policy.

Sudo versions affected:
    Sudo 1.6.0 through 1.7.10p7 and sudo 1.8.0 through 1.8.6p7.

Details:
    By default, sudo displays a lecture when the user's time stamp
    file is not present.  In sudo 1.6, the -k option was changed
    to reset the time stamp file to the epoch rather than remove
    it to prevent the lecture from being displayed the next time
    sudo was run.  No special case was added for handling a time
    stamp file set to the epoch since the clock should never
    legitimately be set to that value.

    However, there are two common ways for the clock to be reset
    to the epoch.  The first way is when the clock is reset due to
    a fully drained battery on some systems.  The other way is by
    a user logged in to a desktop environment that allows changes
    to the date and time.

    As long as the user has successfully run sudo before, they are
    able to run "sudo -k" to reset the time stamp file.  This action
    does not require a password and is not logged.  If the user is
    also able to reset the date and time to the epoch (1970-01-01
    01:00:00), they will be able to run sudo without having to
    authenticate.

Impact:
    The flaw may allow someone with physical access to a machine
    that is not password-protected to run sudo commands without
    knowing the logged in user's password.  On systems where sudo
    is the principal way of running commands as root, such as on
    Ubuntu and Mac OS X, there is a greater chance that the logged
    in user has run sudo before and thus that an attack would
    succeed.

Fix:
    The bug is fixed in sudo 1.8.6p7 and 1.7.10p7.  These versions
    will ignore a time stamp file that is set to the epoch.

Workaround:
    Using "sudo -K" instead of "sudo -k" will completely remove the
    time stamp file instead of just resetting it.

Credit:
    I'd like to thank Marco Schoepl for finding and reporting this
    long-standing bug.


Please use CVE-2013-1775 for this issue.

- -- 
Kurt Seifried Red Hat Security Response Team (SRT)
PGP: 0x5E267993 A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.13 (GNU/Linux)
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=kQGP
-----END PGP SIGNATURE-----


  By Date           By Thread  

Current thread:
[ Nmap | Sec Tools | Mailing Lists | Site News | About/Contact | Advertising | Privacy ]
AlienVault