Date: Sat, 3 May 2014 03:10:35 -0400 (EDT) From: cve-assign@...re.org To: marc.deslauriers@...onical.com Cc: cve-assign@...re.org, oss-security@...ts.openwall.com Subject: Re: Ubuntu 14.04: security problem in the lock screen -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Issues #1, #2, and #3 are clearly within the scope of CVE, and have their CVE IDs below. The common theme is "the user intended to lock the screen, the UI indicates that the screen is successfully locked, the user physically leaves, but this locking can then be bypassed by a physically present attacker." Two of the other bugs referenced within pages for #1, #2, and #3 are https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1308572/comments/6 and https://bugs.launchpad.net/ubuntu/+source/gnome-screensaver/+bug/49579 Quite possibly, these should also have CVE IDs, but there are potentially valid counterarguments. First, at a high level, neither of these matches the "common theme" described above. For 1308572/comments/6, one counterargument is that a user isn't entitled to expect that screen locking will continue to work flawlessly if he decides to kill arbitrary processes that are, more or less, related to screen/display functionality. Also, the risk is very low in the sense that, before a user physically left, it would usually be obvious that the screen was not successfully locked. However, there is conceivably a scenario in which killing compiz is a supported (or, at least, reasonable) user activity, and the user must leave immediately after a screen-locking attempt without waiting even a few seconds. For 49579, there are many ways to summarize the long discussion: here is one of them. A typical end user may expect that automatic screen locking succeeds regardless of what the user had been doing (e.g., if the user was in the middle of a menu operation). A developer may expect that automatic screen locking succeeds in cases where the implementation is achievable in a reasonable amount of time. There are (at least) three possible conclusions: 1. The end user wins. This is a vulnerability regardless of what documentation exists, because it is unreasonable to expect an end user to learn about the failure conditions. 2. This is a vulnerability if the documentation is not "good enough." For example, if the only documentation is bug 49579 itself, maybe that's not enough. 3. The developer wins. This is never a vulnerability. Yes, it would be nice for automatic screen locking to succeed in more cases, but this is not a high-value security feature for all users, and it's OK for development to use a "reasonable effort" approach rather than a "must cover every possible case at all costs" approach. > Issue #1 (Before 14.04 came out): > > Marco Agnese discovered that Unity 7.2.0 incorrectly handled entry activation on > the lock screen, resulting in the lock screen crashing and the session becoming > unlocked. > > Reference: > https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1308572 > http://bazaar.launchpad.net/~unity-team/unity/trunk/revision/3787 Use CVE-2014-3202. > Issue #2: > > Giovanni Mellini discovered that Unity 7.2.0 could display the Dash in certain > conditions when the screen was locked. A local attacker could possibly use > this issue to run commands, and unlock the current session. > > Reference: > https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1308850 > http://bazaar.launchpad.net/~unity-team/unity/trunk/revision/3789 > http://www.ubuntu.com/usn/usn-2184-1/ Use CVE-2014-3203. > Issue #3: > > Frederic Bardy discovered that Unity 7.2.0 incorrectly filtered keyboard > shortcuts when the screen was locked. A local attacker could possibly use > this issue to run commands, and unlock the current session. > > Reference: > https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1313885 > https://code.launchpad.net/~3v1n0/unity/lockscreen-keys-disable/+merge/217528 > http://www.ubuntu.com/usn/usn-2184-1/ Use CVE-2014-3204. - -- CVE assignment team, MITRE CVE Numbering Authority M/S M300 202 Burlington Road, Bedford, MA 01730 USA [ PGP key available through http://cve.mitre.org/cve/request_id.html ] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (SunOS) iQEcBAEBAgAGBQJTZJVNAAoJEKllVAevmvms96YH/iwHSHG581FZ0v2fAjEEqXlP aAi1Fy65ejwxP1mEnpgw15p9mu8OTD1vYNn4+ibdvQ/MuGKuS/uSsTeH6vixhB/f U4SmcOqTGc0ejEiRIG9Pf1CoLZnP8fYuwPRYKuF4ah8AZKNbfnwmL3AO8/SaUtN2 7E/f+KuajcUOvbKBTcANPffILUufyNSzXWc+DxsRcNYjaDs9K4B5VDLZbT8NbquB rUFWPPhiAWFlKq+XAz6uLLcKug8L775xhbB60iPzhYa6tqatuJSuHm9CGb/5HwJT NXK8VyfaPfg+/iTzyjNHNO8wKq6QdlM9C3Qn6hyBIhUTa37WjnSqVBpPtQMwCzg= =kdSf -----END PGP SIGNATURE-----
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