OS-S Security Advisory 2016-03 Date: January 1st, 2016 Updated: January 1st, 2016 Authors: Oguzhan Cicek, Hendrik Schwartke, Ralf Spenneberg CVE: Not yet assigned CVSS: 6.2 (AV:L/AC:L/Au:S/C:C/I:C/A:N) Title: Insufficient Integrity Protection in Winkhaus Bluesmart locking systems using Hitag S Severity: Critical. The locking permissions may be restored by the attacker after modification by the system Ease of Exploitation: Trivial Vulnerability: Insufficient integrity protection Product: Winkhaus Bluesmart using Hitag S and Bluecontrol Virtuell 5.2.0 Abstract The Winkhaus Bluesmart locking system stores the locking permissions and the time windows, when the permissions may be executed, on a Hitag S transponder located oin the tip of the plastic key. If an attacker is able to extract the data stored on the transponder according to our advisory 2016-2 he also has access to the locking permissions and time windows. Although the information is protected against manipulation via encryption, if the permissions or the time windows are modified by the system later the attacker is still able to restore the orginal permissions and time windows. The locks will not detect this manipulation. Scenario Often when deploying a new RFID based locking system not all required locking permissions are known. To ease the launch very often all users get initially global almost unlimited access. The actually required permissions are analyzed and then enforced in a second step. This is especially true in case of the Winkhaus Bluesmart system. Here the users may be required to retrieve new permissions and time windows in a daily routine using a special reader. The attacker may restore his original permissions and time windows if such a restriction took place. The locks do not detect the modification of these permissions. Technical Background The memory layout of the transponder used by the Winkhaus Bluesmart is shown below: see online pdf version: http://www.os-s.de/advisories/oss-advisory-2016-03.pdf The red information is read-protected. The grey areas are encrypted using AES. The time windows and the locking permissions are stored in different areas. They may be read and written using a replay attack or if the actual Hitag-S key has been broken. Copying the data to a different key is detected by the system. Vendor contact We reached out to Winkhaus on Juli 13th, 2015 via phone. On Juli 16th, 2015 we elaborated our findings in a personal meeting. -- OpenSource Security Ralf Spenneberg http://www.os-s.de Am Bahnhof 3-5 48565 Steinfurt Germany Fon: +49(0)2552 638 755 Fax: +49(0)2552 638 757