[securemac] Local vulnerability: MacOSX Screensaver locking bypass.

From: kang (kang_at_insecure.ws)
Date: 10/28/03

  • Next message: _at_stake Advisories: "Mac OS X Systemic Insecure File Permissions" 
    Date: Tue, 28 Oct 2003 17:46:41 +0100
To: full-disclosure@lists.netsys.com, bugtraq@securityfocus.com

          Mac OS X 10.3 Panther Screen Lock Bypass

    *Advisory Title*: Keys Getting Past Panther Screen Lock
    *Release Date*: 2003 October 28
    *Affected Product*: Mac OS X 10.3 Build 7B85
    *Severity*: Low
    *Impact*: Security Bypass
    *Where*: Local System
    *Author*: CodeSamurai (codesamurai@mac.com)

    *VULNERABILITY*
    With access to the keyboard, an unauthorized user can access the
    currently active screen-locked user environment. However, there is only
    a relatively small opening in the period of time in which the keys
    events get through; completing complicated operations at the keyboard
    have shown to be highly tedious in actual practice thus far.

    *EXPLOIT*
    With the screen effect active, keys pressed before the authentication
    window appears will be sent to the general user environment.

    *PRACTICAL TESTS*
    Tested Examples:
    - An open word processing document can be typed in.
    - Shortcut operations via the keyboard are executed.
    - New windows can be spawned.
    - New folders can be created in the Finder.
    - Switching between running applications is possible.
    - One can navigate through the file system and launch applications.
    - Terminal was launched and binary was executed from the command line.

    *CONCLUSION*
    Although the potential risk due to malicious intent via this
    vulnerability is obvious, tentatively it appears that in real-world
    practicality, the impact will most likely be statistically small. (But a
    chain is only as strong as its weakest link.)

    *SecureMac Notes*: For the first-time-user actually executing anything
    useful before the screen lock appears is hard. For the user who
    practices and knows where items are stored and can quickly move around
    with the keys could change information or even disable authentication
    and gain access to the desktop.

    Full advisory is available here:
    http://www.securemac.com/macosx-screenlock-bypass.php

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