[UNIX] kcheckpass Insecure File Operation

From: SecuriTeam (support_at_securiteam.com)
Date: 09/26/05

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    Date: 26 Sep 2005 11:06:32 +0200

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      kcheckpass Insecure File Operation


     <http://kde.org> kcheckpass - KDE pam client that allows you to auth as a
    specified user without actually doing anything as that user.

    kcheckpass creates lockfile in an insecure way, exploiting this
    vulnerability allows malicious attacker to create a world writable file


    Vulnerable Systems:
     * kdebase versions 3.2.0 to 3.4.2

    kcheckpass is a utility used to authenticate users. It's used by tools
    such as kscreensaver. The code that's used to create a lockfile doesn't
    check for or sets the umask. Besides the umask problem it will also
    happily follow symlinks, as shown by the following code snippet:
    sprintf(fname, "/var/lock/kcheckpass.%d", uid);
    if ((lfd = open(fname, O_RDWR | O_CREAT)) >= 0) {

    In order for an attacker to be able to exploit this /var/lock would have
    to be world writable and kcheckpass would have to be suid. When these
    conditions are met an attacker can create a world writable file anywhere.

    When properly exploited users can gain root privileges (given that the
    previously mentioned conditions are met).

    CVE Information:


    The information has been provided by <mailto:advisories@suresec.org> Ilja
    van Sprundel.
    The original article can be found at:


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