Bug#433259: gdm: switched user get access to previous logged in user without a password

[Martin Dimitrov]

Package: gdm
Version: 2.18.2-1
Severity: critical
Tags: security
Justification: root security hole

When loged user make a "switch user" and other user log on. After new user finish his work
and want to log off he immediately get access to previous loged in user without need to type a password!

-- System Information:
Debian Release: lenny/sid
  APT prefers testing-proposed-updates
  APT policy: (500, 'testing-proposed-updates'), (500, 'proposed-updates'), (500, 'testing'), (500, 'stable')
Architecture: i386 (i686)

Kernel: Linux 2.6.18-5-k7 (SMP w/1 CPU core)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages gdm depends on:
ii  adduser                    3.103         Add and remove users and groups
ii  debconf [debconf-2.0]      1.5.13        Debian configuration management sy
ii  gksu                       2.0.0-4       graphical frontend to su
ii  gnome-session              2.18.2-2      The GNOME 2 Session Manager
ii  gnome-terminal [x-terminal 2.18.1-1      The GNOME 2 terminal emulator appl
ii  libart-2.0-2               2.3.19-3      Library of functions for 2D graphi
ii  libatk1.0-0                1.18.0-2      The ATK accessibility toolkit
ii  libattr1                   1:2.4.32-1.1  Extended attribute shared library
ii  libc6                      2.5-9+b1      GNU C Library: Shared libraries
ii  libcairo2                  1.4.10-1      The Cairo 2D vector graphics libra
ii  libdbus-1-3                1.1.1-3       simple interprocess messaging syst
ii  libdbus-glib-1-2           0.73-2        simple interprocess messaging syst
ii  libdmx1                    1:1.0.2-2     X11 Distributed Multihead extensio
ii  libfontconfig1             2.4.2-1.2     generic font configuration library
ii  libglade2-0                1:2.6.1-1     library to load .glade files at ru
ii  libglib2.0-0               2.12.12-1+b1  The GLib library of C routines
ii  libgnomecanvas2-0          2.14.0-3      A powerful object-oriented display
ii  libgtk2.0-0                2.10.13-1     The GTK+ graphical user interface 
ii  libpam-modules             0.79-4        Pluggable Authentication Modules f
ii  libpam-runtime             0.79-4        Runtime support for the PAM librar
ii  libpam0g                   0.79-4        Pluggable Authentication Modules l
ii  libpango1.0-0              1.16.4-1      Layout and rendering of internatio
ii  libpopt0                   1.10-3        lib for parsing cmdline parameters
ii  librsvg2-2                 2.16.1-2      SAX-based renderer library for SVG
ii  librsvg2-common            2.16.1-2      SAX-based renderer library for SVG
ii  libselinux1                2.0.15-2+b1   SELinux shared libraries
ii  libwrap0                   7.6.dbs-13    Wietse Venema's TCP wrappers libra
ii  libx11-6                   2:1.0.3-7     X11 client-side library
ii  libxau6                    1:1.0.3-2     X11 authorisation library
ii  libxcursor1                1:1.1.8-2     X cursor management library
ii  libxdmcp6                  1:1.0.2-2     X11 Display Manager Control Protoc
ii  libxext6                   1:1.0.3-2     X11 miscellaneous extension librar
ii  libxfixes3                 1:4.0.3-2     X11 miscellaneous 'fixes' extensio
ii  libxi6                     1:1.0.1-4     X11 Input extension library
ii  libxinerama1               1:1.0.2-1     X11 Xinerama extension library
ii  libxml2                    2.6.29.dfsg-1 GNOME XML library
ii  libxrandr2                 2:1.2.1-1     X11 RandR extension library
ii  libxrender1                1:0.9.2-1     X Rendering Extension client libra
ii  lsb-base                   3.1-23.1      Linux Standard Base 3.1 init scrip
ii  metacity [x-window-manager 1:2.14.5-4    A lightweight GTK2 based Window Ma
ii  rxvt [x-terminal-emulator] 1:2.6.4-10    VT102 terminal emulator for the X 
ii  twm [x-window-manager]     1:1.0.3-2     Tab window manager
ii  xbase-clients              1:7.2.ds2-2   miscellaneous X clients
ii  xterm [x-terminal-emulator 226-1         X terminal emulator

Versions of packages gdm recommends:
ii  dialog                    1.1-20070604-1 Displays user-friendly dialog boxe
ii  gdm-themes                0.5.1          Themes for the GNOME Display Manag
ii  whiptail                  0.52.2-10      Displays user-friendly dialog boxe
ii  zenity                    2.18.2-1       Display graphical dialog boxes fro

-- debconf information:
  gdm/daemon_name: /usr/bin/gdm
* shared/default-x-display-manager: gdm