Ubuntu Manpage: XSecureLock - X11 screen lock utility

NAME

       XSecureLock - X11 screen lock utility

SYNPOSIS

       [options] xsecurelock [– command-to-run-when-locked]

DESCRIPTION

       XSecureLock is an X11 screen lock utility designed with the primary goal of security.

       It  locks  the current X11 session, and only allows unlocking if the user authenticates to
       it (typically with the login password).

       While locked, it can launch a screen saver process and then waits for input events.   Upon
       an input event, it displays a login dialog to allow for unlocking.

OPTIONS

Options are set as environment variables prior to invoking XSecureLock; the following
variables are available:

• XSECURELOCK_AUTH: specifies the desired authentication module (the part that displays
the authentication prompt).

• XSECURELOCK_AUTHPROTO: specifies the desired authentication protocol module (the part
that talks to the system).

• XSECURELOCK_AUTH_BACKGROUND_COLOR: specifies the X11 color (see manpage of XParseColor)
for the background of the auth dialog.

• XSECURELOCK_AUTH_SOUNDS: specifies whether to play sounds during authentication to
indicate status. Sounds are defined as follows:

• High-pitch ascending: prompt for user input.

• High-pitch constant: an info message was displayed.

• Low-pitch descending: an error message was displayed.

• Medium-pitch ascending: authentication successful.

• XSECURELOCK_AUTH_FOREGROUND_COLOR: specifies the X11 color (see manpage of XParseColor)
for the foreground text of the auth dialog.

• XSECURELOCK_AUTH_TIMEOUT: specifies the time (in seconds) to wait for response to a
prompt by auth_x11 before giving up and reverting to the screen saver.

• XSECURELOCK_AUTH_WARNING_COLOR: specifies the X11 color (see manpage of XParseColor) for
the warning text of the auth dialog.

• XSECURELOCK_BLANK_TIMEOUT: specifies the time (in seconds) before telling X11 to fully
blank the screen; a negative value disables X11 blanking. The time is measured since
the closing of the auth window or xsecurelock startup. Setting this to 0 is rather
nonsensical, as key-release events (e.g. from the keystroke to launch xsecurelock or
from pressing escape to close the auth dialog) always wake up the screen.

• XSECURELOCK_BLANK_DPMS_STATE: specifies which DPMS state to put the screen in when
blanking (one of standby, suspend, off and on, where “on” means to not invoke DPMS at
all).

• XSECURELOCK_BURNIN_MITIGATION: specifies the number of pixels the prompt of auth_x11 may
be moved at startup to mitigate possible burn-in effects due to the auth dialog being
displayed all the time (e.g. when spurious mouse events wake up the screen all the
time).

• XSECURELOCK_BURNIN_MITIGATION_DYNAMIC: if set to a non-zero value, auth_x11 will move
the prompt while it is being displayed, but stay within the bounds of
XSECURELOCK_BURNIN_MITIGATION. The value of this variable is the maximum allowed shift
per screen refresh. This mitigates short-term burn-in effects but is probably annoying
to most users, and thus disabled by default.

• XSECURELOCK_COMPOSITE_OBSCURER: create a second full-screen window to obscure window
content in case a running compositor unmaps its own window. Helps with some instances
of bad compositor behavior (such as compositor crashes/restarts, but also compton has
been caught at drawing notification icons above the screen locker when not using the GLX
backend), should prevent compositors from unredirecting as it’s 1 pixel smaller than the
screen from every side, and should otherwise be harmless, so it’s enabled by default.

• XSECURELOCK_DATETIME_FORMAT: the date format to show. Defaults to the locale settings.

• XSECURELOCK_DEBUG_ALLOW_LOCKING_IF_INEFFECTIVE: Normally we don’t allow locking sessions
that are likely not any useful to lock, such as the X11 part of a Wayland session (one
could still use Wayland applicatione when locked) or VNC sessions (as it’d only lock the
server side session while users will likely think they locked the client, allowing for
an easy escape). These checks can be bypassed by setting this variable to 1. Not
recommended other than for debugging XSecureLock itself via such connections.

• XSECURELOCK_DEBUG_WINDOW_INFO: When complaining about another window misbehaving, print
not just the window ID but also some info about it. Uses the xwininfo and xprop tools.

• XSECURELOCK_DIM_ALPHA: Linear-space opacity to fade the screen to.

• XSECURELOCK_DIM_COLOR: X11 color to fade the screen to.

• XSECURELOCK_DIM_FPS: Target framerate to attain during the dimming effect of dimmer.
Ideally matches the display refresh rate.

• XSECURELOCK_DIM_OVERRIDE_COMPOSITOR_DETECTION: When set to 1, always try to use
transparency for dimming; when set to 0, always use a dither pattern. Default is to
autodetect whether transparency will likely work.

• XSECURELOCK_DIM_TIME_MS: Milliseconds to dim for when above xss-lock command line with
dimmer is used; also used by wait_nonidle to know when to assume dimming and waiting has
finished and exit.

• XSECURELOCK_DISCARD_FIRST_KEYPRESS: If set to 0, the key pressed to stop the screen
saver and spawn the auth child is sent to the auth child (and thus becomes part of the
password entry). By default we always discard the key press that started the
authentication flow, to prevent users from getting used to type their password on a
blank screen (which could be just powered off and have a chat client behind or similar).

• XSECURELOCK_FONT: X11 or FontConfig font name to use for auth_x11. You can get a list
of supported font names by running xlsfonts and fc-list.

• XSECURELOCK_FORCE_GRAB: When grabbing fails, try stealing the grab from other windows (a
value of 2 steals from all descendants of the root window, while a value of 1 only
steals from client windows). This works only sometimes and is incompatible with many
window managers, so use with care. See the “Forcing Grabs” section below for details.

• XSECURELOCK_GLOBAL_SAVER: specifies the desired global screen saver module (by default
this is a multiplexer that runs XSECURELOCK_SAVER on each screen).

• XSECURELOCK_IDLE_TIMERS: comma-separated list of idle time counters used by
until_nonidle. Typical values are either empty (relies on the X Screen Saver extension
instead), “IDLETIME” and “DEVICEIDLETIME ” where n is an XInput device index (run xinput
to see them). If multiple time counters are specified, the idle time is the minimum of
them all. All listed timers must have the same unit.

• XSECURELOCK_IMAGE_DURATION_SECONDS: how long to show each still image played by
saver_mpv. Defaults to 1.

• XSECURELOCK_KEY_%s_COMMAND where %s is the name of an X11 keysym (find using xev): a
shell command to execute when the specified key is pressed. Useful e.g. for media
player control. Beware: be cautiuous about what you run with this, as it may yield
attackers control over your computer.

• XSECURELOCK_LIST_VIDEOS_COMMAND: shell command to list all video files to potentially
play by saver_mpv or saver_mplayer. Defaults to find ~/Videos -type f.

• XSECURELOCK_NO_COMPOSITE: disables covering the composite overlay window. This switches
to a more traditional way of locking, but may allow desktop notifications to be visible
on top of the screen lock. Not recommended.

• XSECURELOCK_NO_PAM_RHOST: do not set PAM_RHOST to localhost, despite recommendation
(http://www.linux-pam.org/Linux-PAM-html/adg-security-user-identity.html) to do so by
the Linux-PAM Application Developers’ Guide. This may work around bugs in third-party
PAM authentication modules. If this solves a problem for you, please report a bug
against said PAM module.

• XSECURELOCK_NO_XRANDR: disables multi monitor support using XRandR.

• XSECURELOCK_NO_XRANDR15: disables multi monitor support using XRandR 1.5 and fall back
to XRandR 1.2. Not recommended.

• XSECURELOCK_PAM_SERVICE: pam service name. You should have a file with that name in
/etc/pam.d.

• XSECURELOCK_PASSWORD_PROMPT: Choose password prompt mode:

• asterisks: shows asterisks, like classic password prompts. This is the least secure
option because password length is visible.

***_
*******_

• cursor: shows a cursor that jumps around on each key press. This is the default.

________|_______________________
___________________|____________

• disco: shows dancers, which dance around on each key press. Requires a font that can
handle Unicode line drawing characters, and FontConfig.

┏(･o･)┛ ♪ ┗(･o･)┓ ♪ ┏(･o･)┛ ♪ ┗(･o･)┓ ♪ ┏(･o･)┛
┗(･o･)┓ ♪ ┏(･o･)┛ ♪ ┏(･o･)┛ ♪ ┏(･o･)┛ ♪ ┏(･o･)┛

• emoji: shows an emoji, changing which one on each key press. Requires a font that can
handle emoji, and FontConfig.

👍
🎶
💕

• emoticon: shows an ascii emoticon, changing which one on each key press.

:-O
d-X
X-\

• hidden: completely hides the password, and there’s no feedback for keypresses. This
would almost be most secure - however as it gives no feedback to input whatsoever, you
may not be able to notice accidentally typing to another computer and sending your
password to some chatroom.

• kaomoji: shows a kaomoji (Japanese emoticon), changing which one on each key press.
Requires a Japanese font, and FontConfig.

(͡°͜ʖ͡°)
(＾ｕ＾)
¯\_(ツ)_/¯

• time: shows the current time since the epoch on each keystroke. This may be the most
secure mode, as it gives feedback to keystroke based exclusively on public
information, and does not carry over any state between keystrokes whatsoever - not
even some form of randomness.

1559655410.922329

• time_hex: same as time, but in microseconds and hexadecimal. “Because we can”.

0x58a7f92bd7359

• XSECURELOCK_SAVER: specifies the desired screen saver module.

• XSECURELOCK_SAVER_RESET_ON_AUTH_CLOSE: specifies whether to reset the saver module when
the auth dialog closes. Resetting is done by sending SIGUSR1 to the saver, which may
either just terminate, or handle this specifically to do a cheaper reset.

• XSECURELOCK_SHOW_DATETIME: whether to show local date and time on the login. Disabled
by default.

• XSECURELOCK_SHOW_HOSTNAME: whether to show the hostname on the login screen of auth_x11.
Possible values are 0 for not showing the hostname, 1 for showing the short form, and 2
for showing the long form.

• XSECURELOCK_SHOW_USERNAME: whether to show the username on the login screen of auth_x11.

• XSECURELOCK_SINGLE_AUTH_WINDOW: whether to show only a single auth window from auth_x11,
as opposed to one per screen.

• XSECURELOCK_SWITCH_USER_COMMAND: shell command to execute when Win-O or Ctrl-Alt-O are
pressed (think “other user”). Typical values could be lxdm -c USER_SWITCH, dm-tool
switch-to-greeter, gdmflexiserver or kdmctl reserve, depending on your desktop
environment.

• XSECURELOCK_WAIT_TIME_MS: Milliseconds to wait after dimming (and before locking) when
above xss-lock command line is used. Should be at least as large as the period time set
using “xset s”. Also used by wait_nonidle to know when to assume dimming and waiting
has finished and exit.

• XSECURELOCK_XSCREENSAVER_PATH: Location where XScreenSaver hacks are installed for use
by saver_xscreensaver.

Additionally, XSecureLock spawns the command-to-run-when-locked once locking is complete;
this can be used as a notification mechanism if desired.

REPORTING BUGS

       The official bug tracker is at <https://github.com/google/xsecurelock/issues/>.

COPYRIGHT

       The code is released unser the Apache 2.0 license.  See the LICENSE file for more details.

AUTHORS

       Rudolf Polzer.