Screenlock backdoors and how to close them The 2019 Stack Overflow Developer Survey Results Are In Announcing the arrival of Valued Associate #679: Cesar Manara Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern) 2019 Community Moderator Election ResultsHow can I lock my screen in Gnome 3 without GDM?Myth or reality: SELinux can confine the root user?How to show time away from computer?How to get Kali Linux to not go to sleep?How to configure XFCE (or X itself or whatever) to run a custom command when the user has been idle for some time?Keyboard doesn't work in X11 after resuming from sleep/suspendHow to display a video on my lock-screen instead of a wallpaper?How to determine if screensaver is active on another sessionScreen turns off after 10 minutes and I can't find out whyHow to unlock Gnome3 screen from command line?
Example of compact Riemannian manifold with only one geodesic.
First use of “packing” as in carrying a gun
How do spell lists change if the party levels up without taking a long rest?
Can the DM override racial traits?
Would an alien lifeform be able to achieve space travel if lacking in vision?
Does Parliament hold absolute power in the UK?
Single author papers against my advisor's will?
Variable with quotation marks "$()"
Can a flute soloist sit?
Student Loan from years ago pops up and is taking my salary
Python - Fishing Simulator
Why are PDP-7-style microprogrammed instructions out of vogue?
Did the UK government pay "millions and millions of dollars" to try to snag Julian Assange?
Didn't get enough time to take a Coding Test - what to do now?
My body leaves; my core can stay
Do warforged have souls?
What do I do when my TA workload is more than expected?
Why don't hard Brexiteers insist on a hard border to prevent illegal immigration after Brexit?
Why not take a picture of a closer black hole?
What's the point in a preamp?
Do I have Disadvantage attacking with an off-hand weapon?
Is it ok to offer lower paid work as a trial period before negotiating for a full-time job?
How to politely respond to generic emails requesting a PhD/job in my lab? Without wasting too much time
Keeping a retro style to sci-fi spaceships?
Screenlock backdoors and how to close them
The 2019 Stack Overflow Developer Survey Results Are In
Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)
2019 Community Moderator Election ResultsHow can I lock my screen in Gnome 3 without GDM?Myth or reality: SELinux can confine the root user?How to show time away from computer?How to get Kali Linux to not go to sleep?How to configure XFCE (or X itself or whatever) to run a custom command when the user has been idle for some time?Keyboard doesn't work in X11 after resuming from sleep/suspendHow to display a video on my lock-screen instead of a wallpaper?How to determine if screensaver is active on another sessionScreen turns off after 10 minutes and I can't find out whyHow to unlock Gnome3 screen from command line?
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;
There is a warning in the Archlinux List of security applications. It says that of all possible screen-lockers, only four block tty access: sflock, physlock, Cinnamon Screensaver, MATE Screensaver and GNOME Screensaver.
The XScreenSaver FAQ, meanwhile, lists four backdoors by which someone can gain access to your system when your screen is locked:
- Ctrl-Alt-Backspace (kill X server, perhaps raise text console)
- Ctrl-Alt-F1 (F2, ..., etc)(open a virtual console)
- Alt-SysRq-F (randomly kill a long-running process)
- Ctrl-Alt-KP_Multiply (kill any X11 app that holds a lock)
The Xscreensaver FAQ gives ways to disable the backdoors.
But are there others? And do those screen-lockers that Archlinux implies are actually block all those backdoors listed in the xscreensaver faq, and whatever other ones there might be?
And if you block all the backdoors in the way suggested in the xscreensaver faq, will your system then be secure enough for you to leave it after locking the screen, suspending the system and closing the lid?
A word from xscreensaver author Jamie Zawinski:
Shouldn't xscreensaver disable Ctrl-Alt-Backspace while the screen is locked?
Yes, it should. Unfortunately, that's not possible with current versions of XFree86 or XOrg. It's as if the developers of X11 and the Linux kernel want to make it as hard as possible for you to lock your screen.
...
There's little that I can do to make the screen locker secure so long
as the kernel and X11 developers are actively working against
security. The strength of the lock on your front door doesn't matter
much so long as someone else in the house insists on leaving a key
under the welcome mat.
In an ideal world, there would be a single X11 request named something like XGrabMagicKeys() that would, analagously to
XGrabKeyboard(), disable all of these magic keystrokes until the
grab was released or the program exited. It should be an X11 call, not
an ioctl(), and especially not a root-only ioctl(). Needless to
say, no such interface exists.
security xorg screen-lock screensaver backdoor
asked Apr 9 at 10:43
marklingmarkling
657
add a comment |
There is a warning in the Archlinux List of security applications. It says that of all possible screen-lockers, only four block tty access: sflock, physlock, Cinnamon Screensaver, MATE Screensaver and GNOME Screensaver.
The XScreenSaver FAQ, meanwhile, lists four backdoors by which someone can gain access to your system when your screen is locked:
- Ctrl-Alt-Backspace (kill X server, perhaps raise text console)
- Ctrl-Alt-F1 (F2, ..., etc)(open a virtual console)
- Alt-SysRq-F (randomly kill a long-running process)
- Ctrl-Alt-KP_Multiply (kill any X11 app that holds a lock)
The Xscreensaver FAQ gives ways to disable the backdoors.
But are there others? And do those screen-lockers that Archlinux implies are actually block all those backdoors listed in the xscreensaver faq, and whatever other ones there might be?
And if you block all the backdoors in the way suggested in the xscreensaver faq, will your system then be secure enough for you to leave it after locking the screen, suspending the system and closing the lid?
A word from xscreensaver author Jamie Zawinski:
Shouldn't xscreensaver disable Ctrl-Alt-Backspace while the screen is locked?
Yes, it should. Unfortunately, that's not possible with current versions of XFree86 or XOrg. It's as if the developers of X11 and the Linux kernel want to make it as hard as possible for you to lock your screen.
...
There's little that I can do to make the screen locker secure so long
as the kernel and X11 developers are actively working against
security. The strength of the lock on your front door doesn't matter
much so long as someone else in the house insists on leaving a key
under the welcome mat.
In an ideal world, there would be a single X11 request named something like XGrabMagicKeys() that would, analagously to
XGrabKeyboard(), disable all of these magic keystrokes until the
grab was released or the program exited. It should be an X11 call, not
an ioctl(), and especially not a root-only ioctl(). Needless to
say, no such interface exists.
security xorg screen-lock screensaver backdoor
asked Apr 9 at 10:43
marklingmarkling
657
add a comment |
There is a warning in the Archlinux List of security applications. It says that of all possible screen-lockers, only four block tty access: sflock, physlock, Cinnamon Screensaver, MATE Screensaver and GNOME Screensaver.
The XScreenSaver FAQ, meanwhile, lists four backdoors by which someone can gain access to your system when your screen is locked:
- Ctrl-Alt-Backspace (kill X server, perhaps raise text console)
- Ctrl-Alt-F1 (F2, ..., etc)(open a virtual console)
- Alt-SysRq-F (randomly kill a long-running process)
- Ctrl-Alt-KP_Multiply (kill any X11 app that holds a lock)
The Xscreensaver FAQ gives ways to disable the backdoors.
But are there others? And do those screen-lockers that Archlinux implies are actually block all those backdoors listed in the xscreensaver faq, and whatever other ones there might be?
And if you block all the backdoors in the way suggested in the xscreensaver faq, will your system then be secure enough for you to leave it after locking the screen, suspending the system and closing the lid?
A word from xscreensaver author Jamie Zawinski:
Shouldn't xscreensaver disable Ctrl-Alt-Backspace while the screen is locked?
Yes, it should. Unfortunately, that's not possible with current versions of XFree86 or XOrg. It's as if the developers of X11 and the Linux kernel want to make it as hard as possible for you to lock your screen.
...
There's little that I can do to make the screen locker secure so long
as the kernel and X11 developers are actively working against
security. The strength of the lock on your front door doesn't matter
much so long as someone else in the house insists on leaving a key
under the welcome mat.
In an ideal world, there would be a single X11 request named something like XGrabMagicKeys() that would, analagously to
XGrabKeyboard(), disable all of these magic keystrokes until the
grab was released or the program exited. It should be an X11 call, not
an ioctl(), and especially not a root-only ioctl(). Needless to
say, no such interface exists.
security xorg screen-lock screensaver backdoor
asked Apr 9 at 10:43
marklingmarkling
657
There is a warning in the Archlinux List of security applications. It says that of all possible screen-lockers, only four block tty access: sflock, physlock, Cinnamon Screensaver, MATE Screensaver and GNOME Screensaver.
The XScreenSaver FAQ, meanwhile, lists four backdoors by which someone can gain access to your system when your screen is locked:
- Ctrl-Alt-Backspace (kill X server, perhaps raise text console)
- Ctrl-Alt-F1 (F2, ..., etc)(open a virtual console)
- Alt-SysRq-F (randomly kill a long-running process)
- Ctrl-Alt-KP_Multiply (kill any X11 app that holds a lock)
The Xscreensaver FAQ gives ways to disable the backdoors.
But are there others? And do those screen-lockers that Archlinux implies are actually block all those backdoors listed in the xscreensaver faq, and whatever other ones there might be?
And if you block all the backdoors in the way suggested in the xscreensaver faq, will your system then be secure enough for you to leave it after locking the screen, suspending the system and closing the lid?
A word from xscreensaver author Jamie Zawinski:
Shouldn't xscreensaver disable Ctrl-Alt-Backspace while the screen is locked?
Yes, it should. Unfortunately, that's not possible with current versions of XFree86 or XOrg. It's as if the developers of X11 and the Linux kernel want to make it as hard as possible for you to lock your screen.
...
There's little that I can do to make the screen locker secure so long
as the kernel and X11 developers are actively working against
security. The strength of the lock on your front door doesn't matter
much so long as someone else in the house insists on leaving a key
under the welcome mat.
In an ideal world, there would be a single X11 request named something like XGrabMagicKeys() that would, analagously to
XGrabKeyboard(), disable all of these magic keystrokes until the
grab was released or the program exited. It should be an X11 call, not
an ioctl(), and especially not a root-only ioctl(). Needless to
say, no such interface exists.
security xorg screen-lock screensaver backdoor
security xorg screen-lock screensaver backdoor
asked Apr 9 at 10:43
marklingmarkling
657
asked Apr 9 at 10:43
marklingmarkling
657
edited Apr 9 at 10:50
markling
asked Apr 9 at 10:43
marklingmarkling
657
asked Apr 9 at 10:43
marklingmarkling
657
asked Apr 9 at 10:43
marklingmarkling
657
657
add a comment |
add a comment |
0
active
oldest
votes
Your Answer
StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "106"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);
else
createEditor();
);
function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);
);
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f511428%2fscreenlock-backdoors-and-how-to-close-them%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
0
active
oldest
votes
0
active
oldest
votes
active
oldest
votes
active
oldest
votes
Thanks for contributing an answer to Unix & Linux Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f511428%2fscreenlock-backdoors-and-how-to-close-them%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
