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Bug #15641

Persistence preset: screen locking password

Added by Gaff 5 months ago. Updated 3 months ago.

Status:
Confirmed
Priority:
Low
Assignee:
Category:
Persistence
Target version:
-
Start date:
06/08/2018
Due date:
% Done:

0%

QA Check:
Info Needed
Feature Branch:
Type of work:
Code
Blueprint:
Starter:
Affected tool:
Greeter

Description

I'm using tor with a persisted volume. If I set the screen lock password and reboot the screen lock password isn't persisted.

Proposed design for a persistent password:

In the persistence configuration
================================

Add an option for a persistent password.

In the screen locking dialog
============================

Add an option to persist the password.

In Tails Greeter
================

If persistence unlocked after [Start Tails]
-------------------------------------------

- If admin password is the same as persistent password:

  Don't ask anything

- If admin password is different than persistent password:

  Ask to choose between two alternatives:

    * Ignore the persistent password
      Use the administration password for administration and unlocking the screen

    * Reset persistent password

If persistence unlocked before [Start Tails] (optional)
-------------------------------------------------------

- If persistence unlocked + persistent password:

  Display alternate layout (and explain why):

    [ ] Enable administration access

    [Reset persistent password]

- If persistence unlocked + persistent password feature + no persistent password (yet)

  Display original layout with an option to persist password:

    Set password: [               ]
    Confirm:      [               ]

    [ ] Persist this password

History

#1 Updated by mercedes508 5 months ago

  • Status changed from New to Rejected

Hi,

It's been discussed in the past, during design and implementation of this new feature, but there's definitely more work than benefit, because you'll only have to type it twice when using the screen locker for the first time in your session.

#2 Updated by Gaff 5 months ago

Oh right - can you point me to the discussion?

The main risk here is that it saves the users from themselves. Users will forget to lock the screen and then risk having their unattended machine accessed. See also: #15488

I can think of a few ways to solve this:

  • Demand users setup a password when they first use the machine.
  • Persist /etc/shadow via the persistence mechanism.
  • Change the tails-locker script to save the (encrypted) password and have a startup servers that does `usermod -p` on startup using this data.

Would any of these solutions be acceptable?

#3 Updated by intrigeri 5 months ago

  • Status changed from Rejected to New
  • Assignee set to mercedes508
  • QA Check set to Info Needed

#4 Updated by mercedes508 5 months ago

  • Assignee changed from mercedes508 to segfault
  • Type of work changed from Code to Discuss

Gaff wrote:

Oh right - can you point me to the discussion?

https://labs.riseup.net/code/issues/5684#note-34

The main risk here is that it saves the users from themselves. Users will forget to lock the screen and then risk having their unattended machine accessed. See also: #15488

But what if the user forget his/her pwd? I don't think we really can protect people that forget to lock, plus leave their computer unattended from certain risks.

I can think of a few ways to solve this:

  • Demand users setup a password when they first use the machine.
  • Persist /etc/shadow via the persistence mechanism.
  • Change the tails-locker script to save the (encrypted) password and have a startup servers that does `usermod -p` on startup using this data.

Would any of these solutions be acceptable?

#5 Updated by Gaff 5 months ago

In such rare circumstances, swtting a root password in the greeter would override the persisted password. Simple ;)

Most users are familiar with the pattern that your computer locks automatically if you leave it idle. I think it is surprising / dangerous that tails does not do this by default. Especially for persistent users who may not be certain if they have locked their desktop manually this session or not.

#6 Updated by segfault 5 months ago

  • Status changed from New to Confirmed
  • Priority changed from Normal to Low
  • QA Check deleted (Info Needed)

Gaff wrote:

The main risk here is that it saves the users from themselves. Users will forget to lock the screen and then risk having their unattended machine accessed. See also: #15488

For the longest time we didn't have a screen locker in Tails at all (except if you set the admin password), and I don't recall getting a lot of requests for this by users (@tails-support: please correct me if this is wrong). So I will set the priority of this to 'low' for now.

I also see the risk that users might forget their password (especially existing users who are used to our session passwords) and lose their unsaved work because they can't unlock the screen.

Another UX problem could be that the admin password set in the greeter will overwrite the screen locker password.

I can think of a few ways to solve this:

  • Demand users setup a password when they first use the machine.

That doesn't solve the problem of how to persist the password.

  • Persist /etc/shadow via the persistence mechanism.

This could break things if user accounts change between Tails versions.

  • Change the tails-locker script to save the (encrypted) password and have a startup servers that does `usermod -p` on startup using this data.

This is the only sensible way I see for doing this: Storing the hashed password on the persistent partition and having a service run after the greeter, which sets the password if there is none set already. (`chpasswd -e` allows supplying a hashed password.)

In case we decide to implement this, I think we should add a "Screen Locker Password" entry to tails-persistence-setup.

#7 Updated by segfault 5 months ago

segfault wrote:

Gaff wrote:

  • Demand users setup a password when they first use the machine.

That doesn't solve the problem of how to persist the password.

... but we could still consider asking for the password after running tails-persistence-setup, if the user chose to persist the screen locker password.

#8 Updated by intrigeri 5 months ago

For the longest time we didn't have a screen locker in Tails at all (except if you set the admin password), and I don't recall getting a lot of requests for this by users (@tails-support: please correct me if this is wrong).

FWIW the lack of a screen locker was reported to me (in person) as one of the most painful aspects of Tails many times.

#9 Updated by Gaff 5 months ago

segfault wrote:

I also see the risk that users might forget their password (especially existing users who are used to our session passwords) and lose their unsaved work because they can't unlock the screen.

Another UX problem could be that the admin password set in the greeter will overwrite the screen locker password.

You could go the extra mile and replace "admin password" with "enable sudo" for the case where a password is persisted. Though having an option in the greeter to overwrite the password solves the problem of users forgetting their persisted password.

Gaff wrote:

  • Demand users setup a password when they first use the machine.

That doesn't solve the problem of how to persist the password.

My thinking here is that it's more important that a password is configured each session, than to have it persisted. But yeah this is an inferior option.

we could still consider asking for the password after running tails-persistence-setup, if the user chose to persist the screen locker password.

Presumably the Debian default is to ask for a user password after boot? So this should be simple-ish.

#10 Updated by sajolida 5 months ago

  • Assignee deleted (segfault)
  • Affected tool set to Greeter

Thanks for starting the discussion Gaff!

I really want to avoid having two different passwords for our users to handle. I think that would add complexity that most user wouldn't find justified or easy to understand, especially users who are not used to Linux with two different password, say the vast majority of our target Audience: Windows, macOS, and Ubuntu users.

But this would imply to redesign the Administration Password option of Tails Greeter. Let's say you persisted your password:

  • If you don't enable an Administration Password in Tails Greeter, then it could mean that your password is for unlocking the screen only.
  • But if we leave the option to enable an Administration Password in Tails Greeter, then what would it mean?

Then, inside Tails, I think this option should appear in two places:

  • In the persistent setting, like segfault said. I would call it "Password" and explain that it's both for administration and locking the screen.
  • In the dialog to configure the screen locking password, as a checkbox to make it persistent.

That said, as I'm quite opposed to having two different passwords and seeing that this might require rethinking important parts of Tails Greeter, this seems quite complicated and I'm not sure we should work on this any time soon. I don't mean to turn you down but to be realistic.

#11 Updated by Gaff 5 months ago

Without redesigning Linux passwords / sudo significantly it's only possible to have one password! Or are you referring to the encryption password?

Personally I think it's important to have a screen lock option, even if users don't like it. There's plenty of other things tails / tor does to save users from themselves, this should be on that list.

(I'm also happy to do some of the dev work here).

I think the options are:

  • When an administrative password is set any persisted password is ignored.
    • This is slightly surprising, but only affects uses who use the admin option (which should be used rarely).
    • Simple to implement
  • When the admin password is set the persisted password is replaced.
    • The danger here is the users may not know this has happened
  • When you unlock the greeter it loads and persisted password, and if found replaces the "administration password" option with an "enable administration" checkbox.
    • This is neat, although leaves no user friendly way to replace forgotten passwords.
  • Always demand a screen lock password (if none is persisted). Replace the admin password with a checkbox. Add options to replace persisted passwords.
    • Good for security, follows the Tails threat model
    • It is an extra hurdle for users. Though users are often used to entering passwords when setting things up.
    • Means we could retire the non-standard screen lock password stuff and replace it with regular gnome.
  • Use the encryption password as the screen lock / admin password. Replace the admin password with a checkbox for persistence users.
    • Not ideal for security
    • Convenient

My thinking was to go with the first option initially and see how things pan out. A lot rests on how we encourage users to set screen lock passwords. Though the more I think about it the more I'm leaning towards always demanding a lock password.

#12 Updated by sajolida 4 months ago

Without redesigning Linux passwords / sudo significantly it's only possible to have one password!

I don't understand this sentence. Can you rephrase maybe?

Personally I think it's important to have a screen lock option, even if users don't like it. There's plenty of other things tails / tor does to save users from themselves, this should be on that list.

The thing is that Tails already has a screen locker. This ticket is only
about making it possible to save it to persistence.

Users can already use the same screen locker password every time they
lock their screen.

So the only benefit of making the screen locker password persistent is
to have to screen locker enabled automatically when people start Tails.
I see two scenarios where this makes a difference:

  • People leaving their computer unattended (going to the toilets at the
    library). It's still much safer for them to lock the screen manually
    than to rely on an automatic screen locker and I would expect most Tails
    users to already have this habit.
  • People closing their laptop and putting it in their bag (I do this a
    lot). Not having the screen locker enabled automatically might make a
    big difference in case they are searched, their loose their laptop or
    leave their bad unattended.

If we agree on this, then let's keep in mind that we're talking about
this particular scenario as a benefit when discussing the costs in terms
of UX, which might affect all other scenarios.

  • When an administrative password is set any persisted password is ignored.
    • This is slightly surprising, but only affects uses who use the admin option (which should be used rarely).
    • Simple to implement
  • When the admin password is set the persisted password is replaced.
    • The danger here is the users may not know this has happened

So what about asking the user what they want to do?

We could check whether the administration password that was entered is
the same as the persisted password:

  • If the passwords are the same, don't ask anything and start Tails.
  • If the passwords are different, ask the user what to do:
  1. Ignore the persisted password = Use the administration password for
    administration and unlocking the screen. If people always set an
    administration password (like I do), they will quickly get bothered by
    this message but can disable the persisted password.
  1. Replace the persisted password with the new administration password.
    That would also serve as a recovery mechanism for the persisted
    password in a way...

What do you think?

  • When you unlock the greeter it loads and persisted password, and if found replaces the "administration password" option with an "enable administration" checkbox.
    • This is neat, although leaves no user friendly way to replace forgotten passwords.

I think that this option would require more evolved changes in Tails
Greeter, like inspecting the content of the partition as soon as it
opens, adjusting to the persistence being unlocked either before or
after the administration password is set, etc.

  • Always demand a screen lock password (if none is persisted). Replace the admin password with a checkbox. Add options to replace persisted passwords.
    • Good for security, follows the Tails threat model
    • It is an extra hurdle for users. Though users are often used to entering passwords when setting things up.
    • Means we could retire the non-standard screen lock password stuff and replace it with regular gnome.

I really want to avoid doing this. Thankfully I think that we have
better options to consider. If it was the only option, I would probably
reject this proposal.

  • Use the encryption password as the screen lock / admin password. Replace the admin password with a checkbox for persistence users.
    • Not ideal for security
    • Convenient

I also thought about having "one password to rule them all". But I'm
afraid this would require even more discussion and even more work than
the first options we have, so let's keep this for later...

My thinking was to go with the first option initially and see how things pan out. A lot rests on how we encourage users to set screen lock passwords. Though the more I think about it the more I'm leaning towards always demanding a lock password.

Not me :)

#13 Updated by sajolida 4 months ago

  • Category set to Persistence
  • Assignee set to Gaff

#14 Updated by Gaff 4 months ago

  • Assignee changed from Gaff to sajolida

sajolida wrote:

Without redesigning Linux passwords / sudo significantly it's only possible to have one password!

I don't understand this sentence. Can you rephrase maybe?

"It's only possible for a linux account to have one password" :) Ignore my fluff.

So the only benefit of making the screen locker password persistent is
to have to screen locker enabled automatically when people start Tails.
I see two scenarios where this makes a difference:

  • People leaving their computer unattended [...]
  • People closing their laptop and putting it in their bag [...]

Also:

  • People forced to abandon their laptop under duress (fire alarm, arrest while in use, ...). Granted in this scenario locking the computer 30 minutes later is unlikely to save them - but it's certainly better than nothing!
  • People who fall asleep while using their laptop (admit it - we've all done this! ;)).

So what about asking the user what they want to do?

We could check whether the administration password that was entered is
the same as the persisted password:

  • If the passwords are the same, don't ask anything and start Tails.
  • If the passwords are different, ask the user what to do: [...]

What do you think?

We could, but it's a bunch of UX work for an edge case. And as you point out it means the tails greeter would need to load persistent settings. It's not that surprising that the admin password trumps the persisted password, and the user will have recently typed it in anyway - so I don't think it's worth the effort.

  • When you unlock the greeter it loads and persisted password, and if found replaces the "administration password" option with an "enable administration" checkbox.
    • This is neat, although leaves no user friendly way to replace forgotten passwords.

I think that this option would require more evolved changes in Tails
Greeter [...]

I'm inclined to agree - not worth the cost IMO.

  • Use the encryption password as the screen lock / admin password. Replace the admin password with a checkbox for persistence users.
    • Not ideal for security
    • Convenient

I also thought about having "one password to rule them all". But I'm
afraid this would require even more discussion and even more work than
the first options we have, so let's keep this for later...

I agree that this would be controversial. However thinking about it more - it might be better to use the persistence password than no password at all!

  • Always demand a screen lock password (if none is persisted). Replace the admin password with a checkbox. Add options to replace persisted passwords.
    • Good for security, follows the Tails threat model
    • It is an extra hurdle for users. Though users are often used to entering passwords when setting things up.
    • Means we could retire the non-standard screen lock password stuff and replace it with regular gnome.

I really want to avoid doing this. Thankfully I think that we have
better options to consider. If it was the only option, I would probably
reject this proposal.

Can you explain why?

I guess it comes down to philosophy. I firmly believe that an automatic screen lock, plus a deadman switch (#15488), are as important as many of the other defences that tails implements. Tails is after all aimed at non-expert users and whilst there's no cure for bad opsec discipline everything we can do to assist users is a bonus.

#15 Updated by segfault 4 months ago

sajolida wrote:

  • When an administrative password is set any persisted password is ignored.
    • This is slightly surprising, but only affects uses who use the admin option (which should be used rarely).
    • Simple to implement
  • When the admin password is set the persisted password is replaced.
    • The danger here is the users may not know this has happened

So what about asking the user what they want to do?

We could check whether the administration password that was entered is
the same as the persisted password:

  • If the passwords are the same, don't ask anything and start Tails.
  • If the passwords are different, ask the user what to do:
  1. Ignore the persisted password = Use the administration password for
    administration and unlocking the screen. If people always set an
    administration password (like I do), they will quickly get bothered by
    this message but can disable the persisted password.
  1. Replace the persisted password with the new administration password.
    That would also serve as a recovery mechanism for the persisted
    password in a way...

I like to give the choice to the user, but instead of asking after they entered a password I would prefer giving them the following choices in the greeter, if there is already a persisted password:

  1. Enable administration access (enables sudo with the persisted password)
  2. Reset password (changes the persisted password, in case the user forgot it)

If there is no persisted password yet, the option would look like it currently does (Set password). But I think in that case the password should also be persisted, if that was enabled in the persistence settings. So the next time the user boots, it would be the two choices from above.

In this design, we should use the same name for the password in both the greeter and the screen locker dialog (because it would be the same password), for example user password.

What do you think?

#16 Updated by sajolida 4 months ago

  • Subject changed from user screen lock password not saved / persisted to Persistence feature for screen locking password

Improving the title.

#17 Updated by sajolida 4 months ago

Answering to Gaff:

  • People who fall asleep while using their laptop (admit it - we've all done this! ;)).

Indeed :)

So what about asking the user what they want to do?

We could check whether the administration password that was entered is
the same as the persisted password:

  • If the passwords are the same, don't ask anything and start Tails.
  • If the passwords are different, ask the user what to do: [...]

What do you think?

We could, but it's a bunch of UX work for an edge case.

With the introduction of the "Additional Software" feature in Tails 3.9,
hopefully many more people will set an administration password (at least
some of the times), people who are otherwise not used to Linux and doing
stuff as root, and this might not be an edge case anymore.

And as you point out it means the tails greeter would need to load persistent settings.

The problem that I was pointing out with Tails Greeter inspecting the
content of the persistence is about doing this while the main window of
the Greeter is displayed.

When you start Tails, the persistence is locked and Tails Greeter
doesn't know whether there's a persistent password. It could only know
this after you unlock your persistence. Then Tails Greeter would have to
adjust its UI accordingly.

I don't think this is much of a technical problem but it would be more
complicated for the user. For example, the interface for the
administration password is hidden by default and might change invisibly
depending on whether the persistence is unlocked already or not. The
user might set an administration password before unlocking the
persistence, etc. The user might click "Start Tails" without clicking
"Unlock" and benefit from the automatic unlocking of the persistence by
then (that's what I do all the time). It's add much more complexity to
the UX problem...

In my solution, I'm proposing to inspect the content of the persistence
only after the user clicks "Start Tails". By then we can know for sure
whether there's a persistent password or not.

It's not that surprising that the admin password trumps the persisted password, and the user will have recently typed it in anyway - so I don't think it's worth the effort.

We are not the user and we don't know how surprising it is:

https://www.nngroup.com/articles/false-consensus/

I agree that this would be controversial. However thinking about it more - it might be better to use the persistence password than no password at all!

Agreed. But let's keep this controversial proposal in mind for a
unspecified point in the future :)

  • Always demand a screen lock password (if none is persisted). Replace the admin password with a checkbox. Add options to replace persisted passwords.
    • Good for security, follows the Tails threat model
    • It is an extra hurdle for users. Though users are often used to entering passwords when setting things up.
    • Means we could retire the non-standard screen lock password stuff and replace it with regular gnome.

I really want to avoid doing this. Thankfully I think that we have
better options to consider. If it was the only option, I would probably
reject this proposal.

Can you explain why?

Right now (and unfortunately), it seems like most people using Tails
don't use it with persistence. I don't want to add a question that
people without persistence would have to answer every time.

Especially since we already have a nice design to ask for a screen
locking password when people do that for the first time.

#18 Updated by sajolida 4 months ago

I like to give the choice to the user, but instead of asking after they entered a password I would prefer giving them the following choices in the greeter, if there is already a persisted password:

  • As explained in my previous note, the thing is that you might not know
    whether there is a persistent password or not until the user clicks on
    "Start Tails". How would you handle the user not unlocking the
    persistence until they click on "Start Tails"? Or are you thinking about
    saving the persistent password outside of persistence?
  • Can you explain why you would prefer this in terms of benefits for the
    user?

I'll comment on the rest of your proposal after I understand this better...

#19 Updated by sajolida 4 months ago

  • Assignee changed from sajolida to segfault

#20 Updated by segfault 4 months ago

sajolida wrote:

I like to give the choice to the user, but instead of asking after they entered a password I would prefer giving them the following choices in the greeter, if there is already a persisted password:

  • As explained in my previous note, the thing is that you might not know
    whether there is a persistent password or not until the user clicks on
    "Start Tails". How would you handle the user not unlocking the
    persistence until they click on "Start Tails"?

Ah, I didn't think about that.

  • Can you explain why you would prefer this in terms of benefits for the
    user?
  • It's less surprising
  • It makes it clear to the user what the password they enter will be used for before they enter it
  • They can learn about the password reset feature via the UI, and not only by accidentally stumbling upon it when they enter a different password than the persisted one
  • It doesn't use two different names for the same thing: there would only be a "persisted password", no administration password

#21 Updated by segfault 4 months ago

  • Assignee changed from segfault to sajolida

#22 Updated by sajolida 4 months ago

  • Description updated (diff)
  • Assignee deleted (sajolida)
  • Type of work changed from Discuss to Code

Ah, I didn't think about that.

Ok, then we anyway need to:

1. Implement a dialog between [Start Tails] and the desktop in case people prefer saving a click and don't do [Unlock] in the Greeter.

On top of that we could also:

2. Do smart things with the "Administration Password" dialog in the Greeter in case people take the extra step of clicking [Unlock] before doing [Start Tails].

I would propose to implement #1 as a first iteration because it's needed anyway.

  • Can you explain why you would prefer this in terms of benefits for the
    user?
  • It's less surprising

In your proposal, the "Administration Password" dialog could have two different layouts depending on whether the persistence is unlocked or not. Given that this dialog is hidden until the user displays it, having two different version might also be surprising as well.

Then I think than when it is in its second state (persistence unlocked) it should make it clear why it changed from the original layout.

  • It makes it clear to the user what the password they enter will be used for before they enter it
  • They can learn about the password reset feature via the UI, and not only by accidentally stumbling upon it when they enter a different password than the persisted one> * It doesn't use two different names for the same thing: there would only be a "persisted password", no administration password

You're right on these three, as long as the user takes the extra step of clicking [Unlock] in Tails Greeter instead of benefiting from the automatic unlock when clicking [Start Tails].

I'm updating the description of this ticket with a summary of our discussions. Once we reached an agreement, I'd like to see some prototype code before going into the details of each dialogs, their strings, etc. Just to avoid doing UI work that might not get implemented. But don't rely on what's in the description to be the final UI design, only hopefully the right flow of dialogs.

#23 Updated by segfault 4 months ago

  • Assignee set to sajolida
  • QA Check set to Info Needed

sajolida wrote:

Ah, I didn't think about that.

Ok, then we anyway need to:

1. Implement a dialog between [Start Tails] and the desktop in case people prefer saving a click and don't do [Unlock] in the Greeter.

On top of that we could also:

2. Do smart things with the "Administration Password" dialog in the Greeter in case people take the extra step of clicking [Unlock] before doing [Start Tails].

I would propose to implement #1 as a first iteration because it's needed anyway.

  • Can you explain why you would prefer this in terms of benefits for the
    user?
  • It's less surprising

In your proposal, the "Administration Password" dialog could have two different layouts depending on whether the persistence is unlocked or not. Given that this dialog is hidden until the user displays it, having two different version might also be surprising as well.

Well, that was not my proposal. I now spent some more thought on this and I think we can we can make it work without having #1 at all, by redesigning the Greeter workflow a bit: We could make it a multi-step dialog, adding an "Additional Settings" button left to the "Start Tails" button, which unlocks the persistence partition if a password was set, and then displays the additional settings in the main window. Do you understand what I mean? What do you think about this idea?

#24 Updated by segfault 4 months ago

We could make it a multi-step dialog, adding an "Additional Settings" button left to the "Start Tails" button, which unlocks the persistence partition if a password was set, and then displays the additional settings in the main window.

I think something similar will also be needed when we store the locale settings on the persistent partition (that's what #5501 is about, IIUC).

#25 Updated by intrigeri 4 months ago

I think something similar will also be needed when we store the locale settings on the persistent partition (that's what #5501 is about, IIUC).

#5501 is explicitly about saving these settings "in the Tails system cleartext partition", not on the encrypted persistent one.

#26 Updated by segfault 4 months ago

intrigeri wrote:

I think something similar will also be needed when we store the locale settings on the persistent partition (that's what #5501 is about, IIUC).

#5501 is explicitly about saving these settings "in the Tails system cleartext partition", not on the encrypted persistent one.

Ah, I see. Well, if that's the plan, we can also consider whether we want to store the hashed password on the system partition. My point is that what we want here is basically to persistently store a setting that can be configured by the greeter, which we also want to support for other settings (locale).

#27 Updated by sajolida 3 months ago

  • Assignee changed from sajolida to segfault

Well, that was not my proposal.

Then I need more help to understand it...

I now spent some more thought on this and I think we can we can make it work without having #1 at all, by redesigning the Greeter workflow a bit: We could make it a multi-step dialog, adding an "Additional Settings" button left to the "Start Tails" button, which unlocks the persistence partition if a password was set, and then displays the additional settings in the main window. Do you understand what I mean? What do you think about this idea?

We released a brand new Greeter last year after a very long and painful process of over 2 years (granted our process was very bad). One of the main goal was precisely to have a single window and avoid having a multi-step dialog like we had until Tails 3.0. We also had some extensive collective discussions on the current design, several iterations on the design, and performed some user testing.

So I'm not ready to put all this work in question and change the foundations of the Greeter to accommodate for this feature. Especially while I think that we already have a solid design that's worth being implemented (and tested maybe).

Ah, I see. Well, if that's the plan, we can also consider whether we want to store the hashed password on the system partition. My point is that what we want here is basically to persistently store a setting that can be configured by the greeter, which we also want to support for other settings (locale).

Allowing persisting some data outside of persistence is "potentially hard" (see #5501#note-13) but I don't think anybody really investigated this. I'm personally much more intersted in #5501 than in this ticket, so I would be super happy if you worked on #5501. But otherwise, I propose we stick to a design that saves the persistent password inside the persistence.

Also, at first sight, having a hashed password outside of the persistence looks tiny bit less secure than having it stored inside the persistence. We also never did such a thing before. So I'd like some security discussion that makes it clear that it's ok. For example, would it be more vulnerable to bruce force? Do people use as strong password for locking their screen than for locking their persistence? (I personally don't)

So please tell me if you prefer:

  • Helping me refine the design that is summarized in the description of this ticket
  • Work on #5501 (even a feasibility study would be useful) and lead a security discussion about storing this password outside of persistence

#28 Updated by Gaff 3 months ago

Just to add my 2 cents to this:

  • I can't see any sane way to store password data outside of persistence.
  • Having the greeter load stuff once it has been unlocked (such as locale info, persisted screen lock passwords, ...) is a little tricky but not impossible.

Also a data-point: Android has full disk encryption and is used by millions. The design there is that the persistence-password is also the screen-lock-password. Simple. Perhaps tails should follow Android? I must confess I'm worried about the risk of people shoulder-surfing the persistence password in this scenario.

Another suggestion: How about making the last 3 characters of the persistence password the screen-lock password? It's a system used bye KeyPassX and others. It's simple to understand and setup. If you buy into this then here's what the flow would look like:

1. User unlocks persistence
2. Greeter code sets the account password to the last 3 characters.
3. Admin password is replaced with Admin checkbox (aka enable sudo).
3a - Need to indicate to users that the sudo password is the last 3 characters of their persistence password
4. Lock screen prompt says "please enter the last 3 characters of your persistence password"

This is pretty simple to implement across the board. WDYT?

#29 Updated by Gaff 3 months ago

Alternatively:

1. User unlocks persistence
2. Greeter code sets the account password to the last 3 characters.
3. Leave the Admin as it is, if the user specifies an admin password it will override the last-3-characters password
4. Lock screen prompt says "please enter the last 3 characters of your persistence password"

This is really simple to implement - probably a handful of lines of code! :p

#30 Updated by sajolida 3 months ago

Also a data-point: Android has full disk encryption and is used by millions. The design there is that the persistence-password is also the screen-lock-password. Simple. Perhaps tails should follow Android?

Good point :)

I must confess I'm worried about the risk of people shoulder-surfing the persistence password in this scenario.

Yeap. The persistence password is meant to be typed only once and you
can take extra precautions when typing it. While the screen locking
password is meant to be typed several times and might be harder to
protect from shoulder-surfing, cameras, etc.

I personally use a different screen locking password when I'm at
conferences or in public places because of that.

Another suggestion: How about making the last 3 characters of the persistence password the screen-lock password? It's a system used bye KeyPassX and others. It's simple to understand and setup. If you buy into this then here's what the flow would look like:

As I proposed in #15641#note-17, let's stick to having different
passwords for persistence and screen locking for the time as this might
be a very controversial topic. I'd rather see implemented what we
already agreed upon on this ticket first.

#31 Updated by u 3 months ago

  • Subject changed from Persistence feature for screen locking password to Persistence preset: screen locking password

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