Bug 679907 - please add atomic request to plymouth protocol for asking for cached passwords and input passwords
please add atomic request to plymouth protocol for asking for cached password...
Product: Fedora
Classification: Fedora
Component: plymouth (Show other bugs)
Unspecified Unspecified
unspecified Severity unspecified
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Assigned To: Ray Strode [halfline]
Fedora Extras Quality Assurance
Depends On:
Blocks: 677438 749027
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Reported: 2011-02-23 15:15 EST by Lennart Poettering
Modified: 2012-08-07 14:16 EDT (History)
10 users (show)

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Doc Type: Bug Fix
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Last Closed: 2012-08-07 14:16:03 EDT
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Description Lennart Poettering 2011-02-23 15:15:51 EST
Currently, if multiple clients want to query passwords via plymouth at the same time, and want to make use of cached passwords they will first ask for the cached passwords. Then get an empty response. Then rerequest the password from user input. Hence: even though passwords are cached the user will be asked twice.

Here's the request I'd like to see:

A) Client sends to Plymouth the passwords it already knows
B) If Plymouth' cache contains new passwords that do not appear the client's list it sends those back.
C) If Plymouth' cache contains no new passwords it asks the user for one and sends it back.

It is important that the Plymouth does not process any other password requests while B or C are active. Most importantly: it should NOT process requests from other clients if it is currently asking a question to the user. This password entered by the user must already be considered when returning a reply to the caller.

The packet payload in both directions would be really simply, just a list of NUL terminated strings.
Comment 1 Lennart Poettering 2011-02-24 10:38:38 EST
Hmm, here's a simpler idea:

every time plymouth acquires a password it should increase a generation counter. Then, when a client wants to know cached passwords it just passes its last seen generation counter to Plymouth (0 initially). Plymouth then sends all passwords with a newer generation counter back. If there aren't any it asks the user for a new password, and assigns it the next free generation counter id. And in its response it always sends back to the client the newest generation counter it has.


client → server: Hey, give me all passwords with genid > 0
server → client: Hey, here are two. And my generation counter is currently 2.

And since those two were wrong, the client keeps asking:

client → server: Hey, give me all passwords with genid > 2
                 <server asks user for password, since it has no other passwords cached. Then assigns the new password genid 3>
server → client: here's a new one. And my generation counter is currently 3.

Client is happy now.
Comment 2 Lennart Poettering 2011-02-24 19:52:38 EST
The big advantage of the second proposal is that we never have to send passwords we already know from the client to the server. This makes it easier to support similar agents that are unprivileged which then send passwords to clients, but never the other way round.
Comment 3 Bruno Wolff III 2011-04-02 17:22:34 EDT
I am not sure if this is really the same bug I am seeing. I provide a password early in the boot process for the / filesystem. Sometimes I get asked for the /home password later in the boot process, but not always. (This is the place that things used to hang.)
Comment 4 Andy Walls 2011-06-12 22:15:26 EDT
I appear to have a bug related to password caching between systemd and plymouth.

I have a newly installed Fedora 15 x86_64.

I have a number of encrypted LVs:


All use the same LUKS passphrase.

Graphical passphrase entry for / (and swap?) appears to go OK.

When /var needs to get unlocked, plymouth pauses the display of the "f" bubble filling in, and the graphics screen sometimes goes to a black screen.

By pressing the up-arrow key on the keyboard, I get to a text console screen where there is a prompt to enter the passphrase for /var with two * characters already apparently typed.  After backspacing over them and entering the passphase, /var gets unlocked and boot proceeds normally.

Comment 5 Andy Walls 2011-06-13 06:08:54 EDT
I forgot to mention two things:

1. The problem is intermittent.  Sometimes I do not need to type the password in againn at the text console.

2. The volume group and non-encrypted LVs from a previous install are still on the disk in another physical partition but are not in fstab.  The text console show two messges about starting RAID, LVM,...)

Comment 6 Frank Murphy 2011-11-05 08:53:45 EDT
Any update on this problem?

Will the comment from:

work in with grub2?
And which of the /etc/grub.d/* should it go?
Comment 7 Jonas Thiem 2011-11-14 06:46:49 EST
Can we get an estimate when this will be resolved? This has to be by far the biggest regression of Fedora 15 and if it will be around for yet another year, I'll consider moving to another distribution.

Imagine you're in a rather public place and then have to enter your password 4 times, or even 5 times because you typo it once (since hard disk passwords are usually long)! That is such a nuisance and yet it doesn't seem to be an impossible task to fix this.
Comment 8 Frank Murphy 2011-11-20 07:15:37 EST
Have just noticed, on an upgrade from F14 > F15.
The option for "Global Password" is gone.
Which was there on F13,F14
Could that be part of the "plymouth" problem?
Comment 9 Andy Walls 2011-11-20 08:30:45 EST
(In reply to comment #8)
> Have just noticed, on an upgrade from F14 > F15.
> The option for "Global Password" is gone.
> Which was there on F13,F14
> Could that be part of the "plymouth" problem?

It is my understanding the architecture changed in F15.

From what I can tell:

1. The initramfs scripts are responsible for unlocking the root and swap partitions listed on the kernel command line.  The do this by doing something like:

 /bin/plymouth ask-for-password \
                --prompt "$prompt" --number-of-tries=5 \
                --command="/sbin/cryptsetup luksOpen -T1 $device $luksname"

To ask the running plymouthd to prompt for a password.  I assume plymouthd is also capable of caching passwords, so the user isn't asked more than once.

2. Once the system have done a pivot root out of the initramfs filesystem and over to the real root filesystem, systemd is run and it is responsible for unlocking the rest of the partitions.

I assume systemd ultimately invokes systemd-ask-password to prompt for the password.  It has password agents which I assume will ask plymouth for any cached password or to ask plymouth to reprompt the user.  From man systemd-ask-password:

"Existing agents are: a boot-time password agent asking the user for
 passwords using Plymouth; a boot-time password agent querying the user
 directly on the console;..."

I speculate there is a breakdown of communications between the systemd-ask-password boot-time agent for Plymouth and the running plymouthd daemon.  I also will speculate that systemd-ask-password is them falling back to it's console boot-time password agent.

I don't know why turning on plymouth debug fixes the communications for me, but it does.


Comment 10 Fedora End Of Life 2012-08-07 14:16:07 EDT
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