Red Hat Bugzilla – Bug 475803
fingerprint authentication in PolicyKit dialogs leads to lockup
Last modified: 2013-03-05 22:57:32 EST
As you said,
The problem is that we have a nice loop.
- UI asks PolicyKit for auth
- auth uses pam, thus pam_fprintd
- pam_fprintd talks to fprintd
- fprintd needs PolicyKit ack
By default fprintd should allow users in an active session on the local console access. I mean, why is it useful to lock down access to local users? I can see why it's useful to lock down access to remote users but...
(it's actually a serious question, what kind of threat model are we looking at here? I'm not a domain expert so I don't know.)
Also, I think it's a pam_fprintd bug that there's a loop. If polkit tells fprintd that the user isn't authorized, it should tell it to pam_fprintd. Then pam_fprintd should back out and PAM should fall back to unix_passwd.
(Then you can enter your UNIX password in order to then swipe your finger or type your password again! Very useless, I know!)
(In reply to comment #1)
> By default fprintd should allow users in an active session on the local console
> access. I mean, why is it useful to lock down access to local users?
It's not useful, and that's not what we do by default. but it's possible using the PolicyKit GNOME UI, so any admin could screw up their system.
> I can see
> why it's useful to lock down access to remote users but...
> (it's actually a serious question, what kind of threat model are we looking at
> here? I'm not a domain expert so I don't know.)
> Also, I think it's a pam_fprintd bug that there's a loop.
We exit the loop as soon as the call to VerifyStart fails.
> If polkit tells
> fprintd that the user isn't authorized, it should tell it to pam_fprintd. Then
> pam_fprintd should back out and PAM should fall back to unix_passwd.
Which is what it does.
> (Then you can enter your UNIX password in order to then swipe your finger or
> type your password again! Very useless, I know!)
So do I. This bug wouldn't happen by default, only when the admin changes the default PolicyKit config.
This bug appears to have been reported against 'rawhide' during the Fedora 11 development cycle.
Changing version to '11'.
More information and reason for this action is here:
I believe this is fixed in PolicyKit 0.92. Not sure if it is feasible (or worthwhile) to consider backporting the fix to the F11 polkit.
I'm not sure if I understand the comment #2 correctly, but the definitely happens here once I enrol a fingerprint for root. thinkfinger worked fine btw.
David was mentioning changes in the PAM stack for the polkit in F12.
Yeah, it works in F-12. On the other hand, there is no way to auth with password without failing the swipe 3 times (upek_ts), but that's a separate issue.
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