https://fedoraproject.org/wiki/Changes/RemovePamConsole
This document represents a proposed Change. As part of the Changes process, proposals are publicly announced in order to receive community feedback. This proposal will only be implemented if approved by the Fedora Engineering Steering Committee.
== Summary == Remove pam_console as it is not enabled by default, can be replaced by systemd and has security issues.
== Owner == * Name: [[User:ipedrosa| Iker Pedrosa]] * Email: ipedrosa@redhat.com
== Detailed Description == pam_console give users at the physical console additional capabilities when authenticating, and removes those capabilities when the user logs out. The module changes the permissions and ownership of files and devices.
pam_console has some limitations and flaws: * Only one user can have those additional capabilities at the same time (no multi-seat) * Potential security problems of device file ownership if the PAM conversation ending isn't executed * Remove ACL and call revoke() on device nodes for fast-user-switching. This is to prevent the user of the inactive session B spying on the user of the active session A using webcam, sound cards, etc. * As of today the module does nothing because one of the configuration files use to define the permissions (50-default.perms) is not installed in the distribution. Other packages may install their own configuration files to specify the permissions, but I haven't found any.
These additional capabilities that pam_console provides are useful to simplify the work for console users. Usually, the permissions are set for devices like the CD/DVD reader, or the disk drives. This functionality is still useful today, and it should be managed with systemd-logind, rather than with a PAM module. This systemd service takes care of user sessions, multi-seat management, device access management... This would increase the security level of the system, and enable multi-seat for the file and device permissions. For more information on systemd-logind implementation refer to the documentation on how to [https://www.freedesktop.org/wiki/Software/systemd/writing-display-managers/ Write Display Managers] and [https://www.freedesktop.org/wiki/Software/systemd/writing-desktop-environmen... Write Desktop Environments].
In 2007 there was a [[Releases/FeatureRemovePAMConsole|System-Wide Change]] proposal to remove pam_console, but it wasn't finished. My plan is to continue that work and remove the pam_console module.
== Feedback ==
== Benefit to Fedora == By removing pam_console and moving to systemd-logind the distribution would benefit from the multi-seat functionality and higher security levels.
== Scope == * Proposal owners: # Provide PRs to remove pam_console from the PAM stack of the identified software packages (see Dependencies). # Remove pam_console from [https://pagure.io/pam-redhat pam-redhat] project and rebuild the PAM package without it.
* Other developers: # Identified software package maintainers should review and merge the pam_console removal PRs.
* Release engineering: [https://pagure.io/releng/issue/11223 #11223]
* Policies and guidelines: N/A
* Trademark approval: N/A
* Alignment with Objectives: N/A
== Upgrade/compatibility impact == No impact is expected.
== How To Test == No special hardware or configuration is required to test this change. Once the change is in place, check that the pam_console isn't installed in your system (default location: /lib64/security/pam_console.so) and do a user authentication (i.e. graphical interface, su, ssh, and whatever else comes to your mind).
== User Experience == Users won't experience any change.
== Dependencies == This change depends on other packages removing pam_console from their PAM stack. I have identified five packages and I have opened a bugzilla for all of them: * xorg-x11-server - https://bugzilla.redhat.com/show_bug.cgi?id=1822209 * lxdm - https://bugzilla.redhat.com/show_bug.cgi?id=1822227 * xorg-x11-xdm - https://bugzilla.redhat.com/show_bug.cgi?id=1822225 * slim - https://bugzilla.redhat.com/show_bug.cgi?id=1822229 * gdm - https://bugzilla.redhat.com/show_bug.cgi?id=1822228
From the above list only the first item is a blocker as it requires pam_console to succeed in the authentication. In all other cases it is optional, so not removing the module from their PAM stack will only cause a message printed in the security file.
== Contingency Plan ==
* Contingency mechanism: Postpone to the next release. * Contingency deadline: Beta freeze. * Blocks release? No.
== Documentation == No documentation.
== Release Notes == No need to update the release notes for this change.
- As of today the module does nothing because one of the configuration
files use to define the permissions (50-default.perms) is not installed in the distribution. Other packages may install their own configuration files to specify the permissions, but I haven't found any.
So basically, pam_console was obsoleted by systemd-logind eons ago. Not sure why we still ship it then. I guess it can just go away.
For the record, the one third-party RPM I maintain that used to use pam_console for device permissions (libticables2) switched away from pam_console back in 2009! (I had to rework the ACL handling several times between 2009 and 2012, with HAL and ConsoleKit coming and going, then it stabilized on udev rules, using systemd-logind internally.)
pam_console used to be a great selling point for Fedora over other distributions back when it was introduced, but by now, systemd-logind has completely subsumed its functionality.
Kevin Kofler
Ben Cotton wrote:
== Summary == Remove pam_console as it is not enabled by default, can be replaced by systemd and has security issues.
Just to make sure -- pam_console provided an "auth" feature (see https://bugzilla.redhat.com/show_bug.cgi?id=137802 ), which allows to log just once when working on several virtual consoles (and yes, it was 19 years ago :) ). Is it possible with systemd-logind now?
~buc
Hi Dmitry,
If I understand it correctly, what you mean is that once a user is authenticated in a system with pam_console, then all subsequent authentication attempts by this user are successful without having to input the password. This is kind of dangerous, as somebody could open a session for an already authenticated user without them knowing it. I'd recommend you to use pam_timestamp instead, as it offers the same functionality with additional security features (authentication origin, timeout, etc.).
On Tue, Jan 17, 2023 at 3:48 PM Dmitry Butskoy buc@buc.me wrote:
Ben Cotton wrote:
== Summary == Remove pam_console as it is not enabled by default, can be replaced by systemd and has security issues.
Just to make sure -- pam_console provided an "auth" feature (see https://bugzilla.redhat.com/show_bug.cgi?id=137802 ), which allows to log just once when working on several virtual consoles (and yes, it was 19 years ago :) ). Is it possible with systemd-logind now?
~buc _______________________________________________ devel mailing list -- devel@lists.fedoraproject.org To unsubscribe send an email to devel-leave@lists.fedoraproject.org Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue
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Ben Cotton -
Dmitry Butskoy -
Iker Pedrosa -
Kevin Kofler