Latest revision as of 16:36, 2 February 2023

Remove pam_console

Summary

Remove pam_console as it is not enabled by default, can be replaced by systemd and has security issues.

Owner

Name: Iker Pedrosa
Email: ipedrosa@redhat.com

Current status

Targeted release: Fedora Linux 39
Last updated: 2023-02-02
devel thread
FESCo issue: #2945
Tracker bug: #2166692
Release notes tracker: #965

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 Write Display Managers and Write Desktop Environments.

In 2007 there was a 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 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: #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.

@@ Line 1: / Line 1: @@
-<!-- The actual name of your proposed change page should look something like: Changes/Your_Change_Proposal_Name.  This keeps all change proposals in the same namespace -->
 = Remove pam_console =
-{{Change_Proposal_Banner}}
 == Summary ==
-Remove pam_console as it's broken and no longer under use.
+Remove pam_console as it is not enabled by default, can be replaced by systemd and has security issues.
 == Owner ==
@@ Line 17: / Line 13: @@
 == Current status ==
-[[Category:ChangePageIncomplete]]
+[[Category:ChangeAcceptedF39]]
+<!-- TODO: -->
 <!-- When your change proposal page is completed and ready for review and announcement -->
 <!-- remove Category:ChangePageIncomplete and change it to Category:ChangeReadyForWrangler -->
@@ Line 26: / Line 23: @@
 [[Category:SystemWideChange]]
-* Targeted release: [https://docs.fedoraproject.org/en-US/releases/f<VERSION>/ Fedora Linux <VERSION>]
+* Targeted release: [https://docs.fedoraproject.org/en-US/releases/f39/ Fedora Linux 39]
 * Last updated: <!-- this is an automatic macro — you don't need to change this line -->  {{REVISIONYEAR}}-{{REVISIONMONTH}}-{{REVISIONDAY2}}
 <!-- After the change proposal is accepted by FESCo, tracking bug is created in Bugzilla and linked to this page
@@ Line 34: / Line 31: @@
 ON_QA -> change is fully code complete
 -->
-* FESCo issue: <will be assigned by the Wrangler>
+* [https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/thread/3MV5G32UF2TQ3U7JZXPRLQWCQUPR7QT2/ devel thread]
-* Tracker bug: <will be assigned by the Wrangler>
+* FESCo issue: [https://pagure.io/fesco/issue/2945 #2945]
-* Release notes tracker: <will be assigned by the Wrangler>
+* Tracker bug: [https://bugzilla.redhat.com/show_bug.cgi?id=2166692 #2166692]
+* Release notes tracker: [https://pagure.io/fedora-docs/release-notes/issue/965 #965]
 == Detailed Description ==
-Currently, the pam_console module is broken as one of the files needed to define the permissions (50-default.perms) is not installed in the distribution. Indeed, there was a [[Releases/FeatureRemovePAMConsole|System-Wide Change]] proposal in 2007 to remove pam_console, but it wasn't finished.
+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-environments/ 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 ==
@@ Line 45: / Line 54: @@
 == Benefit to Fedora ==
-<!-- What is the benefit to the distribution?  Will the software we generate be improved? How will the process of creating Fedora releases be improved?
+By removing pam_console and moving to systemd-logind the distribution would benefit from the multi-seat functionality and higher security levels.
-      Be sure to include the following areas if relevant:
-      If this is a major capability update, what has changed?
-           For example: This change introduces Python 5 that runs without the Global Interpreter Lock and is fully multithreaded.
-      If this is a new functionality, what capabilities does it bring?
-           For example: This change allows package upgrades to be performed automatically and rolled-back at will.
-      Does this improve some specific package or set of packages?
-           For example: This change modifies a package to use a different language stack that reduces install size by removing dependencies.
-      Does this improve specific Spins or Editions?
-           For example: This change modifies the default install of Fedora Workstation to be more in line with the base install of Fedora Server.
-      Does this make the distribution more efficient?
-           For example: This change replaces thousands of individual %post scriptlets in packages with one script that runs at the end.
-      Is this an improvement to maintainer processes?
-           For example: Gating Fedora packages on automatic QA tests will make rawhide more stable and allow changes to be implemented more smoothly.
-      Is this an improvement targeted as specific contributors?
-           For example: Ensuring that a minimal set of tools required for contribution to Fedora are installed by default eases the onboarding of new contributors.
-     When a Change has multiple benefits, it's better to list them all.
-     Consider these Change pages from previous editions as inspiration:
-     https://fedoraproject.org/wiki/Changes/Annobin (low-level and technical, invisible to users)
-     https://fedoraproject.org/wiki/Changes/ParallelInstallableDebuginfo (low-level, but visible to advanced users)
-     https://fedoraproject.org/wiki/Changes/VirtualBox_Guest_Integration (primarily a UX change)
-     https://fedoraproject.org/wiki/Changes/NoMoreAlpha (an improvement to distro processes)
-     https://fedoraproject.org/wiki/Changes/perl5.26 (major upgrade to a popular software stack, visible to users of that stack)
--->
-<!-- TODO: the module is not included into the upstream Linux PAM sources, thus it is not maintained by the community.
-On top of that, it is just used in Fedora and some of its derivatives.
-This should be managed by the HAL ACL -->
 == Scope ==
 * Proposal owners:
-<!-- What work do the feature owners have to accomplish to complete the feature in time for release?  Is it a large change affecting many parts of the distribution or is it a very isolated change? What are those changes?-->
+# 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: <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+* Other developers:
-<!-- What work do other developers have to accomplish to complete the feature in time for release?  Is it a large change affecting many parts of the distribution or is it a very isolated change? What are those changes?-->
+# Identified software package maintainers should review and merge the pam_console removal PRs.
-* Release engineering: [https://pagure.io/releng/issues #Releng issue number] <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+* Release engineering: [https://pagure.io/releng/issue/11223 #11223]
-<!-- Does this feature require coordination with release engineering (e.g. changes to installer image generation or update package delivery)?  Is a mass rebuild required?  include a link to the releng issue.
-The issue is required to be filed prior to feature submission, to ensure that someone is on board to do any process development work and testing and that all changes make it into the pipeline; a bullet point in a change is not sufficient communication -->
-* Policies and guidelines: N/A (not needed for this Change) <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+* Policies and guidelines: N/A
-<!-- Do the packaging guidelines or other documents need to be updated for this feature?  If so, does it need to happen before or after the implementation is done?  If a FPC ticket exists, add a link here. Please submit a pull request with the proposed changes before submitting your Change proposal. -->
-* Trademark approval: N/A (not needed for this Change)
+* Trademark approval: N/A
-<!-- If your Change may require trademark approval (for example, if it is a new Spin), file a ticket ( https://pagure.io/Fedora-Council/tickets/issues ) requesting trademark approval from the Fedora Council. This approval will be done via the Council's consensus-based process. -->
-* Alignment with Objectives:
+* Alignment with Objectives: N/A
-<!-- Does your proposal align with the current Fedora Objectives: https://docs.fedoraproject.org/en-US/project/objectives/ ? It's okay if it doesn't, but it's something to consider -->
 == Upgrade/compatibility impact ==
-<!-- What happens to systems that have had a previous versions of Fedora installed and are updated to the version containing this change? Will anything require manual configuration or data migration? Will any existing functionality be no longer supported? -->
+No impact is expected.
-<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 == How To Test ==
-<!-- This does not need to be a full-fledged document. Describe the dimensions of tests that this change implementation is expected to pass when it is done.  If it needs to be tested with different hardware or software configurations, indicate them.  The more specific you can be, the better the community testing can be.
+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).
-Remember that you are writing this how to for interested testers to use to check out your change implementation - documenting what you do for testing is OK, but it's much better to document what *I* can do to test your change.
-A good "how to test" should answer these four questions:
-. What special hardware / data / etc. is needed (if any)?
-. How do I prepare my system to test this change? What packages
-need to be installed, config files edited, etc.?
-. What specific actions do I perform to check that the change is
-working like it's supposed to?
-. What are the expected results of those actions?
--->
-<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 == User Experience ==
-<!-- If this change proposal is noticeable by users, how will their experiences change as a result?
+Users won't experience any change.
- This section partially overlaps with the Benefit to Fedora section above. This section should be primarily about the User Experience, written in a way that does not assume deep technical knowledge. More detailed technical description should be left for the Benefit to Fedora section.
- Describe what Users will see or notice, for example:
-  - Packages are compressed more efficiently, making downloads and upgrades faster by 10%.
-  - Kerberos tickets can be renewed automatically. Users will now have to authenticate less and become more productive. Credential management improvements mean a user can start their work day with a single sign on and not have to pause for reauthentication during their entire day.
- - Libreoffice is one of the most commonly installed applications on Fedora and it is now available by default to help users "hit the ground running".
- - Green has been scientifically proven to be the most relaxing color. The move to a default background color of green with green text will result in Fedora users being the most relaxed users of any operating system.
--->
 == Dependencies ==
-<!-- What other packages (RPMs) depend on this package?  Are there changes outside the developers' control on which completion of this change depends?  In other words, completion of another change owned by someone else and might cause you to not be able to finish on time or that you would need to coordinate?  Other upstream projects like the kernel (if this is not a kernel change)? -->
+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
-<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+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.
-<!-- TODO:
-    https://bugzilla.redhat.com/show_bug.cgi?id=1822209
-    https://bugzilla.redhat.com/show_bug.cgi?id=1822227
-    https://bugzilla.redhat.com/show_bug.cgi?id=1822225 (orphaned and probably it will be retired soon)
-    https://bugzilla.redhat.com/show_bug.cgi?id=1822229 (orphaned)
-    https://bugzilla.redhat.com/show_bug.cgi?id=1822228
--->
 == Contingency Plan ==
-<!-- If you cannot complete your feature by the final development freeze, what is the backup plan?  This might be as simple as "Revert the shipped configuration".  Or it might not (e.g. rebuilding a number of dependent packages).  If you feature is not completed in time we want to assure others that other parts of Fedora will not be in jeopardy.  -->
+* Contingency mechanism: Postpone to the next release.
-* Contingency mechanism: (What to do?  Who will do it?) N/A (not a System Wide Change)  <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+* Contingency deadline: Beta freeze.
-<!-- When is the last time the contingency mechanism can be put in place?  This will typically be the beta freeze. -->
+* Blocks release? No.
-* Contingency deadline: N/A (not a System Wide Change)  <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-<!-- Does finishing this feature block the release, or can we ship with the feature in incomplete state? -->
-* Blocks release? N/A (not a System Wide Change), Yes/No <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 == Documentation ==
-<!-- Is there upstream documentation on this change, or notes you have written yourself?  Link to that material here so other interested developers can get involved. -->
+No documentation.
-<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-N/A (not a System Wide Change)
 == Release Notes ==
-<!-- The Fedora Release Notes inform end-users about what is new in the release.  Examples of past release notes are here: http://docs.fedoraproject.org/release-notes/ -->
+No need to update the release notes for this change.
-<!-- The release notes also help users know how to deal with platform changes such as ABIs/APIs, configuration or data file formats, or upgrade concerns.  If there are any such changes involved in this change, indicate them here.  A link to upstream documentation will often satisfy this need.  This information forms the basis of the release notes edited by the documentation team and shipped with the release.
-Release Notes are not required for initial draft of the Change Proposal but has to be completed by the Change Freeze.
--->

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