Tumbleweed has adopted SELinux as the default Linux Security Module (LSM) for new installations after a recent snapshot.

The transition was announced on the mailing list in July and marks a significant development for the rolling release. A new announcement on the factory mailing list yesterday confirms this to take place with the release of Tumbleweed snapshot 20250211. This change also applies to the openSUSE Tumbleweed minimalVM, which will ship with SELinux enabled by default.

“Users installing openSUSE Tumbleweed via the ISO image will see SELinux in enforcing mode as default option in the installer,” wrote SELinux Security Engineer Cathy Hu in the email announcement. “If the user prefers to use AppArmor instead of SELinux, they are able to change the selection to AppArmor manually in the installer.”

Tumbleweed has used AppArmor as its default LSM. This marks a shift in the default Mandatory Access Control (MAC) system for new installations as SELinux replaces AppArmor as the default choice. SELinux will be enabled in enforcing mode by default only for new installations. Existing installations will not be affected by the change and will retain the option to select AppArmor during installation if they prefer.

The switch to install SELinux by default is going through implementation and aligns with a decision to grow adoption of SELinux for both SUSE and openSUSE. It’s expected to increase security by confining more services by default. SELinux is known for its rich security features and widespread use in enterprise environments.

The move is expected to bring tighter access controls to Tumbleweed. Users may encounter bugs or issues, but openQA tests for Tumbleweed have played a key role in identifying and resolving potential problems in the early adoption phase.

Contributors were encouraged to report any bugs that arise and can refer to the SELinux bug report guide for help.

There is no plan to change the kernel configuration yet, with the installer handling SELinux activation on new installations.

The community response to this change has been largely positive, though some users, particularly those who rely on highly customized AppArmor profiles, expressed concerns. AppArmor will continue to be supported and users can opt to install it manually if desired.

The change does not affect the Leap 15.x release. The first boot might take a little time. Expect updates for SELinux to roll out with fixes and tweeks over the next several weeks.

Developers of the openSUSE community continue their commitment toward improving legal compliance and software transparency with the release of the Cavil Legal Text dataset on Hugging Face.

This dataset is designed to enhance automated legal text classification, which reduces manual review efforts and improves accuracy in identifying legal snippets within software projects.

“Open sourcing the dataset is cooler than just open sourcing the weights to a model fine-tuned by us because everyone can use it to make their own versions based on whatever open weight model they want,” said Sebastian Riedel, one of the developers behind the project.

The Cavil Legal Text dataset supports Cavil, which is a system built to automate the extraction and classification of potential legal texts in software packages. By leveraging AI, Cavil minimizes false positives when detecting license information, copyright statements and compliance-related content; this ensures that legal experts can focus on critical cases rather than sorting through large amounts of irrelevant data.

With 150,000 labeled samples, the dataset is instrumental in training AI models to distinguish between legal and non-legal text with a high degree of accuracy. It enables legal review workflows by improving text classifications, pattern matching and reduces the dependency of human intervention.

Cavil consists of three key parts: a user-friendly web application with a REST API, a job queue for handling background tasks like pattern matching and analysis, and an AI-powered text classification server that continually improves its ability to recognize legal texts. All these components interact seamlessly through PostgreSQL and HTTP; this allows human experts and lawyers to efficiently validate software licenses at scale.

Currently, Cavil employs a Character-level Convolutional Neural Network (CNN) model in production due to its efficiency and compatibility with existing infrastructure. However, an alternative approach using fine-tuned LLMs is under exploration. The LLM-lawyer experiment suggests that large language models could provide more adaptable and context-aware classifications with less frequent retraining.

The dataset is licensed under GPL-2.0-or-later and is freely available on Hugging Face for researchers, developers, and compliance teams to explore and contribute. Open-source contributors can refine AI classification models, propose new legal text patterns, and support the ongoing improvement of automated legal compliance in software projects.

Those interested can explore the dataset on Hugging Face, read the Cavil documentation, experiment with Llama-3 through the Llama-Lawyer repository, and contribute to openSUSE’s compliance efforts through GitHub.

The promising new package management tool Myrlyn now includes a much-requested feature: repository configuration. Users can now easily manage their repos, adjust priorities, enable auto-refresh, and even add well-known community repositories like packman, openh264, libdvdcss, and NVIDIA; all with Myrlyn’s streamlined UI!

Key Features:

• View repo details, including priority, auto-refresh status, and URL.
• Modify repo settings directly from the interface.
• Add custom repos with libzypp variables like $releasever.
• Select community repos automatically tailored for Leap, Tumbleweed or Slowroll.
• Enable read-only mode for non-privileged users.

Some users have been exclusively managing their systems with Myrlyn, which showcases its reliability. Myrlyn was developed during Hack Week 24 and is a standalone Qt-based package manager, free from YaST dependencies.

Ready to configure your repos? Head to Extras → Configure Repositories (Ctrl+Shift+O) and give it a spin!

texte en français ci desous

After the blog post on the Sauna adventure in 2013 in Marseille (German), this is the 2nd story of unexpected and awkward evenings. Unfortunately, this one is sad and no recommendation to try yourself. To the contrary.

Low value for money, bad service, few people, people smoke inside, 0 out of 5 stars.

When a friend cancelled a dinner and home party invitation as he caught the flu, Jeanne (name changed) and I thought of other plans for Saturday night. We could not agree on a night out for dancing due to divergences on music taste (Jamaican music: one vote in favour, one vote against). Then, I proposed to go instead to the pretenious and stylish Imperial Premium Bar Brussels (map) who would host at this day event orgainsed by ‘Coeur à Coeur’: Grande Soirée Célibataire (on Facebook, on Eventbrite). After some hesitation and some giggling 🤣🤣, Jeanne and I decide to actually give it a try. 4 hours before the start, we can still buy an early bird ticket for 10€. On top, 1.68€ on Eventbrite fees.

The Cloakroom (Part 1)

We plan to get there quite early and Jeanne arrives on time ahead of me. She texts that cloak room is mendatory and I notice to not have any cash with me. Once I found my way to the cloak room in a separate entrace inside the building, I am relieved that they take also card payments. There is no queue and I learn immediately: It is 2€ per piece.

I put my scraf into my cap and stuff both into my heavy winter jacket. I hand my jacket over and proceed to pay contactless. Only then, I notice on my phone, that I have been charged 4€. I remark that I have been charged 4€. The lady on the other side of the desk explains me that it is 2€ per piece. I look at her. She looks at me. We do not understand each other – obviously. She explains then that out of curtesy, my hat would be for free and only my jacket and my scraf would be charged. 2 pieces makes 4€. Her voice lets no doubt on her being serious. I feel cheated for two reasons:

1. Since when do cloakrooms charge also per scarf stuffed in jackets? Is this now a thing?
2. Did she pay so carefully attention of what I put in my pockets and arms of the jacket? Should I be glad that I put my headphones in the pockets before I entered the cloakroom? 😳 I decide to not bring it up.

Instead, I decide that this way of doing cloakroom business is immoral and usury, which – if confirmed – would be prohibted under German law (BGB § 138). Of course, I am not in Germany and I am not aquinted enough with Belgium law. I ask if such unevitable fees should not be stated at the booking page Eventbrite and that this reservation is after all subject to a contract amongst two parties. The lady does not care. It remains totally unclear who would be the contracting party. So I ask instead to speak her superior. The lady tells me that she is her own superior. At this time, the subjective temperature in the cloakroom dropped already significantly. Jeanne texts me if I arrived already. I confirm. Jeanne may be already surrounded by single men. Obviously, Jeanne knows how to defend herself, but I better want to check soon and not get further delayed.

I ask the lady in front of me to issue my a paper receipt and then – if I find the motivation – complain later in writing. In this moment, a man in his 50s steps into the cloakroom. I make an attempt to find a comrade in my endeavour to fight against cloakroom injustice and start to talk to him in French. I say he better ought to be careful and keep his hat – because everything can be a piece and charged separately in this cloakroom. The man is obviously irritated and decides – that may come with the theme of the evening – to side with the lady. He asks rethorically if we would know each other. Then, he offers his jacket to the cloakroom, but keeps his hat on.

Eventually, I get the paper receipt.

The Bar

Eventually, I find Jeanne at the far-out corner. I pass by many tables with mostly men of which some seem to have brought female companions dressed in revealing clothing/style. The purpose of this is not clear to me given the theme of a Singles’ night.

Jeanne tells me how she ordered her distilled beverage. When she complaint that the liquor would barely spread out over the entire glass bottom, she was given a supplementary fill. The she was charged for two of them (for the record: 20€ in total). The bar keeper would offer then an excuse – but only after Jeanne paid the bill.

Prepared with these insights, I get to the bar myself with the goal to buy for us a Coke and a glass of Water. Indeed, the choice of softs is very limited. You got 5 refreshments of the Coca Cola Company to choose from or still or sparkling water from Evian. I have a short moment of feeling triumph, when I recognise that Coke and Water is bottled in this place and there can be no discussion on quantitities this way. I was wrong. The Impérial Premium Bar has at 21h45 no water anymore – at least not from Evian. They propose the much less premium water Chaudfontaine (also owned by Coca Cola) instead (for the same 5€/bottle 33cl). I am not a water gourmet anyway and accept. Unfortunately, this water doesn’t come in bottles. The barkeeper opens the 2cl Coke bottle, puts it on the bar and then fills up to a third a glass with water.

So Impérial Premium Bar seems to be consistent on their glass filling practices. Though I am prepared. I ask the bar keeper, if this should be 33cl in this glas. The bar keeper nods. I explain to the bar keeper that if I empty by 2cl Coke bottle in my Coke glass and then fill the water into the Coke bottle, it would need to overflow. The bar keeper looks now self critic and then asks his colleague to find him a larger glass.

The Socialising

Jeanne and I had a chat, we had a sip. Someone else talked for a moment to Jeanne. Otherwise not much happened. It is not clear if anyone from the organisers Coeur à Coeur is in the room (unclear if this would be good or bad). 3 musicians play some classical pieces and some Jazz Mannouche. Occasion for the audience to gather footage for their next Insta/TikTok/X/Facebook stories that give evidence of this privileged evening in the Impérial Premium Bar.

Twice we try out the dance floor in the cellar. For some reason, people smoke here and we only stay 2 songs.

Around midnight, we recognise that the crowd fill not change substantially. Few guests have left already. So we make our way to the exit. We bump into a distant friend of mine who also accompanied someone to this venue. We say hello. We stay a bit. We talk about Salsa at other venues. The girls change numbers. So for Jeanne, it was not all for nothing.

The Cloakroom (Part 2)

Jeanne and I found ourself in a small crowd waiting in front of the closed cloakroom. It is unclear what happened. Then, we learn that the lady from the cloakroom is also the lady from the bar and that the cloakroom is only available every now and then. Eventually, the lady appears and asks us for our cloakroom paper snippets. She gathers a few before she leaves, but unfortunately without the one from Jeanne. The cloakroom stays closed. Jeanne and I try to chase the lady through half of the venue.

Eventually, the lady decides it is easier to open the cloakroom for some time. We all get in at the same time and find our jackets spread out in the room. We manage to find our belongings and leave this place for good.

Dear Tumbleweed users and hackers,

This week, we held back a few snapshots as we were unhappy with the openQA presented results. The main hold-up was a scripting error in gtk3-tools, which was exposed by RPM 4.20. It was bad enough to lead to crashes in multiple applications and thus definitively not something we wanted to release to the users. Once the issue was identified it was – as usual – a straightforward fix and Tumbleweed started rolling again. In total, we delivered 3 snapshots during this week (0130, 0204, and 0205)

The most relevant changes that were part of those snapshots are:

• timezone 2025a
• Meson 1.7.0
• RPM 4.20.0 – as a packager, please familiarize yourself with https://rpm.org/wiki/Releases/4.20.0
• Qt 6.8.2
• fwupd 2.0.5
• Linux kernel 6.13.1
• Mozilla Firefox 135.0
• GStreamer 1.24.12
• Python2 interpreter has been removed for good

The relevant changes coming your way as part of the next few snapshots should include:

• KDE Gear 24.12.2
• KDE Plasma 6.3
• Boost 1.87
• glibc 2.41: please help work out the errors in https://build.opensuse.org/project/show/openSUSE:Factory:Staging:O
• Python 3.13 as the default Python interpreter: Pending issues can be seen at https://build.opensuse.org/project/show/openSUSE:Factory:Staging:A
• The change of default LSM from AppArmor to SELinux is progressing, it’s expected to be switched during the next week

This year, I was back in Brussels. I visited two conferences: CentOS Connect and FOSDEM. As usual, both events were fantastic, with great talks and nice people. And as usual, they were also exhausting and not just for introverts like me. I stayed to Belgium to recover, but that’s another story… :-)

CentOS Connect

Some people still ask me why I visit Red Hat events, especially because I am a proud openSUSE desktop user, while FreeBSD feels the closest to me when it comes to software design and philosophy – not to mention that it is the OS that I have been using the longest (since 1994). The answer is easy: over 70% of syslog-ng users run syslog-ng on RHEL, CentOS or a compatible operating system. This means that regardless of my OS preferences, I have the strongest connections with the Fedora / RHEL / CentOS & Co. communities. And over the past 15 years, many of these professional relationships evolved into friendships.

As expected, the main topic of CentOS Connect was CentOS Stream 10, EPEL 10 and of course, the upcoming RHEL 10 release. To me, the event’s main message was that version 10 is an evolution and not a revolution. In other words, if a piece of software worked on RHEL 9, then there is a very good chance that it will also work on RHEL 10 without any changes. All components were updated to the latest available versions, but there were no groundbreaking changes like the introduction of systemd a decade ago.

Last year, I started experimenting with Alma UBI / RHEL UBI containers for syslog-ng. This year, I plan to keep going and check these containers in a Kubernetes environment. Knowing our users, the obvious choice would be Red Hat OpenShift. Just as testing and developing on CentOS Stream is recommended for those targeting RHEL, OKD is the way to go for those who want to support a new OpenShift version from day one. I plan to start with OKD.

We already test syslog-ng on Fedora Rawhide and CentOS Stream 9 before each commit: https://www.syslog-ng.com/community/b/blog/posts/rolling-rpm-platforms-added-to-the-syslog-ng-package-build-system Creating automatic tests for OKD / OpenShift will be a bit more challenging, but I hope to start testing them at least manually soon.

As an introvert, I easily get people overdose. Luckily, there was a beautiful botanical garden right next to the CentOS Connect venue:

FOSDEM

This year, I presented syslog-ng in the BSD devroom. As I mentioned earlier, I have a special bond with FreeBSD, as I have been using it for the past 31 years. A few months ago, I was at EuroBSDCon, where I was asked if we could add a syslog-ng source for FreeBSD audit logs. I did it as soon as I got back from the conference: https://www.syslog-ng.com/community/b/blog/posts/freebsd-audit-source-for-syslog-ng I presented this effort at FOSDEM and also added some information on how to make it general, that is how to integrate any application output with syslog-ng. After my talk, I had some great discussions with happy users inspired by my syslog-ng talks and one of our contributors. Expect some news about these in the coming months! :-)

Of course, many FOSDEM rooms operated at full capacity and there were quite a few talks which I will watch once their recordings are on-line. I do not want to list individual talks here, just some major takeaways:

• AArch64 packages are available for everything. There was only one project without it, but even they promised to have it utilized in the next few months. Expect some syslog-ng news on this topic… :-)

• Risc-V is getting popular among developers, but it’s still far from being usable for average users.

• Documentation is an integral part of a software release. Without it, a piece of software is useless and not worth releasing. Previously, I only heard this opinion from users and documentation people, so it was good to hear it from developers as well!

• SBOM (Software Bill of Materials) is becoming a hot topic.

• Both admins and developers are now expected to know Kubernetes. Of course, there were some people who complained about it, but for most, it was normal. For me, this means that it’s time to gather some practical semi-production experience about Kubernetes, instead of just simply learning about it… :-)

To summarize both events as simply as possible: I hope to see you again next year! And maybe I’ll also go to Configuration Management Camp…

Table of Contents

• 1) Introduction
• 2) Discovery of the Issue / Relation to GDM Smart Card Authentication
• 3) The PAM_IGNORE Issue in pam_pkcs11
• 4) Affected Distributions and Configurations
• 5) Possible Workaround
• 6) Bugfix
• 7) Lessons Learned
  • On the use of PAM_IGNORE
  • On the use of PAM_SUCCESS
  • Conservative PAM Stack Configuration
• 8) Timeline
• 9) References

1) Introduction

This report is about a regression in pam_pkcs11 version 0.6.12. In this release the implementation of pam_sm_authenticate() has been changed to return PAM_IGNORE in many exit paths, which can lead to a complete authentication bypass in some scenarios. This report is based on upstream Git tag “pam_pkcs11-0.6.12”. A bugfix is found in release 0.6.13.

Whether this issue can be exploited is a complex question that depends a lot on the system configuration. The following section gives some insight into how we discovered the issue and why its severity can be high in some circumstances. Section 3) looks in detail into the issue found in pam_pkcs11. The rest of the report explores which Linux distributions might be affected by the issue, a possible workaround and the upstream bugfix. Finally we will be taking a look at the lessons that can be learned from this finding.

2) Discovery of the Issue / Relation to GDM Smart Card Authentication

Fellow SUSE engineer Marcus Rückert uses a YubiKey for login at his openSUSE Tumbleweed desktop system. In October 2024 he noticed a change in behaviour in his GDM login setup. By digging a bit deeper he noticed that in some situations login was possible without entering a password or using his YubiKey at all.

While analysing the issue we found that there is a bug (or a feature?) in GDM 3 that causes YubiKeys to be treated as smart cards. This is one ingredient that comes into play here. A number of Linux distributions use a dedicated “gdm-smartcard” PAM stack configuration file for smart card login in GDM. On openSUSE we rely on pam_pkcs11 as the sole (proper) authentication module in this gdm-smartcard PAM stack. It took us a while to understand where exactly this gdm-smartcard PAM stack is used in GDM. The logic to select this PAM stack is found in a wholly different Gnome component, namely gnome-shell. There, some JavaScript is responsible for detecting smart cards via the D-Bus interface of the gnome-settings-daemon, and for changing the authentication mode of GDM.

We reproduced the situation by using smart card emulation in a QEMU Virtual machine, to be able to achieve proper smart card detection in both GDM and pam_pkcs11. As soon as the smart card is properly setup in the system, GDM switches into smart card authentication mode (support for this is enabled by default). A user list is no longer shown in the display manager, instead the username has to be entered manually. After entering the username, the “gdm-smartcard” PAM stack is executed, and with it pam_pkcs11. No password is asked for and login succeeds.

What happens in this test setup, as well as in the real life setup using a YubiKey, is that pam_pkcs11 stops execution after logging “Failed to initialize crypto” and, surprisingly, login succeeds. The reason for this lies in pam_pkcs11, as is described in the next section.

We did not investigate why exactly the “initialize crypto” error occurs, as we don’t believe it is relevant for the security issue. Even when errors occur, the outcome of the PAM stack execution shouldn’t allow authentication without providing credentials.

3) The PAM_IGNORE Issue in pam_pkcs11

The successful login without proper authentication in pam_pkcs11 stems from a change that found its way into pam_pkcs11 version 0.6.12. The issue has been introduced with commit bac6cf8 (note that there seems to exist an artifact in the upstream Git repository: a seemingly identical commit 88a87d5 in the commit log on “master”).

With this change, many exit paths of the pam_sm_authenticate() function now return PAM_IGNORE instead of PAM_CRED_INSUFFICIENT. In particular, the code found at line 284 means that the default return value on error conditions is PAM_IGNORE, if there is no “login token name”:

if (!configuration->card_only || !login_token_name) {
    /* Allow to pass to the next module if the auth isn't
       restricted to card only. */
    pkcs11_pam_fail = PAM_IGNORE;
} else {
  pkcs11_pam_fail = PAM_CRED_INSUFFICIENT;
}

The card_only flag refers to a module parameter, whose meaning seems to have changed over time and is no longer fully conforming to what is documented. It is enabled in the “gdm-smartcard” stack, thus this part of the if condition will not trigger. The background of the login_token_name is that the PAM module contains special logic for unlocking the screen saver, but only if the session login was performed using pam_pkcs11. This will always be false during initial login, and thus this part of the if condition applies in this case.

When a PAM module returns PAM_IGNORE, its outcome should not be used to determine the result of the PAM stack execution. openSUSE uses the required control setting for pam_pkcs11 in its “gdm-smartcard” configuration. In extended PAM syntax required is expressed like this:

    required
        [success=ok new_authtok_reqd=ok ignore=ignore default=bad]

When pam_pkcs11 returns PAM_IGNORE then the “required” control setting no longer results in what the average administrator will expect, namely that authentication fails if no successful smart card authentication is possible.

What happens instead depends on the rest of the modules present in the “auth” section on the PAM stack. When no other PAM module at all is on the stack, then authentication fails, because the PAM library expects at least one decisive return value from any module on the stack. When there is another PAM module on the stack that actually authenticates, then that module will set a failed state if no credentials are provided, thereby preventing successful login.

To judge the situation with the “gdm-smartcard” PAM stack, let’s look more closely at its “auth” section:

auth       requisite                   pam_faillock.so      preauth
auth       required                    pam_pkcs11.so        wait_for_card card_only
auth       required                    pam_shells.so
auth       requisite                   pam_nologin.so
auth       optional                    pam_permit.so
auth       required                    pam_env.so
auth       [success=ok default=1]      pam_gdm.so
auth       optional                    pam_gnome_keyring.so

There are a lot of other modules configured, alas, none of them is actually authenticating. These are what we like to call “utility modules” in this discussion: they provide support functions. Examples are the pam_faillock module which checks whether excess authentication errors occurred, or pam_gnome_keyring which attempts to intercept the cleartext password used for login to transparently unlock the user keyring. Commonly, such modules return PAM_SUCCESS in most situations. As a result, when pam_pkcs11 returns PAM_IGNORE, the overall outcome of the PAM authentication will become PAM_SUCCESS, supplied by non-authenticating modules in the “gdm-smartcard” PAM stack.

Below the code location in pam_sm_authenticate() function shown above, only two code paths return something other than PAM_IGNORE:

• in line 510 if pkcs11_login() fails
• in line 695 if verify_signature() fails

Both return paths will reset pkcs11_pam_fail to a safe PAM_AUTH_ERR value. The following is a list of all the other return paths which will return PAM_IGNORE:

• line 305: if a user is logging in from remote, or can control the DISPLAY environment variable (e.g. in sudo context).
• line 316: if the crypto_init() call fails.
• line 328: if a screen saver context is detected and no login token is recorded, then an explicit jump to a PAM_IGNORE return is performed.
• lines 343, 357: if loading or initializing the PKCS#11 module fails.
• line 374: if the configured token is not found and card_only is not set. This might be okay in light of the semantics of card_only, but it is still strange. If system administrators want to make pam_pkcs11 authentication optional then they can do so by using the PAM stack configuration already, by using the optional control setting. Changing the module result semantics this drastically through a seemingly harmless module option is unusual.
• line 416: if no smart card is found even after potentially waiting for it. If a smart card is found, but one of various PKCS#11 library functions or certificate checks fail, then further PAM_IGNORE returns can happen if any of the following operations fail:
  • open_pkcs11_session() (line 432)
  • get_slot_login_required() (line 443)
  • when reading in a password fails (line 471)
  • empty password was read without nullok set (line 486)
  • get_certificate_list() (line 522)
  • pam_set_item(..., PAM_USER, ...) (line 597)
  • match_user() (line 613)
  • (no matching certificate found) (line 634)
  • get_random_value() (line 663)
  • sign_value() (line 677)
  • close_pkcs11_session() (line 776)

As this long list demonstrates, it is likely that a local attacker will be able to provoke a PAM_IGNORE return value in pam_pkcs11. For a physical attacker the simplest way is to insert an arbitrary smart card into an existing reader, or attach a peripheral smart card device to the system. The pam_pkcs11 module, if configured, will attempt to access the smart card: if the access fails, then the module returns PAM_IGNORE, resulting in a possible authentication bypass.

4) Affected Distributions and Configurations

The issue was introduced in pam_pkcs11 version 0.6.12, released in July 2021. Any PAM stack that relies on pam_pkcs11 as the only authentication factor will be affected by the issue.

On openSUSE Tumbleweed the issue became apparent only due to the mentioned changes in GDM, which cause YubiKeys to be treated as smart cards in some situations. We believe plugging in any kind of mismatching smart card (or YubiKey) on openSUSE Tumbleweed with GDM as a display manager will allow to bypass login.

Similar situations could occur on other Linux distributions if GDM smart card login is enabled and smart cards are autodetected. Even then, an affected “gdm-smartcard” PAM stack still needs to be in place for the issue to trigger. gdm-smartcard PAM stacks relying on pam_pkcs11 are found in the GDM repository for:

• Arch Linux
• Exherbo Linux
• Linux from Scratch

We tried reproducing the issue on Arch Linux. There the gdm-smartcard PAM stack is installed along with GDM, but there is no pam_pkcs11 package in the standard repositories. It can be installed from the AUR, however. When doing so and also installing the gdm and ccid packages, then the issue becomes basically exploitable as well. We only tested this with a crafted sudo PAM stack, though, since we did not manage to get gdm into smart card authentication mode on Arch Linux. It seems some ingredient was still missing to trigger that.

On Arch Linux we also noticed that the AUR pam_pkcs11 package does not place any default “pam_pkcs11.conf” file into /etc. This also avoids the security problem, because when the slot_num setting is left unconfigured to its built-in default value of -1, then pam_sm_authenticate() will return early with PAM_AUTHINFO_UNAVAIL. On openSUSE we do ship a default configuration of slot_num = 0, however.

Current Fedora Linux does not use pam_pkcs11 for smart card authentication anymore (pam_sss is used instead). Older versions of Fedora might still be affected.

5) Possible Workaround

A quick workaround to prevent login bypass is to use the following PAM stack configuration line instead of what is found e.g. in the gdm-smartcard PAM stacks:

auth [success=ok default=bad] pam_pkcs11.so wait_for_card card_only

Instead of using ignore=ignore as seen in the required control setting shown in section 3), the PAM library will consider ignore (actually any other outcome than success) a bad result for the authentication stack. This will cause authentication to fail even if pam_pkcs11 returns PAM_IGNORE.

6) Bugfix

After extensive discussions about the nature of the problem and potential compatibility issues, upstream arrived at a rather straightforward bugfix which is found in commit 2ecba68d40. Basically the PAM_IGNORE return values have been changed into PAM_CRED_INSUFFICIENT again.

This bugfix is part of upstream release 0.6.13, which also fixes another vulnerability in the PAM module, which has been discovered independently.

7) Lessons Learned

We could not find any clear advice in PAM admin or developer documentation regarding the proper use of PAM_IGNORE. Therefore we try to give an overview of the current situation and suggested best practices in this section.

On the use of PAM_IGNORE

As there have been doubts if pam_pkcs11 is to blame for its use of PAM_IGNORE, we made a survey of other PAM modules packaged in openSUSE. We found one PAM module, pam_u2f, that also had problematic uses of PAM_IGNORE in error situations and we published the issue already in a previous report. This report already resulted in a discussion on the oss-security mailing list about possible structural problems when implementing PAM modules.

Apart from this we found the following uses of PAM_IGNORE:

Core PAM Modules

• pam_wheel: this is only kind of a filter module, such that non-root will be denied, while for root it returns PAM_IGNORE; the actual authentication decision is made by other modules.
• pam_sepermit: returns PAM_IGNORE if users are not listed in the configuration file.
• pam_lastlog: uses PAM_IGNORE if the lastlog file (in a privileged location) cannot be read.
• pam_userdb: returns PAM_IGNORE if no database is configured.
• pam_listfile: returns PAM_IGNORE if the user about to login does not match the configured criteria.

Third Party PAM Modules

• pam_google_authenticator: returns PAM_IGNORE if there is no state file and the nullok option is passed the module.
• nss-pam-ldapd: returns PAM_IGNORE if the user is unknown or no auth info is available, but only if explicitly configured to do so (cfg->ignore_authinfo_unavail, cfg->ignore_unknown_user)
• pam_krb5:
  • returns PAM_IGNORE if the user it not known, but only if options->ignore_unknown_principals is set.
  • returns PAM_IGNORE if a minimum_uid is configured and the user doesn’t match that.
• pam_radius: returns PAM_IGNORE if the network is unavailable and ignore has been explicitly configured via the localifdown option.
• pam_yubico: returns PAM_IGNORE if there are no tokens for the user and the nullok option is passed to the module.

As can be seen from this list, most PAM modules only return PAM_IGNORE if there is an explicit opt-in either through a configuration option or a setting in a privileged configuration file. Most of the time the meaning of the return value is that the authentication mechanism is not configured at all, or not configured for the user that is authenticated. Such configurations can only be used in a safe way if the module in question is an optional authentication mechanism, and a fallback PAM module for authentication is present on the stack.

From the issues seen in pam_pkcs11 and pam_u2f we believe it is especially important for PAM module implementations to take care not to use PAM_IGNORE in unclear error situations, since local or physically present attackers might be able to trigger them.

On the use of PAM_SUCCESS

PAM modules that only serve utility functions but do not actually authenticate could consider not returning PAM_SUCCESS but PAM_IGNORE instead. This would avoid unintended successful authentication in a situation like described in this report. It seems natural to PAM module authors to return PAM_SUCCESS if nothing in their module failed, however. A lot of modules work this way and changing them all would be a big effort.

Conservative PAM Stack Configuration

Sadly PAM can be difficult to understand for non-developers and sometimes even for PAM module authors. Even more so admins and integrators should be careful when writing PAM stacks, especially when less common PAM modules are used as the only authentication requirement. Extended PAM syntax like used in our suggested workaround could be used in such situations for hardening purposes, to make sure no unexpected authentication outcomes can occur.

8) Timeline

9) References

• pam_pkcs11 repository
• pam_pkcs11 GitHub Security Issue Discussion and Advisory
• upstream bugfix for the issue
• upstream bugfix release 0.6.13
• problematic gdm-smartcard PAM stack used in openSUSE
• previous blog post about bad PAM_IGNORE use in pam-u2f

Dear Tumbleweed users and hackers,

It seemed like a quiet week to me. Probably people are getting ready to meet up in Brussels for FOSDEM. Make sure to visit the booth area and talk to the people there. We have managed to release 4 snapshots (0124, 0125, 0127, and 0128)

The most relevant changes delivered this week are:

• Mesa 24.3.4
• Mozilla Firefox 134.0.2
• Drop of nscd
• Systemd 257.2
• FWupd 2.0.4+4
• Wine 10.0
• Removal of python 2

The outlook for the future sounds interesting too:

• Meson 1.7.0
• Timezone 2025a
• RPM 4.20: support for declarative build systems. I started playing with this a little bit using meson.
• KDE Plasma 6.3: beta 2 is currently staged
• Change of default LSM from AppArmor to SELinux is progressing, status is tracked at https://bugzilla.opensuse.org/show_bug.cgi?id=1230118.