Introduce container_write_proc_files interface (bsc#1253469) #416

ca-hu · 2025-11-25T15:32:19Z

account-utils needs to write /proc/<pid_of_containers>/uid_map and gid_map.

We are currently working to confining three systemd services of account-utils in the openSUSE
policy (downstream of fedora policy) and this needs an interface from the container-selinux side.

Context:

Summary by Sourcery

New Features:

Introduce a container_write_proc_files interface for writing uid_map and gid_map under /proc of container processes from account-utils-related services.

sourcery-ai · 2025-11-25T15:32:25Z

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Introduce a new SELinux interface to allow confined services (like account-utils) to write container /proc uid_map and gid_map files via the container-selinux policy.

File-Level Changes

Change	Details	Files
Add a new SELinux interface to permit writing container /proc uid_map and gid_map files.	Define the container_write_proc_files interface with appropriate SELinux permissions to write uid_map and gid_map under /proc for container processes Wire the new interface into the container policy so confined services can use it to manage container UID/GID mappings	`container.if`

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gemini-code-assist · 2025-11-25T15:32:32Z

Summary of Changes

Hello @ca-hu, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new SELinux interface, container_write_proc_files, designed to grant necessary write permissions to /proc files within container runtimes. This is a targeted enhancement to support the account-utils project's ability to manage UID and GID mappings for containers, thereby enabling the proper confinement of its systemd services under the openSUSE policy.

Highlights

New SELinux Interface: Introduced a new SELinux interface named container_write_proc_files to manage permissions for container processes.
Purpose of Interface: This interface allows a specified domain to write to /proc/<PID>/uid_map and gid_map files within a container runtime, which is crucial for setting user and group ID mappings.
Addressing account-utils Needs: The change directly supports the account-utils project, specifically its newidmapd.c component, which requires these write permissions for proper container confinement in openSUSE policy.

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Code Review

This pull request introduces a new SELinux interface, container_write_proc_files, to allow confined services to write to /proc/<pid>/uid_map and gid_map for container processes. While the new interface is useful, the permissions granted are overly broad, which could introduce security risks. I've suggested restricting the permissions to only what is necessary for the intended operation.

gemini-code-assist · 2025-11-25T15:33:14Z

container.if

+		type container_runtime_t;
+	')
+
+	allow $1 container_runtime_t:file write_file_perms;


The write_file_perms macro is overly permissive for the intended purpose of writing to uid_map and gid_map. It grants permissions like create, unlink, and rename, which could lead to unintended and potentially insecure operations on the /proc filesystem for the container runtime process. The linked account-utils code only requires open and write permissions. To follow the principle of least privilege, it's better to grant only the necessary permissions.

allow $1 container_runtime_t:file { open write };

packit-as-a-service · 2025-11-25T15:48:13Z

Tests failed. @containers/packit-build please check.

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lsm5

@ca-hu thanks for the PR. Change LGTM, but needs DCO, could you please signoff on the commit?

@rhatdan @haircommander PTAL.

haircommander · 2025-11-25T18:50:45Z

container.if

+		type container_runtime_t;
+	')
+
+	allow $1 container_runtime_t:file { open write };


the description seems to imply that this account-utils needs to run inside the container, but I'd xpect container_runtime_t to be used by an oci runtime tosetup for the container. can you explain the case a bit more to make sure we're targeting the right type?

no, account-utils runs outside of the containers on the host and newidmapd is used to write to the /proc/<pid_of_container_runtime>/uid_map of the container runtime on the host for UID mapping between host and containers. and the /proc of the container runtime is labelled as container_runtime_t

see: https://www.thkukuk.de/blog/no_new_privs/

account-utils needs to write /proc/<pid_of_containers>/uid_map and gid_map https://github.com/thkukuk/account-utils/blob/bf57c14f254570b4e5ad24925d8e481bff2ab828/src/newidmapd.c#L216 Signed-off-by: Cathy Hu <cathy.hu@suse.com>

packit-as-a-service · 2025-11-26T11:06:18Z

Ephemeral COPR build failed. @containers/packit-build please check.

packit-as-a-service · 2025-11-26T11:06:18Z

Ephemeral COPR build failed. @containers/packit-build please check.

packit-as-a-service · 2025-11-26T11:06:18Z

Ephemeral COPR build failed. @containers/packit-build please check.

lsm5 · 2025-11-26T14:49:47Z

/packit build
/packit test

packit-as-a-service · 2025-11-26T15:05:30Z

Tests failed. @containers/packit-build please check.

haircommander · 2025-11-26T16:09:16Z

LGTM @lsm5 are you worried about the fedora failures?

lsm5 · 2025-11-26T16:38:34Z

LGTM @lsm5 are you worried about the fedora failures?

looks like the ELN image changed the rootless user. Can be fixed elsewhere.

lsm5

LGTM

lsm5

/lgtm

openshift-ci · 2025-11-26T16:39:14Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ca-hu, lsm5, sourcery-ai[bot]

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lsm5 · 2025-11-26T16:40:55Z

wonder if something's wrong with mergebot. Alternatively, might be good to follow whatever podman's gonna do for mergebot replacement.

lsm5 · 2025-11-26T16:42:58Z

@ca-hu would you like a new release cut right away?

ca-hu · 2025-11-26T16:54:43Z

@ca-hu would you like a new release cut right away?

sure if that is fine with you, thanks!

lsm5 · 2025-11-26T18:51:45Z

/cherrypick rhaos-maint

openshift-cherrypick-robot · 2025-11-26T18:52:25Z

@lsm5: new pull request created: #418

In response to this:

/cherrypick rhaos-maint

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sourcery-ai bot approved these changes Nov 25, 2025

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ca-hu marked this pull request as draft November 25, 2025 15:36

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ca-hu force-pushed the account-utils-set-uidmap branch from 9c06175 to 4d92724 Compare November 25, 2025 15:39

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ca-hu force-pushed the account-utils-set-uidmap branch from 4d92724 to c6349ab Compare November 26, 2025 08:23

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openshift-merge-bot bot merged commit d72cbcb into containers:main Nov 26, 2025
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openshift-cherrypick-robot mentioned this pull request Nov 26, 2025

[rhaos-maint] Introduce container_write_proc_files interface (bsc#1253469) #418

Merged

Introduce container_write_proc_files interface (bsc#1253469) #416

Introduce container_write_proc_files interface (bsc#1253469) #416

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