udev_selinux(8)

📦
version 20250627+git412.dbf877ab7 · 7 versions
, in opensuse-leap 16.0

💖 udev_selinux — the glow-up edition 💖

Okay so bestie, this is the udev_selinux(8) manual page — yes, the one from the SELinux Policy udev fam — and I'm about to make it make sense. No cap.

🌸 NAME 🌸

udev_selinux — the Security Enhanced Linux Policy for the udev processes, and honestly? It's giving security queen energy.

✨ DESCRIPTION ✨

Security-Enhanced Linux secures the udev processes via flexible mandatory access control. That's the whole vibe.

The udev processes execute with the udev_t SELinux type. You can check if you have these processes running by executing the ps command with the -Z qualifier. Like:

ps -eZ | grep udev_t

Slay. Go check. I'll wait. 💅

🦋 ENTRYPOINTS 🦋

The udev_t SELinux type can be entered via the udev_helper_exec_t, udev_exec_t file types. That's how you get in, iykyk.

The default entrypoint paths for the udev_t domain are the following:

  • /etc/dev.d/.+
  • /etc/udev/scripts/.+
  • /etc/hotplug.d/default/udev.*
  • /usr/bin/udev
  • /usr/bin/udevd
  • /lib/udev/udevd
  • /usr/bin/udevadm
  • /usr/bin/udevinfo
  • /usr/bin/udevsend
  • /lib/udev/udev-acl
  • /usr/bin/udevstart
  • /usr/bin/start_udev
  • /usr/lib/udev/udevd
  • /usr/lib/udev/udev-acl
  • /usr/bin/wait_for_sysfs
  • /usr/lib/systemd/systemd-udevd

Look at all those paths. Obsessed with the organization. 🎀

👑 PROCESS TYPES 👑

SELinux defines process types (domains) for each process running on the system. Main character energy for every single process, honestly.

You can see the context of a process using the -Z option to ps.

Policy governs the access confined processes have to files. SELinux udev policy is very flexible, allowing users to setup their udev processes in as secure a method as possible.

The following process types are defined for udev:

  • udev_t
Lowkey important note, bestie: semanage permissive -a udev_t can be used to make the process type udev_t permissive. SELinux does not deny access to permissive process types, but the AVC (SELinux denials) messages are still generated. So it's like, not really getting away with anything. The receipts still exist. 😭

⭐ BOOLEANS ⭐

SELinux policy is customizable based on least access required. The udev policy is extremely flexible and has several booleans that allow you to manipulate the policy and run udev with the tightest access possible. Let's go through every single one, no skips:

If you want to dontaudit all daemons scheduling requests (setsched, sys_nice), you must turn on the daemons_dontaudit_scheduling boolean. Enabled by default.

setsebool -P daemons_dontaudit_scheduling 1

If you want to control the ability to mmap a low area of the address space, as configured by /proc/sys/vm/mmap_min_addr, you must turn on the mmap_low_allowed boolean. Disabled by default.

setsebool -P mmap_low_allowed 1

If you want to allow system to run with NIS, you must turn on the nis_enabled boolean. Disabled by default.

setsebool -P nis_enabled 1

If you want to disable kernel module loading, you must turn on the secure_mode_insmod boolean. Disabled by default.

setsebool -P secure_mode_insmod 1

If you want to allow unconfined executables to make their heap memory executable — and bestie, doing this is a really bad idea, probably indicates a badly coded executable, but could indicate an attack, and this executable should be reported in bugzilla — you must turn on the selinuxuser_execheap boolean. Disabled by default.

setsebool -P selinuxuser_execheap 1

If you want to allow unconfined executables to make their stack executable — and this should never, ever be necessary, probably indicates a badly coded executable, but could indicate an attack, and this executable should be reported in bugzilla — you must turn on the selinuxuser_execstack boolean. Disabled by default.

setsebool -P selinuxuser_execstack 1

Red flags all around on those last two, but I'm just the messenger. 🚩

🌈 MANAGED FILES 🌈

The SELinux process type udev_t can manage files labeled with the following file types. The paths listed are the default paths for these file types. Note the processes UID still need to have DAC permissions.

  • file_type — literally all files on the system

That's it. That's the list. Main character energy. 👑

💜 FILE CONTEXTS 💜

SELinux requires files to have an extended attribute to define the file type.

You can see the context of a file using the -Z option to ls.

Policy governs the access confined processes have to these files. SELinux udev policy is very flexible, allowing users to setup their udev processes in as secure a method as possible.

🌸 STANDARD FILE CONTEXT 🌸

SELinux defines the file context types for the udev, and if you wanted to store files with these types in a different paths, you need to execute the semanage command to specify alternate labeling and then use restorecon to put the labels on disk.

semanage fcontext -a -t udev_exec_t '/srv/udev/content(/.*)?'
restorecon -R -v /srv/myudev_content
Note: SELinux often uses regular expressions to specify labels that match multiple files. Regex girlies stay winning. 💅

The following file types are defined for udev:

  • udev_etc_t — Set files with the udev_etc_t type, if you want to store udev files in the /etc directories.
  • udev_exec_t — Set files with the udev_exec_t type, if you want to transition an executable to the udev_t domain.

Paths:

  • /usr/bin/udev
  • /usr/bin/udevd
  • /lib/udev/udevd
  • /usr/bin/udevadm
  • /usr/bin/udevinfo
  • /usr/bin/udevsend
  • /lib/udev/udev-acl
  • /usr/bin/udevstart
  • /usr/bin/start_udev
  • /usr/lib/udev/udevd
  • /usr/lib/udev/udev-acl
  • /usr/bin/wait_for_sysfs
  • /usr/lib/systemd/systemd-udevd
  • udev_helper_exec_t — Set files with the udev_helper_exec_t type, if you want to transition an executable to the udev_helper_t domain.

Paths:

  • /etc/dev.d/.+
  • /etc/udev/scripts/.+
  • /etc/hotplug.d/default/udev.*
  • udev_rules_t — Set files with the udev_rules_t type, if you want to treat the files as udev rules data.

Paths:

  • /etc/udev/rules.d(/.*)?
  • /run/udev/rules.d(/.*)?
  • udev_tmp_t — Set files with the udev_tmp_t type, if you want to store udev temporary files in the /tmp directories.
  • udev_var_run_t — Set files with the udev_var_run_t type, if you want to store the udev files under the /run or /var/run directory.

Paths:

  • /run/udev(/.*)?
  • /dev/.udev(/.*)?
  • /run/libgpod(/.*)?
  • /run/PackageKit/udev(/.*)?
  • /dev/.udevdb
  • /dev/udev.tbl
Note: File context can be temporarily modified with the chcon command. If you want to permanently change the file context you need to use the semanage fcontext command. This will modify the SELinux labeling database. You will need to use restorecon to apply the labels. Temporary vs permanent — know the difference, bestie. 🫶

🧚 COMMANDS 🧚

semanage fcontext can also be used to manipulate default file context mappings.

semanage permissive can also be used to manipulate whether or not a process type is permissive.

semanage module can also be used to enable/disable/install/remove policy modules.

semanage boolean can also be used to manipulate the booleans

system-config-selinux is a GUI tool available to customize SELinux policy settings. A whole GUI, because sometimes clicking is self-care. 💖

🎀 AUTHOR 🎀

This manual page was auto-generated using sepolicy manpage.

(I know. Auto-generated and still ate. 💅)

🌟 SEE ALSO 🌟

selinux(8), udev(8), semanage(8), restorecon(8), chcon(1), sepolicy(8), setsebool(8)

That's the whole page, bestie — udev fam, version 26-10-06, brought to you by udev_selinux(8). Go forth and be secure. Periodt. 💖✨

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