xserver_selinux(8)

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

🦋 xserver_selinux(8) — SELinux policy for xserver, bestie 🦋

🌸 NAME 🌸

xserver_selinux — the Security Enhanced Linux policy page for the xserver processes. That's the whole name vibe, periodt. 💅

✨ DESCRIPTION ✨

Okay so Security-Enhanced Linux secures the xserver processes via flexible mandatory access control. Iconic of SELinux, honestly.

The xserver processes execute with the xserver_t SELinux type. You can check if you have these processes running by executing the ps command with the -Z qualifier.

For example:

ps -eZ | grep xserver_t

🚪 ENTRYPOINTS 🚪

The xserver_t SELinux type can be entered via the xserver_exec_t file type. It's giving "one special doorway" energy.

The default entrypoint paths for the xserver_t domain are literally these:

/usr/bin/nvidia.*, /usr/bin/Xair, /usr/bin/Xorg, /usr/bin/Xvnc,
/usr/bin/Xephyr, /usr/bin/x11vnc, /usr/X11R6/bin/X, /usr/bin/Xwayland,
/usr/X11R6/bin/Xorg, /usr/X11R6/bin/Xipaq, /usr/libexec/Xorg.bin,
/usr/X11R6/bin/XFree86, /usr/libexec/Xorg.wrap, /usr/X11R6/bin/Xwrapper,
/usr/libexec/gsd-backlight-helper

👑 PROCESS TYPES 👑

SELinux defines process types, aka domains, for each process running on the system. Main character behavior fr fr.

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

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

The following process types are defined for xserver:

  • xserver_t
Note: semanage permissive -a xserver_t can be used to make the process type xserver_t permissive. SELinux does not deny access to permissive process types, but the AVC (SELinux denials) messages are still generated. So yeah, bestie, permissive means "still logs the drama" 💀

🎀 BOOLEANS 🎀

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

  • xserver_execmem — want to allow XServer to execute writable memory? Turn this on. Disabled by default.
setsebool -P xserver_execmem 1
  • xserver_object_manager — want to support X userspace object manager? Turn this on. Disabled by default.
setsebool -P xserver_object_manager 1
  • deny_execmem — want to deny user domains applications to map a memory region as both executable and writable? This is dangerous and the executable should be reported in bugzilla. Turn this on to do that. Disabled by default.
setsebool -P deny_execmem 1
  • mmap_low_allowed — want to control the ability to mmap a low area of the address space, as configured by /proc/sys/vm/mmap_min_addr? Turn this on. Disabled by default.
setsebool -P mmap_low_allowed 1
  • nis_enabled — want to allow the system to run with NIS? Turn this on. Disabled by default.
setsebool -P nis_enabled 1
  • secure_mode_insmod — want to disable kernel module loading? Turn this on. Disabled by default.
setsebool -P secure_mode_insmod 1
  • selinuxuser_execheap — want to allow unconfined executables to make their heap memory executable? Doing this is a really bad idea. Probably indicates a badly coded executable, but could indicate an attack. This executable should be reported in bugzilla. Turn this on if you must. Disabled by default.
setsebool -P selinuxuser_execheap 1
  • selinuxuser_execstack — want to allow unconfined executables to make their stack executable? This should never, ever be necessary. Probably indicates a badly coded executable, but could indicate an attack. This executable should be reported in bugzilla. Turn this on if you must. Disabled by default.
setsebool -P selinuxuser_execstack 1

🔌 PORT TYPES 🔌

SELinux defines port types to represent TCP and UDP ports. Very demure, very mindful.

You can see the types associated with a port by using the following command:

semanage port -l

Policy governs the access confined processes have to these ports. SELinux xserver policy is very flexible, allowing users to set up their xserver processes in as secure a method as possible.

The following port types are defined for xserver:

  • xserver_port_t

Default Defined Ports: tcp 6000-6020 — slay, that's the range. 🌈

📁 MANAGED FILES 📁

The SELinux process type xserver_t can manage files labeled with the following file types. The paths listed are the default paths for these file types. Note: the process's UID still needs to have DAC permissions, iykyk.

file_type

  • all files on the system

🗂️ FILE CONTEXTS 🗂️

SELinux requires files to have an extended attribute to define the file type. It's literally how the labeling works, bestie.

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 xserver policy is very flexible, allowing users to set up their xserver processes in as secure a method as possible.

🎀 STANDARD FILE CONTEXT 🎀

SELinux defines the file context types for xserver. If you wanted to store files with these types in 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 xserver_var_lib_t '/srv/xserver/content(/.*)?'
restorecon -R -v /srv/myxserver_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 xserver:

  • xserver_etc_t — set files with the xserver_etc_t type if you want to store xserver files in the /etc directories.
  • xserver_exec_t — set files with the xserver_exec_t type if you want to transition an executable to the xserver_t domain.

Paths:

/usr/bin/nvidia.*, /usr/bin/Xair, /usr/bin/Xorg, /usr/bin/Xvnc,
/usr/bin/Xephyr, /usr/bin/x11vnc, /usr/X11R6/bin/X, /usr/bin/Xwayland,
/usr/X11R6/bin/Xorg, /usr/X11R6/bin/Xipaq, /usr/libexec/Xorg.bin,
/usr/X11R6/bin/XFree86, /usr/libexec/Xorg.wrap, /usr/X11R6/bin/Xwrapper,
/usr/libexec/gsd-backlight-helper
  • xserver_log_t — set files with the xserver_log_t type if you want to treat the data as xserver log data, usually stored under the /var/log directory.

Paths:

/var/[xgkw]dm(/.*)?, /usr/var/[xgkw]dm(/.*)?,
/var/log/gdm(3)?(/.*)?, /var/log/Xorg.*, /var/log/XFree86.*,
/var/log/lightdm(/.*)?, /var/log/nvidia-installer.log.*
  • xserver_tmpfs_t — set files with the xserver_tmpfs_t type if you want to store xserver files on a tmpfs file system.
  • xserver_var_lib_t — set files with the xserver_var_lib_t type if you want to store the xserver files under the /var/lib directory.
  • xserver_var_run_t — set files with the xserver_var_run_t type if you want to store the xserver files under the /run or /var/run directory.

Paths:

/run/xorg(/.*)?, /run/video.rom
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. Don't skip that step, 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 port can also be used to manipulate the port definitions.
  • semanage boolean can also be used to manipulate the booleans.
  • system-config-selinux is a GUI tool available to customize SELinux policy settings. Iconic little GUI moment. 🌸

💜 AUTHOR 💜

This manual page was auto-generated using sepolicy manpage. Not me writing it by hand, the tooling ate. 💅

🔥 SEE ALSO 🔥

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

Source/version: xserver; date: 26-10-06; manual: xserver_selinux(8). Byeee, go check your contexts bestie 🫶💖

📦 where this page comes from