prelink_selinux(8)

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

okay so this is prelink_selinux(8), straight out of the SELinux Policy prelink collection, and it's literally your whole guide to how SELinux locks down the prelink processes. no cap, it's a good one 🫶

✨ NAME ✨

prelink_selinux — the Security Enhanced Linux Policy for the prelink processes, periodt.

🌸 DESCRIPTION 🌸

Security-Enhanced Linux secures the prelink processes via flexible mandatory access control. that's the whole vibe: flexible, but mandatory. she does not ask twice 💅

The prelink processes execute with the prelink_t SELinux type. you can check if you've got these processes running by executing the ps command with the -Z qualifier. like, -Z is the magic little letter here, don't forget it.

For example:

ps -eZ | grep prelink_t

run that and see who's out there living their prelink_t truth 🦋

🚪 ENTRYPOINTS 🚪

The prelink_t SELinux type can be entered via the prelink_exec_t file type. that's the doorway, bestie — executables with that label walk through it and become prelink_t.

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

/usr/bin/prelink(.bin)?

so yeah, that regex covers both prelink and prelink.bin. iconic ✨

👑 PROCESS TYPES 👑

SELinux defines process types (domains) for each process running on the system. every process gets a little domain fit, and honestly? slay.

You can see the context of a process using the -Z option to ps. yes, -Z again. it's giving main character option.

Policy governs the access confined processes have to files. SELinux prelink policy is very flexible, allowing users to setup their prelink processes in as secure a method as possible. flexible and secure, we love a both/and 💖

The following process types are defined for prelink:

  • prelink_t
  • prelink_cron_system_t
Note: semanage permissive -a prelink_t can be used to make the process type prelink_t permissive. SELinux does not deny access to permissive process types, but the AVC (SELinux denials) messages are still generated. so like, she stops blocking you but she's still taking notes 📝

🎀 BOOLEANS 🎀

SELinux policy is customizable based on least access required. prelink policy is extremely flexible and has several booleans that allow you to manipulate the policy and run prelink with the tightest access possible. tightest access possible, that's the goal, no wasted permissions 🔥

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

setsebool -P secure_mode_insmod 1

both of these are disabled by default btw, so don't come for me if they're off — that's just how she ships 🙈

🗂️ MANAGED FILES 🗂️

The SELinux process type prelink_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 — SELinux is powerful but she is not doing DAC's job for it, bestie 😭

file_type

  • all files on the system

like. literally all files on the system. she's got range 💀

🗃️ FILE CONTEXTS 🗃️

SELinux requires files to have an extended attribute to define the file type. no attribute, no label, no entry, that's the rule.

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 prelink policy is very flexible, allowing users to setup their prelink processes in as secure a method as possible.

📁 EQUIVALENCE DIRECTORIES 📁

prelink policy stores data with multiple different file context types under the /var/log/prelink directory. If you would like to store the data in a different directory you can use the semanage command to create an equivalence mapping. If you wanted to store this data under the /srv directory you would execute the following command:

semanage fcontext -a -e /var/log/prelink /srv/prelink
restorecon -R -v /srv/prelink

see how we do both? semanage writes the mapping, restorecon actually applies it. two steps, both required, don't skip the second one 🫶

⭐ STANDARD FILE CONTEXT ⭐

SELinux defines the file context types for the prelink, 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 prelink_exec_t '/srv/prelink/content(/.*)?'
restorecon -R -v /srv/myprelink_content
Note: SELinux often uses regular expressions to specify labels that match multiple files. so yes, that (/.*)? is doing real work, it's not just cute punctuation ✨

The following file types are defined for prelink:

  • prelink_cache_t — Set files with the prelink_cache_t type, if you want to store the files under the /var/cache directory.
  • prelink_cron_system_exec_t — Set files with the prelink_cron_system_exec_t type, if you want to transition an executable to the prelink_cron_system_t domain.
  • prelink_exec_t — Set files with the prelink_exec_t type, if you want to transition an executable to the prelink_t domain.
  • prelink_log_t — Set files with the prelink_log_t type, if you want to treat the data as prelink log data, usually stored under the /var/log directory.

Paths:

/var/log/prelink(/.*)?, /var/log/prelink.log.*
  • prelink_tmp_t — Set files with the prelink_tmp_t type, if you want to store prelink temporary files in the /tmp directories.
  • prelink_tmpfs_t — Set files with the prelink_tmpfs_t type, if you want to store prelink files on a tmpfs file system.
  • prelink_var_lib_t — Set files with the prelink_var_lib_t type, if you want to store the prelink files under the /var/lib directory.

Paths:

/var/lib/prelink(/.*)?, /var/lib/misc/prelink.*
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 chcon vs. permanent semanage fcontext — know the difference or your labels will ghost you 💀

🛠️ 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. for the girlies who prefer a window over a terminal, no judgement 🌈

💜 AUTHOR 💜

This manual page was auto-generated using sepolicy manpage . — yes the trailing space and the period are in the original, we keep it exactly as-is, character for character, iykyk.

🔗 SEE ALSO 🔗

selinux(8), prelink(8), semanage(8), restorecon(8), chcon(1), sepolicy(8), setsebool(8), prelink_cron_system_selinux(8), prelink_cron_system_selinux(8)

(yes, prelink_cron_system_selinux(8) shows up twice in the original list. she's just that relevant 💅)

and that's the whole page, bestie!! 🎀 this one's from the prelink package, dated 26-10-06, and it lives at prelink_selinux(8) in the manual. go forth and label responsibly, mwah 🫶✨

📦 where this page comes from