bootloader_selinux(8)

✨ bootloader_selinux(8) ✨

okay bestie, so like... this is bootloader_selinux, the manual page for the SELinux policy that governs bootloader processes, and honestly? it's giving security, it's giving mandatory access control, it's giving let me explain your whole bootloader situation to you 💅

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🌸 NAME 🌸

bootloader_selinux — the Security Enhanced Linux Policy for the bootloader processes, periodt 🫶

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🦋 DESCRIPTION 🦋

Security-Enhanced Linux secures the bootloader processes via flexible mandatory access control. like, it's literally locking things down so nothing sketchy can happen. no cap 🔥

The bootloader processes execute with the bootloader_t SELinux type. wanna check if you've got these processes running? just run the ps command with the -Z qualifier, easy peasy ✨

For example:

ps -eZ | grep bootloader_t

see? iconic. 💖

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🎀 ENTRYPOINTS 🎀

The bootloader_t SELinux type can be entered via the bootloader_exec_t file type. that's the doorway, bestie 🚪✨

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

/usr/bin/grub.*, /usr/bin/lilo.*, /usr/bin/ybin.*, /usr/bin/zipl

those are literally the VIP list. 🔥

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👑 PROCESS TYPES 👑

okay so SELinux defines process types (domains) for each process running on the system. that's just how it do 💅

You can see the context of a process using the -Z option to ps. go off, check those vibes.

Policy governs the access confined processes have to files. SELinux bootloader policy is very flexible allowing users to setup their bootloader processes in as secure a method as possible. it's giving customizable but make it safe 🫶

The following process types are defined for bootloader:

bootloader_t

Note: semanage permissive -a bootloader_t can be used to make the process type bootloader_t permissive. SELinux does not deny access to permissive process types, but the AVC (SELinux denials) messages are still generated. so like, it's chill but it's still watching 👀

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🌈 BOOLEANS 🌈

SELinux policy is customizable based on least access required. bootloader policy is extremely flexible and has several booleans that allow you to manipulate the policy and run bootloader with the tightest access possible. we love a configurable queen 👑

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. 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, you must turn on the selinuxuser_execheap boolean. Disabled by default.

setsebool -P selinuxuser_execheap 1

like bestie, please don't do this unless you absolutely have to, it's giving red flag 🚩

If you 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, you must turn on the selinuxuser_execstack boolean. Disabled by default.

setsebool -P selinuxuser_execstack 1

literally never ever, the way that phrase is so serious 😭

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💜 MANAGED FILES 💜

The SELinux process type bootloader_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. (that part's important, don't forget it ✨)

file_type

• all files on the system

like, all of them. it's giving main character energy, the whole filesystem is the vibe 🌍

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🍓 FILE CONTEXTS 🍓

SELinux requires files to have an extended attribute to define the file type. it's like a little name tag for your files 🏷️

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

Policy governs the access confined processes have to these files. SELinux bootloader policy is very flexible allowing users to setup their bootloader processes in as secure a method as possible. again, flexible but safe, we stan 🫶

🧚 STANDARD FILE CONTEXT 🧚

SELinux defines the file context types for the bootloader, 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 bootloader_exec_t '/srv/bootloader/content(/.*)?'
restorecon -R -v /srv/mybootloader_content

Note: SELinux often uses regular expressions to specify labels that match multiple files. regex girlies rise ✨

The following file types are defined for bootloader:

bootloader_etc_t

• Set files with the bootloader_etc_t type, if you want to store bootloader files in the /etc directories.

Paths:

/etc/lilo.conf.*, /etc/zipl.conf.*, /etc/yaboot.conf.*, /etc/default/grub

bootloader_exec_t

• Set files with the bootloader_exec_t type, if you want to transition an executable to the bootloader_t domain.

Paths:

/usr/bin/grub.*, /usr/bin/lilo.*, /usr/bin/ybin.*, /usr/bin/zipl

bootloader_tmp_t

• Set files with the bootloader_tmp_t type, if you want to store bootloader temporary files in the /tmp directories.

bootloader_var_lib_t

• Set files with the bootloader_var_lib_t type, if you want to store the bootloader files under the /var/lib directory.

bootloader_var_run_t

• Set files with the bootloader_var_run_t type, if you want to store the bootloader files under the /run or /var/run directory.

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 💅

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⭐ 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 when you want the clicky-clicky experience 🖱️✨

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💖 AUTHOR 💖

This manual page was auto-generated using sepolicy manpage. the robots did this one, not me 🤖💅

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🔥 SEE ALSO 🔥

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

like, go read those too if you wanna be a SELinux scholar 👑📚

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and that's the whole vibe, bestie! this was page bootloader from 26-10-06, part of bootloader_selinux(8) — go forth and secure those bootloaders, you've got this 💜✨🦋