chronyc_selinux(8)

✨ chronyc_selinux(8) ✨

Hey bestie! Welcome to the chronyc_selinux(8) glow-up 💅 This is your full guide to the SELinux policy vibes for chronyc processes, and we're gonna get into it. No cap, every detail is here — flags, paths, booleans, the whole thing. Let's go 🚀

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💫 NAME 💫

chronyc_selinux — the whole ~vibe~ of Security Enhanced Linux Policy for the chronyc processes 🕐✨

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🌸 DESCRIPTION 🌸

Okay so Security-Enhanced Linux secures the chronyc processes via flexible mandatory access control. That's the whole point — SELinux is out here protecting your chronyc processes with mandatory access control, and it's flexible about it 🫶

The chronyc processes execute with the chronyc_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 chronyc_t

Run that and see what's up 💖

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🚪 ENTRYPOINTS 🚪

The chronyc_t SELinux type can be entered via the chronyc_exec_t file type.

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

/usr/bin/chronyc

That's the one path, bestie — /usr/bin/chronyc and that's it 🎯

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👑 PROCESS TYPES 👑

SELinux defines process types (domains) for each process running on the system.

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

Policy governs the access confined processes have to files. SELinux chronyc policy is very flexible allowing users to setup their chronyc processes in as secure a method as possible. We love safe and flexible 💅

The following process types are defined for chronyc:

• chronyc_t

Note: semanage permissive -a chronyc_t can be used to make the process type chronyc_t permissive. SELinux does not deny access to permissive process types, but the AVC (SELinux denials) messages are still generated. So like, it's not a full free pass — you still get the receipts 😭

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🎀 BOOLEANS 🎀

SELinux policy is customizable based on least access required. chronyc policy is extremely flexible and has several booleans that allow you to manipulate the policy and run chronyc with the tightest access possible. Tightest access? We stan 🫶

If you want to allow all domains to execute in fips_mode, you must turn on the fips_mode boolean. Enabled by default.

setsebool -P fips_mode 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

That's the two booleans, bestie — fips_mode (enabled by default) and nis_enabled (disabled by default) ✨

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📁 MANAGED FILES 📁

The SELinux process type chronyc_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. Don't forget the DAC permissions, okay? 👀

krb5_host_rcache_t

/var/tmp/krb5_0.rcache2
/var/cache/krb5rcache(/.*)?
/var/tmp/nfs_0
/var/tmp/DNS_25
/var/tmp/host_0
/var/tmp/imap_0
/var/tmp/HTTP_23
/var/tmp/HTTP_48
/var/tmp/ldap_55
/var/tmp/ldap_487
/var/tmp/ldapmap1_0

non_security_file_type

That's it — those are the file types and paths, all listed, no skips 💖

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🗂️ 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 chronyc policy is very flexible allowing users to setup their chronyc processes in as secure a method as possible. Same energy as before — safe and flexible 🫶

🌈 STANDARD FILE CONTEXT 🌈

SELinux defines the file context types for the chronyc. 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. Like this:

semanage fcontext -a -t chronyc_exec_t '/srv/chronyc/content(/.*)?'
restorecon -R -v /srv/mychronyc_content

Note: SELinux often uses regular expressions to specify labels that match multiple files. Regex era 💅

The following file types are defined for chronyc:

• chronyc_exec_t — Set files with the chronyc_exec_t type, if you want to transition an executable to the chronyc_t domain. That's the one file type, bestie 🎯

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, okay? 😭

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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.

That's the command lineup — go off 👑