ssh_selinux(8)

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

🌸 ssh_selinux(8) — the SELinux tea for ssh 💅

okay so welcome to the manual page for ssh_selinux, which lives in section 8 of the manual (that's the "system administration" section, iykyk) and is brought to you by the SELinux Policy ssh package. The title is ssh_selinux(8) bestie, in case you were wondering what you were reading. Let's get into it ✨

🎀 NAME 🎀

ssh_selinux — the Security Enhanced Linux Policy for the ssh processes, fr fr. That's the whole name section, we love a short one 🫶

✨ DESCRIPTION ✨

Security-Enhanced Linux secures the ssh processes via flexible mandatory access control. That's the whole vibe — SELinux is the bouncer at the club and it's checking everybody's ID 🪪

The ssh processes execute with the ssh_t SELinux type. You can check if you have these processes running by executing the ps command with the -Z qualifier. Like this, queen:

ps -eZ | grep ssh_t

That's it. That's the check. Go off 💅

🚪 ENTRYPOINTS 🚪

The ssh_t SELinux type can be entered via the ssh_exec_t file type. (Think of entrypoints as the door a process walks through to become a domain — main character energy, honestly.)

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

/usr/bin/ssh, /usr/libexec/nm-ssh-service

Two doors. Both iconic. 🚪✨

👑 PROCESS TYPES 👑

SELinux defines process types (domains) for each process running on the system. Yes, every single process gets a little type. Very demure, very mindful 🌸

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

Policy governs the access confined processes have to files. SELinux ssh policy is very flexible allowing users to setup their ssh processes in as secure a method as possible. Flexible AND secure? We love range 💜

The following process types are defined for ssh:

sshd_t, sshd_sandbox_t, sshd_net_t, ssh_keygen_t, sshd_keygen_t, sshd_session_t, sshd_auth_t, ssh_t, ssh_keysign_t
Note: semanage permissive -a ssh_t can be used to make the process type ssh_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 get-out-of-jail-free card — the receipts still exist 😭

🔘 BOOLEANS 🔘

SELinux policy is customizable based on least access required. ssh policy is extremely flexible and has several booleans that allow you to manipulate the policy and run ssh with the tightest access possible. Tightest access possible = the toggles, bestie 🎛️

If you want to allow host key based authentication, you must turn on the ssh_keysign boolean. Disabled by default.

setsebool -P ssh_keysign 1

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

If you want to allow regular users direct dri device access, you must turn on the selinuxuser_direct_dri_enabled boolean. Disabled by default.

setsebool -P selinuxuser_direct_dri_enabled 1

If you want to allow users to run TCP servers (bind to ports and accept connection from the same domain and outside users) disabling this forces FTP passive mode and may change other protocols, you must turn on the selinuxuser_tcp_server boolean. Disabled by default.

setsebool -P selinuxuser_tcp_server 1

If you want to allows clients to write to the X server shared memory segments, you must turn on the xserver_clients_write_xshm boolean. Disabled by default.

setsebool -P xserver_clients_write_xshm 1
lowkey the -P in setsebool -P is the "make it permanent" of it all, so your toggle survives a reboot. Do NOT skip it unless you love redoing work 🙈

🔌 PORT TYPES 🔌

SELinux defines port types to represent TCP and UDP ports. Ports have types now. Everything has a type. That's the SELinux lifestyle 💅

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

The following port types are defined for ssh:

ssh_port_t

Default Defined Ports:

tcp 22

tcp 22, the classic. the blueprint. the moment 🔥

📂 MANAGED FILES 📂

The SELinux process type ssh_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 said "I'll handle the MAC, you handle the DAC" — teamwork, bestie 🤝)

cifs_t

ecryptfs_t

/home/[^/]+/.Private(/.*)?
/home/[^/]+/.ecryptfs(/.*)?

fusefs_t

/run/user/[0-9]+/gvfs

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

nfs_t

ssh_tmpfs_t

user_tmp_type

all user tmp files

🗂️ FILE CONTEXTS 🗂️

SELinux requires files to have an extended attribute to define the file type. Yes, files have to carry their own little label around. Relatable, honestly 🏷️

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

🌈 STANDARD FILE CONTEXT 🌈

SELinux defines the file context types for the ssh, 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 ssh_keygen_exec_t '/srv/ssh/content(/.*)?'
restorecon -R -v /srv/myssh_content
Note: SELinux often uses regular expressions to specify labels that match multiple files. Regex jumpscare, but make it fashion 🦋

The following file types are defined for ssh:

ssh_agent_exec_t

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

Paths:

/usr/libexec/(open)?ssh/ssh-pkcs11-helper, /usr/bin/ssh-agent

ssh_agent_tmp_t

  • Set files with the ssh_agent_tmp_t type, if you want to store ssh agent temporary files in the /tmp directories.

ssh_exec_t

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

Paths:

/usr/bin/ssh, /usr/libexec/nm-ssh-service

ssh_home_t

  • Set files with the ssh_home_t type, if you want to store ssh files in the users home directory.

Paths:

/var/lib/[^/]+/.ssh(/.*)?, /root/.ssh(/.*)?,
/var/lib/one/.ssh(/.*)?, /srv/gitolite/.ssh(/.*)?,
/srv/gitolite3/.ssh(/.*)?, /var/lib/pgsql/.ssh(/.*)?,
/var/lib/openshift/[^/]+/.ssh(/.*)?, /var/lib/amanda/.ssh(/.*)?,
/var/lib/stickshift/[^/]+/.ssh(/.*)?, /var/lib/nocpulse/.ssh(/.*)?,
/var/lib/openshift/gear/[^/]+/.ssh(/.*)?, /root/.shosts,
/home/[^/]+/.ssh(/.*)?, /home/[^/]+/.ansible/cp/.*,
/home/[^/]+/.shosts

ssh_keygen_exec_t

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

ssh_keygen_tmp_t

  • Set files with the ssh_keygen_tmp_t type, if you want to store ssh keygen temporary files in the /tmp directories.

ssh_keysign_exec_t

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

Paths:

/usr/libexec/(open)?ssh/ssh-keysign, /usr/lib/openssh/ssh-keysign

ssh_tmpfs_t

  • Set files with the ssh_tmpfs_t type, if you want to store ssh files on a tmpfs file system.

sshd_auth_exec_t

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

sshd_exec_t

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

Paths:

/usr/bin/sshd, /usr/bin/gsisshd

sshd_initrc_exec_t

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

sshd_key_t

  • Set files with the sshd_key_t type, if you want to treat the files as sshd key data.

Paths:

/etc/ssh/ssh_host.*_key, /etc/ssh/ssh_host.*_key.pub,
/etc/ssh/primes

sshd_keygen_exec_t

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

Paths:

/usr/libexec/(open)?ssh/sshd-keygen, /usr/bin/sshd-keygen,
/usr/bin/sshd-gen-keys-start

sshd_keygen_unit_file_t

  • Set files with the sshd_keygen_unit_file_t type, if you want to treat the files as sshd keygen unit content.

sshd_keytab_t

  • Set files with the sshd_keytab_t type, if you want to treat the files as kerberos keytab files.

sshd_session_exec_t

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

sshd_session_tmpfs_t

  • Set files with the sshd_session_tmpfs_t type, if you want to store sshd session files on a tmpfs file system.

sshd_session_var_run_t

  • Set files with the sshd_session_var_run_t type, if you want to store the sshd session files under the /run or /var/run directory.

sshd_tmpfs_t

  • Set files with the sshd_tmpfs_t type, if you want to store sshd files on a tmpfs file system.

sshd_unit_file_t

  • Set files with the sshd_unit_file_t type, if you want to treat the files as sshd unit content.

sshd_var_run_t

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

Paths:

/run/sshd.pid, /run/sshd.init.pid
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. chcon is giving "temporary tattoo", semanage fcontext is giving "actual legal name change" — choose wisely 💀

🛠️ 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. A GUI! For when the terminal is doing too much 🖱️✨

💖 AUTHOR 💖

This manual page was auto-generated using sepolicy manpage . (Yes the robot wrote it. Respect the robot. 🤖)

👀 SEE ALSO 👀

selinux(8), ssh(8), semanage(8), restorecon(8), chcon(1), sepolicy(8), setsebool(8), ssh_keygen_selinux(8), ssh_keygen_selinux(8), ssh_keysign_selinux(8), ssh_keysign_selinux(8)

(and yes, some of those appear twice in the source. we don't fix what we didn't break, bestie 💅)

and that's the whole page!! go forth and be secure 🦋🍓 this gem was served up by the ssh package, version/date line 26-10-06, and you just read ssh_selinux(8) — periodt, that's the post 💜✨

📦 where this page comes from