# pam_systemd_home

## NAME



           pam_systemd_home - Authenticate users and mount home directories
           via systemd-homed.service
    


## SYNOPSIS



           pam_systemd_home.so
    


## DESCRIPTION



           **pam_systemd_home** ensures that home directories managed by
           systemd-homed.service(8) are automatically activated (mounted) on
           user login, and are deactivated (unmounted) when the last session
           of the user ends. For such users, it also provides authentication
           (when per-user disk encryption is used, the disk encryption key is
           derived from the authentication credential supplied at login
           time), account management (the **JSON user record******[1] embedded in the
           home store contains account details), and implements the updating
           of the encryption password (which is also used for user
           authentication).


## OPTIONS



           The following options are understood:
    
           _suspend=_
               Takes a boolean argument. If true, the home directory of the
               user will be suspended automatically during system suspend; if
               false it will remain active. Automatic suspending of the home
               directory improves security substantially as secret key
               material is automatically removed from memory before the
               system is put to sleep and must be re-acquired (through user
               re-authentication) when coming back from suspend. It is
               recommended to set this parameter for all PAM applications
               that have support for automatically re-authenticating via PAM
               on system resume. If multiple sessions of the same user are
               open in parallel the user's home directory will be left
               unsuspended on system suspend as long as at least one of the
               sessions does not set this parameter to on. Defaults to off.
    
               Note that TTY logins generally do not support
               re-authentication on system resume. Re-authentication on
               system resume is primarily a concept implementable in
               graphical environments, in the form of lock screens brought up
               automatically when the system goes to sleep. This means that
               if a user concurrently uses graphical login sessions that
               implement the required re-authentication mechanism and console
               logins that do not, the home directory is not locked during
               suspend, due to the logic explained above. That said, it is
               possible to set this field for TTY logins too, ignoring the
               fact that TTY logins actually do not support the
               re-authentication mechanism. In that case the TTY sessions
               will appear hung until the user logs in on another virtual
               terminal (regardless of whether via another TTY session or
               graphically) which will resume the home directory and unblock
               the original TTY session. (Do note that lack of screen locking
               on TTY sessions means even though the TTY session appears
               hung, keypresses can still be queued into it, and the existing
               screen contents be read without re-authentication; this
               limitation is unrelated to the home directory management
               **pam_systemd_home** and systemd-homed.service implement.)
    
               Turning this option on by default is highly recommended for
               all sessions, but only if the service managing these sessions
               correctly implements the aforementioned re-authentication.
               Note that the re-authentication must take place from a
               component running outside of the user's context, so that it
               does not require access to the user's home directory for
               operation. Traditionally, most desktop environments do not
               implement screen locking this way, and need to be updated
               accordingly.
    
               This setting may also be controlled via the
               _$SYSTEMD_HOME_SUSPEND_ environment variable (see below), which
               **pam_systemd_home** reads during initialization and sets for
               sessions. If both the environment variable is set and the
               module parameter specified the latter takes precedence.
    
               Added in version 245.
    
           _debug_[=]
               Takes an optional boolean argument. If yes or without the
               argument, the module will log debugging information as it
               operates.
    
               Added in version 245.
    


## HOME AREA SUPPORT



           Home directories managed by systemd-homed.service(8) support
           multiple home "areas", which are additional secondary home
           directories of the user within the primary home directory. An
           example: at login time if a user "lennart" with a home directory
           of /home/lennart specifies "lennart%versuch1" as account name
           during login, then **pam_systemd_home** will execute a login into
           "lennart" but ensure that the _$HOME_ variable is set to
           /home/lennart/Areas/versuch1 instead of the usual /home/lennart.
    
           This is particularly useful when sharing the same home directory
           between multiple systems (for example between a host and a VM),
           with the desire to share the home directory to a large degree, but
           still have separate session configuration in place.
    
           Note that the default area to log into can also be encoded in the
           user record, and it can be specified among pam_systemd(8)
           configuration parameters. However, an explicit area specified at
           login time (via the "%" described above) overrides any such
           default. Also note that simply suffixing an account with "%" at
           login time (i.e. specifying an empty area name) has the effect of
           ensuring a login into the primary home directory, overriding any
           default area configuration via the user record or PAM.
    
           Note that not all login mechanisms are compatible with the "%"
           syntax at login time. Most notably **ssh**(8) is not.
    
           Note that the area directory to log into must exist for the area
           specification to be respected. If an area is specified during
           login via the "%" logic (or the other mentioned mechanisms) and it
           does not actually exist the request will be ignored, and the user
           will log into the primary home directory instead.
    
           Typically, in order to make use of the mechanism set up an area
           first, like this:
    
               lennart@zeta$ mkdir -p ~/Areas
               lennart@zeta$ cp -av /etc/skel ~/Areas/versuch1
    
           This should be enough to log into the newly created area, either
           via a regular terminal (using "lennart%versuch1" when prompted for
           a user name), or via run0(1):
    
               lennart@zeta$ run0 --area=versuch1
    


## MODULE TYPES PROVIDED



           The module implements all four PAM operations: **auth**(to allow
           authentication using the encrypted data), **account**(because users
           with systemd-homed.service user accounts are described in a **JSON**
           **user record******[1] and may be configured in more detail than in the
           traditional Linux user database),**session**(because user sessions
           must be tracked in order to implement automatic release when the
           last session of the user is gone), **password**(to change the
           encryption password — also used for user authentication — through
           PAM).
    


## ENVIRONMENT



           The following environment variables are initialized by the module
           and available to the processes of the user's session:
    
           _$SYSTEMD_HOME=1_
               Indicates that the user's home directory is managed by
               systemd-homed.service.
    
               Added in version 245.
    
           _$SYSTEMD_HOME_SUSPEND=_
               Indicates whether the session has been registered with the
               suspend mechanism enabled or disabled (see above). The
               variable's value is either "0" or "1". Note that the module
               both reads the variable when initializing, and sets it for
               sessions.
    
               Added in version 246.
    


## EXAMPLE



           Here's an example PAM configuration fragment that permits users
           managed by systemd-homed.service to log in:
    
               #%PAM-1.0
                   **-auth     [success=done authtok_err=bad perm_denied=bad maxtries=bad default=ignore] pam_systemd_home.so**
               auth      sufficient pam_unix.so
               auth      required   pam_deny.so
    
               account   required   pam_nologin.so
               **-account  [success=done authtok_expired=bad new_authtok_reqd=bad maxtries=bad acct_expired=bad default=ignore] pam_systemd_home.so**
               account   required   pam_unix.so
    
               **-password sufficient pam_systemd_home.so**
               password  sufficient pam_unix.so sha512 shadow try_first_pass
               password  required   pam_deny.so
    
               -session  optional   pam_keyinit.so revoke
               -session  optional   pam_loginuid.so
               **-session  optional   pam_systemd_home.so**
               -session  optional   pam_systemd.so
               session   required   pam_unix.so
    


## NOTES



            1. JSON user record
               https://systemd.io/USER_RECORD/
    


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