PAM_NAMESPACE(8)                         Linux-PAM Manual                        PAM_NAMESPACE(8)



NAME
       pam_namespace - PAM module for configuring namespace for a session

SYNOPSIS
       pam_namespace.so [debug] [unmnt_remnt] [unmnt_only] [require_selinux] [gen_hash]
                        [ignore_config_error] [ignore_instance_parent_mode] [unmount_on_close]
                        [use_current_context] [use_default_context] [mount_private]

DESCRIPTION
       The pam_namespace PAM module sets up a private namespace for a session with
       polyinstantiated directories. A polyinstantiated directory provides a different instance
       of itself based on user name, or when using SELinux, user name, security context or both.
       If an executable script /etc/security/namespace.init exists, it is used to initialize the
       instance directory after it is set up and mounted on the polyinstantiated directory. The
       script receives the polyinstantiated directory path, the instance directory path, flag
       whether the instance directory was newly created (0 for no, 1 for yes), and the user name
       as its arguments.

       The pam_namespace module disassociates the session namespace from the parent namespace.
       Any mounts/unmounts performed in the parent namespace, such as mounting of devices, are
       not reflected in the session namespace. To propagate selected mount/unmount events from
       the parent namespace into the disassociated session namespace, an administrator may use
       the special shared-subtree feature. For additional information on shared-subtree feature,
       please refer to the mount(8) man page and the shared-subtree description at
       http://lwn.net/Articles/159077 and http://lwn.net/Articles/159092.

OPTIONS
       debug
           A lot of debug information is logged using syslog

       unmnt_remnt
           For programs such as su and newrole, the login session has already setup a
           polyinstantiated namespace. For these programs, polyinstantiation is performed based
           on new user id or security context, however the command first needs to undo the
           polyinstantiation performed by login. This argument instructs the command to first
           undo previous polyinstantiation before proceeding with new polyinstantiation based on
           new id/context

       unmnt_only
           For trusted programs that want to undo any existing bind mounts and process instance
           directories on their own, this argument allows them to unmount currently mounted
           instance directories

       require_selinux
           If selinux is not enabled, return failure

       gen_hash
           Instead of using the security context string for the instance name, generate and use
           its md5 hash.

       ignore_config_error
           If a line in the configuration file corresponding to a polyinstantiated directory
           contains format error, skip that line process the next line. Without this option, pam
           will return an error to the calling program resulting in termination of the session.

       ignore_instance_parent_mode
           Instance parent directories by default are expected to have the restrictive mode of
           000. Using this option, an administrator can choose to ignore the mode of the instance
           parent. This option should be used with caution as it will reduce security and
           isolation goals of the polyinstantiation mechanism.

       unmount_on_close
           Explicitly unmount the polyinstantiated directories instead of relying on automatic
           namespace destruction after the last process in a namespace exits. This option should
           be used only in case it is ensured by other means that there cannot be any processes
           running in the private namespace left after the session close. It is also useful only
           in case there are multiple pam session calls in sequence from the same process.

       use_current_context
           Useful for services which do not change the SELinux context with setexeccon call. The
           module will use the current SELinux context of the calling process for the level and
           context polyinstantiation.

       use_default_context
           Useful for services which do not use pam_selinux for changing the SELinux context with
           setexeccon call. The module will use the default SELinux context of the user for the
           level and context polyinstantiation.

       mount_private
           This option can be used on systems where the / mount point or its submounts are made
           shared (for example with a mount --make-rshared / command). The module will mark the
           whole directory tree so any mount and unmount operations in the polyinstantiation
           namespace are private. Normally the pam_namespace will try to detect the shared /
           mount point and make the polyinstantiated directories private automatically. This
           option has to be used just when only a subtree is shared and / is not.

           Note that mounts and unmounts done in the private namespace will not affect the parent
           namespace if this option is used or when the shared / mount point is autodetected.

MODULE TYPES PROVIDED
       Only the session module type is provided. The module must not be called from multithreaded
       processes.

RETURN VALUES
       PAM_SUCCESS
           Namespace setup was successful.

       PAM_SERVICE_ERR
           Unexpected system error occurred while setting up namespace.

       PAM_SESSION_ERR
           Unexpected namespace configuration error occurred.

FILES
       /etc/security/namespace.conf
           Main configuration file

       /etc/security/namespace.d
           Directory for additional configuration files

       /etc/security/namespace.init
           Init script for instance directories

EXAMPLES
       For the <service>s you need polyinstantiation (login for example) put the following line
       in /etc/pam.d/<service> as the last line for session group:

       session required pam_namespace.so [arguments]

       To use polyinstantiation with graphical display manager gdm, insert the following line,
       before exit 0, in /etc/gdm/PostSession/Default:

       /usr/sbin/gdm-safe-restart

       This allows gdm to restart after each session and appropriately adjust namespaces of
       display manager and the X server. If polyinstantiation of /tmp is desired along with the
       graphical environment, then additional configuration changes are needed to address the
       interaction of X server and font server namespaces with their use of /tmp to create
       communication sockets. Please use the initialization script /etc/security/namespace.init
       to ensure that the X server and its clients can appropriately access the communication
       socket X0. Please refer to the sample instructions provided in the comment section of the
       instance initialization script /etc/security/namespace.init. In addition, perform the
       following changes to use graphical environment with polyinstantiation of /tmp:

                 1. Disable the use of font server by commenting out "FontPath"
                    line in /etc/X11/xorg.conf. If you do want to use the font server
                    then you will have to augment the instance initialization
                    script to appropriately provide /tmp/.font-unix from the
                    polyinstantiated /tmp.
                 2. Ensure that the gdm service is setup to use pam_namespace,
                    as described above, by modifying /etc/pam.d/gdm.
                 3. Ensure that the display manager is configured to restart X server
                    with each new session. This default setup can be verified by
                    making sure that /usr/share/gdm/defaults.conf contains
                    "AlwaysRestartServer=true", and it is not overridden by
                    /etc/gdm/custom.conf.



SEE ALSO
       namespace.conf(5), pam.d(5), mount(8), pam(7).

AUTHORS
       The namespace setup scheme was designed by Stephen Smalley, Janak Desai and Chad Sellers.
       The pam_namespace PAM module was developed by Janak Desai <janak AT us.com>, Chad Sellers
       <csellers AT tresys.com> and Steve Grubb <sgrubb AT redhat.com>. Additional improvements by
       Xavier Toth <txtoth AT gmail.com> and Tomas Mraz <tmraz AT redhat.com>.



Linux-PAM Manual                            09/19/2013                           PAM_NAMESPACE(8)