pam_namespace

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@us.ibm.com>, Chad Sellers <csellers@tresys.com> and Steve
       Grubb <sgrubb@redhat.com>. Additional improvements by Xavier Toth
       <txtoth@gmail.com> and Tomas Mraz <tmraz@redhat.com>.

Linux-PAM Manual                  05/18/2017                  PAM_NAMESPACE(8)