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
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:
SEE ALSO
namespace.conf(5), pam.d(5), mount(8), pam(8).
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 <[email protected]>, Chad Sellers <[email protected]> and Steve Grubb
<[email protected]>. Additional improvements by Xavier Toth <[email protected]> and Tomas Mraz
<[email protected]>.
Linux-PAM Manual 09/19/2013 PAM_NAMESPACE(8)
Back to main site | Back to man page index