PAM_NAMESPACE(8) Linux-PAM Manual PAM_NAMESPACE(8)NAMEpam_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] [no_unmount_on_close]
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 namespace every time a new instance directory is setup. The script
receives the polyinstantiated directory path and the instance directory
path 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.
no_unmount_on_close
For certain trusted programs such as newrole, open session is
called from a child process while the parent perfoms close
session and pam end functions. For these commands use this
option to instruct pam_close_session to not unmount the bind
mounted polyinstantiated directory in the parent.
MODULE SERVICES PROVIDED
The session service is supported.
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
Configuration file
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 ALSOnamespace.conf(5), pam.d(8), 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 <janak@us.ibm.com>, Chad Sellers <csellers@tresys.com> and Steve
Grubb <sgrubb@redhat.com>.
Linux-PAM Manual 01/09/2013 PAM_NAMESPACE(8)
