NAME
pam_namespace - PAM module for configuring namespace for a sessionSYNOPSIS
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
debugA 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_SUCCESSNamespace 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.confMain 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, please refer to gdm's documentation.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 <[email protected]>, Chad Sellers <[email protected]> and Steve Grubb <[email protected]>. Additional improvements by Xavier Toth <[email protected]> and Tomas Mraz <[email protected]>.09/03/2021 | Linux-PAM Manual |