модуль PAM для настройки пространства имен для сеанса (PAM module for configuring namespace for a session)
Имя (Name)
pam_namespace - PAM module for configuring namespace for a
session
Синопсис (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]
Описание (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.
Параметры (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.
Предоставляемые типы модулей (Module types provided)
Only the session module type is provided. The module must not be
called from multithreaded processes.
Возвращаемое значение (Return value)
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.
Файлы (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
Примеры (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.
Смотри также (See also)
namespace.conf(5), pam.d(5), mount(8), pam(8).
