????
Your IP : 3.141.30.13
| Current Path : /usr/share/doc/pam/txts/ |
|
|
| Current File : //usr/share/doc/pam/txts/README.pam_namespace |
pam_namespace -- PAM module for configuring namespace for a session
--------------------------------------------------------------------------
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.
DESCRIPTION
The pam_namespace.so module allows setup of private namespaces with
polyinstantiated directories. Directories can be polyinstantiated based on
user name or, in the case of SELinux, user name, sensitivity level or
complete security context. If an executable script
/etc/security/namespace.init exists, it is used to initialize the
namespace every time an instance directory is set up and mounted. The
script receives the polyinstantiated directory path and the instance
directory path as its arguments.
The /etc/security/namespace.conf file specifies which directories are
polyinstantiated, how they are polyinstantiated, how instance directories
would be named, and any users for whom polyinstantiation would not be
performed.
When someone logs in, the file namespace.conf is scanned. Comments are
marked by # characters. Each non comment line represents one
polyinstantiated directory. The fields are separated by spaces but can be
quoted by " characters also escape sequences \b, \n, and \t are
recognized. The fields are as follows:
polydir instance_prefix method list_of_uids
The first field, polydir, is the absolute pathname of the directory to
polyinstantiate. The special string $HOME is replaced with the user's home
directory, and $USER with the username. This field cannot be blank.
The second field, instance_prefix is the string prefix used to build the
pathname for the instantiation of <polydir>. Depending on the
polyinstantiation method it is then appended with "instance
differentiation string" to generate the final instance directory path.
This directory is created if it did not exist already, and is then bind
mounted on the <polydir> to provide an instance of <polydir> based on the
<method> column. The special string $HOME is replaced with the user's home
directory, and $USER with the username. This field cannot be blank.
The third field, method, is the method used for polyinstantiation. It can
take these values; "user" for polyinstantiation based on user name,
"level" for polyinstantiation based on process MLS level and user name,
"context" for polyinstantiation based on process security context and user
name, "tmpfs" for mounting tmpfs filesystem as an instance dir, and
"tmpdir" for creating temporary directory as an instance dir which is
removed when the user's session is closed. Methods "context" and "level"
are only available with SELinux. This field cannot be blank.
The fourth field, list_of_uids, is a comma separated list of user names
for whom the polyinstantiation is not performed. If left blank,
polyinstantiation will be performed for all users. If the list is preceded
with a single "~" character, polyinstantiation is performed only for users
in the list.
The method field can contain also following optional flags separated by :
characters.
create=mode,owner,group - create the polyinstantiated directory. The mode,
owner and group parameters are optional. The default for mode is
determined by umask, the default owner is the user whose session is
opened, the default group is the primary group of the user.
iscript=path - path to the instance directory init script. The base
directory for relative paths is /etc/security/namespace.d.
noinit - instance directory init script will not be executed.
shared - the instance directories for "context" and "level" methods will
not contain the user name and will be shared among all users.
mntopts=value - value of this flag is passed to the mount call when the
tmpfs mount is done. It allows for example the specification of the
maximum size of the tmpfs instance that is created by the mount call. In
addition to options specified in the tmpfs(5) manual the nosuid, noexec,
and nodev flags can be used to respectively disable setuid bit effect,
disable running executables, and disable devices to be interpreted on the
mounted tmpfs filesystem.
The directory where polyinstantiated instances are to be created, must
exist and must have, by default, the mode of 0000. The requirement that
the instance parent be of mode 0000 can be overridden with the command
line option ignore_instance_parent_mode
In case of context or level polyinstantiation the SELinux context which is
used for polyinstantiation is the context used for executing a new process
as obtained by getexeccon. This context must be set by the calling
application or pam_selinux.so module. If this context is not set the
polyinstatiation will be based just on user name.
The "instance differentiation string" is <user name> for "user" method and
<user name>_<raw directory context> for "context" and "level" methods. If
the whole string is too long the end of it is replaced with md5sum of
itself. Also when command line option gen_hash is used the whole string is
replaced with md5sum of itself.
EXAMPLES
These are some example lines which might be specified in
/etc/security/namespace.conf.
# The following three lines will polyinstantiate /tmp,
# /var/tmp and user's home directories. /tmp and /var/tmp
# will be polyinstantiated based on the security level
# as well as user name, whereas home directory will be
# polyinstantiated based on the full security context and user name.
# Polyinstantiation will not be performed for user root
# and adm for directories /tmp and /var/tmp, whereas home
# directories will be polyinstantiated for all users.
#
# Note that instance directories do not have to reside inside
# the polyinstantiated directory. In the examples below,
# instances of /tmp will be created in /tmp-inst directory,
# where as instances of /var/tmp and users home directories
# will reside within the directories that are being
# polyinstantiated.
#
/tmp /tmp-inst/ level root,adm
/var/tmp /var/tmp/tmp-inst/ level root,adm
$HOME $HOME/$USER.inst/inst- context
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]
This module also depends on pam_selinux.so setting the context.