1PAM_NAMESPACE(8)               Linux-PAM Manual               PAM_NAMESPACE(8)
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NAME

6       pam_namespace - PAM module for configuring namespace for a session
7

SYNOPSIS

9       pam_namespace.so [debug] [unmnt_remnt] [unmnt_only] [require_selinux]
10                        [gen_hash] [ignore_config_error]
11                        [ignore_instance_parent_mode] [unmount_on_close]
12                        [use_current_context] [use_default_context]
13                        [mount_private]
14

DESCRIPTION

16       The pam_namespace PAM module sets up a private namespace for a session
17       with polyinstantiated directories. A polyinstantiated directory
18       provides a different instance of itself based on user name, or when
19       using SELinux, user name, security context or both. If an executable
20       script /etc/security/namespace.init exists, it is used to initialize
21       the instance directory after it is set up and mounted on the
22       polyinstantiated directory. The script receives the polyinstantiated
23       directory path, the instance directory path, flag whether the instance
24       directory was newly created (0 for no, 1 for yes), and the user name as
25       its arguments.
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27       The pam_namespace module disassociates the session namespace from the
28       parent namespace. Any mounts/unmounts performed in the parent
29       namespace, such as mounting of devices, are not reflected in the
30       session namespace. To propagate selected mount/unmount events from the
31       parent namespace into the disassociated session namespace, an
32       administrator may use the special shared-subtree feature. For
33       additional information on shared-subtree feature, please refer to the
34       mount(8) man page and the shared-subtree description at
35       http://lwn.net/Articles/159077 and http://lwn.net/Articles/159092.
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OPTIONS

38       debug
39           A lot of debug information is logged using syslog
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41       unmnt_remnt
42           For programs such as su and newrole, the login session has already
43           setup a polyinstantiated namespace. For these programs,
44           polyinstantiation is performed based on new user id or security
45           context, however the command first needs to undo the
46           polyinstantiation performed by login. This argument instructs the
47           command to first undo previous polyinstantiation before proceeding
48           with new polyinstantiation based on new id/context
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50       unmnt_only
51           For trusted programs that want to undo any existing bind mounts and
52           process instance directories on their own, this argument allows
53           them to unmount currently mounted instance directories
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55       require_selinux
56           If selinux is not enabled, return failure
57
58       gen_hash
59           Instead of using the security context string for the instance name,
60           generate and use its md5 hash.
61
62       ignore_config_error
63           If a line in the configuration file corresponding to a
64           polyinstantiated directory contains format error, skip that line
65           process the next line. Without this option, pam will return an
66           error to the calling program resulting in termination of the
67           session.
68
69       ignore_instance_parent_mode
70           Instance parent directories by default are expected to have the
71           restrictive mode of 000. Using this option, an administrator can
72           choose to ignore the mode of the instance parent. This option
73           should be used with caution as it will reduce security and
74           isolation goals of the polyinstantiation mechanism.
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76       unmount_on_close
77           Explicitly unmount the polyinstantiated directories instead of
78           relying on automatic namespace destruction after the last process
79           in a namespace exits. This option should be used only in case it is
80           ensured by other means that there cannot be any processes running
81           in the private namespace left after the session close. It is also
82           useful only in case there are multiple pam session calls in
83           sequence from the same process.
84
85       use_current_context
86           Useful for services which do not change the SELinux context with
87           setexeccon call. The module will use the current SELinux context of
88           the calling process for the level and context polyinstantiation.
89
90       use_default_context
91           Useful for services which do not use pam_selinux for changing the
92           SELinux context with setexeccon call. The module will use the
93           default SELinux context of the user for the level and context
94           polyinstantiation.
95
96       mount_private
97           This option can be used on systems where the / mount point or its
98           submounts are made shared (for example with a mount --make-rshared
99           / command). The module will mark the whole directory tree so any
100           mount and unmount operations in the polyinstantiation namespace are
101           private. Normally the pam_namespace will try to detect the shared /
102           mount point and make the polyinstantiated directories private
103           automatically. This option has to be used just when only a subtree
104           is shared and / is not.
105
106           Note that mounts and unmounts done in the private namespace will
107           not affect the parent namespace if this option is used or when the
108           shared / mount point is autodetected.
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MODULE TYPES PROVIDED

111       Only the session module type is provided. The module must not be called
112       from multithreaded processes.
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RETURN VALUES

115       PAM_SUCCESS
116           Namespace setup was successful.
117
118       PAM_SERVICE_ERR
119           Unexpected system error occurred while setting up namespace.
120
121       PAM_SESSION_ERR
122           Unexpected namespace configuration error occurred.
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FILES

125       /etc/security/namespace.conf
126           Main configuration file
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128       /etc/security/namespace.d
129           Directory for additional configuration files
130
131       /etc/security/namespace.init
132           Init script for instance directories
133

EXAMPLES

135       For the <service>s you need polyinstantiation (login for example) put
136       the following line in /etc/pam.d/<service> as the last line for session
137       group:
138
139       session required pam_namespace.so [arguments]
140
141       To use polyinstantiation with graphical display manager gdm, insert the
142       following line, before exit 0, in /etc/gdm/PostSession/Default:
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144       /usr/sbin/gdm-safe-restart
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146       This allows gdm to restart after each session and appropriately adjust
147       namespaces of display manager and the X server. If polyinstantiation of
148       /tmp is desired along with the graphical environment, then additional
149       configuration changes are needed to address the interaction of X server
150       and font server namespaces with their use of /tmp to create
151       communication sockets. Please use the initialization script
152       /etc/security/namespace.init to ensure that the X server and its
153       clients can appropriately access the communication socket X0. Please
154       refer to the sample instructions provided in the comment section of the
155       instance initialization script /etc/security/namespace.init. In
156       addition, perform the following changes to use graphical environment
157       with polyinstantiation of /tmp:
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159                 1. Disable the use of font server by commenting out "FontPath"
160                    line in /etc/X11/xorg.conf. If you do want to use the font server
161                    then you will have to augment the instance initialization
162                    script to appropriately provide /tmp/.font-unix from the
163                    polyinstantiated /tmp.
164                 2. Ensure that the gdm service is setup to use pam_namespace,
165                    as described above, by modifying /etc/pam.d/gdm.
166                 3. Ensure that the display manager is configured to restart X server
167                    with each new session. This default setup can be verified by
168                    making sure that /usr/share/gdm/defaults.conf contains
169                    "AlwaysRestartServer=true", and it is not overridden by
170                    /etc/gdm/custom.conf.
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SEE ALSO

175       namespace.conf(5), pam.d(5), mount(8), pam(8).
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AUTHORS

178       The namespace setup scheme was designed by Stephen Smalley, Janak Desai
179       and Chad Sellers. The pam_namespace PAM module was developed by Janak
180       Desai <janak@us.ibm.com>, Chad Sellers <csellers@tresys.com> and Steve
181       Grubb <sgrubb@redhat.com>. Additional improvements by Xavier Toth
182       <txtoth@gmail.com> and Tomas Mraz <tmraz@redhat.com>.
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186Linux-PAM Manual                  05/18/2017                  PAM_NAMESPACE(8)
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