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pam_namespace -- PAM module for configuring namespace for a session

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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.
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