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 script is invoked with full root privileges and
   accessing the instance directory in this context needs to be done with
   caution, as it is controlled by the unprivileged user for which it has
   been created.

   If /etc/security/namespace.init does not exist,
   %vendordir%/security/namespace.init is the alternative to be used for
   it.

   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 script is invoked with full root
   privileges and accessing the instance directory in this context needs
   to be done with caution, as it is controlled by the unprivileged user
   for which it has been created.

   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.

   The /etc/security/namespace.conf file ( or
   %vendordir%/security/namespace.conf if it does not exist) 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. Then individual *.conf files
   from the /etc/security/namespace.d/ and
   %vendordir%/security/namespace.d directories are taken too. If
   /etc/security/namespace.d/@filename@.conf exists, then
   %vendordir%/security/namespace.d/@filename@.conf will not be used. All
   namespace.d/*.conf files are sorted by their @filename@.conf in
   lexicographic order regardless of which of the directories they reside
   in.

   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>. The path must end in a
   trailing slash, or in a directory prefix used to build the full
   per-instance path. 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 polyinstantiation 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 na
   me.
         # 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.
