================================
CephFS Client Capabilities
================================

Use Ceph authentication capabilities to restrict your filesystem clients
to the lowest possible level of authority needed.

.. note::

    Path restriction and layout modification restriction are new features
    in the Jewel release of Ceph.

Path restriction
================

By default, clients are not restricted in what paths they are allowed to mount.
Further, when clients mount a subdirectory, e.g., /home/user, the MDS does not
by default verify that subsequent operations
are ‘locked’ within that directory.

To restrict clients to only mount and work within a certain directory, use
path-based MDS authentication capabilities.

Syntax
------

To grant rw access to the specified directory only, we mention the specified
directory while creating key for a client following the undermentioned syntax. ::

./ceph auth get-or-create client.*client_name* mon 'allow r' mds 'allow r, allow rw path=/*specified_directory*' osd 'allow rw pool=data'

for example, to restrict client ``foo`` to writing only in the ``bar`` directory,
we will use: ::

./ceph auth get-or-create client.foo mon 'allow r' mds 'allow r, allow rw path=/bar' osd 'allow rw pool=data'

To completely restrict the client to the ``bar`` directory, omit the
unqualified "allow r" clause: ::

./ceph auth get-or-create client.foo mon 'allow r' mds 'allow rw path=/bar' osd 'allow rw pool=data'

Note that if a client's read access is restricted to a path, they will only
be able to mount the filesystem when specifying a readable path in the
mount command (see below).


See `User Management - Add a User to a Keyring`_. for additional details on user management

To restrict a client to the specfied sub-directory only, we mention the specified
directory while mounting following the undermentioned syntax. ::

./ceph-fuse -n client.*client_name* *mount_path* -r *directory_to_be_mounted*

for example, to restrict client ``foo`` to ``mnt/bar`` directory, we will use. ::

./ceph-fuse -n client.foo mnt -r /bar

Free space reporting
--------------------

By default, when a client is mounting a sub-directory, the used space (``df``)
will be calculated from the quota on that sub-directory, rather than reporting
the overall amount of space used on the cluster.

If you would like the client to report the overall usage of the filesystem,
and not just the quota usage on the sub-directory mounted, then set the
following config option on the client:

::

    client quota df = false

If quotas are not enabled, or no quota is set on the sub-directory mounted,
then the overall usage of the filesystem will be reported irrespective of
the value of this setting.

OSD restriction
===============

To prevent clients from writing or reading data to pools other than
those in use for CephFS, set an OSD authentication capability that
restricts access to the CephFS data pool(s):

::

    client.0
        key: AQAz7EVWygILFRAAdIcuJ12opU/JKyfFmxhuaw==
        caps: [mds] allow rw
        caps: [mon] allow r
        caps: [osd] allow rw pool=data1, allow rw pool=data2

.. note::

    Without a corresponding MDS path restriction, the OSD capabilities above do
    **not** restrict file deletions outside of the ``data1`` and ``data2``
    pools.

You may also restrict clients from writing data by using 'r' instead of
'rw' in OSD capabilities.  This does not affect the ability of the client
to update filesystem metadata for these files, but it will prevent them
from persistently writing data in a way that would be visible to other clients.

Layout and Quota restriction (the 'p' flag)
===========================================

To set layouts or quotas, clients require the 'p' flag in addition to 'rw'.
This restricts all the attributes that are set by special extended attributes
with a "ceph." prefix, as well as restricting other means of setting
these fields (such as openc operations with layouts).

For example, in the following snippet client.0 can modify layouts and quotas, 
but client.1 cannot.

::

    client.0
        key: AQAz7EVWygILFRAAdIcuJ12opU/JKyfFmxhuaw==
        caps: [mds] allow rwp
        caps: [mon] allow r
        caps: [osd] allow rw pool=data

    client.1
        key: AQAz7EVWygILFRAAdIcuJ12opU/JKyfFmxhuaw==
        caps: [mds] allow rw
        caps: [mon] allow r
        caps: [osd] allow rw pool=data


.. _User Management - Add a User to a Keyring: ../../rados/operations/user-management/#add-a-user-to-a-keyring