ceph/doc/cephfs/client-auth.rst

================================
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 using the following syntax. ::

 ceph fs authorize *filesystem_name* client.*client_name* /*specified_directory* rw

for example, to restrict client ``foo`` to writing only in the ``bar`` directory of filesystem ``cephfs``, use ::

 ceph fs authorize cephfs client.foo / r /bar rw

 results in:

 client.foo
   key: *key*
   caps: [mds] allow r, allow rw path=/bar
   caps: [mon] allow r
   caps: [osd] allow rw tag cephfs data=cephfs_a

To completely restrict the client to the ``bar`` directory, omit the
root directory ::

 ceph fs authorize cephfs client.foo /bar rw

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).

Supplying ``all`` or ``*`` as the filesystem name will grant access to every
file system. Note that it is usually necessary to quote ``*`` to protect it from
the shell.

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 using the following 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.

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
on the filesystem cephfs_a, but client.1 cannot.

::

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

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


Snapshot restriction (the 's' flag)
===========================================

To create or delete snapshots, clients require the 's' flag in addition to 'rw'.
Note that when capability string also contains the 'p' flag, the 's' flag must
appear after it (all flags except 'rw' must be specified in alphabetical order).

For example, in the following snippet client.0 can create or delete snapshots
in the ``bar`` directory of filesystem ``cephfs_a``.

::

    client.0
        key: AQAz7EVWygILFRAAdIcuJ12opU/JKyfFmxhuaw==
        caps: [mds] allow rw, allow rws path=/bar
        caps: [mon] allow r
        caps: [osd] allow rw tag cephfs data=cephfs_a


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