client-auth.rst

CephFS Client Capabilities

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

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 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 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

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

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 modification restriction

To prevent clients from modifying the data pool used for files or directories, use the 'p' modifier in MDS authentication capabilities.

For example, in the following snippet client.0 can modify the pool used for files, 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