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252 lines
9.1 KiB
ReStructuredText
252 lines
9.1 KiB
ReStructuredText
================================
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CephFS Client Capabilities
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================================
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Use Ceph authentication capabilities to restrict your file system clients
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to the lowest possible level of authority needed.
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.. note:: Path restriction and layout modification restriction are new features
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in the Jewel release of Ceph.
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.. note:: Using Erasure Coded(EC) pools with CephFS is supported only with the
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BlueStore Backend. They cannot be used as metadata pools and overwrites must
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be enabled on the data pools.
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Path restriction
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================
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By default, clients are not restricted in what paths they are allowed to
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mount. Further, when clients mount a subdirectory, e.g., ``/home/user``, the
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MDS does not by default verify that subsequent operations are ‘locked’ within
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that directory.
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To restrict clients to only mount and work within a certain directory, use
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path-based MDS authentication capabilities.
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Syntax
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------
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To grant rw access to the specified directory only, we mention the specified
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directory while creating key for a client using the following syntax::
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ceph fs authorize <fs_name> client.<client_id> <path-in-cephfs> rw
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For example, to restrict client ``foo`` to writing only in the ``bar``
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directory of file system ``cephfs_a``, use ::
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ceph fs authorize cephfs_a client.foo / r /bar rw
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results in:
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client.foo
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key: *key*
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caps: [mds] allow r, allow rw path=/bar
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caps: [mon] allow r
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caps: [osd] allow rw tag cephfs data=cephfs_a
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To completely restrict the client to the ``bar`` directory, omit the
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root directory ::
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ceph fs authorize cephfs_a client.foo /bar rw
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Note that if a client's read access is restricted to a path, they will only
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be able to mount the file system when specifying a readable path in the
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mount command (see below).
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Supplying ``all`` or ``*`` as the file system name will grant access to every
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file system. Note that it is usually necessary to quote ``*`` to protect it
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from the shell.
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See `User Management - Add a User to a Keyring`_. for additional details on
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user management
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To restrict a client to the specified sub-directory only, we mention the
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specified directory while mounting using the following syntax::
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ceph-fuse -n client.<client_id> <mount-path> -r *directory_to_be_mounted*
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For example, to restrict client ``foo`` to ``mnt/bar`` directory, we will
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use::
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ceph-fuse -n client.foo mnt -r /bar
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Free space reporting
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--------------------
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By default, when a client is mounting a sub-directory, the used space (``df``)
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will be calculated from the quota on that sub-directory, rather than reporting
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the overall amount of space used on the cluster.
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If you would like the client to report the overall usage of the file system,
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and not just the quota usage on the sub-directory mounted, then set the
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following config option on the client::
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client quota df = false
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If quotas are not enabled, or no quota is set on the sub-directory mounted,
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then the overall usage of the file system will be reported irrespective of
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the value of this setting.
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Layout and Quota restriction (the 'p' flag)
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===========================================
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To set layouts or quotas, clients require the 'p' flag in addition to 'rw'.
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This restricts all the attributes that are set by special extended attributes
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with a "ceph." prefix, as well as restricting other means of setting
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these fields (such as openc operations with layouts).
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For example, in the following snippet client.0 can modify layouts and quotas
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on the file system cephfs_a, but client.1 cannot::
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client.0
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key: AQAz7EVWygILFRAAdIcuJ12opU/JKyfFmxhuaw==
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caps: [mds] allow rwp
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caps: [mon] allow r
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caps: [osd] allow rw tag cephfs data=cephfs_a
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client.1
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key: AQAz7EVWygILFRAAdIcuJ12opU/JKyfFmxhuaw==
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caps: [mds] allow rw
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caps: [mon] allow r
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caps: [osd] allow rw tag cephfs data=cephfs_a
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Snapshot restriction (the 's' flag)
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===========================================
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To create or delete snapshots, clients require the 's' flag in addition to
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'rw'. Note that when capability string also contains the 'p' flag, the 's'
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flag must appear after it (all flags except 'rw' must be specified in
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alphabetical order).
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For example, in the following snippet client.0 can create or delete snapshots
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in the ``bar`` directory of file system ``cephfs_a``::
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client.0
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key: AQAz7EVWygILFRAAdIcuJ12opU/JKyfFmxhuaw==
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caps: [mds] allow rw, allow rws path=/bar
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caps: [mon] allow r
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caps: [osd] allow rw tag cephfs data=cephfs_a
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.. _User Management - Add a User to a Keyring: ../../rados/operations/user-management/#add-a-user-to-a-keyring
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Network restriction
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===================
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::
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client.foo
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key: *key*
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caps: [mds] allow r network 10.0.0.0/8, allow rw path=/bar network 10.0.0.0/8
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caps: [mon] allow r network 10.0.0.0/8
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caps: [osd] allow rw tag cephfs data=cephfs_a network 10.0.0.0/8
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The optional ``{network/prefix}`` is a standard network name and
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prefix length in CIDR notation (e.g., ``10.3.0.0/16``). If present,
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the use of this capability is restricted to clients connecting from
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this network.
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.. _fs-authorize-multifs:
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File system Information Restriction
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===================================
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If desired, the monitor cluster can present a limited view of the file systems
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available. In this case, the monitor cluster will only inform clients about
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file systems specified by the administrator. Other file systems will not be
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reported and commands affecting them will fail as if the file systems do
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not exist.
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Consider following example. The Ceph cluster has 2 FSs::
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$ ceph fs ls
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name: cephfs, metadata pool: cephfs_metadata, data pools: [cephfs_data ]
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name: cephfs2, metadata pool: cephfs2_metadata, data pools: [cephfs2_data ]
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But we authorize client ``someuser`` for only one FS::
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$ ceph fs authorize cephfs client.someuser / rw
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[client.someuser]
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key = AQAmthpf89M+JhAAiHDYQkMiCq3x+J0n9e8REQ==
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$ cat ceph.client.someuser.keyring
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[client.someuser]
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key = AQAmthpf89M+JhAAiHDYQkMiCq3x+J0n9e8REQ==
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caps mds = "allow rw fsname=cephfs"
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caps mon = "allow r fsname=cephfs"
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caps osd = "allow rw tag cephfs data=cephfs"
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And the client can only see the FS that it has authorization for::
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$ ceph fs ls -n client.someuser -k ceph.client.someuser.keyring
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name: cephfs, metadata pool: cephfs_metadata, data pools: [cephfs_data ]
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Standby MDS daemons will always be displayed. Note that the information about
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restricted MDS daemons and file systems may become available by other means,
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such as ``ceph health detail``.
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MDS communication restriction
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=============================
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By default, user applications may communicate with any MDS, whether or not
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they are allowed to modify data on an associated file system (see
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`Path restriction` above). Client's communication can be restricted to MDS
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daemons associated with particular file system(s) by adding MDS caps for that
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particular file system. Consider the following example where the Ceph cluster
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has 2 FSs::
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$ ceph fs ls
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name: cephfs, metadata pool: cephfs_metadata, data pools: [cephfs_data ]
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name: cephfs2, metadata pool: cephfs2_metadata, data pools: [cephfs2_data ]
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Client ``someuser`` is authorized only for one FS::
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$ ceph fs authorize cephfs client.someuser / rw
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[client.someuser]
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key = AQBPSARfg8hCJRAAEegIxjlm7VkHuiuntm6wsA==
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$ ceph auth get client.someuser > ceph.client.someuser.keyring
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exported keyring for client.someuser
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$ cat ceph.client.someuser.keyring
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[client.someuser]
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key = AQBPSARfg8hCJRAAEegIxjlm7VkHuiuntm6wsA==
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caps mds = "allow rw fsname=cephfs"
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caps mon = "allow r"
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caps osd = "allow rw tag cephfs data=cephfs"
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Mounting ``cephfs1`` with ``someuser`` works::
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$ sudo ceph-fuse /mnt/cephfs1 -n client.someuser -k ceph.client.someuser.keyring --client-fs=cephfs
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ceph-fuse[96634]: starting ceph client
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ceph-fuse[96634]: starting fuse
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$ mount | grep ceph-fuse
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ceph-fuse on /mnt/cephfs1 type fuse.ceph-fuse (rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other)
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But mounting ``cephfs2`` does not::
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$ sudo ceph-fuse /mnt/cephfs2 -n client.someuser -k ceph.client.someuser.keyring --client-fs=cephfs2
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ceph-fuse[96599]: starting ceph client
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ceph-fuse[96599]: ceph mount failed with (1) Operation not permitted
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Root squash
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===========
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The ``root squash`` feature is implemented as a safety measure to prevent
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scenarios such as accidental ``sudo rm -rf /path``. You can enable
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``root_squash`` mode in MDS caps to disallow clients with uid=0 or gid=0 to
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perform write access operations -- e.g., rm, rmdir, rmsnap, mkdir, mksnap.
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However, the mode allows the read operations of a root client unlike in
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other file systems.
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Following is an example of enabling root_squash in a filesystem except within
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'/volumes' directory tree in the filesystem::
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$ ceph fs authorize a client.test_a / rw root_squash /volumes rw
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$ ceph auth get client.test_a
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[client.test_a]
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key = AQBZcDpfEbEUKxAADk14VflBXt71rL9D966mYA==
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caps mds = "allow rw fsname=a root_squash, allow rw fsname=a path=/volumes"
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caps mon = "allow r fsname=a"
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caps osd = "allow rw tag cephfs data=a"
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