.. index::
   single: Access Control List (ACL)

.. _acl:

Access Control Lists (ACLs)
---------------------------

By default, the ``root`` user or any user in the |CRM_DAEMON_GROUP| group can
modify Pacemaker's CIB without restriction. Pacemaker offers *access control
lists (ACLs)* to provide more fine-grained authorization.
   
.. important::

   Being able to modify the CIB's resource section allows a user to run any
   executable file as root, by configuring it as an LSB resource with a full
   path.

ACL Prerequisites
#################
   
In order to use ACLs:

* The ``enable-acl`` :ref:`cluster option <cluster_options>` must be set to
  true.

* Desired users must have user accounts in the |CRM_DAEMON_GROUP| group on all
  cluster nodes in the cluster.

* If your CIB was created before Pacemaker 1.1.12, it might need to be updated
  to the current schema (using ``cibadmin --upgrade`` or a higher-level tool
  equivalent) in order to use the syntax documented here.

* Prior to the 2.1.0 release, the Pacemaker software had to have been built
  with ACL support. If you are using an older release, your installation
  supports ACLs only if the output of the command ``pacemakerd --features``
  contains ``acls``. In newer versions, ACLs are always enabled.
   

.. index::
   single: Access Control List (ACL); acls
   pair: acls; XML element

ACL Configuration
#################

ACLs are specified within an ``acls`` element of the CIB. The ``acls`` element
may contain any number of ``acl_role``, ``acl_target``, and ``acl_group``
elements.
   

.. index::
   single: Access Control List (ACL); acl_role
   pair: acl_role; XML element

ACL Roles
#########

An ACL *role* is a collection of permissions allowing or denying access to
particular portions of the CIB. A role is configured with an ``acl_role``
element in the CIB ``acls`` section.
   
.. table:: **Properties of an acl_role element**
   :widths: 1 3

   +------------------+-----------------------------------------------------------+
   | Attribute        | Description                                               |
   +==================+===========================================================+
   | id               | .. index::                                                |
   |                  |    single: acl_role; id (attribute)                       |
   |                  |    single: id; acl_role attribute                         |
   |                  |    single: attribute; id (acl_role)                       |
   |                  |                                                           |
   |                  | A unique name for the role *(required)*                   |
   +------------------+-----------------------------------------------------------+
   | description      | .. index::                                                |
   |                  |    single: acl_role; description (attribute)              |
   |                  |    single: description; acl_role attribute                |
   |                  |    single: attribute; description (acl_role)              |
   |                  |                                                           |
   |                  | Arbitrary text (not used by Pacemaker)                    |
   +------------------+-----------------------------------------------------------+

An ``acl_role`` element may contain any number of ``acl_permission`` elements.
   
.. index::
   single: Access Control List (ACL); acl_permission
   pair: acl_permission; XML element

.. table:: **Properties of an acl_permission element**
   :widths: 1 3

   +------------------+-----------------------------------------------------------+
   | Attribute        | Description                                               |
   +==================+===========================================================+
   | id               | .. index::                                                |
   |                  |    single: acl_permission; id (attribute)                 |
   |                  |    single: id; acl_permission attribute                   |
   |                  |    single: attribute; id (acl_permission)                 |
   |                  |                                                           |
   |                  | A unique name for the permission *(required)*             |
   +------------------+-----------------------------------------------------------+
   | description      | .. index::                                                |
   |                  |    single: acl_permission; description (attribute)        |
   |                  |    single: description; acl_permission attribute          |
   |                  |    single: attribute; description (acl_permission)        |
   |                  |                                                           |
   |                  | Arbitrary text (not used by Pacemaker)                    |
   +------------------+-----------------------------------------------------------+
   | kind             | .. index::                                                |
   |                  |    single: acl_permission; kind (attribute)               |
   |                  |    single: kind; acl_permission attribute                 |
   |                  |    single: attribute; kind (acl_permission)               |
   |                  |                                                           |
   |                  | The access being granted. Allowed values are ``read``,    |
   |                  | ``write``, and ``deny``. A value of ``write`` grants both |
   |                  | read and write access.                                    |
   +------------------+-----------------------------------------------------------+
   | object-type      | .. index::                                                |
   |                  |    single: acl_permission; object-type (attribute)        |
   |                  |    single: object-type; acl_permission attribute          |
   |                  |    single: attribute; object-type (acl_permission)        |
   |                  |                                                           |
   |                  | The name of an XML element in the CIB to which the        |
   |                  | permission applies. (Exactly one of ``object-type``,      |
   |                  | ``xpath``, and ``reference`` must be specified for a      |
   |                  | permission.)                                              |
   +------------------+-----------------------------------------------------------+
   | attribute        | .. index::                                                |
   |                  |    single: acl_permission; attribute (attribute)          |
   |                  |    single: attribute; acl_permission attribute            |
   |                  |    single: attribute; attribute (acl_permission)          |
   |                  |                                                           |
   |                  | If specified, the permission applies only to              |
   |                  | ``object-type`` elements that have this attribute set (to |
   |                  | any value). If not specified, the permission applies to   |
   |                  | all ``object-type`` elements. May only be used with       |
   |                  | ``object-type``.                                          |
   +------------------+-----------------------------------------------------------+
   | reference        | .. index::                                                |
   |                  |    single: acl_permission; reference (attribute)          |
   |                  |    single: reference; acl_permission attribute            |
   |                  |    single: attribute; reference (acl_permission)          |
   |                  |                                                           |
   |                  | The ID of an XML element in the CIB to which the          |
   |                  | permission applies. (Exactly one of ``object-type``,      |
   |                  | ``xpath``, and ``reference`` must be specified for a      |
   |                  | permission.)                                              |
   +------------------+-----------------------------------------------------------+
   | xpath            | .. index::                                                |
   |                  |    single: acl_permission; xpath (attribute)              |
   |                  |    single: xpath; acl_permission attribute                |
   |                  |    single: attribute; xpath (acl_permission)              |
   |                  |                                                           |
   |                  | An `XPath <https://www.w3.org/TR/xpath-10/>`_             |
   |                  | specification selecting an XML element in the CIB to      |
   |                  | which the permission applies. Attributes may be specified |
   |                  | in the XPath to select particular elements, but the       |
   |                  | permissions apply to the entire element. (Exactly one of  |
   |                  | ``object-type``, ``xpath``, and ``reference`` must be     |
   |                  | specified for a permission.)                              |
   +------------------+-----------------------------------------------------------+

.. important::

   * Permissions are applied to the selected XML element's entire XML subtree
     (all elements enclosed within it).
   
   * Write permission grants the ability to create, modify, or remove the
     element and its subtree, and also the ability to create any "scaffolding"
     elements (enclosing elements that do not have attributes other than an
     ID).
   
   * Permissions for more specific matches (more deeply nested elements) take
     precedence over more general ones.
   
   * If multiple permissions are configured for the same match (for example, in
     different roles applied to the same user), any ``deny`` permission takes
     precedence, then ``write``, then lastly ``read``.
   

ACL Targets and Groups
######################
   
ACL targets correspond to user accounts on the system.

.. index::
   single: Access Control List (ACL); acl_target
   pair: acl_target; XML element

.. table:: **Properties of an acl_target element**
   :widths: 1 3

   +------------------+-----------------------------------------------------------+
   | Attribute        | Description                                               |
   +==================+===========================================================+
   | id               | .. index::                                                |
   |                  |    single: acl_target; id (attribute)                     |
   |                  |    single: id; acl_target attribute                       |
   |                  |    single: attribute; id (acl_target)                     |
   |                  |                                                           |
   |                  | A unique identifier for the target (if ``name`` is not    |
   |                  | specified, this must be the name of the user account)     |
   |                  | *(required)*                                              |
   +------------------+-----------------------------------------------------------+
   | name             | .. index::                                                |
   |                  |    single: acl_target; name (attribute)                   |
   |                  |    single: name; acl_target attribute                     |
   |                  |    single: attribute; name (acl_target)                   |
   |                  |                                                           |
   |                  | If specified, the user account name (this allows you to   |
   |                  | specify a user name that is already used as the ``id``    |
   |                  | for some other configuration element) *(since 2.1.5)*     |
   +------------------+-----------------------------------------------------------+

ACL groups correspond to groups on the system. Any role configured for these
groups apply to all users in that group *(since 2.1.5)*.
   
.. index::
   single: Access Control List (ACL); acl_group
   pair: acl_group; XML element

.. table:: **Properties of an acl_group element**
   :widths: 1 3

   +------------------+-----------------------------------------------------------+
   | Attribute        | Description                                               |
   +==================+===========================================================+
   | id               | .. index::                                                |
   |                  |    single: acl_group; id (attribute)                      |
   |                  |    single: id; acl_group attribute                        |
   |                  |    single: attribute; id (acl_group)                      |
   |                  |                                                           |
   |                  | A unique identifier for the group (if ``name`` is not     |
   |                  | specified, this must be the group name) *(required)*      |
   +------------------+-----------------------------------------------------------+
   | name             | .. index::                                                |
   |                  |    single: acl_group; name (attribute)                    |
   |                  |    single: name; acl_group attribute                      |
   |                  |    single: attribute; name (acl_group)                    |
   |                  |                                                           |
   |                  | If specified, the group name (this allows you to specify  |
   |                  | a group name that is already used as the ``id`` for some  |
   |                  | other configuration element)                              |
   +------------------+-----------------------------------------------------------+

Each ``acl_target`` and ``acl_group`` element may contain any number of ``role``
elements.

.. note::

   If the system users and groups are defined by some network service (such as
   LDAP), the cluster itself will be unaffected by outages in the service, but
   affected users and groups will not be able to make changes to the CIB.


.. index::
   single: Access Control List (ACL); role
   pair: role; XML element

.. table:: **Properties of a role element**
   :widths: 1 3

   +------------------+-----------------------------------------------------------+
   | Attribute        | Description                                               |
   +==================+===========================================================+
   | id               | .. index::                                                |
   |                  |    single: role; id (attribute)                           |
   |                  |    single: id; role attribute                             |
   |                  |    single: attribute; id (role)                           |
   |                  |                                                           |
   |                  | The ``id`` of an ``acl_role`` element that specifies      |
   |                  | permissions granted to the enclosing target or group.     |
   +------------------+-----------------------------------------------------------+

.. important::

   The ``root`` and |CRM_DAEMON_USER| user accounts always have full access to
   the CIB, regardless of ACLs. For all other user accounts, when ``enable-acl``
   is true, permission to all parts of the CIB is denied by default (permissions
   must be explicitly granted).
   
ACL Examples
############
   
.. code-block:: xml

   <acls>
   
      <acl_role id="read_all">
          <acl_permission id="read_all-cib" kind="read" xpath="/cib" />
      </acl_role>
   
      <acl_role id="operator">
   
          <acl_permission id="operator-maintenance-mode" kind="write"
              xpath="//crm_config//nvpair[@name='maintenance-mode']" />
   
          <acl_permission id="operator-maintenance-attr" kind="write"
              xpath="//nvpair[@name='maintenance']" />
   
          <acl_permission id="operator-target-role" kind="write"
              xpath="//resources//meta_attributes/nvpair[@name='target-role']" />
   
          <acl_permission id="operator-is-managed" kind="write"
              xpath="//resources//nvpair[@name='is-managed']" />
   
          <acl_permission id="operator-rsc_location" kind="write"
              object-type="rsc_location" />
   
      </acl_role>
   
      <acl_role id="administrator">
          <acl_permission id="administrator-cib" kind="write" xpath="/cib" />
      </acl_role>
   
      <acl_role id="minimal">
   
          <acl_permission id="minimal-standby" kind="read"
              description="allow reading standby node attribute (permanent or transient)"
              xpath="//instance_attributes/nvpair[@name='standby']"/>
   
          <acl_permission id="minimal-maintenance" kind="read"
              description="allow reading maintenance node attribute (permanent or transient)"
              xpath="//nvpair[@name='maintenance']"/>
   
          <acl_permission id="minimal-target-role" kind="read"
              description="allow reading resource target roles"
              xpath="//resources//meta_attributes/nvpair[@name='target-role']"/>
   
          <acl_permission id="minimal-is-managed" kind="read"
              description="allow reading resource managed status"
              xpath="//resources//meta_attributes/nvpair[@name='is-managed']"/>
   
          <acl_permission id="minimal-deny-instance-attributes" kind="deny"
              xpath="//instance_attributes"/>
   
          <acl_permission id="minimal-deny-meta-attributes" kind="deny"
              xpath="//meta_attributes"/>
   
          <acl_permission id="minimal-deny-operations" kind="deny"
              xpath="//operations"/>
   
          <acl_permission id="minimal-deny-utilization" kind="deny"
              xpath="//utilization"/>
   
          <acl_permission id="minimal-nodes" kind="read"
              description="allow reading node names/IDs (attributes are denied separately)"
              xpath="/cib/configuration/nodes"/>
   
          <acl_permission id="minimal-resources" kind="read"
              description="allow reading resource names/agents (parameters are denied separately)"
              xpath="/cib/configuration/resources"/>
   
          <acl_permission id="minimal-deny-constraints" kind="deny"
              xpath="/cib/configuration/constraints"/>
   
          <acl_permission id="minimal-deny-topology" kind="deny"
              xpath="/cib/configuration/fencing-topology"/>
   
          <acl_permission id="minimal-deny-op_defaults" kind="deny"
              xpath="/cib/configuration/op_defaults"/>
   
          <acl_permission id="minimal-deny-rsc_defaults" kind="deny"
              xpath="/cib/configuration/rsc_defaults"/>
   
          <acl_permission id="minimal-deny-alerts" kind="deny"
              xpath="/cib/configuration/alerts"/>
   
          <acl_permission id="minimal-deny-acls" kind="deny"
              xpath="/cib/configuration/acls"/>
   
          <acl_permission id="minimal-cib" kind="read"
              description="allow reading cib element and crm_config/status sections"
              xpath="/cib"/>
   
      </acl_role>
   
      <acl_target id="alice">
         <role id="minimal"/>
      </acl_target>
   
      <acl_target id="bob">
         <role id="read_all"/>
      </acl_target>
   
      <acl_target id="carol">
         <role id="read_all"/>
         <role id="operator"/>
      </acl_target>
   
      <acl_target id="dave">
         <role id="administrator"/>
      </acl_target>
   
   </acls>

In the above example, the user ``alice`` has the minimal permissions necessary
to run basic Pacemaker CLI tools, including using ``crm_mon`` to view the
cluster status, without being able to modify anything. The user ``bob`` can
view the entire configuration and status of the cluster, but not make any
changes. The user ``carol`` can read everything, and change selected cluster
properties as well as resource roles and location constraints. Finally,
``dave`` has full read and write access to the entire CIB.

Looking at the ``minimal`` role in more depth, it is designed to allow read
access to the ``cib`` tag itself, while denying access to particular portions
of its subtree (which is the entire CIB).

This is because the DC node is indicated in the ``cib`` tag, so ``crm_mon``
will not be able to report the DC otherwise. However, this does change the
security model to allow by default, since any portions of the CIB not
explicitly denied will be readable. The ``cib`` read access could be removed
and replaced with read access to just the ``crm_config`` and ``status``
sections, for a safer approach at the cost of not seeing the DC in status
output.

For a simpler configuration, the ``minimal`` role allows read access to the
entire ``crm_config`` section, which contains cluster properties. It would be
possible to allow read access to specific properties instead (such as
``stonith-enabled``, ``dc-uuid``, ``have-quorum``, and ``cluster-name``) to
restrict access further while still allowing status output, but cluster
properties are unlikely to be considered sensitive.


ACL Limitations
###############

Actions performed via IPC rather than the CIB
_____________________________________________

ACLs apply *only* to the CIB.

That means ACLs apply to command-line tools that operate by reading or writing
the CIB, such as ``crm_attribute`` when managing permanent node attributes,
``crm_mon``, and ``cibadmin``.

However, command-line tools that communicate directly with Pacemaker daemons
via IPC are not affected by ACLs. For example, users in the |CRM_DAEMON_GROUP|
group may still do the following, regardless of ACLs:

* Query transient node attribute values using ``crm_attribute`` and
  ``attrd_updater``.

* Query basic node information using ``crm_node``.

* Erase resource operation history using ``crm_resource``.

* Query fencing configuration information, and execute fencing against nodes,
  using ``stonith_admin``.

ACLs and Pacemaker Remote
_________________________

ACLs apply to commands run on Pacemaker Remote nodes using the Pacemaker Remote
node's name as the ACL user name.

The idea is that Pacemaker Remote nodes (especially virtual machines and
containers) are likely to be purpose-built and have different user accounts
from full cluster nodes.