Add certificate plugin page

Add a page detailing the certificate plugin, including classes and
the interaction of plugin methods with barbican 'core' logic.

Change-Id: Iade34e4b021fe12afb7e4eeba107327cbb70e43f

barbican/plugin/interface/certificate_manager.py

@@ -266,7 +266,22 @@ class CertificatePluginBase(object):
 
 
 class CertificateStatus(object):
-    """Defines statuses for certificate request process."""
+    """Defines statuses for certificate request process.
+
+    In particular:
+
+    CERTIFICATE_GENERATED - Indicates a certificate was created
+
+    WAITING_FOR_CA - Waiting for Certificate authority (CA) to complete order
+
+    CLIENT_DATA_ISSUE_SEEN - Problem was seen with client-provided data
+
+    CA_UNAVAILABLE_FOR_REQUEST - CA was not available, will try again later
+
+    REQUEST_CANCELED - The client or CA cancelled this order
+
+    INVALID_OPERATION - Unexpected error seen processing order
+    """
 
     CERTIFICATE_GENERATED = "certificate generated"
     WAITING_FOR_CA = "waiting for CA"
@@ -277,7 +292,12 @@ class CertificateStatus(object):
 
 
 class ResultDTO(object):
-    """This object is the result data transfer object (DTO)."""
+    """Result data transfer object (DTO).
+
+    An object of this type is returned by most certificate plugin methods, and
+    is used to guide follow on processing and to provide status feedback to
+    clients.
+    """
     def __init__(self, status, status_message=None, certificate=None,
                  intermediates=None, retry_msec=RETRY_MSEC, retry_method=None):
         """Creates a new ResultDTO.

doc/source/plugin/certificate.rst

@@ -0,0 +1,211 @@
+.. module:: barbican.plugin.interface.certificate_manager
+
+==============================
+Certificate Plugin Development
+==============================
+
+This guide describes how to develop a custom certificate plugin for use by
+Barbican.
+
+Barbican core orchestrates generating SSL certificates, delegating to
+certificate plugins any required actions. Certificate actions include
+initiating a certificate order, checking for order updates, and retrieving
+generated certificates. Barbican plans to include the following certificate
+plugins:
+
+1. A Red Hat Dogtag certificate authority (CA) plugin capable of generating
+   certificates once the order is initiated.
+
+2. A Symantec plugin able to interact with the Symantec CA service, requiring
+   periodic status updates to see if certificates are ready.
+
+3. A DigiCert plugin able to interact with the DigiCert CA service, with a
+   similar interactions as with Symantec.
+
+
+
+
+``certificate_manager`` Module
+==============================
+
+The ``barbican.plugin.interface.certificate_manager`` module contains the
+classes needed to implement a custom plugin.  These classes include the
+``CertificatePluginBase`` abstract base class which custom plugins should
+inherit from, as well as any Data Transfer Object (DTO) classes used to pass
+information into and from plugin methods.
+
+
+Data Transfer Objects
+=====================
+
+The DTO classes are used to wrap data that is passed from Barbican to the
+plugin as well as data that is returned from the plugin back to Barbican.
+They provide a level of isolation between the plugins and Barbican's internal
+data models.
+
+.. autoclass:: ResultDTO
+
+
+.. _plugin-certificate-status-label:
+
+Certificate Status Class
+========================
+
+When certificate plugin methods are invoked, they return a ``ResultDTO`` that
+includes one of the status response constants defined by the
+``CertificateStatus`` class. As detailed in the
+:ref:`plugin-certificate-sequence-label` section below Barbican core directs
+follow on processing for a certificate order based on these returned status
+constants.
+
+.. autoclass:: CertificateStatus
+   :members:
+
+
+Certificate Parameter Objects
+=============================
+
+Two dictionaries are available to most certificate plugin methods:
+
+1. ``order_meta`` - A dictionary of values provided by the client when they
+   initiated the Barbican certificate order, including information needed to
+   create a certificate, such as CSR.
+
+2. ``plugin_meta`` - A dictionary of values determined by the plugin itself
+   on behalf of a specific certificate order. Barbican core persists this
+   dictionary into the Barbican data store for a given order, and then provides
+   this data back plugin method invocations thereafter.
+
+   Plugins are free to update this data as required, or else ignore to it if not
+   required. For example, plugins that interact with remote CAs could store the
+   CA's unique order ID, for use with future interactions with that CA.
+
+
+Plugin Base Class
+=================
+
+Barbican secret store plugins should implement the abstract base class
+``CertificatePluginBase``. Concrete plugin implementations of
+``CertificatePluginBase`` should be exposed to Barbican using ``stevedore``
+mechanisms explained in the configuration portion of this guide.
+
+.. autoclass:: CertificatePluginBase
+   :members:
+
+
+Barbican Order's Status Versus ResultDTO's Status
+=================================================
+
+When Barbican starts processing orders, it sets the order's ``status``
+attribute to ``PENDING``. Barbican will invoke methods on the certificate
+plugin to process the order, and most of those methods return a ``ResultDTO``
+result object, which also has a ``status`` field. Barbican core uses the
+result's ``status`` to determine follow on processing for the order as
+detailed in :ref:`plugin-certificate-sequence-label` below.
+
+The result's ``status`` field should be set to one of the constants defined
+in ``CertificateStatus``, per :ref:`plugin-certificate-status-label` above. If
+the result's ``status`` calls for terminating the order, Barbican core will set
+the order's status to either ``ACTIVE`` or ``ERROR``. Otherwise the order's
+``status`` will stay ``PENDING``, and the order's ``sub_status`` and
+``sub_status_message`` will be updated with the result's ``status`` and
+``status_message`` respectively.
+
+Clients that wish to track the progress of potentially long running certificate
+orders can poll the order, using the ``sub_status`` and ``sub_status_message``
+to track the results. Hence plugins should provide a meaningful
+message for ``sub_status_message``, especially on error conditions.
+
+
+.. _plugin-certificate-sequence-label:
+
+Barbican Core Plugin Sequence
+=============================
+
+The sequence that Barbican invokes methods on ``CertificatePluginBase`` is
+detailed next. Note that these methods are invoked via the
+``barbican.tasks.certificate_resources`` module, which in turn is invoked via
+Barbican's Worker processes.
+
+Barbican core calls the following methods:
+
+1. ``supports()`` -  Asks the plugin if it can support generating a certificate
+   based on the Barbican order's ``order_meta``.
+
+2. ``issue_certificate_request()`` - Asks the plugin to initiate a certificate
+   order from the provided ``order_meta`` parameter information. An empty
+   dictionary is passed in for the ``plugin_meta`` parameter, which the plugin
+   can update as it sees fit. Barbican core will persist and then provide the
+   ``plugin_meta`` for subsequent method calls for this order.
+
+   The plugin method returns a ``ResultDTO`` instance which Barbican core uses
+   to determine subsequent order processing based on its ``status`` field. This
+   ``status`` field should be set to one of the constants defined in
+   ``CertificateStatus`` per :ref:`plugin-certificate-status-label` above.
+
+   If ``status`` is ``CertificateStatus.WAITING_FOR_CA`` then Barbican core
+   will invoke the ``check_certificate_status`` method after the delay
+   specified in the result's ``retry_msec`` field.
+
+   If ``status`` is ``CertificateStatus.CERTIFICATE_GENERATED`` then Barbican
+   core expects that this order is completed and sets its ``status`` to
+   ``ACTIVE``. Barbican also expects that the result's ``certificate`` and
+   (optionally) ``intermediates`` fields are filled out with PEM-formatted SSL
+   certificate data. Barbican will then create a
+   ``barbican.model.models.Container`` record with
+   ``barbican.model.models.Secret`` records to hold the certificate data.
+
+   If ``status`` is ``CertificateStatus.CA_UNAVAILABLE_FOR_REQUEST`` then
+   Barbican core will invoke the same method after the delay specified in the
+   result's ``retry_msec`` field. This condition typically means that a remote
+   CA was not available, so should be retried in the future.
+
+   If ``status`` is set to ``CertificateStatus.CLIENT_DATA_ISSUE_SEEN`` then
+   Barbican considers the order to have problems with the client-provided data,
+   but otherwise the order is viable. Barbican will keep the order in the
+   ``PENDING`` state, and update the order's ``sub_status`` to
+   ``CertificateStatus.CLIENT_DATA_ISSUE_SEEN`` and ``sub_status_message`` to
+   the result's ``status_message``.
+
+   Note that client data issues can include missing or incorrect information
+   that the CA reports on. The CA still considers the order open, but clients
+   must provide updates to correct the data. Since the client could either
+   update this order via Barbican, or else work directly with a remote CA,
+   Barbican will invoke the ``check_certificate_status`` method after the delay
+   specified in the result's ``retry_msec`` field.
+
+   If ``status`` is set to ``CertificateStatus.REQUEST_CANCELED`` then Barbican
+   core expects that this order is completed and sets its ``status`` to
+   ``ACTIVE``. It also updates the order's ``sub_status`` and
+   ``sub_status_message`` to the result's status information. This condition
+   could arise (for example) if a remote CA indicated that the certificate
+   order is cancelled.
+
+   If ``status`` is set to ``CertificateStatus.INVALID_OPERATION`` (or else
+   the plugin raises an exception) then Barbican core considers this a failed
+   order and sets the order's ``status`` to ``ERROR``. It also updates the
+   order's ``sub_status`` and ``sub_status_message`` to the result's status
+   information.
+
+3. ``check_certificate_status()`` - This method is called as needed after the
+   ``issue_certificate_request()`` method and is intended to allow plugins to
+   check to see if a certificate has been issued yet.
+
+   The result's ``status`` is processed similarly to the
+   ``issue_certificate_request()`` method.
+
+4. ``modify_certificate_request`` - This method is invoked if clients provide
+   updates to the order metadata after the certificate order has been
+   initiated.
+
+   The result's ``status`` is processed similarly to the
+   ``issue_certificate_request()`` method.
+
+5. ``cancel_certificate_request`` - This method is invoked if clients delete
+   or cancel a certificate order.
+
+   Note that if a remote CA is involved the cancellation may not be processed
+   immediately, in which case Barbican core will invoke the
+   ``check_certificate_status`` method after the delay specified in the
+   result's ``retry_msec`` field. Otherwise the result's ``status`` is
+   processed similarly to the ``issue_certificate_request()`` method.

doc/source/plugin/index.rst

@@ -29,3 +29,4 @@ Barbican, as well as configuration and deployment options.
 
    secret_store
    crypto
+   certificate