KMIP devices are key managers and since Castellan is a key manager interface it seems likely that someone would want Castellan to go directly to a KMIP device instead of a Barbican with a KMIP device on the backend. This blueprint offers a solution to directly talk to a KMIP device using Castellan.
In order to currently talk to a KMIP device with Castellan, Castellan must first talk to a Barbican that is hooked up with a KMIP device on the backend. By creating a KMIP key manager interface, Castellan can interact with the KMIP device directly.
This has the added benefit of allowing a client to decide whether or not they require Barbican sitting in front of their KMIP device. Whether they have their own device or purchase one from the cloud provider, they might not need all of the Barbican functionality or resources and simply want a direct line to the KMIP device.
This will allow for a private or dedicated cloud to use Castellan without needing Barbican.
An important thing to keep in mind is that multi-tenancy is not guaranteed with KMIP devices. Some devices offer the ability to create separate users which does separate keys based on unique user accounts. However, not all devices support this feature. Moreover, KMIP devices do not currently support keystone as a means of authentication. The section below details the future changes and possible support for both multi-tenancy and keystone authentication.
A module will be created titled kmip_key_manager. This module will live where the key manager interfaces live now and can be used to directly interface with a KMIP device.
In order for the KMIP key manager to take in a context object, two new credential types needs to be created. One is Certificate which will just take in the location of a certificate and the other is KMIP which will be an extension of Certificate. The KMIP credential object will take in all the necessary values in order to establish a connection to the KMIP device including a certificate.
The values used by the KMIP credential object will be the same variables used by Barbican to establish a connection to a KMIP device and can be modified via the castellan.conf file or through castellan itself. This will make it possible for KMIP devices that support separate user accounts to provide some multi-tenant capabilities.
When KMIP devices start supporting keystone tokens, the KMIP key manager class can be updated to take in either the KMIP credential object or keystone token credential object as a context. This will allow for full multi-tenant capabilities that we see today in Barbican.
Here is an example of the new values that will be added to the castellan.conf file:
[kmip] # # From castellan.config # # Username for user authorized to access KMIP device (string value) #username = admin # Password for KMIP authenticated user (string value) #password = password # Use this endpoint to connect to the KMIP device (string value) #host = localhost # Port that KMIP device is listening on (string value) #port = 5696 # Keyfile used by castellan (string value) #keyfile = '/path/to/certs/cert.key' # Certificate used by castellan to talk to KMIP device (string value) #certfile = '/path/to/certs/cert.crt' # List of certificates and CA's that castellan willaccept (string value) #ca_certs = '/path/to/certs/LocalCA.crt'
These values can reside in the castellan.conf file or can be added to an already existing configuration file. Castellan just needs to be given the location of the file to read.
The rest of the code will be very similar to the KMIP secret store code within Barbican.
KMIP devices do not guarantee multi-tenant functionality. This means users should be aware that when Castellan is the interface to the KMIP device, any user that has access to the KMIP credentials might be able to talk to the device. There is no differentiation based to the user’s role or project because keystone cannot currently be used as a form of authentication. This will need to be heavily documented.
Any CRUD request to the device will need to be logged. Establishing and ending the connection should also be logged to make sure the connection is successful and successfully terminated.
New unit tests and functional tests need to be added.
Castellan documentation should be updated to reflect the addition of the new backend.