title: Device Schema Extensions to the SCIM model abbrev: SCIM Device Schema Extensions docname: draft-shahzad-scim-device-model-02 submissionType: IETF category: std
ipr: trust200902 keyword: Internet-Draft
stand_alone: yes pi: [toc, sortrefs, symrefs]
author:
- ins: M. Shahzad
name: Muhammad Shahzad
org: North Carolina State University
street:
- Department of Computer Science
- 890 Oval Drive
- Campus Box 8206 city: Raleigh, NC code: 27695-8206 country: USA email: mshahza@ncsu.edu
- ins: H. Iqbal
name: Hassan Iqbal
org: North Carolina State University
street:
- Department of Computer Science
- 890 Oval Drive
- Campus Box 8206 city: Raleigh, NC code: 27695-8206 country: USA email: hiqbal@ncsu.edu
- ins: E. Lear name: Eliot Lear org: Cisco Systems street: Richtistrasse 7 code: CH-8304 city: Wallisellen country: Switzerland phone: +41 44 878 9200 email: lear@cisco.com
normative: BLE53: title: Bluetooth Core Specification, Version 5.3 author: - org: Bluetooth SIG date: 2021
DPP2: title: Wi-Fi Easy Connect Specification, Version 2.0 author: - org: Wi-Fi Alliance date: 2020
--- abstract
The initial core schema for SCIM (System for Cross Identity Management) was designed for provisioning users. This memo specifies schema extensions that enables provisioning of devices, using various underlying bootstrapping systems, such as Wifi EasyConnect, RFC 8366 vouchers, and BLE passcodes.
--- middle
The Internet of Things presents a management challenge in many dimensions. One of them is the ability to onboard and manage large number of devices. There are many models for bootstrapping trust between devices and network deployments. Indeed it is expected that different manufacturers will make use of different methods.
SCIM (System for Cross Identity Management) {{!RFC7643}} {{!RFC7644}} defines a protocol and a schema for provisioning of users. However, it can easily be extended to provision devices. The protocol and core schema were designed to permit just such extensions. Bulk operations are supported. This is good because often devices are procured in bulk.
Some might ask why SCIM is well suited for this purpose and not, for example, NETCONF or RESTCONF with YANG. After all, there are all sorts of existing models available. The answer is that the only information being passed about the device is neither state nor device configuration information, but only information necessary to bootstrap trust so that the device may establish connectivity.
In the normal SCIM model, it was presumed that large federated deployments would be SCIM clients who provision and remove employees and contractors as they are enter and depart those deployments, and federated services such as sales, payment, or conferencing services would be the servers.
In the device model, the roles are reversed, and may be somewhat more varied. A deployment network management system gateway (NMS gateway) plays the role of the server, receiving information about devices that are expected to be connected to its network. That server will apply appropriate local policies regarding whether/how the device should be connected.
The client may be one of a number of entities:
-
A vendor who is authorized to add devices to a network as part of a sales transaction. This is similar to the sales integration sometimes envisioned by Bootstrapping Remote Key Infrastructure (BRSKI) {{?RFC8995}}.
-
A client application that administrators or employees use to add, remove, or get information about devices. An example might be an tablet or phone app that scans Easyconnect QR codes.
+-----------------------------------+
| |
+-----------+ Request | +---------+ |
| onboarding|------------->| SCIM | |
| app |<-------------| Server | |
+-----------+ Ctrl Endpt +---------+ |
| |
+-----------+ | +------------+ +-------+ |
| Control |...........|..| ALG |.........|device | |
| App | | +------------+ +-------+ |
+-----------+ | |
| |
+-----------------------------------+
{: #arch title="Basic Architecture"}
In {{arch}}, the onboarding app provides the device particulars. As part of the response, the SCIM server might provide additional information, especially in the case of non-IP devices, where an application-layer gateway may need to be used to communicate with the device. The control endpoint is one among a number of objects that may be returned.
RFC 7643 does not prescribe a language to describe a schema. We have chosen the JSON schema language {{!I-D.bhutton-json-schema}} for this purpose. This implies that use of XML for this device extension is not supported.
Several additional schemas specify specific onboarding mechanisms, such as BLE and Wifi Easy Connect.
Attributes defined in the device core schema and extensions comprise characteristics and SCIM datatypes defined in Sections 2.2 and 2.3 of the {{!RFC7643}}. This RFC does not define new characteristics and datatypes for the SCIM attributes.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 {{!RFC2119}} {{!RFC8174}} when, and only when, they appear in all capitals, as shown here.
Device grouping occurs using the core SCIM group object, as defined in {{!RFC7643}} Section 4.2.
This section defines a new resource type, 'Device'. The "ResourceType" schema specifies the metadata about a resource type (see section 6 of {{!RFC7643}}). The resource "Devices" comprises a core device schema and several extension schemas. The core schema provides a minimal resource representation, whereas extension schemas extend the core schema depending on the device's capability.
<CODE BEGINS>
{::include SCIM_resource_type.json}
<CODE ENDS>
The core device schema provides the minimal representation of a resource "Device". It contains only those attributes that any device may need. Not all attributes are optional. The core schema for "Device" is identified using the schema URI: "urn:ietf:params:scim:schemas:core:2.0:Device". The following attributes are defined in the device core schema, and details of their characteristics are presented in .
The Device schema contains three common attributes as defined in the {{!RFC7643}}.
id
An id is a required and unique attribute of the device core schema (see section 3.1 of {{!RFC7643}}).
externalID
An externalID is an optional attribute (see section 3.1 of {{!RFC7643}}).
meta
Meta is a complex attribute and is required (see section 3.1 of {{!RFC7643}}).
deviceDisplayName
This is a human-readable device name suitable for displaying to end-users. It is a mutable, non-unique, and not required string value. For example, "BLE Heart Monitor".
adminState
This is a required mutable boolean value indicating the device's administrative status. If this variable is set to True, then the device is expected to be accessible. Note that the SCIM server may apply whatever policy it may to establish and control this state.
mudUrl
A URL to the MUD file of the device. When present, the mudUrl may be associated with this device, and used as described in {{!RFC8520}}.
Following is the JSON representation of the Device core schema. Common attributes such as "id" and "externalID" are not presented below.
<CODE BEGINS>
{::include SCIM_device_core_schema_representation.json}
<CODE ENDS>
Following is the minimal example of a device object that does not contain any extension representing the device's communication capability.
<CODE BEGINS>
{::include examples/SCIM_device_core_schema_object.json}
<CODE ENDS>
This section presents various extension schemas, their attributes, JSON representation, and example object. These schemas extend the core device schema based on the device's capability (communication stack). This RFC presents an additional hierarchical level by introducing extensions within an extension. See below for more details.
[[ DISCUSS: Is this okay with the working group? ]]
This schema extends the device schema to represent the devices supporting BLE. The attributes are as follows:
deviceMacAddress
this is the public MAC address assigned by the manufacturer. It is a unique 48-bit value. The regex pattern is the following:
^[0-9A-Fa-f]{2}(:[0-9A-Fa-f]{2}){5}
addressType
This flag is taken from the BLE core specification, 5.3. If FALSE, the device is using a public MAC address. If TRUE, the device uses a Random address resolved using IRK.
irk
Identity resolving key, which is unique for every device. It is used to resolve the random address.
versionSupport
This field provides an array of all the BLE versions supported by the device. For example, [4.1, 4.2, 5.0, 5.1, 5.2, 5.3].
pairingMethods
This attribute is the array of pairing methods associated with the BLE device. The pairing methods may require sub-attributes, such as key/password, for the device pairing process. To enable the scalability of pairing methods in the future, they are represented as extensions to incorporate various attributes that are part of the respective pairing process. Pairing method extensions are nested inside the BLE extension.
The details on pairing methods and their associated attributes are in section 2.3 of {{BLE53}}. This memo defines extensions for four pairing methods that are nested insided the BLE extension schema. They are as follows.
urn:ietf:params:scim:schemas:extension:pairingNull:2.0:Device
This extension does not have any attribute. It allows pairing for BLE devices that do not require a pairing method.
urn:ietf:params:scim:schemas:extension:pairingJustWorks:2.0:Device
Just works pairing method does not require a key to pair devices. For completeness, the key value is set to 'null'.
urn:ietf:params:scim:schemas:extension:pairingPassKey:2.0:Device
The pass key pairing method requires a 6-digit key to pair devices. This extension has one singular attribute, "key". The key pattern is as follows:
^[0-9]{6}$
urn:ietf:params:scim:schemas:extension:pairingOOB:2.0:Device
The out-of-band pairing method includes three singular attributes, i.e., key, randomNumber, and confirmationNumber. The key value is required and received from out-of-bond sources such as NFC. randomNumber is also a required attribute which is nounce added to the key. confirmationNumber is a non-required attribute, which some solutions require in RESTful message exchange.
<CODE BEGINS>
{::include extensions/SCIM_BLE_extension_schema.json}
<CODE ENDS>
<CODE BEGINS>
{::include examples/SCIM_device_ble_object.json}
<CODE ENDS>
This schema extends the device schema to enable WiFi EasyConnect (otherwise known as Device Provisioning Protocol). The attributes in this extension are adopted from {{DPP2}}. The attributes are as follows:
dppVersion This attribute represents the version of DPP the device supports.
bootstrapKey
This key is Elliptic-Curve Diffie–Hellman (ECDH) public key. The base64 encoded lengths for P-256, P-384, and P-521 are 80, 96, and 120 characters.
deviceMacAddress
The manufacturer assigns the MAC address. It is a unique 48-bit value. The regex pattern is as follows:
^[0-9A-Fa-f]{2}(:[0-9A-Fa-f]{2}){5}.
serialNumber
An alphanumeric serial number may also be passed as bootstrapping information.
bootstrappingMethod
It is the array of all the bootstrapping methods available on the enrollee device. For example, [QR, NFC].
classChannel
This attribute is an array of global operating class and channel shared as bootstrapping information. It is formatted as class/channel. For example, ['81/1','115/36'].
<CODE BEGINS>
{::include extensions/SCIM_DPP_extension_schema.json}
<CODE ENDS>
<CODE BEGINS>
{::include examples/SCIM_device_dpp_object.json}
<CODE ENDS>
This schema extends the device schema to enable the provisioning of Zigbee devices. It has one singular attribute and one multivalued attribute. The attributes are as follows:
deviceEui64Address
this attribute is an EUI-64 (Extended Unique Identifier) device address. The regex pattern is as follows:
^[0-9A-Fa-f]{16}$
versionSupport
This attribute provides an array of all the Zigbee versions supported by the device. For example, [3.0].
<CODE BEGINS>
{::include extensions/SCIM_zigbee_extension_schema.json}
<CODE ENDS>
<CODE BEGINS>
{::include examples/SCIM_device_zigbee_object.json}
<CODE ENDS>
Sometimes non-IP devices such as those using BLE or Zigbe require an application gateway interface to manage them. SCIM clients MUST NOT specify this to describe native IP-based devices.
The device schema is a base schema upon which specific onboarding technology schemas are built. This extension provides two complex attributes deviceControl, and dataReceiver to represent two types of partner endpoint applications, device control, and data receiver applications, respectively. These complex attributes and their respective sub-attributes are as follows:
This complex attribute represents the application responsible for controlling the device. Device control applications provide access control for the device. It determines which other applications can access the data from the device. Depending on the use case, there can be more than one device control application.
"deviceControl" has two attributes: i) a multvalued client-tokens attribute" and ii) a singular attribute called "enterpriseEndpoint". Their details are as follows:
client-tokens
This attribute contains a list of tokens that the client will used to authenticate itself. Each token may be a string up to 500 characters in length.
[[ We probably need something better here. ]]
enterpriseEndpoint
Device control apps use the URL of the enterprise endpoint to reach the network gateway. When the enterprise receives the SCIM object from the onboarding app, it adds this attribute to it and sends it back as a response to the onboarding app.
This complex attribute represents the application that receives data from the device. Depending on the use case, there can be more than one data receiver application.
"dataReceiver" has two attributes:
-
a multi-valued attribute called "client-tokens".
-
a singular attribute called "enterpriseEndpoint".
The complex attribute "apps" provides the URLs and root certificates of the respective data receiver applications in an array. Their details are as follows:
client-tokens
This attribute contains a list of tokens that the client will used to authenticate itself. Each token may be a string up to 500 characters in length.
[[ We probably need something better here. ]]
enterpriseEndpoint
Data receiver apps use the URL of the enterprise endpoint to reach the network gateway. When the enterprise receives the SCIM object from the onboarding app, it adds this attribute to it and sends it back as a response to the onboarding app.
<CODE BEGINS>
{::include extensions/SCIM_endpoint_extension_schema.json}}
<CODE ENDS>
This example object below presents a BLE device along with the application endpoints.
<CODE BEGINS>
{::include examples/SCIM_device_endpoints_with_ble_object.json}}
<CODE ENDS>
Because provisioning operations are senstive, each client must be appropriately authenticated. Certain objects may be read-only or not visible based on who is connected.
[ More to be added here. ]
TBD
Draft -01:
- Doh! We forgot the core device schemea!
Draft -00:
- Initial revision