Internet DRAFT - draft-vattaparambil-iotops-poa-based-onboarding
draft-vattaparambil-iotops-poa-based-onboarding
IOTOPS Sreelakshmi
Internet-Draft Olov
Intended status: Informational Ulf
Expires: 29 September 2023 Lulea University of Technology
28 March 2023
draft-vattaparambil-iotops-poa-based-onboarding-01
draft-vattaparambil-iotops-poa-based-onboarding-01
Abstract
Industrial network layer onboarding demands a technique that is
efficient, scalable, and secure. In this document, we propose Power
of Attorney based authorization technique as a decentralized solution
for onboarding devices. This enables users such as integrators and
subcontractors to onboard devices permanently or temporarily
according to terms and requirements set in the PoAs.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on 29 September 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Onboarding basics . . . . . . . . . . . . . . . . . . . . . . 3
2.1. State of the art . . . . . . . . . . . . . . . . . . . . 3
2.2. Problem description . . . . . . . . . . . . . . . . . . . 4
3. Power of Attorney based authorization . . . . . . . . . . . . 4
4. Power of Attorney based Onboarding . . . . . . . . . . . . . 5
5. PoA Structure . . . . . . . . . . . . . . . . . . . . . . . . 7
6. Related Works . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7.1. Attacks out of scope . . . . . . . . . . . . . . . . . . 11
7.2. Attacks in scope . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . 11
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
Onboarding devices in industrial setting must be efficient, scalable,
and secure. NIST guidelines on network layer onboarding [NIST]
explain essential features required by an ideal onboarding model.
Many zero touch onboarding models require the manufacturer to build
and configure devices with specific onboarding features based on the
destination network. It is complex to gather the onboarding
requirements from multiple parties involved based on a centralized
infrastructure, which makes it expensive and inefficient.
The Power of Attorney (PoA) based onboarding can secure the device
with unique onboarding credentials during deployment rather than at
the time of manufacture. This approach is based on subgranting or
delegation based authorization, in which power or delegation can be
granted to another entity for a limited time. This can be used
between different parties in the supply chain and with integrators
for ultimate onboarding in at the customer site. It can also be used
in typical industrial subcontractor usecases where devices owned by
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subcontractors must/should temporarily (ie., for limited time) be
onboarded to an industrial site while the formal ownership is
retained by the subcontractor. The PoA based onboarding primarily
addresses autonomous or semi-autonomous devices that are not resource
constrained. The PoA ensures authorization between the device and
the industrial site onboarding controller, which ultimately approves
the onboarding based on certificates. In the proposed model, we
establish a trust chain between the subcontractor, device, and the
onboarding component for automatic onboarding of devices using power
of attorney based authorization technique.
Note that in this document we focus on the onboarding case using PoA
while indeed PoA is completely generic and can be used in various
other subgranting, ownership transfer, and data sharing usecases, not
covered in this document.
1.1. Requirements Language
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.
2. Onboarding basics
2.1. State of the art
Device onboarding can be defined as an automated process of securely
provisioning the device at the destination network from the
manufacturer’s site via the supplychain. One aspect of onboarding is
providing the device with network access [nordmark-iotops]. There
are different definitions for onboarding; Intel zero touch onboarding
[Intel] refers it as an ”Automated service that enables a device to
be drop-shipped and powered on to dynamically provision to a
customer’s IoT platform of choice in seconds”. According to Amazon
Web Services (AWS), ”IoT device onboarding or provisioning refers to
the process of configuring devices with unique identities,
registering these identities with their IoT endpoint, and associating
required permissions”. NIST guidelines are also referred by IETF
[t2trg], ”Onboarding is sometimes used as a synonym for bootstrapping
and at other times is defined as a subprocess of bootstrapping”.
According to the guidelines provided by NIST, onboarding can be
performed in two different layers:
* Network layer onboarding
* Application layer onboarding.
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The network layer onboarding may ensure device integrity and
authorized ownership throughout the initial phases of onboarding.
The information gathered during network layer onboarding is passed to
application layer onboarding to make the device operational in the
application layer.
2.2. Problem description
The main issues in a device lifecycle are device ownership transfer,
management of the device after bootstrapping such as installing
required software, its maintenance, and disposition of the device
when transitioning to a new owner. Because of the large number of
external devices and the security issues caused by their
communication, device onboarding is considered as an important
process. Multiple entities, transportation methods, sensitive data
sharing, and other factors make the onboarding process difficult,
necessitating automation and security. Hence, there is a need for an
efficient onboarding procedure that secures devices with unique
onboarding credentials during deployment rather than at the time of
manufacture.
3. Power of Attorney based authorization
PoA-based authorization is a generic authorization technique used to
authorize devices to access protected resources on behalf of the
user, who owns the device (principal), even if the user is not
online. The PoA model in its base form is completely decentralized
(like for example Pretty Good Privacy (PGP)), where the user
subgrants their power in the form of a self- contained PoA that
contains public information such as public keys and a specific set of
permissions for a predefined time. It is a decentralized
authorization technique, where the different entities involved can
access and verify the PoA using a downloadable image or library
similar to PGP. Some centralization can be added by optional
signatory registers and/or traditional Certificate Authorities (CA).
The entities involved in PoA based authorization system are:
* Principal: The entity that generates and sends the PoA to the
agent.
* Agent: The device which receives the PoA to sign on behalf of the
principal with limited features for a pre-defined time.
* Resource server: The third party with a server that stores the
information and credentials entitled to the principal. It serves
agents according to subgrants defined in PoAs.
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* Signatory registry: A database system where PoAs and system-
related metadata are stored. It can serve as a trusted third-
party in certifying and verifying PoA. This component is
optional.
The principal generates the PoA in advance to entitle an agent to
autonomously execute tasks in the absence of the principal. The PoA
is digitally signed by the principal and the agent uses the limited
features of the principal’s account to execute tasks allowed by the
PoA.
4. Power of Attorney based Onboarding
This document consider the network layer onboarding and subgranting
the power to onboard from one entity to another in the bootstrapping
stage. The different roles are:
* Subcontractor (Principal): The subcontractor is the device owner,
who obtains the device from the supplychain.
* Device (Agent): The device to be onboarded.
* Gateway: We assume that all the communication between the IoT
device, subcontractor, and the onboarding controller is through a
secure gateway for better security.
* Onboarding component: Onboards the device to the destination
network.
* Certificate Authority (CA): It provides the local cloud compliant
certificate to the device for onboarding.
Figure 1 shows the Protocol flow diagram of the proposed model.
+---------+ +--------+ +-----------+ +-----+
| |---B)->| |-Ca,b)->| | | |
| Subcon | | Device | | Onboarding|---D)->| |
| tractor | |(Agent) |<--F)---| Component | | CA |
| (Princi | +--------+ | | | |
| pal) |<-----------A)-----------| |<--E)--| |
+---------+ +-----------+ +-----+
Figure 1: Protocol flow of PoA based onboarding
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* A) Onboarding component sends the PoA1 (PoA generated by the
onboarding component) to the subcontractor through the gateway.
By this, the onboarding component grants authorization to a
specific subcontractor to bootstrap any of its trusted devices.
Before this step, both entities should be mutually authenticated
using public key certificates.
* B) Subcontractor generates PoA2 and sends it to his/her specific
trusted device. This enables the device to work on behalf of the
subcontractor. This means, the onboarding component that trusts
the subcontractor (through PoA1) implicitly trusts the device. In
this step, the subcontractor may add the complete ownership of the
device's proof-of-chain information to PoA2, if so required (e.g.,
as specified in PoA1).
* Ca) The device sends the PoA2 including metadata such as device
hash and device bootstrapping credentials to the onboarding
component through the gateway. The device bootstrapping
credentials can includes device identifier (e.g., X.509
certificate-DevID, Device Identifier Composition Engine [DICE]
Compound Device Identifier [CDI], public key), device private key
or csr, Wi-Fi channel that the device will use (optional),
communications protocols (optional) etc.
* Cb) Secure channel establishment using Mutual TLS (MTLS).
* D) Onboarding component authorizes the device by verifying the
PoA2 and sends a certificate request using device private key or
csr to the local cloud CA.
* E) The local cloud CA verifies the submitted documents and
generates the a local cloud compliant device certificate and sends
it to the onboarding component.
* F) The network bootstrapping credentials are sent to the device by
the onboarding component via the gateway. This can include
network identifier (e.g., X.509 certificate, Service Set
Identifier [SSID]). The device validates the network by comparing
the network details in the network bootstrapping credentials to
the network details in the digitally signed PoA2. This helps the
device to determine if the target network is authorized to onboard
the device.
The revocation of PoA can be accomplished by setting a low expiration
time depending on the use case. In that case the PoA must be
reissued periodically.
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Once the device obtains the network bootstrapping credentials, it can
start communicating with the local cloud. This model for onboarding
enables the subcontractor to onboard devices by subgranting his/her
power to the device to act on behalf of the subcontractor. A proof
of concept of the proposed model can be found at
"https://github.com/sreelakshmivs/PoAimplementationinJava" under the
MIT license.
5. PoA Structure
The PoAs are self-contained tokens that are structured in JWT format.
The entire PoA in the JWT form is digitally signed by the principal
using his/her private key. It is compressed into binary format
(e.g., CBOR). The various parameters included in a PoA are the
following:
Principal Public Key
REQUIRED. The public key, which uniquely identifies the principal
who generates the PoA. We assume that the public key is generated
using a secure public-key algorithm by the principal. With this
parameter, the authorization server can identify the person who
generated the PoA.
Principal Name
OPTIONAL. The human-readable name of the principal, which is
additional information about the principal.
Resource Owner ID
REQUIRED. The unique identifier or the public key of the resource
owner from where the protected resources are granted.
Agent Public Key
REQUIRED. The public key, which uniquely identifies the agent who
receives the PoA from the principal. We assume that the agent
public key is generated using a secure public-key algorithm by the
owner. This parameter helps the trusted server to identify the
agent and check whether it is genuine or not.
Agent Name
OPTIONAL. The human-readable name of the agent, which is
additional information about the agent.
Signing Algorithm
OPTIONAL. The name of the signature algorithm used by the
principal to digitally sign the PoA.
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Transferable
REQUIRED. It is a positive integer defining how many steps the
PoA can be transferred. Default is 0, which means that it is not
transferable. A PoA can be transferred by including it in another
PoA, i.e., it is signed in several delegation steps (where the
number is decreased by one in each step).
iat (Issued at)
REQUIRED. The time at which the PoA is issued by the principal to
the agent.
eat (Expires at)
REQUIRED. The time at which the PoA expires. This parameter is
predefined by the principal in the PoA and the PoA will be invalid
after eat.
Metadata
OPTIONAL. The metadata is associated with the specific
application use-case. This parameter includes different sub-
parameters that add application-specific information to the PoA.
6. Related Works
[nordmark-iotops] recognize the need for an effective onboarding
system in both network and application layers. This approach doesn't
require much dependency on the manufacturer and the manufacturer
certificates. They define the flexibility of devices that are not
resource constrained such as Raspberry Pi and larger. The use of
large smart devices enables executing functions that are not
envisioned during their manufacturing.
Fast IDentity Online Alliance (FIDO) [fidospec] defines an automatic
onboarding protocol for IoT devices. With the late binding feature
of this protocol, the IoT platform for the IoT device doesn't need to
be selected in the early stage of its life cycle, and reduces the
cost and complexity in the supplychain. FIDO uses a rendezvous
server for device registration and to find the device owner location,
by assuming that the device has an IP connectivity to the rendezvous
server. An important feature of FIDO is the tracking of transfer of
ownership and the device's late-bound owner throughout the
supplychain using the ownership voucher. FIDO Device Onboard enabled
Device is configured with required software and hardware along with a
Restricted Operating Environment (ROE) and a Management Agent, that
manages the device ownership voucher using the onboarding protocols.
Another important parameter is the device credentials, it does not
permanently identify the user and is only used for the purpose of the
ownership transfer. FIDO expects that both the manufacturer and the
owner will change their keys frequently. Main protocols in FIDO
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onboarding are Device initialization protocol (DI), Transfer
Ownership Protocol (TO0), TO1, and TO2. The function of DI is to
insert FIDO Device Onboard credentials into the device during the
manufacturing process. TO0 is used by the owner to identify itself
to the rendezvous server, and similarly TO1 is used by the device to
identify itself and to interact with the rendezvous server using the
device ROE. TO2 is used by the device ROE to contact and interact
with the owner or device onboarding service. After TO2 successfully
completes, the device onboarding credentials except the attestation
key is replaced by the owner onboarding service.
[eap-onboarding] defines an onboarding method where an unconfigured
device can be added to the network using EAP, which later can be
onboarded. Here, the onboarding process is divided into different
stages such as discovery, authentication, authorization, onboarding,
and full network access. The devices that obtained network access
using unauthenticated EAP undergoes onboarding process once they
enter the captive portal.
[t2trg] provides a survey on different standards and protocols for
onboarding. Onboarding is referred using different names as part of
the initial security setup of devices. This list of names include
bootstrapping, provisioning, enrollment, commissioning,
initialization, and configuration. Most approaches rely on an
external anchor such as rendezvous server, bootstrap server, chip or
QR code.
The communication protocol [mobileIP] uses a home agent and a foreign
agent to facilitate mobility. The home agent provides an anchor
point for connectivity, while a mobile node can register with a
foreign agent to get seamless connectivity at the visited network.
This allows the user to move between different networks while having
both the home and visitor IP addresses. However, this is primarily
to obtain internet access, not to onboard a local realm.
PoA based authorization can be added as a new grant type for OAuth
protocol, that introduces a new role "principal" who controls the
client, and enables the client to access resources through the OAuth
authorization server on behalf of the principal, even if the
principal is not available online [poa-oauth-grant-type].
PoA-based authorization is an industrial authorization technique for
CPS devices that is designed with different cryptographic algorithms,
is a similar work as the proxy signature with warrant
[proxy-signature]. The proxy signature is a significant security
cryptographic algorithm that strengthens its security by patching
newer security loopholes. The main differences are seen in the
applicability of the technique and the design methodology. In proxy
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signature, the agent or proxy signer is required to perform several
cryptographic calculations to sign a message, as described in the
warrant on behalf of the principal. PoA can be seen as a more
industry oriented technique, where the device acts/works on behalf of
the principal as described in the PoA. Here, the agent is only
required to verify and forward the PoA (received from the principal)
to the resource owner and provide its strong identity, to obtain the
resources on behalf of the principal.
The different techniques mentioned above use a delegation-based
authorization model for security, which relies on centralized servers
or complex cryptographic algorithms, limiting their flexibility in
the onboarding process. The PoA-based authorization technique, that
does not rely on a centralized server and employs an industry-
friendly PoA structure, enables for a reliable and flexible
onboarding process.
7. Security Considerations
The security of the entire onboarding process relies on issues with
security in different phases such as manufacturing, supply chain,
bootstrapping, and application. The characteristics of these phases
differ depending on the onboarding approach. The following are the
different approaches:
* Use hardware manufacturer certificates. Using the manufacturing
certificate, this method authenticates the device. However, there
is no option to authorize the target network, which prevents the
device from being onboarded to fraudulent networks.
* Tracking ownership transfers throughout the supply chain. This
secure late binding to the management system/controller allows the
controller to trust the device and ensure that it is not
compromised during the supply chain transmission.
* Imprinting/configuring for/by the owner of the device. This
approach configures the device for its future owner/controller by
imprinting the future owner's identity. This methods enables the
device to only onboard to the trusted owner/controller. However,
it requires the manufacture to build devices with customized
features based on their future owner/controller.
* PoA based onboarding. This decentralized approach employs the
subgranting based authorization technique, that enables the
controller to grant authorization to the subcontractor (principal)
and the device to obtain authorization from the subcontractor.
PoA approach compliments the above three approaches with the use
of digitally signed PoAs that enables mutual authorization between
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the device and the controller, and the use of PoA to keep track of
the ownership transfer, which is submitted to the controller on
demand.
7.1. Attacks out of scope
The payload data in the form of PoAs is immutable and protected by
cryptographic signatures. Therefore, integrity threats like replay,
message insertion, modification and man in the middle are out of
scope.
7.2. Attacks in scope
Confidentiality threats like eavesdropping exist when PoAs are sent
as clear data. However, this can be resolved by e2e encryption. For
authentication, the PoAs rely on strong unique identities, e.g., the
identity of an must be verified when it turns up with a PoA where it
obtains some authorized credentials based on its public key. In some
cases, a private key can serve for proving identity, but it should be
noted that a private key can be stolen (Identity theft). This can be
resolved by coupling the identity uniquely to the device, e.g., a
device hash, X.509 certificate–DevID, Device Identifier Composition
Engine [DICE], Compound Device Identifier [CDI], public key. The
protocol interface for receiving and processing PoAs is susceptible
to denial-of-service attacks, where potential overload attacks using
meaningless or unacceptable PoAs could be issued. Possible
resolutions to this threat will be addressed in future versions of
this draft.
We will conform to prefer industry standards e.g., as described in
[draft-moran-iot-nets-01]
8. References
8.1. Normative References
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
8.2. Informative References
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[NIST] National Institute of Standards and Technology, "Trusted
Internet of Things (IoT) device network-layer onboarding
and lifecycle management (draft) No. NIST CSWP 16 ipd",
2020.
[Intel] INTEL, "Intel® secure device onboard,” More secure,
automated IoT device onboarding in seconds, pp. 1–4",
2017.
[t2trg] Internet Engineering Task Force, "draft-irtf-t2trg-secure-
bootstrapping-02", 2022.
[nordmark-iotops]
Internet Engineering Task Force, "draft-nordmark-iotops-
onboarding-00", 2021.
[fidospec] Fido Alliance, "Fast Identity Online Alliance, "FIDO
Device Onboard Specification"", 2021,
<https://fidoalliance.org/specifications/download-iot-
specifications/>.
[mobileIP] "IP mobility support. No. rfc2002", 1996.
[proxy-signature]
"Proxy signatures: Delegation of the power to sign
messages,” IEICE transactions on fundamentals of
electronics, communications and computer sciences, vol.
79, no. 9, pp. 1338–1354", 1996.
[draft-moran-iot-nets-01]
Internet Engineering Task Force, "A summary of security-
enabling technologies for IoT devices", 12062022.
[poa-oauth-grant-type]
Internet Engineering Task Force, "draft-vattaparambil-
oauth-poa-grant-type-00", 11032023.
[eap-onboarding]
Internet Engineering Task Force, "draft-richardson-emu-
eap-onboarding-02", 4022023.
Contributors
Thanks to all of the contributors.
Authors' Addresses
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Sreelakshmi
Lulea University of Technology
SE-97187 Lulea
Sweden
Email: srevat@ltu.se
Olov
Lulea University of Technology
SE-97187 Lulea
Sweden
Email: olov.schelen@ltu.se
Ulf
Lulea University of Technology
SE-97187 Lulea
Sweden
Email: ulf.bodin@ltu.se
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