Authentication and Authorization for Constrained Environments
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Authentication and Authorization for Constrained Environments WG
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Authentication and Authorization for Constrained
The IETF has recently developed protocols for use in constrained
environments, where network nodes are limited in CPU, memory and power.
REST architecture is widely used for such constrained environments.
It has been observed that Internet protocols can be applied to these
constrained environments, often only requiring minor tweaking and
profiling. In other cases, new protocols have been defined to address
the specific requirements of constrained environments. An example of
such a protocol is the Constrained Application Protocol (CoAP).
As in other environments, authentication and authorization questions
also arise in constrained environments. For example, a door lock has to
authorize the person seeking access using a "digital key". Where is
the authorization policy stored? How does the digital key communicate with the
lock? Does the lock interact with an authorization server to obtain
authorization information? How can access be temporarily granted to other
persons? How can access be revoked? These types of questions have been answered
by existing protocols for use cases outside constrained environments, however
in constrained environments, additional and different requirements pose
challenges for the use of various security protocols. In particular, the need
arises for a dynamic and fine grained access control mechanism, where clients
and/or resource servers are constrained.
The IETF has a long history in developing three-party authentication and
authorization protocols for distributed environments. Examples include
Kerberos, the Public Key Infrastructure (PKI), the Authentication,
Authorization and Accounting (AAA) infrastructure, and the Web
Authorization Protocol (OAuth). All these protocols enjoy widespread
deployment on the Internet. Although they all aim to solve a similar
goal, at an abstract level, they offer quite different functions and
utilize different message exchanges. These differences result from the
main deployment use cases they were designed for respectively.
Requirements derived from use cases may indicate that existing work is
useful as basis for a solution for constrained environments. These protocols,
however, were not optimized for constrained environments. Additional
requirements that need to be taken into account are the lack of a
suitable user-interface and the inability of embedded devices to contact
an authorization server in real-time with every resource access request
due to intermittent connectivity, etc.
This working group therefore aims to produce a standardized solution for
authentication and authorization to enable authorized access (Get, Put,
Post, Delete) to resources identified by a URI and hosted on a resource
server in constrained environments. As a starting point, the working
group will assume that access to resources at a resource server by a
client device takes place using CoAP and is protected by DTLS. Both
resource server and client may be constrained. This access will be
mediated by an authorization server, which is not considered to be
Existing authentication and authorization protocols will be used where
applicable to build the constrained-environment solution. This requires
relevant specifications to be reviewed for suitability, selecting a
subset of them and restricting the options within each of the
specifications. Some functionality, however, may not be available in
existing protocols, in which case the solution may also involve new
protocol work. Leveraging existing work means the working group benefits
from available security analysis, implementation, and deployment
experience. Moreover, a standardized solution for federated
authentication and authorization will help to stimulate the deployment
of constrained devices that provide increased security.
Once progress in identifying suitable candidate solutions has been made,
the working group will verify whether the same mechanisms are also
applicable beyond the use of CoAP and DTLS, which are the two main
protocols the group will focus on for access to resources. In
particular, the ability to use the developed solution over HTTP and TLS
will be investigated. Note that the initial focus is on CoAP and HTTP with
DTLS and TLS. Other security protocols may be considered as long as the
primary focus is maintained. The group is scoped to work only on the web
protocols and data carried within them. Furthermore, to guarantee smooth
transition, the integration with existing deployments will be studied,
particularly concerning the use of protocol translation proxies.
This work does not make the assumption that the party offering
application layer services is always the same party offering network
The working group has the following tasks:
1) Produce use cases and requirements
2) Identify authentication and authorization mechanisms suitable for
resource access in constrained environments.
Jul 2014 Submit "Use cases and Requirements" as a WG item.
Dec 2014 Submit "Authentication and Authorization Solution" as a WG
item. Apr 2015 Optionally, submit "Use cases and Requirements"
document to the IESG for publication as an Informational RFC. Jul 2016 Submit
"Authentication and Authorization Solution" specification to the IESG
for publication as a Proposed Standard.