Authentication/Authorization

This page describes how authentication and authorization of devices, consumers (back end applications) and system components works in Hono.

Requirements

  1. Devices are authenticated and authorized when they connect to a protocol adapter.
  2. Consumers are authenticated and authorized when they connect to a Dispatch Router instance.
  3. System components are authenticated and authorized when they connect to each other.
  4. Credentials and authorization rules can be managed centrally, i.e. credentials and rules do not need to be configured manually on each component.

How it works today

The following diagram provides an overview of the components involved in use cases requiring authentication and authorization.

Device Auth

Both the HTTP adapter as well as the MQTT adapter require devices to authenticate during connection establishment by default. Both rely on the Credentials API to help in verifying credentials provided by a device. Please refer to Device Authentication for a general overview of Hono’s approach to authenticating devices and to the protocol adapter user guides for specifics regarding how devices can authenticate to the corresponding protocol adapters.

System Component Auth

Client components opening an AMQP connection to a server component are authenticated using SASL PLAIN as specified in RFC 4422. The server component takes the authentication information provided by the client component and opens a connection to the Auth Server, using the credentials provided by the client in its SASL PLAIN exchange with the server component. On successful authentication the Auth Server issues a JSON Web Token (JWT) asserting the client’s identity and its granted authorities to the server component. The server component then attaches this token to its AMQP connection with the client and from then on uses it to make authorization decisions regarding the client’s requests. See Authentication API for details regarding the authentication process and the format of the tokens issued by the Auth Server.

Based on the components shown above, the following sequence diagram shows how the MQTT Adapter connects to the Device Registry and gets authenticated transparently using the Auth Server.

Client components are authorized whenever they open a new AMQP link on an existing connection to the server. When a client tries to open a receiver link, the server checks if the client is authorized to read from the source address the client has specified in its AMQP attach frame. Analogously, when a client tries to open a sender link, the server checks if the client is authorized to write to the target address from the client’s attach frame.

Service implementations may additionally authorize individual (request) messages received from the client, e.g. based on the message’s subject property which is used by Hono’s AMQP 1.0 based APIs to indicate the operation to invoke. In such a case the server checks if the client is authorized to execute the operation indicated by the message subject on the link’s target address.

Application Auth

Business Applications connect to the AMQP 1.0 Messaging Network in order to consume telemetry data and events and send commands to devices. It is therefore the responsibility of the AMQP Network to properly authenticate and authorize the application.

The Apache Qpid Dispatch Router which is used in Hono’s example deployment can be configured to authenticate consumers using arbitrary SASL mechanisms. Access to addresses for receiving messages can be restricted to certain identities. The Dispatch Router instance which is used in the example deployment is configured to delegate authentication of clients to the Auth Server by means of its Auth Service Plugin mechanism. This mechanism works in a very similar way as described above for the authentication of system components. The main difference is that the clients’ authorities are not transferred by means of a JSON Web Token but instead are carried in a property of the Auth Server’s AMQP open frame.

Management of Identities and Authorities

The identities and corresponding authorities that the Auth Server uses for verifying credentials and issuing tokens are defined in a configuration file (services/auth/src/main/resources/permissions.json) read in during start-up of the Auth Server. These authorities are used for authenticating and authorizing system components as well as Business Applications.

Please refer to the Dispatch Router documentation for details regarding configuration of Dispatch Router security.

Future Approach

In the long run Hono will still use tokens for authenticating clients but will use a policy based approach for authorizing requests, i.e. authorization decisions will be made by a central policy enforcement component. Hono services will pass in the client’s token, the resource being accessed and the intended action along with potentially other attributes to the policy enforcement component which will then make the authorization decision based on the configured rules (policy) and return the outcome to the component.