MongoDB Based Device Registry Configuration

The MongoDB based Device Registry component provides an implementation of Eclipse Hono™’s Device Registration, Credentials and Tenant APIs. Protocol adapters use these APIs to determine a device’s registration status, e.g. if it is enabled and if it is registered with a particular tenant, and to authenticate a device before accepting any data for processing from it. In addition to the above, this Device Registry also provides an implementation of Device Registry Management APIs for managing tenants, registration information and credentials of devices.

The registry is implemented as a Quarkus application, using a MongoDB database as the persistence store. It can be run either directly from the command line or by means of starting the corresponding Docker image created from it.

The registry is compatible and known to work with following MongoDB versions:

• MongoDB 4.4
• MongoDB 5.0
• MongoDB 6.0

Service Configuration

The following table provides an overview of the configuration variables and corresponding system properties for configuring the MongoDB based Device Registry.

The variables only need to be set if the default value does not match your environment.

In addition to the options described in the table above, this component supports the following standard configuration options:

• Common Java VM Options
• Common vert.x Options
• Monitoring Options

Port Configuration

The device registry supports configuration of both an AMQP based endpoint exposing the Tenant, Device Registration and Credentials APIs as well as an HTTP based endpoint providing resources for managing tenants, registration information and credentials as defined by the Registry Management API. Both endpoints can be configured to listen for connections on

• a secure port only (default) or
• an insecure port only or
• both a secure and an insecure port (dual port configuration)

The registry will fail to start if none of the ports is configured properly.

The following sections apply to configuring both the AMQP and the HTTP endpoint. The environment variables to use for configuring the HTTP endpoint are the same as the ones for the AMQP endpoint, substituting _AMQP_ with _HTTP_, e.g. HONO_REGISTRY_HTTP_KEYPATH instead of HONO_REGISTRY_AMQP_KEYPATH.

Secure Port Only

The server needs to be configured with a private key and certificate in order to open a TLS secured port.

There are two alternative ways for doing so:

1. Setting the HONO_REGISTRY_AMQP_KEYSTOREPATH and the HONO_REGISTRY_AMQP_KEYSTOREPASSWORD variables in order to load the key & certificate from a password protected key store, or
2. setting the HONO_REGISTRY_AMQP_KEYPATH and HONO_REGISTRY_AMQP_CERTPATH variables in order to load the key and certificate from two separate PEM files in PKCS8 format.

When starting up, the server will bind a TLS secured socket to the default secure port (5671 for AMQP and 8443 for HTTP). The port number can also be set explicitly using the HONO_REGISTRY_AMQP_PORT variable.

The HONO_REGISTRY_AMQP_BINDADDRESS variable can be used to specify the network interface that the port should be exposed on. By default, the port is bound to the loopback device only, i.e. the port will only be accessible from the local host. Setting this variable to 0.0.0.0 will let the port being bound to all network interfaces (be careful not to expose the port unintentionally to the outside world).

Insecure Port Only

The secure port will mostly be required for production scenarios. However, it might be desirable to expose a non-TLS secured port instead, e.g. for testing purposes. In any case, the non-secure port needs to be explicitly enabled either by

• explicitly setting HONO_REGISTRY_AMQP_INSECUREPORT to a valid port number, or
• implicitly configuring the default port (5672 for AMQP and 8080 for HTTP) to be used by setting HONO_REGISTRY_AMQP_INSECUREPORTENABLED to true.

The server issues a warning on the console if one of the insecure ports is set to the corresponding default secure port.

The HONO_REGISTRY_AMQP_INSECUREPORTBINDADDRESS variable can be used to specify the network interface that the port should be exposed on. By default, the port is bound to the loopback device only, i.e. the port will only be accessible from the local host. This variable might be used to e.g. expose the non-TLS secured port on a local interface only, thus providing easy access from within the local network, while still requiring encrypted communication when accessed from the outside over public network infrastructure.

Setting this variable to 0.0.0.0 will let the port being bound to all network interfaces (be careful not to expose the port unintentionally to the outside world).

Dual Port

In test setups and some production scenarios Hono server may be configured to open one secure and one insecure port at the same time.

This is achieved by configuring both ports correctly (see above). The server will fail to start if both ports are configured to use the same port number.

Since the secure port may need different visibility in the network setup compared to the secure port, it has its own binding address HONO_REGISTRY_AMQP_INSECUREPORTBINDADDRESS. This can be used to narrow the visibility of the insecure port to a local network e.g., while the secure port may be visible worldwide.

Ephemeral Ports

Both the secure as well as the insecure port numbers may be explicitly set to 0. The registry will then use arbitrary (unused) port numbers determined by the operating system during startup.

Authentication Service Connection Configuration

The service requires a connection to an implementation of Hono’s Authentication API in order to authenticate and authorize client requests.

The connection is configured according to the Hono Client Configuration where the ${PREFIX} is set to HONO_AUTH. The properties for configuring the client’s response caching will be ignored because Hono’s Authentication Service does not allow caching of responses.

In addition to the standard client configuration properties, the following properties are supported:

Metrics Configuration

See Monitoring & Tracing Admin Guide for details on how to configure the reporting of metrics.

Encrypting Secrets

Hono’s CoAP protocol adapter supports authentication of devices during the DTLS handshake based on a pre-shared key. A pre-shared key is an arbitrary sequence of bytes which both the device as well as the protocol adapter need to present during the handshake in order to prove their identity. The Mongo DB based registry implementation supports managing these keys by means of PSK credentials which can be set for devices. By default, the bytes representing the key are stored as a base64 encoded string property of the credentials document. In order to better protect these keys from unintended disclosure, the registry can be configured to encrypt these keys before they are written to the database collection. During read operations the keys are then decrypted again before they are returned to an authorized client.

In order to activate this transparent encryption/decryption, the HONO_CREDENTIALS_SVC_ENCRYPTIONKEYFILE configuration variable needs to be set to the path to a YAML file containing the definition of the symmetric keys that should be used for encryption. The file is expected to have the following format:

defaultKey: 2
keys:
- version: 1
  key: hqHKBLV83LpCqzKpf8OvutbCs+O5wX5BPu3btWpEvXA=
- version: 2
  key: ge2L+MA9jLA8UiUJ4z5fUoK+Lgj2yddlL6EzYIBqb1Q=

The file needs to contain at least all versions of the key that values in the database collection have been encrypted with. Otherwise the registry will not be able to decrypt these values during reading. The defaultKey property indicates the version of the key that should be used when encrypting values. Please refer to the CryptVault project for additional information regarding key rotation.

Messaging Configuration

The Device Registry uses a connection to an AMQP 1.0 Messaging Network and/or an Apache Kafka cluster to

• send Device Provisioning Notification event messages to convey provisioning related changes regarding a device, to be received by downstream applications,
• send notification messages about changes to tenant/device/credentials data, to be processed by other Hono components.

For the event messages a connection to a Apache Kafka cluster is used by default, if configured. If both kinds of messaging are configured, the decision which one to use is done according to the Tenant Configuration.

For notification messages, the Kafka connection is used by default, if configured. Otherwise the AMQP messaging network is used.

AMQP 1.0 Messaging Network Connection Configuration

The connection to the AMQP 1.0 Messaging Network is configured according to the Hono Client Configuration with HONO_MESSAGING being used as ${PREFIX}. Since there are no responses being received, the properties for configuring response caching can be ignored.

Kafka based Messaging Configuration

The connection to an Apache Kafka cluster can be configured according to the Hono Kafka Client Configuration.

The following table shows the prefixes to be used to individually configure the Kafka clients used by the Device Registry. The individual client configuration is optional, a minimal configuration may only contain a common client configuration consisting of properties prefixed with HONO_KAFKA_COMMONCLIENTCONFIG_ and hono.kafka.commonClientConfig. respectively.