IRMA backend

This module can be used for handling messages from and to the irma server in the following way:

const IrmaBackend = require('@privacybydesign/irma-backend');
const irmaBackend = new IrmaBackend(serverUrl, options);

Constructor parameters

• serverUrl should be the URL where your irma server is running.
• options (optional) specifies a struct where additional options can be specified. We currently support the following options:
  • serverToken field to enable requestor authentication. By default this field is set to false, meaning that no authorization headers will be sent. The default setting can only be used if the IRMA server is configured to accept unauthenticated requests or when only sending signed JWT session requests.
  • debugging field to enable printing helpful output to the console for debugging. By default this field is set to false.

Available methods

startSession(request)

This method starts a session at the IRMA server. The request parameter may either be a session request object or a signed JWT session request. The function returns a promise which on resolve gives the session identifiers {sessionPtr: ..., token: ...}.

cancelSession(sessionToken)

This method cancels the session with token sessionToken at the IRMA server. The parameter sessionToken concerns the token as being returned by startSession. It returns a promise. On resolve the session is cancelled successfully.

getSessionResult(sessionToken)

This method fetches the session result object. The parameter sessionToken concerns the token as being returned by startSession. It returns a promise which on resolve gives the session result object. When the result is not available yet, the promise is rejected.

getSessionResultJwt(sessionToken)

This method behaves the same as getSessionResult, but fetches the session result JWT instead.

getSessionStatus(sessionToken)

This method fetches the current status of the IRMA session. The parameter sessionToken concerns the token as being returned by startSession. The function returns a promise which on resolve gives the current session status. A struct with the possible values for the session status can be retrieved using the static call IrmaBackend.SessionStatus.

getServerPublicKey()

This method fetches the JWT public key of the IRMA server. It returns a promise which on resolve gives the public key in a PEM encoded string. When no JWT public key is configured at the IRMA server, the promise will be rejected.

Important remark: when using method hmac for JWT signing, the same key is used for both signing and verification. This means in this case there is no public key and therefore this function will also not return one.

subscribeStatusEvents(sessionToken, eventCallback)

With this method you can subscribe on receiving events on status updates of a particular IRMA session. The parameter sessionToken concerns the token as being returned by startSession. The parameter eventCallback concerns a 'error-first' callback function to receive the events.

The callback function signature is (error, status) => {}. When error is being null, the status parameter will contain the new session status. A struct with the possible values for the session status can be retrieved using the static call IrmaBackend.SessionStatus.

Code example

Below a small example of how irma-backend can be used:

const IrmaBackend = require('@privacybydesign/irma-backend');
const irmaBackend = new IrmaBackend(serverUrl, options);

const irmaRequest = {
  '@context': 'https://irma.app/ld/request/disclosure/v2',
  'disclose': [
    [
      [ 'irma-demo.MijnOverheid.ageLower.over18' ]
    ]
  ]
};

irmaBackend.startSession(irmaRequest)
.then(({sessionPtr, token}) => {

  // Send sessionPtr to the frontend

  // Fetch the result if present
  irmaBackend.subscribeStatusEvents(token, (error, status) => {
    if (error != null) {
      throw error;
    }
    if (status === IrmaBackend.SessionStatus.Done) {
      irmaBackend.getSessionResult(token)
      .then( result => { 
        // Do something with result
      });
    }
  });
});