@ausweisapp2/identglue

This library allows webpages to integrate seamlessly with the German eID system. It provides client-side helpers to detect or open an eID client and start an identification process from the browser.

Features

• Detection if an eID client is running on desktop systems ¹
• Helpers for creating spec-compliant eID client URLs
  • Use them with frameworks and libaries like React, Vue, Svelte, etc. or server side rendered pages.
• Rules out cross platform differences
• Experimental: Detection on mobile platforms

Installation

Option 1 – Install with npm/yarn/pnpm:

npm install @ausweisapp2/identglue

Option 2 – Load the script via a CDN:

<script defer src="https://unpkg.com/@ausweisapp2/identglue"></script>

The script exports all functions under the AusweisApp2 namespace on the global object.

Usage

You can find more detailed usage examples in the docs/examples folder.

There are different possible ways of launching the eID client suitable for different platforms or scenarios:

1. Stationary Desktop Flow: The user visits the webpage on his desktop browser. Here, the user is expected to install an eID client on its desktop operating system and have a card reader attached.
2. Mobile Flow: The user visits the webpage on his mobile device and completes the identification flow on the same device.
3. QR-Code Flow: This is a hybrid flow, where the users lands on the web service using his desktop machine, but wants to use his mobile device to complete the identification.

Each of the three flows is explained in detail below.

1. Stationary Desktop Flow

import { StationaryStatusObserver } from "@ausweisapp2/identglue";

const observer = new StationaryStatusObserver((status) => {
  // status changed! now, update your UI
  if (status.status === "available") {
    // TODO: enable the "Start Identification" button
  } else if (status.status === "unavailable") {
    // TODO: display a message to the users, asking to install and start the eID client.
  } else {
    // TODO: display a generic warning message and enable the "Start Identification" button
  }
});

observer.observe();

2. Mobile Flow

import { observeEIDLink, getClientURL } from "@ausweisapp2/identglue";

const btn = document.getElementById("eid_btn");

btn.href = getClientURL({
  action: "connect",
  tcTokenURL: "https://yourserver.com/api/eid/start",
});

observeEIDLink(btn, () => {
  // show alert ...
});

3. QR-Code Flow

import { getClientURL } from "@ausweisapp2/identglue";

const url = getClientURL({
  mobile: true,
  action: "connect",
  tcTokenURL: "https://yourserver.com/api/eid/start",
});

Use your favorite QR-code library to render a QR-code (for example the qrcode npm library).

import qrcode from "qrcode";

const dataURL = await qrcode.toDataURL(
  url /* the value from the previous snippet */,
  { scale: 4 }
);

const img = document.createElement("img");
img.src = dataURL;
// insert the <img> element at the appropriate place:
document.body.appendChild(img);

Learn more

If you want to learn more about integrating the eID functionality into your system, the following resources might be usefull:

• TR-03124-1 eID-Client – Part 1: Specifications
• AusweisApp2 SDK Documentation

Usage with IE11:

This library supports all modern browsers by default. To use this library in older browsers like Internet Explorer 11 you need to polyfill the fetch and the Promise Web-APIs. We recommend using whatwg-fetch and promise-polyfill.

Limitations

• The Safari browser treats localhost as mixed-content and therefore blocks fetch calls to it. Here, we have no way of detecting wether an eID client is installed and running.¹
• The detection on mobile systems via the localhost server is not possible. Instead we are trying to guess, after the user clicks on a link to open the eID client, if the app really opened or not. This detection is highly dependent on the mobile browser used and might break in the future. A service provider should always use this information only as a hint and still provide a guided user experience (e.g. by showing a dialog to the user, asking if she has an eID client installed).

API Reference

StationaryStatusObserver

StationaryStatusObserver()

The StationaryStatusObserver() constructor creates and returns a new StationaryStatusObserver object.

Syntax:

const observer = new StationaryStatusObserver(callback[, options]);

Parameters:

• callback – A function which is called when the status changes. The callback is called with the observer instance as the this value and receives one input parameter:

  • status – The new status object. See the AusweisApp2Status type for available properties.

• options (optional) – An object which customizes the behavior of the observer. You can provide any combination of the following options:

  Option	Type	Description
  refreshInterval = 10000	number	polling interval (set to 0 to disable, time in milliseconds)
  refreshWhenHidden = false	boolean	polling when the window is invisible (if refreshInterval is enabled)
  refreshOnFocus = true	boolean	refresh when the window gets focused
  focusThrottleInterval = 5000	number	only refresh once during this time span (in milliseconds)

Example:

const observer = new StationaryStatusObserver(
  (status) => {
    // ...
  },
  {
    refreshInterval: 10000,
    refreshOnFocus: true,
  }
);

StationaryStatusObserver.observe()

Start observing the status.

On mobile platforms it directly emits the "unknown" status and doesn't start any timers or adds event listeners.

Syntax:

observer.observe();

This function takes no arguments and its return value is void.

StationaryStatusObserver.unobserve()

Stops observing the status.

Make sure to call this function, when the user navigates away from the eID section on your page, to free resources and stop the timers.

Syntax:

observer.unobserve();

This function takes no arguments and its return value is void.

StationaryStatusObserver.refresh()

Manually trigger a refresh of the current eID client status.

The callback function passed to the constructor on instance creation is only invoked if the new status is different from the last one. To get the current status use the StationaryStatusObserver.status getter.

Syntax:

observer.refresh();

This function takes no arguments.

Return value:

The function returns a Promise<void>, that resolves, when the new status is determined.

StationaryStatusObserver.status

The status getter returns the last status observed by this observer instance.

Syntax:

const status = observer.status;

Return value:

The getter returns either null if no status was observed, yet, or a status object of the AusweisApp2Status type.

getStationaryStatus()

Retrieve the current status of the eID client on the host platform. Only works on desktop environments, where the eID client starts a background http service.

Syntax:

const status = await getStationaryStatus();

This function takes no arguments.

Return value:

The getStationaryStatus function returns a Promise that resolves with a status object of the AusweisApp2Status type.

Notes:

Works by trying to reach the status endpoint of the eID client as specified in TR-03124-1 eID-Client – Part 1: Specifications

Some browsers (as of the time writing only Safari) block requests to localhost origins due to mixed-content restrictions. This function returns the "unknown" status in this case.

eID clients don't start a background http server on mobile platforms. The returned state is undefined in this case and one should check the platform before using this function with the isMobile function. (The StationaryStatusObserver class has this check already built in and emits the unknown state in this case.)

observeEIDLink()

Augments a HTML anchor element to provide feedback, if the user had an eID client installed and the identification process started or not.

Syntax:

observeEIDLink(targetElement, callback);

Parameters:

• targetElement - reference to the target DOM anchor element.

• callback - A function, which is called after the user clicked the link and this library decided, that the click was unsuccessful and no app was installed. The callback receives no arguments and its return value is ignored.

Return value:

The return value is undefined.

Example:

const btn = document.getElementById("eid_btn");
observeEIDLink(btn, () => {
  // show alert ...
});

getClientURL()

The getClientURL function is a helper function to construct correct URLs to interact with the eID-client.

Syntax:

const clientURL = getClientURL([options]);

Parameters:

• options (optional) – An object which customizes the returned URL.

  • mobile (optional) - common boolean flag to switch between the ClientURLStationary and ClientURLMobile base URLs. Uses isMobile as the default.

  • action (optional) - one of the following string values: "status", "connect", "showui". Depending on the selected action there might be more options available.

    • action = "connect" - starts the identification procedure

      • tcTokenURL - a string pointing to your backend, used by the eID-client to fetch the tcToken necessary for starting an identification.

    • action = "status" - used to query status information from the eID-client

      • json = false (optional) - tell the eID-client to return the status response in json format.

    • action = "showui" - opens the UI of the eID-client

      • module (optional) - specify the UI module to open, possible values are "PINManagement" and "Settings"

Return value:

The function returns a string containing a valid eID client URL.

Example:

const clientURL = getClientURL({
  action: "connect",
  tcTokenURL: "https://yourserver.com/api/eid/start",
});

// will return "http://127.0.0.1:24727/eID-Client?tcTokenURL=https%3A%2F%2Fyourserver.com%2Fapi%2Feid%2Fstart" on desktop

Notes:

For a better understanding of what an eID clientURL is see Section 2.2 in TR-03124-1 eID-Client – Part 1: Specifications.

ClientURLStationary / ClientURLMobile

The library exports two string constants representing the base URLs for the eID client URLs.

Definition:

export const ClientURLStationary = "http://127.0.0.1:24727/eID-Client";
export const ClientURLMobile = "eid://127.0.0.1:24727/eID-Client";

See:

• TR-03124-1 eID-Client – Part 1: Specifications, Section 2.2 Full eID-Client

isMobile()

The isMobile function tries to guess, if the user is visiting the service on a mobile device.

It uses the Client Hints API and falls back to manual userAgent string parsing if not available.

Syntax:

const mobile = isMobile();

This function takes no arguments.

Return value:

This function returns a boolean value:

• true, if the user is on a mobile device (SmartPhone or Tablet).
• false otherwise.

Example:

if (isMobile()) {
  // Hurray!
} else {
  // E.g. use StationaryStatusObserver or
  // display QR-code for QR-Code flow.
}

AusweisApp2Status

The type of the object returned by the getStationaryStatus function and in the StationaryStatusObserver callback.

Property	Type	Description
status	string	One of "available", "unavailable" or "unknown"
details	null or object	Only not null if status equals "available"
details.implementationTitle	string
details.implementationVendor	string
details.implementationVersion	string
details.name	string
details.specificationTitle	string
details.specificationVendor	string
details.specificationVersion	string

Footnotes

1 Currently the detection doesn't work on Safari due to a webkit bug. ↩