Get authorization tokens

The Consumer SDK provides authorization using JSON Web Tokens. A JSON Web Token (JWT) is an authorization token that provides one or more claims on a service.

The Consumer SDK uses the JSON Web Token provided by the application to communicate with the Fleet Engine. For details of the tokens expected by the Fleet Engine server, see JSON Web Tokens and Issue JSON Web tokens.

The authorization token provides access to the following Fleet Engine services:

• TripService - Gives the Consumer SDK access to trip details, including vehicle position, route, and ETA. Authorization tokens for the trip service must include a tripid:TRIP_ID claim in the token's authorization header, where TRIP_ID is the trip ID of the on-demand trip being shared.

• VehicleService - Gives the Consumer SDK information about the approximate vehicle location for displaying the vehicle density layer and estimating pickup point ETAs. Because the Consumer SDK uses only approximate locations, authorization tokens for the vehicle service don't require a vehicleid claim.

What is a token?

Fleet Engine requires the use of JSON Web Tokens (JWTs) for API method calls from low-trust environments: smartphones and browsers.

A JWT originates on your server, is signed, encrypted, and passed to the client for subsequent server interactions until it expires or is no longer valid.

Key details

• Use Application Default Credentials to authenticate and authorize against Fleet Engine.
• Use an appropriate service account to sign JWTs. See Fleet Engine serviceaccount roles in Fleet Engine Basics.

For more information about JSON Web Tokens, see JSON Web Tokens in Fleet Engine Essentials.

How do clients get tokens?

Once a driver or consumer logs in to your app using the appropriate authorization credentials, any updates issued from that device must use appropriate authorization tokens, which communicates to Fleet Engine the permissions for the app.

As the developer, your client implementation should provide the ability to do the following:

• Fetch a JSON Web Token from your server.
• Reuse the token until it expires to minimize token refreshes.
• Refresh the token when it expires.

The AuthTokenFactory class generates authorization tokens at location update time. The SDK must package the tokens with the update information to send to Fleet Engine. Make sure that your server-side implementation can issue tokens before initializing the SDK.

For details of the tokens expected by the Fleet Engine service, see Issue JSON Web Tokens for Fleet Engine.

Example of an authorization token fetcher

The following code example demonstrates how to implement an authorization token callback.

Java

class JsonAuthTokenFactory implements AuthTokenFactory {

  private static final String TOKEN_URL =
      "https://yourauthserver.example/token";

  private static class CachedToken {
    String tokenValue;
    long expiryTimeMs;
    String tripId;
  }

  private CachedToken token;

  /*

*   This method is called on a background thread. Blocking is OK. However, be
*   aware that no information can be obtained from Fleet Engine until this
*   method returns.
*/
@Override
public String getToken(AuthTokenContext context) {
  // If there is no existing token or token has expired, go get a new one.
  String tripId = context.getTripId();
  if (tripId == null) {
    throw new RuntimeException("Trip ID is missing from AuthTokenContext");
  }
  if (token == null || System.currentTimeMillis() > token.expiryTimeMs ||
      !tripId.equals(token.tripId)) {
    token = fetchNewToken(tripId);
  }
  return token.tokenValue;
}

  private static CachedToken fetchNewToken(String tripId) {
    String url = TOKEN_URL + "/" + tripId;
    CachedToken token = new CachedToken();

    try (Reader r = new InputStreamReader(new URL(url).openStream())) {
      com.google.gson.JsonObject obj
          = com.google.gson.JsonParser.parseReader(r).getAsJsonObject();

      token.tokenValue = obj.get("ServiceToken").getAsString();
      token.expiryTimeMs = obj.get("TokenExpiryMs").getAsLong();

      /*

    *   The expiry time could be an hour from now, but just to try and avoid
    *   passing expired tokens, we subtract 5 minutes from that time.
    */
    token.expiryTimeMs -= 5 * 60 * 1000;
  } catch (IOException e) {
    /*
    *   It's OK to throw exceptions here. The error listeners will receive the
    *   error thrown here.
    */
    throw new RuntimeException("Could not get auth token", e);
  }
  token.tripId = tripId;

    return token;
  }
}

Kotlin

class JsonAuthTokenFactory : AuthTokenFactory() {

  private var token: CachedToken? = null

  /*

*   This method is called on a background thread. Blocking is OK. However, be
*   aware that no information can be obtained from Fleet Engine until this
*   method returns.
*/
override fun getToken(context: AuthTokenContext): String {
  // If there is no existing token or token has expired, go get a new one.
  val tripId =
    context.getTripId() ?:
      throw RuntimeException("Trip ID is missing from AuthTokenContext")

    if (token == null || System.currentTimeMillis() > token.expiryTimeMs ||
        tripId != token.tripId) {
      token = fetchNewToken(tripId)
    }

    return token.tokenValue
  }

  class CachedToken(
    var tokenValue: String? = "",
    var expiryTimeMs: Long = 0,
    var tripId: String? = "",
  )

  private companion object {
    const val TOKEN_URL = "https://yourauthserver.example/token"

    fun fetchNewToken(tripId: String) {
      val url = "$TOKEN_URL/$tripId"
      val token = CachedToken()

      try {
        val reader = InputStreamReader(URL(url).openStream())

        reader.use {
          val obj = com.google.gson.JsonParser.parseReader(r).getAsJsonObject()

          token.tokenValue = obj.get("ServiceToken").getAsString()
          token.expiryTimeMs = obj.get("TokenExpiryMs").getAsLong()

          /*

        *   The expiry time could be an hour from now, but just to try and avoid
        *   passing expired tokens, we subtract 5 minutes from that time.
        */
        token.expiryTimeMs -= 5 * 60 * 1000
      }
    } catch (e: IOException) {
      /*
            *   It's OK to throw exceptions here. The error listeners will receive the
            *   error thrown here.
      */
      throw RuntimeException("Could not get auth token", e)
    }

      token.tripId = tripId

      return token
    }
  }
}

What's next

Initialize the Consumer SDK