JSON Web Tokens

A JSON Web Token (JWT) is an open web standard that's used for authenticating and authorizing information exchanges between a client and a server. When an app user first signs in with the appropriate role credentials, the server creates and returns an encoded, digitally-signed JWT for use with subsequent requests. This process both authenticates the user and authorizes them to access routes, services, and resources based on their account role.

For API method calls from low-trust environments, Fleet Engine requires the use of JSON Web Tokens (JWTs) signed by an appropriate service account. Low-trust environments include smartphones and browsers. A JWT originates on your server, which is a fully-trusted environment. The JWT is signed, encrypted, and passed to the client for subsequent server interactions until it expires or is no longer valid.

Your backend should authenticate and authorize against Fleet Engine using standard Application Default Credentials mechanisms. Make sure to use JWTs that have been signed by an appropriate service account. For a list of service-account roles, see Fleet Engine service account roles in Fleet Engine Basics.

In contrast, your backend should authenticate and authorize against Fleet Engine using standard Application Default Credentials mechanisms.

Unlike API keys, JWTs are short lived and limit operations to only those that the role is authorized to perform. For more information on JWTs, see JSON Web Tokens on Wikipedia. For detail on access roles, see Service account roles in this guide.

JWT elements

JWTs contain a header and a claim section. The header section contains information such as the private key obtained from service accounts, and the encryption algorithm. The claim section contains information such as the JWT's create time, time to live, the services that the JWT claims access to, and other authorization information to scope access; for example, the delivery vehicle ID.

The following table provides descriptive details about JWT fields in general, as well as specific information about where you can find the values for these fields in your Fleet Engine Cloud project.

JWT header fields

Field

Description

alg

The algorithm to use. `RS256`.

typ

The type of token. `JWT`.

kid

Your service account's private key ID. You can find this value in the private_key_id field of your service account JSON file. Make sure to use a key from a service account with the correct level of permissions.
JWT claims fields

Field

Description

iss

Your service account's email address, found in the client_email field of your service account JSON file.

sub

Your service account's email address, found in the client_email field of your service account JSON file.

aud

Your service account's SERVICE_NAME, in this case https://fleetengine.googleapis.com/

iat

The timestamp when the JWT was created, specified in seconds elapsed since 00:00:00 UTC, January 1, 1970. Allow 10 minutes for skew. If the timestamp is too far in the past, or in the future, the server might report an error.

exp

The timestamp when the JWT expires, specified in seconds elapsed since 00:00:00 UTC, January 1, 1970. The request fails if the timestamp is more than one hour in the future.

authorization

Depending on the use case, may contain deliveryvehicleid, trackingid, taskid, or taskids.

If specifying taskids, the authorization scope must be an array in one of the following forms:

"taskids": ["task_id_one","task_id_two"]

or

"taskids": ["*"]

Fleet Engine JWT claims

Fleet Engine uses private claims. Using private claims ensures that only authorized clients can access their own data.

For example, when your server issues a JSON Web Token for a driver's mobile device, it should contain either the vehicleid claim or the deliveryvehicleid claim with the value of that driver's vehicle ID. Then, depending on the driver role, JWTs enable access only for the specific vehicle ID and not any other arbitrary vehicle ID.

Fleet Engine uses the following private claims:

On-demand trips

  • vehicleid:
    • The Driver SDK always uses this claim, whether operating on a trip or vehicle. The Fleet Engine backend assures that the vehicle is associated with the requested trip before doing the modification.
    • The JWT can cover both vehicle and trip operations, even if not required, which may simplify the JWT signing implementation.
  • tripid:
    • The Consumer SDK always uses this claim.
    • The JWT can cover both vehicle and trip operations, even if not required, which may simplify the token signing implementation.

Scheduled tasks

  • deliveryvehicleid

    Use when calling per-delivery-vehicle APIs.

  • taskid

    Use when calling per-task APIs.

  • taskids

    Use when calling BatchCreateTasksAPI. This claim must be in array form, and the array should contain all task IDs necessary to complete the request. Don't include delivervehicleid, trackingid, or taskid claims.

  • trackingid

    Use when calling the GetTaskTrackingInfoAPI. The claim must match the tracking ID in the request. Don't include delivervehicleid, taskid, or taskids claims.

What's next