Tutorial: Validate a JSON Web Token (JWT)

This tutorial shows you how to define and implement a REST API definition that validates a JSON Web Token (JWT).

About this tutorial

In this tutorial you will complete the following lessons:
  1. Validate a JWT
  2. Testing the REST API
Note: The Sandbox catalog must be configured to use either a DataPower® Gateway (v5 compatible) or a DataPower API Gateway or both. See Creating and configuring Catalogs.

Before You Begin

You must also do the following steps.

Validate a JWT

Create a REST API to validate a JSON Web Token (JWT).

To add and define this REST API, complete the following steps:
  1. Log in to API Manager.
  2. In the Welcome page, click the Develop APIs and Products tile.

    API Manager screen

  3. Click Add > API.

    Add API screen

  4. Select New OpenAPI. Click Next.

    Select OpenAPI

  5. Enter the appropriate information to create a REST API definition.
    1. In the Title field, enter JWTVAL.
    2. The Name and Base Path fields autopopulate with the terms jwtval and /jwtval respectively.
    3. Enter 1.0.0 in the Version field.

    Basic information screen

  6. Click Next.
  7. Make no changes on the Secure screen. Click Next.

    Secure API

  8. You see the progress as the new API gets created. When it is done, you see a Summary. Click Edit API.

    New API summary

  9. In the side bar of the Design page, select Paths to display the Paths panel.

    Paths page

  10. Click Add.
  11. In the Path name field, enter /val.
  12. In the Operations section, click Add.
  13. Select GET and click Add.

    Path info

  14. Click Save.
  15. Click /val in the list of available paths.

    Path list

  16. Click GET in the list of Operations.
  17. Scroll down. In the Parameters section, click Add.
    1. Select REQUIRED.
    2. Enter Authorization in the NAME field.
    3. Select header in the LOCATED IN field.
    4. Select string in the TYPE field.
    5. Enter Enter Bearer <jwt> in the DESCRIPTION field.

    Path Parameter settings

  18. In the Response section, change the description of the pre-supplied 200 status code to 200 OK.

    Path Response settings

  19. Click Save.
  20. Click Assemble.

    Path list

  21. Hover the mouse over the existing Proxy or Invoke action and click the trash can icon to delete it.

    Proxy action

  22. Drag the Set Variable action onto the processing flow line. A configuration panel automatically opens.

    Setvar action added

  23. Click + Action field.
  24. Enter hs256-key in the Set field.
  25. Select string in the Type field.
  26. Enter a JWK in the Value field. Here is an example. { "alg": "HS256", "kty": "oct", "use": "sig", "k": "o5yErLaE-dbgVpSw65Rq57OA9dHyaF66Q_Et5azPa-XUjbyP0w9iRWhR4kru09aFfQLXeIODIN4uhjElYKXt8n76jt0Pjkd2pqk4t9abRF6tnL19GV4pflfL6uvVKkP4weOh39tqHt4TmkBgF2P-gFhgssZpjwq6l82fz3dUhQ2nkzoLA_CnyDGLZLd7SZ1yv73uzfE2Ot813zmig8KTMEMWVcWSDvy61F06vs_6LURcq_IEEevUiubBxG5S2akNnWigfpbhWYjMI5M22FOCpdcDBt4L7K1-yHt95Siz0QUb0MNlT_X8F76wH7_A37GpKKJGqeaiNWmHkgWdE8QWDQ", "kid": "hs256-key" }

    Setvar properties

  27. Close the property panel. Click Save.
  28. Drag the Validate JWT action onto the processing flow line after the set-variable icon. A configuration panel automatically opens.

    JWT Validate action added

  29. Enter hs256-key in the Verify Crypto JWK variable name field.

    JWT Validate properties

  30. Close the property panel. Click Save.
  31. Drag the GatewayScript action onto the processing flow line after the Validate JWT icon. A configuration panel automatically opens.
  32. Enter the following code: 
    var apim = require('apim');
apim.setvariable('message.body',apim.getvariable('decoded.claims'));

    GatewayScript action added

  33. Close the property panel. Click Save.
  34. Ensure that the Show catches option is enabled so that the catch area is displayed.

    Assemble page catch

  35. Click Catch. A property panel opens.

    Assemble page catch

  36. Click + Default.
  37. Drag the GatewayScript policy action onto the catch flow line.
  38. Enter the following code: 
    var apim = require('apim');
apim.setvariable('message.body',apim.getvariable('jwt-validate.error-message'));

    Assemble page catch flow

  39. Close the property panel. Click Save.

Testing the REST API

Note: Due to Cross-Origin Resource Sharing (CORS) restrictions, the assembly test tool cannot be used with the Chrome or Safari browsers on the macOS Catalina platform.
To test the REST API, you will need a valid JWT. You can obtain such a JWT by invoking the API created in the Tutorial: Generate a JSON Web Token (JWT). To complete testing, take the following steps:
  1. Click the Test icon The Test icon.

    Assemble page

  2. Click Activate API.

    Test setup

  3. Select the get /val Operation.
  4. Enter Bearer followed by a space followed by a valid JWT generated with the same sign key in the Authorization field. Invoking the API created by the Generate JWT tutorial will produce such a key.

    Test invoke

  5. Click Invoke. You may encounter a yellow error box with a URL embedded in it. Click this URL to override a browser certificate error.

    Test invoke

  6. Click Invoke again. The response contains branch data.

    Repeat invoke

Manage your API definition

Now that your new API works correctly, you can manage this API. To see your immediate options, take the following steps.

  1. Click the Develop icon Develop icon on the navigation bar.

    Navigation bar

  2. Click the Options icon The manage icon alongside the Mapper API.

    Manage API

  3. Select Download.

What you did in this tutorial

In this tutorial, you completed the following activities:
  • Created a new API definition that validates a JSON Web Token (JWT).
  • Tested the new API.