Secure a Basic Node.js App with the Authorization and Trust Management Service (XSUAA)

To secure this product list application, two components are used. One is called the XSUAA service and the other one is called application router. The application router is used in combination with the XSUAA service to authenticate a user and route the user to the secured application.

The XSUAA plays the role of an OAuth authorization service whereas the application router plays the role of an OAuth client. Furthermore, the application router works as a central entry point to the application. For more information, check the links at the end of this tutorial.

Prepare the index.js file

To prevent a direct call to your application without authentication, it is necessary to add some code to your application. In our example, you use the Node.js passport authentication middleware and configure it with the XSUAA JWT strategy.

1. Go to the product-list/myapp folder.

2. Open the index.js file.

3. To use additional libraries, add the following lines of code below the line // secure the direct call to the application

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   const passport = require('passport');
   const { JWTStrategy } = require('@sap/xssec');
   const xsenv = require('@sap/xsenv');
   
   // XSUAA Middleware
   passport.use(new JWTStrategy(xsenv.getServices({uaa:{tag:'xsuaa'}}).uaa));
   
   app.use(passport.initialize());
   app.use(passport.authenticate('JWT', { session: false }));
   

   This code prevents direct calls to the product list application without a valid JWT.

4. To secure the product list with authorization checks, replace the line app.get('/products', getProducts); in the index.js file with the following code:

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   app.get('/products', checkReadScope, getProducts);
   
   // Scope check
   function checkReadScope(req, res, next) {
     if (req.authInfo.checkLocalScope('read')) {
       return next();
     } else {
         console.log('Missing the expected scope');
         res.status(403).end('Forbidden');
     }
   }
   

   The checkReadScope function ensures that only a user with the correct authorizations can look at the products.

5. Save the file.

Prepare the package.json file

Since there are now more modules used beside the express module, you have to add the relevant dependencies to your package.json file. In this case the dependencies for the modules passport, @sap/xsenv and @sap/xssec have to be added.

1. Open the package.json file.

2. Add the following dependencies:

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   "dependencies": {
     "express": "^4.17.1",
     "@sap/xsenv": "^3.1.0",
     "@sap/xssec": "^3.0.10",
     "passport": "^0.4.1"
   }
   

3. Save the file.

To use the XSUAA service, a file named xs-security.json is necessary. The file can define properties of the XSUAA service instance as well as different roles and authorizations. In this example the file contains a role template and a role collection with a Product List Viewer role, that enables the user later to view the products.

1. Add a folder named security to your product-list folder.

2. Within the folder, create a file named xs-security.json.

3. Add the following content:

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   {
     "xsappname": "product-list",
     "tenant-mode": "dedicated",
     "scopes": [
       {
         "name": "$XSAPPNAME.read",
         "description": "With this scope, USER can read products."
       }
     ],
   
     "role-templates": [
       {
         "name": "Viewer",
         "description": "Role to get the list of products",
         "scope-references": [
           "$XSAPPNAME.read"
         ]
       }
     ],
     "role-collections": [
       {
         "name": "ProductListViewer",
         "description": "Product List Viewer",
         "role-template-references": [
           "$XSAPPNAME.Viewer"
         ]
       }
     ],
     "oauth2-configuration":
       {
         "redirect-uris": ["https://approuter-product-list-ap25.cfapps.eu10.hana.ondemand.com/login/callback"]
         }
   }
   

   This creates a role collection with a role template and a role with a reading scope, so a user with this role can view the products.
   It also adds the redirect URI parameter, which calls the URL of the application router that you will create in the next step. For more information, see Listing Allowed Redirect URIs.

4. Save the file

To learn more about the xs-security.json file, check the links at the end of this tutorial.

The approuter will enable you to create a secure route to your application.

1. Add a folder named approuter to your product-list folder.

2. Within that folder create a file named package.json.

3. Add the following content:

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   {
       "name": "approuter",
       "dependencies": {
           "@sap/approuter": "^9.0.2"
       },
       "scripts": {
           "start": "node node_modules/@sap/approuter/approuter.js"
       }
   }
   

4. Save the file.

5. In the same folder, create a file named xs-app.json.

6. Add the following content to that file:

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   {
     "routes": [{
       "source": "^/products",
       "target": "/",
       "destination": "products-destination"
     }]
   }
   

   This will create a destination called products-destination. The destination is later referenced in the manifest.yml.

7. Save the file.

   To learn more about the xs-app.json file, check the links at the end of this tutorial.

For performance reasons it is better to put the images of the application into a static resources folder with the application router.

1. Navigate to the approuter folder.

2. Add a folder named resources.

3. Move the images folder from myapp/static/ into the approuter/resources folder.

By the end of these steps, your folder structure should look like this:

product-list
├── approuter
  ├──resources
    ├── images
      ├── HT-1000.jpg
      ├── HT-1010.jpg
      ├── HT-1030.jpg
  ├── package.json
  ├──  xs-app.json
├── myapp
    ├── lib
        ├── repository.js
        ├── products.json
    ├── static
        ├── index.html
    ├── index.js
    ├── package.json
├── security
    ├── xs-security.json
├── manifest.yaml

In the manifest file you have to define a hostname for your application and add a destination. The manifest file is used to bind the XSUAA service instance to your application.

The steps show incrementally what parameters and values have to be added. To avoid indentation errors, you can just copy the whole code at the end.

1. Navigate to the product-list folder.

2. Open the file manifest.yaml.

3. Give your application a specific host name with the parameter route. The route has to be unique in the whole Cloud Foundry landscape, so make sure to add a random part to the route, for example your initials and your day of birth, like product-list-ap25 and approuter-product-list-ap25. You also need the route to configure a destination later.

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   applications:
   # Product List Application
   - name: product-list
     instances: 1
     memory: 128M
     routes:
       - route: product-list-ap25.cfapps.eu10.hana.ondemand.com
     path: myapp
     buildpacks:
       - nodejs_buildpack
     timeout: 180
   

4. Add the binding for the XSUAA service to your application, in the same file.

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     ...
     services:
       - xsuaa-service-tutorial
   

5. Add the configuration data for the approuter:

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   applications:
   ...
   
   # Application Router
   - name: approuter
     routes:
       - route: approuter-product-list-ap25.cfapps.eu10.hana.ondemand.com
     path: approuter
     buildpacks:
       - nodejs_buildpack
     memory: 128M
   

6. Add the bindings for the XSUAA service to the approuter.

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   ...
     services:
       - xsuaa-service-tutorial
   

7. Add a destination to the approuter.

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   # Application Router
   ...
     env:
       destinations: >
         [
           {"name":"products-destination",
             "url":"https://product-list-ap25.cfapps.eu10.hana.ondemand.com",
             "forwardAuthToken": true}
         ]
   

   The name parameter is the same as previously defined in the file xs-app.json. the url parameter is the result of the host name of your application and the region of your Cloud Foundry landscape (https://<hostname>.cfapps.<region>.hana.ondemand.com). The forwardAuthToken parameter set to true ensures that the approuter forwards the JWT token to the destination.

   Ensure that the landscape mentioned in the route is the same as in the previous steps.

8. Save the file.

When you have completed the steps, your manifest.yml file should look like this:

applications:
# Application
- name: product-list
  instances: 1
  memory: 128M
  routes:
    - route: product-list-ap25.cfapps.eu10.hana.ondemand.com
  path: myapp
  buildpacks:
    - nodejs_buildpack
  timeout: 180
  services:
    - xsuaa-service-tutorial

# Application Router
- name: approuter
  routes:
    - route: approuter-product-list-ap25.cfapps.eu10.hana.ondemand.com
  path: approuter
  buildpacks:
    - nodejs_buildpack
  memory: 128M
  services:
    - xsuaa-service-tutorial
  env:
    destinations: >
      [
        {"name":"products-destination",
         "url":"https://product-list-ap25.cfapps.eu10.hana.ondemand.com",
         "forwardAuthToken": true}
      ]

Because your are calling the product list over the approuter with /products you need to make a small change within the index.html file.

1. Navigate to the product-list/myapp/static folder.

2. Replace line 24 in the index.html file with the following code.

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   var productsUrl = "/products/products"; //  contains path mapping which is specified in xs-app.json
   

3. Save the file.

Before you can deploy your application, you need to create the service instance for the XSUAA.

1. Log in to your Cloud Foundry account with the Cloud Foundry CLI.

2. Navigate to the product-list folder.

3. Create the XSUAA service instance with the xs-security.json security descriptor file.

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   cf create-service xsuaa application xsuaa-service-tutorial -c security/xs-security.json
   

4. Deploy the application.

cf push

Your application has two routes that are defined in the manifest.yml. The direct route to the application should return an error message saying unauthorized (because you don’t have a valid JWT yet). The secure route through the approuter redirects to a login screen. After logging in, the application opens but shows the message no data. To see the product data, you need to assign your user the role collection with the necessary authorizations.

1. First make sure that your application can’t be reached on its direct URL:

   https://product-list-ap25.cfapps.eu10.hana.ondemand.com

   If everything is working correctly, this will result in an error message reading unauthorized.

2. Navigate to your application with the secure route of your application router:

   https://approuter-product-list-ap25.cfapps.eu10.hana.ondemand.com/products

3. Enter the e-mail and password of your trial account.

   You should see the no data message. This is because you don’t have the role assigned yet to view the products. You will do this in the next step.

Assign your user the role collection that contains the necessary role to view the products in the product list.

1. Open the SAP BTP cockpit.

2. Navigate to your subaccount.

3. Choose the Security tab and choose Role Collections.

4. Choose the ProductListViewer role collection.

5. Edit the list of users in the configuration to include your ID (e-mail address), identity provider, and e-mail address.

6. Save the ProductListViewer configuration.

7. Call the URL of the approuter again (you might have to delete your cookies/cache before).

   https://approuter-product-list-ap25.cfapps.eu10.hana.ondemand.com/products

   The application will now show you the products.

Error message: the hostname of your application is already taken

To resolve this error, please edit the manifest.yml file and change the route parameter of the product list application or the route parameter of the approuter (depending on which hostname is already taken). If you change the parameter of the product list application, make sure to change the url parameter under destinations as well.

500 internal error when calling your application from its secure route

To resolve this error, please check that you have added the bindings for the XSUAA service to the approuter. See Step 6: Substep 6 for more details.

• Info on the xs-app.json
• Info on the xs-security.json
• Access Management in the Cloud Foundry Environment