Add Security to the SAP SuccessFactors Extension

So far, you have been working on a local project which only developers would have access to. Therefore, it’s OK to leave your service “unprotected” as it’s not yet publicly available. But, as soon as you deploy it to the cloud, it will be available to anyone who knows the service endpoint (which is not quite difficult).

In such scenario, anyone can access the service anonymously and freely make OData calls to it, which will probably cause a big mess in your application and related data. So, it’s imperative to “protect” your service against such risky situation by granting access only to authenticated users.

Then, to make the service available only to authenticated users, you just need to add the requires annotation to the service definition (in the projman-service.cds file), like demonstrated below:

Now, in the service home page, when you click on any entity link (i.e. SFSF_User) a pop-up in the browser will ask for the username and password.

As you are still in development you can provide whatever information you like and click sign in, because in this environment CAP is using what we call mocked authentication which does not utilize real users. So, after clicking sign in, you may see the data from the selected entity:

But, in an administrative scenario like this one, just being an authenticated user is not enough. It’s appropriate that, additionally, the authenticated user must be granted some administrative role (i.e. an Admin role).

Therefore, you need to specify that the entities from our service are only viewable and maintainable by users with the Admin role. To do so, you also annotate your entities with the requires annotation, but now you specify the Admin role, instead of authenticated-user, like demonstrated below:

Now, if you click again on the same entity link (i.e. SFS_User) you should receive an HTTP 403 (Forbidden) error:

It happened because the mocked user (any dummy data you provided) was not granted the Admin role, thus cannot access any entity annotated as such.

So, you should fix it now. To do so, you just need to add an auth block into the cds.requires section of the package.json file, like demonstrated below:

This block instructs CAP to use the mock strategy (which is default) during development and it creates two mock users: John who’s granted the Admin role and Mary who’s granted the Viewer role (which has no authorization in the context of your application).

Now, you need to login as john (with any password that you like), but CAP has already opened a session to the first mock user you utilized (who has no Admin role granted) and won’t pop-up for a new login (so, you stick with the forbidden error).

To work this around, you will need to completely close your browser (not only the Business Application Studio tab), open it again and go back to your SAP BTP cockpit to access Business Application Studio from the Instances and Subscriptions page. Click on your Dev Space and when the IDE loads again make sure that cds watch is properly running, if not, run it again. Launch the service home page and click any entity link (i.e. SFSF_User).

NOTE: you can also try to open the http://localhost:4040 in an incognito window to achieve that goal

This time the sign in pop-up should appear and you must login with john to overcome the forbidden error:

To learn more about authentication and authorization in CAP, you can refer to this two links from the official documentation:

• Authentication
• Authorization and Access Control

OK, so far you have defined a simple authorization schema to secure all service entities and verified that it’s working as expected. But, in production, security will be handled by the User Account and Authentication (UAA) mechanism of Cloud Foundry which, in SAP BTP, is implemented by the XSUAA service.

Therefore, you need to configure the XSUAA service instance to recognize and apply the schema you have defined when the application is deployed on SAP BTP.

For that, you need to create a file named xs-security.json in the project root folder, and the good news is that CAP can do it for you automatically based on the security schema from the service definition.

In the Terminal press CTRL+C to terminate the cds watch command, then type the command:

• cds compile srv/ --to xsuaa >xs-security.json

Then, press Enter.

On the left-hand pane click on the xs-security.json file to open it. Examine the contents and add the two lines indicated in the screenshot below right before “scopes” (if not already generated by the compiler, as older versions of it used to add them automatically). In the role-templates collection, change the description of the Admin role from “generated” to “Project Administrator”:

This file is used during the creation or update of the XSUAA service instance and controls the roles, scopes, attributes and role templates that will be part of the security for your application.

Now, quickly understand what’s done in this descriptor.

Basically, you define a scope named Admin for the application and assign it to the Admin role template. This way, when the application is deployed to SAP BTP the Admin role will be automatically created in the platform and associated to the sfsf-projman application.

But roles are not directly assigned to the application’s users. The assignment is done through role collections. So, just add one to the file like demonstrated in the screenshot below:

After deployment, you just need to assign it to the user who should be granted such authorization.

Now, you just need to add four dependencies to the CAP service for it to properly handle security and other related stuff – such as the user JSON Web Token (JWT) – during runtime. Those are:

• @sap/cds-dk
• @sap/xsenv
• @sap/xssec
• passport

Therefore, in the Terminal, just type the following commands pressing Enter after each one:

• npm install @sap/xsenv
• npm install @sap/cds-dk
• npm install @sap/xssec
• npm install passport

When the commands complete, your package.json file should like the screenshot below: