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Conditional UI Rendering

A common pattern for leveraging authorization in the UI is to conditionally render components based on the user’s access to a resource. We'll now expand our policy to include decisions that will be used by our application to conditionally render as well as disable/enable a couple of buttons.

  1. We want to create a section in the application containing a message that will be visible only to a user with an admin role.
  2. We want to change the behavior of our "Get Sensitive Information" button such that:
    • The viewer will be able to see the button - but they will not be able to click it.
    • The editor will be able to click the button, but the resource will not be accessible to them.
    • The admin will be able to see the button and they will have access to the protected resource.

Update the policy#

First, we’ll update our policy to include clauses for visible and enabled. They will look very similar to the allowed clause:

package asertodemo.GET.api.protected
import input.user.attributes.roles as user_roles
default allowed = false
default visible = false
default enabled = false
allowed {    some i    data.roles[user_roles[i]].perms[path].allowed}
visible {    some i    data.roles[user_roles[i]].perms[path].visible}
enabled {    some i    data.roles[user_roles[i]].perms[path].enabled}

Next, we'll update the data.json file to include the visible and enabled properties for each role:

{  "roles": {    "viewer": {      "description": "A viewer with no access to sensitive asset",      "perms": {        "asertodemo.GET.api.protected": {          "allowed": false,          "enabled": false,          "visible": false        }      }    },    "editor": {      "description": "A editor with access to sensitive asset",      "perms": {        "asertodemo.GET.api.protected": {          "allowed": false,          "enabled": true,          "visible": false        }      }    },    "admin": {      "description": "An admin user with access to sensitive asset",      "perms": {        "asertodemo.GET.api.protected": {          "allowed": true,          "enabled": true,          "visible": true        }      }    }  }}

Push the policy#

Commit, tag and push the changes you made:

git commit -m "updated policy to include visible and enabled clauses"git tag v0.0.3git push origin mastergit push --tags

Use The Display State Map middleware#

Aserto provides a utility called Display State Map that will return the visible and enabled decisions from the authorizer to the server and finally to the application. To enable support for the Display State Map, we first need to update the Express.js service: let's add the reference to displayStateMap in the object destructuring for the express-jwt-aserto dependencies:

Change the line:

const { jwtAuthz } = require("express-jwt-aserto");

to:

const { displayStateMap, jwtAuthz } = require("express-jwt-aserto");

After the app.use(cors()) statement, add the following line:

app.use(displayStateMap(authzOptions));

Update the Application#

Next, we’ll add the Aserto React SDK to our application. In the root folder of our application, execute the following command:

yarn add @aserto/aserto-react

In src/index.js add the following dependency after the oidc-react dependency:

import { AsertoProvider } from "@aserto/aserto-react";

We'll wrap the <App /> component with the <AsertoProvider> provider:

<React.StrictMode>  <AuthProvider {...configuration}>    <AsertoProvider>      <App />    </AsertoProvider>  </AuthProvider></React.StrictMode>

In App.js, we’ll add the useAserto hook, as well as a stateful object that will track the result coming back from getDisplayState. Add the useAserto hook dependency below the useAuth dependency:

import { useAserto } from "@aserto/aserto-react";

Then, find the code block:

const auth = useAuth();const isAuthenticated = auth.userData?.id_token ? true : false;const [message, setMessage] = useState(false);

And add the following right after it:

const { init, loading, getDisplayState, error: asertoError } = useAserto();

We’ll add an effect to initialize the Aserto SDK. Add the following after the definition of the accessSensitiveInformation callback:

useEffect(() => {  async function initAserto() {    try {      const token = auth.userData?.id_token;
      if (token) {        await init({          serviceUrl: "http://localhost:8080",          accessToken: token,          policyRoot: "asertodemo",          throwOnError: false,        });      }    } catch (error) {      console.error(error);    }  }  if (!asertoError && isAuthenticated) {    initAserto();  }
  // eslint-disable-next-line react-hooks/exhaustive-deps}, [isAuthenticated, auth.userData?.id_token]);

We’ll add some error handling - if the Aserto SDK ran into an error, we’ll display it and not render anything else. Add the following right after the effect we just added:

if (asertoError) {  return (    <div>      <h1>Error encountered</h1>      <p>{asertoError}</p>    </div>  );}

Next, we’ll add a to call getDisplayState:

const displayState =  loading || asertoError    ? { visible: false, enabled: false }    : getDisplayState("GET", "/api/protected");

In case the SDK is not yet loaded or returns an error, the displayState variable will be set to { visible: false, enabled: false }. If the SDK completed loading successfully, the getDisplayState function will retrieve the visible and enabled decisions for the HTTP method (GET) and the path (/api/protected).

Lastly, we’ll update the main section of the app again. Replace it with the following:

<div className="main">  {loading && <div className="loading">Loading...</div>}  {!loading && isAuthenticated && (    <>      <div className="top-main">        <div className="welcome-message">          Welcome {auth.userData?.profile?.email}!        </div>        <div>          {!message && (            <button              className="primary-button"              disabled={!displayState.enabled}              onClick={() => accessSensitiveInformation()}            >              Get Sensitive Resource            </button>          )}          <div className="message-container">            {message && message !== 403 && message !== 401 && (              <>                <div className="lottie"></div>                <div className="message">{message}</div>              </>            )}            {message && message === 401 && (              <>                <div className="sad-lottie"></div>                <div className="message">                  No access to sensitive information                </div>              </>            )}            {message && message === 403 && (              <>                <div className="sad-lottie"></div>                <div className="message">                  No access to sensitive information                </div>              </>            )}          </div>        </div>      </div>      <div className="center-main">        {displayState.visible && (          <div>You have been identified as an `admin`.</div>        )}      </div>    </>  )}</div>

Based on our current policy:

  1. The button we added will be disabled for anyone who doesn’t have the admin or editor roles (for example, a viewer)
  2. While the editor will be able to click the button “Get Sensitive Information”, only the admin will be able to access the protected resource and receive the message.
  3. The div showing the “You have been identified as an admin” message will only be visible to users with the admin role.

Using the Aserto React SDK with the displayStateMap middleware, we can make use of these decisions - which were previously only exposed to the server - directly in the UI.

Summary

Congratulations! You've completed the Aserto React.js and Express.js tutorial. You learned how to create an Aserto policy and how to use it with the Aserto Express.js middleware. You also learned how to set up a React application that can authenticate the user, and conditionally render the UI based on the authenticated user's role. Read more about the React.js SDK and Express.js SDK to learn about other ways to use them in your own applications.

The finished application code is available in here.