Accessing non-Google resources programmatically

This article shows you how to programmatically access a resource protected by Identity-Aware Proxy (IAP) using external identities.

There are several situations where you might want to do this:

Your frontend application leverages Identity Platform directly. Your backend API server is built using App Engine, and protected by IAP using external identities.
Your application is designed for use in a non-traditional browser environment, such as on Android, iOS, or the command-line, where using a browser redirect to authenticate users is infeasible.

Accessing resources

To access a resource programmatically, follow these steps:

Retrieve the user's ID token.

Node.js

Ensure the user is signed in. The code below shows a simple example of signing in a user with an email and password:

// If signing in using project-level email/password IdP.
// auth.tenantId = null; // This is null by default.
// For signing in to a specific tenant using email/password.
auth.tenantId = 'myTenantId';
auth.signInWithEmailAndPassword(email, password)
  .then((user) => {
    // User signed in. ID token can now be retrieved.
  })
  .catch((error) => {
    // Handler error.
  });

You can then retrieve an ID token on the user object:

user.getIdToken()
  .then((idToken) => {
    // idToken is now available and can be sent to API server.
  })
  .catch((error) => {
    // Handler error.
  });

REST

Calling signInWithPassword returns an ID token in the response:

curl 'https://identitytoolkit.googleapis.com/v1/accounts:signInWithPassword?key=API-KEY' \
-H 'Content-Type: application/json' \
--data-binary '{
  "email":"EMAIL",
  "password":"PASSWORD",
  "returnSecureToken":true,
  "tenantId":"TENANT-ID" # Only used in multi-tenancy
  }'

Include the ID token in the authorization header when calling an endpoint protected by IAP.
```
curl -H "Authorization: Bearer GCIP-ID-TOKEN" "https://example.appspot.com/api"
```