Aadsts9002325: proof key for code exchange is required for cross-origin authorization code redemption.

The error message aadsts9002325 indicates that when attempting to redeem an authorization code for cross-origin usage, a proof key for code exchange is required.

Cross-origin authorization code redemption refers to the process of exchanging an authorization code obtained from one domain for an access token from a different domain. This is often necessary in scenarios where the authorization server and the resource server are hosted on separate domains.

To successfully redeem the authorization code in a cross-origin context, the client application needs to generate a proof key for code exchange (PKCE). PKCE is a security enhancement for authorization code flow, primarily used in native and mobile applications. It mitigates the risk of interception and replay attacks.

Here is an example of how PKCE can be implemented using JavaScript:

  // Generate a random code verifier
  var codeVerifier = generateRandomString();

  // Create a code challenge from the code verifier
  var codeChallenge = base64UrlEncode(sha256(codeVerifier));

  // Include the code challenge in the authorization request
  var authorizationUrl = 'https://authorization-server.com/oauth/authorize' +
    '?response_type=code' +
    '&client_id=your_client_id' +
    '&redirect_uri=your_redirect_uri' +
    '&code_challenge=' + codeChallenge +
    '&code_challenge_method=S256';

  // Redirect the user to the authorization URL

  // Upon receiving the authorization response with the authorization code,
  // extract the code verifier from storage

  // Exchange the authorization code and the code verifier for an access token
  var tokenUrl = 'https://authorization-server.com/oauth/token';
  var tokenRequestData = {
    grant_type: 'authorization_code',
    client_id: 'your_client_id',
    redirect_uri: 'your_redirect_uri',
    code: 'authorization_code',
    code_verifier: codeVerifier
  };

  // Send a POST request to the token URL with the token request data
  // Upon successful completion, you will receive an access token

  

In the example above, the client application generates a random code verifier and creates a code challenge using a cryptographic hash function. The code challenge and the code challenge method (S256 in this case) are included in the authorization request.

Upon receiving the authorization code, the client application extracts the code verifier from storage and includes it in the token request. The authorization server then verifies the code verifier against the previously generated code challenge. If the verification is successful, the server issues an access token.

By utilizing PKCE, the client application enhances the security of the authorization code flow, specifically in cross-origin scenarios where the transmission of the authorization code is more susceptible to interception.