Forbidden 403 error in EasyAuth

Hello Gibran Myageri,

Thank you for submitting your question on Microsoft Q&A.

Receiving a 403 error without any logs typically indicates a platform-level rejection by EasyAuth, usually due to a configuration mismatch in the Azure Portal rather than an issue with your code.

Below are some key Microsoft Learn resources to help you resolve this issue:

1. EasyAuth Main Documentation

This central guide covers App Service authentication and authorization, explaining relevant flows and configuration settings.

• Authentication and Authorization in Azure App Service: Be sure to review the "client-directed flow" section, which details how the React app obtains a token from Azure AD and sends it to the backend, and how the middleware validates the token.

2. End-to-End Tutorial

This step-by-step tutorial outlines setting up a similar architecture and helps identify any missing configuration steps.

• Tutorial: Authenticate and authorize users end-to-end in Azure App Service: It covers permissions for the front-end to access the back-end API, exposing scopes, and configuring EasyAuth for both services.

3. 403 Error Guidance

This documentation discusses common authorization errors, including 403s.

• Resolve Microsoft Graph authorization errors: While focused on Microsoft Graph, it explains token validation principles, such as the importance of the correct audience claim. A mismatched audience claim is a frequent cause of 403 errors.

Key Configuration Checks

Double-check these items in the Azure Portal:

• Backend App Registration: Expose an API
  • Set the Application ID URI (e.g., api://<backend-client-id>).
    • Define and enable a scope (e.g., access_as_user).
    • Frontend App Registration: API Permissions
      • Add the backend registration as an API under "Configured permissions."
        • Grant the specific backend scope to the frontend.
          • Click "Grant admin consent" for permissions.
• Backend App Service: EasyAuth Settings
  • Verify the "Client ID" field under Microsoft identity provider settings matches the backend app registration's Application (client) ID. If set incorrectly, a 403 will occur.Receiving a 403 error without any logs typically indicates a platform-level rejection by EasyAuth, usually due to a configuration mismatch in the Azure Portal rather than an issue with your code. Below are some key Microsoft Learn resources to help you resolve this issue: 1. EasyAuth Main Documentation This central guide covers App Service authentication and authorization, explaining relevant flows and configuration settings.
    • Authentication and Authorization in Azure App Service: Be sure to review the "client-directed flow" section, which details how the React app obtains a token from Azure AD and sends it to the backend, and how the middleware validates the token.
    2. End-to-End Tutorial This step-by-step tutorial outlines setting up a similar architecture and helps identify any missing configuration steps.
    • Tutorial: Authenticate and authorize users end-to-end in Azure App Service: It covers permissions for the front-end to access the back-end API, exposing scopes, and configuring EasyAuth for both services.
    3. 403 Error Guidance This documentation discusses common authorization errors, including 403s.
    • Resolve Microsoft Graph authorization errors: While focused on Microsoft Graph, it explains token validation principles, such as the importance of the correct audience claim. A mismatched audience claim is a frequent cause of 403 errors.
    Key Configuration Checks Double-check these items in the Azure Portal:
    • Backend App Registration: Expose an API
      • Set the Application ID URI (e.g., api://<backend-client-id>).
      • Define and enable a scope (e.g., access_as_user).
    • Frontend App Registration: API Permissions
      • Add the backend registration as an API under "Configured permissions."
      • Grant the specific backend scope to the frontend.
      • Click "Grant admin consent" for permissions.
    • Backend App Service: EasyAuth Settings
      • Verify the "Client ID" field under Microsoft identity provider settings matches the backend app registration's Application (client) ID. If set incorrectly, a 403 will occur.