MSAL Runtime Documentation

Oct 13, 2025 by wbrum.org 120 views

On Behalf of: A Comprehensive Guide to OAuth 2.0 Workflows with MSAL Runtime

Introduction

As a CPP developer, you're likely familiar with the Microsoft Authentication Library (MSAL) runtime, which provides a convenient and efficient way to handle authentication and authorization in your applications. However, when it comes to implementing OAuth 2.0 workflows, such as the "on behalf of" scenario, you may find yourself wondering if this functionality is supported or if you're looking in the wrong place.

In this article, we'll delve into the world of OAuth 2.0 and explore how to use the MSAL runtime to complete an "on behalf of" workflow. We'll cover the basics of OAuth 2.0, the "on behalf of" scenario, and provide a step-by-step guide on how to implement this workflow using the MSAL runtime.

Understanding OAuth 2.0

OAuth 2.0 is an authorization framework that allows users to grant third-party applications limited access to their resources on another service provider's website, without sharing their login credentials. This framework is widely used in modern web development, and it's essential to understand its basics before diving into the "on behalf of" scenario.

Key Concepts:

Client: The application requesting access to the user's resources.
Resource Server: The server hosting the user's resources.
Authorization Server: The server responsible for authenticating the user and issuing an access token.
Access Token: A token granted to the client, allowing it to access the user's resources.

The "On Behalf of" Scenario

The "on behalf of" scenario is a specific use case in OAuth 2.0 where a client requests access to a user's resources on behalf of another user. This is commonly used in scenarios such as:

Service Accounts: A service account is a special type of user account that can be used by applications to access resources on behalf of other users.
API Gateways: An API gateway is a server that acts as an intermediary between clients and resource servers, and it may need to access resources on behalf of other users.

Key Challenges:

User Consent: The client needs to obtain consent from the user whose resources it wants to access.
Access Token: The client needs to obtain an access token that grants it access to the user's resources.

Implementing the "On Behalf of" Workflow with MSAL Runtime

Now that we've covered the basics of OAuth 2.0 and the "on behalf of" scenario, let's dive into the implementation details using the MSAL runtime.

Step 1: Initialize the MSAL Runtime

To start using the MSAL runtime, you need to initialize it with your application's client ID and client secret. You can do this by creating an instance of the IApplication class and passing in your client ID and client secret.

#include <msal/ClientApplication.h>

// Initialize the MSAL runtime
IApplication* app = ClientApplication::Create(
    L"https://login.microsoftonline.com/{tenant_id}/v2.0",
    L"{client_id}",
    L"{client_secret}",
    nullptr);

Step 2: Acquire an Access Token

To access the user's resources, you need to acquire an access token. You can do this by calling the AcquireTokenSilentAsync method, passing in the user's account and the scopes you want to access.

// Acquire an access token
IAccount* account = app->GetAccountAsync(L"{user_id}").get();
IAuthenticationResult* result = app->AcquireTokenSilentAsync(
    L"https://graph.microsoft.com/.default",
    account).get();

Step 3: Use the Access Token

Once you have the access token, you can use it to access the user's resources. You can do this by calling the GetAccessTokenAsync method, passing in the access token and the scopes you want to access.

// Use the access token
IAuthenticationResult* result = app->GetAccessTokenAsync(
    L"https://graph.microsoft.com/.default",
    L"{access_token}").get();

Step 4: Handle Errors

Finally, you need to handle errors that may occur during the authentication process. You can do this by catching the MsalException exception and handling it accordingly.

// Handle errors
try {
    // Acquire an access token
    IAccount* account = app->GetAccountAsync(L"{user_id}").get();
    IAuthenticationResult* result = app->AcquireTokenSilentAsync(
        L"https://graph.microsoft.com/.default",
        account).get();
} catch (MsalException& e) {
    // Handle the error
    wprintf(L"Error: %s\n", e.what());
}

Conclusion

In this article, we've covered the basics of OAuth 2.0 and the "on behalf of" scenario, and provided a step-by-step guide on how to implement this workflow using the MSAL runtime. We've also discussed the key challenges and considerations when implementing the "on behalf of" workflow.

By following the steps outlined in this article, you should be able to implement the "on behalf of" workflow using the MSAL runtime and access the user's resources on behalf of another user.

Additional Resources

For more information on OAuth 2.0 and the MSAL runtime, please refer to the following resources:

MSAL Runtime Documentation: https://docs.microsoft.com/en-us/azure/active-directory/develop/msal-overview
OAuth 2.0 Specification: https://tools.ietf.org/html/rfc6749
MSAL Runtime GitHub Repository: https://github.com/AzureAD/microsoft-authentication-library-for-cpp

Frequently Asked Questions

Q: What is the "on behalf of" scenario? A: The "on behalf of" scenario is a specific use case in OAuth 2.0 where a client requests access to a user's resources on behalf of another user.

Q: How do I implement the "on behalf of" workflow using the MSAL runtime? A: To implement the "on behalf of" workflow using the MSAL runtime, you need to initialize the MSAL runtime, acquire an access token, use the access token, and handle errors.

Q: What are the key challenges when implementing the "on behalf of" workflow? A: The key challenges when implementing the "on behalf of" workflow include user consent, access token, and error handling.

Q: Where can I find more information on OAuth 2.0 and the MSAL runtime? A: You can find more information on OAuth 2.0 and the MSAL runtime on the following resources:

MSAL Runtime Documentation: https://docs.microsoft.com/en-us/azure/active-directory/develop/msal-overview
OAuth 2.0 Specification: https://tools.ietf.org/html/rfc6749
MSAL Runtime GitHub Repository: https://github.com/AzureAD/microsoft-authentication-library-for-cpp
On Behalf of: A Comprehensive Guide to OAuth 2.0 Workflows with MSAL Runtime - Q&A

Introduction

In our previous article, we covered the basics of OAuth 2.0 and the "on behalf of" scenario, and provided a step-by-step guide on how to implement this workflow using the MSAL runtime. However, we understand that you may still have questions and concerns about implementing the "on behalf of" workflow.

In this article, we'll address some of the most frequently asked questions about the "on behalf of" workflow and provide additional guidance on how to implement this workflow using the MSAL runtime.

Q&A

Q: What is the "on behalf of" scenario?

A: The "on behalf of" scenario is a specific use case in OAuth 2.0 where a client requests access to a user's resources on behalf of another user.

Q: How do I implement the "on behalf of" workflow using the MSAL runtime?

A: To implement the "on behalf of" workflow using the MSAL runtime, you need to initialize the MSAL runtime, acquire an access token, use the access token, and handle errors.

Q: What are the key challenges when implementing the "on behalf of" workflow?

A: The key challenges when implementing the "on behalf of" workflow include user consent, access token, and error handling.

Q: How do I obtain user consent for the "on behalf of" workflow?

A: To obtain user consent for the "on behalf of" workflow, you need to redirect the user to the authorization server and prompt them to grant consent for the client to access their resources on behalf of another user.

Q: How do I handle errors in the "on behalf of" workflow?

A: To handle errors in the "on behalf of" workflow, you need to catch the MsalException exception and handle it accordingly. You can also use the GetErrorDetailsAsync method to get more information about the error.

Q: Can I use the MSAL runtime to implement the "on behalf of" workflow in a web application?

A: Yes, you can use the MSAL runtime to implement the "on behalf of" workflow in a web application. However, you need to ensure that the web application is configured to use the MSAL runtime and that the client ID and client secret are properly configured.

Q: Can I use the MSAL runtime to implement the "on behalf of" workflow in a mobile application?

A: Yes, you can use the MSAL runtime to implement the "on behalf of" workflow in a mobile application. However, you need to ensure that the mobile application is configured to use the MSAL runtime and that the client ID and client secret are properly configured.

Q: How do I troubleshoot issues with the "on behalf of" workflow?

A: To troubleshoot issues with the "on behalf of" workflow, you can use the GetErrorDetailsAsync method to get more information about the error and the GetDebugInfoAsync method to get more information about the debug information.

Q: Can I use the MSAL runtime to implement the "on behalf of" workflow in a server-side application?

A: Yes, you can use the MSAL runtime to implement the "on behalf of" workflow in a server-side application. However, you need to ensure that the server-side application is configured to use the MSAL runtime and that the client ID and client secret are properly configured.

Conclusion

In this article, we've addressed some of the most frequently asked questions about the "on behalf of" workflow and provided additional guidance on how to implement this workflow using the MSAL runtime. We hope that this information has been helpful in answering your questions and concerns about implementing the "on behalf of" workflow.

Additional Resources

For more information on OAuth 2.0 and the MSAL runtime, please refer to the following resources:

MSAL Runtime Documentation: https://docs.microsoft.com/en-us/azure/active-directory/develop/msal-overview
OAuth 2.0 Specification: https://tools.ietf.org/html/rfc6749
MSAL Runtime GitHub Repository: https://github.com/AzureAD/microsoft-authentication-library-for-cpp

Frequently Asked Questions

Q: What is the "on behalf of" scenario? A: The "on behalf of" scenario is a specific use case in OAuth 2.0 where a client requests access to a user's resources on behalf of another user.

Q: How do I obtain user consent for the "on behalf of" workflow? A: To obtain user consent for the "on behalf of" workflow, you need to redirect the user to the authorization server and prompt them to grant consent for the client to access their resources on behalf of another user.

Q: How do I handle errors in the "on behalf of" workflow? A: To handle errors in the "on behalf of" workflow, you need to catch the MsalException exception and handle it accordingly. You can also use the GetErrorDetailsAsync method to get more information about the error.

Q: Can I use the MSAL runtime to implement the "on behalf of" workflow in a web application? A: Yes, you can use the MSAL runtime to implement the "on behalf of" workflow in a web application. However, you need to ensure that the web application is configured to use the MSAL runtime and that the client ID and client secret are properly configured.

Q: Can I use the MSAL runtime to implement the "on behalf of" workflow in a mobile application? A: Yes, you can use the MSAL runtime to implement the "on behalf of" workflow in a mobile application. However, you need to ensure that the mobile application is configured to use the MSAL runtime and that the client ID and client secret are properly configured.

Q: How do I troubleshoot issues with the "on behalf of" workflow? A: To troubleshoot issues with the "on behalf of" workflow, you can use the GetErrorDetailsAsync method to get more information about the error and the GetDebugInfoAsync method to get more information about the debug information.

Q: Can I use the MSAL runtime to implement the "on behalf of" workflow in a server-side application? A: Yes, you can use the MSAL runtime to implement the "on behalf of" workflow in a server-side application. However, you need to ensure that the server-side application is configured to use the MSAL runtime and that the client ID and client secret are properly configured.