How to Fix 500 Internal Server Error on AAD Callback in Azure AD Authentication?

Question

Hi there,

I’m encountering an issue with Azure Active Directory (AAD) authentication when attempting to handle the callback at my application's endpoint. Specifically, the callback endpoint is receiving a 500 Internal Server Error after attempting a POST request.

I have verified that the redirect URI in the Azure AD app registration matches my application's callback URL (https://myappurl/.auth/login/aad/callback).

I have confirmed that the API permissions and consent are correctly set, including User.Read permissions.

I'm using Managed Identity instead of secrets for authentication, and I've updated the relevant configurations accordingly.

When I enable the client secret, the app works fine, even though I am not using it directly in my code. This suggests that the issue may be related to how the callback is being processed when using Managed Identity.

What might be causing the 500 Internal Server Error during the callback when using Managed Identity?

Are there any additional checks or configurations I should perform in the Azure AD app registration or App Service authentication settings to work without the client secret?

How can I ensure that the token exchange process is handled correctly, and that the callback parameters are valid?

Is there a way to retrieve more detailed error logs from Azure App Service or Application Insights to debug this?

• I’m using Managed Identity for authentication and Azure AD for the identity provider.

The application works when the client secret is enabled, even though it's not being used in the code.

I’ve enabled logging and am actively checking logs for more information, but I haven't found anything that stands out yet.

Thanks for your help!Hi there,

I’m encountering an issue with Azure Active Directory (AAD) authentication when attempting to handle the callback at my application's endpoint. Specifically, the callback endpoint is receiving a 500 Internal Server Error after attempting a POST request.

I have verified that the redirect URI in the Azure AD app registration matches my application's callback URL (https://myappurl/.auth/login/aad/callback).

I have confirmed that the API permissions and consent are correctly set, including User.Read permissions.

I'm using Managed Identity instead of secrets for authentication, and I've updated the relevant configurations accordingly.

When I enable the client secret, the app works fine, even though I am not using it directly in my code. This suggests that the issue may be related to how the callback is being processed when using Managed Identity.

What might be causing the 500 Internal Server Error during the callback when using Managed Identity?

Are there any additional checks or configurations I should perform in the Azure AD app registration or App Service authentication settings to work without the client secret?

How can I ensure that the token exchange process is handled correctly, and that the callback parameters are valid?

Is there a way to retrieve more detailed error logs from Azure App Service or Application Insights to debug this?

I’m using Managed Identity for authentication and Azure AD for the identity provider.

The application works when the client secret is enabled, even though it's not being used in the code.

I’ve enabled logging and am actively checking logs for more information, but I haven't found anything that stands out yet.

Thanks for your help!

Answer 1

Hello @Abhiram Adusumilli (LTIMINDTREE LIMITED)

I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this!

If your application is returning 500 Errors when it starts, there could be a few reasons:

Issue is related to middleware configured with client secrets, you typically need to reconfigure it to ensure that the client secrets are correctly set up and used securely.

For OAuth2 Middleware: Ensure that the correct client secret is configured and verify that the middleware can authenticate properly with the identity provider (IDP).

{

"client_id": "your-client-id",

"client_secret": "your-client-secret"

}

or also check

Node.exe is not present at the correct location. Check nodeProcessCommandLine setting.

Main script file is not present at the correct location. Check web.config and make sure the name of the main script file in the handler's section matches the main script file.

Web.config configuration is not correct – check the settings names/values.

Cold Start – Your application is taking too long to start. If your application takes longer than (maxNamedPipeConnectionRetry * namedPipeConnectionRetryDelay) / 1000 seconds, iisnode returns a 500 error. Increase the values of these settings to match your application start time to prevent iisnode from timing out and returning the 500 error.

Do you have a firewall, VNETs, and NSGs installed? We've seen this mistake happen to customers before, and it's usually caused by networking restrictions that block the underlying AAD traffic during the OAuth procedure. Additionally, have you seen https://stackoverflow.com/questions/47789655/azure-web-app-easyauth-callback-throws-error/47792917#47792917

Refer to this document link for troubleshooting- https://learn.microsoft.com/en-us/azure/app-service/app-service-web-nodejs-best-practices-and-troubleshoot-guide

To check the logs, I'd recommend enabling logging service for Azure App Service:

Enable diagnostics logging for apps in Azure App Service

https://learn.microsoft.com/en-us/azure/app-service/troubleshoot-diagnostic-logs

Click on App Service logs in settings option and Turn on Application logging (Filesystem).

These logs will be able to give you more insight into what is causing the app to error out.

If above steps didn't fix the issue, please refer the below troubleshooting document.

https://azureossd.github.io/2022/10/17/troubleshooting-common-iisnode-issues/index.html

References

Assign Azure Roles to Managed Identities

I hope this clarifies things. Please contact us if you have any additional questions.  

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Best regards,

Sakshi Devkante