Network Programming in .NET

Deploying an Azure Function to an App Service can sometimes result in an authentication error, preventing successful publishing. One common error developers encounter is:

Error: The attempt to publish the ZIP file through https://<function-name>.scm.azurewebsites.net/api/zipdeploy failed with HTTP status code Unauthorized.

This error typically occurs when the deployment process lacks the necessary authentication permissions to publish to Azure. Below, we outline the steps to resolve this issue by enabling SCM Basic Auth Publishing in the Azure Portal.

Understanding the Issue

The error indicates that Azure is rejecting the deployment request due to authentication failure. This often happens when the SCM (Kudu) deployment service does not have the correct permissions enabled, preventing the publishing process from proceeding.

Solution: Enable SCM Basic Auth Publishing

To resolve this issue, follow these steps:

1. Open the Azure Portal and navigate to your Function App.
2. In the left-hand menu, select Configuration.
3. Under the General settings tab, locate SCM Basic Auth Publishing.
4. Toggle the setting to On.
5. Click Save and restart the Function App if necessary.

Once this setting is enabled, retry the deployment from Visual Studio or your chosen deployment method. The unauthorized error should now be resolved.

Additional Considerations

• Use Deployment Credentials: If you prefer not to enable SCM Basic Auth, consider setting up deployment credentials under Deployment Center → FTP/Credentials.
• Check Azure Authentication in Visual Studio: Ensure that you are logged into the correct Azure account in Visual Studio under Tools → Options → Azure Service Authentication.
• Use Azure CLI for Deployment: If problems persist, try deploying with the Azure CLI:az functionapp deployment source config-zip \ --resource-group <resource-group> \ --name <function-app-name> \ --src <zip-file-path>

By enabling SCM Basic Auth Publishing, you ensure that Azure’s deployment service can authenticate and process your function’s updates smoothly. This quick fix saves time and prevents unnecessary troubleshooting steps.