Rewriting HTTP headers in Azure Application Gateway is now supported.
You can add, remove, or update HTTP request and response headers while the request and response packets move between the client and backend application. You can also add conditions to ensure that the headers you specify are rewritten only when the conditions are met. Rewriting headers helps you accomplish several important scenarios such as removing port information from X-Forwarded-For headers, adding security-related header fields like HSTS/ X-XSS-Protection, removing response header fields which may reveal sensitive information, etc.
For more details, please see https://aka.ms/HeaderRewriteInfo