How can I remove excessive response header information from Azure Web-Apps?
Don't use code to remove response headers. It is unstable according Microsoft
Use the Web.config custom Headers section instead as defined here:
<system.webServer>
<httpProtocol>
<!-- Security Hardening of HTTP response headers -->
<customHeaders>
<!--Sending the new X-Content-Type-Options response header with the value 'nosniff' will prevent
Internet Explorer from MIME-sniffing a response away from the declared content-type. -->
<add name="X-Content-Type-Options" value="nosniff" />
<!-- X-Frame-Options tells the browser whether you want to allow your site to be framed or not.
By preventing a browser from framing your site you can defend against attacks like clickjacking.
Recommended value "x-frame-options: SAMEORIGIN" -->
<add name="X-Frame-Options" value="SAMEORIGIN" />
<!-- Setting X-Permitted-Cross-Domain-Policies header to “master-only” will instruct Flash and PDF files that
they should only read the master crossdomain.xml file from the root of the website.
https://www.adobe.com/devnet/articles/crossdomain_policy_file_spec.html -->
<add name="X-Permitted-Cross-Domain-Policies" value="master-only" />
<!-- X-XSS-Protection sets the configuration for the cross-site scripting filter built into most browsers.
Recommended value "X-XSS-Protection: 1; mode=block". -->
<add name="X-Xss-Protection" value="1; mode=block" />
<!-- Referrer-Policy allows a site to control how much information the browser includes with navigations away from a document and should be set by all sites.
If you have sensitive information in your URLs, you don't want to forward to other domains
https://scotthelme.co.uk/a-new-security-header-referrer-policy/ -->
<add name="Referrer-Policy" value="no-referrer-when-downgrade" />
<!-- Remove x-powered-by in the response header, required by OWASP A5:2017 - Do not disclose web server configuration -->
<remove name="X-Powered-By" />
<!-- Set the cache-control per your Security settings (will affect performance) -->
<add name="Cache-Control" value="No-cache" />
</customHeaders>
</httpProtocol>
<!-- Prerequisite for the <rewrite> section
Install the URL Rewrite Module on the Web Server https://www.iis.net/downloads/microsoft/url-rewrite -->
<rewrite>
<!-- Remove Server response headers (OWASP Security Measure) -->
<outboundRules rewriteBeforeCache="true">
<rule name="Remove Server header">
<match serverVariable="RESPONSE_Server" pattern=".+" />
<!-- Use custom value for the Server info -->
<action type="Rewrite" value="Your Custom Value Here." />
</rule>
</outboundRules>
</rewrite>
</system.webServer>
Try this instead:
protected void Application_PreSendRequestHeaders(object sender, EventArgs e)
{
HttpContext.Current.Response.Headers.Remove("Server");
HttpContext.Current.Response.Headers.Remove("X-AspNet-Version");
HttpContext.Current.Response.Headers.Remove("X-AspNetMvc-Version");
}
Additionally, in the Application_Start call it with the following instruction
PreSendRequestHeaders += Application_PreSendRequestHeaders;
To remove X-AspNet-Version, in the web.config find/create and add:
<system.web>
<httpRuntime enableVersionHeader="false" />
...
</system.web>
To remove X-AspNetMvc-Version, go to Global.asax, find/create the Application_Start event and add a line as follows:
protected void Application_Start() {
MvcHandler.DisableMvcResponseHeader = true;
}
To remove X-Powered-By, in the web.config find/create and add:
<system.webServer>
<httpProtocol>
<customHeaders>
<remove name="X-Powered-By" />
</customHeaders>
</httpProtocol>
...
</system.webServer>
You should be able to force all requests to go through your managed code by adding this to your webconfig:
<modules runAllManagedModulesForAllRequests="true">
Even static files and not-found resources should obey your header rules.
References:
http://www.troyhunt.com/2012/02/shhh-dont-let-your-response-headers.html
http://consultingblogs.emc.com/howardvanrooijen/archive/2009/08/25/cloaking-your-asp-net-mvc-web-application-on-iis-7.aspx