Web Cache Deception

McBride, Michael 1

Having a problem with our classic webforms webapp.

The problem is, if you go to /SensitivePage.aspx/image.jpg, then a web cache server may cache the response because it ends with .jpg. WebForms will allow going to /SensitivePage.aspx/image.jpg, it treats the URL as if it were /SensitivePage.aspx.

How can I change this so going to /SensitivePage.aspx/image.jpg will return a 404 because the file does not actually exist?

Yijing Sun-MSFT 7,071 Reputation points

2021-08-31T07:28:47.827+00:00
hi @McBride, Michael ,
As far as I think,you could use Server.MapPath to verify the existence of the file and then route to the url.

if(File.Exists(Server.MapPath("/images/items/"+item.Name+".jpg")))

Best regards,
Yijing Sun
McBride, Michael 1 Reputation point

2021-09-06T02:10:13.28+00:00

I found that I can either rely on Request.PathInfo being empty, or use the Request's Uri without query string to check if the file exists or not.
Request.PathInfo seems to be non-empty whenever you have a request like this: /SensitivePage.aspx/image.jpg, and it will be "/image.jpg".
Yijing Sun-MSFT 7,071 Reputation points

2021-09-06T08:19:25.927+00:00
Hi @McBride, Michael ,

The pathInfo is ignored. There are two ways:

You need to use absolute path instead of relative path.

You can try to check the Request's PathInfo property to see whether it exists.
void Application_BeginRequest(object sender, EventArgs e){ //Code that runs when an unhandled error occurs string strPathInfo=Context.Request.PathInfo; //if strPathInfo is not correct, then redirect user to another page
//Response.Redirect("error.page");
}

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Web Cache Deception