How to recognize if a request came from URL rewrite module

Question

Apologize if the title is not clear, basically I have a web proxy that listening on port 80 and I set up URL rewrite on IIS, (the rule on web.config as following), it does

http://example.com/api/blah/blah ->
http://example.com:8095/api/blah/blah

  <rule name="api-example" enabled="true" patternSyntax="ECMAScript" stopProcessing="true">
     <match url="^.*/api/.*$" />
     <conditions logicalGrouping="MatchAll" trackAllCaptures="false" />
     <action type="Rewrite" url="http://localhost:8095/{R:0}" appendQueryString="true" logRewrittenUrl="false" />
  </rule>

it works fine, no problems, also works when I request localhost:8095 directly

but I'd also like to be able to recognize if a request was directly requested or it was via URL rewrite module.

My idea is, to append a query string onto the URL, when the url gets rewrited on IIS so that I can check if the query string exists then it was via URL rewrite if not, then it's a direct request

examples:

http://example.com/api/blah/blah?from=proxy -> http://example.com:8095/api/blah/blah?from=proxy

http://example.com/api/blah/blah?existing_query_string=blah&from=proxy -> http://example.com:8095/api/blah/blah?existing_query_string=blah&from=proxy

How can I achieve this? or is there any other way to do it?

Many thanks

Ming

score 1 · Answer 1 · answered Dec 13 '13 at 15:33

I eventually went to my own solution, which is add a query string when IIS does url rewrite and the Url rewrite module clever enough to append the querystring arr=1 to url doesn't matter whether or not the url has already had query string,

then I add code to check if the querystring contains arr=1 or not if has, then the request comes via url rewrites

<rule name="api-example" enabled="true" patternSyntax="ECMAScript" stopProcessing="true">
     <match url="^.*/api/.*$" />
      <conditions logicalGrouping="MatchAll" trackAllCaptures="false">
        <add input="{QUERY_STRING}" pattern="(.*)" negate="false" />
      </conditions>
     <action type="Rewrite" url="http://localhost:8095/{R:0}?arr=1" appendQueryString="true" logRewrittenUrl="false" />
  </rule>

score 0 · Answer 2 · answered Dec 12 '13 at 17:38

0

You can try to access

Request.ServerVariables["HTTP_X_ORIGINAL_URL"]

and compare it to Request.Url.PathAndQuery. Alternatively,

Request.RawUrl

should also contain the original URL.

answered Dec 12 '13 at 17:38

Olaf

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Hi I had a try, and the HTTP_X_ORIGINAL_URL shows me only the original path and querystring before url rewrite, but doesn't have domain value, this won't help if I forward to another web server that has exactly same path and query string. And the raw url doesn't help at all. – Ming Dec 13 '13 at 15:29

How to recognize if a request came from URL rewrite module

2 Answers2