How to restrict direct calls to WebAPI – SharePoint 2013

Sathish Nadarajan
SharePoint MVP
Published On :   19 Oct 2015
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In the previous articles, (WebAPI and Create WEBAPI) we saw how to create and call the WebAPI from our Javascripts in SharePoint 2013. Now, there is one more check, we need to do. i.e., while calling the WebAPI, from the Javascript, we would have given the WebAPI URL on the client Side. Hence, if some one who is having a knowledge of viewing the source, the end user will come to know the WebAPI. Obviously that is not a good practice. We expect the Users to access the WebAPI through our application. Not directly. So a validation needs to be done on the WebAPI.

         public string MyMethod(string sampleParameter)
             Uri urlReferrer = ((System.Web.HttpContextWrapper)Request.Properties["MS_HttpContext"]).Request.UrlReferrer;
             if (urlReferrer != null)
                 if (urlReferrer.AbsolutePath.ToLower().Contains("/sites/MySiteCollection") && urlReferrer. Host.ToLower().Contains(“MyDomain”))
                     // Do the actual stuff 
                     return returnValue;
             return "Not a Valid Request";

Hence, on the above code, if the WebAPI is being called directly, the urlReferrer will not have our site collection url. Hence, the Method will return a “Not a valid Request” message.

When the request comes from our site collection, then only the web api will respond.

Though this looks very small, it is really important when considering the security.

Happy Coding,

Sathish Nadarajan.