How to make a request to SharePoint 2013 REST service from code that runs inside SharePoint server (NOT from App/External code)

Question

I have a page hosted in _layouts in SharePoint 2013. I want to make REST call to SharePoint REST api from this page using current user credentials. I don't want to do it from client-side (jquery etc)

So basically I want to make Web Request to the SharePoint REST api on the same server and pass current user authentication. I was able to do that in SharePoint 2010 by using default network credentials, but in 2013 it returns 401 Unauthorized.

Same thing with ClientContext. I cannot just do "new ClientContext(SPContext.Current.Web.Url)" Note: yes, there are Server APIs, but for things like Excel Services using REST API was just easier.

As I understand you need to pass access token for OAuth, but how do I get it for current user in SharePoint? Without making him reenter login/password and without using SharePoint Apps.

Answer 1

Claims Authentication uses an authentication cookie. You can create a 'cookie aware' WebClient that sets the cookies for the new request:

public class CookieAwareWebClient : WebClient
{
    private readonly CookieContainer m_container = new CookieContainer();

    protected override WebRequest GetWebRequest(Uri address)
    {
        WebRequest request = base.GetWebRequest(address);
        HttpWebRequest webRequest = request as HttpWebRequest;
        if (webRequest != null)
        {
            webRequest.CookieContainer = m_container;
        }
        return request;
    }
}

You can make use of it as follows:

CookieAwareWebClient wc = new CookieAwareWebClient();
wc.UseDefaultCredentials = true;
string s = wc.DownloadString(url);