/** 
* CASP.cs 
* CAS over ASP.NET! 
*  
* Created by John Tantalo, john.tantalo@case.edu 
* Case Western Reserve University 
*  
* Modification History: 
*  
* 12/09/05 jnt5, created class 
* 12/12/05 jnt5, removed cookie check 
*                                stores CASNetworkID in session instead of cache 
*                                clears Page session variable after ticket verification 
* 12/13/05 jnt5, removed Page session variable 
*                                fixed bug which would cause loop due to incorrect service parameter 
* 04/04/06 jnt5, adapted serviceURL code courtesy Ali Cakmak 
* 04/10/06 jnt5, added new comments 
*  
* References: 
*  
* http://wiki.case.edu/Central_Authentication_Service 
* https://clearinghouse.ja-sig.org/wiki/display/CAS/CAS+2.0+Protocol+Specification 
*/ 
 
using System ; 
using System.Web.UI ; 
using System.Net ; 
using System.IO ; 
using System.Web.SessionState; 
 
/** 
* CASP general usage: 
*  
*      private void Page_Load(object sender, System.EventArgs e) 
*      { 
*              String NetworkID = CASP.Authenticate( "https://bb5.fsu.edu/cas/login", "https://bb5.fsu.edu/cas/validate", this ) ; 
*      } 
*/ 
          
public class CASP 
{ 
        /** 
         * Authenticates a user with the given login and validation pages. After authentication 
         * the user's browser is redirected to the original page. 
         */ 
         
        public static String Authenticate( String LoginURL, String ValidateURL, Page Page ) 
        { 
                return Authenticate( LoginURL, ValidateURL, Page, Page.Request.Url.AbsoluteUri.Split('?')[0] ) ; 
        } 
 
        /** 
         * Authenticates a user with the given login and validation pages. After authentication 
         * the user's browser is redirected to the location given as the service URL. 
         */ 
 
        public static String Authenticate( String LoginURL, String ValidateURL, Page Page, String ServiceURL ) 
        { 
                if( Page.Session["CASNetworkID"] != null ) // user already logged in 
                        return Page.Session["CASNetworkID"].ToString() ; 
                else // user hasn't logged in 
                { 
                        if( Page.Request.QueryString["ticket"] != null ) // ticket received 
                        { 
                                try // read ticket and request validation 
                                { 
                                        StreamReader Reader = new StreamReader( new WebClient().OpenRead( ValidateURL + "?ticket=" + Page.Request.QueryString["ticket"] + "&service=" + ServiceURL ) ) ; 
                                 
                                        if( "yes".Equals( Reader.ReadLine() ) ) // ticket validated 
                                        { 
                                                // store network id in sesssion, return value 
 
                                                return (String) ( Page.Session["CASNetworkID"] = Reader.ReadLine() ) ; 
 
                                        } 
                                }  
                                catch( WebException ) {} 
                        }  
         
                        // ticket was invalid, or didn't exist, so request ticket 
                 
                        Page.Response.Redirect( LoginURL + "?service=" + ServiceURL, true ) ; 
                        return null ; 
                 } 
        } 
}