Chilli with WPA Captive Portal

This page describes how Coova's version of ChilliSpot can be used as a proxy for WPA authentication with the following twist:

user's presenting valid credentials get on-line without restriction while
user's presenting in-valid credentials will still gain WPA access, but be subject to a captive portal and walled garden.

There are many ways to implement what is described here. For this example, however, we are using CoovaAP combined with FreeRADIUS and JRadius. You will also find this feature in the CoovaAAA services.

CoovaChilli

To 'enable' this feature within chilli itself, an option was defined. By setting the configuration flag wpaguests (in combination with the chillispot's proxylisten, proxyport, and proxysecret settings) chilli will do a couple things:

sends a ChilliSpot-Config = allow-wpa-guests in proxy RADIUS Access-Request and
looks for ChilliSpot-Config = require-uam-auth in the Access-Accept reply such that
- if not found, the access-accept is passed on normally giving the user full access;
- if found, the access-accept is passed on, but the session is not marked as authenticated and is subject to ChilliSpot's walled garden.

If the reply is an Access-Reject, then, of course, that is sent on by proxy and WPA is not granted.

FreeRADIUS

Actual authentication of the WPA RADIUS is handled by FreeRADIUS. It must be configured for EAP, TLS, and PEAP. Additionally, this example uses the JRadius module to easily code our "GuestWPA" RADIUS logic.

For basics on FreeRADIUS and EAP authentication, see:

JRadius

For information on installing and using JRadius with FreeRADIUS, see:

For this example, the following JRadius handler is defined (abbreviated for readability):

public class WPACaptivePortal extends PacketHandlerBase 
{
   public boolean handle(JRadiusRequest request)
   {
       try
       {
           /*
            * Gather some information about the JRadius request
            */
           AttributeList ci = request.getConfigItems();
           RadiusPacket req = request.getRequestPacket();
           RadiusPacket rep = request.getReplyPacket();

           /*
            * Find the username in the request packet
            */
           String username = (String)req.getAttributeValue(Attr_UserName.TYPE);

           if (rep instanceof AccessAccept)
           {
               RadiusLog.info("Allowing WPA access for username: " + username);
           }
           else
           {   // Is an Access-Reject
               if ("allow-wpa-guests".
                               equals((String)req.getAttributeValue(Attr_ChilliSpotConfig.TYPE))) 
               {   // Allowing WPA "guest" access
                   if (req.findAttribute(Attr_EAPMessage.TYPE) != null)
                   {   // Is EAP (802.1x)
                       if (req.findAttribute(Attr_FreeRADIUSProxiedTo.TYPE) != null)
                       {   // Is the inner request, TLS termianted
                           rep = new AccessAccept();
                           rep.addAttribute(new Attr_ChilliSpotConfig("require-uam-auth"));
                           request.setReplyPacket(rep);

                           ci.add(new Attr_AuthType("Accept"));
                           request.setReturnValue(JRadiusServer.RLM_MODULE_UPDATED);

                           RadiusLog.error("Allowing Guest WPA access for username: " + username);
                           return true;
                       }
                   }
               }
               RadiusLog.info("Authentication failed for username: " + username);
           }
       }
       catch (RadiusException e) { e.printStackTrace(); }
        
       request.setReturnValue(JRadiusServer.RLM_MODULE_UPDATED);
       return false;
   }
}

This handler is to be ran in the post-auth section of FreeRADIUS, as defined in this JRadius config.xml snippit:

 <chain name="post_auth">
   <init-session          name="post_auth-init-session"
                          description="Initialize The Radius Session"/>

   <command               className="org.coova.jradius.example.WPACaptivePortal" />

   <class-post-auth       name="post_auth-class"
                          description="Post-Auth Class Attribute Handler"/>
 </chain>

And requires that FreeRADIUS is configured such that Access-Rejects are processed in the post-auth section too (by default, they are not):

 # in radiusd.conf
 post-auth {
       jradius
       Post-Auth-Type REJECT {
               jradius
       }
 }

CoovaAP Example

Putting it all together, with a (FreeRADIUS/JRadius) RADIUS server up and running, the setup is tested using a Linksys running the CoovaAP firmware (version beta.4 or better).

On the HotSpot / RADIUS configuration page in the firmware, you can select to allow/enable "WPA Guests".

It is important that chilli is started after everything else because it will actually rewrite some configurations (so that the nas program uses chillispot for RADIUS) and restarts other programs.

Some tests:

Some simple tests using Mac OS X as the client (PEAP).

Example User Login

Just using a FreeRADIUS raddb/users entry to define the user:

david   User-Password == "testing"
        WISPr-Redirection-URL = "http://coova.org/"

The user experience, at least on Mac OS X, is summarized by:

Found the SSID and was asked for a username, password, and 802.1x authentication type.
I entered my valid credentials leaving the auth type on "Automatic".
I had to acknowledge the SSL (TLS) certificate because it is self signed ;)
I was logged in and able to browse the Internet

FreeRADIUS/JRadius log (highlights only):

Access-Request packet from host 192.168.100.200:2084, id=2, length=170
       User-Name = "david"
       EAP-Message = 0x020200061900
       ChilliSpot-Config = "allow-wpa-guests"
       Calling-Station-Id = "00-11-24-90-XX-XX"
       Called-Station-Id = "00-06-25-C5-XX-XX"
       NAS-Port-Type = Wireless-802.11
       NAS-Port = 1
       NAS-IP-Address = 192.168.100.200
       NAS-Identifier = "00:06:25:c6:xx:xx"

       [.. EAP Access Challenge/Request and TLS Termination ..]
 
Sending Access-Accept of id 8 to 192.168.100.200 port 2084
       User-Name = "david"
       MS-MPPE-Recv-Key = 0x239ae8a15596cc224f6990e0713e3524dcac4cc22de68226d2de01fee7b4e77f
       MS-MPPE-Send-Key = 0x938b61d3487a87a6e1a2442767cd6c10036384f6b368d23e553ab53caf13e742
       EAP-Message = 0x03080004

Example Guest Login

This time, I did the following:

Found the SSID and connected to it
When asked for username and password, I just put in anything
I still had to acknowledge the SSL (TLS) certificate because it is self signed
Got onto the WPA network, but got the captive portal page when trying to browse the Internet