Serving an iCalendar file in ASPNET MVC with authentication - asp.net-mvc

Question

I'm trying to serve an iCalendar file (.ics) in my MVC application.
So far it's working fine. I have an iPhone subscribing to the URL for the calendar but now I need to serve a personalised calendar to each user.
When subscribing to the calendar on the iPhone I can enter a username and password, but I don't know how to access these in my MVC app.
Where can I find details of how the authentication works, and how to implement it?

Answer 1

It turns out that Basic Authentication is what is required. I half had it working but my IIS configuration got in the way. So, simply returning a 401 response when there is no Authorization header causes the client (e.g. iPhone) to require a username/password to subscribe to the calendar.
On the authorization of the request where there is an Authorization request header, the basic authentication can be processed, retrieving the username and password from the base 64 encoded string.
Here's some useful code for MVC:
public class BasicAuthorizeAttribute : AuthorizeAttribute
{
public override void OnAuthorization(AuthorizationContext filterContext)
{
if (filterContext == null)
{
throw new ArgumentNullException("filterContext");
}
var auth = filterContext.HttpContext.Request.Headers["Authorization"];
if (!String.IsNullOrEmpty(auth))
{
var encodedDataAsBytes = Convert.FromBase64String(auth.Replace("Basic ", ""));
var value = Encoding.ASCII.GetString(encodedDataAsBytes);
var username = value.Substring(0, value.IndexOf(':'));
var password = value.Substring(value.IndexOf(':') + 1);
if (MembershipService.ValidateUser(username, password))
{
filterContext.HttpContext.User = new GenericPrincipal(new GenericIdentity(username), null);
}
else
{
filterContext.Result = new HttpStatusCodeResult(401);
}
}
else
{
if (AuthorizeCore(filterContext.HttpContext))
{
var cachePolicy = filterContext.HttpContext.Response.Cache;
cachePolicy.SetProxyMaxAge(new TimeSpan(0));
cachePolicy.AddValidationCallback(CacheValidateHandler, null);
}
else
{
filterContext.HttpContext.Response.Clear();
filterContext.HttpContext.Response.StatusDescription = "Unauthorized";
filterContext.HttpContext.Response.AddHeader("WWW-Authenticate", "Basic realm=\"Secure Calendar\"");
filterContext.HttpContext.Response.Write("401, please authenticate");
filterContext.HttpContext.Response.StatusCode = 401;
filterContext.Result = new EmptyResult();
filterContext.HttpContext.Response.End();
}
}
}
private void CacheValidateHandler(HttpContext context, object data, ref HttpValidationStatus validationStatus)
{
validationStatus = OnCacheAuthorization(new HttpContextWrapper(context));
}
}
Then, my controller action looks like this:
[BasicAuthorize]
public ActionResult Calendar()
{
var userName = HttpContext.User.Identity.Name;
var appointments = GetAppointments(userName);
return new CalendarResult(appointments, "Appointments.ics");
}

Answer 2

I found this really helpful, but i hit a few problems during the development and i thought i would share some of them to help save other people some time.
I was looking to get data from my web application into the calendar for an android device and i was using discountasp as a hosting service.
The first problem i hit was that the validation did not work when uploaded to the server, stangely enough it was accepting my control panel login for discountasp but not my forms login.
The answer to this was to turn off Basic Authentication in IIS manager. This resolved the issue.
Secondly, the app i used to sync the calendar to the android device was called iCalSync2 - its a nice app and works well. But i found that it only worked properly when the file was delivered as a .ics (duh for some reason i put it as a .ical.. it must have been late) and i also had to choose the webcal option
Lastly i found i had to add webcal:// to the start of my url instead of http://
Also be careful as the code posted above ignores the roles input variable and always passes nothing so you might need to do some role based checks inside your calendar routine or modify the code above to process the roles variable.