SharePoint Provider Apps High Security why Windows Auth - authentication

Question

I have setup a SharePoint dev environment and managed to get a provider hosted app working with Certs etc (High Security)
This is all on-premise and we won't have a connection to ACS (now, I may have miss understood ACS, I presume its azure based and servers need to talk to server outside of the server room :) ).
My problem is:
The SharePoint site will not be using Windows Auth, we will be using a login form which will read details from another store.
If I review the code that VS generates I can see that it expects a Windows identity.
Can this be done? I would have expected my provider app not to need any auth as its hosted via SharePoint, it gets the claim from SharePoint so why does it need a Windows Identity as well as the SharePoint Claims.

Answer 1

As you said : The SharePoint site will not be using Windows Auth, we will be using a login form which will read details from another store.
Ans : You are talking about Form based authentication.
If I review the code that VS generates I can see that it expects a Windows identity.
Ans : You are correct. VS generates the code that expects windows identity [For dev environments]. You need to write separate function to get clientcontext for FBA using SharePointContextProvider class.
Context can be :CreateAppOnlyClientContextForSPHost(),CreateUserClientContextForSPHost()
I would have expected my provider app not to need any auth as its hosted via SharePoint
Ans : You can make IIS site [Hosting your provider hosted apps] to allow annonymous authentication.
You can get access token with this code.
var contextTokenString = TokenHelper.GetContextTokenFromRequest(Page.Request);
var appWeb = new Uri(clientContext.Web.Url);
if (contextTokenString != null)
{
SharePointContextToken contextToken =
TokenHelper.ReadAndValidateContextToken(contextTokenString, Request.Url.Authority);
string accessToken =
TokenHelper.GetAccessToken(contextToken, appWeb.Authority).AccessToken;
}
Get current user :-
// Get current context to get load siteurl
var spContext = SharePointContextProvider.Current.GetSharePointContext(HttpContext);
string webUrl =spContext.SPHostUrl.ToString();
//using (var clientContext = spContext.CreateUserClientContextForSPHost())
using (ClientContext clientContext = new ClientContext(webUrl))
{
clientContext.AuthenticationMode = ClientAuthenticationMode.FormsAuthentication;
clientContext.FormsAuthenticationLoginInfo = new FormsAuthenticationLoginInfo(uName, pswd);
Web web = clientContext.Web;
clientContext.Load(web);
clientContext.ExecuteQuery();
// Load SP user from login name found from httpcontext
string currentSPUser = string.Concat("<<<FBADomainPrefix>>>",User.Identity.Name);
var currentUser = clientContext.Web.EnsureUser(currentSPUser);
clientContext.Load(currentUser);
clientContext.ExecuteQuery();
}