Sharepoint Client Authentication - sharepoint

Question

I'm developing a web application that uses Office 365 authentication.
I need to access users' SharePoint files. The app is a Multi-Tenant application, it means that I don't know the Sharepoint URL, but I can use Microsoft Discover API to discover the Sharepoint URL of the current user.
I want to acess sharepoint files using the Microsoft.Sharepoint.Client library. Consider the following code:
ClientContext context = new ClientContext("https://discoveredserver.sharepoint.com");
// The SharePoint web at the URL.
Web web = context.Web;
// We want to retrieve the web's properties.
context.Load(web);
I get a 403 not authorized because the client object doesn't have the credentials. The problem is that I can't set credentials during runtime because I don't have it, the only thing that I have is the Bearer token, which allows the connection to the Sharepoint API, using an HTTP header authorization.
Is there any way to set the Bearer token in the Sharepoint client to call Sharepoint Web Services?

Answer 1

The following example demonstrates how to explicitly specify Bearer Token in ClientContext:
public static ClientContext GetClientContext(Uri webUri)
{
var ctx = new ClientContext(webUri);
ctx.ExecutingWebRequest += delegate(object sender, WebRequestEventArgs e)
{
string realm = TokenHelper.GetRealmFromTargetUrl(webUri); //get the realm
string accessToken = TokenHelper.GetAppOnlyAccessToken(TokenHelper.SharePointPrincipal, webUri.Authority, realm).AccessToken; //get access token
e.WebRequestExecutor.WebRequest.Headers.Add("Authorization", "Bearer " + accessToken);
};
return ctx;
}
Usage
using (var ctx = GetClientContext(webUri))
{
ctx.Load(ctx.Web);
ctx.ExecuteQuery();
}

Answer 2

The ACS-based access token used by a SharePoint provider-hosted app cannot be used for other services such as the Discovery Service.
http://blogs.msdn.com/b/kaevans/archive/2015/03/20/an-architecture-for-sharepoint-apps-that-call-other-services.aspx
If you need to use the Discovery Service or other services protected by Azure AD, you will need to first authenticate the user using Azure AD.
http://blogs.msdn.com/b/kaevans/archive/2015/03/23/using-openid-connect-with-sharepoint-apps.aspx
Once authenticated, you need to request an access token specific to the resource requested. My example shows Exchange Online, but you can change this to use the SharePoint Online API easily.
http://blogs.msdn.com/b/kaevans/archive/2015/03/23/call-o365-exchange-online-api-from-a-sharepoint-app.aspx

Answer 3

use the secure setting
string pass="your password"
SecureString password = new SecureString();
foreach (var item in pass.ToCharArray())
{
password.AppendChar(item);
}
var ctx = new ClientContext("yourSiteName");
ctx.Credentials = new SharePointOnlineCredentials(username, password);