I have a MVC Web Application makes use of Windows Authentication and Exchange Web Services. While in development, this worked great, since the application pool in IIS on my development machine is set to run under my windows user and the Exchange Server is on the same domain.
On the web server, though, all our applications are set to run under a system user that has access to all the database servers etc. The database connection uses Integrated Security, so I cannot impersonate a user over an application level.
I've been trying to impersonate the current windows user through the code as follows:
public abstract class ExchangeServiceImpersonator
{
private static WindowsImpersonationContext _ctx;
public Task<string> CreateMeetingAsync(string from, List<string> to, string subject, string body, string location, DateTime begin, DateTime end)
{
var tcs = new TaskCompletionSource<string>();
EnableImpersonation();
try
{
tcs.TrySetResult(CreateMeetingImpersonated(from, to, subject, body, location, begin, end));
}
catch(Exception e)
{
tcs.TrySetException(e);
}
finally
{
DisableImpersonation();
}
return tcs.Task;
}
public abstract string CreateMeetingImpersonated(string from, List<string> to, string subject, string body, string location, DateTime begin, DateTime end);
private static void EnableImpersonation()
{
WindowsIdentity winId = (WindowsIdentity)HttpContext.Current.User.Identity;
_ctx = winId.Impersonate();
}
private static void DisableImpersonation()
{
if (_ctx != null)
_ctx.Undo();
}
}
Then, the class that implements the abstract methods:
public class ExchangeServiceExtensionsBase : ExchangeServiceImpersonator
{
private ExchangeService _service;
public ExchangeService Service
{
get
{
if (this._service == null)
{
this._service = new ExchangeService(ExchangeVersion.Exchange2013);
this._service.Url = new Uri(WebConfigurationManager.AppSettings["ExchangeServer"]);
this._service.UseDefaultCredentials = true;
}
return this._service;
}
set { return; }
}
public override string CreateMeetingImpersonated(string from, List<string> to, string subject, string body, string location, DateTime begin, DateTime end)
{
//this.Service.ImpersonatedUserId = new ImpersonatedUserId(ConnectingIdType.SmtpAddress, from);
Appointment meeting = new Appointment(Service);
string meetingID = Guid.NewGuid().ToString();
meeting.Subject = subject;
meeting.Body = "<span style=\"font-family:'Century Gothic'\" >" + body.Replace(Environment.NewLine, "<br/>") + "<br/><br/>" +
"<span style=\"color: white;\">Meeting Identifier: " + meetingID + "</span></span><br/><br/>";
meeting.Body.BodyType = BodyType.HTML;
meeting.Start = begin;
meeting.End = end;
meeting.Location = location;
meeting.ReminderMinutesBeforeStart = 60;
foreach (string attendee in to)
{
meeting.RequiredAttendees.Add(attendee);
}
meeting.Save(SendInvitationsMode.SendToAllAndSaveCopy);
return meetingID;
}
}
Then, the methods are accessed as follows:
public static class ExchangeServiceExtensions
{
public static async Task<string> CreateMeetingAsync(string from, List<string> to, string subject, string body, string location, DateTime begin, DateTime end)
{
ExchangeServiceImpersonator serviceImpersonator = new ExchangeServiceExtensionsBase();
return await serviceImpersonator.CreateMeetingAsync(from, to, subject, body, location, begin, end);
}
}
This still works on my local dev machine, but no matter what I do, the user accessing from the server keeps getting an access denied from the exchange server:
The request failed. The remote server returned an error: (401) Unauthorized.
I've tried leaving it on default credentials:
this._service.UseDefaultCredentials = true;
And attempting to manually set the credentials to the current (supposedly impersonated) user:
this._service.Credentials = new WebCredentials(CredentialCache.DefaultNetworkCredentials);
Also, I've tried using the Exchange ImpersonatedUserId
object using the email address:
this._service.ImpersonatedUserId = new ImpersonatedUserId(ConnectingIdType.SmtpAddress, from);
which returns the following exception:
The account does not have permission to impersonate the requested user.