/// <summary>
/// Impersonates the specified user.
/// </summary>
/// <param name="domainUser">The domain user.</param>
/// <param name="processFilter">Predicate to find the process suitable for impersonation. If it's <see langword="null"/>, the first <paramref name="domainUser"/>'s process will be used.</param>
/// <returns>
/// Impersonated context.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="domainUser"/> is <see langword="null"/> or empty.</exception>
/// <exception cref="ArgumentException"><paramref name="domainUser"/> is not in the <c>DOMAIN\username</c> format.</exception>
/// <exception cref="InvalidOperationException">
/// No processes are running for the <paramref name="domainUser"/>.
/// <para>-or-</para>
/// Process handle cannot be duplicated.
/// </exception>
/// <remarks>
/// This method looks for the existing <paramref name="domainUser"/> process running in the system, obtains and duplicates
/// its token, and uses it to impersonate the caller. So it won't work, if the user is logged out or has no processes running.
/// </remarks>
public static WindowsImpersonationContext Impersonate(string domainUser, Predicate <Process> processFilter)
{
if (string.IsNullOrEmpty(domainUser))
{
throw new ArgumentNullException(nameof(domainUser));
}
// Process returned by the ProcessHelper.FindUserProcesses may already be closed, so we want to retry.
return(RetryHelper.Retry(
() =>
{
using (Process process = ProcessHelper.FindUserProcesses(domainUser).FirstOrDefault(p => processFilter == null || processFilter(p)))
{
if (process == null)
{
throw new InvalidOperationException("No suitable user processes found.");
}
return WindowsIdentity.Impersonate(Impersonator.DuplicateProcessHandle(process));
}
},
Impersonator.DefaultRetryCount,
Impersonator.DefaultRetryDelay,
new[] { typeof(InvalidOperationException) }));
}
/// <summary>
/// Impersonates the currently logged on user in the current thread context.
/// </summary>
/// <returns>Impersonation context.</returns>
public static WindowsImpersonationContext ImpersonateCurrentUser()
{
try
{
return(Impersonator.Impersonate(UserHelper.LoggedOnUser));
}
catch
{
// Exception might occur, if we have outdated username information.
// Maybe, that user has logged out. So, try to find a new username.
string previousUserName = UserHelper.LoggedOnUser;
string newUserName = UserHelper.GetCurrentUser();
// If username is the same, don't retry.
if (string.Equals(previousUserName, newUserName, StringComparison.OrdinalIgnoreCase))
{
throw;
}
UserHelper.LoggedOnUser = newUserName;
}
return(Impersonator.Impersonate(UserHelper.LoggedOnUser));
}
/// <summary>
/// Impersonates the specified user within the <c>Explorer</c> process context.<br/>
/// <c>Explorer</c> process is vital for the system and should always be there, if the user is logged in.
/// </summary>
/// <param name="domainUser">The domain user.</param>
/// <returns>
/// Impersonated context.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="domainUser"/> is <see langword="null"/> or empty.</exception>
/// <exception cref="ArgumentException"><paramref name="domainUser"/> is not in the <c>DOMAIN\username</c> format.</exception>
/// <exception cref="InvalidOperationException">
/// No processes are running for the <paramref name="domainUser"/>.
/// <para>-or-</para>
/// Process handle cannot be duplicated.
/// </exception>
/// <seealso cref="Impersonate(string,Predicate{Process})"/>
public static WindowsImpersonationContext Impersonate(string domainUser)
{
return(Impersonator.Impersonate(domainUser, p => p.ProcessName.Equals("explorer", StringComparison.OrdinalIgnoreCase)));
}