WindowsSystemIdentity.cs

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using System;
using System.DirectoryServices.AccountManagement;
using System.Security.Principal;
using System.Threading;
using System.Threading.Tasks;

namespace Tgstation.Server.Host.Security
{
    sealed class WindowsSystemIdentity : ISystemIdentity
    {
        public string Uid => (userPrincipal?.Sid ?? identity.User).ToString();

        public string Username => userPrincipal?.Name ?? identity.Name;

        public bool CanCreateSymlinks => canCreateSymlinks ?? throw new NotSupportedException();

        readonly WindowsIdentity identity;

        readonly UserPrincipal userPrincipal;

        readonly bool? canCreateSymlinks;

        public WindowsSystemIdentity(WindowsIdentity identity)
        {
            this.identity = identity ?? throw new ArgumentNullException(nameof(identity));
            canCreateSymlinks = new WindowsPrincipal(identity).IsInRole(WindowsBuiltInRole.Administrator);
        }

        public WindowsSystemIdentity(UserPrincipal userPrincipal)
        {
            this.userPrincipal = userPrincipal ?? throw new ArgumentNullException(nameof(userPrincipal));
        }

        public void Dispose()
        {
            if (identity != null)
                identity.Dispose();
            else
            {
                var context = userPrincipal.Context;
                userPrincipal.Dispose();
                context.Dispose();
            }
        }

        public ISystemIdentity Clone()
        {
            if (identity != null)
            {
                // var newIdentity = (WindowsIdentity)identity.Clone(); //doesn't work because of https://github.com/dotnet/corefx/issues/31841
                var newIdentity = new WindowsIdentity(identity.Token); // the handle is cloned internally

                return new WindowsSystemIdentity(newIdentity);
            }

            // can't clone a UP, shouldn't be trying to anyway, cloning is for impersonation
            throw new InvalidOperationException("Cannot clone a UserPrincipal based WindowsSystemIdentity!");
        }

        public Task RunImpersonated(Action action, CancellationToken cancellationToken) => Task.Factory.StartNew(() =>
        {
            if (action == null)
                throw new ArgumentNullException(nameof(action));
            if (identity == null)
                throw new InvalidOperationException("Impersonate using a UserPrincipal based WindowsSystemIdentity!");
            WindowsIdentity.RunImpersonated(identity.AccessToken, action);
        }, cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Current);
    }
}