c# - Can't list some folders

Question

I'm getting an "Access denied" exception when trying to list some folders on my PC, such as 'c:Documents and Settings'. My application is running from an administrator account and with elevated privileges (<requestedExecutionLevel level="requireAdministrator" uiAccess="false" />)

What else I need to do to access such folders?

Answer 1

Running as administrator is necessary, but not enough, you also need to enable the Backup privilege, as implicitely documented here: Junction Points

%SystemDrive%Documents and Settings directory is now stored in the %SystemDrive%Users directory [...] Backup applications must be capable of backing up and restoring junction points.

So here is an example that works:

using (Privilege p = new Privilege(Privilege.Backup))
{
    foreach (string path in Directory.GetFileSystemEntries(@"c:documents and settings"))
    {
        Console.WriteLine(path);
    }
}

Note there is no public .NET class to enable privilege programmatically to my knowledge, but there is one internal in System.Security.AccessControl (mscorlib) that I have exposed using a thin wrapper. It's based on the fully public Windows AdjustTokenPrivileges function.

/// <summary>
/// Defines a Windows privilege.
/// </summary>
public sealed class Privilege : IDisposable
{
    private static Type _privilegeType;
    private object _privilege;

    static Privilege()
    {
        _privilegeType = typeof(string).Assembly.GetType("System.Security.AccessControl.Privilege", false); // mscorlib
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="Privilege"/> class and enable the privilege.
    /// </summary>
    /// <param name="name">The privilege name.</param>
    public Privilege(string name)
        : this(name, true)
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="Privilege" /> class.
    /// </summary>
    /// <param name="name">The privilege name.</param>
    /// <param name="enable">if set to <c>true</c> the privilege is enabled.</param>
    public Privilege(string name, bool enable)
    {
        if (name == null)
            throw new ArgumentNullException("name");

        if (_privilegeType == null)
            throw new NotSupportedException();

        _privilege = _privilegeType.GetConstructors()[0].Invoke(new object[] { name });
        if (enable)
        {
            Enable();
        }
    }

    /// <summary>
    /// Disable this privilege from the current thread. 
    /// </summary>
    public void Revert()
    {
        _privilegeType.InvokeMember("Revert", BindingFlags.Public | BindingFlags.Instance | BindingFlags.InvokeMethod, null, _privilege, null);
    }

    /// <summary>
    /// Gets a value indicating whether Revert must be called.
    /// </summary>
    /// <value>
    ///   <c>true</c> if Revert must be called; otherwise, <c>false</c>.
    /// </value>
    public bool NeedToRevert
    {
        get
        {
            return (bool)_privilegeType.InvokeMember("NeedToRevert", BindingFlags.Public | BindingFlags.Instance | BindingFlags.GetProperty, null, _privilege, null);
        }
    }

    /// <summary>
    /// Enables this privilege to the current thread. 
    /// </summary>
    public void Enable()
    {
        _privilegeType.InvokeMember("Enable", BindingFlags.Public | BindingFlags.Instance | BindingFlags.InvokeMethod, null, _privilege, null);
    }

    /// <summary>
    /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
    /// </summary>
    public void Dispose()
    {
        if (NeedToRevert)
        {
            Revert();
        }
    }

    /// <summary>
    /// The SE_ASSIGNPRIMARYTOKEN_NAME privilege.
    /// </summary>
    public const string AssignPrimaryToken = "SeAssignPrimaryTokenPrivilege";

    /// <summary>
    /// The SE_AUDIT_NAME privilege.
    /// </summary>
    public const string Audit = "SeAuditPrivilege";

    /// <summary>
    /// The SE_BACKUP_NAME privilege.
    /// </summary>
    public const string Backup = "SeBackupPrivilege";

    /// <summary>
    /// The SE_CHANGE_NOTIFY_NAME privilege.
    /// </summary>
    public const string ChangeNotify = "SeChangeNotifyPrivilege";

    /// <summary>
    /// The SE_CREATE_GLOBAL_NAME privilege.
    /// </summary>
    public const string CreateGlobal = "SeCreateGlobalPrivilege";

    /// <summary>
    /// The SE_CREATE_PAGEFILE_NAME privilege.
    /// </summary>
    public const string CreatePageFile = "SeCreatePagefilePrivilege";

    /// <summary>
    /// The SE_CREATE_PERMANENT_NAME privilege.
    /// </summary>
    public const string CreatePermanent = "SeCreatePermanentPrivilege";

    /// <summary>
    /// The SE_CREATE_SYMBOLIC_LINK_NAME privilege.
    /// </summary>
    public const string CreateSymbolicLink = "SeCreateSymbolicLinkPrivilege";

    /// <summary>
    /// The SE_CREATE_TOKEN_NAME privilege.
    /// </summary>
    public const string CreateToken = "SeCreateTokenPrivilege";

    /// <summary>
    /// The SE_DEBUG_NAME privilege.
    /// </summary>
    public const string Debug = "SeDebugPrivilege";

    /// <summary>
    /// The SE_ENABLE_DELEGATION_NAME privilege.
    /// </summary>
    public const string EnableDelegation = "SeEnableDelegationPrivilege";

    /// <summary>
    /// The SE_IMPERSONATE_NAME privilege.
    /// </summary>
    public const string Impersonate = "SeImpersonatePrivilege";

    /// <summary>
    /// The SE_INC_BASE_PRIORITY_NAME privilege.
    /// </summary>
    public const string IncreaseBasePriority = "SeIncreaseBasePriorityPrivilege";

    /// <summary>
    /// The SE_INCREASE_QUOTA_NAME privilege.
    /// </summary>
    public const string IncreaseQuota = "SeIncreaseQuotaPrivilege";

    /// <summary>
    /// The SE_INC_WORKING_SET_NAME privilege.
    /// </summary>
    public const string IncreaseWorkingSet = "SeIncreaseWorkingSetPrivilege";

    /// <summary>
    /// The SE_LOAD_DRIVER_NAME privilege.
    /// </summary>
    public const string LoadDriver = "SeLoadDriverPrivilege";

    /// <summary>
    /// The SE_LOCK_MEMORY_NAME privilege.
    /// </summary>
    public const string LockMemory = "SeLockMemoryPrivilege";

    /// <summary>
    /// The SE_MACHINE_ACCOUNT_NAME privilege.
    /// </summary>
    public const string MachineAccount = "SeMachineAccountPrivilege";

    /// <summary>
    /// The SE_MANAGE_VOLUME_NAME privilege.
    /// </summary>
    public const string ManageVolume = "SeManageVolumePrivilege";

    /// <summary>
    /// The SE_PROF_SINGLE_PROCESS_NAME privilege.
    /// </summary>
    public const string ProfileSingleProcess = "SeProfileSingleProcessPrivilege";

    /// <summary>
    /// The SE_RELABEL_NAME privilege.
    /// </summary>
    public const string Relabel = "SeRelabelPrivilege";

    /// <summary>
    /// The SE_REMOTE_SHUTDOWN_NAME privilege.
    /// </summary>
    public const string RemoteShutdown = "SeRemoteShutdownPrivilege";

    ///// <summary>
    ///// The SE_RESERVE_PROCESSOR_NAME privilege.
    ///// </summary>
    //public const string ReserveProcessor = "SeReserveProcessorPrivilege";

    /// <summary>
    /// The SE_RESTORE_NAME privilege.
    /// </summary>
    public const string Restore = "SeRestorePrivilege";

    /// <summary>
    /// The SE_SECURITY_NAME privilege.
    /// </summary>
    public const string Security = "SeSecurityPrivilege";

    /// <summary>
    /// The SE_SHUTDOWN_NAME privilege.
    /// </summary>
    public const string Shutdown = "SeShutdownPrivilege";

    /// <summary>
    /// The SE_SYNC_AGENT_NAME privilege.
    /// </summary>
    public const string SyncAgent = "SeSyncAgentPrivilege";

    /// <summary>
    /// The SE_SYSTEM_ENVIRONMENT_NAME privilege.
    /// </summary>
    public const string SystemEnvironment = "SeSystemEnvironmentPrivilege";

    /// <summary>
    /// The SE_SYSTEM_PROFILE_NAME privilege.
    /// </summary>
    public const string SystemProfile = "SeSystemProfilePrivilege";

    /// <summary>
    /// The SE_SYSTEMTIME_NAME privilege.
    /// </summary>
    public const string SystemTime = "SeSystemtimePrivilege";

    /// <summary>
    /// The SE_TAKE_OWNERSHIP_NAME privilege.
    /// </summary>
    public const string TakeOwnership = "SeTakeOwnershipPrivilege";

    /// <summary>
    /// The SE_TCB_NAME privilege.
    /// </summary>
    public const string TrustedComputingBase = "SeTcbPrivilege";

    /// <summary>
    /// The SE_TIME_ZONE_NAME privilege.
    /// </summary>
    public const string TimeZone = "SeTimeZonePrivilege";

    /// <summary>
    /// The SE_TRUSTED_CREDMAN_ACCESS_NAME privilege.
    /// </summary>
    public const string TrustedCredentialManagerAccess = "SeTrustedCredManAccessPrivilege";

    /// <summary>
    /// The SE_UNDOCK_NAME privilege.
    /// </summary>
    public const string Undock = "SeUndockPrivilege";

    /// <summary>
    /// The SE_UNSOLICITED_INPUT_NAME privilege.
    /// </summary>
    public const string UnsolicitedInput = "SeUnsolicitedInputPrivilege";
}