I'd like to use C# to determine which privileges are assigned to my process/thread token, and adjust them as necessary. For example, in order for my program to restart the computer, it must first enable the SeShutdownPrivilege privilege.
How can that be done safely from managed code?
This turns out to be non-trivial because there's no built-in mechanism for it. Not only is P/Invoke required, but you must code carefully to make sure that you don't "leak" privileges by enabling them and then not disabling them soon enough (though not an issue if you're restarting the computer).
For a complete code sample with description, read the MSDN magazine article from March 2005 "Manipulate Privileges in Managed Code Reliably, Securely, and Efficiently" by Mark Novak.
Here's the P/Invoke declarations:
using System;
using System.Runtime.InteropServices;
using System.Runtime.ConstrainedExecution;
namespace PrivilegeClass
{
[Flags]
internal enum TokenAccessLevels
{
AssignPrimary = 0x00000001,
Duplicate = 0x00000002,
Impersonate = 0x00000004,
Query = 0x00000008,
QuerySource = 0x00000010,
AdjustPrivileges = 0x00000020,
AdjustGroups = 0x00000040,
AdjustDefault = 0x00000080,
AdjustSessionId = 0x00000100,
Read = 0x00020000 | Query,
Write = 0x00020000 | AdjustPrivileges | AdjustGroups | AdjustDefault,
AllAccess = 0x000F0000 |
AssignPrimary |
Duplicate |
Impersonate |
Query |
QuerySource |
AdjustPrivileges |
AdjustGroups |
AdjustDefault |
AdjustSessionId,
MaximumAllowed = 0x02000000
}
internal enum SecurityImpersonationLevel
{
Anonymous = 0,
Identification = 1,
Impersonation = 2,
Delegation = 3,
}
internal enum TokenType
{
Primary = 1,
Impersonation = 2,
}
internal sealed class NativeMethods
{
internal const uint SE_PRIVILEGE_DISABLED = 0x00000000;
internal const uint SE_PRIVILEGE_ENABLED = 0x00000002;
[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode)]
internal struct LUID
{
internal uint LowPart;
internal uint HighPart;
}
[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode)]
internal struct LUID_AND_ATTRIBUTES
{
internal LUID Luid;
internal uint Attributes;
}
[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode)]
internal struct TOKEN_PRIVILEGE
{
internal uint PrivilegeCount;
internal LUID_AND_ATTRIBUTES Privilege;
}
internal const string ADVAPI32 = "advapi32.dll";
internal const string KERNEL32 = "kernel32.dll";
internal const int ERROR_SUCCESS = 0x0;
internal const int ERROR_ACCESS_DENIED = 0x5;
internal const int ERROR_NOT_ENOUGH_MEMORY = 0x8;
internal const int ERROR_NO_TOKEN = 0x3f0;
internal const int ERROR_NOT_ALL_ASSIGNED = 0x514;
internal const int ERROR_NO_SUCH_PRIVILEGE = 0x521;
internal const int ERROR_CANT_OPEN_ANONYMOUS = 0x543;
[DllImport(
KERNEL32,
SetLastError=true)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
internal static extern bool CloseHandle(IntPtr handle);
[DllImport(
ADVAPI32,
CharSet=CharSet.Unicode,
SetLastError=true)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
internal static extern bool AdjustTokenPrivileges (
[In] SafeTokenHandle TokenHandle,
[In] bool DisableAllPrivileges,
[In] ref TOKEN_PRIVILEGE NewState,
[In] uint BufferLength,
[In,Out] ref TOKEN_PRIVILEGE PreviousState,
[In,Out] ref uint ReturnLength);
[DllImport(
ADVAPI32,
CharSet=CharSet.Auto,
SetLastError=true)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
internal static extern
bool RevertToSelf();
[DllImport(
ADVAPI32,
EntryPoint="LookupPrivilegeValueW",
CharSet=CharSet.Auto,
SetLastError=true)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
internal static extern
bool LookupPrivilegeValue (
[In] string lpSystemName,
[In] string lpName,
[In,Out] ref LUID Luid);
[DllImport(
KERNEL32,
CharSet=CharSet.Auto,
SetLastError=true)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
internal static extern
IntPtr GetCurrentProcess();
[DllImport(
KERNEL32,
CharSet=CharSet.Auto,
SetLastError=true)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
internal static extern
IntPtr GetCurrentThread ();
[DllImport(
ADVAPI32,
CharSet=CharSet.Unicode,
SetLastError=true)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
internal static extern
bool OpenProcessToken (
[In] IntPtr ProcessToken,
[In] TokenAccessLevels DesiredAccess,
[In,Out] ref SafeTokenHandle TokenHandle);
[DllImport
(ADVAPI32,
CharSet=CharSet.Unicode,
SetLastError=true)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
internal static extern
bool OpenThreadToken(
[In] IntPtr ThreadToken,
[In] TokenAccessLevels DesiredAccess,
[In] bool OpenAsSelf,
[In,Out] ref SafeTokenHandle TokenHandle);
[DllImport
(ADVAPI32,
CharSet=CharSet.Unicode,
SetLastError=true)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
internal static extern
bool DuplicateTokenEx(
[In] SafeTokenHandle ExistingToken,
[In] TokenAccessLevels DesiredAccess,
[In] IntPtr TokenAttributes,
[In] SecurityImpersonationLevel ImpersonationLevel,
[In] TokenType TokenType,
[In,Out] ref SafeTokenHandle NewToken);
[DllImport
(ADVAPI32,
CharSet=CharSet.Unicode,
SetLastError=true)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
internal static extern
bool SetThreadToken(
[In] IntPtr Thread,
[In] SafeTokenHandle Token);
static NativeMethods()
{
}
}
}