Grant the current process token the specified privilege

GrantTokenPrivileges.cs

using System;
using System.Runtime.InteropServices;

public static void SetTokenPrivilege(ref IntPtr hToken, string privName)
{
    Console.WriteLine("[*] Adding {0} to token", privName);
    LUID luid = new LUID();
    if (!LookupPrivilegeValue(null, privName, ref luid))
    {
        Console.WriteLine("[-] LookupPrivilegeValue failed!");
        return;
    }
    Console.WriteLine("[+] Received LUID");

    LUID_AND_ATTRIBUTES luidAndAttributes = new LUID_AND_ATTRIBUTES();
    luidAndAttributes.Luid = luid;
    luidAndAttributes.Attributes = SE_PRIVILEGE_ENABLED;

    TOKEN_PRIVILEGES newState = new TOKEN_PRIVILEGES();
    newState.PrivilegeCount = 1;
    newState.Privileges = luidAndAttributes;

    TOKEN_PRIVILEGES previousState = new TOKEN_PRIVILEGES();
    uint retLen = 0;
    Console.WriteLine("[*] Adjusting token");
    if (!AdjustTokenPrivileges(hToken, false, ref newState, (uint)Marshal.SizeOf(newState), ref previousState, out retLen))
    {
        Console.WriteLine("[-] AdjustTokenPrivileges failed!");
        return;
    }

    Console.WriteLine("[+] {0} added!", privName);
    return;
}

public static bool CheckTokenPrivs()
{
    return false;
}

[DllImport("kernel32.dll")]
internal static extern Boolean OpenProcessToken(
    IntPtr hProcess,
    uint dwDesiredAccess,
    out IntPtr hToken);

[DllImport("advapi32.dll", SetLastError = true)]
public static extern Boolean AdjustTokenPrivileges(
    IntPtr TokenHandle,
    bool DisableAllPrivileges,
    ref TOKEN_PRIVILEGES NewState,
    uint BufferLengthInBytes,
    ref TOKEN_PRIVILEGES PreviousState,
    out uint ReturnLengthInBytes);

[DllImport("advapi32.dll", SetLastError = true)]
public static extern Boolean LookupPrivilegeValue(
    string lpSystemName,
    string lpName,
    ref LUID luid);

[StructLayout(LayoutKind.Sequential)]
public struct LUID_AND_ATTRIBUTES
{
    public LUID Luid;
    public uint Attributes;
}

[StructLayout(LayoutKind.Sequential)]
public struct LUID
{
    public uint LowPart;
    public uint HighPart;
}
public struct TOKEN_PRIVILEGES
{
    public uint PrivilegeCount;
    public LUID_AND_ATTRIBUTES Privileges;
}

public const uint STANDARD_RIGHTS_REQUIRED = 0x000F0000;
public const uint STANDARD_RIGHTS_READ = 0x00020000;
public const uint TOKEN_ASSIGN_PRIMARY = 0x0001;
public const uint TOKEN_DUPLICATE = 0x0002;
public const uint TOKEN_IMPERSONATE = 0x0004;
public const uint TOKEN_QUERY = 0x0008;
public const uint TOKEN_QUERY_SOURCE = 0x0010;
public const uint TOKEN_ADJUST_PRIVILEGES = 0x0020;
public const uint TOKEN_ADJUST_GROUPS = 0x0040;
public const uint TOKEN_ADJUST_DEFAULT = 0x0080;
public const uint TOKEN_ADJUST_SESSIONID = 0x0100;
public const uint TOKEN_READ = (STANDARD_RIGHTS_READ | TOKEN_QUERY);
public const uint TOKEN_ALL_ACCESS = (STANDARD_RIGHTS_REQUIRED | TOKEN_ASSIGN_PRIMARY |
    TOKEN_DUPLICATE | TOKEN_IMPERSONATE | TOKEN_QUERY | TOKEN_QUERY_SOURCE |
    TOKEN_ADJUST_PRIVILEGES | TOKEN_ADJUST_GROUPS | TOKEN_ADJUST_DEFAULT |
    TOKEN_ADJUST_SESSIONID);

public const uint SE_PRIVILEGE_ENABLED = 0x2;
public const uint SE_PRIVILEGE_ENABLED_BY_DEFAULT = 0x1;
public const uint SE_PRIVILEGE_REMOVED = 0x4;
public const uint SE_PRIVILEGE_USED_FOR_ACCESS = 0x3;