Passing multiple parameters using CreateRemoteThread in C#

Question

My goal is to call a function in a remote process using P/Invoke in C# (CreateRemoteThread). The problem is that the function takes more than one parameter. Is there a way to pass multiple parameters to the function?

Answer 1

[DllImport("kernel32.dll", SetLastError = true, ExactSpelling = true)]
static extern IntPtr OpenProcess(int dwDesiredAccess, bool bInheritHandle, int dwProcessId);

[DllImport("kernel32.dll", SetLastError = true, ExactSpelling = true)]
static extern IntPtr VirtualAllocEx(IntPtr hProcess, IntPtr lpAddress,
uint dwSize, AllocationType flAllocationType, MemoryProtection flProtect);

[DllImport("kernel32.dll", SetLastError = true)]
static extern bool WriteProcessMemory(IntPtr hProcess, IntPtr lpBaseAddress, IntPtr lpBuffer, uint nSize, out UIntPtr lpNumberOfBytesWritten);

[Flags]
public enum AllocationType
{
    Commit = 0x1000,
    Reserve = 0x2000,
    Decommit = 0x4000,
    Release = 0x8000,
    Reset = 0x80000,
    Physical = 0x400000,
    TopDown = 0x100000,
    WriteWatch = 0x200000,
    LargePages = 0x20000000
}

[Flags]
public enum MemoryProtection
{
    Execute = 0x10,
    ExecuteRead = 0x20,
    ExecuteReadWrite = 0x40,
    ExecuteWriteCopy = 0x80,
    NoAccess = 0x01,
    ReadOnly = 0x02,
    ReadWrite = 0x04,
    WriteCopy = 0x08,
    GuardModifierflag = 0x100,
    NoCacheModifierflag = 0x200,
    WriteCombineModifierflag = 0x400
}

[StructLayout(LayoutKind.Sequential, Pack=1]
public struct RemoteThreadParams
{
    [MarshalAs(UnmanagedType.U1)]
    public byte Param1;

    [MarshalAs(UnmanagedType.I4)]
    public int Param2;

    ...
}

[DllImport("kernel32")]
public static extern IntPtr CreateRemoteThread(        
  IntPtr hProcess,
  IntPtr lpThreadAttributes,
  uint dwStackSize,
  IntPtr lpStartAddress,
  IntPtr lpParameter,
  uint dwCreationFlags,
  out uint lpThreadId
);

RemoteThreadParams params = new RemoteThreadParams();
parms.Param1 = 10;
parms.Param2 = 200;

// Allocate some native heap memory in your process big enough to store the
// parameter data
IntPtr iptrtoparams = Marshal.AllocHGlobal(Marshal.SizeOf(RemoteThreadParams));

// Copies the data in your structure into the native heap memory just allocated
Marshal.StructureToPtr(params, iptrtoparams, false);

// Use to get a handle to the process you intend to create a thread in.
OpenProcess(...,...,...);

// Use to alloc "committed" memory that is addressable by other process
IntPtr iptrremoteallocatedmemory = VirtualAllocEx()...

// Copy from your process memory to the memory the remoteprocess will be accessing
WriteProcessMemory(...,iptrremoteallocatedmemory,iptrtoparams,...,...);

Marshal.FreeHGlobal(iptrtoparams); // safe to free, as you have done the copy

CreateRemoteThread(...,...,...,...,iptrremoteallocatedmemory,...,...);

// Free the memory that was allocated for the other process...but be
// careful of its lifetime.
//
// Only free when the thread will no longer be accessing the allocated native
// memory i.e. when it's finished.

VirtualFreeEx(...,...,...,...);

In your C/C++ code have:

#pragma pack(push,1)
struct tagRemoteThreadParams
{
    BYTE Param1;
    int Param2;
} RemoteThreadParams, *PRemoteThreadParams;
#pragma pack(pop)

Cast the LPVOID received by the thread function to PRemoteThreadParams (i.e. *RemoteThreadParams).

If you have some "strings" that you want as one of your parameters, then you would have to do some more work to marshal them across. For more help see:

• http://www.developerfusion.com/article/84519/mastering-structs-in-c/

Some other references:

• Dll injection. Execute CreateRemoteThread with parameter
• http://social.msdn.microsoft.com/Forums/vstudio/en-US/e044a6ff-c463-4b9b-8c82-f791c35dbaa1/virtualallocexwriteprocessmemory-and-writing-c-char-arrays?forum=csharpgeneral