Windows Python / DLL Proxying

Code

from ctypes import cdll

# Function prototype for the function that will be used to redirect calls to the legitimate DLL
ProxyFunction = ctypes.CFUNCTYPE(ctypes.c_int, ctypes.c_int)

def DllMain():
    # Load the legitimate DLL
    hLegitDLL = ctypes.windll.LoadLibrary("legit.dll")
    if not hLegitDLL:
        # Handle error

    # Retrieve the address of the function in the legitimate DLL
    # This example uses a function named "FunctionA", but the function name can be anything
    FunctionA = ProxyFunction(hLegitDLL.FunctionA)
    if not FunctionA:
        # Handle error

# Function that will be used to redirect calls to the legitimate DLL
def ProxyFunction(arg):
    # Call the function
    return FunctionA(arg)