Windows Kernel: Retrieving function addresses inside modules

Retrieving function addresses inside modules in the Windows Kernel is similar to doing it in user-mode applications, but with some differences due to the Kernel's protected and privileged nature. Here's a general outline of how you can do this:

1. Obtain Module Base Address: To access functions inside a module (e.g., a driver), you first need to obtain the base address of the loaded module. You can do this using various Windows Kernel functions like MmGetSystemRoutineAddress, PsLookupProcessByProcessId, PsGetProcessSectionBaseAddress, or LdrGetDllHandle.

2. Calculate Function Address: Once you have the base address of the module, you can calculate the address of a specific function inside the module by adding the function's offset to the module's base address.

3. Access Function Address Safely: Since you are in Kernel mode, direct memory access is allowed, but it's essential to be cautious when accessing user-mode addresses to avoid kernel-mode crashes or security vulnerabilities.

Here's a basic example of how you can retrieve a function address from a loaded module in the Windows Kernel:

cCopy code
#include <ntddk.h>



// Function pointer type for the function you want to retrieve

typedef NTSTATUS (*MyFunctionPointer)(PVOID arg1, PVOID arg2);



NTSTATUS DriverEntry(_In_ PDRIVER_OBJECT DriverObject, _In_ PUNICODE_STRING RegistryPath) {

    UNREFERENCED_PARAMETER(RegistryPath);



    // Load the target module (e.g., "ntoskrnl.exe")

    UNICODE_STRING moduleName;

    RtlInitUnicodeString(&moduleName, L"ntoskrnl.exe");

    PVOID moduleBase = NULL;

    NTSTATUS status = STATUS_SUCCESS;



    status = ZwLoadDriver(&moduleName);



    // Get the base address of the loaded module

    status = ZwQuerySystemInformation(SystemModuleInformation, &moduleBase, sizeof(moduleBase), NULL);



    // Calculate the function address based on its offset in the module

    ULONG functionOffset = 0x123456; // Replace with the actual offset

    MyFunctionPointer myFunction = (MyFunctionPointer)((ULONG_PTR)moduleBase + functionOffset);



    // Now you can call the function

    NTSTATUS result = myFunction(NULL, NULL);

    return result;

}

Keep in mind that accessing kernel-mode structures, functions, or modules can be risky if not done correctly. Incorrect usage can lead to system instability, crashes, or security vulnerabilities. Always exercise caution and thoroughly test your code. Additionally, using undocumented functions or structures is not recommended, as they may change between Windows versions. Always refer to official Windows Kernel documentation and supported APIs.