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Getting the address of a function in a DLL loaded in another process

, 27 Dec 2010
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Ideal for finding LoadLibrary() in 32 bit programs from a 64 bit program but it works for any function in any DLL and supports forwarded functions and ordinals.
What started as an attempt at making a program that inject DLLs into both 64 bit and 32 bit programs led me on a wild goose chase that resulted in me writing my own remote version of GetModuleHandle() and GetProcAddress(). They work the same way (as far as I can tell). But they take the target process' ID as the first parameter and GetRemoteProcAddress() can take two more parameters: an ordinal and the BOOL flag that determines if it uses the ordinal or the name.
 
Both functions work if your program is 64 bit and the target program is 64 or 32 bit, or if your program is 32 bit and the target program is also 32 bit. Anyway, enough of that! It's time to share my code and hopefully help someone else avoid the extensive search I had to go through to find any useful information on this topic. If anyone has suggestions or notices a problem let me know.
 
StdAfx.h:
// stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently, but
// are changed infrequently
//

#pragma once
 
#include "targetver.h"

#define WIN32_LEAN_AND_MEAN             // Exclude rarely-used stuff from Windows headers
// Windows Header Files:
#include <windows.h>
#include <commctrl.h>

// C RunTime Header Files
#include <stdlib.h>
#include <malloc.h>
#include <memory.h>
#include <tchar.h>

 
// TODO: reference additional headers your program requires here
 
RemoteOps.h:
/* RemoteOps.h */
 
#ifndef REM_OPS_H
#define REM_OPS_H
 
HMODULE WINAPI GetRemoteModuleHandle(HANDLE hProcess, LPCSTR lpModuleName);
FARPROC WINAPI GetRemoteProcAddress (HANDLE hProcess, HMODULE hModule, LPCSTR lpProcName, UINT Ordinal = 0, BOOL UseOrdinal = FALSE);
 
#endif //REM_OPS_H
 
RemoteOps.cpp:
/* RempteOps.cpp */
 
#include "stdafx.h" // SDKDDKVer.h, windows.h, stdlib.h, malloc.h, memory.h, tchar.h
#include "RemoteOps.h" // Function prototypes
#include <string>
#include <windows.h>
#include <psapi.h>

using std::string;
 

//-----------------------------------------------------------------------------

HMODULE WINAPI GetRemoteModuleHandle(HANDLE hProcess, LPCSTR lpModuleName)
{
	HMODULE* ModuleArray = NULL;
	DWORD ModuleArraySize = 100;
	DWORD NumModules = 0;
	CHAR lpModuleNameCopy[MAX_PATH] = {0};
	CHAR ModuleNameBuffer[MAX_PATH] = {0};
 
	/* Make sure we didn't get a NULL pointer for the module name */
	if(lpModuleName == NULL)
		goto GRMH_FAIL_JMP;
 
	/* Convert lpModuleName to all lowercase so the comparison isn't case sensitive */
	for (size_t i = 0; lpModuleName[i] != '\0'; ++i)
	{
		if (lpModuleName[i] >= 'A' && lpModuleName[i] <= 'Z')
			lpModuleNameCopy[i] = lpModuleName[i] + 0x20; // 0x20 is the difference between uppercase and lowercase
		else
			lpModuleNameCopy[i] = lpModuleName[i];
 
		lpModuleNameCopy[i+1] = '\0';
	}
	
	/* Allocate memory to hold the module handles */
	ModuleArray = new HMODULE[ModuleArraySize];
 
	/* Check if the allocation failed */
	if(ModuleArray == NULL)
		goto GRMH_FAIL_JMP;
 
	/* Get handles to all the modules in the target process */
	if(!::EnumProcessModulesEx(hProcess, ModuleArray,
		ModuleArraySize * sizeof(HMODULE), &NumModules, LIST_MODULES_ALL))
		goto GRMH_FAIL_JMP;
 
	/* We want the number of modules not the number of bytes */
	NumModules /= sizeof(HMODULE);
 
	/* Did we allocate enough memory for all the module handles? */
	if(NumModules > ModuleArraySize)
	{
		delete[] ModuleArray; // Deallocate so we can try again
		ModuleArray = NULL; // Set it to NULL se we can be sure if the next try fails
		ModuleArray = new HMODULE[NumModules]; // Allocate the right amount of memory

		/* Check if the allocation failed */
		if(ModuleArray == NULL)
			goto GRMH_FAIL_JMP;
 
		ModuleArraySize = NumModules; // Update the size of the array
		
		/* Get handles to all the modules in the target process */
		if( !::EnumProcessModulesEx(hProcess, ModuleArray,
			ModuleArraySize * sizeof(HMODULE), &NumModules, LIST_MODULES_ALL) )
			goto GRMH_FAIL_JMP;
 
		/* We want the number of modules not the number of bytes */
		NumModules /= sizeof(HMODULE);
	}
 
	/* Iterate through all the modules and see if the names match the one we are looking for */
	for(DWORD i = 0; i <= NumModules; ++i)
	{
		/* Get the module's name */
		::GetModuleBaseName(hProcess, ModuleArray[i],
			ModuleNameBuffer, sizeof(ModuleNameBuffer));
 
		/* Convert ModuleNameBuffer to all lowercase so the comparison isn't case sensitive */
		for (size_t i = 0; ModuleNameBuffer[i] != '\0'; ++i)
		{
			if (ModuleNameBuffer[i] >= 'A' && ModuleNameBuffer[i] <= 'Z')
				ModuleNameBuffer[i] += 0x20; // 0x20 is the difference between uppercase and lowercase
		}
 
		/* Does the name match? */
		if(strstr(ModuleNameBuffer, lpModuleNameCopy) != NULL)
		{
			/* Make a temporary variable to hold return value*/
			HMODULE TempReturn = ModuleArray[i];
 
			/* Give back that memory */
			delete[] ModuleArray;
 
			/* Success */
			return TempReturn;
		}
 
		/* Wrong module let's try the next... */
	}
 
/* Uh Oh... */
GRMH_FAIL_JMP:
 
	/* If we got to the point where we allocated memory we need to give it back */
	if(ModuleArray != NULL)
		delete[] ModuleArray;
 
	/* Failure... */
	return NULL;
}
 

//-----------------------------------------------------------------------------

FARPROC WINAPI GetRemoteProcAddress (HANDLE hProcess, HMODULE hModule, LPCSTR lpProcName, UINT Ordinal, BOOL UseOrdinal)
{
	BOOL Is64Bit = FALSE;
	MODULEINFO RemoteModuleInfo = {0};
	UINT_PTR RemoteModuleBaseVA = 0;
	IMAGE_DOS_HEADER DosHeader = {0};
	DWORD Signature = 0;
	IMAGE_FILE_HEADER FileHeader = {0};
	IMAGE_OPTIONAL_HEADER64 OptHeader64 = {0};
	IMAGE_OPTIONAL_HEADER32 OptHeader32 = {0};
	IMAGE_DATA_DIRECTORY ExportDirectory = {0};
	IMAGE_EXPORT_DIRECTORY ExportTable = {0};
	UINT_PTR ExportFunctionTableVA = 0;
	UINT_PTR ExportNameTableVA = 0;
	UINT_PTR ExportOrdinalTableVA = 0;
	DWORD* ExportFunctionTable = NULL;
	DWORD* ExportNameTable = NULL;
	WORD* ExportOrdinalTable = NULL;
 
	/* Temporary variables not used until much later but easier
	/* to define here than in all the the places they are used */
	CHAR TempChar;
	BOOL Done = FALSE;
 
	/* Check to make sure we didn't get a NULL pointer for the name unless we are searching by ordinal */
	if(lpProcName == NULL && !UseOrdinal)
		goto GRPA_FAIL_JMP;
 
	/* Get the base address of the remote module along with some other info we don't need */
	if(!::GetModuleInformation(hProcess, hModule,&RemoteModuleInfo, sizeof(RemoteModuleInfo)))
		goto GRPA_FAIL_JMP;
	RemoteModuleBaseVA	= (UINT_PTR)RemoteModuleInfo.lpBaseOfDll;
 
	/* Read the DOS header and check it's magic number */
	if(!::ReadProcessMemory(hProcess, (LPCVOID)RemoteModuleBaseVA, &DosHeader,
		sizeof(DosHeader), NULL) || DosHeader.e_magic != IMAGE_DOS_SIGNATURE)
		goto GRPA_FAIL_JMP;
 
	/* Read and check the NT signature */
	if(!::ReadProcessMemory(hProcess, (LPCVOID)(RemoteModuleBaseVA + DosHeader.e_lfanew),
		&Signature, sizeof(Signature), NULL) || Signature != IMAGE_NT_SIGNATURE)
		goto GRPA_FAIL_JMP;
	
	/* Read the main header */
	if(!::ReadProcessMemory(hProcess,
		(LPCVOID)(RemoteModuleBaseVA + DosHeader.e_lfanew + sizeof(Signature)),
		&FileHeader, sizeof(FileHeader), NULL))
		goto GRPA_FAIL_JMP;
 
	/* Which type of optional header is the right size? */
	if(FileHeader.SizeOfOptionalHeader == sizeof(OptHeader64))
		Is64Bit = TRUE;
	else if(FileHeader.SizeOfOptionalHeader == sizeof(OptHeader32))
		Is64Bit = FALSE;
	else
		goto GRPA_FAIL_JMP;
 
	if(Is64Bit)
	{
		/* Read the optional header and check it's magic number */
		if(!::ReadProcessMemory(hProcess,
			(LPCVOID)(RemoteModuleBaseVA + DosHeader.e_lfanew + sizeof(Signature) + sizeof(FileHeader)),
			&OptHeader64, FileHeader.SizeOfOptionalHeader, NULL)
			|| OptHeader64.Magic != IMAGE_NT_OPTIONAL_HDR64_MAGIC)
			goto GRPA_FAIL_JMP;
	}
	else
	{
		/* Read the optional header and check it's magic number */
		if(!::ReadProcessMemory(hProcess,
			(LPCVOID)(RemoteModuleBaseVA + DosHeader.e_lfanew + sizeof(Signature) + sizeof(FileHeader)),
			&OptHeader32, FileHeader.SizeOfOptionalHeader, NULL)
			|| OptHeader32.Magic != IMAGE_NT_OPTIONAL_HDR32_MAGIC)
			goto GRPA_FAIL_JMP;
	}
 
	/* Make sure the remote module has an export directory and if it does save it's relative address and size */
	if(Is64Bit && OptHeader64.NumberOfRvaAndSizes >= IMAGE_DIRECTORY_ENTRY_EXPORT + 1)
	{
		ExportDirectory.VirtualAddress = (OptHeader64.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT]).VirtualAddress;
		ExportDirectory.Size = (OptHeader64.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT]).Size;
	}
	else if(OptHeader32.NumberOfRvaAndSizes >= IMAGE_DIRECTORY_ENTRY_EXPORT + 1)
	{
		ExportDirectory.VirtualAddress = (OptHeader32.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT]).VirtualAddress;
		ExportDirectory.Size = (OptHeader32.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT]).Size;
	}
	else
		goto GRPA_FAIL_JMP;
 
	/* Read the main export table */
	if(!::ReadProcessMemory(hProcess, (LPCVOID)(RemoteModuleBaseVA + ExportDirectory.VirtualAddress),
		&ExportTable, sizeof(ExportTable), NULL))
		goto GRPA_FAIL_JMP;
 
	/* Save the absolute address of the tables so we don't need to keep adding the base address */
	ExportFunctionTableVA = RemoteModuleBaseVA + ExportTable.AddressOfFunctions;
	ExportNameTableVA = RemoteModuleBaseVA + ExportTable.AddressOfNames;
	ExportOrdinalTableVA = RemoteModuleBaseVA + ExportTable.AddressOfNameOrdinals;
 
	/* Allocate memory for our copy of the tables */
	ExportFunctionTable	= new DWORD[ExportTable.NumberOfFunctions];
	ExportNameTable		= new DWORD[ExportTable.NumberOfNames];
	ExportOrdinalTable	= new WORD[ExportTable.NumberOfNames];
 
	/* Check if the allocation failed */
	if(ExportFunctionTable == NULL || ExportNameTable == NULL || ExportOrdinalTable == NULL)
		goto GRPA_FAIL_JMP;
 
	/* Get a copy of the function table */
	if(!::ReadProcessMemory(hProcess, (LPCVOID)ExportFunctionTableVA,
		ExportFunctionTable, ExportTable.NumberOfFunctions * sizeof(DWORD), NULL))
		goto GRPA_FAIL_JMP;
 
	/* Get a copy of the name table */
	if(!::ReadProcessMemory(hProcess, (LPCVOID)ExportNameTableVA,
		ExportNameTable, ExportTable.NumberOfNames * sizeof(DWORD), NULL))
		goto GRPA_FAIL_JMP;
 
	/* Get a copy of the ordinal table */
	if(!::ReadProcessMemory(hProcess, (LPCVOID)ExportOrdinalTableVA,
		ExportOrdinalTable, ExportTable.NumberOfNames * sizeof(WORD), NULL))
		goto GRPA_FAIL_JMP;
 
	/* If we are searching for an ordinal we do that now */
	if(UseOrdinal)
	{
		/* NOTE:
		/* Microsoft's PE/COFF specification does NOT say we need to subtract the ordinal base
		/* from our ordinal but it seems to always give the wrong function if we don't */
 
		/* Make sure the ordinal is valid */
		if(Ordinal < ExportTable.Base || (Ordinal - ExportTable.Base) >= ExportTable.NumberOfFunctions)
			goto GRPA_FAIL_JMP;
 
		UINT FunctionTableIndex = Ordinal - ExportTable.Base;
 
		/* Check if the function is forwarded and if so get the real address*/
		if(ExportFunctionTable[FunctionTableIndex] >= ExportDirectory.VirtualAddress &&
			ExportFunctionTable[FunctionTableIndex] <= ExportDirectory.VirtualAddress + ExportDirectory.Size)
		{
			Done = FALSE;
			string TempForwardString;
			TempForwardString.clear(); // Empty the string so we can fill it with a new name

			/* Get the forwarder string one character at a time because we don't know how long it is */
			for(UINT_PTR i = 0; !Done; ++i)
			{
				/* Get next character */
				if(!::ReadProcessMemory(hProcess,
					(LPCVOID)(RemoteModuleBaseVA + ExportFunctionTable[FunctionTableIndex] + i),
					&TempChar, sizeof(TempChar), NULL))
					goto GRPA_FAIL_JMP;
 
				TempForwardString.push_back(TempChar); // Add it to the string

				/* If it's NUL we are done */
				if(TempChar == (CHAR)'\0')
					Done = TRUE;
			}
 
			/* Find the dot that seperates the module name and the function name/ordinal */
			size_t Dot = TempForwardString.find('.');
			if(Dot == string::npos)
				goto GRPA_FAIL_JMP;
 
			/* Temporary variables that hold parts of the forwarder string */
			string RealModuleName, RealFunctionId;
			RealModuleName = TempForwardString.substr(0, Dot - 1);
			RealFunctionId = TempForwardString.substr(Dot + 1, string::npos);
 
			HMODULE RealModule = GetRemoteModuleHandle(hProcess, RealModuleName.c_str());
			FARPROC TempReturn;// Make a temporary variable to hold return value 

 
			/* Figure out if the function was exported by name or by ordinal */
			if(RealFunctionId.at(0) == '#') // Exported by ordinal
			{
				UINT RealOrdinal = 0;
				RealFunctionId.erase(0, 1); // Remove '#' from string

				/* My version of atoi() because I was too lazy to use the real one... */
				for(size_t i = 0; i < RealFunctionId.size(); ++i)
				{
					if(RealFunctionId[i] >= '0' && RealFunctionId[i] <= '9')
					{
						RealOrdinal *= 10;
						RealOrdinal += RealFunctionId[i] - '0';
					}
					else
						break;
				}
 
				/* Recursively call this function to get return value */
				TempReturn = GetRemoteProcAddress(hProcess, RealModule, NULL, RealOrdinal, TRUE);
			}
			else // Exported by name
			{
				/* Recursively call this function to get return value */
				TempReturn = GetRemoteProcAddress(hProcess, RealModule, RealFunctionId.c_str(), 0, FALSE);
			}
			
			/* Give back that memory */
			delete[] ExportFunctionTable;
			delete[] ExportNameTable;
			delete[] ExportOrdinalTable;
			
			/* Success!!! */
			return TempReturn;
		}
		else // Not Forwarded
		{
 
			/* Make a temporary variable to hold return value*/
			FARPROC TempReturn = (FARPROC)(RemoteModuleBaseVA + ExportFunctionTable[FunctionTableIndex]);
				
			/* Give back that memory */
			delete[] ExportFunctionTable;
			delete[] ExportNameTable;
			delete[] ExportOrdinalTable;
			
			/* Success!!! */
			return TempReturn;
		}
	}
 

	/* Iterate through all the names and see if they match the one we are looking for */
	for(DWORD i = 0; i<exporttable.numberofnames;>	{
		string TempFunctionName;
 
		Done = FALSE;// Reset for next name
		TempFunctionName.clear(); // Empty the string so we can fill it with a new name

		/* Get the function name one character at a time because we don't know how long it is */
		for(UINT_PTR j = 0; !Done; ++j)
		{
			/* Get next character */
			if(!::ReadProcessMemory(hProcess, (LPCVOID)(RemoteModuleBaseVA + ExportNameTable[i] + j),
				&TempChar, sizeof(TempChar), NULL))
				goto GRPA_FAIL_JMP;
 
			TempFunctionName.push_back(TempChar); // Add it to the string

			/* If it's NUL we are done */
			if(TempChar == (CHAR)'\0')
				Done = TRUE;
		}
 
		/* Does the name match? */
		if(TempFunctionName.find(lpProcName) != string::npos)
		{
			/* NOTE:
			/* Microsoft's PE/COFF specification says we need to subtract the ordinal base
			/*from the value in the ordinal table but that seems to always give the wrong function */
 
			/* Check if the function is forwarded and if so get the real address*/
			if(ExportFunctionTable[ExportOrdinalTable[i]] >= ExportDirectory.VirtualAddress &&
				ExportFunctionTable[ExportOrdinalTable[i]] <= ExportDirectory.VirtualAddress + ExportDirectory.Size)
			{
				Done = FALSE;
				string TempForwardString;
				TempForwardString.clear(); // Empty the string so we can fill it with a new name

				/* Get the forwarder string one character at a time because we don't know how long it is */
				for(UINT_PTR j = 0; !Done; ++j)
				{
					/* Get next character */
					if(!::ReadProcessMemory(hProcess,
						(LPCVOID)(RemoteModuleBaseVA + ExportFunctionTable[i] + j),
						&TempChar, sizeof(TempChar), NULL))
						goto GRPA_FAIL_JMP;
 
					TempForwardString.push_back(TempChar); // Add it to the string

					/* If it's NUL we are done */
					if(TempChar == (CHAR)'\0')
						Done = TRUE;
				}
 
				/* Find the dot that seperates the module name and the function name/ordinal */
				size_t Dot = TempForwardString.find('.');
				if(Dot == string::npos)
					goto GRPA_FAIL_JMP;
 
				/* Temporary variables that hold parts of the forwarder string */
				string RealModuleName, RealFunctionId;
				RealModuleName = TempForwardString.substr(0, Dot);
				RealFunctionId = TempForwardString.substr(Dot + 1, string::npos);
 
				HMODULE RealModule = GetRemoteModuleHandle(hProcess, RealModuleName.c_str());
				FARPROC TempReturn;// Make a temporary variable to hold return value 

 
				/* Figure out if the function was exported by name or by ordinal */
				if(RealFunctionId.at(0) == '#') // Exported by ordinal
				{
					UINT RealOrdinal = 0;
					RealFunctionId.erase(0, 1); // Remove '#' from string

					/* My version of atoi() because I was to lazy to use the real one... */
					for(size_t i = 0; i < RealFunctionId.size(); ++i)
					{
						if(RealFunctionId[i] >= '0' && RealFunctionId[i] <= '9')
						{
							RealOrdinal *= 10;
							RealOrdinal += RealFunctionId[i] - '0';
						}
						else
							break;
					}
 
					/* Recursively call this function to get return value */
					TempReturn = GetRemoteProcAddress(hProcess, RealModule, NULL, RealOrdinal, TRUE);
				}
				else // Exported by name
				{
					/* Recursively call this function to get return value */
					TempReturn = GetRemoteProcAddress(hProcess, RealModule, RealFunctionId.c_str(), 0, FALSE);
				}
				
				/* Give back that memory */
				delete[] ExportFunctionTable;
				delete[] ExportNameTable;
				delete[] ExportOrdinalTable;
					
				/* Success!!! */
				return TempReturn;
			}
			else // Not Forwarded
			{
 
				/* Make a temporary variable to hold return value*/
				FARPROC TempReturn;
				
				/* NOTE:
				/* Microsoft's PE/COFF specification says we need to subtract the ordinal base
				/*from the value in the ordinal table but that seems to always give the wrong function */
				//TempReturn = (FARPROC)(RemoteModuleBaseVA + ExportFunctionTable[ExportOrdinalTable[i] - ExportTable.Base]);
				
				/* So we do it this way instead */
				TempReturn = (FARPROC)(RemoteModuleBaseVA + ExportFunctionTable[ExportOrdinalTable[i]]);
				
				/* Give back that memory */
				delete[] ExportFunctionTable;
				delete[] ExportNameTable;
				delete[] ExportOrdinalTable;
				
				/* Success!!! */
				return TempReturn;
			}
		}
 
		/* Wrong function let's try the next... */
	}
 
/* Uh Oh... */
GRPA_FAIL_JMP:
 
	/* If we got to the point where we allocated memory we need to give it back */
	if(ExportFunctionTable != NULL)
		delete[] ExportFunctionTable;
	if(ExportNameTable != NULL)
		delete[] ExportNameTable;
	if(ExportOrdinalTable != NULL)
		delete[] ExportOrdinalTable;
 
	/* Falure... */
	return NULL;
}
 
//-----------------------------------------------------------------------------

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Mr Nukealizer

United States United States
No Biography provided

Comments and Discussions

 
QuestionThanks a lot for the code. PinmemberGautam Jain7-Jul-14 6:24 
QuestionNested for loops using the same variable name (i) Pinmembersziadan1-Mar-14 18:53 
Questiontypo PinmemberSapien28-Dec-13 0:23 
Questionhow to use it ? Pingroupdnybz1-Aug-12 20:32 

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