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/*
Userspace Virtual Filesystem
Copyright (C) 2015 Sebastian Herbord. All rights reserved.
This file is part of usvfs.
usvfs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
usvfs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with usvfs. If not, see <http://www.gnu.org/licenses/>.
*/
#include "utility.h"
#include "exceptionex.h"
#include <cstdlib>
namespace HookLib
{
FARPROC MyGetProcAddress(HMODULE module, LPCSTR functionName)
{
// determine position of the exports of the module
PIMAGE_DOS_HEADER dosHeader = (PIMAGE_DOS_HEADER)module;
if (dosHeader->e_magic != IMAGE_DOS_SIGNATURE) {
return nullptr;
}
PIMAGE_NT_HEADERS ntHeaders =
(PIMAGE_NT_HEADERS)(((LPBYTE)dosHeader) + dosHeader->e_lfanew);
if (ntHeaders->Signature != IMAGE_NT_SIGNATURE) {
return nullptr;
}
PIMAGE_OPTIONAL_HEADER optionalHeader = &ntHeaders->OptionalHeader;
if (optionalHeader->NumberOfRvaAndSizes <= IMAGE_DIRECTORY_ENTRY_EXPORT) {
return nullptr;
}
PIMAGE_DATA_DIRECTORY dataDirectory =
&optionalHeader->DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT];
PIMAGE_EXPORT_DIRECTORY exportDirectory =
(PIMAGE_EXPORT_DIRECTORY)((LPBYTE)dosHeader + dataDirectory->VirtualAddress);
ULONG* addressOfNames = (ULONG*)((LPBYTE)module + exportDirectory->AddressOfNames);
ULONG* funcAddr = (ULONG*)((LPBYTE)module + exportDirectory->AddressOfFunctions);
// search exports for the specified name
for (DWORD i = 0; i < exportDirectory->NumberOfNames; ++i) {
char* curFunctionName = (char*)((LPBYTE)module + addressOfNames[i]);
USHORT* nameOrdinals =
(USHORT*)((LPBYTE)module + exportDirectory->AddressOfNameOrdinals);
if (strcmp(functionName, curFunctionName) == 0) {
if (funcAddr[nameOrdinals[i]] >= dataDirectory->VirtualAddress &&
funcAddr[nameOrdinals[i]] <
dataDirectory->VirtualAddress + dataDirectory->Size) {
char* forwardLibName = _strdup((LPSTR)module + funcAddr[nameOrdinals[i]]);
ON_BLOCK_EXIT([forwardLibName]() {
free(forwardLibName);
});
char* forwardFunctionName = strchr(forwardLibName, '.');
*forwardFunctionName = 0;
++forwardFunctionName;
HMODULE forwardLib = LoadLibraryA(forwardLibName);
FARPROC forward = nullptr;
if (forwardLib != nullptr) {
forward = MyGetProcAddress(forwardLib, forwardFunctionName);
FreeLibrary(forwardLib);
}
return forward;
}
return (FARPROC)((LPBYTE)module + funcAddr[nameOrdinals[i]]);
}
}
return nullptr;
}
} // namespace HookLib
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