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curl/lib/system_win32.c
Steve Holme 6df916d751 loadlibrary: Only load system DLLs from the system directory
Inspiration provided by: Daniel Stenberg and Ray Satiro

Bug: https://curl.haxx.se/docs/adv_20160530.html

Ref: Windows DLL hijacking with curl, CVE-2016-4802
2016-05-30 08:14:27 +02:00

131 lines
4.5 KiB
C

/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 2016, Steve Holme, <steve_holme@hotmail.com>.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at https://curl.haxx.se/docs/copyright.html.
*
* You may opt to use, copy, modify, merge, publish, distribute and/or sell
* copies of the Software, and permit persons to whom the Software is
* furnished to do so, under the terms of the COPYING file.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
***************************************************************************/
#include "curl_setup.h"
#if defined(WIN32)
#if defined(USE_WINDOWS_SSPI) || (!defined(CURL_DISABLE_TELNET) && \
defined(USE_WINSOCK))
#include <curl/curl.h>
#include "system_win32.h"
/* The last #include files should be: */
#include "curl_memory.h"
#include "memdebug.h"
#if !defined(LOAD_WITH_ALTERED_SEARCH_PATH)
#define LOAD_WITH_ALTERED_SEARCH_PATH 0x00000008
#endif
#if !defined(LOAD_LIBRARY_SEARCH_SYSTEM32)
#define LOAD_LIBRARY_SEARCH_SYSTEM32 0x00000800
#endif
/* We use our own typedef here since some headers might lack these */
typedef HMODULE (APIENTRY *LOADLIBRARYEX_FN)(LPCTSTR, HANDLE, DWORD);
/* See function definitions in winbase.h */
#ifdef UNICODE
# ifdef _WIN32_WCE
# define LOADLIBARYEX L"LoadLibraryExW"
# else
# define LOADLIBARYEX "LoadLibraryExW"
# endif
#else
# define LOADLIBARYEX "LoadLibraryExA"
#endif
/*
* Curl_load_library()
*
* This is used to dynamically load DLLs using the most secure method available
* for the version of Windows that we are running on.
*
* Parameters:
*
* filename [in] - The filename or full path of the DLL to load. If only the
* filename is passed then the DLL will be loaded from the
* Windows system directory.
*
* Returns the handle of the module on success; otherwise NULL.
*/
HMODULE Curl_load_library(LPCTSTR filename)
{
HMODULE hModule = NULL;
LOADLIBRARYEX_FN pLoadLibraryEx = NULL;
/* Get a handle to kernel32 so we can access it's functions at runtime */
HMODULE hKernel32 = GetModuleHandle(TEXT("kernel32"));
if(!hKernel32)
return NULL;
/* Attempt to find LoadLibraryEx() which is only available on Windows 2000
and above */
pLoadLibraryEx = (LOADLIBRARYEX_FN) GetProcAddress(hKernel32, LOADLIBARYEX);
/* Detect if there's already a path in the filename and load the library if
there is. Note: Both back slashes and forward slashes have been supported
since the earlier days of DOS at an API level although they are not
supported by command prompt */
if(_tcspbrk(filename, TEXT("\\/")))
hModule = pLoadLibraryEx ?
pLoadLibraryEx(filename, NULL, LOAD_WITH_ALTERED_SEARCH_PATH) :
LoadLibrary(filename);
/* Detect if KB2533623 is installed, as LOAD_LIBARY_SEARCH_SYSTEM32 is only
supported on Windows Vista, Windows Server 2008, Windows 7 and Windows
Server 2008 R2 with this patch or natively on Windows 8 and above */
else if(pLoadLibraryEx && GetProcAddress(hKernel32, "AddDllDirectory")) {
/* Load the DLL from the Windows system directory */
hModule = pLoadLibraryEx(filename, NULL, LOAD_LIBRARY_SEARCH_SYSTEM32);
}
else {
/* Attempt to get the Windows system path */
UINT systemdirlen = GetSystemDirectory(NULL, 0);
if(systemdirlen) {
/* Allocate space for the full DLL path (Room for the null terminator
is included in systemdirlen) */
size_t filenamelen = _tcslen(filename);
TCHAR *path = malloc(sizeof(TCHAR) * (systemdirlen + 1 + filenamelen));
if(path && GetSystemDirectory(path, systemdirlen)) {
/* Calculate the full DLL path */
_tcscpy(path + _tcslen(path), TEXT("\\"));
_tcscpy(path + _tcslen(path), filename);
/* Load the DLL from the Windows system directory */
hModule = pLoadLibraryEx ?
pLoadLibraryEx(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH) :
LoadLibrary(path);
free(path);
}
}
}
return hModule;
}
#endif /* USE_WINDOWS_SSPI || (!CURL_DISABLE_TELNET && USE_WINSOCK) */
#endif /* WIN32 */