[glib/glib-2-24] Reduce DLL hijack risk on Windows

[Tor Lillqvist <tml src gnome org>]

commit 86156c28b3b5a6cc2a3e22def530c355e9606504
Author: Tor Lillqvist <tml iki fi>
Date:   Thu Sep 2 22:55:43 2010 +0300

    Reduce DLL hijack risk on Windows
    
    Don't call LoadLibrary() on shell32.dll or kernel32.dll. kernel32.dll
    is always loaded. Shell32.dll is also already loaded as glib links to
    functions in it. So just call GetModuleHandle() on them.
    
    For mlang.dll in win_iconv.c and winhttp.dll in gwinhttpvfs.c, always
    try loading them from a complete path, from the Windows system
    directory.
    
    Use the "tool help" API to enumerate modules in gmodule-win32.c. It is
    present in all Windows versions since Windows 2000, which is all we
    support anyway. Thus no need to look that API up dynamically. Just
    link to it normally. We can bin the fallback code that attempts to use
    the psapi API.

 gio/win32/gwinhttpvfs.c |   15 +++++++-
 glib/gutils.c           |    6 ++-
 glib/win_iconv.c        |   14 +++++++-
 gmodule/gmodule-win32.c |   82 ++--------------------------------------------
 4 files changed, 33 insertions(+), 84 deletions(-)
---
diff --git a/gio/win32/gwinhttpvfs.c b/gio/win32/gwinhttpvfs.c
index 494f53f..1e40324 100644
--- a/gio/win32/gwinhttpvfs.c
+++ b/gio/win32/gwinhttpvfs.c
@@ -42,12 +42,23 @@ static GWinHttpDllFuncs funcs;
 static void
 lookup_funcs (void)
 {
-  HMODULE winhttp;
+  HMODULE winhttp = NULL;
+  char winhttp_dll[MAX_PATH + 100];
+  int n;
 
   if (lookup_done)
     return;
 
-  winhttp = LoadLibrary ("winhttp.dll");
+  n = GetSystemDirectory (winhttp_dll, MAX_PATH);
+  if (n > 0 && n < MAX_PATH)
+    {
+        if (winhttp_dll[n-1] != '\\' &&
+            winhttp_dll[n-1] != '/')
+            strcat (winhttp_dll, "\\");
+        strcat (winhttp_dll, "winhttp.dll");
+        winhttp = LoadLibrary (winhttp_dll);
+    }
+
   if (winhttp != NULL)
     {
       funcs.pWinHttpCloseHandle = (BOOL (WINAPI *) (HINTERNET)) GetProcAddress (winhttp, "WinHttpCloseHandle");
diff --git a/glib/gutils.c b/glib/gutils.c
index 8698746..b89351b 100644
--- a/glib/gutils.c
+++ b/glib/gutils.c
@@ -2262,13 +2262,15 @@ load_user_special_dirs (void)
 						    HANDLE hToken,
 						    PWSTR *ppszPath);
   t_SHGetKnownFolderPath p_SHGetKnownFolderPath;
+
   static const GUID FOLDERID_Downloads =
     { 0x374de290, 0x123f, 0x4565, { 0x91, 0x64, 0x39, 0xc4, 0x92, 0x5e, 0x46, 0x7b } };
   static const GUID FOLDERID_Public =
     { 0xDFDF76A2, 0xC82A, 0x4D63, { 0x90, 0x6A, 0x56, 0x44, 0xAC, 0x45, 0x73, 0x85 } };
+
   wchar_t *wcp;
 
-  p_SHGetKnownFolderPath = (t_SHGetKnownFolderPath) GetProcAddress (LoadLibrary ("shell32.dll"),
+  p_SHGetKnownFolderPath = (t_SHGetKnownFolderPath) GetProcAddress (GetModuleHandle ("shell32.dll"),
 								    "SHGetKnownFolderPath");
 
   g_user_special_dirs[G_USER_DIRECTORY_DESKTOP] = get_special_folder (CSIDL_DESKTOPDIRECTORY);
@@ -2594,7 +2596,7 @@ get_module_for_address (gconstpointer address)
   if (!beenhere)
     {
       p_GetModuleHandleExA =
-	(t_GetModuleHandleExA) GetProcAddress (LoadLibrary ("kernel32.dll"),
+	(t_GetModuleHandleExA) GetProcAddress (GetModuleHandle ("kernel32.dll"),
 					       "GetModuleHandleExA");
       beenhere = TRUE;
     }
diff --git a/glib/win_iconv.c b/glib/win_iconv.c
index ea19240..6d726d7 100644
--- a/glib/win_iconv.c
+++ b/glib/win_iconv.c
@@ -706,10 +706,20 @@ static RFC1766TOLCIDA Rfc1766ToLcidA;
 static int
 load_mlang()
 {
-    HMODULE h;
+    HMODULE h = NULL;
+    char mlang_dll[MAX_PATH + 100];
+    int n;
     if (ConvertINetString != NULL)
         return TRUE;
-    h = LoadLibrary("mlang.dll");
+    n = GetSystemDirectory(mlang_dll, MAX_PATH);
+    if (n > 0 && n < MAX_PATH)
+    {
+        if (mlang_dll[n-1] != '\\' &&
+            mlang_dll[n-1] != '/')
+            strcat(mlang_dll, "\\");
+        strcat(mlang_dll, "mlang.dll");
+        h = LoadLibrary(mlang_dll);
+    }
     if (!h)
         return FALSE;
     ConvertINetString = (CONVERTINETSTRING)GetProcAddress(h, "ConvertINetString");
diff --git a/gmodule/gmodule-win32.c b/gmodule/gmodule-win32.c
index 98d3fb9..439fb5d 100644
--- a/gmodule/gmodule-win32.c
+++ b/gmodule/gmodule-win32.c
@@ -110,45 +110,22 @@ _g_module_close (gpointer handle,
 static gpointer
 find_in_any_module_using_toolhelp (const gchar *symbol_name)
 {
-  typedef HANDLE (WINAPI *PFNCREATETOOLHELP32SNAPSHOT)(DWORD, DWORD);
-  static PFNCREATETOOLHELP32SNAPSHOT pfnCreateToolhelp32Snapshot = NULL;
-
-  typedef BOOL (WINAPI *PFNMODULE32FIRST)(HANDLE, MODULEENTRY32*);
-  static PFNMODULE32FIRST pfnModule32First= NULL;
-
-  typedef BOOL (WINAPI *PFNMODULE32NEXT)(HANDLE, MODULEENTRY32*);
-  static PFNMODULE32NEXT pfnModule32Next = NULL;
-
-  static HMODULE kernel32;
-
   HANDLE snapshot; 
   MODULEENTRY32 me32;
 
   gpointer p;
 
-  if (!pfnCreateToolhelp32Snapshot || !pfnModule32First || !pfnModule32Next)
-    {
-      if (!kernel32)
-	if (!(kernel32 = GetModuleHandle ("kernel32.dll")))
-	  return NULL;
-
-      if (!(pfnCreateToolhelp32Snapshot = (PFNCREATETOOLHELP32SNAPSHOT) GetProcAddress (kernel32, "CreateToolhelp32Snapshot"))
-	  || !(pfnModule32First = (PFNMODULE32FIRST) GetProcAddress (kernel32, "Module32First"))
-	  || !(pfnModule32Next = (PFNMODULE32NEXT) GetProcAddress (kernel32, "Module32Next")))
-	return NULL;
-    }
-
-  if ((snapshot = (*pfnCreateToolhelp32Snapshot) (TH32CS_SNAPMODULE, 0)) == (HANDLE) -1)
+  if ((snapshot = CreateToolhelp32Snapshot (TH32CS_SNAPMODULE, 0)) == (HANDLE) -1)
     return NULL;
 
   me32.dwSize = sizeof (me32);
   p = NULL;
-  if ((*pfnModule32First) (snapshot, &me32))
+  if (Module32First (snapshot, &me32))
     {
       do {
 	if ((p = GetProcAddress (me32.hModule, symbol_name)) != NULL)
 	  break;
-      } while ((*pfnModule32Next) (snapshot, &me32));
+      } while (Module32Next (snapshot, &me32));
     }
 
   CloseHandle (snapshot);
@@ -157,62 +134,11 @@ find_in_any_module_using_toolhelp (const gchar *symbol_name)
 }
 
 static gpointer
-find_in_any_module_using_psapi (const gchar *symbol_name)
-{
-  static HMODULE psapi = NULL;
-
-  typedef BOOL (WINAPI *PFNENUMPROCESSMODULES) (HANDLE, HMODULE *, DWORD, LPDWORD) ;
-  static PFNENUMPROCESSMODULES pfnEnumProcessModules = NULL;
-
-  HMODULE *modules;
-  HMODULE dummy;
-  gint i, size;
-  DWORD needed;
-  
-  gpointer p;
-
-  if (!pfnEnumProcessModules)
-    {
-      if (!psapi)
-	if ((psapi = LoadLibrary ("psapi.dll")) == NULL)
-	  return NULL;
-
-      if (!(pfnEnumProcessModules = (PFNENUMPROCESSMODULES) GetProcAddress (psapi, "EnumProcessModules")))
-	return NULL;
-    }
-
-  if (!(*pfnEnumProcessModules) (GetCurrentProcess (), &dummy,
-				 sizeof (HMODULE), &needed))
-    return NULL;
-
-  size = needed + 10 * sizeof (HMODULE);
-  modules = g_malloc (size);
-
-  if (!(*pfnEnumProcessModules) (GetCurrentProcess (), modules,
-				 size, &needed)
-      || needed > size)
-    {
-      g_free (modules);
-      return NULL;
-    }
-  
-  p = NULL;
-  for (i = 0; i < needed / sizeof (HMODULE); i++)
-    if ((p = GetProcAddress (modules[i], symbol_name)) != NULL)
-      break;
-
-  g_free (modules);
-
-  return p;
-}
-
-static gpointer
 find_in_any_module (const gchar *symbol_name)
 {
   gpointer result;
 
-  if ((result = find_in_any_module_using_toolhelp (symbol_name)) == NULL
-      && (result = find_in_any_module_using_psapi (symbol_name)) == NULL)
+  if ((result = find_in_any_module_using_toolhelp (symbol_name)) == NULL)
     return NULL;
   else
     return result;