[Full-disclosure] Defense in depth -- the Microsoft way (part 13): surprising and inconsistent behaviour, sloppy coding, sloppy QA, sloppy documentation

["Stefan Kanthak" <stefan.kanthak () nexgo de>]

Hi @ll,

the Win32 API is full of idiosyncrasies resp. surprising and inconsistent,
poorly tested and documented behaviour.

Just to pick one: NULL pointer as string argument.

0. lstrlen(NULL)
   lstrcat(NULL, ...)      and  lstrcat(..., NULL)
   lstrcmp(NULL, ...)      and  lstrcmp(..., NULL)
   lstrcmpi(NULL, ...)     and  lstrcmpi(..., NULL)
   lstrcpy(NULL, ...)      and  lstrcpy(..., NULL)
   lstrcpyn(NULL, ..., 0)  and  lstrcpy(..., NULL, ...)

   do not yield an exception, but treat their NULL arguments like an
   empty string (when used as source), resp. return NULL (when used as
   destination).


1. wsprintf(NULL, ...)       and  wvsprintf(NULL, ...)
   wsprintf(..., NULL, ...)  and  wvsprintf(..., NULL, ...)

   yield an access violation in USER32.DLL.


2. CommandLineToArgvW(NULL, ...)

   yields an access violation in SHELL32.DLL.


3. CreateProcess(NULL, NULL, ...)
   CreateProcessAsUser(..., NULL, NULL, ...)
   CreateProcessWithLogonW(..., ..., ..., ..., NULL, NULL, ...)
   CreateProcessWithTokenW(..., ..., NULL, NULL, ...)

   yield an access violation in KERNEL32.DLL.


4. GetFileAttributes(NULL)

   does not yield an exception, but treats the NULL argument like an
   empty string.


5. GetBinaryType(NULL, ...)

   does not yield an exception, but treats the NULL argument like an
   empty string.


6. MessageBox(..., NULL, ...)  and  MessageBox(..., ..., NULL, ...)

   do not yield an exception, but treat the NULL argument like an
   empty string.


7. FatalAppExit(0, NULL)

   does not yield an exception, but treats the NULL argument like an
   empty string.


8. GetCurrentDirectory(..., NULL)

   returns an error if the buffer size (the argument shown as ... here)
   is sufficient to hold the result, else the required buffer size.

   GetTempPath(..., NULL)
   GetSystemDirectory(NULL, ...)
   GetSystemWindowsDirectory(NULL, ...)
   GetSystemWow64Directory(NULL, ...)
   GetWindowsDirectory(NULL, ...)
   GetComputerName(NULL, ...)

   yield an access violation in NTDLL.DLL resp. KERNEL32.DLL if the
   buffer size is sufficient to hold the result, else the required
   buffer size.

   GetUserName(NULL, ...)
   GetComputerObjectName(..., NULL, ...)

   do not yield an access violation, but return an error with
   GetLastError() == ERROR_INSUFFICIENT_BUFFER.


9. GetUserName(NULL, NULL)
   GetComputerName(NULL, NULL)

   yield an access violation in KERNEL32.DLL.

   GetComputerNameEx(..., NULL, NULL)
   GetComputerObjectName(..., NULL, NULL)

   do not yield an access violation, but return an error with
   GetLastError() == ERROR_INVALID_PARAMETER.

   JFTR: only the documentation of the last function (see
         <http://msdn.microsoft.com/en-us/library/ms724301.aspx>)
         explicitly says about the value of the third argument
         "If lpBuffer is NULL, this parameter must be zero."
         and checks this contraint properly.


The expected behavior in all cases is but to return an error with
GetLastError() == ERROR_INVALID_PARAMETER or similar.


FIX: ALL interfaces of the Win32 API should^WMUST verify (ALL) their
     arguments properly before using them and return an appropriate,
     documented error code.


stay tuned
Stefan Kanthak

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