Re: Windows MS-DOS Device Name DoS vulnerabilities

["Pavel Kankovsky" <peak () argo troja mff cuni cz>]

On Fri, 6 Jul 2001, 3APA3A wrote:

> ... and the problem is definitely in software, not in operation
> system, because operation system behaves exactly as expected and
> documented.

But it is still OS's problem when the specification / documentation it
conforms to is braindead. Adding implicit entries for devices into EVERY
directory is definitely braindead.

BTW: What will happen when Joe Luser creates a file called XYZ on day 1,
installs a device driver called XYZ--adding XYZ to the list of magical
filenames--on day 2, and tries to access XYZ on day 3? Inquiring minds
want to know...

> if( GetFileType(hFile) != FILE_TYPE_DISK ) {
>      lstrcpy( lpszPath, TEXT("Invalid File Type") );
>      return( 0 );
>   }
[...]
> Checks  like  this  must be in "best coding practice", because even if
> security  is  not  in question user can specify special device name by
> accident.

Unfortunately, a user can specify such a name deliberately in order to do
something meaningful (e.g. the old good "copy con filename"). Adding such
a check to programs interpreting filenames given by an untrusted party is
probably a good idea (both on MS Windows and unix-like OSes) but it is a
more a desperate attempt to circumvent the lack of a better mechanism than
"the best coding practice."

BTW2: GetFileType() seems to take a handle as its argument, i.e. the
caller must already have called OpenFile() in order to be able to use
it--and call CloseFile() (CloseHandle()?) afterwards. Are OpenFile() and
CloseFile() guaranteed to be free of dangerous side effects?

--Pavel Kankovsky aka Peak  [ Boycott Microsoft--http://www.vcnet.com/bms ]
"Resistance is futile. Open your source code and prepare for assimilation."