Hi Stefan,
See below.
On 09-03-16 13:18, Stefan Kanthak wrote:
"Securify B.V." wrote:
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Windows Mail Find People DLL side loading vulnerability
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Yorick Koster, September 2015
This vulnerability demonstrates Microsoft's terrible SLOPPY coding
horror^Wpractice: it needs two mistakes to create this kind of bug!
"%CommonProgramFiles%\System\wab32res.dll" is (as its name implies)
a resource DLL, which means that it contains no code, but only
(localized) resources, and SHOULD (better: MUST) be loaded via
LoadLibraryEx("%CommonProgramFiles%\System\wab32res.dll", NULL, LOAD_LIBRARY_AS_DATAFILE)
to avoid the call of its DllMain() startup code!
See <https://msdn.microsoft.com/en-us/library/ms684179.aspx>
JFTR: LOAD_LIBRARY_AS_DATAFILE was introduced in the last millennium!
Either
LoadLibrary("%CommonProgramFiles%\System\wab32res.dll")
or
LoadLibraryEx("wab32res.dll", NULL, LOAD_LIBRARY_AS_DATAFILE)
were sufficient to avoid this vulnerability.
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Fix
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Microsoft released MS16-025 that fixes this vulnerability.
Have you checked how Microsoft fixed it?
Did they exercise all due diligence now, practised defense in depth
and replaced the call to
LoadLibrary("wab32res.dll")
with a call to
LoadLibraryEx("%CommonProgramFiles%\System\wab32res.dll", NULL, LOAD_LIBRARY_AS_DATAFILE)?
They still use LoadLibrary() to load wab32res.dll. Previously, the
fetched a path from HKLM\Software\Microsoft\WAB\DLLPath and appended
wab32res.dll to the result, which was fed into LoadLibrary().
With MS16-025 they sanitize DLLpath using PathRemoveFileSpec(). By
default DLLPath is set to %CommonProgramFiles%\System\wab32.dll,
PathRemoveFileSpec() removes wab32.dll from the path. They also call
ExpandEnvironmentStrings(), but that was also the case previously.
With kind regards,
Yorick
