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DonHopkins
I just ran across a COM interface in the MOST unexpected of places:

Apple's CoreMediaIO CFPlugIn video capture device plugin interface!

https://github.com/phracker/MacOSX-SDKs/blob/master/MacOSX10...

    /*
         File:       CMIOHardwarePlugIn.h

         Contains:   API for the CFPlugIn that implements an CMIO driver for the DAL from user space

         Copyright:  © 2004-2010 by Apple Inc., all rights reserved.
    */
[...]

    /*!
        @method         QueryInterface
        @abstract       The IUnknown method for finding an interface on a CFPlugIn type.
        @param          self
                            The CFPlugIn type to query.
        @param          uuid
                            The UUID of the interface to find.
        @param          interface
                            The returned interface or NULL if none was found.
        @result         An error code indicating success of failure.
    */
        HRESULT
        (STDMETHODCALLTYPE *QueryInterface)(    void*   self,
                                                REFIID  uuid,
                                                LPVOID* interface);
BUSTED!

https://github.com/lvsti/CoreMediaIO-DAL-Example/blob/0392cb...

saagarjha
They're probably there for iTunes on Windows or similar.
jjoonathan
There are a bunch of COM interfaces in CoreFoundation. My first COM tutorial came from Apple documentation!
alasdairking
The best way is to use Visual Basic 6 and add a reference to the DLL or EXE. Turn on hidden items in the Object Browser and play around!
vsareto
That's convenient. I wonder if pentesters/security researchers know about that.
pjmlp
Or use the Windows SDK and the COM type library browser.
[deleted]
(comment deleted)
kazinator
The API of a COM object is described in a Type Library file (.tlb suffix).

This is is not necessarily available for every COM object.

COM objects intended for use with C++ work without it, because the COM interface is based on calling C++ virtual functions, for which you just need a declaration from a header file.

To discover the API of a COM object without the .idl file or type library, you have to do binary reverse engineering: disassemble the functions linked into the object's vtable.

dblohm7
Don’t forget about the proxy/stub DLLs: if the COM interface was specified using IDL, its metadata is also encoded inside those using a more descriptive format than typelibs.
pjmlp
Old style COM is defined in tlb files.

Modern COM (UWP) uses .NET metadata and is stored in .winmd files.

C#, VB.NET, JS(Chakra), C++/CX can use them directly, while with C++/WinRT a source file generator was introduced that generates the necessary boilerplate to access the objects in a C++17 friendly way.

Microsoft now calls to COM libraries without type libraries, like DirectX, mini-COM.