Re: little tool for cracking VxDs (or: how to write a driver without...)

From: Jochen Eisinger (jochen.eisinger@gno.de)
Date: Sun Sep 03 2000 - 02:56:10 PDT

  • Next message: Jochen Eisinger: "Re: (Mustek_pp SM4800P)"

    Hi!

    With the help of this little tool, I captured the whole port IO of the
    TWAIN driver for the ScanMagic 1200 ED Plus (ASIC 1015, CCD 01)... in a
    few days, there will be a new version of the mustek_pp backend :)

    -- jochen

    >
    > Hi!
    >
    > Since most of my work consists of reversing stupid TWAIN drivers, I've
    > written a little (hopefully) handy tool:
    >
    > it's called vxd (because it works on VXDs :) Since TWAIN drivers (for
    > the parallel port) need to access the parallel port, they all come with
    > a ring-0 DLL, a so called VxD, that handles the port IO.
    >
    > In my case, this VxD implements similiar commands to sanei_pa4s2. If I
    > can log the calls to these functions I basically know how to operate the
    > scanner. To do this, I just need to disassemble the VxD, add some lines
    > of code and assemble it again. Unfurtonally, a) I don't have neither
    > masm nor the win98-ddk (both needed to compile a windows driver) b) the
    > output of normal disassemblers just won't assemble :-(
    >
    > So I wrote a tool (vxd) to disassemble a VxD in form, I can assemble it
    > again using NASM (avoiding the whole damn microsoft stuff :)
    >
    > This tool won't work for any VxD:
    >
    > - it must be pure 32bit PM code
    > - only one segment (LCODE/LDATA)
    > - no VxD service table
    > - no stupid tricky code
    >
    > but it works for the vxd I want to crack...
    >
    > however I don't know, whether this tool works because of two things:
    >
    > a) you still need the link.exe from microsoft to produce the VxD
    > b) I don't have windows (which is needed to run link.exe & test the
    > resulting VxD)
    >
    > furthermore, I'm still looking for these "some lines of code" that log
    > the function calls (after all, I'm not really experienced in writing
    > windows code...) when I've figured out some good code, I'll let you
    > know...
    >

    --
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