USBDriveBite

A few months back, I learned of the USBDriveby device developed by Samy Kamkar that was able to infect MacOS computers by posing as a USB keyboard and mouse and executing a scripted sequence of mouse movements and key presses. His device used the Teensy 3.0 microcontroller dev board and requires a micro-USB cable to plug into. In my classic fashion of never having any good ideas of my own, but seeing other people's cool ideas and thinking "I can do that better" I started thinking of ways that I could improve on the hardware used, rather than utilizing a general purpose dev board like the Teensy.

I immediately knew that I wanted to use my favorite USB microcontroller, the PIC16F1455. It comes in packages with as few as 14 pins, or as small as a QFN-16, and requires no external components beyond a pair of simple bypass capacitors, making it perfect for small, simple USB devices. It's also supported by the free USB M-Stack, which means I'm not tied down by the frustrating license stipulations of the Microchip USB stack.

The real design revelation came when I tore apart a cheap $2 DealExtreme Bluetooth dongle to find that all of the electronics, including the actual USB pads, were all on a single PCB that could be easily removed from the shell.

The tricky part was that the PCB was 0.6mm thick, and finding a manufacturer willing to produce boards at that thickness for less than $100 took some doing. Once I realized SeeedStudio would handle such a board, it was a simple matter of measuring the original board and throwing together a replacement in EAGLE.

The firmware isn't quite done yet, but I do have the device enumerating as a keyboard and mouse and can send arbitrary mouse movements and button presses, as well as keyboard key presses, so all that really remains is setting up a queue-based event processor and then feeding it the original USBDriveby script. All in all, I'm pretty happy with how it turned out, and now I'm trying to come up with other ideas for how to use this thing, since I'm probably not going to get much use out of it as a MacOS exploit. The board has a single push button and LED (plus an additional power LED), so I can probably find another purpose for it eventually.

Generating tiles for Google Maps API

I use Google Maps API to render the maps on my Zelda Parallel Worlds walkthrough, and as a result I needed to generate the necessary tiles for the Maps API to use.  My source image was a 4,096x4,096 image, and I needed to generate 256x256 tiles at various zoom levels, starting at fully zoomed out, where the entire map was contained in a single tile, up to however large I could reasonable render (which ended up being a whopping 16,384x16,384).  GIMP's script-fu functionality was perfect for the task, but I couldn't find a script that quite did what I wanted, including scaling the map to the various zoom levels, so I made my own.  I used the tiles-to-files plugin as my starting point and went from there.  The end result gives the following options

Tile size is adjustable (though I've only tested powers of 2, such as 64, 128, and 256)

Max zoom level determines how many zoom levels should be generated.  The lowest zoom level is 0, which is a single tile in size.

Output file type is selectable between PNG and JPEG

Interpolation mode can be chosen separately for shrinking and growing.  In my case, I didn't want any interpolation when growing, since I was growing a pixel-perfect image by a factor of 2 each zoom level, so I wanted to retain the pixel-perfect aspect and just create "big pixels".

Here's the script:

; Google Maps Tiles, V1.0
;
; Based on the tiles-to-files script by theilr
; http://registry.gimp.org/node/20868
;
; http://www.qwertymodo.com
;
(define (script-fu-google-maps-tiles inImage inDrawable inTileSize inMaxZoom
                                     inFileType inShrinkMethod inGrowMethod outDir)
  (gimp-image-undo-group-start inImage)
  (let* (
          (fullWidth  (car (gimp-image-width  inImage)))
          (fullHeight (car (gimp-image-height inImage)))
          (tileWidth  inTileSize)
          (tileHeight inTileSize)
          (zoomWidth  tileWidth)
          (zoomHeight tileHeight)
          (newImage (car (gimp-image-new tileWidth tileHeight RGB)))
          (tmpImage)
          (tmpLayer)
          (selLayer)
          (outfname)
          (hcnt 0)
          (vcnt 0)
          (zcnt 0)
    )
   
    (set! zcnt 0)
    (while (<= zcnt inMaxZoom)
      (set! zoomWidth (* tileWidth (expt 2 zcnt)))
      (set! zoomHeight (* tileHeight (expt 2 zcnt)))
     
      (gimp-rect-select inImage
                        0
                        0
                        fullWidth
                        fullHeight
                        CHANNEL-OP-ADD FALSE 0)
                       
      (gimp-edit-copy-visible inImage)
      (gimp-selection-none inImage)
     
      (set! tmpImage
        (car (gimp-image-new zoomWidth zoomHeight RGB)))
         
      (set! tmpLayer
        (car (gimp-layer-new tmpImage fullWidth fullHeight
                     RGB-IMAGE "Background" 100
                     NORMAL-MODE)))                    
      (gimp-image-add-layer tmpImage tmpLayer -1)
      (set! selLayer
        (car (gimp-edit-paste tmpLayer FALSE)))
      (gimp-floating-sel-anchor selLayer)
     
      (if (< zoomWidth fullWidth)
        (begin
          (gimp-context-set-interpolation inShrinkMethod)
          (gimp-layer-scale tmpLayer zoomWidth zoomHeight FALSE)
          (gimp-image-resize-to-layers tmpImage)
        )
      )
     
      (if (> zoomWidth fullWidth)
        (begin
          (gimp-context-set-interpolation inGrowMethod)
          (gimp-layer-scale tmpLayer zoomWidth zoomHeight FALSE)
          (gimp-image-resize-to-layers tmpImage)
        )
      )
   
      (set! hcnt 0)
      (while (< (* hcnt tileWidth) zoomWidth)
        (set! vcnt 0)
        (while (< (* vcnt tileHeight) zoomHeight)
          (gimp-rect-select tmpImage
                            (* tileWidth hcnt)
                            (* tileHeight vcnt)
                            tileWidth
                            tileHeight
                            CHANNEL-OP-ADD FALSE 0)
          (gimp-edit-copy-visible tmpImage)
          (gimp-selection-none tmpImage)
         
          (set! tmpLayer
            (car (gimp-layer-new newImage tileWidth tileHeight
                         RGB-IMAGE "Background" 100
                         NORMAL-MODE)))
          (gimp-image-add-layer newImage tmpLayer -1)
          (set! selLayer
            (car (gimp-edit-paste tmpLayer FALSE)))
          (gimp-floating-sel-anchor selLayer)
         
          (if (= inFileType 0)
            (begin
              (set! outfname (string-append outDir
                                            "/"
                                            (number->string zcnt)
                                            "-"
                                            (number->string hcnt)
                                            "-"
                                            (number->string vcnt)
                                            ".png"))
         
              (file-png-save  RUN-NONINTERACTIVE
                              newImage
                              tmpLayer
                              outfname
                              outfname
                              0 9 1 0 0 1 1 )
              )
            )
         
          (if (= inFileType 1)
            (begin
              (set! outfname (string-append outDir
                                            "/"
                                            (number->string zcnt)
                                            "-"
                                            (number->string hcnt)
                                            "-"
                                            (number->string vcnt)
                                            ".jpg"))
         
              (file-jpeg-save RUN-NONINTERACTIVE
                              newImage
                              tmpLayer
                              outfname
                              outfname
                              0.95 ; JPEG compression level
                              0    ; Smoothing
                              1    ; Optimize
                              1    ; Progressive
                              ""   ; Comment
                              0    ; Subsampling (0-4)
                              1    ; Baseline
                              0    ; Restart
                              0    ; DCT
                              )
              )
            )
     
          (set! vcnt (+ vcnt 1))
          )
        (set! hcnt (+ hcnt 1))
        )
       
      (gimp-image-delete tmpImage)
     
      (set! zcnt (+ zcnt 1))
      )
     
    (gimp-image-delete newImage)
    (gimp-image-undo-group-end inImage)
    (gimp-displays-flush)
  )
)
(script-fu-register
  "script-fu-google-maps-tiles"            ; function name
  "<Image>/Filters/Tiles/_Google Maps"     ; menu label
  "Split an image into tiles suitable\     ; description
   for use with Google Maps API"
  "qwertymodo"                             ; author
  "(c) 2015, qwertymodo"                   ; copyright notice
  "25 May 2015"                            ; date created
  "RGB*"                                   ; image type
  SF-IMAGE      "Image"   0
  SF-DRAWABLE   "Drawable" 0
  SF-ADJUSTMENT "Tile Size (px)"           '(128 8 1024 1 8 0 SF-SPINNER)
  SF-ADJUSTMENT "Max Zoom Level"           '(4 0 10 1 2 0 SF-SPINNER)
  SF-OPTION     "Output File Type"         '("png" "jpg")
  SF-ENUM       "Interpolation (Shrink)"   '("InterpolationType" "cubic")
  SF-ENUM       "Interpolation (Grow)"     '("InterpolationType" "cubic")
  SF-DIRNAME    "Output Folder"            "tiles"
)