Cxbx Progress

There was some amount of activity in a private branch in the Cxbx project recently..

I have been talking to a developer, Martin, who has spent some of his extra time fiddling with Cxbx. He was able to get some teaser screenshots from Battlestar Galactica. The game displays the menu, and even some in-game. I won’t get into too many details, but here are a couple screenshots.

Battlestar Galactica - menu 2 Battlestar Galactica - menu 3

Battlestar Galactica - in-game (fullscreen) Battlestar Galactica - in-game (windowed)

I have not started to work on Cxbx on a regular basis — but I think this progress is very motivating, and it is tempting me to boot back up my development setup and take another look after a very long absence.

Many thanks to Martin for the contributions and for allowing me to post about his progress. Cheers.

Chumby Antics

I have been working at Chumby for a few months now. If you have never heard about Chumby – basically, it is a small squishy wifi-internet connected device with a touchscreen and some other nifty hardware features. So, I am around Chumby devices pretty often, obviously, since it is my full time job.

Sometime’s I goof off a little..

This is a video of a small application I made on the Chumby. You touch the screen, and a small blob of “lava” follows your finger around. You basically get the sense of smearing the blobs around the touch screen.

And this is a funny video of a Chumby with two USB dogs humping it.

Function Hijacking via Export Directory

I have been working on a contract that has necessitated the use of function hooking. Basically, I need to intercept an arbitrary program’s usage of a system dll library in order to interject my own logic, and interact with the objects produced by that binary.

There is a nice tool created by Microsoft Research, called Detours. This is basically an API which helps you to perform binary function interception and instrumentation. This API is fairly robust and well thought out, and I use it in this project. However, there is certainly a fair amount of missing functionality.

While testing my application against a popular product that uses the “unicows” library, I stumbled across a very interesting situation during which the Detours method of function interception will not apply.

Basically, unicows has it’s own custom version of GetProcAddress build in. This custom code crawls through the in memory PE header and obtains function offsets by hand. This means that, for dynamically loaded function addresses, using the Detours functionality I am unable to intercept functions loaded at run-time.

So, in order to properly intercept these functions, it was necessary to create an additional API from within Detours. This function needs to crawl through the PE header, and replace the Export Directory entry for a given API with the virtual address of the function you wish to be called, instead. The function will also return the original virtual address, so that you can call that function within your intercepted version.

The new code is here: DetourReplaceExport.txt

So, now I have a working solution for hijacking an API which is linked dynamically using a non-standard GetProcAddress. Yays!

Windows Genuine Advantage hacking

Windows has a great new feature which helps notify you when you may have inadvertently pirated your copy of the operating system. This feature is really handy, because sometimes people will slip and fall and accidentally steal a copy of Microsoft Windows.

Windows Genuine Advantage will detect this situation and provide you with valueable feedback so that you may address the issue by going out and buying a new copy of the operating system and reinstalling.

Here is a screenshot of WGA in action:

Now, I greatly appreciate this information. I for one would immediately take corrective action if my copy of Windows was actually pirated.

Fortunately, sometimes your situation is a little different. Maybe an innocent user has, one way or another, lost possession of their original product key. Tornado, earthquake, fire, air raid, black holes and ninja stars are some possible ways this could occur.

What do you do in this situation? Now, it seems rather silly to go buy another product key – just because you lost yours. It’s a simple misunderstanding.

Luckily, Microsoft was polite and left the binaries for WGA lightly protected. This means you can easily go in and inform WGA that you have, in fact, purchased your copy of Windows.

There are programs out there to make this modification for you. I took a slightly different approach, however, and decided that I would like to keep the warning message bubbles. I just wished to slightly modify the contents of those messages.

Now, whenever I come back to my computer – and sometimes just at random moments – WGA gives me a few words of appreciation. What used to be a depressing accusation of guilt, is now replaced with a friendly greeting! How nice.

The change is simple. Just pop open the WGA app in your favorite hex editor or resource editor, and search for the original messages. Replace with a message of your choice, and voila – your own personal motivational notification program.


Next, just open up task manager and kill the process “WgaTray.exe”. Don’t worry, it is such a user-friendly program that it will automatically restart itself!

DOS “debug” fun

Sometimes you get the urge to do some programming, but you don’t have access to a compiler. Luckily, virtually every Windows PC in the world has a utility called “debug” installed. This little program lets you input 16-bit x86 assembly language, and allows you to write it out to create a .com file. This file can then be executed inside of a DOS shell.

The following is an example of something simple but cool you can do with this program. I will be using some basic DOS interrupts in order to do console input and output. (Lookup ‘DOS interrupt 21h’ on google to find out more).

I’ll highlight everything i’m typing in green so you can try this at home. You won’t need to type the optional comments (anything after the semicolon is ignored), and they get lost when you write the file anyway.


-a 100
1476:0100 mov cl, d7 ; default cl to character 'd7'
1476:0102 mov ah, 6  ; ah:6 is console input/output
1476:0104 mov dl, ff ; dl:ff specifies input
1476:0106 int 21     ; interrupt 21 call
1476:0108 jz 10c     ; skip next instruction if failure
1476:010A mov cl, al ; save result of console input
1476:010C mov dl, cl ; load current character as output
1476:010E int 21     ; interrupt 21 call
1476:0110 jmp 102    ; loop forever!
-r cx
CX 0012
Writing 00012 bytes

Now, when you execute “”, you will see the screen swamped with the funky ‘d7’ ASCII character.

Whenever you type a character, the screen with update to display that character. Try alternating between visible characters and not visible characters (like space). For more fun, try to as quickly as possible type “|/-|/-” (animates like a little progress bar).

Note that you cant really exit the program. Pressing ctrl+c will actually just display a little heart character. It would be easy to modify the code to accept a character (like escape or control+c) to exit, but i’ll leave that up to you :].

This is just one basic thing you can make a .com file do. For a cooler example, check out neetro. Neetro is a little bit more complex than the program above, so it would have been a pain to write using “debug”. The source is instead compiled using nasm.

Here goes

This is my first blog posting. Should get interesting. I won’t bother to explain the title of this blog, because that is sort of the point.