Bingolfing

For this last years Binary Golf Grand Prix the goal was to: Create the smallest self-replicating file. Requirements: Produce exactly 1 copy of itself Name the copy “4” Not execute the copied file Print, return, or display the number 4 I sat down with some beer, as one does, and resolved that my personal twist on the challenge would be to not just do a single filetype, but a chain of obscure filetypes. I scripted out enumeration of all of the default file handlers for Windows 7 in a blog I titled Obscure Windows File Type.

For this years Binary Golf Grand Prix I started off by learning to fuzz properly, use a debugger properly, and various tooling. The objective was originally to hit all of the bonus points: +1024 pts, if you submit a writeup about your process and details about the crash +1024 pts, if the program counter is all 3’s when the program crashes +2048 pts, if you hijack execution and print or return “3” +4096 pts, if you author a patch for your bug which is merged before the end of the competition Well, life happens, and I ended up using the majority of my 2 week break from work doing more important things like taking care of my sick infant son (He’s doing much better now).

Let’s build the smallest WASM / GBA ROM / 7Zip polyglot in 584 bytes for the Binary Golf Grand Prix 2021. Rules: The host file must be a binary executable. This is any binary executable that stores either machine code (such as ELF, PE etc.) or bytecode (wasm, pyc, etc.) Overlap with at least one additional file of any type to create a polyglot. The host binary must return or print the number 2 when executed. Entry: Valid WebAssembly binary that calls host.print(2) Gameboy Advance ROM that fills the screen with Green 7Zip Archive containing a single empty file named “a” Download: bggp.wasm (584 Bytes)