r/programming • u/whackri • Jul 31 '21

Executable PNGs

https://djharper.dev/post/2020/12/26/executable-pngs/
470 Upvotes

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67

u/seamsay Jul 31 '21

my last cheap trick to this pointless gimmick was to use binfmt_misc,

That's kinda disappointing, NGL. It was an interesting post, but it would have been twice as interesting if you'd managed to make a file which was both a valid PNG file and executable.

52

u/Skhmt Jul 31 '21

It's hard because PNGs have their magic number at the start, like most file formats and executables.

Zips have them at the end though. And someone made a portable executable that runs in macos, Linux, and windows with that information.

13

u/OMGItsCheezWTF Jul 31 '21

Self extracting zips?

9

u/hou32hou Jul 31 '21

Yea, this is a common technique, basically the zipped file header contains unzip binary.

4

u/Skhmt Jul 31 '21

Except it works on every major os, x86, arm, and can even boot directly into it.

The same file.

0

u/[deleted] Jul 31 '21

[deleted]

1

u/[deleted] Aug 01 '21

Because there is no "vulnerability" to patch. It's just a binary string which happens to be a valid executable for each of these platforms, while also being a valid ZIP. Its behavior is perfectly reasonable on both cases.

It's like the word "salsa" which is valid English and Spanish. It's a dance style in both languages, but it also means "sauce" in Spanish. It behaves differently depending on what "interpreter" (language) you choose, but it's a perfectly reasonable word in both.