Run with (using the included sample files) :
./gen_poly.py --out magic.pdf --in "CAMUS, Albert - The Stranger.pdf" --message monalisa_joconde_ascii.txt --zip hyeronimus_bosch.jpg --header sample.nes
Let's break this up :
--outis the path/name of the resulting file – which will be a perfectly valid PDF file--inis your original PDF file- in my example : The Stranger, by Camus
--messageis the plaintext message that should appear when the resulting file will be opened in a hex editor, or directlycat-ed in a terminal- in my example : a splendid rendition of the Mona Lisa in ASCII
- additional feature : a command to directly output this message (and only this message without any surrounding gibberish) will be added just before the message itself
- this command looks like
tail -c +offset of message in file magic.pdf | head -c length of message
- this command looks like
--zipis the (list of) file(s) that are to be zipped and appended in the original PDF- in my example : a famous painting by Hyeronimus Bosch
- additional feature : when unzipped, the original PDF will also appear, although it is not duplicated in the resulting file – ain't this magic :)
--headeris the file that is to be included at the beginning of the file, before the PDF itself- in my example : a NES game, for emulators. So that you can also the PDF in an emulator !
Still, with all this stuff appended to and included at the beginning of the PDF, it stays valid and viewable in any standard PDF viewer (such as Adobe Reader, Preview on macOS, etc...) All of this is possible thanks to the fact that the PDF header does not have to be at the beginning of the file, for it to be a valid PDF.
Inspired by PoC||GTFO-0x14, though this would seem very basic to @angea