data-exfiltration

An encoding and a decoding tool for use in storing data in PNG files.

File Index

• makefile is the makefile. Simple run make and you should be good to go.

• encoder.c contains the main() for the encoding program. The encoder takes in two arguments: the name of the PNG file that will hide the payload, and the name of the payload itself. It creates a file called output.png that contains the hidden payload. It's usage is

./encoder <input PNG filepath> <payload filepath>.

• decoder.c contains the main() for the decoding program. The decoder takes in two arguments: the name of the PNG file that is hiding a payload, and the name of the file that the payload will be dumped into. It creates a file with the name given that will contain the hidden payload. It's usage is

./decoder <input PNG filepath> <output payload filepath>

• png.h contains my own custom interface to the PNG file format. There are many like it, but this one is mine.

What all can I exfiltrate with these programs?

Really anything. I tried it on some generic text, executables, and even another PNG file. Pretty much anything under the PNG maximum allowed chunk size of about 4 GB. I think that in my code it limits you to a payload file of 2 GB in size. Most operating systems won't let you allocate and fill 4 GB of physical memory in user space anyways but, hey, you can try. Besides, who is going to see a 4 GB PNG file and think, "Yeah that's normal"?

If you really need to store a ridiculous amount of data in a PNG file, you can! Just break your payload up into several files (each under the 2 GB limit) and run the encoder multiple times. Take the output PNG from the first run and use it as the input PNG for the second run, and so on.