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dc2020q - biooosless reversing shellcoding

by reyammer

This was a jeopardy challenge, part of dc2020q. (CTFtime)

Points: 145
Was solved by: 29 teams
PCAPs: download

You may spawn the server:

On your laptop
  • Install docker
  • docker pull archiveooo/pub:biooosless (docker-saved download)
  • docker run -d --name biooosless archiveooo/pub:biooosless
  • Local IP: docker inspect biooosless -f '{{ .NetworkSettings.Networks.bridge.IPAddress }}'
  • Connect to that IP:6543 — Remember to docker rm -f when done.
On your laptop (full source)
  • Install docker and pip install PyYAML coloredlogs
  • git clone https://github.com/o-o-overflow/dc2020q-biooosless-public
  • cd biooosless
  • ./spawner --log-level=INFO
  • Connect to the ip:port displayed
Hosted by OOO Right now we're asking players to login first.

Description

Q: can you read from a floppy?


A: LOL, yes, just mount it and read its content ...


Q: OK. But what if there is no OS?


A: ahah, ROFLT, yes, just invoke BIOS routines and read it ...


Q: OK. But if there is no BIOS?


A: F. M. L.


Hint: this is mostly a shellcoding challenge, not a reversing one.


Hint #2: the files in the bundle allow you to test everything locally -- no need to hammer the server. Please be nice!

line_weight local-setup.tgz

Hints

None yet :(
If you wish, you can contribute some.

Source

Spoilers ahead! Code for this challenge is publicly available.