- Category:
misc - Challenge author: Kalle Fagerberg
Santas wrapping machine got bonkers and used all different papers it could find. Can you help unwrap this mess?
sudo apt update
sudo apt install make p7zip-full gzip zip lz4 xz-utils
# Seem to have forgotten brotli in challenge. Oops.
#sudo apt install brotliThe long extension is a givaway; if you know what they mean:
.7z: 7zip compressed archive (https://www.7-zip.org/).lz4: LZ4 compression (https://www.lz4.org/).zip: Well known ZIP compressed archive (https://en.wikipedia.org/wiki/ZIP_(file_format)), used and supported near to everywhere..br: Brotli compression (https://github.com/google/brotli), most commonly used by websites as a GZIP alternative for even smaller downloads..gz: GZIP compression (https://www.gzip.org/), commonly used as de-facto compression in GNU/Linux eco-system and by websites..b64: Non-standard extension of Base-64 encoding. Actually only increases the file size by ~33%, but uses a very limited set of ASCII characters making it very portable..xz: XZ compression (https://tukaani.org/xz/) which trades off speed for better compression compared to many other algorithms.tar: TAR archive, sans-compression (https://en.wikipedia.org/wiki/Tar_(computing)), used to bundle/archive files and directories, where resulting "tarball" file size is always nearly equal to the sum of its content.
To obtain the flag.txt hidden in these nested formats you need the above
dependencies. If on Windows, suggest running inside a Docker container, such as
docker run --rm -it -v ./:/root/ -w /root ubuntu:20.04 bash7z x flag.tar.xz.b64.gz.br.zip.lz4.7z
lz4 flag.tar.xz.b64.gz.br.zip.lz4
unzip flag.tar.xz.b64.gz.br.zip
# Seem to have forgotten brotli in challenge. Oops.
#brotli flag.tar.xz.b64.gz.br
gunzip flag.tar.xz.b64.gz
base64 -d flag.tar.xz.b64 > flag.tar.xz
# The -J flag tells tar to use xz
tar -xJvf flag.tar.xz
cat flag.txt