DEB package BGGP3/4/5/6

[dominikfhnw]

Entry Info

• Date: 17.1.2026
• BGGP Challenge: 3+4+5+6
• Name: dominikr
• Contact Info: Discord dominikr, github dominikfhnw
• Online Presence: -
• Writeup Link: https://github.com/dominikfhnw/bggp6-writeup/tree/main/deb (WiP)

File Info

• Target File Type: Debian Package and shell script
• Target File Size: 182 bytes
• SHA256 Hash: ab8040e9fab2ca6e6c39045d66bb3290dec2f375bb9b4e14ec750e20b8651c29

File Contents

Please encode the file as Base64

MC45MzY2NgoxNzAKH4sICApjdXJsIC1MIDZsLmFsCgDt0wEHwlAUBeAL4P2KizGCbVUPCSIIGAiE
zX1XPb3e5u6mv98CoAA25n0HzvkBh7qo0gWYw66En9bV1kIyiaPQ3SuTvoT32IZg6pYe7W0c1lxY
Bt/Fb4VFSnphHweFOVj77/+2gkkk5LBYFVldn09mYMVGBfNrmeOYAz1d8JEbQw7p7Qz1mG3QmgYW
IvkAJjMRewAIAAA=

Environment Info

Target Software and Version

Debian GNU/Linux or any derivative like Ubuntu

Does not work with dpkg from busybox

Environment Setup

Most commands must be run as root. Use a VM and not your regular distro...

Additional Info

Try to install the deb/output for BGGP6:

root@VM:/tmp/bggp6/writeup/deb# dpkg -i bggp456.deb
dpkg: warning: parsing file '/var/lib/dpkg/tmp.ci/control' near line 4 package '6':
 missing 'Description' field
dpkg: warning: parsing file '/var/lib/dpkg/tmp.ci/control' near line 4 package '6':
 missing 'Maintainer' field
(Reading database ... 138190 files and directories currently installed.)
Preparing to unpack bggp456.deb ...
/var/lib/dpkg/tmp.ci/preinst: 5: Syntax error: EOF in backquote substitution
dpkg: error processing archive bggp456.deb (--install):
 new 6 package pre-installation script subprocess returned error exit status 2
Errors were encountered while processing:
 bggp456.deb

Check BGGP4:

root@VM:/tmp/bggp6/writeup/deb# ls -l bggp456.deb 6
-rw-r--r-- 1 root  root  182 Jan 17 01:26 6
-rw-r--r-- 1 root root 182 Jan  8 14:30 bggp456.deb

BGGP6 is implemented as a shellscript polyglot (embedded in the header of the gzip file which is part of the deb):

# bash 6
6: line 1: 0.93666: command not found
6: line 2: 170: command not found
6: line 3: $'\037\213\b\b': command not found
Another #BGGP6 download!!!!!! Hi @binarygolf https://binary.golf/6
6: line 5: $'\352\226\036\355m\034\326X\006\337\305o\205EJza\037\a\2059X\373\357\377\266\202I$\344\260X\025Y]\237Of': command not found
6: line 5: $'3\021{\b': command not found
6: line 5: $'\355\323\001\a\302P\024\005\340\v\340\375\212\2131\202mU\017': command not found

Edit: It also does BGGP3 by crashing dpkg with an error message, as seen above

[dominikfhnw]

I didn't submit these two variants separately:

• 58 byte minimal deb
• 125 byte deb with code execution while executing it with dpkg -i
  See https://github.com/dominikfhnw/bggp6-writeup/tree/main/deb#odds--ends for the two files