TeXyC

ASIS CTF

Task: recover a flag hashed by a custom LFSR-based algorithm embedded in a pdfTeX document. Solution: extract the TeX source and hash values from the PDF, reverse-engineer the LFSR hash with shifted hex encoding (MOP/MEP), then brute-force each 4-character chunk in parallel.

brute_force reverse_engineering pdf tex latex crc lfsr hash pdfTeX multiprocessing

PDF content extraction with pdftotextTeX source code reverse engineeringLFSR-based hash algorithm analysisParallel brute-force with multiprocessing

$ ls tags/ techniques/

brute_force reverse_engineering pdf tex latex crc lfsr hash pdfTeX multiprocessing

PDF content extraction with pdftotextTeX source code reverse engineeringLFSR-based hash algorithm analysisParallel brute-force with multiprocessing

Analysis

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$ python3 exploit.py --target 192.168.1.1 --port 8080
[*] Connecting to target...
[+] Shell obtained!

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