$ objdump -d payload_decrypted.bin | less The binary is small (≈2 KB). Scanning the disassembly reveals a :
def xor(data, key): return bytes(a ^ b for a, b in zip(data, itertools.cycle(key))) codsmp.zip
# Grab any flag inside the inner archive for f in inner_dir.rglob('*'): if f.is_file(): data = f.read_bytes() flag = extract_flag(data) if flag: print(f'[inner] Flag in f.relative_to(work): flag') $ objdump -d payload_decrypted
Scope – This write‑up assumes you have obtained the codsmp.zip archive from a CTF or a reverse‑engineering challenge. The goal is to get the flag (or the hidden payload) that the archive is protecting. Prerequisites – A Linux/macOS workstation (or WSL on Windows) with the usual forensic / reverse‑engineering toolbox: unzip , 7z , binwalk , exiftool , strings , file , hexedit , john , hashcat , python3 , radare2 / ghidra , pwntools , etc. 1. Initial Inspection $ file codsmp.zip codsmp.zip: Zip archive data, at least v2.0 to extract, compressed size 1.3 MB, uncompressed size 5.6 MB, name=codsmp.zip Prerequisites – A Linux/macOS workstation (or WSL on
$ strings -a payload_decrypted.bin | head -20 /lib64/ld-linux-x86-64.so.2 libc.so.6 GLIBC_2.2.5 puts printf ...