Fish CTF Challenge — Solution Flag 1 lactf{7h3r3_m4y_83_50m3_155u35_w17h_7h15_1f_7h3_c011472_c0nj3c7ur3_15_d15pr0v3n} “there may be some issues with this if the collatz conjecture is disproven”
Overview The challenge provides a Python-based ><> (Fish) esoteric language interpreter and a one-line Fish program (the “fisherator”) that checks user input against a hardcoded large integer.
Algorithm (Forward) The fisherator transforms the flag in two stages:
Stage 1 — Base-256 Encoding The flag string is converted into a single big integer by treating its ASCII bytes as a big-endian base-256 number:
ReezS When I take the very first look at this program i was just thinking this must be a basic flag_checker program
so I basically just wrote a script in order to get the flag but all I got is sorry_this_is_fake_flag!!!!!!!!!
I took me more than 4 hours finding sussy stuff in this program. Fortunately, I realized that when I use debugger to run the program with key sorry_this_is_fake_flag!!!!!!!!!, it always returns Yes but when I run the program in my shell with the same key, it returns No.
M1n10n'5_53cr37 Sau khi decompile file minions.apk bằng jadx-gui ta được các source files, kiểm tra file MainActivity nhưng có vẻ file không có gì hữu ích trong việc tìm flag
Từ hint 2 : Any interesting source files? -> Navigation -> Text search -> tìm với từ khóa "interesting"
1 android:text="Look into me my Banana Value is interesting" Vậy nhiệm vụ tiếp theo là tìm xem Banana Value là gì bằng cách tiếp tục sử dụng text search để tìm bằng các từ khóa như Banana, Banana Value, Value, bananavalue,…