Incognito wtfCTF 2021: H3ll0R3v

H3ll0R3v

Category: Reverse

chal

100 points

Hello bois!

Author: Xyroscar

file: Hello

Solution

Given file is a python bytecode.

file Hello.pyc 
Hello.pyc: python 3.8 byte-compiled

I’ve used uncompyle6 to get the source code as below.

(ctf) [email protected]:~/tmp$ uncompyle6 Hello 
# uncompyle6 version 3.7.4
# Python bytecode 3.8 (3413)
# Decompiled from: Python 3.9.1+ (default, Feb  5 2021, 13:46:56) 
# [GCC 10.2.1 20210110]
# Embedded file name: Hello.py
# Compiled at: 2021-05-19 07:23:46
# Size of source mod 2**32: 1923 bytes



def main(input):
    j = -4
    for c in input:
        if j == 1:
            if c != 'Z':
                exit(43)
            else:
                if j == -7:
                    if c != 'w':
                        exit(133)
                    else:
                        if j == -5:
                            if c != 'f':
                                exit(42069)
                            else:
                                if j == -4:
                                    if c != 'C':
                                        exit(11037)
                                else:
                                    if j == 7:
                                        if c != 'R':
                                            exit(9001)
                                        else:
                                            if j == -2:
                                                if c != 'F':
                                                    exit(11037)
                                            if j == -1 and c != '{':
                                                exit(11037)
                                    if j == 4 and c != '3':
                                        exit(11037)
                        elif j == 0 and c != '3':
                            exit(11037)
                else:
                    if j == -3:
                        if c != 'T':
                            exit(82)
                        if j == 2:
                            if c != '_':
                                exit(11037)
                        if j == -6:
                            if c != 't':
                                exit(133)
                        if j == 6:
                            if c != 'E':
                                exit(133)
                    elif j == 9 and c != '3':
                        exit(7223)
        else:
            if j == 3:
                if c != 'R':
                    exit(133)
                if j == 5:
                    if c != 'V':
                        exit(133)
                if j == 8:
                    if c != '5':
                        exit(6738)
            elif j == 10:
                if c != '}':
                    exit(1111)
            j += 1
    else:
        print('Hello World')
# okay decompiling Hello.pyc

I’ve made some changes in the code. Not sure if it’s uncompyle6 thing or it was intended, but I had also correct some indentations. I’ve ended with below code, which gave me the flag.

def main(input):
    j = -15
    for c in input:
        j += 1
        if j == 1:
            if c != 'Z':
                print('Z', end='')
                continue
        if j == -7:
            if c != 'w':
                print('w', end='')
                continue
        if j == -5:
            if c != 'f':
                print('f', end='')
                continue
        if j == -4:
            if c != 'C':
                print('C', end='')
                continue
        if j == 7:
            if c != 'R':
                print('R', end='')
                continue
        if j == -2:
            if c != 'F':
                print('F', end='')
                continue
        if j == -1 and c != '{':
            print('{', end='')
            continue
        if j == 4 and c != '3':
            print('3', end='')
            continue
        if j == 0 and c != '3':
            print('3', end='')
            continue
        if j == -3:
            if c != 'T':
                print('T', end='')
                continue
        if j == 2:
            if c != '_':
                print('_', end='')
                continue
        if j == -6:
            if c != 't':
                print('t', end='')
                continue
        if j == 6:
            if c != 'E':
                print('E', end='')
                continue
        if j == 9 and c != '3':
            print('3', end='')
            continue
        if j == 3:
            if c != 'R':
                print('R', end='')
                continue
        if j == 5:
            if c != 'V':
                print('V', end='')
                continue
        if j == 8:
            if c != '5':
                print('5', end='')
                continue
        if j == 10:
            if c != '}':
                print('}', end='')
                continue
    else:
        print('Hello World')

main('11111111111111111111111111111111111111111')

Output:

wtfCTF{3Z_R3VER53}Hello World

Flag

wtfCTF{3Z_R3VER53}

Privacy Policy
luc © 2021