PicoCTF Writeup – fixme1.py
# Information:
CTF Name: PicoCTF
CTF Challenge: fixme1.py
Challenge Category: General Skills
Challenge Points: 100
Beginner picoMini 2022.
# Used Tools:
- Python3
# Challenge Description:
Fix the syntax error in this Python script to print the flag. Download Python script
Hints:
# Writeup:
This is a challenge to help learn how to read python code.
As you probably know, python is a language that uses indentation to identify blocks of code. In java, they use {}, in python indentation.
Below you have the python3 code:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | import random def str_xor(secret, key): #extend key to secret length new_key = key i = 0 while len(new_key) < len(secret): new_key = new_key + key[i] i = (i + 1) % len(key) return "".join([chr(ord(secret_c) ^ ord(new_key_c)) for (secret_c,new_key_c) in zip(secret,new_key)]) flag_enc = chr(0x15) + chr(0x07) + chr(0x08) + chr(0x06) + chr(0x27) + chr(0x21) + chr(0x23) + chr(0x15) + chr(0x5a) + chr(0x07) + chr(0x00) + chr(0x46) + chr(0x0b) + chr(0x1a) + chr(0x5a) + chr(0x1d) + chr(0x1d) + chr(0x2a) + chr(0x06) + chr(0x1c) + chr(0x5a) + chr(0x5c) + chr(0x55) + chr(0x40) + chr(0x3a) + chr(0x58) + chr(0x0a) + chr(0x5d) + chr(0x53) + chr(0x43) + chr(0x06) + chr(0x56) + chr(0x0d) + chr(0x14) flag = str_xor(flag_enc, 'enkidu') print('That is correct! Here\'s your flag: ' + flag) |
By performing a quick read of the code. I noticed a miss indentation on the last line, the print.
The previous line is in the “normal” block, not inside any function or anything. And what is done on that line is simply assign the variable flag to a string value.
After that line, we have a print with 2 spaces (some indentation). However, this print is also on the “normal” block, therefore it should be on the same “level” (indentation speaking) as of the flag variable.
To solve this, I simply fixed the indentation by removing the 2 spaces before the last print.
Below you have the last part (fixed) of the code snippet above:
flag = str_xor(flag_enc, ‘enkidu’)
print(‘That is correct! Here\’s your flag: ‘ + flag)
And the flag is:
If you want to checkout the code for the python 3 script with me solution, take a look here.
Thank you very much for reading!
Cheers,
MRegra
