0xL4ugh CTF 2023 Snake
Snake
Here I was given a text file on looking at, I recognazied that it’s a python file exported as manually_decompile.py
those sections are easley eplaned as : 1- Section number — every section is separated with a spacebar and will be numbered accordingly. Each section is a line in the original Python script.
2- Line number in the current section — this line number will be reset for every function.
3-Instruction — the instruction that will be executed.
4-Relevant to conditions — contains the line number where the condition ends.
5-Parameter —the relevant parameter according to the instruction.
here I tried to use Uncompyle6 but there was a problem in magic bites of the original file generated
first I tried to modify them but didn’t work so easley made it manually using this documentation “http://vega.lpl.arizona.edu/python/lib/bytecodes.html”
the translation is section by section -as said before- ever section is code line
here this easely translated into two import lines
import base64
from cryptography.fernet import Fernet
this load a costant value (the flag) into a variable
encMessage=b'gAAAAABj7Xd90ySo11DSFyX8t-9QIQvAPmU40mWQfpq856jFl1rpwvm1kyE1w23fyyAAd9riXt-JJA9v6BEcsq6LNroZTnjExjFur_tEp0OLJv0c_8BD3bg='
make variable (key_bytes) decode and assign its value using base64
key_bytes = base64.b64decode(b'7PXy9PSZmf/r5pXB79LW1cj/7JT6ltPEmfjk8sHljfr6x/LyyfjymNXR5Z0=')
creat an empty list called key
make Var to loop into key_bytes then Xor the char and append it to the key_list
for k_b in key_bytes:
key.append(k_b^160)
then turn key into bytes
make a var fernet and call Fernet method with the key passed to it
that decrypts the message using fernet then store this in decMessage
Finally print the the flag and close the program
import base64
from cryptography.fernet import Fernet
encMessage=b'gAAAAABj7Xd90ySo11DSFyX8t-9QIQvAPmU40mWQfpq856jFl1rpwvm1kyE1w23fyyAAd9riXt-JJA9v6BEcsq6LNroZTnjExjFur_tEp0OLJv0c_8BD3bg='
key_bytes = base64.b64decode(b'7PXy9PSZmf/r5pXB79LW1cj/7JT6ltPEmfjk8sHljfr6x/LyyfjymNXR5Z0=')
key=[]
for k_b in key_bytes:
key.append(k_b^160)
key=bytes(key)
fernet = Fernet(key)
decMessage = fernet.decrypt(encMessage).decode()
print(decMessage)
And here you are your flag
