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CTF

DownUnderCTF 2020: Pretty Good Pitfall

Pretty Good Pitfall

200 points

Author: k0wa1ski#6150

PGP/GPG/GnuPG/OpenPGP is great! I reckon you can't find the message, because it looks scrambled!

Attached files: flag.txt.gpg (sha256: dad03ac28b7294c8696eeac21d11159c3dcfc8ed226438804fe82b4fb9f6ad87)

Solution

gpg --output doc flag.txt.gpg

DUCTF{S1GN1NG_A1NT_3NCRYPT10N}

DownUnderCTF 2020: Addition

Addition

200 points

Author: n00bmaster

Joe is aiming to become the next supreme coder by trying to make his code smaller and smaller. His most recent project is a simple calculator which he reckons is super secure because of the "filters" he has in place. However, he thinks that he knows more than everyone around him. Put Joe in his place and grab the flag.

https://chal.duc.tf:30302/

Solution

Ok, so we've got a webpage with calculator and a hint it's written in python.

I've found the flag using this payload '{}'.format(open('main.py','r').read())

DUCTF{3v4L_1s_D4ng3r0u5}

DownUnderCTF 2020: In a pickle

In a pickle

200 points

Author: n00bmaster

We managed to intercept communication between und3rm4t3r and his hacker friends. However it is obfuscated using something. We just can't figure out what it is. Maybe you can help us find the flag?

data

(dp0
I1
S'D'
p1
sI2
S'UCTF'
p2
sI3
S'{'
p3
sI4
I112
sI5
I49
sI6
I99
sI7
I107
sI8
I108
sI9
I51
sI10
I95
sI11
I121
sI12
I48
sI13
I117
sI14
I82
sI15
I95
sI16
I109
sI17
I51
sI18
I53
sI19
I53
sI20
I52
sI21
I103
sI22
I51
sI23
S'}'
p4
sI24
S"I know that the intelligence agency's are onto me so now i'm using ways to evade them: I am just glad that you know how to use pickle. Anyway the flag is "
p5
s.

Solution

I've written python script to resolve this challenge:

import re
i = 0

string_re = re.compile("S'(.*)'")

with open('data', 'r') as f:
for line in f:
i += 1
finding = string_re.findall(line)
if finding:
print(finding[0], end='')
elif line.startswith('I'):
print(chr(int(line[1:])), end='')

DUCTF{p1ckl3_y0uR_m3554g3}