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51d9347 · Jan 7, 2021

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Nov 5, 2020

OUR FIRST WRITEUP :?

Web

Leggos

Points: 100

Description

I <3 Pasta! I won't tell you what my special secret sauce is though!

https://chal.duc.tf:30101

Solution

We are prompted with a page containing some text and an image. Trying to view the source HTML we notice that we can't do a Right Click.

image

No problem, we append in the URL view-source:, so it becomes view-source:https://chal.duc.tf:30101/. Inside the HTML we have a hint saying <!-- almost there -->. We open the source code of an imported JS file and we get the flag.

image

Flag: DUCTF{n0_k37chup_ju57_54uc3_r4w_54uc3_9873984579843}

Misc

Welcome

Points: 100

Description

Welcome to DUCTF!

ssh ductf@chal.duc.tf -p 30301

Password: ductf

Solution

When you connect to the machine a bounch of messages are displayed and you can not execute any command. I tried to scp the whole home directory, but the script that displayed the messages on ssh connection was throwing some error. Looking more closely, the flag is displayed among the other messages.

image

Flag: DUCTF{w3lc0m3_t0_DUCTF_h4v3_fun!}

16 Home Runs

Points: 100

Description

How does this string relate to baseball in anyway? What even is baseball? And how does this relate to Cyber Security? ¯(ツ)/¯

RFVDVEZ7MTZfaDBtM19ydW41X20zNG41X3J1bm4xbjZfcDQ1N182NF9iNDUzNX0=

Solution

I have no idea about baseball, but I know that the string looks like encoding and it's not base 16 (hex). Base64 deconding it gives us the flag.

image

Flag: DUCTF{16_h0m3_run5_m34n5_runn1n6_p457_64_b4535}

Tim Tams

Points : 273

Description


WARNING You will want to turn down your audio for this one!

Download: https://storage.googleapis.com/files.duc.tf/uploads/Clive.wav

File Hash (SHA256): 4C1CC12D002956A83E168CA650B776B55AAC36F2131D0DF617BE7D55DBEF93D1 

SOLUTION

We are given a really noisy wav audio file, I had no clue of solving this at first when my regular audio steganography tools failed. But my teammate came into play with a really good suggestion. QSSTV !

https://storage.googleapis.com/files.duc.tf/uploads/Clive.wav

QSSTV is a utility for dealing with slow scan television signals. From the challenge description, we can pick out a hint “When I eat too many Tim Tams, I get rather slow!”.

I used the following commands to setup qsstv on linux

sudo apt-get install pavucontrol
sudo apt-get install qsstv

We need the pavucontrol utility to be able to open audio files.

Type qsstv on the terminal to open the program and select the audio file you’re going to work with

image

qsstv maps the wav audio into an image and we can see at the top left what appears to be an encoded flag.QHGPS{UHZOYR_Z3Z3_1BEQ}

This is ROT13, we decode the flag to: DUTCF{HUMBLE_M3M3_1ORD}

Flag: DUTCF{HUMBLE_M3M3_1ORD}

Discord

Points : 10

Description

JOIN OUR DISCORD!
image.jpg

Solution

Take a look at the official Discord. It was written in general. discord.png

Flag : DUCTF{c0n6r475_y0u_h4v3_n0w_j01n3d_0ur_4m4z1n6_d15c0rd}

Twitter

Points : 10

Description

Check out our Twitter! Find the post with the flag! You can give us a follow if you like <3

Solution

Take a look at the official Twitter. There are those tweets, but they seem to be base64 encoded.

twitter.png

Decode.

$ python
>>> import base64
>>> text = "RFVDVEZ7aHR0cHM6Ly93d3cueW91dHViZS5jb20vd2F0Y2g/dj1YZlI5aVk1eTk0c30="
>>> print(base64.b64decode(text))
b'DUCTF{https://www.youtube.com/watch?v=XfR9iY5y94s}'

Flag : DUCTF{https://www.youtube.com/watch?v=XfR9iY5y94s}

Forensics

On the spectrum

Points: 100

Description

My friend has been sending me lots of WAV files, I think he is trying to communicate with me, what is the message he sent?

Author: scsc

Attached files:

message_1.wav (sha256: 069dacbd6d6d5ed9c0228a6f94bbbec4086bcf70a4eb7a150f3be0e09862b5ed)

Solution

We get a .wav file and, as the title suggest, we might find the flag in the spectogram. For viewing it I used Sonic Visualizer. I played a little with the settings to view it better.

image

Flag: DUCTF{m4bye_n0t_s0_h1dd3n}