We were given a website that has a countdown, viewing the page source and the flag was in a comment

 Caesar. Probably a caesar shift cipher, use 

Google “UnduplicitousCorp” result in a YouTube Channel. Flag was found at about channel page.

Login code was client sided at js/login.js. The code seems to use md5, finding the reverse lookup of the hashes and obtain the username and password flag format is CDDC20{username_password}

Flag can be found in the slack text channel

Download Organisation_Chart.pdf found in the website. Opening this pdf file in photoshop allow you to extract the flag image.

This challenge, we are given an image file that is black. Flag can be found in the comment metadata of the image. Can be view by right clicking img.jpg > Properties > Details > Comments. Mirror the text to obtain the flag.

netcat to given domain and port to obtain the flag

hq hm kbq jipoox yhnnhatoq qb abkmqjtaq p mijhim bn hknijikaim, ipaS yidikyikq tdbk hqm djIyiaimmbJ pky ipas mhcdoi hk hqmion. hn, pnqij ybhkg mb, bkI mhcdox rkbarm btq poo qsi aikQjpo hknijikaim pky djimikqm bki’m ptyhikai vhqs qsi mqpjqhkg-dbhkq pky qsi abkaoTmhbk, bki cpx dJbytai p mqpjqohKg, qsbtgs dbmmhlox p cijiqjhahbtM, inniaq.

My teammate Ethan found out that the ciphertext was encrypted with a substitution cipher. Use 

 and group all capitalized letters to obtain flag.

Viewing the pcap in wireshark show us a bunch of HTTP traffic including images. Export objects and flag is found in one of the images.

Also similar to the previous network challenge. Extracting the HTTP object and the flag can be found in a text file.

Download the virtual machine and run the machine. The flag can be found in the .bashhistory in user home directory.

My teammate Ethan multiple 2^31-1 by 2 and able to get the program to print out 0 which results in the flag. However, the answer is simple, 2^32-1.

Key: GZ2gXZ3bD2qqNyNxXb5LJ8HfHQtTL5VHA Execute the binary and feed the key

Reverse Search Image in Yandex reveal that this is a Dancing Men Cipher. Decrypt the image to obtain the flag.

Annotated PDF have bolded text in some pages, combine all of them to obtain flag

Send a post request to website with Authorization header set to the base64 of “Yes”

My teammate Jun Yan discovered the website 

tt7ncdhj367dh8mu2pb6.unduplicitouscorp.tech

 by using a internet tools to find subdomains, under this domain there is a 

flag.tt7ncdhj367dh8mu2pb6.unduplicitouscorp.tech

TopSecret is a .ad1 file, can be view in FTK Imager software and flag is hidden in a text file with lorem texts.

FSB also known as Format String Bug, able to leak out flag by inputting many 

 is mountable file, mount it to extract the content. In the folder, there is a test.zip which is an excel file document. Rename test.zip to test.xlsx to obtain the flag.

A Maxicode QR Code, invert the image and use online decoder

Great Sphinx of Unduplicitous Corp (Unsolved)

We were given a website where we can upload GIF

The website has File Upload Vulnerability, you are able to upload a simple backdoor code by modifying the Content-Type header.

After uploading the backdoor, we can execute our commands in the url.

Use des decryptor tool online, key is “ilovedes” 

Using Ghidra, a free and open source reverse engineering tool. It was able to reconstruct some of the source code back, however we were not sure on how to go on from here.

The website above solves some challenges that my team did not, you may want to read it.

Cyber Defenders Discovery Camp (CDDC) Capture-The-Flag competition

CDDC2020 CTF Writeup