Category: MISC/Networking
Author: Amogh Umesh
Answer / Flag: WEC{7cp_h4nd5h4k35_4r3_fun}
You are a secret agent trying to gain access to a highly secure facility where the Web Enthusiasts' club is headquartered. In order to infiltrate their network, you must crack a TCP challenge. To practice your espionage skills, we've provided you with a docker image that mimics the server image, but without the flag. Can you use your cunning and expertise to crack the WEC code and gain access to the network? Good luck, agent.
docker run --cap-add NET_ADMIN -d -p 80:80 am0gh/network_magic
Dockerfile: https://drive.google.com/file/d/1LWs9cJ-mz0xwdZa7fKQJpxw2ZQdHENrA/view?usp=sharing
Explore the docker container and you can find out that server blocks all tcp packets if they dont start with sequence number 0x00574543. So we need to send a packet with sequence number 0x00574543 make 3 way TCP handshake and make GET request for flag.html. Solution given here.