Rating:

MetaCTF 2021

Sharing Files and Passwords (150pts)

Description:

FTP servers are made to share files, but if its communications are not encrypted, it might be sharing passwords as well. The password in this pcap to get the flag

Included Files:

ftp_challenge.pcapng

Step 1 - Explore Pcap Data:

As with every .pcap or .pcapng file, we want to open it in Wireshark and explore the packets first. <br /> <br /> image

We can see there is indeed FTP communications in the packet capture, so we can filter our search and begin to look for a plaintext flag.

Step 2 - Filter and Find:

By using ftp in the filter bar, we can filter to look at only FTP connections. We can now right-click and follow the TCP stream (since FTP uses TCP for connection) and see the requests and responses being made between the two clients.

image

It does indeed look like there is a password being sent in plaintext over the network, and we can now use that to solve.

Additionally, we could have just looked at the info column without following any streams, as the password is also shown there.

image

<details> <summary> Flag Spoiler </summary> ftp_is_better_than_dropbox </details>

Learning Takeaways

We learned that FTP may send unencrypted credentials over a network - it's important to use SFTP or an equivalent secure method of transferring files to prevent malicious users from having access to credentials.

Original writeup (https://github.com/team23ctf/writeups/blob/main/metactf2021/Sharing%20Files%20and%20Passwords/Sharing%20Files%20and%20Passwords.md).