csaw21

Writeups for CSAW 2021 CTF

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Writeup by: OreoByte

Team: OnlyFeet

Writeup URL: GitHub


Veronica sent a message to her client via their website's Contact Us page. Can you find the message?

Author: moat, Pacific Northwest National Laboratory

Using Wireshark Decrypt The SSL Traffic

Using the given files sslkeyfile.txt and ContactUs.pcap we can start to decrypt the pcap.

Navigate through Edit -> Preferences -> Protocols -> TLS -> (Pre)-Master-Secret log filename, click browse and select the sslkeyfile.txt file.

Decrypt TLS in Wireshark\

Find the decrypted flag in the packet capture.

Search for the Flag\


Using Tshark

You can do the same thing but with tshark:

  1. Decrypt Pcap into a new file
    • tshark -r ContactUs.pcap -V -x -o tls.keylog_file:key.log > results
  2. grep to win for the flag
    • grep 'flag{' results

Tshark\


Victory

Submit the flag and claim the points:

flag{m@r$hm3ll0w$}