PicoCTF - m00nwalk

tags: PicoCTF CTF Misc

Challenge: m00nwalk

Description & Hint

Decode this message from the moon. Hint:

• How did pictures from the moon landing get sent back to Earth?
• What is the CMU mascot?, that might help select a RX option

Background

慢掃描電視 - slow-scan television(sstv)

Source code

Exploit - qsstv +

1. First, I thought it might be a mp3stego problem but found nothing. So, I tried to find the write up about this question.
2. Use QSSTV

    $ sudo apt-get install pavucontrol
    $ sudo apt-get install qsstv
    $ pactl load-module module-null-sink sink_name=virtual-cable
    22
   

3. The Setting
   • pavucontrol

      $ pavucontrol # then it should show up a GUI interface
     

     

   • Note that must set the output from Null(Monitor of Null Output)

• qsstv

    $ qsstv # again, it should show up a GUI interface
  

  * Note that the Audio Interface should be PaulseAudio

  • Then we can start to record in qsstv and set the command

      $ paplay -d virtual-cable message.wav
    

1. After finish the recording, we’ll got a png file that contains the flag
   • Note that, the sequence of the audio is message.wmv $\to$ pavucontrol $\to$ qsstv. The main job of pavucontrol is to manage the audio that we play and send it to the right application(e.g. qsstv)

Reference

m00nwalk - write up