Time Travel (90 pts)


Problem

I tried setting up Google Apps for TJCTF a while ago, but it wasn't working. Don't worry, I'm pretty sure it's fixed now.


Solution

From the problem statement, we are given the idea of time travel, which brings to mind the Wayback Machine. Then, from the hint, we get that there is something about a <meta> tag, and since it's Google Apps we know we're supposed to look at <meta name="google-site-verification">.

I wrote a quick script to mine this data from the wayback machine site:

from bs4 import BeautifulSoup

import requests

url = 'https://web.archive.org/web/*/tjctf.org'
baseurl = 'https://web.archive.org'
r = requests.get(url)

data = r.text

soup = BeautifulSoup(data)

for link in soup.find_all('a'):
    a = link.get('href')
    print(a)
    if 'tjctf' in a and 'web' in a:
        r2 = requests.get(baseurl+a)
        data2=r2.text
        ind = data2.find('google–site–verification')
        print(data2[ind:ind+100])

Although it takes a while to run, it's easier than manually clicking through all those links. We soon see that one of the "verification codes" is longer than the rest: dGpjdGZ7dzFzaF9pX2MwdWxkX3R1cm5fYjRja190MW0zfSAg. We convert from base 64 to ascii for the flag.


Flag

tjctf{w1sh_i_c0uld_turn_b4ck_t1m3}

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