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[Write-Up] RC3 CTF : Bridge of Cyber

November 21, 2016 | Posted in How to

Tittle : Bridge of Cyber


Category : Misc


Point : 200


Description : Welcome to the "Bridge of Cyber"! It's the same concept as the "Bridge of Death" in Holy Grail. Our DNS servers aren't very good at their job because they ask more questions then they answer. Let's see if you can get the flag from our DNS.



Nameserver: ns-920.awsdns-51.net


Domain: misc200.ctf.rc3.club



HINT:

  • Dig deeper

  • Subdomains


====================

[POC]


Need to find the answer from TXT zone record using dig then using Google-FU!

$ dig +noall +answer @ns-920.awsdns-51.net misc200.ctf.rc3.club any

misc200.ctf.rc3.club. 172800 IN NS ns-1526.awsdns-62.org.
misc200.ctf.rc3.club. 172800 IN NS ns-1842.awsdns-38.co.uk.
misc200.ctf.rc3.club. 172800 IN NS ns-489.awsdns-61.com.
misc200.ctf.rc3.club. 172800 IN NS ns-920.awsdns-51.net.
misc200.ctf.rc3.club. 900 IN SOA ns-1526.awsdns-62.org. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
misc200.ctf.rc3.club. 300 IN TXT "What is the air-speed velocity of an unladen swallow"

That’s Monty Python quote in TXT zone record, let’s check it from Google.

image

That’s a clue from Google (European swallow). Then the answer for "What is the air-speed velocity of an unladen swallow" is European.

$ dig +noall +answer @ns-920.awsdns-51.net european.misc200.ctf.rc3.club any

european.misc200.ctf.rc3.club. 300 IN TXT "The roundest knight at king arthurs table was sir cumference. He acquired his size from too much __"

The next result from TXT is a joke. Googling for the entire Googling for the entire text got “pi  as the answer.

$ dig +noall +answer @ns-920.awsdns-51.net pi.european.misc200.ctf.rc3.club any

pi.european.misc200.ctf.rc3.club. 300 IN TXT "What is it that no man ever yet did see, which never was, but always is to be?"

The next hint is another puzzle, of which the answer is ‘tomorrow

$ dig +noall +answer @ns-920.awsdns-51.net tomorrow.pi.european.misc200.ctf.rc3.club any

tomorrow.pi.european.misc200.ctf.rc3.club. 300 IN TXT "My favorite things in life don't cost any money. It's really clear that the most precious resource we all have is ___"

This one is a quote from Steve Jobs and the answer for this puzzle is ‘time

$ dig +short +answer @ns-920.awsdns-51.net time.tomorrow.pi.european.misc200.ctf.rc3.club any

time.tomorrow.pi.european.misc200.ctf.rc3.club. 300 IN SPF "RC3-2016-cyb3rxr05"


Finally get the flag at the last moment.



FLAG: RC3-2016-cyb3rxr05

Taged in: bridge, ctf, Cyber, rc3ctf, writeup