DRG
DRG Online Challenge December 2013 Solution
2014-02-03

We received only one submission for the December challenge. Vytautaus Krakauskas, the standard bearer for which all DRG challenge players will be judged has turned in a correct submission again. By default, but certainly well deserved, bragging rights this month go to Vytautaus Krakauskas, take it away Vytautaus...

To get an acknowledgment, you need to connect from source port 46368, and provide 75025 as an input.

The form page had a comment with Fibonacci sequence "0,1,1,2,3,5..." so I tried entering variuos forms of the next numbers from the sequence but the form was "silent". Then I paid more attention to the wording of the challenge "use F(n)" so I tried using it as a source port with curl, but still no acknowledgment. Tried using hex and swapping the bytes - no answer. Finally wrote a small bash script to try all values which are within a valid port range (n = [1..25]):

url="http://dragonresearchgroup.org/cgi-bin/201312.cgi"
n0=0
n1=1

for ((i=2; i<=25; i++)); do
    n=$((n0+n1))
    curl -o $i.html --local-port $n1 -F "input=$n" -F "Submit=Submit" -F ".action=check_input" "$url"
    n0=$n1
    n1=$n
done

The last reply had a message "Fibonacci sequence submitted correctly".

Thanks as usual :)

For further details on how the challenge was constructed along with notes and write-ups from all challenge players who solved solved the challenge, please see the updated DRG Online Challenge December 2013 page. The newest, DRG Online Challenge February 2014 is now available. Visit the DRG Challenges page for information about all current, future and past challenges.

posted at 8:17 pm | permanent link



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