To_Be_And_Not_To_Be

To Be And Not To Be:Miscellaneous:261pts

To be and not to be, that is the question. (Note: the correct input solution to this challenge is alphanumeric.)

Connect with:

nc challenge.nahamcon.com 32518

Solution

接続先が与えられるのでnetcatで繋ぐと以下のようであった。

$ nc challenge.nahamcon.com 32518
we've got a funky shell over here, and we're going to feed it your input!
the shell will run the following:
console.log(%s !== (%s));
And the flag is `flag{<md5>}, where <md5> is the md5sum of the input that prints true!
>>>A
yeah that's gonna be a no from me dog
>>>aaaaa
way too much or bad dater...
>>>0
Nope!

console.log(%s !== (%s));をtrueにすればよいようだ。
JavaScriptにはNaNなるものがあり、これらの厳密な比較はfalseとなる。

$ node
~~~
> 1 === 1
true
> NaN === NaN
false
> NaN !== NaN
true

NaNが答えのようだ。

$ nc challenge.nahamcon.com 32518
we've got a funky shell over here, and we're going to feed it your input!
the shell will run the following:
console.log(%s !== (%s));
And the flag is `flag{<md5>}, where <md5> is the md5sum of the input that prints true!
>>>NaN
Congrats!

$ echo -n 'NaN' | md5sum
7ecfb3bf076a6a9635f975fe96ac97fd  -

ハッシュを指定された形式にするとflagとなった。

flag{7ecfb3bf076a6a9635f975fe96ac97fd}