Hi guys,
I tried for fun to write a parallel brute-force password cracker. I
particularly thought that if I can generate lazily all the possible
combinations, I'll have no trouble finding the match (memory-wise).
something like this:
(def token-types "All the possible characters grouped."
{:numbers (->> 10 range (apply str) seq)
:letters {:upper (seq "ABCDEFGHIJKLMNOPQRSTUVWXYZ")
:lower (seq "abcdefghijklmnopqrstuvwxyz")}
:punctuation (seq ".,?!-")
:arithmetic (seq "+-*/%=")
:fancy (seq "@#$^&()~")} )
(definline generic-pred "" [tester candidate]
`(when-let [x# (~tester ~candidate)] x#))
(defn brute-force "Tries a brute-force attack of a collection of the
specified size. check-pred should return the match when it finds one,
otherwise nil."
([target-size check-pred & possibilities]
(let [all-poss (reduce #(into % (get-in token-types (-> %2 list flatten)
:numbers)) #{} possibilities)
perms (combi/selections all-poss target-size)
answers *(help/pool-map check-pred perms 4)*]
(some #(when % %) answers)))
([check-pred possibilities]
(apply brute-force 4 check-pred possibilities)) )
(defn pred-builder "Predicate builder" [^String target-value]
(partial generic-pred
#(when (= % (seq target-value))
(apply str %))))
(def PIN-pred "a dummy predicate for PINs. Returns the matching PIN"
(pred-builder "6427"));;example PIN
Now, no matter what mapping fn I choose, there is going to be an GC
memory limit exceeded error, if I try it with more than 6-7 characters.
My pool-map simply submit jobs to executors and polls for results lazily
(in a 'for'). I also tried r/foldcat but the same error appears after a
while.
Of course now someone is going to say that this is not the right
approach for password cracking. Ideally you want to stop searching as
soon as you find a match. But that approach is not really parallelisable.
I thought that laziness would save me here but instead it's biting me!
any ideas anyone?
btw, for sizes less than 8 it's quite fast!
thanks in advance,
Jim
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