CTF-BR! – p100 – Choose the number

p100 – Choose the number

Posted 7 de dezembro de 2014

> SECCON > SECCON CTF 2014 > p100 - Choose the number

nc number.quals.seccon.jp 31337

Solução

Execuntando este comando, iremos notar que ele nos fornece números e espera que respondemos adequadamente.

-3, -4
The maximum number?

1 2	-3, -4 The maximum number?

Ao fazer um código para responder a essa pergunta, percebemos que uma hora ele também começa perguntar sobre o minimum. Então bastou fazer um script para responder a essas perguntas de max() e min() para obter a flag!

Script

import telnetlib

tn = telnetlib.Telnet('number.quals.seccon.jp', 31337)

while True:
    s = tn.read_until('?')
    print s

    l = s.split('\n')[0].strip().split(', ')
    if len(l) == 1:
        break

    m = max(map(int, l)) if s.find('maximum') != -1 else min(map(int, l))
    print m

    tn.write(str(m) + '\n')

import telnetlib

tn = telnetlib.Telnet('number.quals.seccon.jp', 31337)

while True:

s = tn.read_until('?')

print s

l = s.split('\n')[0].strip().split(', ')

if len(l) == 1:

break

m = max(map(int, l)) if s.find('maximum') != -1 else min(map(int, l))

print m

tn.write(str(m) + '\n')

Flag

Executando durante uns minutos para resolver uma série de perguntas, terminou em:

 2177838478, 3918532950, -2411029813, -1471628567, 698903317, -1758243253, 3493640021, 24715295, -694496324, -4193274474, 224139374, -2312950321, 3388506934, -4154796311, 4217272006, -3380320771, 994143094, -1733185271, -3810375222, -1522077340, -1555369380, 562227484, 478751910, -730775222, -2203827220, 1748536973, 2021531989, -602172644, 91708934, -2901284432, -3752970643, 3005879675, -522292455, -1122046425, 2685224048, 1660141495, -3105856403, -1700311985, -3258984654, -1993266500, -1229121415, -291133335, -4099198442, -3318687675, 2864334555, -2718327363, 2819474383, 4165823254, -2972699728, -1813922319, 2930097515, -3090060261, 1697009671, -1014937535, 3197512148, 3875548047, 2335068040, -2631899466, -509738443, 4173433664, -310127523, 316937860, 2885573427, 3344636570, 2976933565, 1938365346, -2497190064, 1572032204, 1157311097, -4106135770, -760963063, 3169299172, 3109506332, 1528793147, -3473316825, -3617377730, 1701339109, 4056326320, 137294904, 975775467, 2051213805, -32348885, 2630954953, -2143230745, -3494630485, 3557403165, 4222409181, -2462636026, 3234873933, 3487427673, -2226921227, -3529241363, 2750277919, 1781103149, 643438511, -2597741468, 4250958118, 175084963, -1442228520, -3510327711, 1293177350
The minimum number?
-4193274474
 Congratulations!
The flag is SECCON{Programming is so fun!}

2177838478, 3918532950, -2411029813, -1471628567, 698903317, -1758243253, 3493640021, 24715295, -694496324, -4193274474, 224139374, -2312950321, 3388506934, -4154796311, 4217272006, -3380320771, 994143094, -1733185271, -3810375222, -1522077340, -1555369380, 562227484, 478751910, -730775222, -2203827220, 1748536973, 2021531989, -602172644, 91708934, -2901284432, -3752970643, 3005879675, -522292455, -1122046425, 2685224048, 1660141495, -3105856403, -1700311985, -3258984654, -1993266500, -1229121415, -291133335, -4099198442, -3318687675, 2864334555, -2718327363, 2819474383, 4165823254, -2972699728, -1813922319, 2930097515, -3090060261, 1697009671, -1014937535, 3197512148, 3875548047, 2335068040, -2631899466, -509738443, 4173433664, -310127523, 316937860, 2885573427, 3344636570, 2976933565, 1938365346, -2497190064, 1572032204, 1157311097, -4106135770, -760963063, 3169299172, 3109506332, 1528793147, -3473316825, -3617377730, 1701339109, 4056326320, 137294904, 975775467, 2051213805, -32348885, 2630954953, -2143230745, -3494630485, 3557403165, 4222409181, -2462636026, 3234873933, 3487427673, -2226921227, -3529241363, 2750277919, 1781103149, 643438511, -2597741468, 4250958118, 175084963, -1442228520, -3510327711, 1293177350

The minimum number?

-4193274474

Congratulations!

The flag is SECCON{Programming is so fun!}

Criado por

Epic Leet Team

Felipe Pena