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import os, base64, time, random, string
from Crypto.Cipher import AES
from Crypto.Hash import *
key = os.urandom(16)
def pad(msg):
pad_length = 16-len(msg)%16
return msg+chr(pad_length)*pad_length
def unpad(msg):
return msg[:-ord(msg[-1])]
def encrypt(iv,msg):
msg = pad(msg)
cipher = AES.new(key,AES.MODE_CBC,iv)
encrypted = cipher.encrypt(msg)
return encrypted
def decrypt(iv,msg):
cipher = AES.new(key,AES.MODE_CBC,iv)
decrypted = cipher.decrypt(msg)
decrypted = unpad(decrypted)
return decrypted
def send_msg(msg):
iv = '2jpmLoSsOlQrqyqE'
encrypted = encrypt(iv,msg)
msg = iv+encrypted
msg = base64.b64encode(msg)
print msg
return
def recv_msg():
msg = raw_input()
try:
msg = base64.b64decode(msg)
assert len(msg)<500
decrypted = decrypt(msg[:16],msg[16:])
return decrypted
except:
print 'Error'
exit(0)
def proof_of_work():
proof = ''.join([random.choice(string.ascii_letters+string.digits) for _ in xrange(20)])
digest = SHA256.new(proof).hexdigest()
print "SHA256(XXXX+%s) == %s" % (proof[4:],digest)
x = raw_input('Give me XXXX:')
if len(x)!=4 or SHA256.new(x+proof[4:]).hexdigest() != digest:
exit(0)
print "Done!"
return
if __name__ == '__main__':
proof_of_work()
with open('flag.txt') as f:
flag = f.read().strip()
assert flag.startswith('hitcon{') and flag.endswith('}')
send_msg('Welcome!!')
while True:
try:
msg = recv_msg().strip()
if msg.startswith('exit-here'):
exit(0)
elif msg.startswith('get-flag'):
send_msg(flag)
elif msg.startswith('get-md5'):
send_msg(MD5.new(msg[7:]).digest())
elif msg.startswith('get-time'):
send_msg(str(time.time()))
elif msg.startswith('get-sha1'):
send_msg(SHA.new(msg[8:]).digest())
elif msg.startswith('get-sha256'):
send_msg(SHA256.new(msg[10:]).digest())
elif msg.startswith('get-hmac'):
send_msg(HMAC.new(msg[8:]).digest())
else:
send_msg('command not found')
except:
exit(0)
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