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from hashlib import sha512,sha1
import random,sys,struct
import SocketServer
import base64 as b64
import os
import hmac
from time import time
password = open('password.txt','rb').read()
flag = open('flag.txt','rb').read()
N = 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
class HandleCheckin(SocketServer.BaseRequestHandler):
accepted = {}
def hashToInt(self,*params):
sha = sha512()
for el in params:
sha.update("%r"%el)
return int(sha.hexdigest(), 16)
def cryptrand(self,n = 2048):
p1 = self.hashToInt(os.urandom(40))<<1600
p1+= self.hashToInt(p1)<<1000
p1+= self.hashToInt(p1)<<500
p1+= self.hashToInt(p1)
bitmask = ((2<<(n+1))-1)
p1 = (p1&bitmask)
return (p1 % N)
def sendInt(self,toSend):
s = hex(toSend)
s = s[2:]
if s[-1] =="L":
s = s[:-1]
self.request.sendall(s+"\n")
def readInt(self):
req = self.request
leng = struct.unpack("H", req.recv(2))[0]
if leng>520:
req.sendall("Sorry that is too long a number\n")
req.close()
return None
toRead = ""
while len(toRead) < leng:
toRead += req.recv(leng - len(toRead))
if len(toRead) > leng:
req.sendall("Length does not match input data size\n")
req.close()
return None
return int(toRead.strip('Ll'),16)
def checkBlacklist(self):
foreign = self.request.getpeername()[0]
if foreign in self.accepted:
while(len(self.accepted[foreign]) >0 and
self.accepted[foreign][0]<time()-600):
del self.accepted[foreign][0]
if len(self.accepted[foreign])>35:
self.request.send("Too many requests too quick sorry\n")
self.request.close()
return False
else:
self.accepted[foreign] = []
return True
def doChallenge(self):
req = self.request
proof = b64.b64encode(os.urandom(12))
req.sendall("You must first solve a puzzle, a sha1 sum ending in 24 bit's set to 1, it must be of length %s bytes, starting with %s" % (len(proof)+5, proof))
test = req.recv(21)
ha = sha1()
ha.update(test)
if(not self.checkBlacklist()):
return False
if (test[0:16] != proof or
ha.digest()[-3:] != "\xff\xff\xff"):
req.sendall("NOPE")
req.close()
return False
self.accepted[self.request.getpeername()[0]].append(time())
return True
def getClientParams(self):
req = self.request
index = self.readInt()
if index is None:
return
if index<2 or index>N/2:#we don't have nearly that many users, we wish we did but lets be honest ,brute force attempt
req.sendall("Invalid nonce\n")
req.close()
return None
req.sendall("Please provide your ephemeral key\n")
cEphemeral = self.readInt()
if cEphemeral is None:
return None
if cEphemeral%N ==0:
req.sendall("Invalid ephemeral key\n")
req.close()
return None
return cEphemeral,index
def authenticate(self,index,cEphemeral,salt):
hashToInt = self.hashToInt
salt = hashToInt(index)
storedKey = pow(index, hashToInt(salt, password), N)
multiplierSlush = 3
sEphemeralPriv = self.cryptrand()
sEphemeral = (multiplierSlush * storedKey +
pow(index, sEphemeralPriv, N)) % N
self.sendInt(salt)
self.sendInt(sEphemeral)
slush = hashToInt(cEphemeral, sEphemeral)
agreedKey = hashToInt(pow(cEphemeral * pow(storedKey, slush, N), sEphemeralPriv, N))
return agreedKey,sEphemeral
def handle(self):
hashToInt = self.hashToInt
req = self.request
if (not self.doChallenge()):
return
req.sendall("""Welcome to the new cryptographic authentication server. Log in or be square!
Note: passwords must contain at least one uppercase, one lowercase, and one digit. Sorry for the inconvienence but we've had problems with weak passwords lately.
To begin, please provide a randomly generated nonce.
""")
cEphemeral,index = self.getClientParams()
salt = self.hashToInt(index)
agreedKey,sEphemeral = self.authenticate(index,cEphemeral,salt)
gennedKey = hashToInt(hashToInt(N) ^ hashToInt(index), hashToInt(index), salt,
cEphemeral, sEphemeral, agreedKey)
check = self.readInt()
if (check == gennedKey):
req.sendall(flag+"\n")
req.close()
class ThreadedServer(SocketServer.ThreadingMixIn, SocketServer.TCPServer):
pass
if __name__ == "__main__":
HOST, PORT = sys.argv[1], int(sys.argv[2])
print 'Running on port', PORT
server = ThreadedServer((HOST, PORT), HandleCheckin)
server.allow_reuse_address = True
server.serve_forever()