def clock_sync_protocol(self):
if len(data) != 1 : return
# Parse uname and use it to find the shared key
uname = data[0]
shared_key = connected_clients[uname]['shared_key']
shared_iv = connected_clients[uname]['shared_iv']
# Create a nonce, encrypt it with the shared key, send it to the client
nonce1 = Random.new().read( 32 )
encrypted_nonce1 = common.aes_encrypt(nonce1, shared_key, shared_iv)
encrypt_msg = common.encode_msg([encrypted_nonce1])
data = common.send_and_receive(encrypt_msg, self.client_address, self.socket, 1024, 2)
# Return if nonce doesn't match
user_nonce1 = base64.b64decode( data[0] )
if nonce1 != user_nonce1 : return
encrypted_n2 = base64.b64decode( data[1] )
# Decrypt the client's nonce
incr_shared_key = SHA256.new(str( common.increment_key(shared_key) )).digest()
nonce2 = common.aes_decrypt(encrypted_n2, incr_shared_key, shared_iv)
# Get the current server timestamp and encrypt it
timestamp = datetime.datetime.now().strftime(fmt)
encrypted_timestamp = common.aes_encrypt(timestamp, shared_key, shared_iv)
final_msg = common.encode_msg([nonce2, encrypted_timestamp])
self.socket.sendto(final_msg, self.client_address)
def list_protocol(self, data):
if len(data) != 1 : return
# Parse uname and use it to find the shared key
uname = data[0]
shared_key = connected_clients[uname]['shared_key']
shared_iv = connected_clients[uname]['shared_iv']
# Create a nonce, encrypt it with the shared key, send it to the client
nonce1 = Random.new().read( 32 )
encrypted_nonce1 = common.aes_encrypt(nonce1, shared_key, shared_iv)
encrypt_msg = common.encode_msg([encrypted_nonce1])
data = common.send_and_receive(encrypt_msg, self.client_address, self.socket, 1024, 2)
# Return if the nonce doesn't match
user_nonce1 = base64.b64decode( data[0] )
if nonce1 != user_nonce1 : return
encrypted_n2 = base64.b64decode( data[1] )
# Decrypt the client's nonce
incr_shared_key = SHA256.new(str( common.increment_key(shared_key) )).digest()
nonce2 = common.aes_decrypt(encrypted_n2, incr_shared_key, shared_iv)
# Build the list of connected clients
client_list = ''
for key, value in connected_clients.iteritems():
client_list += key + ','
# Encrypt the list and send it to the client (along with the decrypted nonce)
encrypted_client_list = common.aes_encrypt(client_list, shared_key, shared_iv)
final_msg = common.encode_msg([nonce2, encrypted_client_list])
self.socket.sendto(final_msg, self.client_address)
def ticket_protocol(self, data):
if len(data) != 2 : return
# Parse uname and use it to find the shared key
uname = data[0]
shared_key = connected_clients[uname]['shared_key']
shared_iv = connected_clients[uname]['shared_iv']
# Decrypt the requested user and timestamp
msg = common.aes_decrypt(base64.b64decode(data[1]), shared_key, shared_iv).split(",",2)
if len(msg) != 2 : return
requested_user = msg[0]
requested_user_ip = connected_clients[requested_user]['ip']
requested_user_port = str(connected_clients[requested_user]['port'])
user_timestamp_str = ''
user_timestamp = ''
try:
user_timestamp_str = msg[1]
user_timestamp = datetime.datetime.strptime(msg[1], fmt)
except ValueError:
print "timestamp import issue"
return
# Verify timestamp is within acceptable range
if common.verify_timestamp(user_timestamp, 5):
# Lookup public key requested_user and create shared key
requested_user_pub_key_str = self.get_user_pub_key(requested_user).exportKey()
shared_user_key = self.create_shared_key()
# Create ticket to requested_user
encrypted_keys, ciphertext = self.create_ticket(requested_user, uname, shared_user_key)
# Encrypt response with the shared key + 1
encrypt_msg = user_timestamp_str + ',' + requested_user + ',' + shared_user_key + ',' + encrypted_keys + ',' + \
ciphertext + ',' + requested_user_pub_key_str + ',' + requested_user_ip + ',' + requested_user_port
incr_shared_key = SHA256.new(str( common.increment_key(shared_key) )).digest()
encrypted_msg = common.aes_encrypt(encrypt_msg, incr_shared_key, shared_iv)
# Encode the response (with ticket) and send it to the client
final_msg = common.encode_msg([encrypted_msg])
self.socket.sendto(final_msg, self.client_address)
else:
print "Timestamp not current enough"
return
def sync_clocks(self):
# Send the "SYNC" server request
self.sock.sendto("SYNC", self.server_address)
# Receive the dos cookie
dos_cookie = self.sock.recv(1024)
# Send the dos cookie back, along with the username
msg = "SYNC," + dos_cookie + "," + self.username
self.sock.sendto(msg, (HOST, PORT))
# Receive an encrypted nonce and decrypt it
encrypted_nonce = self.sock.recv(1024)
decoded_encrypted_nonce = base64.b64decode(encrypted_nonce)
decrypted_nonce = common.aes_decrypt(decoded_encrypted_nonce, self.shared_key, self.shared_iv)
# Create a new nonce and encrypt with the shared key + 1
nonce2 = Random.new().read( 32 )
incr_shared_key = SHA256.new(str( common.increment_key(self.shared_key) )).digest()
encrypted_nonce2 = common.aes_encrypt(nonce2, incr_shared_key, self.shared_iv)
# Send the decrypted nonce and encrypted second nonce to the server
send_msg = common.encode_msg([decrypted_nonce, encrypted_nonce2])
data = common.send_and_receive(send_msg, self.server_address, self.sock, 8192, 2)
# Check the nonce
serv_nonce2 = base64.b64decode( data[0] )
if serv_nonce2 != nonce2 : return
encrypted_timestamp = base64.b64decode(data[1])
# Decrypt the timestamp
timestamp_str = common.aes_decrypt(encrypted_timestamp, self.shared_key, self.shared_iv)
timestamp = ''
try:
timestamp = datetime.datetime.strptime(timestamp_str, fmt)
except ValueError:
print "timestamp import issue"
return
# Not sure if this legal, please check it!!!
time_offset = datetime.datetime.now() - timestamp
def get_client_list(self):
# Send the "LIST" server request
self.sock.sendto("LIST", self.server_address)
# Receive the dos cookie
dos_cookie = self.sock.recv(1024)
# Send the dos cookie back, along with the username
msg = "LIST," + dos_cookie + "," + self.username
self.sock.sendto(msg, (HOST, PORT))
# Receive an encrypted nonce and decrypt it
encrypted_nonce = self.sock.recv(1024)
decoded_encrypted_nonce = base64.b64decode(encrypted_nonce)
decrypted_nonce = common.aes_decrypt(decoded_encrypted_nonce, self.shared_key, self.shared_iv)
# Create a new nonce and encrypt with the shared key + 1
nonce2 = Random.new().read( 32 )
incr_shared_key = SHA256.new(str( common.increment_key(self.shared_key) )).digest()
encrypted_nonce2 = common.aes_encrypt(nonce2, incr_shared_key, self.shared_iv)
# Send the decrypted nonce and encrypted second nonce to the server
#send_msg = encoded_decrypted_nonce + "," + encrypted_nonce2
send_msg = common.encode_msg([decrypted_nonce, encrypted_nonce2])
data = common.send_and_receive(send_msg, self.server_address, self.sock, 8192, 2)
# Check the nonce
serv_nonce2 = base64.b64decode( data[0] )
if serv_nonce2 != nonce2 : return
encrypted_unames = base64.b64decode(data[1])
# Decrypt and print names
unames = common.aes_decrypt(encrypted_unames, self.shared_key, self.shared_iv)
unames = unames.split(',')
for name in unames:
print name
def handle_request(self, data, addr):
data = data.split(',', 4)
if data[0] == 'AUTH':
if len(data) != 3 : return
# Decrypt message with our private key and break out message
msg = common.public_key_decrypt(data[1], data[2], self.priv_key)
decoded_msg = common.decode_msg(msg)
connected_uname = decoded_msg[0]
encr_ticket_key = decoded_msg[1]
encr_ticket_ciphert = decoded_msg[2]
iv2 = decoded_msg[3]
signature = decoded_msg[4]
encrypted_nonce = decoded_msg[5]
# Decrypt ticket
ticket = common.public_key_decrypt(encr_ticket_key, encr_ticket_ciphert, self.priv_key)
ticket = common.decode_msg(ticket)
if len(ticket) != 6 : return
iv = ticket[0]
serv_signature = ticket[1]
shared_user_key = ticket[2]
requesting_user = ticket[3]
requesting_user_pub_key_str = ticket[4]
expiration_datetime_str = ticket[5]
# Verify ticket is not expired and username from ticket matches requesting username
expiration_timestamp = ''
try:
expiration_timestamp = datetime.datetime.strptime(expiration_datetime_str, fmt)
except ValueError:
return
# Check offset!!!
if common.is_timestamp_current(expiration_timestamp + time_offset) != True : return
if requesting_user != connected_uname: return
# Verify server's signature
h = SHA256.new(str(iv))
verifier = PKCS1_v1_5.new(server_pub_key)
if verifier.verify(h, str(serv_signature)):
# Now verify signature of initiating user
requesting_user_pub_key = RSA.importKey(requesting_user_pub_key_str)
h = SHA256.new(str(iv2))
verifier = PKCS1_v1_5.new(requesting_user_pub_key)
if verifier.verify(h, str(signature)):
# Create signature
iv3 = Random.new().read( 16 )
signature_msg = SHA256.new(str(iv3))
signature = common.sign(signature_msg, self.priv_key)
# Add user to authenticated users
self.authenticated_users[requesting_user]['shared_key'] = shared_user_key
self.authenticated_users[requesting_user]['shared_iv'] = iv3
self.authenticated_users[requesting_user]['sequence_n'] = int(iv3.encode('hex'), 16)
self.authenticated_users[requesting_user]['address'] = addr
# Now decrypt nonce, and encrypt back with kab + 1
nonce = common.aes_decrypt(encrypted_nonce, shared_user_key, iv2)
incr_shared_key = SHA256.new(str( common.increment_key(shared_user_key) )).digest()
our_encrypted_nonce = common.aes_encrypt(nonce, incr_shared_key, iv3)
# Send final message back to initiating user, encrypted with their pub key
encrypt_msg = common.encode_msg([iv3, signature, our_encrypted_nonce])
encrypted_keys, ciphertext = common.public_key_encrypt(encrypt_msg, requesting_user_pub_key)
send_msg = encrypted_keys + "," + ciphertext
self.sock.sendto(send_msg, addr)
else:
return
return
if data[0] == 'MESSAGE':
if len(data) != 4 : return
decoded_msg = common.decode_msg(data[1:])
if len(decoded_msg) != 3 : return
connected_uname = decoded_msg[0]
user_hmac_key = decoded_msg[1]
encrypted_msg = decoded_msg[2]
# Retrieve session info for user
if self.authenticated_users.get(connected_uname) == None : return
shared_key = self.authenticated_users[connected_uname]['shared_key']
shared_iv = self.authenticated_users[connected_uname]['shared_iv']
user_addr = self.authenticated_users[connected_uname]['address']
self.authenticated_users[connected_uname]['sequence_n'] += 1
sequence_n = self.authenticated_users[connected_uname]['sequence_n']
# Decrypt message
msg = common.aes_decrypt(encrypted_msg, shared_key, shared_iv).split(',',1)
if len(msg) != 2 : return
user_seq_n = msg[0]
user_msg = msg[1]
# Verify sequence number matches our sequence number
if user_seq_n != str(sequence_n) : return
# Verify hmac key
hmac_key = hmac.new(shared_key, str(user_seq_n) + ',' + user_msg).digest()
if user_hmac_key != hmac_key : return
print connected_uname + ': ' + user_msg
return
else:
return
def get_ticket_from_server(self, user):
try:
self.sock.sendto("TICKET", self.server_address)
dos_cookie = self.sock.recv(1024)
# Request to talk to given user, sending current timestamp
# Please not sure if adding the offset here is legal, please check!!!
timestamp = (datetime.datetime.now() + time_offset).strftime(fmt)
msg = user + "," + timestamp
encrypted_msg = common.aes_encrypt(msg, self.shared_key, self.shared_iv)
encoded_encrypted_msg = common.encode_msg([encrypted_msg])
# Send request to server
send_msg = "TICKET," + dos_cookie + ',' + self.username + ',' + encoded_encrypted_msg
self.sock.settimeout(5)
data = common.send_and_receive(send_msg, self.server_address, self.sock, 16384, 1)
if len(data) != 1 : return
# Decrypt the message with shared key + 1
msg = base64.b64decode( data[0] )
incr_shared_key = SHA256.new(str( common.increment_key(self.shared_key) )).digest()
msg = common.aes_decrypt(msg, incr_shared_key, self.shared_iv).split(',', 8)
if len(msg) != 8 : return
serv_timestamp = msg[0]
serv_user_to_talk_to = msg[1]
shared_key_ab = msg[2]
encr_ticket_key = msg[3]
encr_ticket_ciphert = msg[4]
user_pk = msg[5]
user_ip = msg[6]
user_port = msg[7]
# Not sure what to do with timestamp offset here!!!
if serv_timestamp == timestamp and serv_user_to_talk_to == user:
nonce = Random.new().read( 32 )
iv2 = Random.new().read( 16 )
signature_msg = SHA256.new(str(iv2))
signature = common.sign(signature_msg, self.priv_key)
# Encrypt nonce with our shared key
encrypted_nonce = common.aes_encrypt(nonce, shared_key_ab, iv2)
# Encrypt mesage with pub key of the user
user_pk = RSA.importKey(user_pk)
encrypt_msg = common.encode_msg([self.username, encr_ticket_key, encr_ticket_ciphert, iv2, signature, encrypted_nonce])
encrypted_keys, ciphertext = common.public_key_encrypt(encrypt_msg, user_pk)
user_address = (user_ip,int(user_port))
send_msg = "AUTH" + ',' + encrypted_keys + ',' + ciphertext
data = common.send_and_receive(send_msg, user_address, self.sock, 2048, 2)
if len(data) != 2 : return
# Decrypt message with our private key and break out message
msg = common.public_key_decrypt(data[0], data[1], self.priv_key)
decoded_msg = common.decode_msg(msg)
iv3 = decoded_msg[0]
signature = decoded_msg[1]
encrypted_nonce = decoded_msg[2]
# Decrypt nonce with shared key + 1
incr_shared_key = SHA256.new(str( common.increment_key(shared_key_ab) )).digest()
connected_nonce = common.aes_decrypt(encrypted_nonce, incr_shared_key, iv3)
# Verify nonce is correct
if connected_nonce == nonce:
self.authenticated_users[serv_user_to_talk_to]['shared_key'] = shared_key_ab
self.authenticated_users[serv_user_to_talk_to]['shared_iv'] = iv3
self.authenticated_users[serv_user_to_talk_to]['sequence_n'] = int(iv3.encode('hex'), 16)
self.authenticated_users[serv_user_to_talk_to]['address'] = user_address
return
except socket.timeout as e:
print "Server is not responding"
sys.exit()
