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dtlsClient.py
564 lines (484 loc) · 20 KB
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dtlsClient.py
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import socket, os, logging, time, struct, ssl
import ctypes, ssl, datetime
import traceback
import hmac
import base64
import re,hashlib, binascii
from os import urandom
from cryptography import x509
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.asymmetric import padding
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.serialization import load_pem_private_key
from cryptography.hazmat.primitives.hashes import Hash, MD5, SHA1, SHA256, SHA384, SHA512, HashAlgorithm
from cryptography.hazmat.primitives.ciphers.aead import AESGCM
from cryptography.hazmat.primitives.hmac import HMAC
from cryptography.hazmat.primitives.ciphers import (
Cipher, algorithms, modes
)
uint8 = ctypes.c_uint8.__ctype_be__
uint16 = ctypes.c_uint16.__ctype_be__
uint32 = ctypes.c_uint32.__ctype_be__
uint64 = ctypes.c_uint64.__ctype_be__
client_hello_flag = True
server_hello_flag = True
certificate_flag = True
server_hello_done_flag = True
client_key_exchange_flag = True
encrypted_handshake_flag = True
#For 3 bytes data
def uint24(val):
return bytearray(uint32(val))[1:]
#For 6 bytes data
def uint48(val):
return bytearray(uint64(val))[2:]
#Encode to bytes
def bytes_encode(x):
if isinstance(x, str):
return x.encode("base64")
return bytes(x)
DTLS_VERSION = b'\xfe\xfd'
handshake_messages = []
count = -1
packetCount = 0
serverIP = '127.0.0.1'
serverPort = 28000
bufferSize = 4096
dtlsVersion = 65277
handshake = 22
cipherList = [156, 157]
cipherLen = 4
#TLS_DHE_RSA_WITH_AES_128_GCM_SHA256(0x009c)
#TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256(0x009d)
#TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 (0x0067)
CA_List = ['wipro.com', 'broadcom.com', 'google.com']
bb = bytearray()
bb.extend(uint32(int(time.time())))
bb.extend(urandom(28))
clientRandom = bb
preMasterSecret = DTLS_VERSION + urandom(46)
preMasterSecret1 = urandom(48)
client_hello = 1
server_hello = 2
hello_verify_request = 3
certificate = 11
server_hello_done = 14
client_key_exchange = 16
change_cipher_spec = 20
finished = 0
application_data = 23
class Record_Layer:
def __init__(self):
self.contentType = handshake
self.version = dtlsVersion
self.epoch = 0
self.seqNumber = 0
self.length = 0
class Handshake:
def __init__(self):
self.handShakeType = None
self.version = dtlsVersion
self.fragmentOffset = 0
self.msgSequence = 0
self.sessionID = 0
self.cookieLength = 0
self.cookie=None
self.serverRandom = None
self.cipherSuitesLength = 0
self.cipherSuites=None
self.length = 0
self.fragmentLength = 0
self.sharedPublicKey = None
self.rsaEncryptedPreMasterLength = 0
self.rsaEncryptedPreMasterSecret = None
self.preMasterSecret = None
self.masterSecret = None
self.extension = None
class keyDerivation():
def __init__(self):
client_write_MAC_key = None
server_write_MAC_key = None
client_write_key = None
server_write_key = None
client_write_IV = None
server_write_IV = None
class DTLS:
def __init__(self):
self.recObj = Record_Layer()
self.handObj = Handshake()
self.keyObj = keyDerivation()
def _p_hash(self, hash_algorithm, secret, seed, output_length):
result = bytearray()
i = 1
while len(result) < output_length:
h = HMAC(secret, hash_algorithm, default_backend())
h.update(self._a(secret, hash_algorithm, i, seed))
h.update(seed)
result.extend(h.finalize())
i += 1
return bytes(result[:output_length])
def _a(self, secret, hash_algorithm, n, seed):
if n == 0:
return seed
else:
h = HMAC(secret, hash_algorithm, default_backend())
h.update(self._a(secret, hash_algorithm, n - 1, seed))
return h.finalize()
def prf(self, secret, label, seed, hash_algorithm, output_length):
return self._p_hash(hash_algorithm, secret, label + seed, output_length)
def int_to_bytes(self, value, length):
result = []
for i in range(0, length):
result.append(value >> (i * 8) & 0xff)
result.reverse()
return str(result)
def nb_to_n_bytes(self, number, size):
h = '%x' % number
s = binascii.unhexlify('0'*(size*2 - len(h)) + h)
return s
def clientHello(self, rObj, hObj, socket, isCookie):
global packetCount
global count
#print("count", count)
packetCount += 1
serialize = bytearray()
serialize.extend(uint8(rObj.contentType))
serialize.extend(uint16(rObj.version))
serialize.extend(uint16(rObj.epoch))
count += 1
rObj.seqNumber = count
serialize.extend(uint48(rObj.seqNumber))
if isCookie is not None:
serialize.extend(uint16(111))
print("clientHello with cookie.....")
else:
serialize.extend(uint16(95))
print("clientHello.....")
record_layer_msg = serialize
del serialize
serialize = bytearray()
hObj.handShakeType = client_hello
serialize.extend(uint8(hObj.handShakeType))
if isCookie is not None:
serialize.extend(uint24(99))
else:
serialize.extend(uint24(83))
if count <= 1:
hObj.msgSequence = count
else:
hObj.msgSequence = 1
serialize.extend(uint16(hObj.msgSequence))
serialize.extend(uint24(hObj.fragmentOffset))
if isCookie is not None:
serialize.extend(uint24(99))
else:
serialize.extend(uint24(83))
serialize.extend(uint16(hObj.version))
serialize.extend(clientRandom)
serialize.extend(uint8(hObj.sessionID))
if isCookie is not None:
hObj.cookieLength = len(isCookie)
serialize.extend(uint8(hObj.cookieLength))
serialize.extend(isCookie)
else:
serialize.extend(uint8(hObj.cookieLength))
hObj.cipherSuitesLength = cipherLen
serialize.extend(uint16(hObj.cipherSuitesLength))
hObj.cipherSuites = cipherList
serialize.extend(uint16(hObj.cipherSuites[0]))
serialize.extend(uint16(hObj.cipherSuites[1]))
serialize.extend(uint8(1))
serialize.extend(uint8(0))
#For extension attributes
serialize.extend(uint16(37))
serialize.extend(uint16(11))
serialize.extend(uint16(4))
serialize.extend(uint8(3))
serialize.extend(uint8(0))
serialize.extend(uint8(1))
serialize.extend(uint8(2))
serialize.extend(uint16(10))
serialize.extend(uint16(6))
serialize.extend(uint16(4))
serialize.extend(uint16(23))
serialize.extend(uint16(25))
serialize.extend(uint16(35))
serialize.extend(uint16(0))
serialize.extend(uint16(13))
serialize.extend(uint16(6))
serialize.extend(uint16(4))
serialize.extend(uint16(1026))
serialize.extend(uint16(1538))
serialize.extend(uint16(15))
serialize.extend(uint16(1))
serialize.extend(uint8(1))
handshake_layer_msg = serialize
del serialize
global client_hello_flag
if isCookie is None and client_hello_flag == True:
handshake_messages.append(str(handshake_layer_msg))
client_hello_flag = False
socket.sendto(record_layer_msg + handshake_layer_msg, (serverIP, serverPort))
def getPEMFormatCert(self, aData):
aData = aData[:529]
p_type = "CERTIFICATE"
data = '-'*5+"BEGIN "+p_type+'-'*5+'\n'+ aData.encode("base64")+'-'*5+"END "+p_type+'-'*5
cert = x509.load_pem_x509_certificate(data, default_backend())
return cert
def verifyCertificate(self, hObj, data):
cert = self.getPEMFormatCert(data)
before = cert.not_valid_before
after = cert.not_valid_after
BEFORE_DATE = datetime.datetime(day=before.day, month=before.month, year=before.year)
AFTER_DATE = datetime.datetime(day=after.day, month=after.month, year=after.year)
TODAY_DATE = datetime.datetime.now()
if BEFORE_DATE <= TODAY_DATE <= AFTER_DATE:
print("Validity passed....")
else:
raise Exception("Certificate expired...")
issuer_public_key = cert.public_key()
hObj.sharedPublicKey = issuer_public_key
#print("ssss", cert.signature, cert.signature_hash_algorithm, dir(cert))
# sigCheck = issuer_public_key.verify(
# cert.signature,
# cert.tbs_certificate_bytes,
# padding.PKCS1v15(),
# cert.signature_hash_algorithm,
# )
# if sigCheck is not None:
# raise Exception("CA's Public key unable to validate issuer digital signature")
# print("Server Certificate verified......")
def getRSAEncryptedSecret(self, hObj):
publicKey = hObj.sharedPublicKey
hObj.preMasterSecret = preMasterSecret
encryptedSecret = publicKey.encrypt(hObj.preMasterSecret, padding.PKCS1v15())
hObj.rsaEncryptedPreMasterSecret = encryptedSecret
hObj.rsaEncryptedPreMasterLength = len(hObj.rsaEncryptedPreMasterSecret)
def clientKeyExchange(self, rObj, hObj, b):
print("clientKeyExchange.....")
global count
serialize = bytearray()
serialize.extend(uint8(rObj.contentType))
serialize.extend(uint16(rObj.version))
rObj.epoch = 0
serialize.extend(uint16(rObj.epoch))
count += 1
rObj.seqNumber = count
serialize.extend(uint48(rObj.seqNumber))
rObj.length = hObj.rsaEncryptedPreMasterLength + 14
serialize.extend(uint16(rObj.length))
record_layer_msg = serialize
del serialize
serialize = bytearray()
hObj.handShakeType = client_key_exchange
serialize.extend(uint8(hObj.handShakeType))
hObj.length = hObj.rsaEncryptedPreMasterLength + 2
serialize.extend(uint24(hObj.length))
hObj.msgSequence = 2
serialize.extend(uint16(hObj.msgSequence))
serialize.extend(uint24(hObj.fragmentOffset))
hObj.fragmentLength = hObj.rsaEncryptedPreMasterLength + 2
serialize.extend(uint24(hObj.fragmentLength))
serialize.extend(uint16(hObj.rsaEncryptedPreMasterLength))
serialize.extend(hObj.rsaEncryptedPreMasterSecret)
handshake_layer_msg = serialize
del serialize
b += record_layer_msg + handshake_layer_msg
global client_key_exchange_flag
if client_key_exchange_flag == True:
handshake_messages.append(str(handshake_layer_msg))
client_key_exchange_flag = False
def cipherSpecChange(self, rObj, b):
print("cipherSpecChange.....")
serialize = bytearray()
global count
serialize.extend(uint8(change_cipher_spec))
serialize.extend(uint16(rObj.version))
rObj.epoch = 0
serialize.extend(uint16(rObj.epoch))
count += 1
rObj.seqNumber = count
serialize.extend(uint48(rObj.seqNumber))
rObj.length = 1
serialize.extend(uint16(rObj.length))
changeCipherSpecMessage = 1
serialize.extend(uint8(changeCipherSpecMessage))
b += serialize
del b
def encryptedHandshakeMessage(self, rObj, hObj, kObj, b):
print("encryptedHandshakeMessage.....")
serialization = bytearray()
serialization.extend(uint8(rObj.contentType))
serialization.extend(uint16(rObj.version))
rObj.epoch = 1
serialization.extend(uint16(rObj.epoch))
rObj.seqNumber = 0
serialization.extend(uint48(rObj.seqNumber))
masterSecretVal = self.prf(hObj.preMasterSecret, b'master secret', clientRandom + hObj.serverRandom,
hashes.SHA256(), 48)
hObj.masterSecret = masterSecretVal
key_expansion = self.prf(masterSecretVal, b'key expansion', clientRandom + hObj.serverRandom,
hashes.SHA256(), 200)
digest = hashes.Hash(hashes.SHA256(), backend=default_backend())
h = b''.join(handshake_messages)
digest.update(h)
seed = digest.finalize()
final_handshake_msg = self.prf(masterSecretVal, b'client finished', seed, hashes.SHA256(), 12)
bytes_to_msg = b'\x14' + self.nb_to_n_bytes(len(final_handshake_msg), 3) + final_handshake_msg
handshake_messages.append(bytes_to_msg)
self.deriveKey(hObj, kObj, key_expansion)
iv = kObj.client_write_IV
nonce = urandom(8)
algorithm = algorithms.AES(kObj.client_write_key)
auth_data = self.nb_to_n_bytes(0,8) + self.nb_to_n_bytes(22, 1) + DTLS_VERSION + self.nb_to_n_bytes(len(bytes_to_msg), 2)
encryptor = Cipher(algorithm, modes.GCM(iv + nonce), backend=default_backend()).encryptor()
encryptor.authenticate_additional_data(auth_data)
result = encryptor.update(final_handshake_msg) + encryptor.finalize()
print("length,,,,,", len(result), len(encryptor.tag), len(nonce))
finalSecretMessage = nonce + result + encryptor.tag
rObj.length = len(finalSecretMessage)
serialization.extend(uint16(rObj.length))
serialization.extend(finalSecretMessage)
b += serialization
del serialization
def deriveKey(self, hObj, kObj, key_block):
# kObj.client_write_MAC_key = key_block[0:0]
# kObj.server_write_MAC_key = key_block[20:40]
kObj.client_write_key = key_block[0:16]
kObj.server_write_key = key_block[16:32]
kObj.client_write_IV = key_block[32:36]
kObj.server_write_IV = key_block[36:40]
def startApplicationLayerMsg(self, hObj, kObj, rObj, socket):
msgFromClient = "Hello"
iv = kObj.client_write_IV
encryptor = Cipher(
algorithms.AES(kObj.client_write_key),
modes.GCM(iv),
backend=default_backend()
).encryptor()
encryptor.authenticate_additional_data(kObj.client_write_MAC_key)
ciphertext = encryptor.update(msgFromClient) + encryptor.finalize()
serialize = bytearray()
serialize.extend(uint8(application_data))
serialize.extend(uint16(rObj.version))
serialize.extend(uint16(1))
rObj.seqNumber = 1
serialize.extend(uint48(rObj.seqNumber))
rObj.length = len(ciphertext) + len(encryptor.tag)
serialize.extend(uint16(rObj.length))
serialize.extend(encryptor.tag)
serialize.extend(ciphertext)
socket.sendto(serialize, (serverIP, serverPort))
del serialize
def decryptMessage(self, rObj, kObj, aVal):
iv = kObj.server_write_IV
tag = aVal[0:16]
ciphertext = aVal[16:]
decryptor = Cipher(
algorithms.AES(kObj.server_write_key),
modes.GCM(iv, tag),
backend=default_backend()
).decryptor()
decryptor.authenticate_additional_data(kObj.server_write_MAC_key)
decryptedVal = decryptor.update(ciphertext) + decryptor.finalize()
print("decryptedVal", decryptedVal)
def pickRequest(self, sock, reqType, addValue):
if reqType == client_hello or reqType == hello_verify_request:
self.clientHello(self.recObj, self.handObj, sock, addValue)
elif reqType == server_hello_done:
if addValue is not None:
self.verifyCertificate(self.handObj, addValue)
if self.handObj.rsaEncryptedPreMasterSecret is None:
self.getRSAEncryptedSecret(self.handObj)
else:
serialization = bytearray()
self.clientKeyExchange(self.recObj, self.handObj, serialization)
self.cipherSpecChange(self.recObj, serialization)
self.encryptedHandshakeMessage(self.recObj, self.handObj, self.keyObj, serialization)
sock.sendto(serialization, (serverIP, serverPort))
del serialization
elif reqType == handshake:
print("Handshake Completed b/w server and client..................")
self.startApplicationLayerMsg(self.handObj, self.keyObj, self.recObj, sock)
elif reqType == application_data:
self.decryptMessage(self.recObj, self.keyObj, addValue)
def updateRandom(self, ranVal):
self.handObj.serverRandom = ranVal
def main():
clientSocket = socket.socket(family=socket.AF_INET, type=socket.SOCK_DGRAM)
clientSocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
clientSocket.settimeout(1)
seqNo = client_hello
seqFlag = True
certFlag = True
addVal = ""
certVal = ""
certVal2 = ""
epochNO = ""
dtlsObj = DTLS()
global server_hello_flag
global certificate_flag
global server_hello_done_flag
while(True):
if seqNo == client_hello:
dtlsObj.pickRequest(clientSocket, seqNo, None)
elif seqNo == hello_verify_request:
dtlsObj.pickRequest(clientSocket, seqNo, addVal)
elif seqNo == certificate:
pass
elif seqNo == server_hello_done:
dtlsObj.pickRequest(clientSocket, seqNo, certVal)
certFlag = False
#print("Handshake Negotiation finished from server side...")
dtlsObj.pickRequest(clientSocket, seqNo, None)
#seqFlag = False
elif seqNo == change_cipher_spec:
print("Subsequent records will be protected now...")
elif seqNo == handshake and epochNO == 1:
dtlsObj.pickRequest(clientSocket, seqNo, None)
try:
msg = clientSocket.recvfrom(bufferSize)
print("receiving........")
except socket.timeout:
continue
except socket.error:
break
else:
data = msg[0]
if seqFlag:
seqNo = int(data[13:14].encode('hex'), 16)
else:
seqNo = int(data[0:1].encode('hex'), 16)
epochNO = int(data[3:5].encode('hex'), 16)
if seqNo == hello_verify_request:
addVal = data[28:]
elif seqNo == server_hello:
print("server_hello")
handshake_layer_msg = data[13:]
if server_hello_flag == True:
handshake_messages.append(str(handshake_layer_msg))
dtlsObj.updateRandom(data[27:59])
elif seqNo == certificate and certFlag == True:
server_hello_flag = False
if int(data[5:11].encode('hex'), 16) == 2:
certLen = int(data[28:31].encode('hex'), 16)
certVal += data[31:31+certLen]
certVal2 += data
elif int(data[5:11].encode('hex'), 16) == 3:
certLen = int(data[37:40].encode('hex'), 16)
certVal += data[40:40+certLen]
certVal2 += data[37:40] + data[40:40+certLen]
else:
pass
elif seqNo == server_hello_done:
if certificate_flag == True:
handshake_messages.append(str(certVal2[13:]))
certificate_flag = False
if server_hello_done_flag == True:
handshake_messages.append(str(data[13:]))
server_hello_done_flag == False
elif seqNo == application_data:
adVal = data[13:]
dtlsObj.pickRequest(clientSocket, seqNo, adVal)
if __name__ == "__main__":
main()