class HttpCredSSPAuth(AuthBase):
"""
"""
def __init__(self, domain, username, password):
self.credssp_regex = re.compile('(?:.*,)*\s*CredSSP\s*([^,]*),?', re.I)
self.password_authenticator = PasswordAuthentication(domain, username, password)
# Windows 2008 R2 and earlier are unable to negotiate TLS 1.2 by default so use TLS 1.0
# TODO: provide an mechanism to enable TLS 1.2 which works with modern Windows servers
self.tls_context = SSL.Context(SSL.TLSv1_METHOD)
# OpenSSL introduced a fix to CBC ciphers by adding empty fragments, but this breaks Microsoft's TLS 1.0
# implementation. OpenSSL added a flag we need to use which ensures OpenSSL does not send empty fragments
# SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS (0x00000800) | SSL_OP_TLS_BLOCK_PADDING_BUG (0x00000200)
self.tls_context.set_options(0x00000800 | 0x00000200)
self.tls_context.set_cipher_list('ALL')
self.tls_connection = None
def _get_credssp_header(self, response):
authenticate_header = response.headers.get('www-authenticate', None)
if authenticate_header:
match_obj = self.credssp_regex.search(authenticate_header)
if match_obj and len(match_obj.groups()) > 0:
encoded = match_obj.group(1)
return base64.b64decode(encoded)
return None
@staticmethod
def _set_credssp_header(request, value):
request.headers['Authorization'] = "CredSSP {0}".format(base64.b64encode(value))
return request
@staticmethod
def _get_rsa_public_key(cert):
"""
PyOpenSSL does not provide a public method to export the public key from a certificate as a properly formatted
ASN.1 RSAPublicKey structure. There are 'hacks' which use dump_privatekey(crypto.FILETYPE_ASN1, <public_key>),
but this dumps the public key within a PrivateKeyInfo structure which is not suitable for a comparison. This
approach uses the PyOpenSSL CFFI bindings to invoke the i2d_RSAPublicKey() which correctly extracts the key
material in an ASN.1 RSAPublicKey structure.
:param cert: The ASN.1 Encoded Certificate
:return: The ASN.1 Encoded RSAPublicKey structure containing the supplied certificates public Key
"""
openssl_pkey = cert.get_pubkey()
openssl_lib = _util.binding.lib
ffi = _util.binding.ffi
buf = ffi.new("unsigned char **")
rsa = openssl_lib.EVP_PKEY_get1_RSA(openssl_pkey._pkey)
length = openssl_lib.i2d_RSAPublicKey(rsa, buf)
public_key = ffi.buffer(buf[0], length)[:]
ffi.gc(buf[0], openssl_lib.OPENSSL_free)
return public_key
def _credssp_processor(self, context):
"""
Implements a state machine
:return:
"""
http_response = (yield)
credssp_context = self._get_credssp_header(http_response)
if credssp_context is None:
raise Exception('The remote host did not respond with a \'www-authenticate\' header containing '
'\'CredSSP\' as an available authentication mechanism')
# 1. First, secure the channel with a TLS Handshake
if not credssp_context:
self.tls_connection = SSL.Connection(self.tls_context)
self.tls_connection.set_connect_state()
while True:
try:
self.tls_connection.do_handshake()
except SSL.WantReadError:
http_response = yield self._set_credssp_header(http_response.request, self.tls_connection.bio_read(4096))
credssp_context = self._get_credssp_header(http_response)
if credssp_context is None or not credssp_context:
raise Exception('The remote host rejected the CredSSP TLS handshake')
self.tls_connection.bio_write(credssp_context)
else:
break
# add logging to display the negotiated cipher (move to a function)
openssl_lib = _util.binding.lib
ffi = _util.binding.ffi
cipher = openssl_lib.SSL_get_current_cipher(self.tls_connection._ssl)
cipher_name = ffi.string( openssl_lib.SSL_CIPHER_get_name(cipher))
log.debug("Negotiated TLS Cipher: %s", cipher_name)
# 2. Send an TSRequest containing an NTLM Negotiate Request
context_generator = context.initialize_security_context()
negotiate_token = context_generator.send(None)
log.debug("NTLM Type 1: %s", AsHex(negotiate_token))
ts_request = TSRequest()
ts_request['negoTokens'] = negotiate_token
self.tls_connection.send(ts_request.getData())
http_response = yield self._set_credssp_header(http_response.request, self.tls_connection.bio_read(4096))
# Extract and decrypt the encoded TSRequest response struct from the Negotiate header
authenticate_header = self._get_credssp_header(http_response)
if not authenticate_header or authenticate_header is None:
raise Exception("The remote host rejected the CredSSP negotiation token")
self.tls_connection.bio_write(authenticate_header)
# NTLM Challenge Response and Server Public Key Validation
ts_request = TSRequest()
ts_request.fromString(self.tls_connection.recv(8192))
challenge_token = ts_request['negoTokens']
log.debug("NTLM Type 2: %s", AsHex(challenge_token))
server_cert = self.tls_connection.get_peer_certificate()
# not using channel bindings
#certificate_digest = base64.b16decode(server_cert.digest('SHA256').replace(':', ''))
## channel_binding_structure = gss_channel_bindings_struct()
## channel_binding_structure['application_data'] = "tls-server-end-point:" + certificate_digest
public_key = HttpCredSSPAuth._get_rsa_public_key(server_cert)
# The _RSAPublicKey must be 'wrapped' using the negotiated GSSAPI mechanism and send to the server along with
# the final SPNEGO token. This step of the CredSSP protocol is designed to thwart 'man-in-the-middle' attacks
# Build and encrypt the response to the server
ts_request = TSRequest()
type3= context_generator.send(challenge_token)
log.debug("NTLM Type 3: %s", AsHex(type3))
ts_request['negoTokens'] = type3
public_key_encrypted, signature = context.wrap_message(public_key)
ts_request['pubKeyAuth'] = signature + public_key_encrypted
self.tls_connection.send(ts_request.getData())
enc_type3 = self.tls_connection.bio_read(8192)
http_response = yield self._set_credssp_header(http_response.request, enc_type3)
# TLS decrypt the response, then ASN decode and check the error code
auth_response = self._get_credssp_header(http_response)
if not auth_response or auth_response is None:
raise Exception("The remote host rejected the challenge response")
self.tls_connection.bio_write(auth_response)
ts_request = TSRequest()
ts_request.fromString(self.tls_connection.recv(8192))
# TODO: determine how to validate server certificate here
#a = ts_request['pubKeyAuth']
# print ":".join("{:02x}".format(ord(c)) for c in a)
# 4. Send the Credentials to be delegated, these are encrypted with both NTLM v2 and then by TLS
tsp = TSPasswordCreds()
tsp['domain'] = self.password_authenticator.get_domain()
tsp['username'] = self.password_authenticator.get_username()
tsp['password'] = self.password_authenticator.get_password()
tsc = TSCredentials()
tsc['type'] = 1
tsc['credentials'] = tsp.getData()
ts_request = TSRequest()
encrypted, signature = context.wrap_message(tsc.getData())
ts_request['authInfo'] = signature + encrypted
self.tls_connection.send(ts_request.getData())
token = self.tls_connection.bio_read(8192)
http_response.request.body = self.body
http_response = yield self._set_credssp_header(self._encrypt(http_response.request, self.tls_connection), token)
if http_response.status_code == 401:
raise Exception('Authentication Failed')
#does the server need to respond with a final credssp header, probably not.
#if we arrive here something probably went wrong?
#if self._get_credssp_header(http_response) is None:
# raise Exception('Authentication Failed')
@staticmethod
def _encrypt(request, context):
body = '--Encrypted Boundary\r\n'
body += '\tContent-Type: application/HTTP-CredSSP-session-encrypted\r\n'
body += '\tOriginalContent: type=application/soap+xml;charset=UTF-8;Length=' + str(len(request.body)) + '\r\n'
body += '--Encrypted Boundary\r\n'
body += 'Content-Type: application/octet-stream\r\n'
# CredSSP uses the initial TLS context for encryption
context.send(request.body)
body += struct.pack('<i', 16)
body += context.bio_read(8192)
body += '--Encrypted Boundary--\r\n'
request.body = body
request.headers['Content-Length'] = str(len(body))
request.headers['Content-Type'] = 'multipart/encrypted;'
request.headers['Content-Type'] += 'protocol="application/HTTP-CredSSP-session-encrypted";'
request.headers['Content-Type'] += 'boundary="Encrypted Boundary"'
return request
@staticmethod
def _decrypt(response, context):
# TODO: there is some extra validation to sanitise the incoming response here
mime_parts = response.content.split('--Encrypted Boundary')
length = int(mime_parts[1].split(';Length=')[1].strip())
parts = mime_parts[2].split("application/octet-stream")
payload = parts[1][2:]
# The first 4 bytes of the response indicate the length of the signature. When using CredSSP the signature
# is not computed or sent, we simply validate this is 0x10
signature_length = struct.unpack('<i', payload[:4])[0]
tls_text = payload[4:]
#if len(tls_text) != length:
# raise Exception("extracted length not equal to expected length")
context.bio_write(tls_text)
plaintext = context.recv(8192)
return plaintext
def handle_401(self, response, **kwargs):
self.context = NtlmContext(self.password_authenticator, session_security='encrypt')
credssp_processor = self._credssp_processor(self.context)
next(credssp_processor)
while response.status_code == 401:
# This is required
response.content
response.raw.release_conn()
client_request = credssp_processor.send(response)
response = response.connection.send(client_request, **kwargs)
return response
def handle_response(self, response, **kwargs):
#if self.pos is not None:
# Rewind the file position indicator of the body to where
# it was to resend the request.
# response.request.body.seek(self.pos)
if response.status_code == 401:
response = self.handle_401(response, **kwargs)
log.debug("handle_response(): returning {0}".format(response))
# TODO: check the response header to see if the response is encrypted first
if response.status_code == 200:
logging.debug("decrypting body")
message = self._decrypt(response, self.tls_connection)
response._content = message
return response
def __call__(self, request):
request.headers["Connection"] = "Keep-Alive"
# TODO: implement support for unencrypted requests
request.register_hook('response', self.handle_response)
# We should not send any content to the target host until we have established a security context through the
# 'handle_response' hook, so we stash the original request body and remove it from the current request
if self.context is None:
self.body = str(request.body)
request.body = ""
request.headers["Content-Type"] = "application/soap+xml;charset=UTF-8"
request.headers['Content-Length'] = 0
else:
logging.debug("encrypting body")
self._encrypt(request, self.tls_connection)
return request
def test_get_username(self):
authentication = PasswordAuthentication('asgard', 'odin', 'yggdrasill')
self.assertEqual(authentication.get_username(), 'odin')