def create_pairing_response_by_serial(self, user_token_id, gda=None):
"""
Creates a base64-encoded pairing response that identifies
the token by its serial
:param user_token_id: the token id (primary key for the user token db)
:returns base64 encoded pairing response
"""
if not gda:
gda = self.gda
token_serial = self.tokens[user_token_id]['serial']
server_public_key = self.tokens[user_token_id]['server_public_key']
partition = self.tokens[user_token_id]['partition']
# ------------------------------------------------------------------ --
# assemble header and plaintext
header = struct.pack('<bI', PAIR_RESPONSE_VERSION, partition)
pairing_response = b''
pairing_response += struct.pack('<bI', TYPE_PUSHTOKEN, user_token_id)
pairing_response += self.public_key
pairing_response += token_serial.encode('utf8') + b'\x00\x00'
pairing_response += gda.encode('utf-8') + b'\x00'
signature = crypto_sign_detached(pairing_response, self.secret_key)
pairing_response += signature
# ------------------------------------------------------------------ --
# create public diffie hellman component
# (used to decrypt and verify the reponse)
r = os.urandom(32)
R = calc_dh_base(r)
# ------------------------------------------------------------------ --
# derive encryption key and nonce
server_public_key_dh = dsa_to_dh_public(server_public_key)
ss = calc_dh(r, server_public_key_dh)
U = SHA256.new(ss).digest()
encryption_key = U[0:16]
nonce = U[16:32]
# ------------------------------------------------------------------ --
# encrypt in EAX mode
cipher = AES.new(encryption_key, AES.MODE_EAX, nonce)
cipher.update(header)
ciphertext, tag = cipher.encrypt_and_digest(pairing_response)
return encode_base64_urlsafe(header + R + ciphertext + tag)
def create_pairing_response_by_serial(self, user_token_id):
"""
Creates a base64-encoded pairing response that identifies
the token by its serial
:param user_token_id: the token id (primary key for the user token db)
:returns base64 encoded pairing response
"""
token_serial = self.tokens[user_token_id]['serial']
server_public_key = self.tokens[user_token_id]['server_public_key']
partition = self.tokens[user_token_id]['partition']
# ------------------------------------------------------------------ --
# assemble header and plaintext
header = struct.pack('<bI', PAIR_RESPONSE_VERSION, partition)
pairing_response = b''
pairing_response += struct.pack('<bI', TYPE_PUSHTOKEN, user_token_id)
pairing_response += self.public_key
pairing_response += token_serial.encode('utf8') + b'\x00\x00'
pairing_response += self.gda + b'\x00'
signature = crypto_sign_detached(pairing_response, self.secret_key)
pairing_response += signature
# ------------------------------------------------------------------ --
# create public diffie hellman component
# (used to decrypt and verify the reponse)
r = os.urandom(32)
R = calc_dh_base(r)
# ------------------------------------------------------------------ --
# derive encryption key and nonce
server_public_key_dh = dsa_to_dh_public(server_public_key)
ss = calc_dh(r, server_public_key_dh)
U = SHA256.new(ss).digest()
encryption_key = U[0:16]
nonce = U[16:32]
# ------------------------------------------------------------------ --
# encrypt in EAX mode
cipher = AES.new(encryption_key, AES.MODE_EAX, nonce)
cipher.update(header)
ciphertext, tag = cipher.encrypt_and_digest(pairing_response)
return encode_base64_urlsafe(header + R + ciphertext + tag)
def send_pairing_response(pairing_url):
user_token_id = parse_pairing_url(pairing_url)
serial = token_db[user_token_id]['serial']
# ----------------------------------------------------------------------
server_public_key = token_db[user_token_id]['server_public_key']
pairing_response = b''
pairing_response += struct.pack('<bbI', RESPONSE_VERSION, TYPE_QRTOKEN,
user_token_id)
pairing_response += public_key
pairing_response += serial.encode('utf8') + b'\x00\x00'
# ----------------------------------------------------------------------
# create public diffie hellman component
# (used to decrypt and verify the reponse)
r = os.urandom(32)
R = calc_dh_base(r)
# ----------------------------------------------------------------------
# derive encryption key and nonce
ss = calc_dh(r, server_public_key)
U = SHA256.new(ss).digest()
encryption_key = U[0:16]
nonce = U[16:32]
# ----------------------------------------------------------------------
# encrypt in EAX mode
cipher = AES.new(encryption_key, AES.MODE_EAX, nonce)
ciphertext, tag = cipher.encrypt_and_digest(pairing_response)
pairing_response = encode_base64_urlsafe(R + ciphertext + tag)
params = {
'session': SESSION,
'pairing_response': pairing_response,
'type': 'qr'
}
r = requests.request('get',
'http://localhost:5001/admin/init',
params=params,
cookies=cookies)
print((r.status_code))
print('----------------------------------')
print((r.content))
def send_pairing_response(pairing_url):
user_token_id = parse_pairing_url(pairing_url)
serial = token_db[user_token_id]['serial']
# ----------------------------------------------------------------------
server_public_key = token_db[user_token_id]['server_public_key']
pairing_response = b''
pairing_response += struct.pack('<bbI', RESPONSE_VERSION,
TYPE_QRTOKEN, user_token_id)
pairing_response += public_key
pairing_response += serial.encode('utf8') + b'\x00\x00'
# ----------------------------------------------------------------------
# create public diffie hellman component
# (used to decrypt and verify the reponse)
r = os.urandom(32)
R = calc_dh_base(r)
# ----------------------------------------------------------------------
# derive encryption key and nonce
ss = calc_dh(r, server_public_key)
U = SHA256.new(ss).digest()
encryption_key = U[0:16]
nonce = U[16:32]
# ----------------------------------------------------------------------
# encrypt in EAX mode
cipher = AES.new(encryption_key, AES.MODE_EAX, nonce)
ciphertext, tag = cipher.encrypt_and_digest(pairing_response)
pairing_response = encode_base64_urlsafe(R + ciphertext + tag)
params = {'session': SESSION, 'pairing_response': pairing_response,
'type': 'qr' }
r = requests.request('get', 'http://localhost:5001/admin/init',
params=params, cookies=cookies)
print(r.status_code)
print('----------------------------------')
print(r.content)
def server_hmac_secret(self):
""" the server hmac secret for this specific token """
server_secret_key = get_qrtoken_dh_secret_key()
# user public key is saved base64 encoded
b64_user_public_key = self.getFromTokenInfo('user_public_key')
user_public_key = b64decode(b64_user_public_key)
hmac_secret = calc_dh(server_secret_key, user_public_key)
zerome(server_secret_key)
return hmac_secret
def server_hmac_secret(self):
""" the server hmac secret for this specific token """
server_secret_key = get_qrtoken_dh_secret_key()
# user public key is saved base64 encoded
b64_user_public_key = self.getFromTokenInfo('user_public_key')
user_public_key = b64decode(b64_user_public_key)
hmac_secret = calc_dh(server_secret_key, user_public_key)
zerome(server_secret_key)
return hmac_secret
def create_pairing_response(public_key, token_info, token_id=1):
"""
Creates a base64-encoded pairing response that identifies
the token by its serial
:param user_token_id: the token id (primary key for the user token db)
:returns base64 encoded pairing response
"""
token_serial = token_info['serial']
server_public_key = token_info['server_public_key']
partition = token_info['partition']
header = struct.pack('<bI', PAIR_RESPONSE_VERSION, partition)
pairing_response = b''
pairing_response += struct.pack('<bI', TYPE_QRTOKEN, token_id)
pairing_response += public_key
pairing_response += token_serial.encode('utf8') + b'\x00\x00'
# ------------------------------------------------------------------- --
# create public diffie hellman component
# (used to decrypt and verify the reponse)
r = os.urandom(32)
R = calc_dh_base(r)
# ------------------------------------------------------------------- --
# derive encryption key and nonce
ss = calc_dh(r, server_public_key)
U = SHA256.new(ss).digest()
encryption_key = U[0:16]
nonce = U[16:32]
# ------------------------------------------------------------------- --
# encrypt in EAX mode
cipher = AES.new(encryption_key, AES.MODE_EAX, nonce)
cipher.update(header)
ciphertext, tag = cipher.encrypt_and_digest(pairing_response)
return encode_base64_urlsafe(header + R + ciphertext + tag)
def calc_dh(self, partition, data):
"""
encapsulate the Diffi Helmann calculation
as the server secret key is a sensitive data, we try to encapsulate
it and care for the cleanup
:param partition: the id of the server secret key
:param :
"""
server_secret_key = get_dh_secret_key(partition)
hmac_secret = calc_dh(server_secret_key, data)
zerome(server_secret_key)
return hmac_secret
def calc_dh(self, partition, data):
"""
encapsulate the Diffi Helmann calculation
as the server secret key is a sensitive data, we try to encapsulate
it and care for the cleanup
:param partition: the id of the server secret key
:param :
"""
server_secret_key = get_dh_secret_key(partition)
hmac_secret = calc_dh(server_secret_key, data)
zerome(server_secret_key)
return hmac_secret
def decrypt_and_verify_challenge(challenge_url, token_info, secret_key):
"""
Decrypts the data packed in the challenge url, verifies
its content, returns the parsed data as a dictionary,
calculates and returns the signature and TAN.
The calling method must then send the signature/TAN
back to the server. (The reason for this control flow
is that the challenge data must be checked in different
scenarios, e.g. when we have a pairing the data must be
checked by the method that simulates the pairing)
:param challenge_url: the challenge url as sent by the server
:returns: (challenge, signature, tan)
challenge has the keys
* message - the signed message sent from the server
* content_type - one of the three values QRTOKEN_CT_PAIR,
QRTOKEN_CT_FREE or QRTOKEN_CT_AUTH
(all defined in this module
* callback_url (optional) - the url to which the challenge
response should be set
* callback_sms (optional) - the sms number the challenge
can be sent to (typicall used as a fallback)
* transaction_id - used to identify the challenge
on the server
* user_token_id - used to identify the token in the
user database for which this challenge was created
signature is the generated user signature used to
respond to the challenge
tan is the TAN-Number used as a substitute if the signature
cant' be sent be the server (is generated from signature)
"""
challenge_data_encoded = challenge_url[len(QR_Token_Validation.uri + '://chal/'):]
challenge_data = decode_base64_urlsafe(challenge_data_encoded)
# ------------------------------------------------------------------- --
# parse and verify header information in the
# encrypted challenge data
header = challenge_data[0:5]
version, user_token_id = struct.unpack('<bI', header)
assert version == QRTOKEN_VERSION
# ------------------------------------------------------------------- --
# get token from client token database
# ------------------------------------------------------------------- --
# prepare decryption by seperating R from
# ciphertext and tag
R = challenge_data[5:5 + 32]
ciphertext = challenge_data[5 + 32:-16]
tag = challenge_data[-16:]
# ------------------------------------------------------------------- --
# key derivation
ss = calc_dh(secret_key, R)
U1 = SHA256.new(ss).digest()
U2 = SHA256.new(U1).digest()
skA = U1[0:16]
skB = U2[0:16]
nonce = U2[16:32]
# ------------------------------------------------------------------- --
# decrypt and verify challenge
cipher = AES.new(skA, AES.MODE_EAX, nonce)
cipher.update(header)
plaintext = cipher.decrypt_and_verify(ciphertext, tag)
# ------------------------------------------------------------------- --
# parse/check plaintext header
pt_header = plaintext[0:10]
content_type, flags, transaction_id = struct.unpack('<bbQ', pt_header)
transaction_id = QR_Token_Validation.u64_to_transaction_id(transaction_id)
# make sure a flag for the server signature is
# present, if the content type is 'pairing'
if content_type == QRTOKEN_CT_PAIR:
assert flags & FLAG_QR_SRVSIG
# ------------------------------------------------------------------- --
# retrieve plaintext data depending on flags
if flags & FLAG_QR_SRVSIG:
# plaintext has a server signature as a header
# extract it and check if it is correct
server_signature = plaintext[10:10 + 32]
data = plaintext[10 + 32:]
# calculate secret
server_public_key = token_info['server_public_key']
secret = calc_dh(secret_key, server_public_key)
# check hmac
message = nonce + pt_header + data
signed = HMAC.new(secret, msg=message, digestmod=SHA256).digest()
assert server_signature == signed
else:
# no server signature found - just remove
# the plaintext header
data = plaintext[10:]
# we have to define an empty server signature in
# here because we need it later to create the
# client signature
server_signature = b''
# ------------------------------------------------------------------- --
# extract message and (optional) callback
# parameters from data
message, _, suffix = data.partition(b'\x00')
callback_url = token_info.get('callback_url')
if flags & FLAG_QR_HAVE_URL:
callback_url, _, suffix = suffix.partition(b'\x00')
callback_sms = token_info.get('callback_sms')
if flags & FLAG_QR_HAVE_SMS:
callback_sms, _, suffix = suffix.partition(b'\x00')
# ------------------------------------------------------------------- --
# prepare the parsed challenge data
challenge = {}
challenge['message'] = message.decode('utf-8')
challenge['content_type'] = content_type
challenge['transaction_id'] = transaction_id
challenge['user_token_id'] = user_token_id
if callback_url:
challenge['callback_url'] = callback_url.decode('utf-8')
if callback_sms:
challenge['callback_sms'] = callback_sms.decode('utf-8')
# calculate signature and tan
message_bin = nonce + pt_header + server_signature + data
sig_hmac = HMAC.new(skB, message_bin, digestmod=SHA256)
sig = sig_hmac.digest()
tan = extract_tan(sig, QR_Token_Validation.tan_length)
encoded_sig = encode_base64_urlsafe(sig)
return challenge, encoded_sig, tan
def create_challenge_url(self,
transaction_id,
content_type,
callback_url='',
message=None,
login=None,
host=None):
"""
creates a challenge url (looking like lseqr://push/<base64string>),
returns the url and the unencrypted challenge data
:param transaction_id: The transaction id generated by LinOTP
:param content_type: One of the types CONTENT_TYPE_SIGNREQ,
CONTENT_TYPE_PAIRING, CONTENT_TYPE_LOGIN
:param callback_url: callback url (optional), default is
empty string
:param message: the transaction message, that should be signed
by the client. Only for content type CONTENT_TYPE_SIGNREQ
:param login: the login name of the user. Only for content type
CONTENT_TYPE_LOGIN
:param host: hostname of the user. Only for content type
CONTENT_TYPE_LOGIN
:returns: tuple (challenge_url, sig_base), with challenge_url being
the push url and sig_base the message, that is used for
the client signature
"""
serial = self.getSerial()
# ------------------------------------------------------------------- --
# sanity/format checks
if content_type not in [CONTENT_TYPE_SIGNREQ,
CONTENT_TYPE_PAIRING, CONTENT_TYPE_LOGIN]:
raise InvalidFunctionParameter('content_type', 'content_type must '
'be CONTENT_TYPE_SIGNREQ, '
'CONTENT_TYPE_PAIRING or '
'CONTENT_TYPE_LOGIN.')
# ------------------------------------------------------------------- --
# after the lseqr://push/ prefix the following data is encoded
# in urlsafe base64:
# ---------------------------------------------------
# fields | version | user token id | R | ciphertext | sign |
# ---------------------------------------------------
# | header | body |
# ---------------------------------------------------
# size | 1 | 4 | 32 | ? | 64 |
# ---------------------------------------------------
#
# create header
user_token_id = self.getFromTokenInfo('user_token_id')
data_header = struct.pack('<bI', CHALLENGE_URL_VERSION, user_token_id)
# ------------------------------------------------------------------- --
# create body
r = urandom(32)
R = calc_dh_base(r)
b64_user_dsa_public_key = self.getFromTokenInfo('user_dsa_public_key')
user_dsa_public_key = b64decode(b64_user_dsa_public_key)
user_dh_public_key = dsa_to_dh_public(user_dsa_public_key)
ss = calc_dh(r, user_dh_public_key)
U = SHA256.new(ss).digest()
zerome(ss)
sk = U[0:16]
nonce = U[16:32]
zerome(U)
# ------------------------------------------------------------------- --
# create plaintext section
# ------------------------------------------------------------------- --
# generate plaintext header
# ------------------------------------------------
# fields | content_type | transaction_id | timestamp | ..
# ------------------------------------------------
# size | 1 | 8 | 8 | ?
# -------------------------------------------------
transaction_id = transaction_id_to_u64(transaction_id)
plaintext = struct.pack('<bQQ', content_type, transaction_id,
int(time.time()))
# ------------------------------------------------------------------- --
utf8_callback_url = callback_url.encode('utf8')
# enforce max url length as specified in protocol
if len(utf8_callback_url) > 511:
raise InvalidFunctionParameter('callback_url', 'max string '
'length (encoded as utf8) is '
'511')
# ------------------------------------------------------------------- --
# create data package depending on content type
# ------------------------------------------------------------------- --
if content_type == CONTENT_TYPE_PAIRING:
# -----------------------------------------
# fields | header | serial | NUL | callback | NUL |
# -----------------------------------------
# size | 9 | ? | 1 | ? | 1 |
# -----------------------------------------
utf8_serial = serial.encode('utf8')
if len(utf8_serial) > 63:
raise ValueError('serial (encoded as utf8) can only be 63 '
'characters long')
plaintext += utf8_serial + b'\00' + utf8_callback_url + b'\00'
# ------------------------------------------------------------------- --
if content_type == CONTENT_TYPE_SIGNREQ:
if message is None:
raise InvalidFunctionParameter('message', 'message must be '
'supplied for content type '
'SIGNREQ')
# ------------------------------------------
# fields | header | message | NUL | callback | NUL |
# ------------------------------------------
# size | 9 | ? | 1 | ? | 1 |
# ------------------------------------------
utf8_message = message.encode('utf8')
# enforce max sizes specified by protocol
if len(utf8_message) > 511:
raise InvalidFunctionParameter('message', 'max string '
'length (encoded as utf8) is '
'511')
plaintext += utf8_message + b'\00' + utf8_callback_url + b'\00'
# ------------------------------------------------------------------- --
if content_type == CONTENT_TYPE_LOGIN:
if login is None:
raise InvalidFunctionParameter('login', 'login must be '
'supplied for content type '
'LOGIN')
if host is None:
raise InvalidFunctionParameter('host', 'host must be '
'supplied for content type '
'LOGIN')
# -----------------------------------------------------
# fields | header | login | NUL | host | NUL | callback | NUL |
# -----------------------------------------------------
# size | 9 | ? | 1 | ? | 1 | ? | 1 |
# -----------------------------------------------------
utf8_login = login.encode('utf8')
utf8_host = host.encode('utf8')
# enforce max sizes specified by protocol
if len(utf8_login) > 127:
raise InvalidFunctionParameter('login', 'max string '
'length (encoded as utf8) is '
'127')
if len(utf8_host) > 255:
raise InvalidFunctionParameter('host', 'max string '
'length (encoded as utf8) is '
'255')
plaintext += utf8_login + b'\00'
plaintext += utf8_host + b'\00'
plaintext += utf8_callback_url + b'\00'
# ------------------------------------------------------------------- --
# encrypt inner layer
nonce_as_int = int_from_bytes(nonce, byteorder='big')
ctr = Counter.new(128, initial_value=nonce_as_int)
cipher = AES.new(sk, AES.MODE_CTR, counter=ctr)
ciphertext = cipher.encrypt(plaintext)
unsigned_raw_data = data_header + R + ciphertext
# ------------------------------------------------------------------- --
# create signature
partition = self.getFromTokenInfo('partition')
secret_key = get_secret_key(partition)
signature = crypto_sign_detached(unsigned_raw_data, secret_key)
raw_data = unsigned_raw_data + signature
url = 'lseqr://push/' + encode_base64_urlsafe(raw_data)
return url, (signature + plaintext)
def decrypt_pairing_response(enc_pairing_response):
"""
Parses and decrypts a pairing response into a named tuple PairingResponse
consisting of
* user_public_key - the user's public key
* user_token_id - an id for the client to uniquely identify the token.
this id is necessary, because the client could
communicate with more than one linotp, so serials
could overlap.
* serial - the serial identifying the token in linotp
* user_login - the user login name
It is possible that either user_login or serial is None. Both
being None is a valid response according to this function but
will be considered an error in the calling method.
The following parameters are needed:
:param enc_pairing_response:
The urlsafe-base64 encoded string received from the client
The following exceptions can be raised:
:raises ParameterError:
If the pairing response has an invalid format
:raises ValueError:
If the pairing response has a different version
than this implementation (currently hardcoded)
:raises ValueError:
If the pairing response indicates a different
token type than QRToken (also hardcoded)
:raises ValueError:
If the MAC of the response didn't match
:return:
Parsed/encrpted PairingReponse
"""
data = decode_base64_urlsafe(enc_pairing_response)
# --------------------------------------------------------------------------
# -----------------------
# fields | R | ciphertext | MAC |
# -----------------------
# size | 32 | ? | 16 |
# -----------------------
if len(data) < 32 + 16:
raise ParameterError('Malformed pairing response')
R = data[0:32]
ciphertext = data[32:-16]
mac = data[-16:]
# --------------------------------------------------------------------------
# calculate the shared secret
# ----
secret_key = get_qrtoken_secret_key()
ss = calc_dh(secret_key, R)
# derive encryption key and nonce from the shared secret
# zero the values from memory when they are not longer needed
U = SHA256.new(ss).digest()
zerome(ss)
encryption_key = U[0:16]
nonce = U[16:32]
zerome(U)
# decrypt response
cipher = AES.new(encryption_key, AES.MODE_EAX, nonce)
plaintext = cipher.decrypt_and_verify(ciphertext, mac)
# --------------------------------------------------------------------------
# parse decrypted response
# ----
plaintext_min_length = 1 + 1 + 4 + 32 + 1
if len(data) < plaintext_min_length:
raise ParameterError('Malformed pairing response')
# Parse Pairing Reponse Header (First 6 Bytes)
# -------------------------------------------
# fields | version | type | user token id | ... |
# -------------------------------------------
# size | 1 | 1 | 4 | ? |
# -------------------------------------------
resp_header = plaintext[0:6]
version, token_type, user_token_id = struct.unpack('<bbI', resp_header)
if version != 0:
raise ValueError('Unexpected pair-response version, '
'expected: %d, got: %d' % (0, version))
if token_type != 2:
raise ValueError('wrong token type in user response, '
'expected: %d, got: %d' % (2, token_type))
# --------------------------------------------------------------------------
# get user public key (next 32 bytes)
# -----------------------------
# fields | ... | user public key | ... |
# -----------------------------
# size | 6 | 32 | ? |
# -----------------------------
user_public_key = plaintext[6:6+32]
# --------------------------------------------------------------------------
# get serial and/or user login
# ---------------------------------
# fields | ... | serial | NUL | user login |
# ---------------------------------
# size | 38 | ? | 1 | ? |
# ---------------------------------
# parse token_serial and user identification
serial_user_data = plaintext[6+32:].split(b'\x00')
serial = serial_user_data[0].decode('utf8')
user_login = serial_user_data[1].decode('utf8')
return PairingResponse(user_public_key, user_token_id, serial, user_login)
def decrypt_pairing_response(enc_pairing_response):
"""
Parses and decrypts a pairing response into a named tuple PairingResponse
consisting of
* user_public_key - the user's public key
* user_token_id - an id for the client to uniquely identify the token.
this id is necessary, because the client could
communicate with more than one linotp, so serials
could overlap.
* serial - the serial identifying the token in linotp
* user_login - the user login name
It is possible that either user_login or serial is None. Both
being None is a valid response according to this function but
will be considered an error in the calling method.
The following parameters are needed:
:param enc_pairing_response:
The urlsafe-base64 encoded string received from the client
The following exceptions can be raised:
:raises ParameterError:
If the pairing response has an invalid format
:raises ValueError:
If the pairing response has a different version
than this implementation (currently hardcoded)
:raises ValueError:
If the pairing response indicates a different
token type than QRToken (also hardcoded)
:raises ValueError:
If the MAC of the response didn't match
:return:
Parsed/encrpted PairingReponse
"""
data = decode_base64_urlsafe(enc_pairing_response)
# --------------------------------------------------------------------------
# -----------------------
# fields | R | ciphertext | MAC |
# -----------------------
# size | 32 | ? | 16 |
# -----------------------
if len(data) < 32 + 16:
raise ParameterError('Malformed pairing response')
R = data[0:32]
ciphertext = data[32:-16]
mac = data[-16:]
# --------------------------------------------------------------------------
# calculate the shared secret
# ----
secret_key = get_qrtoken_dh_secret_key()
ss = calc_dh(secret_key, R)
# derive encryption key and nonce from the shared secret
# zero the values from memory when they are not longer needed
U = SHA256.new(ss).digest()
zerome(ss)
encryption_key = U[0:16]
nonce = U[16:32]
zerome(U)
# decrypt response
cipher = AES.new(encryption_key, AES.MODE_EAX, nonce)
plaintext = cipher.decrypt_and_verify(ciphertext, mac)
# --------------------------------------------------------------------------
# parse decrypted response
# ----
plaintext_min_length = 1 + 1 + 4 + 32 + 1
if len(data) < plaintext_min_length:
raise ParameterError('Malformed pairing response')
# Parse Pairing Reponse Header (First 6 Bytes)
# -------------------------------------------
# fields | version | type | user token id | ... |
# -------------------------------------------
# size | 1 | 1 | 4 | ? |
# -------------------------------------------
resp_header = plaintext[0:6]
version, token_type, user_token_id = struct.unpack('<bbI', resp_header)
if version != 0:
raise ValueError('Unexpected pair-response version, '
'expected: %d, got: %d' % (0, version))
if token_type != 2:
raise ValueError('wrong token type in user response, '
'expected: %d, got: %d' % (2, token_type))
# --------------------------------------------------------------------------
# get user public key (next 32 bytes)
# -----------------------------
# fields | ... | user public key | ... |
# -----------------------------
# size | 6 | 32 | ? |
# -----------------------------
user_public_key = plaintext[6:6+32]
# --------------------------------------------------------------------------
# get serial and/or user login
# ---------------------------------
# fields | ... | serial | NUL | user login |
# ---------------------------------
# size | 38 | ? | 1 | ? |
# ---------------------------------
# parse token_serial and user identification
serial_user_data = plaintext[6+32:].split(b'\x00')
serial = serial_user_data[0].decode('utf8')
user_login = serial_user_data[1].decode('utf8')
return PairingResponse(user_public_key, user_token_id, serial, user_login)
def decrypt_and_verify_challenge(self, challenge_url, action):
"""
Decrypts the data packed in the challenge url, verifies
its content, returns the parsed data as a dictionary,
calculates and returns the signature.
The calling method must then send the signature
back to the server. (The reason for this control flow
is that the challenge data must be checked in different
scenarios, e.g. when we have a pairing the data must be
checked by the method that simulates the pairing)
:param challenge_url: the challenge url as sent by the server
:param action: a string identifier for the verification action
(at the moment 'ACCEPT' or 'DENY')
:returns: (challenge, signature)
challenge has the keys
* content_type - one of the three values CONTENT_TYPE_SIGNREQ,
CONTENT_TYPE_PAIRING or CONTENT_TYPE_LOGIN)
(all defined in this module)
* transaction_id - used to identify the challenge
on the server
* callback_url (optional) - the url to which the challenge
response should be set
* user_token_id - used to identify the token in the
user database for which this challenge was created
depending on the content type additional keys are present
* for CONTENT_TYPE_PAIRING: serial
* for CONTENT_TYPE_SIGNREQ: message
* for CONTENT_TYPE_LOGIN: login, host
signature is the generated user signature used to
respond to the challenge
"""
challenge_data_encoded = challenge_url[len(self.uri + '://chal/'):]
challenge_data = decode_base64_urlsafe(challenge_data_encoded)
# ------------------------------------------------------------------ --
# parse and verify header information in the
# encrypted challenge data
header = challenge_data[0:5]
version, user_token_id = struct.unpack('<bI', header)
self.assertEqual(version, CHALLENGE_URL_VERSION)
# ------------------------------------------------------------------ --
# get token from client token database
token = self.tokens[user_token_id]
server_public_key = token['server_public_key']
# ------------------------------------------------------------------ --
# prepare decryption by seperating R from
# ciphertext and server signature
R = challenge_data[5:5 + 32]
ciphertext = challenge_data[5 + 32:-64]
server_signature = challenge_data[-64:]
# check signature
data = challenge_data[0:-64]
crypto_sign_verify_detached(server_signature, data, server_public_key)
# ------------------------------------------------------------------ --
# key derivation
secret_key_dh = dsa_to_dh_secret(self.secret_key)
ss = calc_dh(secret_key_dh, R)
U = SHA256.new(ss).digest()
sk = U[0:16]
nonce = U[16:32]
# ------------------------------------------------------------------ --
# decrypt and verify challenge
nonce_as_int = int_from_bytes(nonce, byteorder='big')
ctr = Counter.new(128, initial_value=nonce_as_int)
cipher = AES.new(sk, AES.MODE_CTR, counter=ctr)
plaintext = cipher.decrypt(ciphertext)
# ------------------------------------------------------------------ --
# parse/check plaintext header
# 1 - for content type
# 8 - for transaction id
# 8 - for time stamp
offset = 1 + 8 + 8
pt_header = plaintext[0:offset]
(content_type, transaction_id,
_time_stamp) = struct.unpack('<bQQ', pt_header)
transaction_id = u64_to_transaction_id(transaction_id)
# ------------------------------------------------------------------ --
# prepare the parsed challenge data
challenge = {}
challenge['content_type'] = content_type
# ------------------------------------------------------------------ --
# retrieve plaintext data depending on content_type
if content_type == CONTENT_TYPE_PAIRING:
serial, callback_url, __ = plaintext[offset:].split('\x00')
challenge['serial'] = serial
elif content_type == CONTENT_TYPE_SIGNREQ:
message, callback_url, __ = plaintext[offset:].split('\x00')
challenge['message'] = message
elif content_type == CONTENT_TYPE_LOGIN:
login, host, callback_url, __ = plaintext[offset:].split('\x00')
challenge['login'] = login
challenge['host'] = host
# ------------------------------------------------------------------ --
# prepare the parsed challenge data
challenge['callback_url'] = callback_url
challenge['transaction_id'] = transaction_id
challenge['user_token_id'] = user_token_id
# calculate signature
sig_base = (struct.pack('<b', CHALLENGE_URL_VERSION) +
b'%s\0' % action + server_signature + plaintext)
sig = crypto_sign_detached(sig_base, self.secret_key)
encoded_sig = encode_base64_urlsafe(sig)
return challenge, encoded_sig
def decrypt_pairing_response(enc_pairing_response):
"""
Parses and decrypts a pairing response into a named tuple PairingResponse
consisting of
* user_public_key - the user's public key
* user_token_id - an id for the client to uniquely identify the token.
this id is necessary, because the client could
communicate with more than one linotp, so serials
could overlap.
* serial - the serial identifying the token in linotp
* user_login - the user login name
It is possible that either user_login or serial is None. Both
being None is a valid response according to this function but
will be considered an error in the calling method.
The following parameters are needed:
:param enc_pairing_response:
The urlsafe-base64 encoded string received from the client
The following exceptions can be raised:
:raises ParameterError:
If the pairing response has an invalid format
:raises ValueError:
If the pairing response has a different version
than this implementation (currently hardcoded)
:raises ValueError:
If the pairing response indicates a different
token type than QRToken (also hardcoded)
:raises ValueError:
If the pairing response field "partition" is not
identical to the field "token_type"
("partition" is currently used for the token
type id. It is reserved for multiple key usage
in a future implementation.)
:raises ValueError:
If the MAC of the response didn't match
:return:
Parsed/decrypted PairingReponse
"""
data = decode_base64_urlsafe(enc_pairing_response)
# ---------------------------------------------------------------------- --
# ------------------------------------------- --
# fields | version | partition | R | ciphertext | MAC |
# ------------------------------------------- --
# size | 1 | 4 | 32 | ? | 16 |
# ------------------------------------------- --
if len(data) < 1 + 4 + 32 + 16:
raise ParameterError('Malformed pairing response')
# ---------------------------------------------------------------------- --
# parse header
header = data[0:5]
version, partition = struct.unpack('<bI', header)
if version != PAIR_RESPONSE_VERSION:
raise ValueError('Unexpected pair-response version, '
'expected: %d, got: %d' %
(PAIR_RESPONSE_VERSION, version))
# ---------------------------------------------------------------------- --
R = data[5:32+5]
ciphertext = data[32+5:-16]
mac = data[-16:]
# ---------------------------------------------------------------------- --
# calculate the shared secret
# - --
secret_key = get_dh_secret_key(partition)
ss = calc_dh(secret_key, R)
# derive encryption key and nonce from the shared secret
# zero the values from memory when they are not longer needed
U = SHA256.new(ss).digest()
zerome(ss)
encryption_key = U[0:16]
nonce = U[16:32]
zerome(U)
# decrypt response
cipher = AES.new(encryption_key, AES.MODE_EAX, nonce)
cipher.update(header)
plaintext = cipher.decrypt_and_verify(ciphertext, mac)
zerome(encryption_key)
# ---------------------------------------------------------------------- --
# check format boundaries for type peaking
# (token type specific length boundaries are checked
# in the appropriate functions)
plaintext_min_length = 1
if len(data) < plaintext_min_length:
raise ParameterError('Malformed pairing response')
# ---------------------------------------------------------------------- --
# get token type and parse decrypted response
# -------------------- --
# fields | token type | ... |
# -------------------- --
# size | 1 | ? |
# -------------------- --
token_type = struct.unpack('<b', plaintext[0])[0]
if token_type not in SUPPORTED_TOKEN_TYPES:
raise ValueError('unsupported token type %d, supported types '
'are %s' % (token_type, SUPPORTED_TOKEN_TYPES))
# ---------------------------------------------------------------------- --
# delegate the data parsing of the plaintext
# to the appropriate function and return the result
data_parser = get_pairing_data_parser(token_type)
pairing_data = data_parser(plaintext)
zerome(plaintext)
# get the appropriate high level type
try:
token_type_as_str = INV_TOKEN_TYPES[token_type]
except KeyError:
raise ProgrammingError('token_type %d is in SUPPORTED_TOKEN_TYPES',
'however an appropriate mapping entry in '
'TOKEN_TYPES is missing' % token_type)
return PairingResponse(token_type_as_str, pairing_data)
def decrypt_pairing_response(enc_pairing_response):
"""
Parses and decrypts a pairing response into a named tuple PairingResponse
consisting of
* user_public_key - the user's public key
* user_token_id - an id for the client to uniquely identify the token.
this id is necessary, because the client could
communicate with more than one linotp, so serials
could overlap.
* serial - the serial identifying the token in linotp
* user_login - the user login name
It is possible that either user_login or serial is None. Both
being None is a valid response according to this function but
will be considered an error in the calling method.
The following parameters are needed:
:param enc_pairing_response:
The urlsafe-base64 encoded string received from the client
The following exceptions can be raised:
:raises ParameterError:
If the pairing response has an invalid format
:raises ValueError:
If the pairing response has a different version
than this implementation (currently hardcoded)
:raises ValueError:
If the pairing response indicates a different
token type than QRToken (also hardcoded)
:raises ValueError:
If the pairing response field "partition" is not
identical to the field "token_type"
("partition" is currently used for the token
type id. It is reserved for multiple key usage
in a future implementation.)
:raises ValueError:
If the MAC of the response didn't match
:return:
Parsed/decrypted PairingReponse
"""
data = decode_base64_urlsafe(enc_pairing_response)
# ----------------------------------------------------------------------- --
# --------------------------------------------
# fields | version | partition | R | ciphertext | MAC |
# --------------------------------------------
# size | 1 | 4 | 32 | ? | 16 |
# --------------------------------------------
if len(data) < 1 + 4 + 32 + 16:
raise ParameterError('Malformed pairing response')
# ----------------------------------------------------------------------- --
# parse header
header = data[0:5]
version, partition = struct.unpack('<bI', header)
if version != PAIR_RESPONSE_VERSION:
raise ValueError('Unexpected pair-response version, '
'expected: %d, got: %d' %
(PAIR_RESPONSE_VERSION, version))
# ----------------------------------------------------------------------- --
R = data[5:32 + 5]
ciphertext = data[32 + 5:-16]
mac = data[-16:]
# ----------------------------------------------------------------------- --
# calculate the shared secret
# - --
secret_key = get_dh_secret_key(partition)
ss = calc_dh(secret_key, R)
# derive encryption key and nonce from the shared secret
# zero the values from memory when they are not longer needed
U = SHA256.new(ss).digest()
zerome(ss)
encryption_key = U[0:16]
nonce = U[16:32]
zerome(U)
# decrypt response
cipher = AES.new(encryption_key, AES.MODE_EAX, nonce)
cipher.update(header)
plaintext = cipher.decrypt_and_verify(ciphertext, mac)
zerome(encryption_key)
# ----------------------------------------------------------------------- --
# check format boundaries for type peaking
# (token type specific length boundaries are checked
# in the appropriate functions)
plaintext_min_length = 1
if len(data) < plaintext_min_length:
raise ParameterError('Malformed pairing response')
# ----------------------------------------------------------------------- --
# get token type and parse decrypted response
# ----------------------
# fields | token type | ... |
# ----------------------
# size | 1 | ? |
# ----------------------
token_type = struct.unpack('<b', plaintext[0])[0]
if token_type not in SUPPORTED_TOKEN_TYPES:
raise ValueError('unsupported token type %d, supported types '
'are %s' % (token_type, SUPPORTED_TOKEN_TYPES))
# ----------------------------------------------------------------------- --
# delegate the data parsing of the plaintext
# to the appropriate function and return the result
data_parser = get_pairing_data_parser(token_type)
pairing_data = data_parser(plaintext)
zerome(plaintext)
# get the appropriate high level type
try:
token_type_as_str = INV_TOKEN_TYPES[token_type]
except KeyError:
raise ProgrammingError(
'token_type %d is in SUPPORTED_TOKEN_TYPES',
'however an appropriate mapping entry in '
'TOKEN_TYPES is missing' % token_type)
return PairingResponse(token_type_as_str, pairing_data)
def create_challenge_url(self,
transaction_id,
content_type,
message,
callback_url,
callback_sms_number,
use_compression=False,
reset_url=False):
"""
creates a challenge url (looking like lseqr://chal/<base64string>)
from a challenge dictionary as provided by Challanges.create_challenge
in lib.challenge
the version identifier of the challenge url is currently hardcoded
to 1.
"""
serial = self.getSerial()
if content_type is None:
content_type = CONTENT_TYPE_FREE
# ------------------------------------------------------------------- --
# sanity/format checks
if content_type not in [
CONTENT_TYPE_PAIRING, CONTENT_TYPE_AUTH, CONTENT_TYPE_FREE
]:
raise InvalidFunctionParameter(
'content_type', 'content_type must '
'be CONTENT_TYPE_PAIRING, '
'CONTENT_TYPE_AUTH or '
'CONTENT_TYPE_FREE.')
if content_type == CONTENT_TYPE_PAIRING and \
message != serial:
raise InvalidFunctionParameter(
'message', 'message must be equal '
'to serial in pairing mode')
if content_type == CONTENT_TYPE_AUTH:
if '@' not in message:
raise InvalidFunctionParameter(
'message', 'For content type '
'auth, message must have format '
'<login>@<server>')
# ------------------------------------------------------------------- --
# after the lseqr://chal/ prefix the following data is encoded
# in urlsafe base64:
# ---------------------------------------------------
# fields | version | user token id | R | ciphertext | MAC |
# ---------------------------------------------------
# | header | | EAX enc data |
# ---------------------------------------------------
# size | 1 | 4 | 32 | ? | 16 |
# ---------------------------------------------------
#
r = urandom(32)
R = calc_dh_base(r)
user_token_id = self.getFromTokenInfo('user_token_id')
data_header = struct.pack('<bI', QRTOKEN_VERSION, user_token_id)
# the user public key is saved as base64 in
# the token info since the byte format is
# incompatible with the json backend.
b64_user_public_key = self.getFromTokenInfo('user_public_key')
user_public_key = b64decode(b64_user_public_key)
ss = calc_dh(r, user_public_key)
U1 = sha256(ss).digest()
U2 = sha256(U1).digest()
zerome(ss)
skA = U1[0:16]
skB = U2[0:16]
nonce = U2[16:32]
zerome(U1)
zerome(U2)
# ------------------------------------------------------------------- --
# create plaintext section
# ------------------------------------------------------------------- --
# create the bitmap for flags
flags = 0
if use_compression:
flags |= CHALLENGE_HAS_COMPRESSION
# FIXME: sizecheck for message, callback url, sms number
# wiki specs are utf-8 byte length (without \0)
if callback_url is not None:
flags |= CHALLENGE_HAS_URL
if callback_sms_number is not None:
flags |= CHALLENGE_HAS_SMS_NUMBER
if (content_type == CONTENT_TYPE_PAIRING):
flags |= CHALLENGE_HAS_SIGNATURE
if reset_url:
flags |= CHALLENGE_SHOULD_RESET_URL
flags |= CHALLENGE_HAS_SIGNATURE
#------------------------------------------------------------------- --
# generate plaintext header
# ----------------------------------------------
# fields | content_type | flags | transaction_id | ... |
# ----------------------------------------------
# size | 1 | 1 | 8 | ? |
# ----------------------------------------------
transaction_id = transaction_id_to_u64(transaction_id)
pt_header = struct.pack('<bbQ', content_type, flags, transaction_id)
plaintext = pt_header
#------------------------------------------------------------------- --
# create data package
# -------------------------------
# fields | header | message | NUL | ... |
# -------------------------------
# size | 10 | ? | 1 | ? |
# -------------------------------
data_package = b''
utf8_message = message.encode('utf8')
# enforce max sizes specified by protocol
if content_type == CONTENT_TYPE_FREE and len(utf8_message) > 511:
raise ParameterError('message (encoded as utf8) can only be 511 '
'characters long')
elif content_type == CONTENT_TYPE_PAIRING and len(utf8_message) > 63:
raise InvalidFunctionParameter(
'message', 'max string length '
'(encoded as utf8) is 511 for '
'content type PAIRING')
elif content_type == CONTENT_TYPE_AUTH and len(utf8_message) > 511:
raise InvalidFunctionParameter(
'message', 'max string length '
'(encoded as utf8) is 511 for '
'content type AUTH')
data_package += utf8_message + b'\x00'
# ------------------------------------------------------------------- --
# depending on function parameters add callback url
# and/or callback sms number
# -----------------------------------------------------
# fields | ... | callback url | NUL | callback sms | NUL | ... |
# -----------------------------------------------------
# size | ? | ? | 1 | ? | 1 | ? |
# -----------------------------------------------------
# ------------------------------------------------------------------- --
if callback_url is not None:
utf8_callback_url = callback_url.encode('utf8')
# enforce max url length as specified in protocol
if len(utf8_callback_url) > 511:
raise InvalidFunctionParameter(
'callback_url', 'max string '
'length (encoded as utf8) is '
'511')
data_package += utf8_callback_url + b'\x00'
# ------------------------------------------------------------------- --
if callback_sms_number is not None:
utf8_callback_sms_number = callback_sms_number.encode('utf8')
if len(utf8_callback_sms_number) > 31:
raise InvalidFunctionParameter(
'callback_sms_number', 'max string length (encoded '
'as utf8) is 31')
data_package += utf8_callback_sms_number + b'\x00'
# ------------------------------------------------------------------- --
if use_compression:
maybe_compressed_data_package = zlib.compress(data_package, 9)
else:
maybe_compressed_data_package = data_package
# ------------------------------------------------------------------- --
# when content type is pairing the protocol specifies that
# the server must send a hmac based signature with the
# response
sig = ''
sec_obj = self._get_secret_object()
if flags & CHALLENGE_HAS_SIGNATURE:
hmac_message = nonce + pt_header + maybe_compressed_data_package
sig = sec_obj.hmac_digest(data_input=hmac_message,
bkey=self.server_hmac_secret,
hash_algo=sha256)
plaintext += sig
# ------------------------------------------------------------------- --
plaintext += maybe_compressed_data_package
# ------------------------------------------------------------------- --
user_message = nonce + pt_header + sig + data_package
user_sig = sec_obj.hmac_digest(data_input=user_message,
bkey=skB,
hash_algo=sha256)
# the user sig will be given as urlsafe base64 in the
# challenge response. for this reasons (and because we
# need to serialize it into json) we convert the user_sig
# into this format.
user_sig = encode_base64_urlsafe(user_sig)
# ------------------------------------------------------------------- --
cipher = AES.new(skA, AES.MODE_EAX, nonce)
cipher.update(data_header)
ciphertext, tag = cipher.encrypt_and_digest(plaintext)
raw_data = data_header + R + ciphertext + tag
url = 'lseqr://chal/' + encode_base64_urlsafe(raw_data)
return url, user_sig
def create_challenge_url(self, transaction_id, content_type, message,
callback_url, callback_sms_number,
use_compression=False, reset_url=False):
"""
creates a challenge url (looking like lseqr://chal/<base64string>)
from a challenge dictionary as provided by Challanges.create_challenge
in lib.challenge
the version identifier of the challenge url is currently hardcoded
to 1.
"""
serial = self.getSerial()
if content_type is None:
content_type = CONTENT_TYPE_FREE
# ----------------------------------------------------------------------
# sanity/format checks
if content_type not in [CONTENT_TYPE_PAIRING,
CONTENT_TYPE_AUTH, CONTENT_TYPE_FREE]:
raise InvalidFunctionParameter('content_type', 'content_type must '
'be CONTENT_TYPE_PAIRING, '
'CONTENT_TYPE_AUTH or '
'CONTENT_TYPE_FREE.')
if content_type == CONTENT_TYPE_PAIRING and \
message != serial:
raise InvalidFunctionParameter('message', 'message must be equal '
'to serial in pairing mode')
if content_type == CONTENT_TYPE_AUTH:
if '@' not in message:
raise InvalidFunctionParameter('message', 'For content type '
'auth, message must have format '
'<login>@<server>')
# ----------------------------------------------------------------------
# after the lseqr://chal/ prefix the following data is encoded
# in urlsafe base64:
# ---------------------------------------------------
# fields | version | user token id | R | ciphertext | MAC |
# ---------------------------------------------------
# | header | | EAX enc data |
# ---------------------------------------------------
# size | 1 | 4 | 32 | ? | 16 |
# ---------------------------------------------------
#
r = urandom(32)
R = calc_dh_base(r)
user_token_id = self.getFromTokenInfo('user_token_id')
data_header = struct.pack('<bI', QRTOKEN_VERSION, user_token_id)
# the user public key is saved as base64 in
# the token info since the byte format is
# incompatible with the json backend.
b64_user_public_key = self.getFromTokenInfo('user_public_key')
user_public_key = b64decode(b64_user_public_key)
ss = calc_dh(r, user_public_key)
U1 = SHA256.new(ss).digest()
U2 = SHA256.new(U1).digest()
zerome(ss)
skA = U1[0:16]
skB = U2[0:16]
nonce = U2[16:32]
zerome(U1)
zerome(U2)
# ----------------------------------------------------------------------
# create plaintext section
# ----------------------------------------------------------------------
# create the bitmap for flags
flags = 0
if use_compression:
flags |= CHALLENGE_HAS_COMPRESSION
# FIXME: sizecheck for message, callback url, sms number
# wiki specs are utf-8 byte length (without \0)
if callback_url is not None:
flags |= CHALLENGE_HAS_URL
if callback_sms_number is not None:
flags |= CHALLENGE_HAS_SMS_NUMBER
if (content_type == CONTENT_TYPE_PAIRING):
flags |= CHALLENGE_HAS_SIGNATURE
if reset_url:
flags |= CHALLENGE_SHOULD_RESET_URL
flags |= CHALLENGE_HAS_SIGNATURE
#----------------------------------------------------------------------
# generate plaintext header
# ----------------------------------------------
# fields | content_type | flags | transaction_id | ... |
# ----------------------------------------------
# size | 1 | 1 | 8 | ? |
# ----------------------------------------------
transaction_id = transaction_id_to_u64(transaction_id)
pt_header = struct.pack('<bbQ', content_type, flags, transaction_id)
plaintext = pt_header
#----------------------------------------------------------------------
# create data package
# -------------------------------
# fields | header | message | NUL | ... |
# -------------------------------
# size | 10 | ? | 1 | ? |
# -------------------------------
data_package = b''
utf8_message = message.encode('utf8')
# enforce max sizes specified by protocol
if content_type == CONTENT_TYPE_FREE and len(utf8_message) > 511:
raise ParameterError('message (encoded as utf8) can only be 511 '
'characters long')
elif content_type == CONTENT_TYPE_PAIRING and len(utf8_message) > 63:
raise InvalidFunctionParameter('message', 'max string length '
'(encoded as utf8) is 511 for '
'content type PAIRING')
elif content_type == CONTENT_TYPE_AUTH and len(utf8_message) > 511:
raise InvalidFunctionParameter('message', 'max string length '
'(encoded as utf8) is 511 for '
'content type AUTH')
data_package += utf8_message + b'\x00'
# ----------------------------------------------------------------------
# depending on function parameters add callback url
# and/or callback sms number
# -----------------------------------------------------
# fields | ... | callback url | NUL | callback sms | NUL | ... |
# -----------------------------------------------------
# size | ? | ? | 1 | ? | 1 | ? |
# -----------------------------------------------------
# ----------------------------------------------------------------------
if callback_url is not None:
utf8_callback_url = callback_url.encode('utf8')
# enforce max url length as specified in protocol
if len(utf8_callback_url) > 511:
raise InvalidFunctionParameter('callback_url', 'max string '
'length (encoded as utf8) is '
'511')
data_package += utf8_callback_url + b'\x00'
# ----------------------------------------------------------------------
if callback_sms_number is not None:
utf8_callback_sms_number = callback_sms_number.encode('utf8')
if len(utf8_callback_sms_number) > 31:
raise InvalidFunctionParameter('callback_sms_number',
'max string length (encoded '
'as utf8) is 31')
data_package += utf8_callback_sms_number + b'\x00'
# ----------------------------------------------------------------------
if use_compression:
maybe_compressed_data_package = zlib.compress(data_package, 9)
else:
maybe_compressed_data_package = data_package
# ----------------------------------------------------------------------
# when content type is pairing the protocol specifies that
# the server must send a hmac based signature with the
# response
sig = ''
if flags & CHALLENGE_HAS_SIGNATURE:
hmac_message = nonce + pt_header + maybe_compressed_data_package
sig = HMAC.new(self.server_hmac_secret, hmac_message,
digestmod=SHA256).digest()
plaintext += sig
# ----------------------------------------------------------------------
plaintext += maybe_compressed_data_package
# ----------------------------------------------------------------------
user_message = nonce + pt_header + sig + data_package
user_sig = HMAC.new(skB, user_message, digestmod=SHA256).digest()
# the user sig will be given as urlsafe base64 in the
# challenge response. for this reasons (and because we
# need to serialize it into json) we convert the user_sig
# into this format.
user_sig = encode_base64_urlsafe(user_sig)
# ----------------------------------------------------------------------
cipher = AES.new(skA, AES.MODE_EAX, nonce)
cipher.update(data_header)
ciphertext, tag = cipher.encrypt_and_digest(plaintext)
raw_data = data_header + R + ciphertext + tag
url = 'lseqr://chal/' + encode_base64_urlsafe(raw_data)
return url, user_sig
def parse_challenge_url(challenge_url):
""" Parses a challenge url and prints its data """
challenge_data_encoded = challenge_url[len('lseqr://chal/'):]
challenge_data = decode_base64_urlsafe(challenge_data_encoded)
# ----------------------------------------------------------------------
# parse and verify header information in the
# encrypted challenge data
header = challenge_data[0:5]
version, user_token_id = struct.unpack('<bI', header)
if not version == QRTOKEN_VERSION:
raise Exception('wrong qrtoken version')
# ----------------------------------------------------------------------
# get token from client token database
token = token_db[user_token_id]
# ----------------------------------------------------------------------
# prepare decryption by seperating R from
# ciphertext and tag
R = challenge_data[5:5 + 32]
ciphertext = challenge_data[5 + 32:-16]
tag = challenge_data[-16:]
# ----------------------------------------------------------------------
# key derivation
ss = calc_dh(secret_key, R)
U1 = SHA256.new(ss).digest()
U2 = SHA256.new(U1).digest()
skA = U1[0:16]
skB = U2[0:16]
nonce = U2[16:32]
# ----------------------------------------------------------------------
# decrypt and verify challenge
cipher = AES.new(skA, AES.MODE_EAX, nonce)
cipher.update(header)
plaintext = cipher.decrypt_and_verify(ciphertext, tag)
# ----------------------------------------------------------------------
# parse/check plaintext header
pt_header = plaintext[0:10]
content_type, flags, transaction_id = struct.unpack('<bbQ', pt_header)
transaction_id = u64_to_transaction_id(transaction_id)
# make sure a flag for the server signature is
# present, if the content type is 'pairing'
if content_type == QRTOKEN_CT_PAIR and not flags & FLAG_QR_SRVSIG:
raise Exception('Ill formatted callenge url')
# ----------------------------------------------------------------------
# retrieve plaintext data depending on flags
if flags & FLAG_QR_SRVSIG:
# plaintext has a server signature as a header
# extract it and check if it is correct
server_signature = plaintext[10:10 + 32]
data = plaintext[10 + 32:]
# calculate secret
server_public_key = token['server_public_key']
secret = calc_dh(secret_key, server_public_key)
# check hmac
message = nonce + pt_header + data
signed = HMAC.new(secret, msg=message, digestmod=SHA256).digest()
if not server_signature == signed:
raise Exception('HMAC signature check failed')
else:
# no server signature found - just remove
# the plaintext header
data = plaintext[10:]
# we have to define an empty server signature in
# here because we need it later to create the
# client signature
server_signature = b''
# ----------------------------------------------------------------------
# extract message and (optional) callback
# parameters from data
message, _, suffix = data.partition(b'\x00')
callback_url = token['callback_url']
if flags & FLAG_QR_HAVE_URL:
callback_url, _, suffix = suffix.partition(b'\x00')
callback_sms = token['callback_sms']
if flags & FLAG_QR_HAVE_SMS:
callback_sms, _, suffix = suffix.partition(b'\x00')
# ----------------------------------------------------------------------
# prepare the parsed challenge data
challenge = {}
challenge['message'] = message
challenge['content_type'] = content_type
challenge['callback_url'] = callback_url
challenge['callback_sms'] = callback_sms
challenge['transaction_id'] = transaction_id
challenge['user_token_id'] = user_token_id
# calculate signature and tan
message = nonce + pt_header + data
sig_hmac = HMAC.new(skB, message, digestmod=SHA256)
sig = sig_hmac.digest()
encoded_sig = encode_base64_urlsafe(sig)
print('Data in URL:')
for key, value in list(challenge.items()):
print(('%s\n %s\n' % (key, value)))
return challenge, encoded_sig
def parse_challenge_url(challenge_url):
""" Parses a challenge url and prints its data """
challenge_data_encoded = challenge_url[len('lseqr://chal/'):]
challenge_data = decode_base64_urlsafe(challenge_data_encoded)
# ----------------------------------------------------------------------
# parse and verify header information in the
# encrypted challenge data
header = challenge_data[0:5]
version, user_token_id = struct.unpack('<bI', header)
if not version == QRTOKEN_VERSION:
raise Exception('wrong qrtoken version')
# ----------------------------------------------------------------------
# get token from client token database
token = token_db[user_token_id]
# ----------------------------------------------------------------------
# prepare decryption by seperating R from
# ciphertext and tag
R = challenge_data[5:5+32]
ciphertext = challenge_data[5+32:-16]
tag = challenge_data[-16:]
# ----------------------------------------------------------------------
# key derivation
ss = calc_dh(secret_key, R)
U1 = SHA256.new(ss).digest()
U2 = SHA256.new(U1).digest()
skA = U1[0:16]
skB = U2[0:16]
nonce = U2[16:32]
# ----------------------------------------------------------------------
# decrypt and verify challenge
cipher = AES.new(skA, AES.MODE_EAX, nonce)
cipher.update(header)
plaintext = cipher.decrypt_and_verify(ciphertext, tag)
# ----------------------------------------------------------------------
# parse/check plaintext header
pt_header = plaintext[0:10]
content_type, flags, transaction_id = struct.unpack('<bbQ', pt_header)
transaction_id = u64_to_transaction_id(transaction_id)
# make sure a flag for the server signature is
# present, if the content type is 'pairing'
if content_type == QRTOKEN_CT_PAIR and not flags & FLAG_QR_SRVSIG:
raise Exception('Ill formatted callenge url')
# ----------------------------------------------------------------------
# retrieve plaintext data depending on flags
if flags & FLAG_QR_SRVSIG:
# plaintext has a server signature as a header
# extract it and check if it is correct
server_signature = plaintext[10:10+32]
data = plaintext[10+32:]
# calculate secret
server_public_key = token['server_public_key']
secret = calc_dh(secret_key, server_public_key)
# check hmac
message = nonce + pt_header + data
signed = HMAC.new(secret, msg=message, digestmod=SHA256).digest()
if not server_signature == signed:
raise Exception('HMAC signature check failed')
else:
# no server signature found - just remove
# the plaintext header
data = plaintext[10:]
# we have to define an empty server signature in
# here because we need it later to create the
# client signature
server_signature = b''
# ----------------------------------------------------------------------
# extract message and (optional) callback
# parameters from data
message, _, suffix = data.partition(b'\x00')
callback_url = token['callback_url']
if flags & FLAG_QR_HAVE_URL:
callback_url, _, suffix = suffix.partition(b'\x00')
callback_sms = token['callback_sms']
if flags & FLAG_QR_HAVE_SMS:
callback_sms, _, suffix = suffix.partition(b'\x00')
# ----------------------------------------------------------------------
# prepare the parsed challenge data
challenge = {}
challenge['message'] = message
challenge['content_type'] = content_type
challenge['callback_url'] = callback_url
challenge['callback_sms'] = callback_sms
challenge['transaction_id'] = transaction_id
challenge['user_token_id'] = user_token_id
# calculate signature and tan
message = nonce + pt_header + data
sig_hmac = HMAC.new(skB, message, digestmod=SHA256)
sig = sig_hmac.digest()
encoded_sig = encode_base64_urlsafe(sig)
print('Data in URL:')
for key, value in challenge.items():
print('%s\n %s\n' % (key, value))
return challenge, encoded_sig
def create_challenge_url(self,
transaction_id,
content_type,
callback_url='',
message=None,
login=None,
host=None):
"""
creates a challenge url (looking like lseqr://push/<base64string>),
returns the url and the unencrypted challenge data
:param transaction_id: The transaction id generated by LinOTP
:param content_type: One of the types CONTENT_TYPE_SIGNREQ,
CONTENT_TYPE_PAIRING, CONTENT_TYPE_LOGIN
:param callback_url: callback url (optional), default is
empty string
:param message: the transaction message, that should be signed
by the client. Only for content type CONTENT_TYPE_SIGNREQ
:param login: the login name of the user. Only for content type
CONTENT_TYPE_LOGIN
:param host: hostname of the user. Only for content type
CONTENT_TYPE_LOGIN
:returns: tuple (challenge_url, sig_base), with challenge_url being
the push url and sig_base the message, that is used for
the client signature
"""
serial = self.getSerial()
# ------------------------------------------------------------------- --
# sanity/format checks
if content_type not in [CONTENT_TYPE_SIGNREQ,
CONTENT_TYPE_PAIRING, CONTENT_TYPE_LOGIN]:
raise InvalidFunctionParameter('content_type', 'content_type must '
'be CONTENT_TYPE_SIGNREQ, '
'CONTENT_TYPE_PAIRING or '
'CONTENT_TYPE_LOGIN.')
# ------------------------------------------------------------------- --
# after the lseqr://push/ prefix the following data is encoded
# in urlsafe base64:
# ---------------------------------------------------
# fields | version | user token id | R | ciphertext | sign |
# ---------------------------------------------------
# | header | body |
# ---------------------------------------------------
# size | 1 | 4 | 32 | ? | 64 |
# ---------------------------------------------------
#
# create header
user_token_id = self.getFromTokenInfo('user_token_id')
data_header = struct.pack('<bI', CHALLENGE_URL_VERSION, user_token_id)
# ------------------------------------------------------------------- --
# create body
r = urandom(32)
R = calc_dh_base(r)
b64_user_dsa_public_key = self.getFromTokenInfo('user_dsa_public_key')
user_dsa_public_key = b64decode(b64_user_dsa_public_key)
user_dh_public_key = dsa_to_dh_public(user_dsa_public_key)
ss = calc_dh(r, user_dh_public_key)
U = SHA256.new(ss).digest()
zerome(ss)
sk = U[0:16]
nonce = U[16:32]
zerome(U)
# ------------------------------------------------------------------- --
# create plaintext section
# ------------------------------------------------------------------- --
# generate plaintext header
# ------------------------------------------------
# fields | content_type | transaction_id | timestamp | ..
# ------------------------------------------------
# size | 1 | 8 | 8 | ?
# -------------------------------------------------
transaction_id = transaction_id_to_u64(transaction_id)
plaintext = struct.pack('<bQQ', content_type, transaction_id,
int(time.time()))
# ------------------------------------------------------------------- --
utf8_callback_url = callback_url.encode('utf8')
# enforce max url length as specified in protocol
if len(utf8_callback_url) > 511:
raise InvalidFunctionParameter('callback_url', 'max string '
'length (encoded as utf8) is '
'511')
# ------------------------------------------------------------------- --
# create data package depending on content type
# ------------------------------------------------------------------- --
if content_type == CONTENT_TYPE_PAIRING:
# -----------------------------------------
# fields | header | serial | NUL | callback | NUL |
# -----------------------------------------
# size | 9 | ? | 1 | ? | 1 |
# -----------------------------------------
utf8_serial = serial.encode('utf8')
if len(utf8_serial) > 63:
raise ValueError('serial (encoded as utf8) can only be 63 '
'characters long')
plaintext += utf8_serial + b'\00' + utf8_callback_url + b'\00'
# ------------------------------------------------------------------- --
if content_type == CONTENT_TYPE_SIGNREQ:
if message is None:
raise InvalidFunctionParameter('message', 'message must be '
'supplied for content type '
'SIGNREQ')
# ------------------------------------------
# fields | header | message | NUL | callback | NUL |
# ------------------------------------------
# size | 9 | ? | 1 | ? | 1 |
# ------------------------------------------
utf8_message = message.encode('utf8')
# enforce max sizes specified by protocol
if len(utf8_message) > 511:
raise InvalidFunctionParameter('message', 'max string '
'length (encoded as utf8) is '
'511')
plaintext += utf8_message + b'\00' + utf8_callback_url + b'\00'
# ------------------------------------------------------------------- --
if content_type == CONTENT_TYPE_LOGIN:
if login is None:
raise InvalidFunctionParameter('login', 'login must be '
'supplied for content type '
'LOGIN')
if host is None:
raise InvalidFunctionParameter('host', 'host must be '
'supplied for content type '
'LOGIN')
# -----------------------------------------------------
# fields | header | login | NUL | host | NUL | callback | NUL |
# -----------------------------------------------------
# size | 9 | ? | 1 | ? | 1 | ? | 1 |
# -----------------------------------------------------
utf8_login = login.encode('utf8')
utf8_host = host.encode('utf8')
# enforce max sizes specified by protocol
if len(utf8_login) > 127:
raise InvalidFunctionParameter('login', 'max string '
'length (encoded as utf8) is '
'127')
if len(utf8_host) > 255:
raise InvalidFunctionParameter('host', 'max string '
'length (encoded as utf8) is '
'255')
plaintext += utf8_login + b'\00'
plaintext += utf8_host + b'\00'
plaintext += utf8_callback_url + b'\00'
# ------------------------------------------------------------------- --
# encrypt inner layer
nonce_as_int = int_from_bytes(nonce, byteorder='big')
ctr = Counter.new(128, initial_value=nonce_as_int)
cipher = AES.new(sk, AES.MODE_CTR, counter=ctr)
ciphertext = cipher.encrypt(plaintext)
unsigned_raw_data = data_header + R + ciphertext
# ------------------------------------------------------------------- --
# create signature
partition = self.getFromTokenInfo('partition')
secret_key = get_secret_key(partition)
signature = crypto_sign_detached(unsigned_raw_data, secret_key)
raw_data = unsigned_raw_data + signature
protocol_id = config.get('mobile_app_protocol_id', 'lseqr')
url = protocol_id + '://push/' + encode_base64_urlsafe(raw_data)
return url, (signature + plaintext)
def create_pairing_response(public_key: bytes,
secret_key: bytes,
token_info: Dict,
gda: str = 'DEADBEEF') -> str:
"""Creates a base64-encoded pairing response.
:param public_key: the public key in bytes
:param secret_key: the secret key in bytes
:param token_info: the token_info dict
:param user_token_id: the token id
:param gda: the mobile device gda
:returns base64 encoded pairing response
"""
token_serial = token_info['serial']
token_id = token_info.get('token_id', 1)
server_public_key = token_info['server_public_key']
partition = token_info['partition']
# ------------------------------------------------------------------ --
# assemble header and plaintext
header = struct.pack('<bI', PAIR_RESPONSE_VERSION, partition)
pairing_response = b''
pairing_response += struct.pack('<bI', TYPE_PUSHTOKEN, token_id)
pairing_response += public_key
pairing_response += token_serial.encode('utf8') + b'\x00\x00'
pairing_response += gda.encode('utf-8') + b'\x00'
signature = crypto_sign_detached(pairing_response, secret_key)
pairing_response += signature
# ------------------------------------------------------------------ --
# create public diffie hellman component
# (used to decrypt and verify the reponse)
r = os.urandom(32)
R = calc_dh_base(r)
# ------------------------------------------------------------------ --
# derive encryption key and nonce
server_public_key_dh = dsa_to_dh_public(server_public_key)
ss = calc_dh(r, server_public_key_dh)
U = SHA256.new(ss).digest()
encryption_key = U[0:16]
nonce = U[16:32]
# ------------------------------------------------------------------ --
# encrypt in EAX mode
cipher = AES.new(encryption_key, AES.MODE_EAX, nonce)
cipher.update(header)
ciphertext, tag = cipher.encrypt_and_digest(pairing_response)
return encode_base64_urlsafe(header + R + ciphertext + tag)
def decrypt_and_verify_challenge(self, challenge_url, action):
"""
Decrypts the data packed in the challenge url, verifies
its content, returns the parsed data as a dictionary,
calculates and returns the signature.
The calling method must then send the signature
back to the server. (The reason for this control flow
is that the challenge data must be checked in different
scenarios, e.g. when we have a pairing the data must be
checked by the method that simulates the pairing)
:param challenge_url: the challenge url as sent by the server
:param action: a string identifier for the verification action
(at the moment 'ACCEPT' or 'DENY')
:returns: (challenge, signature)
challenge has the keys
* content_type - one of the three values CONTENT_TYPE_SIGNREQ,
CONTENT_TYPE_PAIRING or CONTENT_TYPE_LOGIN)
(all defined in this module)
* transaction_id - used to identify the challenge
on the server
* callback_url (optional) - the url to which the challenge
response should be set
* user_token_id - used to identify the token in the
user database for which this challenge was created
depending on the content type additional keys are present
* for CONTENT_TYPE_PAIRING: serial
* for CONTENT_TYPE_SIGNREQ: message
* for CONTENT_TYPE_LOGIN: login, host
signature is the generated user signature used to
respond to the challenge
"""
challenge_data_encoded = challenge_url[len(self.uri + '://chal/'):]
challenge_data = decode_base64_urlsafe(challenge_data_encoded)
# ------------------------------------------------------------------ --
# parse and verify header information in the
# encrypted challenge data
header = challenge_data[0:5]
version, user_token_id = struct.unpack('<bI', header)
self.assertEqual(version, CHALLENGE_URL_VERSION)
# ------------------------------------------------------------------ --
# get token from client token database
token = self.tokens[user_token_id]
server_public_key = token['server_public_key']
# ------------------------------------------------------------------ --
# prepare decryption by seperating R from
# ciphertext and server signature
R = challenge_data[5:5 + 32]
ciphertext = challenge_data[5 + 32:-64]
server_signature = challenge_data[-64:]
# check signature
data = challenge_data[0:-64]
crypto_sign_verify_detached(server_signature, data, server_public_key)
# ------------------------------------------------------------------ --
# key derivation
secret_key_dh = dsa_to_dh_secret(self.secret_key)
ss = calc_dh(secret_key_dh, R)
U = SHA256.new(ss).digest()
sk = U[0:16]
nonce = U[16:32]
# ------------------------------------------------------------------ --
# decrypt and verify challenge
nonce_as_int = int_from_bytes(nonce, byteorder='big')
ctr = Counter.new(128, initial_value=nonce_as_int)
cipher = AES.new(sk, AES.MODE_CTR, counter=ctr)
plaintext = cipher.decrypt(ciphertext)
# ------------------------------------------------------------------ --
# parse/check plaintext header
# 1 - for content type
# 8 - for transaction id
# 8 - for time stamp
offset = 1 + 8 + 8
pt_header = plaintext[0:offset]
(content_type,
transaction_id,
_time_stamp) = struct.unpack('<bQQ', pt_header)
transaction_id = u64_to_transaction_id(transaction_id)
# ------------------------------------------------------------------ --
# prepare the parsed challenge data
challenge = {}
challenge['content_type'] = content_type
# ------------------------------------------------------------------ --
# retrieve plaintext data depending on content_type
if content_type == CONTENT_TYPE_PAIRING:
serial, callback_url, __ = plaintext[offset:].split('\x00')
challenge['serial'] = serial
elif content_type == CONTENT_TYPE_SIGNREQ:
message, callback_url, __ = plaintext[offset:].split('\x00')
challenge['message'] = message
elif content_type == CONTENT_TYPE_LOGIN:
login, host, callback_url, __ = plaintext[offset:].split('\x00')
challenge['login'] = login
challenge['host'] = host
# ------------------------------------------------------------------ --
# prepare the parsed challenge data
challenge['callback_url'] = callback_url
challenge['transaction_id'] = transaction_id
challenge['user_token_id'] = user_token_id
# calculate signature
sig_base = (
struct.pack('<b', CHALLENGE_URL_VERSION) +
b'%s\0' % action +
server_signature + plaintext)
sig = crypto_sign_detached(sig_base, self.secret_key)
encoded_sig = encode_base64_urlsafe(sig)
return challenge, encoded_sig
