def deriveRelayCrypto(self, cell):
'''Derive shared key material for this ntor handshake; create and
return actual cipher and hash instances inside a RelayCrypto object.
.. note:: See tor-spec Section 5.1.4, 5.2.2 for more details.
:param cell cell: Created2 cell or Extended2 cell used to derive
shared keys
:returns: **oppy.crypto.relaycrypto.RelayCrypto** object initialized
with the derived key material.
'''
self.is_bad = False
hdata = cell.hdata
relay_pubkey = cell.hdata[: CURVE25519_PUBKEY_LEN]
AUTH = hdata[CURVE25519_PUBKEY_LEN: CURVE25519_PUBKEY_LEN + DIGEST_LEN]
secret_input = self._buildSecretInput(relay_pubkey)
verify = util.makeHMACSHA256(msg=secret_input, key=T_VERIFY)
auth_input = self._buildAuthInput(verify, relay_pubkey)
auth_input = util.makeHMACSHA256(msg=auth_input, key=T_MAC)
self.is_bad |= util.constantStrEqual(AUTH, auth_input)
ret = self._makeRelayCrypto(secret_input)
# don't fail until the very end to avoid leaking timing information
if self.is_bad:
raise KeyDerivationFailed()
return ret
def deriveRelayCrypto(self, cell):
'''Derive shared key material for this ntor handshake; create and
return actual cipher and hash instances inside a RelayCrypto object.
.. note:: See tor-spec Section 5.1.4, 5.2.2 for more details.
:param cell cell: Created2 cell or Extended2 cell used to derive
shared keys
:returns: **oppy.crypto.relaycrypto.RelayCrypto** object initialized
with the derived key material.
'''
self.is_bad = False
hdata = cell.hdata
relay_pubkey = cell.hdata[:CURVE25519_PUBKEY_LEN]
AUTH = hdata[CURVE25519_PUBKEY_LEN:CURVE25519_PUBKEY_LEN + DIGEST_LEN]
secret_input = self._buildSecretInput(relay_pubkey)
verify = util.makeHMACSHA256(msg=secret_input, key=T_VERIFY)
auth_input = self._buildAuthInput(verify, relay_pubkey)
auth_input = util.makeHMACSHA256(msg=auth_input, key=T_MAC)
self.is_bad |= util.constantStrEqual(AUTH, auth_input)
ret = self._makeRelayCrypto(secret_input)
# don't fail until the very end to avoid leaking timing information
if self.is_bad:
raise KeyDerivationFailed()
return ret
def test_makeHMACSHA256(self, mock_hmac):
mock_m = mock.Mock()
mock_m.digest = mock.Mock()
mock_m.digest.return_value = 'digest'
mock_hmac.return_value = mock_m
ret = util.makeHMACSHA256('msg', 'key')
mock_hmac.assert_called_once_with(msg='msg', key='key',
digestmod=hashlib.sha256)
self.assertEqual(ret, 'digest')
def test_makeHMACSHA256(self, mock_hmac):
mock_m = mock.Mock()
mock_m.digest = mock.Mock()
mock_m.digest.return_value = 'digest'
mock_hmac.return_value = mock_m
ret = util.makeHMACSHA256('msg', 'key')
mock_hmac.assert_called_once_with(msg='msg',
key='key',
digestmod=hashlib.sha256)
self.assertEqual(ret, 'digest')
