commit 73ba1f3506d44e8d65c439b404f7cd40eed5ceb9 Author: Damian Johnson atagar@torproject.org Date: Tue Jan 30 11:35:25 2018 -0800

Add kdf_tor function

Supporting KDF-TOR for the CREATE_FAST handshake. Test data is derived from what endosome's function provides. --- stem/client/__init__.py | 24 ++++++++++++++++++++++++ stem/client/cell.py | 3 +-- test/settings.cfg | 1 + test/unit/client/__init__.py | 1 + test/unit/client/kdf_tor.py | 19 +++++++++++++++++++ 5 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/stem/client/__init__.py b/stem/client/__init__.py index fb0f899d..663bc048 100644 --- a/stem/client/__init__.py +++ b/stem/client/__init__.py @@ -12,6 +12,7 @@ a wrapper for :class:`~stem.socket.RelaySocket`, much the same way as ::

split - splits bytes into substrings + kdf_tor - calculates the derived key using the KDF-TOR protocol

Field - Packable and unpackable datatype. |- Size - Field of a static size. @@ -106,6 +107,7 @@ a wrapper for :class:`~stem.socket.RelaySocket`, much the same way as ===================== =========== """

+import hashlib import io import struct

@@ -115,6 +117,8 @@ import stem.util.enum from stem.util import _hash_attr

ZERO = '\x00' +HASH_LEN = 20 +KEY_LEN = 16

__all__ = [ 'cell', @@ -457,6 +461,26 @@ class Certificate(Field): return _hash_attr(self, 'type_int', 'value')

+def kdf_tor(key): + """ + Tor's key derivation function used by TAP, CREATE_FAST handshakes, and hidden + service protocols as defined in section 5.2.1 of the tor spec. + + :param bytes key: shared key with endpoint (K0 in the spec) + + :returns: **bytes** with the KDF-TOR of the key + """ + + derived_key_len = KEY_LEN * 2 + HASH_LEN * 3 + derived_key, counter = '', 0 + + while len(derived_key) < derived_key_len: + derived_key += hashlib.sha1(key + Size.CHAR.pack(counter)).digest() + counter += 1 + + return derived_key[:derived_key_len] + + setattr(Size, 'CHAR', Size('CHAR', 1, '!B')) setattr(Size, 'SHORT', Size('SHORT', 2, '!H')) setattr(Size, 'LONG', Size('LONG', 4, '!L')) diff --git a/stem/client/cell.py b/stem/client/cell.py index 59fbc14c..9b0c3274 100644 --- a/stem/client/cell.py +++ b/stem/client/cell.py @@ -47,12 +47,11 @@ import sys import stem.client

from stem import UNDEFINED -from stem.client import ZERO, Address, Size, split +from stem.client import HASH_LEN, ZERO, Address, Size, split from stem.util import _hash_attr, datetime_to_unix

FIXED_PAYLOAD_LEN = 509 AUTH_CHALLENGE_SIZE = 32 -HASH_LEN = 20

class Cell(object): diff --git a/test/settings.cfg b/test/settings.cfg index 518ae2b2..7af57181 100644 --- a/test/settings.cfg +++ b/test/settings.cfg @@ -233,6 +233,7 @@ test.unit_tests |test.unit.client.size.TestSize |test.unit.client.address.TestAddress |test.unit.client.certificate.TestCertificate +|test.unit.client.kdf_tor.TestKdfTor |test.unit.client.cell.TestCell |test.unit.connection.authentication.TestAuthenticate |test.unit.connection.connect.TestConnect diff --git a/test/unit/client/__init__.py b/test/unit/client/__init__.py index 7e745352..ba93b3e6 100644 --- a/test/unit/client/__init__.py +++ b/test/unit/client/__init__.py @@ -6,6 +6,7 @@ __all__ = [ 'address', 'cell', 'certificate', + 'kdf_tor', 'size', ]

diff --git a/test/unit/client/kdf_tor.py b/test/unit/client/kdf_tor.py new file mode 100644 index 00000000..894d4fae --- /dev/null +++ b/test/unit/client/kdf_tor.py @@ -0,0 +1,19 @@ +""" +Unit tests for stem.client.kdf_tor. +""" + +import unittest + +import stem.client + +KEY_1 = '\xec\xec.\xeb7R\xf2\n\xcb\xce\x97\xf4\x86\x82\x19#\x10\x0f\x08\xf0\xa2Z\xdeJ\x8f2\x8cc\xf6\xfa\x0e\t\x83f\xc5\xe2\xb3\x94\xa8\x13' +KEY_2 = '\xe0v\xe4\xfaTB\x91\x1c\x81Gz\xa0\tI\xcb{\xc56\xcfV\xc2\xa0\x19\x9c\x98\x9a\x06\x0e\xc5\xfa\xb0z\x83\xa6\x10\xf6r"<b' + +DERIVED_1 = '\xca+\x81\x05\x14\x9d)o\xa6\x82\xe9B\xa8?\xf2\xaf\x85\x1b]6\xac\xcc\xbc\x91\xb1\xaf\xd7\xe0\xe9\x9dF#\xd8\xdbz\xe8\xe6\xca\x83,*\xe5scX\xbb+\xca \xcb\xa4\xbc\xad\x0f\x95\x0cO\xcc\xac\xf1\xc3\xbe\xc9\xe1\xf4\x90f\xdai\xf3\xf3\xf5\x14\xb5\xb9\x03U\xaf\x1e\x1b\xb1q||\x86A<_\xf7\xa0%\x86' +DERIVED_2 = '\xbc0\xf99\x8e;Te\xbb+\xdb\xabR3l\xb9f?\x07KZC8\xe7\xa15\xd1IS\xd9\xd4\x1e\x96\xf6\xcd\x82\x91\x0b}r\x7f\xc5\xc0\xb1/[\x97dW\xba\x82g\xe7m^\x06[\xe6\xf8\xb4\x83f>c\x8b\x0f\x03\xcc\x98\x1f~t\x88\xe1\x83\xec\xbf*_\x8cF\x0e1\xa9\x17\xce\xa6\xa3\xd1+]\x1f' + + +class TestKdfTor(unittest.TestCase): + def test_kdf_tor(self): + self.assertEqual(DERIVED_1, stem.client.kdf_tor(KEY_1)) + self.assertEqual(DERIVED_2, stem.client.kdf_tor(KEY_2))