commit e2e7b5d58fdc14014df8c476c59457b1b5483c2e Author: Damian Johnson atagar@torproject.org Date: Tue Jan 30 12:21:04 2018 -0800

Replace kdf_tor function with a KDF class

On reflection callers actually don't care about the KDF-TOR value. Rather, they care about its derived attributes. --- stem/client/__init__.py | 47 ++++++++++++++++++++++++++++++++------------- test/unit/client/kdf_tor.py | 21 +++++++++++++++++--- 2 files changed, 52 insertions(+), 16 deletions(-)

diff --git a/stem/client/__init__.py b/stem/client/__init__.py index 663bc048..4c6bdb12 100644 --- a/stem/client/__init__.py +++ b/stem/client/__init__.py @@ -12,7 +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 + KDF - KDF-TOR key derivative for TAP, CREATE_FAST handshakes, and hidden serivces

Field - Packable and unpackable datatype. |- Size - Field of a static size. @@ -461,24 +461,45 @@ class Certificate(Field): return _hash_attr(self, 'type_int', 'value')

-def kdf_tor(key): +class KDF(object): + """ + Tor's derived key for TAP, CREATE_FAST handshakes, and hidden service + protocols as defined tor-spec section 5.2.1. + + :var bytes key_hash: expected derived key that proves knowledge of our shared + computed key + :var bytes forward_digest: forward digest hash seed + :var bytes backward_digest: backward digest hash seed + :var bytes forward_key: forward encryption key + :var bytes backward_key: backward encryption 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) + def __init__(self, key_material): + value = KDF._value(key_material)

- :returns: **bytes** with the KDF-TOR of the key - """ + self.key_hash, value = split(value, HASH_LEN) + self.forward_digest, value = split(value, HASH_LEN) + self.backward_digest, value = split(value, HASH_LEN) + self.forward_key, value = split(value, KEY_LEN) + self.backward_key, value = split(value, KEY_LEN) + + @staticmethod + def _value(key): + """ + Computes the KDF-TOR value... + + K = H(K0 | [00]) | H(K0 | [01]) | H(K0 | [02]) | ... + """

- derived_key_len = KEY_LEN * 2 + HASH_LEN * 3 - derived_key, counter = '', 0 + derived_key = '' + derived_key_len = KEY_LEN * 2 + HASH_LEN * 3 + counter = 0

- while len(derived_key) < derived_key_len: - derived_key += hashlib.sha1(key + Size.CHAR.pack(counter)).digest() - counter += 1 + 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] + return derived_key[:derived_key_len]

setattr(Size, 'CHAR', Size('CHAR', 1, '!B')) diff --git a/test/unit/client/kdf_tor.py b/test/unit/client/kdf_tor.py index 894d4fae..f356d2cd 100644 --- a/test/unit/client/kdf_tor.py +++ b/test/unit/client/kdf_tor.py @@ -14,6 +14,21 @@ DERIVED_2 = '\xbc0\xf99\x8e;Te\xbb+\xdb\xabR3l\xb9f?\x07KZC8\xe7\xa15\xd1IS\xd9\

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)) + def test_kdf_value(self): + self.assertEqual(DERIVED_1, stem.client.KDF._value(KEY_1)) + self.assertEqual(DERIVED_2, stem.client.KDF._value(KEY_2)) + + def test_kdf_attributes(self): + k1 = stem.client.KDF(KEY_1) + self.assertEqual('\xca+\x81\x05\x14\x9d)o\xa6\x82\xe9B\xa8?\xf2\xaf\x85\x1b]6', k1.key_hash) + self.assertEqual('\xac\xcc\xbc\x91\xb1\xaf\xd7\xe0\xe9\x9dF#\xd8\xdbz\xe8\xe6\xca\x83,', k1.forward_digest) + self.assertEqual('*\xe5scX\xbb+\xca \xcb\xa4\xbc\xad\x0f\x95\x0cO\xcc\xac\xf1', k1.backward_digest) + self.assertEqual('\xc3\xbe\xc9\xe1\xf4\x90f\xdai\xf3\xf3\xf5\x14\xb5\xb9\x03', k1.forward_key) + self.assertEqual('U\xaf\x1e\x1b\xb1q||\x86A<_\xf7\xa0%\x86', k1.backward_key) + + k2 = stem.client.KDF(KEY_1) + self.assertEqual('\xca+\x81\x05\x14\x9d)o\xa6\x82\xe9B\xa8?\xf2\xaf\x85\x1b]6', k2.key_hash) + self.assertEqual('\xac\xcc\xbc\x91\xb1\xaf\xd7\xe0\xe9\x9dF#\xd8\xdbz\xe8\xe6\xca\x83,', k2.forward_digest) + self.assertEqual('*\xe5scX\xbb+\xca \xcb\xa4\xbc\xad\x0f\x95\x0cO\xcc\xac\xf1', k2.backward_digest) + self.assertEqual('\xc3\xbe\xc9\xe1\xf4\x90f\xdai\xf3\xf3\xf5\x14\xb5\xb9\x03', k2.forward_key) + self.assertEqual('U\xaf\x1e\x1b\xb1q||\x86A<_\xf7\xa0%\x86', k2.backward_key)