commit ba91f20beebab6e8ec0496f75bfef37c1c124c52 Author: Damian Johnson atagar@torproject.org Date: Thu Jan 11 17:54:08 2018 -0800

VersionsCell unpacking

Implementing our first cell unpack function. --- stem/client/cell.py | 29 ++++++++++++++++++++++++++--- test/unit/client/cell.py | 5 +++++ 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/stem/client/cell.py b/stem/client/cell.py index 7a1644b3..e29e404f 100644 --- a/stem/client/cell.py +++ b/stem/client/cell.py @@ -36,15 +36,16 @@ Messages communicated over a Tor relay's ORPort. +- unpack - Decodes bytes for this cell class. """

-import collections import inspect import sys

from stem import UNDEFINED from stem.client import ZERO, Size

+MAX_FIXED_PAYLOAD_LEN = 509

-class Cell(collections.namedtuple('Cell', ['name', 'value', 'fixed_size', 'for_circuit'])): + +class Cell(object): """ Metadata for ORPort cells.

@@ -109,7 +110,14 @@ class Cell(collections.namedtuple('Cell', ['name', 'value', 'fixed_size', 'for_c

circ_id, content = Size.LONG.pop(content) if link_version > 3 else Size.SHORT.pop(content) command, content = Size.CHAR.pop(content) - return Cell.by_value(command)._unpack(content, link_version, circ_id) + cls = Cell.by_value(command) + + if cls.IS_FIXED_SIZE: + payload_len = MAX_FIXED_PAYLOAD_LEN + else: + payload_len, content = Size.SHORT.pop(content) + + return cls._unpack(content, link_version, circ_id)

@classmethod def _pack(cls, link_version, payload, circ_id = 0): @@ -234,12 +242,17 @@ class CreatedFastCell(CircuitCell): class VersionsCell(Cell): """ Link version negotiation cell. + + :var list versions: link versions """

NAME = 'VERSIONS' VALUE = 7 IS_FIXED_SIZE = False

+ def __init__(self, versions): + self.versions = versions + @classmethod def pack(cls, versions): """ @@ -256,6 +269,16 @@ class VersionsCell(Cell): payload = b''.join([Size.SHORT.pack(v) for v in versions]) return cls._pack(3, payload)

+ @classmethod + def _unpack(cls, content, circ_id, link_version): + link_versions = [] + + while content: + version, content = Size.SHORT.pop(content) + link_versions.append(version) + + return VersionsCell(link_versions) +

class NetinfoCell(Cell): NAME = 'NETINFO' diff --git a/test/unit/client/cell.py b/test/unit/client/cell.py index 857cab84..9502975e 100644 --- a/test/unit/client/cell.py +++ b/test/unit/client/cell.py @@ -35,3 +35,8 @@ class TestCell(unittest.TestCase): self.assertEqual('\x00\x00\x07\x00\x00', VersionsCell.pack([])) self.assertEqual('\x00\x00\x07\x00\x02\x00\x01', VersionsCell.pack([1])) self.assertEqual('\x00\x00\x07\x00\x06\x00\x01\x00\x02\x00\x03', VersionsCell.pack([1, 2, 3])) + + def test_versions_unpack(self): + self.assertEqual([], Cell.unpack('\x00\x00\x07\x00\x00', 2).versions) + self.assertEqual([1], Cell.unpack('\x00\x00\x07\x00\x02\x00\x01', 2).versions) + self.assertEqual([1, 2, 3], Cell.unpack('\x00\x00\x07\x00\x06\x00\x01\x00\x02\x00\x03', 2).versions)