commit 56f41833173aca0c5e78ca2095935f8a474c6430 Author: Damian Johnson atagar@torproject.org Date: Fri Aug 24 03:49:17 2018 -0700

Simplify rollback of key/digest during errors

The reason I asked for our functions to return a new copy of our key/digest is because it lets us simplify this calling code a bit.

Rather than explicitly reverting the key/digest we can simply wait to record the new values until cells are successfully sent and received. --- stem/client/__init__.py | 53 ++++++++++++++++++++++--------------------------- 1 file changed, 24 insertions(+), 29 deletions(-)

diff --git a/stem/client/__init__.py b/stem/client/__init__.py index 8c96b8c2..0ee8cbf0 100644 --- a/stem/client/__init__.py +++ b/stem/client/__init__.py @@ -25,7 +25,6 @@ a wrapper for :class:`~stem.socket.RelaySocket`, much the same way as +- close - closes this circuit """

-import copy import hashlib import threading

@@ -234,18 +233,16 @@ class Circuit(object): """

with self.relay._orport_lock: - orig_forward_digest = self.forward_digest.copy() - orig_forward_key = copy.copy(self.forward_key) + cell = stem.client.cell.RelayCell(self.id, command, data, stream_id = stream_id) + encrypted_cell, new_forward_digest, new_forward_key = cell.encrypt(self.forward_digest, self.forward_key)

- try: - cell = stem.client.cell.RelayCell(self.id, command, data, stream_id = stream_id) - encrypted_cell, self.forward_digest, self.forward_key = cell.encrypt(self.forward_digest, self.forward_key) + self.relay._orport.send(encrypted_cell.pack(self.relay.link_protocol))

- self.relay._orport.send(encrypted_cell.pack(self.relay.link_protocol)) - except: - self.forward_digest = orig_forward_digest - self.forward_key = orig_forward_key - raise + # Only recoding our new digest/key if the cell's successfully sent. If + # the above raises we should leave them alone. + + self.forward_digest = new_forward_digest + self.forward_key = new_forward_key

reply = self.relay._orport.recv() reply_cells = [] @@ -253,24 +250,22 @@ class Circuit(object): relay_cell_cmd = stem.client.cell.RelayCell.VALUE

while reply: - orig_backward_digest = self.backward_digest.copy() - orig_backward_key = copy.copy(self.backward_key) - - try: - raw_cell, reply = stem.client.cell.Cell.pop(reply, self.relay.link_protocol) - - if raw_cell.VALUE != relay_cell_cmd: - raise stem.ProtocolError('RELAY cell responses should be %i but was %i' % (relay_cell_cmd, raw_cell.VALUE)) - elif raw_cell.circ_id != self.id: - raise stem.ProtocolError('Response should be for circuit id %i, not %i' % (self.id, raw_cell.circ_id)) - - decrypted_cell, fully_decrypted, self.backward_digest, self.backward_key = raw_cell.decrypt(self.backward_digest, self.backward_key, interpret = True) - if not fully_decrypted: - raise stem.ProtocolError('Response for circuit id %i was not fully decrypted, when expected to be' % self.id) - except: - self.backward_digest = orig_backward_digest - self.backward_key = orig_backward_key - raise + raw_cell, reply = stem.client.cell.Cell.pop(reply, self.relay.link_protocol) + + if raw_cell.VALUE != relay_cell_cmd: + raise stem.ProtocolError('RELAY cell responses should be %i but was %i' % (relay_cell_cmd, raw_cell.VALUE)) + elif raw_cell.circ_id != self.id: + raise stem.ProtocolError('Response should be for circuit id %i, not %i' % (self.id, raw_cell.circ_id)) + + decrypted_cell, fully_decrypted, new_backward_digest, new_backward_key = raw_cell.decrypt(self.backward_digest, self.backward_key, interpret = True) + + if not fully_decrypted: + raise stem.ProtocolError('Response for circuit id %i was not fully decrypted, when expected to be' % self.id) + + # Again, if the above raises the digest/key should remain unchanged. + + self.backward_digest = new_backward_digest + self.backward_key = new_backward_key

reply_cells.append(decrypted_cell)