Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
-+-
 Reporter:  pulls|  Owner:
 |  mikeperry
 Type:  defect   | Status:
 |  assigned
 Priority:  Medium   |  Milestone:  Tor:
 |  0.4.3.x-final
Component:  Core Tor/Tor |Version:  Tor:
 |  0.4.1.5
 Severity:  Normal   | Resolution:
 Keywords:  wtf-pad circpad-researchers-want |  Actual Points:
  042-should |
Parent ID:   | Points:
 Reviewer:   |Sponsor:
-+-
Changes (by nickm):

 * milestone:  Tor: 0.4.2.x-final => Tor: 0.4.3.x-final


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Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
-+-
 Reporter:  pulls|  Owner:
 |  mikeperry
 Type:  defect   | Status:
 |  assigned
 Priority:  Medium   |  Milestone:  Tor:
 |  0.4.2.x-final
Component:  Core Tor/Tor |Version:  Tor:
 |  0.4.1.5
 Severity:  Normal   | Resolution:
 Keywords:  wtf-pad circpad-researchers-want |  Actual Points:
  042-should |
Parent ID:   | Points:
 Reviewer:   |Sponsor:
-+-

Comment (by mikeperry):

 In his writeup, Nate documented a crash when using the always-schedule
 workaround: https://github.com/notem/tor-rbp-padding-machine-doc (Issues
 section).

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Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
-+-
 Reporter:  pulls|  Owner:
 |  mikeperry
 Type:  defect   | Status:
 |  assigned
 Priority:  Medium   |  Milestone:  Tor:
 |  0.4.2.x-final
Component:  Core Tor/Tor |Version:  Tor:
 |  0.4.1.5
 Severity:  Normal   | Resolution:
 Keywords:  wtf-pad circpad-researchers-want |  Actual Points:
  042-should |
Parent ID:   | Points:
 Reviewer:   |Sponsor:
-+-

Comment (by pulls):

 For 1, I would guess it's mostly due to how people collect traces and do
 evaluation, but as is the case for 2, I don't really know. As discussed
 for the simulator, I think the first order of business is to get
 reasonably efficient machines that can defend against deep learning
 attacks without time and then take it from there.

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Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
-+-
 Reporter:  pulls|  Owner:
 |  mikeperry
 Type:  defect   | Status:
 |  assigned
 Priority:  Medium   |  Milestone:  Tor:
 |  0.4.2.x-final
Component:  Core Tor/Tor |Version:  Tor:
 |  0.4.1.5
 Severity:  Normal   | Resolution:
 Keywords:  wtf-pad circpad-researchers-want |  Actual Points:
  042-should |
Parent ID:   | Points:
 Reviewer:   |Sponsor:
-+-

Comment (by mikeperry):

 Bleh. It is unfortunate that clients need more accurate timers than
 relays.

 1. Do you have any sense as to if client-side timing is more important
 because most test crawls tend to use client-side timings as opposed to
 guard-side timings (and thus inherently get very high client-side timing
 resolution and visibility into Firefox delays), or because of something
 else that is just inherent to the HTTP protocol?

 2. If I were to write a patch that allowed either clients or relays to
 correctly fast-path this 0ms case to insert bursts of back-to-back packets
 without the circuit failure, would that help?

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Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
-+-
 Reporter:  pulls|  Owner:
 |  mikeperry
 Type:  defect   | Status:
 |  assigned
 Priority:  Medium   |  Milestone:  Tor:
 |  0.4.2.x-final
Component:  Core Tor/Tor |Version:  Tor:
 |  0.4.1.5
 Severity:  Normal   | Resolution:
 Keywords:  wtf-pad circpad-researchers-want |  Actual Points:
  042-should |
Parent ID:   | Points:
 Reviewer:   |Sponsor:
-+-

Comment (by pulls):

 Yeah, that's not great, a delay of 0-10 ms is massive. Even worse,
 basically how timers behave becomes a function of load? Simulations based
 on unit-tests (#31788) will be harder to tweak since one should account
 for relay load as well.

 At the relay, this kind of variability may not be all that bad. Time is
 messy for classifiers and you already have a lot of natural variability at
 this end together with typically many cells going towards the client (so
 you can make a machine start to create a cell train from the early cells,
 working around some possible delay). The client-side delay is the worst I
 think, because here the natural variability is typically the time it takes
 for Firefox to queue up more GET requests.

 I think adding priority for padding timers is a good #circpad-researchers-
 want and in the meantime we can recommend that researchers working on
 defenses focus on Deep Fingerprinting, since it doesn't use time. Deep
 Fingerprinting shares architecture with Var-CNN and Tik-Tok, so it would
 be really interesting to see a defense that works on Deep Fingerprinting
 in the circpad framework but fails to the other attacks.

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Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
-+-
 Reporter:  pulls|  Owner:
 |  mikeperry
 Type:  defect   | Status:
 |  assigned
 Priority:  Medium   |  Milestone:  Tor:
 |  0.4.2.x-final
Component:  Core Tor/Tor |Version:  Tor:
 |  0.4.1.5
 Severity:  Normal   | Resolution:
 Keywords:  wtf-pad circpad-researchers-want |  Actual Points:
  042-should |
Parent ID:   | Points:
 Reviewer:   |Sponsor:
-+-

Comment (by mikeperry):

 Tobias: FYI I have noticed a perf issue with this solution. Going back
 into libevent for the callback introduces anywhere from 0-10ms delay, at
 random, on just a client. On relays, it may be much worse.. Or maybe
 better, if they are not building circuits (client path construction can
 block the event loop for a long time).

 For origin/master, this means we need to fast-path the 0-delay case still
 somehow without callbacks, and also warn about this in the developer doc.
 I bet trying to compose a packet train to fake a burst that actually has
 9ms delay between packets is going to get seen by classifiers pretty
 easily :/.

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Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
-+-
 Reporter:  pulls|  Owner:
 |  mikeperry
 Type:  defect   | Status:
 |  assigned
 Priority:  Medium   |  Milestone:  Tor:
 |  0.4.2.x-final
Component:  Core Tor/Tor |Version:  Tor:
 |  0.4.1.5
 Severity:  Normal   | Resolution:
 Keywords:  wtf-pad circpad-researchers-want |  Actual Points:
  042-should |
Parent ID:   | Points:
 Reviewer:   |Sponsor:
-+-

Comment (by nickm):

 ("not before oct 22" is okay if the fix itself is simple.  Mike also says
 he might be able to do a simple fix later next week)

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Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
-+-
 Reporter:  pulls|  Owner:
 |  mikeperry
 Type:  defect   | Status:
 |  assigned
 Priority:  Medium   |  Milestone:  Tor:
 |  0.4.2.x-final
Component:  Core Tor/Tor |Version:  Tor:
 |  0.4.1.5
 Severity:  Normal   | Resolution:
 Keywords:  wtf-pad circpad-researchers-want |  Actual Points:
  042-should |
Parent ID:   | Points:
 Reviewer:   |Sponsor:
-+-
Changes (by nickm):

 * owner:  none => mikeperry


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Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
-+-
 Reporter:  pulls|  Owner:  none
 Type:  defect   | Status:
 |  assigned
 Priority:  Medium   |  Milestone:  Tor:
 |  0.4.2.x-final
Component:  Core Tor/Tor |Version:  Tor:
 |  0.4.1.5
 Severity:  Normal   | Resolution:
 Keywords:  wtf-pad circpad-researchers-want |  Actual Points:
  042-should |
Parent ID:   | Points:
 Reviewer:   |Sponsor:
-+-
Changes (by mikeperry):

 * owner:  mikeperry => none


Comment:

 I thought I could do this quickly; turns out I can't. Not before Oct 22
 (Firefox ESR deadline)

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Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
-+-
 Reporter:  pulls|  Owner:
 |  mikeperry
 Type:  defect   | Status:
 |  assigned
 Priority:  Medium   |  Milestone:  Tor:
 |  0.4.2.x-final
Component:  Core Tor/Tor |Version:  Tor:
 |  0.4.1.5
 Severity:  Normal   | Resolution:
 Keywords:  wtf-pad circpad-researchers-want |  Actual Points:
  042-should |
Parent ID:   | Points:
 Reviewer:   |Sponsor:
-+-

Comment (by mikeperry):

 This is a tricky thing to fix; not because of the fix itself, but because
 our unit tests frequently schedule 0usec padding (often with only some
 probability) and expect a direct call.

 Fixing all the tests to ensure that there are no places where they can
 still flap is more complicated than I have time for right now.

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Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
-+-
 Reporter:  pulls|  Owner:
 |  mikeperry
 Type:  defect   | Status:
 |  assigned
 Priority:  Medium   |  Milestone:  Tor:
 |  0.4.2.x-final
Component:  Core Tor/Tor |Version:  Tor:
 |  0.4.1.5
 Severity:  Normal   | Resolution:
 Keywords:  wtf-pad circpad-researchers-want |  Actual Points:
  042-should |
Parent ID:   | Points:
 Reviewer:   |Sponsor:
-+-
Changes (by mikeperry):

 * status:  new => assigned
 * owner:  (none) => mikeperry


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Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
-+-
 Reporter:  pulls|  Owner:  (none)
 Type:  defect   | Status:  new
 Priority:  Medium   |  Milestone:  Tor:
 |  0.4.2.x-final
Component:  Core Tor/Tor |Version:  Tor:
 |  0.4.1.5
 Severity:  Normal   | Resolution:
 Keywords:  wtf-pad circpad-researchers-want |  Actual Points:
  042-should |
Parent ID:   | Points:
 Reviewer:   |Sponsor:
-+-
Changes (by nickm):

 * keywords:  wtf-pad circpad-researchers-want => wtf-pad circpad-
 researchers-want 042-should


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Re: [tor-bugs] #31653 [Core Tor/Tor]: Padding cells sent with 0ms delay cause circuit failures (was: padding machine sending padding from relay to client closes circuit)

[Tor Bug Tracker & Wiki]

#31653: Padding cells sent with 0ms delay cause circuit failures
--+
 Reporter:  pulls |  Owner:  (none)
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:  Tor:
  |  0.4.2.x-final
Component:  Core Tor/Tor  |Version:  Tor:
  |  0.4.1.5
 Severity:  Normal| Resolution:
 Keywords:  wtf-pad circpad-researchers-want  |  Actual Points:
Parent ID:| Points:
 Reviewer:|Sponsor:
--+

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