Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
-+-
 Reporter:  asn  |  Owner:  (none)
 Type:  defect   | Status:  new
 Priority:  Medium   |  Milestone:  Tor:
 |  unspecified
Component:  Core Tor/Tor |Version:
 Severity:  Normal   | Resolution:
 Keywords:  tor-pt, 031-deferred-20170425,   |  Actual Points:
  034-triage-20180328, 034-removed-20180328, |
  tbb-needs, user-feedback, blog |
Parent ID:   | Points:  1.5
 Reviewer:   |Sponsor:
-+-
Changes (by gaba):

 * keywords:
 tor-pt, 031-deferred-20170425, 034-triage-20180328,
 034-removed-20180328, tbb-needs
 =>
 tor-pt, 031-deferred-20170425, 034-triage-20180328,
 034-removed-20180328, tbb-needs, user-feedback, blog


Comment:

 Some comments on this bug here:
 !https://blog.torproject.org/comment/280961#comment-280961

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Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
-+-
 Reporter:  asn  |  Owner:  (none)
 Type:  defect   | Status:  new
 Priority:  Medium   |  Milestone:  Tor:
 |  unspecified
Component:  Core Tor/Tor |Version:
 Severity:  Normal   | Resolution:
 Keywords:  tor-pt, 031-deferred-20170425,   |  Actual Points:
  034-triage-20180328, 034-removed-20180328, |
  tbb-needs  |
Parent ID:  #30471   | Points:  1.5
 Reviewer:   |Sponsor:
-+-
Changes (by phw):

 * parent:   => #30471


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Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
-+-
 Reporter:  asn  |  Owner:  (none)
 Type:  defect   | Status:  new
 Priority:  Medium   |  Milestone:  Tor:
 |  0.3.4.x-final
Component:  Core Tor/Tor |Version:
 Severity:  Normal   | Resolution:
 Keywords:  tor-pt, 031-deferred-20170425, tbb-  |  Actual Points:
  wants  |
Parent ID:   | Points:  1.5
 Reviewer:   |Sponsor:
-+-
Changes (by gk):

 * keywords:  tor-pt, 031-deferred-20170425 => tor-pt,
 031-deferred-20170425, tbb-wants


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Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
---+---
 Reporter:  asn|  Owner:  (none)
 Type:  defect | Status:  new
 Priority:  Medium |  Milestone:  Tor:
   |  0.3.4.x-final
Component:  Core Tor/Tor   |Version:
 Severity:  Normal | Resolution:
 Keywords:  tor-pt, 031-deferred-20170425  |  Actual Points:
Parent ID: | Points:  1.5
 Reviewer: |Sponsor:
---+---
Changes (by arlolra):

 * cc: arlolra (added)


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Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
---+---
 Reporter:  asn|  Owner:  (none)
 Type:  defect | Status:  new
 Priority:  Medium |  Milestone:  Tor:
   |  0.3.4.x-final
Component:  Core Tor/Tor   |Version:
 Severity:  Normal | Resolution:
 Keywords:  tor-pt, 031-deferred-20170425  |  Actual Points:
Parent ID: | Points:  1.5
 Reviewer: |Sponsor:
---+---
Changes (by nickm):

 * milestone:  Tor: 0.3.2.x-final => Tor: 0.3.4.x-final


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Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
--+
 Reporter:  asn   |  Owner:
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:  Tor: 0.3.1.x-final
Component:  Core Tor/Tor  |Version:
 Severity:  Normal| Resolution:
 Keywords:  tor-pt|  Actual Points:
Parent ID:| Points:  1.5
 Reviewer:|Sponsor:
--+

Comment (by arma):

 Wugh. There's some sort of subtlety in pt_configure_remaining_proxies()
 where it restarts managed proxies sometimes, and it might implicitly drop
 transports it doesn't know it needs, or something. See the call to
 sweep_transport_list() in proxy_prepare_for_restart(). But by then it's
 too late because pt_kickstart_proxy set mp->marked_for_removal to 0 and
 nothing ever marks it again.

 (Whoever decided that transport_t should have a marked_for_removal flag,
 and managed_proxy_t should have an identically named marked_for_removal
 flag, is not a nice person.)

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Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
--+
 Reporter:  asn   |  Owner:
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:  Tor: 0.3.1.x-final
Component:  Core Tor/Tor  |Version:
 Severity:  Normal| Resolution:
 Keywords:  tor-pt|  Actual Points:
Parent ID:| Points:  1.5
 Reviewer:|Sponsor:
--+

Comment (by arma):

 Ok, that turns out to have been the easy part of the fix.

 The fix above does indeed sweep unconfigured bridges from the bridge_list.

 But the managed proxy still stays running.

 That's because the transports and managed proxies get marked:
 {{{
   mark_transport_list();
   pt_prepare_proxy_list_for_config_read();
 }}}

 but then they (both the transport and the managed proxy) get rescued in
 pt_kickstart_proxy:
 {{{
 if (mp->was_around_before_config_read) {
   /* If this managed proxy was around even before we read the
  config this time, it means that it was already enabled before
  and is not useless and should be kept. If it's marked for
  removal, unmark it and make sure that we check whether it
  needs to be restarted. */
   if (mp->marked_for_removal) {
 mp->marked_for_removal = 0;
 check_if_restarts_needed = 1;
   }

   /* For each new transport, check if the managed proxy used to
  support it before the SIGHUP. If that was the case, make sure
  it doesn't get removed because we might reuse it. */
   SMARTLIST_FOREACH_BEGIN(with_transport_list, const char *,
 transport) {
 old_transport = transport_get_by_name(transport);
 if (old_transport)
   old_transport->marked_for_removal = 0;
   } SMARTLIST_FOREACH_END(transport);
 }
 }}}

 And with comments like that...are we sure this ever worked? It sure seems
 to be intentional about keeping them around.

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Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
--+
 Reporter:  asn   |  Owner:
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:  Tor: 0.3.1.x-final
Component:  Core Tor/Tor  |Version:
 Severity:  Normal| Resolution:
 Keywords:  tor-pt|  Actual Points:
Parent ID:| Points:  1.5
 Reviewer:|Sponsor:
--+

Comment (by arma):

 Replying to [comment:5 arma]:
 > If we moved the mark and sweep to outside the if, then we would clear
 out bridge_list in the case where options->Bridges is 0. That seems wise.

 Compare to how it's done for Transports:
 {{{
   mark_transport_list();
   pt_prepare_proxy_list_for_config_read();
   if (!options->DisableNetwork) {
 if (options->ClientTransportPlugin) {
   [...]
 }
   }
   sweep_transport_list();
 }}}

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Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
--+
 Reporter:  asn   |  Owner:
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:  Tor: 0.3.1.x-final
Component:  Core Tor/Tor  |Version:
 Severity:  Normal| Resolution:
 Keywords:  tor-pt|  Actual Points:
Parent ID:| Points:  1.5
 Reviewer:|Sponsor:
--+

Comment (by arma):

 Replying to [comment:4 yawning]:
 > Removing Bridges with `RESETCONF` doesn't seem to affect `bridge_list`
 at the time when pts would be torn down either.

 Check out this code in config.c:
 {{{
   if (options->Bridges) {
 mark_bridge_list();
 for (cl = options->Bridges; cl; cl = cl->next) {
   bridge_line_t *bridge_line = parse_bridge_line(cl->value);
   if (!bridge_line) {
 log_warn(LD_BUG,
  "Previously validated Bridge line could not be added!");
 return -1;
   }
   bridge_add_from_config(bridge_line);
 }
 sweep_bridge_list();
   }
 }}}

 If we moved the mark and sweep to outside the if, then we would clear out
 bridge_list in the case where options->Bridges is 0. That seems wise.

 Or if we prefered, we could start this stanza with
 {{{
   if (!options->Bridges) {
 clear_bridge_list();
   } else {
 ...
 }}}

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Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
--+
 Reporter:  asn   |  Owner:
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:  Tor: 0.3.1.x-final
Component:  Core Tor/Tor  |Version:
 Severity:  Normal| Resolution:
 Keywords:  tor-pt|  Actual Points:
Parent ID:| Points:  1.5
 Reviewer:|Sponsor:
--+

Comment (by yawning):

 > Seems like Tor does not successfuly kill obfs4proxy when it's no longer
 used. It's unclear why.
 > Maybe obfs4proxy never receives the SIGTERM, or never notices that the
 stdin is closed?

 It's "tor never issues the `SIGTERM`, or close `stdin`".

 As far as I can tell, the `Bridge` directives are always parsed,
 regardless of the `UseBridges` setting, so if a `Bridge` entry exists for
 a transport at all (regardless of it if is used), the PT will always
 exist.

 Removing Bridges with `RESETCONF` doesn't seem to affect `bridge_list` at
 the time when pts would be torn down either.

 All of this is crap is half broken on the tor side basically, and it has
 nothing to do with the process teardown code.

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Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
--+
 Reporter:  asn   |  Owner:
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:  Tor: 0.3.1.x-final
Component:  Core Tor/Tor  |Version:
 Severity:  Normal| Resolution:
 Keywords:  tor-pt|  Actual Points:
Parent ID:| Points:  1.5
 Reviewer:|Sponsor:
--+

Comment (by arma):

 (Thanks asn! We first noticed this bug in #21314, but it's good to get it
 its own dedicated ticket here.)

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Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
--+
 Reporter:  asn   |  Owner:
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:  Tor: 0.3.1.x-final
Component:  Core Tor/Tor  |Version:
 Severity:  Normal| Resolution:
 Keywords:  tor-pt|  Actual Points:
Parent ID:| Points:  1.5
 Reviewer:|Sponsor:
--+
Changes (by gk):

 * cc: gk (added)


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Re: [tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
--+
 Reporter:  asn   |  Owner:
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:  Tor: 0.3.1.x-final
Component:  Core Tor/Tor  |Version:
 Severity:  Normal| Resolution:
 Keywords:  tor-pt|  Actual Points:
Parent ID:| Points:  1.5
 Reviewer:|Sponsor:
--+
Changes (by mcs):

 * cc: mcs (added)


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[tor-bugs] #21967 [Core Tor/Tor]: obfs4proxy not killed when unused

[Tor Bug Tracker & Wiki]

#21967: obfs4proxy not killed when unused
--+
 Reporter:  asn   |  Owner:
 Type:  defect| Status:  new
 Priority:  Medium|  Milestone:  Tor: 0.3.1.x-final
Component:  Core Tor/Tor  |Version:
 Severity:  Normal|   Keywords:  tor-pt
Actual Points:|  Parent ID:
   Points:  1.5   |   Reviewer:
  Sponsor:|
--+
 Seems like Tor does not successfuly kill obfs4proxy when it's no longer
 used. It's unclear why. Maybe obfs4proxy never receives the SIGTERM, or
 never notices that the stdin is closed?

 Experiment:
 - Startup Tor Browser using default obfs4 bridges.
 - Check that obfs4proxy process has spawned (`ps -fax | grep obfs`)
 - Reconfigure Tor Browser to not use bridges at all.
 - Check that obfs4proxy process is still there...

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