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[tor-bugs] #31091 [Core Tor/Tor]: Bug stracktrace when pluggable transport cannot bind to port
#31091: Bug stracktrace when pluggable transport cannot bind to port
------------------------------+------------------------------
Reporter: s7r | Owner: (none)
Type: defect | Status: new
Priority: Medium | Milestone:
Component: Core Tor/Tor | Version: Tor: unspecified
Severity: Normal | Keywords:
Actual Points: | Parent ID:
Points: | Reviewer:
Sponsor: |
------------------------------+------------------------------
I have just setup some new obfs4 fast bridges running latest obfs4proxy
from yawning / master (locally compiled on my server) and Tor 0.4.2.0
-alpha-dev and encountered a bug stack trace when started to try with the
pluggable transport listening on a port < 1024. This is well known, which
is why even in the wiki page it is recommended and properly documented to
use setcap in order to grant permission to the PT executable to bind to
lower ports, but shouldn't it just warn and exit, instead of offering all
this:
{{{
Jul 06 05:51:18.000 [warn] Server managed proxy encountered a method
error. (obfs4 listen tcp <ipv4>:<port>: bind: permission denied)
Jul 06 05:51:18.000 [warn] Managed proxy at '/usr/local/bin/obfs4proxy'
failed the configuration protocol and will be destroyed.
Jul 06 05:51:18.000 [err] tor_assertion_failed_(): Bug:
../src/feature/client/transports.c:1836: managed_proxy_stdout_callback:
Assertion mp->conf_state == PT_PROTO_COMPLETED failed; aborting. (on Tor
0.4.2.0-alpha-dev )
Jul 06 05:51:18.000 [err] Bug: Assertion mp->conf_state ==
PT_PROTO_COMPLETED failed in managed_proxy_stdout_callback at
../src/feature/client/transports.c:1836: . Stack trace: (on Tor 0.4.2.0
-alpha-dev )
Jul 06 05:51:18.000 [err] Bug: /usr/bin/tor(log_backtrace_impl+0x47)
[0x559a576f5d87] (on Tor 0.4.2.0-alpha-dev )
Jul 06 05:51:18.000 [err] Bug:
/usr/bin/tor(tor_assertion_failed_+0x147) [0x559a576f0ed7] (on Tor 0.4.2.0
-alpha-dev )
Jul 06 05:51:18.000 [err] Bug: /usr/bin/tor(+0xd4a89) [0x559a575b8a89]
(on Tor 0.4.2.0-alpha-dev )
Jul 06 05:51:18.000 [err] Bug: /usr/bin/tor(+0x1e4e4b)
[0x559a576c8e4b] (on Tor 0.4.2.0-alpha-dev )
Jul 06 05:51:18.000 [err] Bug: /usr/lib/x86_64-linux-
gnu/libevent-2.0.so.5(event_base_loop+0x6a0) [0x7f6f343265a0] (on Tor
0.4.2.0-alpha-dev )
Jul 06 05:51:18.000 [err] Bug: /usr/bin/tor(do_main_loop+0x105)
[0x559a57555ed5] (on Tor 0.4.2.0-alpha-dev )
Jul 06 05:51:18.000 [err] Bug: /usr/bin/tor(tor_run_main+0x1245)
[0x559a57543905] (on Tor 0.4.2.0-alpha-dev )
Jul 06 05:51:18.000 [err] Bug: /usr/bin/tor(tor_main+0x3a)
[0x559a57540cfa] (on Tor 0.4.2.0-alpha-dev )
Jul 06 05:51:18.000 [err] Bug: /usr/bin/tor(main+0x19)
[0x559a57540879] (on Tor 0.4.2.0-alpha-dev )
Jul 06 05:51:18.000 [err] Bug: /lib/x86_64-linux-
gnu/libc.so.6(__libc_start_main+0xf1) [0x7f6f32b7b2e1] (on Tor 0.4.2.0
-alpha-dev )
Jul 06 05:51:18.000 [err] Bug: /usr/bin/tor(_start+0x2a)
[0x559a575408ca] (on Tor 0.4.2.0-alpha-dev )
}}}
What if it just stopped here:
{{{
Jul 06 05:51:18.000 [warn] Server managed proxy encountered a method
error. (obfs4 listen tcp <ip>:<port>: bind: permission denied)
Jul 06 05:51:18.000 [warn] Managed proxy at '/usr/local/bin/obfs4proxy'
failed the configuration protocol and will be destroyed.
}}}
Or maybe even exit entirely so the operator can know something is really
wrong.
Also, I don't know if this is related or not, I will try to make more
tests to confirm or infirm this, but under Debian stable the bridges that
are not run with setcap don't get a reasonable measured speed. Those with
setcap that listen to lower ports have a bw of 2.5 - 3.5 MiB/s and those
without setcap have a bw of 12 KiB/s - 70 KiB/s and they are all on the
same infrastructure / hardware resources / internet speed. I will do some
more digging to confirm this, right now 2 out of 2 obfs4 bridges that were
configured without setcap did not get good bandwidth measurement even
after 15 days of continuous uptime.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/31091>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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