[tor-bugs] #9330 [Pluggable transport]: Pluggable Transports on windows are killed with ProcessTerminate

Tor Bug Tracker & Wiki blackhole at torproject.org
Thu Jul 25 10:58:40 UTC 2013

#9330: Pluggable Transports on windows are killed with ProcessTerminate
 Reporter:  yawning                         |          Owner:  asn             
     Type:  defect                          |         Status:  new             
 Priority:  normal                          |      Milestone:                  
Component:  Pluggable transport             |        Version:  Tor: unspecified
 Keywords:  pt, win32, pluggable transport  |         Parent:                  
   Points:                                  |   Actualpoints:                  
 The pluggable transport that I am writing needs to do cleanup on shutdown
 (It write files to the pt_state directory, and use a child process).

 The way that tor terminates pluggable transports under Windows currently
 is via ProcessTerminate (common/util.c:tor_terminate_process), which is
 the rough windows equivalent of SIGKILL (Immediate termination, no child
 processes killed, no further code in the application gets executed).

 In theory Tor is supposed to send SIGINT for a graceful shutdown but it
 doesn't appear to be doing this on Windows (Does it do this at all?
 obfsproxy doesn't appear to install a SIGINT handler to handle graceful
 teardown per the PT spec), and furthermore Microsoft's documentation hints
 at horrible evil happening if SIGINT is actually used

 Some way to properly handle graceful shutdown that works across all
 platforms would be nice.  Apparently the way Real Windows Apps approach
 this problem is with GenerateConsoleCtrlEvent or with PostMessage, neither
 which are portable.

 Note: I don't do Windows development as a general rule so I may be missing
 something obvious.

Ticket URL: <https://trac.torproject.org/projects/tor/ticket/9330>
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