[tor-bugs] #25979 [Core Tor/Stem]: Stem, Tor LTS, broken exit policies, and maybe microdescriptor issues too

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#25979: Stem, Tor LTS, broken exit policies, and maybe microdescriptor issues too
-------------------------------+--------------------
     Reporter:  pastly         |      Owner:  atagar
         Type:  defect         |     Status:  new
     Priority:  Medium         |  Milestone:
    Component:  Core Tor/Stem  |    Version:
     Severity:  Normal         |   Keywords:
Actual Points:                 |  Parent ID:
       Points:                 |   Reviewer:
      Sponsor:                 |
-------------------------------+--------------------
 [https://github.com/pastly/simple-bw-
 scanner/blob/656619f51ecfb88ff8909b79c5bd7c6830ec7872/sbws/lib/relaylist.py#L71
 Here in sbws ] I'm wanting to see what exits in the Tor network allow
 exiting to an ip:port.

 However, there seems to be an issue revolving around microdescriptors and
 the "exit policy summaries" contained in them. Perhaps related to #24110,
 I can't tell because I don't understand these details enough.



 stem version: 1.6.0

 Tor version: 0.2.9.14

 torrc:
 {{{
 ORPort 3537
 SocksPort 3538
 ControlPort 3536
 CookieAuthentication 1
 DataDirectory /home/pastly/run/livenet1
 PidFile /home/pastly/run/livenet1/tor.pid
 Log notice file /home/pastly/run/livenet1/notice.log
 ControlSocket /home/pastly/run/livenet1/control_socket
 ContactInfo XXXXXXXXXXXX
 RunAsDaemon 1
 Nickname XXXXXXXXXXXXX
 SafeLogging 0
 DisableDebuggerAttachment 0
 MaxAdvertisedBandwidth 8 Mbits
 ExitRelay 1
 ExitPolicyRejectPrivate 0
 # The public IP address of this machine, and a port on it
 ExitPolicy accept xx.xx.xx.xx:yyyy
 ExitPolicy reject *:*
 }}}

 Traceback:

 Mostly unhelpful, since it's mostly code in my "http"  branch of sbws. But
 you can see the exception.

 `e` is a RouterStatusEntryV3 for a relay with the Exit flag

 {{{
 Traceback (most recent call last):
   File "/home/pastly/src/simple-bw-scanner/sbws/core/scanner.py", line
 247, in dispatch_worker_thread
     return measure_relay(*a, **kw)
   File "/home/pastly/src/simple-bw-scanner/sbws/core/scanner.py", line
 193, in measure_relay
     exits = rl.exits_can_exit_to(dest.hostname, dest.port)
   File "/home/pastly/src/simple-bw-scanner/sbws/lib/relaylist.py", line
 100, in exits_can_exit_to
     if e.exit_policy.can_exit_to(host, port):
 KeyError: (<stem.exit_policy.MicroExitPolicy object at 0x7f9c8c5f5ac8>,
 '144.217.254.208', 80)
 }}}

 If I try only giving a port, same basic traceback (only last few lines
 included) ...

 {{{
   File "/home/pastly/src/simple-bw-scanner/sbws/lib/relaylist.py", line
 101, in exits_can_exit_to
     if e.exit_policy.can_exit_to(port=port):
 KeyError: (<stem.exit_policy.MicroExitPolicy object at 0x7fb97545fd30>,
 <object object at 0x7fb992dba080>, ('port', 80))
 }}}



 Additional information:

 - If I use an 02914 client without setting `UseMicrodescriptors 0`, the
 exit_policy members are None. (hence some disconnect between line numbers
 in the tracebook in order to find and log Nones)

 - If I use an 02914 client with `UseMicrodescriptors 0`, I get the above
 tracebacks

 - If I use an 02914 relay as the client, I get the above traceback

 - This wasn't an issue when I was using an 03210 authority as the client


 My theories:

 - In 02914, one must tell Tor to NOT use microdescs in order to get
 SOMETHING stored as a RouterStatusEntryV3's exit policy
 - Even when you get SOMETHING stored in a RouterStatusEntryV3's exit
 policy when using 02914, it is buggy/missing information/something bad.
 - Something changed between 02914 and 03210 regarding the way Tor tells
 its controllers about (micro)descriptors and the exit policies within.
 This is most likely a stem bug, possibly exacerbated by a Tor bug.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25979>
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