Re: [Twisted-Python] Negative error code breaks twisted.conch

15 Jan 2019

      Thank you!

Filed: https://twistedmatrix.com/trac/ticket/9573

I'll go off and read about submitting a fix now.

Peter.

On Tue, 15 Jan 2019, at 07:41, Glyph wrote:
...
...
On Jan 14, 2019, at 7:23 AM, Peter Westlake
 wrote:>> 
An SSCCE:
from twisted.internet import error
from twisted.python import failure
from twisted.conch.ssh.session import SSHSessionProcessProtocol
from mock import MagicMock
err = error.ProcessTerminated(-1)
fail = failure.Failure(err)
session = MagicMock()
proto = SSHSessionProcessProtocol(session)
proto.processEnded(fail)
That fails with:
Traceback (most recent call last):
  File ".../negexit.py", line 10, in <module>
    proto.processEnded(fail)
  File "/usr/lib64/python2.7/site-
  packages/twisted/conch/ssh/session.py", line 279, in processEnded>>     struct.pack('>L', err.exitCode))
struct.error: integer out of range for 'L' format code
I'm running an SSH server on Windows, where negative exit codes can
happen.>> 
Passing negative numbers to a ">L" format was allowed in Python
before 2.6, where the number was treated as an unsigned int of the
same bit pattern. It was deprecated in 2.6, and became an error in
2.7. It's only just become a problem for me because I'm updating a 10
year old SSH server that has been running under 2.4 all this time.>> 
Presumably the fix is to bit-mask the exitCode? I was able to work
around the error by doing that in a copy of _dumbwin32proc.py which
was copied into the project (historical reasons, don't ask) but it
would be nice to have a proper upstream fix. Not least because I want
to purge the copied-in file, as you can imagine.> This is a great bug!  Thanks for raising it.  Sounds like the fix is
to simply reinterpret it as unsigned.
https://en.wikipedia.org/wiki/Exit_status#Windows:>
...
...
Windows uses 32-bit unsigned integers as exit codes,[11] although
the command interpreter treats them as signed.[12] If a process
fails initialization, a Windows system error code may be
returned.[13][14]> 
Please do submit this fix upstream (file a ticket on Trac, open a PR,
etc), it seems like one of the easier ones to integrate :-).> 
-g

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