openssh unix dev - Apr 2018 - OpenSSH 7.7p1 interop failure with Twisted Conch 8.0.0-17.9.0

This isn't an OpenSSH bug, but just in case anyone else is ambitious
enough to automatically run interoperability tests against other SSH
implementations, here's a heads-up:

  https://twistedmatrix.com/trac/ticket/9422

TL;DR: commit 7c856857607112a3dfe6414696bf4c7ab7fb0cb3 caused there to
be an SSH_MSG_DEBUG message sent where there wasn't one before, which
tripped over an implementation bug in Twisted.  I'm guessing slightly at
the affected version range based on git history.

-- 
Colin Watson                                       [cjwatson at debian.org]

On Sat, 14 Apr 2018, Colin Watson wrote:
> This isn't an OpenSSH bug, but just in case anyone else is ambitious
> enough to automatically run interoperability tests against other SSH
> implementations, here's a heads-up:
> 
>   https://twistedmatrix.com/trac/ticket/9422
> 
> TL;DR: commit 7c856857607112a3dfe6414696bf4c7ab7fb0cb3 caused there to
> be an SSH_MSG_DEBUG message sent where there wasn't one before, which
> tripped over an implementation bug in Twisted.  I'm guessing slightly
at
> the affected version range based on git history.
Thanks for letting is know - we could set SSH_BUG_DEBUG to disable debug
messages for the affected versions if they are readily identifiable
from their version strings. What do you think?

-d

On Sun, Apr 15, 2018 at 06:38:37PM +1000, Damien Miller
wrote:
> On Sat, 14 Apr 2018, Colin Watson wrote:
> > This isn't an OpenSSH bug, but just in case anyone else is
ambitious
> > enough to automatically run interoperability tests against other SSH
> > implementations, here's a heads-up:
> > 
> >   https://twistedmatrix.com/trac/ticket/9422
> > 
> > TL;DR: commit 7c856857607112a3dfe6414696bf4c7ab7fb0cb3 caused there to
> > be an SSH_MSG_DEBUG message sent where there wasn't one before,
which
> > tripped over an implementation bug in Twisted.  I'm guessing
slightly at
> > the affected version range based on git history.
> 
> Thanks for letting is know - we could set SSH_BUG_DEBUG to disable debug
> messages for the affected versions if they are readily identifiable
> from their version strings. What do you think?
I think that would be a good idea.  The version string is unfortunately
just "Twisted".  That's actually OK for past versions since the
bug goes
back so far, but it would be a shame for future versions.  I've filed
https://twistedmatrix.com/trac/ticket/9424 with a patch to improve the
version string.

Assuming my patch is accepted, I think you could make "Twisted" be
SSH_BUG_DEBUG and "Twisted_*" not.

-- 
Colin Watson                                       [cjwatson at debian.org]