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

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]

On Sun, 15 Apr 2018, Colin Watson wrote:
> 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.
Ok, I'll hold off until it's submitted (or looks like it will be).

-d

On Sun, 15 Apr 2018, Colin Watson wrote:
> On Sun, Apr 15, 2018 at 06:38:37PM +1000, Damien Miller wrote:
> 
> Assuming my patch is accepted, I think you could make "Twisted"
be
> SSH_BUG_DEBUG and "Twisted_*" not.
Here's the diff for that BTW.

diff --git a/compat.c b/compat.c
index 7ff3759..36a92c7 100644
--- a/compat.c
+++ b/compat.c
@@ -137,6 +137,8 @@ compat_datafellows(const char *version)
 					SSH_OLD_DHGEX },
 		{ "ConfD-*",
 					SSH_BUG_UTF8TTYMODE },
+		{ "Twisted_*",		0 },
+		{ "Twisted*",		SSH_BUG_DEBUG },
 		{ NULL,			0 }
 	};

On Sun, Apr 15, 2018 at 09:27:59PM +1000, Damien Miller
wrote:
> On Sun, 15 Apr 2018, Colin Watson wrote:
> > 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.
> 
> Ok, I'll hold off until it's submitted (or looks like it will be).
My patch has been applied, so I think you can go ahead with that now.
Thanks.

-- 
Colin Watson                                       [cjwatson at debian.org]