[Ovmsdev] openssh 6.7 cipher aes128-cbc

Stephen Casner casner at acm.org
Sat Apr 28 05:45:55 HKT 2018

On Fri, 27 Apr 2018, Robin O'Leary wrote:

> On Thu, Apr 26, 2018 at 11:33:46PM -0700, Stephen Casner wrote:
> > The use case is not so much debugging the internals of wolfssh, rather
> > diagnosing incompatibilities between clients and the the wolfssh
> > server.  Enabling DEBUG_WOLFSSH basically compiles in more log
> > statements, but those don't print unless "log level debug wolfssh" is
> > entered.
> At least for the specific problem with cipher algorithm choice that
> at least two people (including me) have encountered, a better solution
> would be to avoid having to resort to debug mode at all by giving that
> condition its own unique error code that could be returned to the caller.
> With the additional reporting you have already added, I guess there'd
> be a clear message logged somewhere---and maybe reported back to the
> connecting client?

Clearly what you say here is correct.  I was coming to that conclusion
myself last evening.  The reason I have not pursued this solution is
that I'm trying to avoid changes to the wolfssh code, such as
extending the list of error codes, that would not be part of their
release.  But since I have established my credentials with them by
providing the SCP code, perhaps I can make this change and issue a
pull request for it.

Reporting back to the connecting client may not be possible because
the algorithms have to be agreed before the channel is open.
Unfortunately the client diagnostics don't give the necessary details,
either, just "SSH2_MSG_KEXINIT sent" and then the connection closes.

> I would still be good to have a working menu config option to define
> DEBUG_WOLFSSH where it really is necessary to dig deeper.

Agreed.  I'll see if I can figure out how to properly avoid the
_impure_ptr problem.

                                                        -- Steve

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