Re: -current dropping ssh connections

On Thu, Jun 22, 2023 at 11:38:50PM +0100, Jamie Landeg-Jones wrote:
> bob prohaska <fbsd@www.zefox.net> wrote:
> 
> > That seems worth a try.
> > The notion of an ssh escape (~. in this case) finding its way into the data stream is new to me.
> 
> Thinking again, that looks like corruption coming down the ssh connection.
> For the ssh escape char to affect anything (note it needs to be preceeded
> by a new line) it would have to be sent up the line.
> 
> For an example, assuming ssh has the default escape char, look at the difference between:
> 
> printf 'pwd;\n~.;echo sleeping.; sleep 5' | ssh -tt user@host
> 
> and with the same printf, but no escape char:
> 
> printf 'pwd;\n~.;echo sleeping.; sleep 5' | ssh -tt -e none user@host
> 
> You can see how the former closes the connection due to the \n~.
> 
> (The -tt forces a terminal/interactive session to be set up - normally, as we are
> piping input to ssh in this case, the terminal isnt set up, and the escape character
> isn't used - it's only recongnised in interactive sesions by default)
> 
> I personally have "EscapeChar none" in my ssh_config, but I suspect this
> is probably not the issue here, still, can't hurt to try it!

Indeed, connection was dropped with escape character set to none.
There does seem to be a some dependence on system load. Connections
survive at light or no load and drop when the sshd side is busy. 

Thanks for writing!

bob prohaska