bin/52898: ssh -v prints debug message on every keystroke

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         52898
>Category:       bin
>Synopsis:       ssh -v prints debug message on every keystroke
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jan 04 15:05:00 +0000 2018
>Originator:     Andreas Gustafsson
>Release:        NetBSD 7, NetBSD-current
>Organization:
>Environment:
System: NetBSD guava.gson.org 7.1_STABLE NetBSD 7.1_STABLE (GUIDO) #0: Fri Nov 10 10:29:06 EET 2017 gson%guido.araneus.fi@localhost:/bracket/prod/7/amd64/obj/sys/arch/amd64/compile/GUIDO amd64
Architecture: x86_64
Machine: amd64
>Description:

For many years, I have been in the habit of using the "-v" option of
ssh because it prints useful information about the progress of the
connection setup, the ciphers used, etc.

However, in recent versions of NetBSD, including NetBSD 7 and
-current, "ssh -v" has started printing a debug message for every
keystroke sent to the server, even at the lowest verbosity setting
implied by the single "-v" option.  For example, if I type "ls -al",
it is echoed as:

$ debug1: mac 0x7f7ff7b1d6b0, 1 1
ldebug1: mac 0x7f7ff7b1d6b0, 1 1
sdebug1: mac 0x7f7ff7b1d6b0, 1 1
 debug1: mac 0x7f7ff7b1d6b0, 1 1
-debug1: mac 0x7f7ff7b1d6b0, 1 1
adebug1: mac 0x7f7ff7b1d6b0, 1 1
ldebug1: mac 0x7f7ff7b1d6b0, 1 1

Since this makes the echoed commands effectively unreadable, it means
that every time I type "ssh -v" either out of old habit, or because
there was some issue with the connection that I actually needed to
diagnose, I will have to log out and log in again without the "-v".

Can we please have the old behavior back?

>How-To-Repeat:

ssh -v some.server
type a shell command

>Fix: