Re: [PATCH] Ensure that SSH runs in non-interactive mode

From: Jeff King <peff@peff.net>
Date: Jul 21, 2008, 00:14 UTC
Message-ID: <20080721001422.GB12454@sigill.intra.peff.net>
In-Reply-To: <7v63r0bejy.fsf@gitster.siamese.dyndns.org>

On Sun, Jul 20, 2008 at 11:23:13AM -0700, Junio C Hamano wrote:

Show 5 quoted lines

> I think that is a very sensible approach, but just like we have a few
> "built-in" function-header regexps with customization possibilities for
> the user, we might want to:
> 
>  * Have that "-x", "-T" in the command line we generate for OpenSSH;

I am slightly negative on this, because we are setting OpenSSH preferences behind the user's back that they would not normally expect git to be tampering with.

I think the expectation for this is that it impacts only the ssh session used by git. But because OpenSSH supports the concept of "master" and "slave" sessions (i.e., it can multiplex many sessions over a single ssh session, avoiding authentication and thus reducing latency until the start of the session), what you do in one session can impact other sessions. In particular, if the 'master' does not have x11 forwarding (because it happens to be started by git), then slave connections do not get it. So a user with X11Forwarding and ControlMaster set in his config would usually have everything work, but bad timing with the git-initiated session as the master would unexpectedly break his X11Forwarding for other sessions.

I don't know how commonly the ControlMaster option for openssh is used. I also don't know if this should simply be considered a bug in openssh, since it silently ignores the request for X forwarding. Personally, I will not be affected because I don't do X forwarding by default, anyway. But I thought I would raise the point.

-Peff