News Group Posts

sshd stty login

From: Bela Lubkin <belal@sco.com>
Subject: Re: sco-list: [OFF] OpenSSH on OpenServer 5.0.6a
Date: Wed, 1 May 2002 02:11:59 GMT
References: <NEBBLMPLNKHMEHJGNPIHIEEAEBAA.bill@mwdental.com>
<Pine.LNX.4.42.0204291600310.20499-100000@nimbus.anzio.com>
<20020429233814.GF14460@jpradley.jpr.com>
<Pine.LNX.4.42.0204300846210.30676-100000@nimbus.anzio.com> 

Bob Rasmussen wrote:

> OK. After sshd validates the user, it must interact with the OS to get a shell
> prompt. It may use the "login" program for this, I don't recall. Let's assume
> it does. When it gets a connection through login, the user sees a shell
> prompt, through a pseudo tty session.

OpenSSH can be configured, both at compile and at runtime, whether to
use login or not.  If it's compiled not to support login or
runtime-configured not to use it, it does its own pty setup.

> In other Unix/Linux systems, the login program seems to hand to sshd a pty
> with the stty settings already configured in a sane manner. Thus an <enter>
> key, which sends a CR, gets converted to a LF (icrnl). Not so with OSR 5. It
> seems to hand off a pty with stty set to "all zeros".

OSR5 /bin/login configures the pty in a sane manner.  However, OpenSSH
"out of the box" (i.e. if you configure/make it yourself) does _not_ by
default use the OS's login program.  This causes quite a few problems on
OSR5, one of the most visible of which is this pty settings problem.

> Part of both the ssh1 and ssh2 protocols allows the client to send stty
> settings to the server. Some Windows clients do this, some do not. I'm not
> sure about OpenSSH client on Unix, but from your comments I assume it does.
> 
> So:
> 
> OSR5 to Linux: Linux hands off a sane pty, no problem.
> 
> OSR5 to OSR5, or Linux to OSR5: Login hands off a bad pty, but the ssh client
                                  ^^^^^ OpenSSH sshd
> sends the stty settings, so no problem.
> 
> Some Windows SSH client to OSR5: Login hands off a bad pty, the client doesn't
                                   ^^^^^ OpenSSH sshd
> send stty settings, so things don't work well.
> 
> AnzioWin SSH client (current version) to OSR5: Client sends stty settings, all
> is good.

>Bela<
 

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