Re: [uml-devel] Changes to port_user

["roland" <for_spam@gmx.de>]

hi!

> If you want to be able to telnet to the port, then you need something which
> speaks telnet, hence you need telnetd.

> > Now what I'm trying to do is replace in.telnetd with something else, for
> > the moment netcat as a simple case, or something that gives the same
> > effect.

mhhh - as security oriented person i would like to admit:
should such "new technology" like uml really "support" unencrypted remote logins and should it support exposing "non encrypted
communication ports" to the outside world ?

telnet is ancient and IMHO it should be replaced by something more secure like ssh. sshd is installed by default on all major
distro`s and it has an "inetd" mode, too.
maybe telnetd can easily be replaced sshd ?

just my 10 eurocents....

regards
roland



----- Original Message ----- 
From: "Jeff Dike" <jdike@addtoit.com>
To: "Dan Shearer" <dan@shearer.org>
Cc: <user-mode-linux-devel@lists.sourceforge.net>
Sent: Thursday, January 22, 2004 5:20 PM
Subject: Re: [uml-devel] Changes to port_user


> On Fri, Jan 23, 2004 at 01:10:20AM +1030, Dan Shearer wrote:
> > I've done some minor work in drivers/port_user.c, including replacing
> > the binding to INADDR_ANY with a gethostbyname(passed_ip), so you
> > can specify which single IP to listen on.
>
> Cool, that's needed doing for a while.
>
> > Now what I'm trying to do is replace in.telnetd with something else, for
> > the moment netcat as a simple case, or something that gives the same
> > effect.
>
> If you want to be able to telnet to the port, then you need something which
> speaks telnet, hence you need telnetd.
>
> If you can connect with something else and have terminal stuff continue
> to work, and replace the telnetd dependency with something that works more
> widely out of the box, then I'm all for it.
>
> > That involves understanding the significance of port_helper and
> > kernel/helper.c, which I don't yet.
>
> What happens is that UML runs telnetd with the port helper as its "login"
> program (problem - not every telnetd out there supports -L, even if it is
> installed, which it often isn't).
>
> When there's a connection, UML gets a descriptor with the telnet on the
> other end.  It needs to get telnetd talking on that to do the telnet
> protocol and another descriptor coming out of telnetd with actual characters
> that the user typed.  So, it does this as follows:
> it execs telnetd with stdin, stderr, stdout duped from the portal
> file descriptor
> telnetd also gets a unix socket on descriptor 3
> port_helper gets the desired telnetd output descriptor on its
> stdin/stdout
> it passes this back to UML over the unix socket on descriptor 3
> which it inherited from telnetd
>
> Jeff
>
>
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