[3847] in linux-net channel archive
Re: Why retain privileged ports?
daemon@ATHENA.MIT.EDU (Hans Davidson)
Thu Jul 25 08:55:38 1996
Date: Thu, 25 Jul 1996 09:41:01 +0200 (METDST)
From: Hans Davidson <Hans.Davidson@it.ki.se>
To: Boris Tobotras <tobotras@jet.msk.su>
Cc: linux-net@vger.rutgers.edu
In-Reply-To: <m0uj73r-000EpfC@jet.msk.su>
On Wed, 24 Jul 1996, Boris Tobotras wrote:
> Hello,
Hi,
>
> As far as I understand, the concept of having privileged TCP/UDP ports
> opens one of biggest security hole in Un*x world. And, it's ability to
> protect net services from unprivileged access has been compromised many
> years ago with emerging of personal systems without any real root account
> protection.
Maybe you have missunderstod what priveleged TCP/UDP ports are. As I know,
the meaning of privileged ports is to give the system administrator some
control of what server programs will or will not respond on which
port in the range of ports numbered [0,1023]. That itself does not, as I
know, restrict who is allowed to do connections through the network into
that ports, unless that limit has been built into the server program.
Without priviledged ports it may have been a nightmare to deliver e-mail into
a multiuser computer. Without priviledged port, you cannot just assume that
for example SMTP access to the system is bound to port 25/TCP. Perhaps, you
instead had have to scan all ports until finding something that looks as a
SMTP server and hope that you not only are connected to sombody who want to
look at others e-mail. With future protocols, it may be more common to aut-
henticate the server before using its services, but anyway you do not want
to just guess and hope to find a specific service on a specific port.
If you do not trust the network, and probably you should not do that in
most, or at least important, cases, then priviledged ports are only a basic
level security feature that need to be complemented with stronger
authentification mechanisms, but if that security mechanisms are implemen-
ted at application level, then priviledged ports may still guard against a
simple type of service denial attacks from an insider.
>
> What I can't understand is why are Linux (and all other unices) still
> bound themselves with this outdated constraints?
>
As I can see it, priviledged ports are meningful and needed only on
multiuser computers that have several users with ability to start user
processes. Linux is that kind of multiuser operating system.
Maybe there exist one or more protocols (well known or more obscure) that
relies on the initiators port number to decide to trust or not trust the
initiator, but if you have no idea (previous knowledge) about the initiating
computer and how it is administered, then that kind of trust looks very
stupid to me.
> --
> Best regards, -- Boris.
>
Regards,
Harley
. . . ___ ___ ___ ___ ___ ___ ___ . . . ___ . . ___ ___ ___ ___
Hans Davidson Karolinska Institutet tel: +46 8 728 7127
System Analyst S-171 77 STOCKHOLM fax: +46 8 34 00 32
IT-avdelningen SWEDEN/SUEDE/SCHWEDEN visit: Doktorsringen 6C, Solna
