Re: [han.holl@pobox.com] libc/1172: rresvport should avoid well known ports

[Andreas Jaeger <aj@arthur.rhein-neckar.de>]

>>>>> Thorsten Kukuk writes:

Thorsten> Hello,

Thorsten> On Fri, Jun 25, Andreas Jaeger wrote:

>> 
>> We've received the appended bug report.  I understand the problem the
>> user has but I'm not sure that we should follow the suggestion.
>> 
>> Could you please comments on this?

Thorsten> I would say programs which uses fixed port numbers between 512 - 1023 are 
Thorsten> broken. For this, we have the numbers less 512.
Thorsten> 512 - 1023 are reserved for dynamically used privileged ports.

Check RFC1700, the ports are reserved until 1023 - and there're some
well known programs in the range like kerberos,syslog,talk.

Andreas

P.S. Some exceperts from RFC1700

WELL KNOWN PORT NUMBERS

The Well Known Ports are controlled and assigned by the IANA and on
most systems can only be used by system (or root) processes or by
programs executed by privileged users.

Ports are used in the TCP [RFC793] to name the ends of logical
connections which carry long term conversations.  For the purpose of
providing services to unknown callers, a service contact port is
defined.  This list specifies the port used by the server process as
its contact port.  The contact port is sometimes called the
"well-known port".

To the extent possible, these same port assignments are used with the
UDP [RFC768].

The assigned ports use a small portion of the possible port numbers.
For many years the assigned ports were in the range 0-255.  Recently,
the range for assigned ports managed by the IANA has been expanded to
the range 0-1023.

Port Assignments:
[...]
login           513/tcp    remote login a la telnet;
#                          automatic authentication performed
#                          based on priviledged port numbers
#                          and distributed data bases which
#                          identify "authentication domains"
who             513/udp    maintains data bases showing who's
#                          logged in to machines on a local
#                          net and the load average of the
#                          machine
cmd             514/tcp    like exec, but automatic
#                          authentication is performed as for
#                          login server


syslog          514/udp
printer         515/tcp    spooler
printer         515/udp    spooler
#               516/tcp    Unassigned
#               516/udp    Unassigned
talk            517/tcp    like tenex link, but across
#                          machine - unfortunately, doesn't
#                          use link protocol (this is actually
#                          just a rendezvous port from which a
#                          tcp connection is established)
talk            517/udp    like tenex link, but across
#                          machine - unfortunately, doesn't
#                          use link protocol (this is actually
#                          just a rendezvous port from which a
                           tcp connection is established)
ntalk           518/tcp
ntalk           518/udp
utime           519/tcp    unixtime
utime           519/udp    unixtime
efs             520/tcp    extended file name server
router          520/udp    local routing process (on site);
#                          uses variant of Xerox NS routing
#                          information protocol
#               521-524    Unassigned
timed           525/tcp    timeserver
timed           525/udp    timeserver
[...]
mdbs_daemon     800/tcp
mdbs_daemon     800/udp
device          801/tcp
device          801/udp
xtreelic        996/tcp        Central Point Software
xtreelic        996/udp        Central Point Software
#                              Dale Cabell <dacabell@smtp.xtree.com>
maitrd          997/tcp
maitrd          997/udp
busboy          998/tcp
puparp          998/udp
garcon          999/tcp
applix          999/udp        Applix ac
puprouter       999/tcp
puprouter       999/udp
cadlock         1000/tcp
ock             1000/udp
                1023/tcp       Reserved
                1024/udp       Reserved
#                              IANA <iana@isi.edu>

-- 
 Andreas Jaeger   aj@arthur.rhein-neckar.de    jaeger@informatik.uni-kl.de
  for pgp-key finger ajaeger@aixd1.rhrk.uni-kl.de