[lug] Xinetd Based Services

D. Stimits stimits at idcomm.com
Tue Jan 29 12:14:43 MST 2002

Add this to the list: They are often useful for developing network
applications as a kind of blank "stub" function. I would never make
those ports accessible to the whole world, but I do on occasion use echo
and chargen and daytime to test things (not very often, but they are
quite useful when needed). They should all be off unless you are
debugging or developing. Turn them on temporarily and telnet to those
ports just to see (only for tcp versions).

D. Stimits, stimits at idcomm.com

chris wrote:
> On Tue, Jan 29, 2002 at 05:11:22AM -0700, SoloCDM wrote:
> > What do the following xinetd based services provide?
> >
> > chargen: off
> > chargen-udp: off
> (provides...)
> a stream of characters to the connecting process.
> only of use for debugging purposes as far as i know (perhaps your ppp
> connection doesn't handle escaping the character 'a' properly--this would
> be a quick way to tell what isn't making it thru, for the printable ascii
> characters anyway.
> turned off by default due to its extremely bandwidth consumptive nature
> (it was a player in a denial of service attack in recent memory) and
> extremely infrequent usefulness.
> > daytime: off
> > daytime-udp: off
> a human readable version of the current time on the server.  i personally
> leave this one enabled on fileservers so i can very that clocks are in sync
> (ntpd fails occasionally on some hosts i use) with some the server (mostly,
> i only care about time in relation to the fileserver and logserver), ie:
> date ; telnet server daytime
> > echo: off
> > echo-udp: off
> an echo of whatever you give it.  also of minimal actual usefulness except
> in aforementioned denial of service attack (string together chargen on one
> host and echo on another and you get a saturated network between the
> two, quickly).
> > time: off
> > time-udp: off
> computer readable version of the current time on the server.  applications
> like "rdate(1)" use it to query the time.
> you can see what these services do with a telnet client--enable them and
> "telnet host servicename" (ie telnet localhost daytime) to see their
> output.  recall, when you hit chargen especially, that the escape key
> for the telnet client is usually control-[
> > Also, do the above services have anything to do with telnet or ftp?
> well, in the sense that you can access the tcp versions with a telnet
> client, yes.  but in the way i suspect you meant it (ie do they allow
> access to some potentially vulnerable part of the system like telnetd
> or ftpd), no.  and no services on a machine except possibly identd affect
> outgoing telnet or ftp from that machine.
> hope that helps.
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