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RLOGIND(8)		  BSD System Manager's Manual		    RLOGIND(8)

     rlogind --	remote login server

     rlogind [-ahlLn]

     Rlogind is	the server for the rlogin(1) program.  The server provides a
     remote login facility with	authentication based on	privileged port	num-
     bers from trusted hosts.

     Options supported by rlogind:

     -a	     Ask hostname for verification.

     -h	     Permit use	of superuser ".rhosts" files.

     -l	     Prevent any authentication	based on the user's ".rhosts" file. If
	     the user is logging in as the superuser and the -h	option is
	     used, ".rhosts" processing	is still enabled.

     -L	     Prevent any authentication	based on ".rhosts" or "hosts.equiv"

     -n	     Disable keep-alive	messages.

     The -h, -l, and -L	flags are not used if PAM (Pluggable Authentication
     Module) support is	in use.	In this	case the same effects can be achieved
     by	editing	/etc/pam.conf.

     The -h and	-l options should also not be trusted without verifying	that
     they work as expected with	the particular version of libc installed on
     your system (and should be	tested again after any libc update) because
     some versions of libc may not honor the internal flags used by rlogind.
     As	the -L option bypasses the libc	functions entirely, it is not subject
     to	this problem.

     Also note that the	design of the .rhosts system is	COMPLETELY INSECURE
     except on a carefully firewalled private network. Always use the -L op-
     tion under	all other circumstances. Also, since rlogind does not encrypt
     communications, it	should not, in general,	be used	at all.	Consider

     Rlogind listens for service requests at the port indicated	in the ``lo-
     gin'' service specification; see services(5).  When a service request is
     received the following protocol is	initiated:

     1.	  The server checks the	client's source	port.  If the port is not in
	  the range 512-1023, the server aborts	the connection.

     2.	  The server checks the	client's source	address	and requests the cor-
	  responding host name (see gethostbyaddr(3), hosts(5) and named(8)).
	  If the hostname cannot be determined,	the dot-notation representa-
	  tion of the host address is used.  If	the hostname is	in the same
	  domain as the	server (according to the last two components of	the
	  domain name),	or if the -a option is given, the addresses for	the
	  hostname are requested, verifying that the name and address corre-
	  spond.  Normal authentication	is bypassed if the address verifica-
	  tion fails.

     Once the source port and address have been	checked, rlogind proceeds with
     the authentication	process	described in rshd(8).  It then allocates a
     pseudo terminal (see pty(4)), and manipulates file	descriptors so that
     the slave half of the pseudo terminal becomes the stdin, stdout, and
     stderr for	a login	process.  The login process is an instance of the
     login(1) program, invoked with the	-f option if authentication has	suc-
     ceeded.  If automatic authentication fails, the user is prompted to log
     in	as if on a standard terminal line.

     The parent	of the login process manipulates the master side of the	pseudo
     terminal, operating as an intermediary between the	login process and the
     client instance of	the rlogin program.  In	normal operation, the packet
     protocol described	in pty(4) is invoked to	provide	`^S/^Q'	type facili-
     ties and propagate	interrupt signals to the remote	programs.  The login
     process propagates	the client terminal's baud rate	and terminal type, as
     found in the environment variable,	`TERM';	see environ(7).	 The screen or
     window size of the	terminal is requested from the client, and window size
     changes from the client are propagated to the pseudo terminal.

     Transport-level keepalive messages	are enabled unless the -n option is
     present.  The use of keepalive messages allows sessions to	be timed out
     if	the client crashes or becomes unreachable.

     All initial diagnostic messages are indicated by a	leading	byte with a
     value of 1, after which any network connections are closed.  If there are
     no	errors before login is invoked,	a null byte is returned	as in indica-
     tion of success.

     Try again.
	     A fork by the server failed.

     login(1), ruserok(3), rshd(8)

     The authentication	procedure used here assumes the	integrity of each
     client machine and	the connecting medium.	This is	insecure, but is use-
     ful in an ``open''	environment.

     A facility	to allow all data exchanges to be encrypted should be present.

     A more extensible protocol	should be used.

     The rlogind command appeared in 4.2BSD.

Linux NetKit (0.17)		March 16, 1991		   Linux NetKit	(0.17)


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