2.11BSD#431 - /usr/man/cat8/rlogind.0

RLOGIND(8)	    UNIX Programmer's Manual	       RLOGIND(8)


NAME
     rlogind - remote login server

SYNOPSIS
     rlogind [ -aln ]

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

     Rlogind listens for service requests at the port indicated
     in the ``login'' 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 corresponding host name (see IR gethost-
	  byaddr (3), hosts(5) and named(8)).  If the hostname
	  cannot be determined, the dot-notation representation
	  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 correspond.  Normal
	  authentication is bypassed if the address verification
	  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 authen-
     tication has succeeded.  If automatic authentication fails,
     the user is prompted to log in as if on a standard terminal
     line.  The -l option prevents any authentication based on
     the user's ``.rhosts'' file, unless the user is logging in
     as the superuser.

     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 pro-
     gram.  In normal operation, the packet protocol described in
     pty(4) is invoked to provide ^S/^Q type facilities and pro-
     pagate interrupt signals to the remote programs.  The login
     process propagates the client terminal's baud rate and


Printed 11/24/99       September 11, 1989			1


RLOGIND(8)	    UNIX Programmer's Manual	       RLOGIND(8)


     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 termi-
     nal.

     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.

DIAGNOSTICS
     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 indication of success.

     ``Try again.''
     A fork by the server failed.

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

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

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

     A more extensible protocol should be used.


Printed 11/24/99       September 11, 1989			2