# 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

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