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RLOGIND(8)									       RLOGIND(8)

       rlogind - remote login server

       rlogind [ -aln ]

       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 speci-
       fication;  see  services(5).  When a service request is received the following protocol is

       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 gethostbyaddr (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  authentica-
	      tion is bypassed if the address verification fails.

       Once  the source port and address have been checked, rlogind proceeds with the authentica-
       tion 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 succeeded.  If auto-
       matic 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,  oper-
       ating  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  pro-
       vide  ^S/^Q  type  facilities 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 ter-
       minal 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

       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.

       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 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.

4.2 Berkeley Distribution		September 11, 1989			       RLOGIND(8)
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