RLOGIND(8)						      System Manager'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 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 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 allo-
       cates 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 authenti-
       cation 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 program.  In normal operation, the packet protocol described in pty(4) is invoked	to  provide  ^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 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.

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.

4.2 Berkeley Distribution					September 11, 1989							RLOGIND(8)