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RLOGIND(8)                BSD 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.

     Options supported by rlogind:

     -a      Ask hostname for verification.

     -l      Prevent any authentication based on the user's ``.rhosts'' file, unless the user is logging in
             as the superuser.

     -n      Disable keep-alive messages.

     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
          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 allocates a pseudo terminal (see pty(4)), and manipulates file descrip-tors descriptors
     tors 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 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 opera-tion, operation,
     tion, the packet protocol described in pty(4) is invoked to provide `^S/^Q' type facilities and propa-gate propagate
     gate 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 net-work network
     work 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.

HISTORY
     The rlogind command appeared in 4.2BSD.

4.2 Berkeley Distribution        June 4, 1993        4.2 Berkeley Distribution