RLOGIND(8) BSD System Manager's Manual RLOGIND(8)

NAME
     rrllooggiinndd - remote login server

SYNOPSIS
     rrllooggiinndd [-aallnn]

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

     Options supported by rrllooggiinndd:

     -aa      Ask hostname for verification.

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

     -nn      Disable keep-alive messages.

     RRllooggiinndd 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 cor-
          responding host name (see gethostbyaddr(3), hosts(5) and named(8)).
          If the hostname cannot be determined, the dot-notation representa-
          tion 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 -aa option is given, the addresses for the
          hostname are requested, verifying that the name and address corre-
          spond.  Normal authentication is bypassed if the address verifica-
          tion fails.

     Once the source port and address have been checked, rrllooggiinndd 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 -ff option if authentication has suc-
     ceeded.  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 operation, the packet
     protocol described in pty(4) is invoked to provide `^S/^Q' type facili-
     ties 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 -nn 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 indica-
     tion of success.

     TTrryy aaggaaiinn..
             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 use-
     ful 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 rrllooggiinndd command appeared in 4.2BSD.

4.2 Berkeley Distribution        June 4, 1993        4.2 Berkeley Distribution