rlogind(ADMN)                   19 June 1992                   rlogind(ADMN)


 Name

    rlogind - remote login server

 Syntax

    /etc/rlogind

 Description

    rlogind is the server for the rlogin(TC) program.  The server provides a
    remote login facility with authentication based on privileged port num-
    bers from trusted hosts.  It is started by the ``super-server'' inetd,
    and therefore must have an entry in inetd's configuration file,
    /etc/inetd.conf (see inetd(ADMN) and inetd.conf(SFF)).

    rlogind listens for service requests at the port indicated in the "login"
    service specification; see services(SFF).  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 corre-
        sponding host name (see gethostbyaddr(SLIB), hosts(SFF), and
        named(ADMN)).  If the hostname cannot be determined, the dot-notation
        representation of the host address is used.

    Once the source port and address have been checked, rlogind proceeds with
    the authentication process described in rshd(ADMN).  It then allocates a
    pseudo terminal 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(M) 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 -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.  Login propagates the client
    terminal's baud rate and terminal type, as found in the environment vari-
    able, TERM; see environ(M).

    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 diagnostic messages are returned on the connection associated with
    the stderr, after which any network connections are closed.  An error is
    indicated by a leading byte with a value of 1.


    Try again.     A fork by the server failed.

    ``/bin/sh:...  The user's login shell could not be started.


 Notes

    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.

 See also

    inetd(ADMN), rshd(ADMN), rlogin(TC), ruserok(SLIB), inetd.conf(SFF),
    rhosts(SFF), services(SFF)