RLOGIND(8) BSD System Manager's Manual RLOGIND(8)
rlogind -- remote login server
rlogind 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 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.
-L Log all successful accesses to syslogd(8) as auth.info 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 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 -a 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-
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 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 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(1) 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 termi-
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.
At the end of a login session, rlogind invokes the ttyaction(3) facility
with an action of "rlogind" and user "root" to execute site-specific com-
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(1) is invoked, a null byte is returned as in indi-
cation of success.
A fork(2) by the server failed.
login(1), ruserok(3), ttyaction(3), rshd(8)
The rlogind command appeared in 4.2BSD.
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.
rlogind intentionally rejects accesses from IPv4 mapped address on top of
AF_INET6 socket, since IPv4 mapped address complicates host-address based
authentication. If you would like to accept connections from IPv4 peers,
you will need to run rlogind on top of AF_INET socket, not AF_INET6
BSD November 8, 1996 BSD