RLOGIND(8) MachTen 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 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.
Rlogind listens for service
requests at the port indicated in the ‘‘lo-
gin’’ 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-
tion 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
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 lo-
gin(1) program, invoked with the -f option if authentication
has succeed-
ed. 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 -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 indica-
tion 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 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 rlogind command appeared in 4.2BSD.
4.2 Berkeley Distribution June 4, 1993 2