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.
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 gethostbyname(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
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 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. 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 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 indication of success.
"Try again."
A fork by the server failed.
SEE ALSO
login(1), rshd(8), ruserpass(3)*
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.
__________
* Not currently supported under MachTen