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RLOGIND(8) | System Manager's Manual | RLOGIND(8) |
NAME¶
rlogind
—
remote login server
SYNOPSIS¶
rlogind |
[-afhlLn |
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.
Options supported by rlogind
:
-a
- This option exists for compatibility with historical systems.
-f
- Disable the Nagle algorithm. This is only needed to work around some broken operating systems.
-h
- Permit use of superuser “.rhosts” files.
-l
- Prevent any authentication based on the user's “.rhosts” file. If the user is logging in as the superuser and the -h option is used, “.rhosts” processing is still enabled.
-L
- Prevent any authentication based on “.rhosts” or “hosts.equiv” information.
-n
- Disable keep-alive messages.
-h
and
-l
options should also not be trusted
without verifying that they work as expected with the particular version of
libc installed on your system (and should be tested again after any libc
update) because some versions of libc may not honor the internal flags used by
rlogind
. As the
-L
option bypasses the libc functions
entirely, it is not subject to this problem.
Also note that the design of the .rhosts
system is COMPLETELY INSECURE except on a carefully firewalled private
network. Always use the -L
option under all
other circumstances. Also, since rlogind
does not encrypt communications, it should not, in general, be used at all.
Consider ssh(8).
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:
- The server checks the client's source port. If the port is not in the range 512-1023, the server aborts the connection.
- The server checks the client's source address and requests the corresponding host name (see gethostbyaddr(3), hosts(5) and named(8)). If the hostname cannot be determined, the dot-notation representation of the host address is used. The addresses for the hostname are requested, verifying that the name and address correspond. Normal authentication is bypassed if the address verification fails.
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 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), 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 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.HISTORY¶
Therlogind
command appeared in
4.2BSD.March 16, 1991 | Linux NetKit (0.17) |