RLOGIND(1M)RLOGIND(1M)NAMErlogind - remote login server
SYNOPSIS
/usr/etc/rlogind [ -aln ]
DESCRIPTION
Rlogind is the server for the rlogin(1C) program. The server provides a
remote login facility with authentication based on privileged port
numbers from trusted hosts. The -a option verifies the remote host name
and address match on all incoming connections. Normally this check is
performed only for connections from hosts in the local domain. The -l
option disables validation using .rhosts files, unless the user is
logging in as the superuser. Transport-level keep-alive messages are
enabled unless the -n option is present. The use of keep-alive messages
allows sessions to be timed out if the client crashes or becomes
unreachable. These options should specified in the /etc/inetd.conf file
(see inetd(1M)).
Rlogind listens for service requests at the port indicated in the
``login'' service specification; see services(4). 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 gethostbyaddr(3N), hosts(4) and
named(1M)). 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. Address verification
failures are logged with syslog(3B). If the hostname cannot be
determined or verified, the dot-notation representation of the host
address is used for authentication.
Once the source port and address have been checked, rlogind allocates a
pseudo terminal (see pty(7M)), 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 -r or -R options. The login process
then proceeds with the authentication process as described in rshd(1M),
but if automatic authentication fails, it reprompts the user to login as
one finds 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(7M) 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(5). The screen
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or window size of the terminal is requested from the client, and window
size changes from the client are propagated to the pseudo terminal.
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.
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.
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