rlogind(1M) — ADMINISTRATOR COMMANDS

NAME

rlogind − remote login server

SYNOPSIS

in.rlogind [−l] [-n] host.port

DESCRIPTION

in.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. It is started from inetd , and therefore must have an entry in inetd ’s configuration file /etc/inetd.conf [see inetd(1M) and inetd.conf(4)].

in.rlogind listens for service requests on the port indicated by the login specification; [see services(4)]. When a service request is received in.rlogind executes the following protocol:

1) The server checks the client’s source port. If the port is not in the range 512-1023, the server aborts the connection. The client’s address and port number are passed as arguments to in.rlogind by inetd in the form host.port with host in hexadecimal and port in decimal.

2) The server checks the client’s source address and requests the corresponding host name [see gethostbyaddr(3), hosts(4) and named(1M)]. If the hostname cannot be determined, the dot-notation representation of the host address is used. If the hostname can be determined, and an entry for it exists in both /etc/hosts and /etc/hosts.equiv, a user logging in from the client is not prompted for a password. If the address is associated with a host for which no corresponding hostname can be determined in /etc/hosts, the user is prompted for a password, regardless of whether or not an entry for the client is present in /etc/hosts.equiv [see hosts(4) and hosts.equiv(4)].

Once the source port and address have been checked, in.rlogind allocates a pseudo-terminal 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 option. 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 −l option prevents any authentication based on the users .rhosts file.

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, a packet protocol is invoked to provide Ctrl-S / Ctrl-Q type facilities and propagate interrupt signals to the remote programs. The rlogin process propagates the client terminal’s baud rate and terminal type, as found in the environment variable, TERM; see environ(4).

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 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.

Hostname for your address unknown.
No entry in the host name database existed for the client’s machine.

Try again.
A fork by the server failed.

/usr/bin/sh: ...
The user’s login shell could not be started.

CAVEATS

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.

It is possible for in.rlogind to respond slowly when Domain Name Service is in place and the primary nameserver is unreachable or slow to respond. If your nameserver or network is heavily loaded, refer to the resolv.conf(4) man page for details on how to configure DNS under these conditions.

— TCP/IP

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