`rlogind`

Remote login daemon

You must be root to start this daemon.

Syntax:

rlogind [-aln]

Options:

-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 keepalive messages.

Description:

The rlogind daemon is the server for the rlogin utility. The daemon provides a remote login facility with authentication based on privileged port numbers from trusted hosts.

The rlogind daemon is started when inetd receives a service request at the port indicated by the login entry (inetd listens for service requests specified in the inetd.conf file at a port defined in the services file). The following protocol is initiated:

The server checks the client's source port. If the port isn't in the range 512-1023, the server aborts the connection.
The server checks the client's source address and requests the corresponding hostname (see gethostbyaddr(), the /etc/hosts file, and named). If the hostname can't 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, rlogind requests the addresses for the hostname and verifies 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. It then allocates a pseudo terminal, and manipulates file descriptors so that the slave half of the pseudo terminal becomes the standard input, standard output, and standard error for a login process.

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 rlogin. In most cases, “^S/^Q” facilities are provided to propagate interrupt signals to the remote programs. The login process propagates the client terminal's baud rate and terminal type, as found in the TERM environment variable. 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, which are enabled unless -n is given, allow 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 an indication of success.

Try again: A fork by the server failed.

Caveats:

The authentication procedure used here assumes the integrity of each client machine and the connecting medium. This is insecure, but useful in an “open” environment.