in.rlogind is the server for the rlogin(1) program. The server provides a remote login facility with authentication based on privileged port numbers.
in.rlogind is invoked by inetd(1M) when a remote login connection is established, and executes the following protocol:
The server checks the client's source port. If the port is not in the range 0-1023, the server aborts the connection.
The server checks the client's source address. If an entry for the client 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 entry exists in /etc/hosts, the user is prompted for a password, regardless of whether 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.
The login process then proceeds with the in.rshd(1M) authentication 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 the rlogin program. In normal operation, a packet protocol is invoked to provide Ctrl-S and Ctrl-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(4).
The -U option is used to pass the UID of the client to login(1). The -T option is used if the client has the trusted path attribute.
rlogind and in.rlogind are IPv6–enabled. See ip6(7P).
Two new options (-U and -T) are used in the call to login(1).
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
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.
No entry in the host name database existed for the client's machine.
A fork by the server failed.
The user's login shell could not be started.
The authentication procedure used here assumes the integrity of each client machine and the connecting medium. This is insecure, but it is useful in an ``open'' environment.
A facility to allow all data exchanges to be encrypted should be present.