RLOGIND(8)RLOGIND(8)NAMErlogind - remote login server
SYNOPSISrlogind [ -aln ]
DESCRIPTION
Rlogind is the server for the rlogin(1) program. The server provides a
remote login facility with authentication based on privileged port num‐
bers from trusted hosts.
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:
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 IR gethostbyaddr (3), hosts(5) and
named(8)). If the hostname cannot be determined, the dot-nota‐
tion representation of the host address is used. If the host‐
name 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. 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(8). It then allo‐
cates a pseudo terminal (see pty(4)), and manipulates file descriptors
so that the slave half of the pseudo terminal becomes the stdin , std‐
out , 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 -l option prevents
any authentication based on the user's ``.rhosts'' file, unless the
user is logging in as the superuser.
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 termi‐
nal type, as found in the environment variable, ``TERM''; see envi‐
ron(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 ALSOlogin(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.
4.2 Berkeley Distribution June 24, 1990 RLOGIND(8)
