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.
Options supported by
rlogind :
-tag -width Ds
Fl a
Ask hostname for verification.
Fl h
Permit use of superuser
Pa .rhosts
files.
Fl l
Prevent any authentication based on the user's
Pa .rhosts
file. If the user is logging in as the superuser and the -h
option is used,
Pa .rhosts
processing is still enabled.
Fl L
Prevent any authentication based on
Pa .rhosts
or
Pa hosts.equiv
information.
Fl n
Disable keep-alive messages.
The -h, -l, and -L flags are not used if PAM (Pluggable
Authentication Module) support is in use. In this case the same
effects can be achieved by editing
/etc/pam.conf .
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:
-enum
The server checks the client's source port.
If the port is not in the range 512-1023, the server
aborts the connection.
The server checks the client's source address
and requests the corresponding host name (see
gethostbyaddr 3 ,
hosts 5
and
named 8 ) .
If the hostname cannot 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,
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 allocates a pseudo terminal (see
pty 4 ) ,
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
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 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 terminal type,
as found in the environment variable,
Ev TERM ;
see
environ 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.