Each line of these files has the format:
hostname [username]
The
hostname
may be specified as a host name (typically a fully qualified host
name in a DNS environment) or address,
``+@netgroup
''
(from which only the host names are checked),
or a
``+
''
wildcard (allow all hosts).
The
username,
if specified, may be given as a user name on the remote host,
``+@netgroup
''
(from which only the user names are checked),
or a
``+
''
wildcard (allow all remote users).
If a username is specified, only that user from the specified host may login to the local machine. If a username is not specified, any user may login with the same user name.
somehost
A common usage: users on somehost may login to the local host as the same user name.
somehost
username
The user username on somehost may login to the local host. If specified in/etc/hosts.equiv
, the user may login with only the same user name.
+@anetgroup
username
The user username may login to the local host from any machine listed in the netgroup anetgroup.
+
+ +
Two severe security hazards. In the first case, allows a user on any machine to login to the local host as the same user name. In the second case, allows any user on any machine to login to the local host (as any user, if in/etc/hosts.equiv
).
A numeric host address instead of a host name can help security considerations somewhat; the address is then used directly by iruserok(3).
When a username (or netgroup, or +) is specified in
/etc/hosts.equiv
,
that user (or group of users, or all users, respectively) may login to
the local host as
any local user.
Usernames in
/etc/hosts.equiv
should therefore be used with extreme caution, or not at all.
A
.rhosts
file must be owned by the user whose home directory it resides in, and
must be writable only by that user.
Logins as root only check root's
.rhosts
file; the
/etc/hosts.equiv
file is not checked for security.
Access permitted through root's
.rhosts
file is typically only for
rsh(1),
as root must still login on the console for an interactive login such as
rlogin(1).
/etc/hosts.equiv
~/.rhosts
-
''
sign) and does not treat them as ``short-circuit'' negative entries.