hosts.equiv, .rhosts - trusted remote hosts and host-user
The hosts.equiv and .rhosts files list hosts and users which
``trusted'' by the local host when a connection is made via
any other server that uses ruserok(3). This mechanism bypasses password
checks, and is required for access via rsh(1).
Each line of these files has the format:
The hostname may be specified as a host name (typically a
host name in a DNS environment) or address, +@netgroup (from
the host names are checked), or a `+' wildcard (allow all
The username, if specified, may be given as a user name on
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.
A common usage; users on somehost may login to the local host as
the same user name.
The user username on somehost may login to the local
specified in /etc/hosts.equiv, the user may login with
same user name.
The user username may login to the local host from any
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).
The user name checks provided by this mechanism are not secure, as the
remote user name is received by the server unchecked for validity.
Therefore this mechanism should only be used in an environment where all
hosts are completely trusted.
A numeric host address instead of a host name can help security considerations
somewhat; the address is then used directly by
When a user name (or netgroup, or `+') is specified in
that user (or group of users, or all users, respectively)
may login to
the local host as any local user. Usernames in
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
is not checked for security. Access permitted through
file is typically only for rsh(1).
/etc/hosts.equiv global trusted host-user pairs list
~/.rhosts per-user trusted host-user pairs list
rcp(1), rsh(1), rcmd(3), ruserok(3), netgroup(5)
The .rhosts file format appeared in 4.2BSD.
The ruserok(3) implementation currently skips negative entries (preceded
with a `-' sign) and does not treat them as ``short-circuit'' negative
OpenBSD 3.6 November 26, 1997
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