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HOSTS.EQUIV(5)            OpenBSD Programmer's Manual           HOSTS.EQUIV(5)

NAME
     hosts.equiv, .rhosts - trusted remote hosts and host-user pairs

DESCRIPTION
     The hosts.equiv and .rhosts files list hosts and users which are
     ``trusted'' by the local host when a connection is made via rshd(8), or
     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:

           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.

EXAMPLES
     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 lo-
           cal host (as any user, if in /etc/hosts.equiv).

WARNINGS
     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 consider-
     ations somewhat; the address is then used directly by iruserok(3).

     When a user name (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).

FILES
     /etc/hosts.equiv  global trusted host-user pairs list
     ~/.rhosts         per-user trusted host-user pairs list

SEE ALSO
     rcp(1), rsh(1), rcmd(3), ruserok(3), netgroup(5)

HISTORY
     The .rhosts file format appeared in 4.2BSD.

BUGS
     The ruserok(3) implementation currently skips negative entries (preceded
     with a `-' sign) and does not treat them as ``short-circuit'' negative
     entries.

OpenBSD 3.6                    November 26, 1997                             2