hosts.equiv(5) - NetBSD Manual Pages

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HOSTS.EQUIV(5)            NetBSD 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 rlogind(8),
     rshd(8), or any other server that uses ruserok(3).  This mechanism by-
     passes 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 username checks provided by this mechanism are not secure, as the re-
     mote user name is received by the server unchecked for validity.  There-
     fore 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 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 con-
     sole for an interactive login such as rlogin(1).


FILES

     /etc/hosts.equiv  Global trusted host-user pairs list
     ~/.rhosts         Per-user trusted host-user pairs list


SEE ALSO

     rcp(1), rlogin(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.

NetBSD 1.6.1                   November 26, 1997                             2