hosts.equiv(5) - NetBSD Manual Pages

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HOSTS.EQUIV(5)            NetBSD File Formats 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
     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.


FILES

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


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
           local host (as any user, if in /etc/hosts.equiv).


WARNINGS

     The username 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 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).


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 8.2                     November 26, 1997                    NetBSD 8.2