hosts.equiv man page on OpenBSD

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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
     log in to the local machine.  If a username is not specified, any user
     may log in 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 log in to the local host as the
     same user name.

     somehost username
     The user username on somehost may log in to the local host.  If specified
     in /etc/hosts.equiv, the user may log in with only the same user name.

     +@anetgroup username
     The user username may log in 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 log in to the local host as the same user name.	 In the second
     case, allows any user on any machine to log in to the local host (as any
     user, if in /etc/hosts.equiv).

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

HISTORY
     The .rhosts file format appeared in 4.2BSD.

CAVEATS
     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
     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 log in 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).

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

OpenBSD 4.9			 April 1, 2010			   OpenBSD 4.9
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