1.\" $NetBSD: hosts.equiv.5,v 1.1 1997/11/26 17:49:35 tv Exp $ 2.\" 3.\" Copyright (c) 1997 Todd Vierling 4.\" Copyright (c) 1997 The NetBSD Foundation, Inc. 5.\" All rights reserved. 6.\" 7.\" This code is derived from software contributed to The NetBSD Foundation 8.\" by Todd Vierling <tv@pobox.com>. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. All advertising materials mentioning features or use of this software 19.\" must display the following acknowledgement: 20.\" This product includes software developed by the NetBSD 21.\" Foundation, Inc. and its contributors. 22.\" 4. Neither the name of The NetBSD Foundation nor the names of its 23.\" contributors may be used to endorse or promote products derived 24.\" from this software without specific prior written permission. 25.\" 26.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36.\" POSSIBILITY OF SUCH DAMAGE. 37.\" 38.Dd November 26, 1997 39.Dt HOSTS.EQUIV 5 40.Os NetBSD 1.3 41.Sh NAME 42.Nm hosts.equiv , 43.Nm .rhosts 44.Nd trusted remote hosts and host-user pairs 45.Sh DESCRIPTION 46The 47.Nm hosts.equiv 48and 49.Nm .rhosts 50files list hosts and users which are ``trusted'' by the local host when a 51connection is made via 52.Xr rlogind 8 , 53.Xr rshd 8 , 54or any other server that uses 55.Xr ruserok 3 . 56This mechanism bypasses password checks, and is required for access via 57.Xr rsh 1 . 58.Pp 59Each line of these files has the format: 60.Pp 61.Bd -unfilled -offset indent -compact 62hostname [username] 63.Ed 64.Pp 65The 66.Em hostname 67may be specified as a host name (typically a fully qualified host 68name in a DNS environment) or address, 69.Em +@netgroup 70(from which only the host names are checked), 71or a ``+'' wildcard (allow all hosts). 72.Pp 73The 74.Em username , 75if specified, may be given as a user name on the remote host, 76.Em +@netgroup 77(from which only the user names are checked), 78or a ``+'' wildcard (allow all remote users). 79.Pp 80If a 81.Em username 82is specified, only that user from the specified host may login to the 83local machine. If a 84.Em username 85is not specified, any user may login with the same user name. 86.Sh EXAMPLES 87.Li somehost 88.Bd -filled -offset indent -compact 89A common usage: users on 90.Em somehost 91may login to the local host as the same user name. 92.Ed 93.Li somehost username 94.Bd -filled -offset indent -compact 95The user 96.Em username 97on 98.Em somehost 99may login to the local host. If specified in 100.Em /etc/hosts.equiv , 101the user may login with only the same user name. 102.Ed 103.Li +@anetgroup username 104.Bd -filled -offset indent -compact 105The user 106.Em username 107may login to the local host from any machine listed in the netgroup 108.Em anetgroup . 109.Ed 110.Bd -literal -compact 111+ 112+ + 113.Ed 114.Bd -filled -offset indent -compact 115Two severe security hazards. In the first case, allows a user on any 116machine to login to the local host as the same user name. In the second 117case, allows any user on any machine to login to the local host (as any 118user, if in 119.Em /etc/hosts.equiv ) . 120.Ed 121.Sh WARNINGS 122The username checks provided by this mechanism are 123.Em not 124secure, as the remote user name is received by the server unchecked 125for validity. Therefore this mechanism should only be used 126in an environment where all hosts are completely trusted. 127.Pp 128A numeric host address instead of a host name can help security 129considerations somewhat; the address is then used directly by 130.Xr iruserok 3 . 131.Pp 132When a username (or netgroup, or +) is specified in 133.Em /etc/hosts.equiv , 134that user (or group of users, or all users, respectively) may login to 135the local host as 136.Em any local user . 137Usernames in 138.Em /etc/hosts.equiv 139should therefore be used with extreme caution, or not at all. 140.Pp 141A 142.Em .rhosts 143file must be owned by the user whose home directory it resides in, and 144must be writable only by that user. 145.Pp 146Logins as root only check root's 147.Em .rhosts 148file; the 149.Em /etc/hosts.equiv 150file is not checked for security. Access permitted through root's 151.Em .rhosts 152file is typically only for 153.Xr rsh 1 , 154as root must still login on the console for an interactive login such as 155.Xr rlogin 1 . 156.Sh FILES 157.Bl -tag -width /etc/hosts.equiv -compact 158.It Pa /etc/hosts.equiv 159Global trusted host-user pairs list 160.It Pa ~/.rhosts 161Per-user trusted host-user pairs list 162.El 163.Sh SEE ALSO 164.Xr rcp 1 , 165.Xr rlogin 1 , 166.Xr rsh 1 , 167.Xr rcmd 3 , 168.Xr ruserok 3 , 169.Xr netgroup 5 170.Re 171.Sh HISTORY 172The 173.Nm .rhosts 174file format appeared in 175.Bx 4.2 . 176.Sh BUGS 177The 178.Xr ruserok 3 179implementation currently skips negative entries (preceded with a 180``-'' sign) and does not treat them as ``short-circuit'' negative entries. 181