util.subproj/hosts.equiv.5

   1 .\"     $OpenBSD: hosts.equiv.5,v 1.1 1997/11/30 05:35:25 deraadt Exp $
   2 .\"
   3 .\" Copyright (c) 1997 Todd Vierling
   4 .\" Copyright (c) 1997 The NetBSD Foundation, Inc.
   5 .\" All rights reserved.
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   7 .\" This code is derived from software contributed to The NetBSD Foundation
   8 .\" by Todd Vierling <tv@pobox.com>.
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  11 .\" modification, are permitted provided that the following conditions
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  20 .\"        This product includes software developed by the NetBSD
  21 .\"        Foundation, Inc. and its contributors.
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  38 .Dd November 26, 1997
  39 .Dt HOSTS.EQUIV 5
  40 .Os
  41 .Sh NAME
  42 .Nm hosts.equiv ,
  43 .Nm .rhosts
  44 .Nd trusted remote hosts and host-user pairs
  45 .Sh DESCRIPTION
  46 The
  47 .Nm hosts.equiv
  48 and
  49 .Nm .rhosts
  50 files list hosts and users which are ``trusted'' by the local host when a
  51 connection is made via
  52 .Xr rlogind 8 ,
  53 .Xr rshd 8 ,
  54 or any other server that uses
  55 .Xr ruserok 3 .
  56 This mechanism bypasses password checks, and is required for access via
  57 .Xr rsh 1 .
  58 .Pp
  59 Each line of these files has the format:
  60 .Pp
  61 .Bd -unfilled -offset indent -compact
  62 hostname [username]
  63 .Ed
  64 .Pp
  65 The
  66 .Em hostname
  67 may be specified as a host name (typically a fully qualified host
  68 name in a DNS environment) or address,
  69 .Em +@netgroup
  70 (from which only the host names are checked),
  71 or a ``+'' wildcard (allow all hosts).
  72 .Pp
  73 The
  74 .Em username ,
  75 if specified, may be given as a user name on the remote host,
  76 .Em +@netgroup
  77 (from which only the user names are checked),
  78 or a ``+'' wildcard (allow all remote users).
  79 .Pp
  80 If a
  81 .Em username
  82 is specified, only that user from the specified host may login to the
  83 local machine.  If a
  84 .Em username
  85 is not specified, any user may login with the same user name.
  86 .Sh EXAMPLES
  87 .Li somehost
  88 .Bd -filled -offset indent -compact
  89 A common usage:  users on
  90 .Em somehost
  91 may login to the local host as the same user name.
  92 .Ed
  93 .Li somehost username
  94 .Bd -filled -offset indent -compact
  95 The user
  96 .Em username
  97 on
  98 .Em somehost
  99 may login to the local host.  If specified in
 100 .Em /etc/hosts.equiv ,
 101 the user may login with only the same user name.
 102 .Ed
 103 .Li +@anetgroup username
 104 .Bd -filled -offset indent -compact
 105 The user
 106 .Em username
 107 may 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
 115 Two severe security hazards.  In the first case, allows a user on any
 116 machine to login to the local host as the same user name.  In the second
 117 case, allows any user on any machine to login to the local host (as any
 118 user, if in
 119 .Em /etc/hosts.equiv ) .
 120 .Ed
 121 .Sh WARNINGS
 122 The username checks provided by this mechanism are
 123 .Em not
 124 secure, as the remote user name is received by the server unchecked
 125 for validity.  Therefore this mechanism should only be used
 126 in an environment where all hosts are completely trusted.
 127 .Pp
 128 A numeric host address instead of a host name can help security
 129 considerations somewhat; the address is then used directly by
 130 .Xr iruserok 3 .
 131 .Pp
 132 When a username (or netgroup, or +) is specified in
 133 .Em /etc/hosts.equiv ,
 134 that user (or group of users, or all users, respectively) may login to
 135 the local host as
 136 .Em any local user .
 137 Usernames in
 138 .Em /etc/hosts.equiv
 139 should therefore be used with extreme caution, or not at all.
 140 .Pp
 141 A
 142 .Em .rhosts
 143 file must be owned by the user whose home directory it resides in, and
 144 must be writable only by that user.
 145 .Pp
 146 Logins as root only check root's
 147 .Em .rhosts
 148 file; the
 149 .Em /etc/hosts.equiv
 150 file is not checked for security.  Access permitted through root's
 151 .Em .rhosts
 152 file is typically only for
 153 .Xr rsh 1 ,
 154 as 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
 159 Global trusted host-user pairs list
 160 .It Pa ~/.rhosts
 161 Per-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 .Sh HISTORY
 171 The
 172 .Nm .rhosts
 173 file format appeared in
 174 .Bx 4.2 .
 175 .Sh BUGS
 176 The
 177 .Xr ruserok 3
 178 implementation currently skips negative entries (preceded with a
 179 ``-'' sign) and does not treat them as ``short-circuit'' negative entries.