xhost
server access control program for X
see also :
X - xauth
Synopsis
xhost
[[+-]name ...]
add an example, a script, a trick and tips
examples
source
xhost +local:
xterm &
exec twm
description
The
xhost program is used to add and delete host names or
user names to the list allowed to make connections to the X
server. In the case of hosts, this provides a rudimentary
form of privacy control and security. It is only sufficient
for a workstation (single user) environment, although it
does limit the worst abuses. Environments which require more
sophisticated measures should implement the user-based
mechanism or use the hooks in the protocol for passing other
authentication data to the server.
options
Xhost
accepts the following command line options described below.
For security, the options that affect access control may
only be run from the "controlling host". For
workstations, this is the same machine as the server. For X
terminals, it is the login host.
-help
Prints a usage message.
[+]name
The given name (the plus sign is optional) is
added to the list allowed to connect to the X server. The
name can be a host name or a complete name (See
NAMES for more details).
-name
The given name is removed from the list of
allowed to connect to the server. The name can be a host
name or a complete name (See NAMES for
more details). Existing connections are not broken, but new
connection attempts will be denied. Note that the current
machine is allowed to be removed; however, further
connections (including attempts to add it back) will not be
permitted. Resetting the server (thereby breaking all
connections) is the only way to allow local connections
again.
+
Access is granted to everyone, even if they aren’t
on the list (i.e., access control is turned off).
-
Access is restricted to only those on the list (i.e.,
access control is turned on).
nothing
If no command line arguments are given, a message
indicating whether or not access control is currently
enabled is printed, followed by the list of those allowed to
connect. This is the only option that may be used from
machines other than the controlling host.
diagnostics
For each name added to the access control list, a line of the
form "name being added to access control list" is printed.
For each name removed from the access control list, a line of the
form "name being removed from access control list" is
printed.
display
to get the default host and display to use.
environment
names
A complete name has the syntax ’’family:name’’ where the families
are as follows:
inet Internet host (IPv4)
inet6
Internet host (IPv6)
dnet
DECnet host
nis
Secure RPC network name
krb
Kerberos V5 principal
local
contains only one name, the empty string
si
Server Interpreted
The family is case insensitive. The format of the name varies
with the family.
When Secure RPC is being used, the network independent netname
(e.g., "nis:unix.uid@domainname") can be specified,
or a local user can be specified with just the username and a
trailing at-sign (e.g., "nis:pat@").
For backward compatibility with pre-R6 xhost, names that
contain an at-sign (@) are assumed to be in the nis family.
Otherwise they are assumed to be Internet addresses. If compiled
to support IPv6, then all IPv4 and IPv6 addresses returned by
getaddrinfo(3) are added to the access list in the appropriate
inet or inet6 family.
The local family specifies all the local connections at once.
However, the server interpreted address
"si:localuser:username" can be used to specify a single
local user. (See the Xsecurity(7) manual page for more
details.)
Server interpreted addresses consist of a case-sensitive type tag
and a string representing a given value, separated by a colon.
For example, "si:hostname:almas" is a server interpreted address
of type hostname, with a value of almas. For more
information on the available forms of server interpreted
addresses, see the Xsecurity(7) manual page.
The initial access control list for display number n may
be set by the file /etc/Xn.hosts, where
n is the display number of the server. See
Xserver(1) for details.
bugs
You can’t
specify a display on the command line because
-display is a valid command line argument
(indicating that you want to remove the machine named
’’display’’ from the access
list).
The X server
stores network addresses, not host names, unless you use the
server-interpreted hostname type address. If somehow you
change a host’s network address while the server is
still running, and you are using a network-address based
form of authentication, xhost must be used to add the
new address and/or remove the old address.
see also
X ,
Xsecurity, Xserver, xdm, xauth ,
getaddrinfo
authors
Bob Scheifler,
MIT Laboratory for Computer Science,
Jim Gettys, MIT Project Athena (DEC).