xauth
X authority file utility
see also :
X - xhost - startx
Synopsis
xauth [
-f authfile ] [ -vqibn ] [
command arg ... ]
add an example, a script, a trick and tips
examples
source
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description
The
xauth program is used to edit and display the
authorization information used in connecting to the X
server. This program is usually used to extract
authorization records from one machine and merge them in on
another (as is the case when using remote logins or granting
access to other users). Commands (described below) may be
entered interactively, on the xauth command line, or
in scripts. Note that this program does not contact
the X server except when the generate command is used.
Normally xauth is not used to create the authority
file entry in the first place; the program that starts the X
server (often xdm or startx) does that.
options
The following
options may be used with xauth. They may be given
individually (e.g., -q -i) or may
combined (e.g., -qi).
-f authfile
This option specifies the name
of the authority file to use. By default, xauth will
use the file specified by the XAUTHORITY environment
variable or .Xauthority in the user’s home
directory.
-q
This option indicates that xauth should operate
quietly and not print unsolicited status messages. This is
the default if an xauth command is given on the
command line or if the standard output is not directed to a
terminal.
-v
This option indicates that xauth should operate
verbosely and print status messages indicating the results
of various operations (e.g., how many records have been read
in or written out). This is the default if xauth is
reading commands from its standard input and its standard
output is directed to a terminal.
-i
This option indicates that xauth should ignore
any authority file locks. Normally, xauth will refuse
to read or edit any authority files that have been locked by
other programs (usually xdm or another
xauth).
-b
This option indicates that xauth should attempt
to break any authority file locks before proceeding. Use
this option only to clean up stale locks.
-n
This option indicates that xauth should not
attempt to resolve any hostnames, but should simply always
print the host address as stored in the authority file.
commands
The following commands may be used to manipulate authority files:
add displayname protocolname hexkey
An authorization entry for the indicated display using the given
protocol and key data is added to the authorization file. The
data is specified as an even-lengthed string of hexadecimal
digits, each pair representing one octet. The first digit of each
pair gives the most significant 4 bits of the octet, and the
second digit of the pair gives the least significant 4 bits. For
example, a 32 character hexkey would represent a 128-bit value. A
protocol name consisting of just a single period is treated as an
abbreviation for MIT-MAGIC-COOKIE-1.
generate displayname protocolname
[trusted|untrusted]
[timeout seconds] [group group-id]
[data hexdata]
This command is similar to add. The main difference is that
instead of requiring the user to supply the key data, it connects
to the server specified in displayname and uses the
SECURITY extension in order to get the key data to store in the
authorization file. If the server cannot be contacted or if it
does not support the SECURITY extension, the command fails.
Otherwise, an authorization entry for the indicated display using
the given protocol is added to the authorization file. A protocol
name consisting of just a single period is treated as an
abbreviation for MIT-MAGIC-COOKIE-1.
If the trusted option is used, clients that connect using
this authorization will have full run of the display, as usual.
If untrusted is used, clients that connect using this
authorization will be considered untrusted and prevented from
stealing or tampering with data belonging to trusted clients. See
the SECURITY extension specification for full details on the
restrictions imposed on untrusted clients. The default is
untrusted.
The timeout option specifies how long in seconds this
authorization will be valid. If the authorization remains unused
(no clients are connected with it) for longer than this time
period, the server purges the authorization, and future attempts
to connect using it will fail. Note that the purging done by the
server does not delete the authorization entry from the
authorization file. The default timeout is 60 seconds.
The group option specifies the application group that
clients connecting with this authorization should belong to. See
the application group extension specification for more details.
The default is to not belong to an application group.
The data option specifies data that the server should use
to generate the authorization. Note that this is not the
same data that gets written to the authorization file. The
interpretation of this data depends on the authorization
protocol. The hexdata is in the same format as the
hexkey described in the add command. The default is to
send no data.
[n]extract filename displayname...
Authorization entries for each of the specified displays are
written to the indicated file. If the nextract command is
used, the entries are written in a numeric format suitable for
non-binary transmission (such as secure electronic mail). The
extracted entries can be read back in using the merge and
nmerge commands. If the filename consists of just a single
dash, the entries will be written to the standard output.
[n]list [displayname...]
Authorization entries for each of the specified displays (or all
if no displays are named) are printed on the standard output. If
the nlist command is used, entries will be shown in the
numeric format used by the nextract command; otherwise,
they are shown in a textual format. Key data is always displayed
in the hexadecimal format given in the description of the
add command.
[n]merge [filename...]
Authorization entries are read from the specified files and are
merged into the authorization database, superseding any matching
existing entries. If the nmerge command is used, the
numeric format given in the description of the extract
command is used. If a filename consists of just a single dash,
the standard input will be read if it hasn’t been read before.
remove displayname...
Authorization entries matching the specified displays are removed
from the authority file.
source filename
The specified file is treated as a script containing xauth
commands to execute. Blank lines and lines beginning with a sharp
sign (#) are ignored. A single dash may be used to indicate the
standard input, if it hasn’t already been read.
info
Information describing the authorization file, whether or not any
changes have been made, and from where xauth commands are
being read is printed on the standard output.
exit
If any modifications have been made, the authority file is
written out (if allowed), and the program exits. An end of file
is treated as an implicit exit command.
quit
The program exits, ignoring any modifications. This may also be
accomplished by pressing the interrupt character.
help [string]
A description of all commands that begin with the given string
(or all commands if no string is given) is printed on the
standard output.
?
A short list of the valid commands is printed on the standard
output.
display names
Display names for the add, [n]extract,
[n]list, [n]merge, and remove commands use
the same format as the DISPLAY environment variable and the
common -display command line argument. Display-specific
information (such as the screen number) is unnecessary and will
be ignored. Same-machine connections (such as local-host sockets,
shared memory, and the Internet Protocol hostname
localhost) are referred to as
hostname/unix:displaynumber so that local entries
for different machines may be stored in one authority file.
environment
This xauth program uses the following environment
variables:
XAUTHORITY
to get the name of the authority file to use if the -f
option isn’t used.
HOME
to get the user’s home directory if XAUTHORITY isn’t defined.
example
The most common use for xauth is to extract the entry for
the current display, copy it to another machine, and merge it
into the user’s authority file on the remote machine:
% xauth extract - $DISPLAY | ssh otherhost xauth merge -
The following command contacts the server :0 to create an
authorization using the MIT-MAGIC-COOKIE-1 protocol. Clients that
connect with this authorization will be untrusted.
% xauth generate :0 .
files
$HOME/.Xauthority
default authority file if XAUTHORITY isn’t defined.
bugs
Users that have
unsecure networks should take care to use encrypted file
transfer mechanisms to copy authorization entries between
machines. Similarly, the MIT-MAGIC-COOKIE-1 protocol
is not very useful in unsecure environments. Sites that are
interested in additional security may need to use encrypted
authorization mechanisms such as Kerberos.
Spaces are
currently not allowed in the protocol name. Quoting could be
added for the truly perverse.
see also
X ,
Xsecurity, xhost , Xserver, xdm, startx ,
Xau.
author
Jim Fulton, MIT
X Consortium