The X authority file is a binary data file that contains
information used to authorize connections to the X server on a
system running DECwindows Motif Version 1.3 or higher.
Each time a client application attempts to connect to an X
server system that uses an authorization protocol, it references
the current X authority file to determine the appropriate
authorization key to apply in order to authenticate the
connection. Each authorization key consists of the protocol name
and token, which can be one of the following depending on the
protocol in use:
o MIT-MAGIC-COOKIE-1 + random numeric code
o MIT-KERBEROS-5 + encrypted string (cached separately)
By default, an X authority file is created automatically the
first time a user logs into a desktop on a system configured
for MIT-MAGIC-COOKIE-1 or MIT-KERBEROS-5 authentication.
The file is stored in that user's OpenVMS login directory
(SYS$LOGIN:DECW$XAUTHORITY.DECW$XAUTH). Each time the user
subsequently logs into a desktop on that system, a new
authorization key is generated, passed to the X server, and
written to the user's X authority file. This key controls access
to the X server during the DECwindows Motif session.
A separate X authority file can be manually defined on a server
level (using the DECW$SERVER_XAUTHORITY symbol) for those client
applications that require access to the X server outside of the
normal DECwindows Motif login process.
If the SECURITY extension is enabled, authorization keys can also
be manually generated. Manually-generated keys can be used to
further restrict server access. The generated key is stored in
the X authority file on the client system overwriting any value
already present for the specified display server. The key can be
distributed to different client systems to allow connections
to a specific server and can be revoked to stop subsequent
connections.
Generated keys are assigned an authorization ID that associates
the key with the user who generated the key. As a result, only
the user who generated the key can revoke the key.
1 – Format of File Entries
Each entry in an X authority file corresponds to a particular X
display server and is composed of three main components:
display-name protocol token
1.1 – display-name
Identifies the name of the X display to which you are authorizing
access. The display name follows the supported display name
format:
[transport/]host:[:]server[.screen]
This format enables you to use a single X authority file to
grant varying levels of access to different X display servers
and connection families.
For example, the following entries grant access to the local
display server on node HUBBUB and the remote display server on
node ZEPHYR via the DECnet transport:
local/HUBBUB:0 MIT-MAGIC-COOKIE-1 cfcc5ef98f9718f90154f355c0ae9f62
decnet/ZEPHYR::0 MIT-MAGIC-COOKIE-1 cfcc5ef98f9718f90154f355c0ae9f62
o [transport/]
Identifies the network transport used to connect to an X
display server. See the DECwindows Motif documentation for
a list of the supported transport values. If a transport value
is not specified, the default value is interpreted from the
format of the remaining portions of the display-name entry,
for example:
Host address and one colon (116.94.24.187:0) (TCP/IP)
Two colons (::0 or ZEPHYR::0) (DECnet)
No host name or address and one colon (:0) (local)
o host[:]
Identifies the name of the host system where the X display
server is located. A value of 0 is interpreted as the local
host, which is the default. The type of host is determined
by the transport value. See the DECwindows documentation for
examples of valid host name and address formats.
o :server
Identifies the server. This value is required and must be
preceded by a single colon (:). Typically the value for a
single-server system is :0. If you are specifying a display
on a multi-server system (such as when using a proxy server),
additional values may apply depending on the number of servers
in the configuration. If you have specified a display device
(with the SET DISPLAY command), the server portion of the
entry is assumed from the device specification.
o [.screen]
Identifies the screen. On OpenVMS Alpha and OpenVMS I64
systems, the screen value is not held in the X authority file
and is ignored when included in a command. All screens on a
single server have the same authorization.
1.2 – protocol
Indicates the authentication protocol in use. Valid values are
MIT-MAGIC-COOKIE-1 and MIT-KERBEROS-5.
1.3 – token
A random alphanumeric string that functions as a password
authorizing a server connection. The format of the token depends
on the authorization scheme in use. MIT-MAGIC-COOKIE-1 uses a
128-bit string known as a magic cookie. MIT-KERBEROS-5 uses an
encrypted string to authorize server connections. This string
is stored separately. The token entry in the X authority file
represents the encoded location of the Kerberos keytab file and
associated principal name, which is referenced by the server to
locate the encrypted string.
2 – Specifying an X Authority File
By default, the X authority file referenced by client
applications and the xauth utility is defined as
SYS$LOGIN:DECW$XAUTHORITY.DECW$XAUTH. You can override this
default and specify an alternate X authority file in either of
the following ways:
o You can create alternate X authority files and switch between
them using the DECW$XAUTHORITY logical. For example, the
following command changes the X authority file in use for
the current DECwindows Motif session to UNTRUSTED.DECW$AUTH:
$ DEFINE DECW$XAUTHORITY-
_$ SYS$MANAGER:[SYSMGR]UNTRUSTED.DECW$XAUTH
The logical definition remains in use until it is
redefined or an alternate value is specified using the SET
DISPLAY/XAUTHORITY command.
o If a display device is used to create a client connection to
an X server, you can specify an alternate X authority file
using the SET DISPLAY/CREATE/XAUTHORITY command. Note that the
file specified on this command line overrides both the default
and any file referenced by the DECW$XAUTHORITY logical.