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OpenWindows Advanced User's Guide

D.2.4 Manipulating Access to the Server

Unless the -noauth option is used with openwin (see "D.2.3.3 Changing the Default Authorization Protocol"), both the user-based access control mechanism and the host-based access control mechanism are active. The server first checks the user-based mechanism, then the host-based mechanism. The default security configuration uses MIT-MAGIC-COOKIE-1 as the user-based mechanism, and an empty list for the host-based mechanism. Since the host-based list is empty, only the user-based mechanism is effectively active. Using the -noauth option instructs the server to inactivate the user-based access control mechanism, and initializes the host-based list by adding the local host.

You can use either of two programs to change a server's access control mechanism: xhost and xauth. For more information, see these man pages. These programs access two binary files created by the authorization protocol. These files contain session-specific authorization data. One file is for server internal use only. The other file is located in the user's $HOME directory: 

.Xauthority 

Client Authority file

Use the xhost program to change the host-based access list in the server. You can add hosts to, or delete hosts from the access list. If you are starting with the default configuration -- an empty host-based access list -- and use xhost to add a machine name, you will lower the level of security. The server will allow access to the host you added, as well as to any user specifying the default authorization protocol. See "D.2.2.2 Host-Based Access" for an explanation of why the host-based access control mechanism is considered a lower level of security.

The xauth program accesses the authorization protocol data in the .Xauthority client file. You can extract this data from your .Xauthority file so that another user can merge the data into their .Xauthority file, thus allowing them access to your server, or to the server to which you connect.

See "D.2.4.2 Allowing Access When Using MIT-MAGIC-COOKIE-1"for examples of how to use xhost and xauth.

D.2.4.1 Client Authority File

The client authority file is .Xauthority. It contains entries of the form: 

connection-protocol          auth-protocol          auth-data

By default, .Xauthority contains MIT-MAGIC-COOKIE-1 as the auth-protocol, and entries for the local display only as the connection-protocol and auth-data. For example, on host anyhost, the .Xauthority file may contain the following entries: 

anyhost:0      MIT-MAGIC-COOKIE-1  82744f2c4850b03fce7ae47176e75localhost:0    MIT-MAGIC-COOKIE-1  82744f2c4850b03fce7ae47176e75anyhost/unix:0 MIT-MAGIC-COOKIE-1   82744f2c4850b03fce7ae47176e75

When the client starts up, an entry corresponding to the connection-protocol is read from .Xauthority, and the auth-protocol and auth-data are sent to the server as part of the connection packet. In the default configuration, xhost returns empty host-based access lists and state that authorization is enabled.

If you have changed the authorization protocol from the default to SUN-DES-1 the entries in .Xauthority contain SUN-DES-1 as the auth-protocol and the netname of the user as auth-data. The netname is in the following form: 

unix.userid@NISdomainname

For example, on host, anyhost the .Xauthority file may contain the following entries, where unix.15339@EBB.Eng.Sun.COM is the machine-independent netname of the user:

anyhost:0        SUN-DES-1            "unix.15339@EBB.Eng.Sun.COM"
localhost:0      SUN-DES-1            "unix.15339@EBB.Eng.Sun.COM"
anyhost/unix:0   SUN-DES-1            "unix.15339@EBB.Eng.Sun.COM"

Note -

If you do not know your network name, or machine independent netname, ask your system administrator.

D.2.4.2 Allowing Access When Using MIT-MAGIC-COOKIE-1

If you are using the MIT-MAGIC-COOKIE-1 authorization protocol, follow these steps to allow another user access to your server:

  1. On the machine running the server, use xauth to extract an entry corresponding to hostname:0 into a file.

    For this example, hostname is anyhost and the file is xauth.info:

    myhost% /usr/openwin/bin/xauth nextract - anyhost:0 > $HOME/xauth.info

  2. Send the file containing the entry to the user requesting access (using Mail Tool, rcp or some other file transfer method).

    Note -

    Mailing the file containing your authorization information is a safer method than using rcp. If you do use rcp, do not place the file in a directory that is easily accessible by another user.

  3. The other user must merge the entry into his/her.Xauthority file.

    For this example, userhost merges xauth.info into the other user's .Xauthority file: 

    userhost% /usr/openwin/bin/xauth nmerge - < xauth.info

    Note -

    The auth-data is session-specific; therefore, it is valid only as long as the server is not restarted.

D.2.4.3 Allowing Access When Using SUN-DES-1

If you are using the SUN-DES-1 authorization protocol, follow these steps to allow another user access to your server:

  1. On the machine running the server, use xhost to make the new user known to the server.

    For this example, to allow new user somebody to run on myhost:

    myhost% xhost + somebody@

  2. The new user must use xauth to add the entry into their .Xauthority file.

    For this example, the new user's machine independent netname is unix.15339@EBB.Eng.Sun.COM. Note that this command should be typed on one line with no carriage return. After the pipe symbol, type a space followed by the remainder of the command. 

    userhost% echo 'add myhost:0 SUN-DES-1 "unix.15339@EBB.Eng.Sun.COM"' |
$OPENWINHOME/bin/xauth