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Solaris Advanced User's Guide

Running Networked Applications

Normally, all the applications on your system are programs that are running on your local machine. However, if your workstation is part of a network, you can run applications on another machine and display them on your local screen. Running an application on another machine saves computing cycles on your local machine, and gives you access to an entire network of applications.

This section describes how to run an application on a remote machine and display it on your local screen. See More About Security for additional information on the complexities of running networked applications.

Note –

The process for running a networked application in your computing environment might vary.

Using rlogin to Run a Networked Application

To use the following procedure to run a remote application, you must meet these requirements.

Contact your system administrator if you do not understand these requirements.

To run a networked application on a remote machine, set your environment variables with the following values.

The following procedure describes how to run an application on a remote machine with the rlogin command.

How to Run an Application on a Remote Machine

  1. Use the xhost command on the local machine to give the remote machine display access.


    starbug$ xhost + venus

  2. Log in to the remote machine.


    starbug$ rlogin venus -l user2
Password: 
Last login: Wed Nov  1 16:06:21 from starbug
Sun Microsystems Inc.   SunOS 5.9       Generic February 2002

  3. Set the DISPLAY variable to the local machine.


    venus$ DISPLAY=starbug:0.0

  4. Export the DISPLAY variable to the local machine.


    venus$ export DISPLAY

  5. Run the application.


    venus$ bigprogram &

Even though you interact with this application just as you would with any other application on your screen, the application runs on the remote machine.

The benefit from running an application in this way is that it uses fewer computing resources than an application that is installed on your machine. This example shows how to run any remote application to which you have access.

More About Security

This section describes some fundamentals of network security that you might find useful as you run applications across the network, including:

Who Should Read this Section

You do not need to change the default security configuration in the Solaris operating environment, at minimum, unless you run applications on a remote server.

Access Control Mechanisms

An access control mechanism controls which clients or applications have access to the X11 server. Only properly authorized clients can connect to the server. All other clients are denied access, and are terminated with the following error message. 


Xlib: connection to hostname refused by server
Xlib: Client is not authorized to connect to server

The connection attempt logs to the server console as:


AUDIT: <Date Time Year>: X: client 6 rejected from IP 129.144.152.193 
   port 3485	Auth name: MIT-MAGIC-COOKIE-1

Two different types of access control mechanisms are used: user based and host based. That is, one mechanism grants access to a particular user's account, while the other mechanism grants access to a particular host, or machine. Unless the -noauth option is used with Xsun, both the user-based access control mechanism and the host-based access control mechanism are active. For more information see Manipulating Access to the Server.

User-Based Access

A user-based, or authorization-based, mechanism allows you to give access explicitly to a particular user on any host machine. The user's client passes authorization data to the server. If the data match the server's authorization data, the user is allowed access.

Host-Based Access

A host-based mechanism is a general-purpose mechanism. This type of mechanism enables you to give access to a particular host, in which all users on that host can connect to the server. A host-based mechanism is a weaker form of access control. If the host has access to the server, all users on that host are allowed to connect to the server.

The Solaris environment provides the host-based mechanism for backward compatibility.

Note –

Relink clients that are linked with older versions of Xlib or libcps to enable them to connect to the server with the new user-based access control mechanism.

Authorization Protocols

Two authorization protocols are supported in this version of the Solaris operating environment: MIT-MAGIC-COOKIE-1 and SUN-DES-1. They differ in the authorization data used. The protocols are similar in the access control mechanism used. The MIT-MAGIC-COOKIE-1 protocol that uses the user-based mechanism is the default in the Solaris operating environment.

MIT-MAGIC-COOKIE-1

The MIT-MAGIC-COOKIE-1 authorization protocol was developed by the Massachusetts Institute of Technology. At server startup, a magic cookie is created for the server and the user who started the system. On every connection attempt, the user's client sends the magic cookie to the server as part of the connection packet. This magic cookie is compared with the servers' magic cookie. The connection is allowed if the magic cookies match, or denied if they do not match.

SUN-DES-1

The SUN-DES-1 authorization protocol, developed by Sun Microsystems, is based on Secure Remote Procedure Call (RPC) and requires Data Encryption Standard (DES) support. The authorization information is the machine-independent netname, or network name, of a user. This information is encrypted and sent to the server as part of the connection packet. The server decrypts the information and, if the netname is known, allows the connection.

This protocol provides a higher level of security than the MIT-MAGIC-COOKIE-1 protocol. No other user can use your machine-independent netname to access a server, but another user can use the magic cookie to access a server.

This protocol is available only in libraries in the Solaris 1.1 and compatible environments. Any applications built with static libraries cannot use this authorization protocol.

Allowing Access When Using SUN-DES-1 describes how to allow another user access to your server by adding that person's netname to your server's access list.

Changing the Default Authorization Protocol

You can change the default authorization protocol, MIT-MAGIC-COOKIE-1, to SUN_DES-1, the other supported authorization protocol, or to no user-based access mechanism at all. You can change the default authorization protocol by editing the Xsun line in the /usr/dt/config/Xservers file. For example, to change the default from MIT-MAGIC-COOKIE-1 to SUN-DES-1, add the -auth sun-des option to the Xsun command by editing the following line in the /usr/dt/config/Xservers file. 


:0  Local local_uid@console root /usr/openwin/bin/Xsun :0 -nobanner -auth sun-des

If you must run the Solaris operating environment without the user-based access mechanism, add the -noauth option to the Xsun command by editing the following line in the /usr/dt/config/Xservers file. 


:0  Local local_uid@console root /usr/openwin/bin/Xsun :0 -nobanner -noauth
Caution – Caution –

By using the -noauth option, you weaken security. It is equivalent to running Solaris software with the host-based access control mechanism only. The server inactivates the user-based access control mechanism. Anyone who can run applications on your local machine is allowed access to your server.

Manipulating Access to the Server

Unless the -noauth option is used with Xsun (see 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. Because 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 that are 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:

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 lower the level of security. The server allows access to the host you added, as well as to any user who specifies the default authorization protocol. See Host-Based Access or 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 other users can merge the data into their .Xauthority files, thus allowing them access to your server, or to the server to which you connect.

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

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 might contain the following entries: 


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

When the client starts, 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 states 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 might contain the following entries, where unix.15339@EBB.Sun.COM is the machine-independent netname of the user:


anyhost:0        SUN-DES-1            ”unix.15339@EBB.Sun.COM”
localhost:0      SUN-DES-1            ”unix.15339@EBB.Sun.COM”
anyhost/unix:0   SUN-DES-1            ”unix.15339@EBB.Sun.COM”
Note –

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

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 that is running the server, use xauth to extract an entry that corresponds 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 that contains the entry to the user who requests access,

    Use an email tool, the rcp command, or some other file transfer method to send the file.

    Note –

    Mailing the file that contains 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 or 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.

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 that runs 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 the xauth command to add the entry into his or her .Xauthority file.

    For this example, the new user's machine independent netname is unix.15339@EBB.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.Sun.COM”' |
$OPENWINHOME/bin/xauth

Running Clients Remotely, or Locally as Another User

X clients use the value of the DISPLAY environment variable to get the name of the server to which they should connect.

To run clients remotely, or locally as another user, follow these steps:

  1. On the machine that runs the server, allow another user access.

    Depending on which authorization protocol you use, follow the steps outlined in either Allowing Access When Using MIT-MAGIC-COOKIE-1 or Allowing Access When Using SUN-DES-1.

  2. Set DISPLAY to the name of the host that runs the server.

    For this example, the host is remotehost:


    myhost% setenv DISPLAY remotehost:0

  3. Run the client program as shown. 


    myhost% client_program&

    The client is displayed on the remote machine, remotehost.