HOWTO: Use DCOM Config (DCOMCNFG.EXE) with Windows 95

 Last reviewed: March 10, 1998
Article ID: Q182248
The information in this article applies to:
  • Microsoft Visual Basic Professional and Enterprise Editions for Windows, version 5.0

SUMMARY

DCOMCNFG.EXE (known as DCOM Config) is a utility that can be used to secure distributed COM (DCOM) objects that have been created.

Because security is much more advanced on Windows NT, the options differ on Windows NT systems. This article, written for those running DCOM Config on Windows 95 systems, describes the options and settings in DCOM Config.

MORE INFORMATION

The DCOM Config's main window is divided into three tabs:

  1. Applications Tab.

  2. Default Properties Tab.

  3. Default Security Tab.

The following explains each tab in DCOM Config, beginning with the Applications tab.

Applications Tab

The Applications tab shows each of the items registered under the following registry key: 

   HKEY_CLASSES_ROOT\AppId\
Beneath this key are all of the objects that can be launched on a remote machine. DCOM Config displays just the ProgIDs (friendly names) of each object, such as "Microsoft Word Document" or "Microsoft Access Database." Some objects may register without registering a ProgID; in these cases, the GUID of the object will be displayed, such as "{4E6B942A-01B0-11D1-A9CB- 00AA00B7B36F}."

Properties for each application listed in the Applications tab can be viewed either by selecting an item and choosing the "Properties" button, or by double-clicking the application name.

Default Properties Tab

Each of the values displayed under the Default Properties tab may be found under the following key in the registry: 

   HKEY_LOCAL_MACHINE\Software\Microsoft\OLE
The first item in the Default Properties tab is a check box: 

   "Enable Distributed COM on this computer"
This is a global setting for the entire machine. When this option is checked, the machine allows the creation of DCOM objects. If it is not checked, no objects may be created via DCOM.

NOTE: You must reboot the system in order for a change in this setting to take effect.

The second part of the Default Properties tab is the Default Distributed COM Communication properties, which consists of two parts:

  1. Default Authentication Level

  2. Default Impersonation Level

These two options can only be modified if DCOM is enabled on this system.

  1. Default Authentication Level

Authentication Levels are as follows: 

Name                         Description



None                         No authentication.

Connect                      Authentication occurs when a connection
                             is made to the server. Connectionless
                             protocols do not use this.
Unlike Windows NT, Windows 95 machines can only accept calls on the 'None' or 'Connect' levels.

  1. Default Impersonation Level

If no security is set at the object level, the server uses the security setting specified here as the default. The possible values are: 

Name                         Description



Identify                     The server can impersonate the client to
                             check permissions in the ACL (Access Control
                             List) but cannot access system objects.

Impersonate                  The server can impersonate the client and
                             access system objects on the client's behalf.
The last item on the Default Properties tab is a check box: 

    "Provide additional security for reference tracking"
This tells the server to track connected client applications by keeping an additional reference count. Checking this box uses more memory and may slow down COM, but it ensures that a client application cannot kill a server process by artificially forcing a reference count to zero.

Default Security Tab

On Windows 95 machines, there is an option under the Default Security tab for Default Access Permission. The value displayed here may be found in the Windows registry at the following location: 

   HKEY_LOCAL_MACHINE\Software\Microsoft\OLE
Default Access Permission - This value determines the users who can access an object when no other access permissions are provided. For information on how to give individual access permissions to specific DCOM objects, see the "Application Properties" section later in this document.

An additional option under the Default Security tab is "Enable remote connection." This option must be selected in order to enable remote connections to DCOM Servers running on Windows 95. The value is stored as a Yes or No value in the Windows registry at the following location: 

   HKEY_LOCAL_MACHINE\Software\Microsoft\OLE\EnableRemoteConnect

Application Properties

You may specify custom settings for individual DCOM applications by choosing the Properties button on the "Applications" tab in DCOM Config. This section describes each tab (General, Location, and Security) and setting found within Application Properties.

General

The General tab provides general information about the application. This tab displays the Application name, type (local server or remote server), and location (local path or remote computer). These settings are not modifiable through the DCOM Config interface.

The General Tab retrieves all of its information from subkeys of the following registry key: 

   HKEY_CLASSES_ROOT\CLSID\{...CLSID...}
where {...CLSID...} is the unique CLSID for the Object Server currently being viewed.

Location

This tab is used to determine where DCOM will execute the application. There are three possible choices:

  1. Run application on the computer where the data is located - If selected, DCOM will execute the application where the data is located. This is useful only if the application provides a data file for the server application.

  2. Run application on this computer - Indicates that the DCOM application should run on the local machine.

  3. Run application on the following computer - Allows you to specify a computer to execute on. This option should only be selected on DCOM Client machines to specify where the DCOM server is located. For DCOM Servers this option will not work as expected, Windows 95 machines cannot delegate an application to execute on a different machine

Security

On this tab, you may customize settings for individual application permissions. This tab is only available for objects capable of performing as DCOM Servers. You may customize the settings for the following permissions:

  • Use default access permissions.
  • Use custom access permissions.

With custom access permissions, you may specify individual users who may access the application. If you do not choose to use custom access permissions, the default security settings are used. For more information about the Security tab see the "Default Security" section earlier in this article.

REFERENCES

For additional information, please see the following articles in the Microsoft Knowledge Base: 

   ARTICLE-ID: Q158508
   TITLE     : INFO: COM Security Frequently Asked Questions

   ARTICLE-ID: Q165101
   TITLE     : HOWTO: Use Win95 as a DCOM Server

   ARTICLE-ID: Q176799
   TITLE     : INFO: Use DCOM Config (DCOMCNFG.EXE) on Windows NT

Keywords          : vb5all vb5howto VBKBDCOM VBKBRegistry
Version           : WINDOWS:5.0
Platform          : Win95 WINDOWS
Issue type        : kbhowto

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Last reviewed: March 10, 1998
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