Microsoft KB Archive/281837

= INFO: COM EXE Servers Run in SYSTEM Context When Called from IIS =

Article ID: 281837

Article Last Modified on 2/22/2007

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APPLIES TO


 * Microsoft Windows NT Server 4.0, Terminal Server Edition Service Pack 4
 * Microsoft Windows NT Server 4.0, Terminal Server Edition Service Pack 5
 * Microsoft Windows NT Server 4.0, Terminal Server Edition Service Pack 6
 * Microsoft Windows NT Server 4.0 Terminal Server Edition SP7
 * Microsoft Internet Information Server 4.0

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This article was previously published under Q281837



SUMMARY
A COM object that is hosted in a separate EXE that is marked to run as the launching user will run in the security context of SYSTEM when it is called from an Active Server Pages (ASP) page that is running in an in-process application in Internet Information Server (IIS). This is because the Inetinfo process runs in the SYSTEM context. COM objects that are running in a separate EXE that is marked to run as the launching user get started with the security context of the caller's process token, not the thread token. Therefore, for IIS in-process applications, this will be the SYSTEM context.

Additionally, script authors can use a script engine's &quot;CreateObject&quot; method directly to launch a COM object, bypassing ASP's built-in checks for COM objects that are hosted out-of-process.



MORE INFORMATION
System administrators can take these steps to tighten security:  Configure the IIS site or application to run in a separate process. To do this:

 Open Properties for the Web site or virtual directory application, and then click the Home Directory tab. Select Run in separate memory space (isolated process). Click ok.

If you intend to call out-of-process COM objects from this application, you may have to configure the object's security in the Distributed COM Configuration Properties application (DCOMCNFG). For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

198432 PRB: Server Object Error 'ASP 0178' Instantiating COM Object

 Use DCOMCNFG to limit access to COM objects. To do this:

 Point to Start, click Run, and then type DCOMCNFG. Press enter.</li> Click the Applications tab, which contains a list of the COM objects organized by either name or CLSID. Find the appropriate object, select it, and click Properties.</li> Click the Security tab. Select Use custom access permissions. Click Edit.</li> Remove the users who should not have access to this object. For example, SYSTEM, INTERACTIVE, EVERYONE, IUSR_<COMPUTER NAME>, IWAM_<COMPUTER NAME>. Click ok.</li> Select Use custom launch permissions, and then click Edit. Remove the same users as previously.</li></ol>

NOTE: regardless of the settings on the COM object, the EXE will still start, although COM will return an &quot;access denied&quot; error message, and no methods may be called. The EXE is started, however, and remains in memory. This is a behavior of COM.

For additional information on using DCOMCNFG, click the article numbers below to view the articles in the Microsoft Knowledge Base:

176799 INFO: Using DCOM Config (DCOMCNFG.EXE) on Windows NT

246054 INFO: DCOMCNFG and AppID\.exe Mapping and Implications

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Keywords: kbinfo KB281837

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