Module 4: Internet Information Services Authentication

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Module 4: Internet Information Services Authentication

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This module provides students with information about the Web client authentication methods that are supported by Internet Information Services (IIS) and Microsoft® Windows® 2000 Server. Initial Web client authentication and the flow of user identities through the Web application are the focus of this module. After completing this module, students will be able to select the best IIS authentication method for a given set of requirements.

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  1. Module 4: Internet Information Services Authentication Contents Overview 1 Lesson: Introduction to Web Client Authentication 3 Lesson: Configuring Access Permissions for a Web Server 16 Lesson: Selecting a Secure Client Authentication Method 25 Lesson: Running Services As an Authenticated User 45 Review 54 Lab 4: Authentication and Access Control 56
  2. Information in this document, including URL and other Internet Web site references, is subject to change without notice. Unless otherwise noted, the example companies, organizations, products, domain names, e-mail addresses, logos, people, places, and events depicted herein are fictitious, and no association with any real company, organization, product, domain name, e-mail address, logo, person, place or event is intended or should be inferred. Complying with all applicable copyright laws is the responsibility of the user. Without limiting the rights under copyright, no part of this document may be reproduced, stored in or introduced into a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise), or for any purpose, without the express written permission of Microsoft Corporation. Microsoft may have patents, patent applications, trademarks, copyrights, or other intellectual property rights covering subject matter in this document. Except as expressly provided in any written license agreement from Microsoft, the furnishing of this document does not give you any license to these patents, trademarks, copyrights, or other intellectual property..  2002 Microsoft Corporation. All rights reserved. Microsoft, MS-DOS, Windows, Windows NT, ActiveX, Active Directory, Authenticode, Hotmail, JScript, Microsoft Press, MSDN, PowerPoint, Visual Basic, Visual C++, Visual Studio, and Windows Media are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries. The names of actual companies and products mentioned herein may be the trademarks of their respective owners.
  3. Module 4: Internet Information Services Authentication iii Instructor Notes Presentation: This module provides students with information about the Web client 75 minutes authentication methods that are supported by Internet Information Services (IIS) and Microsoft® Windows® 2000 Server. Initial Web client authentication Lab: and the flow of user identities through the Web application are the focus of this 30 minutes module. After completing this module, students will be able to select the best IIS authentication method for a given set of requirements. After completing this module, students will be able to: ! Explain how Web client authentication is used to pass user identity through a Web application. ! Use Information Protocol (IP) address and domain name restrictions, and IIS Web-based permissions, to effectively control who can access the resources on a Web server. ! List and explain all of the authentication methods that are supported by IIS and select the best method for a given set of requirements. ! Explain how the identity of an authenticated Web client is mapped to a Windows 2000 user identity and passed to Web applications and COM+ components. Required materials To teach this module, you need the following materials: ! Microsoft PowerPoint® file 2300A_04.ppt ! Hypertext Markup Language (HTML) and Flash animation files: 2300A_04_A05_1570.htm, 2300A_04_A05_1570.swf Preparation tasks To prepare for this module: ! Read all of the materials for this module. ! Complete the demonstrations and lab. ! Read Module 5, “Implementing Security on a Web Server,” in Course 2295, Implementing and Supporting Microsoft Internet Information Services 5.0. ! Read Module 12, “Configuring a Web Server,” in Course 2153, Implementing a Microsoft Windows 2000 Network Infrastructure. ! Read the article “Principal and Identity Objects” in the Microsoft .NET Framework documentation. ! For background information on COM+ and role-based security, see Course 2557, Building COM+ Applications Using Microsoft .NET Enterprise Services. ! Read the Microsoft MSDN® Magazine article, “An Introductory Guide to Building and Deploying More Secure Sites with ASP.NET and IIS,” which is available at http://msdn.microsoft.com/msdnmag/issues/02/04/ ASPSec/ASPSec.asp.
  4. iv Module 4: Internet Information Services Authentication ! Read the MSDN Magazine article, “Web Security: Part 2: Introducing the Web Application Manager, Client Authentication Options, and Process Isolation,” which is available at http://msdn.microsoft.com/msdnmag/ issues/0700/websecure2/websecure2.asp. ! Read the MSDN article, “Securing Your Web Application,” which is available at http://msdn.microsoft.com/library/en-us/vsentpro/html/ veconsecuringyourwebapplication.asp. ! Read the MSDN article, “Implementing a Secure Site with ASP,” which is available at http://msnd.microsoft.com/library/en-us/dnsecure/html/ msdn_implement.asp. ! Read the MSDN article, “Untangling Web Security: Getting the Most from IIS Security,” which is available at http://msdn.microsoft.com/library/en-us/ dnsecure/html/WebsecIISsec.asp.
  5. Module 4: Internet Information Services Authentication v How to Teach This Module This section contains information that will help you to teach this module. Lesson: Introduction to Web Client Authentication This section describes the instructional methods for teaching each topic in this lesson. Why Web Servers Are Explain the ways and reasons why a Web server is the target of so many Attacked attacks. Authentication and Define authentication and authorization. This module is about authentication. Authorization Module 5, “Securing Web Pages,” in Course 2300, Developing Secure Web Applications, is about authentication and authorization. These terms will be revisited many times throughout Course 2300, Developing Secure Web Applications. Impersonation and The primary difference between impersonation and delegation is that Delagation impersonation occurs on the Web server, while delegation occurs across computer boundaries. User Identities and Introduce the user and group accounts listed on the slide. Permissions IWAM_computername will be covered at the end of this module. The ASPNET account is new in Microsoft .NET, and it secures the Microsoft ASP.NET pages by limiting the rights of the account that the pages run as. How IIS Impersonates a Expand on the subject of impersonation by explaining how IIS performs work Windows User Account on behalf of an authenticated client. The identity under which IIS performs this work varies, based on the type of authentication that is used and the platform that you use to develop the Web application (Active Server Pages (ASP) or ASP.NET). Programmatically In ASP.NET, you use the code User.Identity.Name to discover the name of the Accessing User Identity authenticated user. In this code, User is a Principal object and User.Identity is an Identity object. This property uses the User property of the HttpContext object to determine where the request has originated from. The HttpContext object provides access to the intrinsic Request, Response, and Server objects for the request. This topic also introduces how to enable impersonation in an ASP.NET Web application by setting an attribute in the Web.config file. This may be the first time some students have heard about the Web.config configuration file. Quickly explain its purpose and use. Web.config will be covered again in Modules 5, “Securing Web Pages,” and Module 6, “Securing File System Data,” in Course 2300, Developing Secure Web Applications. Demonstration: This demonstration is performed with the Web site configured to allow Programmatically Anonymous access. Therefore, the code will not show a name for the user. The Accessing User Identity same page will be demonstrated in the next lesson to show how the page changes based on the authentication method selected for IIS.
  6. vi Module 4: Internet Information Services Authentication Lesson: Configuring Access Permissions for a Web Server Using IP Address and One reason to use IP address restriction is that if there is a known proxy server Domain Name that is waging attacks, you can restrict access to your Web site for that IP Restrictions address. The http://www.ntbugtraq.com Web site has a list of servers that known hackers use. Using Web-Based Web-based permissions are one way to protect files that are not handled “by Permissions default” by the Web server, such as .inc files. Practice: Using Web- This practice reinforces the point that some of the default permissions settings Based Permissions in IIS can expose Web application implementation files to users. It is important to understand what the default permission settings are and how to modify these settings to best protect Web application files. Using the Permissions Quickly demonstrate the Permissions Wizard. Many of the settings in the Wizard Permissions Wizard are beyond the scope of this course, but the wizard does provide a quick way to configure Web-based permissions for common scenarios, such as a public Web site or a secure Web site. The students do not run the Permission Wizard in this course because they will manually implement the same settings. Lesson: Selecting a Secure Client Authentication Method Overview of IIS Web The term “identified access” may be new to students. Explain the difference Client Authentication between identified access, which is typically used for the personalization of a Web site, and authenticated access. Demonstration: Setting The demonstration should set the different authentication methods on the IIS Authentication Mod04 subfolder of the 2300Demos Web application. Discuss the results after Methods each authentication method is applied. Using Anonymous You might want to mention that Anonymous access plays an important role in Authentication forms-based authentication, which is the topic of Module 5, “Securing Web Pages,” in Course 2300, Developing Secure Web Applications. Using Basic Basic authentication is not a secure way of adding authentication to your Web Authentication application because the password that is entered by the user is sent to the Web server in Base64 encoding. In Module 8, “Protecting Communication Privacy and Data Integrity,” in Course 2300, Developing Secure Web Applications, you will explain Secure Sockets Layer (SSL) and show how the students can secure the Basic authentication method by securing the Basic-protected folder by using SSL. Then, the user name and password (in addition to all of the other data on the secured pages) will be sent to the Web server by using SSL. Using Digest Digest authentication is included for a complete look at authentication, but you Authentication do not need to discuss this authentication method in detail. Digest authentication requires the Active Directory® directory service, which is beyond the scope of this course. Using Integrated Although Integrated Windows authentication is a very secure authentication Windows Authentication method because it takes advantage of the security features that are built into the Windows operating system, it is important to note its limitations and why is it not appropriate in most Web applications that are designed for use on the Internet.
  7. Module 4: Internet Information Services Authentication vii Using the Kerberos V5 The most important difference between the Kerberos V5 protocol and NTLM is Protocol vs. NTLM that NTLM is limited to impersonation on the Web server, whereas Kerberos can use delegation to access resources across the network. It is also important to note that you do not have control over which protocol is used. IIS will always attempt to use Kerberos first and will use NTLM only if Kerberos is not available. Using Multiple Review the guidelines for using multiple authentication methods so that the Authentication Methods students will understand how IIS determines which authentication method to use when multiple authentication methods are specified. Practice: Selecting a In this practice, students will review some common scenarios and decide which Web Client authentication method or methods to use in each scenario. You can add value to Authentication Method this practice by asking students to determine the order in which IIS will try each of the authentication methods to find a valid one. Lesson: Running Services As an Authenticated User Multimedia: User This animation explains how the identity flow can be passed either by using Identity Flow in a Web application parameters or the Windows operating system. The animation shows Application all parts of the process; however, only the client authentication in IIS and COM+ pieces are discussed here. Microsoft SQL Server™ is covered in Module 7, “Securing Microsoft SQL Server,” in Course 2300, Developing Secure Web Applications. COM+ is beyond the scope of this course. If students do not know what a COM+ component is, start out with a brief description: COM+ was introduced by Microsoft in 2000. COM+ builds on the integrated services and features of the Component Object Model (COM), making it easier for developers to create and use software components in any language, by using any tool. For more information about COM+, see the article “COM+ Programming Overview,” which is available at http://msdn.microsoft.com/library/en-us/ cossdk/htm/pgintro_programmingoverview_9kjb.asp. Selecting an IIS Note that the application protection setting applies only to ASP Web Application Protection applications. Level Demonstrate where you configure this setting in IIS, which is in the Properties dialog box, on the Directory tab, of a Web application. Describe the process in which ASP.NET Web applications are run, ASPNet_wp.exe. Explain that IIS always runs ASP.NET Web applications in a single instance of the ASPNet_wp.exe process and that developers do not have control over this.
  8. viii Module 4: Internet Information Services Authentication Configuring COM+ Demonstrate the Component Services dialog box to show where the students Applications to Run can set the identity of a COM+ application: Under a Specific User Identity 1. On the Start menu, point to Programs, point to Administrative Tools, and then click Component Services. 2. In the Component Services dialog box, expand Component Services, expand Computers, expand My Computer, and then expand COM+ Applications. 3. Right-click a COM+ application, such as IIS Out-Of-Process Pooled Applications, and then click Properties. 4. In the Properties dialog box, on the Identity tab, show how the IIS Out-Of- Process Pooled applications are configured to run as the IWAM_computername user. 5. Click Cancel to close the Properties dialog box. Configuring Role-Based This topic is beyond the scope of this course. Direct students to Course 2557, Security for COM+ Building COM+ Applications Using Microsoft .NET Enterprise Services, to Applications learn more about this topic. Lab 4: Authentication and Access Control Introduce the lab with a group brainstorming session about which users need to have access to the TailspinToys and TailpsinToysAdmin Web applications, and therefore, what authentication method should be applied to each Web application: ! The TailspinToys Web application must be available to everyone; therefore, it will be configured to allow Anonymous access. ! The TailspinToysAdmin Web application must be available only to the employees of Tailspin Toys; therefore, it will be configured to use Integrated Windows authentication. At the end of the lab, reiterate which authentication methods were applied to the two Web applications and why.
  9. Module 4: Internet Information Services Authentication ix Customization Information This section identifies the lab setup requirements for a module and the configuration changes that occur on student computers during the labs. This information is provided to assist you in replicating or customizing Microsoft Official Curriculum (MOC) courseware. Lab Setup To complete this lab, students can continue working in the Tailspin Toys Microsoft Visual Studio® .NET projects that they used in previous labs, or they can start with new files. To start with new files, students must complete the following steps. ! Create the Web applications for the ASP exercises 1. Copy all of the contents of the ASP starter folder install_folder\Labfiles\ Lab04\ASP\Starter\TailspinToys to the TailspinToys IIS virtual directory at C:\Inetpub\wwwroot\TailspinToys. 2. Copy all of the contents of the ASP starter folder install_folder\Labfiles\ Lab04\ASP\Starter\TailspinToysAdmin to the TailspinToys IIS virtual directory at C:\Inetpub\wwwroot\TailspinToysAdmin. ! Create the Web applications for the ASP.NET exercises 1. Copy all of the contents of the ASP.NET folder install_folder\Labfiles\ Lab04\ASPXVB\Starter\TailspinToys.NET to the TailspinToys.NET IIS virtual directory at C:\Inetpub\wwwroot\TailspinToys.NET. 2. Copy all of the contents of the ASP.NET folder, install_folder\Labfiles\ Lab04\ASPXVB\Starter\TailspinToysAdmin.NET, to the TailspinToysAdmin.NET IIS virtual directory at C:\Inetpub\wwwroot\TailspinToysAdmin.NET. Lab Results Performing the lab in this module introduces the following configuration change: ! The TailspinToys and TailspinToys.NET Web applications should be configured in IIS to only allow Anonymous access. ! The TailspinToysAdmin and TailspinToysAmin.NET Web applications should be configured in IIS to allow only Integrated Windows authentication.
  10. Module 4: Internet Information Services Authentication 1 Overview ! Introduction to Web Client Authentication ! Configuring Access Permissions for a Web Server ! Selecting a Secure Client Authentication Method ! Running Services As an Authenticated User *****************************ILLEGAL FOR NON-TRAINER USE****************************** Introduction Implementing the correct security settings on your Web servers can safeguard your Web application against security threats, such as unauthorized individuals trying to gain access to restricted information, along with protecting against well-intentioned users who might accidentally alter important files. Security in Internet Information Services (IIS) version 5.0 consists of an interaction of permissions, policies, authentication methods, and secure communications protocols. By configuring security correctly on your Web server, you can ensure that your servers are protected from unauthorized access. This module provides insight into the Web client authentication methods that are supported by IIS and Microsoft® Windows® 2000 Server. After the Web client user is identified, that identity is then mapped to a Windows 2000 user identity. Servicing a Web page request can involve several processes that have different security identities. The initial authentication and the flow of those identities are the focus of this module. Note The code samples in this module are provided in both Microsoft Visual Basic® .NET and C#.
  11. 2 Module 4: Internet Information Services Authentication Objectives After completing this module, you will be able to: ! Explain how Web client authentication is used to pass user identity through a Web application. ! Use Information Protocol (IP) address and domain name restrictions, and IIS Web-based permissions, to effectively control who can access the resources on a Web server. ! List and explain all of the authentication methods that are supported by IIS and select the best method for a given set of requirements. ! Explain how the identity of an authenticated Web client is mapped to a Windows 2000 user identity and passed to Web applications and COM+ components.
  12. Module 4: Internet Information Services Authentication 3 Lesson: Introduction to Web Client Authentication ! Why Web Servers Are Attacked ! Authentication and Authorization ! Impersonation and Delegation ! User Identities and Permissions ! How IIS Impersonates a Windows User Account ! Programmatically Accessing User Identity ! Demonstration: Programmatically Accessing User Identity *****************************ILLEGAL FOR NON-TRAINER USE****************************** Introduction IIS serves as the gatekeeper to the resources that are on your Web server by authenticating clients as they attempt to access your Web application. In this lesson, you will learn how IIS authenticates clients and passes user identity through a Web application. Lesson objectives After completing this lesson, you will be able to: ! Describe why and how Web servers are attacked. ! Describe the difference between authentication and authorization in a Web application. ! Explain the difference between impersonation and delegation. ! List and explain the standard user identities that are on an IIS server. ! Explain how a Web client identity is translated into the process identity or a series of identities that are used by processes that fulfill the Web application request. ! Use code to determine the identity of the user of the currently running Web application.
  13. 4 Module 4: Internet Information Services Authentication Why Web Servers Are Attacked ! Reasons for an attack " Easy public access to a company's network ! Weaknesses that might lead to an attack " Unpatched IIS server " Unprotected Web application files " Web application not secured against anonymous access " Incorrect Web-based permissions set on Web application pages *****************************ILLEGAL FOR NON-TRAINER USE****************************** Introduction Web servers are an easily reached gateway to a company’s network because they are often available for all Internet users to browse. Therefore, Web servers pose a very public arena for attack. Some files on the Web server need to be available for read access, but must not be available for write access or execute access. Some pages on the Web server should be accessible only to the Web server itself (such as include files or code- behind pages in a Microsoft ASP.NET Web application). The files on the Web server contain useful information for attackers. Server script files, such as .asp and .aspx files, contain implementation source code that can be useful for determining a Web site’s architecture. This implementation source code may also describe database structures. Source code may also contain database connection strings, trusted user names and passwords, and other configuration data that can be useful to an attacker.
  14. Module 4: Internet Information Services Authentication 5 Accessing a Web server A Web server can become available to an attacker through a variety of mechanisms. Some of these mechanisms are the results of the weakness in a system. You can prevent most of the attacks on the Web server by ensuring that certain weaknesses are addressed. Specific weaknesses are described in the following table. Weakness Use IIS server not current with Staying current with IIS patches helps to ensure a secure patches server. Historically, there have been IIS holes that permit access to the implementation file source. For example, appending ::$DATA to an .asp file Uniform Resource Locator (URL) allows an attacker to access the .asp file source code. Alternate routes to the file Running more applications on the Web server than required makes the Web application vulnerable to attack because it provides alternate routes to attackers to access the Web application data. For example, Web application implementation files can also be accessed through applications, such as File Transfer Protocol (FTP) and Web Distributed Authoring and Versioning (WebDAV). If a Web server is running these applications and they have a weakness or security hole, Web application implementation files may be accessible to external users. You should disable all of the applications that are not required on the server. Unprotected configuration File types that are not explicitly disallowed are by files default accessible through IIS. If you add any new file types (for example, .inc files) to your Web application, you must ensure that those files are secured. Securing private portions of Ensure that anonymous users are allowed only to visit Web sites public Web sites and secure all private sites for authenticated users. Incorrect Web-based Ensure that the pages of your Web application are permissions on files available for read access and possibly available for execution. Do not apply write, directory browsing, or execute permission to files and folders unless it is needed by the Web application.
  15. 6 Module 4: Internet Information Services Authentication Authentication and Authorization ! Authentication " The process of verifying the identity of a principal by accepting credentials and validating those credentials ! Authorization " The process of confirming that an authenticated principal is allowed access to one or more resources *****************************ILLEGAL FOR NON-TRAINER USE****************************** Introduction The ability to authenticate Web application users and authorize them to use Web application resources is one of the foundations of Web security. What is authentication? Authentication is the process of obtaining user identification credentials, such as a name and a password, and then validating those credentials against some authority, such as a database. If the identification credentials are valid, the user that submitted the credentials is considered an authenticated user. For example, all users must provide a user name and password every time that they log on to a network. These credentials are then authenticated by an authority, such as a database or a Windows-based domain controller. What is authorization? After an identity has been authenticated, the authorization process determines whether that identity has access to a specified resource. The authorization process limits access rights by granting or denying specific permissions to an already authenticated identity. For example, you can authorize user Robert Brown to access the color printer, but deny access to user Bob Hohman. Similarly, you can authorize only the users of a company’s Media group to be able to access the color printer and deny access to the rest of the company’s users. The user of a Web application should always execute code with just enough access privilege to accomplish the intended task, and no more. This is referred to as running with least privileges. By limiting access to resources to only those users who are authorized, you can help prevent accidental or malicious damage to Web application and system resources.
  16. Module 4: Internet Information Services Authentication 7 Impersonation and Delegation SQL Server Code Code Client Client IIS IIS Authenticated Authenticated User User Network Server Network ! Impersonation ! Delegation " Code executes " Enables the in the context of server to an authenticated access remote client resources while acting as the client *****************************ILLEGAL FOR NON-TRAINER USE****************************** Introduction Impersonation and delegation are used to control the flow of user identity through a Web application. What is impersonation? The pages in your Web application are run by either the Active Server Pages (ASP) process or the ASP.NET process. These processes run in many threads on the computer running Windows 2000 Server. Impersonation is the ability of a thread to execute by using different security information than the process that owns the thread. Typically, a thread in a server application impersonates a client. Impersonation allows the thread to act on behalf of that client to access objects on the server or to validate access to the client’s own objects. The primary reason for impersonation is to cause access checks to be performed against the client’s identity. Access checks identify the user when a thread interacts with a securable object or tries to perform a system task that requires access privileges. Using the client’s identity for access checks can cause access to be either restricted or expanded, depending on what the client has permission to do. For example, assume that a file server has files containing confidential information and that each of these files is protected by an Access Control List (ACL). To prevent a client from obtaining unauthorized access to the information in these files, the server can impersonate the client before accessing the files. What is delegation? Delegation, which is a more powerful form of impersonation, enables the server to access remote resources over the network while acting as the client; impersonation is limited to accessing resources on the server computer.
  17. 8 Module 4: Internet Information Services Authentication User Identities and Permissions ! Windows 2000 and IIS create special accounts for Web applications that help you to control user access to resources " Interactive group " Network group " IUSR_computername account " IWAM_computername account " ASPNET account *****************************ILLEGAL FOR NON-TRAINER USE****************************** Introduction Windows 2000 includes several built-in group accounts that assist you in granting the minimum permissions possible. These group accounts include the Interactive and Network groups. Additionally, when IIS is installed, the IUSR_computername and IWAM_computername user accounts are created for use, by IIS, when IIS is running ASP Web applications. When you install the Microsoft .NET Framework, an account called ASPNET is also created. The aspnet_wp.exe process (which runs all ASP.NET Web applications) runs as the ASPNET account. Note You will learn more about the different authentication methods that are supported by IIS in the lesson “Selecting a Secure Client Authentication Method” in this module. Interactive group The Interactive group is a built-in, automatically maintained group in Windows 2000 that consists of all of the users who are logged on locally to the server computer. A local log on is one that appears to the server to have occurred on the server itself, instead of occurring remotely. Before a user or group can perform a local log on, he or she must have the Log on Locally user right. You can use the Interactive group to restrict or permit access to all of the users that are authenticated by Basic authentication. Network group The Network group is a built-in, automatically maintained group in Windows 2000 that consists of all of the users who are logged on to the server over the network. Before a user or group can perform a network log on, they must have the Access This Computer from the Network user right. You can use the Network group to control access for all of the users that are authenticated by Digest or Integrated Windows authentication.
  18. Module 4: Internet Information Services Authentication 9 IUSR_computername The Internet Guest Account is named IUSR_computername (where account computername is the name of the computer on which IIS is running), and this account is used to provide Anonymous access to a Web application, a folder, or a file. Managing NTFS file system permissions for the Internet Guest Account is critical to the security of your Web server and network. The Internet Guest Account should be permitted only the minimum permissions that are necessary to gain access to the Web server. IWAM_computername The IWAM_computername account is also created by IIS, and it is used solely account for Web applications that run in Medium or High application protection. In some situations, you will need to provide the appropriate permissions to server resources for this account. For example, if there is a program gaining access to a database on behalf of a user, and that program is running in Medium or High application protection, you will need to provide appropriate database permissions to this account. Note You will learn more about IIS application protection levels in the topic “Selecting an IIS Application Protection Level” in this module. ASPNET account The ASPNET account is created by the .NET Framework, and it is used solely for ASP.NET Web applications. In some situations, you will need to provide the appropriate permissions to server resources for this account. For example, if a Web application needs to write to a file, you will have to give the ASPNET user write permission to access the folder where the file is located.
  19. 10 Module 4: Internet Information Services Authentication How IIS Impersonates a Windows User Account LocalSystem 1 Takes client request 1 2 Impersonates the 2 user by mapping the IUSR_computername Internet Internet request to a Windows Information Information user account IWAM_computername Services Services Windows Windows 3 3 Performs the user user appropriate tasks Windows users accounts accounts and groups 4 4 Reverts to the process identity, ASPNET LocalSystem LocalSystem *****************************ILLEGAL FOR NON-TRAINER USE****************************** Introduction When IIS receives a request from a Web client, it authenticates the client and then performs the work under the identity of the authenticated client by using a Windows user or group account. IIS impersonates the client by using the IUSR_computername or IWAM_computername account for ASP Web applications or the ASPNET or IUSR_computername account for ASP.NET Web applications. ASP and impersonation Whereas IIS impersonates the client, IIS operates within the confines of the authenticated user’s security context. This security context may change during the various stages of request processing, depending on the nature of the client request and what resources are required to service that request. The security context of the IIS process (Inetinfo.exe) is known as LocalSystem. However, when IIS is processing a client request, it will impersonate the context of the client that originally generated the request. The Windows user account that is used depends on the authentication method, as described in the following table. Authentication method Windows user account Anonymous IUSR_computername for in-process Web applications and IWAM_computername for Web applications running in an isolated process. Basic, Digest, and Integrated The Windows user account for which the client Windows (NTLM) supplied the user name and password. Integrated Windows (Kerberos) The Windows user account for which the client supplied the user name and password. Kerberos also supports delegation, which allows access to the resources of another system, under the client’s identity.
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