Chapter 10ASP.NET Security

Yingcai Xiao

Introduction to Web SecurityCategories

IssuesComponents

Building a Secure Web Site

Three Categories of Web Security:– Content freely available to everyone (public).– Serve the general population but require a login

(application-level security, protected). – Intranet sites for a controlled population of users — a

company’s employees (private).

Security Issues:– Application-level security (users). – Deployment security (programmers).

Web Security Components:– Authentication identifies the originator of requests (who).– Authorization defines who can access which pages (what).

Authentication ASP.NET supports a few types of authentication:

– Forms (Page-wide)– Windows (Machine-wide)– None

Web.config<configuration>  <system.web> 

    <authentication mode="Forms"/>  </system.web> </configuration>

Note: The authentication mode is an application-wide setting

that can be set only in the application root and can’t be overridden in subordinate Web.config files.

You can’t use Windows authentication in one part of an application and forms authentication in another.

Setting authentication mode in the root Web.config

Authorization ASP.NET supports two forms of authorization:

– ACL (access control list) authorization, also known as file authorization, based on file system permissions, typically used with Windows authentication.

– URL authorization, relies on configuration directives in Web.config files, most often used with forms authentication.

Three Typical Security Scenarios for Web Applications

– Pages can be freely browsed by any: no application-level security

– Intranet application: use Windows authentication and ACL authorization.

– Internet application with secure page access: use forms authentication and URL authorization.

The Internal Working of IIS and ASP.NET

Security

IIS Security IIS (Internet Information Services) Server

– a Web server– runs in process Inetinfo.exe as SYSTEM– accepts connections– responds to HTTP requests

Web applications are deployed in application directories. Remote clients can’t arbitrarily grab files outside application directories.

IIS assigns every request an access token representing a Windows security principal. The access token enables the operating system to perform ACL checks on resources targeted.

IIS supports IP address and domain name restrictions.

IIS supports encrypted HTTP connections using the Secure Sockets Layer (SSL) family of protocols.

IIS Security

Anonymous access (access by unauthenticated users)

Request from anonymous users are tagged with IUSR_machinename’s access token. IUSR_machinename is an Internet guest account created when IIS is installed, where machinename is usually the Web server’s machine name.

The relationship between IIS and ASP.NET.

IIS 6.0

IIS 6.0 has a driver named http.sys to listen all HTTP requests.

When an ASP.NET related request comes in, http.sys will stat w3wp.exe as an IIS 6.0 worker process.

W3wp now loads aspnet_isapi.dll as CLR host.

The rest is the same as before.

ASP.NET Security Server Side Processing: (1) Client accesses .ASPX files => (2) Inetinfo.exe (IIS) generates an access token

=> Aspnet_isapi.dll sents the request and the token through named pipe or local procedure calls (LPCs) => (3) Aspnet_wp.exe (ASP.NET) makes ACL checks on the requested resource and passes access token to the targeted application =>

(4) Targeted application uses a HTTP pipeline => HTTP modules => HTTP handlers (mapped in Machine.config).

Two types of access tokens:– Authenticated user: authenticated security principal– Unauthenticated user: IUSR_machinename for

anonymous login

– Start->Settings->Control Panel->Administrative Tools->Computer Management->Local Users and Groups->Users

– Start->Settings->Control Panel->Administrative Tools->Computer Management->Event Viewer->Security

The ASPNET Account

Created when ASP.NET is installed.

A member of the “Users” group (hidden now).

Aspnet_wp.exe runs as ASPNET by default.

Requests executed by ASP.NET use Aspnet_wp.exe’s

identity.

ASP.NET can impersonate to use the request’s access

token.

To make Aspnet_wp.exe to run as SYSTEM, change

processModel in Machine.config to

<processModel userName="SYSTEM" ... />

The ASPNET Account

You can also run the ASP.NET worker process

(aspnet_wp.exe or w3wp.exe) under a user account:

https://msdn.microsoft.com/en-us/library/bakfs900.aspx

Programming Forms Authentication

Forms Authentication ► Forms authentication allows applications to setup web

authentications independently from the authentications of the operating systems. It works well with URL authorization, which relies on configuration directives in Web.config files.

► Forms/URL security is useful to protect an e-commerce site (an external Internet application for servicing customs of a company).

Forms Authentication: Static Structure

– Security settings in an ASP.NET-based web application are configured in the Web.config files.

– The Web.config file in the root directory (which must be an application directory) specifies the authentication mode, application-specific login page.

– The Web.config file in a subdirectory sets the authorization specifics for the directory.

– User credentials can be stored in a database (preferred) or in the root Web.config file.

Forms Authentication : Dynamic Behavior

– The first time a user accesses a protected resource, ASP.NET redirects the user to the login page.

– If the login is successful, ASP.NET then issues the user an authentication ticket in the form of a cookie (cookies need to be enabled by the client) and redirects the user to the page originally requested.

– The ticket allows that user to revisit protected portions without having to login again.

– The ticket’s lifetime can be controlled to determine how long the login is good for.

A First Look at Forms Authentication

► Forms1 Web Application– T:\Xiao\Windows Programming\Examples\C10\Forms1

– At the application root• PublicPage.aspx can be viewed by anyone• Web.config• LoginPage.aspx

– In the Secret subdirectory• ProtectedPage.aspx is available only to

authenticated users (wp/wp). • Web.config

Deploy Forms1 on Winserv1

– Create a web application (Forms1).C:\inetpub\wwwroot\xiaotest\Forms1You need to have admin privilege.

– On winserv1, use an existing web application directory already created for you.

– Copy everything from T:\Xiao\Windows Programming\Examples\C10\Forms1to the above directory.

http://winserv1.cs.uakron.edu/xiaotest/Forms1/PublicPage.aspx can be viewed by everyone. (http://winserv1.cs.uakron.edu/Examples/C10/Forms1/PublicPage.aspx)

Deploy Forms1 on Winserv1

– http://winserv1.cs.uakron.edu/xiaotest/Forms1/Secret/ProtectedPage.aspx is available only to authenticated users (wp/wp).

– “Authenticated users” means anyone who has successfully logged in through LoginPage.aspx.

– Valid users are stored in Web.config.– The cookie containing the authentication ticket is a

session cookie, destroyed when the browser is closed. – You are not prompted for password again during a

session.

Programming Forms Security► Authentication in the root Web.config

<authentication mode="Forms">  

<forms loginUrl="LoginPage.aspx">

<credentials passwordFormat="Clear">  

<user name="wp" password=“wp"/> 

<user name="John" password="redrover" />

► Authorization (directory-wise) in Secret/Web.config

<authorization>  

<deny users="?" />

URL authorization to deny “?” (anonymous) users.

Programming Forms Security► PublicPage.aspx

void OnViewSecret (Object sender, EventArgs e)    { Response.Redirect ("Secret/ProtectedPage.aspx"); }

► LoginPage.aspx.

void OnLogIn (Object sender, EventArgs e)  

{ if(FormsAuthentication.Authenticate(UserName.Text,  Password.Text))     

FormsAuthentication.RedirectFromLoginPage (UserName.Text, false);

// “true” for persistent cookie      

else Output.Text = "Invalid login";  

}

System.Web.Security.FormsAuthentication.Authentic method returns true if the user name and password are in the credentials section of Web.config.

Internal Works► ASP.NET creates an authentication cookie,

attaches it to the outgoing response, and redirects the user to the page that he or she originally requested. The lifetime of a persistent cookie is independent of the browser session.

► Authorization is applied on a directory-by-directory basis. Web.config files in each directory specify exactly how the files are to be protected.

► ASP.NET checks to see whether a valid authentication cookie is attached to the request. If the cookie exists, ASP.NET extracts identity information. If the cookie doesn’t exist, ASP.NET redirects the request to the login page.

Real-World Forms AuthenticationForms2Forms3

Real-World Forms Authentication – (Forms2)

► Storing user names and passwords in a database (MySQL).

► Creating the database, creating the “users” table and adding users.

• Logo on to winserv1.• Start->All Programs->My SQL->My SQL Query Browser.• Server Host: db1.cs.uakron.edu• Port 3306• Username: yourLoginID• Password: yourPassword for MySQL• Default Schema: your DB name• File->Open Script:

T:\Xiao\Windows Programming\Examples\C10\MySQL-Table-Creation\Weblogin.sql

• Execute! 

Real-World Forms AuthenticationWeblogin.sql

CREATE TABLE users( username varchar(32) NOT NULL, password varchar(32) NOT NULL, role varchar(32));

INSERT INTO users (username, password, role) VALUES (‘dev', ‘dev', 'Developer');INSERT INTO users (username, password, role) VALUES (‘mgr', ‘mgr', 'Manager');…

AddUsers.sql

• INSERT INTO users (username, password, role) VALUES ('wpd1', 'wp2009', 'Developer');• INSERT INTO users (username, password, role) VALUES ('wpd2', 'wp2009', 'Developer');…

Deploy Forms2 on Winserv1

– Create a web application directory.C:\inetpub\wwwroot\xiaotest\Forms2You need to have admin privilege.

– On winserv1, use an existing web application directory already created for you.

– Copy everything from T:\Xiao\Windows Programming\Examples\C10\Forms2to the above directory.

Deploy Forms2 on Winserv1

► To access– http://winserv1.cs.uakron.edu/xiaotest/Forms2/

PublicPage.aspx, can be viewed by anyone.– http://winserv1.cs.uakron.edu/xiaotest/Forms2/Secret/

ProtectedPage.aspx and is available only to authenticated users (dev/dev).

Deploy Forms2 on Winserv1

– “Authenticated users” means anyone who has successfully logged in through LoginPage.aspx.

– Valid users are stored in the database.– The cookie containing the authentication ticket is a

session cookie, destroyed when the browser is closed. – You are not prompted for password again during a

session.

Real-World Forms Authentication LoginPage.aspx► Credential Matching:

SQL: select count(*) from users where username = ‘dev' and pwd = ‘dev’; 

It returns 0 if no matching credentials found.

► MySQL notes: (1) count (*) works for SQL Server but not MySQL due to the extra space after count.(2) password is a keyword in MySQL (not SQL Server), therefore can’t be used as database column names. (3) ExecuteScalar returns Int64 for “count” query.

► FormsAuthentication.RedirectFromLoginPage (UserName.Text, Persistent.Checked); Persistent authentication cookie: be able to get back without logging in again, even after shutting down. No expiration.

Authentication Cookie Lifetime► Session authentication cookie.

Machine.config<forms ... timeout="30"> // 30 minutesWeb.config<forms loginUrl="LoginPage.aspx" timeout="10080" /> // 7 days

► Proramming cookies.HttpCookie cookie = Response.Cookies[FormsAuthentication.FormsCookieName]; cookie.Expires = DateTime.Now

+ new TimeSpan (7, 0, 0, 0); // 7 days

► Removing cookies as a user.IE->Tools->Internet Options->General->Delete Cookies.Netscape->Tools->Cookie Manager->Manage stored cookies->Remove all.

FireFox->Tools->Clear Recent History: check Cookies.Google Chrome->Costumize->More Tools->Clear Browser Data->Cookies

Forms AuthenticationRole-Based Security

http://winserv1.cs.uakron.edu/xiaotest/Forms3/PublicPage.aspx http://winserv1.cs.uakron.edu/xiaotest/Forms3/Secret/ProtectedPage.aspx

Forms Authentication and Role-Based Security (Forms3)

► Use role membership to allow only some authenticated users to view Secret/ProtectedPage.aspx.

► Without roles:Deny all unauthenticated users.

<deny users="?" /> Deny all users (users=“*”) except John and Alice.

<allow users="John, Alice" />      <deny users="*" />

Allow all except Jeff, Bob, and Mary:<deny users="Jeff, Bob, Mary" />      <allow users="*" />

<allow> and <deny> are order-sensitive. ASP.NET will stop at <…= “*”> and ignore any statements that appear after it.

Forms Authentication and Role-Based Security (Forms3)

► With roles:– “Users” table has a field named “role” that stores each user’s role

(group) membership.– Grant Developer access to Secret. <allow roles="Developer" />      <deny users="*" /> – Map the roles to user accounts so that ASP.NET can determine

whether the requestor is a developer or not.– Place the mapping in the AuthenticateRequest event handler

(invoked at the beginning of every request).– Can be done in a custom HTTP module or in Global.asax.

http://winserv1.cs.uakron.edu/Examples/C10/Forms3/PublicPage.aspx

http://winserv1.cs.uakron.edu/xiaotest/Forms3/PublicPage.aspx

dev/dev/Developer can view ProtectedPage.aspx.

mgr/mgr/Manager can’t.

Programming Role-based Authentication Getting Information about Authenticated Users in Your

Code– ASP.NET stores user information in the HttpContext.User

property.– Access User through Page.Context.User or simply

Page.User, or HttpApplication.User.– The “User” property is of the type IPrincipal (an interface

defined in System.Security.Principal).– Implemented by the WindowsPrincipal class for Windows

authentication and GenericPrincipal class for other forms of authentication (along with Windows authentication).

– GenericPrincipal is a device for representing user identities independent of the authentication protocol being used. ASP.NET compares the role name in the GenericPrincipal to the roles granted access through Web.config.

– User.Identity contains some usefull properties:

Properties in User.Identity

Property Description

AuthenticationType Reveals which form of authentication was used

IsAuthenticated Reveals whether the user is authenticated

Name Reveals an authenticated user’s name

if (User.Identity.IsAuthenticated) {string name = User.Identity.Name;

… }

Name is of the form domain-name\user-name for Windows authentication,

user-typed login for forms authentication.

Programming Authentication - RolesRetrieve a user’s role and create a Principal for the user.

<%@ Import Namespace="System.Security.Principal" %><script language="C#" runat="server">• void Application_AuthenticateRequest (Object sender, EventArgs e)• {• HttpApplication app = (HttpApplication) sender;• if (app.Request.IsAuthenticated &&• app.User.Identity is FormsIdentity) {• FormsIdentity identity = (FormsIdentity) app.User.Identity;

• // Find out what role (if any) the user belongs to• string role = GetUserRole (identity.Name);

• // Create a GenericPrincipal containing the role name• // and assign it to the current request• if (role != null)• app.Context.User = new GenericPrincipal (identity,• new string[] { role });• }• }

Programming Authentication - Rolesstring GetUserRole (string name) { MySqlConnection connection = new MySqlConnection ("server=db1.cs.uakron.edu;database=xiaotest;uid=xiaotest;pwd=wp2009;

allow zero datetime=yes“) try { connection.Open (); StringBuilder builder = new StringBuilder (); builder.Append ("select role from users " + "where username = \'"); builder.Append (name); builder.Append ("\'"); MySqlCommand command = new MySqlCommand (builder.ToString (),

connection); object role = command.ExecuteScalar (); if (role is DBNull) return null; return (string) role; } catch (MySqlException) { return null; } finally { connection.Close ();} }

More on Forms Authentication► Multiple Roles

Coding:app.Context.User = new GenericPrincipal (identity,

new string[] { "Developer", "Manager" });

Web.config<allow roles="Manager, Developer" /><deny users="*" />

► Configure subdirectories in root Web.config <location path="Secret"> <system.web> <authorization> <allow roles=" Developer" /> <deny users="*" /> </authorization> </system.web> </location>

More on Forms Authentication► Signing Out

<asp:Button Text="Log Out" OnClick="OnLogOut" RunAt="server" />

<script language="C#" runat="server"> void OnLogOut (Object sender, EventArgs e) { FormsAuthentication.SignOut (); }

FormsAuthentication.SignOut( ): returns a Set-Cookie header, sets the cookie’s value to a null string and sets the cookie’s expiration date to a date in the past.

More on Forms AuthenticationAttributes of forms element in Web.config:

Attribute Description Default

name Name assigned to authentication cookies .ASPXAUTH

loginUrl URL of the login page login.aspx

protection Level of protection (validation and encryption) applied to authentication cookies

All

timeout Lifetime of session authentication tickets in minutes

30

path Scope of authentication cookies /

The protection attributes specifies the desired level of protection for the authentication cookies. “All” instructs ASP.NET to both encrypt and validate authentication cookies.

Encrypt and Validate Authentication Cookies

– Validation works by appending the machineKey element’s validationKey to the cookie, the resulting value is hashed, and the hash is appended to the cookie. When the cookie is returned in a request, ASP.NET verifies that it wasn’t tampered with by rehashing the cookie and comparing the new hash to the one accompanying the cookie.

– Encryption works by encrypting the cookie—hash value and all—with machineKey’s decryptionKey attribute.

Encrypt and Validate Authentication Cookies

– Validation consumes less CPU time than encryption and prevents tampering. It does not prevent someone from intercepting an authentication cookie and reading its contents.

– To validate but not encrypt authentication cookies:

<forms ... protection="Validation" /> – Encryption provides insurance against

tampering and prevents the cookie’s contents being read.

– To encrypt but not validate cookies:<forms ... protection=" Encryption " />

Encrypt and Validate Authentication Cookies

– To disable both:<forms ... protection="None" />

– Encrypted cookies can’t be read or altered, but can be stolen and used illicitly. Time-outs are the only protection.

– The most reliable way to prevent someone from spoofing your site with a stolen authentication cookie is to use an encrypted communications link (HTTPS).

<forms ... loginUrl="https://www.wintellect.com/login.aspx" />This assumes the server supports HTTPS and Login.aspx is stored in a

directory configured to use HTTPS.

►Caveat Emptor: ASP.NET does not protect HTML pages. Just renaming .html to .aspx to protect it.

► http://winserv1.cs.uakron.edu/xiaotest/Forms3/PublicPage.aspx ► http://winserv1.cs.uakron.edu/xiaotest/Forms3/Secret/ProtectedPage.aspx► http://winserv1.cs.uakron.edu/xiaotest/Forms3/Secret/Calc.html► http://winserv1.cs.uakron.edu/xiaotest/Forms3/Secret/Calc.aspx

Windows Authentication

Windows Authentication It maps incoming requests to accounts on the

Web server or in the Web server’s domain. Serve content to a well-defined populace

(intranet.) Requires no programming. Authentication is done

by the system.

Windows Authentication Don’t use it to generically expose content to all

comers over the Internet. Windows authentication on the front end is

typically paired with ACL authorization (administrator controlled) on the back end.

Can be also used with URL authorization (programmer controlled).

Windows Authentication

Categories of Windows Authentication:– Basic authentication: login, piggyback on HTTP. – Digest authentication: login, piggyback on HTTP.– Integrated Windows authentication: Windows login.– SSL client certificates: limited primarily to intranet.

Basic Authentication An HTTP standard (documented in RFC 2617,

ftp://ftp.isi.edu/in-notes/rfc2617.txt.) How it works:

– For the first time access, the Web server returns a 401 status code indicating what type of authentication is required.

– HTTP/1.1 401 Access Denied

Server: Microsoft IIS-5.0  .  .  .WWW-Authenticate: Basic realm="uakron.edu"

– A realm is a logical security space that encompasses all or part of a web site.

– The browser pops up a dialog box (not part of your ASP generated HTML) asking for a user name and password.

Basic Authentication It concatenates the user name and password to

an encoded string in the Authorization header of an HTTP request. Authorization: Basic SmVmZjppbWJhdG1hbg==

The browser includes the same Authorization header in each future request to the same realm.

IIS maps the user name and password to an account on the web server, producing an access token.

The access token is used to perform ACL-based security checks.

Basic Authentication Pros of Basic Authentication:

– It works with virtually all browsers.– Easy to use.– It works well with firewalls.

Cons of Basic Authentication:– Nothing prevents the HTTP requests with Authorization

header from being intercepted and used to gain access to your server.

– Some users consider pop-up dialogs intrusive.– Better to be used with HTTPS, not HTTP.

Digest Authentication Documented in RFC 2617

(ftp://ftp.isi.edu/in-notes/rfc2617.txt).

Similar to basic authentication.

The browser solicits a user name and password by popping up a dialog box. The server uses the credentials to assign an identity to the request.

The big difference between basic and digest authentication is that digest doesn’t transmit clear-text passwords. Instead, it passes an authentication token that is cryptographically secure. As a result, you can use it over unencrypted channels without fear of compromising your Web server.

Digest Authentication Cont. When the client first requests a resource guarded by

digest authentication, the server returns a 401 error and includes a “nonce”—a string of 1s and 0s—in a HTTP-Authenticate header.

The browser responds by prompting for a user name and password. It then transmits the user name back to the server, along with a hash or “digest” computed from the combined user name, password, and nonce.

The server authenticates the request by performing its own hash on the user name, password, and nonce. The password the server uses doesn’t come from the client; it comes from the server itself.

If the hashes match, the user is authenticated. It’s also compatible with proxy servers.

Digest Authentication Cont.

Pros of Digest Authentication:– Easy to understand.– Works with firewalls.– Far more secure over ordinary HTTP than basic

authentication. Cons of Digest Authentication:

– Uses pop-up dialog boxes for user names and passwords.

– Doesn’t support delegation (the ability to make a call from one machine to another and have the call execute as the caller on the remote machine) on Windows 2000 servers.

– Digest authentication is not widely used.

Integrated Windows Authentication Uses Windows login credentials to authenticate users.

Identifies the user (on the server) by using that person’s login identity on the client.

The browser asks for a user name and password only if the user does not have a valid account on the server.

The client and server negotiate a trust in a series of exchanges that involve user names, domain names, nonces, and hashes.

All done automatically by the OS on the server and the browser on the client.

Integrated Windows Authentication Pros of Windows Authentication:

– Doesn’t force users who have already logged in to Windows to provide a user name and password again.

– Secure, even over unencrypted channels, because plain-text passwords are never transmitted.

– Good for in-house use and behind firewalls.

Cons of Windows Authentication:– Can’t work through firewalls.– Proprietary to Windows and Internet Explorer.– Not for general Internet use.

Windows Authentication / ACL Authorization in Action CorpNet

Examples\C10\Basic

About “CorpNet” – It models a simple intranet-type application (e.g. an internal

application for a company).– It uses Windows (basic) authentication and ACL authorization

to restrict access to its pages.

Code:– General.aspx provides general information.– Salaries.aspx lists the salary.– Bonuses.aspx lists the bonuses.

Anyone in the company can view General.aspx, only selected individuals can view Salaries.aspx and Bonuses.aspx.

Windows Authentication / ACL Authorization in Action

Deployment on your home computer:– Create your own directory:

C:\inetpub\wwwroot\yourLoginID– Copy

Examples\C10\Basic To C:\inetpub\wwwroot\yourLoginID

– Make the directory a web application. – Access the aspx pages (as an anonymous user):

http://localhost/yourLogin/Basic/general.aspxhttp://localhost/yourLoginI/Basic/salaries.aspx (access accepted but no salary entry).http://localhost/yourLoginID/Basic/bonuses.aspx

Windows Authentication and Anonymous Access (No Authorization Control)

Use Web.config in the root directory to set the authentication mode.<configuration>  

<system.web>    <authentication mode="Windows"/>  </system.web>

</configuration>

• Access CorpNet as an anonymous user on winserv1http://winserv1.cs.uakron.edu/xiaotest/basic/general.aspxhttp://winserv1.cs.uakron.edu/xiaotest/basic/salaries.aspxhttp://winserv1.cs.uakron.edu/xiaotest/basic/bonuses.aspx

• Access CorpNet as an anonymous on your own computerhttp://localhost/xiaotest/basic/general.aspxhttp://localhost/xiaotest/basic/salaries.aspxhttp://localhost/xiaotest/basic/bonuses.aspx

Basic Authentication, No Authorization Control (on your own computer)

Use Control Panel -> Administrative Tools -> IIS manager to configure the application to require authentication and to

disallow anonymous access. • In IIS Manager, find and click on Basic application.

(WINSERV1\Sites\Default Web Site\xiaotest\Basic)• In the IIS pane, double-click on Authentication• Disable “Anonymous Authentication”• Enable “Basic Authentication”• http://winserv1.cs.uakron.edu/xiaotest/basic/salaries.aspx• Login prompt provided by the browser.• User Name: CS\xiao, Password: ???

No salary information is available for xiaotest • Modify salaries.aspx to enter a salary for xiaotest

ACL Authorization• Change the permissions on Salaries.aspx and Bonuses.xml to

deny CS\xiaotest read privilege. Right-click on the file -> properties ->Security->Edit->Add location: CS object name: xiaotestokDeny: Readok; ok(advanced for inheritance)If you don’t see the security tab in the properties window:right-click on “Start”, open, tools, folder options, view, advanced settings, files and folders, uncheck “Use simple file sharing”.

• Tests:http://winserv1.cs.uakron.edu/xiaotest/basic/general.aspx (ok)http://winserv1.cs.uakron.edu/xiaotest/basic/salaries.aspx (denied)http://winserv1.cs.uakron.edu/xiaotest/basic/bonuses.aspx (ok)

Security Inside• Note: ACL Control is set per user and per file

manually. – User: xiaotest access denied for Basic/Bonuses.xml

• Why you can still read Bonuses.xml through Bonuses.aspx?

– IIS checks the login and passes access token to ASP.NET if the login is correct.

– ASP.NET makes ACL checks using the caller’s identity against the ASPX files to be accessed and passes access token to the application (ASPX files).

– Web applications run inside ASP.NET which is run by user “ASPNET”, and can programmatically access anything that ASPNET is allowed to access.

Impersonation– To execute a request using the access token

provided by IIS.– Add the following in Web.config

<identity impersonate="true" /> – The identities assigned to the ASP.NET worker

process and to the requests that it executes play crucial roles in ASP.NET security.

– After IIS 6.0, W3WP.exe connects to aspnet_isapi.dll.

Impersonation– Impersonation makes web applications run as the caller. Any

programmatically access will subject ACL check using the caller’s identity.

<configuration> <system.web> <authentication mode="Windows" /> <identity impersonate="true" /> </system.web></configuration>

– Start a new browser– http://winserv1.cs.uakron.edu/xiaotest/basic/bonuses.aspx– “500 - Internal error occurred.”– The following does work on winserv1

• IIS Manager, double-click on the Basic application.• In the IIS pane, double-click on Authentication• Enable “ASP.NET Impersonation”

CorpNet demonstrates several important principles for using Windows authentication:– Windows authentication is enabled in ASP.NET by including an

<authentication mode=“Windows” /> statement in Web.config. It has the scope of the Web.config at application level (not page level).

– ASP.NET applications that use Windows authentication can prevent users from viewing files by using ACLs to deny access to selected security principals.

– ASP.NET applications that use Windows authentication must enable impersonation if they want resources protected by ACLs to be protected from programmatic accesses by code executed within a request.

– ASP.NET applications that use Windows authentication can personalize content for individual users by reading user names from Page.User.Identity.Name.

– ACL authorization requires system administrators of the web server to manually set the security control for each application (even each page/file).

Windows Authentication and URL Authorizations

► Change web.config to use URL authorization so the programmer can set the security control (per directory not per file). <configuration> <system.web> <authorization> <deny users="CS\YourUnixID" /> <allow users="*" /> </authorization> </system.web>

</configuration>

► “CS\YourUnixID" is not allowed to access any APSX pages in Basic. Note only one “\” after “CS”.

► Based on string names not Windows security IDs (SIDs).► The deny statement needs to be before the allow statement in the

above case.► URL authorizations usually not used with Windows authentication.

Windows Authentication and Role-Based Security

► Role-based security restricts access based on “roles” (groups) that the users belong to. For ACL authorizations, control the access by giving permission to the selected groups.

► For URL authorizations, use Web.config to restrict groups. e.g. add the “WP” group and a “test2” user in the group.Start->Settings->Control Panel->User Accounts->Advanced->Advanced->GroupsAction->New GroupStart->Settings->Control Panel->User Accounts->Advanced->Advanced->Userstest2->properties->Member Of->AddAction->New Users

► Web.config <authorization> <allow roles=“ServerName\WP" /> <deny users="*" /> </authorization>

► Deny test but allow test2.► Allow should be first here. (“*” should be at the end).

SummarySecurityAuthentication

FormsWindows

Basic, Digest, Integrated, SSL Client CertificatesPassport

Authorization: ACL, URLIIS/ASP.NET Server-Side Security ProcessingApplication Security ScenariosEncryption and Validation Database Based AuthenticationRole Based AuthorizationAnonymous LoginImpersonationRealm

Good References

Microsoft Security Tutorialshttp://www.asp.net/web-forms/tutorials/security

ASP.NET authentication and authorization

by Shivprasad Koirala http://www.codeproject.com/Articles/98950/ASP-NET-authentication-and-

authorization#Authentication%20and%20Authorization