PRB: Mobile Forms Authentication and Different Web Applications (310415)

CAUSE

Mobile forms authentication is built on the ASP.NET forms authentication platform. A security issue exists when multiple Web applications are using mobile forms authentication with the same cookie name, keys, and (or) cookie path. In this scenario, it is possible to be authenticated in one application and to make a request to the other application without being redirected to the logon page for authentication. However, authorization rules still apply, which means that even though the user is authenticated on the second application (even though the user did not explicitly log on), the user may still be denied access to a resource because of the configuration.

RESOLUTION

To resolve this behavior, use one of the following methods:

Method 1

Provide a different value for the name attribute of the <form> element in the Web.config files:

Web.config in application 1:

<forms name=".ASPXAUTH" loginUrl="login.aspx" protection="All" >

Web.config in application 2:

<forms name=".ASPXAUTH2" loginUrl="login.aspx" protection="All" >

Method 2

Provide a different value for the path attribute of the <form> element in the Web.config files:

Web.config in application 1:

<forms name=".ASPXAUTH" loginUrl="login.aspx" protection="All" path="/app1" >

Web.config in application 2:

<forms name=".ASPXAUTH" loginUrl="login.aspx" protection="All" path="/app2">

Method 3

Configure different keys for each application. Add a <machineKey> element to the Web.config file, and then set the values:

<machineKey validationKey="<validationKey>" decryptionKey="<decryptionKey>" validation="SHA1" />

NOTE: See the articles in the "More Information" section to generate valid validation and decryption keys.

MORE INFORMATION

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

312906 HOW TO: Create Keys by Using Visual C# .NET for Use in Forms Authentication

313091 HOW TO: Create Keys by Using Visual Basic .NET for Use in Forms Authentication

313116 PRB: Forms Authentication Requests Are Not Directed to loginUrl Page