SYMPTOMS
When you use Active Server Pages (ASP) in Internet Information Server (IIS) 4.0 or Internet Information Services (IIS) 5.0, a session cookie is sent to a user's browser. This cookie identifies the user for the time that they are on the site. These cookies are sometimes called memory cookies, because they are never stored on the user's hard drive like a regular cookie. In reality, this is an additional header that is sent to the browser. Anytime a Web site sends additional information such as this, the browser is required to send it back with each request (provided the server name does not change). The following is an example of an ASP Session Cookie:
Set-Cookie: ASPSESSIONIDGQQGGLIC=HKEDPNNBNBBKMOCFFBEIJENM; path=/
HTTP is a stateless protocol, which means that every time a user connects to a Web site it is just like the first time they connected to the Web server. This is a problem in an environment where you store server-side information for users. The session cookie is a means of performing such tasks.
A problem can occur if developers decide to store confidential or sensitive information in the session. For example, if a developer writes a piece of ASP code that requests a user's credit card number, the developer can store this information in a session variable (session variables are linked to the session cookie) on the server. The user can then browse to a page that lists the information they entered (for example, an authorization page or an order confirmation page). The credit card (when the list is generated) may be pulled from a session variable. If so, this information may be at risk.
If a malicious user performs a network trace or something similar, they could possibly obtain the session cookie from the user's browser when it is sent back to the server. If the malicious user makes a request to the server and presents that cookie (or actually replays the request), they could effectively see that users information stored in the session variables. The malicious user only needs to know the page that generated the output (for example, the order confirmation page).
Microsoft recommends that developers use SSL to encrypt sensitive information in order to hide the session cookie. In most cases, this will work fine; however, if the user goes from an HTTPS (secured) connection, and then back to HTTP (non-secured), the cookie is readable. This presents a problem, because the session cookie issued by a secured and non-secured request is the same.
RESOLUTION
For IIS 5.0 (Windows 2000)
To resolve this problem, obtain the latest service pack for Windows 2000. For additional information, click the following article number to view the article in the
Microsoft Knowledge Base:
260910 How to Obtain the Latest Windows 2000 Service Pack
The following file is available for download from the Microsoft Download Center:
NOTE: After you apply the patch, run the following commands to enable secure cookies (this example enables them for site 1):
cd c:\inetpub\AdminScripts
cscript adsutil.vbs set w3svc/1/AspKeepSessionIDSecure 1
For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:
119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on secure servers that prevent any unauthorized changes to the file.
The English version of this fix should have the following file attributes or later:
Date Time Version Size File name
-----------------------------------------------------------------
5/31/2001 03:31p 5.0.2195.3649 245,520 Adsiis.dll
5/31/2001 03:31p 5.0.2195.3649 332,560 Asp.dll
5/31/2001 03:31p 5.0.2195.3649 13,584 Infoadmn.dll
5/31/2001 03:31p 5.0.2195.3649 245,520 Infocomm.dll
5/31/2001 03:31p 5.0.2195.3649 62,736 Isatq.dll
5/30/2001 03:40p 5.0.2195.3651 6,928 Schmupd.exe
5/31/2001 03:32p 5.0.2195.3649 7,440 W3ctrs.dll
For IIS 4.0 (Windows NT Server 4.0)
A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that you determine are at risk of attack. Evaluate the computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to the computer. See the associated
Microsoft Security Bulletin to help determine the degree of risk. This hotfix may receive additional testing. If the computer is sufficiently at risk, we recommend that you apply this hotfix now.
To resolve this problem immediately, download the hotfix by following the instructions later in this article or contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:
Note In special cases, charges that are ordinarily incurred for support calls may be canceled, if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question. The following file is available for download from the Microsoft Download Center:
NOTE: After applying the patch, run the following commands to enable secure cookies (this example enables them for site 1):
cd %windir%\system32\inetsrv\adminsamples
adsutil set w3svc/1/AspKeepSessionIDSecure 1
For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:
119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.
The English version of this fix should have the following file attributes or later:
Date Time Size File name
-----------------------------------------
11/08/2000 03:29p 214,544 Adsiis.dll
11/09/2000 05:32p 330,672 Asp.dll
11/08/2000 02:39p 11,396 Httpext.h
11/09/2000 05:38p 55,904 Httpodbc.dll
11/08/2000 03:29p 98,912 Iischema.dll
11/08/2000 02:39p 28,851 Iiscnfg.h
11/08/2000 03:27p 185,792 Infocomm.dll
11/08/2000 03:32p 9,680 Schmupd.exe
11/09/2000 05:38p 38,256 Ssinc.dll
11/08/2000 03:28p 25,360 Sspifilt.dll
11/09/2000 05:37p 229,008 W3svc.dll
Windows NT Server version 4.0, Terminal Server Edition
To resolve this problem, obtain the Windows NT Server 4.0, Terminal Server Edition, Security Rollup Package (SRP). For additional information about the SRP, click the article number below
to view the article in the Microsoft Knowledge Base:
317636 Windows NT Server 4.0, Terminal Server Edition, Security Rollup Package
