fyi there's a couple of kb's on this kind of thing Q184717 - AspEnableParentPaths MetaBase Property Should Be Set To False as well as one on removing samples. also note, that the exair sample (which is NOT installed by default) also has showcode functionality. Cheers, MH IIS Security PM -----Original Message----- From: Weld Pond [mailto:weldat_private] Sent: Friday, May 07, 1999 7:29 AM To: BUGTRAQat_private Subject: L0pht Advisory: NT IIS 4.0 - showcode file viewing vulnerability L0pht Security Advisory ------------- URL Origin: http://www.l0pht.com/advisories.html Release Date: May 7th, 1999 Application: Microsoft IIS 4.0 Web Server Severity: Web users can view ASP source code and other sensitive files on the web server Author: weldat_private Operating Sys: Microsoft NT Server 4.0 -------------- I. Description Internet Information Server (IIS) 4.0 ships with a set of sample files to help web developers learn about Active Server Pages (ASP). One of these sample files, showcode.asp, is designed to view the source code of the sample applications via a web browser. The showcode.asp file does inadequate security checking and allows anyone with a web browser to view the contents of any text file on the web server. This includes files that are outside of the document root of the web server. Many ecommerce web servers store transaction logs and other customer information such as credit card numbers, shipping addresses, and purchase information in text files on the web server. This is the type of data that could be accessed with this vulnerability. The L0pht would like to thank Parcens for doing the initial research on this problem. II. Details The showcode.asp file is installed by default at the URL: http://www.someserver.com/msadc/Samples/SELECTOR/showcode.asp It takes 1 argument in the URL, which is the file to view. The format of this argument is: source=/path/filename So to view the contents of the showcode.asp file itself the URL would be: http://www.someserver.com/msadc/Samples/SELECTOR/showcode.asp?source=/msadc/ Samples/SELECTOR/showcode.asp This looks like a fairly dangerous sample file. It can view the contents of files on the system. The author of the ASP file added a security check to only allow the viewing of the sample files which were in the '/msadc' directory on the system. The problem is the security check does not test for the '..' characters within the URL. The only checking done is if the URL contains the string '/msadc/'. This allows URLs to be created that view, not only files outside of the samples directory, but files anywhere on the entire file system that the web server's document root is on. For example, a URL that will view the contents of the boot.ini file, which is in the root directory of an NT system is: http://www.someserver.com/msadc/Samples/SELECTOR/showcode.asp?source=/msadc/ Samples/../../../../../boot.ini This URL requires that IIS 4.0 was installed in its default location. III. Solution For production servers, sample files should never be installed so delete the entire /msadc/samples directory. If you must have the showcode.asp capability on development servers the showcode.asp file should be modified to test for URLs with '..' in them and deny those requests. For specific questions about this advisory, please contact weldat_private --------------- For more L0pht (that's L - zero - P - H - T) advisories check out: http://www.l0pht.com/advisories.html ---------------
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