[VIGILANTE-2001001] ASP source code retrieved with Unicode extens ion

[Hack Kampbjørn <hack.kampbjorn () vigilante com>]

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http://www.vigilante.com/inetsecurity/advisories/VIGILANTE-20010001.htm


Title:
        ASP source code retrieved with Unicode extension
Advisory Code:
        VIGILANTE-2001001
Author:
        Hack Kampbjørn
Release Date:
        2001-06-22.

System affected:
        Windows NT4 + IIS4 + sp3 (on FAT)
        Windows 2000 Server (on FAT)
        Windows 2000 Server + sp2 (on FAT)
Systems not affected:
        Windows NT4 + IIS4 + sp3 (on NTFS)
        Windows 2000 Server (on NTFS)
        Windows 2000 Server + sp2 (on NTFS)

The problem:
        Active Server Pages (ASP) are web scripts that are executed on
        the Internet Information Server (IIS) and the result is send to
        the user. IIS determines if a file is an ASP script or not by
        the .asp extension. 
        With Unicode there are many ways the asp extension can be
        encoded. On FAT file systems some of them will not be
        recognized as an ASP script by IIS and executed on the server
        but instead IIS will disclouse the source code of the script.

Vendor status:
        Microsoft contacted 2001-05-28 and responded the same day:
        "The Microsoft Security Response Center has investigated the
        report, but we note that the problem as reported would only
        affect an IIS server that has been configured to use a FAT
        volume.  However, by design, FAT doesn't provide a security
        mechanism, and it's never an appropriate file system to use on
        a production web server.  Instead, as discussed in Microsoft's
        best practices guides and security checklists
        (http://www.microsoft.com/technet/security/tools.asp),
        production servers should always use NTFS volumes. The reported
        problem does not affect systems using NTFS".

Vulnerability Assessment:
        A test-case to detect this vulnerability was added to
        SecureScan NX on June 22, 2001

Fix:
        As a workaround convert the file system to NTFS. And consider
        removing reading access right for the IUSR_<hostname> from ASP
        scripts (only giving IUSR_<hostname> execute rights)
        In general follow Microsoft's Security Best Practices:
          http://www.microsoft.com/technet/security/bestprac.asp
        Internet Information Server 4.0 Security Checklist:
          http://www.microsoft.com/technet/security/iischk.asp
        or Secure Internet Information Services 5 Checklist:
          http://www.microsoft.com/technet/security/iis5chk.asp



Copyright VIGILANTe.com, Inc. 2001-06-22

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        IS condition. There are NO warranties with regard to this
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        Please send suggestions, updates, and comments to
        isis () vigilante com 

VIGILANTe Vulnerability Disclosure Policy:
http://www.vigilante.com/inetsecurity/advisories/vulnerability_disclosure_po
licy.htm

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