Perl.exe and IIS security advisory

From: mnemonix (mnemonixat_private)
Date: Fri Jan 22 1999 - 12:58:33 PST

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    There is a problem with perl.exe similar to the issue discussed in KB
    article Q193689 where the physical disk location of a virtual web directory
    can be ascertained.
    
    In all versions of IIS, where a  website has been configured to interpret
    perl scripts using the perl executable (perl.exe), a problem exists where a
    request for a non-existent file will return the physical location on a disk
    of a web directory. A request for:
    
    http://www.server.com/scripts/no-such-file.pl
    
    will return information similar to the following:
    
    CGI Error
    The specified CGI application misbehaved by not returning a complete set of
    HTTP headers. The headers it did return are:
    Can't open perl script "C:\InetPub\scripts\no-such-file.pl": No such file or
    directory
    
    Previously this was a problem when requesting a non-existent .IDC file but
    this was resolved with Service Pack 4.
    
    To resolve this problem in IIS 2 and 3 you can use perlis.dll, the ISAPI
    version of the perl interpreter,  instead of the executable. You can  use
    this in IIS 4 as well, however, if you still want to use perl.exe you can
    configure IIS to check for the file's existence.
    
    NTInfoScan, downloadable from
    http://www.infowar.co.uk/mnemonix/ntinfoscan.htm , checks for this problem
    and the .IDC issue as well as other security checks.
    
    Cheers,
    David Litchfield
    



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