OSEC

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From: Crist Clark (crist.clarkGLOBALSTAR.COM)
Date: Thu Apr 26 2001 - 18:03:55 CDT

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    John Bumgarner wrote:
    >
    > Tony,
    >
    > Here the information concerning converting to IP address to a number string:
    >
    > With some firewall implementations, you can bypass the URL filtering rules:
    >
    > Obtain IP address of a filtered URL: http://www.netaddress.com or
    > http://204.68.24.100
    > Convert IP address to binary using calc.exe - 11001100 01000100 00011000
    > 01100100
    > Concatenate the binary together 11001100010001000001100001100100
    > Convert this number to decimal using calc.exe - 3427014756
    > Enter this in your browser - http://3427014756

      100 + 24*256 + 68*256^2 + 204*256^3 = 3427014756

    Is a lot less work than doing the middle conversion.

    Actually, (for those who think in reverse-Polish notation, this
    is the obvious way), the easiest is more like,

      ((((204*256) + 68)*256 + 24)*256 + 100 = 3427014756

    On calc.exe, keystrokes are like,

      204*256+68<enter>*256+24<enter>*256+100<enter>

    Of course, another fun way to get by stoopid filters that don't really
    understand URLs is to,

      % printf "0%o.0%o.0%o.0%o\n" 204 68 24 100
      0314.0104.030.0144

    To give,

      http://0314.0104.030.0144/

    Or even just convert 3427014756 to octal,

      http://031421014144/

    Or how about mix and match,

      http://204.0104.24.0144/

    Or,

      http://204.0104.6244/
      http://204.0104.014144/
      .
      .
      .

    There are a _lot_ of ways to write an IP address in a URL.

    --
    Crist J. Clark                                Network Security Engineer
    crist.clarkglobalstar.com                    Globalstar, L.P.
    (408) 933-4387                                FAX: (408) 933-4926
    

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