How webservers react on specific characters

One thing I did during my Master Thesis a while ago, was to test how different webservers react to all kind of characters. One of the first things I tested was all characters represented by one byte (00 to FF) and their percent encoded equivalents (%00 to %FF). Of course the results may vary with other server versions, server configurations, server side code, client libraries or the sent HTTP headers. For example python’s urllib2 is not able to send 0A (line feed) in an URI (which makes sense). I tried to use standard components as best as I could. The webservers I used were:

  • An Apache 2.2.12 server (port 80), Ubuntu 9.10 machine with PHP 5.2.10
  • On the same machine a Tomcat 6.0.26 server (port 8080) with JSP (Java Server Pages)
  • On a Microsoft-IIS/6.0, Windows 2003 Server R2/SP2 with ASP.NET 2.0.50727 a script in C# on Virtualbox 3.1.8

So here are the main results in one picture:

character_table_for_testing_webservers

The ‘Name’ column means that the character was injected into the parameter name, e.g. na%00me=value&a=b. The fields with ‘S’ are explained in another section of my Master Thesis, but some of the time you can guess the behavior. E.g. I think you know what & stands for in GET parameters, right? 😉

This kind of information is useful when you are trying to write a fuzzer, that is more focused to do some tests that make sense. Would be interesting if this table is useful for someone else.

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