The Web Application Hacker’s Handbook Discovering and Exploiting Security Flaws

Chapter 4 

■

Mapping the Application

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File Extensions

File extensions used within URLs often disclose the platform or programming

language used to implement the relevant functionality. For example:

■■

asp

— Microsoft Active Server Pages

■■

aspx

— Microsoft ASP.NET

■■

jsp

— Java Server Pages 

■■

cfm

— Cold Fusion

■■

php

— the PHP language

■■

d2w

— WebSphere

■■

pl

— the Perl language

■■

py

— the Python language

■■

dll

— usually compiled native code (C or C++)

■■

nsf

or 

ntf

— Lotus Domino

Even if an application does not employ a particular file extension in its pub-

lished content, it is usually possible to verify whether the technology support-

ing that extension is implemented on the server. For example, if ASP.NET is

installed, requesting a nonexistent 

.aspx

file will return a customized error

page generated by the ASP.NET framework, as shown in Figure 4-7, whereas

requesting a nonexistent file with a different extension returns a generic error

message generated by the web server, as shown in Figure 4-8.

Figure 4-7:  A customized error page indicating that the ASP.NET platform is present 

on the server