Security Testing/Debugging

From Rich Helton’s October 2010 C# Web Security

Security Testing-FXCop

-CAT.NET-Nunit

-HTMLUnit-Seleniumin

White Box Testing

White-Box testing is testing the system based on the internal perspective of the system.

In this case, this is also known as Static Analysis. These tools can find issues with the source code before

the code is actually executed. A list of tools can be found at

http://en.wikipedia.org/wiki/List_of_tools_for_static_code_analysis

CAT.NET(A plugin that can be added from the Windows SDK)

CAT.NET can be used with Visual Studio to analyze the current solution, here is a Visual Studio 2008 popup after selecting Tools->CAT.NET Analysis Tool from the menu:

CAT.NET(After pushing the Excel report button)

FXCop

CAT.NET rules can can be run in FXCop instead of Visual Studio.

FXCop examines the assemblies and object code and not the source. It can be downloaded as part of the Windows SDK.

NUNIT

White-Box testing is testing the system based on the internal perspective of the system.

See www.nunit.org These tools can find issues with the source code before

the code is actually executed. A list of tools can be found at

http://en.wikipedia.org/wiki/List_of_tools_for_static_code_analysis

NUNIT

Headless Browser

Headless Browser Automation Can replicate a real world browser. Can automate the test. Provides low-level control over the HTML and HTTP. Reference

http://blog.stevensanderson.com/2010/03/30/using-htmlunit-on-net-for-headless-browser-automation/

HTMLUnit steps

Download HTMLUnit http://sourceforge.net/projects/htmlunit/

Download IKVM http://sourceforge.net/projects/ikvm/files/

Create the HTMLUnit DLL: Run “ikvmc –out:htmlunit-2.7.dll *.jar”

Include the htmlunit, IKVM.OpenJDK, and nunit dll’s in the external assemblies.

Can automate the test. Provides low-level control over the HTML and HTTP. Reference

http://blog.stevensanderson.com/2010/03/30/using-htmlunit-on-net-for-headless-browser-automation/

What about the HTML?

HTTPUnit is great for HTTP Requests and Responses, but what if I want to parse the HTML code directly from the Web Server and examine the HTML before doing any work.

HTMLUnit allows a “getPage()” routine to examine the HTML source code. This allows the walking through of “HREF”, images, and others

pieces of the HTML code before executing on the item.

Selenium IDE is another Open Source concept that is a Integrated Development Environment running on top of the FireFox browser as a plugin. This allows a recording of the browser actions that can be played

back execute buttons being pushed and actions inside the browser. Assertions can be executed on the HTML pages itself for checking

specific information. The test itself can be exported into Junit Java code to execute in Java.

HtmlUnit on C#

HtmlUnit on C# (Nunit Test)(Under Construction page)

HtmlUnit on C# (Nunit Test)(Page not found)

Selenium IDE

Selenium IDE is another Open Source concept that is a Integrated Development Environment running on top of the FireFox browser as a plugin.

Supports load testing. This allows a recording of the browser actions that can be

played back execute buttons being pushed and actions inside the browser.

Assertions can be executed on the HTML pages itself for checking specific information.

The test itself can be exported into Java, .NET, Perl, Ruby, etc, and then code to execute the tests in that language.

Selenium IDE Test

Does the framework matter?

JWebUnit wraps both HTMLUnit and Selenium so that code can be written for either framework using a unified framwork.

This way code can once in a single framework and executed using multiple HTML frameworks. http://jwebunit.sourceforge.net/

Security Debugging-Logging

-Exceptions-Log4Net

-NLog-Error Pages

Has my system been compromised?

Logging and Error handling is one of the most important concept in Security.

When an incident happens, the first questions are always “How did they get in?” and “What data was compromised?”.

The least favorite answer is usually “No one knows.” With efficient logging of authorization, access to secure

information, and any anomalous interaction with the system, a proper recovery of the system is usually insured.

The logs should be store into a different system in case the Web system is ever compromised, one where the Web system sends them but never asks for them back.

Logging is a fundamental API that comes with the Java and .NET languages.

Logging the C# way….

using System;

using System.Diagnostics;

class EventLogExample

{

static void Main(string[] args)

{

string sSource = "my warning message";

string sLog = "Application";

string sEvent = "Sample Event";

if (!EventLog.SourceExists(sSource))

EventLog.CreateEventSource(sSource, sLog);

EventLog.WriteEntry(sSource, sEvent);

EventLog.WriteEntry(sSource, sEvent,

EventLogEntryType.Warning, 234);

}

}

The C# Logger output….

Exception Handling

Exception handling has helped debugging immensely. It allows a programmer to code for anomalies and handle a bizarre behavior.

There are 3 components of handling an exception, and they are the “try”, “catch” and “finally” blocks.

The “try” block will throw an exception from normal code, the “catch” block will catch the exception and handle it, and the “finally” block will process the cleanup afterwards.

The “catch” block can log the anomaly, stop the program, or process it in a hundred different ways.

You can write your own custom exception classes to trace specific pieces of code.

C# Exception Handling code….

class TestException{

static void Main(string[] args){

StreamReader myReader = null;

try{

// constructor will throw FileNotFoundException

myReader = new StreamReader("IamNotHere.txt");

}catch (FileNotFoundException e){

Console.WriteLine("FileNotFoundException was {0}", e.Message);

}catch (IOException e){

Console.WriteLine("IOException was {0}" + e.Message);

}finally{

if (myReader != null){

try{

myReader.Close();

}catch (IOException e){

Console.WriteLine("IOException was {0}" + e.Message);}}}}}

Output-> FileNotFoundException was Could not find file ‘C:\IamNotHere.txt'.

Log4net

The previous logging and exception handling example has many hard coded pieces. Log4Net offers more de-coupling by being separated as highly configurable framework.

http://logging.apache.org/log4net/ Even though the basic CLR logging framework can

accept changes on destination through its Handler in the “logging.properties”, Log4Net offers more advanced features in its XML use of its Appender class.

Log4Net supports XML configuration and a text configuration in log4Net.properties.

Log4Net supports Appenders that will append the logs to databases, emails, files, etc. http://logging.apache.org/log4net/release/config-examples.html

Log4Net ASP.NET code

Log4j Console output

Adding an Appender #1

Let’s read the XML Appender from app.config. Change the BasicConfigurator to XmlConfigurator:

Adding an Appender #2

Add app.config for "c:\\Log\\log.txt”:

Adding an Appender Running

Reading "c:\\Log\\log.txt”:

NLog

Nlog is similar to Log4Net. The difference is that Log4Net is a .Net version of Log4J and is a framework. NLog is a plugin to Visual Studio with templates.

http://nlog-project.org/

NLog

Adding log configuration with Visual 2010 plugin:

NLog

When debugging from VS2010, the default logging directory maps to C:\Program Files\Common Files\Microsoft Shared\DevServer\10.0 .

This Nlog.config will append the logger in to a file named after the classname, i.e Webapplication1._Default.txt:

Nlog code

From the WebApplication1 Class, Default.aspx.cs code:

Nlog log file

Printing the Webapplication1._Default.txt:

Error Pages

Default Error pages may display unintentional information. For instance, some error pages may display database information in an exception.

An error page giving details, like a database or table name, may be more than enough to give an attacker enough information launch an attack at the website.

To correct bad error handling in pages, Tomcat, Struts and other Web engines will allow default configurations to throw a specific error page for any unknown exceptions. For instance, many Web Application Firewalls (WAFs) will generate a error page 500 “Internal Server Error” for blocking an attack.

Hackme Books(Bad error handling)

Send something more generic(based on business input)

Web Error pages….

Many web sites use the default error pages that show the user exceptions and even exceptions into the database. The database exceptions have a tendency to display table names and invalid SQL statements that can be used for further probing.

To send all errors to a custom Error page, the web.config file for IIS:

<customErrors mode="On"

defaultRedirect="errors/ErrorPage.aspx"></customErrors>

Custom Errors in ASP.NET

A good resource on the issue is http://www.codeproject.com/KB/aspnet/customerrorsinaspnet.aspx

The idea is to redirect the error to a generic error.html page by the web.config configuration.

Send something more generic(based on business input)