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Few common web.xml misconfigurations-Part I

While doing code review usually I find various misconfigurations. I am trying to compile them here.
Although they might not be a comprehensive list and something I may miss, but will touch most of the common points: Refer-http://software-security.sans.org

1. Authentication & Authorization Bypass:

<security-constraint>
<web-resource-collection>
<web-resource-name>secure</web-resource-name>
<url-pattern>/secure/*</url-pattern>
<http-method>GET</http-method>
<http-method>POST</http-method>
</web-resource-collection>
<auth-constraint>
<role-name>admin</role-name>
</auth-constraint>
</security-constraint>

The above configuration shows how to setup web-based control. Here the assumption is that the everything in 'secure' directory must be accessible by 'admin' user only by using methods listed in tags i.e, GET and POST. No other methods should be allowed. But that is not the case!
In fact any HTTP method which is not explicitly enlisted here (HEAD,or any junk values like, JEFF,TEST etc) can be used to access the resources under 'secure' directory. It's also called HTTP verb tampering. Arshan Dabirsiaghi has a nice paper that summarizes this issue.
The solutions is just simply remove all above elements from above code and configuration will be properly applied to all requests.

2. Absence of Secure Flag: Sometimes some websites revert back to non-SSL connection or can be accessed over non-SSL connections (http://). This leaves the sessionID vulnerable to capturing which may lead to session hijacking. The sessionID must be marked with 'secure' flag.
In order to do that the following configuration can be defined in web.xml:

<session-config>
<cookie-config>
<secure>true</secure>
</cookie-config>
</session-config>


3. Customized Error pages are not defined: Sometimes the application faces unexpected error and is not able to handle it properly following which it displays it directly to the end user in form of stack traces or other signs. This may be a useful information for an adversary to launch attacks as it may reveal sensitive information about the code/platform/technology of the application and also tell about the application's input validation strategies. The developer should avoid these errors to be leaked to the end user. They should define some custom pages in the web.xml so that in case of error the applications should present a generic and customized page to the user instead of specific information-no matter what error occurs.
The following setting can be used:
Using the following configuration a nice error page will be displayed whenever the application responds with an HTTP 500 error. You can add additional entries for other HTTP status codes as well.

<error-page>
<error-code>500</error-code>
<location>/path/to/error.jsp</location>
</error-page>

Comments

Great information.Great thoughts.It is very important to know all the people.It is great and happy to read this blogs.Thanks for making it.
Anonymous said…
Here is the original article published in Aug 2010. Plagiarism? Decide for yourself:

http://software-security.sans.org/blog/2010/08/11/security-misconfigurations-java-webxml-files

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