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https://issues.apache.org/jira/browse/WICKET-4196?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13147593#comment-13147593
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Olivier Jaquemet commented on WICKET-4196:
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Duplicating this behavior is not on your control, your either developp the 
webapp or the container, rarely both. Therefore you must ensure security of 
your own development, and this will probably be done on both side whether or no 
you know it. And I would expect the app server to provide such basic security 
feature, like I expect application to follow security best practice.

Regarding the servletfilter to filter response content, this is an approach 
available in the OWASP ESAPI library with its SecurityWrapperReponse :
https://www.owasp.org/index.php/Category:OWASP_Enterprise_Security_API

Though output filtering is not enough, and I would strongly recommend proper 
filtering of input, not using a filter, but with a real semantic validation of 
parameter for each use case (eg \n\r are authorized for an article submitted 
thourhg textearea, not for a price submitted in a textfield)
                
> Accessing Wicket through AJP makes Wicket vulnerable to HTTP Response 
> Splitting Attack
> --------------------------------------------------------------------------------------
>
>                 Key: WICKET-4196
>                 URL: https://issues.apache.org/jira/browse/WICKET-4196
>             Project: Wicket
>          Issue Type: Bug
>          Components: wicket
>    Affects Versions: 1.4.19
>         Environment: CentOS 5.6, Apache HTTPD 2.2.3 with mod_jk 1.2.31 and 
> Apache Tomcat 6
>            Reporter: Gert-Jan Schouten
>            Assignee: Martin Grigorov
>              Labels: http, security
>             Fix For: 1.4.20
>
>
> Hello all,
> When having a Wicket application installed on Tomcat and you call that 
> application through HTTP, Wicket is protected against HTTP Response 
> Splitting. However, when you call Tomcat through AJP (for example through an 
> apache httpd proxy), HTTP Response Splitting becomes possible.
> To demonstrate, I created a simple application and called it through an AJP 
> proxy with the curl command:
> curl --max-redirs 0 -Dfoo 
> 'http:///myapp/home?wicket:bookmarkablePage=:org.apache.wicket.markup.html.pages.BrowserInfoPage&cto=Foobar%3f%0d%0aEvilHeader:%20SPLIT%2f-%0d%0aAnotherEvilHeader:%20HEADER'
> Note the '%0d%0a', a CRLF in the request. When calling Wicket through Tomcat, 
> these are replaced by spaces, but when calling Wicket through AJP, these are 
> left intact, getting us the following response:
> HTTP/1.1 302 Moved Temporarily
> Date: Wed, 02 Nov 2011 14:34:32 GMT
> Server: Apache
> Set-Cookie: JSESSIONID=4F403B53D091B40F6C3FBC2321A2E348.pub-app04; 
> Path=/myapp; HttpOnly Location: 
> http://<ip-address>/myapp/Foobar;jsessionid=4F403B53D091B40F6C3FBC2321A2E348.pub-app04?
> EvilHeader: SPLIT/-
> AnotherEvilHeader: HEADER
> Content-Length: 0
> Connection: close
> Content-Type: text/plain; charset=UTF-8
> Here we have 2 Evil Headers, that could be inserted by hackers by adding 
> %0d%0a to the get-request.
> The problem is that a hacker can now post URL's that look like they're going 
> to your site on some forum or in an email. But when the user actually clicks 
> on the link, a custom header could redirect the user to a malicious site. In 
> the example, I used "EvilHeader", but it could be any header, like an HTTP 
> 301 redirect. Basically, the hacker can include any header he wants in the 
> response that the user is going to get when he clicks on the link.
> Note we are not vulnerable if you connect directly to tomcat with HTTP - it 
> appears that the Coyote HTTP Connector is sanitising the HTTP headers and 
> replacing the CRLF with two spaces. You have to connect via Apache and AJP to 
> reproduce.
> For a more detailed description of HTTP Response Splitting (which is on the 
> OWASP list of security vulnerabilities), you can check:
> https://www.owasp.org/index.php/HTTP_Response_Splitting
> http://www.acunetix.com/vulnerabilities/CRLF-injectionHTTP-respon.htm
> http://packetstormsecurity.org/papers/general/whitepaper_httpresponse.pdf
> http://www.infosecwriters.com/text_resources/pdf/HTTP_Response.pdf 

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