Andres, what is status of new XSS.py?
Where can we get it to test?:)
> your scenario looks good! But don't forget to notify user that xss.py
> have found potential XSS flaw (as info) if on the second stage we will
> not get good result from second response.
>
>> While trying to code the new xss.py I've found myself in a
>> situation where I see that it's difficult to cover all cases. Just to
>> make sure we're talking about the same thing, what we're trying to do
>> is to detect reflected XSS vulnerabilities with the lowest amount of
>> HTTP requests, lowest false positive and false negative rate.
>> This is the algorithm that I'm implementing and I would like to get your
>> feedback on:
>>
>> * Send hN<97>97"97'97(97)hN or a similar payload [0]
>> * Analyze the HTML response and identify WHERE in the HTML
>> structure the payload is echoed back and WHICH special characters were
>> allowed in each context.
> We can determine it by searching backwards for HTML special chars from
> echoed point.
>
>> The context is one or more of the following
>> places (taking into account that the input might be echoed more than
>> once):
>> TAG
>> ATTR_NAME
>> ATTR_DOUBLE_QUOTE
>> ATTR_SINGLE_QUOTE
> + simple ATTR without quotes?
>> TEXT
>> COMMENT
>> SCRIPT
>> CDATA
>> * This should give us a result similar to this:
>> [ (ATTR_NAME, ['<','>', '"' ...]) , (TEXT, ['"', '\'', '(', ')']) ]
>> * Then we could analyze that result and say: "For an XSS
>> vulnerability to appear in an ATTR_NAME I have to be able to send a
>> double quote". If it is possible in this case then the plugin should
>> send a specific payload for that case, something similar to --"
>> onload="foo()"--
>> * Finally, analyze the second response body and if there is an
>> attribute in one of the DOM objects that's called "onload" and it's
>> text is "foo()" then we have a XSS.
>>
>> Ideas? Does this cover all major cases? Should we have two or more
>> XSS detection algorithms and run them all (configurable by the user)?
> old one and new smart? I think we can regard new one as evolution
> version and save only it:)
>
>> [0] The problem with this are filters that say: "If special char X in
>> input then don't echo anything", where "X" might be "<" and that
>> affects our possibility to detect if any of the rest of the chars are
>> allowed
>>
>> Regards,
>>
>> On Thu, Feb 16, 2012 at 4:13 PM, Martin Holst Swende<[email protected]>
>> wrote:
>>> On 02/16/2012 07:54 PM, Andres Riancho wrote:
>>>> <RANDOM><>"'(); and find the same string in the response, that doesn't
>>>> confirm a XSS (there might be a filter that removes the inputs with
>>>> "script" in it)
>>> That may be true, but if input can break HTML context - it's a
>>> vulnerability. Actually finding
>>> an XSS is the next step - exploitation of said vulnerability. I think a
>>> better scheme would be to
>>> first discover the vulnerability with a minimum of probes then go to
>>> the second stage where
>>> a lot of requests can be staged (better to massively bombard 1% of all
>>> functions than to medium
>>> assault 95% :)).
>>>
>>>
>>>>> Another suggestion is to try determine context of echoed back string:
>>>>> html (including attributes), js, css and so on [1]. Good illustration
>>>>> of such behavior is RatProxy [2]
>>> The stuff I was working on earlier is better described here :
>>> http://sourceforge.net/mailarchive/message.php?msg_id=24638992
>>> Looking at the ratproxy code, I see that it does a somewhat similar
>>> thing (but probably with more cleverness). It tries to determine the
>>> html context of the injection. I think the XSS plugin should do those
>>> steps as a preliminary, then move on to exploitaition (which I never
>>> implemented in my final version :
>>> http://sourceforge.net/mailarchive/message.php?msg_id=24682898 ) .
>>>
>>> Cheers,
>>> Martin
>>>
>>>
>>>> RatProxy's code is crazy, reading through it give me nightmares ;)
>>>> Just read through the XSS context detection [0] and I have some
>>>> concerns about how well that would work in real scenarios. What I was
>>>> trying to do in my code is:
>>>>
>>>> * Send the payload
>>>> * Get the HTML response DOM
>>>> * Iterate through the DOM items and verify (based on the DOM
>>>> objects) where I get the string echoed back
>>>>
>>>> I was just working on that last week, there are some issues with
>>>> the code I was working on so I simply left it in my local box. I'll
>>>> work some more today and send it in this email thread.
>>>>
>>>> [0] http://code.google.com/p/ratproxy/source/browse/trunk/ratproxy.c#428
>>>>
>>>>> [0]
>>>>> http://w3af.svn.sourceforge.net/viewvc/w3af/trunk/plugins/audit/xss.py?view=markup
>>>>> [1]
>>>>> https://www.owasp.org/index.php/XSS_%28Cross_Site_Scripting%29_Prevention_Cheat_Sheet
>>>>> [2] http://code.google.com/p/ratproxy/source/browse/trunk/ratproxy.c
>>>>>
>>>>> --
>>>>> Taras
>>>>> http://oxdef.info
>>>>>
>>>>> ------------------------------------------------------------------------------
>>>>> Virtualization& Cloud Management Using Capacity Planning
>>>>> Cloud computing makes use of virtualization - but cloud computing
>>>>> also focuses on allowing computing to be delivered as a service.
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>>>>> _______________________________________________
>>>>> W3af-develop mailing list
>>>>> [email protected]
>>>>> https://lists.sourceforge.net/lists/listinfo/w3af-develop
>>>>
>>>>
>>>
>>>
>>> ------------------------------------------------------------------------------
>>> Virtualization& Cloud Management Using Capacity Planning
>>> Cloud computing makes use of virtualization - but cloud computing
>>> also focuses on allowing computing to be delivered as a service.
>>> http://www.accelacomm.com/jaw/sfnl/114/51521223/
>>> _______________________________________________
>>> W3af-develop mailing list
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>>
>>
>>
>
>
--
Taras
http://oxdef.info
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