18 Mar
2010
18 Mar
'10
4:47 a.m.
On 03/16/2010 09:33 AM, Caleb James DeLisle wrote:
I don't want this proposal to die because of
unnecessary noise which I introduced,
I have thought about it and I am in agreement with the general idea of sending the user a
hash which
must be returned with the post in order for the data to be saved.
I don't like adding code to xwiki-core so I suggest this be made into a component.
We would need 2 functions:
String getToken()
boolean isTokenValid(String token)
getToken uses org.xwiki.bridge.DocumentAccessBridge.getCurrentUser() to get the user who
called it
and the user name is stored in a HashMap of <String, String> with a random string
of text.
If getToken finds a token already in the map, it returns that token (so it may be called
multiple times
in the generation of a page)
isTokenValid checks the current user against the token then removes the entry from the
HashMap so the token
may not be reused.
Did I understand the idea correctly that isTokenValid should be called
from all macros that modify data, but not from the old core directly? So
for example the SaveAction (which saves edited documents at the moment)
would not be protected for now, but the future action component would
also use isTokenValid at some point?
If a configuration parameter is specified to disable
the component, getToken returns "" and isTokenValid
returns true.
WDYT?
Caleb
Caleb James DeLisle wrote:
Sergiu Dumitriu wrote:
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On 03/10/2010 07:44 PM, Caleb James DeLisle
wrote:
I just did a few tests on iframes and I was wrong, they do have good same origin policy.
Caleb
Take a look at the "sammy is my hero"
worm, myspace sent a hash to the user like the one you propose,
the worm made the required get request to get the hash, then made the post along with the
hash.
What prevents javascript from opening the page with the hash in an iframe and then
reading in the iframe
to get the hash, then creating a form with the required data and posting it to the save
action?
If we were to combine a requirement for post requests with checking of the referrer
header, then we
would block links, forms and javascript based attacks leaving only an attack through
older versions
of flash which support referrer forgery and at this point the difficulty of the attack
becomes such that
we need to consider a wider array of attack vectors.
Sammy also required that XSS
is enabled.
Protecting from attacks originating in the wiki is kind of impossible at
the moment, since JS can be inserted anywhere, and there's no (nice) way
to prevent attacks from JS inside the application. As long as JS can be
inserted, an attacker can do all the steps that the client would do to
perform an action.
The secret token works as a prevention mechanism when the attack comes
from another site because the browser security model prevents the attack
code to read the form. Caleb
Alex Busenius wrote:
> Unfortunately, using POST requests instead of GET requests is not
> enough. It will not prevent attacks that use forms and/or JavaScript to
> generate POST requests.
>
> Alex
>
>
> On 03/09/2010 02:48 PM, Caleb James DeLisle wrote:
>> I had thought about proposing this myself but decided against it because it
seems
>> to me like a workaround for problems which can be solved in other ways.
>>
>> Suppose we were to add a check to the actions which alter data which made sure
the request method
>> was 'post' and made it configurable in one of the configuration files? We
would have
>> to look over the default skins for incorrect links and leave the configuration
>> option off by default for backward compatibility at least until the next major
version
>> but we could provide wiki operators the ability to prevent CSRF.
>>
>> Caleb
>>
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