[jsr-314-open-mirror] [jsr-314-open] [Spec-869-Specify CSRF Solution] PROPOSAL(s)

[Blake Sullivan]

  Roger,

Di you answer Alexander's question regarding whether this feature is 
even necessary?  In the current releases, with no explicit CSRF 
defenses, we have attacks against:
1) GET attack
2) POST attack against a page with token state saving
3) POST attack against a page with client state saving

1) For GET attacks, it appears that we are saying that we aren't going 
to defend against these anyway for this release.

2) For POST attacks against a page with token state saving.  As long as 
the view state token is cryptographically strong, the attacker can't 
guess the token anyway.  At that point, it comes down to what the 
behavior is for a request that has an invalid token--we can either 
return an error page or we can treat the request as a GET.  If we treat 
the request as a GET, we are in 1

3) For POST attacks against a page with client state saving, as long as 
attackers can't forge the client state, they can't do anything.  Since, 
they can't, we're safe here as well.

Therefore, it isn't clear what the feature is buying us.  If there is no 
clear need for the feature, it should not be added to the specification.

-- Blake Sullivan


On 9/21/10 10:15 AM, Roger Kitain wrote:
>
> There are two proposals for enhancing CSRF attacks in JSF.  We need to 
> pick one.
>
> Proposal 1: Form Action URL Approach (Approach provided by Kito Mann)
>
> This approach does the following:      - Token is generated on the 
> server consisting (minimally) of a randomly generated "secret key
>      (stored in session).
>    - ViewHandler.getActionURL method must include the token parameter
>      named "javax.faces.Token", and whose value is the token value.
>    - At render time this token will be included in Form's action URL - 
> and it will be
>      posted back to the server.
>    - Restore View Phase processing compares the incoming token request 
> parameter value
>      with the token value generated from the secret key in the session.
>
> Spec Document Modifications:
>
> Section 7.5.1:
>
> getActionURL:
>
> "The URL must contain the parameter constant defined by 
> ResponseStateManager.VIEW_TOKEN_PARAM
> The value of this parameter must be a cryptographically produced value 
> minimally consisting
> of a "secret key". The "secret key" is a random generated value that 
> was stored in the session
> (preferably around session creation time).  Implementations may also 
> choose to combine other
> values with the secret key to produce a more complex token."
>
> Section 2.2.1
>
>  "Verify the "javax.faces.Token" request parameter value is the same 
> as the token value generated
>    from the "secret key" stored in the session.  If the values do not 
> match, throw a meaningful
>    exception."
>
>
> Proposal 2: Form Hidden Field Approach
>
> This approach is similar to Approach 1, except a Form hidden field 
> "javax.faces.Token"
> is used instead of appending to the Form's Action URL.
>
> Spec Document Modifications:
>
> Standard RenderKit Docs
>
> - Form Rendering
>
> "Render a hidden field named "javax.faces.Token" using the 
> ResponseStateManager.VIEW_TOKEN_PARAM
>  constant.  The value of this hidden field is a cryptographically 
> produced value that must at least
>  consist of a "secret key".  The "secret key" is a random generated 
> value that was stored in the
>  session (preferably around session creation time).  Implementations 
> may also choose to combine
>  other values with the secret key to produce a more complex token."
>
> Specification Document
>
> Section 2.2.1
>   "Verify the "javax.faces.Token" request parameter value is the same 
> as the token value generated
>    from the "secret key" stored in the session.  If the values do not 
> match, throw a FacesException.
>
>
> For both approaches see:
>
>
> [1] 
> https://javaserverfaces-spec-public.dev.java.net/issues/show_bug.cgi?id=869
>
> Look at the two latest change bundles attached to the issue.
>
> Please review by COB Friday as we have no time left for 2.1.
>
> Kudos to Kito Mann for helping out with the implementation.
>
> -roger