#45: Don't use gensym for actions to avoid XSS attacks ------------------------+--------------------------------------------------- Reporter: anonymous | Owner: sakhmechet Type: defect | Status: new Priority: medium | Milestone: 0.1 Component: weblocks | Version: pre-0.1 Resolution: | Keywords: security ------------------------+--------------------------------------------------- Changes (by sakhmechet):
* milestone: 0.2 => 0.1 * priority: low => medium
Comment:
On 8/1/07, Alexander Kjeldaas alexander.kjeldaas@gmail.com wrote:
One user accessing another user's stuff is not the attack I am
describing.
The attack I am describing is a purely destructive *someone making a
user do
stuff* attack. Get a user to do something that they didn't really
intend to
do. In order to do this, one only need to get the user to click on a
link
that has a guessed action in it.
I see.
A multistep solution that comes to mind is this: 1. Split actions into destructive actions that modify back-end data, and 'pure' actions. 2. Ensure that destructive actions are only executed if the HTTP request is initiated via POST. I'll have to double check, but I think browsers don't allow forms to send POST requests to domains different from where HTML originally came from. 3. Programmers will sometimes make mistakes and create destructive actions as regular ones (we could prevent them from doing it in Haskell, but unfortunately not in Lisp). This means all actions, not just destructive ones must have URLs that are hard to guess.
I'm not sure if I want to implement #1 (and therefore #2) because it forces a programmer to choose between two ways of creating an action. On the other hand this might be a good thing - this is something that needs to be thought out.
#3 should definetly be implemented.