[cl-weblocks-devel] Re: #45: Don't use gensym for actions to avoid XSS attacks

[Vyacheslav Akhmechet]

On 8/1/07, Alexander Kjeldaas <alexander.kjeldaas at 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. I'll change the ticket accordingly.

P.S. Could you use weblocks at googlegroups.com (or the UI interface)
instead of cl-weblocks-devel?