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   <H1>[99s-extend] Reading body_qs multiple times</H1>
    <B>rambocoder</B> 
    <A HREF="mailto:extend%40lists.ninenines.eu?Subject=Re%3A%20%5B99s-extend%5D%20Reading%20body_qs%20multiple%20times&In-Reply-To=%3CCAJ0zLRPYmtXEMd6G78D5Dc9-ebrdRzxyWmVHnzGE%3DYrH%2BhA6fg%40mail.gmail.com%3E"
       TITLE="[99s-extend] Reading body_qs multiple times">erlang at rambocoder.com
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    <I>Tue Apr 16 02:13:44 CEST 2013</I>
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<PRE>Loic,

After giving the CSRF middleware some thought and reading
<A HREF="https://www.owasp.org/index.php/Cross-Site_Request_Forgery_(CSRF">https://www.owasp.org/index.php/Cross-Site_Request_Forgery_(CSRF</A>)_Prevention_Cheat_Sheet#Disclosure_of_Token_in_URL
I
came to conclusion that it is best to just not create the middleware and
instead deal with CSRF on as needed basis.

I know that node's Connect middleware
<A HREF="http://www.senchalabs.org/connect/csrf.html#defaultValue">http://www.senchalabs.org/connect/csrf.html#defaultValue</A> for example allows
for the csrf token to be passed as a query string parameter, however, the
OWASP article made me think that it is not the most secure approach.

For example, AngularJS <A HREF="http://docs.angularjs.org/api/ng.$http">http://docs.angularjs.org/api/ng.$http</A> has a section
on how their AJAX component behaves to do CSRF out of the box, and they are
talking about the server sending a cookie XSRF-TOKEN that is not HttpOnly.
That makes me realize that csrf is a process more than just slapping some
middleware into the pipeline.

Btw, I noticed that when the result of the middleware execute function is:
{error, StatusCode, Req}
if I set the reply on the request via cowboy_req:reply before returning the
{error.. , the status code of that reply will be used.

Such as:
{ok, Req3} = cowboy_req:reply(403, [], &quot;Invalid CSRF Token.&quot;, Req2),
{error, 500, Req3}; % 500 is ignored, 403 is returned

Is that by design?

Sincerely,

rambocoder



On Mon, Apr 15, 2013 at 4:47 PM, Lo&#239;c Hoguin &lt;<A HREF="https://lists.ninenines.eu/listinfo/extend">essen at ninenines.eu</A>&gt; wrote:

&gt;<i> Why not just put the token in the URL instead? if it's CSRF then it's
</I>&gt;<i> probably used only once and only for POST and the like, so not cached or
</I>&gt;<i> anything.
</I>&gt;<i>
</I>&gt;<i>
</I>&gt;<i> On 04/15/2013 10:45 PM, rambocoder wrote:
</I>&gt;<i>
</I>&gt;&gt;<i> Hello group,
</I>&gt;&gt;<i>
</I>&gt;&gt;<i> I am trying to put together a CSRF middleware
</I>&gt;&gt;<i> <A HREF="https://github.com/rambocoder/**stable/commit/**">https://github.com/rambocoder/**stable/commit/**</A>
</I>&gt;&gt;<i> b26980d292ac42aadfe9921a961436**e28cdbb693&lt;<A HREF="https://github.com/rambocoder/stable/commit/b26980d292ac42aadfe9921a961436e28cdbb693">https://github.com/rambocoder/stable/commit/b26980d292ac42aadfe9921a961436e28cdbb693</A>&gt;and
</I>&gt;&gt;<i> if the body of the request contains &quot;_csrf&quot; token, I check to make sure
</I>&gt;&gt;<i> it matches the csrf token in the session.
</I>&gt;&gt;<i>
</I>&gt;&gt;<i> Currently I am doing it in middleware using cowboy_req:body_qs/1 however
</I>&gt;&gt;<i> when in the handler I need to read another body parameter, such as in
</I>&gt;&gt;<i> the rest_pastebin example:
</I>&gt;&gt;<i>
</I>&gt;&gt;<i> {ok, BodyQs, Req3} = cowboy_req:body_qs(Req),
</I>&gt;&gt;<i> Paste = proplists:get_value(&lt;&lt;&quot;paste&quot;&gt;**&gt;, BodyQs),
</I>&gt;&gt;<i>
</I>&gt;&gt;<i> cowboy_req:body_qs/1 returns [] due to the body of the request being
</I>&gt;&gt;<i> already read {body_state,done}
</I>&gt;&gt;<i>
</I>&gt;&gt;<i> Is it pointless to have the type of CSRF middleware that I am writing
</I>&gt;&gt;<i> and just do the CSRF in the handler's callback, where I can deal with
</I>&gt;&gt;<i> all the body_qs at once?
</I>&gt;&gt;<i>
</I>&gt;&gt;<i> Thank you,
</I>&gt;&gt;<i>
</I>&gt;&gt;<i> rambocoder
</I>&gt;&gt;<i>
</I>&gt;&gt;<i>
</I>&gt;&gt;<i> ______________________________**_________________
</I>&gt;&gt;<i> Extend mailing list
</I>&gt;&gt;<i> <A HREF="https://lists.ninenines.eu/listinfo/extend">Extend at lists.ninenines.eu</A>
</I>&gt;&gt;<i> <A HREF="http://lists.ninenines.eu:81/**listinfo/extend&lt;http://lists.ninenines.eu:81/listinfo/extend">http://lists.ninenines.eu:81/**listinfo/extend&lt;http://lists.ninenines.eu:81/listinfo/extend</A>&gt;
</I>&gt;&gt;<i>
</I>&gt;&gt;<i>
</I>&gt;<i>
</I>&gt;<i> --
</I>&gt;<i> Lo&#271;c Hoguin
</I>&gt;<i> Erlang Cowboy
</I>&gt;<i> Nine Nines
</I>&gt;<i> <A HREF="http://ninenines.eu">http://ninenines.eu</A>
</I>&gt;<i>
</I>&gt;<i>
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