Re: FireFox re-using HTTP2 connection to a wrong IP address & MITM attacks.

On Thu, 9 Jun 2016, [email protected] wrote:

> Forget about TLS for the moment.  FF will NOT reuse existing connection for 
> regular HTTP connection.  Why ?

A) Because Firefox doesn't do HTTP/2 at all without TLS

B) Without TLS there's no certificate that provides that extra hint so it 
gives the browser less confidence. But really, see (A).

> Because it would be wrong behaviour and will definitely lead to very easy 
> MITM attacks,

HTTP (*not HTTPS*) isn't exactly known for being effective againts MITM 
attacks!

> As you may see, RFC clearly states that valid certificate is an ADDITIONAL 
> condition.  In other words, if existing connection CAN be reused for HTTP, 
> only then you should check for additional requirement - certificate should 
> be valid.

So you're now arguing that if a browser would speak HTTP/2 over plain TCP you 
think it should reuse connections for this setup even when there's no certs 
involved?

That seems like a side track we don't need to take right now. Let's instead 
focus on what we think Firefox should and shouldn't do.

> In case of FF what happens is exactly the opposite - FF will not reuse the 
> connection for HTTP, but believe it's good for HTTPS.

Firefox speaks HTTP/1.1 over TCP and HTTP/2 over HTTPS, that's the bigger and 
important diference here.

I think we're mostly moving in circles. You think Firefox acts wrongly, and 
I've tried to explain the reasoning behind its behaviors. I think Firefox 
follows the spec both as written as well as in spirit.

I've not seen you explain how this causes actual real-life problems (in a 
scenario where you don't install a malicous party's CA cert yourself). Can you 
help me understand?

-- 

  / daniel.haxx.se