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Re: breaking TLS (Was: Re: multiplexing -- don't do it)

From: Adrien W. de Croy <adrien@qbik.com>
Date: Mon, 02 Apr 2012 21:43:10 +0000
To: "Stephen Farrell" <stephen.farrell@cs.tcd.ie>, "Mike Belshe" <mike@belshe.com>
Cc: "Peter Lepeska" <bizzbyster@gmail.com>, "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
Message-Id: <emf8a96fcd-7d2d-4ebb-b155-41c45a75de81@boist>
  
  

------ Original Message ------
From: "Stephen Farrell" <stephen.farrell@cs.tcd.ie>
To: "Mike Belshe" <mike@belshe.com>
Cc: "Peter Lepeska" <bizzbyster@gmail.com>;"ietf-http-wg@w3.org" 
<ietf-http-wg@w3.org>
Sent: 3/04/2012 9:36:32 a.m.
Subject: breaking TLS (Was: Re: multiplexing -- don't do it)
>
>
>On 04/02/2012 10:20 PM, Mike Belshe wrote: 
>>I was trying to describe https to the proxy, which breaks the SSL, 
>>and then 
>>initiates a new SSL connection to FB. 
>>
>>I call this a "trusted proxy". The browser in this case must have 
>>explicitly specified the proxy to use and also that it is okay to let 
>>it 
>>break SSL. 
>
>TLS MITM has been proposed before and rejected. 
I don't think that's what Mike was proposing when he said break.
  
the proposal is that TLS would terminate on the proxy, then the client 
would additionally / optionally be able to specify that the proxy make 
an SSL connection to the server.
  
It's all explicit, no MITM, no underhandedness.
  
>
>
>Even for FB, but definitely for banking, I don't want that middlebox 
>getting my re-usable credentials and I don't see how to avoid that 
>problem. 
  
You're right, the proxy would still get this, which is why it would 
need to be trusted.  There's no other way.
  
This issue won't be going away.  Unless you think you can convince 
every boss/parent on the planet that their employees/kids should be 
able to do whatever they like.
>
>
>I do understand that there are percieved-real requirements here 
>for enterprise middleboxes to snoop but we've not gotten IETF 
>consensus to support that kind of feature in our protocols. 
  
sure we do.  2616 already contemplates and supports proxies - just not 
with https.  
  
>
>
>Stephen. 
>
>PS: I'm not angling for better http auth here. Even if we get that 
>there will be many passwords and other re-usable credentials in use 
>for pretty much ever and the argument against breaking TLS will 
>remain. 
  
Auth in fact may be the answer to the issue of trust for a server to 
place in a proxy (re the client cert issue).
  
There may not be a good answer for client certs, and it may be the only 
way to support them is to continue to tunnel.
  
At least they are not that prevalent so that in cases where they are 
required, tunneling can be allowed.
  
Adrien
>
>
>
>>
>>Mike 
>>
>>
>>
>>
>>>
>>>The proxy can still not see the facebook traffic in the clear so the 
>>>admin 
>>>will still either need to block facebook entirely or do a MITM. 
>>>
>>>Peter 
>>>
>>>On Mon, Apr 2, 2012 at 5:11 PM, Mike Belshe<mike@belshe.com> wrote: 
>>>
>>>>
>>>>
>>>>On Mon, Apr 2, 2012 at 2:08 PM, Adrien W. de 
>>>>Croy<adrien@qbik.com>wrote: 
>>>>
>>>>>
>>>>>------ Original Message ------ 
>>>>>From: "Mike Belshe"<mike@belshe.com> 
>>>>>To: "Adrien W. de Croy"<adrien@qbik.com> 
>>>>>Cc: "Amos Jeffries"<squid3@treenet.co.nz>;"ietf-http-wg@w3.org"< 
>>>>>ietf-http-wg@w3.org> 
>>>>>Sent: 3/04/2012 8:52:22 a.m. 
>>>>>Subject: Re: multiplexing -- don't do it 
>>>>>
>>>>>
>>>>>
>>>>>On Mon, Apr 2, 2012 at 1:43 PM, Adrien W. de Croy< 
>>>>><adrien@qbik.com> 
>>>>>adrien@qbik.com> wrote: 
>>>>>
>>>>>>
>>>>>>------ Original Message ------ 
>>>>>>From: "Mike Belshe"<mike@belshe.com>mike@belshe.com 
>>>>>>
>>>>>>
>>>>>>
>>>>>>On Mon, Apr 2, 2012 at 6:57 AM, Amos Jeffries< 
>>>>>><squid3@treenet.co.nz><squid3@treenet.co.nz> 
>>>>>>squid3@treenet.co.nz> wrote: 
>>>>>>
>>>>>>>On 1/04/2012 5:17 a.m., Adam Barth wrote: 
>>>>>>>
>>>>>>>On Sat, Mar 31, 2012 at 4:54 AM, Mark Nottingham wrote: 
>>>>>>>>
>>>>>>>>>On 31/03/2012, at 1:11 PM, Mike Belshe wrote: 
>>>>>>>>>
>>>>>>>>>For the record - nobody wants to avoid using port 80 for new 
>>>>>>>>>>protocols. I'd love to! There is no religious reason that we 
>>>>>>>>>>don't - its 
>>>>>>>>>>just that we know, for a fact, that we can't do it without 
>>>>>>>>>>subjecting a 
>>>>>>>>>>non-trivial number of users to hangs, data corruption, and 
>>>>>>>>>>other errors. 
>>>>>>>>>>  You might think its ok for someone else's browser to throw 
>>>>>>>>>>reliability out 
>>>>>>>>>>the window, but nobody at Microsoft, Google, or Mozilla has 
>>>>>>>>>>been willing to 
>>>>>>>>>>do that… 
>>>>>>>>>>
>>>>>>>>>Mike - 
>>>>>>>>>
>>>>>>>>>I don't disagree on any specific point (as I think you know), 
>>>>>>>>>but I 
>>>>>>>>>would observe that the errors you're talking about can 
>>>>>>>>>themselves be viewed 
>>>>>>>>>as transient. I.e., just because they occur in experiments 
>>>>>>>>>now, doesn't 
>>>>>>>>>necessarily mean that they won't be fixed in the 
>>>>>>>>>infrastructure in the 
>>>>>>>>>future -- especially if they generate a lot of support calls, 
>>>>>>>>>because they 
>>>>>>>>>break a lot MORE things than they do now. 
>>>>>>>>>
>>>>>>>>>Yes, there will be a period of pain, but I just wanted to 
>>>>>>>>>highlight 
>>>>>>>>>one of the potential differences between deploying a standard 
>>>>>>>>>and a 
>>>>>>>>>single-vendor effort. It's true that we can't go too far here; 
>>>>>>>>>if we 
>>>>>>>>>specify a protocol that breaks horribly 50% of the time, it 
>>>>>>>>>won't get 
>>>>>>>>>traction. However, if we have a good base population and 
>>>>>>>>>perhaps a good 
>>>>>>>>>fallback story, we *can* change things. 
>>>>>>>>>
>>>>>>>>That's not our experience as browser vendors. If browsers offer 
>>>>>>>>an 
>>>>>>>>HTTP/2.0 that has a bad user experience for 10% of users, then 
>>>>>>>>major 
>>>>>>>>sites (e.g., Twitter) won't adopt it. They don't want to punish 
>>>>>>>>their 
>>>>>>>>users any more than we do. 
>>>>>>>>
>>>>>>>>Worse, if they do adopt the new protocol, users who have 
>>>>>>>>trouble will 
>>>>>>>>try another browser (e.g., one that doesn't support HTTP/2.0 
>>>>>>>>such as 
>>>>>>>>IE 9), observe that it works, and blame the first browser for 
>>>>>>>>being 
>>>>>>>>buggy. The net result is that we lose a user and no pressure is 
>>>>>>>>exerted on the intermediaries who are causing the problem in 
>>>>>>>>the first 
>>>>>>>>place. 
>>>>>>>>
>>>>>>>>These are powerful market force that can't really be ignored. 
>>>>>>>>
>>>>>>>
>>>>>>>So the takeway there is pay attention to the intermediary people 
>>>>>>>when 
>>>>>>>they say something cant be implemented (or won't scale 
>>>>>>>reasonably). 
>>>>>>>
>>>>>>
>>>>>>I agree we should pay attention to scalability - and we have. 
>>>>>>
>>>>>>Please don't disregard that Google servers switched to SPDY with 
>>>>>>zero 
>>>>>>additional hardware (the google servers are fully conformant 
>>>>>>http/1.1 
>>>>>>proxies with a lot more DoS logic than the average site). I know, 
>>>>>>some 
>>>>>>people think Google is some magical place where scalability 
>>>>>>defies physics 
>>>>>>and is not relevant, but this isn't true. Google is just like 
>>>>>>every other 
>>>>>>site, except much much bigger. If we had a 10% increase in server 
>>>>>>load 
>>>>>>with SPDY, Google never could have shipped it. Seriously, who 
>>>>>>would roll 
>>>>>>out thousands of new machines for an experimental protocol? 
>>>>>>Nobody. How 
>>>>>>would we have convinced the executive team "this will be faster", 
>>>>>>if they 
>>>>>>were faced with some huge cap-ex bill? Doesn't sound very 
>>>>>>convincing, does 
>>>>>>it? In my mind, we have already proven clearly that SPDY scales 
>>>>>>just fine. 
>>>>>>
>>>>>>But I'm open to other data. So if you have a SPDY implementation 
>>>>>>and 
>>>>>>want to comment on the effects on your server, lets hear it! And 
>>>>>>I'm not 
>>>>>>saying SPDY is free. But, when you weigh costs (like compression 
>>>>>>and 
>>>>>>framing) against benefits (like 6x fewer connections), there is 
>>>>>>no 
>>>>>>problem. And could we make improvements still? Of course. But 
>>>>>>don't 
>>>>>>pretend that these are the critical parts of SPDY. These are the 
>>>>>>mice nuts. 
>>>>>>
>>>>>>
>>>>>>For a forward proxy, there are several main reasons to even 
>>>>>>exist: 
>>>>>>
>>>>>>a) implement and enforce access control policy 
>>>>>>b) audit usage 
>>>>>>c) cache 
>>>>>>
>>>>>>you block any of these by bypassing everything with TLS, you have 
>>>>>>a 
>>>>>>non-starter for corporate environments. Even if currently admins 
>>>>>>kinda 
>>>>>>turn a blind eye (because they have to) and allow port 443 
>>>>>>through, as more 
>>>>>>and more traffic moves over to 443, more pressure will come down 
>>>>>>from 
>>>>>>management to control it. 
>>>>>>
>>>>>>Best we don't get left with the only option being MITM. 
>>>>>>
>>>>>
>>>>>In my talk at the IETF, I proposed a solution to this. 
>>>>>
>>>>>Browsers need to implement SSL to trusted proxies, which can do 
>>>>>all of 
>>>>>the a/b/c that you suggested above. This solution is better 
>>>>>because the 
>>>>>proxy becomes explicit rather than implicit. This means that the 
>>>>>user 
>>>>>knows of it, and it IT guys knows of it. If there are problems, it 
>>>>>can be 
>>>>>configured out of the system. Implicit proxies are only known the 
>>>>>the IT 
>>>>>guy (maybe), and can't be configured out from a client. The 
>>>>>browser can be 
>>>>>made to honor HSTS so that end-to-end encryption is always 
>>>>>enforced 
>>>>>appropriately. 
>>>>>
>>>>>Further, proxies today already need this solution, even without 
>>>>>SPDY. 
>>>>>  Traffic is moving to SSL already, albeit slowly, and corporate 
>>>>>firewalls 
>>>>>can't see it today. Corporate firewall admins are forced to do 
>>>>>things like 
>>>>>block facebook entirely to prevent data leakage. But, with this 
>>>>>solution, 
>>>>>they could allow facebook access and still protect their IP. (Or 
>>>>>they 
>>>>>could block it if they wanted to, of course). 
>>>>>
>>>>>Anyway, I do agree with you that we need better solutions so that 
>>>>>we 
>>>>>don't incur more SSL MITM. Many corporations are already looking 
>>>>>for 
>>>>>expensive SSL MITM solutions (very complex to rollout due to key 
>>>>>management) because of the reasons I mention above, and its a 
>>>>>technically 
>>>>>inferior solution. 
>>>>>
>>>>>So lets do it! 
>>>>>
>>>>>
>>>>>I basically agree with all the above, however there is the ISP 
>>>>>intercepting proxy to think about. 
>>>>>
>>>>>Many ISPs here in NZ have them, it's just a fact of life when 
>>>>>you're 
>>>>>150ms from the US and restricted bandwidth. Pretty much all the 
>>>>>big ISPs 
>>>>>have intercepting caching proxies. 
>>>>>
>>>>>There's just no way to make these work... period... 
>>>>>
>>>>>unless the ISP is to 
>>>>>
>>>>>a) try and support all their customers to use an explicit proxy, 
>>>>>or 
>>>>>b) get all their customers to install a root cert so they can do 
>>>>>MITM. 
>>>>>
>>>>
>>>>
>>>>>Maybe we need a better way to force a client to use a proxy, and 
>>>>>take 
>>>>>the pain out of it for administration. And do it securely (just 
>>>>>remembering why 305 was deprecated). 
>>>>>
>>>>
>>>>  Do proxy pacs or dhcp work for this? 
>>>>
>>>>Note that we also need the browsers to honor HSTS end-to-end, even 
>>>>if we 
>>>>turn on "GET https://". 
>>>>Mike 
>>>>
>>>>
>>>>
>>>>
>>>>>Adrien 
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>Mike 
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>
>>>>>>Adrien 
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>Mike 
>>>>>>
>>>>>>
>>>>>>
>>>>>>>With plenty of bias, I agree. 
>>>>>>>
>>>>>>>AYJ 
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
Received on Monday, 2 April 2012 21:43:43 GMT

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