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

From: Roberto Peon <grmocg@gmail.com>
Date: Mon, 2 Apr 2012 14:43:41 -0700
Message-ID: <CAP+FsNf3c8PN8sbrxq905Y3COUjStyZQ0kO1ECM4MYpcR8N=OA@mail.gmail.com>
To: Stephen Farrell <stephen.farrell@cs.tcd.ie>
Cc: Mike Belshe <mike@belshe.com>, Peter Lepeska <bizzbyster@gmail.com>, ietf-http-wg@w3.org
On Mon, Apr 2, 2012 at 2:36 PM, Stephen Farrell
<stephen.farrell@cs.tcd.ie>wrote:

>
>
> 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.
>
> 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.
>
> 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.
>

You can "MITM" tcp instead of at the plaintext layer too.
The choice should be up to the user-- they choose to use an explicit proxy
The alternative is for them to send everything in the clear.

Note as well that you're probably conflating "runs over TLS" for "the user
requested trust+security", which isn't necessarily the case here.
The intent is to make it so that all queries run over a TLS channel, even
when there is no expectation for trust.. because that is far, far better
than just doing it in the clear at your internet cafe.

Those with an expectation of trust should probably not allow the MITM for
the HTTPS content, unless there is no choice (which is effectively the case
today as well, since blocking :443 is trivial).

-=R



> 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.
>
>
>
>> 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<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>>
>>>>>> 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 thatů
>>>>>>>>>>
>>>>>>>>>>  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 21:44:10 GMT

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