Re: Comments on Explicit/Trusted Proxy

["Adrien W. de Croy" <[e-mail]>]

sorry I should have been more clear, my questions weren't in the context 
of your proposal, but in the context of what the current situation is, 
and mostly in response to Stephen's comments.

Concerns were raised about creating a requirement for servers to 
authenticate proxies.

My questions were about how does a server know it's a proxy, so how can 
a client be trusted more, and therefore how is a proxy less trustworthy.

HTTP auth only covers one small part of the picture, and doesn't lock a 
proxy out of the conversation, only out of the authentication.  The 
proxy can still modify anything else about the requests.

Regards

Adrien


------ Original Message ------
From: "Roberto Peon" <[e-mail]>
To: "Adrien W. de Croy" <[e-mail]>
Cc: "Stephen Farrell" <[e-mail]>; "HTTP Working Group" 
<[e-mail]>
Sent: 4/05/2013 9:07:44 a.m.
Subject: Re: Comments on Explicit/Trusted Proxy
>The client has no need to do TLS in TLS and wouldn't do it by default.
>The proxy has no choice but to do TLS in TLS (since that is what the 
>client sends it), and, since it doesn't have the integrity keys, it 
>can't change the data, etc. without detection by the client or server.
>
>So, if the server receives a stream which indicates that it is doing 
>TLS, it knows this should be treated as having come through a proxy.
>
>-=R
>
>
>On Fri, May 3, 2013 at 1:27 PM, Adrien W. de Croy <[e-mail]> 
>wrote:
>>
>>my next question, is how can the server tell the difference between a 
>>proxy and a client?
>>
>>
>>------ Original Message ------
>>From: "Roberto Peon" <[e-mail]>
>>To: "Adrien W. de Croy" <[e-mail]>
>>Cc: "Stephen Farrell" <[e-mail]>; "HTTP Working 
>>Group" <[e-mail]>
>>Sent: 4/05/2013 4:23:10 a.m.
>>Subject: Re: Comments on Explicit/Trusted Proxy
>>>
>>>A proxy can represent the interests of a 3rd party which has nothing 
>>>to do with the client or server. The motivations of this 3rd party 
>>>may not be known, and are often enough antithetical to the wishes of 
>>>the client or server.
>>>
>>>The motivation of the client is more likely known-- they simply want 
>>>the content the server is providing, without allowing it to be 
>>>modified in ways which make for a poor experience (not just that page 
>>>load, but overall, including things like not having their bank 
>>>account mysteriously go to zero).
>>>
>>>-=R
>>>
>>>
>>>On Fri, May 3, 2013 at 4:16 AM, Adrien W. de Croy <[e-mail]> 
>>>wrote:
>>>>
>>>>As far as a server is concerned, why would a client be any more 
>>>>trustable than a proxy?
>>>>
>>>>
>>>>
>>>>Adrien
>>>>
>>>>------ Original Message ------
>>>>From: "Stephen Farrell" <[e-mail]>
>>>>To: "HTTP Working Group" <[e-mail]>
>>>>Sent: 3/05/2013 8:16:33 p.m.
>>>>Subject: Re: Comments on Explicit/Trusted Proxy
>>>>>
>>>>>The contrast between this arm-waving nonsense and the precision
>>>>>with which this wg are tackling HTTP/2.0 performance is frankly
>>>>>astounding.
>>>>>
>>>>>Every web site in the world (and all the non-HTTP uses of TLS)
>>>>>are supposed to be able to authenticate every proxy in the world
>>>>>and know when its ok for a particular set of proxies to MITM an
>>>>>TLS session? That's just BS.
>>>>>
>>>>>Note, I'm not specifically directing this at Roberto - I mean
>>>>>the entire discussion rests on BS notions like the above.
>>>>>
>>>>>S.
>>>>>
>>>>>On 05/03/2013 01:53 AM, Roberto Peon wrote:
>>>>>>  The scheme allows for injection of bytes, but not within any of 
>>>>>>the secure
>>>>>>  tunnels. Instead, the proxy's bytes are clearly demarqued as 
>>>>>>different.
>>>>>>
>>>>>>  The idea here is that the client or server should always know 
>>>>>>when the
>>>>>>  proxy has changed bytes, and it shouldn't, though it may inject
>>>>>>  bytes/requests/whatever in either direction.
>>>>>>
>>>>>>
>>>>>>  Sure, a client cert is one way of authenticating to the server. I 
>>>>>>didn't go
>>>>>>  into that much detail, but rather pointed out that the scheme 
>>>>>>proposed in
>>>>>>  that doc, that servers may decide they don't want to service 
>>>>>>queries from
>>>>>>  (some) proxies, and direct the client to either try directly, or 
>>>>>>allow the
>>>>>>  request to fail.
>>>>>>
>>>>>>  -=R
>>>>>>
>>>>>>  On Thu, May 2, 2013 at 5:48 PM, Adrien W. de Croy 
>>>>>><[e-mail]> wrote:
>>>>>>
>>>>>>>
>>>>>>>  proxies need to be able to modify the bytes or at least inject 
>>>>>>>messages
>>>>>>>  back to the client.
>>>>>>>
>>>>>>>  e.g.
>>>>>>>
>>>>>>>  * request denied by policy (e.g. you can't POST to that site due 
>>>>>>>to DLP
>>>>>>>  rules)
>>>>>>>  * serving from cache
>>>>>>>  * ad stripping
>>>>>>>  * malware blocking
>>>>>>>  * etc etc etc
>>>>>>>
>>>>>>>  let alone stripping hop-by-hop headers etc
>>>>>>>
>>>>>>>  So I don't think anyone will bother with a scheme that doesn't 
>>>>>>>allow for
>>>>>>>  that. If the only option of the intermediary is to delay or drop 
>>>>>>>the
>>>>>>>  connection, the client is going to be in the dark as to why. 
>>>>>>>Already the
>>>>>>>  user experience in this area is poor.
>>>>>>>
>>>>>>>  As for intercepting proxies. Whilst I agree they are a PITN, 
>>>>>>>they are
>>>>>>>  strongly favoured by customers for several obvious reasons.
>>>>>>>
>>>>>>>  Until we can get a wide-spread mechanism deployed to securely 
>>>>>>>FORCE
>>>>>>>  clients to use a proxy, we're going to see interception.
>>>>>>>
>>>>>>>  As for MITM. Whilst we continue to think of it as an attack, we 
>>>>>>>will
>>>>>>>  continue to see resistance. It's clear some people see it only 
>>>>>>>negatively,
>>>>>>>  where others see this as an opportunity to improve things 
>>>>>>>compared to
>>>>>>>  current MITMs.
>>>>>>>
>>>>>>>  Personally I would rather know what is going on, than be in the 
>>>>>>>dark and
>>>>>>>  be forced to swallow whatever I receive simply because I was 
>>>>>>>forced (by
>>>>>>>  company policy) to install a root cert for the spoofed certs. 
>>>>>>>Sites using
>>>>>>>  EV certs will show me what is going on if I know a site uses EV 
>>>>>>>certs,
>>>>>>>  since the EV breaks on spoofed certs. Or I need to check the 
>>>>>>>cert path on
>>>>>>>  any site to see if I can find the forced cert at the root. But 
>>>>>>>that's me,
>>>>>>>  not everyday punters.
>>>>>>>
>>>>>>>  As for the server trusting the proxy. Why is that any different 
>>>>>>>to the
>>>>>>>  server trusting the client. Use a client cert. Can always fall 
>>>>>>>back to a
>>>>>>>  tunnel if the server indicates it needs a client cert. Currently 
>>>>>>>there's
>>>>>>>  no way around this issue in today's MITM systems except for 
>>>>>>>installing the
>>>>>>>  client cert on the proxy.
>>>>>>>
>>>>>>>  Adrien
>>>>>>>
>>>>>>>
>>>>>>>  ------ Original Message ------
>>>>>>>  From: "Roberto Peon" <[e-mail]>
>>>>>>>  To: "Peter Lepeska" <[e-mail]>
>>>>>>>  Cc: "HTTP Working Group" <[e-mail]>
>>>>>>>  Sent: 3/05/2013 12:13:21 p.m.
>>>>>>>  Subject: Re: Comments on Explicit/Trusted Proxy
>>>>>>>
>>>>>>>   responses inline.
>>>>>>>
>>>>>>>
>>>>>>>   On Thu, Apr 25, 2013 at 1:38 PM, Peter Lepeska 
>>>>>>><[e-mail]>
>>>>>>>   wrote:
>>>>>>>
>>>>>>>>  Some comments on Roberto's doc:
>>>>>>>>
>>>>>>>>    In the case where the user-agent has been configured with 
>>>>>>>>Chris as a
>>>>>>>>     trusted-proxy, either Anne's connect-stream MUST use either 
>>>>>>>>a null-
>>>>>>>>     cipher, or Anne MUST provide the decryption key material to 
>>>>>>>>Chris
>>>>>>>>     immediately after tunnel establishment, and before any data 
>>>>>>>>traverses
>>>>>>>>     the tunnel.
>>>>>>>>
>>>>>>>>
>>>>>>>>  This seems like a showstopper to me. Even if we can get past 
>>>>>>>>the problems
>>>>>>>>  associated with a trusted proxy in general, I can't see getting 
>>>>>>>>acceptance
>>>>>>>>  of any approach that involves sending a session key from one 
>>>>>>>>machine to
>>>>>>>>  another. But why not just use two full SSL sessions like the 
>>>>>>>>typical MITM
>>>>>>>>  proxy 
>>>>>>>>(http://crypto.stanford.edu/ssl-mitm/orhttp://mitmproxy.org/)
>>>>>>>>  approach? But instead of forging certificates like they do, 
>>>>>>>>just give the
>>>>>>>>  trusted proxy its own certificate and then display both the 
>>>>>>>>trusted proxy
>>>>>>>>  certificate and the content server certificate in the browser 
>>>>>>>>when the user
>>>>>>>>  wants info about the two point-to-point SSL sessions.
>>>>>>>>
>>>>>>>>
>>>>>>>  Using two connections may require two separate connections at 
>>>>>>>the eventual
>>>>>>>  endpoint, and it contributes to bufferbloat.
>>>>>>>  Also, the proxy may wish to influence the private channel (e.g. 
>>>>>>>don't talk
>>>>>>>  to site X). With connection sharing, this is 
>>>>>>>difficult/impossible otherwise
>>>>>>>  (that other connection may not only go to example.com).
>>>>>>>
>>>>>>>
>>>>>>>>   "For the purpose of this document, it is assumed that the user 
>>>>>>>>locates
>>>>>>>>
>>>>>>>>     a piece of paper upon a wall and reads it, typing these 
>>>>>>>>proxy
>>>>>>>>     settings into a configuration field for their user-agent. 
>>>>>>>>This is
>>>>>>>>     obviously not the only possible configuration mechanism, but 
>>>>>>>>it may,
>>>>>>>>     sadly, be the most secure. It is assumed that alternate 
>>>>>>>>distribution
>>>>>>>>     techniques may be discussed.
>>>>>>>>
>>>>>>>>  "
>>>>>>>>
>>>>>>>>  While explicit proxy configuration may be the most secure, it 
>>>>>>>>is very
>>>>>>>>  difficult to manage for mobile devices especially, as others 
>>>>>>>>have mentioned
>>>>>>>>  on this list. Transparent interception is the more widely 
>>>>>>>>adopted approach
>>>>>>>>  -- not because of security but because of stability and 
>>>>>>>>manageability.
>>>>>>>>
>>>>>>>>
>>>>>>>  There is no secure automatic proxy configuration unless a 
>>>>>>>completely
>>>>>>>  separate trust chain is somehow created and is reliable (or at 
>>>>>>>least moreso
>>>>>>>  than what we have with TLS today).
>>>>>>>  Transparent proxying causes problems in upgrading the protocol 
>>>>>>>as nobody
>>>>>>>  knows where the problem lies. If this wasn't such a painful 
>>>>>>>point, we'd
>>>>>>>  have been using SPDY over port 80...
>>>>>>>  I'm fundamentally opposed to transparent proxying because it 
>>>>>>>makes
>>>>>>>  protocol evolution next to impossible when you can't figure out 
>>>>>>>who is
>>>>>>>  messing up...
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>   What about "transparent" proxies that advertise themselves? Is 
>>>>>>>>it
>>>>>>>>  possible to use NPN (
>>>>>>>>  https://technotes.googlecode.com/git/nextprotoneg.html) to 
>>>>>>>>advertise the
>>>>>>>>  presence of an intercepting proxy for 443 traffic? Then the 
>>>>>>>>user can be
>>>>>>>>  notified that a proxy wants to be trusted for X reasons and the 
>>>>>>>>user would
>>>>>>>>  then make the opt in or opt out decision. Then, similar to 
>>>>>>>>SPDY, the
>>>>>>>>  presence of the trusted proxy in the end-to-end path could be 
>>>>>>>>signaled to
>>>>>>>>  the end user via icons in the browser.
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>>  MITM is used today with no user knowledge. At least in this 
>>>>>>>>approach, a
>>>>>>>>  user has the ability to opt in or out and to also be aware of 
>>>>>>>>the presence
>>>>>>>>  of the intermediate proxy.
>>>>>>>>
>>>>>>>
>>>>>>>  That is the idea.
>>>>>>>  Additionally, and this is important, the server gets to decide 
>>>>>>>if the MITM
>>>>>>>  is acceptable, and, in the proposed scheme the MITM doesn't get 
>>>>>>>to modify
>>>>>>>  bytes. It merely gets to advise the recipient of how to deal 
>>>>>>>with them,
>>>>>>>  delay them, or disconnect.
>>>>>>>
>>>>>>>  -=R
>>>>>>>
>>>>>>>
>>>>>>>  On Thu, Apr 25, 2013 at 1:38 PM, Peter Lepeska 
>>>>>>><[e-mail]>wrote:
>>>>>>>
>>>>>>>>  Some comments on Roberto's doc:
>>>>>>>>
>>>>>>>>    In the case where the user-agent has been configured with 
>>>>>>>>Chris as a
>>>>>>>>     trusted-proxy, either Anne's connect-stream MUST use either 
>>>>>>>>a null-
>>>>>>>>     cipher, or Anne MUST provide the decryption key material to 
>>>>>>>>Chris
>>>>>>>>     immediately after tunnel establishment, and before any data 
>>>>>>>>traverses
>>>>>>>>     the tunnel.
>>>>>>>>
>>>>>>>>
>>>>>>>>  This seems like a showstopper to me. Even if we can get past 
>>>>>>>>the problems
>>>>>>>>  associated with a trusted proxy in general, I can't see getting 
>>>>>>>>acceptance
>>>>>>>>  of any approach that involves sending a session key from one 
>>>>>>>>machine to
>>>>>>>>  another. But why not just use two full SSL sessions like the 
>>>>>>>>typical MITM
>>>>>>>>  proxy (http://crypto.stanford.edu/ssl-mitm/ or 
>>>>>>>>http://mitmproxy.org)
>>>>>>>>  approach? But instead of forging certificates like they do, 
>>>>>>>>just give the
>>>>>>>>  trusted proxy its own certificate and then display both the 
>>>>>>>>trusted proxy
>>>>>>>>  certificate and the content server certificate in the browser 
>>>>>>>>when the user
>>>>>>>>  wants info about the two point-to-point SSL sessions.
>>>>>>>>
>>>>>>>>  "For the purpose of this document, it is assumed that the user 
>>>>>>>>locates
>>>>>>>>
>>>>>>>>     a piece of paper upon a wall and reads it, typing these 
>>>>>>>>proxy
>>>>>>>>     settings into a configuration field for their user-agent. 
>>>>>>>>This is
>>>>>>>>     obviously not the only possible configuration mechanism, but 
>>>>>>>>it may,
>>>>>>>>     sadly, be the most secure. It is assumed that alternate 
>>>>>>>>distribution
>>>>>>>>     techniques may be discussed.
>>>>>>>>
>>>>>>>>  "
>>>>>>>>
>>>>>>>>  While explicit proxy configuration may be the most secure, it 
>>>>>>>>is very
>>>>>>>>  difficult to manage for mobile devices especially, as others 
>>>>>>>>have mentioned
>>>>>>>>  on this list. Transparent interception is the more widely 
>>>>>>>>adopted approach
>>>>>>>>  -- not because of security but because of stability and 
>>>>>>>>manageability.
>>>>>>>>
>>>>>>>>  What about "transparent" proxies that advertise themselves? Is 
>>>>>>>>it
>>>>>>>>  possible to use NPN (
>>>>>>>>  https://technotes.googlecode.com/git/nextprotoneg.html) to 
>>>>>>>>advertise the
>>>>>>>>  presence of an intercepting proxy for 443 traffic? Then the 
>>>>>>>>user can be
>>>>>>>>  notified that a proxy wants to be trusted for X reasons and the 
>>>>>>>>user would
>>>>>>>>  then make the opt in or opt out decision. Then, similar to 
>>>>>>>>SPDY, the
>>>>>>>>  presence of the trusted proxy in the end-to-end path could be 
>>>>>>>>signaled to
>>>>>>>>  the end user via icons in the browser.
>>>>>>>>
>>>>>>>>  MITM is used today with no user knowledge. At least in this 
>>>>>>>>approach, a
>>>>>>>>  user has the ability to opt in or out and to also be aware of 
>>>>>>>>the presence
>>>>>>>>  of the intermediate proxy.
>>>>>>>>
>>>>>>>>  Thoughts?
>>>>>>>>
>>>>>>>>  Peter
>>>>>>>>
>>>>>>>>
>>>>>>>>   On Apr 24, 2013, at 12:49 PM, William Chan (陈智昌) 
>>>>>>>><[e-mail]>
>>>>>>>>  wrote:
>>>>>>>>
>>>>>>>>   Yep, but no, it hasn't gone anywhere.
>>>>>>>>
>>>>>>>>
>>>>>>>>  On Wed, Apr 24, 2013 at 7:44 AM, Peter Lepeska 
>>>>>>>><[e-mail]>wrote:
>>>>>>>>
>>>>>>>>>  Hi William,
>>>>>>>>>
>>>>>>>>>  Is this draft by Roberto Peon the one you were referring to?
>>>>>>>>>
>>>>>>>>>  http://tools.ietf.org/html/draft-rpeon-httpbis-exproxy-00
>>>>>>>>>
>>>>>>>>>  Has this gone anywhere?
>>>>>>>>>
>>>>>>>>>  I'm looking to design and build a "trusted proxy" that aligns 
>>>>>>>>>with the
>>>>>>>>>  browser development roadmap/vision in order to provide web 
>>>>>>>>>acceleration
>>>>>>>>>  functionality and so would like to get involved in this 
>>>>>>>>>process if still
>>>>>>>>>  active.
>>>>>>>>>
>>>>>>>>>  Thanks,
>>>>>>>>>
>>>>>>>>>  Peter
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>  On Mon, Apr 30, 2012 at 5:57 PM, William Chan (陈智昌) <
>>>>>>>>>  [e-mail]> wrote:
>>>>>>>>>
>>>>>>>>>>  On the contrary, I think it's great to have multiple 
>>>>>>>>>>proposals. If you
>>>>>>>>>>  have your own vision for how this should work, please send it 
>>>>>>>>>>out! :) My
>>>>>>>>>>  statement was simply an FYI, not a "back off, we've got 
>>>>>>>>>>this!"
>>>>>>>>>>
>>>>>>>>>>  On Mon, Apr 30, 2012 at 2:45 PM, Peter Lepeska 
>>>>>>>>>><[e-mail]>wrote:
>>>>>>>>>>
>>>>>>>>>>>  Perfect then I'll sit tight.
>>>>>>>>>>>
>>>>>>>>>>>  Thanks,
>>>>>>>>>>>
>>>>>>>>>>>  Peter
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>  On Mon, Apr 30, 2012 at 5:43 PM, William Chan (陈智昌) <
>>>>>>>>>>>  [e-mail]> wrote:
>>>>>>>>>>>
>>>>>>>>>>>>  FYI, we (google spdy team) have been discussing a "trusted 
>>>>>>>>>>>>proxy"
>>>>>>>>>>>>  internally and I think Roberto's got a draft in the works.
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>  On Mon, Apr 30, 2012 at 2:22 PM, Peter Lepeska 
>>>>>>>>>>>><[e-mail]>wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>>  Hi Mark,
>>>>>>>>>>>>>
>>>>>>>>>>>>>  Earlier this group discussed the idea of a "trusted 
>>>>>>>>>>>>>proxy". Does
>>>>>>>>>>>>>  that fall under the HTTP/2.0 category?
>>>>>>>>>>>>>
>>>>>>>>>>>>>  I may have some cycles for this.
>>>>>>>>>>>>>
>>>>>>>>>>>>>  Thanks,
>>>>>>>>>>>>>
>>>>>>>>>>>>>  Peter
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>  On Fri, Apr 27, 2012 at 1:28 AM, Mark Nottingham 
>>>>>>>>>>>>><[e-mail]>wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>>  Just a reminder that we're still accepting proposals for:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>  1. HTTP/2.0
>>>>>>>>>>>>>>  2. New HTTP authentication schemes
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>  As per our charter 
>>>>>>>>>>>>>><http://datatracker.ietf.org/wg/httpbis/charter/
>>>>>>>>>>>>>>>  .
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>  So far, we've received the following proposals applicable 
>>>>>>>>>>>>>>to
>>>>>>>>>>>>>>  HTTP/2.0:
>>>>>>>>>>>>>>   
>>>>>>>>>>>>>><http://trac.tools.ietf.org/wg/httpbis/trac/wiki/Http2Proposals>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>  But none yet for authentication schemes:
>>>>>>>>>>>>>>   
>>>>>>>>>>>>>><http://trac.tools.ietf.org/wg/httpbis/trac/wiki/HttpAuthProposals
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>  As communicated in Paris, the deadline for proposals is 
>>>>>>>>>>>>>>15 June,
>>>>>>>>>>>>>>  2012. It's fine if your proposal isn't complete, but we 
>>>>>>>>>>>>>>do need to have a
>>>>>>>>>>>>>>   good sense of it by then, for discussion.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>  Regards,
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>  --
>>>>>>>>>>>>>>  Mark Nottingham http://www.mnot.net/
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>
>