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Re: [Fwd: I-D ACTION:draft-decroy-http-progress-00.txt]

From: Henrik Nordstrom <henrik@henriknordstrom.net>
Date: Wed, 14 Feb 2007 03:05:16 +0100
To: Adrien de Croy <adrien@qbik.com>
Cc: ietf-http-wg@w3.org
Message-Id: <1171418716.4335.65.camel@henriknordstrom.net>
ons 2007-02-14 klockan 11:41 +1300 skrev Adrien de Croy:

> > Well.. no matter what the client only has the choice of either closing
> > the connection or sending the request body. That's the only two
> > available options once the request headers have been sent indicating
> > there will be a request entity body.
> >   
> 
> There is another option.  Waiting for a 100 Continue before sending 
> message body.

Well, what I am trying to say is that this does not change the available
options for finishing this request.

> The aim of the defer status is to remove option 2.  So there is then 
> ONLY option 3.  The client must wait
> for a 100 continue (whilst still keeping the connection open) before 
> sending the request body.

You still have the same window where the client must guess, just
hopefully a bit smaller.. 

And in case of 102 generated by a proxy you also run into the problem of
how to guarantee there finally will be a 100 Continue delivered. And as
result the proxy must also implement the timer and "fake" a 100 Continue
if no 1xx is seen from the next-hop within a reasonable timeframe.

> So, if you have a client that honours a 1xx defer status.
> 
> case 1, proxy requires auth, server does not.
> 
> 1. Client sends request headers only (as per current RFC2616 
> suggestions) and goes into a short wait state
> 2. proxy sees that there will be a request body, so immediately sends 
> "HTTP/1.1 1xx wait please"
> 3. client terminates timer for when it would otherwise send request 
> body.  It does not send request body
> 4 proxy then sends "HTTP/1.1 407 auth required"

* client closes the connection to avoid transmitting the request body

> 5 client establishes auth credentials with proxy, still not sending 
> request body6 proxy connects to upstream server. 
> 7. server sends 100 continue
> 8 proxy sends server response back through to client
> 9 client sends request body
> 10 proxy relays request body.
> 11. server sends 200 ok.
> 12. proxy relays 200 ok.
> 13 done.
> 
> case 2, proxy requires auth, and server also requires auth.
> 
> 1. Client sends request headers only (as per current RFC2616 
> suggestions) and goes into a short wait state
> 2. proxy sees that there will be a request body, so immediately sends 
> "HTTP/1.1 1xx wait please"
> 3. client terminates timer for when it would otherwise send request 
> body.  It does not send request body
> 4 proxy then sends "HTTP/1.1 407 auth required"

* client closes the connection to avoid transmitting the request body.

> 5 client establishes auth credentials with proxy, still not sending 
> request body
> 6 proxy connects to upstream server. 
> 7. server sends 401 auth required
> 8 proxy sends server response back through to client
> 9 client resends request with server credentials  Still no request body
> 10 proxy relays request to server
> 11. server sends 100 continue
> 12. proxy relays 100 continue
> 13. client sends request body
> 14 proxy relays request body
> 15 server sends 200 ok
> 16 proxy relays 200 ok.
> 17 done.
> 
> case 3, only server requires auth
> 
> 1. Client sends request headers only (as per current RFC2616 
> suggestions) and goes into a short wait state
> 2. proxy sees that there will be a request body, so immediately sends 
> "HTTP/1.1 1xx wait please"
> 3. client terminates timer for when it would otherwise send request 
> body.  It does not send request body
> 4 proxy connects to upstream server. 
> 5. server sends 401 auth required
> 6 proxy sends server response back through to client
> 7 client resends request with server credentials  Still no request body
> 8 proxy relays request to server
> 9. server sends 100 continue
> 10. proxy relays 100 continue
> 11. client sends request body
> 12 proxy relays request body
> 13 server sends 200 ok
> 14 proxy relays 200 ok.
> 15 done.


case 4, server does not implement 100 Continue

1. Client sends request headers only (as per current RFC2616
suggestions) and goes into a short wait state
2. proxy sees that there will be a request body, so immediately sends "HTTP/1.1 1xx wait please"
3. client terminates timer for when it would otherwise send request body.  It does not send request body
4. proxy connects to upstream server. 
5. server sends 401 auth required
6. proxy sends server response back through to client
7*. client closes the connection to avoid transmitting the request body
8. client resends request headers with server credentials
8. proxy relays request headers to server
9. server doesn't implement 100 Continue and none gets sent..


> All this can be done on the same connection between client and proxy, 
> proxy and server.
> 
> I should really draw up a flow chart of all this.  from the client's 
> point of view, it sends a request, and if it receives a 102
> wait please, it will then receive any number of:
> 
> a. a 100 continue
> b. an auth challenge
> c. some failure code indicating the request is denied.
> d. connection closed (some failure condition)..
> 
> until it has received a 100 continue however, it won't send the request 
> body.

Yes, but you do understand that for the connection to be reused to
complete authentication etc the first request must first be completed
which requires either sending the request body or closing the
connection.

> I think with the way security and encrytion are moving, we are moving 
> more towards negotiation of credentials
> on a per-connection basis.  Reuse of any crypto derived information is 
> normally seen as a vulnerability, so being
> able to reuse nonces etc is arguably a security hole.  I see pressure to 
> move towards a nonce per connection, or in
> other words session-based credentials like NTLM.  Therefore I see this 
> "problem" growing rather than shrinking.

To use connection oriented schemes effectively HTTP needs a bit or
redesign. The protocol is not designed for connection oriented
authentication, only message oriented authentication.


> Not just this case "where the body is unneededly transmitted before 
> closing the connection" but in
> all cases, whether the connection is closed or not, and it is in fact 
> the intention of this spec that the
> connection remain open.

For the connection to remain open without redefining the HTTP message
format or use chunked the request body MUST be transmitted and
discarded.

> > It does not at all
> > solve the problems of NTLM or other connection oriented authentication
> > methods.
>    
> yes it does.

Only if its short-circuiting the request skipping the request-body where
HTTP message format requires one toe be sent, in which case the
objections in the first message again applies and I did not misread what
you wrote..

> I think there's still some confusion about what I'm proposing.  
> Hopefully that's cleared up with the
> 3 cases I outlined above.

I think I understood what you are proposing the first time, even if it's
not what you have written.

You propose changing the basic HTTP message format telling the client
that if it received a 1xx Defer then it should not only wait
indefinitely before sending the request body but also skip sending the
request body and still keep the connection open if it receives a final
response (i.e. auth challenge) before the body has been sent.

Imho to do this you MUST use chunked encoding, and have the client
terminate the request with a end chunk. Redefining the HTTP message
format to allow skipping transmission of a Content-Length indicated
request body is not possible within HTTP/1.1 as it requires the basic
message format to be redefined to allow the body to be omitted.

Regards
Henrik

Received on Wednesday, 14 February 2007 02:05:28 GMT

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