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Sniffing and HTTP-bis (ACTION-309)

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Wed, 02 Dec 2009 12:23:58 +0000
To: www-tag@w3.org
Message-ID: <f5btyw94l9d.fsf@hildegard.inf.ed.ac.uk>
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At the TAG f2f in September, we discussed [1] Content-Type sniffing
and the then-current state of the HTTPbis [2] insofar as it addresses
this question (see section 3.2.1 *Type*).

As it stands the draft only indirectly alludes to sniffing, in the
following paragraph:

  Content-Type specifies the media type of the underlying data. Any
  HTTP/1.1 message containing an entity-body SHOULD include a
  Content-Type header field defining the media type of that body,
  unless that information is unknown. If the Content-Type header field
  is not present, it indicates that the sender does not know the media
  type of the data; recipients MAY either assume that it is
  "application/octet-stream" ([RFC2046], Section 4.5.1) or examine the
  content to determine its type.

Mark Nottingham joined our discussion in September, and said at one
point:

  "We were asked to confirm that HTTP bis doesn't conflict with
   sniffing, and we decided to accept that."

In later discussion, I said:

  "I heard TBL say things which suggest we should push back on the
   current state of the HTTP bis draft. Because it doesn't say 'Don't
   do that: sniffing breaks things'"

I took an action [3] to review the situation, and suggest further action
if necessary.

I think we should in fact request the HTTPbis editors to reopen their
Ticket #155 [4] with a suggestion that something along the following
lines be added after the above-quoted paragraph in section 3.2.1:

  If the Content-Type header field _is_ present, recipients SHOULD NOT
  examine the content and override the specified type if the change
  would significantly alter the security exposure ('privilege
  escalation').

This change is compatible with _Content-Type Processing Model_, a
draft "responsible sniffing" Internet-Draft [5].

ht
 
[1] http://www.w3.org/2001/tag/2009/09/24-minutes#item03
[2] http://trac.tools.ietf.org/wg/httpbis/trac/export/663/draft-ietf-httpbis/latest/p3-payload.html#rfc.section.3.2.1
[3] http://www.w3.org/2001/tag/group/track/actions/309
[4] http://trac.tools.ietf.org/wg/httpbis/trac/ticket/155
[5] http://ietfreport.isoc.org/idref/draft-abarth-mime-sniff/
- -- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
                         Half-time member of W3C Team
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
                Fax: (44) 131 651-1426, e-mail: ht@inf.ed.ac.uk
                       URL: http://www.ltg.ed.ac.uk/~ht/
[mail really from me _always_ has this .sig -- mail without it is forged spam]
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Received on Wednesday, 2 December 2009 12:24:33 GMT

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