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Re: Content-Disposition (new issue?)

From: Julian Reschke <julian.reschke@gmx.de>
Date: Fri, 25 Jul 2008 13:21:23 +0200
Message-ID: <4889B733.1090809@gmx.de>
To: Henrik Nordstrom <henrik@henriknordstrom.net>
CC: ietf-http-wg@w3.org

Henrik Nordstrom wrote:
> On sön, 2008-07-20 at 18:36 +0200, Julian Reschke wrote:
> 
>> In the meantime I noticed that Content-Disposition really is a second 
>> rate header in RFC2616:
> 
> Indeed. I assumed you alread knew this. It's very obvious from the way
> 2616 is written.. Content-Disposition is not officially part of
> HTTP/1.1, only mentioned in RFC2616 as it is in widespread use so
> implementers are aware what it is and how to best deal with it..
> 
> Quote from 2616:
> 
>   "Content-Disposition is not part of
>    the HTTP standard, but since it is widely implemented, we are
>    documenting its use and risks for implementors"

Yep. However, it really does *not* document any risks: it just states 
that there are some, and the points to the Security Considerations of 
the RFC2183. See 
<http://greenbytes.de/tech/webdav/rfc2616.html#rfc.section.15.5>:

"15.5 Content-Disposition Issues

RFC 1806 [35], from which the often implemented Content-Disposition (see 
Appendix 19.5.1) header in HTTP is derived, has a number of very serious 
security considerations. Content-Disposition is not part of the HTTP 
standard, but since it is widely implemented, we are documenting its use 
and risks for implementors. See RFC 2183 [49] (which updates RFC 1806) 
for details."

> and "documented" in an appendix outside the actual definiiton of
> HTTP/1.1, relying heavily on references to other RFCs and plenty of
> warnings...

I think it's ok to refer to the MIME definition of Content-Disposition. 
What's relevant is to document what parts are useful and how they are 
used, and to state which profile of RFC2231 needs to be supported by 
clients.

>> - more importantly, it doesn't appear in RFC 2068 at all (so how did it 
>> get into the Draft Standard?)
> 
> I wasn't around, but a guess is due to security flaws in multiple
> browser implementations at the time making it a hot topic...

Probably. It's still strange that we have it in RFC 2616, but not in RFC 
2068. Seems that a violation of the standards process to me.

>> Considering that, it's seems best to remove all mentions of C-D from 
>> Part 3, and to create a separate spec that describes the use of 
>> Content-Disposition within HTTP.
> 
> I.e. what 2616 did, only that it used an appendix instead of a separate
> document..

I would argue that an appendix is still part of the specification.

> I am perfectly fine with that, and also keeping that header outside
> standards track. But I'll also bet that a number of people will argue
> that since it's in widespread use it should be within the standard...

Oh, it absolutely should be on the standards track; it's an essential 
feature. However, the current state of the specs (2616/2183/2231) makes 
it needlessly complicated to find out what needs to be implemented.

> Regards
> Henrik

BR, Julian
Received on Friday, 25 July 2008 11:22:11 GMT

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