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Re: Resend: HTTP Performance extension for NAV(network-based anti-virus) systems

From: Adrien de Croy <adrien@qbik.com>
Date: Tue, 07 Aug 2007 09:27:46 +1200
Message-ID: <46B79252.4070100@qbik.com>
To: "Babu.N" <babun@intoto.com>
CC: ietf-http-wg@w3.org


The underlying issue IMO is that of the human user knowing what's going 
on.  If you have some sort of progress notification, that allows the 
progress bar on the bottom of the browser window to show movement, and 
the status area to show activity, then users won't hang up waiting.  
Download managers could show this information as well.

The actual transmission of the file from the proxy to the client is then 
secondary.  It will happen at LAN speed once the file is scanned.  Since 
responses to date have been interim, the result of the scan (e.g. if 
failure) can simply be returned as the response to the request.

Your proposed method seems to assume that transfer of the resource is 
necessary for there to be progress to show.  Having a separate specific 
progress mechanism however does this, and furthermore is applicable to 
more cases than just gateway scanning, in fact is useful any time a 
request will take a while to process, and can be generated by gateways 
and/or servers.

Furthermore the Progress mechanism is transparent to proxies that don't 
understand it, and is much less complicated to implement than a 
multi-part post-abort mechanism, so would find much easier deployment.  
It's arguably safer as well, since a problem in post-aborting a request 
could still leave compromised data on the client system, puts the client 
to more work as well (esp considering client-side processing such as AV, 
caching etc).



Babu.N wrote:
> Hi,
> Thanks for the comments.
> Please see inline.
> At 06:41 AM 8/3/2007, Adrien de Croy wrote:
>> Hi
>> A few months back I submitted an I-D which contained proposals for 
>> progress notifications.
>> the reason I raise that, is because it considers the same scenarios 
>> as your draft, i.e. it was specifically conceived to deal with issues 
>> around gateway scanning.
>> There is a problem with the approach taken by your I-D.
>> It is concerned around the issue of event sending any of the resource 
>> to the client prior to it having been verified as safe.
>> Trying to get the client to ignore the file after it has downloaded a 
>> whole heap of it isn't safe.  The file may have in fact been padded 
>> out to avert such techniques, so an entire workable image may have 
>> been already received by the client, which would run if executed.
> This is the reason I have the following statements in the draft:
> "
>    For some reason, if a client doesn't receive second and
> third (when 
>    applicable) sub-parts, it MUST never store/process the
> already 
>    received data.
> "
> "
>    Some programs like browsers' "Download
> Manager" start storing the 
>    data to disk even before the complete response is received.
> Such 
>    applications should ensure that they delete any partial data
> in the 
>    event of "Proxy response IGNORE" or when
> second/third body (when 
>    applicable) parts are not received. 
> "
> So implementations confirming to this strictly should never 
> run/process a response till the response is completely received. So 
> they should not have an issue ? Please suggest.
> Thanks,
> Babu
>> There's not really any amount of an unscanned resource that can be 
>> guaranteed to be safe to send (well maybe just a few bytes).
>> This is why we're trying to deprecate "drip-feeding" in WinGate, 
>> since it's fundamentally a flawed concept, albeit necessary to 
>> appease the users of browsers.
>> I just submitted a revised draft which I'll also post here, which 
>> just focuses on using interim response messages to report progress.
>> Cheers
>> Adrien
>> babun@intoto.com wrote:
>>> Hi,
>>> I have submitted a draft on "HTTP Performance extension for NAV
>>> (network-based anti-virus) systems":
>>> http://www.ietf.org/internet-drafts/draft-babu-navmime-00.txt
>>> This draft attempts to also solve issues in reporting download progress
>>> and avoiding client connection timeout in presence of network-based
>>> anti-virus/anti-spam proxies.
>>> Like to hear feedback on this.
>>> Thanks,
>>> Babu
>>> PS: Appologies for resending this. Forgot to indicate the subject in my
>>> last email, hence re-sending.
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>> -- 
>> Adrien de Croy - WinGate Proxy Server - http://www.wingate.com 
>> <http://www.wingate.com/>

Adrien de Croy - WinGate Proxy Server - http://www.wingate.com
Received on Monday, 6 August 2007 21:27:28 UTC

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