Re: [Simple] <note> in IMDN

["Hisham Khartabil" <hisham.khartabil at gmail.com>]

The field is not useless. It carries extra information (a reason
phrase, if you like) as to why the IM delivery resulted in an error or
still being processed, etc.

Hisham

2008/6/4 Ben Campbell <ben at estacado.net>:
>
> On May 23, 2008, at 2:21 PM, Eric Burger wrote:
>
>> Actually, IMDNs, even the SIMPLE free-form fields, are fairly
>> constrained.  Any mis-match is an opportunity to filter out bad
>> IMDNs.  The <note> field has three problems:
>>
>> 1. It cannot be filtered, as any content could be real (which
>> introduces the attack vector)
>>
>> 2. It cannot know what language it should use, and thus is not likely
>> to be useful to the recipient
>>
>> 3. It has no protocol value, and is of no value to the UA
>>
>>
>> So, if something has no useful protocol value and introduces a spam
>> opportunity, why would we want to include it?
>>
>
> If something has no useful protocol value, even if it _does_no_harm,
> why would we want to include it?
>
> IMHO, there is no need to prove a vector for harm, if we are fairly
> certain there is no vector for _utility_.
>
> (Note that I am agnostic on whether  the field is truly useless--I am
> merely commenting on the form of the argument.)
>
>
>>
>>
>> On May 21, 2008, at 7:45 PM, Paul Kyzivat wrote:
>>
>>> Its kind of late to be thinking about this now. THe problem is
>>> pervasive
>>> in MSRP.
>>>
>>> In SIP there are lots of unconstrained fields. But they are all
>>> constrained by the overall size of the message, and people commonly
>>> put
>>> limits on that.
>>>
>>> In MSRP, because of chunking, a single MSRP message can be gigabytes
>>> long. So using that to bound the unconstrained parts of the headers
>>> doesn't work very well.
>>>
>>> A robust implementation might take a similar approach - define its
>>> own
>>> limit on the total message size, excluding the body. Then it could
>>> constrain all the unconstrained fields to fit within it.
>>>
>>> But picking on one header isn't a solution to the problem. Either
>>> assume
>>> the developers will be able to deal with it, or else do and MSRPv2
>>> that
>>> eliminates all unconstrained fields.
>>>
>>>      Paul
>>>
>>> Dean Willis wrote:
>>>> On May 13, 2008, at 11:38 PM, Hisham Khartabil wrote:
>>>>
>>>>> Can you explain how it is an attack vector?
>>>>
>>>>
>>>> Unconstrained rich content is one of the most easily exploited
>>>> attack
>>>> vectors.
>>>>
>>>> Buffer overrun attacks as well as all of the typical MIME compound-
>>>> component attacks are likely. For example, the common JPEG
>>>> vulnerabilities might be exploitable:
>>>>
>>>> http://www.news.com/Image-virus-spreads-via-chat/2100-7349_3-5390463.html
>>>>
>>>>
>>>> Or the content-execution weakness that caused the Macintosh Safari
>>>> browse to be most easily exploited in recent hacking contests:
>>>>
>>>> http://www.engadget.com/2007/07/23/safari-exploit-gives-hackers-full-control-of-your-iphone/
>>>>
>>>>
>>>> There have also been exploits against QuickTime, Flash, and most
>>>> other
>>>> plugin components from time to time.
>>>>
>>>> --
>>>> Dean
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