Re: [stir] stir-06: Reality check on numbers (6.1.1)

[Paul Kyzivat <[e-mail]>]

On 12/16/15 9:34 AM, Brian Rosen wrote:
> Please don’t do that.
>
> It would be extremely valuable for calls to any of the n-1-1 numbers to
> be signed, and especially 9-1-1.
>
> Read 1-1-2 for EU.
>
> “Swatting” is a very serious problem, which can only reasonably be
> stopped by having some assurances of the callers identity.  It works
> today because the caller’s identity can be spoofed.
>
> In fact, just because the called party can’t be canonicalized shouldn’t
> make the entire mechanism fail.  I think we should have canonicalization
> rules for service numbers, but even in the absence of canonicalization
> of the “To:”, the mechanism should still work as long as the To is not
> mangled by downstream elements.
>
> It doesn’t have to be foolproof, it just has to work most of the time.
>   The call takers will take extra precautions if the mechanism fails
> occasionally, but if it rarely works, then it’s useless.

I think that is fine. But then some text is needed for how to handle 
such cases. Just assuming that the two ends will figure out how to do 
this is fantasy.

	Thanks,
	Paul

> Brian
>
>> On Dec 16, 2015, at 12:50 AM, Paul Kyzivat <[e-mail]
>> <mailto:[e-mail]>> wrote:
>>
>> On 12/15/15 8:34 PM, Eric Burger wrote:
>>> And local arrangements are… local… out of scope. The PBX/AS/SBC will
>>> have to make To/From into something sensible. At that point, it is an
>>> E.164 number that STIR can deal with.
>>>
>>> There is no point worrying about my phone saying “From: x74107”. You
>>> cannot get there from here unless you are inside my enterprise
>>> already, at which point you are not STIRing anyway.
>>
>> Since you don't live in the US you may not know what 611 is. It is not
>> a local number, like an internal extension on a PBX. It is a service
>> number. It is among the family of N11 numbers, of which 911 is best known.
>>
>> This discussion is, loosely, about most/all of the service numbers.
>> 911 is extra special, and has customized treatments, so we should
>> probably exclude it from this particular discussion.
>>
>> There is in general no E.164 number that the service numbers can be
>> transformed to for purposes of canonicalization.
>>
>> The answer may be that these numbers can't be canonicalized, and calls
>> to/from them cannot be signed.
>>
>> Thanks,
>> Paul
>>
>>>> On Dec 15, 2015, at 6:48 PM, DRAGE, Keith (Keith)
>>>> <[e-mail]
>>>> <mailto:[e-mail]>> wrote:
>>>>
>>>> I am aware that for example, some PBX deployments do this.
>>>>
>>>> But my understanding is that this is an entirely local arrangement
>>>> within the PBX domain that such an arrangement applies, i.e. that a
>>>> set of local numbers within the PBX map to a set of SIP URIs, and
>>>> that that mapping is in this particular form, rather than to any
>>>> other string of digits or alphanumeric characters.
>>>>
>>>> No RFC defines such a mapping, and I would not expect that any other
>>>> domain would be expected to be aware of this local arrangement,
>>>> anymore than it might be expected to know the relationship between
>>>> the PBX numbering plan and E.164 numbers.
>>>>
>>>> I guess any such expectation is the crux of the matter, unless we
>>>> are talking only about such a knowledge being critical for usage
>>>> within the local domain, and that was not expressed within the mails.
>>>>
>>>> Regards
>>>>
>>>> Keith
>>>>
>>>> -----Original Message-----
>>>> From: Paul Kyzivat [mailto:[e-mail]]
>>>> Sent: 15 December 2015 23:04
>>>> To: DRAGE, Keith (Keith); Peterson, Jon; [e-mail]
>>>> <mailto:[e-mail]>
>>>> Subject: Re: [stir] stir-06: Reality check on numbers (6.1.1)
>>>>
>>>> On 12/15/15 5:31 PM, DRAGE, Keith (Keith) wrote:
>>>>> Well what was confusing was that the only way of reading the text
>>>>> in both your messages was that the example URI was prior to
>>>>> conversion to canonical form, i.e. if there were any URI
>>>>> parameters, they were still present. As none were specified, there
>>>>> could be none, and therefore the URI was a SIP URI pure and simple.
>>>>
>>>> Yes, the intent was that these were prior to canonicalization.
>>>> (After all, the results of canonicalization for the bis are not put
>>>> into the URI.)
>>>>
>>>> The simple fact is that URIs of the form sip:nnn@domain are very
>>>> commonly used to represent phone numbers. And servers are very happy
>>>> to conclude that they are numbers solely because the user part is
>>>> all numeric, without the presence of user=phone.
>>>>
>>>> I expect that a domain that wants to use all numeric user parts that are
>>>> *not* phone numbers might have great difficulty interoperating with
>>>> other domains. Probably this isn't a problem in practice because:
>>>> - it just isn't done
>>>> - domains that handle phone numbers don't peer with domains that
>>>>   use non-phone-number URIs.
>>>>
>>>> Thanks,
>>>> Paul
>>>>
>>>>> Keith
>>>>>
>>>>> -----Original Message-----
>>>>> From: Peterson, Jon [mailto:[e-mail]]
>>>>> Sent: 15 December 2015 19:57
>>>>> To: DRAGE, Keith (Keith); Paul Kyzivat; [e-mail]
>>>>> <mailto:[e-mail]>
>>>>> Subject: Re: [stir] stir-06: Reality check on numbers (6.1.1)
>>>>>
>>>>>
>>>>> Sorry if that was baffling, I thought we were entertaining a case
>>>>> where
>>>>> 611 was intended to be a telephone number: say that instead of
>>>>> "foo", that URI contained a carrier's domain, and this happened to
>>>>> be the unhelpful way the carrier in question stored all telephone
>>>>> numbers in SIP URIs. In the case where "611" is instead in a tel
>>>>> URL, or there is a clear user=phone parameter to the SIP URI, it is
>>>>> a bit more obvious - but no less clear how to canonicalize it for
>>>>> international transport or something.
>>>>>
>>>>> Jon Peterson
>>>>> Neustar, Inc.
>>>>>
>>>>> On 12/15/15, 11:45 AM, "DRAGE, Keith (Keith)"
>>>>> <[e-mail]
>>>>> <mailto:[e-mail]>> wrote:
>>>>>
>>>>>> I'm lost.
>>>>>>
>>>>>> sip:[e-mail], before conversion to canonical form, is a SIP URI
>>>>>> belonging to foo.com <http://foo.com>. It is not a telephone
>>>>>> number or a dial string.
>>>>>> Depending on how foo.com <http://foo.com> assigns its SIP URIs it
>>>>>> might relate to a
>>>>>> dialstring 611 in foo.com <http://foo.com> land, but that is an
>>>>>> entirely arbitrary
>>>>>> decision of foo.com <http://foo.com>, and nothing that should be
>>>>>> verified anywhere as
>>>>>> a telephone number.
>>>>>>
>>>>>> This might be a string that exists after conversion of a tel-URI or
>>>>>> dialstring to canonical form, but that is not what is being stated
>>>>>> below.
>>>>>>
>>>>>> As such it is outside the scope of STIR.
>>>>>>
>>>>>> Keith
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> -----Original Message-----
>>>>>> From: Peterson, Jon [mailto:[e-mail]]
>>>>>> Sent: 15 December 2015 19:09
>>>>>> To: Paul Kyzivat; DRAGE, Keith (Keith); [e-mail]
>>>>>> <mailto:[e-mail]>
>>>>>> Subject: Re: [stir] stir-06: Reality check on numbers (6.1.1)
>>>>>>
>>>>>>
>>>>>>
>>>>>> The use of service numbers in the From is a case where our text is
>>>>>> necessarily speculative. This gets into territory where it's unclear
>>>>>> that we even want the verification to work. If a callee in, say,
>>>>>> Austria receives a call from sip:[e-mail] (presumably they
>>>>>> wouldn't see a service number in the To), is it useful for the callee
>>>>>> to know that the call came from "611"? One can argue it isn't even
>>>>>> particularly useful for callees in America.
>>>>>>
>>>>>>
>>>>>> Does that mean we shouldn't allow service numbers in these fields? If
>>>>>> they are permitted in To and From in baseline SIP, we should at least
>>>>>> have a story about them. There is some use in signing the To field
>>>>>> for service numbers to prevent cut-and-paste attacks. On balance, I
>>>>>> don't see any decisive reason to forbid it. Again, the worst thing
>>>>>> that can happen is verification will fail, and if the number is
>>>>>> weird, or has leaked into a place where it shouldn't be, failure
>>>>>> is probably the right thing.
>>>>>>
>>>>>> Jon Peterson
>>>>>> Neustar, Inc.
>>>>>>
>>>>>> On 12/15/15, 10:52 AM, "Paul Kyzivat" <[e-mail]
>>>>>> <mailto:[e-mail]>> wrote:
>>>>>>
>>>>>>> On 12/15/15 1:30 PM, Peterson, Jon wrote:
>>>>>>>>
>>>>>>>> The canonicalization rules are not designed with the assumption
>>>>>>>> that the  string inputted to the algorithm is an E.164 number. They
>>>>>>>> are designed to  be as flexible as possible given the presence of a
>>>>>>>> dial string -  remembering that we canonicalize To as well as From.
>>>>>>>> Ideally, everything  we deal with would follow the dictates of
>>>>>>>> RFC3966, sure. We just proceed  with an abundance of caution.
>>>>>>>
>>>>>>> So, do you assume that a uri of sip:[e-mail] will be
>>>>>>> canonicalized the same way by everybody?
>>>>>>>
>>>>>>> I suppose everyone in the NANP might do so. But what about a
>>>>>>> recipient in some other locale?
>>>>>>>
>>>>>>> I guess the theory is that at the borders between domains numbers
>>>>>>> will be rewritten to be understandable in the receiving domain. If
>>>>>>> the number doesn't contain its country code then it presumably needs
>>>>>>> to be added at a country boundary to be understood. That works for
>>>>>>> numbers that correspond to E.164 numbers. But what about 611? There
>>>>>>> is no standard way to put a country code on it.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Paul
>>>>>>>
>>>>>>>> I would be happy to add some text saying that escaped characters
>>>>>>>> should be  removed as part of the canonicalization process.
>>>>>>>>
>>>>>>>> Jon Peterson
>>>>>>>> Neustar, Inc.
>>>>>>>>
>>>>>>>> On 12/13/15, 9:34 AM, "stir on behalf of DRAGE, Keith (Keith)"
>>>>>>>> <[e-mail] <mailto:[e-mail]> on behalf
>>>>>>>> of [e-mail]
>>>>>>>> <mailto:[e-mail]>>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> The international E.164 number can only be decimal digits.
>>>>>>>>>
>>>>>>>>> That therefore means that the country code, the national
>>>>>>>>> destination code, and the subscriber number, all of which are
>>>>>>>>> component parts of an international E.164 number, can only be
>>>>>>>>> decimal digits.
>>>>>>>>>
>>>>>>>>> That would imply that the only part that could contain such a
>>>>>>>>> character  is a prefix to an E.164 number, or if the number is not
>>>>>>>>> an
>>>>>>>>> E.164 number,  such as a private dial plan.
>>>>>>>>>
>>>>>>>>> I'd note that RFC 3966 states: "All phone numbers MUST use the
>>>>>>>>> global form unless they cannot be represented as such."
>>>>>>>>>
>>>>>>>>> I suspect that "*", "#", etc have more usage in numbers that are
>>>>>>>>> dialstrings rather than telephone numbers.
>>>>>>>>>
>>>>>>>>> Regards
>>>>>>>>>
>>>>>>>>> Keith
>>>>>>>>>
>>>>>>>>> -----Original Message-----
>>>>>>>>> From: stir [mailto:[e-mail]] On Behalf Of Paul
>>>>>>>>> Kyzivat
>>>>>>>>> Sent: 11 December 2015 15:58
>>>>>>>>> To: [e-mail] <mailto:[e-mail]>
>>>>>>>>> Subject: Re: [stir] stir-06: Reality check on numbers (6.1.1)
>>>>>>>>>
>>>>>>>>> On 12/10/15 9:15 PM, Eric Burger wrote:
>>>>>>>>>> Section 6.1.1 on Canonicalization states:
>>>>>>>>>>         Once an implementation has identified a telephone
>>>>>>>>>> number, it must
>>>>>>>>>>         construct a number string.  Implementations MUST drop
>>>>>>>>>> any leading
>>>>>>>>>>         +'s, any internal dashes, parentheses or other non-numeric
>>>>>>>>>>         characters, excepting only the leading "#" or "*" keys
>>>>>>>>>> used in
>>>>>>>>>>         some special service numbers (typically, these will
>>>>>>>>>> appear only  in
>>>>>>>>>>         the To header field value).  This MUST result in an
>>>>>>>>>> ASCII string
>>>>>>>>>>         limited to "#", "*" and digits without whitespace or
>>>>>>>>>> visual
>>>>>>>>>>         separators.
>>>>>>>>>>
>>>>>>>>>> Survey time: does pound or star  EVER appear in a From field?
>>>>>>>>>> E.164 does not allow it.
>>>>>>>>>
>>>>>>>>> pound isn't allowed at all in a sip uri, except via escaping.
>>>>>>>>>
>>>>>>>>> There is no mention of escaping (or unescaping) in the text. If
>>>>>>>>> there is  the possibility of pound coming through then that is
>>>>>>>>> needed.
>>>>>>>>>
>>>>>>>>> Also, * and # (as well as A-D) are never valid in global numbers,
>>>>>>>>> but are  valid within local numbers not just first, but anywhere
>>>>>>>>> in the number.
>>>>>>>>> So
>>>>>>>>> why is there special treatment for a *leading* star or pound?
>>>>>>>>>
>>>>>>>>> ISTM that canonicalization of dialstrings that represent local
>>>>>>>>> rather than global numbers is fraught with difficulty.
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>> Paul
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> _______________________________________________
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>>>>>>>>> [e-mail] <mailto:[e-mail]>
>>>>>>>>> https://www.ietf.org/mailman/listinfo/stir
>>>>>>>>>
>>>>>>>>> _______________________________________________
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>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
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