[Ecrit] PLEASE READ: We need people to comment on planned-changes

[Randall Gellens <[e-mail]>]

Hi ECRIT Members,

There are a few technical choices to be made in the planned-changes 
draft.  Up to now it's been just Brian, Guy, and myself discussing the 
issues.  We need other group members to speak up, please.  If the issues 
aren't clear, please say what is confusing.

--Randall

Forwarded message:

> From: Brian Rosen <[e-mail]>
> To: Randall Gellens <[e-mail]>
> Cc: Caron, Guy <[e-mail]>, ECRIT <[e-mail]>
> Subject: Re: [Ecrit] planned-changes: two questions
> Date: Fri, 3 Sep 2021 12:37:28 -0400
>
> It would be great to hear from others on what they think of these 
> ideas.  If we haven’t explained what we’re talking about 
> sufficiently, what is unclear?
>
> Do you like Randall’s “do the roundtrip notify before completing 
> the findService response, which could then have an error response?  
> (Once per URI) or my “notify immediately after a new URI is 
> presented, and periodically after that (keep alive) with no explicit 
> error on the findService, noting that the client knows the 
> notification is coming and if it doesn’t appear there was an error.
> Do you think we should have an explicit URI-not-stored error or 
> silently discard?
> Do you think periodic keep alives (per URI) should be supported?
> Do you think we need an explicit delete of an ID from triggering 
> notify at a given URI?
> If your answer to the above is “yes” would you prefer an explicit 
> delete “command” or use something in the LI that somehow indicated 
> delete?
>
> Any other concerns?
>
>> On Sep 2, 2021, at 6:04 PM, Randall Gellens 
>> <[e-mail]> wrote:
>>
>> We need to do it once per new URI. If the URI already is stored, 
>> there's no reason to validate it again.
>>
>> The overhead of a new TCP/TLS connection and one round-trip isn't 
>> much, and is only once per new URI.
>>
>> Also, for URI deletion, we should have an explicit way to do this, 
>> perhaps a "delete" parameter along with the URI to be deleted.
>>
>> --Randall
>>
>> On 2 Sep 2021, at 14:51, Brian Rosen wrote:
>>
>> You are proposing that you set up a TLS connection, POST on that 
>> connection, the server sets up a reverse connection, POSTs on that, 
>> the client responds to that POST, and then the server responds to 
>> that post?  Not a great plan I think.  If second TLS connection 
>> already exists, so you are asking to do a complete transaction B->A 
>> before the response to A->B I might be less worried.  Doesn’t sound 
>> like a great plan
>>
>>
>> Also, we need only do this once per client.  Not once per validation.
>>
>> Brian
>>
>>> On Sep 2, 2021, at 5:45 PM, Randall Gellens 
>>> <[e-mail] <mailto:[e-mail]>> 
>>> wrote:
>>>
>>> I think a simpler approach is that when a query includes a URI, 
>>> before returning the response, the server POSTS to the URI. If it 
>>> receives a success response, it stores the URI and returns the 
>>> response. If it receives a non-success response, it informs the 
>>> client that the URI was not stored. We can use uriNotStored or have 
>>> a new warning such as uriTestFailure. This way, the server does not 
>>> need to maintain a pending URI and retry the test, and the client 
>>> knows immediately if there's a problem. Presumably, if the URI is 
>>> bogus, the URI host will not return a success result. I think that 
>>> should be good enough, but if we want stronger protection, we could 
>>> tie in the TLS authentication when the server does the POST.
>>>
>>> --Randall
>>>
>>> On 2 Sep 2021, at 14:29, Brian Rosen wrote:
>>>
>>>
>>>
>>>> On Sep 2, 2021, at 3:48 PM, Caron, Guy <[e-mail] 
>>>> <mailto:[e-mail]>> wrote:
>>>>
>>>> Inline under [GC].
>>>>
>>>> If you agree with my comments inline below, here is how I see the 
>>>> process (building on what Randall initially provided on this 
>>>> thread):
>>>>
>>>> 1) In a validation query, a Client can request to be notified when 
>>>> the proffered LI should be revalidated, and provides a URI to send 
>>>> the notifications to;
>>>> 2) In the validation response, the Server provides an ID that the 
>>>> Client associates with the LI it just validated;
>>>> 3) Immediately thereafter, the Server sends a ‘test’ 
>>>> notification to the URI, without any ID;\
>>> [br[For every new ID?  Or just once?  I wanted this to be a one time 
>>> registration.
>>>> 4) The recipient at the URI is expected to respond with the ID 
>>>> provided in step 2. If it does, the Server stores the URI for 
>>>> future notifications. If it does not, the Server [let’s pick one: 
>>>> reject silently the URI and block the Client permanently/provides a 
>>>> ‘uriNotStored’ warning response to the URI {not compatible with 
>>>> the current proposal to test outside of LoST}/reject silently the 
>>>> URI and block the Client temporarily/other?];
>>> [br]I don’t think an explicit failure is a problem.  The LoST 
>>> server can limit retries if it needs to.
>>>
>>>
>>>> 5) Some time after, the Server notifies the Client of an upcoming 
>>>> planned change by sending a notification to the successfully tested 
>>>> URI with the location ID;
>>>> 6) The client revalidates each LI in its database that matches the 
>>>> ID as of the date of the planned change. If no ID matches, it is a 
>>>> no-op at the Client. Revalidations may also result in no-op at the 
>>>> Client.
>>>> 7) LIs at the Client that are invalidated by the planned change are 
>>>> modified in its database to be valid (which probably mean another 
>>>> revalidation cycle) with an effective date set to <revalidateAsoF> 
>>>> value.
>>> [br]I wanted periodic keep alives.  How would that work?
>>>>
>>>> Guy
>>>>
>>>> De : Brian Rosen <[e-mail] <mailto:[e-mail]>>
>>>> Envoyé : 1 septembre 2021 19:17
>>>> À : Caron, Guy <[e-mail] <mailto:[e-mail]>>
>>>> Cc : Randall Gellens <[e-mail] 
>>>> <mailto:[e-mail]>>; ECRIT <[e-mail] 
>>>> <mailto:[e-mail]>>
>>>> Objet : [EXT]Re: [Ecrit] planned-changes: two questions
>>>>
>>>> Inline
>>>>
>>>>
>>>> On Sep 1, 2021, at 3:28 PM, Caron, Guy <[e-mail] 
>>>> <mailto:[e-mail]>> wrote:
>>>>
>>>> Ok. You have convinced me of the necessity of validating the URI 
>>>> before the Server stores it and that the security considerations in 
>>>> RFC5222 do not cover this threat.
>>>>
>>>> I observe that this vulnerability was already mentioned in the 
>>>> Security section of the planned-changes draft:
>>>>
>>>> The server is subject to abuse by clients because it is being asked 
>>>> to store something and may need to send data to an uncontrolled 
>>>> URI.
>>>>
>>>> However, the original threat vector and associated response is 
>>>> probably insufficient to cover the DoS you raised, hence this new 
>>>> proposal to test the URI.
>>>>
>>>> So, I’m conceptually favorable to adding a mechanism to test the 
>>>> URI before being stored by the Server.
>>>> Good
>>>>
>>>>
>>>>
>>>> I would like this mechanism to be as simple as possible and I think 
>>>> the goals can be achieved by testing the URI and receiving a 
>>>> response with at least one of the IDs previously supplied by the 
>>>> Server. I would leave it to policy at the Server to determine when 
>>>> and how often the URIs would be tested, with a recommendation 
>>>> (MUST? SHOULD?) to test it upon reception before storing it.
>>>> I think you are suggesting we add text that says the LoST server 
>>>> can send a notification to the LoST client that has no changes, and 
>>>> just serves as a keep alive.  I’m sure we can make that work but 
>>>> generally, I find this kind of implicit test to be less 
>>>> satisfactory than an explicit keep alive transaction.   I get that 
>>>> an actual change may not be seen as a change to the client, and 
>>>> thus it works with no real code, but it doesn’t seem as clean as 
>>>> an explicit keep alive.  I’d be interested in herring from others 
>>>> on that
>>>> [GC] Could we not, for example, declare a value/element/attribute 
>>>> 'test' to be passed in the notification with no IDs? Would that 
>>>> meet your idea of an explicit test mechanism?
>>> [br] I suppose.  Doesn’t seem much different than a parameter to 
>>> the findService, but I’m okay with it
>>>>
>>>>
>>>>
>>>> We probably need to say something about what to do if the URI test 
>>>> fails. Do we inform the Client that provided the URI that it may 
>>>> have been compromised? Do we simply drop the URI silently? Do we 
>>>> block the Client that provided the URI entirely?
>>>> At minimum wait and try again, the client could be down for a 
>>>> while.  I would not allow a lot of location records to be marked 
>>>> with the URI that didn’t test valid.
>>>>
>>>> I am somewhat leery of creating circumstances where the client has 
>>>> to go through and revalidate it’s entire record set because the 
>>>> mechanism failed in some way.  There clearly would be circumstances 
>>>> where that happened, but missing a keep alive shouldn’t be one of 
>>>> them.  The initial one however should be a hard block.  If you 
>>>> can’t get the first ID returned, then we have to not accept other 
>>>> registrations.
>>>> [GC] On a second thought, what's the value of testing the URI after 
>>>> the first test? If it passed, it's valid and the Server stores it 
>>>> for use when a planned change occurs. If after that and for some 
>>>> reason, the Client is not responsive to the notification, does the 
>>>> Server care?
>>> Generally when we have things that don’t do anything for months 
>>> and then we need it, I would like to see periodic keep alives.  
>>> Things change on both sides and both sides have a vested interest in 
>>> making sure the mechanism works when they need it.
>>>>
>>>>
>>>>
>>>> I’m not sure if the <command> thing is necessary since it 
>>>> requires the Server to keep state. I would think that if the URI 
>>>> has been tested and stored, it means it is active and valid until 
>>>> it is deleted through the reception of an empty <plannedChange> for 
>>>> example, or replaced through the reception of a new URI in 
>>>> <plannedChange>.
>>>> I don’t think there is any server state other than the URI is 
>>>> valid.  Each transaction stands alone.
>>>>
>>>> Without the delete, you can’t remove one location record from the 
>>>> set that gets notified of planned changes.  You can change the URI, 
>>>> but that changes it for all notifications.
>>>> [GC] Why? A Client that no longer wants to be notified for a given 
>>>> ID sends an empty <plannedChange> for the LI it no longer has. If 
>>>> that ID at the Server is associated with only one location (say one 
>>>> specific civic number), it deletes the Client's URI. If it is 
>>>> associated with more than one record (say a range of civic 
>>>> numbers), it accepts the transaction but keeps the URI. A 
>>>> notification for that ID sent to the Client that only had the civic 
>>>> number would result in a no-op.
>>> That means that the client has to be identified by something like 
>>> the TLS cert, because the URI isn’t there for the delete.  I was 
>>> using the domain of the URI as the ID of the client.
>>>
>>> But we have another problem: I think the server does not track the 
>>> LI.  On any findService with the new option, it looks for a matching 
>>> record and returns the ID it has for that record.  It’s the client 
>>> that tracks possible multiple LIs for one ID, not the server.  So in 
>>> your example, the client would notice that any address in the range 
>>> had the same ID.  It would get one notification if the range record 
>>> changed, and it would update all its records in the range.  But if 
>>> it deleted one of a set of records that have the same ID, it 
>>> wouldn’t request delete.  Only if it got down to one record with a 
>>> given ID, and it needed to delete that record, would it request 
>>> delete for that ID at the server.
>>>>
>>>>
>>>>
>>>> Lastly, I’m not sure we still need the warning ‘uriNotStored’ 
>>>> given that we’re going with one generic URI per Client. The only 
>>>> argument I can think of for keeping it would be the proliferation 
>>>> of Clients within the coverage aria of the Server that would be so 
>>>> large that the Server couldn’t store them all. A counter argument 
>>>> to that would be that doing so could be seen as giving privileges 
>>>> to certain Clients over others.
>>>>
>>>> We’re creating circumstances where the client won’t get a 
>>>> notification.  I think we need to tell them that.
>>>> [GC] Only if the URI fails the validity test.
>>> [br]I wanted to allow the server to limit the number of IDs it was 
>>> tracking for a given client.  I wanted to limit the number of 
>>> queries the server is responding to (although it might well silently 
>>> discard a DOS attack.
>>>>
>>>>
>>>> One limit I might put on a client is how many locations they can 
>>>> ask to be notified.  If they try to set up a situation where no 
>>>> matter what changed, they get a notification, I think that may be 
>>>> too much to ask, and the server can have a limit.  It would be okay 
>>>> if it’s one URI per valid record at the LIS, but the LoST server 
>>>> doesn’t have that data.
>>>> [GC] It's one generic URI per Client with one or more IDs stored by 
>>>> the Client against its LIs, right? As you suggesting we go back to 
>>>> one URI per Client record in its database?
>>> [br]  One generic URI per client.  So if the client asks for its URI 
>>> to be stored against too many IDs, it can be told no.
>>>>
>>>>
>>>>
>>>> Thanks,
>>>>
>>>> Guy
>>>>
>>>>
>>>> De : Brian Rosen <[e-mail] <mailto:[e-mail]>>
>>>> Envoyé : 31 août 2021 13:54
>>>> À : Randall Gellens <[e-mail] 
>>>> <mailto:[e-mail]>>
>>>> Cc : Caron, Guy <[e-mail] <mailto:[e-mail]>>; ECRIT 
>>>> <[e-mail] <mailto:[e-mail]>>
>>>> Objet : [EXT]Re: [Ecrit] planned-changes: two questions
>>>>
>>>> Of course an attacker would conceal itself and register multiple 
>>>> URIs under different identities.  But the bigger  problem is that 
>>>> if a large planned change occurred, the victim could receive a 
>>>> large number of notifications it didn’t expect.
>>>>
>>>> With a test transition, we know that the client expects to see 
>>>> notifications, we only need one per URI (we could specify one per 
>>>> domain — after the scheme and before the first slash).  If we 
>>>> don’t get the ID, we know not to allow that URI to be 
>>>> provisioned.  So it’s one test transaction vs a large number of 
>>>> planned change transactions.
>>>>
>>>> Brian
>>>>
>>>>
>>>>
>>>>
>>>> On Aug 31, 2021, at 1:35 PM, Randall Gellens 
>>>> <[e-mail] <mailto:[e-mail]>> 
>>>> wrote:
>>>>
>>>> If a malicious client registers a URI that is designed to attack a 
>>>> third site, the test transaction causes the LoST server to connect 
>>>> to it and POST a command. Without a test transaction, the LoST 
>>>> server stores the URI and at a future time connects to it and sends 
>>>> a command. Either way, a LoST client can register potentially one 
>>>> URI per queried location, and a LoST server will connect to that 
>>>> URI and POST a message. A queried location could be tied to many 
>>>> other locations, so there could be many locations for which a 
>>>> change would trigger the LoST server to use the URI, but is that 
>>>> worse?
>>>> --Randall
>>>> On 31 Aug 2021, at 10:27, Brian Rosen wrote:
>>>> If the work group wants to have the LoST server keep the URI until 
>>>> expressly deleted, that’s okay with me.
>>>>
>>>> Authenticating the client to the server doesn’t mean the URI is 
>>>> authenticated.  We can’t restrict the URI to be the same entity 
>>>> as the client running the LoST transaction.  And the clients are 
>>>> wide ranging.  Could be an enterprise running its own LIS for 
>>>> example.  We can’t assume the North American PKI is workable 
>>>> everywhere, and even that doesn’t extend to an enterprise LIS.  
>>>> ISTM we have to run a test transaction with the notification 
>>>> service to make sure it’s what we think it is.
>>>>
>>>> Brian
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Aug 31, 2021, at 9:01 AM, Caron, Guy <[e-mail] 
>>>> <mailto:[e-mail]>> wrote:
>>>>
>>>> Inline.
>>>>
>>>> Guy
>>>>
>>>> -----Message d'origine-----
>>>> De : Brian Rosen <[e-mail] <mailto:[e-mail]>>
>>>> Envoyé : 31 août 2021 08:11
>>>> À : Caron, Guy <[e-mail] <mailto:[e-mail]>>
>>>> Cc : Randall Gellens <[e-mail] 
>>>> <mailto:[e-mail]>>; ECRIT <[e-mail] 
>>>> <mailto:[e-mail]>>
>>>> Objet : [EXT]Re: [Ecrit] planned-changes: two questions
>>>>
>>>> You delete the URI when you delete the record in the LIS.
>>>> [GC] That's fine but that was not the question Randall posed. He 
>>>> asked whether the URI is deleted after a notification. I agree that 
>>>> if the Client does not host the location anymore that the URI 
>>>> associated with that location in the Server should be deleted. This 
>>>> could be achieved with an empty <plannedChange>.
>>>>
>>>> I don’t think this is covered in 5222.  The mechanism causes the 
>>>> LoST server to send notifications to the client, but the client is 
>>>> allowed to put any URI in the record, and it can add it to as many 
>>>> records as it wants.
>>>> [GC] I thought we agreed on using one generic URI per Client. 
>>>> Clients should be authenticated by the Servers.
>>>>  An evil implementation could record URIs against multiple targets 
>>>> that were unaware that the evil implementation did it, until they 
>>>> got a large number of PUSH transactions they didn’t expect or 
>>>> understand as a result of a large planned change.
>>>> [GC] Only authenticated Clients should be allowed to provide URIs 
>>>> to be stored by the Servers.
>>>>
>>>> The proposed mechanism qualifies the client URI before its used in 
>>>> a planned change.
>>>>
>>>> Brian
>>>>
>>>>
>>>>
>>>> On Aug 31, 2021, at 7:37 AM, Caron, Guy <[e-mail] 
>>>> <mailto:[e-mail]>> wrote:
>>>>
>>>> Well, this is not going in the direction I thought.
>>>>
>>>> What is the purpose of deleting the URIs at the Server 
>>>> post-validation?
>>>>
>>>> Regarding opening a new DoS, I guess I'm not following. Wouldn't 
>>>> this case be covered by the security considerations in RFC 5222?
>>>>
>>>> What you're proposing puts back significant load on the Servers (a 
>>>> key consideration for creating planned-changes in the first place) 
>>>> and complicates the mechanism.
>>>>
>>>> Guy
>>>>
>>>>
>>>> -----Message d'origine-----
>>>> De : Ecrit <[e-mail] <mailto:[e-mail]>> 
>>>> De la part de Brian Rosen Envoyé :
>>>> 30 août 2021 11:22 À : Randall Gellens <[e-mail] 
>>>> <mailto:[e-mail]>> Cc
>>>> : ECRIT <[e-mail] <mailto:[e-mail]>> Objet : [EXT]Re: 
>>>> [Ecrit] planned-changes: two
>>>> questions
>>>>
>>>> Answer 1: yes.  Since there is going to be a revalidation, just 
>>>> deleting the setting seems right to me.
>>>> Answer 2: Up to server.  If I were implementing, I would hash the 
>>>> real ID with the URI and some kind of predictable nonce.
>>>>
>>>> We probably have to say more about how the server identifies the 
>>>> client, so that replacement of the URI works.  Could we say we use 
>>>> the domain of the URI (the entire domain with all the dots) to 
>>>> identify the client, and anything can occur after it (meaning a 
>>>> slash and whatever)?  If we do that, then how would delete the 
>>>> notification?  Force there to be something other than the domain 
>>>> (ugly).  Explicit delete request?
>>>>
>>>> Hmmm, we’ve opened a DoS attack: a rogue client stores a bunch of 
>>>> URIs for servers it wants to victimize.  In North America we have a 
>>>> real simple solution for that, because we have a PKI, so we know, 
>>>> for sure, who the client is, and could restrict who we allow to 
>>>> store URIs, but that wouldn’t be true in general.  Also, it would 
>>>> be nice for the client to have confidence the mechanism worked 
>>>> before it needed it.
>>>>
>>>> So
>>>> Let’s add a “command” to plannedChange in the findService 
>>>> request.
>>>> And, have the client have a response to the notification which is 
>>>> the
>>>> ID (json with the 200)
>>>>
>>>>
>>>> The client starts by sending a command of “initialize”.  The 
>>>> domain is the identity of the client.  The response is an immediate 
>>>> notification to the with whatever LI was in the request and an ID.  
>>>> The  response by the client (which is the notification web server) 
>>>> is a piece of json containing the ID.  We can say that the LI in 
>>>> this initialize command could be something simple like the Country 
>>>> Code that wouldn’t get a planned change.
>>>>
>>>> Thereafter, the LoST server (notification client) periodically 
>>>> repeats this keepalive notification every day or week with the 
>>>> initialize LI.  The client has to respond with the ID.
>>>>
>>>> The regular notification request is a command of “notify”.  The 
>>>> server ignores a request for notification from an uninitialized 
>>>> client.
>>>> The notification can be deleted with a command of “delete”.  If 
>>>> you delete the initialize LI, then the server won’t send any more 
>>>> notifications to that client and deletes all URIs it was saving for 
>>>> that client.  The client would have to re-initialize to reset.
>>>>
>>>> Brian
>>>>
>>>>
>>>>
>>>> On Aug 27, 2021, at 5:41 PM, Randall Gellens 
>>>> <[e-mail] <mailto:[e-mail]>> 
>>>> wrote:
>>>>
>>>> I think we're moving to a model where:
>>>> - In a query, a client can request to be notified when the location
>>>> should be revalidated;
>>>> - In the response, the server provides an ID which the client
>>>> associates with the location it just validated;
>>>> - The server sends a notification to the URI, containing the ID;
>>>> - The client revalidates each location with which that ID is 
>>>> associated.
>>>>
>>>> Question 1: Does the server delete/inactivate the URI once it has 
>>>> sent the notification?
>>>>
>>>> Question 2: Presumably, when the client revalidates the 
>>>> location(s), it will again request notification.  Does the server 
>>>> return the same ID as before, or a different ID?  A different ID 
>>>> could perhaps be useful in edge cases where the server didn't send 
>>>> or the client didn't get the notification, but any utility seems 
>>>> small.  If it's the same ID, then the answer to question 1 can be 
>>>> that the URI remains active until the client asks to no longer be 
>>>> notified (by sending an empty URI?).
>>>>
>>>> --Randall
>>>>
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>>>
>>