Re: [Masque] Tsvart last call review of draft-ietf-masque-connect-ip-08

[Bob Briscoe <[e-mail]>]

David & Alex, See [BB]

On 30/03/2023 05:47, David Schinazi wrote:
> Hi Bob,
>
> Alex and I sat down to go through your thorough review in detail. I'm 
> sending our responses below marked with "EDITORS:". Important note: in 
> this email, EDITORS refers only to Alex and myself, not all document 
> editors/authors. Apologies if the email formatting comes out strange.
>
> Thanks,
> David
>
>
> On Wed, Mar 29, 2023 at 2:48 PM Magnus Westerlund 
> <[e-mail]> wrote:
>
>     Hi Bob,
>
>     Thanks for the review. We authors will have to go though your
>     comments in details. It is unfortunate that you did not review
>     HTTP Datagram specification (RFC 9297) prior as that is allowing
>     sending of datagrams over HTTP/3. In my initial read through of
>     the comments I think most still applies as they are not directly
>     related to if the tunneled IP are in datagrams (unreliable in
>     delivery order) or in streams (reliable in order delivery).  I do
>     know some of the issues you bring up have been discussed but was
>     not documented. We will have to consider if the choice to not
>     document them should be changed or not.
>
>     Cheers
>
>     Magnus
>
>     *From: *Bob Briscoe via Datatracker <[e-mail]>
>     *Date: *Wednesday, 29 March 2023 at 09:04
>     *To: *[e-mail] <[e-mail]>
>     *Cc: *[e-mail]
>     <[e-mail]>, [e-mail]
>     <[e-mail]>, [e-mail] <[e-mail]>
>     *Subject: *Tsvart last call review of draft-ietf-masque-connect-ip-08
>
>     Reviewer: Bob Briscoe
>     Review result: Not Ready
>
>     This document has been reviewed as part of the transport area
>     review team's
>     ongoing effort to review key IETF documents. These comments were
>     written
>     primarily for the transport area directors, but are copied to the
>     document's
>     authors and WG to allow them to address any issues raised and also
>     to the IETF
>     discussion list for information.
>
>     When done at the time of IETF Last Call, the authors should
>     consider this
>     review as part of the last-call comments they receive. Please
>     always CC
>     [e-mail] if you reply to or forward this review.
>
>     -----------------------------------------------------------------------
>     ==Overall comments==
>
>     How can I say this politely? The HTTP aspects of this document are
>     great work
>     and near-complete. However, the tunnelling aspects, in particular
>     the layering
>     interactions need a lot of work - possibly even a partial redesign
>     in places.
>     Also, the security aspects seem to have been viewed through
>     rose-coloured
>     spectacles; sthg like "Most people who like privacy are nice".
>
>     Well-written, but not an easy read in a single pass (not clear
>     what the point
>     is for quite a few pages and lots of forward x-references). Early
>     overview of
>     the scheme would help. Need to bear in mind that cross-layer work
>     has to be
>     addressed at a wider community who don't necessarily all subscribe
>     to the same
>     mind-share.
>
>     -----------------------------------------------------------------------
>     ==Document Structure==
>
>     I believe §§3-4 are about the tunnel config, and §§5-7 are the
>     per-packet aspects of the tunnel. Might be worth explaining that
>     in a doc roadmap.
>
>     EDITORS: That's a reasonable editorial ask, we'll look into it as
>     editors and see what we can do.
>
>     §6 "Payload Format"
>     This section needs to be split and/or re-titled, 'cos in the
>     middle (from "Client MAY optimistically start sending...") it
>     switches to operation, not format. At "Note that endpoints will
>     decrement..." it switches to TTL handling. Then at "IPv6 requires
>     that.." it switches to MTU discovery, which is another aspect of
>     operation.
>     Just because TTL and packet size are fields of an IP packet,
>     doesn't mean these aspects fall under the heading of "Payload
>     Format" - these paras are about handling these fields, not
>     defining their format.
>
>     EDITORS - We agree, filed an issue to track adding a new
>     Performance Considerations section:
>     https://github.com/ietf-wg-masque/draft-ietf-masque-connect-ip/issues/144
>

[BB] OK, gpod. I'm not convinced the new categorization should be 
'performance'. See my response to issue #144.
Whatever, you've grocked the point and I'm sure you'll deal with it.

>
>     -----------------------------------------------------------------------
>     ==Gaps==
>
>     ===A) No discussion of packet ordering ===
>
>     Although one of the variants of HTTP (http/3) is over UDP, which
>     is unordered, QUIC still delivers an ordered stream to the app
>     (which, in this case, is the inner of the tunnel). So, presumably
>     as packets arrive at the proxy, if there has been misordering or a
>     loss, QUIC will buffer until the next packet in order can be
>     delivered, i.e. head-of-line blocking. Hence, it's not really
>     advisable to forward connectionless packets through a
>     connection-oriented tunnel. The privacy benefit might make the
>     poor latency performance worth it. But this trade off at least
>     needs to be stated, perhaps in an applicability section.
>
>     I don't think an http3 stream is any less granular than an http2
>     stream or an http1.1 connection in this proxy arrangement. But if
>     it is, each need to be discussed separately.
>     If there is a vision to use an unordered variant of QUIC, then
>     there could be problems with Context IDs being processed out of
>     order, which could produce all sorts of unexpected side-effects,
>     given Context IDs are potentially stateful (caveat: you will see
>     that I don't really understand what Context IDs might be used for).
>
>     EDITORS: As discussed, this section is incorrect.
>
>     ===B) Conflicting Congestion Controllers (CCs) ===
>
>     Needs a section sthg like §12.1 of RFC8229, except:
>
>     That text mostly just listed the problems, but the implication of
>     publishing such a section in a spec is essentially, "We've told
>     you the problems, but now go ahead anyway." This is not just a TCP
>     in TCP problem. It's any nesting of two or more CC-controlled
>     protocols (e.g. TCP within QUIC, QUIC within QUIC, etc)
>
>     As above, if this is a trade off between privacy and performance,
>     that needs stating.
>
>     EDITORS: This makes sense, we'll add some text. Tracking in this
>     issue:
>     https://github.com/ietf-wg-masque/draft-ietf-masque-connect-ip/issues/145
>
>     ===C) Overlapping connection life-cycles ===
>
>     If a proxy crashes, powers down, etc. can it be brought back up
>     with all the connection state restored that it held before it
>     failed? Otherwise, all the connections within the tunnel inner
>     depend on the survival of their outer connection. There is no
>     reason to believe that all the inner connections are dispensable.
>
>     Would a soft-state design be more resilient than the hard-state
>     design described?
>
>     EDITORS: This is true of all tunnels, for example IKEv2/IPsec.
>

[BB] It's certainly true of /some/ tunnels, where the tunnel provides a 
service that requires flow state (e.g. IPsec holds traffic selectors, as 
you say).
However, the thinking behind my point is that here /IP/ is the inner, 
and usually tunnel endpoints providing an IP service only hold state 
about the other tunnel endpoint, not about the traffic they carry. So, 
forwarding just continues when it resumes after a failure.

So the Proxied IP service is as generic as IP, but not as resilient.

>     Luckily here we can use ADDRESS_REQUEST to recreate the same state
>     and avoid connections breaking
>

[BB] Are you saying that the design as already written would recreate 
the same state, or that it could?


[I identified the gaps so far by noting that this tunnel has a nearly 
fully featured transport layer between two IP layers, so I worked 
through the 8 functions of the transport layer to check for conflicts. 
One is connection life-cycle management. That led on to the fate-sharing 
principle [RFC1958], which points out that, if state is not e2e, it will 
raise resilience questions.

Critique is intended to be constructive. I'm trying to distil out the 
trade offs that have been made. Operational issues like this come up 
after an initial design - the usual iterative process.
It's good to recognize and articulate them. An RFC naturally starts out 
as a sales brochure, then the review process makes it more rounded. See 
gap (G).]

>
>     [The above points (A-C) are examples of the problems I mentioned
>     when using a connection-oriented protocol to tunnel a
>     connectionless protocol.]
>
>     ===D) Applicable Next Headers (aka IP Protocols) ===
>      No discussion of whether some IPv6 'Next Headers' (or IPv4
>     Protocols) are not applicable / unsafe / poor performing.
>
>     The last time that I proposed a generic UDP tunnel to the Intarea
>     as an alternative to GUE, the criticism was that it was "too
>     generic". I was told that the choice of tunnel protocols is about
>     whether they are sufficiently limiting; the aim is not totally
>     generic.
>
>     EDITORS: This document is about creating an IP tunnel over HTTP so
>     we have a tight scope based on the underlying protocol instead of
>     on the high layer protocols.
>

[BB] By enabling IP you have created an extremely wide scope. My point 
was that this will open Pandora's box. You might not need to go through 
all the implications in this draft. But I think you need to record that 
working out the security implications will be non-trivial.

>
>     === E) Applicable Address Ranges ===
>
>     Are anycast addresses in scope? IP multicast?
>     Link-local multicast is mentioned. What about ARP? Service Discovery?
>
>     EDITORS: We've documented the address types that require
>     implementation involvement. Anycast and (non-link-local) unicast
>     are equal to unicast as far as a single link is concerned. ARP
>     operates at L2 so it doesn't apply to an L3 tunnel. Similarly,
>     service discovery protocols don't need any special guidance.
>

I mentioned ARP and Service Discovery because they are both scoped to a 
subnet. Here, the tunnel creates a disjoint subnet, so the operator 
needs to decide whether and how much it wants the subnet to behave as if 
it is one whole. You might want to say that ops issues like this are out 
of scope. but again record that they will need to be addressed separately.

>
>     ===F) Propagation of IP headers and header fields between inner
>     and outer. ===
>
>     Some IPv6 extension headers are copied from inner to outer on
>     encapsulation; others aren't [RFC2473; §5.1]. The outer IPv6 flow
>     label is often zeroed. The contents of the DSCP, and ECN fields
>     can be propagated from inner to outer and the ECN outer is
>     propagated back to the forwarded header [RFC2983], [RFC6040].
>
>     Because there's a whole stack of headers between the inner and
>     outer IP headers (e.g. IP, UDP, QUIC, HTTP, IP), the draft needs
>     to make it clear that these copying and propagation rules still
>     apply between the two IP headers.
>
>     EDITORS: This is a tunnel operating at L7, not an L3/L4
>     encapsulation format. Copying these fields doesn't make sense
>     because it is possible to have multiple IP packets inside a single
>     IP packet.
>

[BB] Whatever the reason that L7 is in there, you can't escape the fact 
of what you have created, which is a L3 encapsulation. If the packet 
boundaries don't line up, surely it implies a potential problem has been 
created that you have to consider. Not that there aren't any problems.

On thinking about this since having written the review, it wouldn't be 
right to blindly follow the rules. But it would be worth considering the 
intent behind each rule, and whether it still applies in the case of 
your tunnel. For instance, because you have two congestion control 
loops, the proxy does NOT need to propagate ECN from the outer to the inner.
(Altho' two control loops is not good for performance, I guess this is 
one of the few advantages.)

>
>     ===G) No explanation of pros & cons relative to other packet
>     tunnelling ===
>     Yes, we can tunnel anything over anything, but why this one?
>     AFAIK, it's to hide traffic in the HTTP crowd for privacy. But
>     what are the merits relative to hiding in other crowds? And the
>     drawbacks (e.g. HoL blocking as mentioned above). In particular,
>     the pros & cons vs UDP in HTTP.
>
>     EDITORS: There are many motivations for tunneling IP over HTTP,
>     one of them being that it allows traveling through HTTP load
>     balancers. This is discussed in our charter and doesn't need to be
>     added to the document.
>

[BB] Even if the draft referenced the charter (which it doesn't) it 
would not be sufficient, 'cos the masque charter doesn't answer the 
question of what the drawbacks are and why this specific choice of 
technology is a useful tradeoff between the benefits and those 
drawbacks. That comes from the experience of have designed and implemented.

If you had an RFC that motivated this specific solution (not just the WG 
in general), you could certainly refer to it to save keep including it 
in each RFC. But someone does actually have to explain and motivate 
what's been done, and draw conclusions about tradeoffs. Just mandating 
how to build something is not enough. That is the reason that RFCs go 
through wider IETF review - not least to weed out group-think.

>
>     ===H) Role reversal? ===
>
>     It's not made clear whether there's anything intrinsically
>     'clientish' about a client. Or 'proxyish' about a proxy.
>     Especially in a bump in the wire topology (like the site-site VPN
>     example), does it matter which is which? Is it just determined by
>     the administrator setting a proxy up in listen mode? Is there
>     anything that one or the other cannot do by virtue of its role,
>     other than initiate a connection to the other one? Shouldn't the
>     draft speak about this if it requires correct manual set up?
>     Particularly for tunnels consisting of chains (or trees?) of
>     intermediaries.
>
>     EDITORS: The terms "client" and "proxy" are HTTP terminology. The
>     client sends the request, the proxy responds. Once the tunnel is
>     up, the draft talks about endpoints and peers because then it's
>     symmetric.
>

[BB] I know it's HTTP terminology. I've caught up now. I was labouring 
under the misconception (not the fault of the draft, just my earlier 
faulty assumptions) that the decap function was somehow intrinsic to a 
proxy. But it's not, it's created by the particular ADDRESS_REQUEST and 
ADDRESS_ASSIGN messages used. I had (wrongly) thought that each tunnel 
endpoint in the symmetric site-to-site VPN example was both a client and 
a proxy. I've now caught up and grocked that still only one end of such 
a tunnel would be a proxy (as correctly labelled in Fig 17).

>
>     -----------------------------------------------------------------------
>     ==Section by Section==
>
>      1. Introduction (and Abstract)
>
>     "...updates RFC9298"
>     It's not at all clear to me what aspect of RFC9298 this RFC
>     updates. It seems unlikely, given IP Proxying is an alternative to
>     UDP Proxying, not an update. But if it does, the draft needs to
>     say what it updates. And, if RFC9298 were updated by this draft,
>     it would surely be a normative reference, not informative.
>
>     EDITORS: Fair enough, we'll add text. Tracked in this issue:
>     https://github.com/ietf-wg-masque/draft-ietf-masque-connect-ip/issues/146
>
>      3. Configuration of Clients
>
>     Reasoning for each each URI template rule?
>     I can't really judge whether this set of rules leaves the URI
>     template flexible enough, without knowing the reason for each
>     constraint. Is this explained in "Proxying UDP in HTTP"? If so, a
>     ref would be useful.
>

[BB] I think this point got missed (probably the way the review tool 
wraps lines together).

>      "IP proxy deployments SHOULD offer service at this location if
>     they need to interoperate with such clients." Surely "MUST" to
>     interoperate?
>
>     EDITORS: That's right, the MUST was to simplify interoperating. We
>     made these decisions for CONNECT-UDP as a WG and then decided to
>     keep the same ones for CONNECT-IP.
>

[BB] But the draft doesn't say MUST. It says SHOULD, which is my point.
(And similarly the CONNECT-UDP draft says SHOULD in the equivalent 
sentence.)

>
>      4. Tunnelling IP over HTTP
>
>     "When sending its IP proxying request, the client SHALL perform
>     URI template expansion..." Surely just "... the client
>     performs..." (just a necessary process step, not an interop
>     requirement)
>
>     EDITORS: We disagree, making this normative is clearer. This
>     matches our editorial style in 9298.
>

[BB] Doesn't make either of them right. But I won't fight, 'cos too many 
words in caps is on the safe side of interop.

>
>     "IP proxying requests [responses] do not carry any message
>     content." Is it an error if they do?
>
>     EDITORS: The stream is taken over by the capsule protocol. Data on
>     the stream is not message content as the data stream has been
>     taken over. See 9297 for details.
>

[BB] So this becomes an editorial point, i.e. shouldn't this say "IP 
proxying requests [responses] *cannot* carry any message content."

>
>      4.1. IP Proxy Handling
>
>     "...the IP proxy MUST perform DNS resolution..." Surely "... the
>     IP proxy performs..." (just a necessary process step, not an
>     interop requirement)
>
>     EDITORS: We disagree, making this normative is clearer. This
>     matches our editorial style in 9298.
>
>     "IP proxies MAY choose to tear down the tunnel due to a period of
>     inactivity" Better? "IP proxies MAY choose to tear down the
>     tunnel, e.g. due to a period of inactivity" Rationale: there are
>     other possible reasons, e.g responding to an attack.
>
>     EDITORS: It's already clear that the proxy can tear down the
>     tunnel, this bit is about lifetime
>

[BB] OK. Then it becomes editorial, i.e. a slightly more obvious flow of 
word order would be "After a period of inactivity IP proxies MAY choose 
to tear down the tunnel".

>
>     "Any response other than a successful response indicates that the
>     request has
>     failed; thus, the client MUST abort the request." This is repeated
>     at each instance in the subsequent sections. Either not needed
>     here as well, or not needed in each section as well.
>
>     EDITORS: This isn't repeated, they're separate requirements.
>

[BB] Not important, but my point was that there are two separate 
requirements in the two Response subsections after §4.1 (§4.3 & §4.5), 
but also the same requirement in §4.1 covering all cases in general as well.

>
>      4.6. Limiting Request Scope
>
>     "When the IP proxy knows that a request is scoped to a target
>     prefix or protocol, it can leverage this information to optimize
>     its resource allocation..." This highlights that the protocol
>     relies on a perverse incentive for the client to scope its request
>     so that the server can optimize its resources. That smells like
>     potentially the opposite of resource optimization, i.e. a
>     vulnerability; clients can scope their requests to force a server
>     to frag its resources. Perhaps consider redesigning the protocol
>     so that the server initiates the scoping (or at least it can
>     somehow negotiate the outcome)?
>
>     EDITORS: The server is always able to abort the tunnel if it
>     doesn't want to spend resources. The protocol as currently
>     designed is what we need in practice, your proposed redesign is not.
>

[BB] My point wasn't to push my proposed redesign, it was to point out 
the potential vulnerability.

>     "target: ...the IP proxy is expected to perform DNS resolution
>     ..." Might this potentially amplify a resource exhaustion
>     vulnerability, esp. if the client continually gives the proxy
>     DNSSEC work?
>

[BB] This point seems to have been missed.

>     "IP proxies MAY perform access control using the scoping
>     information provided by the client: if the client is not
>     authorized to access any of the destinations included in the
>     scope, then the IP proxy can immediately fail the request." I
>     think the clause after ':' ought to be tagged as an example. I
>     think it's intended to be a degenerate/extreme example. Whatever,
>     its relation with the earlier words is unclear. It's possible this
>     would be better in §4.1, which is where it would fit into the
>     process steps. However, at that point in the draft, scope limiting
>     hasn't been explained. I'm in two minds.
>
>     EDITORS: I agree with you that this change doesn't really improve
>     things, so we'll keep them as-is.
>

[BB] I think this is an editorial point then. I think the problem is the 
colon, which would be better as just a full stop. A colon implies that 
the clause after it is just another way of saying the clause before it. 
But the clause before is the general point, and the clause after is just 
one case where it's easy to decide that it's a fail.

>
>      4.7. Capsules
>
>     Are all control messages to the tunnel on one stream, or can each
>     capsule arrive in a separate stream, or is it up to the operator?
>     IOW, do capsules have to be acted on in the order they are sent,
>     or does it depend?
>
>     EDITORS: Please read RFC 9297 § 3. Capsules are sent on the one
>     (only) stream, and are sent in order. Capsule protocol does not
>     require they be processed in order, but in almost all cases should be.
>

[BB] I was thinking of a case where it would be useful to have >1 
control stream. As I explained before, I did read the relevant parts of 
9297 each time I needed to find the answer to a question like this one.

Actually, this morning I read the whole of 9297 twice. And I've just 
read the capsule section again. I can't find anywhere where it precludes 
more than one stream. However, I admit I don't have a strong grasp of 
large swathes of the recent additions to HTTP. Is there a good tutorial 
anywhere?

>
>      §4.7.1 The last para starting "Note that the IP forwarding
>     tunnels described in this document..." seems more like an
>     architectural point that ought to be stated earlier. It's related
>     to ADDRESS_ASSIGN, but is it really appropriate to bury it here?
>
>     EDITORS: Agreed, tracked in this issue:
>     https://github.com/ietf-wg-masque/draft-ietf-masque-connect-ip/issues/144
>
>      §4.7.2
>     IP version:
>     Address assignment syntax presumes that two request prefixes will
>     return two addresses. I think  this means that an endpoint cannot
>     request just one address, when it doesn't mind whether it's within
>     a certain IPv4 address range or a certain IPv6 address range. In
>     the happy eyeballs example, this returns two addresses. Similarly,
>     I don't think the syntax can express no preference for a prefix
>     length. Only a specific prefix length is possible. Correct? Should
>     these limitations of the syntax be pointed out?
>
>     EDITORS: If a client wants exactly one address, but doesn't care
>     which address family, it should send an ADDRESS_REQUEST for v4 as
>     0.0.0.0/32 <http://0.0.0.0/32>, and if it does not get one
>     assigned, then send a request for v6 as ::/128 (or other mask).
>     (This algorithm can be run in the reverse order as well)  If it
>     wants _at least_ one address of either address family, it should
>     send a single ADDRESS_REQUEST asking for both, and simply not use
>     the assigned address of the address family it is uninterested in.
>

[BB] So, in the case where the client supports both v4 & v6 and doesn't 
care which it gets, but the proxy only supports (say) v6, the allocation 
can require two rounds. That was my concern.

>
>      §4.7.3
>     "...the most recently received ROUTE_ADVERTISEMENT capsule..." I
>     assume this means most recently received after reordering has been
>     corrected. See my first point under Capsules about control message
>     ordering.
>
>     EDITORS: Please read 9297. These capsules are on the reliable
>     stream and are delivered in order.
>

[BB] My premise for this question was also a single ordered stream. As I 
said, you must mean the most recently received after reordering has been 
corrected.
Example: Client sends A then B, which get reordered. So A is "the most 
recently received".
It's just a picky point. Probably best to say "the latest 
ROUTE_ADVERTISEMENT capsule in sequence".

>
>      §5 Context Identifiers
>
>     The point below is in a similar vein to the earlier point about
>     whether generic support of IP Protocols (Next Headers) is a boon
>     or a bane...
>
>     This section seems like it's early research. It's vague, with no
>     examples and no clear purpose (to me). So one cannot reason about
>     what security vulnerabilities it might open up (let alone what
>     flexibility it potentially affords). There is no citation of
>     [HTTP-DGRAM] in this section, nor explanation of the purpose of a
>     Context ID.
>
>     EDITORS: The first paragraph explains the rationale. This feature
>     was discussed at length in the WG and we decided to add context
>     IDs to both CONNECT-UDP and CONNECT-IP.
>

[BB] Sounds experimental. This is a PS.
One purpose of an area review is to highlight this sort of thing to the 
members of the IESG. No need to convince me - I don't make the judgements.

>
>     "The Context ID value of 0 is reserved for IP payloads, " This
>     clearly means that non-IP payloads cannot use 0, but does it also
>     mean that IP payloads cannot use non-zero values? It's not clear,
>     but none of the examples (that all use IP) show a non-zero Context
>     ID. A later para (2nd para under Fig 13 in §6) seems to more
>     unambiguously define a 1:1 mapping between IP and Context ID=0. If
>     so, I don't understand the point of a Context ID in these
>     tunnelling cases. What am I missing?
>
>     EDITORS: Context IDs are registered and can be for any purpose.
>     Context ID 0 is pre-registered for full IP payloads. Future
>     extensions can perform registration to create new context IDs with
>     different payload types
>
>     "it is possible for datagrams to be received with Context IDs that
>     have not yet been registered. For instance, this can be due to
>     reordering of the packet containing the datagram and the packet
>     containing the registration message during transmission." So...,
>     what happens then?
>
>     EDITORS: Datagrams referring to context ids that are not yet
>     registered can either be buffered or dropped by the receiver, at
>     their discretion. We don't provide specific guidance because this
>     behavior will be specified by extensions that use the context ID
>     and that guidance might vary between extensions.
>

[BB] Then pls say this. 'Cos as it stands, it just sounds like an open 
issue that tails off into "um, er, y' know".

>
>      6. HTTP Datagram Payload Format
>
>     "Context ID:
>         A variable-length integer that contains the value of the
>     Context ID. If an HTTP/3 datagram which carries an unknown Context
>     ID is received, the receiver SHALL either drop that datagram
>     silently or buffer it temporarily (on the order of a round trip)
>     while awaiting the registration of the corresponding Context ID."
>
>     A number of problems here:
>     * undefined what happens if an http/2 or http/1.1 datagram carries
>     an   unknown Context ID?
>     *  For TCP, the app layer doesn't know the RTT.
>
>     EDITORS: This won't happen in HTTP/2 or HTTP/1.1, because
>     everything is delivered in order by TCP.
>
>     *  Isn't   this a resource exhaustion vulnerability? the sender
>     contrives packets with Context IDs that cause the receiver to
>     buffer everything, exhausting the   memory available for other
>     senders.
>
>     EDITORS: We're still bound by TCP flow control. Additionally, the
>     receiver is allowed to drop so it'll do that.
>
>     "Endpoints MAY implement additional filtering policies on the IP
>     packets they forward." Eh? This is the first mention of filtering
>     policies.
>
>     EDITORS: Agreed, this is the first mention. Implementers of IP
>     tunnels are familiar with the concept.
>

[BB] My point was the word 'additional' implies you've just been talking 
about other filtering policies. But you've just been talking about 
aborting a whole stream and sending echo requests etc, none of which is 
packet filtering. It felt like this sentence had got left over after 
something before it had been deleted.

>
>
>      7. Error Signalling
>
>     For a bump in the wire topology, can an ICMP error be sent back,
>     from one IP side to the other, through the HTTP tunnel and out the
>     other side? That will probably work. However, presumably an ICMP
>     error raised by the network within the extent of the HTTP tunnel
>     will be directed back to the ingress tunnel endpoint but no further.
>
>     EDITORS: CONNECT-IP conveys ICMP inside the tunnel only and is not
>     responsible for any ICMP messages on the outer connection.
>     Existing handling rules apply and are out of scope of this document.
>

[BB] OK, as I thought.

[Actually, the tunnel /is/ responsible for any ICMP messages on the 
outer connection, it just can't do anything about them, and it's 
well-known that the Internet architecture doesn't give it a way to 
forward the error to their original source either. But that's not 
exclusively your problem.]

>
>      8.4. Proxied Connection Racing
>
>     It might be worth pointing out in a note at the end of this
>     example that, as well as the proxy deciding to set up parallel
>     tunnels, the approach would also allow the client to initiate
>     parallel tunnels.
>
>     EDITORS: We don't see value in adding this note to this example.
>     The proposed note is a completely different example. The proxy
>     cannot set up parallel tunnels; only the client issuing CONNECT-IP
>     can set up a tunnel. The right-hand side are not tunnels in this
>     example.
>

[BB] Sorry, I worded my comment badly/wrongly. Retrying...

Same comment, but s/parallel tunnels/parallel addresses/


>
>      10. Security Considerations
>
>     I find it quite lame/naïve that this section essentially says,
>     "This Proxy design gives arbitrary clients great power, both to
>     toast proxies and to make them appear to be the senders of
>     arbitrary messages to arbitrary destinations" BUT, "That's not a
>     problem, because a proxy SHOULD restrict its use to authorized users."
>
>     This massive "get out of jail free" card begs the question, "What
>     management
>     processes are necessary for this proxy to monitor users to
>     determine whether to remove their authorization?" It's akin to
>     saying, "We're going to issue automatic assault rifles to everyone
>     over the age of 6, but it's not a problem, because it's illegal to
>     shoot someone without a permit."
>
>     EDITORS: Your comment is both ableist and violent. Please rephrase
>     this to be professional and actionable and then we'll discuss more.
>

[BB] One can only rely on authorization for security if the system can 
provide a mechanism for determining  what/who to authorize.

For instance, any attacks that rely on the proxy appearing to send a 
message on behalf of the client are undetectable by the proxy unless the 
attack is detected (e.g. by the victim) and leads to an investigation. 
The proxy will never know about successful attacks that are not 
detected, and therefore cannot deny authorization to the attackers that 
launch them. Authorization is therefore not a sufficient security mechanism.

Hence, the draft needs to address the question of "What management 
processes are necessary for this proxy to monitor users to determine 
whether to remove their authorization?"


Cheers



Bob



>
>     -----------------------------------------------------------------------
>     ==Nits==
>
>     EDITORS: We've looked through these nits and made minor changes to
>     the document for the ones we agree with.
>
>     "HTTP provides the CONNECT method (see Section 9.3.6 of [HTTP])
>     for creating a
>     TCP [TCP] tunnel..."
>         Citation of IETF core protocols like [TCP] is unnecessary. And
>     definitely
>         not normative - this sentence is informatively comparing this
>     draft with a
>         TCP-based alternative.
>
>     §3
>     s/an URI/a URI/
>     (unless we're meant to pronounce URI like Cockney "In an 'urry
>     luv?" :)
>
>     §4
>     Para 1: "To allow negotiation..."
>     Para 3: "To initiate an IP tunnel..."
>     I think these two paras repeat each other. But para 3 is better:
>     a) initiate is
>     a better word than negotiate (AFAICT there is no negotiation), and
>     b) it
>     explains that it's a /single/ HTTP stream.
>
>     "IPv6 scoped addressing zone identifiers..." ref? [RFC6874]?
>
>     §4.7.3
>     Using 'IP Protocol' rather than 'Next Header' as the keyword
>     within an IP
>     Address Range is rather politically incorrect for IPv6 zealots,
>     isn't it? :)
>
>     Is 'equal than' (2 occurrences) correct in US English? It's
>     certainly not in
>     British. I can't find any reference to it.
>
>     §6
>     s/since receiving addresses and routes is/
>      /since receipt of addresses and routes is/
>
>     "When an endpoint receives an HTTP Datagram containing an IP
>     packet, it..."
>     a tunnel endpoint?
>
>     MTU sometimes ought to be PMTU.
>
>     "HTTP Datagrams with payloads of at least 1280 bytes"
>     Fig 13 potentially labels two things as HTTP Datagram Payload.
>     Which is meant
>     here? I assume the inner one, but it needs to be clear.
>
>     "...the endpoints can pad the QUIC INITIAL packets of the
>     underlying QUIC
>     connection that IP proxying is running over. (Assuming QUIC
>     version 1 is in
>     use,..." The parenthesis needs to be tagged as an example.
>
>     §8.1
>     In the format defined in §1.3 of [QUIC] and used in the examples,
>     a value after
>     '=' is normally numeric. the following format threw me:
>         Payload = Encapsulated IP Packet
>     I thought that must imply a field announcing that the type of the
>     payload is
>     the string "Encapsulated IP Packet". Any chance this could be
>     bracketed off
>     somehow, e.g.
>         Payload = <Encapsulated IP Packet>
>     Is there any precedent in RFC9000 for an unquoted/unbracketed
>     description of a
>     binary blob on the RHS of '='?
>
>     §8.4
>         "The IP proxy assigns the client both an IPv4 address
>     (192.0.2.3) and an
>         IPv6 address (2001:db8:1234::a) to the client."
>     Delete first occurrence of 'the client'.
>
>     §10
>     s/IP proxies SHOULD restrict its use to authenticated users./
>      /IP proxies SHOULD restrict their use to authorized users./
>     Reason: as well as the incorrect singular, following the literal
>     rule as
>     originally written would give access to authentic criminals.
>
>     §11.1
>     There's a few places in the IANA section where editor's marks
>     might be useful
>     to identify text that will need to be updated once approved.
>
>     Cheers
>
>     Bob
>

-- 
________________________________________________________________
Bob Briscoehttp://bobbriscoe.net/