Internet DRAFT - draft-eckert-anima-brski-discovery
draft-eckert-anima-brski-discovery
ANIMA T. Eckert, Ed.
Internet-Draft Futurewei
Intended status: Standards Track D. von Oheimb
Expires: 25 April 2024 Siemens
E. Dijk
IoTconsultancy.nl
23 October 2023
Discovery for BRSKI variations
draft-eckert-anima-brski-discovery-01
Abstract
This document specifies how BRSKI entities, such as registrars,
proxies, pledges or others that are acting as responders, can be
discovered and selected by BRSKI entities acting as initiators.
Status of This Memo
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This Internet-Draft will expire on 25 April 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Specification . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Abstracted BRSKI discovery and selection . . . . . . . . 6
3.2. Variation Contexts . . . . . . . . . . . . . . . . . . . 6
3.3. Variation Types and Choices . . . . . . . . . . . . . . . 7
3.4. Variations . . . . . . . . . . . . . . . . . . . . . . . 8
3.5. BRSKI Variations Discovery Registry . . . . . . . . . . . 8
3.5.1. BRSKI Variation Contexts table . . . . . . . . . . . 8
3.5.2. BRSKI Variation Type Choices table . . . . . . . . . 9
3.5.3. BRSKI Discoverable Variations table . . . . . . . . . 10
3.5.4. Extending or modifying the registry . . . . . . . . . 11
3.6. BRSKI Join Proxies support for Variations . . . . . . . . 11
3.6.1. Permissible Variations . . . . . . . . . . . . . . . 12
3.6.2. Join Proxy support for Variations . . . . . . . . . . 12
3.6.3. Co-location of Proxy and Registrar . . . . . . . . . 13
3.7. BRSKI Pledges support for Variations . . . . . . . . . . 14
3.7.1. BRSKI-PLEDGE context . . . . . . . . . . . . . . . . 14
3.8. Variation signaling and encoding rules for different
discovery mechanisms . . . . . . . . . . . . . . . . . . 18
3.8.1. DNS-SD . . . . . . . . . . . . . . . . . . . . . . . 18
3.8.2. GRASP . . . . . . . . . . . . . . . . . . . . . . . . 21
3.8.3. CORE-LF . . . . . . . . . . . . . . . . . . . . . . . 23
4. Updates to existing RFCs . . . . . . . . . . . . . . . . . . 24
4.1. RFC8995 . . . . . . . . . . . . . . . . . . . . . . . . . 24
5. IANA considerations . . . . . . . . . . . . . . . . . . . . . 24
5.1. BRSKI Variations Discovery Registry (section) . . . . . . 24
5.2. Service Names Registry . . . . . . . . . . . . . . . . . 28
5.3. BRSKI Well-Known URIs fixes (opportunistic) . . . . . . . 29
6. Security Considerations . . . . . . . . . . . . . . . . . . . 29
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 30
8. Draft considerations . . . . . . . . . . . . . . . . . . . . 30
8.1. Open Issues . . . . . . . . . . . . . . . . . . . . . . . 30
8.2. Change log . . . . . . . . . . . . . . . . . . . . . . . 30
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
9.1. Normative References . . . . . . . . . . . . . . . . . . 30
9.2. Informative References . . . . . . . . . . . . . . . . . 32
Appendix A. Discovery for constrained BRSKI . . . . . . . . . . 33
A.1. Current constrained text for GRASP . . . . . . . . . . . 33
A.1.1. Issues and proposed change . . . . . . . . . . . . . 35
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36
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1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
This document relies on the terminology defined in Section 1. The
following terms are described partly in addition.
Context: See Variation Context.
Initiator: A host that is using an IP transport protocol to initiate
a connection or transaction to another host called the responder.
Initiator socket: A socket consisting of an initiators IP or IPv6
address, protocol and protocol port number from which it initiates
connections or transactions to a responder (typically UDP or TCP).
Objective Name: See Service Name.
Resource Type: See Service Name.
Responder: A host that is using an IP transport protocol to respond
to transaction or connection requests from an Initiator.
Responder socket: A socket consisting of a responders IP or IPv6
address, protocol and protocol port number on which it responds to
requests of the protocol (typically UDP or TCP).
Role: In the context of this document, a type of entity in a
variation of BRSKI that can act as a responder and whose supported
variations can be discovered. BRSKI roles relevant in this
document include Join Registrar, Join Proxy and Pledge. The IANA
registry defined by this document allows to specify variations for
any roles. See also Variation Context.
Socket: The combination of am IP or IPv6 address, an IP protocol
that utilizes a port number (such as TCP or UDP) and a port number
of that protocol.
Service Name: The name for (a subset of) the functionality/API
provided by a discoverable responder socket. This term is
inherited from Section 1 but unless otherwise specified also used
in this document to apply to any other discovery functionality/
API. The terminology used by other mechanisms typically differs.
For example, when Section 1 is used to discover a responder socket
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for BRSKI, the Objective Name carries the equivalent to the
service name. In Section 1, the Resource Type (rt=) carries the
equivalent of the service name.
Type: See Variation Type.
Variation: A combination one one variation choice each for every
variation type applicable to the variation context of one
discoverable BRSKI communications. For example, in the context of
BRSKI, a variation is one choice for "mode", one choice for
"enroll" and once choice for "vformat".
Variation Context: A set of Services for whom the same set of
variations applies
Variation Type: The name for one aspect of a protocol for which two
or more choices exist (or may exist in the future), and where the
choice can technically be combined orthogonal to other variation
types. This document defined the BRSKI variation types "mode",
"enroll" and "vformat".
Variation Type Choice: The name for different values that a
particular variation type may have. For example, this document
does defines the choices "rrm" and "prm" for the BRSKI variation
"mode".
ACP: "An Autonomic Control Plane", [RFC8994].
BRSKI: "Bootstrapping Remote Secure Key Infrastructure", [RFC8995].
BRSKI-AE: "Alternative Enrollment Protocols in Section 1",
[I-D.ietf-anima-brski-ae].
BRSKI-PRM: "Section 1 with Pledge in Responder Mode",
[I-D.ietf-anima-brski-prm].
cBRSKI: "Constrained Bootstrapping Remote Secure Key Infrastructure
(Section 1)", [I-D.ietf-anima-constrained-voucher].
COAP: "The Constrained Application Protocol (CoAP)", [RFC7252].
CORE-LF: "Constrained RESTful Environments (CoRE) Link Format",
[RFC6690].
cPROXY: "Constrained Join Proxy for Bootstrapping Protocols",
[I-D.ietf-anima-constrained-join-proxy].
DNS-SD: "DNS-Based Service Discovery", [RFC6763].
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EST: "Enrollment over Secure Transport", [RFC7030].
GRASP: "GeneRic Autonomic Signaling Protocol", [RFC8990].
GRASP-DNSSD: "DNS-SD Compatible Service Discovery in GeneRic
Autonomic Signaling Protocol (GRASP)",
[I-D.eckert-anima-grasp-dnssd].
JWS-VOUCHER: "JWS signed Voucher Artifacts for Bootstrapping
Protocols", [I-D.ietf-anima-jws-voucher].
lwCMP: "Lightweight Certificate Management Protocol (CMP) Profile",
[I-D.ietf-lamps-lightweight-cmp-profile].
mDNS: "multicast DNS", [RFC6762].
SCEP: "Simple Certificate Enrolment Protocol", [RFC8894].
2. Overview
The mechanisms described in this document are intended to help solve
the following challenges.
Signaling BRSKI variation for responder selection.
When an initiator such as a proxy or pledge uses a mechanism such as
Section 1 to discover an instance of a role it intends to connect to,
such as a registrar, it may discover more than one such instance. In
the presence of variations of the BRSKI mechanisms that impact
interoperability, performance or security, not all discovered
instances may support exactly what the initiator needs to achieve
interoperability and/or best performance, security or other metrics.
In this case, the service announcement mechanism needs to carry the
necessary additional information beside the name that indicates the
service to aid the initiator in selecting an instance that it can
inter operate and achieve best performance with.
Easier use of additional discovery mechanisms.
In the presence of different discovery mechanisms, such as Section 1,
Section 1, Section 1 or others, the details of how to apply each of
these mechanisms are usually specified individually for each
mechanism, easily resulting in inconsistencies. Deriving as much as
possible the details of discovery from a common specification and
registries can reduce such inconsistencies and easy introduction of
additional discovery mechanisms.
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Generalization of principles related to discovery and operation of
proxies.
Because of the unified approach to discovery of BRSKI Variations
described in this document, it also allows to use Section 1 for
document for Section 1 and Section 1, which may be of interest in
networks such as Thread, which use Section 1.
3. Specification
3.1. Abstracted BRSKI discovery and selection
In the abstract model of discovery used by this document and intended
to apply to all described discovery mechanisms, an entity operating
as an initiator of a transport connection for a particular BRSKI
protocol role, such as a pledge, discovers one or more responder
sockets (IP/IPv6-address, responder-port, IP-protocol) of entities
acting as responders for the peer BRSKI role, such as registrar. The
initiator uses some discovery mechanism such as Section 1, Section 1
or Section 1. In the the initiator looks for a particular
combination of a Service Name and an IP-protocol, and in return
learns about responder sockets from one or more responders that use
this IP-protocol and serve the requested Service Name type service
across it. It also learns the BRSKI variation(s) supported on the
socket.
Service Name is the name of the protocol element used in Section 1,
unless explicitly specified, it is used as a placeholder for the
equivalent protocol elements in other discovery mechanisms. In
Section 1, it is called objective-name, in Section 1 it is called
Resource Type.
Upon discovery of the available sockets, the initiator selects one,
whose supported variation(s) best match the expectations of the
initiator, including performance, security or other preferences.
Selection may also include attempting to establish a connection to
the responder socket, and upon connection failure to attempt
connecting to the next best responder socket. This is for example
necessary when discovery information may not be updated in real-time,
and the best responder has gone offline.
3.2. Variation Contexts
A Variation Context is a set of (Discover Mechanism, Service Names,
IP-protocols) across which this document and the registry of
variations defines a common set of variations. The initial registry
defined in this document defines two variation contexts.
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BRSKI context: context for discovery of BRSKI registrar and proxy
variations by proxies, pledges or agents (as defined in Section 1)
via the Service Names defined for Section 1 and Section 1 via TCP
and hence (by default) TLS (version 1.2 or higher according to
Section 1).
cBRSKI context (constrained BRSKI): context for discovery of BRSKI
registrar and proxy variations by proxies, pledges via the Service
Names defined for Section 1, Section 1 and Section 1 via UDP, and
hence (by default) secure COAP.
Note that the Service Names for cBRSKI include the same Section 1
Service Names as for the BRSKI context, hence enabling the use of
Section 1 with cBRSKI.
This document does not define variations for different end-to-end
encryption mechanisms, so only the "(by default)" options exist at
the time of writing this document. However, the mechanisms described
here can also be used to introduce backward incompatible new secure
transport options. For example when responders start to support only
TLS 1.3 or higher in the presence of TLS 1.2 only initiators, then
new variations can be added, such that those initiators will not
select those responders.
This document does not introduce variation contexts for discovery of
other BRSKI roles, such as discovery of pledges by agents (as defined
in Section 1), or discovery of MASA by registrars. However, the
registry introduced by this document is defined such that it can be
extended by such additional contexts through future documents.
3.3. Variation Types and Choices
A Variation Type is a variation in one aspect of the BRSKI connection
between initiator and responder that ideally orthogonal from
variations in other aspects of the BRSKI connection.
A Variation Type Choice is one alternative (aka: value) for its
Variation Type.
This document, and the initial registry documenting the variation
types introduces three variation types as follows:
mode: A variation in the basic sequence of URI endpoints
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communicated. This document introduces the choices of "rrm" to
indicate the endpoints and sequence as defined in Section 1 and
"prm" to indicate the endpoints and sequence as defined in
Section 1. Note that registrars also act as responders in "prm".
"rrm" was chosen because the more logical "pim" (pledge initiator
mode) term was feared to cause confusion with other technologies
that use that term.
vformat (voucher format): A variation in the encoding format of the
voucher communicated between registrar and pledge. This document
introduces the choices "cms" as defined in Section 1, "cose" as
defined in Section 1 and "jose" as defined in Section 1.
enroll: A variation in the URI endpoints used for enrollment of the
pledge with keying material (trust anchors and certificate
(chain)). This document introduces the following :choices
* "est" as introduced by Section 1 to indicate the Section 1
protocol, which is default
* "cmp" to indicate the CMP protocol according to the Lightweight
CMP profile (Section 1). The respective adaptations to BRSKI
have been introduced by Section 1.
* "scep" to indicate Section 1. This is only a reservation,
because no specification for the use of Section 1 with BRSKI
exists.
3.4. Variations
A Variation is the combination of one Choice each for every Variation
Type applicable to the Variation Context. In other words, a
variation is a possible instance of BRSKI if supported by initiator
and responder. In Section 1, the default variation is "registrar
responder mode" (rrm) and use of the "cms voucher format" (cms).
3.5. BRSKI Variations Discovery Registry
The IANA "BRSKI Variations Registry" as specified by this document,
see Section 5.1 specifies the defined parameters for discovery of
BRSKI variations.
3.5.1. BRSKI Variation Contexts table
This table, Table 1, defines the BRSKI Variations Contexts.
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The "Applicable Variation Types" lists the Variation Types from whose
choices a Variation for this context is formed. The "Service
Name(s)" column lists the discovery mechanisms and their Service
Name(s) that constitute the context.
3.5.2. BRSKI Variation Type Choices table
This table, Table 2, defines the Variations Type Choices.
The "Context" column lists the BRSKI Variation Context(s) to which
this line applies. If it is empty, then the same Context(s) apply as
that of the last prior line with a non-empty Context column.
The "Variation Type" column lists the BRSKI Variation Type to which
this line applies. If it is empty, then the same Variation Type
applies as that of the last prior line with a non-empty Variation
Type column. Variation Types MUST the listed in the order in which
the Variation Types are listed in the Applicable Variation Types
column of the BRSKI Variation Contexts table.
The "Variation Type Choice" column defines a Variation Type Choice
term within the Context(s) of the line. To allow the most flexible
encodings of variations, all Variation Types and Variation Type
Choices MUST be unique strings (across all Variation Types). This
allows to encode Variation Type Choices in a discovery mechanism
without indicating their Variation Type. Variation Types and
Variation Type Choices and MUST be strings from lowercase letters a-z
and digits 0-9 and MUST start with a letter. The maximum length of a
Variation Type Choice is 12 characters.
The "Reference" column specifies the documents which describe the
Variation Type Choice. Relevant specification includes those that
only specify the semantics without referring to the aspects of
discovery and/or those that specify only the Discovery aspects.
Current RFCs for BRSKI variations preceding this RFC typically only
specify the semantics, and this document adds the discovery aspects.
The "Dflt" Flag specifies a Variation Type Choice that is assumed to
be the default Choice for the Context, such as "rrm" for the BRSKI
context. Such a Variation Type Choice is to be assumed to be
supported in discovery if discovery is performed without indication
of any or an empty signaling element to carry the Variation or
Variation Choices. For example, Section 1 specifies the empty string
"" as the objective-value in Section 1 discovery. Because "rrm",
"est" and "cms" are default in the BRSKI context, this Discovery
signaling indicates the support for those Variation Type Choices.
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The "Dflt_" Flag specifies a Variation Type Choice that is only
default in a subset of Discovery options in a context. The Note(s)
column has then to explain which subset this is. Like for "Dflt",
the signaling in this subset of Discovery options can then forego
indication of the "Dflt_" Variation Type Choice.
The "Rsvd" Flag specifies a Variation Type Choice for which no
complete specification exist on how to use it within BRSKI (or more
specifically the context), but which is known to be of potential
interest. "Rsvd" Variation Type Choices MUST NOT be considered for
the Discoverable Variations table. They are documented primarily to
reserve the Variation Type Choice term.
The Note(s) section expands the Variation Type Choice terms and
provides additional beneficial specification references beyond the
"Reference" column.
3.5.3. BRSKI Discoverable Variations table
This table Table 3 enumerates the Discoverable Variations and
categorizes them.
The "Context" column lists the BRSKI Variation Context(s) to which
this line applies. If it is empty, then the same Context(s) apply as
that of the last prior line with a non-empty Context column.
The "Spec / Applicability" lists the document(s) that specify the
variation, if the variation is explicitly described. If the
variation is not described explicitly, but rather a combination of
Variation Type Choices from more than one BRSKI related
specification, then this column will indicate "-" if by expert
opinion it is assumed that this variation should work, or "NA", if by
expert opinion, this variation could not work. The "Explanations"
column includes references to the relevant documents and as necessary
additional explanation.
The "Variation" column lists the Variation Type Choices that form the
Variation. The Variation Type Choices MUST be listed in the order in
which the Variation Types are listed in the Applicable Variation
Types column of the BRSKI Variation Contexts table.
The "Variation String" column has the string term used to indicate
the variation when using the simple encoding of BRSKI Variation
Discovery for GRASP as described in Section 1. It is formed by
concatenating the Choices term from the Variation column with the "-"
character, excluding those Choices terms (and "-" concatenator) which
are Default for the Context. If this procedure ends up with the
empty string, then this is indicated as "" in the column.
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The "Explanations" column explains the "Spec / Applicability" status
of the Variation.
3.5.4. Extending or modifying the registry
Unless otherwise specified below, extension or changes to the
registry require standards action.
Additional Variation Type Choices and Variation Context discovery
mechanism Service Names including additional discovery mechanisms
require (only) specification and expert review if they refer to non
standard action protocols and/or protocol variation aspects. For
example, a specification how to use Section 1 with BRSKI would fall
under this clause as it is an informational RFC.
Non standards action Variation Type Choices can not be Default(Dflt).
They can only be Dflt* for non standards action (sub)Contexts.
Reservation of additional Variation Type Choices requires (only)
expert review.
Additional Contexts MUST be added at the end of the BRSKI Variation
Contexts table.
Additional Variation Types MUST be added at the end of the Applicable
Variation Types column of the BRSKI Variation Contexts table and at
the end of existing lines for the Context in the BRSKI Variation Type
Choices. Additional Variation Types MUST be introduced with a
Default (Dflt) Variation Type Choice. These rules ensures that the
rule to create the Variation String for GRASP (and as desired by
other discovery mechanism), and it also enables to add new Variation
Type and Choices without changing pre-existing Variation Strings: Any
Variations String implicitly include the Default Choice for any
future Variation Types.
When a new Variation Type is added, their Default Choice SHOULD be
added to the Variation Column of existing applicable lines in the
BRSKI Discoverable Variations table. Variations that include new
non-Default Variation Type Choices SHOULD be added at the end of the
existing lines for the Context.
3.6. BRSKI Join Proxies support for Variations
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3.6.1. Permissible Variations
Variations according to the terminology of this document are those
that do not require changes to BRSKI join proxy operations, but that
can transparently pass across existing join proxies without changes
to them - as long as they support the rules outlined in this
document.
Different choices for e.g.: pledge to registrar encryption
mechanisms, voucher format (vformat), use of different URI endpoints
or enrollment protocol endpoints (mode) are all transparent to join
proxies, and hence join proxies can not only support existing, well-
defined Choices of these Variation Types, but without changes to the
proxies also future ones - and only those are permitted to become
Variation Type Choices.
Changes to the BRSKI mechanism that do require additional changes to
join proxies are not considered Variations according to this document
and MUST NOT use the same discovery protocol signaling elements as
those defined for variations by this document. Instead, they SHOULD
use different combinations of Service Name and Protocol (e.g.: TCP
vs. UDP).
For example, the stateless join proxy mode defined by Section 1 is
such a mechanism that requires explicit join proxy support.
Therefore, registrars sockets that support circuit proxy mode use the
GRASP objective "AN_join_registrar", and registrar sockets that
support stateless join proxy mode use the GRASP objective
"AN_join_registrar_rjp". This enables join proxies to select the
registrar and socket according to what the join proxy supports and
prefers. By not using the same signaling element(s) for variations,
join proxies can support discovery of all variations independent of
their support for stateless join proxy operations.
3.6.2. Join Proxy support for Variations
Join proxies supporting the mechanisms of this document MUST signal
for each socket they announce to initiators via a discovery mechanism
the Variation(s) supported on the socket. These Variation(s) MUST
all be supported by the registrar that the join proxy then uses for
the connection from the initiator (e.g.: pledge). Pledges SHOULD
announce sockets to initiators so that all Variations that are
supported by registrars that the join proxy can interoperate with are
also available to the initiators connecting to the join proxy.
To meet these requirements, join proxies can employ different
implementation option. In the most simple one, a join proxy
allocates a separate responder socket for every Variation for which
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it discovers one or more registrars supporting this Variation. It
then announces that socket with only that one Variation in the
discovery mechanism, even if the Registrar(s) are all announcing
their socket with multiple Variations. When the join proxy operates
in circuit mode, it can then select one of the registrars supporting
the variation for every new initiator connection based on policies as
specified by BRSKI specifications and/or discovery parameters, such
as priority and weight when Section 1 is used, and redundant
registrars include those parameters.
TBD: insert example of received Registrar announcement and created
proxy announcement ??
Join proxies MAY reduce the number of sockets announced to initiators
by using a single socket for all Variations for which they have the
same set of registrar sockets supporting those Variations. This
primarily helps to reduce the size of the discovery messages to
initiators and can save socket resources on the join proxy.
Join proxies MAY create multiple sockets in support of other
discovery options, even for the same Variation(s). For example, if
Section 1 is used by two registrars, both announcing the same
priority but different weights, then the join proxy may create a
separate socket for each of these registrars - and their variations,
so that the join proxy can equally announce the same priority and
weight for both sockets to initiators. This allows to maintain the
desired weights of use of registrars, even when the join proxy
operates in stateless mode, in which it can not select a separate
registrar for every client initiating a connection.
3.6.3. Co-location of Proxy and Registrar
In networks using Section 1 and Section 1, registrars must have a co-
located proxy, because pledges can only use single-hop discovery
(DULL-GRASP) and will only discover proxies, but not registrar. Such
a co-located proxy does not constitute additional processing/code on
a registrar supporting circuit mode, it simply implies that the
registrars BRSKI services(s) are announced with a proxy Service Name,
to support pledges, and the registrar service name, to support join
proxies.
To ease consistency of deployment models in the face of different
discovery mechanisms, Variations and non-Variation enhancements to
BRSKI, it is RECOMMENDED that all future options to BRSKI do always
have a Service Name for proxies and a separate Service Name in
support of pledge or other initiators. Pledges and other initiators
SHOULD always only look for the proxy Service Name, and only Proxies
should look for a registrar Service Name. Registrars therefore
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SHOULD always include the proxy functionality according to the prior
paragraph. This only involves additional code on the registrar
beyond the service announcement in case the Registrar would otherwise
not implement circuit mode.
3.7. BRSKI Pledges support for Variations
3.7.1. BRSKI-PLEDGE context
BRSKI-PLEDGE is the context for discovery of pledges by nodes such as
registrar-agents. Pledges supporting Section 1 MUST support it. It
may also be used by other variations of BRSKI when supported by
pledges.
Pledges supporting BRSKI-PLEDGE MUST support DNS-SD for discovery via
mDNS, using link-local scope. For DNS-SD discovery beyond link-local
scope, pledges SHOULD support DNS-SD via [I-D.ietf-dnssd-srp].
TBD: Is there sufficient auto-configuration support in
[I-D.ietf-dnssd-srp], that pledges without any configuration can use
it, and if so, do we need to raise specific additional requirements
to enable this in pledges ?
These DNS-SD requirements are defaults. Specifications for specific
deployment contexts such as specific type of radio network solutions
may need to specify their own requirements overriding or amending
these requirements.
Pledges MUST support to be discoverable via their service instance
name. They MAY be discoverable via DNS-SD browsing, so that
registrar-agents can find even unexpected pledges through DNS-SD
browsing.
Support for browsing is required to discover over the network pledges
supporting only Section 1, but not Section 1 if they have no known
serial-number information from which their service instance name can
be constructed, so it is a crucial feature for robust enrollment.
See Section 6 for more details about discovery and BRSKI-PLEDGE.
When pledges are discoverable vis DNS-SD browsing, they MUST expect
that a large number of pledges exist in the network at the same time,
such as in the order of 100 or more, and schedule their responses
according to the procedures in Section 1 and Section 1 to avoid
simultaneous reply from all pledges.
TBD: What is the best section in mDNS/DNS-SD to point to for this
timed reply to scale ?
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Browsing via DNS-SD for a pledge is circumvented by the pledge not
announcing its PTR RR for "brski-registrar". Technically, the
remaining RR may not constitute full DNS-SD service, but they do
provide the required discovery for the known service instance name of
the pledge.
counter measures such as limiting the number and rate of PRM connects
that they accept, ideally on a per-initiator basis (assuming that
DDoS attacks are more harder to mount than single attacker DoS
attacks).
3.7.1.1. Service Instance Name
The service instance name chosen by a BRSKI pledge MUST be composed
from information which is
* Easily known by BRSKI operations, such as the operational
personnel or software automation, specifically sales integration,
* Available to the pledges BRSKI software itself, for example by
being encoded in some attribute of the IDevID.
Typically, a customer will know the serial number of a product from
sales information, or even from bar-code/QR-codes on the product
itself. If this serial number is used as the service instance name
to discover a pledge from a registrar-agent, then this may lead to
possible duplicate replies from two or more pledges having the same
serial number, such as in the following cases:
1. A manufacturer has different product lines and re-uses serial-
numbers across them.
2. Two different manufacturer re-use the same serial-numbers.
If pledges enable browsing of their service instance name, they MAY
support Section 1 specified procedures to create unique service
instance names when they discover such clashes, by appending a space
and serial number, starting with 2 to the service instance name:
"<service-instance-name> (2)", as described in Section 1 Appendix D.
Nevertheless, this approach to resolving conflicts is not desirable:
* If browsing of DNS-SD service instance name is not supported,
registrar-agents would have to always (and mostly wrongly) guess
that there is a clash and (mostly unnecessarily) search for
"<service-instance-name> (2)".
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* If a clash exists between pledges from the same manufacturer, and
even if the registrar-agent then attempts to start enrolling all
pledges with the same clashing service instance name, it may not
have enough information to determine which the correct pledge is.
This would happen especially if the IDevID from both devices (of
different product type), had the same serial number, and the CA of
both was the same (because they come from the same manufacturer).
Even if some other IDevID field was used to distinguish their
device model, the registrar-agent would not be able to determine
that difference without additional vendor specific programming.
In result:
* Vendors MUST document a scheme how their pledges form a service
instance name from information available to the customer of the
pledge.
* These service instance names MUST be unique across all IDevID of
the manufacturer that share the same CA.
The following mechanisms are recommended:
* Pledges SHOULD encode manufacturer unique product instance
information in their subject name serialNumber. [RFC5280] calls
this the X520SerialNumber.
* Pledges SHOULD make this serialNumber information consistent with
easily accessible product instance information when in physical
possession of the pledge, such as product type code and serial
number on bar-code/QR-code to enable Section 1 discovery without
additional backend sales integration. Note that discovery alone
does not allow for enrollment!
* Pledges SHOULD construct their service instance name by
concatenating their X520SerialNumber with a domain name prefix
that is used by the manufacturer and thus allows to disambiguate
devices from different manufacturer using the same serialNumber
scheme, and hence the likelihood of service instance name clashes.
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Service Instance Name:
"PID:Model-0815 SN:WLDPC2117A99.example.com"
Manufacturer published Service Instance Name schema:
PID:\<PID>\\ SN:\<SN>.example.com
Pledge IDevID certificate information:
; Format as shown by e.g.: openssh
Subject: serialNumber = "PID:Model-0815 SN:WLDPC2117A99",
O = Example, CN = Model-0815
DNS-SD RR for the pledge:
; PTR RR to support browsing / discovery of service instance name
_brski-pledge._tcp.local IN PTR
PID:Model-0815\\ SN:WLDPC2117A99\\.example\\.com._brski-pledge._tcp.local
; SRC and TXT RR for the service instance name
PID:Model-0815\\ SN:WLDPC2117A99\\.example\\.com._brski-pledge._tcp.local
IN SRV 1 1
PID:Model-0815\\ SN:WLDPC2117A99\\.example\\.com.local
PID:Model-0815\\ SN:WLDPC2117A99\\.example\\.com._brski-pledge._tcp.local
IN TXT ""
; AAAA address resolution for the target host name
PID:Model-0815\\ SN:WLDPC2117A99\\.example\\.com.local
IN AAAA fda3:79a6:f6ee:0000::0200:0000:6400:00a1
Figure 1: Example service instance name data
In Figure 1, the manufacturer "example" identifies device instances
through a product identifier <PID> and a serial number <SN>. Both
are printed on labels on the product/packaging and/or communicated
during purchase of the product.
The service instance name of pledges from this manufacturer are using
the string "PID:<PID> SN:<SN>.example.com". "example.com" is assumed
to be a domain owned by this manufacturer. <PID> and <SN> are
replaced by the actual strings.
The IDevID encodes the service instance name without the domain
ending (".example.com") in the X520SerialNumber field. Other fields
of the IDevID are not used.
The resulting DNS-SD RRs that the pledge announces are shown in the
example. " " and "." characters are escaped as recommended by
Section 1.
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In this example, the same string as constructed for the service
instance name is also used as the target host name. This is of
course not necessary, but unless the pledge already obtains a host
name through other DNS means, re-using the same name allows to avoid
coming up with a second method to construct a unique name.
3.8. Variation signaling and encoding rules for different discovery
mechanisms
3.8.1. DNS-SD
3.8.1.1. Signaling
The following definitions apply to any instantiation of DNS-SD
including DNS-SD via mDNS as defined in Section 1, but also via
unicast DNS, for example by registering the necessary DNS-SD Resource
Records (RR) via [I-D.ietf-dnssd-srp] (SRP).
The requirements in this document do not guarantee interoperability
when using DNS-SD, instead, they need to be amended with deployment
specific specifications / requirements as to which signaling
variation, such as mDNS or unicast DNS with SRP is to be supported
between initiator and responder. When using unicast DNS (with SRP),
additional mechanisms are required to learn the IP / IPv6 address(es)
of feasible DNS and SRP servers, and deployment may also need
agreements for the (default) domain they want to use in unicast DNS.
Hence, a mandatory to implement (MTI) profile is not feasible because
of the wide range of variations to deploy DNS-SD.
TBD: We could say that mDNS MUST be supported, unless the network
context defines an interoperable mode to support DNS-SD without mDNS
???
3.8.1.2. Encoding
Variation Type Choices defined in the IANA registry Table 3 are
encoded as Section 1 Keys with a value of 1 in the DNS-SD service
instances TXT RR. This is possible because all Variation Type
Choices are required to be unique across all Variation Types. It
also allows to shorten the encoding from "key=1" to just "key" for
every Variation Type Choice, so that the TXT-DATA encoding can be
more compact.
If the TXT Record does not contain a Variation Type Choice for a
particular applicable Variation Type, then this indicates support for
the Default Choice of this Variation Type in the context of the DNS-
SD Service Name. For example, if the TXT Record is "jose", then this
indicates support for "rrm" and "est", if the Service Name is brski-
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registrar or brski-proxy and the protocol is TCP (BRSKI Context), but
also when the protocol is UDP (cBRSKI context), because "rrm" and
"est" are defaults in both contexts.
If multiple Variation Type Choices for the same Variation Type are
indicated, then this implies that either of these Variation Type
Choices is supported in conjunction with any of the other Variation
Type Choices in the same TXT Record. For example, if the TXT Record
is "prm" "rrm" "cms" "jose", then this implies support for rrm-cms-
est, rrm-jose-est, prm-cms-est and prm-jose-est. This example also
shows that if the default Variation Type Choice, such as "rrm" and
another Choice of the same Variation Type ("prm") are to be indicated
as supported, then both need to be included in the TXT Record.
In Section 1, a responder does not only indicate a Service Name, but
also its Service Instance Name, which needs to be unique across the
domain to support initiators selecting a responder. This
specification makes no recommendation for choosing the Instance
portion of that name. Usually it is the same, or derived from some
form of pre-existing system name.
Registrars SHOULD support support their configuration without
specifying a name to use in the Service Instance Name to minimize the
amount of configuration required. Registrars SHOULD support the
configuration of such a name.
If the responder needs to indicate different sockets for different
(set of) Variations, for example, when operating as a proxy,
according to Section 3.6.2, then it needs to signal for each socket a
separate Service Instance Name with the appropriate port information
in its SRV Record and the supported Variations for that socket in the
TXT Record of that Service Instance Name. In this case, it is
RECOMMENDED that the Instance Name includes the Variation it
supports, such as in the format specified in Section 3.5.3 and used
in the Variation String column of the Table 3 table.
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_brski-registrar._tcp.local
IN PTR 0200:0000:7400._brski-registrar._tcp.local
0200:0000:7400._brski-registrar._tcp.local
IN SRV 1 2 4555 0200:0000:7400.local
0200:0000:7400._brski-registrar._tcp.local IN TXT "rrm" "prm"
0200:0000:7400.local
IN AAAA fda3:79a6:f6ee:0000::0200:0000:6400:0001
_brski-registrar._udp.local
IN PTR 0200:0000:7400._brski-registrar._udp.local
0200:0000:7400._brski-registrar._udp.local
IN SRV 1 2 5684 0200:0000:7400.local
0200:0000:7400._brski-registrar._udp.local IN TXT ""
Figure 2: DNS-SD for a simple BRSKI and cBRSKI registrar
In the above example Figure 3, a registrar supports BRSKI with "rrm"
and "prm" modes across the same TCP socket, port 4555. It uses "cms"
voucher format and "est" enrollment, which are not included in the
TXT strings because both are default for _brski-registrar._tcp. The
registrar also offers cBRSKI with "rrm" mode, "cose" voucher and
"est" enrollment on UDP port 5684, the COAP over DTLS default port.
The TXT RR for this has only an empty string because "rrm", "cose"
and "est" are default for cBRSKI.
As the instance name, the registrar uses in this example the MAC
address "0200:0000:7400", which is MAC address of the interface on
which the registrar has the IPv6 address
"fda3:79a6:f6ee:0000::0200:0000:6400:0001". The registrar should
know that this MAC address is globally unique (assigned by IEEE).
Else it should instead use its IPv6 address as the Instance Name.
For example, if the registrar is just a software application not
knowing the specifics of the hardware it is running on, the MAC
address MUST NOT be used. If only mDNS is used (as in this example),
then the IPv6 link-local address would also suffice as the Instance
Name.
In this example, a single Instance Name suffices, because BRSKI and
cBRSKI are two separate service contexts: they are distinguished by
different protocols: TCP vs. UDP.
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0123456789012345678901234567890123456789012345678901234567890123456789
_brski-registrar._tcp.local
IN PTR 0200:0000:7400-rrm._brski-registrar._tcp.local
0200:0000:7400-rrm._brski-registrar._tcp.local
IN SRV 1 2 4555 0200:0000:7400-rrm.local
0200:0000:7400-rrm._brski-registrar._tcp.local IN TXT ""
0200:0000:7400-rrm.local
IN AAAA fda3:79a6:f6ee:0000::0200:0000:6400:0001
_brski-registrar._tcp.local
IN PTR 0200:0000:7400-prm._brski-registrar._tcp.local
0200:0000:7400-prm._brski-registrar._tcp.local
IN SRV 1 2 4555 0200:0000:7400-prm.local
0200:0000:7400-prm._brski-registrar._tcp.local
IN TXT "prm" "cmp"
0200:0000:7400-prm.local
IN AAAA fda3:79a6:f6ee:0000::0200:0000:6400:0001
Figure 3: DNS-SD for a BRSKI registrar supporting RRM and PRM
In the second example Figure 3, a registrar needs to use two
different Instance Names, because both share the same service
context: BRSKI - TCP with service name brski-registrar. In this
example, the registrar offers "rrm" mode with "cms" voucher and "est"
enrollment. It also offers "prm" mode with "cms" voucher, but (only)
with "cmp" enrollment protocol. Because the registrar does not offer
"rrm" with "cmp", or "prm" with "est", it is not possible to coalesce
all variations under one Instance Name, so instead, two Instance
Names have to be created, and with them the necessary (duplicate) RR.
Note that the "-rrm" and "-prm" in the Instance Names are only
explanatory and could be any mutually unique strings - as is true for
the whole Instance Name.
Note too, that because both Instances share the same port number 4555
(and hence TCP socket), they both have to be provided by the same
BRSKI application. If two separate applications where to be started
on the dame host, one for "rrm", the other for "prm", then they would
have separate sockets and hence port numbers.
3.8.2. GRASP
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3.8.2.1. Signaling
This document does not specify a mandatory to implement set of
signaling options to guarantee interoperability of discovery between
initiator and responders when using GRASP. Like for the other
discovery mechanisms, these requirements will have to come from other
specifications that outline what in Section 1 is called the "security
and transport substrate" to be used for GRASP.
[RFC8994] specifies one such "security and transport substrate",
which is zero-touch deployable. It is mandatory to support for
initiators and responders implementing the so-called "Autonomic
Network Infrastructure" (ANI). DULL GRASP is used for link-local
discovery of proxies, and the ACP is used to automatically and
securely build the connectivity for multi-hop discovery of registrars
by proxies.
3.8.2.2. Encoding
To announce protocol variations with Section 1, the supported
Variation is indicated in the objective-value field of the GRASP
objective, using the method of forming the Variation string term in
Section 3.5.3, and listed in the Variation String column of the
Table 3 table.
If more than one Variation is supported, then multiple objectives
have to be announced, each with a different objective-value, but the
same location information if the different Variations are supported
across the same socket. Different sockets require different
objective structures in GRASP anyhow.
Compared to DNS-SD, the choice of encoding for GRASP optimizes for
minimum parsing effort, whereas the DNS-SD encoding is optimized for
most compact encoding given the limit for DNS-SD TXT records.
[M_FLOOD, 12340815, h'fe800000000000000000000000000001', 180000,
[["AN_Proxy", 4, 1, "",
[O_IPv6_LOCATOR,
h'fe800000000000000000000000000001', IPPROTO_TCP, 4443],
["AN_Proxy", 4, 1, "prm",
[O_IPv6_LOCATOR,
h'fe800000000000000000000000000001', IPPROTO_TCP, 4443],
["AN_Proxy", 4, 1, "",
[O_IPv6_LOCATOR,
h'fe800000000000000000000000000001', IPPROTO_UDP, 4684]]
]
Figure 4: GRASP example for a BRSKI registrar supporting RRM and PRM
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Figure 4 is an example for a GRASP service announcement for
"AN_Proxy" in support of BRSKI with both "rrm" and "prm" supported on
the same socket (TCP port number) and for cBRSKI with COAP over DTLS.
Note that one or more complete service instances (in the example 3)
can be contained within a single GRASP message without the need for
any equivalent to the Service Instance Name of the DNS-SD PTR RR or
the Target name of the DNS-SD SRV RR. DNS-SD requires them because
its encoding is decomposed into different RR, but it also
intentionally introduces the Service Instance Name as an element for
human interaction with selection (browsing and/or diagnostics of
selection), something that the current GRASP objective-value encoding
does not support.
Because this GRASP encoding does not support service instance name,
examples such as
[M_FLOOD, 12340815, h'fe800000000000000000000000000001', 180000,
[["AN_Proxy", 4, 1, "",
[O_IPv6_LOCATOR,
h'fe800000000000000000000000000001', IPPROTO_TCP, 4443],
["AN_Proxy", 4, 1, "",
[O_IPv6_LOCATOR,
h'fe800000000000000000000000000001', IPPROTO_UDP, 4684]]
]
[M_FLOOD, 42310815, h'fe800000000000000000000000000001', 180000,
[["AN_Proxy", 4, 1, "prm",
[O_IPv6_LOCATOR,
h'fe800000000000000000000000000001', IPPROTO_TCP, 44000]]
]
Figure 5: GRASP example with two different processes
In Figure 5, A separate application process supports "prm" and hence
uses a separate socket, with example TCP port 44000. In this case,
there is no need nor significant benefit to merge all service
instance announcements into a single GRASP message. Instead, the
BRSKI-"rrm"/cBRSKI process would be able to generate and send its
own, first, message shown in the example, and the second process
would send its own, second message in the example.
For a more extensive, DNS-SD compatible encoding of the objective-
value that also support Service Instance Names, see
[I-D.eckert-anima-grasp-dnssd].
3.8.3. CORE-LF
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3.8.3.1. Signaling
"Web Linking", [RFC5988] defines defines a format, originally for use
with HTTP headers, to link a HTTP document against other URIs. Web
linking is not a stand alone method for discovery of services for use
with HTTP.
"Constrained RESTful Environments (CoRE) Link Format", Section 1
introduces a stand alone method to discover services instances
(called resources in CORE-LF). An initiator connects to a previously
discovered initiator and uses CORE-LF to discover the available
service instances and their COAP parameters, such as their endpoints
and service parameters.
4. Updates to existing RFCs
4.1. RFC8995
TBD.
5. IANA considerations
5.1. BRSKI Variations Discovery Registry (section)
This document requests a new section named "BRSKI Variations
Discovery Parameters" in the "Bootstrapping Remote Secure Key
Infrastructures (BRSKI) Parameters" registry
(https://www.iana.org/assignments/brski-parameters/brski-
parameters.xhtml). Its initial content is as follows.
[ RFC editor. Please remove the following sentence. Note: This
section contains three tables according to the specifications of this
document. If it is not possible to introduce more than one table per
section, then we will modify the request accordingly for three
sections, but given how the three tables are tightly linked, that
would be unfortunate. ]
Registration Procedure(s): Standards action or expert review based on
registration. See ThisRFC.
Experts: TBD.
Reference: ThisRFC.
Notes:
Dflt flag: Indicates a Variation Type Choice that is assumed to be
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used if the service discover/selection mechanism does not indicate
any variation.
Rsvd Flag: Indicates a Variation Type Choice that is reserved for
use with the mechanism described in the Note(s) column, but for
which no specification yet exists.
Spec / Applicability: A "-" indicates that the variation is
considered to be feasible through existing specifications, but not
explicitly mentioned in them. An "NA" indicates that the
combination is assumed to be not working with the currently
available specifications.
+==============+============+===========+===========================+
| Context | Applicable | Discovery | Service Name(s) |
| | Variation | Mechanism | |
| | Types | | |
+==============+============+===========+===========================+
| BRSKI | mode | GRASP | "AN_join_registrar" / |
| | vformat | | "AN_Proxy" |
| | enroll | | with IPPROTO_TCP |
+--------------+------------+-----------+---------------------------+
| | | DNS-SD | "brski-registrar" / |
| | | | "brski-proxy" |
| | | | with TCP |
+--------------+------------+-----------+---------------------------+
| cBRSKI | mode | GRASP | "AN_join_registrar" / |
| | vformat | | "AN_join_registrar_rjp" |
| | enroll | | / |
| | | | "AN_Proxy" |
| | | | with IPPROTO_UDP |
+--------------+------------+-----------+---------------------------+
| | | DNS-SD | "brski-registrar" / |
| | | | "brski-proxy" |
| | | | with UDP |
+--------------+------------+-----------+---------------------------+
| | | CORE-LF | rt=brski.* |
+--------------+------------+-----------+---------------------------+
| BRSKI-PLEDGE | mode | DNS-SD | "brski-pledge" with TCP |
| | vformat | | |
| | enroll | | |
+--------------+------------+-----------+---------------------------+
Table 1: BRSKI Variation Contexts
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+=======+=========+=========+=========+=====+========================================+
|Context|Variation|Variation|Reference|Flags|Note(s) |
| |Type |Type | | | |
| | |Choice | | | |
+=======+=========+=========+=========+=====+========================================+
|BRSKI, |mode |rrm |[RFC8995]|Dflt |Registrar Responder Mode |
|cBRSKI | | |ThisRFC | |the mode specified in [RFC8995] |
+-------+---------+---------+---------+-----+----------------------------------------+
| | |prm |ThisRFC | |Pledge Responder Mode |
| | | | | |[I-D.ietf-anima-brski-prm] |
+-------+---------+---------+---------+-----+----------------------------------------+
|BRSKI |vformat |cms |[RFC8368]|Dflt |CMS-signed JSON Voucher |
| | | |ThisRFC | | |
+-------+---------+---------+---------+-----+----------------------------------------+
| | |cose |ThisRFC | |CBOR with COSE signature |
+-------+---------+---------+---------+-----+----------------------------------------+
|cBRSKI | |cose |ThisRFC |Dflt |CBOR with COSE signature |
| | | | | |[I-D.ietf-anima-constrained-voucher] |
+-------+---------+---------+---------+-----+----------------------------------------+
| | |cms |[RFC8368]| |CMS-signed JSON Voucher |
| | | |ThisRFC | | |
+-------+---------+---------+---------+-----+----------------------------------------+
|BRSKI, | |jose |ThisRFC |Dflt*|JOSE-signed JSON, Default when prm is |
|cBRSKI | | | | |used |
| | | | | |[I-D.ietf-anima-jws-voucher], |
| | | | | |[I-D.ietf-anima-brski-ae] |
+-------+---------+---------+---------+-----+----------------------------------------+
|BRSKI- |mode |prm |ThisRFC |Dflt |Pledge responder Mode |
|PLEDGE | | | | |[I-D.ietf-anima-brski-prm] |
+-------+---------+---------+---------+-----+----------------------------------------+
| |vformat |jose |ThisRFC |Dflt |JOSE-signed JSON, Default when prm is |
| | | | | |used |
| | | | | |[I-D.ietf-anima-jws-voucher], |
| | | | | |[I-D.ietf-anima-brski-ae] |
+-------+---------+---------+---------+-----+----------------------------------------+
| | |cms |ThisRFC |Rsvd |CMS-signed JSON Voucher, not specified. |
+-------+---------+---------+---------+-----+----------------------------------------+
| | |cose |ThisRFC |Rsvd |CBOR with COSE signature, not specified.|
+-------+---------+---------+---------+-----+----------------------------------------+
|BRSKI, |enroll |est |[RFC8995]|Dflt |Enroll via EST |
|cBRSKI,| | |[RFC7030]| |as specified in [RFC8995], extension for|
|BRSKI- | | | | |Section 1 when used in context BRSKI- |
|PLEDGE | | | | |PLEDGE |
+-------+---------+---------+---------+-----+----------------------------------------+
| | |cmp |ThisRFC | |Lightweight CMP Profile |
| | | | | |{I-D.ietf-anima-brski-ae}}, |
| | | | | |[I-D.ietf-lamps-lightweight-cmp-profile]|
+-------+---------+---------+---------+-----+----------------------------------------+
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| | |scep |ThisRFC |Rsvd |[RFC8894] |
+-------+---------+---------+---------+-----+----------------------------------------+
Table 2: BRSKI Variation Type Choices
Note 1: The Variation String "EST-TLS" is equivalent to the
Variation String "" and is required and only permitted for the
AN_join_registrar objective value in GRASP for backward
compatibility with RFC8995, where it is used for this variation.
Note that AN_proxy uses "".
+=======+====================================+=========+=========+========================================+
|Context|Spec / Applicability |Variation|Variation|Explanations / Notes |
| | |String | | |
+=======+====================================+=========+=========+========================================+
|BRSKI |[RFC8995] |"" / |rrm cms |Note 1 |
| | |"EST-TLS"|est | |
+-------+------------------------------------+---------+---------+----------------------------------------+
| |[I-D.ietf-anima-brski-ae] |cmp |rrm cms | |
| | | |cmp | |
+-------+------------------------------------+---------+---------+----------------------------------------+
| |[I-D.ietf-anima-brski-prm] |prm |prm jose | |
| | | |est | |
+-------+------------------------------------+---------+---------+----------------------------------------+
+-------+------------------------------------+---------+---------+----------------------------------------+
| |- |jose |rrm jose |possible variation of [RFC8995] with |
| | | |est |voucher according to |
| | | | |[I-D.ietf-anima-jws-voucher] |
+-------+------------------------------------+---------+---------+----------------------------------------+
| |- |jose-cmp |rrm jose |possible variation of [RFC8995] with |
| | | |cmp |voucher according to |
| | | | |[I-D.ietf-anima-jws-voucher] and |
| | | | |enrollment according to |
| | | | |[I-D.ietf-lamps-lightweight-cmp-profile]|
+-------+------------------------------------+---------+---------+----------------------------------------+
| |- |cose |rrm cose |possible variation of [RFC8995] with |
| | | |est |voucher according to |
| | | | |[I-D.ietf-anima-constrained-voucher] |
+-------+------------------------------------+---------+---------+----------------------------------------+
| |- |cose-cmp |rrm cose |possible variation of [RFC8995] with |
| | | |cmp |voucher according to |
| | | | |[I-D.ietf-anima-constrained-voucher] and|
| | | | |enrollment according to |
| | | | |[I-D.ietf-lamps-lightweight-cmp-profile]|
+-------+------------------------------------+---------+---------+----------------------------------------+
| |- |prm-cmp |prm jose |possible variation of |
| | | |cmp |[I-D.ietf-anima-brski-prm] and |
| | | | |[I-D.ietf-anima-brski-ae] |
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+-------+------------------------------------+---------+---------+----------------------------------------+
| |- |prm-cose |prm cose |possible variation of |
| | | |est |[I-D.ietf-anima-brski-prm] and |
| | | | |[I-D.ietf-anima-constrained-voucher] |
+-------+------------------------------------+---------+---------+----------------------------------------+
| |- |prm-cose-|prm cose |possible variation of |
| | |cmp |cmp |[I-D.ietf-anima-brski-prm], |
| | | | |[I-D.ietf-anima-constrained-voucher] and|
| | | | |[I-D.ietf-anima-brski-ae] |
+-------+------------------------------------+---------+---------+----------------------------------------+
+-------+------------------------------------+---------+---------+----------------------------------------+
|cBRSKI |[I-D.ietf-anima-constrained-voucher]|"" |rrm cose | |
| | | |est | |
+-------+------------------------------------+---------+---------+----------------------------------------+
+-------+------------------------------------+---------+---------+----------------------------------------+
| |- | | |TBD: all the possible variations as for |
| | | | |BRSKI ??? |
+-------+------------------------------------+---------+---------+----------------------------------------+
Table 3
5.2. Service Names Registry
IANA is asked to modify and amend the "Service Name and Transport
Protocol Port Number Registry" registry
(https://www.iana.org/assignments/service-names-port-numbers/service-
names-port-numbers.txt) as follows:
brski-proxy and brski-registrar are to be added as Service Names for
the "udp" protocol using ThisRFC as the reference.
The registrations for brski-proxy and brski-registrar for the "tcp"
protocol are to be updated to also include ThisRFC as their
reference.
The Defined TXT keys column for brski-proxy and brski-registrar for
both "tcp" and "udp" protocols are to state the following text:
See ThisRFC and the "BRSKI Variation Type Choices" table in the
"Bootstrapping Remote Secure Key Infrastructures (BRSKI) Parameters"
registry.
TBD: This request likely does not include all the necessary
formatting.
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5.3. BRSKI Well-Known URIs fixes (opportunistic)
The following change requests to "https://www.iana.org/assignments/
brski-parameters/brski-parameters.xhtml#brski-well-known-uris" are
cosmetic in nature and are included in this document solely because
support for Endpoint URIs is implied by the mechanisms specified in
this document and the existing registry has these cosmetic issues.
1. IANA is asked to change the name of the first column of the table
from "URI" to "URI Suffix". This is in alignment with other
table columns with the same syntax/semantic, such as
"https://www.iana.org/assignments/well-known-uris/well-known-
uris.xhtml".
2. IANA is asked to change the Reference from [RFC8995] to
[RFC8995], Section 8.3.1.
3. IANA is asked to include the following "Note" text: The following
table contains the assigned BRSKI protocol Endpoint URI suffixes
under "/.well-known/brski"." - This note is added to introduce
the term "Endpoint" into the registry table as that is the term
commonly used (instead of URI) in several of the memos for which
this discovery document was written. It is meant to help readers
map the registry to the terminology used in those documents.
6. Security Considerations
In Section 1, pledges are easier subject to DoS attacks than in
Section 1, because attackers can be initiators and delay or prohibit
enrollment of a pledge by opening so many connections to the pledge
that a valid registrar-agents connection to the pledge may not be
possible. Discovery of the pledge via DNS-SD increases the ability
of attackers to discover pledges against which such DoS attacks can
be attempted.
Especially when supporting DNS-SD browsing across unicast DNS,
Pledges MUST implement DoS prevention measures, such as limiting the
number and rate of accepted TCP connections on a per-initiator basis.
If feasible for the implementation, simultaneous connections SHOULD
be possible, so that an ongoing attacker connection will not delay a
valid registrar-agent connection. When accepting connections, a
strategy such as LRU MAY be used to ensure that an attacker will not
be able to monopolize connections.
Browsing via DNS-SD, especially via unicast DNS which makes
information available network-wide does also introduce a perpass
attack, gathering intelligence against what type and serial number of
devices are installed in the network. Whether or not this is seen as
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a relevant risk is highly installation dependent. Networks SHOULD
implement filtering measures at mDNS and/or DNS RR/services level to
prohibit such data collection if there is a risk, and this is seen as
an undesirable attack vector.
7. Acknowledgments
TBD.
8. Draft considerations
8.1. Open Issues
Questions to the DNS-SD community, potential review with
TBD
8.2. Change log
[RFC Editor: please remove this section.]
Individual version 00:
Initial version.
9. References
9.1. Normative References
[I-D.ietf-anima-brski-ae]
von Oheimb, D., Fries, S., and H. Brockhaus, "BRSKI-AE:
Alternative Enrollment Protocols in BRSKI", Work in
Progress, Internet-Draft, draft-ietf-anima-brski-ae-06, 20
October 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-anima-brski-ae-06>.
[I-D.ietf-anima-brski-prm]
Fries, S., Werner, T., Lear, E., and M. Richardson, "BRSKI
with Pledge in Responder Mode (BRSKI-PRM)", Work in
Progress, Internet-Draft, draft-ietf-anima-brski-prm-10,
23 October 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-anima-brski-prm-10>.
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[I-D.ietf-anima-constrained-join-proxy]
Richardson, M., Van der Stok, P., and P. Kampanakis,
"Constrained Join Proxy for Bootstrapping Protocols", Work
in Progress, Internet-Draft, draft-ietf-anima-constrained-
join-proxy-14, 26 April 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-anima-
constrained-join-proxy-14>.
[I-D.ietf-anima-constrained-voucher]
Richardson, M., Van der Stok, P., Kampanakis, P., and E.
Dijk, "Constrained Bootstrapping Remote Secure Key
Infrastructure (BRSKI)", Work in Progress, Internet-Draft,
draft-ietf-anima-constrained-voucher-21, 7 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-anima-
constrained-voucher-21>.
[I-D.ietf-anima-jws-voucher]
Werner, T. and M. Richardson, "JWS signed Voucher
Artifacts for Bootstrapping Protocols", Work in Progress,
Internet-Draft, draft-ietf-anima-jws-voucher-09, 29 August
2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
anima-jws-voucher-09>.
[I-D.ietf-dnssd-srp]
Lemon, T. and S. Cheshire, "Service Registration Protocol
for DNS-Based Service Discovery", Work in Progress,
Internet-Draft, draft-ietf-dnssd-srp-23, 4 August 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-dnssd-
srp-23>.
[I-D.ietf-lamps-lightweight-cmp-profile]
Brockhaus, H., von Oheimb, D., and S. Fries, "Lightweight
Certificate Management Protocol (CMP) Profile", Work in
Progress, Internet-Draft, draft-ietf-lamps-lightweight-
cmp-profile-21, 17 February 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-lamps-
lightweight-cmp-profile-21>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/rfc/rfc5280>.
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[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
<https://www.rfc-editor.org/rfc/rfc6690>.
[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
DOI 10.17487/RFC6762, February 2013,
<https://www.rfc-editor.org/rfc/rfc6762>.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
<https://www.rfc-editor.org/rfc/rfc6763>.
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013,
<https://www.rfc-editor.org/rfc/rfc7030>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8368] Eckert, T., Ed. and M. Behringer, "Using an Autonomic
Control Plane for Stable Connectivity of Network
Operations, Administration, and Maintenance (OAM)",
RFC 8368, DOI 10.17487/RFC8368, May 2018,
<https://www.rfc-editor.org/rfc/rfc8368>.
[RFC8990] Bormann, C., Carpenter, B., Ed., and B. Liu, Ed., "GeneRic
Autonomic Signaling Protocol (GRASP)", RFC 8990,
DOI 10.17487/RFC8990, May 2021,
<https://www.rfc-editor.org/rfc/rfc8990>.
[RFC8994] Eckert, T., Ed., Behringer, M., Ed., and S. Bjarnason, "An
Autonomic Control Plane (ACP)", RFC 8994,
DOI 10.17487/RFC8994, May 2021,
<https://www.rfc-editor.org/rfc/rfc8994>.
[RFC8995] Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructure (BRSKI)", RFC 8995, DOI 10.17487/RFC8995,
May 2021, <https://www.rfc-editor.org/rfc/rfc8995>.
9.2. Informative References
[I-D.eckert-anima-grasp-dnssd]
Eckert, T. T., Boucadair, M., Jacquenet, C., and M. H.
Behringer, "DNS-SD Compatible Service Discovery in GeneRic
Autonomic Signaling Protocol (GRASP)", Work in Progress,
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Internet-Draft, draft-eckert-anima-grasp-dnssd-05, 10 July
2023, <https://datatracker.ietf.org/doc/html/draft-eckert-
anima-grasp-dnssd-05>.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988,
DOI 10.17487/RFC5988, October 2010,
<https://www.rfc-editor.org/rfc/rfc5988>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/rfc/rfc7252>.
[RFC8894] Gutmann, P., "Simple Certificate Enrolment Protocol",
RFC 8894, DOI 10.17487/RFC8894, September 2020,
<https://www.rfc-editor.org/rfc/rfc8894>.
Appendix A. Discovery for constrained BRSKI
This appendix section is intended to describe the current issues with
Section 1 and Section 1 as of 08/2023, which make both drafts
incompatible with this document. It will be removed if/when those
issues will be fixed.
A.1. Current constrained text for GRASP
The following is the current encodings from Section 1.
* The transport-proto is IPPROTO_UDP
* the objective is AN_join_registrar, identical to Section 1.
* the objective name is "BRSKI_RJP".
Here is an example M_FLOOD announcing the Registrar on example port
5685, which is a port number chosen by the Registrar.
[M_FLOOD, 51804231, h'fda379a6f6ee00000200000064000001', 180000,
[["AN_join_registrar", 4, 255, "BRSKI_RJP"],
[O_IPv6_LOCATOR,
h'fda379a6f6ee00000200000064000001', IPPROTO_UDP, 5685]]]
Figure 6: cBRSKI Fig 5: Example of Registrar announcement message
Most Registrars will announce both a JPY-stateless and stateful
ports, and may also announce an HTTPS/TLS service:
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[M_FLOOD, 51840231, h'fda379a6f6ee00000200000064000001', 180000,
[["AN_join_registrar", 4, 255, ""],
[O_IPv6_LOCATOR,
h'fda379a6f6ee00000200000064000001', IPPROTO_TCP, 8443],
["AN_join_registrar", 4, 255, "BRSKI_JP"],
[O_IPv6_LOCATOR,
h'fda379a6f6ee00000200000064000001', IPPROTO_UDP, 5684],
["AN_join_registrar", 4, 255, "BRSKI_RJP"],
[O_IPv6_LOCATOR,
h'fda379a6f6ee00000200000064000001', IPPROTO_UDP, 5685]]]
Figure 7
The following is the current text from Section 1.
* The transport-proto is IPPROTO_UDP
* the objective is AN_join_registrar, identical to Section 1.
* the objective name is "BRSKI_RJP".
Here is an example M_FLOOD announcing the Registrar on example port
5685, which is a port number chosen by the Registrar.
[M_FLOOD, 51804231, h'fda379a6f6ee00000200000064000001', 180000,
[["AN_join_registrar", 4, 255, "BRSKI_RJP"],
[O_IPv6_LOCATOR,
h'fda379a6f6ee00000200000064000001', IPPROTO_UDP, 5685]]]
Figure 8: Example of Registrar announcement message
Most Registrars will announce both a JPY-stateless and stateful
ports, and may also announce an HTTPS/TLS service:
[M_FLOOD, 51840231, h'fda379a6f6ee00000200000064000001', 180000,
[["AN_join_registrar", 4, 255, ""],
[O_IPv6_LOCATOR,
h'fda379a6f6ee00000200000064000001', IPPROTO_TCP, 8443],
["AN_join_registrar", 4, 255, "BRSKI_JP"],
[O_IPv6_LOCATOR,
h'fda379a6f6ee00000200000064000001', IPPROTO_UDP, 5684],
["AN_join_registrar", 4, 255, "BRSKI_RJP"],
[O_IPv6_LOCATOR,
h'fda379a6f6ee00000200000064000001', IPPROTO_UDP, 5685]]]
Figure 9: Example of Registrar announcing two services
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A.1.1. Issues and proposed change
One goal of this document is to define variations such that proxies
can deal with existing and future variations. This only works for
variations for which proxies would need to perform specific
processing other than passing on data between pledge and registrar.
Changes in protocol that require specific new behavior of proxies
must therefore not be variations signaled via the objective-value
field of GRASP objectives.
In result, this document recommends the following changes to the
encoding for Section 1 and Section 1.
[M_FLOOD, 51840231, h'fda379a6f6ee00000200000064000001', 180000,
[["AN_join_registrar", 4, 255, ""],
[O_IPv6_LOCATOR,
h'fda379a6f6ee00000200000064000001', IPPROTO_TCP, 8443],
["AN_join_registrar", 4, 255, ""],
[O_IPv6_LOCATOR,
h'fda379a6f6ee00000200000064000001', IPPROTO_UDP, 5684],
["AN_join_registrar_rjp", 4, 255, ""],
[O_IPv6_LOCATOR,
h'fda379a6f6ee00000200000064000001', IPPROTO_UDP, 5685]]]
Figure 10: Proposed Encoding of registrar announcements
In summary:
* Circuit proxy operation is indicted with objective-name
"AN_join_registrar" and IPPROTO_UDP. The default for
AN_join_registrar/UDP is the use of COAPs and CBOR encoded
voucher. For this default, the objective-value is "".
* Stateless JPY proxy operations is indicated with objective-name
"AN_join_registrar_rjp" and IPPROTO_UDP. The default for
AN_join_registrar/UDP is the use of COAPs and CBOR encoded
voucher. For this default, the objective-value is "".
Contributors
Thomas Werner
Siemens AG
Germany
Email: thomas-werner@siemens.com
URI: https://www.siemens.com/
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Steffen Fries
Siemens AG
Germany
Email: steffen.fries@siemens.com
URI: https://www.siemens.com/
Hendrik Brockhaus
Siemens AG
Germany
Email: hendrik.brockhaus@siemens.com
URI: https://www.siemens.com/
Michael Richardson
Canada
Phone: +41 44 878 9200
Email: mcr+ietf@sandelman.org
Authors' Addresses
Toerless Eckert (editor)
Futurewei USA
United States of America
Email: tte@cs.fau.de
David von Oheimb
Siemens AG
Otto-Hahn-Ring 6
81739 Munich
Germany
Email: david.von.oheimb@siemens.com
URI: https://www.siemens.com/
Esko Dijk
IoTconsultancy.nl
Email: esko.dijk@iotconsultancy.nl
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