wdiff draft-ietf-mboned-ambi-01.txt draft-ietf-mboned-ambi-02.txt

Mboned J. Holland
Internet-Draft K. Rose
Intended status: Standards Track Akamai Technologies, Inc.
Expires: May 3, January 11, 2022 July 10, 2021 October 30, 2020

Asymmetric Manifest Based Integrity
draft-ietf-mboned-ambi-01
draft-ietf-mboned-ambi-02

Abstract

This document defines Asymmetric Manifest-Based Integrity (AMBI).
AMBI allows each receiver or forwarder of a stream of multicast
packets to check the integrity of the contents of each packet in the
data stream. AMBI operates by passing cryptographically verifiable
hashes of the data packets inside manifest messages, and sending the
manifests over authenticated out-of-band communication channels.

Status of This Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

This Internet-Draft will expire on May 3, 2021. January 11, 2022.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 3
1.1. Comparison with TESLA . . . . . . . . . . . . . . . . . . 4
1.2. Threat Model Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Terminology Notes for Contributors and Reviewers . . . . . . . . . . 4
1.3.1. Venues for Contribution and Discussion . . . . . . . 5
1.3.2. Non-obvious doc choices . . . . . . . . . . . . . . . 5
1.4. Notes for Contributors and Reviewers
2. Threat Model . . . . . . . . . . 5
1.4.1. Venues for Contribution . . . . . . . . . . . . . . 6
2.1. Security Anchors . . . . . . . . . . . . . . . . . . . . 6
2.1.1. Alternatives and Discussion Their Requirements . . . . . . . 5
2. . . 7
2.2. System Security . . . . . . . . . . . . . . . . . . . . . 8
3. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 5
2.1. 8
3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. 8
3.2. Buffering of Packets and Digests . . . . . . . . . . . . 9
3.2.1. Validation Windows . . . . . . . . . . . . 6
2.2.1. Inter-packet Gap . . . . . 10
3.2.2. Preserving Inter-packet Gap . . . . . . . . . . . . . 8
2.3. 11
3.3. Packet Digests . . . . . . . . . . . . . . . . . . . . . 8
2.3.1. 11
3.3.1. Digest Profile . . . . . . . . . . . . . . . . . . . 8
2.3.2. 11
3.3.2. Pseudoheader . . . . . . . . . . . . . . . . . . . . 10
2.4. 13
3.4. Manifests . . . . . . . . . . . . . . . . . . . . . . . . 12
2.4.1. 14
3.4.1. Manifest Layout . . . . . . . . . . . . . . . . . . . 12
2.5. 14
3.5. Transitioning to Other Manifest Streams . . . . . . . . . 13
3. 17
4. Transport Considerations . . . . . . . . . . . . . . . . . . 14
3.1. 18
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2. 18
4.2. HTTPS . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.3. DTLS 18
4.3. TLS . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.4. . 18
4.4. DTLS + FECFRAME . . . . . . . . . . . . . . . . . . . . . 15
4. . . . . . 19
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5. 19
6. YANG Module . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.1. 19
6.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 15
5.2. 19
6.2. Module . . . . . . . . . . . . . . . . . . . . . . . . . 15
6. 20
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
6.1. 23
7.1. The YANG Module Names Registry . . . . . . . . . . . . . 18
6.2. 23
7.2. The XML Registry . . . . . . . . . . . . . . . . . . . . 18
6.3. 24
7.3. Media Type . . . . . . . . . . . . . . . . . . . . . . . 18
7. Security Considerations 24
7.4. URI Schemes . . . . . . . . . . . . . . . . . . . 19
7.1. Predictable Packets . . . . 24
7.4.1. TLS . . . . . . . . . . . . . . . 19
8. Acknowledgements . . . . . . . . . . 24
7.4.2. DTLS . . . . . . . . . . . . 19
9. References . . . . . . . . . . . . 24
8. Security Considerations . . . . . . . . . . . . . 19
9.1. Normative References . . . . . . 24
8.1. Predictable Packets . . . . . . . . . . . . 19
9.2. Informative References . . . . . . . 24
8.2. Attacks on Side Applications . . . . . . . . . . 20
9.3. URIs . . . . 25
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses 25
10. References . . . . . . . . . . . . . . . . . . . . . . . 21

1. Introduction

Multicast transport poses security problems that are not easily
addressed by the same security mechanisms used for unicast . . 26
10.1. Normative References . . . . . . . . . . . . . . . . . . 26
10.2. Informative References . . . . . . . . . . . . . . . . . 26
10.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29

1. Introduction

Multicast transport poses security problems that are not easily
addressed by the same security mechanisms used for unicast transport.

The "Introduction" sections of the documents describing TESLA
[RFC4082], and TESLA in SRTP [RFC4383], and TESLA with ALC and NORM
[RFC5776] present excellent overviews of the challenges unique to
multicast authentication, authentication for use cases like wide scale software or
video distribution with a high data transfer rate. The challenges
are briefly summarized here:

o A MAC based on a symmetric shared secret cannot be used because
each packet has multiple receivers that do not trust each other,
and using a symmetric shared secret exposes the same secret to
each receiver.

o Asymmetric per-packet signatures can handle only very low bit-
rates because of the transport and computational overhead. overhead
associated with signature transmission and verification.

o An asymmetric signature of a larger message comprising multiple
packets requires reliable receipt of all such packets, something
that cannot be guaranteed in a timely manner even for protocols
that do provide reliable delivery, and the retransmission of which
may anyway exceed the useful lifetime for data formats that can
otherwise tolerate some degree of loss.

Aymmetric Manifest-Based Integrity (AMBI) defines a method for
receivers or middle boxes to cryptographically authenticate and
verify the integrity of a stream of packets, packets by communicating comparing the data
packets to a stream of packet "manifests" (described in Section 2.4) 3.4)
received via an out-of-band communication channel that provides
authentication and verifiable integrity.

Each manifest contains a message digest (described in Section 2.3) 3.3)
for each packet in a sequence of packets from the data stream,
hereafter called a "packet digest". The packet digest incorporates a
cryptographic hash of the packet contents and some identifying data
from the packet, according to a defined digest profile for the data
stream.

Each manifest MUST be delivered in a way that provides cryptographic
integrity guarantees of the authenticity of the manifest. For
example, TLS could be used to deliver a stream of manifests over a
unicast data stream from a set

Upon receipt of trusted senders to each receiver,
or a protocol that asymmetrically signs each message could be used to
transport authenticated manifests over packet digest inside a multicast channel. Note
that manifest conveyed in a UDP-based protocol might drop or reorder manifests while still
providing authentication.

Upon successful
secure channel and verification that the packet digest of a manifest and receipt of any subset
of the corresponding received
data packets, packet matches, the receiver has proof of the integrity of the
contents of the data packets packet corresponding to that are listed in the
manifest.

Authenticating digest.

This document defines the integrity of the data packets depends on:

o the authenticity of the manifests

o the authenticity of the digest profile used for construction of
the packet digests

o the difficulty of generating a collision for the packet digests
contained in the manifest.

This document defines a "ietf-ambi" YANG [RFC7950] module that augments the DORMS
[I-D.draft-ietf-mboned-dorms-00] YANG module to provide a way to
communicate a digest profile, described model in
Section 2.3.1, for
construction 6 as an extension of the packet digests, described "ietf-dorms" model defined in Section 2.3. When
obtaining the digest profile by using DORMS, the authenticity
[I-D.draft-ietf-mboned-dorms]. Also defined are new URI schemes for
transport of the
data stream relies on manifests over TLS or DTLS, and a trust relationship with the DORMS server,
since that anchors the authenticity new media type for
transport of the digest profile manifests over HTTPS. The encodings for
constructing packet digests. these are
defined in Section 4.

1.1. Comparison with TESLA

AMBI and TESLA [RFC4082] and [RFC5776] attempt to achieve a similar
goal of authenticating the integrity of streams of multicast packets.
AMBI imposes a higher overhead, overhead than TESLA imposes, as measured in the
amount of extra data required, than TESLA imposes. required. In exchange, AMBI relaxes the
requirement for establishing an upper bound on clock synchronization
between sender and receiver, and allows for the use case of
authenticating multicast traffic before forwarding it through the
network, while also allowing receivers to authenticate the same
traffic. By contrast, this is not possible with TESLA because the
data packets can't be authenticated until a key is disclosed, so
either the middlebox has to forward data packets without first
authenticating them so that the receiver has them prior to key
disclosure, or the middlebox has to hold packets until the key is
disclosed, at which point the receiver can no longer establish their
authenticity.

The other new capability is that because AMBI provides authentication
information out of band, authentication can be retrofitted into some
pre-existing deployments without changing the protocol of the data
packets,
packets under some restrictions outlined in Section 7. 8. By contrast,
TESLA requires a MAC to be added to each authenticated message.

1.2. Threat Model

TBD: Summarize the applicable threat model this protects against. A
diagram plus a cleaned-up version of the on-list explanation here is
probably appropriate: https://mailarchive.ietf.org/arch/msg/mboned/
CG9FLjPwuno3MtvYvgNcD5p69I4/

Reference [RFC3552] https://tools.ietf.org/html/rfc3552#section-3

1.3. 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
[RFC2119] and [RFC8174] when, and only when, they appear in all
capitals, as shown here.

1.4.

1.3. Notes for Contributors and Reviewers

Note to RFC Editor: Please remove this section and its subsections
before publication.

This section is to provide references to make it easier to review the
development and discussion on the draft so far.

1.4.1.

1.3.1. Venues for Contribution and Discussion

This document is in the Github repository at:

https://github.com/GrumpyOldTroll/ietf-dorms-cluster [1]

Readers are welcome to open issues and send pull requests for this
document.

Please note that contributions may be merged and substantially
edited, and as a reminder, please carefully consider the Note Well
before contributing: https://datatracker.ietf.org/submit/note-well/
[2]

Substantial discussion of this document should take place on the
MBONED working group mailing list (mboned@ietf.org).

o Join: https://www.ietf.org/mailman/listinfo/mboned [3]

o Search: https://mailarchive.ietf.org/arch/browse/mboned/

2. Protocol Operation

2.1. Overview

In order to authenticate a data packet, AMBI receivers [4]

1.3.2. Non-obvious doc choices

o TBD: we need a way to hold
these three pieces of information at the same time:

o assert that we provide the data packet

o full set of
packets for an authenticated manifest containing the packet digest (S,G) on all UDP ports and non-UDP protocols.
Naively authenticating UDP for the
data packet

o specified ports and ignoring other
ports means that an attacker could attack a digest profile defining the transformation from the data packet
to its packet digest

The manifests are delivered as separate UDP port by
injecting traffic directed at it, potentially hitting a stream of manifests over different
application that listens on 0.0.0.0, so an (S,G) with legitimately
authenticated data channel. Manifest contents MUST be authenticated
before they can UDP traffic on one port could be used to authenticate data packets.

The manifest stream is composed of an ordered sequence of manifests
that each contain transport
UDP-based attacks to apps on another port or protocol unless they
are firewalled. Passing traffic for an ordered sequence of packet digests,
corresponding (S,G) subscription would
open a new channel to the original packets as sent such targets that otherwise would not be
reachable from their origin, in the same order.

Note that internet for users behind e.g. a manifest contains potentially many packet digests, and
its size can be tuned CPE with nat
or connection-state-based firewalling.

o Dropped intent to fit within support DTLS+FECFRAME in this spec because RFC
6363 seems incomprehensible on a convenient PDU (Protocol Data
Unit) of the manifest transport stream. By doing so, many packet
digests few points, most notably demux
strategy between repair and source ADUs, which as written seems to
require specifying another layer. So support for the multicast data stream can this will have
to be delivered per packet a later separate RFC. However, for future extensibility
made manifest-stream into a list instead of
the manifest transport. The intent is a leaf-list so that even with unicast-based
manifest transport, multicast-style efficiencies of scale it
can still be realized with only a relatively small unicast overhead, when
manifests use a unicast transport.

2.2. Buffering and Validation Windows

Using different communication channels an augment target for a later YANG extension with FEC
selection from the manifest stream likewise-very-confusing semi-overlapping
registries at https://www.iana.org/assignments/rmt-fec-parameters/
rmt-fec-parameters.xhtml [5] defined by RFCs 5052 and 6363. See
also RFC 6363, RFC 6681, and RFC 6865

2. Threat Model

AMBI is designed to operate over the data stream introduces a possibility of desynchronization in the
timing of internet, under the received Internet
Threat Model described in [RFC3552].

AMBI aims to provide Data Integrity for a multicast data between stream,
building on the different channels, so
receivers hold data packets security anchors described in Section 2.1 to do so.
The aim is to enable receivers to subscribe to and packet digests receive multicast
packets from a trusted sender without damage to the manifest
stream in buffers Systems Security
(Section 2.3 of [RFC3552]) for some duration while awaiting those receivers or other entities.

Thus, we assume there might be attackers on-path or off-path with the arrival
capability to inject or modify packets, but that the attackers have
not compromised the sender or discovered any of
their counterparts.

While holding a data packet, if the corresponding packet digest sender's secret
keys. We assume that an attacker may have compromised some receivers
of the multicast traffic, but still aim to provide the above security
properties for receivers that packet arrives in have not been compromised.

Those sending multicast traffic to receivers that include untrusted
receivers should avoid transmitting sensitive information that
requires strong confidentiality guarantees, due to the manifest stream and can be authenticated, risk of
compromise from those receivers. Since multicast transmits the data packet is authenticated.

While holding an authenticated packet digest, if same
packets to potentially many receivers, in the corresponding
data packet arrives with a matching packet digest, presence of potentially
compromised receivers confidentiality of the content cannot be
assured.

However, any protocol that provides encryption of the data packet is
authenticated.

Once a data packet is authenticated,
before generating the corresponding packet digest can be discarded and provide confidentiality
against on-path passive observers who do not possess the data packet decryption
key. This level of confidentiality can be further processed provided by any such
protocols without impact on AMBI's operation.

2.1. Security Anchors

Establishing the
receiving application or forwarded through desired security properties for the receiving network.
Authenticating a multicast data packet consumes
packets relies on secure delivery of some other information:

o Secured unicast connections (providing Data Integrity) to one packet digest and prevents
re-learning, with or
more trusted DORMS [I-D.draft-ietf-mboned-dorms] servers that use
the AMBI extensions to the DORMS YANG model as defined in
Section 6

o Secure delivery (providing Data Integrity) of a hold-down time equal stream of
manifests (Section 3.4)

The secured unicast connection to the hold time for packet
digests. A different manifest might provide DORMS server provides the same packet digest
with Peer
Entity authentication of the same packet sequence number, but DORMS server that's needed to establish
the digest remains consumed
if Data Integrity of the data it has been used to authenticate sends.

Note that DORMS provides a data packet.

If the receiver's hold duration method for a data packet expires without
authenticating the packet, using DNS to bootstrap
discovery of the packet SHOULD DORMS server. In contexts where secure DNS lookup
cannot be dropped provided, it's still possible to establish a secure
connection to a trusted DORMS server as long as
unauthenticated. If the hold duration trusted DORMS
server's hostname is known to the receivers (removing the need to use
DNS for that discovery). Once the server name is known, the ordinary
certificate verification of that hostname while establishing a manifest expires, secure
https connection provides the needed security properties to anchor
the rest.

Receiving unauthenticated data packets and knowing how to generate
packet digests last received in that from the manifest SHOULD be discarded. (Note
that profile provided by the AMBI
extensions in some cases, the DORMS metadata allows the receiver to generate
packet digests based on the contents of the received packet, which
can be sent redundantly in more
than one manifest. In such cases, compared against the latest received time for an
authenticated packet digests that were securely
received.

Comparing the digests and finding the same answer then provides Data
Integrity for the data packets that relies on one more property of
the digest should be used generation algorithm:

o the difficulty of generating a collision for the expiration time.)

Since packet digests are usually smaller than
contained in the manifest.

Taken together, successful validation of the multicast data packets, it's
RECOMMENDED packets
proves within the above constraints that senders generate and send manifests someone with timing such
that control of the packet digests in a
manifest will typically be received URI streams provided by
subscribed receivers before the data DORMS server has verified the
sending of the packets corresponding to those the digests are received.

This strategy reduces the buffering requirements at receivers at, the
cost of introducing some buffering sent in that
stream of data packets at the sender,
since data packets are generated before their packet digests manifests.

2.1.1. Alternatives and Their Requirements

Other protocols that can provide authentication could also be
added to manifests.

The RECOMMENDED default hold times at receivers are:

o 2 seconds for data packets

o 10 seconds for packet digests

The sender MAY recommend different values used
for specific data streams, manifest delivery if defined later in order to tune different data streams for different performance
goals. The YANG model another specification. For
example a protocol that asymmetrically signs each packet, as the one
defined in Section 5 provides 3 of [RFC6584] does, would be a mechanism viable candidate
for senders
to communicate the sender's recommendation a delivery protocol for buffering durations,
when using DORMS.

Receivers SHOULD follow manifests that could be delivered over a
multicast transport, which could have some important scalability
benefits.

Other methods of securely transmitting metadata equivalent to the recommendations for hold times
metadata provided by the sender, subject "ietf-ambi" YANG model could also be used to their capabilities and any administratively
configured limits on buffer sizes at the receiver.

However receivers MAY deviate from
provide the values recommended by same security guarantees with the
sender for a variety manifest channels.
Defining other such possibilities is out of reasons. Decreasing the buffering durations
recommended by the server increases scope for this document.

2.2. System Security

By providing the risk of losing means to authenticate multicast packets, but AMBI aims
to avoid giving attackers who can be an appropriate tradeoff for specific network conditions and
hardware constraints on some devices.

2.2.1. Inter-packet Gap

It's RECOMMENDED that middle boxes forwarding buffered data packets
preserve the inter-packet gap between inject or modify packets in the same data
stream, and that receiving libraries
ability to attack application vulnerabilities that perform AMBI-based
authentication provide mechanisms might be possible
to expose exercise if those applications process the network arrival times attack traffic. Many
of packets to applications.

The purpose for this recommendation is to preserve the capability of
receivers to use techniques for available bandwidth detection or
network congestion based on observation entries in the Common Vulnerabilities and Exposures (CVE) list
at [CVE] (an extensive industry-wide database of packet times. Examples software
vulnerabilities) have documented a variety of
such techniques include paced chirping and pathrate.

Note system security
problems that this recommendation SHOULD NOT prevent the transmission of
an authenticated packet because the prior packet is unauthenticated.
This recommendation only asks implementations to delay the
transmission can result from maliciously generated UDP packets.

TBD: Fold in a mention of an authenticated packet to correspond to how off-path attacks are possible from most
places on the
interpacket gap if internet for interdomain multicast over AMT at an authenticated packet was previously transmitted
ingest point, and how the authentication multicast fanout downstream of the subsequent packet would otherwise burst
the packets that can
make it a good target if multicast sees more quickly.

This does not prevent the transmission use. A diagram plus a
cleaned-up version of packets out the on-list explanation here is probably
appropriate: https://mailarchive.ietf.org/arch/msg/mboned/
CG9FLjPwuno3MtvYvgNcD5p69I4/ [6]. Nightmare scenario is zero-day RCE
by off-path attacker that takes over a significant number of the
devices watching a major sports event.

See also work-in-progress: https://squarooticus.github.io/draft-
krose-multicast-security/draft-krose-multicast-security.html [7]

3. Protocol Operation

3.1. Overview

In order
according to their order of authentication, only the timing authenticate a data packet, AMBI receivers need to hold
these three pieces of
packets that are transmitted, after authentication, in information at the same order
they were received.

For receiver applications, the time that time:

o the original data packet was
received from the network SHOULD be made available to

o an authenticated manifest containing the receiving
application.

2.3. Packet Digests

2.3.1. Digest Profile

A packet digest is a message digest for a the
data packet, built
according to packet

o a digest profile defined by defining the sender.

The digest profile is defined by transformation from the sender, and specifies:

1. A cryptographically secure hash algorithm (REQUIRED)

2. A manifest data packet
to its packet digest

The manifests are delivered as a stream identifier

3. Whether of manifests over an
authenticated data channel. Manifest contents MUST be authenticated
before they can be used to hash the IP payload or the UDP payload. (see
Section 2.3.1.1) authenticate data packets.

The hash algorithm manifest stream is applied composed of an ordered sequence of manifests
that each contain an ordered sequence of packet digests,
corresponding to a pseudoheader followed by the
packet payload, original packets as determined by the digest profile. The computed
hash value is sent from their origin, in
the same order.

Note that a manifest contains potentially many packet digest.

TBD: there should also digests, and
its size can be a way to specify that only packets tuned to fit within a
specific UDP port are applicable. I think this convenient PDU (Protocol Data
Unit) of the manifest transport stream. By doing so, many packet
digests for the multicast data stream can be delivered per packet of
the manifest transport. The intent is not quite right
today and probably should that even with unicast-based
manifest transport, multicast-style efficiencies of scale can still
be done realized with only a grouping in relatively small unicast overhead, when
manifests use a unicast transport.

3.2. Buffering of Packets and Digests

Using different communication channels for the yang model,
so that manifest stream and
the profile appears either inside data stream introduces a "protocol" container
inside the (S,G) or inside possibility of desynchronization in the udp-stream inside
timing of the "protocol", but
am not sure. Follow-up on this after the first reference
implementation...

TBD: As recommended by https://tools.ietf.org/html/rfc7696#section-
2.2 [1], a companion document containing the mandatory-to-implement
cipher suite should also be published separately and referenced by
this document.

2.3.1.1. Payload Type

2.3.1.1.1. UDP vs. IP payload validation

When the digest profile indicates that UDP payloads are validated,
the IP protocol for received data between the different channels, so
receivers hold data packets MUST be UDP (0x11) and the payload
used for calculating the packet digest includes only the UDP payload,
with length as digests from the number of UDP payload octets, as calculated by
subtracting manifest
stream in buffers for some duration while awaiting the size arrival of
their counterparts.

While holding a data packet, if the UDP header from the UDP payload length.

When the corresponding packet digest profile indicates for
that IP payloads are validated, packet arrives in the
IP payload of secured manifest stream, the data packet
is used, using the outermost IP layer that
contains authenticated.

While holding an authenticated packet digest, if the (S,G) corresponding to the (S,G) protected by
data packet arrives with a matching packet digest, the
manifest. There data packet is no restriction on the IP protocols that can be
authenticated. The length field in

Authenticating a data packet consumes one packet digest and prevents
re-learning a digest for the pseudoheader is calculated by
subtracting same sequence number with a hold-down
time equal to the IP Header Length from hold time for packet digests. The hold-down is
necessary because a different manifest can send a duplicate packet
digest for the IP length, and same packet sequence number, either when repeating of
packet digests is equal used for resilience to loss or when rotating
authentication keys, so re-learning the number packet digest could allow a
replay of octets in the payload for a data packet. After authenticating a packet, the digest calculation.

2.3.1.1.2. Motivation

Full IP payloads often aren't available to receivers without extra
privileges on end user operating systems, so it's useful to provide a
way
and any future digests for the same data packet remain consumed if it
has been used to authenticate only a data packet, ignoring repeated
digests for the UDP payload, which is often same sequence number until after the only
portion of holddown timer
expires.

Once the data packet available to many is authenticated it can be further processed by
the receiving applications.

However, application or forwarded through the receiving network.

If the receiver's hold duration for some use cases a full IP payload is appropriate. For
example, when retrofitting some existing protocols, some packets may data packet expires without
authenticating the packet, the packet SHOULD be predictable or frequently repeated. Use dropped as
unauthenticated. If the hold duration of an IPSec
Authentication Header [RFC4302] is one way to disambiguate such
packets. Even though a manifest expires, packet
digests last received in that manifest MUST be discarded.

When multiple digests for the shared secret means same packet sequence number are
received, the Authentication
Header can't itself latest received time for an authenticated packet digest
should be used to authenticate for the expiration time.

3.2.1. Validation Windows

Since packet contents, digests are usually smaller than the
sequence number data packets, it's
RECOMMENDED that senders generate and send manifests with timing such
that the packet digests in a manifest will typically be received by
subscribed receivers before the Authentication Header can ensure that specific data packets corresponding to those
digests are not repeated at received.

This strategy reduces the IP layer, and so it's useful for AMBI
to have buffering requirements at receivers, at the capability
cost of introducing some buffering of data packets at the sender,
since data packets are generated before their packet digests can be
added to manifests.

The RECOMMENDED default hold times at receivers are:

o 2 seconds for data packets

o 10 seconds for packet digests

The sender MAY recommend different values for specific data streams,
in order to tune different data streams for different performance
goals. The YANG model in Section 6 provides a mechanism for senders
to communicate the sender's recommendation for buffering durations.
These parameters are "data-hold-time" and "digest-hold-time",
expressed in milliseconds.

Receivers MAY deviate from the values recommended by the sender for a
variety of reasons, including their own memory constraints or local
administrative configuration (for example, it might improve user
experience in some situations to hold packets longer than the server
recommended when there are receiver-specific delays in the manifest
stream that exceed the server's expectations). Decreasing the
buffering durations recommended by the server increases the risk of
losing packets, but can be an appropriate tradeoff for specific
network conditions and hardware or memory constraints on some
devices.

Receivers SHOULD follow the recommendations for hold times provided
by the sender (including the default values from the YANG model when
unspecified), subject to their capabilities and any administratively
configured overrides at the receiver.

3.2.2. Preserving Inter-packet Gap

It's RECOMMENDED that middle boxes forwarding buffered data packets
preserve the inter-packet gap between packets in the same data
stream, and that receiving libraries that perform AMBI-based
authentication provide mechanisms to expose the network arrival times
of packets to applications.

The purpose for this recommendation is to preserve the capability of
receivers to use techniques for available bandwidth detection or
network congestion based on observation of packet times and packet
dispersal, making use of known patterns in the sending. Examples of
such techniques include those described in [PathChirp], [PathRate],
and [WEBRC].

Note that this recommendation SHOULD NOT prevent the transmission of
an authenticated packet because the prior packet is unauthenticated.
This recommendation only asks implementations to delay the
transmission of an authenticated packet to correspond to the
interpacket gap if an authenticated packet was previously transmitted
and the authentication of the subsequent packet would otherwise burst
the packets more quickly.

This does not prevent the transmission of packets out of order
according to their order of authentication, only the timing of
packets that are transmitted, after authentication, in the same order
they were received.

For receiver applications, the time that the original packet was
received from the network SHOULD be made available to the receiving
application.

3.3. Packet Digests

3.3.1. Digest Profile

A packet digest is a message digest for a data packet, built
according to a digest profile defined by the sender.

The digest profile is defined by the sender, and specifies:

1. A cryptographically secure hash algorithm (REQUIRED)

2. A manifest stream identifier

3. Whether to hash the IP payload or the UDP payload. (see
Section 3.3.1.1)

The hash algorithm is applied to a pseudoheader followed by the
packet payload, as determined by the digest profile. The computed
hash value is the packet digest.

TBD: As recommended by https://tools.ietf.org/html/rfc7696#section-
2.2 [8], a companion document containing the mandatory-to-implement
cipher suite should also be published separately and referenced by
this document.

3.3.1.1. Payload Type

3.3.1.1.1. UDP vs. IP payload validation

When the manifest definition is at the UDP layer, it applies only to
packets with IP protocol of UDP (0x11) and the payload used for
calculating the packet digest includes only the UDP payload with
length as the number of UDP payload octets, as calculated by
subtracting the size of the UDP header from the UDP payload length.

When the manifest definition is at the IP layer, the payload used for
calculating the packet digest includes the full IP payload of the
data packets in the (S,G). There is no restriction on the IP
protocols that can be authenticated. The length field in the
pseudoheader is calculated by subtracting the IP Header Length from
the IP length, and is equal to the number of octets in the payload
for the digest calculation.

3.3.1.1.2. Motivation

Full IP payloads often aren't available to receivers without extra
privileges on end user operating systems, so it's useful to provide a
way to authenticate only the UDP payload, which is often the only
portion of the packet available to many receiving applications.

However, for some use cases a full IP payload is appropriate. For
example, when retrofitting some existing protocols, some packets may
be predictable or frequently repeated. Use of an IPSec
Authentication Header [RFC4302] is one way to disambiguate such
packets. Even though the shared secret means the Authentication
Header can't itself be used to authenticate the packet contents, the
sequence number in the Authentication Header can ensure that specific
packets are not repeated at the IP layer, and so it's useful for AMBI
to have the capability to authenticate such packets.

Another example: some services might need to authenticate the UDP
options [I-D.ietf-tsvwg-udp-options]. When using the UDP payload,
the UDP options would not be part of the authenticated payload, but
would be included when using the IP payload type.

Lastly, since (S,G) subscription operates at the IP layer, it's
possible that some non-UDP protocols will need to be authenticated.

2.3.2. authenticated,
and the IP layer allows for this. However, most user-space transport
applications are expected to use the UDP layer authentication.

3.3.2. Pseudoheader

When calculating the hash for the packet digest, the hash algorithm
is applied to a pseudoheader followed by the payload from the packet.
The complete sequence of octets used to calculate the hash is
structured as follows:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address (32 bits IPv4/128 bits IPv6) |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Address (32 bits IPv4/128 bits IPv6) |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Zeroes | Protocol | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port | Destination Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Manifest Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Data |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.3.2.1.

3.3.2.1. Source Address

The IPv4 or IPv6 source address of the packet.

2.3.2.2.

3.3.2.2. Destination Address

The IPv4 or IPv6 destination address of the packet.

2.3.2.3.

3.3.2.3. Zeroes

All bits set to 0.

2.3.2.4.

3.3.2.4. Protocol

The IP Protocol field from IPv4, or the Next Header field for IPv6.
When UDP payload is indicated, using UDP-layer authentication, this value MUST be is always UDP (0x11).

2.3.2.5. (0x11)
but for IP-layer authentication it can vary per-packet.

3.3.2.5. Length

The length in octets of the Payload Data field, expressed as an
unsigned 16-bit integer.

2.3.2.6.

3.3.2.6. Source Port

The source port of the packet. Zeroes if using a protocol that does
not use source ports.

2.3.2.7. Destination Port

The destination port of the packet. Zeroes if using a protocol that
does not use destination ports.

TBD: there's something I hate about the source and destination ports.
Maybe it should only be active in UDP-payload mode, instead of zeroes
when not UDP? But I suspect there's a better approach than UDP-or-
not, so it's this way Zeroes if using IP-layer
authentication for now, with hopes a non-UDP protocol.

3.3.2.7. Destination Port

The UDP destination port of finding something better
in the next version.

2.3.2.8. packet. Zeroes if using IP-layer
authentication for a non-UDP protocol.

3.3.2.8. Manifest Identifier

The 32-bit identifier for the manifest stream.

2.3.2.9.

3.3.2.9. Payload Data

The payload data includes either the IP payload or the UDP payload,
as indicated by the digest profile.

The payload type is configurable because when sending UDP, some
legacy networks may strip the UDP option space, and it's necessary to
provide a manifest stream capable of authentication that can
interoperate with these networks. However, for non-UDP traffic or in
order to authenticate the UDP options, some use cases may require
support for authenticating the full IP payload.

2.4.

3.4. Manifests

2.4.1.

3.4.1. Manifest Layout

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Manifest Stream Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Manifest sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| First packet sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Refresh Deadline |
|T| Packet Digest Count | TLV Space (present iff T set) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... Packet Content Expansions TLVs (Length=TLV Space or 0 if T unset) ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... Packet Digests ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.4.1.1.

3.4.1.1. Manifest Stream Identifier

A 32-bit unsigned integer chosen by the sender.

2.4.1.2. This value MUST be
equal to the "id" field in the manifest-stream in the "ietf-ambi"
model. If a manifest is seen that does not have the expected value
from the metadata provided for the manifest, the receiver MUST stop
processing this manifest and disconnect from this manifest stream.
It MAY reconnect with an exponential backoff starting at 1s, or it
MAY connect to an alternative manifest stream if one is known.

3.4.1.2. Manifest Sequence Number

A monotonically increasing 32-bit unsigned integer. Each manifest
sent by the sender increases this value by 1. On overflow it wraps
to 0.

It's RECOMMENDED to expire the manifest stream and start a new stream
for the data packets before a sequence number wrap is necessary.

2.4.1.3.

3.4.1.3. First Packet Sequence Number

A monotonically increasing 32-bit unsigned integer. Each packet in
the data stream increases this value by 1.

It's RECOMMENDED to expire the manifest stream and start a new stream
for the data packets before a sequence number wrap is necessary.

Note: for redundancy, especially if using a manifest stream with
unreliable transport, successive manifests MAY provide duplicates of
the same packet digest with the same packet sequence number, using
overapping sets of packet sequence numbers. When received, these
reset the hold timer for the listed packet digests.

2.4.1.4.

3.4.1.4. T bit (TLVs Present)

If 1, this indicates the TLV Length and TLV space fields are present.
If 0, this indicates neither field is present.

3.4.1.5. Packet Digest Count

A 15-bit unsigned integer equal to the count of packet digests in the
manifest.

3.4.1.6. TLV Space

A 16-bit unsigned integer with the length of the TLVs section.

3.4.1.7. TLVs

These are Type-Length-Value blocks, back to back. These may be
extended by future specifications.

These are composed of 3 fields:

o Type: an 8-bit unsigned integer indicating the type. Type values
in 0-127 have an 8-bit length, and type values in 128-255 have a
16-bit length.

o Length: a 8-bit or 16-bit unsigned integer indicating the length
of the value

o Value: a value with semantics defined by the Type field.

Defined values:

+------+----------+-------------------------------------------------+
| Type | Name | Value |
+------+----------+-------------------------------------------------+
| 0 | Pad | Length can be 0-255. Value is filled with 0 and |
| | | ignored by receiver. |
| | | |
| 128 | Refresh Deadline

A zero value When this field is |
| | | absent or zero, it means the current digest |
| | | profile for the current manifest stream is |
| | | stable. A nonzero value means that the |
| | | authentication is transitioning to a new |
| | | manifest stream, and the set of digest profiles |
| | | SHOULD be refreshed by receivers that might stay joined longer than this
duration, and a different manifest stream SHOULD be selected, before this many seconds have elapsed, |
| | | much time has elapsed in order to avoid a |
| | | disruption. See Section 2.5.

2.4.1.5. Packet Digest Count 3.5. |
+------+----------+-------------------------------------------------+

1-120 and 129-248 are unassigned 121-127 and 249-255 are reserved for
experiments

Any unknown values MUST be skipped and ignored by the receiver, using
the Length field to skip.

The count total size of the manifest in octets is exactly equal to:

Size of digests * packet count + 14 if T is 0 Size of digests in *
packet count + 16 + TLV Length if T is 1

The total size of the manifest.

2.4.1.6. TLV space is exactly equal to:

(2 + Length) summed for each TLV

The total size of the TLV space MUST exactly equal TLV Length. If
the TLV space exceeds the TLV Length, the receiver MUST disconnect,
and behave as if the Manifest Stream Identifier was wrong. This
state indicates a failed decoding of the TLV space.

3.4.1.8. Packet Digests

Packet digests appended one after the other, aligned to 8-bit
boundaries with zero 0-bit padding (if at the end if the bit length of the
digests are not multiples of 8 bits).

2.5. bits.

3.5. Transitioning to Other Manifest Streams

It's possible for multiple manifest streams authenticating the same
data stream to be active at the same time. The different manifest
streams can have different hash algorithms, manifest ids, and current
packet sequence numbers for the same data stream. These result in
different sets of packet digests for the same data packets, one
digest per packet per digest profile.

It's necessary sometimes to transition gracefully from one manifest
stream to another. The Refresh Deadline field TLV from the manifest is
used to signal to receivers the need to transition.

When a receiver gets a nonzero refresh deadline in a manifest the
sender SHOULD have an alternate manifest stream ready and available,
and the receiver SHOULD learn the alternate manifest stream, join the
new one, and leave the old one before the number of seconds given in
the refresh deadline. After the refresh deadline has expired, a
manifest stream MAY end. stop transmitting and close connections from the
server side. When multiple manifest-streams are provided in the
metadata, all or all but one SHOULD contain an expire-time, and new
or refreshing receivers SHOULD choose a manifest stream without an
expire-time, or with the latest expire-time if all manifests have an
expire-time.

The receivers SHOULD use start the refresh after a random value time delay
between now and one half the number of seconds in the deadline field, field
after the first manifest they receive containing a nonzero refresh
deadline. This time delay is to desynchronize the refresh attempts
in order to spread the spike of load on the DORMS server while
changing manifest profiles during a large multicast event.

4. Transport Considerations

3.1.

4.1. Overview

AMBI manifests MUST be authenticated, but any transport protocol
providing authentication can be used. This section discusses several
viable options for the use of an authenticating transport, and some
associated design considerations.

TBD: extend the 'manifest-transport' in the YANG model to make an
extensible mechanism to advertise different transport options for
receiving manifest streams. and some
associated design considerations.

TBD: add ALTA to the list when and if it gets further along
[I-D.draft-krose-mboned-alta-01].
[I-D.draft-krose-mboned-alta]. Sending an authenticatable multicast
stream (instead of the below unicast-based proposals) is a worthwhile
goal, else a 1% unicast authentication overhead becomes a new unicast
limit to the scalability.

TBD: probably should add quic also? Or maybe https is sufficient?

TBD: add a recommendation about scalability, like with DORMS, when
using a unicast hash stream. CDN or other kind of fanout solution
that can scale the delivery, and still generally hit the time window.

3.2.

4.2. HTTPS

This document defines a new media type 'application/ambi' for use
with HTTPS. URIs in the manifest-transport list with the scheme
'https' use this transport.

An HTTPS stream carrying the 'application/ambi' media type is
composed of a sequence of binary AMBI manifests. It is RECOMMENDED manifests, sent back to back in
the payload body (payload body is defined in Section 3.3 of
[RFC7230]).

Complete packet digests from partially received manifests MAY be used
by the receiver for authentication of data packets from the multicast
channel, even if the full manifest is not yet delivered.

4.3. TLS

This document defines the new uri scheme 'ambi+tls' for use with TLS
[RFC8446]. URIs in the manifest-transport list with the scheme
'ambi+tls' use Chunked encoding. this transport.

A TLS stream carrying AMBI manifests is composed of a sequence of
binary AMBI manifests, transmitted back to back.

Complete packet Digests from partially received manifests MAY be used
by the receiver for authentication, even if the full manifest is not
yet delivered.

3.3.

4.4. DTLS

TBD: DTLS [RFC6347] can provide authentication

This document defines the new uri scheme 'ambi+dtls' for datagrams, so if
manifests can be constructed use with
DTLS [RFC6347].

Manifests transported with DTLS have the tradeoff (relative to fit within datagrams, it is an
appropriate choice. (IPSec is similar-worth adding as an option?).

This option provides no native redundancy TLS or retransmission, but
packet digests can
HTTPS) that they might be repeated lost and not retransmitted or reordered,
but they will not cause head-of-line blocking or delay in different manifests to provide processing
data packets that arrived later. For some
resilience to loss. Lost manifests applications this is a
worthwhile tradeoff.

Note that loss of a single DTLS packet can result in the loss of blocks
of
multiple packet digests digests, which can be expensive, since they would make received mean failure to authenticate
multiple data packets unauthenticatable. TBD: should we therefore not support
this case? (probably still worthwhile-the manifests can still contain
redundant hashes)

3.4. DTLS + FECFRAME packets.

DTLS transport for manifests that do not fit into single-packet payloads can
still be delivered by using FECFRAME [RFC6363], particularly Reed-
Solomon [RFC6865] or possibly Raptor [RFC6681]. This has some
advantages compared supports one manifest per packet. It's
OPTIONAL to HTTPS because of the absence of HOL-blocking,
while providing provides for tunable redundancy. This has some advantages
relative redundancy in packet digests by
providing overlap in the packet sequence numbers across different
manifests, thereby sending some or all packet digests multiple times
to DTLS because of overhead reduction and non-integer avoid loss.

Future extensions might define extensions that can provide more
efficient redundancy tunability (e.g. 1.5 becomes via FEC. Those future extensions will require a viable redundancy factor).

TBD: define this method, possibly in another RFC.

4.
different URI scheme.

5. Examples

TBD: walk through some examples as soon as we have a build running.
Likely to need some touching up.

5. up of the spec along the way...

6. YANG Module

5.1.

6.1. Tree Diagram

The tree diagram below follows the notation defined in [RFC8340].

module: ietf-ambi

augment /dorms:metadata/dorms:sender/dorms:group/dorms:udp-stream: /dorms:dorms/dorms:metadata/dorms:sender/dorms:group
/dorms:udp-stream:
+--rw ambi
+--rw manifest-stream* [id]
+--rw id uint32
+--rw manifest-transport* manifest-stream* [uri]
| +--rw uri inet:uri
+--rw hash-algorithm iha:hash-algorithm-type
+--rw payload-type enumeration data-hold-time? uint32
+--rw digest-hold-time? uint32
+--rw expiration? yang:date-and-time
augment /dorms:dorms/dorms:metadata/dorms:sender/dorms:group:
+--rw ambi
+--rw manifest-stream* [id]
+--rw id uint32
+--rw manifest-stream* [uri]
| +--rw uri inet:uri
+--rw hash-algorithm iha:hash-algorithm-type
+--rw data-hold-time-ms? data-hold-time? uint32
+--rw digest-hold-time-ms? digest-hold-time? uint32

5.2.
+--rw expiration? yang:date-and-time

6.2. Module

<CODE BEGINS> file ietf-ambi@2020-10-31.yang ietf-ambi@2021-07-11.yang
module ietf-ambi {
yang-version 1.1;

namespace "urn:ietf:params:xml:ns:yang:ietf-ambi";
prefix "ambi";

import ietf-dorms {
prefix "dorms";
reference "I-D.jholland-mboned-dorms";
}

import ietf-inet-types {
prefix "inet";
reference "RFC6991 Section 4";
}

import iana-hash-algs {
prefix "iha";
reference "draft-ietf-netconf-crypto-types";
}
import ietf-yang-types {
prefix "yang";
reference "RFC 6991: Common YANG Data Types";
}

organization "IETF";

contact
"Author: Jake Holland
<mailto:jholland@akamai.com>
";

Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).

This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
for full legal notices.

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 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.

This module contains the definition for the AMBI data types.
It provides metadata for authenticating SSM channels as an
augmentation to DORMS.";

revision 2019-08-25 2021-07-08 {
description "Initial revision as an extension."; "Draft version.";
reference
"";
"draft-ietf-mboned-ambi";
}

augment
"/dorms:metadata/dorms:sender/dorms:group/dorms:udp-stream"

grouping manifest-stream-definition {
description "Definition of the
"This grouping specifies a manifest stream providing
integrity info for the data stream";

list manifest-stream {
key id;
description "Definition of
authenticating a manifest stream."; multicast data stream with AMBI";
leaf id {
type uint32;
mandatory true;
description
"The Manifest ID referenced in a manifest.";
}
leaf-list manifest-transport
list manifest-stream {
key uri;
leaf uri {
type inet:uri;
mandatory true;
description
"The URI for a stream of manifests.";
}
description "A URI that provides a location for the
manifest stream";
}
leaf hash-algorithm {
type iha:hash-algorithm-type;
mandatory true;
description
"The hash algorithm for the packet hashes within
manifests in this stream.";
}
leaf payload-type {
type enumeration {
enum udp {
description "The hash includes only the UDP
payload.";
}
enum ip {
description "The hash includes the full IP
payload.";
}
}
mandatory true;
description "The contents of the payload for the
digest profile";
}
leaf data-hold-time-ms data-hold-time {
type uint32;
default 2000;
units "milliseconds";
description
"The number of milliseconds to hold data packets
waiting for a corresponding digest before
discarding";
}
leaf digest-hold-time-ms digest-hold-time {
type uint32;
default 10000;
units "milliseconds";
description
"The number of milliseconds to hold packet
digests waiting for a corresponding data packet
before discarding";
}
leaf expiration {
type yang:date-and-time;
description
"The time after which this manifest stream may
stop providing authentication for the data stream.
When not present or empty there is no known expiration.";
}

}

augment
"/dorms:dorms/dorms:metadata/dorms:sender/dorms:group/"+
"dorms:udp-stream" {
description "AMBI extensions for securing UDP multicast.";

container ambi {
description "UDP-layer AMBI container for DORMS extension.";
list manifest-stream {
key id;
description "Manifest stream definition list.";
uses manifest-stream-definition;
}
}
}

augment
"/dorms:dorms/dorms:metadata/dorms:sender/dorms:group" {
description "AMBI extensions for securing IP multicast.";

container ambi {
description "IP-layer AMBI container for DORMS extension.";
list manifest-stream {
key id;
description "Definition of a manifest stream.";
uses manifest-stream-definition;
}
}
}
}
<CODE ENDS>

7. IANA Considerations

6.1.

7.1. The YANG Module Names Registry

This document adds one YANG module to the "YANG Module Names"
registry maintained at <https://www.iana.org/assignments/yang-
parameters>. The following registrations are made, per the format in
Section 14 of [RFC6020]:

name: ietf-ambi
namespace: urn:ietf:params:xml:ns:yang:ietf-ambi
prefix: ambi
reference: I-D.draft-jholland-mboned-ambi

6.2.

7.2. The XML Registry

This document adds the following registration to the "ns" subregistry
of the "IETF XML Registry" defined in [RFC3688], referencing this
document.

URI: urn:ietf:params:xml:ns:yang:ietf-ambi
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.

6.3.

7.3. Media Type

TBD: Register 'application/ambi' according to advice from:
https://www.iana.org/form/media-types
https://www.iana.org/form/media-types [9]

TBD: check guidelines in https://tools.ietf.org/html/rfc5226 [10]

7.4. URI Schemes

7.4.1. TLS

TBD: register 'ambi+tls' as a uri scheme according to advice from:
https://datatracker.ietf.org/doc/html/rfc7595 [11]

7.4.2. DTLS

TBD: check guidelines in https://tools.ietf.org/html/rfc5226

7. register 'ambi+dtls' as a uri scheme according to advice from:
https://datatracker.ietf.org/doc/html/rfc7595 [12]

8. Security Considerations

7.1.

8.1. Predictable Packets

Protocols that have predictable packets run the risk of offline
attacks for hash collisions against those packets. When
authenticating packets. When
authenticating a protocol that might have predictable packets, it's
RECOMMENDED to use a hash function secure against such attacks or to
add content to the packets to make them unpredictable, such as an
Authentication Header ([RFC4302]), or the addition of an ignored
field with random content to the packet payload.

TBD: explain attack from generating malicious packets and then
looking for collisions, as opposed to having to generate a collision
on packet contents that include a sequence number and then hitting a
match.

TBD: follow the rest of the guidelines: https://tools.ietf.org/html/
rfc3552

8.2. Attacks on Side Applications

A multicast receiver subscribes to an (S,G) and if it's a UDP
application, listens on a socket with a port number for packets to
arrive.

UDP applications sometimes bind to an "unspecified" address ("::" or
"0.0.0.0") for a particular UDP port, which will make the appliction
receive and process any packet that arrives on said port.

Forwarding multicast traffic opens a new practical attack surface
against receivers that have bound sockets using the "unspecified"
address and were operating behind a firewall and/or NAT. Such
applications will receive traffic from the internet only after
sending an outbound packet, and usually only for return packets with
the reversed source and destination port and IP addresses.

Multicast subscription and routing operates at the IP layer, so when
a multicst receive application subscribes to a channel, traffic with
the IP addresses for that channel will start arriving. There is no
selection for the UDP port at the routing layer that prevents
multicast IP traffic from arriving.

When an insecure application with a vulnerability is listening to a
UDP port on an unspecified address, it will receive multicast packets
arriving at the device and with that destination UDP port. Although
the primary problem lies in the insecure application, accepting
multicast subscriptions increases the attack scope against those
applications to include attackers who can inject a protocol that might have predictable packets, it's packet into a
properly subscribed multicast stream.

It's RECOMMENDED that senders using AMBI to use a hash function secure against such attacks or their traffic
include all IP traffic that they send in their DORMS metadata
information, and that firewalls using AMBI to
add content provide secure access
to the packets multicast traffic block multicast traffic destined to make them unpredictable, such as an
Authentication Header ([RFC4302]), or the addition unsecured
UDP ports on (S,G)s that have AMBI-based security for any traffic.
This mitigation prevents new forwarding of an ignored
field multicast traffic from
providing attackers with random content to the a packet payload.

TBD: explain inject capability access to new
attack surfaces from generating malicious packets and then
looking for collisions, as opposed to having to generate a collision
on packet contents that include a sequence number and then hitting a
match.

TBD: follow the rest of the guidelines: https://tools.ietf.org/html/
rfc3552

8. pre-existing insecure apps.

9. Acknowledgements

Many thanks to Daniel Franke, Eric Rescorla, Christian Worm
Mortensen, Max Franke, and Albert Manfredi for their very helpful
comments and suggestions.

10. References

9.1.

10.1. Normative References

[I-D.draft-ietf-mboned-dorms-00]

[I-D.draft-ietf-mboned-dorms]
Holland, J., "Discovery Of Restconf Metadata for Source-
specific multicast", draft-ietf-mboned-dorms-00 draft-ietf-mboned-dorms-01 (work in
progress), March October 2020.

[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/info/rfc2119>.

[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.

[RFC6363] Watson, M., Begen, A., and V. Roca, "Forward Error
Correction (FEC) Framework", RFC 6363,
DOI 10.17487/RFC6363, October 2011,
<https://www.rfc-editor.org/info/rfc6363>.

[RFC6681] Watson, M., Stockhammer, T.,

[RFC7230] Fielding, R., Ed. and M. Luby, "Raptor Forward
Error Correction (FEC) Schemes for FECFRAME", RFC 6681,
DOI 10.17487/RFC6681, August 2012,
<https://www.rfc-editor.org/info/rfc6681>.

[RFC6865] Roca, V., Cunche, M., Lacan, J., Bouabdallah, A., J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and K.
Matsuzono, "Simple Reed-Solomon Forward Error Correction
(FEC) Scheme for FECFRAME", Routing",
RFC 6865, 7230, DOI 10.17487/RFC6865, February 2013,
<https://www.rfc-editor.org/info/rfc6865>. 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>.

[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.

[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/info/rfc8174>.

[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.

9.2.

[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.

10.2. Informative References

[I-D.draft-krose-mboned-alta-01]

[CVE] MITRE, "Common Vulnerabilities and Exposures", September
1999, <https://cve.mitre.org/>.

[I-D.draft-krose-mboned-alta]
Rose, K. and J. Holland, "Asymmetric Loss-Tolerant
Authentication", draft-krose-mboned-alta-01 (work in
progress), July 2019.

[I-D.ietf-tsvwg-udp-options]
Touch, J., "Transport Options for UDP", draft-ietf-tsvwg-
udp-options-08
udp-options-12 (work in progress), September 2019. May 2021.

[PathChirp]
Ribeiro, V., Riedi, R., Baraniuk, R., Navratil, J.,
Cottrell, L., Department of Electrical and Computer
Engineering Rice University, and SLAC/SCS-Network
Monitoring, Stanford University, "pathChirp: Efficient
Available Bandwidth Estimation for Network Paths", 2003.

[PathRate]
Dovrolis, C., Ramanathan, P., and D. Moore, "Packet
dispersion techniques and a capacity estimation
methodology", IEEE/ACM Transactions on Networking, Volume
12, Issue 6, pp. 963-977. , December 2004.

[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<https://www.rfc-editor.org/info/rfc3552>.

[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.

[RFC4082] Perrig, A., Song, D., Canetti, R., Tygar, J., and B.
Briscoe, "Timed Efficient Stream Loss-Tolerant
Authentication (TESLA): Multicast Source Authentication
Transform Introduction", RFC 4082, DOI 10.17487/RFC4082,
June 2005, <https://www.rfc-editor.org/info/rfc4082>.

[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
DOI 10.17487/RFC4302, December 2005,
<https://www.rfc-editor.org/info/rfc4302>.

[RFC4383] Baugher, M. and E. Carrara, "The Use of Timed Efficient
Stream Loss-Tolerant Authentication (TESLA) in the Secure
Real-time Transport Protocol (SRTP)", RFC 4383,
DOI 10.17487/RFC4383, February 2006,
<https://www.rfc-editor.org/info/rfc4383>.

[RFC5776] Roca, V., Francillon, A., and S. Faurite, "Use of Timed
Efficient Stream Loss-Tolerant Authentication (TESLA) in
the Asynchronous Layered Coding (ALC) and NACK-Oriented
Reliable Multicast (NORM) Protocols", RFC 5776,
DOI 10.17487/RFC5776, April 2010,
<https://www.rfc-editor.org/info/rfc5776>.

[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.

9.3.

[RFC6584] Roca, V., "Simple Authentication Schemes for the
Asynchronous Layered Coding (ALC) and NACK-Oriented
Reliable Multicast (NORM) Protocols", RFC 6584,
DOI 10.17487/RFC6584, April 2012,
<https://www.rfc-editor.org/info/rfc6584>.

[WEBRC] Luby, M. and V. Goyal, "Wave and Equation Based Rate
Control Using Multicast Round Trip Time: Extended Report",
Digital Fountain Technical Report no. DF2002-07-001 ,
September 2002.

10.3. URIs

[1] https://github.com/GrumpyOldTroll/ietf-dorms-cluster

[2] https://datatracker.ietf.org/submit/note-well/

[3] https://www.ietf.org/mailman/listinfo/mboned

[4] https://mailarchive.ietf.org/arch/browse/mboned/

[5] https://www.iana.org/assignments/rmt-fec-parameters/rmt-fec-
parameters.xhtml

[6] https://mailarchive.ietf.org/arch/msg/mboned/
CG9FLjPwuno3MtvYvgNcD5p69I4/

[7] https://squarooticus.github.io/draft-krose-multicast-security/
draft-krose-multicast-security.html

[8] https://tools.ietf.org/html/rfc7696#section-2.2

[9] https://www.iana.org/form/media-types

[10] https://tools.ietf.org/html/rfc5226

[11] https://datatracker.ietf.org/doc/html/rfc7595

[12] https://datatracker.ietf.org/doc/html/rfc7595

Authors' Addresses

Jake Holland
Akamai Technologies, Inc.
150 Broadway
Cambridge, MA 02144
United States of America

Email: jakeholland.net@gmail.com

Kyle Rose
Akamai Technologies, Inc.
150 Broadway
Cambridge, MA 02144
United States of America

Email: krose@krose.org