wdiff rfc9238.original rfc9238.txt

Network Working Group

Independent Submission M. Richardson
Internet-Draft
Request for Comments: 9238 Sandelman Software Works
Intended status:
Category: Informational J. Latour
Expires: 22 September 2022
ISSN: 2070-1721 CIRA Labs
H. Habibi Gharakheili
UNSW Sydney
21 March
May 2022

On loading MUD

Loading Manufacturer Usage Description (MUD) URLs from QR codes
draft-richardson-mud-qrcode-07 Codes

Abstract

This informational document details a protocol to load MUD
definitions for devices which have no integrated Manufacturer
Usage Description (MUD) as described in RFC8520. definitions from RFC 8520 for devices that do
not have them integrated.

This document is published to inform the Internet community of this
mechanism to allow interoperability and to serve as a basis of other
standards work if there is interest.

// RFC-EDITOR-please-remove: This work is tracked at
// https://github.com/mcr/mud-qrcode

Status of This Memo

This Internet-Draft document is submitted in full conformance with not an Internet Standards Track specification; it is
published for informational purposes.

This is a contribution to the
provisions RFC Series, independently of BCP 78 any other
RFC stream. The RFC Editor has chosen to publish this document at
its discretion and BCP 79.

Internet-Drafts makes no statement about its value for
implementation or deployment. Documents approved for publication by
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Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list Standard;
see Section 2 of RFC 7841.

Information about the current Internet-
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Internet-Drafts are draft documents valid for a maximum status of six months this document, any errata,
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This Internet-Draft will expire on 22 September 2022.
https://www.rfc-editor.org/info/rfc9238.

This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. The SQRL Protocol . . . . . . . . . . . . . . . . . . . . 4
3.2. Manufacturer Usage Descriptions in SQRL . . . . . . . . . 5
3.2.1. B000 Company Name . . . . . . . . . . . . . . . . . . 6
3.2.2. B001 Product Name . . . . . . . . . . . . . . . . . . 6
3.2.3. B002 Model Number . . . . . . . . . . . . . . . . . . 6
3.2.4. MUD URL Data Record . . . . . . . . . . . . . . . . . 6
3.2.5. Device MAC Address . . . . . . . . . . . . . . . . . 7
4. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Generic URL or Version Specific Version-Specific URL . . . . . . . . . . . . . 8
6. Crowd Supply of MUD Files . . . . . . . . . . . . . . . . . . 8
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8.1. QR codes are not assurances . . . . . . . . . . . . . . . 9 Codes Are Not Assurances
8.2. MUD files can have signatures . . . . . . . . . . . . . . 10 Files Can Have Signatures
8.3. URL Shortening services can change content . . . . . . . 10 Services Can Change Content
8.4. MUD QR code stickers could be confused . . . . . . . . . 11 Code Stickers Could Be Confused
8.5. QR code can include Code Can Include a MAC address . . . . . . . . . . . . . 11 Address
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
11.1.
10.1. Normative References . . . . . . . . . . . . . . . . . . 12
11.2.
10.2. Informative References . . . . . . . . . . . . . . . . . 12
Acknowledgements
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13

1. Introduction

The Manufacturer Usage Description (MUD) [RFC8520] defines a YANG
data model to express what sort of access a device requires to
operate correctly. That document additionally defines three ways for
the device to to communicate to a network enforcement point the MUD
URL, i.e., URL (i.e., the URL of the resulting
MUD file in JSON [RFC8259]: [RFC8259]) to a network enforcement point: via DHCP,
within an X.509 certificate extension, and via LLDP. the Link Local
Discovery Protocol (LLDP).

Each of the above mechanism mechanisms conveys the MUD URL in-band, in band and requires
modifications to the device firmware. Most small IoT Internet of Things
(IoT) devices do not have LLDP, LLDP and often have very restricted DHCP
clients. Adding the LLDP or DHCP options requires at least some minimal
configuration
change, change and possibly entire entirely new subsystems.
Meanwhile, use of the PKIX certification extension only makes sense
as part of a larger
IDevID based [ieee802-1AR] deployment such based on an Initial Device Identifier
(IDevID) [IEEE802-1AR], for instance, as described in [RFC8995].

In the above cases cases, these mechanisms can only be implemented by
persons with access to modify and update the firmware of the device.

In the meantime meantime, there is a chicken or egg problem ([chickenegg]): [chickenegg].
That is, manufacturers are not motivated to (and thus likely do not)
include MUD URLs in their products, as they believe that there are no
gateways using those URLs. At the same time, gateways have little
incentive to (and thus likely do not) include code that processes MUD
URLs, as it is believed that no products have and or disseminate them. URLs.

The protocol described in this document allows any person with
physical access to the device to affix a reference to a MUD URL that
can later be scanned by an end user.

The QR-based protocol is presented as a convenient alternative when
the mechanisms from RFC 8520 [RFC8520] are not available to use, use on the device
or the gateway.

Affixing a sticker can be done by by:

* the marketing department of the Manufacturer, manufacturer,

* an outsourced assembler plant,

* value added value-added resellers (perhaps in response to a local RFP), request for
proposal (RFP)),

* a company importing the product (possibly to comply with a local
regulation),

* a network administrator (perhaps before sending devices home with
employees,
employees or to remote sites), and

* a retailer as a value added value-added service.

QRcodes

QR codes are informally described in [qrcode] and formally defined in
[isoiec18004]. The protocol described in this document uses a QRcode QR
code to encode the MUD URL. Specifically, the protocol leverages the
data format from the Reverse Logistics Association's Standardized
Quick Response for Logistics [SQRL].

SQRL codes are being put on devices via a sticker or via laser
etching into the case in order to deal with many situations, situations but
specifically for end-of-life processing for the device. An important
idea behind the effort is that clearly identifying a product permits
appropriate disposal, refurbishment refurbishment, or recycling of the components
of the product.

There are also use cases for SQRL described in which the codes are used as part
of regular maintenance for a product.

SQRL is an application of the 12N Data Identifier system specified by
the ANSI MH10.8.2 Committee [mh10] in a format appropriate for
QRcodes QR
codes, as well as other things like NFCs Normalization Form C (NFC)
transmissions.

QRcode

QR code generators are available as web services [qrcodewebservice], or as programs programs, such
as [qrencode].

Section 5 summarizes the considerations contained in
[I-D.ietf-opsawg-mud-acceptable-urls] section 6.1 ("Updating MUD URLs "Updating files
vs Updating MUD files"). URLs" (Section 7.1 of [MUD-URLS]). Due to the
immutable nature of the QRcode, QR code, MUD URLs in this document will need
to be non-firmware specific.

2. Terminology

Although this document is not an IETF Standards Track publication, it
adopts the conventions for normative language to provide clarity of
instructions to the implementer. 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.

Readers should be familiar with the terminology in [RFC8520],
including: MUD file, MUD URL, Manufacturer and manufacturer, MUD manager manager, and
controller.

3. Protocol

This QRcode

The QR code protocol builds upon the work by [SQRL]. That protocol
is very briefly described in Section 3.1. Then Then, the list of needed
Data Records to be filled in is explained.

3.1. The SQRL Protocol

[SQRL] documents an octet protocol that can be efficiently encoded
into QRcodes QR codes using a sequence of ASCII US-ASCII bytes, plus six control
codes (see section Section 3.1 of [SQRL]):

* <RS> Record Separator (ASCII (US-ASCII 30)

* <EoT> End of Transmission (ASCII (US-ASCII 4)

* <FS> Field Separator (ASCII (US-ASCII 28)

* <GS> Group Separator (ASCII (US-ASCII 29)

* <US> Unit Separator (ASCII 31), (US-ASCII 31)

* Concatenation Operator (ASCII (US-ASCII 43: "+"). "+")

Section 7.2 of [SQRL] gives the details, which can be summarized as:

1. The QR code header starts with:

"[)>" <RS> "06" <GS> "12N"

2. Include one or more Data Records. This consists of a four letter four-letter
Field Identifiers Identifier, followed by ASCII US-ASCII characters terminated with
a <Unit Separator>.

3. End with:

There

Additionally, there are additionally optional flags that may be present in every
Data Record Record, as described in section Section 7.4 of [SQRL]. These flags have
no bearing on MUD processing. A parser which that is only collecting MUD
URLs will not need to parse those flags. A general purpose general-purpose SQRL
parser will need more complexity.

Field Separator characters are used in SQRL to signify the beginning
of a new unit of data. A MUD specific MUD-specific parser that encounters a Field
Separator and has not yet collected the right MUD information MUST
ignore the characters collected so far and then restart.

Environment records, as described in [SQRL] section 7.4, Section 7.4 of [SQRL], look and
act exactly as fields, with a special Field Identifier. They serve
no purpose when looking for MUD information, information and MAY be ignored.

3.2. Manufacturer Usage Descriptions in SQRL

3.2.1. B000 Company Name

The B000 Data Record is mandatory in [SQRL]. It MUST be in ASCII US-ASCII
representation. It should be a representation of the company or
brand name. It SHOULD match the ietf-mud/mud/mfg-name in the MUD
file, however
file; however, the MUD file can contain arbitrary UTF8 UTF-8 for this
name, while the SQRL files are expected to be 7-bit US-ASCII.

3.2.2. B001 Product Name

The B001 Data Record is optional in [SQRL]. It is the Product Name
in ASCII. US-ASCII. Its presence is RECOMMENDED. Some third parties that
create QRcode QR code stickers might not know the product name with 100%
certainty,
certainty and MAY prefer to omit this rather than create further
confusion.

3.2.3. B002 Model Number

The B002 Data Record is optional in [SQRL], [SQRL] but is MANDATORY in this
profile. It is the Model Name in ASCII. US-ASCII. It SHOULD match the
optional ietf-mud/mud/model-name in the MUD file if that entry is
present in the MUD file. MUD files can contain arbitrary UTF8 UTF-8 for
the model-name, while the SQRL files are expected to be 7-bit US-
ASCII.

If a third party that is creating QRcodes can not QR codes cannot locate an official
model number when creating their MUD file and QRcode, QR code, then the third
party SHOULD make one up.

3.2.4. MUD URL Data Record

A new Field Identifier has been assigned by the Reverse Logistics
Association (RLA),
Association, which is "M180" "M180". This record MUST be filled with the
MUD URL.

Short URLs are easier to encode into QRcode a QR code because they require
fewer pixels of QRcode. QR code. More content in the QRcode QR code requires a
bigger image.

Use of URL shortening services (see [URLshorten]) can be useful useful,
provided that the service is stable throughout the lifetime of the
device and QRcode, QR code and that the privacy stance of the service is well
understood. The Security Considerations section of [RFC3986]
applies, particularly section Section 7.1.

Section 8.1 of [SQRL] also has some good advice on longevity concerns
with URLs.

The URL provided MUST NOT have a query (?) portion present. If one
is present, the query portion MUST be removed before processing.

3.2.5. Device MAC Address

If a MAC Media Access Control (MAC) address is used as a unique device
identifier (which is RECOMMENDED if possible), then it MUST be
included in this Data Record.

[SQRL] section

Section 9.10 of [SQRL] defines the Data Record: Record "M06C" as the MAC
address. No format for the MAC address is provided in that document.

This document RECOMMENDS

In this document, it is RECOMMENDED that 12 (or 16) hex octets are
used with no spaces or punctuation. (16 octets are used in the IEEE OUI-64
64-bit Extended Unique Identifier (EUI-64) format used in 802.15.4,
[IEEE.802.15.4] and some next generation Ethernet proposals) This
document RECOMMENDS use of upper-case proposals). In
this document, it is RECOMMENDED that uppercase hexadecimal letters. letters
be used.

Parsers that find punctuation (such as colons (":"), dashes ("-"),
US-ASCII Space (32), US-ASCII TAB (0), US-ASCII linefeed (10), or
white space) US-
ASCII carriage return (13)) MUST skip over it. Parses the punctuation. Parsers
MUST tolerate hexadecimal in
both upper, lower uppercase, lowercase, and even mixed
case. Systems SHOULD canonicalize it to upper case. uppercase.

4. Applicability

The use of stickers to convey MUD URLs would appear to have little
value when the stickers are applied by the end user end-user organization and
consumed by the same. This is particularly the case when the QR code
does not include the device MAC address. In such a situation situation, the
installer handling the device would scan the QR code to get the
appropriate MUD file reference, reference and have to input the associated MAC
address as well.

In such a case, one might wonder why the installer couldn't just
enter the appropriate MAC address and select the appropriate ACLs Access
Control Lists (ACLs) for the device. No Then a MUD file or QR code to
convey it the MAC address would not be useful at
all.

The needed. However, the use of a
MUD file (or QR code other or other way to convey it) has the advantage that MAC address) is
advantageous because it offers several layers of indirection:

1. The list of ACLs for a given device may be added or removed.

2. The ACLs may refer to DNS names, which may map to IPv4 or IPv6
addresses.

3. The entire file may be replaced, replaced and may also include supply chain
information, such as Software Bill of Materials (SBOM).

In addition, the mechanism to install a new device (MAC address) to
MUD file mapping does not need to permit any other network security
settings to be alterable by the person doing the installation.

5. Generic URL or Version Specific Version-Specific URL

MUD URLs which that are communicated in-band in band by the device, device and which that are
programmed into the device's firmware may provide a firmware specific firmware-specific
version of the MUD URL. This has the The advantage of this is that the resulting
Access Control Lists (ACLs)
ACLs enforced in the network are specific to the needs of that
version of the firmware.

A MUD URL which that is affixed to the device with a sticker, sticker or etched into
the case can not cannot be changed.

Given the considerations of [I-D.ietf-opsawg-mud-acceptable-urls]
section 6.1 ("Updating "Updating MUD URLs vs Updating MUD files"), files"
(Section 6.1 of [MUD-URLS]), it is prudent to use a MUD URL which that
points to a MUD file which that will only have new features added over time, time
and never have features removed. To recap, if a feature is removed
from the firmware, firmware and the MUD file still permits it it, then there is a
potential hole that could perhaps be exploited. The opposite
situation, where a MUD file wrongly forbids
something something, leads to false
positives in the security system, and the evidence is that this
results in the entire system being ignored. Preventing attacks on
core infrastructure may be more important than getting the ACL
perfect.

When the firmware eventually receives built-in MUD URL support, then
a more specific more-specific URL may be used.

Note that in many cases cases, it will be third parties who are generating
these QRcodes, QR codes, so the MUD file may be hosted by the third party.

6. Crowd Supply of MUD Files

At the time of writing, the IETF MUD is a new IETF Proposed Standard.
Hence, IoT device manufacturers have not yet provided MUD profiles
for their devices. A research group at the University of New South
Wales (UNSW Sydney) has developed an open-source tool, called MUDgee
([MUDgee]),
[MUDgee], which automatically generates a MUD file (profile) for an
IoT device from its traffic trace in order to make this process
faster, easier, and more accurate. Note that the generated profile
completeness solely depends on the completeness of the input traffic
traces. MUDgee assumes that all the activity seen is intended and
benign.

UNSW researchers have applied MUDgee to about 30 consumer IoT devices
from their lab testbed, testbed and publicly released their MUD files
([MUDfiles]).
[MUDfiles]. MUDgee can assist IoT manufacturers in developing and
verifying MUD profiles, while also helping adopters of these devices
to ensure they are compatible with their organisational organizational policies.

Similar processes have been done in a number of other public and
private labs. One of the strong motivations for this specification
is to allow for this work to leave the lab, lab and to be applied in the
field.

7. Privacy Considerations

The presence of the MUD URL in the QR code reveals the manufacturer
of the device, the type or model of the device, and possibly the
firmware version of the device.

The MAC address of the device will also need to be present, and this
is potentially Personally Identifiable Information (PII). Such
QRcodes QR
codes should not be placed on the outside of the packaging, packaging and only
on the device itself, ideally on a non-prominent part of the
device. device
(e.g., the bottom).

The QR code sticker should not be placed on any part of the device
that might become visible to machine vision systems in the same area.
This includes security systems, robotic vacuum cleaners, or anyone
taking a picture with a camera. Such systems may store the
picture(s) in such a way that a future viewer of the image will be
able to decode the QR code, possibly through an assembly of multiple
pictures. Of course, the QR code is not, however, a certain
indicator that the device is present, only that the QR code sticker
that came with the device is present.

The use of URL shorting services discussed in Section 3.2.4 may
result in trading convenience and efficiency with privacy, since the
service provider might leverage per-device or per-customer per-customer, short
URLs to track and correlate requests.

8. Security Considerations

8.1. QR codes are not assurances Codes Are Not Assurances

The mere presence of a QRcode QR code on a device does not in itself create
any security issues on its own. Neither an attached paper sticker or
nor a laser etched laser-etched code in a plastic case will affect the device
operation.

The QRcode QR code is not active, active; in general, it is not in general able to communicate on
using nearby networks. It is conceivable that something more active
is concealed in the sticker: sticker, e.g., an NFC or RFID tag for instance. a Radio Frequency
Identification (RFID) tag. But, any sticker could contain such a thing:
thing, e.g., on some university campuses campuses, stickers are often used as
part of political campaigns, campaigns and can be found attached all over the
place.

Security issues that this protocol create creates are related to assumptions
that the presence of the QRcode QR code might imply. The presence of the
QRcode QR
code may imply to some owners or network operators that the
behaviour behavior
of the device has been vetted by some authority. It is here that
some caution is required.

A possibly bigger risk from application of MUD file stickers to
devices is that they may begin to convey a sense of safety to users
of the device. The presence of the sticker, possibly with the logo
of the physical establishment in which the device is located located, could
convey to occupants of the establishment that this device is an
official device. For device, for instance, a university which that only deploys sensors
on the university campus that have been vetted for compliance against
a MUD definition.

The risk is then of social engineering: engineering, e.g., any device with a reasonable
looking QRcode
reasonable-looking QR code may be seen as a trusted device (even
though such trust is not justified based on that evidence.) evidence). An
attacker that wishes to infiltrate their own devices need only
suitably camouflage the device with an appropriate sticker in order
to convey legitimacy.

8.2. MUD files can have signatures Files Can Have Signatures

The network operator who takes the MUD file designated by the QRcode QR code
needs to be careful that they are validating the signature on the MUD
file. Not only The network operator needs to verify that the file is intact, but intact
and that the signer of the file is authorized to sign MUD files for
that vendor, or that the
network operator has some trust if the a MUD file is a crowd sourced
definition. At the time of writing, crowd-sourced definition, they
need to establish if it can be trusted. [RFC8520] does not define
any infrastructure to authenticate or authorize MUD file signers.

8.3. URL Shortening services can change content Services Can Change Content

If a URL shorterning shortening service is used, it is possible that the MUD
Controller is
controller will be redirected to another MUD file with different
content. The use of MUD signatures can detect attacks on the
integrity of the file. To do this, the MUD controller needs to be
able to verify the signature on the file.

If a Trust On First Use Trust-On-First-Use (TOFU) policy is used for signature trust
anchors, then the URL shortening service can still attack, attack if it
substitutes content and signature on the first use. MUD controllers
and the people operating them need to be cautious when using TOFU.

8.4. MUD QR code stickers could be confused Code Stickers Could Be Confused

Another issue with the stickers is that the wrong sticker could be
applied to a device by a reseller or other another trusted party, either in
error,
error or via some physical or socially engineered attack against that
party. The network operator now onboards a device, device and applies what
they think is a legitimate network policy for the device in their
hands, only it is in fact a policy for another kind of device.

Careful examination of stickers is in order!

8.5. QR code can include Code Can Include a MAC address Address

Inclusion of the device specific device-specific MAC address (described in
Section 3.2.5) in the QRcode QR code makes use of the MUD code much easier easier,
as it identifies the device specifically. If the MAC address is not
included, then a network operator, having the device in their hands,
has to associate the policy with the device through some other
interface.

Despite the significant advantage of having the MAC address included,
it is unlikely that third party third-party stickers will include that. it. Including
the MAC address requires that a unique sticker with a
QRcode QR code be
created for each device. This is possible if the sticker is applied
by a manufacturer: manufacturer; it is already common to have a serial number and
MAC address on the outside of the device. In that case, if the QRcode QR
code is part of that sticker, then the customization problem is not
that complex.

For cases where a third party has produced the QRcode, QR code, it is likely
that every device of a particular model will have the same QRcode QR code
applied, omitting the MAC address. This increases the possibility
that the wrong policy will be applied to a device.

9. IANA Considerations

This document makes has no request for IANA actions.

10. Acknowledgements

This work was supported by the Canadian Internet Registration
Authority (cira.ca).

11. References

11.1.

10.1. Normative References

[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>.

[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>.

[RFC8520] Lear, E., Droms, R., and D. Romascanu, "Manufacturer Usage
Description Specification", RFC 8520,
DOI 10.17487/RFC8520, March 2019,
<https://www.rfc-editor.org/info/rfc8520>.

[SQRL] Reverse Logistics Association, "SQRL Codes: Standardized
Quick Response for Logistics, Using the 12N Data
Identifier", February 2017,
<https://rla.org/resource/12n-documentation>.

11.2.

10.2. Informative References

[chickenegg]
Wikipedia, "Chicken or the egg", December 2019,
<https://en.wikipedia.org/wiki/Chicken_or_the_egg>.

[I-D.ietf-opsawg-mud-acceptable-urls]
Richardson, M., Pan, W., and E. Lear, "Authorized update
to MUD URLs", Work in Progress, Internet-Draft, draft-
ietf-opsawg-mud-acceptable-urls-04, 6 October 2021,
<https://www.ietf.org/archive/id/draft-ietf-opsawg-mud-
acceptable-urls-04.txt>.

[ieee802-1AR] April 2022,
<https://en.wikipedia.org/w/
index.php?title=Chicken_or_the_egg&oldid=1081728488>.

[IEEE.802.15.4]
IEEE, "IEEE Standard for Low-Rate Wireless Networks", IEEE Standard,
Std. 802.15.4-2015, DOI 10.1109/IEEESTD.2016.7460875,
April 2016,
<https://ieeexplore.ieee.org/document/7460875>.

[IEEE802-1AR]
IEEE, "IEEE 802.1AR Standard for Local and Metropolitan Area
Networks - Secure Device Identifier",
2009, <http://standards.ieee.org/findstds/
standard/802.1AR-2009.html>. Identity", IEEE Std 802.1AR-2018,
August 2018,
<https://standards.ieee.org/ieee/802.1AR/6995/>.

[isoiec18004]
ISO/IEC, "Information technology - Automatic
identification and data capture techniques - QR Code bar
code symbology specification (ISO/IEC 18004)", specification", ISO/IEC 18004:2015,
February 2015.

[mh10] "ANSI MH10.8.2 Committee", May 2021, ANSI, "Data Identifier and Application Identifier
Standard", ANSI MH10.8.2-2016, June 2016,
<https://webstore.ansi.org/Standards/MHIA/ANSIMH102016>.

[MUD-URLS] Richardson, M., Pan, W., and E. Lear, "Authorized update
to MUD URLs", Work in Progress, Internet-Draft, draft-
ietf-opsawg-mud-acceptable-urls-04, 6 October 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
mud-acceptable-urls-04>.

[MUDfiles] UNSW Sydney, "MUD Profiles", July 2019,
<https://iotanalytics.unsw.edu.au/mud/>.

[MUDgee] Hamza, A., "MUDgee", commit f63a88d, July 2019,
<https://github.com/ayyoob/mudgee>.

[qrcode] Wikipedia, "QR Code", December 2019,
<https://en.wikipedia.org/wiki/QR_code>.

[qrcodewebservice]
Internet, "QR Code Generators", December 2019,
<https://duckduckgo.com/?q=QR+code+web+generator>. code", April 2022,
<https://en.wikipedia.org/w/
index.php?title=QR_code&oldid=1082559657>.

[qrencode] Fukuchi, K., "QR encode", December 2019,
<https://fukuchi.org/works/qrencode/index.html.en>. "libqrencode", commit 715e29f, September 2020,
<https://github.com/fukuchi/libqrencode>.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.

[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.

[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/info/rfc8995>.

[URLshorten]
Wikipedia, "URL shortening", May 2021,
<https://en.wikipedia.org/wiki/URL_shortening>. April 2022,
<https://en.wikipedia.org/w/
index.php?title=URL_shorteningg&oldid=1084979184>.

Acknowledgements

This work was supported by the Canadian Internet Registration
Authority (cira.ca).

Authors' Addresses

Michael Richardson
Sandelman Software Works
Email: mcr+ietf@sandelman.ca

Jacques Latour
CIRA Labs
Email: Jacques.Latour@cira.ca

Hassan Habibi Gharakheili
UNSW Sydney
Email: h.habibi@unsw.edu.au