ADD WG T. Reddy
Internet-Draft McAfee
Intended status: Standards Track D. Wing
Expires: November 6, 2020 Citrix
M. Richardson
Sandelman Software Works
M. Boucadair
Orange
May 5, 2020
A Bootstrapping Procedure to Discover and Authenticate DNS-over-TLS and
DNS-over-HTTPS Servers for IoT and BYOD Devices
draft-reddy-add-iot-byod-bootstrap-00
Abstract
This document specifies mechanisms to bootstrap endpoints (e.g.,
hosts, IoT devices) to discover and authenticate DNS-over-TLS and
DNS-over-HTTPS servers provided by a local network for IoT/BYOD
devices in Enterprise networks.
Status of This Memo
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provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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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 November 6, 2020.
Copyright Notice
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document authors. All rights reserved.
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carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Bootstrapping Endpoint Devices . . . . . . . . . . . . . . . 5
5. Bootstrapping IoT Devices . . . . . . . . . . . . . . . . . . 8
6. Connection Handshake and Service Invocation . . . . . . . . . 9
7. EST Service Discovery Procedure . . . . . . . . . . . . . . . 10
8. Network Reattachment . . . . . . . . . . . . . . . . . . . . 10
9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 12
10. Security Considerations . . . . . . . . . . . . . . . . . . . 12
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
13.1. Normative References . . . . . . . . . . . . . . . . . . 13
13.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
Traditionally a caching DNS server has been provided by local
networks. This provides benefits such as low latency to reach that
DNS server (owing to its network proximity to the endpoint).
However, if an endpoint is configured to use Internet-hosted or
public DNS-over-TLS (DoT) [RFC7858] or DNS-over-HTTPS (DoH) [RFC8484]
servers, any available local DNS server cannot serve DNS requests
from local endpoints. If public DNS servers are used instead of
using local DNS servers, some operational problems can occur such as
those listed below:
o "Split DNS" [RFC2775] to use the special internal-only domain
names (e.g., "internal.example.com") in enterprise networks will
not work, and ".local" and "home.arpa" names cannot be locally
resolved in home networks.
o Content Delivery Networks (CDNs) that map traffic based on DNS may
lose the ability to direct end-user traffic to a nearby service-
specific cluster in cases where a DNS service is being used that
is not affiliated with the local network and which does not send
"EDNS Client Subnet" (ECS) information [RFC7871] to the CDN's DNS
authorities [CDN].
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If public DNS servers are used instead of local DNS servers, the
following discusses the impacts on network-based security:
o Various network security services are provided by Enterprise
networks to protect endpoints (e.g,. Hosts, IoT devices).
Network-based security solutions such as firewalls (FW) and
Intrusion Prevention Systems (IPS) rely on network traffic
inspection to implement perimeter-based security policies. The
network security services may for example prevent malware
download, block known malicious URLs, enforce use of strong
ciphers, stop data exfiltration, etc. These network security
services act on DNS requests originating from endpoints. However,
if an endpoint is configured to use public DoH/DoT servers,
network security services cannot act on DNS requests from these
endpoints.
o In order to act on DNS requests from endpoints, network security
services can block DoT traffic by dropping outgoing packets to
destination port 853. Identifying DoH traffic is far more
challenging than DoT traffic. Network security services may try
to identify the domains offering DoH servers, and DoH traffic can
be blocked by dropping outgoing packets to these domains. If an
endpoint has enabled strict privacy profile (Section 5 of
[RFC8310]), and the network security service blocks the traffic to
the public DNS server, the DNS service won't be available to the
endpoint and ultimately the endpoint cannot access Internet-
reachable services.
o If an endpoint has enabled opportunistic privacy profile
(Section 5 of [RFC8310]), and the network security service blocks
traffic to the public DNS server, the endpoint will either
fallback to an encrypted connection without authenticating the DNS
server provided by the local network or fallback to clear text
DNS, and cannot exchange encrypted DNS messages.
If the network security service fails to block DoH/DoT traffic, this
can compromise the endpoint security; some of the potential security
threats are listed below:
o The network security service cannot prevent an endpoint from
accessing malicious domains.
o If the endpoint is an IoT device which is configured to use public
DoH/DoT servers, and if a policy enforcement point in the local
network is programmed using, for example, a Manufacturer Usage
Description (MUD) file [RFC8520] by a MUD manager to only allow
intented communications to and from the IoT device, the policy
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enforcement point cannot enforce the network Access Control List
(ACL) rules based on domain names (Section 8 of [RFC8520]).
If the network security service successfully blocks DoT and DoH
traffic, this can still compromise the endpoint security and privacy;
some of the potential security threats are listed below:
o Networks are susceptible to internal attacks as discussed in
Section 3.2 of [I-D.arkko-farrell-arch-model-t]. An internal
attacker can modify the DNS responses to re-direct the client to
malicious servers.
o Pervasive monitoring of DNS traffic.
In addition, the local network's DNS server is advertised using DHCP/
RA which is insecure and also provides no mechanism to securely
authenticate the DNS server. To overcome the above threats, this
document specifies a mechanism to bootstrap endpoints to discover and
authenticate the DoT and DoH servers provided by their local network.
The overall procedure can be structured into the following steps:
o Bootstrapping (Section 4) is necessary only when connecting to a
new network or when the network's DNS certificate has changed.
Bootstrapping procedure authenticates the Enrollment over Secure
Transport (EST) [RFC7030] server to the endpoint. After
authenticating the EST server, DNS server certificate used by the
local network is downloaded to the endpoint. This DNS server
certificate enables subsequent authenticated encrypted
communication with the local DNS server (e.g., DoH) during in the
connection phase.
o Connection handshake and service invocation (Section 6): The DNS
client initiates a TLS handshake with the DNS server learned in
the discovery phase, and validates the DNS server's identity using
the credentials obtained in the bootstrapping phase.
Note: The strict and opportunistic privacy profiles as defined in
[RFC8310] only applies to DoT protocol, there has been no such
distinction made for DoH protocol.
2. Scope
The problems discussed in Section 1 will be encountered in Enterprise
networks. Typically Enterprise networks do not assume that all
devices in their network are managed by the IT team or Mobile Device
Management (MDM) devices, especially in the quite common BYOD ("Bring
Your Own Device") scenario. The mechanisms specified in this
document can be used by BYOD devices to discover and authenticate DoT
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and DoH servers provided by the Enterprise network. This mechanism
can also be used by IoT devices (managed by IT team) after onboarding
to discover and authenticate DoT and DoH servers provided by the
Enterprise network.
WLAN as frequently deployed is vulnerable to various attacks
([Evil-Twin],[Krack] and [Dragonblood]). Because of these attacks,
only cryptographically authenticated communications are trusted on
WLAN networks. This means information provided by the network via
DHCP, DHCPv6, or RA (e.g., NTP server, DNS server, default domain)
are untrusted because DHCP and RA are not authenticated.
[I-D.btw-add-home] discusses DoH/DoT server discovery using DHCP/RA
but requires the DoH/DoT server to be pre-configured in the endpoint
(OS or Browser) or the DNS client must be able cryptographically
identify it is connecting to a DoT/DoH server hosted by a specific
organization (e.g., ISP or Enterprise) (see
[I-D.reddy-add-server-policy-selection]) to prevent the client from
connecting to a attackers server.
Users have to indicate to their system in some way that they desire
bootstrapping to be performed only when connecting to a specific
network (e.g., organization for which a user works or a user works
temporarily within another corporation), similar to the way users
disable VPN connection in specific network (e.g., Enterprise network)
and enable VPN connection by default in other networks. If the
discovered DNS server meets the privacy preserving data policy
requirements of the user, the user can select to use the discovered
DoT and DoH servers.
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 BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
This document makes use of the terms defined in [RFC8499] and
[I-D.ietf-dnsop-terminology-ter].
'DoH/DoT' refers to DNS-over-HTTPS and/or DNS-over-TLS.
4. Bootstrapping Endpoint Devices
If an endpoint uses the credentials (username and password) provided
by the IT admin to mutually authenticate to the Enterprise WLAN
Access Point, the following steps can be used to securely bootstrap
the endpoint with the authentication domain name (ADN, defined in
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[RFC8310] and DNS server certificate of the local network's DoH/DoT
server:
1. The endpoint authenticates to the local network and discovers the
Enrollment over Secure Transport (EST) [RFC7030] server using the
procedure discussed in Section 7.
2. The endpoint establishes provisional TLS connection with that EST
server, i.e., the endpoint provisionally accepts the unverified
TLS server certificate. However, the endpoint MUST authenticate
the EST server before it accepts the DNS server certificate. The
endpoint either uses password-based authenticated key exchange
(PAKE) with TLS 1.3 [I-D.barnes-tls-pake] as an authentication
method or uses the mutual authentication protocol for HTTP
[RFC8120] to authenticate the discovered EST server.
As a reminder, PAKE is an authentication method that allows the
use of usernames and passwords over unencrypted channels without
revealing the passwords to an eavesdropper. Similarly, the
mutual authentication for HTTP is based on PAKE and provides
mutual authentication between an HTTP client and an HTTP server
using username and password as credentials. The cryptographic
algorithms to use with the mutual authentication protocol for
HTTP are defined in [RFC8121].
Note that the Crypto Forum Research Group (cfrg) is discussing
selection of one or more PAKE to recommend to the wider IETF
community. This step will be further updated to reflect the
outcome of the discussion.
3. The endpoint needs to use PAKE scheme to perform authentication
the first time it connects to an EST server. If the EST server
authentication is successful, the server's identity can be used
to authenticate subsequent TLS connections to that EST server.
The endpoint configures the reference identifier for the EST
server using the DNS-ID identifier type in the EST server
certificate. On subsequent connections to the EST server, the
endpoint MUST validate the EST server certificate using the
Implict Trust Anchor database (i.e, the EST server certificate
must pass PKIX certification path validation [RFC6125]) and match
the reference identifier against the EST server's identity
according to the rules specified in Section 6.4 of [RFC6125].
4. The endpoint learns the End-Entity certificates [RFC8295] from
the EST server. The certificate provisioned to the DNS server in
the local network will be treated as a End-Entity certificate.
As a reminder, the End-Entity certificates must be validated by
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the endpoint using an authorized trust anchor (Section 3.2 of
[RFC8295]). The endpoint needs to identify the certificate
provisioned to the DNS server. The SRV-ID identifier type
[RFC6125] within subjectAltName entry MUST be used to identify
the DNS server certificate.
For example, DNS server certificate will include SRV-ID "_domain-
s.example.net" along with DNS-ID "example.net". The SRV service
label "domain-s" is defined in Section 6 of [RFC7858] for DoT
protocol. The SRV service label "doh" is defined in Section 10.4
of [I-D.btw-add-home] for DoH protocol.
5. The endpoint configures the authentication domain name (ADN)
(defined in [RFC8310]) for the DNS server from the DNS-ID
identifier type within subjectAltName entry in the DNS server
certificate. The DNS server certificate is associated with the
ADN to be matched with the certificate given by the DNS server in
TLS. To some extent, this approach is similar to certificate
usage PKIX-EE(1) defined in [RFC7671].
Figure 1 illustrates a sequence diagram for bootstrapping an endpoint
with the local network's ADN and DNS server certificate.
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+----------+ +--------+ +--------+
| Endpoint | | EST | | DNS |
| | | Server | | Server |
+----------+ +--------+ +--------+
| DNS-SD query to discover the EST server | |
|-------------------------------------------------------->|
| | |
| optional: mDNS query to | |
| discover the EST server | |
|--------------------------------------------->| |
| | |
| Establish provisional TLS connection | |
|<-------------------------------------------->| |
| | |
| PAKE scheme to authenticate the EST server | |
|<-------------------------------------------->| |
| | |
[Generate reference identifier for the EST server | |
to compare with the EST server certificate | |
in subsequent TLS connections] | |
| | |
| Get EE certificates | |
|--------------------------------------------->| |
| | |
[Identify the DNS server certificate in EE | |
certificates to match with the certificate | |
by the DNS server in TLS handshake] | |
| |
[Configure ADN and associate DNS server certificate] | |
| | |
Figure 1: Bootstrapping Endpoint Devices
5. Bootstrapping IoT Devices
The following steps explain the mechanism to bootstrap IoT devices
supporting Bootstrapping Remote Secure Key Infrastructures (BRSKI)
discussed in [I-D.ietf-anima-bootstrapping-keyinfra] with local
network's CA certificates, ADN and DNS server certificate:
o Bootstrapping Remote Secure Key Infrastructures (BRSKI) discussed
in [I-D.ietf-anima-bootstrapping-keyinfra] provides a solution for
secure automated bootstrap of devices. BRSKI specifies means to
provision credentials on devices to be used to operationally
access networks. In addition, BRSKI provides an automated
mechanism for the bootstrap distribution of CA certificates from
the EST server. The IoT device can use BRSKI to bootstrap the IoT
device using the IoT manufacturer provisioned X.509 certificate,
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in combination with a registrar provided by the local network and
IoT device manufacturer's authorizing service (MASA):
1. The IoT device authenticates to the local network using the
IoT manufacturer provisioned X.509 certificate. The IoT
device can request and get a voucher from the MASA service via
the registrar. The voucher is signed by the MASA service and
includes the local network's CA public key.
2. The IoT device validates the signed voucher using the
manufacturer installed trust anchor associated with the MASA,
stores the CA's public key and validates the provisional TLS
connection to the registrar.
3. The IoT device requests the full EST distribution of current
CA certificates (Section 5.9.1 in
[I-D.ietf-anima-bootstrapping-keyinfra]) from the registrar
operating as a BRSKI-EST server. The IoT devices stores the
CA certificates as Explicit Trust Anchor database entries.
The IoT device uses the Explicit Trust Anchor database to
validate the DNS server certificate.
4. The IoT device learns the End-Entity certificates from the
BRSKI-EST server. The certificate provisioned to the DNS
server in the local network will be treated as an End-Entity
certificate. The IoT device needs to identify the certificate
provisioned to the DNS server. The SRV-ID identifier type
within subjectAltName entry MUST be used to identify the DNS
server certificate (see Step 4 in Section 4).
5. The endpoint configures the ADN for the DNS server from the
DNS-ID identifier type within subjectAltName entry in the DNS
server certificate. The DNS server certificate is associated
with the ADN to be matched with the certificate given by the
DNS server in TLS.
6. Connection Handshake and Service Invocation
The DNS client resolves the ADN using the mechanism discussed in
Section 7.2 of [RFC8310]. The DNS client initiates TLS handshake
with the DNS server, the DNS server presents its certificate in
ServerHello message, and the DNS client MUST match the DNS server
certificate downloaded in Step 4 in Section 4 or Section 5 with the
certificate provided by the DNS server in TLS handshake. If the
match is successful, the DNS client MUST validate the server
certificate using an authorized trust anchor.
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If the match is successful and server certificate is successfully
validated, the client continues with the connection as normal.
Otherwise, the client MUST treat the server certificate validation
failure as a non-recoverable error. If the DNS client cannot reach
or establish an authenticated and encrypted connection with the
privacy-enabling DNS server provided by the local network, the DNS
client can fallback to the privacy-enabling public DNS server.
Note: This section will be further updated to reflect the outcome of
the discussion in [I-D.btw-add-home] for a DoH client to retrieve the
list of supported URI templates by a DoH server (Section 3 of
[RFC8484]).
7. EST Service Discovery Procedure
An EST client discovers the EST server in the local network by using
DNS-based Service Discovery (DNS-SD) [RFC6763] or Multicast DNS
(mDNS) [RFC6762]. The <Domain> portion specifies the DNS sub-domain
where the service instance is registered. It may be "local.",
indicating the mDNS local domain, or it may be a conventional domain
name such as "example.com.". The <Service> portion of the EST
service instance name MUST be "_est._tcp".
A EST client application can proactively discover an EST server being
advertised in the site by multicasting a PTR query to the following:
"_est._tcp.local"
An EST server can send out gratuitous multicast DNS answer packets
whenever it starts up, wakes from sleep, or detects a change in EST
server configuration. EST client application can receive these
gratuitous packets and cache information contained in them.
8. Network Reattachment
On subsequent attachments to the network, the endpoint discovers the
privacy-enabling DNS server using the authentication domain name
(configured in Step 5 of Section 4 or Section 5), initiates TLS
handshake with the DNS server and follows the mechanism discussed in
Section 6 to validate the DNS server certificate.
If the DNS server certificate is invalid (e.g., revoked or expired)
or the procedure to discover the privacy-enabling DNS server fails
(e.g. The domain name of the privacy-enabling DNS server has changed
because the Enterprise network has switched to a public privacy-
enabling DNS server capable of blocking access to malicious domains),
the endpoint discovers and initiates TLS handshake with the EST
server, and uses the validation techniques described in [RFC6125] to
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compare the reference identifier (created in Step 2 of Section 4 in
this document) to the EST server certificate and verifies the entire
certification path as per [RFC5280]. The endpoint then gets the DNS
server certificate from the EST server. If the DNS-ID identifier
type within subjectAltName entry in the DNS server certificate does
not match the configured ADN, the ADN is replaced with the DNS-ID
identifier type. The DNS server certificate associated with the ADN
is replaced with the one provided by the EST server. If the ADN has
changed, the endpoint discovers the privacy-enabling DNS server,
initiates TLS handshake with the DNS server and follows the mechanism
discussed in Section 6 to validate the DNS server certificate.
Figure 2 illustrates a sequence diagram for re-configuring an
endpoint with ADN and local network's DNS server certificate on
subsequent attachments to the network.
+----------+ +--------+ +--------+
| Endpoint | | EST | | DNS |
| | | Server | | Server |
+----------+ +--------+ +--------+
| DNS-SD query to discover the EST server | |
|-------------------------------------------------------->|
| | |
| optional: mDNS query to | |
| discover the EST server | |
|--------------------------------------------->| |
| | |
| Establish TLS connection | |
| and validate EST server certificate | |
|<-------------------------------------------->| |
| | |
| Get EE certificates | |
|<-------------------------------------------->| |
| | |
[Identify the DNS server certificate in EE | |
certificates to match with the certificate | |
by the DNS server in TLS handshake] | |
| |
[Re-configure ADN and associate DNS server certificate]| |
| | |
Figure 2: Bootstrapping Endpoint Devices on subsequent attachments to
the network
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9. Privacy Considerations
[RFC7626] discusses DNS privacy considerations in both "on the wire"
(Section 2.4 of [RFC7626]) and "in the server" (Section 2.5 of
[RFC7626] contexts. The mechanism defined in
[I-D.reddy-add-server-policy-selection] can be used by the DNS server
to communicate its privacy statement URL and filtering policy to a
DNS client. This communication is cryptographically signed to attest
to its authenticity. By evaluating the DNS privacy statement,
filtering policy and the signatory, the client can use the discovered
DNS server if it meets privacy preserving data policy and filtering
requirements of the user.
10. Security Considerations
The bootstrapping procedure to obtain the certificate of the local
networks DNS server uses a client identity and password to
authenticate the EST server using PAKE schemes. Security
considerations such as those discussed in [I-D.barnes-tls-pake] or
[RFC8120] and [RFC8121] need to be taken into consideration.
Users cannot be expected to enable or disable the bootstrapping or
the discovery procedure as they switch networks. Thus, it is
RECOMMENDED that users indicate to their system in some way that they
desire bootstrapping to be performed when connecting to a specific
network, similar to the way users disable VPN connection in specific
network (e.g., Enterprise network) and enable VPN connection by
default in other networks.
If an endpoint has enabled strict privacy profile, and the network
security service blocks the traffic to the privacy-enabling public
DNS server, a hard failure occurs and the user is notified. The user
has a choice to switch to another network or if the user trusts the
network, the user can enable strict privacy profile with the DoH/DoT
server discovered in the network instead of downgrading to
opportunistic privacy profile.
The primary attacks against the methods described in Section 7 are
the ones that would lead to impersonation of a EST server and
spoofing the DNS response to indicate that the network does not
support any privacy-enabling protocols or point to a malicious DoH/
DoT server. To protect against DNS-vectored attacks, secured DNS
(DNSSEC) can be used to ensure the validity of the DNS records
received. Impersonation of the EST server is prevented by
authenticating the EST server using the PAKE scheme. The PAKE scheme
is only used once to configure the reference identifier of the EST
server and the server certificate is validated for subsequent TLS
connections to the EST server.
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Security considerations in [I-D.ietf-anima-bootstrapping-keyinfra]
need to be taken into consideration for IoT devices.
11. IANA Considerations
IANA is requested to allocate the following service name from the
registry available at: https://www.iana.org/assignments/service-
names-port-numbers/service-names-port-numbers.xhtml.
Service Name: est
Port Number: N/A
Transport Protocol(s): TCP
Description: Enrollment over Secure Transport (EST)
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>
Reference: [ThisDocument]
12. Acknowledgments
Thanks to Joe Hildebrand, Harsha Joshi, Shashank Jain, Patrick
McManus, Bob Harold, Livingood Jason, Winfield Alister, Eliot Lear,
Stephane Bortzmeyer, Ted Lemon and Sara Dickinson for the discussion
and comments.
13. References
13.1. Normative References
[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
keyinfra-41 (work in progress), April 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>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
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[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/info/rfc6125>.
[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
DOI 10.17487/RFC6762, February 2013,
<https://www.rfc-editor.org/info/rfc6762>.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
<https://www.rfc-editor.org/info/rfc6763>.
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013,
<https://www.rfc-editor.org/info/rfc7030>.
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <https://www.rfc-editor.org/info/rfc7858>.
[RFC8121] Oiwa, Y., Watanabe, H., Takagi, H., Maeda, K., Hayashi,
T., and Y. Ioku, "Mutual Authentication Protocol for HTTP:
Cryptographic Algorithms Based on the Key Agreement
Mechanism 3 (KAM3)", RFC 8121, DOI 10.17487/RFC8121, April
2017, <https://www.rfc-editor.org/info/rfc8121>.
[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>.
[RFC8295] Turner, S., "EST (Enrollment over Secure Transport)
Extensions", RFC 8295, DOI 10.17487/RFC8295, January 2018,
<https://www.rfc-editor.org/info/rfc8295>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>.
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13.2. Informative References
[CDN] "End-User Mapping: Next Generation Request Routing for
Content Delivery", 2015,
<https://conferences.sigcomm.org/sigcomm/2015/pdf/papers/
p167.pdf>.
[Dragonblood]
The Unicode Consortium, "Dragonblood: Analyzing the
Dragonfly Handshake of WPA3 and EAP-pwd",
<https://papers.mathyvanhoef.com/dragonblood.pdf>.
[Evil-Twin]
The Unicode Consortium, "Evil twin (wireless networks)",
<https://en.wikipedia.org/wiki/
Evil_twin_(wireless_networks)>.
[I-D.arkko-farrell-arch-model-t]
Arkko, J. and S. Farrell, "Challenges and Changes in the
Internet Threat Model", draft-arkko-farrell-arch-model-
t-03 (work in progress), March 2020.
[I-D.barnes-tls-pake]
Barnes, R. and O. Friel, "Usage of PAKE with TLS 1.3",
draft-barnes-tls-pake-04 (work in progress), July 2018.
[I-D.btw-add-home]
Boucadair, M., Reddy.K, T., Wing, D., and N. Cook, "DNS-
over-HTTPS and DNS-over-TLS Server Discovery and
Deployment Considerations for Home Networks", draft-btw-
add-home-05 (work in progress), April 2020.
[I-D.ietf-dnsop-terminology-ter]
Hoffman, P., "Terminology for DNS Transports and
Location", draft-ietf-dnsop-terminology-ter-01 (work in
progress), February 2020.
[I-D.reddy-add-server-policy-selection]
Reddy.K, T., Wing, D., Richardson, M., and M. Boucadair,
"DNS Server Selection: DNS Server Information with
Assertion Token", draft-reddy-add-server-policy-
selection-01 (work in progress), April 2020.
[Krack] The Unicode Consortium, "Key Reinstallation Attacks",
2017, <https://www.krackattacks.com/>.
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[RFC2775] Carpenter, B., "Internet Transparency", RFC 2775,
DOI 10.17487/RFC2775, February 2000,
<https://www.rfc-editor.org/info/rfc2775>.
[RFC7626] Bortzmeyer, S., "DNS Privacy Considerations", RFC 7626,
DOI 10.17487/RFC7626, August 2015,
<https://www.rfc-editor.org/info/rfc7626>.
[RFC7671] Dukhovni, V. and W. Hardaker, "The DNS-Based
Authentication of Named Entities (DANE) Protocol: Updates
and Operational Guidance", RFC 7671, DOI 10.17487/RFC7671,
October 2015, <https://www.rfc-editor.org/info/rfc7671>.
[RFC7871] Contavalli, C., van der Gaast, W., Lawrence, D., and W.
Kumari, "Client Subnet in DNS Queries", RFC 7871,
DOI 10.17487/RFC7871, May 2016,
<https://www.rfc-editor.org/info/rfc7871>.
[RFC8120] Oiwa, Y., Watanabe, H., Takagi, H., Maeda, K., Hayashi,
T., and Y. Ioku, "Mutual Authentication Protocol for
HTTP", RFC 8120, DOI 10.17487/RFC8120, April 2017,
<https://www.rfc-editor.org/info/rfc8120>.
[RFC8310] Dickinson, S., Gillmor, D., and T. Reddy, "Usage Profiles
for DNS over TLS and DNS over DTLS", RFC 8310,
DOI 10.17487/RFC8310, March 2018,
<https://www.rfc-editor.org/info/rfc8310>.
[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>.
Authors' Addresses
Tirumaleswar Reddy
McAfee, Inc.
Embassy Golf Link Business Park
Bangalore, Karnataka 560071
India
Email: kondtir@gmail.com
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Dan Wing
Citrix Systems, Inc.
USA
Email: dwing-ietf@fuggles.com
Michael C. Richardson
Sandelman Software Works
USA
Email: mcr+ietf@sandelman.ca
Mohamed Boucadair
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com
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