ADD M. Boucadair
Internet-Draft Orange
Intended status: Standards Track T. Reddy
Expires: September 7, 2020 McAfee
D. Wing
Citrix
N. Cook
Open-Xchange
March 6, 2020
DNS-over-HTTPS and DNS-over-TLS server Discovery and Deployment
Considerations for Home and Mobile Networks
draft-btw-add-home-01
Abstract
This document discusses DoT/DoH deployment considerations for home
networks. It particularly sketches the required steps to use DoT/DoH
capabilities provided by local networks.
One of the goals of this document is to assess to what extent
existing tools can be used to provide a DoT/DoH service. As an
outcome, new DHCP and Router Advertisement Options are specified in
order to convey a DNS Authentication Domain Name.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
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 September 7, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Sample Deployment Scenarios . . . . . . . . . . . . . . . . . 4
4. DNS Reference Identifier Option . . . . . . . . . . . . . . . 6
4.1. DHCPv6 DNS Reference Identifier Option . . . . . . . . . 7
4.2. DHCP DNS Reference Identifier Option . . . . . . . . . . 8
4.3. RA DNS Reference Identifier Option . . . . . . . . . . . 8
5. Locating DoH/DoT Servers . . . . . . . . . . . . . . . . . . 9
6. DNS-over-TLS and DNS-over-HTTPS Server Discovery Procedure . 11
7. Hosting DoH/DoT Forwarder in the CPE . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
9.1. DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . . 14
9.2. DHCP Option . . . . . . . . . . . . . . . . . . . . . . . 14
9.3. RA Option . . . . . . . . . . . . . . . . . . . . . . . . 14
9.4. Service Name . . . . . . . . . . . . . . . . . . . . . . 15
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
11.1. Normative References . . . . . . . . . . . . . . . . . . 15
11.2. Informative References . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
Internet Service Providers (ISPs) traditionally provide DNS resolvers
to their customers. Typically, ISPs deploy the following mechanisms
to advertise a list of DNS Recursive DNS server(s) to their
customers:
o Protocol Configuration Options in cellular networks [TS.24008].
o DHCP [RFC2132] (Domain Name Server Option) or DHCPv6
[RFC8415][RFC3646] (OPTION_DNS_SERVERS).
o IPv6 Router Advertisement [RFC4861][RFC8106] (Type 25 (Recursive
DNS Server Option)).
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The communication between a customer's device (UE) (possibly via
Customer Premise Equipment (CPE)) and an ISP-supplied DNS resolver
takes place by using cleartext DNS messages (Do53,
[I-D.ietf-dnsop-terminology-ter]). Some examples are depicted in
Figure 1. In the case of cellular networks, connectivity can be
provided to a UE or to a CPE. Do53 mechanisms used within the LAN
are similar in both fixed and cellular CPE-based broadband service
offerings.
(a) Fixed Networks
,--,--,--. ,--,--,--.
,-' +--+ `-. ,-' ISP `-.
( LAN |UE| CPE----( DNS Server )
`-. +--+ ,-' `-. ,-'
`--'|-'--' `--'--'--'
| |
|<=======Do53========>|
(b) Cellular Networks
|<===========Do53=========>|
,--,-|,--. |
,-' +--+ `-. ,--,--,--.
( LAN |UE| CPE------------+ \
`-. +--+ ,-' ,' ISP `-.
`--'--'--' ( DNS Server )
+-----+-. ,-'
+--+ | `--'--'--'
|UE+-----------+
+--+
Figure 1: Sample Legacy Deployments
ISPs use DNS to provide additional services such as (but not limited
to) malware filtering, parental control, or VoD (Video on Demand)
optimization. DNS is also a central component for mastering the
quality of experience for current latency-sensitive services, but
also emerging ones (such as those services that pertain to the Ultra
Reliability and Low Latency Communications (uRLLC) or Enhanced Mobile
Broadband (eMBB).
For example, the latency targets set in the context of 5G are 1ms
(uRLLC) and 4ms (eMBB). An ISP will be able to address such
demanding latency requirements assuming the corresponding services
rely upon resources (network, compute, storage) that are located
as close to the user as possible (e.g., by means of Edge Computing
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techniques and resources). Such latency requirements are likely
to be addressed by means of optimized designs (DNS, in
particular), too.
Relying upon local DNS resolvers will therefore contribute to meet
the aforementioned service requirements. The use of external
resolvers is likely to induce an extra service delay which exceeds by
far the service target.
This document focuses on the support of DNS-over-HTTPS (DoH)
[RFC8484] or DNS-over-TLS (DoT) [RFC7858] in local networks. In
particular, the document describes how a local DoH/DoT server can be
discovered and used by connected hosts. This document specifies
DHCP/RA options that allows DNS clients to discover local DoT/DoH
servers. Section 4 describes DHCPv4, DHCPv6 and RA options to convey
the authentication domain name information (ADN, defined in
[RFC8310]).
Some ISPs rely upon external resolvers (e.g., outsourced service or
public resolvers); these ISPs provide their customers with the IP
addresses of these resolvers. These addresses are typically
configured on CPEs using the same mechanisms listed above. This
document permits such deployments. It is up to an ISP to decide
which list of DNS resolvers to advertise to its serviced devices.
2. 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.
3. Sample Deployment Scenarios
ISPs have developed an expertise in managing service-specific
configuration information (e.g., CPE WAN Management Protocol
[TR-069]). For example, these tools may be used to provision
authentication domain name information (ADN, defined in [RFC8310]) to
managed CPEs if DoH/DoT is supported by a local network similar to
what is depicted in Figure 2.
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DNS clients may try to establish DoH/DoT sessions with discovered DNS
servers to determine whether these servers support DoH and/or DoT
(Section 5). Alternatively, a DNS client may discover whether the
DNS server in the local network supports DoH/DoT by using the
mechanism discussed in Section 6.
(a) Fixed Networks
,--,--,--. ,--,--,--.
,-' +--+ `-. ,-' ISP `-.
( LAN |UE| CPE----( DNS Server )
`-. +--+ ,-' `-. ,-'
`--'|-'--' `--'--'--'
| |
|<=======DoH/DoT=====>|
(b) Cellular Networks
|<===========DoH/DoT======>|
,--,-|,--. |
,-' +--+ `-. ,--,--,--.
( LAN |UE| CPE------------+ \
`-. +--+ ,-' ,' ISP `-.
`--'--'--' ( DNS Server )
+-----+-. ,-'
+--+ | `--'--'--'
|UE+-----------+
+--+
Figure 2: DoH/DoT in the WAN
Figure 2 shows the scenario where the CPE relays the list of DoT/DoH
servers it learns for the network by using mechanisms like DHCP or a
specific Router Advertisement message. In such context, direct DoH/
DoT sessions will be established between a host serviced by a CPE and
an ISP-supplied DoT/DoH server (see the example depicted in Figure 3
for a DoH/DoT-capable host).
,--,--,--. ,--,--,--.
,-' `-. ,-' ISP `-.
UE----( LAN CPE----( DNS Server )
| `-. ,-' `-. ,-'
| `--'--'--' `--'--'--'
| |
|<==============DoT/DoH============>|
Figure 3: Direct DoH/DoT Sessions
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Figure 4 shows a deployment where the CPE embeds a caching DNS
forwarder. The CPE advertises itself as the default DNS server to
the hosts it serves. The CPE relies upon DHCP or RA to advertise
itself to internal hosts as the default DoT/DoH/Do53 server. When
receiving a DNS request it cannot handle locally, the CPE forwards
the request to an upstream DoH/DoT/Do53 resolver. Such deployment is
required for IPv4 service continuity purposes (e.g.,
[I-D.ietf-v6ops-rfc7084-bis]) or for supporting advanced services
within the home (e.g., malware filtering, parental control,
Manufacturer Usage Description (MUD, [RFC8520] to only allow intended
communications to and from an IoT device). When the CPE behaves as a
DNS forwarder, DNS communications can be decomposed into two legs:
o The leg between an internal host and the CPE.
o The leg between the CPE and an upstream DNS resolver.
Also, an ISP that wants to offer DoH/DoT to its customers may enable
DoH/DoT in both legs as shown in Figure 4. Additional considerations
related to this approach are discussed in Section 7.
,--,--,--. ,--,--,--.
,-' `-. ,-' ISP `-.
UE----( LAN CPE----( DNS Server )
| `-. ,-'| `-. ,-'
| `--'--'--' | `--'--'--'
| | |
|<======DoT/DoH======>|<==DoT/DoH==>|
Figure 4: Proxied DoH/DoT Sessions
4. DNS Reference Identifier Option
This section describes how a DNS client can discover the ADN of local
DoH/DoT server(s) using DHCP (Sections 4.1 and 4.2) and RA
(Section 4.3).
As reported in Section 1.7.2 of [RFC6125]:
"few certification authorities issue server certificates based on
IP addresses, but preliminary evidence indicates that such
certificates are a very small percentage (less than 1%) of issued
certificates".
In order to allow for PKIX-based authentication between a DNS client
and a DoH/DoT server while accommodating the current best practices
for issuing certificates, this document allows for configuring an
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authentication domain name to be presented as a reference identifier
for DNS authentication purposes.
The DNS client establishes a DoH/DoT session with the discovered DNS
IP address(es) (Section 5) and uses the mechanism discussed in
Section 8 of [RFC8310] to authenticate the DNS server certificate
using the authentication domain name conveyed in the DNS Reference
Identifier.
If the DNS Reference Identifier is discovered by a host using both RA
and DHCP, the rules discussed in Section 5.3.1 of [RFC8106] MUST be
followed.
4.1. DHCPv6 DNS Reference Identifier Option
The DHCPv6 DNS Reference Identifier option is used to configure an
authentication domain name of the DoH/DoT server. The format of this
option is shown in Figure 5.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_V6_DNS_RI | Option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| authentication-domain-name |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: DHCPv6 DNS Reference Identifier Option
The fields of the option shown in Figure 5 are as follows:
o Option-code: OPTION_V6_DNS_RI (TBA1, see Section 9.1)
o Option-length: Length of the authentication-domain-name field in
octets.
o authentication-domain-name: A fully qualified domain name of the
DoH/DoT server. This field is formatted as specified in
Section 10 of [RFC8415].
An example of the authentication-domain-name encoding is shown in
Figure 6. This example conveys the FQDN "doh1.example.com.".
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+------+------+------+------+------+------+------+------+------+
| 0x04 | d | o | h | 1 | 0x07 | e | x | a |
+------+------+------+------+------+------+------+------+------+
| m | p | l | e | 0x03 | c | o | m | 0x00 |
+------+------+------+------+------+------+------+------+------+
Figure 6: An example of the authentication-domain-name Encoding
4.2. DHCP DNS Reference Identifier Option
The DHCP DNS Reference Identifier option is used to configure an
authentication domain name of the DoH/DoT server. The format of this
option is illustrated in Figure 7.
Code Length Authentication domain name
+-----+-----+-----+-----+-----+-----+-----+--
|TBA2 | n | s1 | s2 | s3 | s4 | s5 | ...
+-----+-----+-----+-----+-----+-----+-----+--
The values s1, s2, s3, etc. represent the domain name labels in the
domain name encoding.
Figure 7: DHCPv4 DNS Reference Identifier Option
The fields of the option shown in Figure 7 are as follows:
o Code: OPTION_V4_DNS_RI (TBA2, see Section 9.2).
o Length: Includes the length of the "authentication domain name"
field in octets.
o Authentication domain name: The domain name of the DoH/DoT server.
This field is formatted as specified in Section 10 of [RFC8415].
4.3. RA DNS Reference Identifier Option
The IPv6 Router Advertisement (RA) DNS Reference Identifier option is
used to configure an authentication domain name of the DoH/DoT
server. The format of this option is illustrated in Figure 8.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: authentication-domain-name :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: RA DNS Reference Identifier Option
The fields of the option shown in Figure 8 are as follows:
o Type: 8-bit identifier of the DNS Reference Identifier Option as
assigned by IANA (TBA3, see Section 9.3).
o Length: 8-bit unsigned integer. The length of the option
(including the Type and Length fields) is in units of 8 octets.
o Reserved: This field is unused. It MUST be initialized to zero by
the sender and MUST be ignored by the receiver.
o Lifetime: 32-bit unsigned integer. The maximum time in seconds
(relative to the time the packet is received) over which the
authentication domain name MAY be used as a DNS Reference
Identifier. The value of Lifetime SHOULD by default be at least 3
* MaxRtrAdvInterval, where MaxRtrAdvInterval is the maximum RA
interval as defined in [RFC4861]. A value of all one bits
(0xffffffff) represents infinity. A value of zero means that the
DNS Reference Identifier MUST no longer be used.
o Authentication domain name: The domain name of the DoH/DoT server.
This field is formatted as specified in Section 10 of [RFC8415].
5. Locating DoH/DoT Servers
A CPE or a host relies upon discovery mechanisms (such as PCO, DHCP,
or RA) to retrieve DoH and DoT servers' reachability information. In
the various scenarios sketched in Section 3, Do53, DoH, and DoT may
terminate on the same IP address (or distinct IP addresses as
depicted in Figure 9). Terminating Do53/DoH/DoT on the same or
distinct IP addresses is deployment-specific.
From an IP reachability standpoint, DoH/DoT servers SHOULD be located
by their address literals rather than their names. This avoids
adding a dependency on another server to resolve the DoH/DoT name.
Concretely, if Do53/DoH/DoT terminate on same IP addresses, existing
discovery mechanisms [RFC2132][RFC3646][RFC8106] can be leveraged to
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learn the IP addresses of DoT/DoH servers while an authentication
domain name is supplied by one of the options discussed in Section 4.
Legacy Do53
client
|<===RA======|
| {RI,S1,S2} | |
| | |
|========Do53 Query=======>|
| | --,--,-
,+-,--,--. | ,/ S1 \.
,-' `-. | ,-' ISP `-.
DoH/DoT --( LAN CPE----( DNS Servers )
capable `-. ,-'| `-. S2 ,-'
| `--'--'--' | `--'--'--'
|<=========RA==========| |
| {RI, S1,S2} | |
| |
|<===============DoT/DoH===========->|
Figure 9: Locating DoH/DoT/Do53 using RFC8106
Additional considerations are discussed below for the use of DoH and
DoT servers provided by local networks:
o If the DNS server's IP address discovered by using DHCP/RA is pre-
configured in the OS or Browser as a trusted resolver, the DNS
client may auto-upgrade to use the pre-configured DoH/DoT server
tied to the discovered DNS server IP address. In such a case the
DNS client may perform additional check out of band, such as
confirming that the Do53 IP address and the DoH server are owned
and operated by the same organisation.
o If the DNS reference identity (Section 4) is provided by means of
DHCP/RA, the DNS client matches the domain name in the DNS
Reference Identifier DHCP/RA option with the 'DNS-ID' identifier
type within subjectAltName entry in the server certificate
conveyed in the TLS handshake.
Additional options are discussed below:
o The Wi-Fi Alliance has released the Device Provisioning Protocol
(DPP). If DPP is used, the configurator can securely configure
devices in the home network with the local DoT/DoH server using
DPP.
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o If a CPE is co-located with security services within the home
network, the CPE can use WPA-PSK but with unique pre-shared keys
for different endpoints to deal with security issues. In such
networks, [I-D.reddy-dprive-bootstrap-dns-server] may be used to
securely bootstrap endpoint devices with the authentication domain
name (ADN) and DNS server certificate of the local network's DoH/
DoT server.
The OS would not know if the WPA pre-shared-key is the same for
all clients or a unique pre-shared key is assigned to the host.
Hence, the user has to indicate to the system that a unique pre-
shared key is assigned to trigger the bootstrapping procedure.
If the device joins a home network using a single shared password
among all the attached devices, a compromised device can host a
fake access point, and the device cannot be securely bootstrapped
with the home network's DoH/DoT server.
6. DNS-over-TLS and DNS-over-HTTPS Server Discovery Procedure
A DNS client discovers the DNS server in the local network supporting
DNS-over-TLS and DNS-over-HTTPS protocols by using DNS-based Service
Discovery (DNS-SD) [RFC6763]. DNS-SD provides generic solution for
discovering services available in a local network. DNS-SD defines a
set of naming rules for certain DNS record types that they use for
advertising and discovering services. Section 4.1 of [RFC6763]
specifies that a service instance name in DNS-SD has the following
structure:
<Instance> . <Service> . <Domain>
The <Domain> portion specifies the authentication domain name (ADN).
The <Service> portion of the DNS service instance name MUST be
"_domain-s._tcp" or "_doh._tcp". If no DNS-SD records can be
retrieved, the discovery procedure fails for this authentication
domain name. However, before retrying a lookup that has failed, a
DNS client MUST wait a time period that is appropriate for the
encountered error (e.g., NXDOMAIN, timeout, etc.). If no DNS-SD
records can be retrieved, the DNS client can try connecting to the
pre-configured public DNS servers (if any).
If DoH is supported by the DNS server, the DNS client may request the
URI resource record type [RFC7553] using the domain name discovered
using DNS Reference Identifier DHCP/RA option (Section 4) to use the
HTTPS URI scheme (Section 3 of [RFC8484]).
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7. Hosting DoH/DoT Forwarder in the CPE
The following mechanisms can be used to host a DoH/DoT forwarder in
the CPE:
o If a CPE is co-located with security services (e.g., malware
filtering, parental control, MUD), the ISP can assign a unique
FQDN (e.g., cpe1.example.com) and a domain-validated public
certificate to the DoH/DoT forwarder hosted on the CPE. Automatic
Certificate Management Environment (ACME) [RFC8555] can be used to
automate certificate management functions such as domain
validation procedure, certificate issuance and certificate
revocation.
o Alternatively, the security service provider can assign a unique
FQDN to the managed CPE. The DoT/DoH forwarder will act like a
public DoT/DoH server but will only be accessible from within the
home network. DNS queries received outside the home network must
be discarded by the DoH/DoT forwarder. This behavior adheres to
REQ#8 in [RFC6092], and must apply for both IPv4 and IPv6.
o If the ISP DoH resolver is pre-configured as a trusted resolver in
browsers, the CPE is managed by the ISP, and the ISP has assigned
a domain-validated public certificate to the DoH forwarder hosted
on the CPE, the ISP can configure the CPE to convey the ISP DoH/
DoT resolver IP addresses and the ISP DoH/DoT ADN in DHCP/RA to
internal hosts (Section 4). If the ISP DNS server IP address is
pre-configured in the browser as a trusted resolver, the DNS
client auto-upgrades to use the DoH/DoT server tied with the
discovered DNS server IP address.
If the ADN in DHCP/RA is pre-configured in the OS or browser as a
trusted resolver, the client auto-upgrades to establish DoH
session with the ADN.
Once the DoH session is established, the ISP DoH/DoT server uses
HTTP redirection (Section 6.4.4 in [RFC7231]) to redirect the DNS
client to the DoH forwarder hosted on the CPE. The DNS client
uses Do53 to resolve the domain name in the redirected URI and
eventually establishes DoH session with the DoH forwarder on the
CPE.
8. Security Considerations
An attacker can get a domain name, domain-validated public
certificate from a CA, host a DoT/DoH server and claim the best DNS
privacy preservation policy. Also, an attacker within the home
network can use the public IP address, get an 'IP address'-validated
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public certificate from a CA, host a DoT/DoH server and claim the
best DNS privacy preservation policy.
Because DHCP/RA messages are not encrypted or protected against
modification in any way, their content can be spoofed or modified by
compromised devices within the home network. An attacker can spoof
the DHCP/RA response to provide the attacker's DoT/DoH server. Note
that such an attacker can launch other attacks as discussed in
Section 22 of [RFC8415]. Furthermore, if the browser or the OS is
pre-configured with a list of DNS servers and some of which perform
malware filtering while others do not, an attacker can prevent
contacting the preferred filtering DNS servers causing a downgrade
attack to a non-filtering DNS server, which the attacker can leverage
to deliver malware.
The primary attacks against the methods described in Section 6 are
the ones that would lead to impersonation of a DNS server and
spoofing the DNS response to indicate that the DNS server does not
support DoH or DoT. To protect against DNS-vectored attacks, secured
DNS (DNSSEC) can be used to ensure the validity of the received DNS
records received. Impersonation of a DoH/DoT server is prevented by
validating the certificate presented by the DoH/DoT server. If DHCP/
RA conveys an ADN, but the DNS-SD lookup indicates that the DNS
server does not support DoH/DoT, the DNS client can detect the DNS
response is spoofed.
The use of DoH/DoT also depends on the user's policies. For example,
the user may indicate his/her consent to use (or not) the locally-
discovered DoH/DoT server. The DNS client must adhere to these
policies.
DoH/DoT servers discovered using insecure discovery mechanisms like
DHCP/RA are used by a DNS client if the insecurely discovered DoH/DoT
server is pre-configured in the OS or the browser.
If the insecurely discovered DoH/DoT server is not pre-configured in
the OS or browser, its policy information must be cryptographically
attested by the ISP (e.g., [I-D.reddy-dprive-dprive-privacy-policy]);
user consent is required to use the locally-discovered DoH/DoT
server.
DoT/DoH sessions with rogue servers spoofing the IP address of a DNS
server will fail because the DNS client will fail to authenticate
that rogue server based upon PKIX authentication [RFC6125] based upon
the authentication domain name in the Reference Identifier Option.
DNS clients that ignore authentication failures and accept spoofed
certificates will be subject to attacks (e.g., redirect to malicious
servers, intercept sensitive data).
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9. IANA Considerations
9.1. DHCPv6 Option
IANA is requested to assign the following new DHCPv6 Option Code in
the registry maintained in: https://www.iana.org/assignments/dhcpv6-
parameters/dhcpv6-parameters.xhtml#dhcpv6-parameters-2.
+-------+------------------+---------+-------------+----------------+
| Value | Description | Client | Singleton | Reference |
| | | ORO | Option | |
+-------+------------------+---------+-------------+----------------+
| TBA1 | OPTION_V6_DNS_RI | Yes | Yes | [ThisDocument] |
+-------+------------------+---------+-------------+----------------+
9.2. DHCP Option
IANA is requested to assign the following new DHCP Option Code in the
registry maintained in: https://www.iana.org/assignments/bootp-dhcp-
parameters/bootp-dhcp-parameters.xhtml#options.
+------+------------------+-------+----------------+----------------+
| Tag | Name | Data | Meaning | Reference |
| | | Length| | |
+------+------------------+-------+----------------+----------------+
| TBA2 | OPTION_V4_DNS_RI | N | DoT/DoH server | [ThisDocument] |
| | | | authentication | |
| | | | domain name | |
+------+------------------+-------+----------------+----------------+
9.3. RA Option
IANA is requested to assign the following new IPv6 Neighbor Discovery
Option type in the "IPv6 Neighbor Discovery Option Formats" sub-
registry under the "Internet Control Message Protocol version 6
(ICMPv6) Parameters" registry maintained in
http://www.iana.org/assignments/icmpv6-parameters/
icmpv6-parameters.xhtml#icmpv6-parameters-5.
+------+---------------------------------+----------------+
| Type | Description | Reference |
+------+---------------------------------+----------------+
| TBA3 | DNS Reference Identifier Option | [ThisDocument] |
+------+---------------------------------+----------------+
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9.4. Service Name
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: doh
Port Number: N/A
Transport Protocol(s): TCP
Description: DNS-over-HTTPS
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>
Reference: [ThisDocument]
10. Acknowledgements
Many thanks to Christian Jacquenet for the review.
11. References
11.1. 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>.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, DOI 10.17487/RFC2132, March 1997,
<https://www.rfc-editor.org/info/rfc2132>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>.
[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>.
[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>.
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[RFC8106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"IPv6 Router Advertisement Options for DNS Configuration",
RFC 8106, DOI 10.17487/RFC8106, March 2017,
<https://www.rfc-editor.org/info/rfc8106>.
[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>.
[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>.
[RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
Richardson, M., Jiang, S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 8415, DOI 10.17487/RFC8415, November 2018,
<https://www.rfc-editor.org/info/rfc8415>.
[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>.
11.2. Informative References
[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.ietf-v6ops-rfc7084-bis]
Palet, J., "Basic Requirements for IPv6 Customer Edge
Routers", draft-ietf-v6ops-rfc7084-bis-04 (work in
progress), June 2017.
[I-D.reddy-dprive-bootstrap-dns-server]
Reddy.K, T., Wing, D., Richardson, M., and M. Boucadair,
"A Bootstrapping Procedure to Discover and Authenticate
DNS-over-(D)TLS and DNS-over-HTTPS Servers", draft-reddy-
dprive-bootstrap-dns-server-07 (work in progress),
February 2020.
[I-D.reddy-dprive-dprive-privacy-policy]
Reddy.K, T., Wing, D., Richardson, M., and M. Boucadair,
"DNS Server Privacy Statement and Filtering Policy with
Assertion Token", draft-reddy-dprive-dprive-privacy-
policy-03 (work in progress), March 2020.
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[RFC3646] Droms, R., Ed., "DNS Configuration options for Dynamic
Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
DOI 10.17487/RFC3646, December 2003,
<https://www.rfc-editor.org/info/rfc3646>.
[RFC6092] Woodyatt, J., Ed., "Recommended Simple Security
Capabilities in Customer Premises Equipment (CPE) for
Providing Residential IPv6 Internet Service", RFC 6092,
DOI 10.17487/RFC6092, January 2011,
<https://www.rfc-editor.org/info/rfc6092>.
[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>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
[RFC7553] Faltstrom, P. and O. Kolkman, "The Uniform Resource
Identifier (URI) DNS Resource Record", RFC 7553,
DOI 10.17487/RFC7553, June 2015,
<https://www.rfc-editor.org/info/rfc7553>.
[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>.
[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>.
[RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D., and J.
Kasten, "Automatic Certificate Management Environment
(ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019,
<https://www.rfc-editor.org/info/rfc8555>.
[TR-069] The Broadband Forum, "CPE WAN Management Protocol", March
2018, <https://www.broadband-forum.org/technical/download/
TR-069.pdf>.
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[TS.24008]
3GPP, "Mobile radio interface Layer 3 specification; Core
network protocols; Stage 3 (Release 16)", December 2019,
<http://www.3gpp.org/DynaReport/24008.htm>.
Authors' Addresses
Mohamed Boucadair
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Tirumaleswar Reddy
McAfee, Inc.
Embassy Golf Link Business Park
Bangalore, Karnataka 560071
India
Email: TirumaleswarReddy_Konda@McAfee.com
Dan Wing
Citrix Systems, Inc.
USA
Email: dwing-ietf@fuggles.com
Neil Cook
Open-Xchange
UK
Email: neil.cook@noware.co.uk
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