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ADD M. Boucadair
Internet-Draft Orange
Intended status: Standards Track T. Reddy
Expires: March 25, 2021 McAfee
D. Wing
Citrix
N. Cook
Open-Xchange
September 21, 2020
DHCP and Router Advertisement Options for Encrypted DNS Discovery within
Home Networks
draft-btw-add-home-09
Abstract
The document specifies new DHCP and Router Advertisement Options to
discover encrypted DNS servers (e.g., DoH, DoT, DoQ). Particularly,
it allows to learn an Authentication Domain Name together with a list
of IP addresses and optionally a port number to reach such encrypted
DNS servers.
This document focuses on encrypted DNS deployment within home
networks.
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 March 25, 2021.
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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Sample Target Deployment Scenarios . . . . . . . . . . . . . 5
3.1. Managed CPEs . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Unmanaged CPEs . . . . . . . . . . . . . . . . . . . . . 7
4. Encrypted DNS Discovery Options . . . . . . . . . . . . . . . 8
4.1. DHCPv6 Encrypted DNS Options . . . . . . . . . . . . . . 9
4.2. DHCP Encrypted DNS Option . . . . . . . . . . . . . . . . 12
4.3. IPv6 RA Encrypted DNS Options . . . . . . . . . . . . . . 14
5. DoH URI Templates . . . . . . . . . . . . . . . . . . . . . . 17
6. Make Use of Discovered Encrypted DNS Server . . . . . . . . . 18
7. Hosting Encrypted DNS Forwarder in the CPE . . . . . . . . . 19
7.1. Managed CPEs . . . . . . . . . . . . . . . . . . . . . . 19
7.1.1. ACME . . . . . . . . . . . . . . . . . . . . . . . . 19
7.1.2. Auto-Upgrade Based on Domains and their Subdomains . 19
7.2. Unmanaged CPEs . . . . . . . . . . . . . . . . . . . . . 20
8. Legacy CPEs . . . . . . . . . . . . . . . . . . . . . . . . . 21
9. Security Considerations . . . . . . . . . . . . . . . . . . . 22
9.1. Spoofing Attacks . . . . . . . . . . . . . . . . . . . . 22
9.2. Deletion Attacks . . . . . . . . . . . . . . . . . . . . 23
9.3. Passive Attacks . . . . . . . . . . . . . . . . . . . . . 23
9.4. Wireless Security - Authentication Attacks . . . . . . . 23
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
10.1. DHCPv6 Options . . . . . . . . . . . . . . . . . . . . . 24
10.2. DHCP Option . . . . . . . . . . . . . . . . . . . . . . 24
10.3. RA Options . . . . . . . . . . . . . . . . . . . . . . . 24
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
12.1. Normative References . . . . . . . . . . . . . . . . . . 25
12.2. Informative References . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
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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)).
The communication between a customer's device (possibly via Customer
Premises 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, the cellular network
will provide connectivity directly to a host (e.g., smartphone,
tablet) or via a CPE. Do53 mechanisms used within the Local Area
Network (LAN) are similar in both fixed and cellular CPE-based
broadband service offerings.
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(a) Fixed Networks
,--,--,--. ,--,--,--.
,-' +--+ `-. ,-' ISP `-.
( LAN |H | CPE----( )
`-. +--+ ,-' `-. ,-'
`--'|-'--' `--'--'--'
| |
|<=======Do53========>|
(b) Cellular Networks
|<===========Do53=========>|
,--,-|,--. |
,-' +--+ `-. ,--,--,--.
( LAN |H | CPE------------+ \
`-. +--+ ,-' ,' ISP `-.
`--'--'--' ( )
+-----+-. ,-'
+--+ | `--'--'--'
|H +------------+
+--+
Legend:
* H: refers to a host.
Figure 1: Sample Legacy Deployments
This document focuses on the support of encrypted DNS such as DNS-
over-HTTPS (DoH) [RFC8484], DNS-over-TLS (DoT) [RFC7858], or DNS-
over-QUIC (DoQ) [I-D.ietf-dprive-dnsoquic] in local networks. In
particular, the document describes how a local encrypted DNS server
can be discovered and used by connected hosts by means of DHCP,
DHCPv6, and RA options (Section 4). These options are designed to
convey the following information: the DNS Authentication Domain Name
(ADN) [RFC8310], a list of IP addresses, and optionally a port
number.
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. Likewise,
users can modify the default DNS configuration of their CPEs (e.g.,
supplied by their ISP) to configure their favorite DNS servers. This
document permits such deployments.
Both managed and unmanaged CPEs are discussed in the document
(Section 3). Also, considerations related to hosting a DNS forwarder
in the CPE are described (Section 7).
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Hosts and/or CPEs may be connected to multiple networks; each
providing their own DNS configuration using the discovery mechanisms
specified in this document. Nevertheless, it is out of the scope of
this specification to discuss DNS selection of multi-interface
devices. The reader may refer to [RFC6731] for a discussion of
issues and an example of DNS server selection for multi-interfaced
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].
Do53 refers to unencrypted DNS.
'Encrypted DNS' refers to a scheme where DNS exchanges are
transported over an encrypted channel. Examples of encrypted DNS are
DNS-over-TLS (DoT) [RFC7858], DNS-over-HTTPS (DoH) [RFC8484], or DNS-
over-QUIC (DoQ) [I-D.ietf-dprive-dnsoquic].
3. Sample Target Deployment Scenarios
3.1. Managed CPEs
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 the DNS
server's ADN to managed CPEs if an encrypted DNS is supported by a
local network similar to what is depicted in Figure 2.
For example, DoH-capable (or DoT) clients establish the DoH (or DoT)
session with the discovered DoH (or DoT) server.
The DNS client discovers whether the DNS server in the local network
supports DoH/DoT/DoQ by using a dedicated field in the discovery
message: Encrypted DNS Types (Section 4).
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(a) Fixed Networks
,--,--,--. ,--,--,--.
,-' +--+ `-. ,-' ISP `-.
( LAN |H | CPE----( DNS Server )
`-. +--+ ,-' `-. ,-'
`--'|-'--' `--'--'--'
| |
|<===Encrypted DNS===>|
(b) Cellular Networks
|<=====Encrypted DNS======>|
,--,-|,--. |
,-' +--+ `-. ,--,--,--.
( LAN |H | CPE------------+ \
`-. +--+ ,-' ,' ISP `-.
`--'--'--' ( DNS Server )
+-----+-. ,-'
+--+ | `--'--'--'
|H +-----------+
+--+
Figure 2: Encrypted DNS in the WAN
Figure 2 shows the scenario where the CPE relays the list of
encrypted DNS servers it learns for the network by using mechanisms
like DHCP or a specific Router Advertisement message. In such
context, direct encrypted DNS sessions will be established between a
host serviced by a CPE and an ISP-supplied encrypted DNS server (see
the example depicted in Figure 3 for a DoH/DoT-capable host).
,--,--,--. ,--,--,--.
,-' `-. ,-' ISP `-.
Host---( LAN CPE----( DNS Server )
| `-. ,-' `-. ,-'
| `--'--'--' `--'--'--'
| |
|<=========Encrypted DNS===========>|
Figure 3: Direct Encrypted DNS Sessions
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
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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.
An ISP that offers encrypted DNS to its customers may enable
encrypted DNS in both legs as shown in Figure 4. Additional
considerations related to this deployment are discussed in Section 7.
,--,--,--. ,--,--,--.
,-' `-. ,-' ISP `-.
Host---( LAN CPE----( DNS Server )
| `-. ,-'| `-. ,-'
| `--'--'--' | `--'--'--'
| | |
|<=====Encrypted=====>|<=Encrypted=>|
DNS DNS
Figure 4: Proxied Encrypted DNS Sessions
3.2. Unmanaged CPEs
Customers may decide to deploy unmanaged CPEs (assuming the CPE is
compliant with the network access technical specification that is
usually published by ISPs). Upon attachment to the network, an
unmanaged CPE receives from the network its service configuration
(including the DNS information) by means of, e.g., DHCP. That DNS
information is shared within the LAN following the same mechanisms as
those discussed in Section 3.1. A host can thus, for example,
establish DoH/DoT session with a DoH/DoT server similar to what is
depicted in Figure 3.
Customers may also decide to deploy internal home routers (called
hereafter, Internal CPEs) for a variety of reasons that are not
detailed here. Absent any explicit configuration on the internal CPE
to override the DNS configuration it receives from the ISP-supplied
CPE, an Internal CPE relays the DNS information it receives via DHCP/
RA from the ISP-supplied CPE to connected hosts. Encrypted DNS
sessions can be established by a host with the DNS servers of the ISP
(see Figure 5).
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,--,--,--. ,--,--,--.
,-' Internal ,-' ISP `-.
Host--( Network#A CPE----CPE---( DNS Server )
| `-. ,-' `-. ,-'
| `--'--'--' `--'--'--'
| |
|<==============Encrypted DNS=============>|
Figure 5: Direct Encrypted DNS Sessions with the ISP DNS Resolver
(Internal CPE)
Similar to managed CPEs, a user may modify the default DNS
configuration of an unmanaged CPE to use his/her favorite DNS servers
instead. Encrypted DNS sessions can be established directly between
a host and a 3rd Party DNS server (see Figure 6).
,--,--,--. ,--,
,' Internal ,-' '- 3rd Party
Host--( Network#A CPE----CPE---( ISP )--- DNS Server
| `. ,-' `-. -' |
| `-'--'--' `--' |
| |
|<=================Encrypted DNS==================>|
Figure 6: Direct Encrypted DNS Sessions with a Third Party DNS
Resolver
Section 7.2 discusses considerations related to hosting a forwarder
in the Internal CPE.
4. Encrypted DNS Discovery Options
This section describes how a DNS client can discover a local
encrypted DNS server(s) using DHCP (Sections 4.1 and 4.2) and
Neighbor Discovery protocol (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 an encrypted DNS server while accommodating the current best
practices for issuing certificates, this document allows for
configuring an authentication domain name to be presented as a
reference identifier for DNS authentication purposes.
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To avoid adding a dependency on another server to resolve the ADN,
the options return a list of IP addresses to locate the encrypted DNS
server. In the various scenarios sketched in Section 3, encrypted
DNS servers may terminate on the same IP address or distinct IP
addresses. Terminating encrypted DNS servers on the same or distinct
IP addresses is deployment specific. It is RECOMMENDED to return
both the ADN and a list of IP addresses to a requesting host.
Note that in order to optimize the size of discovery messages when
all servers terminate on the same IP address, a host may rely upon
the discovery mechanisms specified in [RFC2132][RFC3646][RFC8106] to
retrieve a list of IP addresses to reach their DNS servers.
Nevertheless, this approach requires a client that supports more than
one encrypted DNS to probe that list of IP addresses. To avoid such
probing, the options defined in the following subsections associate
an IP address with an encrypted DNS type. No probing is required in
such design.
A list of IP addresses to reach an encrypted DNS server can be
returned in the option to accommodate current deployments relying
upon primary and backup servers. Whether one IP address or more are
returned in an option is deployment specific. For example, a home
router embedding a forwarder has to include one single IP address
pointing to one of its LAN-facing interfaces.
If more than one IP address are to be returned in an Encrypted DNS
server option, these addresses are ordered in the preference for use
by the client.
Because DoT and DoQ may make use of customized port numbers instead
of default ones, the Encrypted DNS server options are designed to
return alternate port numbers.
The DNS client establishes an encrypted DNS session with the
discovered DNS IP address(es) and port number, and uses the mechanism
discussed in Section 8 of [RFC8310] to authenticate the DNS server
certificate using the authentication domain name conveyed in the
encrypted DNS options.
If the encrypted DNS 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 Encrypted DNS Options
The DHCPv6 Encrypted DNS ADN option is used to configure an
authentication domain name of the encrypted DNS server. The format
of this option is shown in Figure 7.
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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_ENC_ADN | Option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Enc DNS Type | Unassigned |
+---------------+-----------------------------------------------+
| |
~ DNS Authentication Domain Name ~
| |
+---------------------------------------------------------------+
Figure 7: DHCPv6 Encrypted DNS ADN Option
The fields of the option shown in Figure 7 are as follows:
o Option-code: OPTION_V6_ENC_ADN (TBA1, see Section 10.1)
o Option-length: Length of the enclosed data in octets.
o Encr DNS Types (Encrypted DNS Types): Indicates the type(s) of the
encrypted DNS server conveyed in this attribute. The format of
this 8-bit field is shown in Figure 8.
+-+-+-+-+-+-+-+-+
|U|U|U|U|U|Q|H|T|
+-+-+-+-+-+-+-+-+
Figure 8: Encrypted DNS Types
T: If set, this bit indicates that the server supports DoT
[RFC7858].
H: If set, this bit indicates that the server supports DoH
[RFC8484].
Q: If set, this bit indicates that the server supports DoQ
[I-D.ietf-dprive-dnsoquic].
U: Unassigned bits. These bits MUST be unset by the sender.
Associating a meaning with an unassigned bit can be done via
Standards Action [RFC8126].
In a request, these bits are assigned to indicate the requested
encrypted DNS server type(s) by the client. In a response, these
bits are set as a function of the encrypted DNS supported by the
server and the requested encrypted DNS server type(s).
To keep the packet small, if more than one encrypted DNS type
(e.g., both DoH and DoT) are to be returned to a requesting client
and the same ADN is used for these types, the corresponding bits
must be set in the 'Encrypted DNS Types' field of the same option
instance in a response. For example, if the client requested DoH
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and DoT and the server supports both with the same ADN, then both
T and H bits must be set.
o Authentication Domain Name: A fully qualified domain name of the
encrypted DNS server. This field is formatted as specified in
Section 10 of [RFC8415].
An example of the Authentication Domain Name encoding is shown in
Figure 9. This example conveys the FQDN "doh1.example.com.".
+------+------+------+------+------+------+------+------+------+
| 0x04 | d | o | h | 1 | 0x07 | e | x | a |
+------+------+------+------+------+------+------+------+------+
| m | p | l | e | 0x03 | c | o | m | 0x00 |
+------+------+------+------+------+------+------+------+------+
Figure 9: An example of the authentication-domain-name Encoding
The DHCPv6 Encrypted DNS Address option is used to configure a list
of IP addresses and a port number of the encrypted DNS server. The
format of this option is shown in Figure 10.
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_ENC_ADD | Option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Enc DNS Type | Unassigned | Port Number |
+---------------+---------------+-------------------------------+
| |
| IPv6 Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: DHCPv6 Encrypted DNS Address Option
The fields of the option shown in Figure 10 are as follows:
o Option-code: OPTION_V6_ENC_ADD (TBA2, see Section 10.1)
o Option-length: Length of the enclosed data in octets.
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o Encr DNS Types (Encrypted DNS Types): Indicates the type(s) of the
encrypted DNS server conveyed in this attribute. The format of
this 8-bit field is shown in Figure 8. In a request, these bits
are set to indicate the requested encrypted DNS server type(s) by
the client. In a response, these bits are set as a function of
the encrypted DNS supported by the server and the requested
encrypted DNS server type(s).
o Unassigned: These bits MUST be unset by the sender. Associating a
meaning with an unassigned bit can be done via Standards Action
[RFC8126].
o Port Number: If not null, Indicates the port number to be used for
the encrypted DNS. If this field is to zero, this indicates that
default port numbers should be used. As a reminder, the default
port number is 853 for DoT and 443 for DoH.
o IPv6 Address(es): Indicates one or more IPv6 addresses to reach
the encrypted DNS server.
Multiple instances of OPTION_V6_ENC_ADN (or OPTION_V6_ENC_ADD) may be
returned to a DHCPv6 client; each pointing to a distinct encrypted
DNS server type.
To discover an encrypted DNS server, the DHCPv6 client includes
OPTION_V6_ENC_ADN and OPTION_V6_ENC_ADD in an Option Request Option
(ORO), as in Sections 18.2.1, 18.2.2, 18.2.4, 18.2.5, 18.2.6, and
21.7 of [RFC8415]. The DHCPv6 client sets the Encrypted DNS Types
field to the requested encrypted DNS server type(s).
If the DHCPv6 client requested more than one encrypted DNS server
type, the DHCP client MUST be prepared to receive multiple
OPTION_V6_ENC_ADN (or OPTION_V6_ENC_ADD) options; each option is to
be treated as a separate encrypted DNS server.
If more than one encrypted DNS server types is supported on the same
IP address and default port numbers are used, one instance of
OPTION_V6_ENC_ADD option with the appropriate bits set in "Encr DNS
Types" field should be returned by the DHCP server.
4.2. DHCP Encrypted DNS Option
The DHCP Encrypted DNS option is used to configure an authentication
domain name, a list of IP addresses, and a port number of the
encrypted DNS server. The format of this option is illustrated in
Figure 11.
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBA3 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encr DNS Types| Num Addresses |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ IPv4 Address(es) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Authentication Domain Name ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: DHCP Encrypted DNS Option
The fields of the option shown in Figure 11 are as follows:
o Code: OPTION_V4_ENC_DNS (TBA3, see Section 10.2).
o Length: Length of the enclosed data in octets.
o Encr DNS Types (Encrypted DNS Types): Indicates the type(s) of the
encrypted DNS server conveyed in this attribute. The format of
this field is shown in Figure 8.
o Num Addresses: Indicates the number of included IPv4 addresses.
o Port Number: If not null, it indicates the port number to be used
for the encrypted DNS. A null value indicates that default port
numbers are used. As a reminder, the default port number is 853
for DoT and 443 for DoH.
o IPv4 Addresses: Indicates one or more IPv4 addresses to reach the
encrypted DNS server. The format of this field is shown in
Figure 12.
0 8 16 24 32 40 48
+-----+-----+-----+-----+-----+-----+--
| a1 | a2 | a3 | a4 | a1 | a2 | ...
+-----+-----+-----+-----+-----+-----+--
IPv4 Address 1 IPv4 Address 2 ...
This format assumes that an IPv4 address is encoded as a1.a2.a3.a4.
Figure 12: Format of the IPv4 Addresses Field
o Authentication Domain Name: The domain name of the DoH/DoT server.
This field is formatted as specified in Section 10 of [RFC8415].
The format of this field is shown in Figure 13.
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+-----+-----+-----+-----+-----+--
| s1 | s2 | s3 | s4 | s5 | ...
+-----+-----+-----+-----+-----+--
Authentication Domain Name
The values s1, s2, s3, etc. represent the domain name labels in the
domain name encoding.
Figure 13: Format of the Authentication Domain Name Field
OPTION_V4_ENC_DNS is a concatenation-requiring option. As such, the
mechanism specified in [RFC3396] MUST be used if OPTION_V4_ENC_DNS
exceeds the maximum DHCP option size of 255 octets.
To discover an encrypted DNS server, the DHCP client requests the
Encrypted DNS server by including OPTION_V4_ENC_DNS in a Parameter
Request List option [RFC2132]. The DHCP client sets the Encrypted
DNS Types field to the requested encrypted DNS server.
If the DHCP client requested more than one encrypted DNS server type,
the DHCP client MUST be prepared to receive multiple DHCP
OPTION_V4_ENC_DNS options; each option is to be treated as a separate
encrypted DNS server.
4.3. IPv6 RA Encrypted DNS Options
This section defines two Neighbor Discovery [RFC4861]: IPv6 Router
Advertisement (RA) Encrypted DNS ADN option and IPv6 RA Encrypted DNS
Address option.
The IPv6 RA Encrypted DNS ADN option is used to configure an
authentication domain name of the encrypted DNS server. The format
of this option is illustrated in Figure 14.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBA3 | Length | Encr DNS Types| Unassigned |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Authentication Domain Name :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: RA Encrypted DNS ADN Option
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The fields of the option shown in Figure 14 are as follows:
o Type: 8-bit identifier of the Encrypted DNS Option as assigned by
IANA (TBA3, see Section 10.3).
o Length: 8-bit unsigned integer. The length of the option
(including the Type and Length fields) is in units of 8 octets.
o Encr DNS Types (Encrypted DNS Types): Indicates the type(s) of the
encrypted DNS server conveyed in this attribute. The format of
this field is shown in Figure 8.
o Unassigned: 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
discovered Authentication Domain Name is valid.
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 this Authentication Domain Name MUST no
longer be used.
o Authentication Domain Name: The domain name of the encrypted DNS
server. This field is formatted as specified in Section 10 of
[RFC8415].
This field MUST be padded with zeros so that its size is a
multiple of 8 octets.
The IPv6 RA Encrypted DNS Address option is used to configure a port
number and a list of IPv6 addresses of the encrypted DNS server. The
format of this option is illustrated in Figure 15. All of the
addresses share the same Lifetime value. Simialr to [RFC8106], if it
is desirable to have different Lifetime values per IP address,
multiple Encrypted DNS Address options may be used.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBA5 | Length | Unassigned |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encr DNS Types| Unassigned | Port Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: IPv6 Address(es) :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: RA Encrypted DNS Address Option
The fields of the RA Encrypted DNS Address option shown in Figure 15
are as follows:
o Type: 8-bit identifier of the Encrypted DNS Address Option as
assigned by IANA (TBA5, see Section 10.3).
o Length: 8-bit unsigned integer. The length of the option
(including the Type and Length fields) is in units of 8 octets.
o Unassigned: 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
discovered encrypted DNS IPv6 addresses are valid.
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 these IPv6 addresses MUST no longer be
used.
o Port Number: If not null, it indicates the port number to be used
for the encrypted DNS. A null value indicates that default port
numbers must be used. As a reminder, the default port number is
853 for DoT and 443 for DoH.
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o Encr DNS Types (Encrypted DNS Types): Indicates the type(s) of the
encrypted DNS server conveyed in this attribute. The format of
this field is shown in Figure 8.
o IPv6 Address(es) : One or more IPv6 addresses of the encrypted DNS
server. Link-local addresses MAY be used.
5. DoH URI Templates
DoH servers may support more than one URI Template [RFC8484]. Also,
if the resolver hosts several DoH services (e.g., no-filtering,
blocking adult content, blocking malware), these services can be
discovered as templates. The following discusses a mechanism for a
DoH client to retrieve the list of supported templates by a DoH
server.
Upon discovery of a DoH resolver (Section 4), the DoH client may
contact that DoH server to retrieve the list of supported DoH
services using the well-known URI. DoH clients re-iterates that
request regularly to retrieve an updated list of supported DoH
services.
Let's suppose that a host has discovered an encrypted DNS server that
is DoH-capable. The host has also discovered the following
information:
o ADN: doh.example.com
o Locator: 2001:db8:1::1
The client requests "https://doh.example.com/.well-known/resinfo" to
retrieve the list of the URI Templates associated with this
discovered server.
Alternatively, dedicated DHCP/RA options may be defined to convey an
URI template. An example of such option is depicted in Figure 16.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_V6_DOH_TEMPLATE | Option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ uri-template-data ~
| . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Each instance of the uri-template-data is formatted as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
| uri-template-len | URI Template |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
Figure 16: Example of a DHCPv6 URI Template Option
Note: More feedback form the WG is needed to decide which approach
to follow.
How a DoH client makes use of the configured DoH services is out of
scope of this document.
6. Make Use of Discovered Encrypted DNS Server
Even if the use of a discovered encrypted DNS server is beyond the
discovery process and falls under encrypted server selection, the
following discusses typical conditions under which discovered
encrypted DNS server can be used.
o If the DNS server's IP address discovered by using DHCP/RA is
preconfigured in the OS or Browser as a verified resolver (e.g.,
part of an auto-upgrade program such as [Auto-upgrade]), the DNS
client auto-upgrades to use the preconfigured encrypted DNS server
tied to the discovered DNS server IP address. In such a case the
DNS client will perform additional checks out of band, such as
confirming that the Do53 IP address and the encrypted DNS server
are owned and operated by the same organisation.
o Similarly, if the ADN conveyed in DHCP/RA (Section 4) is
preconfigured in the OS or browser as a verified resolver, the DNS
client auto-upgrades to establish an encrypted a DoH/DoT/DoQ
session with the ADN.
In such case, the DNS client matches the domain name in the
Encrypted DNS DHCP/RA option with the 'DNS-ID' identifier type
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within subjectAltName entry in the server certificate conveyed in
the TLS handshake.
7. Hosting Encrypted DNS Forwarder in the CPE
7.1. Managed CPEs
The following mechanisms can be used to host an encrypted DNS
forwarder in a managed CPE (Section 3.1).
7.1.1. ACME
The ISP can assign a unique FQDN (e.g., cpe1.example.com) and a
domain-validated public certificate to the encrypted DNS forwarder
hosted on the CPE. Automatic Certificate Management Environment
(ACME) [RFC8555] can be used by the ISP to automate certificate
management functions such as domain validation procedure, certificate
issuance and certificate revocation.
The managed CPE should support a configuration parameter to instruct
the CPE whether it has to relay the encrypted DNS server received
from the ISP's network or has to announce itself as a forwarder
within the local network. The default behavior of the CPE is to
supply the encrypted DNS server received from the ISP's network.
7.1.2. Auto-Upgrade Based on Domains and their Subdomains
If the ADN conveyed in DHCP/RA (Section 4) is pre-configured in
popular OSes or browsers as a verified resolver and the auto-upgrade
(Section 6) is allowed for both the pre-configured ADN and its sub-
domains, the encrypted DNS client will learn the local encrypted DNS
forwarder using DHCP/RA and auto-upgrade because the left-most label
of the pre-configured ADN would match the subjectAltName value in the
server certificate. Concretely, the CPE can communicate the ADN of
the local DoH forwarder (Section 7.1.1) to internal hosts using DHCP/
RA (Section 4).
Let's suppose that "example.net" is pre-configured as a verified
resolved in the browser or OS. If the encrypted DNS client discovers
a local forwarder "cpe1-internal.example.net", the encrypted DNS
client will auto-upgrade because the pre-configured ADN would match
subjectAltName value "cpe1-internal.example.net" of type dNSName. As
shown in Figure 17, the auto-upgrade to a rogue server advertising
"rs.example.org" will fail.
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Rogue Server
| |
X<==DHCP=======|
| {ADN= |
| rs.example.org, @rs}
| | --,--,-
| ,+-,--+--. ,/ ISP \.
| ,-' `-. ,-' `-.
DoH/DoT --( LAN CPE----( S (@1) )
capable client `-. ,-'| `-. ,-'
| `--'--'--' | `--'--'--'
|<========DHCP========>|
|{ADN= |
| cpe1-internal.example.net, @i}
|
|<========DoH=========>|
| |
Legend:
* S: DoH/DoT server
* @1: IP address of S
* @i: internal IP address of the CPE
* @rs: IP address of a rogue server
Figure 17: A Simplified Example of Auto-upgrade based on Sub-domains
7.2. Unmanaged CPEs
The approach specified in Section 7.1 does not apply for hosting a
DNS forwarder in an unmanaged CPE.
The unmanaged CPE administrator (referred to as administrator) can
host an encrypted DNS forwarder on the unmanaged CPE. This assumes
the following:
o The encrypted DNS server certificate is managed by the entity in-
charge of hosting the encrypted DNS forwarder.
Alternatively, a security service provider can assign a unique
FQDN to the CPE. The encrypted DNS forwarder will act like a
private encrypted DNS server only be accessible from within the
home network.
o The encrypted DNS forwarder will either be configured to use the
ISP's or a 3rd party encrypted DNS server.
o The unmanaged CPE will advertise the encrypted DNS forwarder ADN
using DHCP/RA to internal hosts.
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Figure 18 illustrates an example of an unmanaged CPE hosting a
forwarder which connects to a 3rd party encrypted DNS server. In
this example, the DNS information received from the managed CPE (and
therefore from the ISP) is ignored by the Internal CPE hosting the
forwarder.
,--,--,--. ,--,
,' Internal Managed ,-' '- 3rd Party
Host--( Network#A CPE--------CPE------( ISP )--- DNS Server
| `. ,-'| | `-. -' |
| `-'--'--' | |<==DHCP==>|`--' |
| |<==DHCP==>| | |
|<======DHCP=======>| | |
| {RI, @i} | |
|<==Encrypted DNS==>|<==========Encrypted DNS==========>|
Legend:
* @i: IP address of the DNS forwarder hosted in the Internal
CPE.
Figure 18: Example of an Internal CPE Hosting a Forwarder
8. Legacy CPEs
Hosts serviced by legacy CPEs that can't be upgraded to support the
options defined in Section 4 won't be able to learn the encrypted DNS
server hosted by the ISP, in particular. If the ADN is not
discovered using DHCP/RA, such hosts will have to fallback to use the
special-use domain name defined in [I-D.pp-add-resinfo] to discover
the encrypted DNS server and to retrieve the list of supported DoH
services using the RESINFO RRtype [I-D.pp-add-resinfo].
If the Do53 and Encrypted DNS servers are hosted on different public
IP addresses, the DNS server certificate can include the IP address
of the Do53 server in the subjectAltName extension. After validating
the server certificate, the client can retrieve the IP address in the
certificate to identify that both Do53 and Encrypted DNS servers are
operated by the same entity.
If the Do53 and Encrypted DNS server are hosted on a private IP
address, they should use the same private IP address to prove to the
client they are operated by the same entity.
The DHCP/RA option to discover ADN takes precedence over special-use
domain name since the special-use domain name is susceptible to both
internal and external attacks whereas DHCP/RA is only vulnerable to
internal attacks.
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9. Security Considerations
9.1. Spoofing Attacks
Because DHCP/RA messages are not encrypted or protected against
modification within the LAN, their content can be spoofed or modified
by active attackers (e.g., compromised devices within the home
network). An active attacker (Section 3.3 of [RFC3552]) can spoof
the DHCP/RA response to provide the attacker's Encrypted DNS server.
Note that such an attacker can launch other attacks as discussed in
Section 22 of [RFC8415]. The attacker can get a domain name, domain-
validated public certificate from a CA, host an Encrypted DNS server
and claim the best DNS privacy preservation policy. Also, an
attacker can use a public IP address, get an 'IP address'-validated
public certificate from a CA, host an Encryptd DNS server and claim
the best DNS privacy preservation policy.
Attacks of spoofed or modified DHCP responses and RA messages by
attackers within the home network may be mitigated by making use of
the following mechanisms:
o DHCPv6-Shield described in [RFC7610], the CPEs discards DHCP
response messages received from any local endpoint.
o RA-Guard described in [RFC7113], the CPE discards RAs messages
received from any local endpoint.
o Source Address Validation Improvement (SAVI) solution for DHCP
described in [RFC7513], the CPE filters packets with forged source
IP addresses.
Encrypted DNS 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], particularly the authentication domain name in the
Encrypted DNS 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).
Encrypted DNS connections received from outside the home network MUST
be discarded by the encrypted DNS forwarder in the CPE. This
behavior adheres to REQ#8 in [RFC6092]; it MUST apply for both IPv4
and IPv6.
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9.2. Deletion Attacks
If the DHCP responses or RAs are dropped by the attacker, the client
can fallback to use a pre-configured encrypted DNS server. However,
the use of policies to select servers is out of scope of this
document.
Note that deletion attack is not specific to DHCP/RA.
9.3. Passive Attacks
A passive attacker (Section 3.2 of [RFC3552]) can identify a host is
using DHCP/RA to discover an encrypted DNS server and can infer that
host is capable of using DoH/DoT/DoQ to encrypt DNS messages.
However, a passive attacker cannot spoof or modify DHCP/RA messages.
9.4. Wireless Security - Authentication Attacks
Wireless LAN (WLAN) as frequently deployed in home networks is
vulnerable to various attacks (e.g., [Evil-Twin], [Krack],
[Dragonblood]). Because of these attacks, only cryptographically
authenticated communications are trusted on WLANs. This means
information provided by such networks via DHCP, DHCPv6, or RA (e.g.,
NTP server, DNS server, default domain) are untrusted because DHCP
and RA are not authenticated.
With the current deployments (2020), the pre-shared-key is the same
for all clients that connect to the same WLAN. This results in the
key being shared to attackers resulting in security breach. Man-in-
the-middle attacks are possible within home networks because WLAN
authentication lacks peer entity authentication.
This leads to the need for provisioning unique credentials for
different clients. Endpoints can be provisioned with unique
credentials (username and password, typically) provided by the home
network administraor to mutually authenticate to the home WLAN Access
Point (e.g., 802.1x Wireless User Authentication on OpenWRT [dot1x],
EAP-pwd [RFC8146]). Not all of endpoint devices (e.g., IoT devices)
support 802.1x supplicant and need an alternate mechanism to connect
to the home network. To address this limitation, unique pre-shared
keys can be created for each such device and WPA-PSK is used (e.g.,
[PSK]).
10. IANA Considerations
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10.1. DHCPv6 Options
IANA is requested to assign the following new DHCPv6 Option Code in
the registry maintained in [DHCPV6].
+-------+-------------------+---------+------------+----------------+
| Value | Description | Client | Singleton | Reference |
| | | ORO | Option | |
+-------+-------------------+---------+------------+----------------+
| TBA1 | OPTION_V6_ENC_ADN | Yes | No | [ThisDocument] |
| TBA2 | OPTION_V6_ENC_ADD | Yes | No | [ThisDocument] |
+-------+-------------------+---------+------------+----------------+
10.2. DHCP Option
IANA is requested to assign the following new DHCP Option Code in the
registry maintained in [BOOTP].
+------+------------------+-------+----------------+----------------+
| Tag | Name | Data | Meaning | Reference |
| | | Length| | |
+------+------------------+-------+----------------+----------------+
| TBA3 | OPTION_V4_ENC_DNS| N | Encrypted DNS | [ThisDocument] |
| | | | Server | |
+------+------------------+-------+----------------+----------------+
10.3. RA Options
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 [ND].
+------+----------------------------------+----------------+
| Type | Description | Reference |
+------+----------------------------------+----------------+
| TBA4 | DNS Encrypted DNS ADN Option | [ThisDocument] |
| TBA5 | DNS Encrypted DNS Address Option | [ThisDocument] |
+------+----------------------------------+----------------+
11. Acknowledgements
Many thanks to Christian Jacquenet for the review.
Thanks to Tommy Jensen, Stephen Farrell, Martin Thomson, Vittorio
Bertola, Stephane Bortzmeyer, Ben Schwartz, and Iain Sharp for the
comments.
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Thanks to Mark Nottingham for the feedback on HTTP redirection.
The use of DHCP to retrieve an authentication domain name was
discussed in Section 7.3.1 of [RFC8310] and
[I-D.pusateri-dhc-dns-driu].
12. References
12.1. 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>.
[RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the
Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396,
DOI 10.17487/RFC3396, November 2002,
<https://www.rfc-editor.org/info/rfc3396>.
[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>.
[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>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.
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[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>.
12.2. Informative References
[Auto-upgrade]
The Unicode Consortium, "DoH providers: criteria, process
for Chrome", <docs.google.com/document/
d/128i2YTV2C7T6Gr3I-81zlQ-_Lprnsp24qzy_20Z1Psw/edit>.
[BOOTP] , <https://www.iana.org/assignments/bootp-dhcp-parameters/
bootp-dhcp-parameters.xhtml#options>.
[DHCPV6] , <https://www.iana.org/assignments/dhcpv6-parameters/
dhcpv6-parameters.xhtml#dhcpv6-parameters-2>.
[dot1x] Cisco, "Basic 802.1x Wireless User Authentication",
<https://openwrt.org/docs/guide-user/network/wifi/
wireless.security.8021x>.
[DPP] The Wi-Fi Alliance, "Device Provisioning Protocol
Specification", <https://www.wi-fi.org/file/device-
provisioning-protocol-specification>.
[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.box-add-requirements]
Box, C., Pauly, T., Wood, C., and T. Reddy.K,
"Requirements for Adaptive DNS Discovery", draft-box-add-
requirements-00 (work in progress), September 2020.
[I-D.ietf-dnsop-terminology-ter]
Hoffman, P., "Terminology for DNS Transports and
Location", draft-ietf-dnsop-terminology-ter-02 (work in
progress), August 2020.
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[I-D.ietf-dprive-dnsoquic]
Huitema, C., Mankin, A., and S. Dickinson, "Specification
of DNS over Dedicated QUIC Connections", draft-ietf-
dprive-dnsoquic-00 (work in progress), April 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.pp-add-resinfo]
Sood, P. and P. Hoffman, "DNS Resolver Information Self-
publication", draft-pp-add-resinfo-02 (work in progress),
June 2020.
[I-D.pusateri-dhc-dns-driu]
Pusateri, T. and W. Toorop, "DHCPv6 Options for private
DNS Discovery", draft-pusateri-dhc-dns-driu-00 (work in
progress), July 2018.
[Krack] The Unicode Consortium, "Key Reinstallation Attacks",
2017, <https://www.krackattacks.com/>.
[ND] , <http://www.iana.org/assignments/icmpv6-parameters/
icmpv6-parameters.xhtml#icmpv6-parameters-5>.
[PSK] Cisco, "Identity PSK Feature Deployment Guide",
<https://www.cisco.com/c/en/us/td/docs/wireless/
controller/technotes/8-5/
b_Identity_PSK_Feature_Deployment_Guide.html>.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<https://www.rfc-editor.org/info/rfc3552>.
[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>.
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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>.
[RFC6731] Savolainen, T., Kato, J., and T. Lemon, "Improved
Recursive DNS Server Selection for Multi-Interfaced
Nodes", RFC 6731, DOI 10.17487/RFC6731, December 2012,
<https://www.rfc-editor.org/info/rfc6731>.
[RFC7113] Gont, F., "Implementation Advice for IPv6 Router
Advertisement Guard (RA-Guard)", RFC 7113,
DOI 10.17487/RFC7113, February 2014,
<https://www.rfc-editor.org/info/rfc7113>.
[RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
June 2014, <https://www.rfc-editor.org/info/rfc7250>.
[RFC7513] Bi, J., Wu, J., Yao, G., and F. Baker, "Source Address
Validation Improvement (SAVI) Solution for DHCP",
RFC 7513, DOI 10.17487/RFC7513, May 2015,
<https://www.rfc-editor.org/info/rfc7513>.
[RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-Shield:
Protecting against Rogue DHCPv6 Servers", BCP 199,
RFC 7610, DOI 10.17487/RFC7610, August 2015,
<https://www.rfc-editor.org/info/rfc7610>.
[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>.
[RFC7969] Lemon, T. and T. Mrugalski, "Customizing DHCP
Configuration on the Basis of Network Topology", RFC 7969,
DOI 10.17487/RFC7969, October 2016,
<https://www.rfc-editor.org/info/rfc7969>.
[RFC8146] Harkins, D., "Adding Support for Salted Password Databases
to EAP-pwd", RFC 8146, DOI 10.17487/RFC8146, April 2017,
<https://www.rfc-editor.org/info/rfc8146>.
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[RFC8305] Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2:
Better Connectivity Using Concurrency", RFC 8305,
DOI 10.17487/RFC8305, December 2017,
<https://www.rfc-editor.org/info/rfc8305>.
[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>.
[RFC8489] Petit-Huguenin, M., Salgueiro, G., Rosenberg, J., Wing,
D., Mahy, R., and P. Matthews, "Session Traversal
Utilities for NAT (STUN)", RFC 8489, DOI 10.17487/RFC8489,
February 2020, <https://www.rfc-editor.org/info/rfc8489>.
[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",
December 2018, <https://www.broadband-
forum.org/technical/download/TR-069.pdf>.
[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
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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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