Outsourcing Home Network Authoritative Naming Service
draft-ietf-homenet-front-end-naming-delegation-08
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9526.
|
|
|---|---|---|---|
| Authors | Daniel Migault , Ralf Weber , Ray Hunter , Chris Griffiths | ||
| Last updated | 2019-05-10 | ||
| Replaces | draft-mglt-homenet-front-end-naming-delegation | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-ietf-homenet-front-end-naming-delegation-08
Homenet D. Migault
Internet-Draft Ericsson
Intended status: Informational R. Weber
Expires: November 11, 2019 Nominum
R. Hunter
Globis Consulting BV
C. Griffiths
W. Cloetens
SoftAtHome<
May 10, 2019
Outsourcing Home Network Authoritative Naming Service
draft-ietf-homenet-front-end-naming-delegation-08
Abstract
Designation of services and devices of a home network is not user
friendly, and mechanisms should enable a user to designate services
and devices inside a home network using names.
In order to enable internal communications while the home network
experiments Internet connectivity shortage, the naming service should
be hosted on a device inside the home network. On the other hand,
home networks devices have not been designed to handle heavy loads.
As a result, hosting the naming service on such home network device,
visible on the Internet exposes this device to resource exhaustion
and other attacks, which could make the home network unreachable, and
most probably would also affect the internal communications of the
home network.
As result, home networks may prefer not serving the naming service
for the Internet, but instead prefer outsourcing it to a third party.
This document describes a mechanisms that enables the Home Network
Authority (HNA) to outsource the naming service to the Outsourcing
Infrastructure.
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/.
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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 November 11, 2019.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Architecture Description . . . . . . . . . . . . . . . . . . 6
4.1. Architecture Overview . . . . . . . . . . . . . . . . . . 6
4.2. Example: Homenet Zone . . . . . . . . . . . . . . . . . . 8
4.3. Example: HNA necessary parameters for outsourcing . . . . 10
5. Synchronization between HNA and the Synchronization Server . 11
5.1. Synchronization with a Hidden Primary . . . . . . . . . . 12
5.2. Securing Synchronization . . . . . . . . . . . . . . . . 13
5.3. HNA Security Policies . . . . . . . . . . . . . . . . . . 14
6. DNSSEC compliant Homenet Architecture . . . . . . . . . . . . 14
6.1. Zone Signing" . . . . . . . . . . . . . . . . . . . . . . 15
6.2. Secure Delegation" . . . . . . . . . . . . . . . . . . . 16
7. Handling Different Views . . . . . . . . . . . . . . . . . . 17
7.1. Misleading Reasons for Local Scope DNS Zone" . . . . . . 17
7.2. Consequences" . . . . . . . . . . . . . . . . . . . . . . 18
7.3. Guidance and Recommendations . . . . . . . . . . . . . . 19
7.4. Homenet Reverse Zone . . . . . . . . . . . . . . . . . . 19
8. Renumbering . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.1. Hidden Primary . . . . . . . . . . . . . . . . . . . . . 20
8.2. Synchronization Server . . . . . . . . . . . . . . . . . 21
9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 22
10. Security Considerations . . . . . . . . . . . . . . . . . . . 23
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10.1. Names are less secure than IP addresses . . . . . . . . 23
10.2. Names are less volatile than IP addresses . . . . . . . 23
10.3. DNS Reflection Attacks . . . . . . . . . . . . . . . . . 24
10.4. "Reflection Attack involving the Hidden Primary . . . . 24
10.5. Reflection Attacks involving the Synchronization Server 25
10.6. Reflection Attacks involving the Public Authoritative
Servers . . . . . . . . . . . . . . . . . . . . . . . . 26
10.7. Flooding Attack . . . . . . . . . . . . . . . . . . . . 26
10.8. Replay Attack . . . . . . . . . . . . . . . . . . . . . 27
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
12. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 28
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 28
13.1. Normative References . . . . . . . . . . . . . . . . . . 28
13.2. Informative References . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
1. Requirements notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Introduction
IPv6 provides global end to end IP reachability. End users prefer to
use names instead of long and complex IPv6 addresses when accessing
services hosted in the home network.
Customer Edge Routers and other Customer Premises Equipment (CPEs)
are already providing IPv6 connectivity to the home network, and
generally provide IPv6 addresses or prefixes to the nodes of the home
network. In addition, [RFC7368] recommends that home networks be
resilient to connectivity disruption from the ISP. This could be
achieved by a dedicated device inside the home network that builds,
serves or manage the Homenet Zone, thus providing bindings between
names and IP addresses.
CPEs are of course good candidates to manage the binding between
names and IP addresses of nodes. However, this could also be
performed by another device in the home network that is not a CPE.
In addition, a given home network may have multiple nodes that may
implement this functionality. Since management of the Homenet Zone
involves DNS specific mechanisms that cannot be distributed (primary
server), when multiple nodes can potentially manage the Homenet Zone,
a single node needs to be selected. This selected node is designated
as the Homenet Naming Authority (HNA).
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CPEs, Homenet Naming Authority, as well as home network devices are
usually low powered devices not designed not for terminating heavy
traffic. As a result, hosting an authoritative DNS service on the
Internet may expose the home network to resource exhaustion and other
attacks. This may isolate the home network from the Internet and
also impact the services hosted by the such an home network device,
thus affecting overall home network communication.
In order to avoid resource exhaustion and other attacks, this
document describes an architecture that outsources the authoritative
naming service of the home network. More specifically, the Homenet
Naming Authority builds the Homenet Zone and outsources it to an
Outsourcing Infrastructure. The Outsourcing Infrastructure in in
charge of publishing the corresponding Public Homenet Zone on the
Internet.
Section 4.1 provides an architecture description that describes the
relation between the Homenet Naming Authority and the Outsourcing
Architecture. In order to keep the Public Homenet Zone up-to-date
Section 5 describes how the Homenet Zone and the Public Homenet Zone
can be synchronized. The proposed architecture aims at deploying
DNSSEC, and the Public Homenet Zone is expected to be signed with a
secure delegation. The zone signing and secure delegation may be
performed either by the Homenet Naming Authority or by the
Outsourcing Infrastructure. Section 6 discusses these two
alternatives. Section 7 discusses the consequences of publishing
multiple representations of the same zone also commonly designated as
views. This section provides guidance to limit the risks associated
with multiple views. Section 7.4 discusses management of the reverse
zone. Section 8 discusses how renumbering should be handled.
Finally, Section 9 and Section 10 respectively discuss privacy and
security considerations when outsourcing the Homenet Zone.
3. Terminology
o Customer Premises Equipment: (CPE) is a router providing
connectivity to the home network.
o Homenet Naming Authority: (HNA) is a home network node responsible
to manage the Homenet Zone. This includes building the Homenet
Zone, as well as managing the distribution of that Homenet Zone
through the Outsourcing Infrastructure.
o Registered Homenet Domain: is the Domain Name associated to the
home network.
o Homenet Zone: is the DNS zone associated with the home network.
It is designated by its Registered Homenet Domain. This zone is
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built by the HNA and contains the bindings between names and IP
addresses of the nodes in the home network. The HNA synchronizes
the Homenet Zone with the Synchronization Server via a hidden
primary / secondary architecture. The Outsourcing Infrastructure
may process the Homenet Zone - for example providing DNSSEC
signing - to generate the Public Homenet Zone. This Public
Homenet Zone is then transmitted to the Public Authoritative
Server(s) that publish it on the Internet.
o Public Homenet Zone: is the public version of the Homenet Zone.
It is expected to be signed with DNSSEC. It is hosted by the
Public Authoritative Server(s), which are authoritative for this
zone. The Public Homenet Zone and the Homenet Zone might be
different. For example some names might not become reachable from
the Internet, and thus not be hosted in the Public Homenet Zone.
Another example of difference may also occur when the Public
Homenet Zone is signed whereas the Homenet Zone is not signed.
o Outsourcing Infrastructure: is the combination of the
Synchronization Server and the Public Authoritative Server(s).
o Public Authoritative Servers: are the authoritative name servers
hosting the Public Homenet Zone. Name resolution requests for the
Homenet Domain are sent to these servers. For resiliency the
Public Homenet Zone SHOULD be hosted on multiple servers.
o Synchronization Server: is the server with which the HNA
synchronizes the Homenet Zone. The Synchronization Server is
configured as a secondary and the HNA acts as primary. There MAY
be multiple Synchronization Servers, but the text assumes a single
server. In addition, the text assumes the Synchronization Server
is a separate entity. This is not a requirement, and when the HNA
signs the zone, the synchronization function might also be
operated by the Public Authoritative Servers.
o Homenet Reverse Zone: The reverse zone file associated with the
Homenet Zone.
o Reverse Public Authoritative Servers: are the authoritative name
server(s) hosting the Public Homenet Reverse Zone. Queries for
reverse resolution of the Homenet Domain are sent to this server.
Similarly to Public Authoritative Servers, for resiliency, the
Homenet Reverse Zone SHOULD be hosted on multiple servers.
o Reverse Synchronization Server: is the server with which the HNA
synchronizes the Homenet Reverse Zone. It is configured as a
secondary and the HNA acts as primary. There MAY be multiple
Reverse Synchronization Servers, but the text assumes a single
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server. In addition, the text assumes the Reverse Synchronization
Server is a separate entity. This is not a requirement, and when
the HNA signs the zone, the synchronization function might also be
operated by the Reverse Public Authoritative Servers.
o Hidden Primary: designates the primary server of the HNA, that
synchronizes the Homenet Zone with the Synchronization Server. A
primary / secondary architecture is used between the HNA and the
Synchronization Server. The hidden primary is not expected to
serve end user queries for the Homenet Zone as a regular primary
server would. The hidden primary is only known to its associated
Synchronization Server.
4. Architecture Description
Architecture Description This section describes the architecture for
outsourcing the authoritative naming service from the HNA to the
Outsourcing Infrastructure. Section 4.1 describes the architecture,
Section 4.2 and Section 4.3 illustrates this architecture and shows
how the Homenet Zone should be built by the HNA. It also lists the
necessary parameters the HNA needs to be able to outsource the
authoritative naming service. These two sections are informational
and non-normative.
4.1. Architecture Overview
Figure 1 provides an overview of the architecture.
The home network is designated by the Registered Homenet Domain Name
- example.com in Figure 1. The HNA builds the Homenet Zone
associated with the home network. How the Homenet Zone is built is
out of the scope of this document. The HNA may host or interact with
multiple services to determine name-to-address mappings, such as a
web GUI, DHCP [RFC6644] or mDNS [RFC6762]. These services may
coexist and may be used to populate the Homenet Zone. This document
assumes the Homenet Zone has been populated with domain names that
are intended to be publicly published and that are publicly
reachable. More specifically, names associated with services or
devices that are not expected to be reachable from outside the home
network or names bound to non-globally reachable IP addresses MUST
NOT be part of the Homenet Zone.
Once the Homenet Zone has been built, the HNA does not host an
authoritative naming service, but instead outsources it to the
Outsourcing Infrastructure. The Outsourcing Infrastructure takes the
Homenet Zone as an input and publishes the Public Homenet Zone. If
the HNA does not sign the Homenet Zone, the Outsourcing
Infrastructure may instead sign it on behalf of the HNA. Figure 1
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provides a more detailed description of the Outsourcing
Infrastructure, but overall, it is expected that the HNA provides the
Homenet Zone. Then the Public Homenet Zone is derived from the
Homenet Zone and published on the Internet.
As a result, DNS queries from the DNS resolvers on the Internet are
answered by the Outsourcing Infrastructure and do not reach the HNA.
Figure 1 illustrates the case of the resolution of node1.example.com.
home network +-------------------+ Internet
| |
| HNA |
| | +-----------------------+
+-------+ |+-----------------+| | Public Authoritative |
| | || Homenet Zone || | Server(s) |
| node1 | || || |+---------------------+|
| | || || || Public Homenet Zone ||
+-------+ || Homenet Domain ||=========|| ||
|| Name || ^ || (example.com) ||
node1.\ || (example.com) || | |+---------------------+|
example.com |+-----------------+| | +-----------------------+
+-------------------+ | ^ |
Synchronization | |
| |
DNSSEC resolution for node1.example.com | v
+-----------------------+
| |
| DNSSEC Resolver |
| |
+-----------------------+
Figure 1: Homenet Naming Architecture Description
The Outsourcing Infrastructure is described in Figure 2. The
Synchronization Server receives the Homenet Zone as an input. The
received zone may be transformed to output the Public Homenet Zone.
Various operations may be performed here, however this document only
considers zone signing as a potential operation. This should occur
only when the HNA outsources this operation to the Synchronization
Server. On the other hand, if the HNA signs the Homenet Zone itself,
the zone would be collected by the Synchronization Server and
directly transferred to the Public Authoritative Server(s). These
policies are discussed and detailed in Section 6 and Section 7.
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Internet
+------------------------------------------------------+
| Outsourcing Infrastructure |
+------------------------------------------------------+
+----------------------+ +----------------------+
| | | |
| Synchronization | | Public Authoritative |
| Server | | Server(s) |
| | | |
| +------------------+ | X |+--------------------+|
| | Homenet Zone | | ^ || Public Homenet Zone||
=========>| | | | || ||
^ | | | | | || ||
| | | (example.com) | | | || (example.com) ||
| | +------------------+ | | |+--------------------+|
| +----------------------+ | +----------------------+
| Homenet to Public Zone
Synchronization transformation
from the HNA
Figure 2: Outsourcing Infrastructure Description
4.2. Example: Homenet Zone
This section is not normative and intends to illustrate how the HNA
builds the Homenet Zone.
As depicted in Figure 1 and Figure 2, the Public Homenet Zone is
hosted on the Public Authoritative Server(s), whereas the Homenet
Zone is hosted on the HNA. Motivations for keeping these two zones
identical are detailed in Section 7, and this section considers that
the HNA builds the zone that will be effectively published on the
Public Authoritative Server(s). In other words "Homenet to Public
Zone transformation" is the identity also commonly designated as "no
operation" (NOP).
In that case, the Homenet Zone should configure its Name Server RRset
(NS) and Start of Authority (SOA) with the values associated with the
Public Authoritative Server(s). This is illustrated in Figure 3.
public.primary.example.net is the FQDN of the Public Authoritative
Server(s), and IP1, IP2, IP3, IP4 are the associated IP addresses.
Then the HNA should add the additional new nodes that enter the home
network, remove those that should be removed, and sign the Homenet
Zone.
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$ORIGIN example.com
$TTL 1h
@ IN SOA public.primary.example.net
hostmaster.example.com. (
2013120710 ; serial number of this zone file
1d ; secondary refresh
2h ; secondary retry time in case of a problem
4w ; secondary expiration time
1h ; maximum caching time in case of failed
; lookups
)
@ NS public.authoritative.servers.example.net
public.primary.example.net A @IP1
public.primary.example.net A @IP2
public.primary.example.net AAAA @IP3
public.primary.example.net AAAA @IP4
Figure 3: Homenet Zone
The SOA RRset is defined in [RFC1033], [RFC1035] and [RFC2308]. This
SOA is specific, as it is used for the synchronization between the
Hidden Primary and the Synchronization Server and published on the
DNS Public Authoritative Server(s)..
o MNAME: indicates the primary. In our case the zone is published
on the Public Authoritative Server(s), and its name MUST be
included. If multiple Public Authoritative Server(s) are
involved, one of them MUST be chosen. More specifically, the HNA
MUST NOT include the name of the Hidden Primary.
o RNAME: indicates the email address to reach the administrator.
[RFC2142] recommends using hostmaster@domain and replacing the '@'
sign by '.'.
o REFRESH and RETRY: indicate respectively in seconds how often
secondaries need to check the primary, and the time between two
refresh when a refresh has failed. Default values indicated by
[RFC1033] are 3600 (1 hour) for refresh and 600 (10 minutes) for
retry. This value might be too long for highly dynamic content.
However, the Public Authoritative Server(s) and the HNA are
expected to implement NOTIFY [RFC1996]. So whilst shorter refresh
timers might increase the bandwidth usage for secondaries hosting
large number of zones, it will have little practical impact on the
elapsed time required to achieve synchronization between the
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Outsourcing Infrastructure and the Hidden Master. As a result,
the default values are acceptable.
o EXPIRE: is the upper limit data SHOULD be kept in absence of
refresh. The default value indicated by [RFC1033] is 3600000
(approx. 42 days). In home network architectures, the HNA
provides both the DNS synchronization and the access to the home
network. This device may be plugged and unplugged by the end user
without notification, thus we recommend a long expiry timer.
o MINIMUM: indicates the minimum TTL. The default value indicated
by [RFC1033] is 86400 (1 day). For home network, this value MAY
be reduced, and 3600 (1 hour) seems more appropriate.
<<!-- ## Considerations on multiple Registered Homenet Domain Names
## are left for future versions When multiple Registered Homenet
Domains are used -like example.com, example.net, example.org, a DNS
Homenet Zone file per Registered Homenet Domain SHOULD be generated.
In order to synchronize the zone contents, the HNA may provide all
bindings in each zone files. As a result, any update MUST be
performed on all zone files, i.e. for all Registered Homenet Domains.
To limit thees updates when multiple Registered Homenet Domains are
involved, the HNA MAY fill all bindings in a specific zone file and
redirect all other zones to that zone. This can be achieved with
redirecting mechanisms like CNAME {{RFC2181}}, {{RFC1034}}, DNAME
{{RFC6672}} or CNAME+DNAME {{I-D.sury-dnsext-cname-dname}}. This is
an implementation issue to determine whether redirection mechanisms
MAY be preferred for large Homenet Zones, or when the number of
Registered Homenet Domain becomes quite large. -->>
4.3. Example: HNA necessary parameters for outsourcing
This section specifies the various parameters required by the HNA to
configure the naming architecture of this document. This section is
informational, and is intended to clarify the information handled by
the HNA and the various settings to be done.
Synchronization Server may be configured with the following
parameters. These parameters are necessary to establish a secure
channel between the HNA and the Synchronization Server as well as to
specify the DNS zone that is in the scope of the communication:
o Synchronization Server: The associated FQDNs or IP addresses of
the Synchronization Server. IP addresses are optional and the
FQDN is sufficient. To secure the binding name and IP addresses,
a DNSSEC exchange is required. Otherwise, the IP addresses should
be entered manually.
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o Authentication Method: How the HNA authenticates itself to the
Synchronization Server. This MAY depend on the implementation but
this should cover at least IPsec, DTLS and TSIG
o Authentication data: Associated Data. PSK only requires a single
argument. If other authentication mechanisms based on
certificates are used, then HNA private keys, certificates and
certification authority should be specified.
o Public Authoritative Server(s): The FQDN or IP addresses of the
Public Authoritative Server(s). It MAY correspond to the data
that will be set in the NS RRsets and SOA of the Homenet Zone. IP
addresses are optional and the FQDN is sufficient. To secure the
binding between name and IP addresses, a DNSSEC exchange is
required. Otherwise, the IP addresses should be entered manually.
o Registered Homenet Domain: The domain name used to establish the
secure channel. This name is used by the Synchronization Server
and the HNA for the primary / secondary configuration as well as
to index the NOTIFY queries of the HNA when the HNA has been
renumbered.
Setting the Homenet Zone requires the following information.
o Registered Homenet Domain: The Domain Name of the zone. Multiple
Registered Homenet Domains may be provided. This will generate
the creation of multiple Public Homenet Zones.
o Public Authoritative Server(s): The Public Authoritative Server(s)
associated with the Registered Homenet Domain. Multiple Public
Authoritative Server(s) may be provided.
5. Synchronization between HNA and the Synchronization Server
The Homenet Reverse Zone and the Homenet Zone MAY be updated either
with DNS UPDATE [RFC2136] or using a primary / secondary
synchronization. The primary / secondary mechanism is preferred as
it scales better and avoids DoS attacks: First the primary notifies
the secondary that the zone must be updated and leaves the secondary
to proceed with the update when possible. Then, a NOTIFY message is
sent by the primary, which is a small packet that is less likely to
load the secondary. Finally, the AXFR query performed by the
secondary is a small packet sent over TCP (section 4.2 [RFC5936]),
which mitigates reflection attacks using a forged NOTIFY. On the
other hand, DNS UPDATE (which can be transported over UDP), requires
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more processing than a NOTIFY, and does not allow the server to
perform asynchronous updates.
This document RECOMMENDS use of a primary / secondary mechanism
instead of the use of DNS UPDATE. This section details the primary /
secondary mechanism.
5.1. Synchronization with a Hidden Primary
Uploading and dynamically updating the zone file on the
Synchronization Server can be seen as zone provisioning between the
HNA (Hidden Primary) and the Synchronization Server (Secondary
Server). This can be handled either in band or out of band.
Note that there is no standard way to distribute a DNS primary
between multiple devices. As a result, if multiple devices are
candidate for hosting the Hidden Primary, some specific mechanisms
should be designed so the home network only selects a single HNA for
the Hidden Primary. Selection mechanisms based on HNCP [RFC7788] are
good candidates.
The Synchronization Server is configured as a secondary for the
Homenet Domain Name. This secondary configuration has been
previously agreed between the end user and the provider of the
Synchronization Server. In order to set the primary / secondary
architecture, the HNA acts as a Hidden Primary Server, which is a
regular authoritative DNS Server listening on the WAN interface.
The Hidden Primary Server SHOULD accept SOA [RFC1033], AXFR
[RFC1034], and IXFR [RFC1995] queries from its configured secondary
DNS server(s). The Hidden Primary Server SHOULD send NOTIFY messages
[RFC1996] in order to update Public DNS server zones as updates
occur. Because, the Homenet Zones are likely to be small, the HNA
MUST implement AXFR and SHOULD implement IXFR.
Hidden Primary Server differs from a regular authoritative server for
the home network by:
o Interface Binding: the Hidden Primary Server listens on the WAN
Interface, whereas a regular authoritative server for the home
network would listen on the home network interface.
o Limited exchanges: the purpose of the Hidden Primary Server is to
synchronize with the Synchronization Server, not to serve any
zones to end users. As a result, exchanges are performed with
specific nodes (the Synchronization Server). Further, exchange
types are limited. The only legitimate exchanges are: NOTIFY
initiated by the Hidden Primary and IXFR or AXFR exchanges
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initiated by the Synchronization Server. On the other hand,
regular authoritative servers would respond to any hosts, and any
DNS query would be processed. The HNA SHOULD filter IXFR/AXFR
traffic and drop traffic not initiated by the Synchronization
Server. The HNA MUST listen for DNS on TCP and UDP and MUST at
least allow SOA lookups of the Homenet Zone.
5.2. Securing Synchronization
Exchange between the Synchronization Server and the HNA MUST be
secured, at least for integrity protection and for authentication.
TSIG [RFC2845] or SIG(0) [RFC2931] MAY be used to secure the DNS
communications between the HNA and the Synchronization Server. TSIG
uses a symmetric key which can be managed by TKEY [RFC2930].
Management of the key involved in SIG(0) is performed through zone
updates. How keys are rolled over with SIG(0) is out-of-scope of
this document. The advantage of these mechanisms is that they are
only associated with the DNS application. Not relying on shared
libraries eases testing and integration. On the other hand, using
TSIG, TKEY or SIG(0) requires these mechanisms to be implemented on
the HNA, which adds code and complexity. Another disadvantage is
that TKEY does not provide authentication mechanisms.
Protocols like TLS [RFC5246] / DTLS [RFC6347] MAY be used to secure
the transactions between the Synchronization Server and the HNA. The
advantage of TLS/DTLS is that this technology is widely deployed, and
most of the devices already embed TLS/DTLS libraries, possibly also
taking advantage of hardware acceleration. Further, TLS/DTLS
provides authentication facilities and can use certificates to
authenticate the Synchronization Server and the HNA. On the other
hand, using TLS/DTLS requires implementing DNS exchanges over TLS/
DTLS, as well as a new service port. This document therefore does
NOT RECOMMEND this option.
IPsec [RFC4301] IKEv2 [RFC7296] MAY also be used to secure
transactions between the HNA and the Synchronization Server.
Similarly to TLS/DTLS, most HNAs already embed an IPsec stack, and
IKEv2 supports multiple authentication mechanisms via the EAP
framework. In addition, IPsec can be used to protect DNS exchanges
between the HNA and the Synchronization Server without any
modifications of the DNS server or client. DNS integration over
IPsec only requires an additional security policy in the Security
Policy Database (SPD). One disadvantage of IPsec is that NATs and
firewall traversal may be problematic. However, in our case, the HNA
is connected to the Internet, and IPsec communication between the HNA
and the Synchronization Server should not be impacted by middle
boxes.
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<<!-- As mentioned above, TSIG, IPsec and TLS/DTLS MAY be used to
secure transactions between the HNA and the Public Authentication
Servers. The HNA and the Synchronization Server SHOULD implement
TSIG and IPsec. -->>
How the PSK can be used by any of the TSIG, TLS/DTLS or IPsec
protocols: Authentication based on certificates implies a mutual
authentication and thus requires the HNA to manage a private key, a
public key, or certificates, as well as Certificate Authorities.
This adds complexity to the configuration especially on the HNA side.
For this reason, we RECOMMEND that the HNA MAY use PSK or certificate
base authentication, and that the Synchronization Server MUST support
PSK and certificate based authentication.
Note also that authentication of message exchanges between the HNA
and the Synchronization Server SHOULD NOT use the external IP address
of the HNA to index the appropriate keys. As detailed in Section 8,
the IP addresses of the Synchronization Server and the Hidden Primary
are subject to change, for example while the network is being
renumbered. This means that the necessary keys to authenticate
transaction SHOULD NOT be indexed using the IP address, and SHOULD be
resilient to IP address changes.
5.3. HNA Security Policies
This section details security policies related to the Hidden Primary
/ Secondary synchronization.
The Hidden Primary, as described in this document SHOULD drop any
queries from the home network. This could be implemented via port
binding and/or firewall rules. The precise mechanism deployed is out
of scope of this document. The Hidden Primary SHOULD drop any DNS
queries arriving on the WAN interface that are not issued from the
Synchronization Server. The Hidden Primary SHOULD drop any outgoing
packets other than DNS NOTIFY query, SOA response, IXFR response or
AXFR responses. The Hidden Primary SHOULD drop any incoming packets
other than DNS NOTIFY response, SOA query, IXFR query or AXFR query.
The Hidden Primary SHOULD drop any non protected IXFR or AXFR
exchange,depending on how the synchronization is secured.
6. DNSSEC compliant Homenet Architecture
[RFC7368] in Section 3.7.3 recommends DNSSEC to be deployed on both
the authoritative server and the resolver. The resolver side is out
of scope of this document, and only the authoritative part of the
server is considered.
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Deploying DNSSEC requires signing the zone and configuring a secure
delegation. As described in Section 4.1, signing can be performed
either by the HNA or by the Outsourcing Infrastructure. Section 6.1
details the implications of these two alternatives. Similarly, the
secure delegation can be performed by the HNA or by the Outsourcing
Infrastructure. Section 6.2 discusses these two alternatives.
6.1. Zone Signing"
This section discusses the pros and cons when zone signing is
performed by the HNA or by the Outsourcing Infrastructure. It is
RECOMMENDED that the HNA signs the zone unless there is a strong
argument against this, such as a HNA that is not capable of signing
the zone. In that case zone signing MAY be performed by the
Outsourcing Infrastructure on behalf of the HNA.
Reasons for signing the zone by the HNA are:
o 1) Keeping the Homenet Zone and the Public Homenet Zone equal to
securely optimize DNS resolution. As the Public Zone is signed
with DNSSEC, RRsets are authenticated, and thus DNS responses can
be validated even though they are not provided by the
authoritative server. This provides the HNA the ability to
respond on behalf of the Public Authoritative Server(s). This
could be useful for example if, in the future, the HNA announces
to the home network that the HNA can act as a local authoritative
primary or equivalent for the Homenet Zone. Currently the HNA is
not expected to receive authoritative DNS queries, as its IP
address is not mentioned in the Public Homenet Zone. On the other
hand most HNAs host a resolving function, and could be configured
to perform a local lookup to the Homenet Zone instead of
initiating a DNS exchange with the Public Authoritative Server(s).
Note that outsourcing the zone signing operation means that all
DNSSEC queries SHOULD be cached to perform a local lookup,
otherwise a resolution with the Public Authoritative Server(s)
would be performed.
o 2) Keeping the Homenet Zone and the Public Homenet Zone equal to
securely address the connectivity disruption independence detailed
in [RFC7368] section 4.4.1 and 3.7.5. As local lookups are
possible in case of network disruption, communications within the
home network can still rely on the DNSSEC service. Note that
outsourcing the zone signing operation does not address
connectivity disruption independence with DNSSEC. Instead local
lookup would provide DNS as opposed to DNSSEC responses provided
by the Public Authoritative Server(s).
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o 3) Keeping the Homenet Zone and the Public Homenet Zone equal to
guarantee coherence between DNS responses. Using a unique zone is
one way to guarantee uniqueness of the responses among servers and
places. Issues generated by different views are discussed in more
details in Section 7.
4) Privacy and Integrity of the DNSSEC Homenet Zone are better
guaranteed. When the Zone is signed by the HNA, it makes
modification of the DNS data - for example for flow redirection -
impossible. As a result, signing the Homenet Zone by the HNA
provides better protection for end user privacy.
Reasons for signing the zone by the Outsourcing Infrastructure are:
1) The HNA may not be capable of signing the zone, most likely
because its firmware does not support this function. However this
reason is expected to become less and less valid over time.
2) Outsourcing DNSSEC management operations. Management operations
involve key roll-over, which can be performed automatically by the
HNA and transparently for the end user. Avoiding DNSSEC management
is mostly motivated by bad software implementations.
3) Reducing the impact of HNA replacement on the Public Homenet Zone.
Unless the HNA private keys can be extracted and stored off-device,
HNA hardware replacement will result in an emergency key roll-over.
This can be mitigated by using relatively small TTLs.
4) Reducing configuration impact on the end user. Unless there are
zero configuration mechanisms in place to provide credentials between
the new HNA and the Synchronization Server, authentication
associations between the HNA and the Synchronization Server would
need to be re-configured. As HNA replacement is not expected to
happen regularly, end users may not be at ease with such
configuration settings. However, mechanisms as described in
[I-D.ietf-homenet-naming-architecture-dhc-options] use DHCP Options
to outsource the configuration and avoid this issue.
5) The Outsourcing Infrastructure is more likely to handle private
keys more securely than the HNA. However, having all private keys in
one place may also nullify that benefit.
6.2. Secure Delegation"
Secure delegation is achieved only if the DS RRset is properly set in
the parent zone. Secure delegation can be performed by the HNA or
the Outsourcing Infrastructures (that is the Synchronization Server
or the Public Authoritative Server(s)).
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The DS RRset can be updated manually with nsupdate for example. This
requires the HNA or the Outsourcing Infrastructure to be
authenticated by the DNS server hosting the parent of the Public
Homenet Zone. Such a trust channel between the HNA and the parent
DNS server may be hard to maintain with HNAs, and thus may be easier
to establish with the Outsourcing Infrastructure. In fact, the
Public Authoritative Server(s) may use Automating DNSSEC Delegation
Trust Maintenance [RFC7344].
7. Handling Different Views
The Homenet Zone provides information about the home network. Some
users may be tempted to have provide responses dependent on the
origin of the DNS query. More specifically, some users may be
tempted to provide a different view for DNS queries originating from
the home network and for DNS queries coming from the Internet. Each
view could then be associated with a dedicated Homenet Zone.
<!--Regarding {{fig-naming-arch}}, an example of an implementation of
two distinct view could be the Homenet Zone that describes the
homenet view and the Public Homenet Zone that contains the Internet
view, with these two zones being different.-->
Note that this document does not specify how DNS queries originating
from the home network are addressed to the Homenet Zone. This could
be done via hosting the DNS resolver on the HNA for example.
This section is not normative. Section 7.1 details why some nodes
may only be reachable from the home network and not from the global
Internet. Section 7.2 briefly describes the consequences of having
distinct views such as a "home network view" and an "Internet view".
Finally, Section 7.3 provides guidance on how to resolve names that
are only significant in the home network, without creating different
views.
7.1. Misleading Reasons for Local Scope DNS Zone"
The motivation for supporting different views is to provide different
answers dependent on the origin of the DNS query, for reasons such
as:
1: An end user may want to have services not published on the
Internet. Services like the HNA administration interface that
provides the GUI to administer your HNA might not seem advisable to
publish on the Internet. Similarly, services like the mapper that
registers the devices of your home network may also not be desirable
to be published on the Internet. In both cases, these services
should only be known or used by the network administrator. To
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restrict the access of such services, the home network administrator
may choose to publish these pieces of information only within the
home network, where it might be assumed that the users are more
trusted than on the Internet. Even though this assumption may not be
valid, at least this may reduce the surface of any attack.
2: Services within the home network may be reachable using non global
IP addresses. IPv4 and NAT may be one reason. On the other hand
IPv6 may favor link-local or site-local IP addresses. These IP
addresses are not significant outside the boundaries of the home
network. As a result, they MAY be published in the home network
view, and SHOULD NOT be published in the Public Homenet Zone.
7.2. Consequences"
Enabling different views leads to a non-coherent naming system.
Depending on where resolution is performed, some services will not be
available. This may be especially inconvenient with devices with
multiple interfaces that are attached both to the Internet via a
3G/4G interface and to the home network via a WLAN interface.
Devices may also cache the results of name resolution, and these
cached entries may no longer be valid if a mobile device moves
between a homenet connection and an internet connection e.g. a device
temporarily loses wifi signal and switches to 3G.
Regarding local-scope IP addresses, such devices may end up with poor
connectivity. Suppose, for example, that DNS resolution is performed
via the WLAN interface attached to the HNA, and the response provides
local-scope IP addresses, but the communication is initiated on the
3G/4G interface. Communications with local-scope addresses will be
unreachable on the Internet, thus aborting the communication. The
same situation occurs if a device is flip / flopping between various
WLAN networks.
Regarding DNSSEC, if the HNA does not sign the Homenet Zone and
outsources the signing process, the two views are different, because
one is protected with DNSSEC whereas the other is not. Devices with
multiple interfaces will have difficulty securing the naming
resolution, as responses originating from the home network may not be
signed.
For devices with all its interfaces attached to a single
administrative domain, that is to say the home network, or the
Internet. Incoherence between DNS responses may still also occur if
the device is able to perform DNS resolutions both using the DNS
resolving server of the home network, or one of the ISP. DNS
resolution performed via the HNA or the ISP resolver may be different
than those performed over the Internet.
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7.3. Guidance and Recommendations
As documented in Section 7.2, it is RECOMMENDED to avoid different
views. If network administrators choose to implement multiple views,
impacts on devices' resolution SHOULD be evaluated.
As a consequence, the Homenet Zone is expected to be an exact copy of
the Public Homenet Zone. As a result, services that are not expected
to be published on the Internet SHOULD NOT be part of the Homenet
Zone, local-scope addresses SHOULD NOT be part of the Homenet Zone,
and when possible, the HNA SHOULD sign the Homenet Zone.
The Homenet Zone is expected to host public information only. It is
not the scope of the DNS service to define local home network
boundaries. Instead, local scope information is expected to be
provided to the home network using local scope naming services. mDNS
[RFC6762] DNS-SD [RFC6763] are two examples of these services.
Currently mDNS is limited to a single link network. However, future
protocols are expected to leverage this constraint as pointed out in
[RFC7558].
7.4. Homenet Reverse Zone
This section is focused on the Homenet Reverse Zone.
Firstly, all considerations for the Homenet Zone apply to the Homenet
Reverse Zone. The main difference between the Homenet Reverse Zone
and the Homenet Zone is that the parent zone of the Homenet Reverse
Zone is most likely managed by the ISP. As the ISP also provides the
IP prefix to the HNA, it may be able to authenticate the HNA using
mechanisms outside the scope of this document e.g. the physical
attachment point to the ISP network. If the Reverse Synchronization
Server is managed by the ISP, credentials to authenticate the HNA for
the zone synchronization may be set automatically and transparently
to the end user. [I-D.ietf-homenet-naming-architecture-dhc-options]
describes how automatic configuration may be performed.
With IPv6, the domain space for IP addresses is so large that reverse
zone may be confronted with scalability issues. How the reverse zone
is generated is out of scope of this document.
[I-D.howard-dnsop-ip6rdns] provides guidance on how to address
scalability issues.
8. Renumbering
This section details how renumbering is handled by the Hidden Primary
server or the Synchronization Server. Both types of renumbering are
discussed i.e. "make-before-break" and "break-before-make".
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In the make-before-break renumbering scenario, the new prefix is
advertised, the network is configured to prepare the transition to
the new prefix. During a period of time, the two prefixes old and
new coexist, before the old prefix is completely removed. In the
break-before-make renumbering scenario, the new prefix is advertised
making the old prefix obsolete.
Renumbering has been extensively described in [RFC4192] and analyzed
in [RFC7010] and the reader is expected to be familiar with them
before reading this section.
8.1. Hidden Primary
In a renumbering scenario, the Hidden Primary is informed it is being
renumbered. In most cases, this occurs because the whole home
network is being renumbered. As a result, the Homenet Zone will also
be updated. Although the new and old IP addresses may be stored in
the Homenet Zone, we recommend that only the newly reachable IP
addresses be published.
To avoid reachability disruption, IP connectivity information
provided by the DNS SHOULD be coherent with the IP plane. In our
case, this means the old IP address SHOULD NOT be provided via the
DNS when it is not reachable anymore. Let for example TTL be the TTL
associated with a RRset of the Homenet Zone, it may be cached for TTL
seconds. Let T_NEW be the time the new IP address replaces the old
IP address in the Homenet Zone, and T_OLD_UNREACHABLE the time the
old IP is not reachable anymore.
In the case of the make-before-break, seamless reachability is
provided as long as T_OLD_UNREACHABLE - T_NEW > 2 * TTL. If this is
not satisfied, then devices associated with the old IP address in the
home network may become unreachable for 2 * TTL - (T_OLD_UNREACHABLE
- T_NEW). In the case of a break-before-make, T_OLD_UNREACHABLE =
T_NEW, and the device may become unreachable up to 2 * TTL.
Once the Homenet Zone file has been updated on the Hidden Primary,
the Hidden Primary needs to inform the Outsourcing Infrastructure
that the Homenet Zone has been updated and that the IP address to use
to retrieve the updated zone has also been updated. Both
notifications are performed using regular DNS exchanges. Mechanisms
to update an IP address provided by lower layers with protocols like
SCTP [RFC4960], MOBIKE [RFC4555] are not considered in this document.
The Hidden Primary SHOULD inform the Synchronization Server that the
Homenet Zone has been updated by sending a NOTIFY payload with the
new IP address. In addition, this NOTIFY payload SHOULD be
authenticated using SIG(0) or TSIG. When the Synchronization Server
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receives the NOTIFY payload, it MUST authenticate it. Note that the
cryptographic key used for the authentication SHOULD be indexed by
the Registered Homenet Domain contained in the NOTIFY payload as well
as the RRSIG. In other words, the IP address SHOULD NOT be used as
an index. If authentication succeeds, the Synchronization Server
MUST also notice the IP address has been modified and perform a
reachability check before updating its primary configuration. The
routability check MAY performed by sending a SOA request to the
Hidden Primary using the source IP address of the NOTIFY. This
exchange is also secured, and if an authenticated response is
received from the Hidden Primary with the new IP address, the
Synchronization Server SHOULD update its configuration file and
retrieve the Homenet Zone using an AXFR or a IXFR exchange.
Note that the primary reason for providing the IP address is that the
Hidden Primary is not publicly announced in the DNS. If the Hidden
Primary were publicly announced in the DNS, then the IP address
update could have been performed using the DNS as described in
Section 8.2.
8.2. Synchronization Server
Renumbering of the Synchronization Server results in the
Synchronization Server changing its IP address. The Synchronization
Server is a secondary, so its renumbering does not impact the Homenet
Zone. In fact, exchanges to the Synchronization Server are
restricted to the Homenet Zone synchronization. In our case, the
Hidden Primary MUST be able to send NOTIFY payloads to the
Synchronization Server.
If the Synchronization Server is configured in the Hidden Primary
configuration file using a FQDN, then the update of the IP address is
performed by DNS. More specifically, before sending the NOTIFY, the
Hidden Primary performs a DNS resolution to retrieve the IP address
of the secondary.
As described in Section 8.1, the Synchronization Server DNS
information SHOULD be coherent with the IP plane. Let TTL be the TTL
associated with the Synchronization Server FQDN, T_NEW the time the
new IP address replaces the old one and T_OLD_UNREACHABLE the time
the Synchronization Server is not reachable anymore with its old IP
address. Seamless reachability is provided as long as
T_OLD_UNREACHABLE - T_NEW > 2 * TTL. If this condition is not met,
the Synchronization Server may be unreachable during 2 * TTL -
(T_OLD_UNREACHABLE - T_NEW). In the case of a break-before-make,
T_OLD_UNREACHABLE = T_NEW, and it may become unreachable up to 2 *
TTL.
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Some DNS infrastructure uses the IP address to designate the
secondary, in which case, other mechanisms must be found. The reason
for using IP addresses instead of names is generally to reach an
internal interface that is not designated by a FQDN, and to avoid
potential bootstrap problems. Such scenarios are considered as out
of scope in the case of home networks.
[]( <!- <section {#sec-dnssec-outsrc" title="DNSSEC outsourcing
configuration}
In this document we assume that the Outsourcing Infrastructure MAY sign the Homenet Zone. Multiple variants MAY be proposed by the Outsourcing Infrastructure. The Outsourcing Infrastructure MAY propose signing the DNS Homenet Zone with keys generated by the Outsourcing Infrastructure and which are unknown to the HNA. Alternatively the Outsourcing Infrastructure MAY propose that the end user provides the private keys. Although not considered in this document, some end users MAY still prefer to sign their zone with their own keys that they do not communicate to the Outsourcing Infrastructure. All these alternatives result from a negotiation between the end user and the Outsourcing Infrastructure. This negotiation is performed out-of-band and is out of scope of this document.
In this document, we consider that the Outsourcing Infrastructure has all the necessary cryptographic elements to perform zone signing and key management operations.
Note that Outsourcing Infrastructure described in this document implements various functions, and thus different entities may be involved.
<list hangIndent="6" style="hanging
<t hangText="- DNS Slave functionsynchronizes the Homenet Zone
between the HNA and the Outsourcing Infrastructures. The DNS Homenet Zone SHOULD NOT be published directly on the Public Authoritative Servers, and the Public Authoritative Server(s MUST NOT respond to any DNS queries for that zone. Instead, the Outsourcing Infrastructure chooses a dedicated set of servers to serve the Public Homenet Zone: the Public Authoritative Server(s.
<t hangText="- DNS Zone Signing functionsigns the DNS Zone Homenet Zone to generate an Public Homenet Zone.
<t hangText="- Public Authoritative Server hosts the naming service for the Public Homenet Zone. Any DNS query associated with the Homenet Zone SHOULD be performed using the specific servers designated as the Public Authoritative Servers
</list>
->)
9. Privacy Considerations
Outsourcing the DNS Authoritative service from the HNA to a third
party raises a few privacy related concerns.
The Homenet Zone contains a full description of the services hosted
in the network. These services may not be expected to be publicly
shared although their names remain accessible through the Internet.
Even though DNS makes information public, the DNS does not expect to
make the complete list of services public. In fact, making
information public still requires the key (or FQDN) of each service
to be known by the resolver in order to retrieve information about
the services. More specifically, making mywebsite.example.com public
in the DNS, is not sufficient to make resolvers aware of the
existence web site. However, an attacker may walk the reverse DNS
zone, or use other reconnaissance techniques to learn this
information as described in [RFC7707].
In order to prevent the complete Homenet Zone being published on the
Internet, AXFR queries SHOULD be blocked on the Public Authoritative
Server(s). Similarly, to avoid zone-walking NSEC3 [RFC5155] SHOULD
be preferred over NSEC [RFC4034]. When the Homenet Zone is
outsourced, the end user should be aware that it provides a complete
description of the services available on the home network. More
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specifically, names usually provides a clear indication of the
service and possibly even the device type, and as the Homenet Zone
contains the IP addresses associated with the service, they also
limit the scope of the scan space.
In addition to the Homenet Zone, the third party can also monitor the
traffic associated with the Homenet Zone. This traffic may provide
an indication of the services an end user accesses, plus how and when
they use these services. Although, caching may obfuscate this
information inside the home network, it is likely that outside your
home network this information will not be cached.
10. Security Considerations
The Homenet Naming Architecture described in this document solves
exposing the HNA's DNS service as a DoS attack vector.
10.1. Names are less secure than IP addresses
This document describes how an end user can make their services and
devices from his home network reachable on the Internet by using
names rather than IP addresses. This exposes the home network to
attackers, since names are expected to include less entropy than IP
addresses. In fact, with IP addresses, the Interface Identifier is
64 bits long leading to up to 2^64 possibilities for a given
subnetwork. This is not to mention that the subnet prefix is also of
64 bits long, thus providing up to 2^64 possibilities. On the other
hand, names used either for the home network domain or for the
devices present less entropy (livebox, router, printer, nicolas,
jennifer, ...) and thus potentially exposes the devices to dictionary
attacks.
10.2. Names are less volatile than IP addresses
IP addresses may be used to locate a device, a host or a service.
However, home networks are not expected to be assigned a time
invariant prefix by ISPs. As a result, observing IP addresses only
provides some ephemeral information about who is accessing the
service. On the other hand, names are not expected to be as volatile
as IP addresses. As a result, logging names over time may be more
valuable than logging IP addresses, especially to profile an end
user's characteristics.
PTR provides a way to bind an IP address to a name. In that sense,
responding to PTR DNS queries may affect the end user's privacy. For
that reason end users may choose not to respond to PTR DNS queries
and MAY instead return a NXDOMAIN response.
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10.3. DNS Reflection Attacks
An attacker performs a reflection attack when it sends traffic to one
or more intermediary nodes (reflectors), that in turn send back
response traffic to the victim. Motivations for using an
intermediary node might be anonymity of the attacker, as well as
amplification of the traffic. Typically, when the intermediary node
is a DNSSEC server, the attacker sends a DNSSEC query and the victim
is likely to receive a DNSSEC response. This section analyzes how
the different components may be involved as a reflector in a
reflection attack. Section 10.4 considers the Hidden Primary,
Section 10.5 the Synchronization Server, and Section 10.6 the Public
Authoritative Server(s).
10.4. "Reflection Attack involving the Hidden Primary
With the specified architecture, the Hidden Primary is only expected
to receive DNS queries of type SOA, AXFR or IXFR. This section
analyzes how these DNS queries may be used by an attacker to perform
a reflection attack.
DNS queries of type AXFR and IXFR use TCP and as such are less
subject to reflection attacks. This makes SOA queries the only
remaining practical vector of attacks for reflection attacks, based
on UDP.
SOA queries are not associated with a large amplification factor
compared to queries of type "ANY" or to query of non existing FQDNs.
This reduces the probability a DNS query of type SOA will be involved
in a DDoS attack.
SOA queries are expected to follow a very specific pattern, which
makes rate limiting techniques an efficient way to limit such
attacks, and associated impact on the naming service of the home
network.
Motivations for such a flood might be a reflection attack, but could
also be a resource exhaustion attack performed against the Hidden
Primary. The Hidden Primary only expects to exchange traffic with
the Synchronization Server, that is its associated secondary. Even
though secondary servers may be renumbered as mentioned in Section 8,
the Hidden Primary is likely to perform a DNSSEC resolution and find
out the associated secondary's IP addresses in use. As a result, the
Hidden Primary is likely to limit the origin of its incoming traffic
based on the origin IP address.
With filtering rules based on IP address, SOA flooding attacks are
limited to forged packets with the IP address of the secondary
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server. In other words, the only victims are the Hidden Primary
itself or the secondary. There is a need for the Hidden Primary to
limit that flood to limit the impact of the reflection attack on the
secondary, and to limit the resource needed to carry on the traffic
by the HNA hosting the Hidden Primary. On the other hand, mitigation
should be performed appropriately, so as to limit the impact on the
legitimate SOA sent by the secondary.
The main reason for the Synchronization Server sending a SOA query is
to update the SOA RRset after the TTL expires, to check the serial
number upon the receipt of a NOTIFY query from the Hidden Primary, or
to re-send the SOA request when the response has not been received.
When a flood of SOA queries is received by the Hidden Primary, the
Hidden Primary may assume it is involved in an attack.
There are few legitimate time slots when the secondary is expected to
send a SOA query. Suppose T_NOTIFY is the time a NOTIFY is sent by
the Hidden Primary, T_SOA the last time the SOA has been queried, TTL
the TTL associated to the SOA, and T_REFRESH the refresh time defined
in the SOA RRset. The specific time SOA queries are expected can be
for example T_NOTIFY, T_SOA + 2/3 TTL, T_SOA + TTL, T_SOA +
T_REFRESH., and. Outside a few minutes following these specific time
slots, the probability that the HNA discards a legitimate SOA query
is very low. Within these time slots, the probability the secondary
may have its legitimate query rejected is higher. If a legitimate
SOA is discarded, the secondary will re-send SOA query every "retry
time" second until "expire time" seconds occurs, where "retry time"
and "expire time" have been defined in the SOA.
As a result, it is RECOMMENDED to set rate limiting policies to
protect HNA resources. If a flood lasts more than the expired time
defined by the SOA, it is RECOMMENDED to re-initiate a
synchronization between the Hidden Primary and the secondaries.
10.5. Reflection Attacks involving the Synchronization Server
The Synchronization Server acts as a secondary coupled with the
Hidden Primary. The secondary expects to receive NOTIFY query, SOA
responses, AXFR and IXFR responses from the Hidden Primary.
Sending a NOTIFY query to the secondary generates a NOTIFY response
as well as initiating an SOA query exchange from the secondary to the
Hidden Primary. As mentioned in [RFC1996], this is a known "benign
denial of service attack". As a result, the Synchronization Server
SHOULD enforce rate limiting on sending SOA queries and NOTIFY
responses to the Hidden Primary. Most likely, when the secondary is
flooded with valid and signed NOTIFY queries, it is under a replay
attack which is discussed in Section 10.8. The key thing here is
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that the secondary is likely to be designed to be able to process
much more traffic than the Hidden Primary hosted on a HNA.
This paragraph details how the secondary may limit the NOTIFY
queries. Because the Hidden Primary may be renumbered, the secondary
SHOULD NOT perform permanent IP filtering based on IP addresses. In
addition, a given secondary may be shared among multiple Hidden
Primaries which make filtering rules based on IP harder to set. The
time at which a NOTIFY is sent by the Hidden Primary is not
predictable. However, a flood of NOTIFY messages may be easily
detected, as a NOTIFY originated from a given Homenet Zone is
expected to have a very limited number of unique source IP addresses,
even when renumbering is occurring. As a result, the secondary, MAY
rate limit incoming NOTIFY queries.
On the Hidden Primary side, it is recommended that the Hidden Primary
sends a NOTIFY as long as the zone has not been updated by the
secondary. Multiple SOA queries may indicate the secondary is under
attack.
10.6. Reflection Attacks involving the Public Authoritative Servers
Reflection attacks involving the Public Authoritative Server(s) are
similar to attacks on any Outsourcing Infrastructure. This is not
specific to the architecture described in this document, and thus are
considered as out of scope.
In fact, one motivation of the architecture described in this
document is to expose the Public Authoritative Server(s) to attacks
instead of the HNA, as it is believed that the Public Authoritative
Server(s) will be better able to defend itself.
10.7. Flooding Attack
The purpose of flooding attacks is mostly resource exhaustion, where
the resource can be bandwidth, memory, or CPU for example.
One goal of the architecture described in this document is to limit
the surface of attack on the HNA. This is done by outsourcing the
DNS service to the Public Authoritative Server(s). By doing so, the
HNA limits its DNS interactions between the Hidden Primary and the
Synchronization Server. This limits the number of entities the HNA
interacts with as well as the scope of DNS exchanges - NOTIFY, SOA,
AXFR, IXFR.
The use of an authenticated channel with SIG(0) or TSIG between the
HNA and the Synchronization Server, enables detection of illegitimate
DNS queries, so appropriate action may be taken - like dropping the
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queries. If signatures are validated, then most likely, the HNA is
under a replay attack, as detailed in Section 10.8
In order to limit the resource required for authentication, it is
recommended to use TSIG that uses symmetric cryptography over SIG(0)
that uses asymmetric cryptography.
10.8. Replay Attack
Replay attacks consist of an attacker either resending or delaying a
legitimate message that has been sent by an authorized user or
process. As the Hidden Primary and the Synchronization Server use an
authenticated channel, replay attacks are mostly expected to use
forged DNS queries in order to provide valid traffic.
From the perspective of an attacker, using a correctly authenticated
DNS query may not be detected as an attack and thus may generate a
response. Generating and sending a response consumes more resources
than either dropping the query by the defender, or generating the
query by the attacker, and thus could be used for resource exhaustion
attacks. In addition, as the authentication is performed at the DNS
layer, the source IP address could be impersonated in order to
perform a reflection attack.
Section 10.3 details how to mitigate reflection attacks and
Section 10.7 details how to mitigate resource exhaustion. Both
sections assume a context of DoS with a flood of DNS queries. This
section suggests a way to limit the attack surface of replay attacks.
As SIG(0) and TSIG use inception and expiration time, the time frame
for replay attack is limited. SIG(0) and TSIG recommends a fudge
value of 5 minutes. This value has been set as a compromise between
possibly loose time synchronization between devices and the valid
lifetime of the message. As a result, better time synchronization
policies could reduce the time window of the attack.
[](<!- <section title="DNSSEC is recommended to authenticate DNS
hosted data
Deploying DNSSEC is recommended, since in some cases the information
stored in the DNS is used by the ISP or an IT department to grant
access. For example some servers may perform PTR DNS queries to
grant access based on host names. DNSSEC mitigates lack of trust in
DNS, and it is RECOMMENDED to deploy DNSSEC on HNAs.
-->)
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11. IANA Considerations
This document has no actions for IANA.
12. Acknowledgment
The authors wish to thank Philippe Lemordant for its contributions on
the early versions of the draft; Ole Troan for pointing out issues
with the IPv6 routed home concept and placing the scope of this
document in a wider picture; Mark Townsley for encouragement and
injecting a healthy debate on the merits of the idea; Ulrik de Bie
for providing alternative solutions; Paul Mockapetris, Christian
Jacquenet, Francis Dupont and Ludovic Eschard for their remarks on
HNA and low power devices; Olafur Gudmundsson for clarifying DNSSEC
capabilities of small devices; Simon Kelley for its feedback as
dnsmasq implementer; Andrew Sullivan, Mark Andrew, Ted Lemon, Mikael
Abrahamson, Michael Richardson and Ray Bellis for their feedback on
handling different views as well as clarifying the impact of
outsourcing the zone signing operation outside the HNA; Mark Andrew
and Peter Koch for clarifying the renumbering.
13. References
13.1. Normative References
[RFC1033] Lottor, M., "Domain Administrators Operations Guide",
RFC 1033, DOI 10.17487/RFC1033, November 1987,
<https://www.rfc-editor.org/info/rfc1033>.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995,
DOI 10.17487/RFC1995, August 1996,
<https://www.rfc-editor.org/info/rfc1995>.
[RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone
Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996,
August 1996, <https://www.rfc-editor.org/info/rfc1996>.
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[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>.
[RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, DOI 10.17487/RFC2136, April 1997,
<https://www.rfc-editor.org/info/rfc2136>.
[RFC2142] Crocker, D., "Mailbox Names for Common Services, Roles and
Functions", RFC 2142, DOI 10.17487/RFC2142, May 1997,
<https://www.rfc-editor.org/info/rfc2142>.
[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
<https://www.rfc-editor.org/info/rfc2181>.
[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,
<https://www.rfc-editor.org/info/rfc2308>.
[RFC2845] Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.
Wellington, "Secret Key Transaction Authentication for DNS
(TSIG)", RFC 2845, DOI 10.17487/RFC2845, May 2000,
<https://www.rfc-editor.org/info/rfc2845>.
[RFC2930] Eastlake 3rd, D., "Secret Key Establishment for DNS (TKEY
RR)", RFC 2930, DOI 10.17487/RFC2930, September 2000,
<https://www.rfc-editor.org/info/rfc2930>.
[RFC2931] Eastlake 3rd, D., "DNS Request and Transaction Signatures
( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September
2000, <https://www.rfc-editor.org/info/rfc2931>.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, DOI 10.17487/RFC4034, March 2005,
<https://www.rfc-editor.org/info/rfc4034>.
[RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for
Renumbering an IPv6 Network without a Flag Day", RFC 4192,
DOI 10.17487/RFC4192, September 2005,
<https://www.rfc-editor.org/info/rfc4192>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
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[RFC4555] Eronen, P., "IKEv2 Mobility and Multihoming Protocol
(MOBIKE)", RFC 4555, DOI 10.17487/RFC4555, June 2006,
<https://www.rfc-editor.org/info/rfc4555>.
[RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol",
RFC 4960, DOI 10.17487/RFC4960, September 2007,
<https://www.rfc-editor.org/info/rfc4960>.
[RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
Security (DNSSEC) Hashed Authenticated Denial of
Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008,
<https://www.rfc-editor.org/info/rfc5155>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5936] Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol
(AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010,
<https://www.rfc-editor.org/info/rfc5936>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC6644] Evans, D., Droms, R., and S. Jiang, "Rebind Capability in
DHCPv6 Reconfigure Messages", RFC 6644,
DOI 10.17487/RFC6644, July 2012,
<https://www.rfc-editor.org/info/rfc6644>.
[RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the
DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012,
<https://www.rfc-editor.org/info/rfc6672>.
[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>.
[RFC7010] Liu, B., Jiang, S., Carpenter, B., Venaas, S., and W.
George, "IPv6 Site Renumbering Gap Analysis", RFC 7010,
DOI 10.17487/RFC7010, September 2013,
<https://www.rfc-editor.org/info/rfc7010>.
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[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <https://www.rfc-editor.org/info/rfc7296>.
[RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating
DNSSEC Delegation Trust Maintenance", RFC 7344,
DOI 10.17487/RFC7344, September 2014,
<https://www.rfc-editor.org/info/rfc7344>.
[RFC7368] Chown, T., Ed., Arkko, J., Brandt, A., Troan, O., and J.
Weil, "IPv6 Home Networking Architecture Principles",
RFC 7368, DOI 10.17487/RFC7368, October 2014,
<https://www.rfc-editor.org/info/rfc7368>.
[RFC7558] Lynn, K., Cheshire, S., Blanchet, M., and D. Migault,
"Requirements for Scalable DNS-Based Service Discovery
(DNS-SD) / Multicast DNS (mDNS) Extensions", RFC 7558,
DOI 10.17487/RFC7558, July 2015,
<https://www.rfc-editor.org/info/rfc7558>.
[RFC7707] Gont, F. and T. Chown, "Network Reconnaissance in IPv6
Networks", RFC 7707, DOI 10.17487/RFC7707, March 2016,
<https://www.rfc-editor.org/info/rfc7707>.
[RFC7788] Stenberg, M., Barth, S., and P. Pfister, "Home Networking
Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April
2016, <https://www.rfc-editor.org/info/rfc7788>.
13.2. Informative References
[I-D.howard-dnsop-ip6rdns]
Howard, L., "Reverse DNS in IPv6 for Internet Service
Providers", draft-howard-dnsop-ip6rdns-00 (work in
progress), June 2014.
[I-D.ietf-homenet-naming-architecture-dhc-options]
Migault, D., Mrugalski, T., Griffiths, C., Weber, R., and
W. Cloetens, "DHCPv6 Options for Homenet Naming
Architecture", draft-ietf-homenet-naming-architecture-dhc-
options-06 (work in progress), June 2018.
[I-D.sury-dnsext-cname-dname]
Sury, O., "CNAME+DNAME Name Redirection", draft-sury-
dnsext-cname-dname-00 (work in progress), April 2010.
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Authors' Addresses
Daniel Migault
Ericsson
8275 Trans Canada Route
Saint Laurent, QC 4S 0B6
Canada
EMail: daniel.migault@ericsson.com
Ralf Weber
Nominum
2000 Seaport Blvd
Redwood City 94063
US
EMail: ralf.weber@nominum.com
Ray Hunter
Globis Consulting BV
Weegschaalstraat 3
Eindhoven 5632CW
NL
EMail: v6ops@globis.net
Chris Griffiths
EMail: cgriffiths@gmail.com
Wouter Cloetens
SoftAtHome<
vaartdijk 3 701
Wijgmaal 3018
BE
EMail: cgriffiths@gmail.com
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