IPv6 Router Advertisement Options for DNS Configuration
draft-ietf-6man-rdnss-rfc6106bis-11
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 8106.
|
|
|---|---|---|---|
| Authors | Jaehoon Paul Jeong , Soohong Daniel Park , Luc Beloeil , Syam Madanapalli | ||
| Last updated | 2016-03-14 | ||
| Replaces | draft-jeong-6man-rdnss-rfc6106-bis | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
OPSDIR Last Call review
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Has Nits
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| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | Fernando Gont | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | "Fernando Gont" <fgont@si6networks.com>, bob.hinden@gmail.com, otroan@employees.org |
draft-ietf-6man-rdnss-rfc6106bis-11
Network Working Group J. Jeong
Internet-Draft Sungkyunkwan University
Obsoletes: 6106 (if approved) S. Park
Intended status: Standards Track Samsung Electronics
Expires: September 15, 2016 L. Beloeil
France Telecom R&D
S. Madanapalli
iRam Technologies
March 14, 2016
IPv6 Router Advertisement Options for DNS Configuration
draft-ietf-6man-rdnss-rfc6106bis-11
Abstract
This document specifies IPv6 Router Advertisement options to allow
IPv6 routers to advertise a list of DNS recursive server addresses
and a DNS Search List to IPv6 hosts.
This document obsoletes RFC 6106 and allows a higher default value of
the lifetime of the RA DNS options to avoid the frequent expiry of
the options on links with a relatively high rate of packet loss.
Status of This Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on September 15, 2016.
Copyright Notice
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Copyright (c) 2016 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
(http://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
1.1. Applicability Statements . . . . . . . . . . . . . . . . . 3
1.2. Coexistence of RA Options and DHCP Options for DNS
Configuration . . . . . . . . . . . . . . . . . . . . . . 4
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Neighbor Discovery Extension . . . . . . . . . . . . . . . . . 5
5.1. Recursive DNS Server Option . . . . . . . . . . . . . . . 6
5.2. DNS Search List Option . . . . . . . . . . . . . . . . . . 7
5.3. Procedure of DNS Configuration . . . . . . . . . . . . . . 8
5.3.1. Procedure in IPv6 Host . . . . . . . . . . . . . . . . 8
5.3.2. Warnings for DNS Options Configuration . . . . . . . . 9
6. Implementation Considerations . . . . . . . . . . . . . . . . 9
6.1. DNS Repository Management . . . . . . . . . . . . . . . . 10
6.2. Synchronization between DNS Server List and Resolver
Repository . . . . . . . . . . . . . . . . . . . . . . . . 10
6.3. Synchronization between DNS Search List and Resolver
Repository . . . . . . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7.1. Security Threats . . . . . . . . . . . . . . . . . . . . . 12
7.2. Recommendations . . . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1. Normative References . . . . . . . . . . . . . . . . . . . 14
10.2. Informative References . . . . . . . . . . . . . . . . . . 14
Appendix A. Changes from RFC 6106 . . . . . . . . . . . . . . . . 15
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1. Introduction
The purpose of this document is to standardize an IPv6 Router
Advertisement (RA) option for DNS Recursive Server Addresses used for
the DNS name resolution in IPv6 hosts. This RA option was originally
specified in an earlier Experimental specification [RFC5006] and was
later published as a Standards Track in [RFC6106]. This document
obsoletes [RFC6106], allowing a higher default value of the lifetime
of the RA DNS options to avoid the frequent expiry of the options on
links with a relatively high rate of packet loss, and also making
additional clarifications, see Appendix A for details.
Neighbor Discovery (ND) for IP version 6 and IPv6 Stateless Address
Autoconfiguration (SLAAC) provide ways to configure either fixed or
mobile nodes with one or more IPv6 addresses, default routers, and
some other parameters [RFC4861][RFC4862]. Most Internet names are
identified by using a DNS name. The two RA options defined in this
document provide the DNS information needed for an IPv6 host to reach
Internet names.
It is infeasible to manually configure nomadic hosts each time they
connect to a different network. While a one-time static
configuration is possible, it is generally not desirable on general-
purpose hosts such as laptops. For instance, locally defined name
spaces would not be available to the host if it were to run its own
recursive name server directly connected to the global DNS.
The DNS information can also be provided through DHCPv6 [RFC3315]
[RFC3736][RFC3646]. However, the access to DNS is a fundamental
requirement for almost all hosts, so IPv6 stateless autoconfiguration
cannot stand on its own as an alternative deployment model in any
practical network without any support for DNS configuration.
These issues are not pressing in dual-stack networks as long as a DNS
server is available on the IPv4 side, but they become more critical
with the deployment of IPv6-only networks. As a result, this
document defines a mechanism based on IPv6 RA options to allow IPv6
hosts to perform the automatic DNS configuration.
1.1. Applicability Statements
RA-based DNS configuration is a useful alternative in networks where
an IPv6 host's address is autoconfigured through IPv6 stateless
address autoconfiguration and where there is either no DHCPv6
infrastructure at all or some hosts do not have a DHCPv6 client. The
intention is to enable the full configuration of basic networking
information for hosts without requiring DHCPv6. However, for
networks that need to distribute additional information, DHCPv6 is
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likely to be employed. In these networks, RA-based DNS configuration
may not be needed.
RA-based DNS configuration allows an IPv6 host to acquire the DNS
configuration (i.e., DNS recursive server addresses and DNS Search
List) for the link(s) to which the host is connected. Furthermore,
the host learns this DNS configuration from the same RA message that
provides configuration information for the link.
The advantages and disadvantages of the RA-based approach are
discussed in [RFC4339] along with other approaches, such as the DHCP
and well-known anycast address approaches.
1.2. Coexistence of RA Options and DHCP Options for DNS Configuration
Two protocols exist to configure the DNS information on a host, the
Router Advertisement options specified in this document and the
DHCPv6 options specified in [RFC3646]. They can be used together.
The rules governing the decision to use stateful configuration
mechanisms are specified in [RFC4861]. Hosts conforming to this
specification MUST extract DNS information from Router Advertisement
messages, unless static DNS configuration has been specified by the
user. If there is DNS information available from multiple Router
Advertisements and/or from DHCP, the host MUST maintain an ordered
list of this information as specified in Section 5.3.1.
2. Requirements Language
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].
3. Terminology
This document uses the terminology defined in [RFC4861] and
[RFC4862]. In addition, four new terms are defined below:
o Recursive DNS Server (RDNSS): Server that provides a recursive DNS
resolution service for translating domain names into IP addresses
or resolving PTR records, as defined in [RFC1034] and [RFC1035].
o RDNSS Option: IPv6 RA option to deliver the RDNSS information to
IPv6 hosts [RFC4861].
o DNS Search List (DNSSL): The list of DNS suffix domain names used
by IPv6 hosts when they perform DNS query searches for short,
unqualified domain names.
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o DNSSL Option: IPv6 RA option to deliver the DNSSL information to
IPv6 hosts.
o DNS Repository: Two data structures for managing DNS Configuration
Information in the IPv6 protocol stack in addition to Neighbor
Cache and Destination Cache for Neighbor Discovery [RFC4861]. The
first data structure is the DNS Server List for RDNSS addresses
and the second is the DNS Search List for DNS search domain names.
o Resolver Repository: Configuration repository with RDNSS addresses
and a DNS Search List that a DNS resolver on the host uses for DNS
name resolution; for example, the Unix resolver file (i.e., /etc/
resolv.conf) and Windows registry.
4. Overview
This document standardizes the ND option called the RDNSS option
defined in [RFC6106] that contains the addresses of recursive DNS
servers. This document also standardizes the ND option called the
DNSSL option defined in [RFC6106] that contains the Domain Search
List. This is to maintain parity with the DHCPv6 options and to
ensure that there is necessary functionality to determine the search
domains.
The existing ND message (i.e., Router Advertisement) is used to carry
this information. An IPv6 host can configure the IPv6 addresses of
one or more RDNSSes via RA messages. Through the RDNSS and DNSSL
options, along with the prefix information option based on the ND
protocol ([RFC4861] and [RFC4862]), an IPv6 host can perform the
network configuration of its IPv6 address and the DNS information
simultaneously without needing DHCPv6 for the DNS configuration. The
RA options for RDNSS and DNSSL can be used on the network that
supports the use of ND.
This approach requires the manual configuration or other automatic
mechanisms (e.g., DHCPv6 or vendor proprietary configuration
mechanisms) to configure the DNS information in routers sending the
advertisements. The automatic configuration of RDNSS addresses and a
DNS Search List in routers is out of scope for this document.
5. Neighbor Discovery Extension
The IPv6 DNS configuration mechanism in this document needs two ND
options in Neighbor Discovery: (i) the Recursive DNS Server (RDNSS)
option and (ii) the DNS Search List (DNSSL) option.
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5.1. Recursive DNS Server Option
The RDNSS option contains one or more IPv6 addresses of recursive DNS
servers. All of the addresses share the same Lifetime value. If it
is desirable to have different Lifetime values, multiple RDNSS
options can be used. Figure 1 shows the format of the RDNSS option.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Addresses of IPv6 Recursive DNS Servers :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Recursive DNS Server (RDNSS) Option Format
Fields:
Type 8-bit identifier of the RDNSS option type as assigned
by the IANA: 25
Length 8-bit unsigned integer. The length of the option
(including the Type and Length fields) is in units of
8 octets. The minimum value is 3 if one IPv6 address
is contained in the option. Every additional RDNSS
address increases the length by 2. The Length field
is used by the receiver to determine the number of
IPv6 addresses in the option.
Lifetime 32-bit unsigned integer. The maximum time in
seconds (relative to the time the packet is received)
over which these RDNSS addresses MAY be used for name
resolution. The value of Lifetime SHOULD by default
be at least 3 * MaxRtrAdvInterval where
MaxRtrAdvInterval is the Maximum RA Interval defined
in [RFC4861]. A value of all one bits (0xffffffff)
represents infinity. A value of zero means that the
RDNSS addresses MUST no longer be used.
Addresses of IPv6 Recursive DNS Servers
One or more 128-bit IPv6 addresses of the recursive
DNS servers. The number of addresses is determined
by the Length field. That is, the number of
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addresses is equal to (Length - 1) / 2.
Note: The addresses for recursive DNS servers in the RDNSS option
MAY be link-local addresses. Such link-local addresses SHOULD be
registered into the resolver repository along with the
corresponding link zone indices of the links that receive the
RDNSS option(s) for them. The link-local addresses MAY be
represented with their link zone indices in the textual format for
scoped addresses as described in [RFC4007]. When a resolver sends
a DNS query message to an RDNSS with a link-local address, it MUST
use the corresponding link.
5.2. DNS Search List Option
The DNSSL option contains one or more domain names of DNS suffixes.
All of the domain names share the same Lifetime value. If it is
desirable to have different Lifetime values, multiple DNSSL options
can be used. Figure 2 shows the format of the DNSSL option.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Domain Names of DNS Search List :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: DNS Search List (DNSSL) Option Format
Fields:
Type 8-bit identifier of the DNSSL option type as assigned
by the IANA: 31
Length 8-bit unsigned integer. The length of the option
(including the Type and Length fields) is in units of
8 octets. The minimum value is 2 if at least one
domain name is contained in the option. The Length
field is set to a multiple of 8 octets to accommodate
all the domain names in the field of Domain Names of
DNS Search List.
Lifetime 32-bit unsigned integer. The maximum time in
seconds (relative to the time the packet is received)
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over which these DNSSL domain names MAY be used for
name resolution. The Lifetime value has the same
semantics as with the RDNSS option. That is,
Lifetime SHOULD by default be at least
3 * MaxRtrAdvInterval. A value of all one bits
(0xffffffff) represents infinity. A value of zero
means that the DNSSL domain names MUST no longer be
used.
Domain Names of DNS Search List
One or more domain names of DNS Search List that MUST
be encoded as described in Section 3.1 of [RFC1035].
By this technique, each domain name is represented as
a sequence of labels ending in a zero octet, defined
as domain name representation. For more than one
domain name, the corresponding domain name
representations are concatenated as they are. Note
that for the simple decoding, the domain names MUST
NOT be encoded in a compressed form, as described in
Section 4.1.4 of [RFC1035]. Because the size of this
field MUST be a multiple of 8 octets, for the minimum
multiple including the domain name representations,
the remaining octets other than the encoding parts of
the domain name representations MUST be padded with
zeros.
5.3. Procedure of DNS Configuration
The procedure of DNS configuration through the RDNSS and DNSSL
options is the same as with any other ND option [RFC4861].
5.3.1. Procedure in IPv6 Host
When an IPv6 host receives DNS options (i.e., RDNSS option and DNSSL
option) through RA messages, it processes the options as follows:
o The validity of DNS options is checked with the Length field; that
is, the value of the Length field in the RDNSS option is greater
than or equal to the minimum value (3), and satisfies that (Length
- 1) % 2 == 0. The value of the Length field in the DNSSL option
is greater than or equal to the minimum value (2). Also, the
validity of the RDNSS option is checked with the "Addresses of
IPv6 Recursive DNS Servers" field; that is, the addresses should
be unicast addresses.
o If the DNS options are valid, the host SHOULD copy the values of
the options into the DNS Repository and the Resolver Repository in
order. Otherwise, the host MUST discard the options. Refer to
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Section 6 for the detailed procedure.
In the case where the DNS options of RDNSS and DNSSL can be obtained
from multiple sources, such as RA and DHCP, the IPv6 host SHOULD keep
some DNS options from all sources. Unless explicitly specified for
the discovery mechanism, the exact number of addresses and domain
names to keep is a matter of local policy and implementation choice
as a local configuration option. However, in the case of multiple
sources, the ability to store a total of at least three RDNSS
addresses (or DNSSL domain names) from the multiple sources is
RECOMMENDED. The DNS options from Router Advertisements and DHCP
SHOULD be stored into the DNS Repository and Resolver Repository so
that information from DHCP appears there first and therefore takes
precedence. Thus, the DNS information from DHCP takes precedence
over that from RA for DNS queries. On the other hand, for DNS
options announced by RA, if some RAs use the Secure Neighbor
Discovery (SEND) protocol [RFC3971] for RA security, they MUST be
preferred over those that do not use SEND. Refer to Section 7 for
the detailed discussion on SEND for RA DNS options.
5.3.2. Warnings for DNS Options Configuration
There are two warnings for DNS options configuration: (i) warning for
multiple sources of DNS options and (ii) warning for multiple network
interfaces. First, in the case of multiple sources for DNS options
(e.g., RA and DHCP), an IPv6 host can configure its IP addresses from
these sources. In this case, it is not possible to control how the
host uses DNS information and what source addresses it uses to send
DNS queries. As a result, configurations where different information
is provided by different sources may lead to problems. Therefore,
the network administrator needs to configure different DNS options in
the multiple sources in order to minimize the impact of such problems
[DHCPv6-SLAAC].
Second, if different DNS information is provided on different network
interfaces, this can lead to inconsistent behavior. The IETF worked
on solving this problem for both DNS and other information obtained
by multiple interfaces [RFC6418][RFC6419], and standardized the
solution for RDNSS selection for multi-interfaced nodes in [RFC6731],
which is based on DHCP.
6. Implementation Considerations
The implementation considerations in this document include the
following three: (i) DNS repository management, (ii) synchronization
between DNS server list and resolver repository, and (iii)
synchronization between DNS search list and resolver repository.
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6.1. DNS Repository Management
For DNS repository management, the kernel or user-space process
(depending on where RAs are processed) should maintain the following
two data structures to be synchronized with each other: (i) DNS
Server List that keeps the list of RDNSS addresses and (ii) DNS
Search List that keeps the list of DNS search domain names. Each
entry in these two lists consists of a pair of an RDNSS address (or
DNSSL domain name) and Expiration-time as follows:
o RDNSS address for DNS Server List: IPv6 address of the Recursive
DNS Server, which is available for recursive DNS resolution
service in the network advertising the RDNSS option.
o DNSSL domain name for DNS Search List: DNS suffix domain names,
which are used to perform DNS query searches for short,
unqualified domain names for the RDNSS address, which is
advertised by the same RA message having the DNSSL option, in the
network advertising the DNSSL option.
o Expiration-time for DNS Server List or DNS Search List: The time
when this entry becomes invalid. Expiration-time is set to the
value of the Lifetime field of the RDNSS option or DNSSL option
plus the current time. Whenever a new RDNSS option with the same
address (or DNSSL option with the same domain name) is received on
the same interface as a previous RDNSS option (or DNSSL option),
this field is updated to have a new Expiration-time. When the
current time becomes larger than Expiration-time, this entry is
regarded as expired. Note that the DNS information for the RDNSS
and DNSSL options need not be dropped if the expiry of the RA
router lifetime happens. This is because these options have their
own lifetime values.
6.2. Synchronization between DNS Server List and Resolver Repository
When an IPv6 host receives the information of multiple RDNSS
addresses within a network (e.g., campus network and company network)
through an RA message with RDNSS option(s), it stores the RDNSS
addresses (in order) into both the DNS Server List and the Resolver
Repository. The processing of the RDNSS consists of (i) the
processing of RDNSS option(s) included in an RA message and (ii) the
handling of expired RDNSSes. The processing of RDNSS option(s) is as
follows:
Step (a): Receive and parse the RDNSS option(s). For the RDNSS
addresses in each RDNSS option, perform Steps (b) through (d).
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Step (b): For each RDNSS address, check the following: If the
RDNSS address already exists in the DNS Server List and the RDNSS
option's Lifetime field is set to zero, delete the corresponding
RDNSS entry from both the DNS Server List and the Resolver
Repository in order to prevent the RDNSS address from being used
any more for certain reasons in network management, e.g., the
termination of the RDNSS or a renumbering situation. That is, the
RDNSS can resign from its DNS service because the machine running
the RDNSS is out of service intentionally or unintentionally.
Also, under the renumbering situation, the RDNSS's IPv6 address
will be changed, so the previous RDNSS address should not be used
any more. The processing of this RDNSS address is finished here.
Otherwise, go to Step (c).
Step (c): For each RDNSS address, if it already exists in the DNS
Server List, then just update the value of the Expiration-time
field according to the procedure specified in the third bullet of
Section 6.1. Otherwise, go to Step (d).
Step (d): For each RDNSS address, if it does not exist in the DNS
Server List, register the RDNSS address and Lifetime with the DNS
Server List and then insert the RDNSS address in front of the
Resolver Repository. In the case where the data structure for the
DNS Server List is full of RDNSS entries (that is, has more
RDNSSes than the sufficient number discussed in Section 5.3.1),
delete from the DNS Server List the entry with the shortest
Expiration-time (i.e., the entry that will expire first). The
corresponding RDNSS address is also deleted from the Resolver
Repository. For the ordering of RDNSS addresses in an RDNSS
option, position the first RDNSS address in the RDNSS option as
the first one in the Resolver Repository, the second RDNSS address
in the option as the second one in the repository, and so on.
This ordering allows the RDNSS addresses in the RDNSS option to be
preferred according to their order in the RDNSS option for the DNS
name resolution. The processing of these RDNSS addresses is
finished here.
The handling of expired RDNSSes is as follows: Whenever an entry
expires in the DNS Server List, the expired entry is deleted from the
DNS Server List, and also the RDNSS address corresponding to the
entry is deleted from the Resolver Repository.
6.3. Synchronization between DNS Search List and Resolver Repository
When an IPv6 host receives the information of multiple DNSSL domain
names within a network through an RA message with DNSSL option(s), it
stores the DNSSL domain names (in order) into both the DNS Search
List and the Resolver Repository. The processing of the DNSSL
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consists of (i) the processing of DNSSL option(s) included in an RA
message and (ii) the handling of expired DNSSLs. The processing of
DNSSL option(s) is the same with that of RDNSS option(s) in Section
6.2 except Step (b).
In Step (b), if the DNSSL domain name already exists in the DNS
Search List and the DNSSL option's Lifetime field is set to zero,
delete the corresponding DNSSL entry from both the DNS Search List
and the Resolver Repository in order to prevent the DNSSL domain name
from being used any more for certain reasons in network management,
e.g., the termination of the usage of the DNSSL domain name. That
is, the DNSSL domain name may not be used any more by the policy of
the network.
7. Security Considerations
In this section, we analyze security threats related to DNS options
and then suggest recommendations to cope with such security threats.
7.1. Security Threats
For the RDNSS option, an attacker could send an RA with a fraudulent
RDNSS address, misleading IPv6 hosts into contacting an unintended
DNS server for DNS name resolution. Also, for the DNSSL option, an
attacker can let IPv6 hosts resolve a host name without a DNS suffix
into an unintended host's IP address with a fraudulent DNS Search
List. These attacks are similar to ND attacks specified in [RFC4861]
that use Redirect or Neighbor Advertisement messages to redirect
traffic to individual addresses of malicious parties.
However, the security of these RA options for DNS configuration does
not affect ND protocol security [RFC4861]. This is because learning
DNS information via the RA options cannot be worse than learning bad
router information via the RA options. Therefore, the vulnerability
of ND is not worse and is a subset of the attacks that any node
attached to a LAN can do.
7.2. Recommendations
The Secure Neighbor Discovery (SEND) protocol [RFC3971] is designed
as a security mechanism for ND. In this case, ND can use SEND to
allow all the ND options including the RDNSS and DNSSL options to be
automatically included in the signatures. Other approaches specified
in [RFC4861] can be used for securing the RA options for DNS
configuration.
It is common for network devices such as switches to include
mechanisms to block unauthorized ports from running a DHCPv6 server
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to provide protection from rogue DHCPv6 servers [RFC7610]. That
means that an attacker on other ports cannot insert bogus DNS servers
using DHCPv6. The corresponding technique for network devices is
RECOMMENDED to block rogue Router Advertisement messages [RFC6104]
including the RDNSS and DNSSL options from unauthorized nodes.
An attacker may provide a bogus DNS Search List option in order to
cause the victim to send DNS queries to a specific DNS server when
the victim queries non-FQDNs (fully qualified domain names). For
this attack, the DNS resolver in IPv6 hosts can mitigate the
vulnerability with the recommendations mentioned in [RFC1535],
[RFC1536], and [RFC3646].
8. IANA Considerations
The RDNSS option defined in this document uses the IPv6 Neighbor
Discovery Option type defined in RFC 6106 [RFC6106], which was
assigned by the IANA as follows:
Option Name Type
Recursive DNS Server Option 25
The DNSSL option defined in this document uses the IPv6 Neighbor
Discovery Option type defined in RFC 6106 [RFC6106], which was
assigned by the IANA as follows:
Option Name Type
DNS Search List Option 31
These options have been registered in the "Internet Control Message
Protocol version 6 (ICMPv6) Parameters" registry (http://
www.iana.org/assignments/icmpv6-parameters/
icmpv6-parameters.xhtml#icmpv6-parameters-5).
9. Acknowledgements
This document has greatly benefited from inputs by Robert Hinden,
Pekka Savola, Iljitsch van Beijnum, Brian Haberman, Tim Chown, Erik
Nordmark, Dan Wing, Jari Arkko, Ben Campbell, Vincent Roca, Tony
Cheneau, Fernando Gont, Jen Linkova, Ole Troan, Mark Smith, Tatuya
Jinmei, Lorenzo Colitti, Tore Anderson, David Farmer, and Bing Liu.
The authors sincerely appreciate their contributions.
This document was supported by Institute for Information &
communications Technology Promotion (IITP) grant funded by the Korea
government (MSIP) [10041244, Smart TV 2.0 Software Platform].
10. References
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10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H.
Soliman, "Neighbor Discovery for IP version 6
(IPv6)", RFC 4861, September 2007.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6
Stateless Address Autoconfiguration", RFC 4862,
September 2007.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E.,
and B. Zill, "IPv6 Scoped Address Architecture",
RFC 4007, March 2005.
10.2. Informative References
[RFC1034] Mockapetris, P., "Domain names - concepts and
facilities", STD 13, RFC 1034, November 1987.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration
Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC3736] Droms, R., "Stateless Dynamic Host Configuration
Protocol (DHCP) Service for IPv6", RFC 3736,
April 2004.
[RFC3646] Droms, R., "DNS Configuration options for Dynamic
Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 3646, December 2003.
[RFC5006] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"IPv6 Router Advertisement Option for DNS
Configuration", RFC 5006, September 2007.
[RFC6106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"IPv6 Router Advertisement Options for DNS
Configuration", RFC 6106, November 2010.
[RFC4339] Jeong, J., "IPv6 Host Configuration of DNS Server
Information Approaches", RFC 4339, February 2006.
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Internet-Draft IPv6 RA DNS Options March 2016
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander,
"SEcure Neighbor Discovery (SEND)", RFC 3971,
March 2005.
[RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router
Advertisement Problem Statement", RFC 6104,
February 2011.
[RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-
Shield: Protecting against Rogue DHCPv6 Servers",
RFC 7610, August 2015.
[RFC1535] Gavron, E., "A Security Problem and Proposed
Correction With Widely Deployed DNS Software",
RFC 1535, October 1993.
[RFC1536] Kumar, A., Postel, J., Neuman, C., Danzig, P., and S.
Miller, "Common DNS Implementation Errors and
Suggested Fixes", RFC 1536, October 1993.
[DHCPv6-SLAAC] Liu, B., Jiang, S., Gong, X., Wang, W., and E. Rey,
"DHCPv6/SLAAC Interaction Problems on Address and DNS
Configuration", Work in Progress, February 2016.
[RFC6418] Blanchet, M. and P. Seite, "Multiple Interfaces and
Provisioning Domains Problem Statement", RFC 6418,
November 2011.
[RFC6419] Wasserman, M. and P. Seite, "Current Practices for
Multiple-Interface Hosts", RFC 6419, November 2011.
[RFC6731] Savolainen, T., Kato, J., and T. Lemon, "Improved
Recursive DNS Server Selection for Multi-Interfaced
Nodes", RFC 6731, December 2012.
Appendix A. Changes from RFC 6106
The following changes were made from RFC 6106 "IPv6 Router
Advertisement Options for DNS Configuration":
o The generation of Router Solicitation to ensure that the RDNSS
information is fresh before the expiry of the RDNSS option is
removed in order to prevent multicast traffic on the link from
increasing.
o The lifetime's upper bound of 2 * MaxRtrAdvInterval was shown to
lead to the expiry of these options on links with a relatively
high rate of packet loss. This revision relaxes the upper bound
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and sets a higher default value to avoid this problem.
o The addresses for recursive DNS servers in the RDNSS option can be
not only global addresses, but also link-local addresses. The
link-local addresses for RDNSSes should be registered into the
resolver repository along with the corresponding link zone
indices.
o The recommendation that at most three RDNSS addresses to maintain
by RDNSS options should be limited is removed. By this removal,
the number of RDNSSes to maintain is up to an implementer's local
policy.
o The recommendation that at most three DNS domains to maintain by
DNSSL options should be limited is removed. By this removal, when
the set of unique DNSSL values are not equivalent, none of them
are ignored for hostname lookups.
o The guidance of the specific implementation for the
synchronization of the DNS Repository and Resolver Repository on
the kernel space and user space is removed.
o The usage of the keywords of SHOULD and RECOMMENDED in RFC 2119 is
removed in the recommendation of using SEND for secure ND.
Instead of using these keywords, SEND is specified as only a
possible solution for secure ND.
Authors' Addresses
Jaehoon Paul Jeong
Department of Software
Sungkyunkwan University
2066 Seobu-Ro, Jangan-Gu
Suwon, Gyeonggi-Do 16419
Republic of Korea
Phone: +82 31 299 4957
Fax: +82 31 290 7996
EMail: pauljeong@skku.edu
URI: http://iotlab.skku.edu/people-jaehoon-jeong.php
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Soohong Daniel Park
Software R&D Center
Samsung Electronics
Seoul R&D Campus D-Tower, 56, Seongchon-Gil, Seocho-Gu
Seoul 06765
Republic of Korea
EMail: soohong.park@samsung.com
Luc Beloeil
France Telecom R&D
42, rue des coutures
BP 6243
14066 CAEN Cedex 4
France
Phone: +33 2 40 44 97 40
EMail: luc.beloeil@orange-ftgroup.com
Syam Madanapalli
iRam Technologies
#H304, Shriram Samruddhi, Thubarahalli
Bangalore - 560066
India
EMail: smadanapalli@gmail.com
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