HIP Working Group P. Nikander
Internet-Draft Ericsson Research Nomadic Lab
Expires: April 18, 2005 J. Laganier
LIP / Sun Microsystems
October 18, 2004
Host Identity Protocol (HIP) Domain Name System (DNS) Extensions
draft-ietf-hip-dns-00
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of section 3 of RFC 3667. By submitting this Internet-Draft, each
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RFC 3668.
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This Internet-Draft will expire on April 18, 2005.
Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
This document specifies two new resource records for the Domain Name
System (DNS), and how to use them with the Host Identity Protocol
(HIP). These records allow a HIP node to store in the DNS its Host
Identity (its public key), Host Identity Tag (a truncated hash of its
public key), and Rendezvous Servers (RVS).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 5
3. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1 Simple static singly homed end-host . . . . . . . . . . . 7
3.2 Mobile end-host . . . . . . . . . . . . . . . . . . . . . 7
3.3 Multi-homed Site or End-host . . . . . . . . . . . . . . . 7
4. Overview of using the DNS with HIP . . . . . . . . . . . . . . 8
4.1 Different types of HITs . . . . . . . . . . . . . . . . . 8
4.1.1 Host Assigning Authority (HAA) field . . . . . . . . . 8
4.2 Storing HI and HIT in DNS . . . . . . . . . . . . . . . . 8
4.3 Storing HAA in DNS . . . . . . . . . . . . . . . . . . . . 8
4.4 Providing multiple IP addresses . . . . . . . . . . . . . 9
4.4.1 Storing Rendezvous Servers in the DNS . . . . . . . . 9
4.5 Initiating connections based on DNS names . . . . . . . . 9
4.6 HI and HIT verification . . . . . . . . . . . . . . . . . 9
5. Storage Format . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 HIPHI RDATA format . . . . . . . . . . . . . . . . . . . . 10
5.1.1 HIT type format . . . . . . . . . . . . . . . . . . . 10
5.1.2 HIT algorithm format . . . . . . . . . . . . . . . . . 10
5.1.3 PK algorithm type format . . . . . . . . . . . . . . . 10
5.1.4 HIT format . . . . . . . . . . . . . . . . . . . . . . 11
5.1.5 Public key format . . . . . . . . . . . . . . . . . . 11
5.2 HIPRVS RDATA format . . . . . . . . . . . . . . . . . . . 11
5.2.1 Preference format . . . . . . . . . . . . . . . . . . 12
5.2.2 Rendezvous server type format . . . . . . . . . . . . 12
5.2.3 Rendezvous server format . . . . . . . . . . . . . . . 12
6. Transition mechanisms . . . . . . . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
7.1 Attacker tampering with an unsecure HIPHI RR . . . . . . . 15
7.2 Attacker tampering with an unsecure HIPRVS RR . . . . . . 15
7.3 Opportunistic HIP . . . . . . . . . . . . . . . . . . . . 16
7.4 Anonymous Initiator . . . . . . . . . . . . . . . . . . . 16
7.5 Hash and HITs Collisions . . . . . . . . . . . . . . . . . 16
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.1 Normative references . . . . . . . . . . . . . . . . . . . . 19
10.2 Informative references . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 20
A. Using multiple HIs with multiple IPs . . . . . . . . . . . . . 21
B. Document Revision History . . . . . . . . . . . . . . . . . . 23
Intellectual Property and Copyright Statements . . . . . . . . 24
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1. Introduction
This document specifies two new resource records (RRs) for the Domain
Name System (DNS) [7], and how to use them with the Host Identity
Protocol (HIP) [9]. These records allow a HIP node to store in the
DNS its Host Identity (its public key), Host Identity Tag (a
truncated hash of its public key), and Rendezvous Servers (RVS) [12].
The current Internet architecture defines two global namespaces: IP
addresses and domain names. The Domain Name System provides a two
way lookup between these two namespaces. The HIP architecture [10]
defines a new third namespace, called the Host Identity Namespace.
This namespace is composed of Host Identifiers (HI) of HIP nodes.
The Host Identity Tag (HIT) is one representation of an HI. This
representation is obtained by taking the output of a secure hash
function applied to the HI, truncated to the IPv6 address size. HITs
are supposed to be used in the place of IP addresses in some ULPs and
applications.
The Host Identity Protocol [9] allows two HIP nodes to establish a
pair of unidirectional IPsec Security Association. These SAs are
bound to the HI instead of IP addresses. The proposed HIP
multi-homing mechanisms [11] allow a node to dynamically change its
set of underlying IP addresses while maintaining IPsec SA and
transport layer session survivability. The HIP rendezvous extensions
[12] proposal allows a HIP node to maintain HIP reachability while
not relying on dynamic DNS updates to make its peers aware of its
current location (the set of IP address(es)).
Although a HIP node can initiate HIP communication
"opportunistically" (without a priori knowledge of its peer's HI),
doing so exposes both endpoints to Man-in-the-Middle attacks on the
HIP handshake. Hence, there is a desire to gain knowledge of peers'
HI before applications and ULPs initiate communication.
Currently, most of the Internet applications that need to communicate
with a remote host first translate a domain name (often obtained via
user input) into one or more IP address(es). This step occurs prior
to communication with the remote host, and relies on a DNS lookup.
With HIP, IP addresses are expected to be used mostly for on-the-wire
communication between end hosts, while most ULPs and applications
uses HIs or HITs instead (ICMP might be an example of an ULP not
using them). Consequently, we need a means to translate a domain
name into an HI. Using the DNS for this translation is pretty
straightforward: We define a new HIPHI (HIP HI) resource record.
Upon query by an application or ULP for a FQDN -> IP lookup, the
resolver would then additionally perform an FQDN -> HI lookup, and
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use it to construct the resulting HI -> IP mapping (which is internal
to the HIP layer). The HIP layer uses the HI -> IP mapping to
translate HIs and their local representations (HITs, IPv4 and
IPv6-compatible LSIs) into IP addresses and vice versa.
This draft introduces the following new DNS Resource Records:
- HIPHI, for storing Host Identifiers and Host Identity Tags
- HIPRVS, for storing rendezvous server information
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2. Conventions used in this document
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].
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3. Use cases
In this section, we briefly introduce a number of use cases where the
DNS is useful with the Host Identity Protocol.
With HIP, most application and ULPs are unaware of the IP addresses
used to carry packets on the wire. Consequently, a HIP node could
take advantage of having multiple IP addresses for fail-over,
redundancy, mobility, or renumbering, in a manner which is
transparent to most ULPs and applications (because they are bound to
HIs, hence they are agnostic to these IP address changes).
In these situations, a node wishing to be reachable by reference to
its FQDN should store the following informations in the DNS:
o A set of IP address(es).
o A Host Identity (HI) and/or Host Identity Tag (HIT).
o An IP address or DNS name of its Rendezvous Server(s) (RVS).
When a HIP node wants to initiate a communication with another HIP
node, it first needs to perform a HIP base exchange to set-up a HIP
association towards its peer. Although such an exchange can be
initiated opportunistically, i.e., without a priori knowledge of the
responder's HI, by doing so both nodes knowingly risk
man-in-the-middle attacks on the HIP exchange. To prevent these
attacks, it is recommended that the initiator first obtain the HI of
the responder, and then initiate the exchange. This can be done, for
example, through manual configuration or DNS lookups. Hence, a new
HIPHI RR is introduced.
When a HIP node is frequently changing its IP address(es), the
dynamic DNS update latency may prevent it from publishing its new IP
address(es) in the DNS. For solving this problem, the HIP
architecture introduces Rendezvous Servers (RVS). A HIP host uses a
Rendezvous Server as a Rendezvous point, to maintain reachability
with possible HIP initiators. Such a HIP node would publish in the
DNS its RVS IP address or DNS name in a HIPRVS RR, while keeping its
RVS up-to-date with its current set of IP addresses.
Then, when some other node wants to initiate a HIP exchange with such
a responder, it retrieves the RVS IP address by looking up a HIPRVS
RR at the FQDN of the responder, and sends an I1 to this IP address.
The I1 will then be relayed by the RVS to the responder, which will
then complete the HIP exchange, either directly or via the RVS [12].
Note that storing HIP RR information in the DNS at a FQDN which is
assigned to a non-HIP node might have ill effects on its reachability
by HIP nodes.
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3.1 Simple static singly homed end-host
A HIP node having a single static network attachment, wishing to be
reachable by reference to its FQDN, would store in the DNS, in
addition to its IP address(es), its Host Identity (HI) in a HIPHI
resource record.
3.2 Mobile end-host
A mobile HIP node wishing to be reachable by reference to its FQDN
would store in the DNS, instead of its IP address(es), its HI in a
HIPHI RR, and the IP address(es) of its Rendezvous Server(s) in
HIPRVS resource record(s). The mobile HIP node also need to notify
its Rendezvous Servers of any change in its set of IP address(es).
A host wanting to reach this mobile host would then send an I1 to one
of its RVS. Following, the RVS will relay the I1 up to the mobile
node, which will complete the HIP exchange.
3.3 Multi-homed Site or End-host
A HIP node with several distinct network attachments is multi-homed.
A HIP node attached to a network with multiple ISPs is in a
multi-homed site will possibly have multiple prefixes and addresses.
Such HIP node might also be reachable via several distinct Rendezvous
Servers. In addition to its set of IP address(es), a multi-homed
end-host would store in the DNS its HI in a HIPHI RR, and possibly
the IP address(es) of its RVS(s) in HIPRVS RRs.
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4. Overview of using the DNS with HIP
4.1 Different types of HITs
There are _currently_ two types of HITs. HITs of the first type
consists just of the least significant bits of the hash of the public
key. HITs of the second type consist of a binary prefix Host
Assigning Authority (HAA) field, and only the last bits come from a
hash of the Host Identity. This latter format for HIT is recommended
for 'well known' systems. It is possible to support a resolution
mechanism for these names in directories like DNS.
Note that the format how HITs are stored in the DNS may be different
form the format actually used in protocols, the HIP base exchange [9]
included. This is because the DNS RR explicitly contains the HIT
type and algorithm, while some protocols may prefer to use a prefix
to indicate the HIT type. The implementations are expected to use
the actual HI when comparing Host Identities.
4.1.1 Host Assigning Authority (HAA) field
The 64 bits of HAA supports two levels of delegation. The first is a
registered assigning authority (RAA). The second is a registered
identity (RI, commonly a company). The RAA is 24 bits with values
assign sequentially by ICANN. The RI is 40 bits, also assigned
sequentially but by the RAA.
As IPv6 "global site-local" addresses were proposed in the IPv6 WG to
replace IPv6 site-local address, it is questionable if HIP needs a
kind of "global site-local" HAA, which would be generated by a given
site by setting the RAA field to 0 while the RI field is filled by
either random or EUI-48 bits.
4.2 Storing HI and HIT in DNS
Any conforming implementation may store Host Identifiers in a DNS
HIPHI RDATA format. An implementation may also store a HIT along
with its associated HI. If a particular form of an HI or HIT does
not already have a specified RDATA format, a new RDATA-like format
SHOULD be defined for the HI or HIT.
4.3 Storing HAA in DNS
Any conforming implementation may store a site's Host Assigning
Authority in a DNS HIPHI RDATA format. A HAA MUST be stored
similarly to a Type 2 HIT, while the least significant bits are set
to 0. If a particular form of a HAA does not already have an
associated HIT specified RDATA format, a new RDATA-like format SHOULD
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be defined for the HIT/HAA.
4.4 Providing multiple IP addresses
With HIP, ULPs doesn't see which IP address is indeed used to carry
packets on the wire. Consequently, a HIP node could take advantage
of having multiple IP addresses for ULPs and applications fail over,
redundancy, etc. This can be achieved either by storing multiple
addresses in the DNS, while these addresses might be those of
different IP interfaces or Rendezvous servers.
4.4.1 Storing Rendezvous Servers in the DNS
The HIP Rendezvous server (HIPRVS) resource record indicates an
address (or a FQDN resolvable into an address) towards which a HIP I1
packet might be sent to trigger the establishment of an association
with the entity named by this resource record.
An RVS receiving such an I1 would then forward it to the appropriate
responder (the owner of the destination HIT in this I1). The
responder will then complete the exchange with the initiator,
possibly without ongoing help from the RVS.
Any conforming implementation may store Rendezvous Server's IP
address(es) or DNS name in a DNS HIPRVS RDATA format. If a
particular form of a RVS reference does not already have a specified
RDATA format, a new RDATA-like format SHOULD be defined for the RVS.
4.5 Initiating connections based on DNS names
A Host Identity Protocol exchange SHOULD be initiated whenever the
DNS lookup returns HIPHI resource records. Furthermore, if the DNS
lookups also returns HIPRVS resource records, the addresses of these
RVS SHOULD be put in the destination IP addresses list while
initiating the afore mentioned HIP exchange. Since some hosts may
choose not to have HIPHI information in DNS, hosts MAY implement
support opportunistic HIP.
4.6 HI and HIT verification
Upon return of a HIPHI RR, a host MUST always calculate the
HI-derivative HIT to be used in the HIP exchange, as specified in the
HIP architecture [10], while the HIT possibly embedded along SHOULD
only be used as an optimization (e.g., table lookup).
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5. Storage Format
5.1 HIPHI RDATA format
The RDATA for a HIPHI RR consists of a HIT type, an algorithm type, a
HIT, and a public key.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HIT type | HIT algorithm | PK algorithm | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ HIT |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| /
/ Public Key /
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
5.1.1 HIT type format
The HIT type field indicates the Host Identity Tag (HIT) type and the
implied HIT format.
The following values are defined:
0 No HIT is present.
1 A Type 1 HIT is present.
2 A Type 2 HIT is present.
3-6 Unassigned
7 A HAA is present.
5.1.2 HIT algorithm format
The HIT algorithm indicates the hash algorithm used to generate the
Host Identity Tag (HIT) from the HI.
The following values are defined:
0 Reserved.
1 SHA1
2-255 Unassigned
5.1.3 PK algorithm type format
The algorithm type indicates the public key cryptographic algorithm
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and the implied public key field format. This document reuse the
values defined for the 'algorithm type' of the IPSECKEY RR [13]
'gateway type' field.
The presently defined values are given only informally:
0 No key is present.
1 A DSA key is present, in the format defined in RFC2536 [3].
2 A RSA key is present, in the format defined in RFC3110 [5].
5.1.4 HIT format
There's currently two types of HITs, and a single type of HAA. Both
of them have a variable length and are stored within a single
<character-string> holding the bits of the HITs or HAA:
o A *Type 1* HIT: least significant bits of the hash (e.g., SHA1) of
the public key (Host Identity), which is possibly following in the
HIPHI RR.
o A *Type 2* HIT: binary prefix (HAA) concatenated with a the least
significant bits of the hash (e.g., SHA1) of the public key (Host
Identity), which is possibly following in the HIPHI RR.
o A HAA: binary prefix (HAA) concatenated with 0, up to the
associated HIT length.
5.1.5 Public key format
Both of the public key types defined in this document (RSA and DSA)
reuse the public key formats defined for the IPSECKEY RR [13] (which
in turns contains the algorithm-specific portion of the KEY RR RDATA,
all of the KEY RR DATA after the first four octets, corresponding to
the same portion of the KEY RR that must be specified by documents
that define a DNSSEC algorithm).
In the future, if a new algorithm is to be used both by IPSECKEY RR
and HIPHI RR, it would probably use the same public key encodings for
both RRs. Unless specified otherwise, the HIPHI public key field
would use the same public key format as the IPSECKEY RR RDATA for the
corresponding algorithm.
The DSA key format is defined in RFC2536 [3].
The RSA key format is defined in RFC3110 [5].
5.2 HIPRVS RDATA format
The RDATA for a HIPRVS RR consists of a preference value, a
Rendezvous server type and either one or more Rendezvous server
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address, or one Rendezvous server FQDN.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| preference | type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rendezvous server |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.2.1 Preference format
This is an 8-bit preference order for this record. This used to
specify the preference given to this RR amongst others at the same
owner. Lower values are preferred. If there is a tie with some RRs,
the server should return a set of RRs ordered in a load balancing
manner (e.g., round robin).
5.2.2 Rendezvous server type format
The Rendezvous server type indicates the format of the information
stored in the Rendezvous server field.
This document reuses the type values for the 'gateway type' field of
the IPSECKEY RR [13]. The presently defined values are given only
informally:
0 Reserved.
1 One or more 4-byte IPv4 address(es) in network byte order are
present.
2 One or more 16-byte IPv6 address(es) in network byte order are
present.
3 One or more variable length wire-encoded domain names as
described in section 3.3 of RFC1035 [1]. The wire-encoded format
is self-describing, so the length is implicit. The domain names
MUST NOT be compressed.
5.2.3 Rendezvous server format
The Rendezvous server field indicates one or more address(es) (or one
or more FQDN(s) resolvable into one or more address(es)) towards
which a HIP I1 packet might be send in order to reach the entity
named by this resource record.
This document reuses the format used for the 'gateway' field of the
IPSECKEY RR [13], but allows to concatenate several IP (v4 or v6)
addresses. The presently defined formats for the data portion of the
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Rendezvous server field are given only informally:
o One or more 32-bit IPv4 address(es) in network byte order.
o One or more 128-bit IPv6 address(es) in network byte order.
o One or more variable length wire-encoded domain names as described
in section 3.3 of RFC1035 [1]. The wire-encoded format is
self-describing, so the length is implicit. The domain names MUST
NOT be compressed.
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6. Transition mechanisms
During a transition period, instead of storing the HI or HIT in a
HIPHI RR, the HIT MAY be stored in an AAAA RR. If a HIT is stored in
an AAAA RR, it MUST be returned as the last item in the set of AAAA
RRs returned to avoid as most as possible conflicts with non-HIP IPv6
nodes.
During a transition period, similarly to what may happen with HITs,
the RVS's IP address might be stored in an A or AAAA RR instead of a
HIPRVS RR. If a RVS IP address is stored in an A or AAAA RR, it MUST
be returned as the last item in the set of returned RRs to avoid as
most as possible conflicts with non-HIP IPv6 nodes.
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7. Security Considerations
Though the security considerations of the HIP DNS extensions still
need to be more investigated and documented, this section contains a
description of the known threats involved with the usage of the HIP
DNS extensions.
In a manner similar to the IPSECKEY RR [13], the HIP DNS Extensions
allows to provision two HIP nodes with the public keying material
(HI) of their peer. These HIs will be subsequently used in a key
exchange between the peers. Hence, the HIP DNS Extensions introduce
the same kind of threats that IPSECKEY does, plus threats caused by
the possibility of using unpublished initiator and opportunistic mode
in HIP.
A HIP node SHOULD obtain both the HIPHI and HIPRVS RRs from a trusted
party trough a secure channel insuring proper data integrity of the
RRs. This might be DNSSEC, or another secure channel to another
directory lookup service.
In the absence of a proper secure channel, both parties are
vulnerable to MitM and DoS attacks, and unrelated parties might be
subject to DoS attacks as well. These threats are described in the
following sections.
7.1 Attacker tampering with an unsecure HIPHI RR
The HIPHI RR contains public keying material in the form of the named
peer's public key (the HI) and its secure hash (the HIT). Both of
these are not sensitive to attacks where an adversary gains knowledge
of them. However, an attacker that is able to mount an active attack
on the DNS, i.e., tampers with this HIPHI RR (e.g., using DNS
spoofing) is able to mount Man-in-the-Middle attacks on the
cryptographic core of the eventual HIP exchange (responder's HIPHI
and HIPRVS rewritten by the attacker).
7.2 Attacker tampering with an unsecure HIPRVS RR
The HIPRVS RR contains a destination IP address where the named peer
is reachable by an I1 (HIP Rendezvous Extensions IPSECKEY RR [12] ).
Thus, an attacker able to tamper with this RRs is able to redirect I1
packets sent to the named peer to a chosen IP address, for DoS or
MitM attacks. Note that this kind of attacks are not specific to HIP
and exist independently to whether or not HIP and the HIPRVS RR are
used. Such an attacker might tamper with A and AAAA RRs as well.
An attacker might obviously use these two attacks in conjunction: It
will replace the responder's HI and RVS IP address by its owns in a
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spoofed DNS packet sent to the initiator HI, then redirect all
exchanged packets through him and mount a MitM on HIP. In this case
HIP won't provide confidentiality nor initiator HI protection from
eavesdroppers.
7.3 Opportunistic HIP
A HIP initiator may not be aware of its peer's HI, and/or its HIT
(e.g., because the DNS does not contains HIP material, or the
resolver isn't HIP-enabled), and attempt an opportunistic HIP
exchange towards its known IP address, filling the responder HIT
field with zeros in the I1 header. Such an initiator is vulnerable
to a MitM attack because it can't validate the HI and HIT contained
in a replied R1. Hence, an implementation MAY choose not to use
opportunistic mode.
7.4 Anonymous Initiator
A HIP initiator may choose to use an unpublished HI, which is not
stored in the DNS by means of a HIPHI RR. A responder associating
with such an initiator knowingly risks a MitM attack because it
cannot validate the initiator's HI. Hence, an implementation MAY
choose not to use unpublished mode.
7.5 Hash and HITs Collisions
As many cryptographic algorithm, some secure hashes (e.g. SHA1, used
by HIP to generate a HIT from an HI) eventually become insecure,
because an exploit has been found in which an attacker with a
reasonable computation power breaks one of the security features of
the hash (e.g., its supposed collision resistance). This is why a
HIP end-node implementation SHOULD NOT authenticate its HIP peers
based solely on a HIT retrieved from DNS, but rather use both the HI
and HIT.
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8. IANA Considerations
IANA needs to allocate two new RR type code for HIPHI and HIPRVS from
the standard RR type space.
IANA does not need to open a new registry for the HIPHI RR type for
public key algorithms because the HIPHI RR reuse 'algorithms types'
defined for the IPSECKEY RR [13]. The presently defined numbers are
given here only informally:
0 is reserved
1 is RSA
2 is DSA
IANA needs to open a new registry for the HIPHI RR HIT type. Defined
types are:
0 No HIT is present
1 A Type 1 HIT is present
2 A Type 2 HIT is present
3-6 Unassigned
7 A HAA is present
Adding new reservations requires IETF consensus RFC2434 [14].
IANA needs to open a new registry for the HIPHI RR HIT algorithm
type. Defined types are:
0 Reserved
1 SHA1
2-255 Unassigned
Adding new reservations requires IETF consensus RFC2434 [14].
IANA does not need to open a new registry for the HIPRVS RR
Rendezvous server type because the HIPHI RR reuse the 'gateway types'
defined for the IPSECKEY RR [13]. The presently defined numbers are
given here only informally:
0 is reserved
1 is IPv4
2 is IPv6
3 is a wire-encoded uncompressed domain name
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9. Acknowledgments
Some parts of this draft stem from [9]. This work is heavily
influenced by [13], which serves as a model for this document.
The authors would like to thanks the following people, who have
provided thoughtful and helpful discussions and/or suggestions, that
have improved this document: Rob Austein, Hannu Flinck, Tom
Henderson, Miika Komu, Andrew McGregor, Erik Nordmark, and Gabriel
Montenegro.
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10. References
10.1 Normative references
[1] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] Eastlake, D., "DSA KEYs and SIGs in the Domain Name System
(DNS)", RFC 2536, March 1999.
[4] Crawford, M., "Binary Labels in the Domain Name System", RFC
2673, August 1999.
[5] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain Name
System (DNS)", RFC 3110, May 2001.
[6] Bush, R., Durand, A., Fink, B., Gudmundsson, O. and T. Hain,
"Representing Internet Protocol version 6 (IPv6) Addresses in
the Domain Name System (DNS)", RFC 3363, August 2002.
[7] Klensin, J., "Role of the Domain Name System (DNS)", RFC 3467,
February 2003.
[8] Thomson, S., Huitema, C., Ksinant, V. and M. Souissi, "DNS
Extensions to Support IP Version 6", RFC 3596, October 2003.
[9] Moskowitz, R., Nikander, P. and P. Jokela, "Host Identity
Protocol", draft-ietf-hip-base-01 (work in progress), October
2004.
[10] Moskowitz, R. and P. Nikander, "Host Identity Protocol
Architecture", draft-ietf-hip-arch-00 (work in progress),
October 2004.
[11] Nikander, P., "End-Host Mobility and Multi-Homing with Host
Identity Protocol", draft-ietf-hip-mm-00 (work in progress),
October 2004.
[12] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extensions", draft-ietf-hip-rvs-00 (work in
progress), October 2004.
[13] Richardson, M., "A method for storing IPsec keying material in
DNS", draft-ietf-ipseckey-rr-10 (work in progress), April 2004.
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10.2 Informative references
[14] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October
1998.
[15] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on
Security Considerations", BCP 72, RFC 3552, July 2003.
Authors' Addresses
Pekka Nikander
Ericsson Research Nomadic Lab
JORVAS FIN-02420
FINLAND
Phone: +358 9 299 1
EMail: pekka.nikander@nomadiclab.com
Julien Laganier
LIP (CNRS-INRIA-ENSL-UCBL) & Sun Labs (Sun Microsystems)
180, Avenue de l'Europe
Saint Ismier CEDEX 38334
France
Phone: +33 476 188 815
EMail: ju@sun.com
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Appendix A. Using multiple HIs with multiple IPs
The RRs defined in this document are "flat", in the sense that the IP
addresses and HIs are associated to an FQDN on an equality basis. In
the case where an FQDN is resolved into multiple HIs (HIPHI RRs) and
IP addresses (A, AAAA or HIPRVS RRs), the requester cannot associate
an IP address with a specific HI, nor the opposite.
Considering the following DNS-IP load balancing model: Multiple
initiators are querying a DNS server with A or AAAA RRs at a given
FQDN. The DNS server replies with a round-robin ordered set of IP
addresses, causing each initiator to connect to a different address
(the first address of the set they received from the DNS). This
model can be extended to HIP by having the DNS returning a
round-robin ordered set of HIs and IP addresses. But then the
problem is that the initiator would need to map each of these HIs to
a subset of the returned set of IP addresses. Hence, perhaps there
is a need for having a "hierarchical" model for these RRs, which will
allows to tie an HI to a specific subset of IP addresses, as
illustrated in the figure below:
FQDN
|
+---+---+
| |
V V
FQDN HI1,HI2 HI3
| | |
+---+---+---+---+---+ +-+-+ |
| | | | | | | | |
V V V V V V V V V
IP1 IP2 IP3 HI1 HI2 HI3 IP1 IP2 IP3
'Flat' DNS model Vs. 'Hierarchical' HI model
However, as HIs and Type 1 HITs are not yet resolvable using the DNS,
implementing such a model would certainly prove to be difficult. The
use of Distributed Hash Tables (DHTs) might help to resolve HIs, but
at this point the whole story isn't known. In the absence of HI
resolvability, there is two solutions: index IP addresses and
HIs/HITs used by HIP with a common key (e.g., the IP address, the
HIT, a 8-bit int, etc.), or use a per-HI DNS name, pointed to by the
FQDN global to the set of HIs, and pointing to the HIs, and IP
addresses associated with this particular set of HIs. to map to
specific HIs, in a manner similar to what is done with NS RRs.
In the first solution (indexing), each HIPHI, HIPRVS, and HIPLOC (a
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new to-be-defined RR carrying the IP address of a HIP node, to be
used by HIP instead of A and AAAA RRs, if present) would contain an
additional HI index field allowing to link an HI with a subset of IP
addresses and vice versa. This solution is neither space-efficient,
nor it is architecturally clean.
In the second solution (parallel DNS names and bindings), the PTR RR
is used to alias the name of a group of node into multiple FQDNs,
which are then bound to set of HIs and IP addresses, as shown in the
figure below. These additional FQDNs are kind of HIP sub-FQDNs; an
easy way to generate them is to suffix, or prefix the unqualified
name with a sufficient number of bits of the HIT to prevent
collisions local to a FQDN (e.g., foo.bar.com might haves multiple
HIP sub-FQDNs: foo_2fa6.bar.com, foo_8cc4.bar.com, etc.).
FQDN
|
+---+---+
| |
V V
FQDN_1<--FQDN-->FQDN_2 HI1,HI2 HI3
| | | |
+---+---+---+ +-+-+ +-+-+ |
| | | | | | | | |
V V V V V V V V V
HI1 HI2 IP1 IP2 HI3 IP3 IP1 IP2 IP3
The 'Hierarchical' HIP model fitting in a 'Flat' DNS model
The current plan is to use the second solution unless HIP WG members
express desire to have the first solution implemented.
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Appendix B. Document Revision History
+-----------+-------------------------------------------------------+
| Revision | Comments |
+-----------+-------------------------------------------------------+
| 00 | Compared to draft-nikander-hip-dns-00: Merge |
| | multihomed site and end-host use cases. Remove HAA |
| | related text not required for Type 2 HIT definition. |
| | Remove IPv6 LSIs definitions. Replace fixed length |
| | and algorithm Type 1 and Type 2 HITs by variable |
| | length, type and algorithm HITs. Remove 'Policy |
| | Considerations' section. Fill-in 'Security |
| | Considerations' section. Allow for several IP |
| | addresses in the same HIPRVS RR. Reuse the type |
| | values and IANA registries of IPSECKEY RR. Add Annex |
| | discussing alternatives for storing multiple |
| | parallels FQDN-to-HI and HI-to-IP at a single FQDN. |
| | Minor fixes to figures and their descriptive text. |
| | Update references. |
+-----------+-------------------------------------------------------+
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