wdiff rfc8005.original rfc8005.txt


Network Working Group
Internet Engineering Task Force (IETF)                       J. Laganier
Internet-Draft
Request for Comments: 8005                       Luminate Wireless, Inc.
Obsoletes: 5205 (if approved)                             August 4,                                             October 2016
Intended status:
Category: Standards Track
Expires: February 5, 2017
ISSN: 2070-1721

    Host Identity Protocol (HIP) Domain Name System (DNS) Extension
                     draft-ietf-hip-rfc5205-bis-10

Abstract

   This document specifies a resource record (RR) for the Domain Name
   System (DNS), (DNS) and how to use it with the Host Identity Protocol (HIP).
   This RR allows a HIP node to store in the DNS its Host Identity (HI, (HI),
   the public component of the node public-private key
   pair), pair; its Host
   Identity Tag (HIT, (HIT), a truncated hash of its public key), key (PK); and the Domain Names
   domain names of its rendezvous servers (RVSs).  This document
   obsoletes RFC5205. RFC 5205.

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 an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list  It represents the consensus of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid the IETF community.  It has
   received public review and has been approved for a maximum publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of six months this document, any errata,
   and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained 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 February 5, 2017.
   http://www.rfc-editor.org/info/rfc8005.

Copyright Notice

   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
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   3
   3.  Usage Scenarios . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Simple Static Single Homed End-Host Single-Homed End Host . . . . . . . . . . .   5
     3.2.  Mobile end-host End Host . . . . . . . . . . . . . . . . . . . . .   6
   4.  Overview of Using the DNS with HIP  . . . . . . . . . . . . .   8   7
     4.1.  Storing HI, HIT, and RVS in the DNS . . . . . . . . . . .   8   7
     4.2.  Initiating Connections Based on DNS Names . . . . . . . .   8
   5.  HIP RR Storage Format . . . . . . . . . . . . . . . . . . . .   9
     5.1.  HIT Length Format . . . . . . . . . . . . . . . . . . . .  10   9
     5.2.  PK Algorithm Format . . . . . . . . . . . . . . . . . . .  10   9
     5.3.  PK Length Format  . . . . . . . . . . . . . . . . . . . .  10
     5.4.  HIT Format  . . . . . . . . . . . . . . . . . . . . . . .  10
     5.5.  Public Key Format . . . . . . . . . . . . . . . . . . . .  10
     5.6.  Rendezvous Servers Format . . . . . . . . . . . . . . . .  10
   6.  HIP RR Presentation Format  . . . . . . . . . . . . . . . . .  11
   7.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  12
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  13  12
     8.1.  Attacker Tampering with an Insecure HIP RR  . . . . . . .  13
     8.2.  Hash and HITs Collisions  . . . . . . . . . . . . . . . .  14  13
     8.3.  DNSSEC  . . . . . . . . . . . . . . . . . . . . . . . . .  14
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   10. Contributors References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
   11. Acknowledgments
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     10.2.  Informative References . . . . .  15
   12. References . . . . . . . . . . . .  16
   Appendix A.  Changes from RFC 5205  . . . . . . . . . . . . .  15
     12.1.  Normative references . .  17
   Acknowledgments . . . . . . . . . . . . . . . .  15
     12.2.  Informative references . . . . . . . . .  17
   Contributors  . . . . . . . .  16
   Appendix A.  Changes from RFC 5205 . . . . . . . . . . . . . . .  18 . . .  17
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   This document specifies a resource record (RR) for the Domain Name
   System (DNS) [RFC1034], [RFC1034] and how to use it with the Host Identity
   Protocol (HIP) [RFC7401].  This RR allows a HIP node to store in the
   DNS its Host Identity (HI, (HI), the public component of the node public-
   private key pair), pair; its Host Identity Tag (HIT, (HIT), a truncated hash of
   its
   HI), HI; and the Domain Names domain names of its rendezvous servers (RVSs)
   [I-D.ietf-hip-rfc5204-bis].
   [RFC8004].

   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 addresses.  This step occurs prior to
   communication with the remote host, host and relies on a DNS lookup.

   With HIP, IP addresses are intended to be used mostly for on-the-wire
   communication between end hosts, while most Upper Layer Protocols
   (ULP)
   (ULPs) and applications use HIs or HITs instead (ICMP might be an
   example of an a 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 HIP resource
   record. RR.  Upon
   query by an application or ULP for a name to IP address name-to-IP-address lookup, the
   resolver would then additionally perform a name to HI
   lookup, name-to-HI lookup and use
   it to construct the resulting HI to IP address HI-to-IP-address mapping (which is
   internal to the HIP layer).  The HIP layer uses the
   HI to IP address HI-to-IP-address
   mapping to translate HIs and HITs into IP addresses addresses, and vice versa.

   The HIP specification [RFC7401] specifies the HIP base exchange
   between a HIP Initiator and a HIP Responder based on a four-way
   handshake involving a total of four HIP packets (I1, R1, I2, and R2).
   Since the HIP packets contain both the Initiator and the Responder
   HIT, the initiator Initiator needs to have knowledge of the Responder's HI and
   HIT prior to initiating the base exchange by sending an I1 packet.. packet.

   The HIP Rendezvous Extension [I-D.ietf-hip-rfc5204-bis] [RFC8004] allows a HIP node to be
   reached via the IP address(es) of a third party, the node's rendezvous server (RVS). RVS.  An
   Initiator willing to establish a HIP association with a Responder
   served by an RVS would typically initiate a HIP base exchange by
   sending the I1 packet initiating the exchange towards the RVS IP
   address rather than towards the Responder IP address.  Consequently,
   we need a means to find the name of a
   rendezvous server an RVS for a given host name.

   This document introduces the HIP DNS resource record RR to store the
   Rendezvous Server (RVS), Host Identity (HI), RVS, HI, and Host Identity Tag
   (HIT) HIT
   information.

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 RFC 2119 [RFC2119].

3.  Usage Scenarios

   In this section, we briefly introduce a number of usage scenarios
   where the DNS is useful with the Host Identity Protocol. HIP.

   With HIP, most applications 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, failover,
   redundancy, mobility, or renumbering, in a manner that 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, for a node to be reachable by reference to its
   Fully Qualified Domain Name (FQDN), the following information should
   be stored in the DNS:

   o  A set of IP address(es) addresses via A [RFC1035] and AAAA [RFC3596] RR sets
      (RRSets [RFC2181]). Resource
      Record Sets (RRSets) [RFC2181].

   o  A Host Identity (HI), Host Identity Tag (HIT),  An HI, a HIT, and possibly a set of rendezvous servers (RVS) RVSs through HIP RRs.

   The HIP RR is class independent.

   When a HIP node wants to initiate 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 prior knowledge of the
   Responder's HI, by doing so both nodes knowingly risk man-in-the-
   middle
   man-in-the-middle (MitM) attacks on the HIP exchange.  To prevent
   these attacks, it is recommended that the Initiator first obtains the
   HI of the Responder, Responder and then initiates the exchange.  This can be
   done, for example, through manual configuration or DNS lookups.
   Hence, a HIP RR is introduced.

   When a HIP node is frequently changing its IP address(es), the
   natural DNS latency for propagating changes may prevent it from
   publishing its new IP address(es) in the DNS.  For solving this
   problem, the HIP Architecture [RFC4423] introduces rendezvous servers
   (RVSs) [I-D.ietf-hip-rfc5204-bis]. RVSs [RFC8004].  A
   HIP host uses a rendezvous
   server an RVS as a rendezvous point to maintain reachability
   with possible HIP Initiators while moving [RFC5206].  Such a HIP node
   would publish in the DNS its RVS domain name(s) in a HIP RR, while
   keeping its RVS up-to-date with its current set of IP addresses.

   When a HIP node wants to initiate a HIP exchange with a Responder, it
   will perform a number of DNS lookups.  Depending on the type of
   implementation, the order in which those lookups will be issued may
   vary.  For instance, implementations using HIT in Application
   Programming Interfaces (APIs) may typically first query for HIP
   resource records RRs
   at the Responder FQDN, while those using an IP address in APIs may
   typically first query for A and/or AAAA resource
   records. RRs.

   In the following, we assume that the Initiator first queries for HIP
   resource records
   RRs at the Responder FQDN.

   If the query for the HIP type was responded to with a DNS answer with
   RCODE=3 (Name Error), then the Responder's information is not present
   in the DNS DNS, and further queries for the same owner name SHOULD NOT be
   made.

   In case the query for the HIP records returned a DNS answer with
   RCODE=0 (No Error) and an empty answer section, it means that no HIP
   information is available at the responder Responder name.  In such a case, if
   the Initiator has been configured with a policy to fallback fall back to
   opportunistic HIP (initiating without knowing the Responder's HI) or
   plain IP, it would send out more queries for A and AAAA types at the
   Responder's FQDN.

   Depending on the combinations of answers, the situations described in
   Section
   Sections 3.1 and Section 3.2 can occur.

   Note that storing HIP RR information in the DNS at an FQDN that is
   assigned to a non-HIP node might have ill effects on its reachability
   by HIP nodes.

3.1.  Simple Static Single Homed End-Host Single-Homed End Host

   In addition to its IP address(es) address or addresses (IP-R), a HIP node (R)
   with a single static network attachment that wishes to be reachable
   by reference to its FQDN (www.example.com) to act as a Responder
   would store in the DNS a HIP resource record RR containing its Host Identity (HI-R)
   and Host Identity Tag (HIT-R).

   An Initiator willing to associate with a node would typically issue
   the following queries:

   o  Query #1: QNAME=www.example.com, QTYPE=HIP

   (QCLASS=IN is assumed and omitted from the examples)

   Which returns a DNS packet with RCODE=0 and one or more HIP RRs with
   the HIT and HI (e.g., HIT-R and HI-R) of the Responder in the answer
   section, but no RVS.

   o  Query #2: QNAME=www.example.com, QTYPE=A

   o  Query #3: QNAME=www.example.com, QTYPE=AAAA

   Which would return DNS packets with RCODE=0 and respectively and, respectively, one or
   more A or AAAA RRs containing the IP address(es) of the Responder
   (e.g., IP-R) in their answer sections.

   Caption: In the remainder of this document, for the sake of keeping
            diagrams simple and concise, several DNS queries and answers
            are represented as one single transaction, while in fact
            there are several queries and answers flowing back and
            forth, as described in the textual examples.

               [HIP? A?        ]
               [www.example.com]            +-----+
          +-------------------------------->|     |
          |                                 | DNS |
          | +-------------------------------|     |
          | |  [HIP? A?        ]            +-----+
          | |  [www.example.com]
          | |  [HIP HIT-R HI-R ]
          | |  [A IP-R         ]
          | v
        +-----+                              +-----+
        |     |--------------I1------------->|     |
        |  I  |<-------------R1--------------|  R  |
        |     |--------------I2------------->|     |
        |     |<-------------R2--------------|     |
        +-----+                              +-----+

                         Static Singly Homed Single-Homed Host

   The Initiator would then send an I1 to the Responder's IP addresses
   (IP-R).

3.2.  Mobile end-host End Host

   A mobile HIP node (R) wishing to be reachable by reference to its
   FQDN (www.example.com) would store in the DNS, possibly in addition
   to its IP address(es) address or addresses (IP-R), its HI (HI-R), its HIT
   (HIT-R), and the domain name(s) name or names of its rendezvous server(s) RVS or servers (e.g.,
   rvs.example.com) in a HIP resource record(s). RR or records.  The mobile HIP node also
   needs to notify its
   rendezvous servers RVSs of any change in its set of IP address(es). addresses.

   An Initiator willing to associate with such a mobile node would
   typically issue the following queries:

   o  Query #1: QNAME=www.example.com, QTYPE=HIP

   Which returns a DNS packet with RCODE=0 and one or more HIP RRs with
   the HIT, HI, and RVS domain name(s) name or names (e.g., HIT-R, HI-R, and
   rvs.example.com) of the Responder in the answer section.

   o  Query #2: QNAME=rvs.example.com, QTYPE=A

   o  Query #3: QNAME=rvs.example.com, QTYPE=AAAA

   Which return DNS packets with RCODE=0 and respectively and, respectively, one or more
   A or AAAA RRs containing an IP address(es) of the Responder's RVS
   (e.g., IP-RVS) in their answer sections.

              [HIP?           ]
              [www.example.com]

              [A?             ]
              [rvs.example.com]                     +-----+
         +----------------------------------------->|     |
         |                                          | DNS |
         | +----------------------------------------|     |
         | |  [HIP?                          ]      +-----+
         | |  [www.example.com               ]
         | |  [HIP HIT-R HI-R rvs.example.com]
         | |
         | |  [A?             ]
         | |  [rvs.example.com]
         | |  [A IP-RVS       ]
         | |
         | |                +-----+
         | | +------I1----->| RVS |-----I1------+
         | | |              +-----+             |
         | | |                                  |
         | | |                                  |
         | v |                                  v
        +-----+                              +-----+
        |     |<---------------R1------------|     |
        |  I  |----------------I2----------->|  R  |
        |     |<---------------R2------------|     |
        +-----+                              +-----+

                              Mobile End-Host End Host

   The Initiator would then send an I1 to the RVS IP address (IP-RVS).
   Following, the RVS will relay the I1 up to the mobile node's IP
   address (IP-R), which will complete the HIP exchange.

4.  Overview of Using the DNS with HIP

4.1.  Storing HI, HIT, and RVS in the DNS

   For any HIP node, its Host Identity (HI), HI, the associated Host
   Identity Tag (HIT), HIT, and the FQDN of its
   possible RVSs can be stored in a DNS HIP RR.  Any conforming
   implementation may store a Host
   Identity (HI) an HI and its associated Host Identity Tag (HIT) HIT in a DNS HIP
   RDATA format.  HI and HIT are defined in Section 3 of the HIP
   specification [RFC7401].

   Upon return of a HIP RR, a host MUST always calculate the HI-
   derivative
   HI-derivative HIT to be used in the HIP exchange, as specified in
   Section 3 of the HIP specification [RFC7401], while the HIT possibly
   embedded along included
   in the HIP RR SHOULD only be used as an optimization (e.g., table
   lookup).

   The HIP resource record RR may also contain one or more domain name(s) names of rendezvous server(s) one or more
   RVSs towards which HIP I1 packets might be sent to trigger the
   establishment of an association with the entity named by this resource record [I-D.ietf-hip-rfc5204-bis]. RR
   [RFC8004].

   The rendezvous server Rendezvous Server field of the HIP resource record RR stored at a given owner
   name MAY include the owner name itself.  A semantically equivalent
   situation occurs if no rendezvous server RVS is present in the HIP resource record RR stored at that
   owner name.  Such situations occur in two cases:

   o  The host is mobile, and the A and/or AAAA resource record(s) RR(s) stored at its host
      name contain the IP address(es) of its
      rendezvous server RVS rather than its own
      one.

   o  The host is stationary, stationary and can be reached directly at the IP
      address(es) contained in the A and/or AAAA resource record(s) RR(s) stored at its
      host name.  This is a degenerate case of rendezvous service where
      the host somewhat acts as a rendezvous server an RVS for itself.

   An RVS receiving such an I1 would then relay it to the appropriate
   Responder (the owner of the I1 receiver HIT).  The Responder will
   then complete the exchange with the Initiator, typically without
   ongoing help from the RVS.

4.2.  Initiating Connections Based on DNS Names

   On a HIP node, a Host Identity Protocol HIP exchange SHOULD be initiated whenever a ULP
   attempts to communicate with an entity entity, and the DNS lookup returns
   HIP resource records.

   The RRs.

   HIP resource records RRs have a Time To Live (TTL) associated with them.  When the
   number of seconds that passed since the record was retrieved exceeds
   the record's TTL, the record MUST be considered to
   be no longer valid and
   deleted by the entity that retrieved it.  If access to the record is
   necessary to initiate communication with the entity to which the
   record corresponds, a new query MUST be be made to retrieve a fresh copy
   of the record.

   There may be multiple HIP RRs associated with a single name.  It is
   outside the scope of this specification as to how a host chooses from
   between multiple RRs when more than one is returned.  The RVS
   information may be copied and aligned across multiple RRs, or may be
   different for each one; a host MUST check that the RVS used is
   associated with the HI being used, when multiple choices are present.

5.  HIP RR Storage Format

   The RDATA for a HIP RR consists of a public key algorithm type, PK Algorithm Type, the HIT
   length, a HIT, a public key PK (i.e., a an HI), and optionally one or more rendezvous server(s). RVSs.

    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 length   | PK algorithm  |          PK length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                           HIT                                 ~
   |                                                               |
   +                     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     |                                         |
   +-+-+-+-+-+-+-+-+-+-+-+                                         +
   |                           Public Key                          |
   ~                                                               ~
   |                                                               |
   +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                                                               |
   ~                       Rendezvous Servers                      ~
   |                                                               |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |
   +-+-+-+-+-+-+-+

   The HIT length, PK algorithm, PK length, HIT, and Public Key fields
   are REQUIRED.  The Rendezvous Servers Server field is OPTIONAL.

5.1.  HIT Length Format

   The HIT length indicates the length in bytes of the HIT field.  This
   is an 8-bit unsigned integer.

5.2.  PK Algorithm Format

   The PK algorithm field indicates the public key PK cryptographic algorithm and
   the implied public key Public Key field format.  This is an 8-bit unsigned
   integer.  This document reuses the values defined for the
   'algorithm type' 'Algorithm
   Type' of the IPSECKEY RR [RFC4025].

   Presently defined values are listed in Section 9 for reference.

5.3.  PK Length Format

   The PK length indicates the length in bytes of the Public key Key field.
   This is a 16-bit unsigned integer in network byte order.

5.4.  HIT Format

   The HIT is stored as a binary value in network byte order.

5.5.  Public Key Format

   Two of the public key PK types defined in this document (RSA and DSA) Digital
   Signature Algorithm (DSA)) reuse the public key PK formats defined for the
   IPSECKEY RR [RFC4025].

   The DSA key format is defined in RFC 2536 [RFC2536].

   The RSA key format is defined in RFC 3110 [RFC3110] [RFC3110], and the RSA key
   size limit (4096 bits) is relaxed in the IPSECKEY RR [RFC4025]
   specification.

   In addition, this document similarly defines the public key PK format of type ECDSA
   Elliptic Curve Digital Signature Algorithm (ECDSA) as the algorithm-specific algorithm-
   specific portion of the DNSKEY RR RDATA for ECDSA [RFC6605], i.e, all
   of the DNSKEY RR DATA after the first four octets, corresponding to
   the same portion of the DNSKEY RR that must be specified by documents
   that define a DNSSEC algorithm.

5.6.  Rendezvous Servers Format

   The Rendezvous Servers Server field indicates one or more variable length
   wire-encoded domain names of rendezvous server(s), concatenated, one or more RVSs, concatenated and
   encoded as described in Section 3.3 of RFC 1035 [RFC1035]: "<domain-
   name>
   "<domain-name> is a domain name represented as a series of labels,
   and terminated by a label with zero length".  Since the wire-encoded
   format is self-describing, the length of each domain-name domain name is
   implicit: The zero length label termination serves as a separator
   between multiple rendezvous server RVS domain names concatenated in the Rendezvous Servers
   Server field of a same HIP RR.  Since the length of the other portion
   of the RR's RRDATA is known, and the overall length of the RR's RDATA
   is also known (RDLENGTH), all the length information necessary to
   parse the HIP RR is available.

   The domain names MUST NOT be compressed.  The rendezvous server(s) RVS or servers are
   listed in order of preference (i.e., the first rendezvous server(s) RVS or servers are
   preferred), defining an implicit order amongst rendezvous servers RVSs of a single RR.

   When multiple HIP RRs are present at the same owner name, this
   implicit order of rendezvous servers RVSs within an RR MUST NOT be used to infer a
   preference order between rendezvous servers RVSs stored in different RRs.

6.  HIP RR Presentation Format

   This section specifies the representation of the HIP RR in a zone
   master file.

   The HIT length field is not represented, as it is implicitly known
   thanks to the HIT field representation.

   The PK algorithm field is represented as unsigned integers.

   The HIT field is represented as the Base16 encoding [RFC4648] (a.k.a.
   hex or hexadecimal) of the HIT.  The encoding MUST NOT contain
   whitespaces to distinguish it from the public key Public Key field.

   The Public Key field is represented as the Base64 encoding of the
   public key, PK,
   as defined in Section 4 of [RFC4648].  The encoding MUST NOT contain
   whitespace(s) to distinguish it from the Rendezvous
   Servers Server field.

   The PK length field is not represented, as it is implicitly known
   thanks to the Public key Key field representation containing no
   whitespaces.

   The Rendezvous Servers Server field is represented by one or more domain
   name(s)
   names separated by whitespace(s).  These whitespace(s) are  Such whitespace is only used in
   the HIP RR representation format, format and are is not part of the HIP RR wire
   format.

   The complete representation of the HIP record is:

   IN  HIP   ( pk-algorithm
               base16-encoded-hit
               base64-encoded-public-key
               rendezvous-server[1]
                       ...
               rendezvous-server[n] )

   When no RVSs are present, the representation of the HIP record is:

   IN  HIP   ( pk-algorithm
               base16-encoded-hit
               base64-encoded-public-key )

7.  Examples

   In the examples below, the public key Public Key field containing no whitespace
   is wrapped wrapped, since it does not fit in a single line of this document.

   Example of a node with an HI and a HIT but no RVS:

   www.example.com.      IN  HIP ( 2 200100107B1A74DF365639CC39F1D578
                                   AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cI
   vM4p9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ry
   ra+bSRGQb1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXd
   XF5D )

   Example of a node with a an HI, a HIT, and one RVS:

   www.example.com.      IN  HIP ( 2 200100107B1A74DF365639CC39F1D578
                                   AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cI
   vM4p9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ry
   ra+bSRGQb1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXd
   XF5D
                                   rvs.example.com. )

   Example of a node with a an HI, a HIT, and two RVSs:

   www.example.com.      IN  HIP ( 2 200100107B1A74DF365639CC39F1D578
                                   AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cI
   vM4p9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ry
   ra+bSRGQb1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXd
   XF5D
                                   rvs1.example.com.
                                   rvs2.example.com. )

8.  Security Considerations

   This section contains a description of the known threats involved
   with the usage of the HIP DNS Extension.

   In a manner similar to the IPSECKEY RR [RFC4025], the HIP DNS
   Extension allows for the provision of 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
   Extension is subject, as the IPSECKEY RR, to threats stemming from
   attacks against unsecured HIP RRs, as described in the remainder of
   this section.

   A HIP node SHOULD obtain HIP RRs from a trusted party trough through a
   secure channel ensuring data integrity and authenticity of the RRs.
   DNSSEC [RFC4033] [RFC4034] [RFC4035] provides such a secure channel.
   However, it should be emphasized that DNSSEC only offers data
   integrity and authenticity guarantees to the channel between the DNS
   server publishing a zone and the HIP node.  DNSSEC does not ensure
   that the entity publishing the zone is trusted.  Therefore, the RRSIG
   signature
   of the HIP RRSet MUST NOT be misinterpreted as a certificate binding
   the HI and/or the HIT to the owner name.

   In the absence of a proper secure channel, both parties are
   vulnerable to MitM and DoS Denial-of-Service (DoS) attacks, and unrelated
   parties might be subject to DoS attacks as well.  These threats are
   described in the following sections.

8.1.  Attacker Tampering with an Insecure HIP RR

   The HIP RR contains public keying material in the form of the named
   peer's public key PK (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 HIP RR (e.g., using DNS spoofing), is
   able to mount Man-in-the-Middle MitM attacks on the cryptographic core of the eventual
   HIP exchange (Responder's HIP RR rewritten by the attacker).

   The HIP RR may contain a rendezvous server an RVS domain name resolved into a destination
   IP address where the named peer is reachable by an I1, as per the HIP
   Rendezvous Extension [I-D.ietf-hip-rfc5204-bis]. [RFC8004].  Thus, an attacker that is able to
   tamper with this RR 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 attack is not specific to HIP and exists independently of
   whether or not HIP and the HIP 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 own in a
   spoofed DNS packet sent to the Initiator HI, and then redirect all
   exchanged packets to him and mount a MitM on HIP.  In this case, HIP
   won't provide confidentiality nor Initiator HI protection from
   eavesdroppers.

8.2.  Hash and HITs Collisions

   As with many cryptographic algorithms, 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
   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 the DNS, but SHOULD rather SHOULD use
   HI-based authentication.

8.3.  DNSSEC

   In the absence of DNSSEC, the HIP RR is subject to the threats
   described in RFC 3833 [RFC3833].

9.  IANA Considerations

   [RFC5205], obsoleted by this document, made the following definition
   and reservation in the IANA Registry for DNS RR Types:

   Value "Resource Record (RR) TYPEs" subregistry under
   "Domain Name System (DNS) Parameters":

   Value   Type
   -----   ----
   55      HIP

   This document updates

   In the IANA Registry for DNS RR Types by replacing "Resource Record (RR) TYPEs" subregistry under "Domain Name
   System (DNS) Parameters", references to [RFC5205] have been replaced
   by references to this document.

   As [RFC5205], this document reuses the Algorithm Types defined by
   [RFC4025] for the IPSEC KEY RR.  Presently defined values are shown
   here for reference only:

   Value   Description
   -----   --------------------------------------------------------
     1     A DSA key is present, in the format defined in [RFC2536]
     2     A RSA key is present, in the format defined in [RFC3110]

   IANA is requested to make has made the following Algorithm Type reservation
   and definition assignment in the IANA Registry for the IPSECKEY RR [RFC4025]
   Algorithm Types: "Algorithm Type Field"
   subregistry under "IPSECKEY Resource Record Parameters" [RFC4025]:

   Value   Description
  --------
   -----   -----------
  TBD-IANA
     3     An ECDSA key is present, in the format defined in [RFC6605]

10.  Contributors

   Pekka Nikander co-authored an earlier, experimental version of this
   specification [RFC5205].

11.  Acknowledgments

   As usual in the IETF, this document is the result of a collaboration
   between many people.  The authors would like to thank the author
   (Michael Richardson), contributors, and reviewers of the IPSECKEY RR
   [RFC4025] specification, after which this document was framed.  The
   authors would also like to thank the following people, who have
   provided thoughtful and helpful discussions and/or suggestions, that
   have helped improve this document: Jeff Ahrenholz, Rob Austein, Hannu
   Flinck, Olafur Gudmundsson, Tom Henderson, Peter Koch, Olaf Kolkman,
   Miika Komu, Andrew McGregor, Erik Nordmark, and Gabriel Montenegro.
   Some parts of this document stem from the HIP specification
   [RFC7401].  Finally, thanks Sheng Jiang for performing the Internet
   Area Directorate review of this document in the course of the
   publication process.

12.  References

12.1.

10.1.  Normative references

   [I-D.ietf-hip-rfc5204-bis]
              Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
              Rendezvous Extension", draft-ietf-hip-rfc5204-bis-07 (work
              in progress), December 2015. References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <http://www.rfc-editor.org/info/rfc1034>.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <http://www.rfc-editor.org/info/rfc1035>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2181]  Elz, R. and R. Bush, "Clarifications to the DNS
              Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
              <http://www.rfc-editor.org/info/rfc2181>.

   [RFC3596]  Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
              "DNS Extensions to Support IP Version 6", RFC 3596,
              DOI 10.17487/RFC3596, October 2003,
              <http://www.rfc-editor.org/info/rfc3596>.

   [RFC4025]  Richardson, M., "A Method for Storing IPsec Keying
              Material in DNS", RFC 4025, DOI 10.17487/RFC4025, March
              2005, <http://www.rfc-editor.org/info/rfc4025>.

   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "DNS Security Introduction and Requirements",
              RFC 4033, DOI 10.17487/RFC4033, March 2005,
              <http://www.rfc-editor.org/info/rfc4033>.

   [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,
              <http://www.rfc-editor.org/info/rfc4034>.

   [RFC4035]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Protocol Modifications for the DNS Security
              Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
              <http://www.rfc-editor.org/info/rfc4035>.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
              <http://www.rfc-editor.org/info/rfc4648>.

   [RFC6605]  Hoffman, P. and W. Wijngaards, "Elliptic Curve Digital
              Signature Algorithm (DSA) for DNSSEC", RFC 6605,
              DOI 10.17487/RFC6605, April 2012,
              <http://www.rfc-editor.org/info/rfc6605>.

   [RFC7401]  Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
              Henderson, "Host Identity Protocol Version 2 (HIPv2)",
              RFC 7401, DOI 10.17487/RFC7401, April 2015,
              <http://www.rfc-editor.org/info/rfc7401>.

12.2.

   [RFC8004]  Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
              Rendezvous Extension", RFC 8004, DOI 10.17487/RFC8004,
              October 2016, <http://www.rfc-editor.org/info/rfc8004>.

10.2.  Informative references References

   [RFC2536]  Eastlake 3rd, D., "DSA KEYs and SIGs in the Domain Name
              System (DNS)", RFC 2536, DOI 10.17487/RFC2536, March 1999,
              <http://www.rfc-editor.org/info/rfc2536>.

   [RFC3110]  Eastlake 3rd, D., "RSA/SHA-1 SIGs and RSA KEYs in the
              Domain Name System (DNS)", RFC 3110, DOI 10.17487/RFC3110,
              May 2001, <http://www.rfc-editor.org/info/rfc3110>.

   [RFC3833]  Atkins, D. and R. Austein, "Threat Analysis of the Domain
              Name System (DNS)", RFC 3833, DOI 10.17487/RFC3833, August
              2004, <http://www.rfc-editor.org/info/rfc3833>.

   [RFC4423]  Moskowitz, R. and P. Nikander, "Host Identity Protocol
              (HIP) Architecture", RFC 4423, DOI 10.17487/RFC4423, May
              2006, <http://www.rfc-editor.org/info/rfc4423>.

   [RFC5205]  Nikander, P. and J. Laganier, "Host Identity Protocol
              (HIP) Domain Name System (DNS) Extensions", RFC 5205,
              DOI 10.17487/RFC5205, April 2008,
              <http://www.rfc-editor.org/info/rfc5205>.

   [RFC5206]  Nikander, P., Henderson, T., Ed., Vogt, C., and J. Arkko,
              "End-Host Mobility and Multihoming with the Host Identity
              Protocol", RFC 5206, DOI 10.17487/RFC5206, April 2008. 2008,
              <http://www.rfc-editor.org/info/rfc5206>.

Appendix A.  Changes from RFC 5205

   o  Updated HIP references to revised HIP specifications.

   o  Extended DNS HIP RR to support for Host Identities based on
      Elliptic Curve Digital Signature Algorithm (ECDSA). ECDSA.

   o  Clarified that new query must be made when the time that passed
      since a an RR was retrieved exceeds the TTL of the RR.

   o  Added considerations related to multiple HIP RRs being associated
      with a single name.

   o  Clarified that the Base64 encoding in use is as per Section 4 of
      [RFC4648].

   o  Clarified the wire format when more than one rendezvous servers
      are RVS is defined in one
      RR.

   o  Clarified that "whitespace" is used as the delimiter in the human-
      readable representation of the RR but is not part of the wire
      format.

Acknowledgments

   As usual in the IETF, this document is the result of a collaboration
   between many people.  The authors would like to thank the author
   (Michael Richardson), contributors, and reviewers of the IPSECKEY RR
   [RFC4025] specification, after which this document was framed.  The
   authors would also like to thank the following people, who have
   provided thoughtful and helpful discussions and/or suggestions, that
   have helped improve this document: Jeff Ahrenholz, Rob Austein, Hannu
   Flinck, Olafur Gudmundsson, Tom Henderson, Peter Koch, Olaf Kolkman,
   Miika Komu, Andrew McGregor, Gabriel Montenegro, and Erik Nordmark.
   Some parts of this document stem from the HIP specification
   [RFC7401].  Finally, thanks to Sheng Jiang for performing the
   Internet Area Directorate review of this document in the course of
   the publication process.

Contributors

   Pekka Nikander coauthored an earlier, experimental version of this
   specification [RFC5205].

Author's Address

   Julien Laganier
   Luminate Wireless, Inc.
   Cupertino, CA
   USA

   EMail:
   United States of America

   Email: julien.ietf@gmail.com