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+Network Working Group P. Nikander
+Request for Comments: 5205 Ericsson Research NomadicLab
+Category: Experimental J. Laganier
+ DoCoMo Euro-Labs
+ April 2008
+
+
+ Host Identity Protocol (HIP) Domain Name System (DNS) Extension
+
+Status of This Memo
+
+ This memo defines an Experimental Protocol for the Internet
+ community. It does not specify an Internet standard of any kind.
+ Discussion and suggestions for improvement are requested.
+ Distribution of this memo is unlimited.
+
+Abstract
+
+ This document specifies a new resource record (RR) for the Domain
+ Name System (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, the public component of the node public-private key
+ pair), Host Identity Tag (HIT, a truncated hash of its public key),
+ and the Domain Names of its rendezvous servers (RVSs).
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+Nikander & Laganier Experimental [Page 1]
+
+RFC 5205 HIP DNS Extension April 2008
+
+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
+ 2. Conventions Used in This Document . . . . . . . . . . . . . . 3
+ 3. Usage Scenarios . . . . . . . . . . . . . . . . . . . . . . . 4
+ 3.1. Simple Static Singly Homed End-Host . . . . . . . . . . . 5
+ 3.2. Mobile end-host . . . . . . . . . . . . . . . . . . . . . 6
+ 4. Overview of Using the DNS with HIP . . . . . . . . . . . . . . 8
+ 4.1. Storing HI, HIT, and RVS in the DNS . . . . . . . . . . . 8
+ 4.2. Initiating Connections Based on DNS Names . . . . . . . . 8
+ 5. HIP RR Storage Format . . . . . . . . . . . . . . . . . . . . 9
+ 5.1. HIT Length Format . . . . . . . . . . . . . . . . . . . . 9
+ 5.2. PK Algorithm Format . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . 10
+ 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
+ 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
+ 8.1. Attacker Tampering with an Insecure HIP RR . . . . . . . . 12
+ 8.2. Hash and HITs Collisions . . . . . . . . . . . . . . . . . 13
+ 8.3. DNSSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 13
+ 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
+ 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
+ 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
+ 11.1. Normative references . . . . . . . . . . . . . . . . . . . 14
+ 11.2. Informative references . . . . . . . . . . . . . . . . . . 15
+
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+Nikander & Laganier Experimental [Page 2]
+
+RFC 5205 HIP DNS Extension April 2008
+
+
+1. Introduction
+
+ This document specifies a new resource record (RR) for the Domain
+ Name System (DNS) [RFC1034], and how to use it with the Host Identity
+ Protocol (HIP) [RFC5201]. This RR allows a HIP node to store in the
+ DNS its Host Identity (HI, the public component of the node public-
+ private key pair), Host Identity Tag (HIT, a truncated hash of its
+ HI), and the Domain Names of its rendezvous servers (RVSs) [RFC5204].
+
+ 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 intended to be used mostly for on-the-wire
+ communication between end hosts, while most Upper Layer Protocols
+ (ULP) and applications use 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 HIP resource
+ record. Upon query by an application or ULP for a name to IP address
+ lookup, the resolver would then additionally perform a name to HI
+ lookup, and use it to construct the resulting HI to IP address
+ mapping (which is internal to the HIP layer). The HIP layer uses the
+ HI to IP address mapping to translate HIs and HITs into IP addresses
+ and vice versa.
+
+ The HIP Rendezvous Extension [RFC5204] allows a HIP node to be
+ reached via the IP address(es) of a third party, the node's
+ rendezvous server (RVS). An Initiator willing to establish a HIP
+ association with a Responder served by an RVS would typically
+ initiate a HIP exchange by sending an I1 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 for a given host
+ name.
+
+ This document introduces the new HIP DNS resource record to store the
+ Rendezvous Server (RVS), Host Identity (HI), and Host Identity Tag
+ (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].
+
+
+
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+Nikander & Laganier Experimental [Page 3]
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+RFC 5205 HIP DNS Extension April 2008
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+3. Usage Scenarios
+
+ In this section, we briefly introduce a number of usage scenarios
+ where the DNS is useful with the Host Identity Protocol.
+
+ 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,
+ 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) via A [RFC1035] and AAAA [RFC3596] RR sets
+ (RRSets [RFC2181]).
+
+ o A Host Identity (HI), Host Identity Tag (HIT), and possibly a set
+ of rendezvous servers (RVS) through HIP RRs.
+
+ 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 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 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) [RFC5204]. A HIP host uses a rendezvous server 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 APIs may typically
+ first query for HIP resource records at the Responder FQDN, while
+
+
+
+Nikander & Laganier Experimental [Page 4]
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+RFC 5205 HIP DNS Extension April 2008
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+
+ those using an IP address in APIs may typically first query for A
+ and/or AAAA resource records.
+
+ In the following, we assume that the Initiator first queries for HIP
+ resource records 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 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 name. In such a case, if
+ the Initiator has been configured with a policy to fallback 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 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 Singly Homed End-Host
+
+ A HIP node (R) with a single static network attachment, wishing to be
+ reachable by reference to its FQDN (www.example.com), would store in
+ the DNS, in addition to its IP address(es) (IP-R), its Host Identity
+ (HI-R) and Host Identity Tag (HIT-R) in a HIP resource record.
+
+ An Initiator willing to associate with a node would typically issue
+ the following queries:
+
+ o QNAME=www.example.com, QTYPE=HIP
+
+ o (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.
+
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+RFC 5205 HIP DNS Extension April 2008
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+ o QNAME=www.example.com, QTYPE=A QNAME=www.example.com, QTYPE=AAAA
+
+ Which returns DNS packets with RCODE=0 and one or more A or AAAA RRs
+ containing IP address(es) of the Responder (e.g., IP-R) in the answer
+ section.
+
+ 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 Host
+
+ The Initiator would then send an I1 to the Responder's IP addresses
+ (IP-R).
+
+3.2. Mobile 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) (IP-R), its HI (HI-R), HIT (HIT-R), and the
+ domain name(s) of its rendezvous server(s) (e.g., rvs.example.com) in
+ HIP resource record(s). The mobile HIP node also needs to notify its
+ rendezvous servers of any change in its set of IP address(es).
+
+ An Initiator willing to associate with such a mobile node would
+ typically issue the following queries:
+
+ o QNAME=www.example.com, QTYPE=HIP
+
+
+
+
+Nikander & Laganier Experimental [Page 6]
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+ Which returns a DNS packet with RCODE=0 and one or more HIP RRs with
+ the HIT, HI, and RVS domain name(s) (e.g., HIT-R, HI-R, and
+ rvs.example.com) of the Responder in the answer section.
+
+ o QNAME=rvs.example.com, QTYPE=A QNAME=www.example.com, QTYPE=AAAA
+
+ Which returns DNS packets with RCODE=0 and one or more A or AAAA RRs
+ containing IP address(es) of the Responder's RVS (e.g., IP-RVS) in
+ the answer section.
+
+ [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
+
+ 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.
+
+
+
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+Nikander & Laganier Experimental [Page 7]
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+RFC 5205 HIP DNS Extension April 2008
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+
+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), the associated Host
+ Identity Tag (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) and its associated Host Identity Tag (HIT) in a DNS HIP
+ RDATA format. HI and HIT are defined in Section 3 of the HIP
+ specification [RFC5201].
+
+ Upon return of a HIP RR, a host MUST always calculate the HI-
+ derivative HIT to be used in the HIP exchange, as specified in
+ Section 3 of the HIP specification [RFC5201], while the HIT possibly
+ embedded along SHOULD only be used as an optimization (e.g., table
+ lookup).
+
+ The HIP resource record may also contain one or more domain name(s)
+ of rendezvous server(s) towards which HIP I1 packets might be sent to
+ trigger the establishment of an association with the entity named by
+ this resource record [RFC5204].
+
+ The rendezvous server field of the HIP resource record stored at a
+ given owner name MAY include the owner name itself. A semantically
+ equivalent situation occurs if no rendezvous server is present in the
+ HIP resource record 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)
+ stored at its host name contain the IP address(es) of its
+ rendezvous server rather than its own one.
+
+ o The host is stationary, and can be reached directly at the IP
+ address(es) contained in the A and/or AAAA resource record(s)
+ stored at its host name. This is a degenerated case of rendezvous
+ service where the host somewhat acts as a rendezvous server 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 exchange SHOULD be initiated
+ whenever a ULP attempts to communicate with an entity and the DNS
+ lookup returns HIP resource records.
+
+
+
+Nikander & Laganier Experimental [Page 8]
+
+RFC 5205 HIP DNS Extension April 2008
+
+
+5. HIP RR Storage Format
+
+ The RDATA for a HIP RR consists of a public key algorithm type, the
+ HIT length, a HIT, a public key, and optionally one or more
+ rendezvous server(s).
+
+ 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 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 cryptographic
+ algorithm and the implied public key field format. This is an 8-bit
+ unsigned integer. This document reuses the values defined for the
+ 'algorithm type' of the IPSECKEY RR [RFC4025].
+
+ Presently defined values are listed in Section 9 for reference.
+
+
+
+
+
+Nikander & Laganier Experimental [Page 9]
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+RFC 5205 HIP DNS Extension April 2008
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+5.3. PK Length Format
+
+ The PK length indicates the length in bytes of the Public 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
+
+ Both of the public key types defined in this document (RSA and DSA)
+ reuse the public key 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] and the RSA key
+ size limit (4096 bits) is relaxed in the IPSECKEY RR [RFC4025]
+ specification.
+
+5.6. Rendezvous Servers Format
+
+ The Rendezvous Servers field indicates one or more variable length
+ wire-encoded domain names of rendezvous server(s), as described in
+ Section 3.3 of RFC 1035 [RFC1035]. The wire-encoded format is self-
+ describing, so the length is implicit. The domain names MUST NOT be
+ compressed. The rendezvous server(s) are listed in order of
+ preference (i.e., first rendezvous server(s) are preferred), defining
+ an implicit order amongst rendezvous servers of a single RR. When
+ multiple HIP RRs are present at the same owner name, this implicit
+ order of rendezvous servers within an RR MUST NOT be used to infer a
+ preference order between rendezvous servers 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 field.
+
+
+
+
+
+Nikander & Laganier Experimental [Page 10]
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+RFC 5205 HIP DNS Extension April 2008
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+
+ The Public Key field is represented as the Base64 encoding [RFC4648]
+ of the public key. The encoding MUST NOT contain whitespace(s) to
+ distinguish it from the Rendezvous Servers field.
+
+ The PK length field is not represented, as it is implicitly known
+ thanks to the Public key field representation containing no
+ whitespaces.
+
+ The Rendezvous Servers field is represented by one or more domain
+ name(s) separated by whitespace(s).
+
+ The complete representation of the HPIHI 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 HPIHI record is:
+
+ IN HIP ( pk-algorithm
+ base16-encoded-hit
+ base64-encoded-public-key )
+
+7. Examples
+
+ In the examples below, the public key field containing no whitespace
+ is wrapped since it does not fit in a single line of this document.
+
+ Example of a node with HI and HIT but no RVS:
+
+www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578
+ AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cIvM4p
+9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ryra+bSRGQ
+b1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXdXF5D )
+
+ Example of a node with a HI, HIT, and one RVS:
+
+www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578
+ AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cIvM4p
+9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ryra+bSRGQ
+b1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXdXF5D
+ rvs.example.com. )
+
+
+
+
+
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+Nikander & Laganier Experimental [Page 11]
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+RFC 5205 HIP DNS Extension April 2008
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+
+ Example of a node with a HI, HIT, and two RVSs:
+
+www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578
+ AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cIvM4p
+9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ryra+bSRGQ
+b1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXdXF5D
+ 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 introduces the same kind of threats that IPSECKEY does,
+ plus threats caused by the possibility given to a HIP node to
+ initiate or accept a HIP exchange using "opportunistic" or
+ "unpublished Initiator HI" modes.
+
+ A HIP node SHOULD obtain HIP RRs from a trusted party trough 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 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 (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 attacks on the
+ cryptographic core of the eventual HIP exchange (Responder's HIP RR
+ rewritten by the attacker).
+
+
+
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+
+ The HIP RR may contain a rendezvous server domain name resolved into
+ a destination IP address where the named peer is reachable by an I1,
+ as per the HIP Rendezvous Extension [RFC5204]. Thus, an attacker
+ 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, 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 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
+
+ IANA has allocated one new RR type code (55) for the HIP RR from the
+ standard RR type space.
+
+ IANA does not need to open a new registry for public key algorithms
+ of the HIP RR because the HIP RR reuses "algorithms types" defined
+ for the IPSECKEY RR [RFC4025]. Presently defined values are shown
+ here for reference only:
+
+ 0 is reserved
+
+ 1 is DSA
+
+ 2 is RSA
+
+
+
+
+Nikander & Laganier Experimental [Page 13]
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+RFC 5205 HIP DNS Extension April 2008
+
+
+ In the future, if a new algorithm is to be used for the HIP RR, a new
+ algorithm type and corresponding public key encoding should be
+ defined for the IPSECKEY RR. The HIP RR should reuse both the same
+ algorithm type and the same corresponding public key format as the
+ IPSECKEY RR.
+
+10. 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
+ [RFC5201].
+
+11. References
+
+11.1. Normative references
+
+ [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
+ STD 13, RFC 1034, November 1987.
+
+ [RFC1035] Mockapetris, P., "Domain names - implementation and
+ specification", STD 13, RFC 1035, November 1987.
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
+ Specification", RFC 2181, July 1997.
+
+ [RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
+ "DNS Extensions to Support IP Version 6", RFC 3596,
+ October 2003.
+
+ [RFC4025] Richardson, M., "A Method for Storing IPsec Keying
+ Material in DNS", RFC 4025, March 2005.
+
+ [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
+ Rose, "DNS Security Introduction and Requirements",
+ RFC 4033, March 2005.
+
+
+
+
+
+Nikander & Laganier Experimental [Page 14]
+
+RFC 5205 HIP DNS Extension April 2008
+
+
+ [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
+ Rose, "Resource Records for the DNS Security Extensions",
+ RFC 4034, March 2005.
+
+ [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
+ Rose, "Protocol Modifications for the DNS Security
+ Extensions", RFC 4035, March 2005.
+
+ [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
+ Encodings", RFC 4648, October 2006.
+
+ [RFC5201] Moskowitz, R., Nikander, P., Jokela, P., Ed., and T.
+ Henderson, "Host Identity Protocol", RFC 5201, April 2008.
+
+ [RFC5204] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
+ Rendezvous Extension", RFC 5204, April 2008.
+
+11.2. Informative references
+
+ [RFC2536] Eastlake, D., "DSA KEYs and SIGs in the Domain Name System
+ (DNS)", RFC 2536, March 1999.
+
+ [RFC3110] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain
+ Name System (DNS)", RFC 3110, May 2001.
+
+ [RFC3833] Atkins, D. and R. Austein, "Threat Analysis of the Domain
+ Name System (DNS)", RFC 3833, August 2004.
+
+ [RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol
+ (HIP) Architecture", RFC 4423, May 2006.
+
+ [RFC5206] Henderson, T., Ed., "End-Host Mobility and Multihoming
+ with the Host Identity Protocol", RFC 5206, April 2008.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
+Authors' Addresses
+
+ Pekka Nikander
+ Ericsson Research NomadicLab
+ JORVAS FIN-02420
+ FINLAND
+
+ Phone: +358 9 299 1
+ EMail: pekka.nikander@nomadiclab.com
+
+
+ Julien Laganier
+ DoCoMo Communications Laboratories Europe GmbH
+ Landsberger Strasse 312
+ Munich 80687
+ Germany
+
+ Phone: +49 89 56824 231
+ EMail: julien.ietf@laposte.net
+ URI: http://www.docomolab-euro.com/
+
+
+
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+
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+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2008).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
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+
+
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+
+
+
+Nikander & Laganier Experimental [Page 17]
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