draft-ietf-hip-rfc4423-bis-02.txt   draft-ietf-hip-rfc4423-bis-03.txt 
Network Working Group R. Moskowitz Network Working Group R. Moskowitz
Internet-Draft Verizon Internet-Draft Verizon
Obsoletes: 4423 (if approved) February 25, 2011 Obsoletes: 4423 (if approved) September 1, 2011
Intended status: Standards Track Intended status: Standards Track
Expires: August 29, 2011 Expires: March 4, 2012
Host Identity Protocol Architecture Host Identity Protocol Architecture
draft-ietf-hip-rfc4423-bis-02 draft-ietf-hip-rfc4423-bis-03
Abstract Abstract
This memo describes a new namespace, the Host Identity namespace, and This memo describes a new namespace, the Host Identity namespace, and
a new protocol layer, the Host Identity Protocol, between the a new protocol layer, the Host Identity Protocol, between the
internetworking and transport layers. Herein are presented the internetworking and transport layers. Herein are presented the
basics of the current namespaces, their strengths and weaknesses, and basics of the current namespaces, their strengths and weaknesses, and
how a new namespace will add completeness to them. The roles of this how a new namespace will add completeness to them. The roles of this
new namespace in the protocols are defined. new namespace in the protocols are defined.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 29, 2011. This Internet-Draft will expire on March 4, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Terms common to other documents . . . . . . . . . . . . . . 5 2.1. Terms common to other documents . . . . . . . . . . . . . . 5
2.2. Terms specific to this and other HIP documents . . . . . . . 5 2.2. Terms specific to this and other HIP documents . . . . . . . 5
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. A desire for a namespace for computing platforms . . . . . . 7 3.1. A desire for a namespace for computing platforms . . . . . . 7
4. Host Identity namespace . . . . . . . . . . . . . . . . . . 9 4. Host Identity namespace . . . . . . . . . . . . . . . . . . 9
4.1. Host Identifiers . . . . . . . . . . . . . . . . . . . . . . 10 4.1. Host Identifiers . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Storing Host Identifiers in DNS . . . . . . . . . . . . . . 10 4.2. Host Identity Hash (HIH) . . . . . . . . . . . . . . . . . . 10
4.3. Host Identity Tag (HIT) . . . . . . . . . . . . . . . . . . 11 4.3. Host Identity Tag (HIT) . . . . . . . . . . . . . . . . . . 11
4.4. Host Identity Hash (HIH) . . . . . . . . . . . . . . . . . . 11 4.4. Local Scope Identifier (LSI) . . . . . . . . . . . . . . . . 11
4.5. Local Scope Identifier (LSI) . . . . . . . . . . . . . . . . 11 4.5. Storing Host Identifiers in Directories . . . . . . . . . . 12
5. New stack architecture . . . . . . . . . . . . . . . . . . . 12 5. New stack architecture . . . . . . . . . . . . . . . . . . . 12
5.1. Transport associations and end-points . . . . . . . . . . . 13 5.1. Transport associations and end-points . . . . . . . . . . . 13
6. End-host mobility and multi-homing . . . . . . . . . . . . . 13 6. End-host mobility and multi-homing . . . . . . . . . . . . . 13
6.1. Rendezvous mechanism . . . . . . . . . . . . . . . . . . . . 14 6.1. Rendezvous mechanism . . . . . . . . . . . . . . . . . . . . 14
6.2. Protection against flooding attacks . . . . . . . . . . . . 14 6.2. Protection against flooding attacks . . . . . . . . . . . . 14
7. HIP and IPsec . . . . . . . . . . . . . . . . . . . . . . . 15 7. HIP and ESP . . . . . . . . . . . . . . . . . . . . . . . . 15
8. HIP and MAC Security . . . . . . . . . . . . . . . . . . . . 16 8. HIP and MAC Security . . . . . . . . . . . . . . . . . . . . 16
9. HIP and NATs . . . . . . . . . . . . . . . . . . . . . . . . 16 9. HIP and NATs . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. HIP and Upper-layer checksums . . . . . . . . . . . . . . . 17 9.1. HIP and Upper-layer checksums . . . . . . . . . . . . . . . 17
10. Multicast . . . . . . . . . . . . . . . . . . . . . . . . . 17 10. Multicast . . . . . . . . . . . . . . . . . . . . . . . . . 18
11. HIP policies . . . . . . . . . . . . . . . . . . . . . . . . 17 11. HIP policies . . . . . . . . . . . . . . . . . . . . . . . . 18
12. Benefits of HIP . . . . . . . . . . . . . . . . . . . . . . 18 12. Benefits of HIP . . . . . . . . . . . . . . . . . . . . . . 18
12.1. HIP's answers to NSRG questions . . . . . . . . . . . . . . 19 12.1. HIP's answers to NSRG questions . . . . . . . . . . . . . . 19
13. Changes from RFC 4423 . . . . . . . . . . . . . . . . . . . 21 13. Changes from RFC 4423 . . . . . . . . . . . . . . . . . . . 21
14. Security considerations . . . . . . . . . . . . . . . . . . 21 14. Security considerations . . . . . . . . . . . . . . . . . . 21
14.1. HITs used in ACLs . . . . . . . . . . . . . . . . . . . . . 23 14.1. HITs used in ACLs . . . . . . . . . . . . . . . . . . . . . 23
14.2. Non-security considerations . . . . . . . . . . . . . . . . 23 14.2. Alternative HI considerations . . . . . . . . . . . . . . . 24
15. IANA considerations . . . . . . . . . . . . . . . . . . . . 24 15. IANA considerations . . . . . . . . . . . . . . . . . . . . 24
16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 24 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 24
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
17.1. Normative References . . . . . . . . . . . . . . . . . . . . 25 17.1. Normative References . . . . . . . . . . . . . . . . . . . . 25
17.2. Informative references . . . . . . . . . . . . . . . . . . . 25 17.2. Informative references . . . . . . . . . . . . . . . . . . . 26
Author's Address . . . . . . . . . . . . . . . . . . . . . . 27 Author's Address . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction 1. Introduction
The Internet has two important global namespaces: Internet Protocol The Internet has two important global namespaces: Internet Protocol
(IP) addresses and Domain Name Service (DNS) names. These two (IP) addresses and Domain Name Service (DNS) names. These two
namespaces have a set of features and abstractions that have powered namespaces have a set of features and abstractions that have powered
the Internet to what it is today. They also have a number of the Internet to what it is today. They also have a number of
weaknesses. Basically, since they are all we have, we try and do too weaknesses. Basically, since they are all we have, we try and do too
much with them. Semantic overloading and functionality extensions much with them. Semantic overloading and functionality extensions
have greatly complicated these namespaces. have greatly complicated these namespaces.
The proposed Host Identity namespace fills an important gap between The proposed Host Identity namespace fills an important gap between
the IP and DNS namespaces. The Host Identity namespace consists of the IP and DNS namespaces. A Host Identity conceptually refers to a
Host Identifiers (HI). A Host Identifier is cryptographic in its computing platform, and there may be multiple such Host Identities
nature; it is the public key of an asymmetric key-pair. Each host per computing platform (because the platform may wish to present a
will have at least one Host Identity, but it will typically have more different identity to different communicating peers). The Host
than one. Each Host Identity uniquely identifies a single host, Identity namespace consists of Host Identifiers (HI). There is
i.e., no two hosts have the same Host Identity. The Host Identity, exactly one Host Identifier for each Host Identity. While this text
and the corresponding Host Identifier, can either be public (e.g. later talks about non-cryptographic Host Identifiers, the
published in the DNS), or unpublished. Client systems will tend to architecture focuses on the case in which Host Identifiers are
have both public and unpublished Identities. cryptographic in nature. Specifically, the Host Identifier is the
public key of an asymmetric key-pair. Each Host Identity uniquely
identifies a single host, i.e., no two hosts have the same Host
Identity. If two or more computing platforms have the same Host
Identifier, then they are instantiating a distributed host. The Host
Identifier can either be public (e.g. published in the DNS), or
unpublished. Client systems will tend to have both public and
unpublished Host Identifiers.
There is a subtle but important difference between Host Identities There is a subtle but important difference between Host Identities
and Host Identifiers. An Identity refers to the abstract entity that and Host Identifiers. An Identity refers to the abstract entity that
is identified. An Identifier, on the other hand, refers to the is identified. An Identifier, on the other hand, refers to the
concrete bit pattern that is used in the identification process. concrete bit pattern that is used in the identification process.
Although the Host Identifiers could be used in many authentication Although the Host Identifiers could be used in many authentication
systems, such as IKEv2 [RFC4306], the presented architecture systems, such as IKEv2 [RFC4306], the presented architecture
introduces a new protocol, called the Host Identity Protocol (HIP), introduces a new protocol, called the Host Identity Protocol (HIP),
and a cryptographic exchange, called the HIP base exchange; see also and a cryptographic exchange, called the HIP base exchange; see also
Section 7. The HIP protocols provide for limited forms of trust Section 7. The HIP protocols provide for limited forms of trust
between systems, enhance mobility, multi-homing and dynamic IP between systems, enhance mobility, multi-homing and dynamic IP
renumbering, aid in protocol translation / transition, and reduce renumbering, aid in protocol translation / transition, and reduce
certain types of denial-of-service (DoS) attacks. certain types of denial-of-service (DoS) attacks.
When HIP is used, the actual payload traffic between two HIP hosts is When HIP is used, the actual payload traffic between two HIP hosts is
typically, but not necessarily, protected with IPsec. The Host typically, but not necessarily, protected with ESP. The Host
Identities are used to create the needed IPsec Security Associations Identities are used to create the needed ESP Security Associations
(SAs) and to authenticate the hosts. When IPsec is used, the actual (SAs) and to authenticate the hosts. When ESP is used, the actual
payload IP packets do not differ in any way from standard IPsec payload IP packets do not differ in any way from standard ESP
protected IP packets. protected IP packets.
Much has been learned about HIP since [RFC4423] was published. This Much has been learned about HIP since [RFC4423] was published. This
document expands Host Identities beyond use to enable IP connectivity document expands Host Identities beyond use to enable IP connectivity
and security to general interhost secure signalling at any protocol and security to general interhost secure signalling at any protocol
layer. The signal may establish a security association between the layer. The signal may establish a security association between the
hosts, or simply pass information within the channel. hosts, or simply pass information within the channel.
2. Terminology 2. Terminology
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| | | | | |
| Host Identity | An abstract concept assigned to a 'computing | | Host Identity | An abstract concept assigned to a 'computing |
| | platform'. See 'Host Identifier', below. | | | platform'. See 'Host Identifier', below. |
| | | | | |
| Host Identity | A name space formed by all possible Host | | Host Identity | A name space formed by all possible Host |
| namespace | Identifiers. | | namespace | Identifiers. |
| | | | | |
| Host Identity | A protocol used to carry and authenticate Host | | Host Identity | A protocol used to carry and authenticate Host |
| Protocol | Identifiers and other information. | | Protocol | Identifiers and other information. |
| | | | | |
| Host Identity | A 128-bit datum created by taking a cryptographic |
| Tag | hash over a Host Identifier. |
| | |
| Host Identity | The cryptograhic hash used in creating the Host | | Host Identity | The cryptograhic hash used in creating the Host |
| Hash | Identity Tag from the Host Identity. | | Hash | Identity Tag from the Host Identity. |
| | | | | |
| Host Identity | A 128-bit datum created by taking a cryptographic |
| Tag | hash over a Host Identifier plus bits to identify |
| | which hash used. |
| | |
| Host | A public key used as a name for a Host Identity. | | Host | A public key used as a name for a Host Identity. |
| Identifier | | | Identifier | |
| | | | | |
| Local Scope | A 32-bit datum denoting a Host Identity. | | Local Scope | A 32-bit datum denoting a Host Identity. |
| Identifier | | | Identifier | |
| | | | | |
| Public Host | A published or publicly known Host Identfier used | | Public Host | A published or publicly known Host Identfier used |
| Identifier | as a public name for a Host Identity, and the | | Identifier | as a public name for a Host Identity, and the |
| and Identity | corresponding Identity. | | and Identity | corresponding Identity. |
| | | | | |
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named in order to interact in a scalable manner. Here we concentrate named in order to interact in a scalable manner. Here we concentrate
on naming computing platforms and packet transport elements. on naming computing platforms and packet transport elements.
There are two principal namespaces in use in the Internet for these There are two principal namespaces in use in the Internet for these
components: IP numbers, and Domain Names. Domain Names provide components: IP numbers, and Domain Names. Domain Names provide
hierarchically assigned names for some computing platforms and some hierarchically assigned names for some computing platforms and some
services. Each hierarchy is delegated from the level above; there is services. Each hierarchy is delegated from the level above; there is
no anonymity in Domain Names. Email, HTTP, and SIP addresses all no anonymity in Domain Names. Email, HTTP, and SIP addresses all
reference Domain Names. reference Domain Names.
IP numbers are a confounding of two namespaces, the names of a host's The IP addressing namespace has been overloaded to name both
networking interfaces and the names of the locations ('confounding' interfaces (at layer-3) and endpoints (for the endpoint-specific part
is a term used in statistics to discuss metrics that are merged into of layer-3, and for layer-4). In their role as interface names, IP
one with a gain in indexing, but a loss in informational value). The addresses are sometimes called "locators" and serve as an endpoint
names of locations should be understood as denoting routing direction within a routing topology.
vectors, i.e., information that is used to deliver packets to their
destinations.
IP numbers name networking interfaces, and typically only when the IP numbers name networking interfaces, and typically only when the
interface is connected to the network. Originally, IP numbers had interface is connected to the network. Originally, IP numbers had
long-term significance. Today, the vast number of interfaces use long-term significance. Today, the vast number of interfaces use
ephemeral and/or non-unique IP numbers. That is, every time an ephemeral and/or non-unique IP numbers. That is, every time an
interface is connected to the network, it is assigned an IP number. interface is connected to the network, it is assigned an IP number.
In the current Internet, the transport layers are coupled to the IP In the current Internet, the transport layers are coupled to the IP
addresses. Neither can evolve separately from the other. IPng addresses. Neither can evolve separately from the other. IPng
deliberations were strongly shaped by the decision that a deliberations were strongly shaped by the decision that a
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because of mobility, rehoming, or renumbering. because of mobility, rehoming, or renumbering.
If the namespace for computing platforms is based on public-key If the namespace for computing platforms is based on public-key
cryptography, it can also provide authentication services. If this cryptography, it can also provide authentication services. If this
namespace is locally created without requiring registration, it can namespace is locally created without requiring registration, it can
provide anonymity. provide anonymity.
Such a namespace (for computing platforms) and the names in it should Such a namespace (for computing platforms) and the names in it should
have the following characteristics: have the following characteristics:
o The namespace should be applied to the IP 'kernel'. The IP kernel o The namespace should be applied to the IP 'kernel' or stack. The
is the 'component' between applications and the packet transport IP stack is the 'component' between applications and the packet
infrastructure. transport infrastructure.
o The namespace should fully decouple the internetworking layer from o The namespace should fully decouple the internetworking layer from
the higher layers. The names should replace all occurrences of IP the higher layers. The names should replace all occurrences of IP
addresses within applications (like in the Transport Control addresses within applications (like in the Transport Control
Block, TCB). This may require changes to the current APIs. In Block, TCB). This may require changes to the current APIs. In
the long run, it is probable that some new APIs are needed. the long run, it is probable that some new APIs are needed.
o The introduction of the namespace should not mandate any o The introduction of the namespace should not mandate any
administrative infrastructure. Deployment must come from the administrative infrastructure. Deployment must come from the
bottom up, in a pairwise deployment. bottom up, in a pairwise deployment.
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were obtained. For 64 bits, this number is roughly 4 billion. A were obtained. For 64 bits, this number is roughly 4 billion. A
hash size of 64 bits may be too small to avoid collisions in a hash size of 64 bits may be too small to avoid collisions in a
large population; for example, there is a 1% chance of collision large population; for example, there is a 1% chance of collision
in a population of 640M. For 100 bits (or more), we would not in a population of 640M. For 100 bits (or more), we would not
expect a collision until approximately 2**50 (1 quadrillion) expect a collision until approximately 2**50 (1 quadrillion)
hashes were generated. hashes were generated.
o The names should have a localized abstraction so that it can be o The names should have a localized abstraction so that it can be
used in existing protocols and APIs. used in existing protocols and APIs.
o It must be possible to create names locally. This can provide o It must be possible to create names locally. When such names are
anonymity at the cost of making resolvability very difficult. not published, this can provide anonymity at the cost of making
resolvability very difficult.
* Sometimes the names may contain a delegation component. This * Sometimes the names may contain a delegation component. This
is the cost of resolvability. is the cost of resolvability.
o The namespace should provide authentication services. o The namespace should provide authentication services.
o The names should be long lived, but replaceable at any time. This o The names should be long lived, but replaceable at any time. This
impacts access control lists; short lifetimes will tend to result impacts access control lists; short lifetimes will tend to result
in tedious list maintenance or require a namespace infrastructure in tedious list maintenance or require a namespace infrastructure
for central control of access lists. for central control of access lists.
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designed, it can deliver all of the above stated requirements. designed, it can deliver all of the above stated requirements.
4. Host Identity namespace 4. Host Identity namespace
A name in the Host Identity namespace, a Host Identifier (HI), A name in the Host Identity namespace, a Host Identifier (HI),
represents a statistically globally unique name for naming any system represents a statistically globally unique name for naming any system
with an IP stack. This identity is normally associated with, but not with an IP stack. This identity is normally associated with, but not
limited to, an IP stack. A system can have multiple identities, some limited to, an IP stack. A system can have multiple identities, some
'well known', some unpublished or 'anonymous'. A system may self- 'well known', some unpublished or 'anonymous'. A system may self-
assert its own identity, or may use a third-party authenticator like assert its own identity, or may use a third-party authenticator like
DNSSEC [RFC2535], PGP, or X.509 to 'notarize' the identity assertion. DNSSEC [RFC2535], PGP, or X.509 to 'notarize' the identity assertion
It is expected that the Host Identifiers will initially be to another namespace. It is expected that the Host Identifiers will
authenticated with DNSSEC and that all implementations will support initially be authenticated with DNSSEC and that all implementations
DNSSEC as a minimal baseline. will support DNSSEC as a minimal baseline.
In theory, any name that can claim to be 'statistically globally In theory, any name that can claim to be 'statistically globally
unique' may serve as a Host Identifier. However, in the authors' unique' may serve as a Host Identifier. However, in the authors'
opinion, a public key of a 'public key pair' makes the best Host opinion, a public key of a 'public key pair' makes the best Host
Identifier. As will be specified in the Host Identity Protocol Base Identifier. As will be specified in the Host Identity Protocol Base
EXchange (BEX) [RFC5201-bis] specification, a public-key-based HI can EXchange (BEX) [RFC5201-bis] specification, a public-key-based HI can
authenticate the HIP packets and protect them for man-in-the-middle authenticate the HIP packets and protect them for man-in-the-middle
attacks. Since authenticated datagrams are mandatory to provide much attacks. Since authenticated datagrams are mandatory to provide much
of HIP's denial-of-service protection, the Diffie-Hellman exchange in of HIP's denial-of-service protection, the Diffie-Hellman exchange in
HIP BEX has to be authenticated. Thus, only public-key HI and HIP BEX has to be authenticated. Thus, only public-key HI and
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challenges. challenges.
4.1. Host Identifiers 4.1. Host Identifiers
Host Identity adds two main features to Internet protocols. The Host Identity adds two main features to Internet protocols. The
first is a decoupling of the internetworking and transport layers; first is a decoupling of the internetworking and transport layers;
see Section 5. This decoupling will allow for independent evolution see Section 5. This decoupling will allow for independent evolution
of the two layers. Additionally, it can provide end-to-end services of the two layers. Additionally, it can provide end-to-end services
over multiple internetworking realms. The second feature is host over multiple internetworking realms. The second feature is host
authentication. Because the Host Identifier is a public key, this authentication. Because the Host Identifier is a public key, this
key can be used for authentication in security protocols like IPsec. key can be used for authentication in security protocols like ESP.
The only completely defined structure of the Host Identity is that of The only completely defined structure of the Host Identity is that of
a public/private key pair. In this case, the Host Identity is a public/private key pair. In this case, the Host Identity is
referred to by its public component, the public key. Thus, the name referred to by its public component, the public key. Thus, the name
representing a Host Identity in the Host Identity namespace, i.e., representing a Host Identity in the Host Identity namespace, i.e.,
the Host Identifier, is the public key. In a way, the possession of the Host Identifier, is the public key. In a way, the possession of
the private key defines the Identity itself. If the private key is the private key defines the Identity itself. If the private key is
possessed by more than one node, the Identity can be considered to be possessed by more than one node, the Identity can be considered to be
a distributed one. a distributed one.
Architecturally, any other Internet naming convention might form a Architecturally, any other Internet naming convention might form a
usable base for Host Identifiers. However, non-cryptographic names usable base for Host Identifiers. However, non-cryptographic names
should only be used in situations of high trust - low risk. That is should only be used in situations of high trust - low risk. That is
any place where host authentication is not needed (no risk of host any place where host authentication is not needed (no risk of host
spoofing) and no use of IPsec. However, at least for interconnected spoofing) and no use of ESP. However, at least for interconnected
networks spanning several operational domains, the set of networks spanning several operational domains, the set of
environments where the risk of host spoofing allowed by non- environments where the risk of host spoofing allowed by non-
cryptographic Host Identifiers is acceptable is the null set. Hence, cryptographic Host Identifiers is acceptable is the null set. Hence,
the current HIP documents do not specify how to use any other types the current HIP documents do not specify how to use any other types
of Host Identifiers but public keys. of Host Identifiers but public keys.
The actual Host Identities are never directly used in any Internet The actual Host Identities are never directly used in any Internet
protocols. The corresponding Host Identifiers (public keys) may be protocols. The corresponding Host Identifiers (public keys) may be
stored in various DNS or LDAP directories as identified elsewhere in stored in various DNS or LDAP directories as identified elsewhere in
this document, and they are passed in the HIP base exchange. A Host this document, and they are passed in the HIP base exchange. A Host
Identity Tag (HIT) is used in other protocols to represent the Host Identity Tag (HIT) is used in other protocols to represent the Host
Identity. Another representation of the Host Identities, the Local Identity. Another representation of the Host Identities, the Local
Scope Identifier (LSI), can also be used in protocols and APIs. Scope Identifier (LSI), can also be used in protocols and APIs.
4.2. Storing Host Identifiers in DNS 4.2. Host Identity Hash (HIH)
The public Host Identifiers should be stored in DNS; the unpublished The Host Identity Hash is the cryptographic hash used in producing
Host Identifiers should not be stored anywhere (besides the the HIT from the HI. It is also the hash used through out the HIP
communicating hosts themselves). The (public) HI along with the protocol for consistancy and simplicity. It is possible to for the
supported HIHs are stored in a new RR type. This RR type is defined two Hosts in the HIP exchange to use different hashes.
in HIP DNS Extension [I-D.ietf-hip-rfc5205-bis].
Alternatively, or in addition to storing Host Identifiers in the DNS, Multiple HIHs within HIP are needed to address the moving target of
they may be stored in various kinds of Public Key Infrastructure creation and eventual compromise of cryptographic hashes. This
(PKI). Such a practice may allow them to be used for purposes other significantly complicates HIP and offers an attacker an additional
than pure host identification. downgrade attack that is mitigated in the HIP protocol.
4.3. Host Identity Tag (HIT) 4.3. Host Identity Tag (HIT)
A Host Identity Tag is a 128-bit representation for a Host Identity. A Host Identity Tag is a 128-bit representation for a Host Identity.
It is created by taking a cryptographic hash over the corresponding It is created from an HIH and other information, like an IPv6 prefix
Host Identifier. There are two advantages of using a hash over using and a hash identifier. There are two advantages of using the HIT
the Host Identifier in protocols. Firstly, its fixed length makes over using the Host Identifier in protocols. Firstly, its fixed
for easier protocol coding and also better manages the packet size length makes for easier protocol coding and also better manages the
cost of this technology. Secondly, it presents the identity in a packet size cost of this technology. Secondly, it presents the
consistent format to the protocol independent of the cryptographic identity in a consistent format to the protocol independent of the
algorithms used. cryptographic algorithms used.
There can be multiple HITs per Host Identifier when multiple hashes There can be multiple HITs per Host Identifier when multiple hashes
are supported. An Initator may have to initially guess which HIT to are supported. An Initator may have to initially guess which HIT to
use for the Responder, typically based on what it perfers, until it use for the Responder, typically based on what it perfers, until it
learns the appropriate HIT through the HIP exchange. learns the appropriate HIT through the HIP exchange.
In the HIP packets, the HITs identify the sender and recipient of a In the HIP packets, the HITs identify the sender and recipient of a
packet. Consequently, a HIT should be unique in the whole IP packet. Consequently, a HIT should be unique in the whole IP
universe as long as it is being used. In the extremely rare case of universe as long as it is being used. In the extremely rare case of
a single HIT mapping to more than one Host Identity, the Host a single HIT mapping to more than one Host Identity, the Host
Identifiers (public keys) will make the final difference. If there Identifiers (public keys) will make the final difference. If there
is more than one public key for a given node, the HIT acts as a hint is more than one public key for a given node, the HIT acts as a hint
for the correct public key to use. for the correct public key to use.
4.4. Host Identity Hash (HIH) 4.4. Local Scope Identifier (LSI)
The Host Identity Hash is the cryptographic hash used in producing
the HIT from the HI. It is also the hash used through out the HIP
protocol for consistancy and simplicity. It is possible to for the
two Hosts in the HIP exchange to use different hashes.
Multiple HIHs within HIP are needed to address the moving target of
creation and eventual compromise of cryptographic hashes. This
significantly complicates HIP and offers an attacker an additional
downgrade attack that is mitigated in the HIP protocol.
4.5. Local Scope Identifier (LSI)
An LSI is a 32-bit localized representation for a Host Identity. The An LSI is a 32-bit localized representation for a Host Identity. The
purpose of an LSI is to facilitate using Host Identities in existing purpose of an LSI is to facilitate using Host Identities in existing
protocols and APIs. LSI's advantage over HIT is its size; its protocols and APIs. LSI's advantage over HIT is its size; its
disadvantage is its local scope. disadvantage is its local scope.
Examples of how LSIs can be used include: as the address in an FTP Examples of how LSIs can be used include: as the address in an FTP
command and as the address in a socket call. Thus, LSIs act as a command and as the address in a socket call. Thus, LSIs act as a
bridge for Host Identities into IPv4-based protocols and APIs. LSIs bridge for Host Identities into IPv4-based protocols and APIs. LSIs
also make it possible for some IPv4 applications to run over an IPv6 also make it possible for some IPv4 applications to run over an IPv6
network. network.
4.5. Storing Host Identifiers in Directories
The public Host Identifiers should be stored in DNS; the unpublished
Host Identifiers should not be stored anywhere (besides the
communicating hosts themselves). The (public) HI along with the
supported HIHs are stored in a new RR type. This RR type is defined
in HIP DNS Extension [I-D.ietf-hip-rfc5205-bis].
Alternatively, or in addition to storing Host Identifiers in the DNS,
they may be stored in various other directories (e.g. LDAP, DHT) or
in a Public Key Infrastructure (PKI). Such a practice may allow them
to be used for purposes other than pure host identification.
5. New stack architecture 5. New stack architecture
One way to characterize Host Identity is to compare the proposed new One way to characterize Host Identity is to compare the proposed new
architecture with the current one. As discussed above, the IP architecture with the current one. As discussed above, the IP
addresses can be seen to be a confounding of routing direction addresses can be seen to be a confounding of routing direction
vectors and interface names. Using the terminology from the IRTF vectors and interface names. Using the terminology from the IRTF
Name Space Research Group Report [nsrg-report] and, e.g., the Name Space Research Group Report [nsrg-report] and, e.g., the
unpublished Internet-Draft Endpoints and Endpoint Names unpublished Internet-Draft Endpoints and Endpoint Names
[chiappa-endpoints], the IP addresses currently embody the dual role [chiappa-endpoints], the IP addresses currently embody the dual role
of locators and end-point identifiers. That is, each IP address of locators and end-point identifiers. That is, each IP address
skipping to change at page 12, line 38 skipping to change at page 13, line 5
In the HIP architecture, the end-point names and locators are In the HIP architecture, the end-point names and locators are
separated from each other. IP addresses continue to act as locators. separated from each other. IP addresses continue to act as locators.
The Host Identifiers take the role of end-point identifiers. It is The Host Identifiers take the role of end-point identifiers. It is
important to understand that the end-point names based on Host important to understand that the end-point names based on Host
Identities are slightly different from interface names; a Host Identities are slightly different from interface names; a Host
Identity can be simultaneously reachable through several interfaces. Identity can be simultaneously reachable through several interfaces.
The difference between the bindings of the logical entities are The difference between the bindings of the logical entities are
illustrated in Figure 1. illustrated in Figure 1.
Service ------ Socket Service ------ Socket Transport ---- Socket Transport ------ Socket
| | association | association |
| | | |
| | | |
| | | |
End-point | End-point --- Host Identity End-point | End-point --- Host Identity
\ | | \ | |
\ | | \ | |
\ | | \ | |
\ | | \ | |
Location --- IP address Location --- IP address Location --- IP address Location --- IP address
Figure 1 Figure 1
5.1. Transport associations and end-points 5.1. Transport associations and end-points
Architecturally, HIP provides for a different binding of transport- Architecturally, HIP provides for a different binding of transport-
layer protocols. That is, the transport-layer associations, i.e., layer protocols. That is, the transport-layer associations, i.e.,
TCP connections and UDP associations, are no longer bound to IP TCP connections and UDP associations, are no longer bound to IP
addresses but to Host Identities. addresses but to Host Identities.
It is possible that a single physical computer hosts several logical It is possible that a single physical computer hosts several logical
skipping to change at page 13, line 43 skipping to change at page 14, line 9
reassignments, or a NAT device remapping its translation. Likewise, reassignments, or a NAT device remapping its translation. Likewise,
a system is considered multi-homed if it has more than one globally a system is considered multi-homed if it has more than one globally
routable IP address at the same time. HIP links IP addresses routable IP address at the same time. HIP links IP addresses
together, when multiple IP addresses correspond to the same Host together, when multiple IP addresses correspond to the same Host
Identity, and if one address becomes unusable, or a more preferred Identity, and if one address becomes unusable, or a more preferred
address becomes available, existing transport associations can easily address becomes available, existing transport associations can easily
be moved to another address. be moved to another address.
When a node moves while communication is already on-going, address When a node moves while communication is already on-going, address
changes are rather straightforward. The peer of the mobile node can changes are rather straightforward. The peer of the mobile node can
just accept a HIP or an integrity protected IPsec packet from any just accept a HIP or an integrity protected ESP packet from any
address and ignore the source address. However, as discussed in address and ignore the source address. However, as discussed in
Section 6.2 below, a mobile node must send a HIP readdress packet to Section 6.2 below, a mobile node must send a HIP readdress packet to
inform the peer of the new address(es), and the peer must verify that inform the peer of the new address(es), and the peer must verify that
the mobile node is reachable through these addresses. This is the mobile node is reachable through these addresses. This is
especially helpful for those situations where the peer node is especially helpful for those situations where the peer node is
sending data periodically to the mobile node (that is re-starting a sending data periodically to the mobile node (that is re-starting a
connection after the initial connection). connection after the initial connection).
6.1. Rendezvous mechanism 6.1. Rendezvous mechanism
skipping to change at page 15, line 11 skipping to change at page 15, line 25
A credit-based authorization approach Host Mobility with the Host A credit-based authorization approach Host Mobility with the Host
Identity Protocol [I-D.ietf-hip-rfc5206-bis] can be used between Identity Protocol [I-D.ietf-hip-rfc5206-bis] can be used between
hosts for sending data prior to completing the address tests. hosts for sending data prior to completing the address tests.
Otherwise, if HIP is used between two hosts that fully trust each Otherwise, if HIP is used between two hosts that fully trust each
other, the hosts may optionally decide to skip the address tests. other, the hosts may optionally decide to skip the address tests.
However, such performance optimization must be restricted to peers However, such performance optimization must be restricted to peers
that are known to be trustworthy and capable of protecting themselves that are known to be trustworthy and capable of protecting themselves
from malicious software. from malicious software.
7. HIP and IPsec 7. HIP and ESP
The preferred way of implementing HIP is to use IPsec to carry the The preferred way of implementing HIP is to use ESP to carry the
actual data traffic. As of today, the only completely defined method actual data traffic. As of today, the only completely defined method
is to use IPsec Encapsulated Security Payload (ESP) to carry the data is to use ESP Encapsulated Security Payload (ESP) to carry the data
packets [I-D.ietf-hip-rfc5202-bis]. In the future, other ways of packets [I-D.ietf-hip-rfc5202-bis]. In the future, other ways of
transporting payload data may be developed, including ones that do transporting payload data may be developed, including ones that do
not use cryptographic protection. not use cryptographic protection.
In practice, the HIP base exchange uses the cryptographic Host In practice, the HIP base exchange uses the cryptographic Host
Identifiers to set up a pair of ESP Security Associations (SAs) to Identifiers to set up a pair of ESP Security Associations (SAs) to
enable ESP in an end-to-end manner. This is implemented in a way enable ESP in an end-to-end manner. This is implemented in a way
that can span addressing realms. that can span addressing realms.
While it would be possible, at least in theory, to use some existing While it would be possible, at least in theory, to use some existing
cryptographic protocol, such as IKEv2 together with Host Identifiers, cryptographic protocol, such as IKEv2 together with Host Identifiers,
to establish the needed SAs, HIP defines a new protocol. There are a to establish the needed SAs, HIP defines a new protocol. There are a
number of historical reasons for this, and there are also a few number of historical reasons for this, and there are also a few
architectural reasons. First, IKE (and IKEv2) were not designed with architectural reasons. First, IKE (and IKEv2) were not designed with
middle boxes in mind. As adding a new naming layer allows one to middle boxes in mind. As adding a new naming layer allows one to
potentially add a new forwarding layer (see Section 9, below), it is potentially add a new forwarding layer (see Section 9, below), it is
very important that the HIP protocols are friendly towards any middle very important that the HIP provides mechanisms for middlebox
boxes. authentication.
Second, from a conceptual point of view, the IPsec Security Parameter Second, from a conceptual point of view, the IPsec Security Parameter
Index (SPI) in ESP provides a simple compression of the HITs. This Index (SPI) in ESP provides a simple compression of the HITs. This
does require per-HIT-pair SAs (and SPIs), and a decrease of policy does require per-HIT-pair SAs (and SPIs), and a decrease of policy
granularity over other Key Management Protocols, such as IKE and granularity over other Key Management Protocols, such as IKE and
IKEv2. In particular, the current thinking is limited to a situation IKEv2. In other words, from an architectural point of view, HIP only
where, conceptually, there is only one pair of SAs between any given supports host-to-host (or endpoint-to-endpoint) Security
pair of HITs. In other words, from an architectural point of view, Associations.
HIP only supports host-to-host (or endpoint-to-endpoint) Security
Associations. If two hosts need more pairs of parallel SAs, they
should use separate HITs for that. However, future HIP extensions
may provide for more granularity and creation of several ESP SAs
between a pair of HITs.
Since HIP is designed for host usage, not for gateways or so called Originally, as HIP is designed for host usage, not for gateways or so
Bump-in-the-Wire (BITW) implementations, only ESP transport mode is called Bump-in-the-Wire (BITW) implementations, only ESP transport
supported. An ESP SA pair is indexed by the SPIs and the two HITs mode is supported. An ESP SA pair is indexed by the SPIs and the two
(both HITs since a system can have more than one HIT). The SAs need HITs (both HITs since a system can have more than one HIT). The SAs
not to be bound to IP addresses; all internal control of the SA is by need not to be bound to IP addresses; all internal control of the SA
the HITs. Thus, a host can easily change its address using Mobile is by the HITs. Thus, a host can easily change its address using
IP, DHCP, PPP, or IPv6 readdressing and still maintain the SAs. Mobile IP, DHCP, PPP, or IPv6 readdressing and still maintain the
Since the transports are bound to the SA (via an LSI or a HIT), any SAs. Since the transports are bound to the SA (via an LSI or a HIT),
active transport is also maintained. Thus, real-world conditions any active transport is also maintained. Thus, real-world conditions
like loss of a PPP connection and its re-establishment or a mobile like loss of a PPP connection and its re-establishment or a mobile
handover will not require a HIP negotiation or disruption of handover will not require a HIP negotiation or disruption of
transport services [Bel1998]. transport services [Bel1998].
It should be noted that there are already BITW implementations. This
is still consistant to the SA bindings above.
Since HIP does not negotiate any SA lifetimes, all lifetimes are Since HIP does not negotiate any SA lifetimes, all lifetimes are
local policy. The only lifetimes a HIP implementation must support local policy. The only lifetimes a HIP implementation must support
are sequence number rollover (for replay protection), and SA timeout. are sequence number rollover (for replay protection), and SA timeout.
An SA times out if no packets are received using that SA. An SA times out if no packets are received using that SA.
Implementations may support lifetimes for the various ESP transforms. Implementations may support lifetimes for the various ESP transforms.
8. HIP and MAC Security 8. HIP and MAC Security
The IEEE 802 standards have been defining MAC layered security. Many The IEEE 802 standards have been defining MAC layered security. Many
of these standards use EAP [RFC3748] as a Key Management System (KMS) of these standards use EAP [RFC3748] as a Key Management System (KMS)
skipping to change at page 17, line 13 skipping to change at page 17, line 23
[RFC2766]. [RFC2766].
In a network environment where identification is based on the IP In a network environment where identification is based on the IP
addresses, identifying the communicating nodes is difficult when NAT addresses, identifying the communicating nodes is difficult when NAT
is used. With HIP, the transport-layer end-points are bound to the is used. With HIP, the transport-layer end-points are bound to the
Host Identities. Thus, a connection between two hosts can traverse Host Identities. Thus, a connection between two hosts can traverse
many addressing realm boundaries. The IP addresses are used only for many addressing realm boundaries. The IP addresses are used only for
routing purposes; they may be changed freely during packet traversal. routing purposes; they may be changed freely during packet traversal.
For a HIP-based flow, a HIP-aware NAT or NAT-PT system tracks the For a HIP-based flow, a HIP-aware NAT or NAT-PT system tracks the
mapping of HITs, and the corresponding IPsec SPIs, to an IP address. mapping of HITs, and the corresponding ESP SPIs, to an IP address.
The NAT system has to learn mappings both from HITs and from SPIs to The NAT system has to learn mappings both from HITs and from SPIs to
IP addresses. Many HITs (and SPIs) can map to a single IP address on IP addresses. Many HITs (and SPIs) can map to a single IP address on
a NAT, simplifying connections on address poor NAT interfaces. The a NAT, simplifying connections on address poor NAT interfaces. The
NAT can gain much of its knowledge from the HIP packets themselves; NAT can gain much of its knowledge from the HIP packets themselves;
however, some NAT configuration may be necessary. however, some NAT configuration may be necessary.
NAT systems cannot touch the datagrams within the IPsec envelope, NAT systems cannot touch the datagrams within the ESP envelope, thus
thus application-specific address translation must be done in the end application-specific address translation must be done in the end
systems. HIP provides for 'Distributed NAT', and uses the HIT or the systems. HIP provides for 'Distributed NAT', and uses the HIT or the
LSI as a placeholder for embedded IP addresses. LSI as a placeholder for embedded IP addresses.
HIP and NAT interaction is defined in [RFC5770]. An experimental HIP and NAT traversal is defined in [RFC5770].
9.1. HIP and Upper-layer checksums 9.1. HIP and Upper-layer checksums
There is no way for a host to know if any of the IP addresses in an There is no way for a host to know if any of the IP addresses in an
IP header are the addresses used to calculate the TCP checksum. That IP header are the addresses used to calculate the TCP checksum. That
is, it is not feasible to calculate the TCP checksum using the actual is, it is not feasible to calculate the TCP checksum using the actual
IP addresses in the pseudo header; the addresses received in the IP addresses in the pseudo header; the addresses received in the
incoming packet are not necessarily the same as they were on the incoming packet are not necessarily the same as they were on the
sending host. Furthermore, it is not possible to recompute the sending host. Furthermore, it is not possible to recompute the
upper-layer checksums in the NAT/NAT-PT system, since the traffic is upper-layer checksums in the NAT/NAT-PT system, since the traffic is
IPsec protected. Consequently, the TCP and UDP checksums are ESP protected. Consequently, the TCP and UDP checksums are
calculated using the HITs in the place of the IP addresses in the calculated using the HITs in the place of the IP addresses in the
pseudo header. Furthermore, only the IPv6 pseudo header format is pseudo header. Furthermore, only the IPv6 pseudo header format is
used. This provides for IPv4 / IPv6 protocol translation. used. This provides for IPv4 / IPv6 protocol translation.
10. Multicast 10. Multicast
Few concrete thoughts exist about how HIP might affect IP-layer or Since its inception, a few studies have looked at how HIP might
application-layer multicast. affect IP-layer or application-layer multicast.
11. HIP policies 11. HIP policies
There are a number of variables that will influence the HIP exchanges There are a number of variables that will influence the HIP exchanges
that each host must support. All HIP implementations should support that each host must support. All HIP implementations should support
at least 2 HIs, one to publish in DNS and an unpublished one for at least 2 HIs, one to publish in DNS or similar directory service
anonymous usage. Although unpublished HIs will be rarely used as and an unpublished one for anonymous usage. Although unpublished HIs
responder HIs, they are likely be common for initiators. Support for will be rarely used as responder HIs, they are likely be common for
multiple HIs is recommended. initiators. Support for multiple HIs is recommended. This provides
new challenges for systems or users to decide which type of HI to
expose when they start a new session.
Opportunistic mode (where the initator starts a HIP exchange without
prior knowledge of the responder's HI) presents a policy tradeoff.
It provides some security benefits but may be subject to MITM.
Many initiators would want to use a different HI for different Many initiators would want to use a different HI for different
responders. The implementations should provide for a policy of responders. The implementations should provide for a policy of
initiator HIT to responder HIT. This policy should also include initiator HIT to responder HIT. This policy should also include
preferred transforms and local lifetimes. preferred transforms and local lifetimes.
Responders would need a similar policy, describing the hosts allowed Responders would need a similar policy, describing the hosts allowed
to participate in HIP exchanges, and the preferred transforms and to participate in HIP exchanges, and the preferred transforms and
local lifetimes. local lifetimes.
skipping to change at page 21, line 15 skipping to change at page 21, line 35
require significant new development and deployment. require significant new development and deployment.
13. Changes from RFC 4423 13. Changes from RFC 4423
This section summarizes the changes made from [RFC4423]. This section summarizes the changes made from [RFC4423].
14. Security considerations 14. Security considerations
HIP takes advantage of the new Host Identity paradigm to provide HIP takes advantage of the new Host Identity paradigm to provide
secure authentication of hosts and to provide a fast key exchange for secure authentication of hosts and to provide a fast key exchange for
IPsec. HIP also attempts to limit the exposure of the host to ESP. HIP also attempts to limit the exposure of the host to various
various denial-of-service (DoS) and man-in-the-middle (MitM) attacks. denial-of-service (DoS) and man-in-the-middle (MitM) attacks. In so
In so doing, HIP itself is subject to its own DoS and MitM attacks doing, HIP itself is subject to its own DoS and MitM attacks that
that potentially could be more damaging to a host's ability to potentially could be more damaging to a host's ability to conduct
conduct business as usual. business as usual.
Resource exhausting denial-of-service attacks take advantage of the Resource exhausting denial-of-service attacks take advantage of the
cost of setting up a state for a protocol on the responder compared cost of setting up a state for a protocol on the responder compared
to the 'cheapness' on the initiator. HIP allows a responder to to the 'cheapness' on the initiator. HIP allows a responder to
increase the cost of the start of state on the initiator and makes an increase the cost of the start of state on the initiator and makes an
effort to reduce the cost to the responder. This is done by having effort to reduce the cost to the responder. This is done by having
the responder start the authenticated Diffie-Hellman exchange instead the responder start the authenticated Diffie-Hellman exchange instead
of the initiator, making the HIP base exchange 4 packets long. There of the initiator, making the HIP base exchange 4 packets long. There
are more details on this process in the Host Identity Protocol under are more details on this process in the Host Identity Protocol under
development. development.
skipping to change at page 22, line 25 skipping to change at page 22, line 44
aborted after some retries). As a drawback, this leads to an 6-way aborted after some retries). As a drawback, this leads to an 6-way
base exchange which may seem bad at first. However, since this only base exchange which may seem bad at first. However, since this only
happens in an attack scenario and since the attack can be handled (so happens in an attack scenario and since the attack can be handled (so
it is not interesting to mount anymore), we assume the additional it is not interesting to mount anymore), we assume the additional
messages are not a problem at all. Since the MitM cannot be messages are not a problem at all. Since the MitM cannot be
successful with a downgrade attack, these sorts of attacks will only successful with a downgrade attack, these sorts of attacks will only
occur as 'nuisance' attacks. So, the base exchange would still be occur as 'nuisance' attacks. So, the base exchange would still be
usually just four packets even though implementations must be usually just four packets even though implementations must be
prepared to protect themselves against the downgrade attack. prepared to protect themselves against the downgrade attack.
In HIP, the Security Association for IPsec is indexed by the SPI; the In HIP, the Security Association for ESP is indexed by the SPI; the
source address is always ignored, and the destination address may be source address is always ignored, and the destination address may be
ignored as well. Therefore, HIP-enabled IPsec Encapsulated Security ignored as well. Therefore, HIP-enabled Encapsulated Security
Payload (ESP) is IP address independent. This might seem to make it Payload (ESP) is IP address independent. This might seem to make it
easier for an attacker, but ESP with replay protection is already as easier for an attacker, but ESP with replay protection is already as
well protected as possible, and the removal of the IP address as a well protected as possible, and the removal of the IP address as a
check should not increase the exposure of IPsec ESP to DoS attacks. check should not increase the exposure of ESP to DoS attacks.
Since not all hosts will ever support HIP, ICMPv4 'Destination Since not all hosts will ever support HIP, ICMPv4 'Destination
Unreachable, Protocol Unreachable' and ICMPv6 'Parameter Problem, Unreachable, Protocol Unreachable' and ICMPv6 'Parameter Problem,
Unrecognized Next Header' messages are to be expected and present a Unrecognized Next Header' messages are to be expected and present a
DoS attack. Against an initiator, the attack would look like the DoS attack. Against an initiator, the attack would look like the
responder does not support HIP, but shortly after receiving the ICMP responder does not support HIP, but shortly after receiving the ICMP
message, the initiator would receive a valid HIP packet. Thus, to message, the initiator would receive a valid HIP packet. Thus, to
protect against this attack, an initiator should not react to an ICMP protect against this attack, an initiator should not react to an ICMP
message until a reasonable time has passed, allowing it to get the message until a reasonable time has passed, allowing it to get the
real responder's HIP packet. A similar attack against the responder real responder's HIP packet. A similar attack against the responder
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come, then the initiator has to assume that the ICMP message is come, then the initiator has to assume that the ICMP message is
valid. Since this is the only point in the HIP base exchange where valid. Since this is the only point in the HIP base exchange where
this ICMP message is appropriate, it can be ignored at any other this ICMP message is appropriate, it can be ignored at any other
point in the exchange. point in the exchange.
14.1. HITs used in ACLs 14.1. HITs used in ACLs
It is expected that HITs will be used in ACLs. Future firewalls can It is expected that HITs will be used in ACLs. Future firewalls can
use HITs to control egress and ingress to networks, with an assurance use HITs to control egress and ingress to networks, with an assurance
level difficult to achieve today. As discussed above in Section 7, level difficult to achieve today. As discussed above in Section 7,
once a HIP session has been established, the SPI value in an IPsec once a HIP session has been established, the SPI value in an ESP
packet may be used as an index, indicating the HITs. In practice, packet may be used as an index, indicating the HITs. In practice,
firewalls can inspect HIP packets to learn of the bindings between firewalls can inspect HIP packets to learn of the bindings between
HITs, SPI values, and IP addresses. They can even explicitly control HITs, SPI values, and IP addresses. They can even explicitly control
IPsec usage, dynamically opening IPsec ESP only for specific SPI ESP usage, dynamically opening ESP only for specific SPI values and
values and IP addresses. The signatures in HIP packets allow a IP addresses. The signatures in HIP packets allow a capable firewall
capable firewall to ensure that the HIP exchange is indeed happening to ensure that the HIP exchange is indeed happening between two known
between two known hosts. This may increase firewall security. hosts. This may increase firewall security.
A potential of HITs in ACLs is their 'flatness' means they cannot be
aggregated and this could result in large table searches
There has been considerable bad experience with distributed ACLs that There has been considerable bad experience with distributed ACLs that
contain public key related material, for example, with SSH. If the contain public key related material, for example, with SSH. If the
owner of a key needs to revoke it for any reason, the task of finding owner of a key needs to revoke it for any reason, the task of finding
all locations where the key is held in an ACL may be impossible. If all locations where the key is held in an ACL may be impossible. If
the reason for the revocation is due to private key theft, this could the reason for the revocation is due to private key theft, this could
be a serious issue. be a serious issue.
A host can keep track of all of its partners that might use its HIT A host can keep track of all of its partners that might use its HIT
in an ACL by logging all remote HITs. It should only be necessary to in an ACL by logging all remote HITs. It should only be necessary to
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HIP-aware NATs, however, are transparent to the HIP aware systems by HIP-aware NATs, however, are transparent to the HIP aware systems by
design. Thus, the host may find it difficult to notify any NAT that design. Thus, the host may find it difficult to notify any NAT that
is using a HIT in an ACL. Since most systems will know of the NATs is using a HIT in an ACL. Since most systems will know of the NATs
for their network, there should be a process by which they can notify for their network, there should be a process by which they can notify
these NATs of the change of the HIT. This is mandatory for systems these NATs of the change of the HIT. This is mandatory for systems
that function as responders behind a NAT. In a similar vein, if a that function as responders behind a NAT. In a similar vein, if a
host is notified of a change in a HIT of an initiator, it should host is notified of a change in a HIT of an initiator, it should
notify its NAT of the change. In this manner, NATs will get updated notify its NAT of the change. In this manner, NATs will get updated
with the HIT change. with the HIT change.
14.2. Non-security considerations 14.2. Alternative HI considerations
The definition of the Host Identifier states that the HI need not be The definition of the Host Identifier states that the HI need not be
a public key. It implies that the HI could be any value; for example a public key. It implies that the HI could be any value; for example
a FQDN. This document does not describe how to support such a non- a FQDN. This document does not describe how to support such a non-
cryptographic HI. A non-cryptographic HI would still offer the cryptographic HI. A non-cryptographic HI would still offer the
services of the HIT or LSI for NAT traversal. It would be possible services of the HIT or LSI for NAT traversal. It would be possible
to carry HITs in HIP packets that had neither privacy nor to carry HITs in HIP packets that had neither privacy nor
authentication. Since such a mode would offer so little additional authentication. Since such a mode would offer so little additional
functionality for so much addition to the IP kernel, it has not been functionality for so much addition to the IP kernel, it has not been
defined. Given how little public key cryptography HIP requires, HIP defined. Given how little public key cryptography HIP requires, HIP
skipping to change at page 25, line 10 skipping to change at page 25, line 32
process owes its impetuous to the three HIP development teams: process owes its impetuous to the three HIP development teams:
Boeing, HIIT (Helsinki Institute for Information Technology), and Boeing, HIIT (Helsinki Institute for Information Technology), and
NomadicLab of Ericsson. Without their collective efforts HIP would NomadicLab of Ericsson. Without their collective efforts HIP would
have withered as on the IETF vine as a nice concept. have withered as on the IETF vine as a nice concept.
17. References 17. References
17.1. Normative References 17.1. Normative References
[RFC5201-bis] [RFC5201-bis]
Moskowitz, R., Jokela, P., Henderson, T., and T. Heer, Moskowitz, R., Heer, T., Jokela, P., and T. Henderson,
"Host Identity Protocol", draft-ietf-hip-rfc5201-bis-04 "Host Identity Protocol Version 2 (HIPv2)",
(work in progress), January 2011. draft-ietf-hip-rfc5201-bis-05 (work in progress),
March 2011.
[I-D.ietf-hip-rfc5202-bis] [I-D.ietf-hip-rfc5202-bis]
Jokela, P., Moskowitz, R., Nikander, P., and J. Melen, Jokela, P., Moskowitz, R., Nikander, P., and J. Melen,
"Using the Encapsulating Security Payload (ESP) Transport "Using the Encapsulating Security Payload (ESP) Transport
Format with the Host Identity Protocol (HIP)", Format with the Host Identity Protocol (HIP)",
draft-ietf-hip-rfc5202-bis-00 (work in progress), draft-ietf-hip-rfc5202-bis-00 (work in progress),
September 2010. September 2010.
[I-D.ietf-hip-rfc5204-bis] [I-D.ietf-hip-rfc5204-bis]
Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", draft-ietf-hip-rfc5204-bis-00 (work Rendezvous Extension", draft-ietf-hip-rfc5204-bis-01 (work
in progress), August 2010. in progress), March 2011.
[I-D.ietf-hip-rfc5205-bis] [I-D.ietf-hip-rfc5205-bis]
Laganier, J., "Host Identity Protocol (HIP) Domain Name Laganier, J., "Host Identity Protocol (HIP) Domain Name
System (DNS) Extension", draft-ietf-hip-rfc5205-bis-00 System (DNS) Extension", draft-ietf-hip-rfc5205-bis-01
(work in progress), August 2010. (work in progress), March 2011.
[I-D.ietf-hip-rfc5206-bis] [I-D.ietf-hip-rfc5206-bis]
Nikander, P., Henderson, T., Vogt, C., and J. Arkko, "Host Nikander, P., Henderson, T., Vogt, C., and J. Arkko, "Host
Mobility with the Host Identity Protocol", Mobility with the Host Identity Protocol",
draft-ietf-hip-rfc5206-bis-01 (work in progress), draft-ietf-hip-rfc5206-bis-02 (work in progress),
October 2010. March 2011.
17.2. Informative references 17.2. Informative references
[RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)", "Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, April 1997. RFC 2136, April 1997.
[RFC2535] Eastlake, D., "Domain Name System Security Extensions", [RFC2535] Eastlake, D., "Domain Name System Security Extensions",
RFC 2535, March 1999. RFC 2535, March 1999.
skipping to change at page 27, line 15 skipping to change at page 27, line 40
Springer, 2002. Springer, 2002.
[Bel1998] Bellovin, S., "EIDs, IPsec, and HostNAT", in Proceedings [Bel1998] Bellovin, S., "EIDs, IPsec, and HostNAT", in Proceedings
of 41th IETF, Los Angeles, CA, of 41th IETF, Los Angeles, CA,
URL http://www1.cs.columbia.edu/~smb/talks/hostnat.pdf, URL http://www1.cs.columbia.edu/~smb/talks/hostnat.pdf,
March 1998. March 1998.
Author's Address Author's Address
Robert Moskowitz Robert Moskowitz
Verizon Telcom and Business Verizon
1000 Bent Creek Blvd, Suite 200 1000 Bent Creek Blvd, Suite 200
Mechanicsburg, PA Mechanicsburg, PA
USA USA
Email: robert.moskowitz@verizonbusiness.com Email: robert.moskowitz@verizon.com
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