HIP R. Moskowitz
Internet-Draft HTT Consulting
Intended status: Standards Track S. Card
Expires: 16 March 2020 A. Wiethuechter
AX Enterprize
13 September 2019
Hierarchical HIT Registries
draft-moskowitz-hip-hhit-registries-00
Abstract
This document describes using the registration protocol and
registries to support hierarchical HITs (HHITs). New and existing
HIP parameters are used to communicate Registry Policies and data
about the HHIT device and the Registries. Further Registries are
expected to provide RVS services for registered HHIT devices.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Terminology . . . . . . . . . . . . . . . . 3
2.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Space . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Desire for administrative control of HHITs . . . . . . . 3
3.2. Desire for administrative control by RVS providers . . . 4
3.3. Defense against fraudulent HITs . . . . . . . . . . . . . 4
4. HHIT Registry services to support hierarchical HITs . . . . . 4
4.1. Hierarchical HIT Registration using X.509
Certificates . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Hierarchical HIT Registration using a PSK . . . . . . . . 5
4.3. HIP Parameters . . . . . . . . . . . . . . . . . . . . . 5
4.3.1. CERT Parameter . . . . . . . . . . . . . . . . . . . 5
4.3.2. Hierarchical HIT Registration Type . . . . . . . . . 5
4.3.3. Hierarchical HIT Registration Failure Type . . . . . 6
4.3.4. CLIENT_INFO . . . . . . . . . . . . . . . . . . . . . 6
4.4. Registration failure behavior . . . . . . . . . . . . . . 7
4.4.1. Example of a simple HDA policy . . . . . . . . . . . 7
5. Using hierarchical HITs . . . . . . . . . . . . . . . . . . . 7
5.1. Contacting a HIP client . . . . . . . . . . . . . . . . . 7
5.2. Defense against fraudulent HITs . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. RAA Management Organization Considerations . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8.1. Privacy Concerns . . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Calculating Collision Probabilities . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
This document expands on Hierarchical HITs
[I-D.moskowitz-hip-hierarchical-hit], defining HIP registration
protocol enhancements, the Registry services to support hierarchical
HITs (HHITs), and given a HHIT, how to get additional information
about the device.
Registries will tend to be organized regionally and by nature of
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their clients. For example, an RAA may be US centric and only have
HDAs that are US-based.
Registries will need to work in a federation. Devices that are
clients of one HDA/RAA will be needing information and connectivity
to devices that are clients of other HDA/RAA. The policies for
establishing such federations are outside the scope of this document.
Access to information at a Registry about a device may require
authorization. The nature and process of such an authorization is
outside the scope of this document.
2. Terms and Definitions
2.1. Requirements Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2.2. Definitions
CSR (Certificate Signing Request): Request to a Certificate
Authority to create an X.509 certificate with the provided
information.
HDA (Hierarchical HIT Domain Authority): The 14 bit field
identifying the HIT Domain Authority under a RAA.
HID (Hierarchy ID): The 32 bit field providing the HIT Hierarchy ID.
RAA (Registered Assigning Authority): The 18 bit field identifying
the Hierarchical HIT Assigning Authority.
3. Problem Space
3.1. Desire for administrative control of HHITs
For HHITs to be effectively used, the HHIT Domain Authorities (HDAs)
need to provide information on the HHIT devices. Minimally this
would be the corresponding HI, information on the device owner (only
to authorized requesters), and where in the network the device has
last reported from.
The HHIT space creates a type of a business labeling for the HDAs.
"These are my customers."
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3.2. Desire for administrative control by RVS providers
An RVS provider may only be willing to provide discovery (RVS)
services to HIP devices it knows and trusts. A flat HIT space does
not provide any intrinsic functionality to support this. A HHIT
space can be mapped to the RVS provider. DNS can effectively be used
to provide the HHIT to IP mapping without Distributed Hash
Table (DHT) [RFC6537].
3.3. Defense against fraudulent HITs
How can a host protect against a fraudulent HIT? That is, a second
pre-image attack on the HI hash that produces the HIT. A strong
defense would require every HIT/HI registered and openly verifiable.
With HHITs, the HDAs can provide the HI and proof of registration
(e.g. X.509 certificate including HHIT).
This would best be done as either part of the R1 and I2 validation,
or anytime a HHIT is presented.
4. HHIT Registry services to support hierarchical HITs
Hierarchical HIT registration SHOULD be performed using the HIP
Registration Extension [RFC8003]. The client either uses an X.509
certificate [RFC8002], or use a PSK, as defined in Appendix A of HIP-
DEX [I-D.ietf-hip-dex], to validate the registration.
The Registration should include additional client information. This
information may be contained within the X.509 certificate (CERT
parameter) and/or is carried in the CLIENT_INFO parameter, see
Section 4.3.4. The Registrar can include its requirements in the R1
packet, and the client provide its information in the I2 packet.
This parameter may be encrypted within the ENCRYPTED parameter. If
the CLIENT_INFO contains Personal Identifying Information (PII), then
it MUST be placed into the ENCRYPTED parameter.
The content and internal format of the CLIENT_INFO parameter is set
by the HDA"s policy and is outside the scope of this document.
Examples of client information can by phone number, IMEI, and ICCID.
4.1. Hierarchical HIT Registration using X.509 Certificates
This requires the HIP client to possess a client certificate trusted
by the HDA/Registrar. Registration will either succeed or fail.
Certificate registration can be a "chicken and egg" problem: where
did the device get its certificate? Thus this is more likely used in
a re-registration situation with updated information.
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4.2. Hierarchical HIT Registration using a PSK
This requires the HIP client and the HDA/Registrar to share a PSK.
The PSK is carried in the ENCRYPTED_KEY parameter [I-D.ietf-hip-dex].
The PSK may already exist prior to starting the registration and just
be used within the registration. A PSK out-of-band exchange may be
triggered by performing the registration without any authentication.
If no client authentication is included in the I2 packet, the
registration fails with "No Authentication provided". If the I2
packet included the proper HDA required client information, the HDA
can use it to set up a side channel for an out-of-band delivery of a
PSK. And example of this would be to send an SMS message with the
PSK. Once the client possesses the PSK, it can rerun the
registration at which point the HI and HIT duplicate checks are
performed.
The I2 packet may contain a CERT parameter containing a CSR, and the
R2 would return the X.509 certificate for later use.
4.3. HIP Parameters
The HIP parameters carry information that is necessary for
establishing and maintaining a HIP association. For example, the
device's public keys as well as the signaling for negotiating ciphers
and payload handling are encapsulated in HIP parameters. Additional
information, meaningful for end hosts or middleboxes, may also be
included in HIP parameters. The specification of the HIP parameters
and their mapping to HIP packets and packet types is flexible to
allow HIP extensions to define new parameters and new protocol
behavior.
4.3.1. CERT Parameter
The CERT parameter, [RFC8002], is a container for certain types of
digital certificates.
A new CERT Type, CSR, is defined here. When CERT Type is CSR, CERT
ID is Zero. There is only ONE CSR in a CERT Parameter.
CERT format Type number RFC
------------- ----------- ----
PKCS#10 - CSR 9 2986
4.3.2. Hierarchical HIT Registration Type
The Registration Type used in the REG_REQUEST is:
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Number Registration Type
------ -----------------
2 HHIT Registration
4.3.3. Hierarchical HIT Registration Failure Type
The Registration may fail. In fact, with PSK, this may be the
response to expect an SMS message with the PSK to use in a second
registration request. Failure Types used in the REG_FAIL are:
Failure Type Reason
------------ -----------------------
[TBD-IANA] Hierarchical HIT Already Registered
[TBD-IANA] HI Already Registered
[TBD-IANA] Previously Registered HI with different
device information
[TBD-IANA] No Authentication provided
[TBD-IANA] Invalid Authentication
[TBD-IANA] Invalid Authentication, new PSK sent via SMS
4.3.4. CLIENT_INFO
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ Client Information /
/ /
/ +-------------------------------+
/ | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type [TBD-IANA]
Length length in octets, excluding Type, Length, and
Padding
Client The information required by the HDA in the format
Information required by the HDA.
This parameter contains client information to include in the HIT
registration. The specific content and format is set by the HDA.
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4.4. Registration failure behavior
If the failure type is "Hierarchical HIT Already Registered", the
client's HI is hashing to an existing HIT and must generate a new HI
and hierarchical HIT and re-register. If the failure is "HI Already
Registered", the client should assume it is registered. If the
failure is "Previously Registered HI with different device
information", either the client managed to generate a duplicate HI,
possibly indicating a weak key generation algorithm, or the client
was previously registered on a different device. Resolving this
conflict will be left to the HDA's policy.
4.4.1. Example of a simple HDA policy
A simple HDA policy would be to require the device to generate a new
HI and thus HHIT and try registration again. The HDA policy may also
provide a URL for "Previous Registration Resolution". This contact
is primarily to assist a device that was registered, but had some
local failure resulting in a new registration attempt.
5. Using hierarchical HITs
All HIP clients with hierarchical HITs maintain an RVS connection
with their HDA's RVS server(s). How the HDA scales this service up
to a potential population in the millions is out of scope of this
document. Lifetime management of these connections is also out of
scope.
One approach an HDA can use to address the scaling challenge is to
add an internal level of hierarchy to assign a set number of devices
per RVS server.
Peering agreements between HDAs would allow for geographically close
RVS to a device. This may reduce the latency for use of a device's
current RVS. This is a subject of another document.
5.1. Contacting a HIP client
A service Initiator uses some service to discover the HIT of the
service Responder. The Initiator uses the hierarchical information
in the HIT to find the Responder's RVS. A trusted RVS discover
method could use the DNS PTR to RVS as shown in Hierarchical HITs
[I-D.moskowitz-hip-hierarchical-hit]. An I1 is sent to that RVS
which forwards it to the Responder.
The potential Responder uses the HIT in the I1 to query the
Initiator's RVS about the Initiator. The nature of information, and
method of communication are determined by the Initiator's HDA and the
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Responder's (and or HDA"s) relationship with it. Based on the
Responder's local policy, this information will be used to determine
if the contact is to be accepted. If accepted, the Responder may
proceed sending an R1 to the Initiator. It may alternatively
initiate some non-HIP process.
It should be noted that this R1 may contain a REG_INFO list for the
Initiator to validate that the Responder does offer the desired
service.
5.2. Defense against fraudulent HITs
Both the Initiator and Responder MAY validate a peer host as a
defense against a second pre-image attack on the HHIT. This may
occur via a CERT [RFC8002] in R1 or I2. It may be through a back end
process associated with the R1 or I2 validation to look up the HHIT
and retrieve the registered HI.
6. IANA Considerations
IANA will need to make the following changes to the "Host Identity
Protocol (HIP) Parameters" registries:
CERT Type: This document defines the new CERT Type for the CERT
parameter "PKCS#10 - CSR" (see Section 4.3.1).
Reg Type: This document defines the new Registration Type for the
REG_REQUEST parameter "HIT Registration" (see Section 4.3.2).
Reg Fail: This document defines the new Failure Types for the
REG_FAIL parameter (see Section 4.3.3).
CLIENT_INFO: This document defines the new CLIENT_INFO parameter
(see Section 4.3.4). The parameter value will be assigned by
IANA.
7. RAA Management Organization Considerations
Introducing the RAA management organization may be the largest hurdle
for hierarchical HITs. Thus it would be best if this were adopted by
an organization already in the business of allocating numbers within
either the Internet or the Mobile, cellular, infrastructure.
One consideration would be to reserve the first N RAA values to map
to the existing DNS TLDs. For example, these TLDs can be organized
in an ascending order and numbered accordingly. Thus the 2 character
TLDs will be a lower number than the 3 character TLDs. After that,
it could be a first come, first numbered assignment process.
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8. Security Considerations
There are potential risks with the hierarchical HIT, the Registry
service, and the discovery of potential peer hosts using its
hierarchical HIT.
A 64 bit hash space presents a real risk of second pre-image attacks.
The HHIT Registry services effectively block attempts to "take over"
a HHIT. It does not stop a rogue attempting to impersonate a known
HHIT. This attack can be mitigated by the Responder using DNS to
find the HI for the HHIT or the RVS for the HHIT that then provides
the registered HI.
The two risks with hierarchical HITs are the use of an invalid HID
and forced HIT collisions. The use of the "hhit.arpa." DNS zone is
a strong protection against invalid HIDs. Querying an HDA's RVS for
a HIT under the HDA protects against talking to unregistered clients.
The Registry service has direct protection against forced or
accidental HIT hash collisions.
By using the HIP Registration Extension, the Registry service is
protected from direct attacks. This service does rely on either the
integrity of a PKI service or an out-of-band PSK delivery process.
Thus the risk to the Registry service is highly related to the trust
in these authentication setup services. Further, the duplicate HI
resolution process may require human interaction with related social
engineering risks.
Finally the peer host discovery process relies on trusting the
finding the proper HDA for the host and its forwarding the I1 to the
proper Responder. A rogue RVS, impersonating the RVS for the HIT,
could redirect the I1 to a client that has forced a collision with
the HIT and the Initiator would be none the wiser. The only defense
against this is if the Initiator has some other source for the
Responder HI and validate the HI in the R1.
8.1. Privacy Concerns
Mobile-privacy-attack [I-D.moskowitz-mobile-privacy-attack] details
how Eve can follow a communication between two mobile peers using the
session Identifiers and deep knowledge about those Identifiers gained
by hacking servers that log PII related to the Identifiers.
Hierarchical HITs not only does not mitigate this attack, it can
actually aggravate it by supplying the HDA where the HHIT is
registered.
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A HIP Privacy Enhanced Base Exchange, to be defined in a separate
draft, along with a Privacy Enhanced ESP tunnel, can be used to hide
all the HIP and ESP Identifiers from Eve.
9. Acknowledgments
Sue Hares of Huawei contributed to the clarity in this document.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
10.2. Informative References
[I-D.ietf-hip-dex]
Moskowitz, R., Hummen, R., and M. Komu, "HIP Diet EXchange
(DEX)", Internet-Draft, draft-ietf-hip-dex-08, 24 June
2019,
<http://www.ietf.org/internet-drafts/draft-ietf-hip-dex-
08.txt>.
[I-D.moskowitz-hip-hierarchical-hit]
Moskowitz, R., Card, S., and A. Wiethuechter,
"Hierarchical HITs for HIPv2", Internet-Draft, draft-
moskowitz-hip-hierarchical-hit-00, 12 September 2019,
<http://www.ietf.org/internet-drafts/draft-moskowitz-hip-
hierarchical-hit-00.txt>.
[I-D.moskowitz-mobile-privacy-attack]
Moskowitz, R., "An Attack on Privacy in Mobile Devices",
Internet-Draft, draft-moskowitz-mobile-privacy-attack-01,
13 November 2017,
<http://www.ietf.org/internet-drafts/draft-moskowitz-
mobile-privacy-attack-01.txt>.
[RFC6537] Ahrenholz, J., "Host Identity Protocol Distributed Hash
Table Interface", RFC 6537, DOI 10.17487/RFC6537, February
2012, <https://www.rfc-editor.org/info/rfc6537>.
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[RFC8002] Heer, T. and S. Varjonen, "Host Identity Protocol
Certificates", RFC 8002, DOI 10.17487/RFC8002, October
2016, <https://www.rfc-editor.org/info/rfc8002>.
[RFC8003] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Registration Extension", RFC 8003, DOI 10.17487/RFC8003,
October 2016, <https://www.rfc-editor.org/info/rfc8003>.
Appendix A. Calculating Collision Probabilities
The accepted formula for calculating the probability of a collision
is:
p = 1 - e^{-k^2/(2n)}
P Collision Probability
n Total possible population
k Actual population
Authors' Addresses
Robert Moskowitz
HTT Consulting
Oak Park, MI 48237
United States of America
Email: rgm@labs.htt-consult.com
Stuart W. Card
AX Enterprize
4947 Commercial Drive
Yorkville, NY 13495
United States of America
Email: stu.card@axenterprize.com
Adam Wiethuechter
AX Enterprize
4947 Commercial Drive
Yorkville, NY 13495
United States of America
Email: adam.wiethuechter@axenterprize.com
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