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PKI4IPSEC Working Group
Internet Draft Chris Bonatti, IECA
draft-ietf-pki4ipsec-mgmt-profile-rqts-01.txt
draft-ietf-pki4ipsec-mgmt-profile-rqts-02.txt Sean Turner, IECA
October 25,
December 12, 2004 Gregory Lebovitz, Netscreen
Expires April 25, June 12, 2005
Requirements for an IPsec Certificate Management Profile
Status of this Memo
By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed,
or will be disclosed, and any of which I become aware will be
disclosed, in accordance with RFC 3668.
This document is an Internet-Draft and is in full conformance with
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Abstract
This informational document describes and identifies the requirements
for a profile of a certificate management protocol to handle Public
Key Certificate (PKC) lifecycle interactions between Internet
Protocol Secuity (IPsec) Virtual Private Network (VPN) Systems using
IKE (versions 1 and 2) and Public Key Infrastructure (PKI) Systems.
These requirements are designed so that they meet the needs of
enterprise scale IPsec VPN deployments. It is intended that a
standards track profile will be created that fulfills these
requirements.
1 INTRODUCTION.....................................................3
1.1 SCOPE..........................................................4
1.2 NON-GOALS......................................................5
STATUS OF THIS MEMO................................................1
ABSTRACT...........................................................1
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1 INTRODUCTION.....................................................3
1.1 SCOPE..........................................................4
1.2 NON-GOALS......................................................5
1.3 DEFINITIONS....................................................5
1.4 REQUIREMENTS TERMINOLOGY.......................................7
2. ARCHITECTURE....................................................7 ARCHITECTURE....................................................8
2.1 VPN SYSTEM.....................................................7 SYSTEM.....................................................8
2.1.1 IPSEC PEER(S)................................................8
2.1.2 VPN ADMINISTRATION FUNCTION (ADMIN)..........................8 (ADMIN)..........................9
2.2 PKI SYSTEM.....................................................9 SYSTEM....................................................10
2.3 VPN-PKI INTERACTION...........................................10 INTERACTION...........................................11
2.3.1 NEW PKC.....................................................11 PKC.....................................................12
2.3.2 RENEWAL PKC.................................................13 PKC.................................................14
2.3.3 REVOCATION..................................................14 REVOCATION..................................................16
3 REQUIREMENTS....................................................15 REQUIREMENTS....................................................17
3.1 GENERAL REQUIREMENTS..........................................15 REQUIREMENTS..........................................17
3.1.1 ONE PROTOCOL................................................15 PROTOCOL................................................17
3.1.2 SECURE TRANSACTIONS.........................................16 TRANSACTIONS.........................................17
3.1.3 PKI AVAILABILITY............................................16 AVAILABILITY............................................17
3.1.4 END-USER TRANSPARENCY.......................................16 TRANSPARENCY.......................................18
3.1.5 ERROR HANDLING..............................................16 HANDLING..............................................18
3.2 AUTHORIZATION TRANSACTIONS....................................17 TRANSACTIONS....................................18
3.2.1 BULK AUTHORIZATION..........................................17 AUTHORIZATION..........................................18
3.2.2 PROTOCOL PREFERENCES FOR AUTHORIZATION......................17 AUTHORIZATION......................18
3.2.3 ADMIN AUTHORIZATION REQUESTS TO PKI.........................18 PKI.........................19
3.2.3.1 SPECIFYING FIELDS WITHIN THE PKC..........................18 PKC..........................19
3.2.3.2 AUTHORIZATIONS FOR RENEWAL AND CHANGE.....................18 UPDATE.....................20
3.2.3.3 OTHER AUTHORIZATION ELEMENTS..............................19 ELEMENTS..............................21
3.2.4 CANCEL CAPABILITY...........................................20 CAPABILITY...........................................21
3.2.5 PKI RESPONSE TO ADMIN.......................................20 ADMIN.......................................22
3.2.6 ERROR HANDLING FOR AUTHORIZATION TRANSACTIONS...............21 TRANSACTIONS...............22
3.3 KEY GENERATION AND PKC REQUEST CONSTRUCTION...................21 CONSTRUCTION...................22
3.3.1 KEY GENERATION SCENARIOS....................................23
3.3.1.1 IPSEC PEER GENERATES KEY PAIR AND CONSTRUCTS REQUEST........21
3.3.2 REQUEST......23
3.3.1.2 IPSEC PEER GENERATES KEY PAIR, ADMIN CONSTRUCTS REQUEST.....21
3.3.3 REQUEST...24
3.3.1.3 ADMIN GENERATES KEY PAIR AND CONSTRUCTS REQUEST.............22
3.3.4 REQUEST...........26
3.3.1.4 PKI GENERATES KEY PAIR AND PASSES TO PEER VIA ADMIN.........22
3.3.5 TRUST ANCHOR PKC ACQUISITION................................22
3.3.6 ADMIN.......27
3.3.1.5 PEER GENERATES KEY PAIR WITHOUT PRIOR AUTHORIZATION.......28
3.3.2 ERROR HANDLING FOR KEY GENERATION AND PKC REQUEST CONSTRUCTION..23 CONSTRUCTION
..................................................................29
3.4 ENROLLMENT (SENDING REQUEST AND PKC RETRIEVAL)................23 RETRIEVAL)................30
3.4.1 ONE PROTOCOL................................................23 PROTOCOL................................................30
3.4.2 ON-LINE PROTOCOL............................................23 PROTOCOL............................................30
3.4.3 SINGLE CONNECTION WITH IMMEDIATE RESPONSE...................23 RESPONSE...................30
3.4.4 MANUAL APPROVAL OPTION......................................24 OPTION......................................30
3.4.5 ENROLLMENT METHOD 1: PEER ENROLLS TO PKI DIRECTLY...........24 DIRECTLY...........30
3.4.6 ENROLLMENT METHOD 2: IPSEC PEER ENROLLS TO PKI THROUGH ADMIN24 ADMIN31
3.4.7 ENROLLMENT METHOD 3: ADMIN ENROLLS TO THE PKI DIRECTLY......26 DIRECTLY......33
3.4.8 ENROLLMENT TYPE FIELD.......................................28 FIELD.......................................35
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3.4.9 CONFIRMATION HANDSHAKE......................................28 HANDSHAKE......................................35
3.4.10 FAILURE CASES..............................................29 CASES..............................................36
3.5 PKC PROFILE FOR PKI INTERACTION...............................30 INTERACTION...............................37
3.5.1 IDENTITY USAGE..............................................30 USAGE..............................................37
3.5.2 PATH VALIDATION.............................................31 VALIDATION.............................................38
3.5.3 KEYUSAGE....................................................31 KEYUSAGE....................................................38
3.5.4 EXTENDED KEY USAGE..........................................31 USAGE..........................................38
3.5.5 POINTER TO REVOCATION CHECKING..............................32
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3.6 PKC RENEWALS AND CHANGES......................................32 UPDATES......................................39
3.6.1 RENEW REQUEST FOR A NEW PKC (BEFORE EXPIRY).................33 EXPIRY).................41
3.6.2 CHANGE UPDATE REQUEST FOR A NEW PKC................................34 PKC................................41
3.6.3 ERROR HANDLING FOR RENEWAL AND CHANGE.......................35 CHANGE.......................42
3.7 FINDING PKCS IN REPOSITORIES..................................35 REPOSITORIES..................................42
3.7.1 ERROR HANDLING FOR REPOSITORY LOOKUPS.......................36 LOOKUPS.......................43
3.8 REVOCATION ACTION.............................................36 ACTION.............................................43
3.9 REVOCATION CHECKING AND STATUS INFORMATION....................37 INFORMATION....................44
3.9.1 ERROR HANDLING IN REVOCATION CHECKING.......................38 CHECKING.......................45
3.10 TRUST ANCHOR PKC ACQUISITION.................................45
4. SECURITY CONSIDERATIONS........................................38 CONSIDERATIONS........................................45
A REFERENCES......................................................38 REFERENCES......................................................46
A.1 NORMATIVE REFERENCES..........................................38
A.1 REFERENCES..........................................46
A.2 NON-NORMATIVE REFERENCES......................................38 REFERENCES......................................46
B. ACKNOWLEDGEMENTS...............................................38 ACKNOWLEDGEMENTS...............................................47
C. EDITOR'S ADDRESS...............................................39 EDITORĘS ADDRESS...............................................47
D. SUMMARY OF REQUIREMENTS........................................39 REQUIREMENTS........................................47
E. SYSTEM OPERATOR CHOICES........................................48
F. CHANGE HISTORY.................................................39 HISTORY.................................................48
1 Introduction
This document enumerates requirements for Public Key Certificate
(PKC) management interaction among different IPsec VPN products and
PKI products in order to better enable large scale, PKI-supported
IPsec VPN deployments. Requirements for both the IPsec and the PKI
products are discussed. The goal is to create a set of requirements
from which a profile document will be derived. The specification will
clarify the transactions necessary between the VPN System and the PKI
System that enable the deployment of easily manageable, easily
scalable VPNs. When implemented, the specification will enable
improved interoperability between IPsec and PKI products. The
requirements are carefully designed to achieve security without
compromising ease of management and deployment, even where the
deployment involves tens of thousands of IPsec users and devices.
Within IPsec VPNs, the PKI supports authentication of IPSec Peers
through digital signatures during security association establishment
using IKE. The protocol and PKI operational usages are considered in
order to define a common, single set of methods (which forces
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interoperability) between PKI Systems and VPN Systems for large-scale
deployments. The requirements address the entire lifecycle for PKI
usage within IPsec transactions: pre-authorization of PKC issuance,
enrollment process (PKC request and retrieval), PKC renewals renewals, updates
and
changes, rekeys, revocation, validation and repository lookups. They
enable a VPN Operator to:
- Authorize individual or batches of PKC issuances based on locally
defined criteria, and do so from the VPN Administration point.
- Provision PKI-based user or machine identity to IPsec Peers, on a
large scale. Provision means the IPsec Peer ends up with a valid
public and private key pair and PKC based on the IETF Public Key
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Infrastructure X.509 (PKIX) PKC profile from [CERTPROFILE]. [CERTPROFILE] and
the specific requirements of IPsec PKCs [IKECERTPROFILE]. These
are used in the IKE negotiation for tunnel setup.
- Set the corresponding gateway or client authorization policy for
remote access and site-to-site connections.
- Establish automatic renewal for PKCs, updates, or changes. rekey.
- Ensure timely revocation information is available for PKCs used
in IKE exchanges.
The desired outcome is that both IPSec and PKI vendors create
interoperable products to enable such scalable deployments, and do so
as quickly as possible. For example, a VPN Operator should be able to
use any conforming IPsec implementation of the certificate management
profile with any conforming PKI vendor's vendorĘs implementation to perform
the VPN rollout and management as described below.
The certificate management profile will also clarify and constrain
existing PKIX and IPsec standards and protocols for easier
understanding and the limiting of complexity in deployment. Some new
elements are identified that may require either a new protocol, or
changes or extensions to an existing protocol, especially in the area
of bulk authorization for PKC issuance. The document introduces the
idea of a VPN Administration function (Admin) within the VPN System.
This VPN Administration function bears great responsibility for the
task of managing pre-authorization for PKC issuance and of
distributing the results between the VPN System and the PKI System.
1.1 Scope
The solution described in this document focuses on the requirements
for the interaction between the VPN Systems and the PKI Systems. The
internals of the operation of these systems are beyond scope.
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The solution focuses on the needs of large-scale rollouts, i.e. VPNs
including hundereds hundreds or thousands of managed VPN gateways or VPN remote
access clients. The needs of small deployments are a stated non-goal,
however service providers employing the scoped solution and applying
it to many smaller deployments in aggregate may address them.
Gateway-to-gateway access and end-user remote access (to a gateway)
are both covered. End-to-end communications are not necessarily
excluded but are intentionally not a focus.
There is no intention to discuss all or other PKI issues here. The
scope is limited to requirements for easing and enabling scalable
IPsec with PKI deployments.
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The requirements strive to meet eighty percent of the market needs
for large-scale deployments. Environments will understandably exist
in which large-scale deployment tools are desired, but local security
policy stringency will not allow for the use of such commercial
tools. The solution will possibly miss the needs of the highest ten
percent of stringency and lowest ten percent of convenience
requirements. Use cases will be considered or rejected based upon
this eighty percent rule.
1.2 Non-Goals
The scenario for PKC cross-certification will not be addressed.
The specification for the communication method and transactions
between VPN Administration function and IPSec Peers is up to vendor
implementation and therefore is not expected to be included in the
certificate management profile. Such a protocol may be standardized
at a later date to enable interoperability between VPN Administration
function stations and IPsec Peers from different vendors, but is far
beyond the scope of this current effort, and will be considered
opaque by the certificate management profile.
1.3 Definitions
VPN System
The VPN System is comprised of the VPN Admininistration Administration function
(defined below), the IPsec Peers, and the communication mechanism
between the VPN Administration and the IPsec Peers. VPN System is
defined in more detail in section 2.1.
PKI System
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The PKI System, or simply PKI, is the set of functions needed to
authorize and issue PKCs and provide revocation information about
those PKCs. PKI System is defined in more detail in section 2.2.
(VPN) Operator
The Operator is the person or group of people that define security
policy and configure the VPN System to enforce that policy.
IPsec Peer (Gateway or Client)
For the purposes of this document, an IPsec Peer, or simply "Peer",
is any IPsec System that communicates IKE and IPsec to another Peer
in order to create a secure tunnel for communications. It can be
either a traditional security gateway (with two network interfaces,
one for the protected network and one for the unprotected network),
or it can be an IPsec client (with a single network interface). In
both cases, the IPsec System can pass traffic with no IPsec
protection, and can add IPsec protection to chosen traffic streams.
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(VPN) Admin
The function of the VPN System that manages and distributes policy to
Peers and who interacts with the PKI System to define policy for PKC
provisioning for the VPN connections. See Section 2.1.1 below for
more details.
End Entity
An end entity is the entity or subject that a PKC exists to
authenticate. The end entity is the one entity that will finally use
a private key associated with a PKC to sign data. In this document,
the end entity
an IPsec Peer is certainly an end entity, but the VPN Admin may also
constitute an IPsec Peer. end entity. Note that end entities may have different
PKCs for different purposes (e.g., signature vs. key exchange).
Community Realm
A community realm is the set of IPsec Peers and VPN Administration
function that operate under a common policy, and PKI authorizations.
PKC Renewal
The acquisition of a new PKC (often accompanied by a new key) with the same public key due to the
expiration of an existing PKC. Renewal occurs prior to the expiration
of the existing PKC to avoid any connection outages.
PKC Change Update
A special case of a renewal-like occurrence where a PKC needs to be
changed prior to expiration due to some change in its subject's subjectĘs
information. Examples might include change in the address, telephone
number, or name change due to marriage of the end entity.
PKC Rekey
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The routine procedure for replacement of a PKC with a new PKC with a
new public key for the same subject name. A rekey process may rely
on the existing key pair to bootstrap authentication for the new
enrollment.
Registration Authority (RA)
An optional entity in a PKI System given responsibility for
performing some of the administrative tasks necessary in the
registration of end entities, such as confirming the subject's subjectĘs
identity and verifying that the subject has possession of the private
key associated with the public key requested for a PKC.
Certificate Authority (CA)
An authority in a PKI System trusted by one or more users to create
and assign PKCs. It is important to note that the CA is responsible
for the PKCs during their whole lifetime, not just for issuing them.
Repository
An Internet-accessible server in a PKI System that stores and makes
available for retrieval PKCs and Certificate Revocation Lists (CRLs).
Root CA/Trust Anchor
A CA that is directly trusted by an end entity; that is, securely
acquiring the value of a Root CA public key requires some out-of-band
step(s). This term is not meant to imply that a Root CA is
necessarily at the top of any hierarchy, simply that the CA in
question is trusted directly.
Certificate Revocation List (CRL)
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A CRL is a time stamped list identifying revoked PKCs that is signed
by a CA and made freely available in a public repository. Peers
retrieve the CRL to verify that a PKC being presented to them as
identity in an IKE transaction has not been revoked.
CRL Distribution Point (CDP)
The CDP extension in a PKC identifies the location from which end
entities should retrieve CRLs to perform local validity checking.
Authority Info Access (AIA)
The AIA extension in a PKC indicates how to access CA information and
services for the issuer of the PKC in which the extension appears.
Information and services may include on-line validation services and
Certificate Policy (CP) data.
1.4 Requirements Terminology
Though this document is not an Internet Draft, we use the convention
that the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD
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NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in [MUSTSHOULD].
2. Architecture
This section describes the overall architecture for a PKI-supported
IPsec VPN deployment. First First, an explanation of the VPN System is
presented. Second, key points about the PKI System are stated. Third,
the architecture picture is presented. Last, the process of the
interaction between the two Systems for large-scale deployment is
described.
2.1 VPN System
The VPN System consists of the IPsec Peers and the VPN Administration
function, as depicted in Figure 1.
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+---------------------------------------------------+
| |
| +----------+ |
| | VPN | |
| +---------->| Admin |<-------+ |
| | | Function | | |
| | +----------+ | |
| v v |
| +---------+ +---------+ |
| | IPsec | | IPsec | |
| | Peer 1 |<=======================>| Peer 2 | |
| +---------+ +---------+ |
| |
| VPN System |
+---------------------------------------------------+
Figure 1: VPN System
2.1.1 IPsec Peer(s)
The Peers are two entities between which the Operator requires an
IPsec tunnel establishment. Two Peers are shown in Figure 1, but
implementations MAY support an actual number in the hundreds or
thousands. The Peers could be either gateway-to-gateway, remote-
access-host-to-gateway, or a mix of both. The Peers authenticate
themselves in the IKE negotiation using digital signatures through a
PKI System.
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2.1.2 VPN Administration Function (Admin)
This document defines the notion of a VPN Administration function,
hereafter referred to as Admin, and gives the Admin great
responsibility within the solution. The Admin is a centralized
function. It defines the VPN System policy and informs the PKI and
Peers how it wants each to enforce that policy. One main role defined
here is that Admin specifies to the PKI the contents and use
parameters of the credentials the PKI will issue, or at least
references a template or policy-set for a Peer or set of Peers (how
do we do this?). Peers. In
this way way, the Admin MAY perform many RA-like functions, for example
authorization of PKC issuance and revocation.
It is important to note that, within this document, Admin is neither
a device nor a person, rather it is a function. Every large-scale VPN
deployment will contain the Admin function. The function may MAY be
performed on a stand-alone work station, workstation, on a gateway, on an
administration software component, etc. It is also possible for the component. The Admin function to MAY also be one
in the same as the gateway or client device or software. They are
represented in the architectural diagram below as different
functions, but they need not be different physical entities. As such, Admin's
the AdminĘs architecture and the means by which it interacts with the
participating IPsec Peers will vary widely from
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implementation. However However, some basic functions of the Admin are
assumed.
- It will be define the place where Certificate Policy (CP) [FRAME] for use in the VPN is defined,
VPN, not the PKI. In VPN Systems the Operator chooses to
strengthen the VPN by using PKI; PKI is a bolt-on to the VPN
System. The PKC characteristics and contents are a function of
the local security policy the VPN serves to enforce. Therefore Therefore,
the Operator will configure policy and contents for PKCs in the
Admin, and apply those templates to groups of IPsec Peers.
- It will interact directly with the PKI System to initiate
authorization for end entity PKCs by sending the parameters and
contents for those PKCs, or by referring to a template or
policy-set on the PKI. (Such templates would likely have been
created in conjunction with the Operator.) It will receive back
from the PKI identification values and unique authorization codes identifiers and one time
tokens to be used in the PKC requests for each of the pre-authorized pre-
authorized PKCs.
- It will deliver instructions to the IPsec Peers, and the Peers
will carry out those instructions. An example of such an
instruction is an IKE policy configuration. Therefore, the
communication mechanism between the Admin and the IPsec Peers
MUST be private, authenticated and authenticated, employ integrity checks. checks, and
support non-repudiation. The contents of some such instructions
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will be defined below. However, the communication mechanism will
be handled completely within the VPN System and is out of the
scope of this document (see Scope, Section 1.1 above).
The Admin MUST be reachable by the Peers. Most implementations will
meet this requirement by ensuring the Peer can connect to the Admin
from anywhere on the network or Internet. However, communication
between the Admin and Peer may not necessarily be "on-line". It may, MAY,
in some environments, be "moving media," i.e. the configuration or
data may MAY be loaded on to a floppy disk or other media and physically
moved to the IPsec Peer. Likewise, it may MAY be entered directly on the
per
IPsec Peer via a User Interface (UI). In this case case, the Admin
function is co-located on the peer Peer device itself. This reality should SHOULD
be considered when requirements are defined, and when supporting
networks are architected.
2.2 PKI System
The PKI System, as depicted in Figure 2, may MAY be set up and operated
by the Operator (in-house), may MAY be provided by third party PKI
providers to which connectivity is available at the time of
provisioning (managed PKI service), or may MAY be integrated with the VPN
product.
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+---------------------------------------------+
| +-------------------------+ |
| v | |
| +--------------+ v |
| | Repository | +----+ +----+ |
| | Certs & CRLs |<-> | CA |<->| RA | |
| +--------------+ +----+ +----+ |
| |
+---------------------------------------------+
Figure 2: PKI System
This framework assumes that all components of the VPN will MUST obtain
PKCs from a single PKI community. An IPsec Peer MAY accept a PKC from
a Peer that is from a CA outside of the PKI community, but the auto
provision and life cycle management for such a PKC or its trust
anchor PKC fall out of scope.
The PKI System will MUST contain a mechanism for handling Admin's AdminĘs
authorization requests and PKC enrollments. These mechanisms are
referred to as the RA. The PKI System contains MUST contain a Repository used by
the for
Peers to look up each other's PKCs. otherĘs PKCs and revocation information. Last,
the PKI System contains the core function of a CA that uses a public
and private key pair and signs PKCs.
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The PKI System SHOULD be built so that lookups resolve directly and
completely at the URL indicated in a CDP, CDP or AIA. The PKI ought to SHOULD be
built such that URL contents do not contain referrals to other hosts
or URLs, as such referral lookups will increase the time to complete
the IKE negotiation, and can cause implementations to timeout.
2.3 VPN-PKI Interaction
The interaction between the VPN System and the PKI System is the key
focus of this requirements document, as shown in Figure 3. It is
therefore sensible to consider the steps necessary to set up, use and
manage PKCs for one Peer to establish an association with another
Peer. Figure 4 (below) illustrates the information flow associated
with the initial PKC generation steps relative to the architecture
diagram. Figure 5 (below) illustrates the information flow associated
with the PKC renewal steps relative to the architecture diagram.
Figure 6 (below) illustrates the information flow associated with the
PKC revocation steps relative to the architecture diagram. For
simplicity
simplicity, only the steps associated with IPsec Peer 1 are shown.
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+---------------------------------------------+
| PKI System |
| |
| +--------------+ |
| | Repository | +----+ +----+ |
| | Certs & CRLs | | CA | | RA | |
| +--------------+ +----+ +----+ |
| |
+---------------------------------------------+
^ ^ ^
| | |
|[E] |[A] |[E]
|[M] |[E] |[M]
|[R] |[R] |[R]
| | |
+--------+------------------+----------------+------+
| | v | |
| | +----------+ | |
| | [G] | VPN | [G] | |
| | +---------->| Admin |<-------+ | |
| | | | Function | | | |
| | | +----------+ | | |
| v v v v |
| +---------+ +---------+ |
| | IPsec | [I] | IPsec | |
| | Peer 1 |<=======================>| Peer 2 | |
| +---------+ +---------+ |
| |
| VPN System |
+---------------------------------------------------+
[A] = Authorization of PKC issuance and revocation
[G] = Generation of public and private key pair, PKC request
[E] = Enrollment (request and retrieval)
[I] = IKE and IPsec communication
[M] = Maintenance: validation, revocation, and repository lookups
[R] = Renewal (and changes) (also update and rekey)
Figure 3. Architectural Framework for VPN-PKI Interaction
2.3.1 New PKC
The steps of the VPN-PKI interaction are summarized here for
generating a new PKC. The letters refer to Figure 3. The numbers
refer to Figure 4. The detailed requirements are described below in
Section 3. Note that there are a number of architectul architectural options
available and that the most common architecture is depecited depicted in Figure
4; IPsec Peer generated Keys and IPsec Peer generated PKC Request.
Other architectural options are discussed in Section 3.
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+--------------+ 7 +-----------------------+
| Repository |<----| Certificate Authority |
+--------------+ +-----------------------+
^ ^ ^
| 8 4, 6 | | 1
| | 2 |
| | v
| | +-------+
| | +- | Admin |
| | | +-------+
| | |
| 9 5 | | 3
v v v
+--------------------+ +--------+
| IPsec | 10 | IPsec |
| Peer 1 |<========>| Peer 2 |
+--------------------+ +--------+
Figure 4. VPN-PKI Interaction Steps:
IPsec Peer Generates Keys and PKC Request,
Enrolls Directly with PKI
1) Authorization [A]. Admin sends a list of IDs and PKC contents for
the PKI System to authorize enrollment. The PKI returns a list of
unique authorization identifiers and one-time tokens to be used for
the enrollment of each PKC. Other PKC usage policy is also set at
this time, for example parameters for renewals renewals, updates or changes, rekeys,
key lengths, etc. The amount of information that the Admin
communicates to the PKI about how it wants the PKCs built could be
very small, perhaps just a reference to a template already existing
in the PKI System. Likewise Likewise, it could be very large, with several
fields being specified along with their contents. [EDITOR'S NOTE: We need some work on this line
of thought.]
2) Authorization Response [A]. The PKI System acknowledges the
authorizations provided in (1). Response may indicate success or
failure for any particular authorization.
3) Generate Keys and PKC Request [G]. The Admin communicates with the
Peer to give the Peer information so that it can generate a public
and private key pair and PKC request and send the request directly to
the PKI.
4) Enrollment [E]. The IPsec Peer requests a PKC from the PKI,
providing the generated public key. The IPsec Peer generates the key
pair and PKC request.
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5) Enrollment Response [E]. The PKI responds to the enrollment
request sent in (4), providing either the new PKC that was generated
or a suitable error indication.
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6) Enrollment Confirmation. Peer must positively acknowledge acknowledges receipt of
new PKC.
7) PKC Posting. The newly-generated PKC for IPsec Peer 1 is posted to
the repository.
8) Maintenance [M]. The IPsec Peer accesses the PKI to support look-
up of PKCs for other IPsec Peers, certification path validation, and
revocation checking. This step consists of sending requests for
specific PKCs or CRLs, or requests for the PKI System to perform
validation checks.
9) Maintenance Response [M]. The PKI responds to the maintenance
request sent in (7), providing either the requested PKC or CRL,
indicating the validity status of a PKC, or indicating an error
condition.
10) IKE/IPsec Communication [I]. The Peers communicate authenticated
by the PKCs they received from the PKI.
2.3.2 Renewal PKC
The steps of the VPN-PKI interaction are summarized here for rewal renewal
of PKCs. The letters refer to Figure 3. The numbers refer to Figure
5. The detailed requirements are described below in Section 3. Note
that there are a number of architectul architectural options available and that
the most common architecture is depecited depicted in Figure 5; IPsec Peer
generated Keys and IPsec Peer generated PKC Request. Other
architectural options are discussed in Section 3.
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+--------------+ 5 +-----------------------+
| Repository |<----| Certificate Authority |
+--------------+ +-----------------------+
^ ^
| 6 | 2, 4
| |
| |
| | +-------+
| | +- | Admin |
| | | +-------+
| | |
| 7 3 | | 1
v v v
+--------------------+ +--------+
| IPsec | 8 | IPsec |
| Peer 1 |<========>| Peer 2 |
+--------------------+ +--------+
Figure 5. VPN-PKI Interaction Steps: Renewal by IPsec Peer 1
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1) Rekey or Renewal Initiation. The Admin communicates renewal renewal,
update or
change rekey instructions to the Peers. Renewal may also be signalled
signaled to the PKI (not shown), particularly if authorization
changes are necessary. Initiation of this process by the Admin
enables IPsec Peers to automatically generate renewal renewal, update or change
rekey requests as needed with minimal user burden, and for those
requests to be immediately granted by the PKI System. Local security
policy will determine whether Admin allows EE renwal renewal without
authorization from Admin. Additionally, local policy will determine
whether EEs must renew or be reissued PKCs.
[EDITOR'S NOTE: Should we call out the decision operator needs to
make as we go?]
2) Renewals and Changes Updates [R]. The IPsec Peer requests renewal or
change
update of an existing PKC. Rekey MAY also occur depending upon policy
constraints. The renewal or change request will either be provided in
(10) above, or will be generated by the IPsec Peer.
3) Renewal/Change Renewal/Update Response [R]. The PKI responds to the renewal or
change
update request sent in (11), providing either the new PKC that was
generated or a suitable error indication.
4) Enrollment Confirmation. Peer must positively acknowledge acknowledges receipt of
new PKC.
5) PKC Posting. The newly-generated PKC for IPsec Peer 1 is posted to
the repository.
6) Maintenance [M]. The IPsec Peer accesses the PKI to support look-
up of PKCs for other IPsec Peers, certification path validation, and
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revocation checking. This step consists of sending requests for
specific PKCs or CRLs, or requests for the PKI System to perform
validation checks.
7) Maintenance Response [M]. The PKI responds to the maintenance
request sent in (7), providing either the requested PKC or CRL,
indicating the validity status of a PKC, or indicating an error
condition.
8) IKE/IPsec Communication [I]. The Peers communicate authenticated
by the PKCs they received from the PKI.
2.3.3 Revocation
The steps of the VPN-PKI interaction are summarized here for
generating a new PKC. The letters refer to Figure 3. The numbers
refer to Figure 6. The detailed requirements are described below in
Section 3.
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+--------------+ 2 +-----------------------+
| Repository |<----| Certificate Authority |
+--------------+ +-----------------------+
^ ^ ^
| 3 | 1 | 1, 1'' 1ĘĘ
| | |
| | |
| | 1' 1Ę +-------+
| | +> | Admin |
| | | +-------+
| | |
| 4 | |
v | |
+--------------------+
| IPsec |
| Peer 1 |
+--------------------+
Figure 6. VPN-PKI Interaction Steps: Revocation
1) Revocation. The IPsec Peer or Admin requests revocation of IPsec
Peer 1's 1Ęs PKC directly from the PKI.
1')
1Ę) Revocation. The IPsec Peer requests revocation of their PKC
through admin.
1'')
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1ĘĘ) Revocation. The Admin forwards IPsec Peer 1's 1Ęs PKC revocation
request to PKI.
2) CRL Posting. The newly-generated CRL revoking IPsec Peer 1's 1Ęs PKC
is posted to the repository.
3) Maintenance [M]. The IPsec Peer accesses the PKI to support look-
up of CRL.
4) Maintenance Response [M]. The PKI responds to the maintenance
request sent in (3), providing either the requested CRL, indicating
the validity status of a PKC, or indicating an error condition.
3 Requirements
3.1 General Requirements
3.1.1 One Protocol
This
The target profile will profile, to be based on this requirements document, MUST
call for ONE PROTOCOL or ONE USE PROFILE for each main element of the
requirements. It is a specific goal to avoid multiple competing
protocols or profiles to solve the same requirement whenever possible
so as to reduce complexity and improve interoperability.
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Meeting some of the requirements may MAY necessitate the creation of a
new protocol or new extension for an existing protocol; however, the
late is much preferred.
Conforming implementations MUST implement the ONE PROTOCOL or ONE USE
PROFILE that is specified for a given requirement.
3.1.2 Secure Transactions
The target profile will MUST specify the transactions for certificate
management between VPN and PKI Systems and their components, as
needed to ease large scale
large-scale VPN deployment and management. Specifically, Admin and
PKI will MUST transmit between themselves policy details, identities, and
keys. As such, the method of communication for these transactions
MUST be secured in a manner that ensures privacy, authentication,
message data integrity and non-repudiation. This communication method will
MUST require that mutual trust be established between the PKI and the
Admin.
3.1.3 PKI Availability
Central availability is required REQUIRED initially for authorization
transactions between the PKI and Admin. Further availability will MAY be
required in most cases, but is a decision point for the Operator.
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Most requirements and scenarios below assume on-line availability of
the PKI and Admin for the life of the VPN.
Off-line interaction between the VPN and PKI Systems (i.e., where
physical media is used as the transport method) is beyond the scope
of this document.
3.1.4 End-User Transparency
PKI interactions are to be transparent to the user. Users need not SHOULD NOT
even be aware that PKI is in use. First time connections need SHOULD
consist of no more than a prompt for some identification and pass
phrase, and a status bar notifying the user that setup is in
progress.
3.1.5 Error Handling
The PKC transaction protocol for the PKI and VPN System transactions
MUST specify error handling for each transaction. Thorough error
condition descriptions and handling instructions will greatly aid
interoperability efforts between the PKI and IPsec products.
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3.2 Authorization Transactions
This section refers to the [A] elements labeled in Figure 3.
3.2.1 Bulk Authorization
Bulk authoriztion authorization MUST be supported by the target profile. Bulk
authorization occurs when the Admin requests of the PKI that
authorization be established for several different subjects with
almost the same contents. A minimum of one value (more is also
acceptable) MUST differ per subject. Because the authorization may
occur before any keys have been generated, the only way to determine
one authorization from another for the purpose of issuing unique
authorization identifiers is by having at least one value differ.
The authorization MAY occur prior to the event of a PKC enrollment
request (in which case it is a "pre-authorization"), or within the
same connection.
3.2.2 Protocol Preferences for Authorization
A single connection per multiple transactions. It is preferred that
the
The setup for all subjects in an authorization batch occurs SHOULD occur in
one single connection to the RA/CA, with the number of subjects being
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one or greater. Implementations should SHOULD be able to handle one thousand
at a time.
ONE protocol must MUST be specified for these Admin to RA/CA interaction.
The PKI responds to the Admin station with Authorization identifiers
(maybe serial numbers or such) and a corresponding pre-authorization authorization key
(not to be confused with the public and private key pair) for each
identifier.
[EDITOR'S NOTE: Do we need to further describe the reason for per-
authoirzation key here?]
It is preferred that the
The transport used to carry the pre-
authorization pre-authorization SHOULD be reliable
(TCP).
The protocol should SHOULD be as lightweight as possible.
A method for securing the communication between the Admin and the PKI
MUST be defined, including privacy, authorization, authentication,
integrity, and integrity. non-repudiation. PKCs and for authorization of the Admin may
MAY need to be initialized by physical rather than on-line means.
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3.2.3 Admin Authorization Requests to PKI
3.2.3.1 Specifying Fields within the PKC
The VPN may Admin MAY send the PKI System the set of PKC contents that make
up a PKC template that it wants the PKI to use. In other words, it
tells the PKI System, "if you see a PKC request that looks like this,
from this person, process it and issue the PKC." Likewise, such a
template
may MAY have already been defined on the PKI System, and the
Admin may simply reference it.
In the former case, the elements that the Admin MAY send to the PKI
to authorize the eventual creation of PKCs include:
- DN fields with CN, C, O, OU naming attributes
- Any number of locally defined CNs with their contents. contents
- Validation Validity Period of the PKC
- Renewal parameters (i.e., N% of renewal not permitted, N% of validity
period, and PKC overlap
duration in N [EDITOR'S NOTE: Should consider other factors.
Measurement? Minutes? Hours? Percentage?], or just let it
expire) the UTC time after which renewal is permitted)
- Key type
- Key length
- Extension fields:
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- KeyUsage set digitalSignature, nonRepudiation, or both bits.
- SubjAltName fields: FQDN, User_FDQN, IPv4_ADDR, and IPv6_ADDR.
- Require a CDP be filled in by the PKI in issuance. The
specification should profile,
based on these requirements, SHOULD define who will handle the
CDP contents.
3.2.3.2 Authorizations for Renewal and Change Update
When the Admin sends its authorization request information it MUST
also send information to the PKI about the local policy regarding PKC
renewal and changes. PKC update. These are:
- Admin MUST specify if automatic renewals are allowed, that is,
the Admin is presently authorizing the PKI to process a future
renewal for the specified end entity PKC.
- Admin MUST specify if any changes are PKC update is allowed, that is, the Admin
is presently authorizing the PKI to accept a future request for
a new PKC creation with some element of the Subject or
SubjectAltName changed.
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If a PKC renewal is authorized, the Admin MUST further specify:
- Whether or not a new key must be used for the new PKC.
- Who can renew, i.e. that is, can only the admin send a renewal request
or can the end entity Peer send a request directly to the PKI,
or either.
- Specify at how long before the PKC expiration date the PKI will
accept and process a renewal.
- Length renewal (i.e., N% of validity period, or
the UTC time (if ever) after PKI receives end entity Peer
confirmation (see 3.4.8 and 3.6.1 below) that the old PKC which renewal is
revoked, and removed from repository. permitted).
If change request PKC update is authorized, the Admin MUST further specify:
- The aspects of non-key-related fields in the Subject and SubjectAltName that are changeable changeable.
- The entity that can send the change PKC Update request, i.e. that is, only
the Admin, only the end entity, or either.
- Length Specify at how long before the PKC expiration date the PKI will
accept and process an update (i.e., N% of validity period, or
the UTC time (if ever) after PKI receives end entity Peer
confirmation (see 3.6.1 below) that which update is permitted).
A new authorization by the old PKC Admin is revoked, and
removed from repository. REQUIRED for PKC rekey. No
parameters of prior authorizations need be considered.
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3.2.3.3 Other Authorization Elements
CDP MUST be flagged as required in the authorization request. The
method MUST also be specified; HTTP is the MUST method, LDAP is MAY.
There will MUST be an option to specify a Validation Period for the
authorization ID and its authorization key. If such a Validation
Period is set, any PKC requests using this authorization id and key
that arrive at the PKI outside of the validation period MUST be
dropped and the event logged.
Ability
The Admin MUST have the ability to communicate the Community Realm
for the PKC to the PKI. Community Realm is an important component in
provisioning that allows the Admin to specify for the Peer various
elements of the PKC's PKCĘs contents that the PKI will fill in, and are not
defined by the Admin. It may be used to specify various local policy
definitions. It also will be used to label different groups to have
different CRLs (for example small CRLs with only gateways in the
listing for use by Remote Access Peers, or large CRLs with all Remote
Access Peers and gateways to be used by the Gateways). There will be
a need for an import and export for easily synchronizing the
Community Realm lists between the Admin and PKI System.
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The Protocol should SHOULD consider what happens when Admin requested
information conflicts with PKI settings such that the Admin request
cannot be issued as requested. (Ex: requested (e.g., Admin requests Validation Period
= 3 weeks and CA is configured to only allow Validation Periods = 1
week.)
week). Proper conflict handling MUST be specified.
3.2.4 Cancel Capability
Either the Admin or the Peer can send a cancel authorization message
to PKI. [EDITOR'S NOTE:
Should the Peer be able to send a cancel message as well?] Admin The canceling entity MUST provide the authorization ID and code
one-time-token in order to cancel the Authorization. At that point,
the authorization will be erased from the PKI, and a log entry of the
event written.
After the cancellation has been verified with the Admin (a Cancel, Cancel ACK, ACK
type of a process is required REQUIRED to cover a lost connections scenario),
the PKI will accept another a new Authorization request with the exact same
contents as the canceled one. one, except that the identifier MUST be new.
The PKI MUST NOT accept a second process duplicate authorization request for the same identity [EDITOR'S NOTE: How do we
decide what defines "identity"?] requests.
Note that if one the PKI has already exists. issued a PKC associated with an
authorization, then cancellation of the authorization is not
possible and SHOULD be refused by the PKI. Once a PKC has been
issued it MUST be revoked in accordance with clause 3.8.
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3.2.5 PKI response to Admin
If the authorization is acceptable, the PKI will respond to the Admin
with a unique identifier per subject authorization required requested and a
one-time-authorization
one-time authorization key per authorization ID. Strongly recommend
the one-time-authorization The one-time
authorization key SHOULD be unique per authorization ID. The more
randomness that can be achieved in the relationship between an
identifier and its key the better. The key MUST be in ASCII format to
avoid incompatibilities that may occur due to international
characters.
All
The PKI MAY alter parameters of the authorization request submitted
by the Admin. In that event, the PKI MUST return all the contents of
the PKC that it intends to issue will be returned authorization template (as modified) to the Admin. Admin with the
confirmation of authorization success. This will allow the Admin to
perform an "operational test" to verify that the issued PKCs will
meet its requirements.
For any request, the PKI cannot change any of the specified values in
request within its response. We need to prevent a change in PKC
contents that may occur due to a change in PKI configuration right in
the middle of a batch pre-authorization request.
[EDITOR'S NOTE: what if If the Admin sends a parameter determines that the PKI
cannot fulfil, i.e. the parameter contradicts PKI policy? Would need
to return an error code and description and refuse to authorize modified
parameters are unacceptable, then the
enrollment.] authorization should be
cancelled in accordance with clause 3.2.4.
After receiving a bulk authorization request from the Admin, the PKI
must
MUST be able to reply YES to those individual PKC authorizations that
it can satisfy and NO or FAILED for those requests that cannot be
satisfied, along with sufficient reason or error codes.
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A method is needed required to identify if there is a change in PKI setting
between the time the authorization is granted and PKC request occurs,
and what to do about the discrepancy.
3.2.6 Error Handling for Authorization Transactions
Thorough error condition descriptions and handling instructions are
required MUST
be provided for each transaction in the authorization process.
Providing such error codes will greatly aid interoperability efforts
between the PKI and IPsec products.
3.3 Key Generation and PKC Request Construction
Once the PKI System has responded with authorization identifiers and
keys, and this information is received at the Admin, the next step is
to generate public and private key pairs and to construct PKC
requests using those key pairs. The key generations MAY occur at one
of two three places, depending on local requirements: at the IPsec Peer Peer,
at the Admin, or at the Admin. PKI. The PKC constructions MAY occur at
either the IPsec Peer or a combination of the Peer and the Admin.
[EDITOR's NOTE: Should we have different arrow diagrams
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option? Option 1 is already depicted in Figure 4. Should we show
the differences amongst the other three?]
3.3.1 IPsec an December 2004
IPsec Certificate Management Profile
3.3.1 Key Generation Scenarios
3.3.1.1 IPsec Peer Generates Key Pair and Constructs Request
This case will be used most often in the field. This is the most
secure method for keying; keying, as the keys are generated on the end entity
and never leave the end entity.
The Admin will send the authorization identifier and authorization
key to the end entity, the IPsec Peer. The Admin will also send any
other parameters needed by the Peer to generate the PKC request,
including key type and size. Recall that the mechanism for how this
information is communicated from the Admin to the Peer is opaque.
Receiving the command and the necessary information from the Admin,
the Peer will proceed to generate the key pair and construct the PKC
request.
3.3.2 Figure 7 illustrates this scenario.
+---------------------------+
| Certificate Authority |
+---------------------------+
^ | ^ |
| | | |
| | 5 1 | | 2
| | | |
| | | v
| | +-----------+
| | | Admin |
4 | | +-----------+
| | |
| | | 3
| | |
| v v
+--------------------+
| IPsec |
| Peer |
+--------------------+
Figure 7. Key Generation and Enrollment
Request Construction by IPsec Peer
1) Authorization
2) Authorization Response
3) PKC Request Information
- PKC Request Unique Identifier
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- One-time Authorization Key
4) Enrollment Request
- Completed PKC field assertions
- PKC Request Unique Identifier
- One-time Authorization Key
- Public Key
- Proof of Possession of Associated Private Key
5) Enrollment Response
- Distribute PKC
3.3.1.2 IPsec Peer Generates Key Pair, Admin Constructs Request
In this case, the Admin sends a command to the Peer to generate the
key pair. The Admin then constructs the PKC request on behalf of the
Peer, except for the signing. It sends the construction to the Peer
for signing, and the Peer returns the signed request construction
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back to the Admin. The Admin then proceeds to enroll on behalf of the
client. Figure 8 illustrates this scenario.
The advantage of this solution is that the private key never leaves
the IPsec Peer, but limits the amount the Peer must know and do
regarding PKC generation.
3.3.3
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+---------------------------+
| Certificate Authority |
+---------------------------+
^ | ^ |
| | | |
| | 5 1 | | 2
| | | |
| | | v
| | +-----------+
| | | Admin Generates |
4 | | +-----------+
| | |
| | | 3
| | |
| v v
+--------------------+
| IPsec |
| Peer |
+--------------------+
Figure 8. Key Pair and Constructs Generation By IPsec Peer with
Admin Construction of Enrollment Request
The use case exists for deployments where end entities cannot
generate their own key pairs.
1) Authorization
2) Authorization Response
3) PKC Request Template
- Pre-authorized PKC fields
- PKC Request Unique Identifier
- One-time Authorization Key
4) Enrollment Request
- PKC Request Template
- Public Key
- Proof of Possession of Associated Private Key
5) Enrollment Response
- Distribute PKC
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3.3.1.3 Admin Generates Key Pair and Constructs Request
The use case exists for deployments where end entities cannot
generate their own key pairs. Figure 9 illustrates the steps
entailed. Some examples are for PDAs and handsets where to generate
an RSA key would be operationally impossible due to processing and
battery constraints. Another case covers key recovery requirements,
where the same PKCs are used for other functions in addition to
IPsec, and key recovery is required (e.g. local data encryption),
therefore key escrow is needed off the end entity station. If key
escrow is performed then the exact requirements and procedures for it
are beyond the scope of this document.
The Admin will generate the key pair, construct the PKC request, and
enroll on behalf of the Peer. Once the PKC has been retrieved, the
keys and PKC will be sent to the Peer using a secure method. The
nature of this secure method is beyond the scope of this document.
Performing a separate pre-authorization step is still of value even
though the Admin is the also performing the key generation. The
Community Realm, Subject fields, SubjectAlt fields and more are part
of the request, and must be communicated in some way from the Admin
to the PKI. Instead of creating a new mechanism, we simply use the
pre-authorize schema again. This also allows for the feature of role-
based administration, where Operator1 Operator 1 is the only one allowed to
have the Admin function pre-authorize PKCs, but Operator2 Operator 2 is the one
doing batch enrollments and VPN device configurations.
3.3.4
+---------------------------+
| Certificate Authority |
+---------------------------+
^ | ^ |
| | | |
| | 5 1 | | 2
| | | |
| | | v
| | +-----------+
| | | Admin |
4 | | +-----------+
| | |
| | | 3
| | |
| v v
+--------------------+
| IPsec |
| Peer |
+--------------------+
Figure 9. Key and Enrollment Request
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Generation By VPN Admin
1) Authorization
2) Authorization Response
3) PKC Request Template
- Pre-authorized PKC fields
- PKC Request Unique Identifier
- One-time Authorization Key
- Public Key
- Private Key
- Proof of Possession of Associated Private Key
4) Enrollment Request
- PKC Request Template
5) Enrollment Response
- Distributed PKC
3.3.1.4 PKI Generates Key Pair and Passes to Peer via Admin
TBD - [EDITOR'S NOTE: There is another
This use case here: allows the PKI generates to generate the key pair AND and the PKC and
after which it simply hands it the PKC down to the Admin for
installation into the Peer. This is, in all likelihood, the easiest
way to deploy Certs, PKCs, though sacrafices a bit in security. Do we just
specify PKCS12 and try to create it sacrifices some requirements for how security since both the Admin
will say, "I need a cert for NNNNN,"
CA and how PKI will respond with the PKCS12?]
3.3.5 Trust Anchor PKC Acquisition Admin have access to the private key. However, in cases
where key escrow is required, this may be acceptable. Figure 10
illustrates this scenario. The root PKC MUST arrive on Admin effectively acts as a proxy for
the Peer via one of two methods: in the PKC enrollment process.
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(a) Peer can get the root PKC via its secure communication with
Admin. This requires the Peer to know less about interaction with the
PKI.
(b)
+---------------------------+
| Certificate Authority |
+---------------------------+
^ |
| |
1 | | 2
| |
| v
+-----------+
| Admin can command |
+-----------+
|
| 3
|
v
+--------------------+
| IPsec |
| Peer to retrieve the root cert directly from
the PKI. How retrieval of the root cert takes place is beyond scope,
but is assumed to occur via an unauthenticated but confidential
enrollment protocol.
3.3.6 Error Handling for |
+--------------------+
Figure 10. Key Generation and Request Construction
Thorough error condition descriptions and handling instructions are
required for each transaction in the authorization process. Providing
such error codes will greatly aid interoperability efforts between
the By PKI and IPsec products.
3.4 with
Proxy Enrollment via VPN Admin
1) Authorization & PKC Enrollment (Sending Request and
- PKC Retrieval)
Regardless field assertions
- Public Key
- Proof of where the keys were generated and the Possession of Associated Private Key
2) Enrollment Response
- Distributed PKC request
constructed, an enrollment process will need to occur to request a
- Associated private key
3) Peer Provisioning
- Distributed PKC creation from
- Associated private key
3.3.1.5 Peer Generates Key Pair Without Prior Authorization
In many situations, a use case in which the PKI and to retrieve that PKC.
The protocol MUST be exactly VPN Peer makes sole
contact with the PKI can simplify the enrollment process. This
would allow individuals or small organizations to obtain PKCs for
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VPNs without a significant administrative footprint. Figure 11
illustrates this scenario.
This scenario uses essentially the same enrollment steps as prior
scenarios, but has the additional facet that some proof of identity
mechanism, proof of payment, or other mechanisms may be required by
the PKI as a precondition of PKC issuance.
+---------------------------+
| Certificate Authority |
+---------------------------+
^ |
| |
1 | | 2
| |
| v
+--------------------+
| IPsec |
| Peer |
+--------------------+
Figure 11. Key Generation By IPsec Peer
Without Prior Authorization
1) Enrollment Request
- PKC field assertions
- Proof of Identity, Payment, etc.
- Public Key
- Proof of Possession of Associated Private Key
2) Enrollment Response
- Distributed PKC
3.3.2 Error Handling for Key Generation and PKC Request Construction
Thorough error condition descriptions and handling instructions MUST
be provided for each transaction in the key generation and PKC
request construction process. Providing such error codes will greatly
aid interoperability efforts between the PKI and IPsec products.
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3.4 Enrollment (Sending Request and PKC Retrieval)
Regardless of where the keys were generated and the PKC request
constructed, an enrollment process will need to occur to request a
PKC creation from the PKI and to retrieve that PKC.
The protocol MUST be exactly the same regardless of whether the
enrollment occurs from the Peer to the PKI or from the Admin to the
PKI (as seen below in sections 3.4.5 through 3.4.7).
3.4.1 One protocol
One protocol MUST be specified for both request enrollment requests and retrieval.
responses.
3.4.2 On-line protocol
The protocol MUST supports automated enrollment that occurs over the Internet
and without the need for manual intervention.
3.4.3 Single Connection with Immediate Response
Request
Enrollment requests and retrieval responses MUST be able to occur in one on-line on-
line connection between the end entity Admin on behalf of the Peer or the Peer
itself and the PKI (RA/CA).
The end entity sends the request, attaching the Authorization
identifier and key.
The RA/CA receives the request and uses the Authorization identifier
and key to match it to the proper pre-authorization entry.
Since the contents of the PKC match, and the Authorization identifier
and key are correct, the PKC is generated immediately, with no need
for manual intervention or review on the PKI System before issuance.
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The PKI makes the PKC available immediately for retrieval, or
possibly sends the PKC to the end entity as a response in the request
or retrieval exchange.
3.4.4 Manual Approval Option
3.4.4 Manual Approval Option
The optional capability to queue and manually approve PKC requests
MUST exist within the protocol for those organizations that will not
permit automation of credential issuing as described above. Likewise,
polling to determine if request has been satisfied and to try to
retrieve the PKC MUST exist within the protocol for those
organizations that will not permit automation of credential issuing
as described above.
End-entities
The Admin and the PKI must disclose and agree upon which mode they
will support (automated approval or manual approval) within the
protocol.
3.4.5 Enrollment Method 1: Peer Enrolls to PKI Directly
The enrollment MAY occur in one of three fashions, and valid use
cases exist for all three. First, and most straight forward,
In this case, the Admin can instruct the IPsec Peer to execute an
enrollment, telling it where to enroll, and providing any necessary
parameters.
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In this case case, the IPsec Peer only talks to communicates with the PKI after
being commanded to do so by the Admin. Note that this enrollment
mode is depicted in Figure 4.
3.4.6 Enrollment Method 2: IPsec Peer Enrolls to PKI through Admin
In this case, the IPsec Peer has generated the key pair and the PKC
request, but does not enroll directly to the PKI System. Instead, it
automatically sends its request to the Admin, and the Admin
automatically performs the enrollment to the PKI System. The PKI
System does not care where the enrollment comes from, as long as it
is a valid enrollment. Once the Admin retrieves the PKC, it then
automatically forwards it to the IPsec Peer, and the Peer can begin
using it in security policy.
The communication of the request, retrieval, renewal, update or change,
rekey, can go directly from the end entity to the PKI, or be passed
from end entity through the Admin to the PKI. In the latter case, the
end entity need not know how to do all the direct communication with
the PKI; the function becomes focused in the Admin station. In either
case, the format of messages should be identical regardless of who is
sending the request.
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Most IPsec Systems have enough CPU power to generate a public and
private key pair of sufficient strength for secure IPsec. In this
case, the end entity needs to prove to the Admin that they have such
a key pair; this is normally done by the Admin sending the end entity
a nonce, which the end entity signs and returns to the Admin along
with the end entity's entityĘs public key.
The steps of the VPN-PKI interaction are summarized here for the
IPSec Peer enrolling through the Admin. The letters refer to Figure
3. The numbers refer to Figure 7. 12.
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+--------------+ 10 +-----------------------+
| Repository |<----| Certificate Authority |
+--------------+ +-----------------------+
^ ^
| 11 | 1, 5, 9
| 2, 6 |
| v
| +-------+
| +> | Admin |
| 4, 8 | +-------+
| |
| 12 | 3,7
v v
+--------------------+ +--------+
| IPsec | 13 | IPsec |
| Peer 1 |<========>| Peer 2 |
+--------------------+ +--------+
Figure 7. 12. VPN-PKI Interaction Steps:
IPsec Peer Generates Keys and PKC Request,
Enrolls Through Admin
1) Authorization [A]. Admin sends a list of IDs and PKC contents for
the PKI System to authorize enrollment. The PKI returns a list of
unique identifiers and one-time tokens to be used for the enrollment
of each PKC. Other PKC usage policy is also set at this time, for
example parameters for renewals renewals, updates or changes, rekey, key lengths, etc.
The amount of information that the Admin communicates to the PKI
about how it wants the PKCs built could be very small, perhaps just a
reference to a template already existing in the PKI System. Likewise
it could be very large, with several fields being specified along
with their contents. [EDITOR'S NOTE: We need some work on this line
of thought.]
2) Authorization Response [A]. The PKI System acknowledges the
authorizations provided in (1). Response may indicate success or
failure for any particular authorization.
3) Generate Keys and PKC Request [G]. The Admin communicates with the
Peer to give it information so that it can generate a public and
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private key pair and PKC request and send the request back to the
Admin.
4) Enrollment [E]. The IPsec Peer requests a PKC from the Admin,
providing the generated public key.
5) Enrollment [E]. The Admin forwards the enrollment request to the
PKI.
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6) Enrollment Response [E]. The PKI responds to the enrollment
request sent in (5), providing either the new PKC that was generated
or a suitable error indication.
7) Enrollment Response [E]. The Admin forwards the enrollment
response back to the IPsec Peer.
8) Enrollment Confirmation. Peer must positively acknowledge receipt
of new PKC back to the Admin.
9) Enrollment Confirmation. Admin forwards enrollment confirmation
back to the PKI.
10) PKC Posting. The newly-generated PKC for IPsec Peer 1 is posted
to the repository.
11) Maintenance [M]. The IPsec Peer accesses the PKI to support look-
up of PKCs for other IPsec Peers, certification path validation, and
revocation checking. This step consists of sending requests for
specific PKCs or CRLs, or requests for the PKI System to perform
validation checks.[EDITOR's NOTE ” is the Admin going to the
repository lookup for the IPsec Peer?] checks.
12) Maintenance Response [M]. The PKI responds to the maintenance
request sent in (11), providing either the requested PKC or CRL,
indicating the validity status of a PKC, or indicating an error
condition.
13) IKE/IPsec Communication [I]. The Peers communicate authenticated
by the PKCs they received from the PKI.
3.4.7 Enrollment Method 3: Admin Enrolls to the PKI Directly
In this instance, the Admin is performing a function similar to that
of a Registration Authority (RA), as defined in [CERTPROFILE]. The
Admin will have likely generated the key pair and constructed the
request on behalf of the IPsec Peer. It proceeds to handle the entire
enrollment directly with the PKI, and returns to the IPsec Peer the
final product of a key pair and PKC. Again, the mechanism for the
Peer to Admin communication is opaque.
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The steps of the VPN-PKI interaction are summarized here for the
Admin enrolling directly to the PKI. The letters refer to Figure 3.
The numbers refer to Figure 8. 13.
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+--------------+ 7 +-----------------------+
| Repository |<----| Certificate Authority |
+--------------+ +-----------------------+
^ ^
| 8 | 1, 4, 6
| 2, 5 |
| v
| 9 +-------+
+--------------+> | Admin | 3
| +-------+
|
10 |
v
+--------------------+ +--------+
| IPsec | 11 | IPsec |
| Peer 1 |<========>| Peer 2 |
+--------------------+ +--------+
Figure 8. 13. VPN-PKI Interaction Steps:
Admin Generates Keys and PKC Request,
Admin Performs Enrollment
1) Authorization [A]. Admin sends a list of IDs and PKC contents for
the PKI System to authorize enrollment. The PKI returns a list of
unique identifiers and one-time tokens to be used for the enrollment
of each PKC. Other PKC usage policy is also set at this time, for
example parameters for renewals renewals, updates or changes, rekey, key lengths, etc.
The amount of information that the Admin communicates to the PKI
about how it wants the PKCs built could be very small, perhaps just a
reference to a template already existing in the PKI System. Likewise
it could be very large, with several fields being specified along
with their contents. [EDITOR'S NOTE: We need some work on this line
of thought.]
2) Authorization Response [A]. The PKI System acknowledges the
authorizations provided in (1). Response may indicate success or
failure for any particular authorization.
3) Generate Keys and PKC Request [G]. The Admin generates the public
private key pair and PKC request.
4) Enrollment [E]. The Admin requests a PKC from the PKI providing
the generated public key.
5) Enrollment Response [E]. The PKI responds to the enrollment
request sent in (4), providing either the new PKC that was generated
or a suitable error indication.
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6) Enrollment Confirmation. Admin must positively acknowledge receipt
of new PKC back to the PKI.
7) PKC Posting. The newly-generated PKC for IPsec Peer 1 is posted to
the repository.
8) Maintenance [M]. The Admin accesses the PKI to retrieve the new
PKC. [EDITOR's NOTE ” is the Admin going to the repository lookup
for the IPsec Peer?]
9) Maintenance Response [M]. The PKI responds to the maintenance
request sent in (8), providing the requested PKC, or indicating an
error condition.
10) Admin sends newly generated PKC and private key to IPsec Peer.
11) IKE/IPsec Communication [I]. The Peers communicate authenticated
by the PKCs they received from the PKI.
3.4.8 Enrollment Type Field
A field must MUST exist in the enrollment request to specify the TYPE of
request being made. Request types include new request, renew request,
update request, and
change rekey request (renewals (renewals, updates and changes rekeys are
discussed in detail in section 3.6). The type field is required for
monitoring, logging and auditing purposes. They will help the
Operator to know exactly what type of request was made so that
suspicious activities, even if the request is denied, can be
identified.
3.4.9 Confirmation Handshake
Any time a new PKC is issued by the PKI, a confirmation must of PKC
receipt MUST be sent back to the PKI. PKI by the Peer or the Admin
(forwarding the PeerĘs confirmation). This is true for first time
issuances, renewals, updates and
changes rekeys alike.
Operationally, the Peer MUST send a confirmation to the PKI verifying
that the end entity it has received the PKC, loaded it, and can use it effectively
in an IKE exchange. This requirement exists so that:
- The PKI does not publish the new PKC in the repository for others
until that PKC is able to be used effectively by the Peer, and;
- A revocation may be invoked if the PKC is not received and
operational within an allowable window of time.
To assert such proof the Peer MUST sign a portion of data with the
new key. The result MUST be sent to the PKI. The entity that actually
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sends the result to the PKI MAY be either the Peer (sending it
directly to the PKI) or Admin (the Peer would send it to Admin, and
Admin can in turn send it to the PKI).
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The Admin MUST acknowledge the successful receipt of the
confirmation, thus signaling to the end entity Peer that it may proceed using
this PKC in IKE connections. The PKI MUST complete all processing
necessary to enable the end entity's PeerĘs operational use of the new PKC (for
example, writing the PKC to the repository) before sending the
confirmation acknowledgement. The PKI MUST also issue a
revoke revocation on
the original PKC before sending the confirmation ACK (see section
4.X). The end entity Peer MUST NOT begin using the PKC until the PKI's PKIĘs
confirmation acknowledgement has been received.
3.4.10 Failure Cases
Thorough error condition descriptions and handling instructions are
required
REQUIRED for each transaction in the enrollment process. Providing
such error codes will greatly aid interoperability efforts between
the PKI and IPsec products.
The profile must will clarify what happens if the request and retrieval
fails for some reason. The following cases will MUST be covered:
- Admin or Peer cannot send the request.
- Admin or Peer sent the request but the PKI did not receive the
request.
- PKI received the request but could not read it effectively.
- PKI received and read the request, but some contents of the
request violated the PKI's PKIĘs configured policy such that the PKI
was unable to generate the PKC.
- The PKI System generated the PKC, but could not send it.
- The PKI sent the PKC, but the requestor (Admin or Peer) did not
receive it.
- The Requestor (Admin or Peer) received the PKC, but could not
process it due to incorrect contents, or other PKC-construction-
related problem.
- The Requestor failed trying to generate the confirmation.
- The Requestor failed trying to send the confirmation.
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- The Requestor sent the confirmation, but the PKI did not receive
it.
- The PKI received the confirmation but could not process.
In each case the following questions MUST be addressed:
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- What does Peer do?
- What does Admin do?
- What does PKI do?
- Is Authorization used?
If a failure occurs after the PKI sends the PKC and before the Peer
receives it, then the Peer MUST re-request with the same
Authorization ID and one-time-key, and the PKI, seeing the ID and
key, MUST send the PKC again.
3.5 PKC Profile for PKI Interaction
A PKC used for identity in IKE transactions MUST include all the
X509v3
[CERTPROFILE] mandatory fields. It must MUST also contain the minimal
contents necessary for path validation and chaining (these items will
be enumerated in the profile).
It is preferable that the PKC profiles for IPsec and certificate
management were the same so that one PKC could be used for both
protocols. If the profiles are inconsistent then different PKCs (and
perhaps different processing requirements) might MAY be required for
certificate management transactions vs. IKE transactions. However,
failure to achieve this requirement in the profile MUST NOT hold up
the standardization effort.
3.5.1 Identity Usage
The IPsec Peer SHALL perform identity verification based on the
fields of the PKC and parameters applicable to the VPN tunnel. The
fields of the PKC used for verification MAY include either the X.500
Distinguished Name (DN) within the Subject Name, or a specific field
within the Extension SubjectAltName (per [DOI] 4.6.2.1 Identification
Type Values). Usage descriptions for each follow.
The PKC field(s) that will be used for identity verification MUST be
included in the PKC request by the Admin or the Peer. In addition to
the DN, the The following
identity-related values may MAY be included in the SubjectAltName:
- Fully-Qualified Domain Name (FQDN)
- RFC 822 (also called USER FQDN)
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- IPv4 Address
- IPv6 Address
While substrings of these identity values may MAY also be present in
elements of the DN, they will not be looked for in the DN, only in
SubjectAltName.
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3.5.2 Path Validation
The Peers must MUST validate the certification path. The contents
necessary in the PKC to allow this will be enumerated in the profile
document.
The Peer MAY have the ability to construct the certification path
itself, however Admin MUST be able to supply Peers with the trust
anchor and any chaining PKCs necessary. The Admin MAY include the AIA
extension in PKCs as a means of facilitating path validation.
DNS SHOULD be supported by the Peers in order to do certification
path lookups, as well as those for revocation.
3.5.3 KeyUsage
The PKC's PKCĘs KeyUsage digialSignature digitalSignature bit as specified [CERTPROFILE]
MUST be flagged on.
[EDITOR'S NOTE: Shouldn't the non-repudiation bit also be required?
It's in the stated requirements, and PKIX treats it separately. Also
check whether the key exchange or key agreement bits should The KeyUsage extension SHOULD be
required. These are employed by both CMC and IPsec.] marked critical
IAW [CERTPROFILE].
3.5.4 Extended Key Usage
EKU's
Extended Key Usage (EKU) indications are not required. The presence
or lack of an EKU MUST NOT cause an implementation to fail an IKE
connection.
Default behavior is to not check EKU. However, local security policy
MAY check EKU, and if so the implementation SHOULD allow the
acceptance or rejection based on the presence of each EKU. Those EKUs
are defined as:
- serverAuth,
- clientAuth,
or an IKE specific EKU which are defined as one of the four currently
issued IANA EKU's: EKUĘs:
- IPsec user,
- IPsec computer,
- IPsec intermediate,
- IKE IPsec intermediate.
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- IPsec intermediate,
- IKE IPsec intermediate.
3.5.5 Pointer to Revocation Checking
The PKC contents must MUST be constructed in a manner such that any Peer
who hold holds the PKC locally will know exactly where to go and how to
request the CRL.
The location and method for either a CDP or an AIA [CERTPROFILE] MUST
be included in the PKC. Including such contents avoids the need to
send the CRL to the Peer, and allows the receiving Peer to look up
the CRL on their own.
PKCs MUST contain the full name of the CDP and AIA. Issuer-relative
names are not considered sufficient.
3.6 PKC Renewals and Changes Updates
In order to allow for continued PKC usage, a new PKC will need to be
issued for an end entity before the end entity's entityĘs currently held PKC
expires. A renewal is defined as a new PKC issuance with the same
SubjectName and SubjectAlternativeName contents as an existing PKC
for the same end entity before expiration of the end entity's entityĘs current
PKC.
A change PKC Update is defined as a new PKC issuance with an altered
SubjectName or SubjectAlternativeName for the same end entity before
expiration of the end entity's entityĘs current PKC. Renewals Renewals, updates and changes
rekeys are variants of a PKC request scenario with unique operational
and management requirements.
Once the PKI has issued a PKC for the end entity Peer, the Peer MUST
be able to either contact the PKI directly or through the Admin for
any subsequent renewals renewals, updates or changes. rekeys. The PKI MUST support
either case.
It is desired that a renew renew, update or change rekey request contain an
element that identifies the request as either type=renewal,
type=update, or type=change. type=rekey. This element MUST be specified in the
profile. This will allow for better management, logging and auditing
of certificate management.
When sending a renew renew, update or change rekey request, the entire contents of
the PKC request needs to be sent to the PKI, just as in the case of
the original enrollment. Keeping the request format as similar as
possible between new, renewal, update and change rekey cases will make for
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easier implementations; e.g. the format of the request is identitical identical
except for a type=[renew | change] update | rekey] instead of type=new.
The renew renew, update and change rekey requests MUST be signed by the private
key of the old PKC. This will allow the PKI to verify the identity of
the requestor, and ensure that an attacker does not submit a request
and receive a PKC with another end entity's entityĘs identity.
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Whether or not a new key is used for the new PKC in a renew and
change or update
scenario is a matter of local security policy, and MUST be specified
by the Admin to the PKI in the original authorization request. Re-using Re-
using the same key is permitted, but not encouraged. If a new key is
used, the change update or renew request must be signed by both the old key
-- to prove the right to make the request -- and the new key -- to
use for the new PKC. [EDITOR'S NOTE: Is there a way to do
this?]
The new PKC resulting from a renew renew, update or change rekey will be retrieved in-
band,
in-band, using the same mechanism as a new PKC request.
For the duration of time after a renew renew, update or change rekey has been
processed and before PKI has received confirmation of the Peer's PeerĘs
successful receipt of the new PKC (as described above in section
3.4.9), both PKCs--the old and the new--for the end entity will be
valid. This will allow the Peer to continue with uninterrupted IKE
connections with the previous PKC while the renewal process occurs.
In the case where new keys were generated for a renew renew, update or change
rekey request, once the end entity Peer receives the confirmation
acknowledgement from the PKI, it is good practice for the old key
pair be destroyed as soon as possible. Deletion of the keys and the
PKC can occur once all connections that used the old PKC have
expired.
After the renewal renewal, update or change rekey occurs, the question now exists
for the PKI of what to do about the old PKC. If the old PKC is to be
made unusable, the PKI will need to add it to the revocation list and
removed from the repository. The decision about if the old PKC should
be made unusable is a decision of local policy. Either the PKI or the
Admin will need to specify this parameter during the authorization
phase. In this case the specifying party --either the Admin or the
PKI-- MUST also specify during authorization the length of time after
the PKI receives the end entity Peer's PeerĘs confirmation (of receipt of
the PKC) that will pass before the old PKC is made unusable.
If a PKC has been revoked, it MUST NOT be allowed a renewal renewal, update
or
change. rekey.
Should the PKC expire without renewal renewal, update or change, rekey, an entirely
new request MUST be made.
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3.6.1 Renew Request for a New PKC (before expiry)
Operators can choose to force renewals for several reasons:
- To enforce an automated "clean up" of unused PKCs that have not
been specifically revoked
- To force re-keys
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- To have manual review control over re-issuance.
In the latter case, automated renewals will likely not be used. In
the former two cases automated renewal is a very attractive option.
At the time of authorization, certain details about renewal
acceptance will be conveyed by the Admin to the PKI, as stated in
section 3.2.3.2 above. The renewal request MUST match the conditions
that were specified in the original authorization for:
- Keys: new or existing or either
- Requestor: End entity Peer, Admin, either
- Renewal Period
- Length of time before making the old PKC unusable
If any of these conditions are not met, the PKI must reject the
renewal and log the event.
3.6.2 Change Update Request for a New PKC
A change in
An update to the contents of a PKC will be necessary when details
about an end entity Peer's PeerĘs identity change, but the Operator does not
want to generate a new PKC from scratch, requiring a whole new
authorization. For example, a gateway device may be moved from one
site to another. Its IPv4 Address will change in the SubjectAltName
extension, but all other information could stay the same. Another
example is an end user who gets married and changes the last name or
moves from one department to another. In either case, only one field
(the Surname or OU in the DN) need change.
A Change
An Update differs from a Renew in a few ways:
- A re-key is not necessary (though MAY be specified)
- The timing of the Change Update event is not predictable, as is the case
with a scheduled renewal Renewal or Rekey
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- The change Update request may occur at any time during a PKC's PKCĘs period of
validity
- Once the Change Update is completed, and the new PKC is confirmed, the
old PKC should cease to be usable, as its contents no longer
accurately describe the subject
- The existence of a "change" "update" type allows for better logging and
tracking of why the new issuance occurred, and why the old PKC
was made unusable.
At the time of authorization, certain details about change update acceptance
MAY be conveyed by the Admin to the PKI, as stated in section 3.2.3.2
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above. The change update request MUST match the conditions that were
specified in the original authorization for:
- Keys: new or existing or either
- Requestor: End entity Peer, Admin, either
- The fields in the Subject and SubjectAltName that are changeable
- Length of time before making the old PKC unusable
If any of these conditions are not met, the PKI must reject the
renewal.
update and log the event.
If a Change an Update authorization was not made at the time of original
authorization, one may be made from Admin to the PKI at any time
during the PKC's PKCĘs valid life. When such a Change an Update is desired, Admin
must notify the PKI System that a chance an update is authorized for the end
entity, and to expect it coming, and specify the new contents. Admin
then initiates the Change Update request with the given contents in whatever
mechanism the VPN System employs (direct from end entity to PKI, from
end entity through Admin, or directly from Admin).
3.6.3 Error Handling for Renewal and Change
Thorough error condition descriptions and handling instructions are
required for each transaction in the renewal renewal, update or change rekey
process. Providing such error codes will greatly aid interoperability
efforts between the PKI and IPsec products.
3.7 Finding PKCs in repositories
The complete hierarchical validation chain (except the trust point)
MUST be able to be searched in their respective repositories. The
information to accomplish these searches MUST be adequately
communicated in the PKCs sent during the IKE transaction.
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All PKCs must be retrievable through a single protocol. The final
specification will identify one protocol as a "MUST", others MAY be
listed as "OPTIONAL".
The general requirements for the retrieval protocol include:
- The protocol can be easily Firewalled (including NAT or PAT);
- The protocol can easily perform some query against a remote
repository on a specific ID element that was given to it in a
standard PKC field.
Other considerations include:
-relative speed
-relative ease of administration
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-scalability
Intermediate PKCs will be needed for the case of re-keying of the CA,
or a PKI System where multiple CAs exist.
PKCs MAY have extendedKeyusage to help identify the proper PKC for
IPsec, though the default behavior is to not use them. See the above
section on extendedKeyUsage.
IPsec Peers MUST be able to resolve Internet domain names and support
the manadatory mandatory repository access protocol at the time of starting up
so they can perform the PKC lookups.
IPsec Peers should cache PKCs to reduce latency in setting up Phase
1. Note that this is an operational issue, not an interoperability
issue.
The use case for accomplishing lookups when PKCs are not sent in IKE
is a stated non-goal of the profile at this time.
3.7.1 Error Handling for Repository Lookups
Thorough error condition descriptions and handling instructions are
required for each transaction in the repository lookup process.
Providing such error codes will greatly aid interoperability efforts
between the PKI and IPsec products.
3.8 Revocation Action
The Peer MUST be able to initiate revocation for its own PKC. In this
case the revocation request MUST be signed by the Peer's PeerĘs current key
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pair for the PKC it wishes to revoke. Whether the actual revocation
request transaction occurs directly with the PKI or is first sent to
Admin who proxies or forwards the request to the PKI is a matter of
implementation.
The Admin MUST be able to initiate revocation for any PKC for which
it authorized the creation. The Admin will identify itself to the PKI
by use of its own PKC; it MUST sign any revocation request to the PKI
with the private key from its own PKC. The PKI MUST have the ability
to configure Admin(s) with revocation authority, as identified by its
PKC. Any PKC authorizations must specify if said PKC may be revoked
by the Admin (see section 3.2.3.2 for more details).
The profile MUST identify the one protocol or transaction within a
protocol to be used for both Peer and Admin initiated revocations.
The profile MUST identify the size of CRL the client will be prepared
to support.
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Below are guidelines for revocation in specific transactions:
- AFTER RENEW, BEFORE EXPIRATION: The PKI MUST be responsible for
the PKC revocation during a renew transaction. PKI MUST revoke
the PKC after receiving the confirm notification from the Peer,
and before sending the confirm-ack to the Peer. The Peer MUST
NOT revoke its own PKC in this case.
- AFTER CHANGE, UPDATE, BEFORE EXPIRATION: The PKI MUST be responsible for
the PKC revocation during a change an update transaction. PKI MUST revoke
the PKC after receiving the confirm notification from the Peer,
and before sending the confirm-ack to the Peer. The Peer MUST
NOT revoke its own PKC in this case.
3.9 Revocation Checking and Status Information
The PKI System MUST provide a mechanism whereby Peers can check the
revocation status of PKCs that are presented to it for IKE identity.
The mechanism should allow for access to extremely fresh revocation
information. CRLs have been chosen as the mechanism for communicating
this information. Operators are RECOMMENDED to refresh CRLs as often
as logistically possible.
A single manadatory mandatory protocol mechanism for performing CRL lookups MUST
be specified by the final specification.
All PKCs used in IKE MUST have cRLDistributionPoint and
authorityInfoAccess fields populated with valid URLs. This will allow
all recipients of the PKC to know immediately how revocation is to be
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accomplished, and where to find the revocation information. The AIA
is needed in an environment where multiple layers of CAs exist and
for the case of a CA key roll-over.
IPsec Systems have an OPTION to turn off revocation checking. Such
may be desired when the two Peers are communicating over a network
without access to the CRL service, such as at a trade show, in a lab,
or in a demo environment. If revocation checking is OFF, the
implementation MUST proceed to use the PKC as valid identity in the
exchange and need not perform any check.
If the revocation of a PKC is used as the only means of deactivation
of access authorization for the Peer (or user), then the speed of
deactivation will be as rapid as the refresh rate of the CRL issued
and published by the PKI. If more immediate deactivation of access is
required than the CRL refreshing can provide, then another mechanism
for authorization that provides more immediate access deactivation
should be layered into the VPN deployment. Such a second mechanism is
out of the scope of this profile. (Examples are Xauth, L2TP's L2TPĘs
authentication, etc.).
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3.9.1 Error Handling in Revocation Checking
Thorough error condition descriptions and handling instructions are
required for each transaction in the revocation checking process.
Providing such error codes will greatly aid interoperability efforts
between the PKI and IPsec products.
4. Security Considerations
TBD
A References
A.1 Normative References
None
A.1 Non-Normative References
[STDPROCESS] Bradner, S., "The Internet Standards Process ” Revision
3", BCP 9, RFC 2026, October 1996.
[MUSTSHOULD] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[CERTPROFILE] Housley, R., et. al. "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List (CRL)
Profile", RFC 3280, April 2002.
[DOI] Piper, D., "Internet IP
3.10 Trust Anchor PKC Acquisition
The root PKC MUST arrive on the Peer via one of two methods:
(a) Peer can get the root PKC via its secure communication with
Admin. This requires the Peer to know less about interaction with the
PKI.
(b) Admin can command Peer to retrieve the root cert directly from
the PKI. How retrieval of the root cert takes place is beyond scope,
but is assumed to occur via an unauthenticated but confidential
enrollment protocol.
4. Security Domain Considerations
This requirements document does not specify an concrete solution,
and as such has no system-related security considerations per se.
However, the PKI4IPSEC model requires profiling and use of Interpretation concrete
Bonatti, Turner, Lebovitz 45
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ISAKMP", RFC 2407, November 1998.
A.1 Non-Normative References
[Frame] Chokhani, S., Ford, W., Sabett, R., Merrill, C., Wu. S.,
"Internet X.509 Public Key Infrastructure: an December 2004
IPsec Certificate Policy Management Profile
protocols for certificate management (e.g., CMC, CMS, CRMF). The
individual security considerations of these protocols should be
carefully considered in the profiling effort.
In addition, this document allows significant flexibility in the
allocation of functions between the roles of IPsec Peer and
Certificate Practices Framework", RFC 3547, November 2003.
B. Acknowledgements VPN
Admin. This draft functional allocation is substantially based crucial both to achieving
successful deployment, and to maintaining the integrity of the PKI
enrollment and management processes. However, much of the
responsibility for this allocation necessarily falls to product
implementers and system operators through the selection of
applicable use cases and development of security policy constraints.
These factors must be carefully considered to ensure the security of
PKI4IPSEC certificate management. Appendix E catalogs some key
system operator choices that are not constrained by this document,
and frames their possible impacts.
A References
A.1 Normative References
None
A.2 Non-Normative References
[STDPROCESS] Bradner, S., "The Internet Standards Process ” Revision
3", BCP 9, RFC 2026, October 1996.
[MUSTSHOULD] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[CERTPROFILE] Housley, R., et. al. "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List (CRL)
Profile", RFC 3280, April 2002.
[DOI] Piper, D., "Internet IP Security Domain of Interpretation for
ISAKMP", RFC 2407, November 1998.
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[FRAME] Chokhani, S., Ford, W., Sabett, R., Merrill, C., Wu. S.,
"Internet X.509 Public Key Infrastructure: Certificate Policy and
Certificate Practices Framework", RFC 3647, November 2003.
[GLOSSARY] Shirey, R., "Internet Security Glossary", RFC 2828, May
2000.
[IKECERTPROFILE] Korver, B., "The Internet IP Security PKI Profile
of IKEv1/ISAKMP, IKEv2, and PKIX",draft-ietf-pki4ipsec-ikecert-
profile-03, 30 September 2004.
B. Acknowledgements
This draft is substantially based on a prior draft draft-dploy-
requirements-00 developed by Project Dploy. The principle editor of
that draft was Gregory M. Lebovitz (NetScreen Technologies).
Contributing authors included Lebovitz, Paul Hoffman (VPN
Consortium), Hank Mauldin (Cisco Systems), and Jussi Kukkonen (SSH
Communications Security). Substantial editorial contributions were
made by Leo Pluswick (ICSA), Tim Polk (NIST), Chris Wells (SafeNet),
Thomas Hardjono(VeriSign), Carlisle Adams (Entrust), and Michael
Shieh (NetScreen).
Once brought to pki4ipsec, the following people made substantial
contributions: [TBD] ...
C. EditorĘs Address
Chris Bonatti
IECA, Inc.
15309 Turkey Foot Road
Darnestown, MD 20878-3640 USA
bonattic@ieca.com
Sean Turner
IECA, Inc.
1421 T Street NW #8
Washington, DC 20009 USA
turners@ieca.com
Gregory M. Lebovitz
NetScreen Technologies, Inc.
gregory@netscreen.com
D. Summary of Requirements
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TBD - EDITORĘS NOTE: Plan to add a summary table similar to those in
RFCs 1122, 1123, and 2975. Table will briefly describe requirement,
state the requirement level (i.e., "MAY", "SHOULD", "MUST", etc.),
and cite the applicable paragraph in this draft.
E. System Operator Choices
This appendix catalogs some key choices that must be made by product
implementers and system operators. These choices are not constrained
by this document, but can have profound impacts on PKI4IPSEC
certificate management operation and overall security. Where
possible we attempt to frames the specific security and operational
impacts associated with these choices.
1. Whether or not PKCs are allowed to be renewed or whether new
PKCs need to be issued.
2. Certificate renewal initiated by the VPN Peer or the VPN Admin
F. Change History
2004-December Draft-ietf-pki4ipsec-mgmt-profile-rqts-02
This issue of the document attempts to close out all non-contentious
issues as perceived after IETF #61. Numerous clarifications to
technical content were introduced, as well as revision to language
for purposes of internal consistency and consistency with the
[IKECERTPROFILE]. The following changes were introduced:
- Description of PKC "renewal" was clarified IAW [GLOSSARY].
- Replaced term "change" with "update" IAW [GLOSSARY].
- Added description of PKC "rekey" to complete the terminology set
employed in [GLOSSARY].
- Added [GLOSSARY] to the set of Non-Normative References.
- Updated use of the terminology throughout the document to align
with the above.
- Scrubbed instances of ambiguous requirements terminology in favor
of statements compliant with [MUSTSHOULD].
- Added reference to [IKECERTPROFILE] in several introductory text.
Bonatti, Turner, Lebovitz 48
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- Resolved editorĘs note concerning renewal parameters in 3.2.3.1
and related text in 3.2.3.2.
- Clarified that any non-key-related field might be changed in a
PKC update operation.
- Resolved editorĘs note concerning canceling authorizations in
3.2.4 so that either the Admin or the Peer may issue a
cancellation.
- Resolved editorĘs note concerning replay attacks in 3.2.4 so
duplicate authorization request MUST have a new identifier.
- Clarified the scenario in 3.2.5 for the PKI modifying the
requested PKC template submitted by the Admin.
- Renumbered previous clauses 3.3.1 through 3.3.4 as subsections of
a new 3.3.1 entitled "Key Generation Scenarios".
- Moved and renumbered the existing clause 3.3.5 as a new clause
3.10 since the topic of trust anchor acquisition applies
generically, and is not specifically subject to key generation
or PKC request construction.
- Added new key generation scenario as 3.3.1.5 in which the Peer
initiates a PKC request without a prior authorization exchange
between the Admin and the PKI.
- Added new Figures 7 through 11 to clauses 3.3.1.1 through 3.3.1.5
respectively to illustrate the steps of the different key
generation scenarios.
- Clarified in several places that the delivery of the requested
PKC is expected to occur directly as an in-band response, not
via lookup in the certificate repository.
- Resolved editorĘs note in 3.5.3 concerning key usage so that only
the "digialSignature" bit will be required to be set based on
the understanding that this does not preclude a system from
using digital signatures as a part of a non-repudiation service.
- Added new text to section 4 on Security Considerations.
- Corrected paragraph numbering on Non-Normative Reference section.
- Incorporated a prior draft draft-dploy-
requirements-00 developed by Project Dploy. The principle editor of new Appendix E to summarize choices that draft was Gregory M. Lebovitz (NetScreen Technologies).
Contributing authors included Lebovitz, Paul Hoffman (VPN
Consortium), Hank Mauldin (Cisco Systems), and Jussi Kukkonen (SSH
Communications Security). Substantial editorial contributions were must be
made by Leo Pluswick (ICSA), Tim Polk (NIST), Chris Wells (SafeNet), VPN implementers and VPN system operators, and describe
some of the potential impact of these decisions.
Bonatti, Turner, Lebovitz 38 49
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Thomas Hardjono(VeriSign), Carlisle Adams (Entrust), and Michael
Shieh (NetScreen).
Once brought to pki4ipsec,
- Applied numerous minor editorial corrections throughout the
document.
2004-October Draft-ietf-pki4ipsec-mgmt-profile-rqts-01
This issue of the document addresses comments identified at IETF #60.
The bulk of the changes were editorial, but some residual technical
impact may have resulted. The following people made substantial
contributions: [TBD] ...
C. Editor's Address
Chris Bonatti
IECA, Inc.
15309 Turkey Foot Road
Darnestown, MD 20878-3640 USA
bonattic@ieca.com
Sean Turner
IECA, Inc.
1421 T Street NW #8
Washington, DC 20009 USA
turners@ieca.com
Gregory M. Lebovitz
NetScreen Technologies, Inc.
gregory@netscreen.com
D. Summary changes were introduced:
- Acronym fixes
- Clarification of Requirements
TBD PKC Change definition
- EDITOR'S NOTE: Plan to add Rearranged and consolidated references
- Clarified what "off-line" communication (out of band) entails.
2004-August Draft-ietf-pki4ipsec-mgmt-profile-rqts-00
This issue of the document was merely a summary table similar reposting of draft-bonatti-
pki4ipsec-profile-reqts-01 to those in
RFCs 1122, 1123, and 2975. Table will briefly describe requirement,
state bring the requirement level (i.e., "MAY", "SHOULD", "MUST", etc.),
and cite document under the applicable paragraph in this draft.
E. Change History WG
auspices after the I-D repository opened. No significant changes
were introduced.
2004-July Draft-bonatti-pki4ipsec-profile-reqts-01
It is
This document was submitted as an individual draft in order to meet a
publication deadline though it has been accepted in to the working
group. The following salient changes were introduced:
- A new Figure 1 was added in section 2.1 to depict just the VPN
System.
- A new Figure 2 was added to depict 2.2 to depict just the PKI
System.
- The old Figure 1 was moved to section 2.3.
- Section 2.3 was split in to three sections to depict the New PKC,
Renewal, and Revocation. Also the text was modified to indicate
Bonatti, Turner, Lebovitz 39
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that the pictures are only for IPsec Peers generating key pairs
and requesting PKCs.
- Text and a Figure was added to Section 3.4.6 to show the
architectural difference for IPsec Peers enrolling through an
Admin.
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- Text and a Figure was added to Section 3.4.7 to show the
architectural difference for Admins performing the entire
enrollment.
2004-January Draft-bonatti-pki4ipsec-profile-reqts-00
This is a revised requirements document based on the existing Project
Dploy requirements draft. It adapts the revisions to adapt the Dploy
requirements to the scope of the proposed charter for an IETF
PKI4IPSEC WG. It is submitted as an individual draft in anticipation
of formation of the WG. The following salient changes were
introduced:
- Rewrote the abstract to focus on the document rather than the
project.
- Rewrote and trimmed introduction to fit proposed scope of
deliverable (2) from IETF PKI4IPSEC charter.
- Rewrote sentences throughout to genericize the document for the
IETF and remove references to Project Dploy objectives.
- Removed reference to the Dploy Business Case.
- Removed the "Audience" subsection of the introduction because it
was redundant with other aspects of the introduction, and
unnecessary with the context of the proposed PKI4IPSEC WG.
- Added definition of Community Realm (used in 3.2.3.3) to the
"Definitions" subsection.
- Added definition of CRL Distribution Points (CDP) and Authority
Info Access (AIA) to the "Definitions" subsection.
- Restructured the "Architecture" section to bring the presentation
of Figure 1 to the front to go along with the overview of the
section, and to add a new step diagram to the "VPN-PKI
Interaction" subsection.
- Added a new subsection 2.1.2 to describe the VPN peer. Text of
the new subsection will be supplied in a subsequent draft.
- Added an editor's editorĘs note to subsection 3.1.2 noting that further
elaboration on the nature of "policy details" may be required.
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- Subsection 3.2 was deleted to maintain the focus on generic
requirements agreed in Minneapolis. Selection of specific
protocols will be done in the deliverable (3) profile.
- Delete the requirement from 3.2.3.1 to include the maximum CRL
size in the certificate template. This may need to be specified
in the profile, but not be in the certificate itself.
- Revised 3.3.3 to to clarify that key escrow requirements and any key
transport between the VPN admin and the peer are beyond scope.
- Adopted consistent spelling "enrollment" vs. "enrolment"
throughout.
- Replaced instances of "and/or" and other slashed terminology with
less ambiguous statements to clarify the requirements.
- Revised the text of 3.5.1 to clarify the proposed requirement in
terms of SHALL and MAY terms.
- Retitled Re-titled 3.5.2 as "Path Validation" instead of "Chaining".
- Added AIA extension as a MAY requirement in 3.5.2.
- Added an editor's editorĘs note to subsection 3.5.3 to question whether
additional keyUsage bits should be set in the certificate.
- Removed the requirement for HTTP support in favor of a
requirement for a single mandatory protocol to be specified in
the profile.
- Removed subsection on "Intra-IKE Considerations" as these should
be dealt with in the existing deliverable (1) PKI profiles.
- Deleted existing sections 5 and 6 dealing with the partipating participating
vendors in Project Dploy.
- Added new section 4 on "Security Considerations". Text of the new
subsection will be supplied in a subsequent draft.
- Revised the "Acknowledgements" section to reflect this revision,
and provide appropriate credit to Project DPloy.
- Normalized "References" section with the ID-Nits promulgated by
the IESG.
- Added a stub for a proposed new Annex D to provide a requirements
summary table. Content of the annex will be supplied in a
subsequent draft.
2002-March Draft-dploy-requirements-00
Bonatti, Turner, Lebovitz 41 52
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2002-March Draft-dploy-requirements-00
- First public draft of the document released.
Copyright (C) The Internet Society 2004. 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."
"This document and the information contained herein are provided on
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REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE
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THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
Expires April June 2005
Bonatti, Turner, Lebovitz 42 53
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