PKI4IPSEC Working Group Internet Draft Chris Bonatti, IECA draft-ietf-pki4ipsec-mgmt-profile-rqts-02.txt Sean Turner, IECA December 12, 2004 Gregory Lebovitz, Netscreen Expires 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 all provisions of Section 10 of [STDPROCESS]. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 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. STATUS OF THIS MEMO................................................1 ABSTRACT...........................................................1 Bonatti, Turner, Lebovitz 1 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 1 INTRODUCTION.....................................................3 1.1 SCOPE..........................................................4 1.2 NON-GOALS......................................................5 1.3 DEFINITIONS....................................................5 1.4 REQUIREMENTS TERMINOLOGY.......................................7 2. ARCHITECTURE....................................................8 2.1 VPN SYSTEM.....................................................8 2.1.1 IPSEC PEER(S)................................................8 2.1.2 VPN ADMINISTRATION FUNCTION (ADMIN)..........................9 2.2 PKI SYSTEM....................................................10 2.3 VPN-PKI INTERACTION...........................................11 2.3.1 NEW PKC.....................................................12 2.3.2 RENEWAL PKC.................................................14 2.3.3 REVOCATION..................................................16 3 REQUIREMENTS....................................................17 3.1 GENERAL REQUIREMENTS..........................................17 3.1.1 ONE PROTOCOL................................................17 3.1.2 SECURE TRANSACTIONS.........................................17 3.1.3 PKI AVAILABILITY............................................17 3.1.4 END-USER TRANSPARENCY.......................................18 3.1.5 ERROR HANDLING..............................................18 3.2 AUTHORIZATION TRANSACTIONS....................................18 3.2.1 BULK AUTHORIZATION..........................................18 3.2.2 PROTOCOL PREFERENCES FOR AUTHORIZATION......................18 3.2.3 ADMIN AUTHORIZATION REQUESTS TO PKI.........................19 3.2.3.1 SPECIFYING FIELDS WITHIN THE PKC..........................19 3.2.3.2 AUTHORIZATIONS FOR RENEWAL AND UPDATE.....................20 3.2.3.3 OTHER AUTHORIZATION ELEMENTS..............................21 3.2.4 CANCEL CAPABILITY...........................................21 3.2.5 PKI RESPONSE TO ADMIN.......................................22 3.2.6 ERROR HANDLING FOR AUTHORIZATION TRANSACTIONS...............22 3.3 KEY GENERATION AND PKC REQUEST CONSTRUCTION...................22 3.3.1 KEY GENERATION SCENARIOS....................................23 3.3.1.1 IPSEC PEER GENERATES KEY PAIR AND CONSTRUCTS REQUEST......23 3.3.1.2 IPSEC PEER GENERATES KEY PAIR, ADMIN CONSTRUCTS REQUEST...24 3.3.1.3 ADMIN GENERATES KEY PAIR AND CONSTRUCTS REQUEST...........26 3.3.1.4 PKI GENERATES KEY PAIR AND PASSES TO PEER VIA 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 ..................................................................29 3.4 ENROLLMENT (SENDING REQUEST AND PKC RETRIEVAL)................30 3.4.1 ONE PROTOCOL................................................30 3.4.2 ON-LINE PROTOCOL............................................30 3.4.3 SINGLE CONNECTION WITH IMMEDIATE RESPONSE...................30 3.4.4 MANUAL APPROVAL OPTION......................................30 3.4.5 ENROLLMENT METHOD 1: PEER ENROLLS TO PKI DIRECTLY...........30 3.4.6 ENROLLMENT METHOD 2: IPSEC PEER ENROLLS TO PKI THROUGH ADMIN31 3.4.7 ENROLLMENT METHOD 3: ADMIN ENROLLS TO THE PKI DIRECTLY......33 3.4.8 ENROLLMENT TYPE FIELD.......................................35 Bonatti, Turner, Lebovitz 2 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 3.4.9 CONFIRMATION HANDSHAKE......................................35 3.4.10 FAILURE CASES..............................................36 3.5 PKC PROFILE FOR PKI INTERACTION...............................37 3.5.1 IDENTITY USAGE..............................................37 3.5.2 PATH VALIDATION.............................................38 3.5.3 KEYUSAGE....................................................38 3.5.4 EXTENDED KEY USAGE..........................................38 3.5.5 POINTER TO REVOCATION CHECKING..............................39 3.6 PKC RENEWALS AND UPDATES......................................39 3.6.1 RENEW REQUEST FOR A NEW PKC (BEFORE EXPIRY).................41 3.6.2 UPDATE REQUEST FOR A NEW PKC................................41 3.6.3 ERROR HANDLING FOR RENEWAL AND CHANGE.......................42 3.7 FINDING PKCS IN REPOSITORIES..................................42 3.7.1 ERROR HANDLING FOR REPOSITORY LOOKUPS.......................43 3.8 REVOCATION ACTION.............................................43 3.9 REVOCATION CHECKING AND STATUS INFORMATION....................44 3.9.1 ERROR HANDLING IN REVOCATION CHECKING.......................45 3.10 TRUST ANCHOR PKC ACQUISITION.................................45 4. SECURITY CONSIDERATIONS........................................45 A REFERENCES......................................................46 A.1 NORMATIVE REFERENCES..........................................46 A.2 NON-NORMATIVE REFERENCES......................................46 B. ACKNOWLEDGEMENTS...............................................47 C. EDITORĘS ADDRESS...............................................47 D. SUMMARY OF REQUIREMENTS........................................47 E. SYSTEM OPERATOR CHOICES........................................48 F. CHANGE 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 Bonatti, Turner, Lebovitz 3 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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, updates and 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 Infrastructure X.509 (PKIX) PKC profile from [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 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 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. Bonatti, Turner, Lebovitz 4 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile The solution focuses on the needs of large-scale rollouts, i.e. VPNs including 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. 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 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 Bonatti, Turner, Lebovitz 5 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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. (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, an IPsec Peer is certainly an end entity, but the VPN Admin may also constitute an 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 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 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 subjectĘs information. Examples might include change in the address, telephone number, or name change due to marriage of the end entity. PKC Rekey Bonatti, Turner, Lebovitz 6 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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 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) 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 Bonatti, Turner, Lebovitz 7 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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, 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. +---------------------------------------------------+ | | | +----------+ | | | 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. Bonatti, Turner, Lebovitz 8 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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. In this 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 be performed on a stand-alone workstation, on a gateway, on an administration software component. The Admin function 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, the AdminĘs architecture and the means by which it interacts with the participating IPsec Peers will vary widely from implementation to implementation. However, some basic functions of the Admin are assumed. - It will define the Certificate Policy (CP) [FRAME] for use in the 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, 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 unique authorization identifiers and one time tokens to be used in the PKC requests for each of the 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, employ integrity checks, and support non-repudiation. The contents of some such instructions Bonatti, Turner, Lebovitz 9 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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, in some environments, be "moving media," i.e. the configuration or data MAY be loaded on to a floppy disk or other media and physically moved to the IPsec Peer. Likewise, it MAY be entered directly on the IPsec Peer via a User Interface (UI). In this case, the Admin function is co-located on the Peer device itself. This reality 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 be set up and operated by the Operator (in-house), MAY be provided by third party PKI providers to which connectivity is available at the time of provisioning (managed PKI service), or MAY be integrated with the VPN product. +---------------------------------------------+ | +-------------------------+ | | v | | | +--------------+ v | | | Repository | +----+ +----+ | | | Certs & CRLs |<-> | CA |<->| RA | | | +--------------+ +----+ +----+ | | | +---------------------------------------------+ Figure 2: PKI System This framework assumes that all components of the VPN 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 MUST contain a mechanism for handling AdminĘs authorization requests and PKC enrollments. These mechanisms are referred to as the RA. The PKI System MUST contain a Repository for Peers to look up each 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. Bonatti, Turner, Lebovitz 10 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile The PKI System SHOULD be built so that lookups resolve directly and completely at the URL indicated in a CDP or AIA. The PKI 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, only the steps associated with IPsec Peer 1 are shown. Bonatti, Turner, Lebovitz 11 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile +---------------------------------------------+ | 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 (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 architectural options available and that the most common architecture is depicted in Figure 4; IPsec Peer generated Keys and IPsec Peer generated PKC Request. Other architectural options are discussed in Section 3. Bonatti, Turner, Lebovitz 12 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile +--------------+ 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, updates or 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, it could be very large, with several fields being specified along with their contents. 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. Bonatti, Turner, Lebovitz 13 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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. 6) Enrollment Confirmation. Peer positively 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 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 architectural options available and that the most common architecture is depicted in Figure 5; IPsec Peer generated Keys and IPsec Peer generated PKC Request. Other architectural options are discussed in Section 3. Bonatti, Turner, Lebovitz 14 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile +--------------+ 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 1) Rekey or Renewal Initiation. The Admin communicates renewal, update or rekey instructions to the Peers. Renewal may also be 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, update or 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 renewal without authorization from Admin. Additionally, local policy will determine whether EEs must renew or be reissued PKCs. 2) Renewals and Updates [R]. The IPsec Peer requests renewal or 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/Update Response [R]. The PKI responds to the renewal or update request sent in (11), providing either the new PKC that was generated or a suitable error indication. 4) Enrollment Confirmation. Peer positively 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 Bonatti, Turner, Lebovitz 15 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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. +--------------+ 2 +-----------------------+ | Repository |<----| Certificate Authority | +--------------+ +-----------------------+ ^ ^ ^ | 3 | 1 | 1, 1ĘĘ | | | | | | | | 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 1Ęs PKC directly from the PKI. 1Ę) Revocation. The IPsec Peer requests revocation of their PKC through admin. Bonatti, Turner, Lebovitz 16 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 1ĘĘ) Revocation. The Admin forwards IPsec Peer 1Ęs PKC revocation request to PKI. 2) CRL Posting. The newly-generated CRL revoking IPsec Peer 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 The target 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. Meeting some of the requirements MAY necessitate the creation of a new protocol or new extension for an existing protocol; however, the late is much preferred. 3.1.2 Secure Transactions The target profile MUST specify the transactions for certificate management between VPN and PKI Systems and their components, to ease large-scale VPN deployment and management. Specifically, Admin and PKI 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 MUST require that mutual trust be established between the PKI and the Admin. 3.1.3 PKI Availability Central availability is REQUIRED initially for authorization transactions between the PKI and Admin. Further availability MAY be required in most cases, but is a decision point for the Operator. Bonatti, Turner, Lebovitz 17 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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 SHOULD NOT even be aware that PKI is in use. First time connections 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. 3.2 Authorization Transactions This section refers to the [A] elements labeled in Figure 3. 3.2.1 Bulk Authorization Bulk 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 The setup for all subjects in an authorization batch SHOULD occur in one single connection to the RA/CA, with the number of subjects being Bonatti, Turner, Lebovitz 18 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile one or greater. Implementations SHOULD be able to handle one thousand at a time. ONE protocol 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 authorization key (not to be confused with the public and private key pair) for each identifier. The transport used to carry the pre-authorization SHOULD be reliable (TCP). The protocol 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 non-repudiation. PKCs for authorization of the Admin MAY need to be initialized by physical rather than on-line means. 3.2.3 Admin Authorization Requests to PKI 3.2.3.1 Specifying Fields within the PKC The 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 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 - Validity Period of the PKC - Renewal parameters (i.e., renewal not permitted, N% of validity period, or the UTC time after which renewal is permitted) - Key type - Key length - Extension fields: Bonatti, Turner, Lebovitz 19 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile - 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 profile, based on these requirements, SHOULD define who will handle the CDP contents. 3.2.3.2 Authorizations for Renewal and 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 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 PKC update is allowed, that is, the Admin is presently authorizing the PKI to accept a future request for a new PKC creation with changes to non-key-related fields. If a PKC renewal is authorized, the Admin MUST further specify: - Who can renew, 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 (i.e., N% of validity period, or the UTC time after which renewal is permitted). If PKC update is authorized, the Admin MUST further specify: - The aspects of non-key-related fields that are changeable. - The entity that can send the PKC Update request, that is, only the Admin, only the end entity, or either. - 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 after which update is permitted). A new authorization by the Admin is REQUIRED for PKC rekey. No parameters of prior authorizations need be considered. Bonatti, Turner, Lebovitz 20 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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 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. 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 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. The Protocol SHOULD consider what happens when Admin requested information conflicts with PKI settings such that the Admin request cannot be issued as requested (e.g., Admin requests Validation Period = 3 weeks and CA is configured to only allow Validation Periods = 1 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. The canceling entity MUST provide the authorization ID and 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 (a Cancel, Cancel ACK, ACK type of a process is REQUIRED to cover a lost connections scenario), the PKI will accept a new Authorization request with the exact same contents as the canceled one, except that the identifier MUST be new. The PKI MUST NOT process duplicate authorization requests. Note that if the PKI has already 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. Bonatti, Turner, Lebovitz 21 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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 requested and a one-time authorization key per authorization ID. 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. 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 authorization template (as modified) to the 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. If the Admin determines that the modified parameters are unacceptable, then the authorization should be cancelled in accordance with clause 3.2.4. After receiving a bulk authorization request from the Admin, the PKI 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. A method is 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 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 three places, depending on local requirements: at the IPsec Peer, at the Admin, or at the PKI. The PKC constructions MAY occur at either the IPsec Peer or a combination of the Peer and the Admin. Bonatti, Turner, Lebovitz 22 Internet-Draft Requirements for 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, 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. 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 Bonatti, Turner, Lebovitz 23 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile - 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 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. Bonatti, Turner, Lebovitz 24 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile +---------------------------+ | Certificate Authority | +---------------------------+ ^ | ^ | | | | | | | 5 1 | | 2 | | | | | | | v | | +-----------+ | | | Admin | 4 | | +-----------+ | | | | | | 3 | | | | v v +--------------------+ | IPsec | | Peer | +--------------------+ Figure 8. Key Generation By IPsec Peer with Admin Construction of Enrollment Request 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 Bonatti, Turner, Lebovitz 25 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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 Operator 1 is the only one allowed to have the Admin function pre-authorize PKCs, but Operator 2 is the one doing batch enrollments and VPN device configurations. +---------------------------+ | Certificate Authority | +---------------------------+ ^ | ^ | | | | | | | 5 1 | | 2 | | | | | | | v | | +-----------+ | | | Admin | 4 | | +-----------+ | | | | | | 3 | | | | v v +--------------------+ | IPsec | | Peer | +--------------------+ Figure 9. Key and Enrollment Request Bonatti, Turner, Lebovitz 26 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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 This use case allows the PKI to generate the key pair and the PKC after which it simply hands the PKC down to the Admin for installation into the Peer. This is, in all likelihood, the easiest way to deploy PKCs, though it sacrifices some security since both the CA and the 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 Admin effectively acts as a proxy for the Peer in the PKC enrollment process. Bonatti, Turner, Lebovitz 27 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile +---------------------------+ | Certificate Authority | +---------------------------+ ^ | | | 1 | | 2 | | | v +-----------+ | Admin | +-----------+ | | 3 | v +--------------------+ | IPsec | | Peer | +--------------------+ Figure 10. Key Generation By PKI with Proxy Enrollment via VPN Admin 1) Authorization & PKC Enrollment Request - PKC field assertions - Public Key - Proof of Possession of Associated Private Key 2) Enrollment Response - Distributed PKC - Associated private key 3) Peer Provisioning - Distributed PKC - Associated private key 3.3.1.5 Peer Generates Key Pair Without Prior Authorization In many situations, a use case in which the VPN Peer makes sole contact with the PKI can simplify the enrollment process. This would allow individuals or small organizations to obtain PKCs for Bonatti, Turner, Lebovitz 28 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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. Bonatti, Turner, Lebovitz 29 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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 enrollment requests and responses. 3.4.2 On-line protocol The protocol MUST supports enrollment that occurs over the Internet and without the need for manual intervention. 3.4.3 Single Connection with Immediate Response Enrollment requests and responses MUST be able to occur in one on- line connection between the Admin on behalf of the Peer or the Peer itself and the PKI (RA/CA). 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. 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 In this case, the Admin can instruct the IPsec Peer to execute an enrollment, telling it where to enroll, and providing any necessary parameters. Bonatti, Turner, Lebovitz 30 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile In this case, the IPsec Peer only 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 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. 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 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 12. Bonatti, Turner, Lebovitz 31 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile +--------------+ 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 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, updates or 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. 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 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. Bonatti, Turner, Lebovitz 32 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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. 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. 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 13. Bonatti, Turner, Lebovitz 33 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile +--------------+ 7 +-----------------------+ | Repository |<----| Certificate Authority | +--------------+ +-----------------------+ ^ ^ | 8 | 1, 4, 6 | 2, 5 | | v | 9 +-------+ +--------------+> | Admin | 3 | +-------+ | 10 | v +--------------------+ +--------+ | IPsec | 11 | IPsec | | Peer 1 |<========>| Peer 2 | +--------------------+ +--------+ Figure 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, updates or 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. 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. Bonatti, Turner, Lebovitz 34 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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. 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 exist in the enrollment request to specify the TYPE of request being made. Request types include new request, renew request, update request, and rekey request (renewals, updates and 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 of PKC receipt MUST be sent back to the PKI by the Peer or the Admin (forwarding the PeerĘs confirmation). This is true for first time issuances, renewals, updates and rekeys alike. Operationally, the Peer MUST send a confirmation to the PKI verifying that 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 Bonatti, Turner, Lebovitz 35 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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). The Admin MUST acknowledge the successful receipt of the confirmation, thus signaling to the Peer that it may proceed using this PKC in IKE connections. The PKI MUST complete all processing necessary to enable the 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 revocation on the original PKC before sending the confirmation ACK (see section 4.X). The Peer MUST NOT begin using the PKC until the PKIĘs confirmation acknowledgement has been received. 3.4.10 Failure Cases Thorough error condition descriptions and handling instructions are 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 will clarify what happens if the request and retrieval fails for some reason. The following cases 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 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. Bonatti, Turner, Lebovitz 36 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile - 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: - 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 [CERTPROFILE] mandatory fields. It 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) 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. The following identity-related values MAY be included in the SubjectAltName: - Fully-Qualified Domain Name (FQDN) - RFC 822 (also called USER FQDN) Bonatti, Turner, Lebovitz 37 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile - IPv4 Address - IPv6 Address While substrings of these identity values MAY also be present in elements of the DN, they will not be looked for in the DN, only in SubjectAltName. 3.5.2 Path Validation The Peers 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 PKCĘs KeyUsage digitalSignature bit as specified [CERTPROFILE] MUST be flagged on. The KeyUsage extension SHOULD be marked critical IAW [CERTPROFILE]. 3.5.4 Extended Key Usage 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 EKUĘs: - IPsec user, - IPsec computer, Bonatti, Turner, Lebovitz 38 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile - IPsec intermediate, - IKE IPsec intermediate. 3.5.5 Pointer to Revocation Checking The PKC contents MUST be constructed in a manner such that any Peer who 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 Updates In order to allow for continued PKC usage, a new PKC will need to be issued for an end entity before the end 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 entityĘs current PKC. A 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 entityĘs current PKC. Renewals, updates and 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, updates or rekeys. The PKI MUST support either case. It is desired that a renew, update or rekey request contain an element that identifies the request as either type=renewal, type=update, or 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, update or 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 rekey cases will make for Bonatti, Turner, Lebovitz 39 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile easier implementations; e.g. the format of the request is identical except for a type=[renew | update | rekey] instead of type=new. The renew, update and 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 entityĘs identity. Whether or not a new key is used for the new PKC in a renew 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 the same key is permitted, but not encouraged. If a new key is used, the 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. The new PKC resulting from a renew, update or rekey will be retrieved in-band, using the same mechanism as a new PKC request. For the duration of time after a renew, update or rekey has been processed and before PKI has received confirmation of the 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, update or 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, update or 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 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, update or rekey. Should the PKC expire without renewal, update or rekey, an entirely new request MUST be made. Bonatti, Turner, Lebovitz 40 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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 - 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 Update Request for a New PKC An update to the contents of a PKC will be necessary when details about an end entity 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. An Update differs from a Renew in a few ways: - A re-key is not necessary (though MAY be specified) - The timing of the Update event is not predictable, as is the case with a scheduled Renewal or Rekey Bonatti, Turner, Lebovitz 41 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile - The Update request may occur at any time during a PKCĘs period of validity - Once the 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 "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 update acceptance MAY be conveyed by the Admin to the PKI, as stated in section 3.2.3.2 above. The 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 update and log the event. If 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 PKCĘs valid life. When such an Update is desired, Admin must notify the PKI System that an update is authorized for the end entity, and to expect it coming, and specify the new contents. Admin then initiates the 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, update or 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. Bonatti, Turner, Lebovitz 42 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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 -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 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 PeerĘs current key Bonatti, Turner, Lebovitz 43 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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. 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 UPDATE, BEFORE EXPIRATION: The PKI MUST be responsible for the PKC revocation during 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 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 Bonatti, Turner, Lebovitz 44 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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, L2TPĘs authentication, etc.). 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. 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 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 concrete Bonatti, Turner, Lebovitz 45 Internet-Draft Requirements for an December 2004 IPsec Certificate 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 VPN Admin. This functional allocation is 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. Bonatti, Turner, Lebovitz 46 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile [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 Bonatti, Turner, Lebovitz 47 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile - 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 new Appendix E to summarize choices that must be made by VPN implementers and VPN system operators, and describe some of the potential impact of these decisions. Bonatti, Turner, Lebovitz 49 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile - 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 changes were introduced: - Acronym fixes - Clarification of PKC Change definition - 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 reposting of draft-bonatti- pki4ipsec-profile-reqts-01 to bring the document under the WG auspices after the I-D repository opened. No significant changes were introduced. 2004-July Draft-bonatti-pki4ipsec-profile-reqts-01 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 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. Bonatti, Turner, Lebovitz 50 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile - 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 editorĘs note to subsection 3.1.2 noting that further elaboration on the nature of "policy details" may be required. Bonatti, Turner, Lebovitz 51 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile - 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 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. - Re-titled 3.5.2 as "Path Validation" instead of "Chaining". - Added AIA extension as a MAY requirement in 3.5.2. - Added an 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 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. Bonatti, Turner, Lebovitz 52 Internet-Draft Requirements for an December 2004 IPsec Certificate Management Profile 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 an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." Expires June 2005 Bonatti, Turner, Lebovitz 53