Network Working Group N. Cam-Winget Internet-Draft D. McGrew Intended status: Informational J. Salowey Expires: September 5, 2007 H. Zhou Cisco Systems March 4, 2007 Dynamic Provisioning using Flexible Authentication via Secure Tunneling Extensible Authentication Protocol (EAP-FAST) draft-cam-winget-eap-fast-provisioning-04 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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. This Internet-Draft will expire on September 5, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Cam-Winget, et al. Expires September 5, 2007 [Page 1] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 Abstract The flexible authentication via secure tunneling EAP method (EAP- FAST) enables secure communication between a client and a server by using Transport Layer Security (TLS) to establish a mutually authenticated tunnel. EAP-FAST also enables the provisioning credentials or other information through this protected tunnel. This document describes the use of EAP-FAST for dynamic provisioning. Cam-Winget, et al. Expires September 5, 2007 [Page 2] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Specification Requirements . . . . . . . . . . . . . . . . 5 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 2. EAP-FAST Provisioning Modes . . . . . . . . . . . . . . . . . 7 3. Dynamic Provisioning using EAP-FAST Conversation . . . . . . . 8 3.1. Network Access after EAP-FAST Provisioning . . . . . . . . 8 3.2. Authenticating Using EAP-MSCHAPv2 . . . . . . . . . . . . 9 3.3. Use of other Inner EAP Methods for EAP-FAST Provisioning . . . . . . . . . . . . . . . . . . . . . . . 10 3.4. Key Derivations Used in the EAP-FAST Provisioning Exchange . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.5. Peer-Id, Server-Id and Session-Id . . . . . . . . . . . . 11 3.6. Provisioning or Refreshment of a PAC . . . . . . . . . . . 11 4. Information Provisioned in EAP-FAST . . . . . . . . . . . . . 13 4.1. Protected Access Credential . . . . . . . . . . . . . . . 13 4.2. PAC TLV Format . . . . . . . . . . . . . . . . . . . . . . 14 4.2.1. Formats for PAC Attributes . . . . . . . . . . . . . . 15 4.2.2. PAC-Key . . . . . . . . . . . . . . . . . . . . . . . 16 4.2.3. PAC-Opaque . . . . . . . . . . . . . . . . . . . . . . 16 4.2.4. PAC-Info . . . . . . . . . . . . . . . . . . . . . . . 17 4.2.5. PAC-Acknowledgement TLV . . . . . . . . . . . . . . . 19 4.2.6. PAC-Type TLV . . . . . . . . . . . . . . . . . . . . . 20 4.3. Trusted Server Root Certificate . . . . . . . . . . . . . 20 4.3.1. Server-Trusted-Root TLV . . . . . . . . . . . . . . . 21 4.3.2. PKCS #7 TLV . . . . . . . . . . . . . . . . . . . . . 22 5. Security Considerations . . . . . . . . . . . . . . . . . . . 24 5.1. Mitigation of Dictionary Attacks . . . . . . . . . . . . . 24 5.2. Mitigation of Man-in-the-middle (MitM) attacks in server- unauthenticated provisioning mode . . . . . . . . 25 5.3. Mitigation of Man-in-the-middle (MitM) attacks in server- authenticated provisioning mode . . . . . . . . . 26 5.4. Diffie-Hellman Groups . . . . . . . . . . . . . . . . . . 26 5.5. PAC Storage Considerations . . . . . . . . . . . . . . . . 27 5.6. Security Claims . . . . . . . . . . . . . . . . . . . . . 28 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 30 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31 8.1. Normative References . . . . . . . . . . . . . . . . . . . 31 8.2. Informative References . . . . . . . . . . . . . . . . . . 31 Cam-Winget, et al. Expires September 5, 2007 [Page 3] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 Appendix A. Appendix: Examples . . . . . . . . . . . . . . . . . 33 A.1. Example 1: Successful Tunnel PAC Provisioning . . . . . . 33 A.2. Example 2: Failed Provisioning . . . . . . . . . . . . . . 34 A.3. Example 3: Provisioning a Authentication Server's Trusted Root Certificate . . . . . . . . . . . . . . . . . 36 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 38 Intellectual Property and Copyright Statements . . . . . . . . . . 39 Cam-Winget, et al. Expires September 5, 2007 [Page 4] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 1. Introduction EAP-FAST [I-D.cam-winget-eap-fast] is an EAP method that can be used to mutually authenticate peer and server. However, to mutually authenticate with EAP-FAST, credentials such as a pre-shared key, trusted anchor or a Protected Access Credential (PAC) must be provisioned to the peer before it can establish a secure communication channel with the server. In many cases, the provisioning of such information presents deployment hurdles. Through the use of the protected tunnel, EAP-FAST can also be used to enable the means for dynamic in-band provisioning to address such deployment obstacles. 1.1. Specification Requirements The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 1.2. Terminology Much of the terminology in this document comes from [RFC3748]. Additional terms are defined below: Man in the Middle (MitM) An adversary that can successfully inject itself between a peer and EAP server. The MitM succeeds by impersonating itself as a valid peer, authenticator or authentication server. Provisioning Providing peer with a trust anchor, shared secret or other appropriate information based on which a security association can be established. Protected Access Credential (PAC) Credentials distributed to a peer for future optimized network authentication. The PAC consists of at most three components: a shared secret, an opaque element and optionally other information. The shared secret part contains the pre-shared key between the peer and authentication server. The opaque part is provided to the peer and is presented to the authentication server when the peer wishes to obtain access to network resources. Finally, a PAC may optionally include other information that may be useful to the peer. Cam-Winget, et al. Expires September 5, 2007 [Page 5] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 Tunnel PAC A set of credentials stored by the peer and consumed by both the peer and the server to establish a TLS tunnel. Cam-Winget, et al. Expires September 5, 2007 [Page 6] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 2. EAP-FAST Provisioning Modes EAP-FAST supports two modes for provisioning: 1. Server-Authenticated Mode - Provisioning inside a TLS tunnel that provides server-side authentication. 2. Server-Unauthenticated Mode Mode - Provisioning inside a TLS tunnel without server-side authentication. The EAP-FAST provisioning modes use the secure TLS tunnel of phase 2 that is established during phase 1. [I-D.cam-winget-eap-fast] describes the EAP-FAST phases in greater detail. In the Server-Authenticated Provisioning mode, the peer has successfully authenticated the EAP server as part of EAP-FAST Phase 1 (i.e. TLS tunnel establishment). Additional exchanges MAY occur inside the tunnel to allow the EAP Server to authenticate the peer before provisioning any information. In the Server-Unauthenticated Provisioning mode, an unauthenticated TLS tunnel is established in the EAP-FAST Phase 1. This provisioning mode enables the bootstrapping of peers where the peer lacks strong credentials usable for mutual authentication with the server. The peer may negotiate a TLS_DH_anon based cipher suites to signal that it wishes to use Server-Unauthenticateded provisioning mode. Other cipher suites requiring the use of server certificates may be used and are considered unauthenticated if the peer may lacks the necessary trust anchors to validate the server certificate chain. Since the server is not authenticated in the Server-Unauthenticated Provisioning mode, it is possible that an attacker may intercept the TLS tunnel. When it is possible an inner EAP method should be used to provide some authentication and MitM detection as outlined in Section 5. If an anonymous tunnel is used then the peer and server MUST negotiate and successfully complete an EAP method supporting mutual authentication and key derivation. The peer then uses the Crypto-Binding TLV to validate the integrity of the TLS tunnel, thereby verifying that the exchange was not subject to a man-in-the- middle attack. Assuming that any inner EAP method and Crypto-Binding TLV exchange is successful, the server will subsequently provide the information such as a shared key or the trusted root(s) of server certificate using a PAC TLV or a Server-Trusted-Root TLV respectively. Once the EAP-FAST Provisioning conversation completes, the peer is expected to use the provisioned credentials in subsequent EAP-FAST authentications. Cam-Winget, et al. Expires September 5, 2007 [Page 7] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 3. Dynamic Provisioning using EAP-FAST Conversation The provisioning EAP-FAST exchange uses same sequence as the EAP-FAST authentication phase 1 to establish a protected TLS tunnel. This version of the EAP-FAST provisioning mode implementation MUST support the following TLS ciphersuites defined in [RFC2246], [RFC4346] and [RFC3268]: TLS_RSA_WITH_RC4_128_SHA TLS_RSA_WITH_AES_128_CBC_SHA TLS_DH_anon_WITH_AES_128_CBC_SHA TLS_DHE_RSA_WITH_AES_128_CBC_SHA Other TLS ciphersuites MAY be supported. To adhere to best security practices, it is highly RECOMMENDED that the peer validate the server's certificate chain when performing server-side authentication. However, as the provisioning of the root public key or trust anchor must also be secured, some deployments may be willing to trade off the security risks for ease of deployment and forgo trust root validation or use an anonymous ciphersuite. Anonymous ciphersuites SHOULD NOT be allowed outside of EAP-FAST provisioning mode. Ciphersuites that are used for provisioning MUST provide encryption. Once a protected tunnel is established, the peer and server can then execute an EAP method and provision credential information. The internal EAP method can be used to authenticate the peer to the server if this was not accomplished in EAP-FAST phase 1. Additionally the internal EAP method can provide an additional check on the integrity of the TLS tunnel if server side authentication was not performed in phase 1. Following a successful authentication exchange and successful Intermediate Result TLV and Crypto-Binding TLV exchange, the server can then provision the peer with a unique PAC. The provisioning is invoked through the a PAC-TLV exchange that is executed following a successful authentication exchange including the Intermediate Result TLV and Crypto-Binding TLV. The PAC-TLV exchange consists of the server distributing the PAC in a corresponding PAC TLV to the peer and the peer confirming its receipt in a final PAC TLV Acknowledgement message. 3.1. Network Access after EAP-FAST Provisioning After successful provisioning, network access may be granted or denied depending upon server policy. For example, in the Server- Authenticated Provisioning Mode, access can be granted after the EAP server has authenticated the peer and provisioned the peer with a Tunnel PAC (i.e. a PAC used to mutually authenticate and establish the EAP-FAST tunnel). Additionally, peer policy may instruct the Cam-Winget, et al. Expires September 5, 2007 [Page 8] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 peer to disconnect the current provisioning connection and initiate a new EAP-FAST exchange for authentication utilizing the newly provisioned information. At the end of the Server-Unauthenticated Provisioning Mode, network access SHOULD NOT be granted as this conversation is intended for provisioning only and thus no network access is authorized. The server MAY grant access at the end of a successful server authenticated provisioning exchange. If after successful provisioning access to the network is denied the EAP Server SHOULD conclude with an EAP Failure. The EAP Server SHALL NOT grant network access or distribute any session keys to the NAS as this exchange is not intended to provide network access. Even though provisioning mode completes with a successful inner termination (e.g. successful Result TLV), server policy defines whether the peer gains network access or not. Thus, it is feasible for the server, while providing a successful Result TLV may conclude with an EAP Failure. The EAP-FAST server, when denying network access after EAP-FAST Provisioning, may choose to instead, immediately invoke another EAP- FAST Start and thus initiate the EAP-FAST Phase 1 conversation. This server based implementation policy may be chosen to avoid applications such as wireless devices from being disrupted (e.g. in 802.11 devices, an EAP Failure may trigger a full 802.11 disassociation) and allow them to smoothly transition to the subsequent EAP-FAST authentications to enable network access. As an alternative, both the peer and server can initiate TLS renegotiation, where the newly provisioned credentials can be used to establish a server authenticated or mutually authenticated TLS tunnel for authentication. Upon completion of the TLS negotiation and subsequent authentication, normal network access policy on EAP-FAST authentication can be applied. 3.2. Authenticating Using EAP-MSCHAPv2 This version of the EAP-FAST provisioning mode implementation MUST support EAP-MSCHAPv2 as the inner authentication method for enabling Server-Unauthenticated Provisioning Mode using an anonymous Diffie- Hellman key agreement. While other authentication methods are allowed and exist to achieve mutual authentication, when using an anonymous or unauthenticated TLS tunnel, EAP-MSCHAPv2 was chosen for several reasons: o Provide the ability of slowing an active attack by using a hash based challeng-response protocol. o The use of a challenge response protocol such as MSCHAPv2 provides some ability to detect a man-in-the-middle attack during server- unauthenticated provisioning. Cam-Winget, et al. Expires September 5, 2007 [Page 9] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 o A large deployed base is already able to support MSCHAPv2 o It allows support for password change during the EAP-FAST Provisioning mode. The MSCHAPv2 [RFC2759] exchange forces the server to provide a valid ServerChallengeResponse which must be a function of the server challenge, client challenge and password as part of its response. This reduces the window of vulnerability in the EAP-FAST for in-band provisioning mode to force the man-in-the-middle, acting as the server, to successfully break the password within the client's challenge response time limit. When using an anonymous DH key agreement and EAP-MSCHAPv2, a binding between the tunnel and the EAP-MSCHAPv2 exchanges is formed by using keying material generated during the EAP-FAST tunnel establishment as the EAP-MSCHAPv2 challenges. A detailed description of the challenge generation is described in Section 3.4. 3.3. Use of other Inner EAP Methods for EAP-FAST Provisioning Once a protected tunnel is established, the peer authenticates itself to the server before the server can provision the peer. If the authentication mechanism is not EAP-MSCHAPv2 a ciphersuite that provides server side authentication, such as TLS_DHE_RSA_WITH_AES_128_CBC_SHA, MUST be used. Within a server side authenticated tunnel authentication mechanisms such as EAP-GTC may be used. This will enable peers using other authentication mechanisms such as password database and one-time passwords to be provisioned in-band as well. This version of the EAP-FAST provisioning mode implementation MUST support both EAP-GTC and EAP-MSCHAPv2 within the tunnel in Server- Authenticated Provisioning Mode. It should be noted that Server-Authenticated Provisioning mode provides significant security advantages over Server-Unauthenticated Provisioning mode even when EAP-MSCHAPv2 is being used as the inner method. It protects the EAP-MSCHAPv2 exchanges from potential MitM attacks by verifying server's authenticity before exchanging MSCHAPv2. Thus Server-Authenticated Provisioning Mode is the preferred provisioning mode. The EAP-FAST peer MUST use the Server- Authenticated Provisioning Mode whenever it is configured with a trust root for the purpose of validating the EAP server's certificate. 3.4. Key Derivations Used in the EAP-FAST Provisioning Exchange The TLS tunnel key is calculated according to the TLS [RFC2246] with an extra 72 octets of key material. Portions of the extra 72 octets Cam-Winget, et al. Expires September 5, 2007 [Page 10] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 are used for the EAP-FAST provisioning exchange session key seed and as the random challenges in the EAP-MSCHAPv2 exchange. To generate the key material, compute key_block = PRF(master_secret, "key expansion", server_random + client_random); until enough output has been generated. Then the key_block is partitioned as follows: client_write_MAC_secret[hash_size] server_write_MAC_secret[hash_size] client_write_key[Key_material_length] server_write_key[key_material_length] client_write_IV[IV_size] server_write_IV[IV_size] session_key_seed[seed_size= 40] MSCHAPv2 ServerChallenge[16] MSCHAPv2 ClientChallenge[16] The extra key material, session_key_seed is used for the EAP-FAST Crypto-Binding TLV exchange while the ServerChallenge and ClientChallenge correspond to the authentication server's MSCHAPv2 challenge and the peer's MSCHAPv2 challenge respectively. The ServerChallenge and ClientChallenge are only used for the MSCHAPv2 exchange when DH anonymous key agreement is used in the EAP-FAST tunnel establishment. 3.5. Peer-Id, Server-Id and Session-Id The provisioning modes of EAP-FAST does not change the general EAP- FAST protocol and thus how the Peer-Id, Server-Id and Session-Id are determined is based on the [I-D.cam-winget-eap-fast] techniques. [I-D.cam-winget-eap-fast] Section 3.4 describes how the Peer-Id and Server-Id are determined; Section 3.5 describes how the Session-Id is generated. 3.6. Provisioning or Refreshment of a PAC The server may provision or refresh information by use of the Protected Access Credential (PAC) anytime after a successful peer authentication followed by a successful Intermediate Result TLV and Cam-Winget, et al. Expires September 5, 2007 [Page 11] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 Crypto-Binding TLV exchange. A PAC TLV is defined to facilitate the distribution and refreshing of information and is defined in Section 4.2. A fresh PAC may be distributed if the server detects that the PAC is expiring soon. A PAC TLV MUST NOT be accepted if it is not encapsulated in an encrypted TLS tunnel. N.B. In-band PAC refreshing is enforced by server policy. The server, based on the PAC-Opaque information, may determine not to refresh a peer's PAC through the PAC TLV mechanism even if the PAC- Key has expired. Cam-Winget, et al. Expires September 5, 2007 [Page 12] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 4. Information Provisioned in EAP-FAST In addition to the Tunnel PAC (used to establish the EAP-FAST Phase 1 TLS tunnel), other types of credentials and information can also be provisioned through EAP-FAST. They may include trusted root certificates, PACs for specific purposes, and user identities to name a few. Typically, provisioning is invoked after both peer and server validate their authenticity and after a successful Crypto-Binding TLV exchange. However, depending on the information being provisioned, mutual authentication may not be needed. At minimum, either the peer or server must prove authenticity before credentials are provisioned to ensure that information is not freely provisioned to or by adversaries. For example, the EAP server may not need to authenticate the peer to provision the peer with trusted root certificates. However, the peer SHOULD authenticate the server before it can accept a trusted server root certificate. 4.1. Protected Access Credential A Protected Access Credential (PAC) is a security credential provided by the Authentication Server (AS) that holds information specific to a peer. The server distributes all PAC information through the use of a PAC TLV. Different types of PAC information are identified through a PAC Type and PAC attributes defined in this section. The type of PAC described in this document is a Tunnel PAC which is used to establish the EAP-FAST TLS tunnel. The server distributes the Tunnel PAC to the peer which uses it when it attempts to establish a secure EAP-FAST TLS tunnel with the server. The Tunnel PAC conveys the server policy of what must and can occur in the tunnel. The server policy can include EAP methods, TLV exchanges and identities allowed in the tunnel. It is up to the server policy to include what's necessary in a PAC to enforce the policy in subsequent authentications that use the PAC. For example, user identity, I-ID, can be included as the part of the server policy. This I-ID information limits the inner EAP methods to be carried only on the specified user identity. Other types of information can also be included, such as which EAP method(s) and which TLS ciphersuites are allowed. If the server policy is not included in a PAC, then there is no limitation imposed by the PAC usage on the inner EAP methods or user identities inside the tunnel established by the use of that PAC. To request provisioning of a Tunnel PAC, a peer sends a PAC TLV containing a PAC attribute of PAC Type set to '1' (Tunnel PAC Type). The request may be issued after the peer has determined that it has successfully authenticated the EAP Server and validated the Crypto- Cam-Winget, et al. Expires September 5, 2007 [Page 13] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 Binding TLV to ensure that the TLS tunnel's integrity is intact. Since anonymous DH ciphersuites are only used for provisioning, if an anonymous ciphersuite is negotiated the Tunnel PAC is provisioned automatically by the server. A PAC-TLV containing PAC-Acknowledge Attribute MUST be sent by peer to acknowledge the receipt of the Tunnel PAC. Please see Appendix A.1 for an example of packet exchanges to provision a Tunnel PAC. 4.2. PAC TLV Format The PAC TLV provides support for provisioning the Protected Access Credential (PAC) defined within [I-D.cam-winget-eap-fast]. The PAC TLV carries the PAC and related information within PAC attribute fields. Additionally, the PAC TLV MAY be used by the peer to request provisioning of a PAC of the type specified in the PAC Type PAC Attribute. A general PAC TLV format is defined as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |M|R| TLV Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PAC Attributes... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ M 0 - Non-mandatory TLV 1 - Mandatory TLV R Reserved, set to zero (0) TLV Type 11 Length Two octets containing length of the PAC Attributes field in octets Cam-Winget, et al. Expires September 5, 2007 [Page 14] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 PAC Attributes A list of PAC attributes in the TLV format 4.2.1. Formats for PAC Attributes Each PAC Attribute in a PAC TLV is formatted as a TLV defined as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type The type field is two octets, denoting the attribute type Allocated Types include: 1 - PAC-Key 2 - PAC-Opaque 3 - PAC-Lifetime 4 - A-ID 5 - I-ID 6 - Reserved 7 - A-ID-Info 8 - PAC-Acknowledgement 9 - PAC-Info 10 - PAC-Type Length Two octets containing the length of the value field in octets. Value The value of the PAC Attribute Cam-Winget, et al. Expires September 5, 2007 [Page 15] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 4.2.2. PAC-Key The PAC-Key is distributed in a PAC attribute of type PAC-Key. The PAC-Key field is included within the PAC TLV whenever the server wishes to issue or renew a PAC that is bound to a key such as a Tunnel PAC. The key is a randomly generated octet string 32 octets in length. The key is represented as an octet string. The generator of this key is the issuer of the credential, identified by the A-ID. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Key ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 1 - PAC-Key Length 2 octet length representing a 32 octet long key Key The value of the PAC key 4.2.3. PAC-Opaque The PAC-Opaque field is included within the PAC TLV whenever the server wishes to issue or renew a PAC. The PAC-Opaque is opaque to the peer and thus the peer MUST NOT attempt to interpret it. A peer that has been issued a PAC-Opaque by a server stores that data, and presents it back to the server according to its PAC Type. The Tunnel PAC is used in the ClientHello SessionTicket extension field defined in [RFC4507]. If a client has opaque data issued to it by multiple servers, then it stores the data issued by each server separately according to A-ID. This requirement allows the client to maintain and use each opaque data as an independent PAC pairing, with a PAC-Key mapping to a PAC-Opaque identified by the A-ID. As there is a one to one correspondence Cam-Winget, et al. Expires September 5, 2007 [Page 16] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 between PAC-Key and PAC-Opaque, the peer determines the PAC-Key and corresponding PAC-Opaque based on the A-ID provided in the EAP-FAST/ Start message and the A-ID provided in the PAC-Info when it was provisioned with a PAC-Opaque. The PAC-Opaque field format is summarized as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 2 - PAC-Opaque Length The Length filed is two octets, which contains the length of the value field in octets Value The value field contains the actual data for PAC-Opaque. 4.2.4. PAC-Info PAC-Info is comprised of a set of PAC attributes as defined in Section 4.2.1. The PAC-Info attribute MUST contain the A-ID, A-ID- Info, and PAC-Type attributes. Other attributes MAY be included in the PAC-Info to provide more information to the peer. The PAC-Info attribute MUST NOT contain the PAC-Key, PAC-Acknowledgement, PAC-Info or PAC-Opaque attributes. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Attributes... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Cam-Winget, et al. Expires September 5, 2007 [Page 17] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 Type 9 - PAC-Info Length Two octet length field containing the length of the Attributes field in octets Attributes The Attributes field contains a list of PAC Attributes Each mandatory and optional field type is defined as follows: PAC-LIFETIME (type 3) This is a 4 octet quantity representing the expiration time of the credential in UNIX UTC time. This attribute MAY be provided to the peer as part of PAC-Info. A-ID (type 4) A-ID is the identity of the authority that issued the PAC. The A-ID is intended to be unique across all issuing servers to avoid namespace collisions. The A-ID is used by the peer to determine which PAC to employ. This attribute MUST be included in the PAC-Info attribute. I-ID (type 5) Initiator identifier (I-ID) is the peer identity associated with the credential. The server employs the I-ID in the EAP-FAST Phase 2 conversation to validate that the same peer identity used to execute EAP-FAST Phase 1 is also used in at minimum one inner EAP method in EAP-FAST Phase 2. If the AS is enforcing the I-ID validation on inner EAP method, then I-ID MUST be included in PAC-Info, to enable the client to also enforce a unique PAC for each unique user. If I-ID is missing from the PAC-Info, it is assumed that the Tunnel PAC can be used for multiple users and client will not enforce the unique Tunnel PAC per user policy. A-ID-Info (type 7) Authority Identifier Information is a mandatory TLV intended to provide a user-friendly name for the A-ID. It may Cam-Winget, et al. Expires September 5, 2007 [Page 18] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 contain the enterprise name and server name in a human- readable format. This TLV serves as an aid to the peer to better inform the end-user about the A-ID. The name is encoded as UTF-8 [RFC3629] format. This attribute MUST be included in the PAC-Info. PAC-type (type 10) PAC-Type is a mandatory TLV intended to provide the type of PAC. This field SHOULD be included in the PAC-Info. For legacy implementations, if PAC-Type is not present, then it defaults to a Tunnel PAC (Type 1). 4.2.5. PAC-Acknowledgement TLV The PAC-Acknowledgement is used to acknowledge the receipt of the PAC by the peer. The peer includes the PAC-Acknowledgement TLV in a PAC- TLV sent to the server to indicate the result of the processing and storing of a new Tunnel PAC. This TLV is only used when Tunnel PAC is provisioned. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Result | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 8 - PAC-Acknowledgement Length The length of this field is two octets containing a value of 2. Result The resulting value MUST be one of the following: 1 - Success 2 - Failure Cam-Winget, et al. Expires September 5, 2007 [Page 19] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 4.2.6. PAC-Type TLV The PAC-Type TLV is a TLV intended to specify the PAC type. It is included in a PAC-TLV sent by the peer to request PAC provisioning from the server. Its format is described below. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Result | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 10 - PAC-Type Length Two Octet length field with a value of 2 PAC Type This two octet field defined the type of PAC being requested or provisioned. The following values are defined: 1 - Tunnel PAC 4.3. Trusted Server Root Certificate Server-Trusted-Root TLV facilitates the request and delivery of a trusted server root certificates. The Server-Trusted-Root TLV can be exchanged in regular EAP-FAST Authentication mode or Provisioning mode. The Server-Trusted-Root TLV is always marked as optional, and cannot be responded to with a NAK TLV. The Server-Trusted-Root TLV can only be sent as an inner TLV (inside the protection of the tunnel). After the peer has determined that it has successfully authenticated the EAP server and validated the Crypto-Binding TLV, it MAY send one or more Server-Trusted-Root TLVs (marked as optional) to request the trusted server root certificates of from the EAP server. **** why would it send more than one *** The EAP server MAY send one or more root certificates with a PKCS#7 TLV inside Server-Trusted-Root TLV. The EAP server MAY also choose not to honor the request. Please see Cam-Winget, et al. Expires September 5, 2007 [Page 20] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 Section Appendix A.3 for an example of a server provisioning a server trusted root certificate. 4.3.1. Server-Trusted-Root TLV The Server-Trusted-Root TLV allows the peer to send a request to the EAP server for a list of trusted roots. The server may respond with one or more root certificates in PKCS#7 [RFC2315] format. If the EAP server sets credential-format to PKCS#7-Server- Certificate-Root, then the Server-Trusted-Root TLV should contain the root of the certificate chain of the certificate issued to the EAP server packaged in a PKCS#7 TLV. If the Server certificate is a self-signed certificate, then the root is the self-signed certificate. If the Server-Trusted-Root TLV credential format contains a value unknown to the peer, then the EAP peer should ignore the TLV. The Server-Trusted-Root TLV is defined as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |M|R| TLV Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Credential-Format | Cred TLVs... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- M 0 - Non-mandatory TLV R Reserved, set to zero (0) TLV Type 18 Length >=2 octets Cam-Winget, et al. Expires September 5, 2007 [Page 21] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 Credential-Format The Credential-Format field is two octets. Values include: 1 - PKCS#7-Server-Certificate-Root Cred TLVs This field is of indefinite length. It contains TLVs associated with the credential format. In the case of the provision request from the peer it is empty. 4.3.2. PKCS #7 TLV The PKCS#7 TLV is sent by the EAP server to the peer inside the Server-Trusted-Root TLV. It contains the PKCS #7 [RFC2315] wrapped X.509 certificate. This field contains a certificate or certificate chain in PKCS#7 format requested by the peer as defined in [RFC2315]. The PKCS#7 TLV is always marked as optional, which cannot be responded to with a NAK TLV. EAP-FAST server implementations that claim to support the dynamic provisioning defined in this document SHOULD support this TLV. EAP-FAST peer implementations MAY support this TLV. If the PKCS#7 TLV contains a certificate or certificate chain that is not acceptable to the peer, then peer MUST ignore the TLV. The PKCS#7 TLV is defined as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |M|R| TLV Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PKCS #7 Data... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- M 0 - Optional TLV R Reserved, set to zero (0) Cam-Winget, et al. Expires September 5, 2007 [Page 22] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 TLV Type 20 (for PKCS #7 TLV) Length The length of the PKCS #7 Data field PKCS #7 Data This field contains the PKCS #7 wrapped X.509 certificate or certificate chain in the PKCS #7 format. Cam-Winget, et al. Expires September 5, 2007 [Page 23] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 5. Security Considerations The Dynamic Provisioning EAP-FAST protocol shares the same security considerations outlined in [I-D.cam-winget-eap-fast]. Additionally, it also has its unique security considerations described below: 5.1. Mitigation of Dictionary Attacks When EAP-FAST is invoked for provisioning, the peer specifies the means for securing the communications for the provisioning. As such, it can invoke the TLS key agreement in one of two ways: anonymously or server-authenticated. With a server-authenticated TLS key agreement, the server provides its certificate and be authenticated by the peer, whereas in an anonymous TLS key agreement, the server is not authenticated as part of the TLS tunnel establishment. In a server authenticated TLS key agreement, the protected communications is assured that the AS is authentic as the peer must have been pre-provisioned with the AS's trusted root certificate or public key prior to the negotiation. In this instance, the AS provides proof of identity through an identity and (certificate) credential, preventing an adversary from posing as an AS to mount a dictionary attack. An EAP-FAST implementation must assure secure provisioning of the AS public key, certificate or root certificate to the peer. While this follows best security practices, it presents deployment issues as, especially for wireless clients where there is little means to provide secure configuration, peers MUST be configured with a means to validate the server's credential (e.g. public key). In an anonymous DH key agreement, an adversary may attempt to impersonate a client and enable EAP-FAST for provisioning. However, it must successfully authenticate inside the DH tunnel to succeed and gain a PAC credential from a server. Thus, peer impersonation is mitigated through the enabling of peer authentication inside a protected tunnel. However, an adversary may impersonate as a valid AS and obtains the MSCHAPv2 exchanges in order to gain peer's identity and credentials. While the adversary must successfully gain contact with a peer that is willing to negotiate EAP-FAST for provisioning and provide a valid A-ID that a client accepts, this occurrence is feasible and enables an adversary to mount a dictionary attack. With MSCHAPv2, a peer may detect it is under attack when the AS fails to provide a successful MSCHAPv2 server challenge response. By employing the ServerChallenge and ClientChallenge derived during tunnel establishment; detection of a MitM is feasible during the MSCHAPv2 exchange. For this reason, an EAP-FAST compliant implementation MUST support an MSCHAPv2 or stronger EAP method for peer authentication when an anonymous DH key agreement is used for Cam-Winget, et al. Expires September 5, 2007 [Page 24] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 the tunnel establishment. Cleartext passwords MUST NOT be used in anonymous provisioning mode. The peer MAY choose to use a more secure out-of-band mechanism for PAC provisioning that affords better security than the anonymous DH key agreement. Similarly, the peer MAY find a means of pre- provisioning the server's public key or trust root certificate securely to invoke the Server-Authenticated provisioning. The anonymous DH key agreement is presented as a viable option as there may be deployments that can physically confine devices during the provisioning or are willing to accept the risk of an active dictionary attack. Further, it is the only option that enables zero out-of-band provisioning and facilitates simpler deployments requiring little to no peer configuration. 5.2. Mitigation of Man-in-the-middle (MitM) attacks in server- unauthenticated provisioning mode EAP-FAST invocation of provisioning addresses MitM attacks in server- unauthenticated provisioning mode in the following way: o Generating MSCHAPv2 server and client challenges as a function of the DH key agreement: in enforcing the dependence of the MSCHAP challenges on the DH exchange, a MitM is prevented from successfully establishing a secure tunnel with both the peer and legitimate server and succeed in obtaining the PAC credential. o Cryptographic binding of EAP-FAST Phase 1 and the Phase 2 authentication method: by cryptographically binding key material generated in all phases, both peer and AS are assured that they were the sole participants of all transpired phases. The binding of the MSCHAPv2 random challenge derivations to the DH key agreement protocol enables early detection of a MitM attack. This is required to guard from adversaries who may otherwise reflect the inner EAP authentication messages between the true peer and AS and enforces that the adversary successfully respond with a valid challenge response. The cryptographic binding is another reassurance that indeed the true peer and AS were the two parties ensuing both the tunnel establishment and inner EAP authentication conversations. While it would be sufficient to only support the cryptographic binding to mitigate the MitM; the extra precaution of binding the MSCHAP challenge to the DH key agreement affords the client earlier detection of a MitM and further guards the peer from having to respond to the success or failure of the adversary's attempt to Cam-Winget, et al. Expires September 5, 2007 [Page 25] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 respond with a challenge response (e.g. indication of whether the adversary succeeded in breaking the peer's identity and password). A failure in either step, results in no PAC provisioning. EAP-FAST invocation of provisioning using an unauthenticated tunnel can invoke certain procedures to guard implementations for potential MitM attacks. Detectors can be devised to warn the user when the peer encounters error conditions that warrant the likelihood of a MitM. For example, when the MSCHAPv2 server challenge response is never received or fails, the peer implementation can impose policy decisions to warn the user and respond to the likelihood that the failure was due to a MitM attack. Similarly, to guard against attacks in the EAP-FAST Authentication that may force a peer to invoke in-band provisioning, guards and detectors can and should be implemented as part of the EAP-FAST Authentication protocols. 5.3. Mitigation of Man-in-the-middle (MitM) attacks in server- authenticated provisioning mode EAP-FAST provisioning in server-authenticated mode addresses MitM attacks by enforcing the server to present a valid certificate as part of the TLS negotiation. To ensure the authenticity of the server and address MitM attacks, the peer MUST verify the validity of the EAP server certificate to guarantee it is not subject to a MitM attack. The cryptographic binding is another reassurance that indeed the true peer and AS were the two parties communicating in both the tunnel establishment and inner EAP authentication conversations. 5.4. Diffie-Hellman Groups Implementations of EAP-FAST anonymous provisioning modes MUST support the Diffie-Hellman groups defined in [RFC3526]. The security of the DH key exchange is based on the difficulty of solving the Discrete Logarithm Problem (DLP). As algorithms and adversaries become more efficient in their abilities to pre-compute values for a given fixed group, it becomes more important for a server to generate new groups as a means to allay this threat. EAP- FAST servers in closed environments may make use of groups outside [RFC3526]. The server could, for instance, constantly compute new groups in the background. Clients in these environments need to employ proper parameter validation. Such an example is cited in [RFC4419]. Cam-Winget, et al. Expires September 5, 2007 [Page 26] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 The server can maintain a list of safe primes and corresponding generators to choose from. A prime p is safe, if: p = 2q + 1 and q is prime Initial implementations of the EAP-FAST provisioning exchange limit the generator to be 2 as it both improves the multiplication efficiency and still covers half of the space of possible residues. Additionally, since the EAP-FAST provisioning exchange employs DH per [RFC3268] to generate AES keys, the DH keys should provide enough entropy to ensure that a strong 128bit results from the DH key agreement. 5.5. PAC Storage Considerations The main goal of EAP-FAST is to protect the authentication stream over the media link. However, host security is still an issue. Some care should be taken to protect the PAC on both the peer and server. The peer must store securely both the PAC-Key and PAC-Opaque, while the server must secure storage of its security association context used to consume the PAC-Opaque. Additionally, if alternate provisioning is employed, the transportation mechanism used to distribute the PAC must also be secured. Most of the attacks described here would require some level of effort to execute; conceivably greater than their value. The main focus therefore, should be to ensure that proper protections are used on both the client and server. There are a number of potential attacks which can be considered against secure key storage such as: o Weak Passphrases On the peer side, keys are usually protected by a passphrase. On some environments, this passphrase may be associated with the user's password. In either case, if an attacker can obtain the encrypted key for a range of users, he may be able to successfully attack a weak passphrase. The tools are already in place today to allow an attacker to easily attack all email users in an enterprise environment. Most viruses or worms of this sort attract attention to themselves by their action, but that need not be the case. A simple, genuine appearing email could surreptitiously access keys from known locations and email them directly to the attacker, attracting little notice. o Key Finding Attacks Key finding attacks are usually mentioned in reference to web Cam-Winget, et al. Expires September 5, 2007 [Page 27] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 servers, where the private SSL key may be stored securely, but at some point it must be decrypted and stored in system memory. An attacker with access to system memory can actually find the key by identifying their mathematical properties. To date, this attack appears to be purely theoretical and primarily acts to argue strongly for secure access controls on the server itself to prevent such unauthorized code from executing. o Key duplication, Key substitution, Key modification Once keys are accessible to an attacker on either the client or server, they fall under three forms of attack: key duplication, key substitution and key modification. The first option would be the most common, allowing the attacker to masquerade as the user in question. The second option could have some use if an attacker could implement it on the server. Alternatively, an attacker could use one of the latter two attacks on either the peer or server to force a PAC re-key, and take advantage of the potential MitM/dictionary attack vulnerability of the EAP-FAST Server- Unauthenticated Provisioning Mode. Another consideration is the use of secure mechanisms afforded by the particular device. For instance, some laptops enable secure key storage through a special chip. It would be worthwhile for implementations to explore the use of such a mechanism. 5.6. Security Claims The [RFC3748] security claims for EAP-FAST are given in Section 7.8 of [I-D.cam-winget-eap-fast]. When using anonymous provisioning mode there is a greater risk of offline dictionary attack since it is possible for a man-in-the-middle to capture the beginning of the inner MSCHAPv2 conversation. However as noted previously it is possible to detect the man-in-the-middle. Cam-Winget, et al. Expires September 5, 2007 [Page 28] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 6. IANA Considerations This section explains the criteria to be used by the IANA for assignment of Type value in PAC attribute, PAC Type value in PAC- Type TLV, Credential-Format value in Server-Trusted-Root TLV. The "Specification Required" policy is used here with the meaning defined in BCP 26 [RFC2434]. A registry of values is needed for the PAC Attribute types. The initial values to populate the registry are: 1 - PAC-Key 2 - PAC-Opaque 3 - PAC-Lifetime 4 - A-ID 5 - I-ID 6 - Reserved 7 - A-ID-Info 8 - PAC-Acknowledgement 9 - PAC-Info 10 - PAC-Type Values from 10 to 63 are reserved. Values 64 to 255 are assigned with a specification required policy. A registry of values is needed for PAC-Type values used in the PAC- Type TLV. The initial values to populate the registry are: 1 - Tunnel PAC Values from 10 to 63 are reserved. Values 64 to 255 are assigned with a specification required policy. A registry of values is needed for Credential-Format values used in Server-Trusted-Root TLV. The initial values to populate the registry are: 1 - PKCS#7-Server-Certificate-Root Values from 10 to 63 are reserved. Values 64 to 255 are assigned with a specification required policy. Cam-Winget, et al. Expires September 5, 2007 [Page 29] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 7. Acknowledgements The EAP-FAST design and protocol specification is based on the ideas and contributions from Pad Jakkahalli, Mark Krischer, Doug Smith, Ilan Frenkel and Jeremy Steiglitz. Cam-Winget, et al. Expires September 5, 2007 [Page 30] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 8. References 8.1. Normative References [I-D.cam-winget-eap-fast] Salowey, J., "The Flexible Authentication via Secure Tunneling Extensible Authentication Protocol Method (EAP- FAST)", draft-cam-winget-eap-fast-06 (work in progress), January 2007. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 2246, January 1999. [RFC2315] Kaliski, B., "PKCS #7: Cryptographic Message Syntax Version 1.5", RFC 2315, March 1998. [RFC2759] Zorn, G., "Microsoft PPP CHAP Extensions, Version 2", RFC 2759, January 2000. [RFC3268] Chown, P., "Advanced Encryption Standard (AES) Ciphersuites for Transport Layer Security (TLS)", RFC 3268, June 2002. [RFC3526] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP) Diffie-Hellman groups for Internet Key Exchange (IKE)", RFC 3526, May 2003. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003. [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. Levkowetz, "Extensible Authentication Protocol (EAP)", RFC 3748, June 2004. [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, April 2006. [RFC4507] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig, "Transport Layer Security (TLS) Session Resumption without Server-Side State", RFC 4507, May 2006. 8.2. Informative References [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, Cam-Winget, et al. Expires September 5, 2007 [Page 31] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 October 1998. [RFC4419] Friedl, M., Provos, N., and W. Simpson, "Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol", RFC 4419, March 2006. Cam-Winget, et al. Expires September 5, 2007 [Page 32] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 Appendix A. Appendix: Examples A.1. Example 1: Successful Tunnel PAC Provisioning The following exchanges show anonymous DH with a successful EAP- MSCHAPv2 exchange within Phase 2 to provision a Tunnel PAC, the conversation will appear as follows: Authenticating Peer Authenticator ------------------- ------------- <- EAP-Request/ Identity EAP-Response/ Identity (MyID1) -> <- EAP-Request/ EAP-Type=EAP-FAST, V=1 (EAP-FAST Start, S bit set, A-ID) EAP-Response/ EAP-Type=EAP-FAST, V=1 (TLS Client Hello without PAC-Opaque extension)-> <- EAP-Request/ EAP-Type=EAP-FAST, V=1 (TLS Server Hello, TLS Server Key Exchange TLS Finished TLS Server Hello Done) EAP-Response/ EAP-Type=EAP-FAST, V=1 -> (TLS Client Key Exchange TLS Change Cipher Spec, ) <- EAP-Request/ EAP-Type=EAP-FAST, V=1 (TLS Change Cipher Spec TLS Finished) EAP-Response/ EAP-Type=EAP-FAST, V=1 -> (Acknowledgement) TLS channel established (messages sent within the TLS channel) <- EAP Payload TLV, EAP-Request/ EAP Identity Request Cam-Winget, et al. Expires September 5, 2007 [Page 33] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 EAP Payload TLV, EAP-Response/ EAP Identity Response -> <- EAP Payload TLV, EAP-Request, EAP-MSCHAPV2, Challenge EAP Payload TLV, EAP-Response, EAP-MSCHAPV2, Response) -> <- EAP Payload TLV, EAP-Request, EAP-MSCHAPV2, Success) EAP Payload TLV, EAP-Response, EAP-MSCHAPV2, Success) -> <- Intermediate Result TLV (Success) Crypto-Binding-TLV(Version=1, EAP-FAST Version=1, Nonce, CompoundMAC) Intermediate Result TLV (Success) Crypto-Binding-TLV=(Version=1, EAP-FAST Version=1, Nonce, CompoundMAC) <- Result TLV (Success) PAC TLV Result TLV (Success) PAC Acknowledgment -> TLS channel torn down (messages sent in cleartext) <- EAP-Failure A.2. Example 2: Failed Provisioning The following exchanges show a failed EAP-MSCHAPV2 exchange within Phase 2, where the peer failed to authenticate the Server. The conversation will appear as follows: Authenticating Peer Authenticator ------------------- ------------- <- EAP-Request/ Identity EAP-Response/ Identity (MyID1) -> <- EAP-Request/ EAP-Type=EAP-FAST, V=1 Cam-Winget, et al. Expires September 5, 2007 [Page 34] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 (EAP-FAST Start, S bit set, A-ID) EAP-Response/ EAP-Type=EAP-FAST, V=1 (TLS Client Hello without Ticket extension)-> <- EAP-Request/ EAP-Type=EAP-FAST, V=1 (TLS Server Hello TLS Server Key Exchange TLS Server Hello Done) EAP-Response/ EAP-Type=EAP-FAST, V=1 -> (TLS Client Key Exchange TLS Change Cipher Spec, TLS Finished) <- EAP-Request/ EAP-Type=EAP-FAST, V=1 (TLS Change Cipher Spec TLS Finished) EAP-Response/ EAP-Type=EAP-FAST, V=1 -> (Acknowledgement) TLS channel established (messages sent within the TLS channel) <- EAP Payload TLV EAP-Request/EAP Identity Request EAP Payload TLV EAP-Response/ EAP Identity Response -> <- EAP Payload TLV, EAP-Request, EAP-MSCHAPV2, Challenge EAP Payload TLV, EAP-Response, EAP-MSCHAPV2, Response -> <- EAP Payload TLV, EAP-Request, EAP-MSCHAPV2, Success) // peer failed to verify server MSCHAPv2 response EAP Payload TLV, EAP-Response, EAP-MSCHAPV2, Failure) -> Cam-Winget, et al. Expires September 5, 2007 [Page 35] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 <- Result TLV (Failure) Result TLV (Failure) -> TLS channel torn down (messages sent in cleartext) <- EAP-Failure A.3. Example 3: Provisioning a Authentication Server's Trusted Root Certificate The following exchanges show a successful provisioning of a server trusted root certificate using anonymous DH and EAP-MSCHAPV2 exchange within Phase 2, the conversation will appear as follows: Authenticating Peer Authenticator ------------------- ------------- <- EAP-Request/ Identity EAP-Response/ Identity (MyID1) -> <- EAP-Request/ EAP-Type=EAP-FAST, V=1 (EAP-FAST Start, S bit set, A-ID) EAP-Response/ EAP-Type=EAP-FAST, V=1 (TLS Client Hello without Ticket extension)-> <- EAP-Request/ EAP-Type=EAP-FAST, V=1 (TLS Server Hello, (TLS Server Key Exchange TLS Server Hello Done) EAP-Response/ EAP-Type=EAP-FAST, V=1 -> (TLS Client Key Exchange TLS Change Cipher Spec, TLS Finished) <- EAP-Request/ EAP-Type=EAP-FAST, V=1 (TLS Change Cipher Spec TLS Finished) EAP-Payload-TLV[ EAP-Request/Identity]) Cam-Winget, et al. Expires September 5, 2007 [Page 36] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 // TLS channel established (messages sent within the TLS channel) // First EAP Payload TLV is piggybacked to the TLS Finished as Application Data and protected by the TLS tunnel EAP-Payload TLV/ [EAP Identity Response] -> <- EAP Payload TLV, EAP-Request, [EAP-MSCHAPV2, Challenge] EAP Payload TLV, EAP-Response, [EAP-MSCHAPV2, Response] -> <- EAP Payload TLV, EAP-Request, [EAP-MSCHAPV2, Success Request] EAP Payload TLV, EAP-Response, [EAP-MSCHAPV2, Success Response] -> <- Crypto-Binding TLV (Version=1, EAP-FAST Version=1, Nonce, CompoundMAC), Crypto-Binding TLV (Version=1 EAP-FAST Version=1, Nonce, CompoundMAC) Server-Trusted-Root TLV [Type = PKCS#7 ] -> <- Result TLV (Success) Server-Trusted-Root TLV [PKCS#7 TLV] Result TLV (Success) -> // TLS channel torn down (messages sent in cleartext) <- EAP-Failure Cam-Winget, et al. Expires September 5, 2007 [Page 37] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 Authors' Addresses Nancy Cam-Winget Cisco Systems 3625 Cisco Way San Jose, CA 95134 US Email: ncamwing@cisco.com David McGrew Cisco Systems San Jose, CA 95134 US Email: mcgrew@cisco.com Joseph Salowey Cisco Systems 2901 3rd Ave Seattle, WA 98121 US Email: jsalowey@cisco.com Hao Zhou Cisco Systems 4125 Highlander Parkway Richfield, OH 44286 US Email: hzhou@cisco.co Cam-Winget, et al. Expires September 5, 2007 [Page 38] Internet-Draft Dynamic Provisioning using EAP-FAST March 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). 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, THE IETF TRUST 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. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Cam-Winget, et al. Expires September 5, 2007 [Page 39]