--- 1/draft-ietf-dime-erp-04.txt 2010-10-25 20:14:38.000000000 +0200 +++ 2/draft-ietf-dime-erp-05.txt 2010-10-25 20:14:38.000000000 +0200 @@ -1,24 +1,24 @@ Network Working Group J. Bournelle Internet-Draft L. Morand Intended status: Standards Track Orange Labs -Expires: March 10, 2011 S. Decugis, Ed. +Expires: April 25, 2011 S. Decugis, Ed. NICT Q. Wu Huawei G. Zorn, Ed. Network Zen - September 6, 2010 + October 22, 2010 Diameter Support for the EAP Re-authentication Protocol (ERP) - draft-ietf-dime-erp-04.txt + draft-ietf-dime-erp-05.txt Abstract The EAP Re-authentication Protocol (ERP) defines extensions to the Extensible Authentication Protocol (EAP) to support efficient re- authentication between the peer and an EAP Re-authentication (ER) server through a compatible authenticator. This document specifies Diameter support for ERP. It defines a new Diameter ERP application to transport ERP messages between an ER authenticator and the ER server, and a set of new AVPs that can be used to transport the @@ -32,21 +32,21 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." - This Internet-Draft will expire on March 10, 2011. + This Internet-Draft will expire on April 25, 2011. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -56,42 +56,42 @@ the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 3. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4 - 5. Bootstrapping the ER Server . . . . . . . . . . . . . . . . . 6 - 5.1. Bootstrapping During the Initial EAP authentication . . . 6 - 5.2. Bootstrapping During the First Re-authentication . . . . . 8 - 6. Re-Authentication . . . . . . . . . . . . . . . . . . . . . . 10 - 7. Application Id . . . . . . . . . . . . . . . . . . . . . . . . 13 - 8. AVPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 8.1. ERP-RK-Request AVP . . . . . . . . . . . . . . . . . . . . 13 - 8.2. ERP-Realm AVP . . . . . . . . . . . . . . . . . . . . . . 13 - 8.3. Key AVP . . . . . . . . . . . . . . . . . . . . . . . . . 14 - 8.3.1. Key-Type AVP . . . . . . . . . . . . . . . . . . . . . 14 - 8.3.2. Keying-Material AVP . . . . . . . . . . . . . . . . . 14 - 8.3.3. Key-Name AVP . . . . . . . . . . . . . . . . . . . . . 14 - 8.3.4. Key-Lifetime AVP . . . . . . . . . . . . . . . . . . . 14 - 9. Open issues . . . . . . . . . . . . . . . . . . . . . . . . . 14 - 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 - 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 - 11.1. Diameter Application Identifier . . . . . . . . . . . . . 15 - 11.2. New AVPs . . . . . . . . . . . . . . . . . . . . . . . . . 15 - 12. Security Considerations . . . . . . . . . . . . . . . . . . . 16 - 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 - 13.1. Normative References . . . . . . . . . . . . . . . . . . . 16 - 13.2. Informative References . . . . . . . . . . . . . . . . . . 17 + 5. Bootstrapping the ER Server . . . . . . . . . . . . . . . . . 5 + 5.1. Bootstrapping During the Initial EAP authentication . . . 5 + 5.2. Bootstrapping During the First Re-authentication . . . . . 7 + 6. Re-Authentication . . . . . . . . . . . . . . . . . . . . . . 9 + 7. Application Id . . . . . . . . . . . . . . . . . . . . . . . . 11 + 8. AVPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 + 8.1. ERP-RK-Request AVP . . . . . . . . . . . . . . . . . . . . 12 + 8.2. ERP-Realm AVP . . . . . . . . . . . . . . . . . . . . . . 12 + 8.3. Key AVP . . . . . . . . . . . . . . . . . . . . . . . . . 12 + 8.3.1. Key-Type AVP . . . . . . . . . . . . . . . . . . . . . 12 + 8.3.2. Keying-Material AVP . . . . . . . . . . . . . . . . . 12 + 8.3.3. Key-Name AVP . . . . . . . . . . . . . . . . . . . . . 12 + 8.3.4. Key-Lifetime AVP . . . . . . . . . . . . . . . . . . . 13 + 9. Open issues . . . . . . . . . . . . . . . . . . . . . . . . . 13 + 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 + 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 + 11.1. Diameter Application Identifier . . . . . . . . . . . . . 14 + 11.2. New AVPs . . . . . . . . . . . . . . . . . . . . . . . . . 14 + 12. Security Considerations . . . . . . . . . . . . . . . . . . . 14 + 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 + 13.1. Normative References . . . . . . . . . . . . . . . . . . . 15 + 13.2. Informative References . . . . . . . . . . . . . . . . . . 16 1. Introduction RFC 5296 [RFC5296] defines the EAP Re-authentication Protocol (ERP). It consists of the following steps: Bootstrapping A root key for re-authentication is derived from the Extended Master Session Key (EMSK) created during EAP authentication [RFC5295]. This root key is transported from the EAP server to @@ -157,83 +157,62 @@ +-------------+ +-----------+ | server | +--------+ (*) Diameter EAP application, explicit bootstrapping scenario only. Figure 1: Diameter ERP Overview The ER server is located either in the home domain (same as EAP server) or in the visited domain (same as authenticator, when it differs from the home domain). - QUESTION: - Can the ER server be located in a third domain (ex: broker's) - according to ERP mechanism? - When the peer initiates an ERP exchange, the authenticator creates a Diameter-EAP-Request message [RFC4072]. The Application Id of the message is set to that of the Diameter ERP application (code: TBD) in the message. The generation of the ERP/DER message is detailed in Section 6. If there is an ER server in the same domain as the authenticator - (local domain), Diameter routing MUST - - QUESTION: - Should this say "SHOULD: instead of "MUST"? - - be configured so that this ERP/DER message reachs this server, even - if the Destination-Realm is not the local domain. + (local domain), Diameter routing must be configured so that this ERP/ + DER message reachs this server, even if the Destination-Realm is not + the local domain. If there is no local ER server, the message is routed according to its Destination-Realm AVP content, extracted from the realm component of the keyName-NAI attribute. As specified in RFC 5296 [RFC5296], this realm is the home domain of the peer in case of a bootstrapping exchange (the 'B' flag is set in the ERP message) or the domain of the bootstrapped ER server otherwise. - NOTE: - This actually might allow the ER server to be in a third party - realm. - If no ER server is available in the home domain either, the ERP/DER message cannot be delivered, and an error DIAMETER_UNABLE_TO_DELIVER is generated [RFC3588] and returned to the authenticator. The authenticator may cache this information (with limited duration) to avoid further attempts for ERP with this realm. It may also fallback to full EAP authentication to authenticate the peer. When an ER server receives the ERP/DER message, it searches its local - database for a root key - - FFS: - and authorization state? - - matching the keyName part of the User-Name AVP. If such key is - found, the ER server processes the ERP message as described in RFC - 5296 [RFC5296] then creates the ERP/DEA answer as described in - Section 6. The rMSK is included in this answer. + database for a root key matching the keyName part of the User-Name + AVP. If such key is found, the ER server processes the ERP message + as described in RFC 5296 [RFC5296] then creates the ERP/DEA answer as + described in Section 6. The rMSK is included in this answer. Finally, the authenticator extracts the rMSK from the ERP/DEA as described in RFC 5296 [RFC5296], and forwards the content of the EAP- Payload AVP, the EAP-Finish/Re-Auth message, to the peer. If the EAP-Initiate/Re-Auth message has its 'B' flag set (Bootstrapping exchange), the ER server should not possess the root - key in its local database - - COMMENT: - This may not be true in future RFC5296bis? - - In this case, the ER server acts as a proxy, and forwards the message - to the home EAP server after changing its Application Id to Diameter - EAP and adding an AVP to request the root key. See Section 5 for - more detail on this process. + key in its local database. In this case, the ER server acts as a + proxy, and forwards the message to the home EAP server after changing + its Application Id to Diameter EAP and adding the ERP-RK-Request AVP + to request the root key. See Section 5 for more detail on this + process. 5. Bootstrapping the ER Server The bootstrapping process involves the home EAP server and the ER server, but also impacts the peer and the authenticator. In ERP, the peer must derive the same keying material as the ER server. To achieve this, it must learn the domain name of the ER server. How this information is acquired is outside the scope of this specification, but it may involves that the authenticator is configured to advertize this domain name, especially in the case of @@ -248,27 +227,26 @@ 5.1. Bootstrapping During the Initial EAP authentication Bootstrapping the ER server during the initial EAP authentication (also known as implicit bootstrapping) offers the advantage that the server is immediatly available for re-authentication of the peer, thus minimizing re-authentication delay. On the other hand, it is possible that only a small number of peers will use re-authentication in the visited domain. Deriving and caching key material for all the peers (for example, for the peers that do not support ERP) is a waste - of resources and SHOULD be avoided. + of resources and should be avoided. - To achieve implicit bootstrapping, the ER server must act as a - Diameter EAP Proxy as defined in the Diameter Base Protocol - [RFC3588], and routing must be configured so that Diameter messages - of a full EAP authentication are routed through this proxy. The - figure bellow illustrates this mechanism. + To achieve implicit bootstrapping, the ER server acts as a Diameter + EAP Proxy, and Diameter routing must be configured so that Diameter + EAP application messages are routed through this proxy. The figure + bellow illustrates this mechanism. ER server & Authenticator EAP Proxy Home EAP server ============= =========== =============== -------------------------> Diameter EAP/DER (EAP-Response) -------------------------> Diameter EAP/DER (EAP-Response) @@ -285,254 +263,216 @@ <------------------------- Diameter EAP/DEA (EAP-Success) (MSK) [ERP-Realm] Figure 2: ERP Bootstrapping During Full EAP Authentication The ER server proxies the first DER of the full EAP authentication and adds the ERP-RK-Request AVP inside, if this AVP is not already in - the message (which might happen if there are ER servers in the - visited and the home domains), then forwards the request. + the message (which might happen if there are several ER servers on + the path), then forwards the request. - If the EAP server does not support the ERP extensions, it will simply - ignore this grouped AVP and continue as specified in RFC 4072 - [RFC4072]. If the server supports the ERP extensions, it caches the - ERP-Realm value with the session data, and continues the EAP - authentication. When the authentication is complete, if it is - successful and the EAP method generated an EMSK, the server MUST - derive the rRK as specified in RFC 5296 [RFC5296], and include an - instance of the Key AVP Section 8.3 in the Diameter-EAP-Answer - message. + If the EAP server does not support the ERP extensions, it simply + ignores the ERP-RK-Request AVP and continues as specified in RFC 4072 + [RFC4072]. If the server supports the ERP extensions, it saves the + value of the ERP-Realm AVP found inside the ERP-RK-Request AVP, and + continues with the EAP authentication. When the authentication + completes, if it is successful and the EAP method has generated an + EMSK, the server MUST derive the rRK as specified in RFC 5296 + [RFC5296], using the saved domain name. It then includes the rRK + inside a Key AVP Section 8.3 with the Key-Type AVP set to rRK, before + sending the DEA as usual. When the ER server proxies a Diameter-EAP-Answer message with a Session-Id corresponding to a message to which it added an ERP-RK- - Answer, and the Result-Code is DIAMETER_SUCCESS, it MUST examine the - message, extract and remove any Key AVP Section 8.3 from the message, - and save its content. If the message does not contain an ERP-RK- - Answer AVP, the ER server MAY cache this information to avoid - possible subsequent re-authentication attempts for this session. In - any case, the information stored SHOULD NOT have a lifetime greater - than the EMSK lifetime - - QUESTION: - How does the ER server knows the EMSK lifetime, if there is no - ERP-RK-Answer? What is the lifetime of the MSK for example? - - If the ER server is successfully bootstrapped, it MAY also add the - ERP-Realm AVP after removing the ERP-RK-Answer AVP in the EAP/DEA - message. This could be used by the authenticator to notify the peer - that ERP is bootstrapped, with the ER domain information. How this - information can be transmitted to the peer is outside the scope of - this document. + Request AVP, and the Result-Code is DIAMETER_SUCCESS, it MUST examine + the message and save and remove any Key AVP Section 8.3 with Key-Type + AVP set to rRK. If the message does not contain such Key AVP, the ER + server may cache the information that ERP is not possible for this + session to avoid possible subsequent attempts. In any case, the + information stored in ER server concerning a session should not have + a lifetime greater than the EMSK for this session. - QUESTION: - Is this possible? It might be useful... + If the ER server is successfully bootstrapped, it should also add the + ERP-Realm AVP after removing the Key AVP with Key-Type of rRK in the + EAP/DEA message. This ERP-Realm information can be used by the + authenticator to notify the peer that ER server is bootstrapped, and + for which domain. How this information can be transmitted to the + peer is outside the scope of this document. This information needs + to be sent to the peer if both implicit and explicit bootstrapping + mechanisms are possible, because the ERP message and the root key + used for protecting this message are different in bootstrapping + exchanges and non-bootstrapping exchanges. 5.2. Bootstrapping During the First Re-authentication Bootstrapping the ER server during the first re-authentication (also - known as explicit bootstrapping) offers several advantages: it saves - resources, since we generate and cache only root keys that we - actually need, and it can accomodate inter-domain handovers or ER - servers that lose their state (for example after reboot). - - COMMENT: - This last point might not be true currently, since the peer would - not issue a bootstrapping exchange... But this might change also - with RFC5296bis AFAIU - - On the other hand, the first re-authentication with the ER server - requires a one-round-trip exchange with the home EAP server, which - adds some delay to the process (but it is more efficient than a full - EAP authentication in any case). It also requires some - synchronization between the peer and the visited domain: since the - ERP message used is different - - QUESTION: - and the root key used also? - - for the explicit bootstrapping exchange than for normal re- - authentication; explicit bootstrapping should not be used if implicit - bootstrapping was already performed. - - QUESTION: - What should we do if the ER server receives an explicit - bootstrapping request but already possess the rDSRK? Can it - answer without going to the home server? That would be simpler -- - planned in rfc5296bis ? + known as explicit bootstrapping) is less resource-consuming, since + root keys are generated and cached only when needed. On the other + hand, in that case first re-authentication requires a one-round-trip + exchange with the home EAP server, which is less efficient than the + implicit bootstrapping scenario. The ER server receives the ERP/DER message containing the EAP- Initiate/Re-Auth message with the 'B' flag set. It proxies this message, and performs the following processing in addition to standard proxy operations: Changes the Application Id in the header of the message to Diameter EAP Application (code 5). Change the content of Application-Auth-Id accordingly. QUESTION: - Is t better to leave it unmodified? + Is it better to leave it unmodified, so that the server can + easily differenciate between ERP and standard EAP message ? Add the ERP-RK-Request AVP, which contains the name of the domain where the ER server is located. - QUESTION: - Add the Destination-Host to reach the appropriate EAP server, - the one with the EMSK. How does the ER server know this - information? + PROBLEM: + Add the Destination-Host AVP to reach the appropriate Diameter + EAP server in case there is more than one in destination + domain, the one with the EMSK. How does the ER server know + this information? Or can we require that all Diameter EAP + servers can be used interchangeably for this purpose? - Then the server forwards the EAP/DER request, which is routed to the - home EAP server. + Then the proxied EAP/DER request is sent and routed to the home + Diameter EAP server. If the home EAP server does not support the ERP extensions, it replies with an error since the encapsulated EAP-Initiate/Re-auth command is not understood. Otherwise, it processes the ERP request as described in [RFC5296]. In particular, it includes the Domain- Name TLV attribute with the content from the ERP-Realm AVP. It creates the EAP/DEA reply message [RFC4072]. including an instance of - the Key AVP Section 8.3. - - QUESTION: - What about authorization AVPs? + the Key AVP Section 8.3 with Key-Type AVP set to rRK. The ER server receives this EAP/DEA and proxies it as follows, in addition to standard proxy operations: - Set the Application Id back to Diameter ERP (code TBD) - - Extract and cache the content of the Key AVP. + Set the Application Id back to Diameter ERP application Id (code + TBD) - QUESTION: - And authorization AVPs ? + Extract and cache the content of the Key AVP with Key-Type set to + rRK, as described in implicit scenario. - The DEA is then forwarded to the authenticator, that can use the rMSK - as described in RFC 5296 [RFC5296]. + The ERP/DEA message is then forwarded to the authenticator, that can + use the rMSK as described in RFC 5296 [RFC5296]. The figure below captures this proxy behavior: Authenticator ER server Home EAP server ============= ========= =============== -----------------------> Diameter ERP/DER (EAP-Initiate) ------------------------> Diameter EAP/DER (EAP-Initiate) (ERP-RK-Request) <------------------------ Diameter EAP/DEA (EAP-Finish) - (Key AVP) + (Key AVP (rRK)) + (Key AVP (rMSK)) <---------------------- Diameter ERP/DEA (EAP-Finish) - (Key AVP) + (Key AVP (rMSK)) Figure 3: ERP Explicit Bootstrapping Message Flow 6. Re-Authentication - This section describes in detail a re-authentication exchange with a - (bootstrapped) ER server. The following figure summarizes the re- - authentication exchange. + This section describes in detail a re-authentication exchange with an + ER server that was previously bootstrapped. The following figure + summarizes the re-authentication exchange. ER server - (bootstrapped) - Peer Authenticator (local or home domain) + Peer Authenticator (bootstrapped) ==== ============= ====================== [ <------------------------ ] - [optional EAP-Initiate/Re-auth-start] + [optional EAP-Initiate/Re-auth-start,] + [ possibly with ERP domain name ] -----------------------> EAP-Initiate/Re-auth ===============================> Diameter ERP, cmd code DER User-Name: Keyname-NAI EAP-Payload: EAP-Initiate/Re-auth <=============================== Diameter ERP, cmd code DEA EAP-Payload: EAP-Finish/Re-auth Key AVP: rMSK <---------------------- EAP-Finish/Re-auth Figure 4: Diameter ERP Re-authentication Exchange - In ERP, the peer sends an EAP-Initiate/Re-auth message to the ER - server via the authenticator. Alternatively, the authenticator may - send an EAP-Initiate/Re-auth-Start message to the peer to trigger the - start of ERP. In this case, the peer responds with an EAP-Initiate/ - Re-auth message. + The peer sends an EAP-Initiate/Re-auth message to the ER server via + the authenticator. Alternatively, the authenticator may send an EAP- + Initiate/Re-auth-Start message to the peer to trigger the mechanism. + In this case, the peer responds with an EAP-Initiate/Re-auth message. - If the authenticator does not support ERP (pure [RFC4072] support), - it discards the EAP packets with an unknown ERP-specific code (EAP- - Initiate). The peer may fallback to full EAP authentication in this - case. + If the authenticator does not support ERP (pure Diameter EAP + [RFC4072] support), it discards the EAP packets with an unknown ERP- + specific code (EAP-Initiate). The peer should fallback to full EAP + authentication in this case. When the authenticator receives an EAP-Initiate/Re-auth message from - the peer, it process as described in [RFC5296] with regards to the + the peer, it processes as described in [RFC5296] with regards to the EAP state machine. It creates a Diameter EAP Request message following the general process of DiameterEAP [RFC4072], with the following differences: The Application Id in the header is set to Diameter ERP (code TBD). The value in Auth-Application-Id AVP is also set to Diameter ERP Application. The keyName-NAI attribute from ERP message is used to create the content of User-Name AVP and Destination-Realm AVP. FFS: - What about Session-ID AVP -- in case of re-auth at the same - place, and in case of handover? - - The Auth-Request-Type AVP content is set to [Editor's note: FFS]. + What about Session-ID AVP ? - QUESTION: - Do we really do authorization with Diameter ERP ? -- need to - pass the authorization attrs to the ER server in that case. - Idea FFS: we do authorization only for explicit bootstrapping - exchanges... + The Auth-Request-Type AVP content is set to [Editor's note: FFS -- + cf. open issues]. - The EAP-Payload AVP contains the ERP message, EAP-Initiate/ - Re-Auth. + The EAP-Payload AVP contains the EAP-Initiate/Re-Auth message. Then this ERP/DER message is sent as described in Section 4. The ER server receives and processes this request as described in Section 4. It then creates an ERP/DEA message following the general processing described in RFC 4072 [RFC4072], with the following differences: The Application Id in the header is set to Diameter ERP (code TBD). The value of the Auth-Application-Id AVP is also set to Diameter ERP Application. - The EAP-Payload AVP contains the ERP message, EAP-Finish/Re-auth. + The EAP-Payload AVP contains the EAP-Finish/Re-auth message. In case of successful authentication, an instance of the Key AVP containing the Re-authentication Master Session Key (rMSK) derived by ERP is included. - QUESTION: - What about all the authorization attributes? If we want to - include them, they have to be present on the ER server... - When the authenticator receives this ERP/DEA answer, it processes it as described in Diameter EAP [RFC4072] and RFC 5296 [RFC5296]: the content of EAP-Payload AVP content is forwarded to the peer, and the contents of the Keying-Material AVP [I-D.ietf-dime-local-keytran] is used as a shared secret for Secure Association Protocol. 7. Application Id We define a new Diameter application in this document, Diameter ERP Application, with an Application Id value of TBD. Diameter nodes @@ -562,88 +502,94 @@ { ERP-Realm } * [ AVP ] Figure 5: ERP-RK-Request ABNF 8.2. ERP-Realm AVP The ERP-Realm AVP (AVP Code TBD) is of type DiameterIdentity. It contains the name of the realm in which the ER server is located. - FFS: - We may re-use Origin-Realm here instead? On the other hand, ERP- - Realm may be useful if the ER server is in a third-party realm, if - this is possible. - This AVP has the M and V bits cleared. 8.3. Key AVP The Key AVP [I-D.ietf-dime-local-keytran] is of type "Grouped" and is - used to carry the rMSK and associated attributes. The usage of the - Key AVP and its constituent AVPs in this application is specified in - the following sub-sections. + used to carry the rRK or rMSK and associated attributes. The usage + of the Key AVP and its constituent AVPs in this application is + specified in the following sub-sections. 8.3.1. Key-Type AVP - The value of the Key-Type AVP MUST be set to 3 for rRK. + The value of the Key-Type AVP MUST be set to 2 for rRK or 3 for rMSK. 8.3.2. Keying-Material AVP The Keying-Material AVP contains rRK sent by the home EAP server to the ER server, in answer to a request containing an ERP-RK-Request - AVP. How this material is derived and used is specified in RFC 5296 - [RFC5296]. + AVP, or the rMSK sent by ER server to authenticator. How this + material is derived and used is specified in RFC 5296 [RFC5296]. 8.3.3. Key-Name AVP This AVP contains the EMSKname which identifies the keying material. The derivation of this name is specified in RGC 5296 [RFC5296]. 8.3.4. Key-Lifetime AVP The Key-Lifetime AVP contains the lifetime of the keying material in seconds. It MUST NOT be greater than the remaining lifetime of the EMSK from which the material was derived. 9. Open issues This document does not address some known issues in Diameter ERP mechanism. The authors would like to hear ideas about how to address them. The main issue is the use of ERP for authentication after a handover of the peer to a new authenticator (or different authenticator port). - Diameter ERP is not meant to be a mobility protocol. A number of - issues appear when we try to do handover in Diameter ERP (alone): how - to manage the Session-Id AVP; how does the ER server provide the - Authorization AVPs; how does the peer learn the ERP domain of the new - authenticator; how does the home server reachs the peer to for - example terminate the session; and so on... Therefore, the - management of the session for a mobile peer is not (yet) addressed in - this document. It must be studied how Diameter ERP can be for - example used in conjunction with a mobility application (Diameter - MIP4, Diameter MIP6) to support the optimized re-authentication in - such situation. + Diameter ERP is not meant to be a mobility application. A number of + issues appear when we try to do handover while using Diameter ERP: + + how to manage the Session-Id AVP -- is it a new session each time, + or do we try to reuse the same Diameter session?; + + how does the ER authenticator acquire the Authorization AVPs? Is + it cached in the Diameter ER server (received during + bootstrapping) or do we use first Authenticate-Only with ER + server, then Authorize-Only with home domain (and in that case how + does the ER authenticator learn what the home domain is?) + + how does the peer learn the ERP domain of the new authenticator -- + this is being addressed in HOKEY architecture draft; + + how does the home server reachs the peer to for example terminate + the session if there is no notification sent to the home domain; Another issue concerns the case where the home realm contains several EAP servers. In multi rounds full EAP authentication, the Destination-Host AVP provides the solution to reach the same server across the exchanges. Only this server possess the EMSK for the session. In case of explicit bootstrapping, the ER server must therefore be able to reach the correct server to request the DSRK. A solution might consist in saving the Origin-Host AVP of all successful EAP/DEA in the ER server, which is a bit similar to the implicit bootstrapping scenario described here -- only we save the server name instead of the root key, and we must then be able to match the DSRK with the user name. + In roaming environments, it might be useful that a broker provides + ERP services. The security implications of storing the DSRK + generated for the visited domain into the broker's server should be + studied. + Finally, this document currently lacks a description of what happens when a Re-Auth-Request is received for a peer on the authenticator. 10. Acknowledgements Hannes Tschofenig wrote the initial draft for this document and provided useful reviews. Vidya Narayanan reviewed a rough draft version of the document and found some errors. @@ -686,44 +633,45 @@ o RFC 4072 [RFC4072] o RFC 5247 [RFC5247] o RFC 5295 [RFC5295] o [RFC5296] FFS: Do we really respect these security considerations with the - mechanism we describe here? Is it safe to use ERP-RK-Request / - Answer AVPs? What is the worst case? + mechanism we describe here? Is it safe to use ERP-RK-Request & + Key AVPs? What is the worst case? For example if a domain tricks + the peer into beliving it is located in a different domain? EAP channel bindings may be necessary to ensure that the Diameter client and the server are in sync regarding the key Requesting Entity's Identity. Specifically, the Requesting Entity advertises its identity through the EAP lower layer, and the user or the EAP peer communicates that identity to the EAP server (and the EAP server communicates that identity to the Diameter server) via the EAP method for user/peer to server verification of the Requesting Entity's Identity. QUESTION: What does this paragraph actually mean? 13. References 13.1. Normative References [I-D.ietf-dime-local-keytran] Zorn, G., Wu, W., and V. Cakulev, "Diameter Attribute-Value Pairs for Cryptographic Key Transport", - draft-ietf-dime-local-keytran-07 (work - in progress), June 2010. + draft-ietf-dime-local-keytran-08 (work + in progress), October 2010. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. Arkko, "Diameter Base Protocol", RFC 3588, September 2003.