Mercurial > hg > ietf
changeset 34:e34f7869b4a1
Initial revision submitted for comments to other authors
| author | Sebastien Decugis <sdecugis@nict.go.jp> |
|---|---|
| date | Fri, 28 Aug 2009 10:27:21 +0900 |
| parents | e883979bfbab |
| children | fa5b03196871 |
| files | draft-ietf-dime-erp-01.xml |
| diffstat | 1 files changed, 870 insertions(+), 0 deletions(-) [+] |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/draft-ietf-dime-erp-01.xml Fri Aug 28 10:27:21 2009 +0900 @@ -0,0 +1,870 @@ +<?xml version="1.0" encoding="US-ASCII"?> +<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [ +<!ENTITY RFC2119 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml"> +<!ENTITY RFC3748 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3748.xml"> +<!ENTITY RFC3588 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3588.xml"> +<!ENTITY RFC4072 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4072.xml"> +<!ENTITY RFC4187 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4187.xml"> +<!ENTITY RFC5247 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5247.xml"> +<!ENTITY RFC5295 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5295.xml"> +<!ENTITY RFC5296 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5296.xml"> +<!ENTITY I-D.ietf-hokey-key-mgm SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-hokey-key-mgm-06.xml"> +<!ENTITY I-D.ietf-dime-app-design-guide SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-dime-app-design-guide-08.xml"> +<!ENTITY I-D.gaonkar-radext-erp-attrs SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-gaonkar-radext-erp-attrs-03.xml"> +<!ENTITY I-D.ietf-dime-erp SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-dime-erp-00.xml"> +<!ENTITY I-D.wu-dime-local-keytran SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-wu-dime-local-keytran-00.xml"> +<!ENTITY nbsp " "> +]> +<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?> +<?rfc strict="yes"?> +<?rfc comments="yes"?> +<?rfc inline="yes"?> +<?rfc editing="no"?> +<?rfc toc="yes"?> +<?rfc tocompact="yes"?> +<?rfc tocdepth="3"?> +<?rfc symrefs="yes"?> +<?rfc sortrefs="yes"?> +<?rfc compact="yes"?> +<?rfc subcompact="no"?> +<?rfc rfcedstyle="yes"?> +<?rfc rfcprocack="no"?> +<?rfc tocindent="yes"?> +<rfc category="std" docName="draft-ietf-dime-erp-01.txt" ipr="trust200902"> + <front> + <title abbrev="Diameter support for ERP">Diameter support for EAP + Re-authentication Protocol (ERP)</title> + + <author fullname="Lakshminath Dondeti" initials="L" surname="Dondeti"> + <organization>QUALCOMM, Inc.</organization> + + <address> + <postal> + <street>5775 Morehouse Dr</street> + + <city>San Diego</city> + + <region>CA</region> + + <country>USA</country> + </postal> + + <phone>+1 858-845-1267</phone> + + <email>ldondeti@qualcomm.com</email> + </address> + </author> + + <author fullname="Julien Bournelle" initials="J." surname="Bournelle"> + <organization abbrev="Orange Labs">Orange Labs</organization> + + <address> + <postal> + <street>38-40 rue du general Leclerc</street> + + <city>Issy-Les-Moulineaux</city> + + <code>92794</code> + + <country>France</country> + </postal> + + <email>julien.bournelle@orange-ftgroup.com</email> + </address> + </author> + + <author fullname="Lionel Morand" initials="L." surname="Morand"> + <organization abbrev="Orange Labs">Orange Labs</organization> + + <address> + <postal> + <street>38-40 rue du general Leclerc</street> + + <city>Issy-Les-Moulineaux</city> + + <code>92794</code> + + <country>France</country> + </postal> + + <email>lionel.morand@orange-ftgroup.com</email> + </address> + </author> + + <author fullname="Sebastien Decugis" initials="S." role="editor" + surname="Decugis"> + <organization abbrev="NICT">NICT</organization> + + <address> + <postal> + <street>4-2-1 Nukui-Kitamachi</street> + + <city>Tokyo</city> + + <code>184-8795</code> + + <country>Koganei, Japan</country> + </postal> + + <email>sdecugis@nict.go.jp</email> + </address> + </author> + + <date year="2009" /> + + <area>Operations & Management</area> + + <workgroup>Diameter Maintenance and Extensions (DIME)</workgroup> + + <keyword>Internet-Draft</keyword> + + <keyword>EAP</keyword> + + <keyword>Diameter</keyword> + + <keyword>Re-authentication</keyword> + + <keyword>inter-authenticator roaming</keyword> + + <abstract> + <t>EAP Re-authentication Protocol (ERP) defines extensions to the + Extensible Authentication Protocol (EAP) to support efficient + re-authentication between the EAP peer and an EAP re-authentication + server through an EAP/ERP authenticator. This document specifies + Diameter support for ERP. It defines a new Diameter ERP application to + transport ERP messages between authenticator and ERP server, and a set + of new AVPs that can be used to transport the cryptographic material + needed by ERP server.</t> + </abstract> + </front> + + <middle> + <section anchor="Introduction" title="Introduction"> + <t><xref target="RFC5296"></xref> defines the EAP Re-authentication + Protocol (ERP). It consists in the following steps:<list style="numbers"> + <t>Bootstrapping: a root key for re-authentication is derived from + the Extended Master Session Key (EMSK) created during EAP + authentication <xref target="RFC5295"></xref>. This root key is + transported from the EAP server to the ER server.</t> + + <t>Re-authentication: a one-round-trip exchange between the peer and + the ER server, resulting in mutual authentication. To accomplish the + EAP reauthentication functionality, ERP defines two new EAP codes - + EAP-Initiate and EAP-Finish.</t> + </list></t> + + <t>This document defines how Diameter transports the ERP messages + (Re-authentication step). For this purpose, we define a new Application + Id for ERP, and re-use the Diameter EAP commands (DER/DEA).</t> + + <t>This document also discusses the distribution of the root key + (bootstrapping step), either during the initial EAP authentication + (implicit bootstrapping) or during the first ERP exchange (explicit + bootstrapping). Security considerations for this key distribution are + detailed in <xref target="RFC5295"></xref>.</t> + + <section title="Differences with previous version"> + <t>In this version, the main difference is that we define a new + Diameter Application for ERP. This allows the routing of Diameter + messages containing ERP payload to the appropriate realm and server, + and permits more flexibility in the deployment of ERP : with the + previous design from version -00, the ER server had to be collocated + with the EAP server (Editor's note: well, it was not written clearly + in the document, but it was the only working situation), which might + result in some deployment and scalability issues.</t> + + <t>The format of the newly defined AVP has also changed: we now define + two grouped AVP to transport the key request and key material. Grouped + AVP allow a more efficient parsing of the message, and keeps the + correlation of related information such as key name, key + lifetime...</t> + </section> + </section> + + <section title="Terminology"> + <t>This document uses terminology defined in <xref + target="RFC3748"></xref>, <xref target="RFC5295"></xref>, <xref + target="RFC5296"></xref>, and <xref target="RFC4072"></xref>.</t> + + <t>"Root key" (RK) or "bootstrapping material" refer to the rRK or rDSRK + derived from an EMSK, depending on the location of the ER server in home + or foreign domain.</t> + + <t>We note in this document ERP/DER a Diameter-EAP-Request command with + the Application Id set to Diameter ERP application. On the same model, + we use ERP/DEA, EAP/DER and EAP/DEA.</t> + + <section title="Requirements Language"> + <t>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 <xref + target="RFC2119"></xref>.</t> + </section> + </section> + + <section title="Assumptions"> + <t>This document makes the following assumptions.</t> + + <t>The Home EAP server of a peer that wants to use ERP is extended to + support:<list> + <t>Cryptographic operations needed to derive the ERP root key from + the EMSK. By deriving the ERP root key for a specific domain, the + home EAP server implicitly authorizes the use of ERP within this + domain.</t> + + <t>Diameter operations to include this root key inside an + appropriate AVP as defined in this document, in an answer message + corresponding to a request that contained a request for this + material (AVP for the request also defined in this document).</t> + + <t>(recommanded) Ability to answer a DER message with EAP-Payload + containing an explicit bootstrapping ERP message.</t> + </list></t> + + <t>The Authenticator (NAS) is extended to support:<list> + <t>Allow the new ERP command codes (EAP-Initiate and EAP-Finish) in + its EAP pass-through mode.</t> + + <t>(optional) Send the EAP-Initiate/Re-Auth-Start message</t> + + <t>(optional) Provide the local domain name via lower layer specific + mechanism or via TLV in the EAP-Initiate/Re-Auth-Start message.</t> + + <t>Encapsulate ERP message and receive corresponding Diameter + answer, as described in this document.</t> + </list></t> + + <t>If one of the components does not match these assumptions, the ERP + mechanism will fail. In such situation, a full EAP authentication may be + attempted as a fallback mechanism.</t> + + <t>We consider at most one logical ER server entity in a domain. If + several physical servers are deployed for robustness, a replication + mechanism must be deployed to synchronize the ERP states (root keys, + <cref>FFS: authorization attributes</cref> ) between these servers. This + replication mechanism is out of the scope of this document. If several + ER servers are deployed in the domain, we assume that they can be used + interchangeably.</t> + </section> + + <section anchor="Overview" title="Protocol Overview"> + <t>The following figure shows the components involved in ERP, and their + interactions.</t> + + <figure title="Figure. Diameter ERP overview."> + <artwork><![CDATA[ + Diameter +--------+ + +-------------+ ERP +-----------+ (*) | Home | +Peer <->|Authenticator|<=======>| ER server | <---> | EAP | + +-------------+ +-----------+ | server | + +--------+ + (*) Diameter EAP application, + explicit bootstraping scenario only.]]></artwork> + </figure> + + <t>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). <cref>Can the ER server be located in a third + domain (ex: broker's) according to ERP mechanism?</cref></t> + + <t>When the peer initiates an ERP exchange, the authenticator creates a + Diameter-EAP-Request message, as described in Diameter EAP application + <xref target="RFC4072"></xref>. The Application Id of the message is set + to Diameter ERP application (code: <cref>TBD IANA</cref>) in the + message. The exact processing to generate the ERP/DER message is + detailed in section <xref target="Re-authentication"></xref>.</t> + + <t>If there is an ER server in the same domain as the authenticator + (local domain), Diameter routing MUST <cref>SHOULD ? FFS...</cref> be + configured so that this ERP/DER message reachs this server, even if the + Destination-Realm is not the local domain.</t> + + <t>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 <xref + target="RFC5296"></xref>, this realm is the home domain of the peer in + case of bootstrapping exchange ('B' flag is set in ERP message) or the + domain of the bootstrapped ER server otherwise <cref>This actually might + allow the ER server to be in a third party realm</cref>.</t> + + <t>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 as specified in <xref target="RFC3588"></xref> 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.</t> + + <t>When an ER server receives the ERP/DER message, it searches its local + database for a root key <cref>and authorization state ?</cref> matching + the keyName part of the User-Name AVP. If such key is found, the ER + server processes the ERP message as described in <xref + target="RFC5296"></xref> then creates the ERP/DEA answer as described in + <xref target="Re-authentication"></xref>. The rMSK is included in this + answer.</t> + + <t>Finally, the authenticator extracts the rMSK from the ERP/DEA as + described in <xref target="RFC5296"></xref>, and forwards the content of + the EAP-Payload AVP, the EAP-Finish/Re-Auth message, to the peer.</t> + + <t>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 <cref>This may not be true in future RFC5296bis + ?</cref>. 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 + <xref target="Bootstrapping"></xref> for more detail on this + process.</t> + </section> + + <section anchor="Bootstrapping" title="Bootstrapping the ER server"> + <t>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 re-authentication after a + handover.</t> + + <t>The bootstrapping of an ER server with a given root key happens + either during the initial EAP authentication of the peer when the EMSK + -- from which the root key is derived -- is created, during the first + re-authentication, or sometime between those events. We only consider + the first two possibilities in this specification, in the following + subsections.</t> + + <section title="Bootstrapping during initial EAP authentication"> + <t>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 the 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.</t> + + <t>To achieve implicit bootstrapping, the ER server must act as a + Diameter EAP Proxy, and routing must be configured so that Diameter + messages of a full EAP authentication are routed through this proxy. + The figure bellow captures this mechanism.</t> + + <figure title="Figure. ERP bootstrapping during full EAP authentication"> + <artwork><![CDATA[ + ER server & +Authenticator EAP Proxy Home EAP server +============= =========== =============== + -------------------------> + Diameter EAP/DER + (EAP-Response) + -------------------------> + Diameter EAP/DER + (EAP-Response) + (ERP-RK-Request) + + <==================================================> + Multi-round Diameter EAP exchanges, unmodified + + <------------------------- + Diameter EAP/DEA + (EAP-Success) + (MSK) + (ERP-RK-Answer) + <------------------------- + Diameter EAP/DEA + (EAP-Success) + (MSK) + [ERP-Realm] +]]></artwork> + </figure> + + <t>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.</t> + + <t>If the EAP server does not support ERP extensions, it will simply + ignore this grouped AVP and continue as specified in <xref + target="RFC4072"></xref>. If the server supports the ERP extensions, + it caches the ERP-Realm value with the session, and continues the EAP + authentication. When the authentication is complete, if it is + successful and the EAP method generated an EMSK, the server MUST + compute the rRK or rDSRK (depending on the value of ERP-Realm) as + specified in <xref target="RFC5296"></xref>, and add an ERP-RK-Answer + AVP in the Diameter-EAP-Request message, in addition to the MSK and + EAP-Success payloads.</t> + + <t>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 ERP-RK-Answer AVP from the + message, and save its content. If the message does not contain an + ERP-RK-Answer AVP, the ER server MAY save 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 <cref>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?</cref></t> + + <t>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. <cref>Is it possible? It would be useful...</cref></t> + </section> + + <section title="Bootstrapping during first re-authentication"> + <t>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 key that we + actually need, and it can accomodate inter-domain handovers or ER + servers that loose their state (for example after reboot) <cref>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</cref>. 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 is different<cref>and the root key used also ?</cref> for + explicit bootstrapping exchange and for normal re-authentication, + explicit bootstrapping should not be used if implicit bootstrapping + was already performed.</t> + + <t><cref>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 ?</cref></t> + + <t>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 do the following processing in addition to standard proxy + operations:<list> + <t>Change the Application Id in the header of the message to + Diameter EAP Application (code 5). <cref>What about the + Application-Auth-Id AVP?</cref></t> + + <t>Add the ERP-RK-Request AVP, which contains the name of the + domain where the ER server is located.</t> + + <t><cref>Add the Destination-Host to reach the appropriate EAP + server, the one with the EMSK. How does the ER server know this + information ?</cref></t> + </list>Then the server forwards the EAP/DER request, which is routed + to the home EAP server.</t> + + <t>If the home EAP server does not support 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 <xref target="RFC5296"></xref>. In particular, it includes the + Domain-Name TLV attribute with the content from the ERP-Realm AVP. It + creates the EAP/DEA reply message following standard processing from + <xref target="RFC4072"></xref> (in particular EAP-Master-Session-Key + AVP is used to transport the rMSK), and includes the ERP-RK-Answer + AVP. <cref>What about authorization AVPs ?</cref></t> + + <t>The ER server receives this EAP/DEA and proxies it as follow, in + addition to standard proxy operations:<list> + <t>Set the Application Id back to Diameter ERP (code <cref>TBD + IANA</cref>)</t> + + <t>Extract and cache the content of the ERP-RK-Answer. <cref>And + authorization AVPs ?</cref></t> + </list>The DEA is then forwarded to the authenticator, that can use + the rMSK as described in <xref target="RFC5296"></xref>.</t> + + <t>The figure below captures this proxy behavior:</t> + + <figure title="Figure. ERP explicit bootstrapping message flow"> + <artwork><![CDATA[ +Authenticator ER server Home EAP server +============= ========= =============== + -----------------------> + Diameter ERP/DER + (EAP-Initiate) + ------------------------> + Diameter EAP/DER + (EAP-Initiate) + (ERP-RK-Request) + + <------------------------ + Diameter EAP/DEA + (EAP-Finish) + (ERP-RK-Answer) + (rMSK) + <---------------------- + Diameter ERP/DEA + (EAP-Finish) + (rMSK) +]]></artwork> + </figure> + </section> + </section> + + <section anchor="Re-authentication" title="Re-Authentication"> + <t>This section describes in detail a re-authentication exchange with a + (bootstrapped) ER server. The following figure summarizes the + re-authentication exchange.</t> + + <figure title="Figure. Diameter ERP exchange. "> + <artwork><![CDATA[ + ER server + (bootstrapped) + Peer Authenticator (local or home domain) + ==== ============= ====================== + [ <------------------------ ] + [optional EAP-Initiate/Re-auth-start] + + -----------------------> + 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 + EAP-Master-Session-Key: rMSK + <---------------------- + EAP-Finish/Re-auth +]]></artwork> + </figure> + + <t>In ERP, the peer sends an EAP-Initiate/Re-auth message to the ER + server via the authenticator. Alternatively, the NAS 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 to the NAS.</t> + + <t>If the authenticator does not support ERP (pure <xref + target="RFC4072"></xref> support), it discards the EAP packets with + unknown ERP-specific code (EAP-Initiate). The peer may fallback to full + EAP authentication in such case.</t> + + <t>When the authenticator receives an EAP-Initiate/Re-auth message from + the peer, it process as described in <xref target="RFC5296"></xref> with + regards to the EAP state machine. It creates a Diameter EAP Request + message following the general process of <xref target="RFC4072">Diameter + EAP</xref>, with the following differences:<list> + <t>The Application Id in the header is set to Diameter ERP (code + <cref>TBD IANA</cref>).</t> + + <t>The value in Auth-Application-Id AVP is also set to Diameter ERP + Application.</t> + + <t>The keyName-NAI attribute from ERP message is used to create the + content of User-Name AVP and Destination-Realm AVP.</t> + + <t><cref>FFS: What about Session-ID AVP -- in case of re-auth at the + same place, and in case of handover?</cref></t> + + <t>The Auth-Request-Type AVP content is set to <cref>FFS -- 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...</cref>.</t> + + <t>The EAP-Payload AVP contains the ERP message, + EAP-Initiate/Re-Auth.</t> + </list>Then this ERP/DER message is sent as described in <xref + target="Overview"></xref>.</t> + + <t>The ER server receives and processes this request as described in + <xref target="Overview"></xref>. It then creates a Diameter answer + ERP/DEA, following the general processing described in <xref + target="RFC4072"></xref>, with the following differences:<list> + <t>The Application Id in the header is set to Diameter ERP (code + <cref>TBD IANA</cref>).</t> + + <t>The value in Auth-Application-Id AVP is also set to Diameter ERP + Application.</t> + + <t>The Result-Code AVP is set to <cref>version -00 stated a SHOULD + here, not sure why ?</cref> an error value in case ERP + authentication fails, or to DIAMETER_SUCCESS if ERP is + successful.</t> + + <t>The EAP-Payload AVP contains the ERP message, + EAP-Finish/Re-auth.</t> + + <t>In case of successful authentication, the EAP-Master-Session-Key + AVP contains the Re-authentication Master Session Key (rMSK) derived + by ERP.</t> + + <t><cref>What about all the authorization attributes? If we want to + include them, they have to be present on the ER server...</cref></t> + </list></t> + + <t>When the authenticator receives this ERP/DEA answer, it processes it + as described in <xref target="RFC4072">Diameter EAP</xref> and <xref + target="RFC5296"></xref>: the content of EAP-Payload AVP content is + forwarded to the peer, and the content of EAP-Master-Session-Key AVP is + used as a shared secret for Secure Association Protocol.</t> + </section> + + <section anchor="ApplicationId" title="Application Id"> + <t>We define a new Diameter application in this document, Diameter ERP + Application, with an Application Id value of <cref>TBD IANA</cref>. + Diameter nodes conforming to this specification in the role of ER server + MUST advertise support by including an Auth-Application-Id AVP with a + value of Diameter ERP Application in the of the + Capabilities-Exchange-Request and Capabilities-Exchange-Answer commands, + as described in <xref target="RFC3588"></xref>.</t> + + <t>The primary use of the Diameter ERP Application Id is to ensure + proper routing of the messages, and that the nodes that advertise the + support for this application do understand the new AVPs defined in + section <xref target="AVPs"></xref> , although these AVP have the 'M' + flag cleared.</t> + </section> + + <section anchor="AVPs" title="AVPs"> + <t>This specification defines the following new AVPs. <cref>FFS: to + align with draft-wu-dime-local-keytran-02 if it becomes a WG + item</cref></t> + + <section title="ERP-RK-Request AVP"> + <t>The ERP-RK-Request AVP (AVP Code <cref>TBD IANA</cref>) is of type + grouped AVP. This AVP is used by the ER server to indicate its + willingness to act as ER server for a particular session.</t> + + <t>This AVP has the M and V bits cleared.</t> + + <figure title="Figure. ERP-RK-Request ABNF"> + <artwork><![CDATA[ + ERP-RK-Request ::= < AVP Header: TBD > + { ERP-Realm } + * [ AVP ] +]]></artwork> + </figure> + </section> + + <section title="ERP-Realm AVP"> + <t>The ERP-Realm AVP (AVP Code <cref>TBD IANA</cref>) is of type + DiameterIdentity. It contains the name of the realm in which the ER + server is located.</t> + + <t><cref>FFS: We may re-use Origin-Realm here instead? On the other + hand, ERP-Realm may be useful if the ER server is not in a third-party + realm, if this is possible.</cref></t> + + <t>This AVP has the M and V bits cleared.</t> + </section> + + <section title="ERP-RK-Answer AVP"> + <t>The ERP-RK-Answer AVP (AVP Code <cref>TBD IANA</cref>) is of type + grouped AVP. It is used by the home EAP server to provide ERP root key + material to the ER server.</t> + + <t>This AVP has the M and V bits cleared.</t> + + <figure title="Figure. ERP-RK-Answer ABNF"> + <artwork><![CDATA[ + ERP-RK-Answer ::= < AVP Header: TBD > + { ERP-RK } + { ERP-RK-Name } + { ERP-RK-Lifetime } + * [ AVP ] +]]></artwork> + </figure> + </section> + + <section title="ERP-RK AVP"> + <t>The ERP-RK AVP (AVP Code <cref>TBD IANA</cref>) is of type + OctetString. It contains the root key (either rRK or rDSRK) sent by + the home EAP server to the ER server, in answer to request containing + an ERP-RK-Request AVP. How this material is derived and used is + specified in <xref target="RFC5296"></xref>.</t> + + <t><cref>Can we re-use EAP-Master-Session-Key here instead? Must check + the exact definition...</cref></t> + + <t>This AVP has the M and V bits cleared.</t> + </section> + + <section title="ERP-RK-Name AVP"> + <t>The ERP-RK-Name AVP (AVP Code <cref>TBD IANA</cref>) is of type + OctetString. This AVP contains the EMSKname which identifies the + keying material. How this name is derived is beyond the scope of this + document and defined in <xref target="RFC5296"></xref>.</t> + + <t><cref>Can we re-use EAP-Key-Name here instead ?</cref></t> + + <t>This AVP has the M and V bits cleared.</t> + </section> + + <section title="ERP-RK-Lifetime AVP"> + <t>The ERP-RK-Lifetime AVP (AVP Code <cref>TBD IANA</cref>) is of type + Unsigned32 <cref>do we really need 64 as in -00 ? 2^32 secs is already + more than 100 years, which is too long for a key lifetime !</cref> and + contains the root key material remaining lifetime in seconds. It MUST + not be greater than the remaining lifetime of the EMSK it is derived + from. <cref>FFS: is it better to pass an absolute value here, for + example expiration date? How to express it then (TZ, ...)? + Synchronization problems?</cref></t> + + <t>This AVP has the M and V bits cleared.</t> + </section> + </section> + + <section anchor="Commands" title="Commands"> + <t>We do not define any new command in this specification. We reuse the + Diameter-EAP-Request and Diameter-EAP-Answer commands defined in <xref + target="RFC4072"></xref>.</t> + + <t>Since the original ABNF of these commands allow other optional AVPs + ("* [ AVP ]"), and the new AVPs defined in this specification do not + have the 'M' flag set, the ABNF does not need any change. Anyway, a + Diameter node that advertizes support for the Diameter ERP application + MUST support the new AVPs defined in this specification.</t> + + <figure title="Figure. Command Codes"> + <artwork><![CDATA[ + Command-Name Abbrev. Code Reference Application + --------------------------------------------------------- + Diameter-EAP-Request DER 268 RFC 4072 Diameter ERP + Diameter-EAP-Answer DEA 268 RFC 4072 Diameter ERP +]]></artwork> + </figure> + </section> + + <section anchor="Issues" title="Open issues"> + <t>This document does not address some known issues in Diameter ERP + mechanism. The authors would like to hear ideas about how to address + them.</t> + + <t>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.</t> + + <t>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.</t> + + <t>Finally, this document currently lacks a description of what happens + when a Re-Auth-Request is received for a peer on the authenticator.</t> + </section> + + <section anchor="Acknowledgements" title="Acknowledgements"> + <t>Hannes Tschofenig wrote the initial draft for this document and + provided useful reviews.</t> + + <t>Vidya Narayanan reviewed a rough draft version of the document and + found some errors.</t> + + <t>Glen Zorn actively participated in the discussions on the design for + Diameter ERP, providing the point of view and experience from HOKEY + workgroup.</t> + + <t>Many thanks to these people!</t> + </section> + + <section anchor="IANA" title="IANA Considerations"> + <t>This document requires IANA registration of the following new + elements in the <eref + target="http://www.iana.org/assignments/aaa-parameters/">Authentication, + Authorization, and Accounting (AAA) Parameters</eref> registries.</t> + + <section title="Diameter ERP application"> + <t>This specification requires IANA to allocate a new value "Diameter + ERP" in the "Application IDs" registry created by in <xref + target="RFC3588"></xref>.</t> + + <figure title="IANA consideration for Diameter ERP application"> + <artwork><![CDATA[ + Application Identifier | Value + -----------------------------------+------ + Diameter ERP | TBD +]]></artwork> + </figure> + </section> + + <section title="New AVPs"> + <t>This specification requires IANA to allocate new values from the + "AVP Codes" registry defined in <xref target="RFC3588"></xref> for the + following AVPs:<list> + <t>ERP-RK-Request</t> + + <t>ERP-Realm</t> + + <t>ERP-RK-Answer</t> + + <t>ERP-RK</t> + + <t>ERP-RK-Name</t> + + <t>ERP-RK-Lifetime</t> + </list>These AVPs are defined in section <xref + target="AVPs"></xref>.</t> + </section> + </section> + + <section anchor="Security" title="Security Considerations"> + <t>The security considerations from the following RFC apply here: <xref + target="RFC3588"></xref>, <xref target="RFC4072"></xref>, <xref + target="RFC5247"></xref>, <xref target="RFC5295"></xref>, and <xref + target="RFC5296"></xref>.</t> + + <t><cref>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?</cref></t> + + <t>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.<cref>Editor: I + really don't understand this paragraph ^^'...</cref></t> + </section> + </middle> + + <back> + <references title="Normative References"> + &RFC2119; + + &RFC3588; + + &RFC4072; + + &RFC5295; + + &RFC5296; + + &RFC3748; + </references> + + <references title="Informative References"> + &RFC4187; + + &RFC5247; + + &I-D.ietf-hokey-key-mgm; + + &I-D.ietf-dime-erp; + + &I-D.wu-dime-local-keytran; + + &I-D.ietf-dime-app-design-guide; + </references> + </back> +</rfc>