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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 6614

RADIUS Extensions Working Group                                S. Winter
Internet-Draft                                                   RESTENA
Intended status: Experimental                                M. McCauley
Expires: September 7, 2009                                           OSC
                                                               S. Venaas
                                                                 UNINETT
                                                             K. Wierenga
                                                                   Cisco
                                                          March 06, 2009


              TLS encryption for RADIUS over TCP (RadSec)
                      draft-ietf-radext-radsec-04

Status of This Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.  This document may contain material
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   This Internet-Draft will expire on September 7, 2009.

Copyright Notice



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   Copyright (c) 2009 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 in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

Abstract

   This document specifies security on the transport layer (TLS) for the
   RADIUS protocol [RFC2865] when transmitted over TCP
   [I-D.dekok-radext-tcp-transport].  This enables dynamic trust
   relationships between RADIUS servers.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  3
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Normative: Transport Layer Security for RADIUS over TCP  . . .  4
     2.1.  TCP port and packet types  . . . . . . . . . . . . . . . .  4
     2.2.  Connection Setup . . . . . . . . . . . . . . . . . . . . .  4
     2.3.  RADIUS Datagrams . . . . . . . . . . . . . . . . . . . . .  5
   3.  Informative: Design Decisions  . . . . . . . . . . . . . . . .  7
     3.1.  X.509 Certificate Considerations . . . . . . . . . . . . .  7
     3.2.  Ciphersuites and Compression Negotiation Considerations  .  8
     3.3.  RADIUS Datagram Considerations . . . . . . . . . . . . . .  8
   4.  Compatibility with other RADIUS transports . . . . . . . . . .  9
   5.  Diameter Compatibility . . . . . . . . . . . . . . . . . . . . 10
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Appendix A.  Implementation Overview: Radiator . . . . . . . . . . 13
   Appendix B.  Implementation Overview: radsecproxy  . . . . . . . . 14












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1.  Introduction

   The RADIUS protocol [RFC2865] is a widely deployed authentication and
   authorisation protocol.  The supplementary RADIUS Accounting
   specification [RFC2866] also provides accounting mechanisms, thus
   delivering a full AAA solution.  However, RADIUS is experiencing
   several shortcomings, such as its dependency on the unreliable
   transport protocol UDP and the lack of security for large parts of
   its packet payload.  RADIUS security is based on the MD5 algorithm,
   which has been proven to be insecure.

   The main focus of RadSec is to provide a means to secure the
   communication between RADIUS/TCP peers on the transport layer.  The
   most important use of RadSec lies in roaming environments where
   RADIUS packets need to be transferred through different
   administrative domains and untrusted, potentially hostile networks.
   An example for a world-wide roaming environment that uses RadSec to
   secure communication is "eduroam", see [eduroam].

   There are multiple known attacks on the MD5 algorithm which is used
   in RADIUS to provide integrity protection and a limited
   confidentiality protection.  RadSec wraps the entire RADIUS packet
   payload into a TLS stream and thus mitigates the risk of attacks on
   MD5.

   Because of the static trust establishment between RADIUS peers (IP
   address and shared secret) the only scalable way of creating a
   massive deployment of RADIUS-servers under control by different
   administrative entities is to introduce some form of a proxy chain to
   route the access requests to their home server.  This creates a lot
   of overhead in terms of possible points of failure, longer
   transmission times as well as middleboxes through which
   authentication traffic flows.  These middleboxes may learn privacy-
   relevant data while forwarding requests.  The new features in RadSec
   obsolete the use of IP addresses and shared MD5 secrets to identify
   other peers and thus allow the dynamic establishment of connections
   to peers that are not previously configured, and thus makes it
   possible to avoid intermediate aggregation proxies.  One mechanism
   discover RadSec peers with DNS is specified in
   [I-D.winter-dynamic-discovery].

1.1.  Requirements Language

   In this document, several words are used to signify the requirements
   of the specification.  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
   RFC 2119.  [RFC2119]



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1.2.  Terminology

   RadSec node: a RadSec client or server

   RadSec Client: a RadSec instance which initiates a new connection.

   RadSec Server: a RadSec instance which listens on a RadSec port and
   accepts new connections

2.  Normative: Transport Layer Security for RADIUS over TCP

2.1.  TCP port and packet types

   The default destination port number for RadSec is TCP/2083.  There
   are no separate ports for authentication, accounting and dynamic
   authorisation changes.  The source port is arbitrary.

2.2.  Connection Setup

   RadSec nodes

   1.  establish TCP connections as per [I-D.dekok-radext-tcp-transport]

   2.  negotiate TLS sessions according to [RFC5246] or its predecessor
       TLS 1.1.  The following restrictions apply:

       *  The authentication MUST be mutual, i.e. both the RadSec server
          and the RadSec client authenticate each other.

       *  The client MUST NOT negotiate cipher suites which only provide
          integrity protection.

       *  The TLS session MAY use mutual PSKs for connection setup.

       *  RADSEC implementations MUST support he mandatory to implement
          cipher suites specified in TLS.  For purposes of compatibility
          with some current deployments implementations SHOULD support
          TLS_RSA_WITH_RC4_128_SHA as well (see Section 3.2 (1) ).

   3.  If TLS is used in an X.509 certificate based operation mode, the
       following list of certificate validation options applies:

       *  Implementations MUST allow to configure a list of acceptable
          Certification Authorities for incoming connections.

       *  Certificate validation MUST include the verification rules as
          per [RFC5280].  If service names as per [RFC4985] are present
          in the certificate and dynamic discovery utilizing SRVs in DNS



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          is used (see [I-D.winter-dynamic-discovery]), the SRV entry
          SHOULD be validated.

       *  Implementations SHOULD indicate their acceptable Certification
          Authorities as per section 7.4.4 (server side) and x.y.z
          ["Trusted CA Indication"] (client side) of [RFC5246] (see
          Section 3.1 (1) )

       *  Implementations SHOULD allow to configure a list of acceptable
          certificates, identified via certificate fingerprint.  When a
          fingerprint configured, the fingerprint is prepended with an
          ASCII label identifying the hash function followed by a colon.
          Implementations MUST support SHA-1 as the hash algorithm and
          use the ASCII label "sha-1" to identify the SHA-1 algorithm.
          The length of a SHA-1 hash is 20 bytes and the length of the
          corresponding fingerprint string is 65 characters.  An example
          certificate fingerprint is: sha-
          1:E1:2D:53:2B:7C:6B:8A:29:A2:76:C8:64:36:0B:08:4B:7A:F1:9E:9D

       *  Peer validation always includes a check on whether the DNS
          name or the IP address of the server that is contacted matches
          its certificate.  DNS names and IP addresses can be contained
          in the Common Name (CN) or subjectAltName entries.  For
          verification, only one these entries is to be considered.  The
          following precedence applies: for DNS name validation,
          subjectAltName:DNS has precedence over CN; for IP address
          validation, subjectAltName:iPAddr has precedence over CN.

       *  Implementations SHOULD allow to configure a set of acceptable
          values for subjectAltName:URI.

   4.  start exchanging RADIUS datagrams.  Note Section 3.3 (1) ).  The
       shared secret to compute the (obsolete) MD5 integrity checks and
       attribute encryption MUST be "radsec" (see Section 3.3 (2) ).

2.3.  RADIUS Datagrams

   Authentication, Accounting and Authorization packets are sent
   according to the following rules:

   RadSec clients handle the following packet types from [RFC2865],
   [RFC2866], [RFC5176] on the connection they initiated (see
   Section 3.3 (3) and (4) ):

   o  send Access-Request

   o  send Accounting-Request




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   o  send Status-Server

   o  send Disconnect-ACK

   o  send Disconnect-NAK

   o  send CoA-ACK

   o  send CoA-NAK

   o  receive Access-Challenge

   o  receive Access-Accept

   o  receive Access-Reject

   o  receive Accounting-Response

   o  receive Disconnect-Request

   o  receive CoA-Request

   RadSec servers handle the following packet types from [RFC2865],
   [RFC2866], [RFC5176] on the connections they serve to clients:

   o  receive Access-Request

   o  receive Accounting-Request

   o  receive Status-Server

   o  receive Disconnect-ACK

   o  receive Disconnect-NAK

   o  receive CoA-ACK

   o  receive CoA-NAK

   o  send Access-Challenge

   o  send Access-Accept

   o  send Access-Reject

   o  send Accounting-Response





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   o  send Disconnect-Request

   o  send CoA-Request

3.  Informative: Design Decisions

   This section explains the design decisions that led to the rules
   defined in the previous section.

3.1.  X.509 Certificate Considerations

   (1) If a RadSec client is in possession of multiple certificates from
   different CAs (i.e. is part of multiple roaming consortia) and
   dynamic discovery is used, the discovery mechanism possibly does not
   yield sufficient information to identify the consortium uniquely
   (e.g.  DNS discovery).  Subsequently, the client may not know by
   itself which client certificate to use for the TLS handshake.  Then
   it is necessary for the server to signal which consortium it belongs
   to, and which certificates it expects.  If there is no risk of
   confusing multiple roaming consortia, providing this information in
   the handshake is not crucial.

   (2) If a RadSec server is in possession of multiple certificates from
   different CAs (i.e. is part of multiple roaming consortia), it will
   need to select one of its certificates to present to the RadSec
   client.  If the client sends the Trusted CA Indication, this hint can
   make the server select the appropriate certificate and prevent a
   handshake failure.  Omitting this indication makes it impossible to
   deterministically select the right certificate in this case.  If
   there is no risk of confusing multiple roaming consortia, providing
   this indication in the handshake is not crucial.

   (4) If dynamic peer discovery as per [I-D.winter-dynamic-discovery]
   is used, peer authentication alone is not sufficient; the peer must
   also be authorised to perform user authentications.  In these cases,
   the trust fabric cannot depend on peer authentication methods like
   DNSSEC to identify RadSec nodes.  The RadSec nodes also need to be
   properly authorised.  Typically, this can be achieved by adding
   appropriate authorisation fields into a X.509 certificate.  Such
   fields include SRV authority (x.y.z... reference), subjectAltName:
   URI, or a defined list of certificate fingerprints.  Operators of a
   RadSec infrastructure should define their own authorisation trust
   model and apply this model to the certificates.  The checks
   enumerated in Section 2.2 provide sufficient flexibility for the
   implementation of authorisation trust models.






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3.2.  Ciphersuites and Compression Negotiation Considerations

   RadSec implementations need not necessarily support all TLS
   ciphersuites listed in [RFC5246]. Not all TLS ciphersuites
   are supported by available TLS tool kits and licenses may be required
   in some cases.  The existing implementations of RadSec use OpenSSL as
   cryptographic backend, which supports all of the ciphersuites listed
   in the rules in the normative section.

   The TLS ciphersuite TLS_RSA_WITH_3DES_EDE_CBC_SHA is mandatory-to-
   implement according to [RFC5246] and thus has to be supported by
   RadSec nodes.

   The two other ciphersuites in the normative section
   (TLS_RSA_WITH_RC4_128_SHA and TLS_RSA_WITH_AES_128_CBC_SHA) are
   widely implemented in TLS toolkits and are considered good practice
   to implement.

   TLS also supports compression.  Compression is an optional
   feature. During the RadSec conversation the client and server may
   negotiate compression, but must continue the conversation even if the
   other peer rejects compression.

3.3.  RADIUS Datagram Considerations

   (1) After the TLS session is established, RADIUS packet payloads are
   exchanged over the encrypted TLS tunnel.  In plain RADIUS, the packet
   size can be determined by evaluating the size of the datagram that
   arrived.  Due to the stream nature of TCP and TLS, this does not hold
   true for RadSec packet exchange.  Instead, packet boundaries of
   RADIUS packets that arrive in the stream are calculated by evaluating
   the packet's Length field.  Special care needs to be taken on the
   packet sender side that the value of the Length field is indeed
   correct before sending it over the TLS tunnel, because incorrect
   packet lengths can no longer be detected by a differing datagram
   boundary.

   (2) Within RADIUS [RFC2865], a shared secret is used for hiding
   of attributes such as User-Password, as well as in computation of
   the Response Authenticator.  In RADIUS accounting [RFC2866], the
   shared secret is used in computation of both the Request
   Authenticator and the Response Authenticator.  Since TLS provides
   integrity protection and encryption sufficient to substitute for
   RADIUS application-layer security, it is not necessary to configure a
   RADIUS shared secret.  The use of a fixed string for the obsolete
   shared secret eliminates possible node misconfigurations.

   (3) RADIUS [RFC2865] uses different UDP ports for authentication,



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   accounting and dynamic authorisation changes.  RadSec allocates a
   single port for all RADIUS packet types.  Nevertheless, in RadSec the
   notion of a client which sends authentication requests and processes
   replies associated with it's users' sessions and the notion of a
   server which receives requests, processes them and sends the
   appropriate replies is to be preserved.  The normative rules about
   acceptable packet types for clients and servers mirror the packet
   flow behaviour from RADIUS.

   (4) RADIUS [RFC2865] used negative ICMP responses to a newly
   allocated UDP port to signal that a peer RADIUS server does not
   support reception and processing of the packet types in [RFC5176].
   These packet types are listed as to be received in RadSec
   implementations.  Note well: it is not required for an implementation
   to actually process these packet types.  It is sufficient that upon
   receiving such a packet, an unconditional NAK is sent back to
   indicate that the action is not supported.

4.  Compatibility with other RADIUS transports

   Ongoing work in the IETF defines multiple alternative transports to
   the classic UDP transport model as defined in [RFC2865], namely
   RADIUS over TCP [I-D.dekok-radext-tcp-transport], RADIUS over DTLS
   [I-D.dekok-radext-dtls] and the present document on RadSec.

   RadSec does not specify any inherent backwards compatibility to
   classic RADIUS or cross compatibility to the other transports, i.e.
   an implementation which implements RadSec only will not be able to
   receive or send RADIUS packet payloads over other transports.  An
   implementation wishing to be backward or cross compatible (i.e.
   wishes to serve clients using other transports than RadSec) will need
   to implement the other transports and RadSec transport and be
   prepared to send and receive on all implemented transports, which is
   called a multi-stack implementation.

   If a given IP device is able to receive RADIUS payloads on multiple
   transports, this may or may not be the same instance of software, and
   it may or may not serve the same purposes.  It is not safe to assume
   that both ports are interchangeable.  In particular, it can not be
   assumed that state is maintained for the packet payloads between the
   transports.  Two such instances MUST be considered separate RADIUS
   server entities.

   As a consequence, the selection of transports to communicate from a
   client to a server is a manual administrative action.  An automatic
   fallback to classic RADIUS is NOT RECOMMENDED, as it may lead to
   down-bidding attacks on the peer communication.




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5.  Diameter Compatibility

   Since RadSec is only a new transport profile for RADIUS,
   compatibility of RadSec - Diameter [RFC3588] vs. RADIUS [RFC2865] -
   Diameter [RFC3588] is identical.  The considerations regarding
   payload size in [I-D.dekok-radext-tcp-transport] apply.

6.  Security Considerations

   The computational resources to establish a TLS tunnel are
   significantly higher than simply sending mostly unencrypted UDP
   datagrams.  Therefore, clients connecting to a RadSec node will more
   easily create high load conditions and a malicious client might
   create a Denial-of-Service attack more easily.

   In the case of dynamic peer discovery as per
   [I-D.winter-dynamic-discovery], a RadSec node needs to be able to
   accept connections from a large, not previously known, group of
   hosts, possibly the whole internet.  In this case, the server's
   RadSec port can not be protected from unauthorised connection
   attempts with measures on the network layer, i.e. access lists and
   firewalls.  This opens more attack vectors for Distributed Denial of
   Service attacks, just like any other service that is supposed to
   serve arbitrary clients (like for example web servers).

   In the case of dynamic peer discovery as per
   [I-D.winter-dynamic-discovery], X.509 certificates are the only proof
   of authorisation for a connecting RadSec nodes.  Special care needs
   to be taken that certificates get verified properly according to the
   chosen trust model (particularly: consulting CRLs, checking critical
   extensions, checking subjectAltNames etc.) to prevent unauthorised
   connections.

   Some TLS ciphersuites only provide integrity validation of their
   payload, and provide no encryption.  This specification forbids the
   use of such ciphersuites.  Since the RADIUS payload's shared secret
   is fixed and well-known, failure to comply with this requirement will
   expose the entire datagram payload in plain text, including User-
   Password, to intermediate IP nodes.

   If peer communication between two devices is configured for both
   RadSec and classic RADIUS, a failover from RadSec to classic RADIUS
   opens the way for a down-bidding attack if an adversary can
   maliciously close the TCP connection, or prevent it from being
   established.  In this case, security of the packet payload is reduced
   from the selected TLS cipher suite packet encryption to the classic
   MD5 per-attribute encryption.




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   The RadSec transport provides authentication and encryption between
   RADIUS peers.  In the presence of proxies, the intermediate proxies
   can still inspect the individual RADIUS packets, i.e. "end-to-end"
   encryption is not provided.  Where intermediate proxies are
   untrusted, it is desirable to use other RADIUS mechanisms to prevent
   RADIUS packet payload from inspection by such proxies.  One common
   method to protect passwords is the use of EAP methods which utilize
   TLS.

7.  IANA Considerations

   This document has no actions for IANA.  The TCP port 2083 was already
   previously assigned by IANA for RadSec.  No new RADIUS attributes or
   packet codes are defined.

8.  Acknowledgements

   RadSec version 1 was first implemented by Open Systems Consultants,
   Currumbin Waters, Australia, for their "Radiator" RADIUS server
   product (see [radsec-whitepaper]).

   Funding and input for the development of this Internet Draft was
   provided by the European Commission co-funded project "GEANT2"
   [geant2] and further feedback was provided by the TERENA Task Force
   Mobility [terena].

9.  References

9.1.  Normative References

   [RFC2119]                         Bradner, S., "Key words for use in
                                     RFCs to Indicate Requirement
                                     Levels", BCP 14, RFC 2119,
                                     March 1997.

   [RFC2865]                         Rigney, C., Willens, S., Rubens,
                                     A., and W. Simpson, "Remote
                                     Authentication Dial In User Service
                                     (RADIUS)", RFC 2865, June 2000.

   [RFC2866]                         Rigney, C., "RADIUS Accounting",
                                     RFC 2866, June 2000.

   [RFC4985]                         Santesson, S., "Internet X.509
                                     Public Key Infrastructure Subject
                                     Alternative Name for Expression of
                                     Service Name", RFC 4985,
                                     August 2007.



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   [RFC5280]                         Cooper, D., Santesson, S., Farrell,
                                     S., Boeyen, S., Housley, R., and W.
                                     Polk, "Internet X.509 Public Key
                                     Infrastructure Certificate and
                                     Certificate Revocation List (CRL)
                                     Profile", RFC 5280, May 2008.

   [RFC5176]                         Chiba, M., Dommety, G., Eklund, M.,
                                     Mitton, D., and B. Aboba, "Dynamic
                                     Authorization Extensions to Remote
                                     Authentication Dial In User Service
                                     (RADIUS)", RFC 5176, January 2008.

   [RFC5246]                         Dierks, T. and E. Rescorla, "The
                                     Transport Layer Security (TLS)
                                     Protocol Version 1.2", RFC 5246,
                                     August 2008.

   [I-D.dekok-radext-tcp-transport]  DeKok, A., "RADIUS Over TCP",
                                     draft-dekok-radext-tcp-transport-01
                                     (work in progress), November 2008.

9.2.  Informative References

   [I-D.dekok-radext-dtls]           DeKok, A., "DTLS as a Transport
                                     Layer for RADIUS",
                                     draft-dekok-radext-dtls-00 (work in
                                     progress), February 2007.

   [I-D.winter-dynamic-discovery]    Winter, S. and M. McCauley, "NAI-
                                     based Dynamic Peer Discovery for
                                     RADIUS over TLS and DTLS",
                                     draft-winter-dynamic-discovery-00
                                     (work in progress), February 2009.

   [RFC3588]                         Calhoun, P., Loughney, J., Guttman,
                                     E., Zorn, G., and J. Arkko,
                                     "Diameter Base Protocol", RFC 3588,
                                     September 2003.

   [radsec-whitepaper]               Open System Consultants, "RadSec -
                                     a secure, reliable RADIUS
                                     Protocol", May 2005, <http://
                                     www.open.com.au/radiator/
                                     radsec-whitepaper.pdf>.

   [radiator-manual]                 Open System Consultants, "Radiator
                                     Radius Server - Installation and



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                                     Reference Manual", 2006, <http://
                                     www.open.com.au/radiator/ref.html>.

   [radsecproxy-impl]                Venaas, S., "radsecproxy Project
                                     Homepage", 2007, <http://
                                     software.uninett.no/radsecproxy/>.

   [eduroam]                         Trans-European Research and
                                     Education Networking Association,
                                     "eduroam Homepage", 2007,
                                     <http://www.eduroam.org/>.

   [geant2]                          Delivery of Advanced Network
                                     Technology to Europe, "European
                                     Commission Information Society and
                                     Media: GEANT2", 2008,
                                     <http://www.geant2.net/>.

   [terena]                          TERENA, "Trans-European Research
                                     and Education Networking
                                     Association", 2008,
                                     <http://www.terena.org/>.

Appendix A.  Implementation Overview: Radiator

   Radiator implements the RadSec protocol for proxying requests with
   the <Authby RADSEC> and <ServerRADSEC> clauses in the Radiator
   configuration file.

   The <AuthBy RADSEC> clause defines a RadSec client, and causes
   Radiator to send RADIUS requests to the configured RadSec server
   using the RadSec protocol.

   The <ServerRADSEC> clause defines a RadSec server, and causes
   Radiator to listen on the configured port and address(es) for
   connections from <Authby RADSEC> clients.  When an <Authby RADSEC>
   client connects to a <ServerRADSEC> server, the client sends RADIUS
   requests through the stream to the server.  The server then handles
   the request in the same way as if the request had been received from
   a conventional UDP RADIUS client.

   Radiator is compliant to version 2 of RadSec if the following options
   are used:

      <AuthBy RADSEC>

      *  Protocol tcp




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      *  UseTLS

      *  TLS_CertificateFile

      *  Secret radsec

      <ServerRADSEC>

      *  Protocol tcp

      *  UseTLS

      *  TLS_RequireClientCert

      *  Secret radsec

   As of Radiator 3.15, the default shared secret for RadSec connections
   is configurable and defaults to "mysecret" (without quotes).  For
   compliance with this document, this setting needs to be configured
   for the shared secret "radsec".  The implementation uses TCP
   keepalive socket options, but does not send Status-Server packets.
   Once established, TLS connections are kept open throughout the server
   instance lifetime.

Appendix B.  Implementation Overview: radsecproxy

   The RADIUS proxy named radsecproxy was written in order to allow use
   of RadSec in current RADIUS deployments.  This is a generic proxy
   that supports any number and combination of clients and servers,
   supporting RADIUS over UDP and RadSec.  The main idea is that it can
   be used on the same host as a non-RadSec client or server to ensure
   RadSec is used on the wire, however as a generic proxy it can be used
   in other circumstances as well.

   The configuration file consists of client and server clauses, where
   there is one such clause for each client or server.  In such a clause
   one specifies either "type tls" or "type udp" for RadSec or UDP
   transport.  For RadSec the default shared secret "mysecret" (without
   quotes), the same as Radiator, is used.  A secret may be specified by
   putting say "secret somesharedsecret" inside a client or server
   clause.

   In order to use TLS for clients and/or servers, one must also specify
   where to locate CA certificates, as well as certificate and key for
   the client or server.  This is done in a TLS clause.  There may be
   one or several TLS clauses.  A client or server clause may reference
   a particular TLS clause, or just use a default one.  One use for
   multiple TLS clauses may be to present one certificate to clients and



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   another to servers.

   If any RadSec (TLS) clients are configured, the proxy will at startup
   listen on port 2083, as assigned by IANA for the OSC RadSec
   implementation.  An alternative port may be specified.  When a client
   connects, the client certificate will be verified, including checking
   that the configured FQDN or IP address matches what is in the
   certificate.  Requests coming from a RadSec client are treated
   exactly like requests from UDP clients.

   The proxy will at startup try to establish a TLS connection to each
   (if any) of the configured RadSec (TLS) servers.  If it fails to
   connect to a server, it will retry regularly.  There is some back-off
   where it will retry quickly at first, and with longer intervals
   later.  If a connection to a server goes down it will also start
   retrying regularly.  When setting up the TLS connection, the server
   certificate will be verified, including checking that the configured
   FQDN or IP address matches what is in the certificate.  Requests are
   sent to a RadSec server just like they would to a UDP server.

   The proxy supports Status-Server messages.  They are only sent to a
   server if enabled for that particular server.  Status-Server requests
   are always responded to.

   This RadSec implementation has been successfully tested together with
   Radiator.  It is a freely available open-source implementation.  For
   source code and documentation, see [radsecproxy-impl].

Authors' Addresses

   Stefan Winter
   Fondation RESTENA
   6, rue Richard Coudenhove-Kalergi
   Luxembourg  1359
   LUXEMBOURG

   Phone: +352 424409 1
   Fax:   +352 422473
   EMail: stefan.winter@restena.lu
   URI:   http://www.restena.lu.











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   Mike McCauley
   Open Systems Consultants
   9 Bulbul Place
   Currumbin Waters  QLD 4223
   AUSTRALIA

   Phone: +61 7 5598 7474
   Fax:   +61 7 5598 7070
   EMail: mikem@open.com.au
   URI:   http://www.open.com.au.


   Stig Venaas
   UNINETT
   Abels gate 5 - Teknobyen
   Trondheim  7465
   NORWAY

   Phone: +47 73 55 79 00
   Fax:   +47 73 55 79 01
   EMail: stig.venaas@uninett.no
   URI:   http://www.uninett.no.


   Klaas Wierenga
   Cisco Systems International BV
   Haarlerbergweg 13-19
   Amsterdam  1101 CH
   The Netherlands

   Phone: +31 (0)20 3571752
   Fax:
   EMail: kwiereng@cisco.com
   URI:   http://www.cisco.com.

















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