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Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- -- The draft header indicates that this document obsoletes RFC3576, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust Copyright Line does not match the current year -- The exact meaning of the all-uppercase expression 'MAY NOT' is not defined in RFC 2119. If it is intended as a requirements expression, it should be rewritten using one of the combinations defined in RFC 2119; otherwise it should not be all-uppercase. == The expression 'MAY NOT', while looking like RFC 2119 requirements text, is not defined in RFC 2119, and should not be used. Consider using 'MUST NOT' instead (if that is what you mean). Found 'MAY NOT' in this paragraph: Where RADIUS is run over IPsec ESP with a non-null transform, the secret shared between the NAS and the RADIUS server MAY NOT be configured. In this case, a shared secret of zero length MUST be assumed. However, a RADIUS server that cannot know whether incoming traffic is IPsec-protected MUST be configured with a non-null RADIUS shared secret. -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- Couldn't find a document date in the document -- date freshness check skipped. -- Found something which looks like a code comment -- if you have code sections in the document, please surround them with '' and '' lines. Checking references for intended status: Informational ---------------------------------------------------------------------------- == Missing Reference: 'Note 1' is mentioned on line 844, but not defined == Missing Reference: 'Note 6' is mentioned on line 875, but not defined == Missing Reference: 'Note 3' is mentioned on line 858, but not defined == Missing Reference: 'Note 2' is mentioned on line 850, but not defined == Missing Reference: 'Note 7' is mentioned on line 897, but not defined == Missing Reference: 'Note 5' is mentioned on line 870, but not defined == Missing Reference: 'Note 4' is mentioned on line 864, but not defined ** Obsolete normative reference: RFC 2409 (Obsoleted by RFC 4306) ** Obsolete normative reference: RFC 3280 (Obsoleted by RFC 5280) ** Obsolete normative reference: RFC 4282 (Obsoleted by RFC 7542) -- Obsolete informational reference (is this intentional?): RFC 3588 (Obsoleted by RFC 6733) -- Obsolete informational reference (is this intentional?): RFC 3576 (Obsoleted by RFC 5176) -- Obsolete informational reference (is this intentional?): RFC 4005 (Obsoleted by RFC 7155) -- Obsolete informational reference (is this intentional?): RFC 4330 (Obsoleted by RFC 5905) Summary: 4 errors (**), 0 flaws (~~), 9 warnings (==), 14 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Murtaza S. Chiba 3 INTERNET-DRAFT Gopal Dommety 4 Obsoletes: 3576 Mark Eklund 5 Category: Informational Cisco Systems, Inc. 6 David Mitton 7 21 March 2007 RSA Security, Inc. 8 Bernard Aboba 9 Microsoft Corporation 11 Dynamic Authorization Extensions to Remote Authentication Dial In User 12 Service (RADIUS) 14 By submitting this Internet-Draft, each author represents that any 15 applicable patent or other IPR claims of which he or she is aware 16 have been or will be disclosed, and any of which he or she becomes 17 aware will be disclosed, in accordance with Section 6 of BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt. 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html. 35 This Internet-Draft will expire on September 25, 2007. 37 Copyright Notice 39 Copyright (C) The IETF Trust (2007). All Rights Reserved. 41 Abstract 43 This document describes a currently deployed extension to the Remote 44 Authentication Dial In User Service (RADIUS) protocol, allowing 45 dynamic changes to a user session, as implemented by network access 46 server products. This includes support for disconnecting users and 47 changing authorizations applicable to a user session. 49 Table of Contents 51 1. Introduction .......................................... 3 52 1.1 Applicability ................................... 3 53 1.2 Requirements Language ........................... 4 54 1.3 Terminology ..................................... 4 55 2. Overview ............................................. 5 56 2.1 Disconnect Messages (DM) ........................ 5 57 2.2 Change-of-Authorization Messages (CoA) .......... 5 58 2.3 Packet Format ................................... 6 59 3. Attributes ............................................ 10 60 3.1 State ........................................... 12 61 3.2 Message-Authenticator ........................... 12 62 3.3 Error-Cause ..................................... 13 63 3.4 Table of Attributes ............................. 16 64 4. Diameter Considerations ............................... 20 65 5. IANA Considerations ................................... 22 66 6. Security Considerations ............................... 22 67 6.1 Authorization Issues ............................ 22 68 6.2 Impersonation ................................... 23 69 6.3 IPsec Usage Guidelines .......................... 24 70 6.4 Replay Protection ............................... 27 71 7. Example Traces ........................................ 27 72 8. References ............................................ 28 73 8.1 Normative References ............................ 28 74 8.2 Informative References .......................... 29 75 ACKNOWLEDGMENTS .............................................. 30 76 AUTHORS' ADDRESSES ........................................... 30 77 Appendix A - Changes from RFC 3576 ........................... 31 78 Full Copyright Statement ..................................... 32 79 Intellectual Property ........................................ 32 80 1. Introduction 82 The RADIUS protocol, defined in [RFC2865], does not support 83 unsolicited messages sent from the RADIUS server to the Network 84 Access Server (NAS). 86 However, there are many instances in which it is desirable for 87 changes to be made to session characteristics, without requiring the 88 NAS to initiate the exchange. For example, it may be desirable for 89 administrators to be able to terminate a user session in progress. 90 Alternatively, if the user changes authorization level, this may 91 require that authorization attributes be added/deleted from a user 92 session. 94 To overcome these limitations, several vendors have implemented 95 additional RADIUS commands in order to be able to support unsolicited 96 messages sent from the RADIUS server to the NAS. These extended 97 commands provide support for Disconnect and Change-of-Authorization 98 (CoA) packets. Disconnect packets cause a user session to be 99 terminated immediately, whereas CoA packets modify session 100 authorization attributes such as data filters. 102 1.1. Applicability 104 This protocol is being recommended for publication as an 105 Informational RFC rather than as a standards-track RFC because of 106 problems that cannot be fixed without creating incompatibilities with 107 deployed implementations. This includes security vulnerabilities, as 108 well as semantic ambiguities resulting from the design of the Change- 109 of-Authorization (CoA) commands. While fixes are recommended, they 110 cannot be made mandatory since this would be incompatible with 111 existing implementations. 113 Existing implementations of this protocol do not support 114 authorization checks, so that an ISP sharing a NAS with another ISP 115 could disconnect or change authorizations for another ISP's users. 116 In order to remedy this problem, a "Reverse Path Forwarding" check is 117 recommended. See Section 6.1. for details. 119 Existing implementations utilize per-packet authentication and 120 integrity protection algorithms with known weaknesses [MD5Attack]. 121 To provide stronger per-packet authentication and integrity 122 protection, the use of IPsec is recommended. See Section 6.3 for 123 details. 125 Existing implementations lack replay protection. In order to support 126 replay detection, it is recommended that an Event-Timestamp Attribute 127 be added to all packets in situations where IPsec replay protection 128 is not employed. See Section 6.4 for details. 130 The approach taken with CoA commands in existing implementations 131 results in a semantic ambiguity. Existing implementations of the 132 CoA-Request identify the affected session, as well as supply the 133 authorization changes. Since RADIUS Attributes included within 134 existing implementations of the CoA-Request can be used for session 135 identification or authorization change, it may not be clear which 136 function a given attribute is serving. 138 The problem does not exist within the Diameter protocol [RFC3588], in 139 which server-initiated authorization change is initiated using a Re- 140 Auth-Request (RAR) command identifying the session via User-Name and 141 Session-Id AVPs and containing a Re-Auth-Request-Type AVP with value 142 "AUTHORIZE_ONLY". This results in initiation of a standard 143 Request/Response sequence where authorization changes are supplied. 144 As a result, in no command can Diameter AVPs have multiple potential 145 meanings. 147 1.2. Requirements Language 149 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 150 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 151 document are to be interpreted as described in [RFC2119]. 153 1.3. Terminology 155 This document frequently uses the following terms: 157 Network Access Server (NAS) 158 The device providing access to the network. 160 service 161 The NAS provides a service to the user, such as IEEE 802 or PPP. 163 session 164 Each service provided by the NAS to a user constitutes a session, 165 with the beginning of the session defined as the point where 166 service is first provided and the end of the session defined as the 167 point where service is ended. A user may have multiple sessions in 168 parallel or series if the NAS supports that. 170 silently discard 171 This means the implementation discards the packet without further 172 processing. The implementation SHOULD provide the capability of 173 logging the error, including the contents of the silently discarded 174 packet, and SHOULD record the event in a statistics counter. 176 2. Overview 178 This section describes the most commonly implemented features of 179 Disconnect and Change-of-Authorization packets. 181 2.1. Disconnect Messages (DM) 183 A Disconnect-Request packet is sent by the RADIUS server in order to 184 terminate a user session on a NAS and discard all associated session 185 context. The Disconnect-Request packet is sent to UDP port 3799, and 186 identifies the NAS as well as the user session to be terminated by 187 inclusion of the identification attributes described in Section 3. 189 +----------+ Disconnect-Request +----------+ 190 | | <-------------------- | | 191 | NAS | | RADIUS | 192 | | Disconnect-Response | Server | 193 | | ---------------------> | | 194 +----------+ +----------+ 196 The NAS responds to a Disconnect-Request packet sent by a RADIUS 197 server with a Disconnect-ACK if all associated session context is 198 discarded and the user session is no longer connected, or a 199 Disconnect-NAK, if the NAS was unable to disconnect the session and 200 discard all associated session context. A Disconnect-ACK MAY contain 201 the Attribute Acct-Terminate-Cause (49) [RFC2866] with the value set 202 to 6 for Admin-Reset. 204 2.2. Change-of-Authorization Messages (CoA) 206 CoA-Request packets contain information for dynamically changing 207 session authorizations. Typically this is used to change data 208 filters. The data filters can be of either the ingress or egress 209 kind, and are sent in addition to the identification attributes as 210 described in section 3. The port used, and packet format (described 211 in Section 2.3), are the same as that for Disconnect-Request packets. 213 The following attributes MAY be sent in a CoA-Request: 215 Filter-ID (11) - Indicates the name of a data filter list 216 to be applied for the session that the 217 identification attributes map to. 219 NAS-Filter-Rule (TBD) - Provides a filter list to be applied 220 for the session that the identification 221 attributes map to [RFCFilter]. 223 +----------+ CoA-Request +----------+ 224 | | <-------------------- | | 225 | NAS | | RADIUS | 226 | | CoA-Response | Server | 227 | | ---------------------> | | 228 +----------+ +----------+ 230 The NAS responds to a CoA-Request sent by a RADIUS server with a CoA- 231 ACK if the NAS is able to successfully change the authorizations for 232 the user session, or a CoA-NAK if the Request is unsuccessful. A NAS 233 MUST respond to a CoA-Request including a Service-Type Attribute with 234 value "Authorize Only" with a CoA-NAK; a CoA-ACK MUST NOT be sent. A 235 NAS MUST respond to a CoA-Request including a Service-Type Attribute 236 with an unsupported value with a CoA-NAK; an Error-Cause Attribute 237 with value "Unsupported Service" MAY be included. 239 2.3. Packet Format 241 For either Disconnect-Request or CoA-Request packets UDP port 3799 is 242 used as the destination port. For responses, the source and 243 destination ports are reversed. Exactly one RADIUS packet is 244 encapsulated in the UDP Data field. 246 A summary of the data format is shown below. The fields are 247 transmitted from left to right. 249 The packet format consists of the fields: Code, Identifier, Length, 250 Authenticator, and Attributes in Type:Length:Value (TLV) format. All 251 fields hold the same meaning as those described in RADIUS [RFC2865]. 252 The Authenticator field MUST be calculated in the same way as is 253 specified for an Accounting-Request in [RFC2866]. 255 0 1 2 3 256 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 | Code | Identifier | Length | 259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 260 | | 261 | Authenticator | 262 | | 263 | | 264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 265 | Attributes ... 266 +-+-+-+-+-+-+-+-+-+-+-+-+- 268 Code 270 The Code field is one octet, and identifies the type of RADIUS 271 packet. Packets received with an invalid Code field MUST be 272 silently discarded. RADIUS codes (decimal) for this extension are 273 assigned as follows: 275 40 - Disconnect-Request [RFC3575] 276 41 - Disconnect-ACK [RFC3575] 277 42 - Disconnect-NAK [RFC3575] 278 43 - CoA-Request [RFC3575] 279 44 - CoA-ACK [RFC3575] 280 45 - CoA-NAK [RFC3575] 282 Identifier 284 The Identifier field is one octet, and aids in matching requests 285 and replies. RADIUS clients implementing this specification MUST 286 be capable of detecting a duplicate request if it has the same 287 server source IP address, source UDP port and Identifier within a 288 short span of time. 290 Unlike RADIUS as defined in [RFC2865], the responsibility for 291 retransmission of Disconnect-Request and CoA-Request packets lies 292 with the RADIUS server. If after sending these packets, the 293 RADIUS server does not receive a response, it will retransmit. 295 The Identifier field MUST be changed whenever the content of the 296 Attributes field changes, or whenever a valid reply has been 297 received for a previous request. For retransmissions where the 298 contents are identical, the Identifier MUST remain unchanged. 300 If the RADIUS server is retransmitting a Disconnect-Request or 301 CoA-Request to the same client as before, and the Attributes 302 haven't changed, the same Request Authenticator, Identifier and 303 source port MUST be used. If any Attributes have changed, a new 304 Authenticator and Identifier MUST be used. 306 If the Request to a primary proxy fails, a secondary proxy must be 307 queried, if available. Issues relating to failover algorithms are 308 described in [RFC3539]. Since this represents a new request, a 309 new Request Authenticator and Identifier MUST be used. However, 310 where the RADIUS server is sending directly to the client, 311 failover typically does not make sense, since Disconnect or CoA 312 packets need to be delivered to the NAS where the session resides. 314 Length 316 The Length field is two octets. It indicates the length of the 317 packet including the Code, Identifier, Length, Authenticator and 318 Attribute fields. Octets outside the range of the Length field 319 MUST be treated as padding and ignored on reception. If the 320 packet is shorter than the Length field indicates, it MUST be 321 silently discarded. The minimum length is 20 and maximum length 322 is 4096. 324 Authenticator 326 The Authenticator field is sixteen (16) octets. The most 327 significant octet is transmitted first. This value is used to 328 authenticate packets between the RADIUS server and client. 330 Request Authenticator 332 In Request packets, the Authenticator value is a 16 octet MD5 333 [RFC1321] checksum, called the Request Authenticator. The 334 Request Authenticator is calculated the same way as for an 335 Accounting-Request, specified in [RFC2866]. 337 Note that the Request Authenticator of a Disconnect or CoA- 338 Request cannot be computed the same way as the Request 339 Authenticator of a RADIUS Access-Request, because there is no 340 User-Password Attribute in a Disconnect-Request or CoA-Request. 342 Response Authenticator 344 The Authenticator field in a Response packet (e.g. Disconnect- 345 ACK, Disconnect-NAK, CoA-ACK, or CoA-NAK) is called the 346 Response Authenticator, and contains a one-way MD5 hash 347 calculated over a stream of octets consisting of the Code, 348 Identifier, Length, the Request Authenticator field from the 349 packet being replied to, and the response Attributes if any, 350 followed by the shared secret. The resulting 16 octet MD5 hash 351 value is stored in the Authenticator field of the Response 352 packet. 354 Administrative note: As noted in [RFC2865] Section 3, the secret 355 (password shared between the client and the RADIUS server) SHOULD 356 be at least as large and unguessable as a well-chosen password. 357 RADIUS clients MUST use the source IP address of the RADIUS UDP 358 packet to decide which shared secret to use, so that requests can 359 be proxied. 361 Attributes 363 In Disconnect and CoA-Request packets, all Attributes are treated 364 as mandatory. A NAS MUST respond to a CoA-Request containing one 365 or more unsupported Attributes or Attribute values with a CoA-NAK; 366 a Disconnect-Request containing one or more unsupported Attributes 367 or Attribute values MUST be answered with a Disconnect-NAK. State 368 changes resulting from a CoA-Request MUST be atomic: if the 369 Request is successful, a CoA-ACK is sent, and all requested 370 authorization changes MUST be made. If the CoA-Request is 371 unsuccessful, a CoA-NAK MUST be sent, and the requested 372 authorization changes MUST NOT be made. Similarly, a state change 373 MUST NOT occur as a result of an unsuccessful Disconnect-Request; 374 here a Disconnect-NAK MUST be sent. 376 Since within this specification attributes may be used for 377 identification, authorization or other purposes, even if a NAS 378 implements an attribute for use with RADIUS authentication and 379 accounting, it may not support inclusion of that attribute within 380 Disconnect-Request or CoA-Request packets, given the difference in 381 attribute semantics. This is true even for attributes specified 382 within [RFC2865], [RFC2868], [RFC2869], [RFC3162] or [RFC3579] as 383 allowable within Access-Accept packets. As a result, if 384 attributes beyond those specified in Section 3.5 are included 385 within Disconnect-Request or CoA-Request packets, the RADIUS 386 server may receive a Disconnect-NAK/CoA-NAK in response, possibly 387 containing an Error-Cause attribute with value Unsupported 388 Attribute (401). 390 If there are any Proxy-State Attributes in a Disconnect-Request or 391 CoA-Request received from the server, the forwarding proxy or NAS 392 MUST include those Proxy-State Attributes in its response to the 393 server. 395 A forwarding proxy or NAS MUST NOT modify existing Proxy-State, 396 State, or Class Attributes present in the packet. The forwarding 397 proxy or NAS MUST treat any Proxy-State attributes already in the 398 packet as opaque data. Its operation MUST NOT depend on the 399 content of Proxy-State attributes added by previous proxies. The 400 forwarding proxy MUST NOT modify any other Proxy-State Attributes 401 that were in the packet; it may choose not to forward them, but it 402 MUST NOT change their contents. If the forwarding proxy omits the 403 Proxy-State Attributes in the request, it MUST attach them to the 404 response before sending it. 406 When the proxy forwards a Disconnect or CoA-Request, it MAY add a 407 Proxy-State Attribute, but it MUST NOT add more than one. If a 408 Proxy-State Attribute is added to a packet when forwarding the 409 packet, the Proxy-State Attribute MUST be added after any existing 410 Proxy-State attributes. The forwarding proxy MUST NOT change the 411 order of any attributes of the same type, including Proxy-State. 412 Other Attributes can be placed before, after or even between the 413 Proxy-State Attributes. 415 When the proxy receives a response to a CoA-Request or Disconnect- 416 Request, it MUST remove its own Proxy-State (the last Proxy- State 417 in the packet) before forwarding the response. Since Disconnect 418 and CoA responses are authenticated on the entire packet contents, 419 the stripping of the Proxy-State Attribute invalidates the 420 integrity check - so the proxy needs to recompute it. 422 3. Attributes 424 In Disconnect-Request and CoA-Request packets, certain attributes are 425 used to uniquely identify the NAS as well as a user session on the 426 NAS. All NAS identification attributes included in a Request packet 427 MUST match in order for a Disconnect-Request or CoA-Request to be 428 successful; otherwise a Disconnect-NAK or CoA-NAK SHOULD be sent. 429 For session identification attributes, the User-Name and Acct- 430 Session-Id Attributes, if included, MUST match in order for a 431 Disconnect-Request or CoA-Request to be successful; other session 432 identification attributes SHOULD match. Where a mismatch of session 433 identification attributes is detected, a Disconnect-NAK or CoA-NAK 434 SHOULD be sent. 436 The ability to use NAS or session identification attributes to map to 437 unique/multiple sessions is beyond the scope of this document. 438 Identification attributes include NAS and session identification 439 attributes, as described below. 441 NAS identification attributes 443 Attribute # Reference Description 444 --------- --- --------- ----------- 445 NAS-IP-Address 4 [RFC2865] The IPv4 address of the NAS. 446 NAS-Identifier 32 [RFC2865] String identifying the NAS. 447 NAS-IPv6-Address 95 [RFC3162] The IPv6 address of the NAS. 449 Session identification attributes 451 Attribute # Reference Description 452 --------- --- --------- ----------- 453 User-Name 1 [RFC2865] The name of the user 454 associated with the session. 455 NAS-Port 5 [RFC2865] The port on which the 456 session is terminated. 457 Framed-IP-Address 8 [RFC2865] The IPv4 address associated 458 with the session. 459 Called-Station-Id 30 [RFC2865] The link address to which 460 the session is connected. 461 Calling-Station-Id 31 [RFC2865] The link address from which 462 the session is connected. 464 Attribute # Reference Description 465 --------- --- --------- ----------- 466 Acct-Session-Id 44 [RFC2866] The identifier uniquely 467 identifying the session 468 on the NAS. 469 Acct-Multi-Session-Id 50 [RFC2866] The identifier uniquely 470 identifying related sessions. 471 NAS-Port-Type 61 [RFC2865] The type of port used. 472 NAS-Port-Id 87 [RFC2869] String identifying the port 473 where the session is. 474 Originating-Line-Info 94 [RFC4005] Provides information on the 475 characteristics of the line 476 from which a session 477 originated. 478 Framed-Interface-Id 96 [RFC3162] The IPv6 Interface Identifier 479 associated with the session; 480 always sent with 481 Framed-IPv6-Prefix. 482 Framed-IPv6-Prefix 97 [RFC3162] The IPv6 prefix associated 483 with the session, always sent 484 with Framed-Interface-Id. 486 To address security concerns described in Section 6.1, and to enable 487 Diameter/RADIUS translation, the User-Name Attribute SHOULD be 488 present in Disconnect-Request or CoA-Request packets; one or more 489 additional session identification attributes MAY also be present. 490 For example, where a Diameter client utilizes the same Session-Id for 491 both authorization and accounting, inclusion of an Acct-Session-Id 492 Attribute in a Disconnect-Request or CoA-Request can assist with 493 Diameter/RADIUS translation, since Diameter RAR and ASR commands 494 include a Session-Id AVP. 496 Where a NAS offers multiple services, confusion may result with 497 respect to interpretation of a CoA-Request or Disconnect-Request. In 498 order to prevent confusion a RADIUS Server SHOULD identify the 499 session as specifically as possible. For example, an Acct-Session-Id 500 attribute SHOULD be included in Disconnect-Request and CoA-Request 501 packets, rather than just the User-Name attribute. 503 To address security concerns described in Section 6.2, one or more of 504 the NAS-IP-Address or NAS-IPv6-Address Attributes SHOULD be present 505 in Disconnect-Request or CoA-Request packets; the NAS-Identifier 506 Attribute MAY be present in addition. 508 If one or more authorization changes specified in a CoA-Request 509 cannot be carried out, or if one or more attributes or attribute- 510 values is unsupported, a CoA-NAK MUST be sent. Similarly, if there 511 are one or more unsupported attributes or attribute values in a 512 Disconnect-Request, a Disconnect-NAK MUST be sent. 514 A CoA-Request containing a Service-Type Attribute with value 515 "Authorize Only" MUST contain only NAS or session identification 516 attributes, as well as Service-Type and State attributes. If other 517 attributes are included in such a CoA-Request, implementations MUST 518 send a CoA-NAK; an Error-Cause Attribute with value "Unsupported 519 Attribute" MAY be included. 521 A Disconnect-Request MUST contain only NAS and session identification 522 attributes (see Section 3). If other attributes are included in a 523 Disconnect-Request, implementations MUST send a Disconnect-NAK; an 524 Error-Cause Attribute with value "Unsupported Attribute" MAY be 525 included. 527 3.1. State 529 [RFC2865] Section 5.44 states: 531 An Access-Request MUST contain either a User-Password or a CHAP- 532 Password or State. An Access-Request MUST NOT contain both a 533 User-Password and a CHAP-Password. If future extensions allow 534 other kinds of authentication information to be conveyed, the 535 attribute for that can be used in an Access-Request instead of 536 User-Password or CHAP-Password. 538 In order to satisfy the requirements of [RFC2865] Section 5.44, an 539 Access-Request with Service-Type="Authorize-Only" MUST contain a 540 State attribute. 542 In order to provide a State attribute to the NAS, a server sending a 543 CoA-Request with a Service-Type value of "Authorize-Only" MUST 544 include a State Attribute, and the NAS MUST include the State 545 Attribute unchanged in the Access-Request. A NAS receiving a CoA- 546 Request containing a Service-Type value of "Authorize-Only" but 547 lacking a State attribute MUST send a CoA-NAK and SHOULD include an 548 Error-Cause attribute with value 402 (Missing Attribute). 550 3.2. Message-Authenticator 552 The Message-Authenticator Attribute MAY be used to authenticate and 553 integrity-protect CoA-Request, CoA-ACK, CoA-NAK, Disconnect-Request, 554 Disconnect-ACK and Disconnect-NAK packets order to prevent spoofing. 556 A RADIUS client receiving a CoA-Request or Disconnect-Request with a 557 Message-Authenticator Attribute present MUST calculate the correct 558 value of the Message-Authenticator and silently discard the packet if 559 it does not match the value sent. A RADIUS server receiving a 560 CoA/Disconnect-ACK or CoA/Disconnect-NAK with a Message-Authenticator 561 Attribute present MUST calculate the correct value of the Message- 562 Authenticator and silently discard the packet if it does not match 563 the value sent. 565 When a Message-Authenticator Attribute is included within a CoA- 566 Request or Disconnect-Request, it is calculated as follows: 568 Message-Authenticator = HMAC-MD5 (Type, Identifier, Length, 569 Request Authenticator, Attributes) 571 When the HMAC-MD5 message integrity check is calculated the 572 Request Authenticator field and Message-Authenticator Attribute 573 should be considered to be sixteen octets of zero. The Message- 574 Authenticator Attribute is calculated and inserted in the packet 575 before the Request Authenticator is calculated. 577 When a Message-Authenticator Attribute is included within a CoA- 578 ACK, CoA-NAK, Disconnect-ACK or Disconnect-NAK, it is calculated 579 as follows: 581 Message-Authenticator = HMAC-MD5 (Type, Identifier, Length, 582 Request Authenticator, Attributes) 584 When the HMAC-MD5 message integrity check is calculated the 585 Message-Authenticator Attribute should be considered to be sixteen 586 octets of zero. The Request Authenticator is taken from the 587 corresponding CoA/Disconnect-Request. The Message-Authenticator 588 is calculated and inserted in the packet before the Response 589 Authenticator is calculated. 591 3.3. Error-Cause 593 Description 595 It is possible that the NAS cannot honor Disconnect-Request or 596 CoA-Request packets for some reason. The Error-Cause Attribute 597 provides more detail on the cause of the problem. It MAY be 598 included within Disconnect-ACK, Disconnect-NAK and CoA-NAK 599 packets. 601 A summary of the Error-Cause Attribute format is shown below. The 602 fields are transmitted from left to right. 604 0 1 2 3 605 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 606 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 607 | Type | Length | Value 608 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 609 Value (cont) | 610 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 612 Type 614 101 for Error-Cause 616 Length 618 6 620 Value 622 The Value field is four octets, containing an integer specifying 623 the cause of the error. Values 0-199 and 300-399 are reserved. 624 Values 200-299 represent successful completion, so that these 625 values may only be sent within Disconnect-ACK or CoA-ACK packets 626 and MUST NOT be sent within a Disconnect-NAK or CoA-NAK. Values 627 400-499 represent fatal errors committed by the RADIUS server, so 628 that they MAY be sent within CoA-NAK or Disconnect-NAK packets, 629 and MUST NOT be sent within CoA-ACK or Disconnect-ACK packets. 630 Values 500-599 represent fatal errors occurring on a NAS or RADIUS 631 proxy, so that they MAY be sent within CoA-NAK and Disconnect-NAK 632 packets, and MUST NOT be sent within CoA-ACK or Disconnect-ACK 633 packets. Error-Cause values SHOULD be logged by the RADIUS 634 server. Error-Code values (expressed in decimal) include: 636 # Value 637 --- ----- 638 201 Residual Session Context Removed 639 202 Invalid EAP Packet (Ignored) 640 401 Unsupported Attribute 641 402 Missing Attribute 642 403 NAS Identification Mismatch 643 404 Invalid Request 644 405 Unsupported Service 645 406 Unsupported Extension 646 501 Administratively Prohibited 647 502 Request Not Routable (Proxy) 648 503 Session Context Not Found 649 504 Session Context Not Removable 650 505 Other Proxy Processing Error 651 506 Resources Unavailable 652 507 Request Initiated 654 "Residual Session Context Removed" is sent in response to a 655 Disconnect-Request if the user session is no longer active, but 656 residual session context was found and successfully removed. This 657 value is only sent within a Disconnect-ACK and MUST NOT be sent 658 within a CoA-ACK, Disconnect-NAK or CoA-NAK. 660 "Invalid EAP Packet (Ignored)" is a non-fatal error that MUST NOT 661 be sent by implementations of this specification. 663 "Unsupported Attribute" is a fatal error sent if a Request 664 contains an attribute (such as a Vendor-Specific or EAP-Message 665 Attribute) that is not supported. 667 "Missing Attribute" is a fatal error sent if critical attributes 668 (such as NAS or session identification attributes) are missing 669 from a Request. 671 "NAS Identification Mismatch" is a fatal error sent if one or more 672 NAS identification attributes (see Section 3) do not match the 673 identity of the NAS receiving the Request. 675 "Invalid Request" is a fatal error sent if some other aspect of 676 the Request is invalid, such as if one or more attributes (such as 677 EAP- Message Attribute(s)) are not formatted properly. 679 "Unsupported Service" is a fatal error sent if a Service-Type 680 Attribute included with the Request is sent with an invalid or 681 unsupported value. This error cannot be sent in response to a 682 Disconnect-Request. 684 "Unsupported Extension" is a fatal error sent due to lack of 685 support for an extension such as Disconnect and/or CoA packets. 686 This will typically be sent by a proxy receiving an ICMP port 687 unreachable message after attempting to forward a Request to the 688 NAS. 690 "Administratively Prohibited" is a fatal error sent if the NAS is 691 configured to prohibit honoring of Request packets for the 692 specified session. 694 "Request Not Routable" is a fatal error which MAY be sent by a 695 RADIUS proxy and MUST NOT be sent by a NAS. It indicates that the 696 RADIUS proxy was unable to determine how to route the Request to 697 the NAS. For example, this can occur if the required entries are 698 not present in the proxy's realm routing table. 700 "Session Context Not Found" is a fatal error sent if the session 701 context identified in the Request does not exist on the NAS. 703 "Session Context Not Removable" is a fatal error sent in response 704 to a Disconnect-Request if the NAS was able to locate the session 705 context, but could not remove it for some reason. It MUST NOT be 706 sent within a CoA-ACK, CoA-NAK or Disconnect-ACK, only within a 707 Disconnect-NAK. 709 "Other Proxy Processing Error" is a fatal error sent in response 710 to a Request that could not be processed by a proxy, for reasons 711 other than routing. 713 "Resources Unavailable" is a fatal error sent when a Request could 714 not be honored due to lack of available NAS resources (memory, 715 non- volatile storage, etc.). 717 "Request Initiated" is a fatal error sent in response to a CoA- 718 Request including a Service-Type Attribute with a value of 719 "Authorize Only". It indicates that the CoA-Request has not been 720 honored, but that a RADIUS Access-Request including a Service-Type 721 Attribute with value "Authorize Only" is being sent to the RADIUS 722 server. 724 3.4. Table of Attributes 726 The following table provides a guide to which attributes may be found 727 in which packets, and in what quantity. 729 Change-of-Authorization Messages 731 Request ACK NAK # Attribute 732 0-1 0 0 1 User-Name [Note 1] 733 0-1 0 0 4 NAS-IP-Address [Note 1] 734 0-1 0 0 5 NAS-Port [Note 1] 735 0-1 0 0-1 6 Service-Type [Note 6] 736 0-1 0 0 7 Framed-Protocol [Note 3] 737 0-1 0 0 8 Framed-IP-Address [Note 1] 738 0-1 0 0 9 Framed-IP-Netmask [Note 3] 739 0-1 0 0 10 Framed-Routing [Note 3] 740 0+ 0 0 11 Filter-ID [Note 3] 741 0-1 0 0 12 Framed-MTU [Note 3] 742 0+ 0 0 13 Framed-Compression [Note 3] 743 0+ 0 0 14 Login-IP-Host [Note 3] 744 0-1 0 0 15 Login-Service [Note 3] 745 0-1 0 0 16 Login-TCP-Port [Note 3] 746 0+ 0 0 18 Reply-Message [Note 2] 747 Request ACK NAK # Attribute 748 Request ACK NAK # Attribute 749 0-1 0 0 19 Callback-Number [Note 3] 750 0-1 0 0 20 Callback-Id [Note 3] 751 0+ 0 0 22 Framed-Route [Note 3] 752 0-1 0 0 23 Framed-IPX-Network [Note 3] 753 0-1 0-1 0-1 24 State [Note 7] 754 0+ 0 0 25 Class [Note 3] 755 0+ 0 0 26 Vendor-Specific [Note 3] 756 0-1 0 0 27 Session-Timeout [Note 3] 757 0-1 0 0 28 Idle-Timeout [Note 3] 758 0-1 0 0 29 Termination-Action [Note 3] 759 0-1 0 0 30 Called-Station-Id [Note 1] 760 0-1 0 0 31 Calling-Station-Id [Note 1] 761 0-1 0 0 32 NAS-Identifier [Note 1] 762 0+ 0+ 0+ 33 Proxy-State 763 0-1 0 0 34 Login-LAT-Service [Note 3] 764 0-1 0 0 35 Login-LAT-Node [Note 3] 765 0-1 0 0 36 Login-LAT-Group [Note 3] 766 0-1 0 0 37 Framed-AppleTalk-Link [Note 3] 767 0+ 0 0 38 Framed-AppleTalk-Network [Note 3] 768 0-1 0 0 39 Framed-AppleTalk-Zone [Note 3] 769 0-1 0 0 44 Acct-Session-Id [Note 1] 770 0-1 0 0 50 Acct-Multi-Session-Id [Note 1] 771 0-1 0-1 0-1 55 Event-Timestamp 772 0-1 0 0 61 NAS-Port-Type [Note 1] 773 0-1 0 0 62 Port-Limit [Note 3] 774 0-1 0 0 63 Login-LAT-Port [Note 3] 775 0+ 0 0 64 Tunnel-Type [Note 5] 776 0+ 0 0 65 Tunnel-Medium-Type [Note 5] 777 0+ 0 0 66 Tunnel-Client-Endpoint [Note 5] 778 0+ 0 0 67 Tunnel-Server-Endpoint [Note 5] 779 0+ 0 0 69 Tunnel-Password [Note 5] 780 0-1 0 0 71 ARAP-Features [Note 3] 781 0-1 0 0 72 ARAP-Zone-Access [Note 3] 782 0+ 0 0 78 Configuration-Token [Note 3] 783 0+ 0-1 0 79 EAP-Message [Note 2] 784 0-1 0-1 0-1 80 Message-Authenticator 785 0+ 0 0 81 Tunnel-Private-Group-ID [Note 5] 786 0+ 0 0 82 Tunnel-Assignment-ID [Note 5] 787 0+ 0 0 83 Tunnel-Preference [Note 5] 788 0-1 0 0 85 Acct-Interim-Interval [Note 3] 789 0-1 0 0 87 NAS-Port-Id [Note 1] 790 0-1 0 0 88 Framed-Pool [Note 3] 791 0+ 0 0 90 Tunnel-Client-Auth-ID [Note 5] 792 0+ 0 0 91 Tunnel-Server-Auth-ID [Note 5] 793 0-1 0 0 94 Originating-Line-Info [Note 1] 794 0-1 0 0 95 NAS-IPv6-Address [Note 1] 795 Request ACK NAK # Attribute 796 Request ACK NAK # Attribute 797 0-1 0 0 96 Framed-Interface-Id [Note 1] 798 0+ 0 0 97 Framed-IPv6-Prefix [Note 1] 799 0+ 0 0 98 Login-IPv6-Host [Note 3] 800 0+ 0 0 99 Framed-IPv6-Route [Note 3] 801 0-1 0 0 100 Framed-IPv6-Pool [Note 3] 802 0 0 0+ 101 Error-Cause 803 0-1 0 0 TBD NAS-Filter-Rule 804 Request ACK NAK # Attribute 806 Disconnect Messages 808 Request ACK NAK # Attribute 809 0-1 0 0 1 User-Name [Note 1] 810 0-1 0 0 4 NAS-IP-Address [Note 1] 811 0-1 0 0 5 NAS-Port [Note 1] 812 0 0 0 6 Service-Type 813 0-1 0 0 8 Framed-IP-Address [Note 1] 814 0+ 0 0 18 Reply-Message [Note 2] 815 0 0 0 24 State 816 0+ 0 0 25 Class [Note 4] 817 0+ 0 0 26 Vendor-Specific 818 0-1 0 0 30 Called-Station-Id [Note 1] 819 0-1 0 0 31 Calling-Station-Id [Note 1] 820 0-1 0 0 32 NAS-Identifier [Note 1] 821 0+ 0+ 0+ 33 Proxy-State 822 0-1 0 0 44 Acct-Session-Id [Note 1] 823 0-1 0-1 0 49 Acct-Terminate-Cause 824 0-1 0 0 50 Acct-Multi-Session-Id [Note 1] 825 0-1 0-1 0-1 55 Event-Timestamp 826 0-1 0 0 61 NAS-Port-Type [Note 1] 827 0+ 0-1 0 79 EAP-Message [Note 2] 828 0-1 0-1 0-1 80 Message-Authenticator 829 0-1 0 0 87 NAS-Port-Id [Note 1] 830 0-1 0 0 94 Orginating-Line-Info [Note 1] 831 0-1 0 0 95 NAS-IPv6-Address [Note 1] 832 0-1 0 0 96 Framed-Interface-Id [Note 1] 833 0+ 0 0 97 Framed-IPv6-Prefix [Note 1] 834 0 0+ 0+ 101 Error-Cause 835 Request ACK NAK # Attribute 837 The following table defines the meaning of the above table entries. 839 0 This attribute MUST NOT be present in packet. 840 0+ Zero or more instances of this attribute MAY be present in packet. 841 0-1 Zero or one instance of this attribute MAY be present in packet. 842 1 Exactly one instance of this attribute MUST be present in packet. 844 [Note 1] Where NAS or session identification attributes are included 845 in Disconnect-Request or CoA-Request packets, they are used for 846 identification purposes only. These attributes MUST NOT be used for 847 purposes other than identification (e.g. within CoA-Request packets 848 to request authorization changes). 850 [Note 2] The Reply-Message Attribute is used to present a displayable 851 message to the user. The message is only displayed as a result of a 852 successful Disconnect-Request or CoA-Request (where a Disconnect-ACK 853 or CoA-ACK is subsequently sent). Where EAP is used for 854 authentication, an EAP-Message/Notification-Request Attribute is sent 855 instead, and Disconnect-ACK or CoA-ACK packets contain an EAP- 856 Message/Notification-Response Attribute. 858 [Note 3] When included within a CoA-Request, these attributes 859 represent an authorization change request. When one of these 860 attributes is omitted from a CoA-Request, the NAS assumes that the 861 attribute value is to remain unchanged. Attributes included in a 862 CoA-Request replace all existing value(s) of the same attribute(s). 864 [Note 4] When included within a successful Disconnect-Request (where 865 a Disconnect-ACK is subsequently sent), the Class Attribute SHOULD be 866 sent unmodified by the client to the accounting server in the 867 Accounting Stop packet. If the Disconnect-Request is unsuccessful, 868 then the Class Attribute is not processed. 870 [Note 5] When included within a CoA-Request, these attributes 871 represent an authorization change request. Where tunnel attribute(s) 872 are included within a successful CoA-Request, all existing tunnel 873 attributes are removed and replaced by the new attribute(s). 875 [Note 6] Support for the Service-Type of "Authorize Only" is OPTIONAL 876 on the NAS and RADIUS server. A NAS supporting the "Authorize Only" 877 Service-Type value within a CoA-Request packet MUST respond with a 878 CoA-NAK containing a Service-Type Attribute with value "Authorize 879 Only", and an Error-Cause Attribute with value "Request Initiated". 880 The NAS then sends an Access-Request to the RADIUS server with a 881 Service-Type Attribute with value "Authorize Only". This Access- 882 Request SHOULD contain the NAS attributes from the CoA-Request, as 883 well as the session attributes from the CoA-Request legal for 884 inclusion in an Access-Request as specified in [RFC2865], [RFC2868], 885 [RFC2869] and [RFC3162]. As noted in [RFC2869] Section 5.19, a 886 Message-Authenticator attribute SHOULD be included in an Access- 887 Request that does not contain a User-Password, CHAP-Password, ARAP- 888 Password or EAP-Message Attribute. The RADIUS server should send 889 back an Access-Accept to (re-)authorize the session or an Access- 890 Reject to refuse to (re-)authorize it. 892 A NAS that does not support the Service-Type Attribute with the value 893 "Authorize Only" within a CoA-Request MUST respond with a CoA-NAK 894 including no Service-Type Attribute; an Error-Cause Attribute with 895 value "Unsupported Service" MAY be included. 897 [Note 7] The State Attribute is available to be sent by the RADIUS 898 server to the NAS in a CoA-Request packet and MUST be sent unmodified 899 from the NAS to the RADIUS server in a subsequent ACK or NAK packet. 900 If a Service-Type Attribute with value "Authorize Only" is included 901 in a CoA-Request then a State Attribute MUST be present, and MUST be 902 sent unmodified from the NAS to the RADIUS server in the resulting 903 Access-Request sent to the RADIUS server, if any. The State 904 Attribute is also available to be sent by the RADIUS server to the 905 NAS in a CoA-Request that also includes a Termination-Action 906 Attribute with the value of RADIUS-Request. If the client performs 907 the Termination-Action by sending a new Access-Request upon 908 termination of the current session, it MUST include the State 909 Attribute unchanged in that Access-Request. In either usage, the 910 client MUST NOT interpret the Attribute locally. A CoA-Request 911 packet must have only zero or one State Attribute. Usage of the 912 State Attribute is implementation dependent. 914 4. Diameter Considerations 916 Due to differences in handling change-of-authorization requests in 917 RADIUS and Diameter, it may be difficult or impossible for a 918 Diameter/RADIUS gateway to successfully translate a Diameter Re-Auth- 919 Request (RAR) to a CoA-Request and vice versa. For example, since a 920 CoA-Request only initiates an authorization change but does not 921 initiate re-authentication, a RAR command containing a Re-Auth- 922 Request-Type AVP with value "AUTHORIZE_AUTHENTICATE" cannot be 923 directly translated to a CoA-Request. A Diameter/RADIUS gateway 924 receiving a CoA-Request containing authorization changes will need to 925 translate this into two Diameter exchange. First, the 926 Diameter/RADIUS gateway will issue a RAR command including a Session- 927 Id AVP and a Re-Auth-Request-Type AVP with value "AUTHORIZE ONLY". 928 Then the Diameter/RADIUS gateway will respond to the ensuing access 929 request with a response including the authorization attributes 930 gleaned from the CoA-Request. For the translation to be possible, 931 the CoA-Request MUST include a Acct-Session-Id Attribute. If the 932 Diameter client uses the same Session-Id for both authorization and 933 accounting, then the Diameter/RADIUS gateway can copy the contents of 934 the Acct-Session-Id Attribute into the Session-Id AVP; otherwise, it 935 will need to map the Acct-Session-Id value to an equivalent Session- 936 Id for use within a RAR command. 938 To simplify translation between RADIUS and Diameter, a server 939 compliant with this specification MAY include a Service-Type 940 Attribute with value "Authorize Only" within a CoA-Request. Such a 941 CoA-Request MUST contain a State Attribute. A NAS supporting the 942 "Authorize Only" Service-Type within a CoA-Request responds with a 943 CoA-NAK containing a Service-Type Attribute with value "Authorize 944 Only", and an Error-Cause Attribute with value "Request Initiated". 945 The NAS will then send an Access-Request containing a Service-Type 946 Attribute with a value of "Authorize Only", along with a State 947 Attribute. A Diameter/RADIUS gateway receiving a CoA-Request 948 containing a Service-Type with value "Authorize Only" translates this 949 to a RAR with Re-Auth-Request-Type AVP with value "AUTHORIZE ONLY". 950 The received RAA is then translated to a CoA-NAK with a Service-Type 951 value of "Authorize Only". If the Result-Code AVP in the RAA has a 952 value in the success category, then an Error-Cause Attribute with 953 value "Request Initiated" is included in the CoA-NAK. If the 954 Result-Code AVP in the RAA has a value indicating a Protocol Error or 955 a Transient or Permanent Failure, then an alternate Error-Cause 956 Attribute is returned as suggested below. 958 Within Diameter, a server can request that a session be aborted by 959 sending an Abort-Session-Request (ASR), identifying the session to be 960 terminated using Session-ID and User-Name AVPs. The ASR command is 961 translated to a Disconnect-Request containing an Acct-Session-Id and 962 User-Name attribute. If the Diameter client utilizes the same 963 Session-Id in both authorization and accounting, then the value of 964 the Session-ID AVP may be placed in the Acct-Session-Id attribute; 965 otherwise the value of the Session-ID AVP will need to be mapped to 966 an appropriate Acct-Session-Id value. For a Disconnect-Request to 967 be translatable to an ASR, an Acct-Session-Id attribute MUST be 968 present. If the Diameter client utilizes the same Session-Id in both 969 authorization and accounting, then the value of the Acct-Session-Id 970 may be placed into the Session-ID AVP within the ASR; otherwise the 971 value of the Acct-Session-Id will need to be mapped to an appropriate 972 Session-ID value. 974 An Abort-Session-Answer (ASA) command is sent in response to an ASR 975 in order to indicate the disposition of the request. A 976 Diameter/RADIUS gateway receiving a Disconnect-ACK translates this to 977 an ASA command with a Result-Code AVP of "DIAMETER_SUCCESS". A 978 Disconnect-NAK received from the server is translated to an ASA 979 command with a Result-Code AVP which depends on the value of the 980 Error-Cause Attribute. Suggested translations between Error-Cause 981 Attribute values and Result-Code AVP values are included below: 983 # Error-Cause Attribute Value Result-Code AVP 984 --- --------------------------- ------------------------ 985 201 Residual Session Context DIAMETER_SUCCESS 986 Removed 987 202 Invalid EAP Packet DIAMETER_LIMITED_SUCCESS 988 (Ignored) 989 401 Unsupported Attribute DIAMETER_AVP_UNSUPPORTED 990 402 Missing Attribute DIAMETER_MISSING_AVP 991 403 NAS Identification DIAMETER_REALM_NOT_SERVED 992 Mismatch 993 404 Invalid Request DIAMETER_UNABLE_TO_COMPLY 994 405 Unsupported Service DIAMETER_COMMAND_UNSUPPORTED 995 406 Unsupported Extension DIAMETER_APPLICATION_UNSUPPORTED 996 501 Administratively DIAMETER_AUTHORIZATION_REJECTED 997 Prohibited 998 502 Request Not Routable (Proxy) DIAMETER_UNABLE_TO_DELIVER 999 503 Session Context Not Found DIAMETER_UNKNOWN_SESSION_ID 1000 504 Session Context Not DIAMETER_AUTHORIZATION_REJECTED 1001 Removable 1002 505 Other Proxy Processing DIAMETER_UNABLE_TO_COMPLY 1003 Error 1004 506 Resources Unavailable DIAMETER_RESOURCES_EXCEEDED 1005 507 Request Initiated DIAMETER_SUCCESS 1007 Since both the ASR/ASA and Disconnect-Request/Disconnect- 1008 NAK/Disconnect-ACK exchanges involve just a request and response, 1009 inclusion of an "Authorize Only" Service-Type within a Disconnect- 1010 Request is not needed to assist in Diameter/RADIUS translation, and 1011 may make translation more difficult. As a result, the Service-Type 1012 Attribute MUST NOT be used within a Disconnect-Request. 1014 5. IANA Considerations 1016 This specification contains no actions for IANA. All protocol 1017 parameters required for this document were previously approved as 1018 part of the publication of [RFC3576]. 1020 6. Security Considerations 1022 6.1. Authorization Issues 1024 Where a NAS is shared by multiple providers, it is undesirable for 1025 one provider to be able to send Disconnect-Request or CoA-Requests 1026 affecting the sessions of another provider. 1028 A NAS or RADIUS proxy MUST silently discard Disconnect-Request or 1029 CoA-Request packets from untrusted sources. By default, a RADIUS 1030 proxy SHOULD perform a "reverse path forwarding" (RPF) check to 1031 verify that a Disconnect-Request or CoA-Request originates from an 1032 authorized RADIUS server. In addition, it SHOULD be possible to 1033 explicitly authorize additional sources of Disconnect-Request or CoA- 1034 Request packets relating to certain classes of sessions. For 1035 example, a particular source can be explicitly authorized to send 1036 CoA-Request packets relating to users within a set of realms. 1038 To perform the RPF check, the proxy uses the session identification 1039 attributes included in Disconnect-Request or CoA-Request packets, in 1040 order to determine the RADIUS server(s) to which an equivalent 1041 Access-Request could be routed. If the source address of the 1042 Disconnect-Request or CoA-Request is within this set, then the 1043 Request is forwarded; otherwise it MUST be silently discarded. 1045 Typically the proxy will extract the realm from the Network Access 1046 Identifier [RFC4282] included within the User-Name Attribute, and 1047 determine the corresponding RADIUS servers in the proxy routing 1048 tables. The RADIUS servers for that realm are then compared against 1049 the source address of the packet. Where no RADIUS proxy is present, 1050 the RPF check will need to be performed by the NAS itself. 1052 Since authorization to send a Disconnect-Request or CoA-Request is 1053 determined based on the source address and the corresponding shared 1054 secret, the NASes or proxies SHOULD configure a different shared 1055 secret for each RADIUS server. 1057 6.2. Impersonation 1059 [RFC2865] Section 3 states: 1061 A RADIUS server MUST use the source IP address of the RADIUS 1062 UDP packet to decide which shared secret to use, so that 1063 RADIUS requests can be proxied. 1065 When RADIUS requests are forwarded by a proxy, the NAS-IP-Address or 1066 NAS-IPv6-Address Attributes will typically not match the source 1067 address observed by the RADIUS server. Since the NAS-Identifier 1068 Attribute need not contain an FQDN, this attribute may not be 1069 resolvable to the source address observed by the RADIUS server, even 1070 when no proxy is present. 1072 As a result, the authenticity check performed by a RADIUS server or 1073 proxy does not verify the correctness of NAS identification 1074 attributes. This makes it possible for a rogue NAS to forge NAS-IP- 1075 Address, NAS-IPv6-Address or NAS-Identifier Attributes within a 1076 RADIUS Access-Request in order to impersonate another NAS. It is 1077 also possible for a rogue NAS to forge session identification 1078 attributes such as the Called-Station-Id, Calling-Station-Id, or 1079 Originating-Line-Info [RFC4005]. This could fool the RADIUS server 1080 into sending Disconnect-Request or CoA-Request packets containing 1081 forged session identification attributes to a NAS targeted by an 1082 attacker. 1084 To address these vulnerabilities RADIUS proxies SHOULD check whether 1085 NAS identification attributes (see Section 3) match the source 1086 address of packets originating from the NAS. Where one or more 1087 attributes do not match, Disconnect-Request or CoA-Request packets 1088 SHOULD be silently discarded. 1090 Such a check may not always be possible. Since the NAS-Identifier 1091 Attribute need not correspond to an FQDN, it may not be resolvable to 1092 an IP address to be matched against the source address. Also, where 1093 a NAT exists between the RADIUS client and proxy, checking the NAS- 1094 IP-Address or NAS-IPv6-Address Attributes may not be feasible. 1096 6.3. IPsec Usage Guidelines 1098 In addition to security vulnerabilities unique to Disconnect or CoA 1099 packets, the protocol exchanges described in this document are 1100 susceptible to the same vulnerabilities as RADIUS [RFC2865]. It is 1101 RECOMMENDED that IPsec be employed to afford better security. 1103 Implementations of this specification SHOULD support IPsec [RFC4301] 1104 along with IKEv1 [RFC2409] for key management. IPsec ESP [RFC4303] 1105 with non-null transform SHOULD be supported, and IPsec ESP with a 1106 non-null encryption transform and authentication support SHOULD be 1107 used to provide per-packet confidentiality, authentication, integrity 1108 and replay protection. IKE SHOULD be used for key management. 1110 Within RADIUS [RFC2865], a shared secret is used for hiding of 1111 Attributes such as User-Password, as well as in computation of the 1112 Response Authenticator. In RADIUS accounting [RFC2866], the shared 1113 secret is used in computation of both the Request Authenticator and 1114 the Response Authenticator. 1116 Since in RADIUS a shared secret is used to provide confidentiality as 1117 well as integrity protection and authentication, only use of IPsec 1118 ESP with a non-null transform can provide security services 1119 sufficient to substitute for RADIUS application-layer security. 1120 Therefore, where IPsec AH or ESP null is used, it will typically 1121 still be necessary to configure a RADIUS shared secret. 1123 Where RADIUS is run over IPsec ESP with a non-null transform, the 1124 secret shared between the NAS and the RADIUS server MAY NOT be 1125 configured. In this case, a shared secret of zero length MUST be 1126 assumed. However, a RADIUS server that cannot know whether incoming 1127 traffic is IPsec-protected MUST be configured with a non-null RADIUS 1128 shared secret. 1130 When IPsec ESP is used with RADIUS, per-packet authentication, 1131 integrity and replay protection MUST be used. 3DES-CBC MUST be 1132 supported as an encryption transform and AES-CBC SHOULD be supported. 1133 AES-CBC SHOULD be offered as a preferred encryption transform if 1134 supported. HMAC-SHA1-96 MUST be supported as an authentication 1135 transform. DES-CBC SHOULD NOT be used as the encryption transform. 1137 A typical IPsec policy for an IPsec-capable RADIUS client is 1138 "Initiate IPsec, from me to any destination port UDP 1812". This 1139 IPsec policy causes an IPsec SA to be set up by the RADIUS client 1140 prior to sending RADIUS traffic. If some RADIUS servers contacted by 1141 the client do not support IPsec, then a more granular policy will be 1142 required: "Initiate IPsec, from me to IPsec-Capable-RADIUS-Server, 1143 destination port UDP 1812." 1145 For a client implementing this specification the policy would be 1146 "Accept IPsec, from any to me, destination port UDP 3799". This 1147 causes the RADIUS client to accept (but not require) use of IPsec. 1148 It may not be appropriate to require IPsec for all RADIUS servers 1149 connecting to an IPsec-enabled RADIUS client, since some RADIUS 1150 servers may not support IPsec. 1152 For an IPsec-capable RADIUS server, a typical IPsec policy is "Accept 1153 IPsec, from any to me, destination port 1812". This causes the 1154 RADIUS server to accept (but not require) use of IPsec. It may not 1155 be appropriate to require IPsec for all RADIUS clients connecting to 1156 an IPsec-enabled RADIUS server, since some RADIUS clients may not 1157 support IPsec. 1159 For servers implementing this specification, the policy would be 1160 "Initiate IPsec, from me to any, destination port UDP 3799". This 1161 causes the RADIUS server to initiate IPsec when sending RADIUS 1162 extension traffic to any RADIUS client. If some RADIUS clients 1163 contacted by the server do not support IPsec, then a more granular 1164 policy will be required, such as "Initiate IPsec, from me to IPsec- 1165 capable-RADIUS-client, destination port UDP 3799". 1167 Where IPsec is used for security, and no RADIUS shared secret is 1168 configured, it is important that the RADIUS client and server perform 1169 an authorization check. Before enabling a host to act as a RADIUS 1170 client, the RADIUS server SHOULD check whether the host is authorized 1171 to provide network access. Similarly, before enabling a host to act 1172 as a RADIUS server, the RADIUS client SHOULD check whether the host 1173 is authorized for that role. 1175 RADIUS servers can be configured with the IP addresses (for IKE 1176 Aggressive Mode with pre-shared keys) or FQDNs (for certificate 1177 authentication) of RADIUS clients. Alternatively, if a separate 1178 Certification Authority (CA) exists for RADIUS clients, then the 1179 RADIUS server can configure this CA as a trust anchor [RFC3280] for 1180 use with IPsec. 1182 Similarly, RADIUS clients can be configured with the IP addresses 1183 (for IKE Aggressive Mode with pre-shared keys) or FQDNs (for 1184 certificate authentication) of RADIUS servers. Alternatively, if a 1185 separate CA exists for RADIUS servers, then the RADIUS client can 1186 configure this CA as a trust anchor for use with IPsec. 1188 Since unlike SSL/TLS, IKE does not permit certificate policies to be 1189 set on a per-port basis, certificate policies need to apply to all 1190 uses of IPsec on RADIUS clients and servers. In IPsec deployment 1191 supporting only certificate authentication, a management station 1192 initiating an IPsec-protected telnet session to the RADIUS server 1193 would need to obtain a certificate chaining to the RADIUS client CA. 1194 Issuing such a certificate migh not be appropriate if the management 1195 station was not authorized as a RADIUS client. 1197 Where RADIUS clients may obtain their IP address dynamically (such as 1198 an Access Point supporting DHCP), Main Mode with pre-shared keys 1199 [RFC2409] SHOULD NOT be used, since this requires use of a group pre- 1200 shared key; instead, Aggressive Mode SHOULD be used. Where RADIUS 1201 client addresses are statically assigned either Aggressive Mode or 1202 Main Mode MAY be used. With certificate authentication, Main Mode 1203 SHOULD be used. 1205 Care needs to be taken with IKE Phase 1 Identity Payload selection in 1206 order to enable mapping of identities to pre-shared keys even with 1207 Aggressive Mode. Where the ID_IPV4_ADDR or ID_IPV6_ADDR Identity 1208 Payloads are used and addresses are dynamically assigned, mapping of 1209 identities to keys is not possible, so that group pre-shared keys are 1210 still a practical necessity. As a result, the ID_FQDN identity 1211 payload SHOULD be employed in situations where Aggressive mode is 1212 utilized along with pre-shared keys and IP addresses are dynamically 1213 assigned. This approach also has other advantages, since it allows 1214 the RADIUS server and client to configure themselves based on the 1215 fully qualified domain name of their peers. 1217 Note that with IPsec, security services are negotiated at the 1218 granularity of an IPsec SA, so that RADIUS exchanges requiring a set 1219 of security services different from those negotiated with existing 1220 IPsec SAs will need to negotiate a new IPsec SA. Separate IPsec SAs 1221 are also advisable where quality of service considerations dictate 1222 different handling RADIUS conversations. Attempting to apply 1223 different quality of service to connections handled by the same IPsec 1224 SA can result in reordering, and falling outside the replay window. 1225 For a discussion of the issues, see [RFC2983]. 1227 6.4. Replay Protection 1229 Where IPsec replay protection is not used, an Event-Timestamp (55) 1230 [RFC2869] Attribute SHOULD be included within CoA-Request and 1231 Disconnect-Request packets, and MAY be included within CoA-ACK, CoA- 1232 NAK, Disconnect-ACK and Disconnect-NAK packets. 1234 When the Event-Timestamp attribute is present, both the NAS and the 1235 RADIUS server MUST check that the Event-Timestamp Attribute is 1236 current within an acceptable time window. If the Event-Timestamp 1237 Attribute is not current, then the packet MUST be silently discarded. 1238 This implies the need for loose time synchronization within the 1239 network, which can be achieved by a variety of means, including SNTP, 1240 as described in [RFC4330]. Implementations SHOULD be configurable to 1241 discard CoA-Request or Disconnect-Request packets not containing an 1242 Event-Timestamp attribute. 1244 If the Event-Timestamp Attribute is included, it represents the time 1245 at which the original packet was sent, and therefore it SHOULD NOT be 1246 updated when the packet is retransmitted. If the Event-Timestamp 1247 attribute is not updated, this implies that the Identifier is not 1248 changed in retransmitted packets. As a result, the ability to detect 1249 replay within the time window is dependent on support for duplicate 1250 detection within that same window. As noted in Section 2.3, 1251 duplicate detection is REQUIRED for RADIUS clients implementing this 1252 specification. 1254 The time window used for duplicate detection MUST be the same as the 1255 window used to detect stale Event-Timestamp Attributes. Since the 1256 RADIUS Identifier cannot be repeated within the selected time window, 1257 no more than 256 Requests can be accepted within the time window. As 1258 a result, the chosen time window will depend on the expected maximum 1259 volume of CoA/Disconnect-Requests, so that unnecessary discards can 1260 be avoided. A default time window of 300 seconds should be adequate 1261 in many circumstances. 1263 7. Example Traces 1265 Disconnect Request with User-Name: 1267 0: xxxx xxxx xxxx xxxx xxxx 2801 001c 1b23 .B.....$.-(....# 1268 16: 624c 3543 ceba 55f1 be55 a714 ca5e 0108 bL5C..U..U...^.. 1269 32: 6d63 6869 6261 1271 Disconnect Request with Acct-Session-ID: 1273 0: xxxx xxxx xxxx xxxx xxxx 2801 001e ad0d .B..... ~.(..... 1274 16: 8e53 55b6 bd02 a0cb ace6 4e38 77bd 2c0a .SU.......N8w.,. 1275 32: 3930 3233 3435 3637 90234567 1277 Disconnect Request with Framed-IP-Address: 1279 0: xxxx xxxx xxxx xxxx xxxx 2801 001a 0bda .B....."2.(..... 1280 16: 33fe 765b 05f0 fd9c c32a 2f6b 5182 0806 3.v[.....*/kQ... 1281 32: 0a00 0203 1283 8. References 1285 8.1. Normative References 1287 [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, 1288 April 1992. 1290 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1291 Requirement Levels", RFC 2119, March 1997. 1293 [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange (IKE)", 1294 RFC 2409, November 1998. 1296 [RFC2865] Rigney, C., Rubens, A., Simpson, W. and S. Willens, "Remote 1297 Authentication Dial In User Service (RADIUS)", RFC 2865, June 1298 2000. 1300 [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000. 1302 [RFC2869] Rigney, C., Willats W. and P. Calhoun, "RADIUS Extensions", 1303 RFC 2869, June 2000. 1305 [RFC3162] Aboba, B., Zorn, G. and D. Mitton, "RADIUS and IPv6", RFC 1306 3162, August 2001. 1308 [RFC3280] Housley, R., Polk, W., Ford, W. and D. Solo, "Internet X.509 1309 Public Key Infrastructure Certificate and Certificate 1310 Revocation List (CRL) Profile", RFC 3280, April 2002. 1312 [RFC3575] Aboba, B., "IANA Considerations for RADIUS", RFC 3575, July 1313 2003. 1315 [RFC3579] Aboba, B. and P. Calhoun, "RADIUS Support for Extensible 1316 Authentication Protocol (EAP)", RFC 3579, September 2003. 1318 [RFC4282] Aboba, B., Beadles, M., Arkko, J. and P. Eronen, "The Network 1319 Access Identifier", RFC 4282, December 2005. 1321 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet 1322 Protocol", RFC 4301, December 2005. 1324 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, 1325 December 2005. 1327 8.2. Informative References 1329 [RFC2868] Zorn, G., Leifer, D., Rubens, A., Shriver, J., Holdrege, M. 1330 and I. Goyret, "RADIUS Attributes for Tunnel Protocol 1331 Support", RFC 2868, June 2000. 1333 [RFC2983] Black, D. "Differentiated Services and Tunnels", RFC 2983, 1334 October 2000. 1336 [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and 1337 Accounting Transport Profile", RFC 3539, June 2003. 1339 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G. and J. 1340 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 1342 [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D. and B. Aboba, 1343 "Dynamic Authorization Extensions to Remote Authentication 1344 Dial In User Service (RADIUS)", RFC 3576, July 2003. 1346 [RFC4005] Calhoun, P., Zorn, G., Spence, D. and D. Mitton, "Diameter 1347 Network Access Server Application", RFC 4005, August 2005. 1349 [RFC4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 for 1350 IPv4, IPv6 and OSI", RFC 4330, January 2006. 1352 [MD5Attack] 1353 Dobbertin, H., "The Status of MD5 After a Recent Attack", 1354 CryptoBytes Vol.2 No.2, Summer 1996. 1356 [RFCFilter] 1357 Congdon, P., Sanchez, M. and B. Aboba, "RADIUS Filter Rule 1358 Attribute", draft-ietf-radext-filter-08.txt, Internet draft 1359 (work in progress), January 2007. 1361 Acknowledgments 1363 This protocol was first developed and distributed by Ascend 1364 Communications. Example code was distributed in their free server 1365 kit. 1367 The authors would like to acknowledge the valuable suggestions and 1368 feedback from the following people: 1370 Avi Lior , 1371 Randy Bush , 1372 Steve Bellovin 1373 Glen Zorn , 1374 Mark Jones , 1375 Claudio Lapidus , 1376 Anurag Batta , 1377 Kuntal Chowdhury 1378 Tim Moore 1379 Russ Housley 1380 Joe Salowey 1382 Authors' Addresses 1384 Murtaza Chiba 1385 Cisco Systems, Inc. 1386 170 West Tasman Dr. 1387 San Jose CA, 95134 1389 EMail: mchiba@cisco.com 1390 Phone: +1 408 525 7198 1392 Gopal Dommety 1393 Cisco Systems, Inc. 1394 170 West Tasman Dr. 1395 San Jose, CA 95134 1397 EMail: gdommety@cisco.com 1398 Phone: +1 408 525 1404 1400 Mark Eklund 1401 Cisco Systems, Inc. 1402 170 West Tasman Dr. 1403 San Jose, CA 95134 1405 EMail: meklund@cisco.com 1406 Phone: +1 865 671 6255 1408 David Mitton 1409 RSA Security, Inc. 1410 174 Middlesex Turnpike 1411 Bedford, MA 01730 1413 EMail: dmitton@circularnetworks.com 1414 Bernard Aboba 1415 Microsoft Corporation 1416 One Microsoft Way 1417 Redmond, WA 98052 1419 EMail: bernarda@microsoft.com 1420 Phone: +1 425 706 6605 1421 Fax: +1 425 936 7329 1423 Appendix A - Changes from RFC 3576 1425 This Appendix lists the major changes between [RFC3576] and this 1426 document. Minor changes, including style, grammar, spelling, and 1427 editorial changes are not mentioned here. 1429 o Added details relating to handling of the Proxy-State Attribute. 1430 Added requirement for duplicate detection on the RADIUS client 1431 (Section 2.3). 1433 o Added requirements for inclusion of the State Attribute in CoA- 1434 Request packets with a Service-Type of "Authorize Only" (Section 1435 3.1). 1437 o Added clarification on the calculation of the Message-Authenticator 1438 Attribute (Section 3.2). 1440 o Added statement that support for "Authorize Only" Service-Type is 1441 optional (Section 3.5). 1443 o Use of a Service-Type Attribute within a Disconnect-Request is 1444 prohibited (Section 4). 1446 o Added Diameter Considerations (Section 5). 1448 o Clarified that the Event-Timestamp Attribute should not be 1449 recalculated on retransmission. The implications for replay and 1450 duplicate detection are discussed (Section 6.4). 1452 Full Copyright Statement 1454 Copyright (C) The IETF Trust (2007). 1456 This document is subject to the rights, licenses and restrictions 1457 contained in BCP 78, and except as set forth therein, the authors 1458 retain all their rights. 1460 This document and the information contained herein are provided on an 1461 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 1462 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 1463 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 1464 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 1465 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 1466 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 1468 Intellectual Property 1470 The IETF takes no position regarding the validity or scope of any 1471 Intellectual Property Rights or other rights that might be claimed to 1472 pertain to the implementation or use of the technology described in 1473 this document or the extent to which any license under such rights 1474 might or might not be available; nor does it represent that it has 1475 made any independent effort to identify any such rights. 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Please address the information to the IETF at ietf- 1490 ipr@ietf.org. 1492 Acknowledgment 1494 Funding for the RFC Editor function is provided by the IETF 1495 Administrative Support Activity (IASA). 1497 Open issues 1499 Open issues relating to this specification are tracked on the 1500 following web site: 1502 http://www.drizzle.com/~aboba/RADEXT/