idnits 2.17.1 draft-ietf-radext-rfc3576bis-04.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** It looks like you're using RFC 3978 boilerplate. You should update this to the boilerplate described in the IETF Trust License Policy document (see https://trustee.ietf.org/license-info), which is required now. -- Found old boilerplate from RFC 3978, Section 5.1 on line 17. -- Found old boilerplate from RFC 3978, Section 5.5, updated by RFC 4748 on line 1515. -- Found old boilerplate from RFC 3979, Section 5, paragraph 1 on line 1526. -- Found old boilerplate from RFC 3979, Section 5, paragraph 2 on line 1533. -- Found old boilerplate from RFC 3979, Section 5, paragraph 3 on line 1539. 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. 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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 10 April 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 October 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 ........................... 13 62 3.3 Error-Cause ..................................... 13 63 3.4 Table of Attributes ............................. 16 64 4. Diameter Considerations ............................... 21 65 5. IANA Considerations ................................... 23 66 6. Security Considerations ............................... 23 67 6.1 Authorization Issues ............................ 23 68 6.2 Impersonation ................................... 24 69 6.3 IPsec Usage Guidelines .......................... 24 70 6.4 Replay Protection ............................... 27 71 7. Example Traces ........................................ 28 72 8. References ............................................ 28 73 8.1 Normative References ............................ 28 74 8.2 Informative References .......................... 29 75 ACKNOWLEDGMENTS .............................................. 30 76 AUTHORS' ADDRESSES ........................................... 31 77 Appendix A - Changes from RFC 3576 ........................... 32 78 Full Copyright Statement ..................................... 33 79 Intellectual Property ........................................ 33 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 (92) - 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 Within this specification attributes may be used for 377 identification, authorization or other purposes. RADIUS Attribue 378 specifications created after publication of this document SHOULD 379 state whether an Attribute can be included in CoA or Disconnect 380 messages and if so, which messages it may be included in and 381 whether it serves as an identification or authorization attribute. 383 Even if a NAS implements an attribute for use with RADIUS 384 authentication and accounting, it may not support inclusion of 385 that attribute within Disconnect-Request or CoA-Request packets, 386 given the difference in attribute semantics. This is true even 387 for attributes specified as allowable within Access-Accept packets 388 (such as those defined within [RFC2865], [RFC2868], [RFC2869], 389 [RFC3162], [RFC3579], [RFC4372], [RFC4675], [RFC4818] and 390 [RFCFilter]). If unsupported attributes are included within a 391 Disconnect/CoA-Request packet, the RADIUS client will send a 392 Disconnect-NAK/CoA-NAK in response, possibly containing an Error- 393 Cause attribute with value Unsupported Attribute (401). 395 If there are any Proxy-State Attributes in a Disconnect-Request or 396 CoA-Request received from the server, the forwarding proxy or NAS 397 MUST include those Proxy-State Attributes in its response to the 398 server. 400 A forwarding proxy or NAS MUST NOT modify existing Proxy-State, 401 State, or Class Attributes present in the packet. The forwarding 402 proxy or NAS MUST treat any Proxy-State attributes already in the 403 packet as opaque data. Its operation MUST NOT depend on the 404 content of Proxy-State attributes added by previous proxies. The 405 forwarding proxy MUST NOT modify any other Proxy-State Attributes 406 that were in the packet; it may choose not to forward them, but it 407 MUST NOT change their contents. If the forwarding proxy omits the 408 Proxy-State Attributes in the request, it MUST attach them to the 409 response before sending it. 411 When the proxy forwards a Disconnect or CoA-Request, it MAY add a 412 Proxy-State Attribute, but it MUST NOT add more than one. If a 413 Proxy-State Attribute is added to a packet when forwarding the 414 packet, the Proxy-State Attribute MUST be added after any existing 415 Proxy-State attributes. The forwarding proxy MUST NOT change the 416 order of any attributes of the same type, including Proxy-State. 417 Other Attributes can be placed before, after or even between the 418 Proxy-State Attributes. 420 When the proxy receives a response to a CoA-Request or Disconnect- 421 Request, it MUST remove its own Proxy-State (the last Proxy- State 422 in the packet) before forwarding the response. Since Disconnect 423 and CoA responses are authenticated on the entire packet contents, 424 the stripping of the Proxy-State Attribute invalidates the 425 integrity check - so the proxy needs to recompute it. 427 3. Attributes 429 In Disconnect-Request and CoA-Request packets, certain attributes are 430 used to uniquely identify the NAS as well as a user session on the 431 NAS. All NAS identification attributes included in a Request packet 432 MUST match in order for a Disconnect-Request or CoA-Request to be 433 successful; otherwise a Disconnect-NAK or CoA-NAK SHOULD be sent. 434 For session identification attributes, the User-Name and Acct- 435 Session-Id Attributes, if included, MUST match in order for a 436 Disconnect-Request or CoA-Request to be successful; other session 437 identification attributes SHOULD match. Where a mismatch of session 438 identification attributes is detected, a Disconnect-NAK or CoA-NAK 439 SHOULD be sent. 441 The ability to use NAS or session identification attributes to map to 442 unique/multiple sessions is beyond the scope of this document. 443 Identification attributes include NAS and session identification 444 attributes, as described below. 446 NAS identification attributes 448 Attribute # Reference Description 449 --------- --- --------- ----------- 450 NAS-IP-Address 4 [RFC2865] The IPv4 address of the NAS. 451 NAS-Identifier 32 [RFC2865] String identifying the NAS. 452 NAS-IPv6-Address 95 [RFC3162] The IPv6 address of the NAS. 454 Session identification attributes 456 Attribute # Reference Description 457 --------- --- --------- ----------- 458 User-Name 1 [RFC2865] The name of the user 459 associated with the session. 460 NAS-Port 5 [RFC2865] The port on which the 461 session is terminated. 463 Attribute # Reference Description 464 --------- --- --------- ----------- 465 Framed-IP-Address 8 [RFC2865] The IPv4 address associated 466 with the session. 467 Called-Station-Id 30 [RFC2865] The link address to which 468 the session is connected. 469 Calling-Station-Id 31 [RFC2865] The link address from which 470 the session is connected. 471 Acct-Session-Id 44 [RFC2866] The identifier uniquely 472 identifying the session 473 on the NAS. 474 Acct-Multi-Session-Id 50 [RFC2866] The identifier uniquely 475 identifying related sessions. 476 NAS-Port-Type 61 [RFC2865] The type of port used. 477 NAS-Port-Id 87 [RFC2869] String identifying the port 478 where the session is. 479 Chargeable-User- 89 [RFC4372] The CUI associated with the 480 Identity session. Needed where a 481 privacy NAI is used, so that 482 the User-Name may not be 483 unique (e.g. "anonymous"). 484 Originating-Line-Info 94 [RFC4005] Provides information on the 485 characteristics of the line 486 from which a session 487 originated. 488 Framed-Interface-Id 96 [RFC3162] The IPv6 Interface Identifier 489 associated with the session; 490 always sent with 491 Framed-IPv6-Prefix. 492 Framed-IPv6-Prefix 97 [RFC3162] The IPv6 prefix associated 493 with the session, always sent 494 with Framed-Interface-Id. 496 To address security concerns described in Section 6.1, and to enable 497 Diameter/RADIUS translation, the User-Name Attribute SHOULD be 498 present in Disconnect-Request or CoA-Request packets; one or more 499 additional session identification attributes MAY also be present. 500 For example, where a Diameter client utilizes the same Session-Id for 501 both authorization and accounting, inclusion of an Acct-Session-Id 502 Attribute in a Disconnect-Request or CoA-Request can assist with 503 Diameter/RADIUS translation, since Diameter RAR and ASR commands 504 include a Session-Id AVP. 506 Where a NAS offers multiple services, confusion may result with 507 respect to interpretation of a CoA-Request or Disconnect-Request. In 508 order to prevent confusion a RADIUS Server SHOULD identify the 509 session as specifically as possible. For example, an Acct-Session-Id 510 attribute SHOULD be included in Disconnect-Request and CoA-Request 511 packets, rather than just the User-Name attribute. 513 To address security concerns described in Section 6.2, one or more of 514 the NAS-IP-Address or NAS-IPv6-Address Attributes SHOULD be present 515 in Disconnect-Request or CoA-Request packets; the NAS-Identifier 516 Attribute MAY be present in addition. 518 If one or more authorization changes specified in a CoA-Request 519 cannot be carried out, or if one or more attributes or attribute- 520 values is unsupported, a CoA-NAK MUST be sent. Similarly, if there 521 are one or more unsupported attributes or attribute values in a 522 Disconnect-Request, a Disconnect-NAK MUST be sent. 524 A CoA-Request containing a Service-Type Attribute with value 525 "Authorize Only" MUST contain only NAS or session identification 526 attributes, as well as Service-Type and State attributes. If other 527 attributes are included in such a CoA-Request, implementations MUST 528 send a CoA-NAK; an Error-Cause Attribute with value "Unsupported 529 Attribute" MAY be included. 531 A Disconnect-Request MUST contain only NAS and session identification 532 attributes (see Section 3). If other attributes are included in a 533 Disconnect-Request, implementations MUST send a Disconnect-NAK; an 534 Error-Cause Attribute with value "Unsupported Attribute" MAY be 535 included. 537 3.1. State 539 [RFC2865] Section 5.44 states: 541 An Access-Request MUST contain either a User-Password or a CHAP- 542 Password or State. An Access-Request MUST NOT contain both a 543 User-Password and a CHAP-Password. If future extensions allow 544 other kinds of authentication information to be conveyed, the 545 attribute for that can be used in an Access-Request instead of 546 User-Password or CHAP-Password. 548 In order to satisfy the requirements of [RFC2865] Section 5.44, an 549 Access-Request with Service-Type="Authorize-Only" MUST contain a 550 State attribute. 552 In order to provide a State attribute to the NAS, a server sending a 553 CoA-Request with a Service-Type value of "Authorize-Only" MUST 554 include a State Attribute, and the NAS MUST include the State 555 Attribute unchanged in the Access-Request. A NAS receiving a CoA- 556 Request containing a Service-Type value of "Authorize-Only" but 557 lacking a State attribute MUST send a CoA-NAK and SHOULD include an 558 Error-Cause attribute with value 402 (Missing Attribute). 560 3.2. Message-Authenticator 562 The Message-Authenticator Attribute MAY be used to authenticate and 563 integrity-protect CoA-Request, CoA-ACK, CoA-NAK, Disconnect-Request, 564 Disconnect-ACK and Disconnect-NAK packets order to prevent spoofing. 566 A RADIUS client receiving a CoA-Request or Disconnect-Request with a 567 Message-Authenticator Attribute present MUST calculate the correct 568 value of the Message-Authenticator and silently discard the packet if 569 it does not match the value sent. A RADIUS server receiving a 570 CoA/Disconnect-ACK or CoA/Disconnect-NAK with a Message-Authenticator 571 Attribute present MUST calculate the correct value of the Message- 572 Authenticator and silently discard the packet if it does not match 573 the value sent. 575 When a Message-Authenticator Attribute is included within a CoA- 576 Request or Disconnect-Request, it is calculated as follows: 578 Message-Authenticator = HMAC-MD5 (Type, Identifier, Length, 579 Request Authenticator, Attributes) 581 When the HMAC-MD5 message integrity check is calculated the 582 Request Authenticator field and Message-Authenticator Attribute 583 should be considered to be sixteen octets of zero. The Message- 584 Authenticator Attribute is calculated and inserted in the packet 585 before the Request Authenticator is calculated. 587 When a Message-Authenticator Attribute is included within a CoA- 588 ACK, CoA-NAK, Disconnect-ACK or Disconnect-NAK, it is calculated 589 as follows: 591 Message-Authenticator = HMAC-MD5 (Type, Identifier, Length, 592 Request Authenticator, Attributes) 594 When the HMAC-MD5 message integrity check is calculated the 595 Message-Authenticator Attribute should be considered to be sixteen 596 octets of zero. The Request Authenticator is taken from the 597 corresponding CoA/Disconnect-Request. The Message-Authenticator 598 is calculated and inserted in the packet before the Response 599 Authenticator is calculated. 601 3.3. Error-Cause 603 Description 605 It is possible that the NAS cannot honor Disconnect-Request or 606 CoA-Request packets for some reason. The Error-Cause Attribute 607 provides more detail on the cause of the problem. It MAY be 608 included within Disconnect-ACK, Disconnect-NAK and CoA-NAK 609 packets. 611 A summary of the Error-Cause Attribute format is shown below. The 612 fields are transmitted from left to right. 614 0 1 2 3 615 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 1 616 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 617 | Type | Length | Value 618 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 619 Value (cont) | 620 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 622 Type 624 101 for Error-Cause 626 Length 628 6 630 Value 632 The Value field is four octets, containing an integer specifying 633 the cause of the error. Values 0-199 and 300-399 are reserved. 634 Values 200-299 represent successful completion, so that these 635 values may only be sent within Disconnect-ACK or CoA-ACK packets 636 and MUST NOT be sent within a Disconnect-NAK or CoA-NAK. Values 637 400-499 represent fatal errors committed by the RADIUS server, so 638 that they MAY be sent within CoA-NAK or Disconnect-NAK packets, 639 and MUST NOT be sent within CoA-ACK or Disconnect-ACK packets. 640 Values 500-599 represent fatal errors occurring on a NAS or RADIUS 641 proxy, so that they MAY be sent within CoA-NAK and Disconnect-NAK 642 packets, and MUST NOT be sent within CoA-ACK or Disconnect-ACK 643 packets. Error-Cause values SHOULD be logged by the RADIUS 644 server. Error-Code values (expressed in decimal) include: 646 # Value 647 --- ----- 648 201 Residual Session Context Removed 649 202 Invalid EAP Packet (Ignored) 650 401 Unsupported Attribute 651 402 Missing Attribute 652 403 NAS Identification Mismatch 653 404 Invalid Request 654 405 Unsupported Service 655 406 Unsupported Extension 656 501 Administratively Prohibited 657 502 Request Not Routable (Proxy) 658 503 Session Context Not Found 659 504 Session Context Not Removable 660 505 Other Proxy Processing Error 661 506 Resources Unavailable 662 507 Request Initiated 664 "Residual Session Context Removed" is sent in response to a 665 Disconnect-Request if the user session is no longer active, but 666 residual session context was found and successfully removed. This 667 value is only sent within a Disconnect-ACK and MUST NOT be sent 668 within a CoA-ACK, Disconnect-NAK or CoA-NAK. 670 "Invalid EAP Packet (Ignored)" is a non-fatal error that MUST NOT 671 be sent by implementations of this specification. 673 "Unsupported Attribute" is a fatal error sent if a Request 674 contains an attribute (such as a Vendor-Specific or EAP-Message 675 Attribute) that is not supported. 677 "Missing Attribute" is a fatal error sent if critical attributes 678 (such as NAS or session identification attributes) are missing 679 from a Request. 681 "NAS Identification Mismatch" is a fatal error sent if one or more 682 NAS identification attributes (see Section 3) do not match the 683 identity of the NAS receiving the Request. 685 "Invalid Request" is a fatal error sent if some other aspect of 686 the Request is invalid, such as if one or more attributes (such as 687 EAP- Message Attribute(s)) are not formatted properly. 689 "Unsupported Service" is a fatal error sent if a Service-Type 690 Attribute included with the Request is sent with an invalid or 691 unsupported value. This error cannot be sent in response to a 692 Disconnect-Request. 694 "Unsupported Extension" is a fatal error sent due to lack of 695 support for an extension such as Disconnect and/or CoA packets. 696 This will typically be sent by a proxy receiving an ICMP port 697 unreachable message after attempting to forward a Request to the 698 NAS. 700 "Administratively Prohibited" is a fatal error sent if the NAS is 701 configured to prohibit honoring of Request packets for the 702 specified session. 704 "Request Not Routable" is a fatal error which MAY be sent by a 705 RADIUS proxy and MUST NOT be sent by a NAS. It indicates that the 706 RADIUS proxy was unable to determine how to route the Request to 707 the NAS. For example, this can occur if the required entries are 708 not present in the proxy's realm routing table. 710 "Session Context Not Found" is a fatal error sent if the session 711 context identified in the Request does not exist on the NAS. 713 "Session Context Not Removable" is a fatal error sent in response 714 to a Disconnect-Request if the NAS was able to locate the session 715 context, but could not remove it for some reason. It MUST NOT be 716 sent within a CoA-ACK, CoA-NAK or Disconnect-ACK, only within a 717 Disconnect-NAK. 719 "Other Proxy Processing Error" is a fatal error sent in response 720 to a Request that could not be processed by a proxy, for reasons 721 other than routing. 723 "Resources Unavailable" is a fatal error sent when a Request could 724 not be honored due to lack of available NAS resources (memory, 725 non- volatile storage, etc.). 727 "Request Initiated" is a fatal error sent in response to a CoA- 728 Request including a Service-Type Attribute with a value of 729 "Authorize Only". It indicates that the CoA-Request has not been 730 honored, but that a RADIUS Access-Request including a Service-Type 731 Attribute with value "Authorize Only" is being sent to the RADIUS 732 server. 734 3.4. Table of Attributes 736 The following table provides a guide to which attributes may be found 737 in which packets, and in what quantity. 739 Change-of-Authorization Messages 741 Request ACK NAK # Attribute 742 0-1 0 0 1 User-Name [Note 1] 743 0-1 0 0 4 NAS-IP-Address [Note 1] 744 0-1 0 0 5 NAS-Port [Note 1] 745 0-1 0 0-1 6 Service-Type [Note 6] 746 0-1 0 0 7 Framed-Protocol [Note 3] 747 0-1 0 0 8 Framed-IP-Address [Note 1][Note 8] 748 0-1 0 0 9 Framed-IP-Netmask [Note 3] 749 0-1 0 0 10 Framed-Routing [Note 3] 750 Request ACK NAK # Attribute 751 Request ACK NAK # Attribute 752 0+ 0 0 11 Filter-ID [Note 3] 753 0-1 0 0 12 Framed-MTU [Note 3] 754 0+ 0 0 13 Framed-Compression [Note 3] 755 0+ 0 0 14 Login-IP-Host [Note 3] 756 0-1 0 0 15 Login-Service [Note 3] 757 0-1 0 0 16 Login-TCP-Port [Note 3] 758 0+ 0 0 18 Reply-Message [Note 2] 759 0-1 0 0 19 Callback-Number [Note 3] 760 0-1 0 0 20 Callback-Id [Note 3] 761 0+ 0 0 22 Framed-Route [Note 3] 762 0-1 0 0 23 Framed-IPX-Network [Note 3] 763 0-1 0-1 0-1 24 State [Note 7] 764 0+ 0 0 25 Class [Note 3] 765 0+ 0 0 26 Vendor-Specific [Note 3] 766 0-1 0 0 27 Session-Timeout [Note 3] 767 0-1 0 0 28 Idle-Timeout [Note 3] 768 0-1 0 0 29 Termination-Action [Note 3] 769 0-1 0 0 30 Called-Station-Id [Note 1] 770 0-1 0 0 31 Calling-Station-Id [Note 1] 771 0-1 0 0 32 NAS-Identifier [Note 1] 772 0+ 0+ 0+ 33 Proxy-State 773 0-1 0 0 34 Login-LAT-Service [Note 3] 774 0-1 0 0 35 Login-LAT-Node [Note 3] 775 0-1 0 0 36 Login-LAT-Group [Note 3] 776 0-1 0 0 37 Framed-AppleTalk-Link [Note 3] 777 0+ 0 0 38 Framed-AppleTalk-Network [Note 3] 778 0-1 0 0 39 Framed-AppleTalk-Zone [Note 3] 779 0-1 0 0 44 Acct-Session-Id [Note 1] 780 0-1 0 0 50 Acct-Multi-Session-Id [Note 1] 781 0-1 0-1 0-1 55 Event-Timestamp 782 0+ 0 0 56 Egress-VLANID [Note 3] 783 0-1 0 0 57 Ingress-Filters [Note 3] 784 0+ 0 0 58 Egress-VLAN-Name [Note 3] 785 0-1 0 0 59 User-Priority-Table [Note 3] 786 0-1 0 0 61 NAS-Port-Type [Note 1] 787 0-1 0 0 62 Port-Limit [Note 3] 788 0-1 0 0 63 Login-LAT-Port [Note 3] 789 0+ 0 0 64 Tunnel-Type [Note 5] 790 0+ 0 0 65 Tunnel-Medium-Type [Note 5] 791 0+ 0 0 66 Tunnel-Client-Endpoint [Note 5] 792 0+ 0 0 67 Tunnel-Server-Endpoint [Note 5] 793 0+ 0 0 69 Tunnel-Password [Note 5] 794 0-1 0 0 71 ARAP-Features [Note 3] 795 0-1 0 0 72 ARAP-Zone-Access [Note 3] 796 0+ 0 0 78 Configuration-Token [Note 3] 797 0+ 0-1 0 79 EAP-Message [Note 2] 798 Request ACK NAK # Attribute 799 Request ACK NAK # Attribute 800 0-1 0-1 0-1 80 Message-Authenticator 801 0+ 0 0 81 Tunnel-Private-Group-ID [Note 5] 802 0+ 0 0 82 Tunnel-Assignment-ID [Note 5] 803 0+ 0 0 83 Tunnel-Preference [Note 5] 804 0-1 0 0 85 Acct-Interim-Interval [Note 3] 805 0-1 0 0 87 NAS-Port-Id [Note 1] 806 0-1 0 0 88 Framed-Pool [Note 3] 807 0-1 0 0 89 Chargeable-User-Identity [Note 1] 808 0+ 0 0 90 Tunnel-Client-Auth-ID [Note 5] 809 0+ 0 0 91 Tunnel-Server-Auth-ID [Note 5] 810 0-1 0 0 92 NAS-Filter-Rule [Note 3] 811 0-1 0 0 94 Originating-Line-Info [Note 1] 812 0-1 0 0 95 NAS-IPv6-Address [Note 1] 813 0-1 0 0 96 Framed-Interface-Id [Note 1][Note 8] 814 0+ 0 0 97 Framed-IPv6-Prefix [Note 1][Note 8] 815 0+ 0 0 98 Login-IPv6-Host [Note 3] 816 0+ 0 0 99 Framed-IPv6-Route [Note 3] 817 0-1 0 0 100 Framed-IPv6-Pool [Note 3] 818 0 0 0+ 101 Error-Cause 819 0+ 0 0 123 Delegated-IPv6-Prefix [Note 3] 820 Request ACK NAK # Attribute 822 Disconnect Messages 824 Request ACK NAK # Attribute 825 0-1 0 0 1 User-Name [Note 1] 826 0-1 0 0 4 NAS-IP-Address [Note 1] 827 0-1 0 0 5 NAS-Port [Note 1] 828 0 0 0 6 Service-Type 829 0-1 0 0 8 Framed-IP-Address [Note 1] 830 0+ 0 0 18 Reply-Message [Note 2] 831 0 0 0 24 State 832 0+ 0 0 25 Class [Note 4] 833 0+ 0 0 26 Vendor-Specific 834 0-1 0 0 30 Called-Station-Id [Note 1] 835 0-1 0 0 31 Calling-Station-Id [Note 1] 836 0-1 0 0 32 NAS-Identifier [Note 1] 837 0+ 0+ 0+ 33 Proxy-State 838 0-1 0 0 44 Acct-Session-Id [Note 1] 839 0-1 0-1 0 49 Acct-Terminate-Cause 840 0-1 0 0 50 Acct-Multi-Session-Id [Note 1] 841 0-1 0-1 0-1 55 Event-Timestamp 842 0-1 0 0 61 NAS-Port-Type [Note 1] 843 0+ 0-1 0 79 EAP-Message [Note 2] 844 0-1 0-1 0-1 80 Message-Authenticator 845 0-1 0 0 87 NAS-Port-Id [Note 1] 846 Request ACK NAK # Attribute 847 Request ACK NAK # Attribute 848 0-1 0 0 89 Chargeable-User-Identity [Note 1] 849 0-1 0 0 94 Orginating-Line-Info [Note 1] 850 0-1 0 0 95 NAS-IPv6-Address [Note 1] 851 0-1 0 0 96 Framed-Interface-Id [Note 1] 852 0+ 0 0 97 Framed-IPv6-Prefix [Note 1] 853 0 0+ 0+ 101 Error-Cause 854 Request ACK NAK # Attribute 856 The following table defines the meaning of the above table entries. 858 0 This attribute MUST NOT be present in packet. 859 0+ Zero or more instances of this attribute MAY be present in packet. 860 0-1 Zero or one instance of this attribute MAY be present in packet. 861 1 Exactly one instance of this attribute MUST be present in packet. 863 [Note 1] Where NAS or session identification attributes are included 864 in Disconnect-Request or CoA-Request packets, they are used for 865 identification purposes only. These attributes MUST NOT be used for 866 purposes other than identification (e.g. within CoA-Request packets 867 to request authorization changes). 869 [Note 2] The Reply-Message Attribute is used to present a displayable 870 message to the user. The message is only displayed as a result of a 871 successful Disconnect-Request or CoA-Request (where a Disconnect-ACK 872 or CoA-ACK is subsequently sent). Where EAP is used for 873 authentication, an EAP-Message/Notification-Request Attribute is sent 874 instead, and Disconnect-ACK or CoA-ACK packets contain an EAP- 875 Message/Notification-Response Attribute. 877 [Note 3] When included within a CoA-Request, these attributes 878 represent an authorization change request. When one of these 879 attributes is omitted from a CoA-Request, the NAS assumes that the 880 attribute value is to remain unchanged. Attributes included in a 881 CoA-Request replace all existing value(s) of the same attribute(s). 883 [Note 4] When included within a successful Disconnect-Request (where 884 a Disconnect-ACK is subsequently sent), the Class Attribute SHOULD be 885 sent unmodified by the client to the accounting server in the 886 Accounting Stop packet. If the Disconnect-Request is unsuccessful, 887 then the Class Attribute is not processed. 889 [Note 5] When included within a CoA-Request, these attributes 890 represent an authorization change request. Where tunnel attribute(s) 891 are included within a successful CoA-Request, all existing tunnel 892 attributes are removed and replaced by the new attribute(s). 894 [Note 6] Support for the Service-Type of "Authorize Only" is OPTIONAL 895 on the NAS and RADIUS server. A NAS supporting the "Authorize Only" 896 Service-Type value within a CoA-Request packet MUST respond with a 897 CoA-NAK containing a Service-Type Attribute with value "Authorize 898 Only", and an Error-Cause Attribute with value "Request Initiated". 899 The NAS then sends an Access-Request to the RADIUS server with a 900 Service-Type Attribute with value "Authorize Only". This Access- 901 Request SHOULD contain the NAS attributes from the CoA-Request, as 902 well as the session attributes from the CoA-Request legal for 903 inclusion in an Access-Request as specified in [RFC2865], [RFC2868], 904 [RFC2869] and [RFC3162]. As noted in [RFC2869] Section 5.19, a 905 Message-Authenticator attribute SHOULD be included in an Access- 906 Request that does not contain a User-Password, CHAP-Password, ARAP- 907 Password or EAP-Message Attribute. The RADIUS server should send 908 back an Access-Accept to (re-)authorize the session or an Access- 909 Reject to refuse to (re-)authorize it. 911 A NAS that does not support the Service-Type Attribute with the value 912 "Authorize Only" within a CoA-Request MUST respond with a CoA-NAK 913 including no Service-Type Attribute; an Error-Cause Attribute with 914 value "Unsupported Service" MAY be included. 916 [Note 7] The State Attribute is available to be sent by the RADIUS 917 server to the NAS in a CoA-Request packet and MUST be sent unmodified 918 from the NAS to the RADIUS server in a subsequent ACK or NAK packet. 919 If a Service-Type Attribute with value "Authorize Only" is included 920 in a CoA-Request then a State Attribute MUST be present, and MUST be 921 sent unmodified from the NAS to the RADIUS server in the resulting 922 Access-Request sent to the RADIUS server, if any. The State 923 Attribute is also available to be sent by the RADIUS server to the 924 NAS in a CoA-Request that also includes a Termination-Action 925 Attribute with the value of RADIUS-Request. If the client performs 926 the Termination-Action by sending a new Access-Request upon 927 termination of the current session, it MUST include the State 928 Attribute unchanged in that Access-Request. In either usage, the 929 client MUST NOT interpret the Attribute locally. A CoA-Request 930 packet must have only zero or one State Attribute. Usage of the 931 State Attribute is implementation dependent. 933 [Note 8] Since the Framed-IP-Address, Framed-IPv6-Prefix and Framed- 934 Interface-Id attributes are used for identification, these attributes 935 cannot be updated by including new values within a CoA-Request. 936 Instead, a CoA-Request with Service-Type="Authorize Only" is used, 937 and the new values can be supplied in response to the ensuing Access- 938 Request. 940 4. Diameter Considerations 942 Due to differences in handling change-of-authorization requests in 943 RADIUS and Diameter, it may be difficult or impossible for a 944 Diameter/RADIUS gateway to successfully translate a Diameter Re-Auth- 945 Request (RAR) to a CoA-Request and vice versa. For example, since a 946 CoA-Request only initiates an authorization change but does not 947 initiate re-authentication, a RAR command containing a Re-Auth- 948 Request-Type AVP with value "AUTHORIZE_AUTHENTICATE" cannot be 949 directly translated to a CoA-Request. A Diameter/RADIUS gateway 950 receiving a CoA-Request containing authorization changes will need to 951 translate this into two Diameter exchange. First, the 952 Diameter/RADIUS gateway will issue a RAR command including a Session- 953 Id AVP and a Re-Auth-Request-Type AVP with value "AUTHORIZE ONLY". 954 Then the Diameter/RADIUS gateway will respond to the ensuing access 955 request with a response including the authorization attributes 956 gleaned from the CoA-Request. For the translation to be possible, 957 the CoA-Request MUST include a Acct-Session-Id Attribute. If the 958 Diameter client uses the same Session-Id for both authorization and 959 accounting, then the Diameter/RADIUS gateway can copy the contents of 960 the Acct-Session-Id Attribute into the Session-Id AVP; otherwise, it 961 will need to map the Acct-Session-Id value to an equivalent Session- 962 Id for use within a RAR command. 964 To simplify translation between RADIUS and Diameter, a server 965 compliant with this specification MAY include a Service-Type 966 Attribute with value "Authorize Only" within a CoA-Request. Such a 967 CoA-Request MUST contain a State Attribute. A NAS supporting the 968 "Authorize Only" Service-Type within a CoA-Request responds with a 969 CoA-NAK containing a Service-Type Attribute with value "Authorize 970 Only", and an Error-Cause Attribute with value "Request Initiated". 971 The NAS will then send an Access-Request containing a Service-Type 972 Attribute with a value of "Authorize Only", along with a State 973 Attribute. A Diameter/RADIUS gateway receiving a CoA-Request 974 containing a Service-Type with value "Authorize Only" translates this 975 to a RAR with Re-Auth-Request-Type AVP with value "AUTHORIZE ONLY". 976 The received RAA is then translated to a CoA-NAK with a Service-Type 977 value of "Authorize Only". If the Result-Code AVP in the RAA has a 978 value in the success category, then an Error-Cause Attribute with 979 value "Request Initiated" is included in the CoA-NAK. If the 980 Result-Code AVP in the RAA has a value indicating a Protocol Error or 981 a Transient or Permanent Failure, then an alternate Error-Cause 982 Attribute is returned as suggested below. 984 Within Diameter, a server can request that a session be aborted by 985 sending an Abort-Session-Request (ASR), identifying the session to be 986 terminated using Session-ID and User-Name AVPs. The ASR command is 987 translated to a Disconnect-Request containing an Acct-Session-Id and 988 User-Name attribute. If the Diameter client utilizes the same 989 Session-Id in both authorization and accounting, then the value of 990 the Session-ID AVP may be placed in the Acct-Session-Id attribute; 991 otherwise the value of the Session-ID AVP will need to be mapped to 992 an appropriate Acct-Session-Id value. For a Disconnect-Request to 993 be translatable to an ASR, an Acct-Session-Id attribute MUST be 994 present. If the Diameter client utilizes the same Session-Id in both 995 authorization and accounting, then the value of the Acct-Session-Id 996 may be placed into the Session-ID AVP within the ASR; otherwise the 997 value of the Acct-Session-Id will need to be mapped to an appropriate 998 Session-ID value. 1000 An Abort-Session-Answer (ASA) command is sent in response to an ASR 1001 in order to indicate the disposition of the request. A 1002 Diameter/RADIUS gateway receiving a Disconnect-ACK translates this to 1003 an ASA command with a Result-Code AVP of "DIAMETER_SUCCESS". A 1004 Disconnect-NAK received from the server is translated to an ASA 1005 command with a Result-Code AVP which depends on the value of the 1006 Error-Cause Attribute. Suggested translations between Error-Cause 1007 Attribute values and Result-Code AVP values are included below: 1009 # Error-Cause Attribute Value Result-Code AVP 1010 --- --------------------------- ------------------------ 1011 201 Residual Session Context DIAMETER_SUCCESS 1012 Removed 1013 202 Invalid EAP Packet DIAMETER_LIMITED_SUCCESS 1014 (Ignored) 1015 401 Unsupported Attribute DIAMETER_AVP_UNSUPPORTED 1016 402 Missing Attribute DIAMETER_MISSING_AVP 1017 403 NAS Identification DIAMETER_REALM_NOT_SERVED 1018 Mismatch 1019 404 Invalid Request DIAMETER_UNABLE_TO_COMPLY 1020 405 Unsupported Service DIAMETER_COMMAND_UNSUPPORTED 1021 406 Unsupported Extension DIAMETER_APPLICATION_UNSUPPORTED 1022 501 Administratively DIAMETER_AUTHORIZATION_REJECTED 1023 Prohibited 1024 502 Request Not Routable (Proxy) DIAMETER_UNABLE_TO_DELIVER 1025 503 Session Context Not Found DIAMETER_UNKNOWN_SESSION_ID 1026 504 Session Context Not DIAMETER_AUTHORIZATION_REJECTED 1027 Removable 1028 505 Other Proxy Processing DIAMETER_UNABLE_TO_COMPLY 1029 Error 1030 506 Resources Unavailable DIAMETER_RESOURCES_EXCEEDED 1031 507 Request Initiated DIAMETER_SUCCESS 1033 Since both the ASR/ASA and Disconnect-Request/Disconnect- 1034 NAK/Disconnect-ACK exchanges involve just a request and response, 1035 inclusion of an "Authorize Only" Service-Type within a Disconnect- 1036 Request is not needed to assist in Diameter/RADIUS translation, and 1037 may make translation more difficult. As a result, the Service-Type 1038 Attribute MUST NOT be used within a Disconnect-Request. 1040 5. IANA Considerations 1042 This specification contains no actions for IANA. All protocol 1043 parameters required for this document were previously approved as 1044 part of the publication of [RFC3576]. 1046 6. Security Considerations 1048 6.1. Authorization Issues 1050 Where a NAS is shared by multiple providers, it is undesirable for 1051 one provider to be able to send Disconnect-Request or CoA-Requests 1052 affecting the sessions of another provider. 1054 A NAS or RADIUS proxy MUST silently discard Disconnect-Request or 1055 CoA-Request packets from untrusted sources. By default, a RADIUS 1056 proxy SHOULD perform a "reverse path forwarding" (RPF) check to 1057 verify that a Disconnect-Request or CoA-Request originates from an 1058 authorized RADIUS server. In addition, it SHOULD be possible to 1059 explicitly authorize additional sources of Disconnect-Request or CoA- 1060 Request packets relating to certain classes of sessions. For 1061 example, a particular source can be explicitly authorized to send 1062 CoA-Request packets relating to users within a set of realms. 1064 To perform the RPF check, the proxy uses the session identification 1065 attributes included in Disconnect-Request or CoA-Request packets, in 1066 order to determine the RADIUS server(s) to which an equivalent 1067 Access-Request could be routed. If the source address of the 1068 Disconnect-Request or CoA-Request is within this set, then the 1069 Request is forwarded; otherwise it MUST be silently discarded. 1071 Typically the proxy will extract the realm from the Network Access 1072 Identifier [RFC4282] included within the User-Name Attribute, and 1073 determine the corresponding RADIUS servers in the proxy routing 1074 tables. The RADIUS servers for that realm are then compared against 1075 the source address of the packet. Where no RADIUS proxy is present, 1076 the RPF check will need to be performed by the NAS itself. 1078 Since authorization to send a Disconnect-Request or CoA-Request is 1079 determined based on the source address and the corresponding shared 1080 secret, the NASes or proxies SHOULD configure a different shared 1081 secret for each RADIUS server. 1083 6.2. Impersonation 1085 [RFC2865] Section 3 states: 1087 A RADIUS server MUST use the source IP address of the RADIUS 1088 UDP packet to decide which shared secret to use, so that 1089 RADIUS requests can be proxied. 1091 When RADIUS requests are forwarded by a proxy, the NAS-IP-Address or 1092 NAS-IPv6-Address Attributes will typically not match the source 1093 address observed by the RADIUS server. Since the NAS-Identifier 1094 Attribute need not contain an FQDN, this attribute may not be 1095 resolvable to the source address observed by the RADIUS server, even 1096 when no proxy is present. 1098 As a result, the authenticity check performed by a RADIUS server or 1099 proxy does not verify the correctness of NAS identification 1100 attributes. This makes it possible for a rogue NAS to forge NAS-IP- 1101 Address, NAS-IPv6-Address or NAS-Identifier Attributes within a 1102 RADIUS Access-Request in order to impersonate another NAS. It is 1103 also possible for a rogue NAS to forge session identification 1104 attributes such as the Called-Station-Id, Calling-Station-Id, or 1105 Originating-Line-Info [RFC4005]. This could fool the RADIUS server 1106 into sending Disconnect-Request or CoA-Request packets containing 1107 forged session identification attributes to a NAS targeted by an 1108 attacker. 1110 To address these vulnerabilities RADIUS proxies SHOULD check whether 1111 NAS identification attributes (see Section 3) match the source 1112 address of packets originating from the NAS. Where one or more 1113 attributes do not match, Disconnect-Request or CoA-Request packets 1114 SHOULD be silently discarded. 1116 Such a check may not always be possible. Since the NAS-Identifier 1117 Attribute need not correspond to an FQDN, it may not be resolvable to 1118 an IP address to be matched against the source address. Also, where 1119 a NAT exists between the RADIUS client and proxy, checking the NAS- 1120 IP-Address or NAS-IPv6-Address Attributes may not be feasible. 1122 6.3. IPsec Usage Guidelines 1124 In addition to security vulnerabilities unique to Disconnect or CoA 1125 packets, the protocol exchanges described in this document are 1126 susceptible to the same vulnerabilities as RADIUS [RFC2865]. It is 1127 RECOMMENDED that IPsec be employed to afford better security. 1129 Implementations of this specification SHOULD support IPsec [RFC4301] 1130 along with IKEv1 [RFC2409] for key management. IPsec ESP [RFC4303] 1131 with non-null transform SHOULD be supported, and IPsec ESP with a 1132 non-null encryption transform and authentication support SHOULD be 1133 used to provide per-packet confidentiality, authentication, integrity 1134 and replay protection. IKE SHOULD be used for key management. 1136 Within RADIUS [RFC2865], a shared secret is used for hiding of 1137 Attributes such as User-Password, as well as in computation of the 1138 Response Authenticator. In RADIUS accounting [RFC2866], the shared 1139 secret is used in computation of both the Request Authenticator and 1140 the Response Authenticator. 1142 Since in RADIUS a shared secret is used to provide confidentiality as 1143 well as integrity protection and authentication, only use of IPsec 1144 ESP with a non-null transform can provide security services 1145 sufficient to substitute for RADIUS application-layer security. 1146 Therefore, where IPsec AH or ESP null is used, it will typically 1147 still be necessary to configure a RADIUS shared secret. 1149 Where RADIUS is run over IPsec ESP with a non-null transform, the 1150 secret shared between the NAS and the RADIUS server MAY NOT be 1151 configured. In this case, a shared secret of zero length MUST be 1152 assumed. However, a RADIUS server that cannot know whether incoming 1153 traffic is IPsec-protected MUST be configured with a non-null RADIUS 1154 shared secret. 1156 When IPsec ESP is used with RADIUS, per-packet authentication, 1157 integrity and replay protection MUST be used. 3DES-CBC MUST be 1158 supported as an encryption transform and AES-CBC SHOULD be supported. 1159 AES-CBC SHOULD be offered as a preferred encryption transform if 1160 supported. HMAC-SHA1-96 MUST be supported as an authentication 1161 transform. DES-CBC SHOULD NOT be used as the encryption transform. 1163 A typical IPsec policy for an IPsec-capable RADIUS client is 1164 "Initiate IPsec, from me to any destination port UDP 1812". This 1165 IPsec policy causes an IPsec SA to be set up by the RADIUS client 1166 prior to sending RADIUS traffic. If some RADIUS servers contacted by 1167 the client do not support IPsec, then a more granular policy will be 1168 required: "Initiate IPsec, from me to IPsec-Capable-RADIUS-Server, 1169 destination port UDP 1812." 1171 For a client implementing this specification the policy would be 1172 "Accept IPsec, from any to me, destination port UDP 3799". This 1173 causes the RADIUS client to accept (but not require) use of IPsec. 1174 It may not be appropriate to require IPsec for all RADIUS servers 1175 connecting to an IPsec-enabled RADIUS client, since some RADIUS 1176 servers may not support IPsec. 1178 For an IPsec-capable RADIUS server, a typical IPsec policy is "Accept 1179 IPsec, from any to me, destination port 1812". This causes the 1180 RADIUS server to accept (but not require) use of IPsec. It may not 1181 be appropriate to require IPsec for all RADIUS clients connecting to 1182 an IPsec-enabled RADIUS server, since some RADIUS clients may not 1183 support IPsec. 1185 For servers implementing this specification, the policy would be 1186 "Initiate IPsec, from me to any, destination port UDP 3799". This 1187 causes the RADIUS server to initiate IPsec when sending RADIUS 1188 extension traffic to any RADIUS client. If some RADIUS clients 1189 contacted by the server do not support IPsec, then a more granular 1190 policy will be required, such as "Initiate IPsec, from me to IPsec- 1191 capable-RADIUS-client, destination port UDP 3799". 1193 Where IPsec is used for security, and no RADIUS shared secret is 1194 configured, it is important that the RADIUS client and server perform 1195 an authorization check. Before enabling a host to act as a RADIUS 1196 client, the RADIUS server SHOULD check whether the host is authorized 1197 to provide network access. Similarly, before enabling a host to act 1198 as a RADIUS server, the RADIUS client SHOULD check whether the host 1199 is authorized for that role. 1201 RADIUS servers can be configured with the IP addresses (for IKE 1202 Aggressive Mode with pre-shared keys) or FQDNs (for certificate 1203 authentication) of RADIUS clients. Alternatively, if a separate 1204 Certification Authority (CA) exists for RADIUS clients, then the 1205 RADIUS server can configure this CA as a trust anchor [RFC3280] for 1206 use with IPsec. 1208 Similarly, RADIUS clients can be configured with the IP addresses 1209 (for IKE Aggressive Mode with pre-shared keys) or FQDNs (for 1210 certificate authentication) of RADIUS servers. Alternatively, if a 1211 separate CA exists for RADIUS servers, then the RADIUS client can 1212 configure this CA as a trust anchor for use with IPsec. 1214 Since unlike SSL/TLS, IKE does not permit certificate policies to be 1215 set on a per-port basis, certificate policies need to apply to all 1216 uses of IPsec on RADIUS clients and servers. In IPsec deployment 1217 supporting only certificate authentication, a management station 1218 initiating an IPsec-protected telnet session to the RADIUS server 1219 would need to obtain a certificate chaining to the RADIUS client CA. 1220 Issuing such a certificate migh not be appropriate if the management 1221 station was not authorized as a RADIUS client. 1223 Where RADIUS clients may obtain their IP address dynamically (such as 1224 an Access Point supporting DHCP), Main Mode with pre-shared keys 1225 [RFC2409] SHOULD NOT be used, since this requires use of a group pre- 1226 shared key; instead, Aggressive Mode SHOULD be used. Where RADIUS 1227 client addresses are statically assigned either Aggressive Mode or 1228 Main Mode MAY be used. With certificate authentication, Main Mode 1229 SHOULD be used. 1231 Care needs to be taken with IKE Phase 1 Identity Payload selection in 1232 order to enable mapping of identities to pre-shared keys even with 1233 Aggressive Mode. Where the ID_IPV4_ADDR or ID_IPV6_ADDR Identity 1234 Payloads are used and addresses are dynamically assigned, mapping of 1235 identities to keys is not possible, so that group pre-shared keys are 1236 still a practical necessity. As a result, the ID_FQDN identity 1237 payload SHOULD be employed in situations where Aggressive mode is 1238 utilized along with pre-shared keys and IP addresses are dynamically 1239 assigned. This approach also has other advantages, since it allows 1240 the RADIUS server and client to configure themselves based on the 1241 fully qualified domain name of their peers. 1243 Note that with IPsec, security services are negotiated at the 1244 granularity of an IPsec SA, so that RADIUS exchanges requiring a set 1245 of security services different from those negotiated with existing 1246 IPsec SAs will need to negotiate a new IPsec SA. Separate IPsec SAs 1247 are also advisable where quality of service considerations dictate 1248 different handling RADIUS conversations. Attempting to apply 1249 different quality of service to connections handled by the same IPsec 1250 SA can result in reordering, and falling outside the replay window. 1251 For a discussion of the issues, see [RFC2983]. 1253 6.4. Replay Protection 1255 Where IPsec replay protection is not used, an Event-Timestamp (55) 1256 [RFC2869] Attribute SHOULD be included within CoA-Request and 1257 Disconnect-Request packets, and MAY be included within CoA-ACK, CoA- 1258 NAK, Disconnect-ACK and Disconnect-NAK packets. 1260 When the Event-Timestamp attribute is present, both the NAS and the 1261 RADIUS server MUST check that the Event-Timestamp Attribute is 1262 current within an acceptable time window. If the Event-Timestamp 1263 Attribute is not current, then the packet MUST be silently discarded. 1264 This implies the need for loose time synchronization within the 1265 network, which can be achieved by a variety of means, including SNTP, 1266 as described in [RFC4330]. Implementations SHOULD be configurable to 1267 discard CoA-Request or Disconnect-Request packets not containing an 1268 Event-Timestamp attribute. 1270 If the Event-Timestamp Attribute is included, it represents the time 1271 at which the original packet was sent, and therefore it SHOULD NOT be 1272 updated when the packet is retransmitted. If the Event-Timestamp 1273 attribute is not updated, this implies that the Identifier is not 1274 changed in retransmitted packets. As a result, the ability to detect 1275 replay within the time window is dependent on support for duplicate 1276 detection within that same window. As noted in Section 2.3, 1277 duplicate detection is REQUIRED for RADIUS clients implementing this 1278 specification. 1280 The time window used for duplicate detection MUST be the same as the 1281 window used to detect stale Event-Timestamp Attributes. Since the 1282 RADIUS Identifier cannot be repeated within the selected time window, 1283 no more than 256 Requests can be accepted within the time window. As 1284 a result, the chosen time window will depend on the expected maximum 1285 volume of CoA/Disconnect-Requests, so that unnecessary discards can 1286 be avoided. A default time window of 300 seconds should be adequate 1287 in many circumstances. 1289 7. Example Traces 1291 Disconnect Request with User-Name: 1293 0: xxxx xxxx xxxx xxxx xxxx 2801 001c 1b23 .B.....$.-(....# 1294 16: 624c 3543 ceba 55f1 be55 a714 ca5e 0108 bL5C..U..U...^.. 1295 32: 6d63 6869 6261 1297 Disconnect Request with Acct-Session-ID: 1299 0: xxxx xxxx xxxx xxxx xxxx 2801 001e ad0d .B..... ~.(..... 1300 16: 8e53 55b6 bd02 a0cb ace6 4e38 77bd 2c0a .SU.......N8w.,. 1301 32: 3930 3233 3435 3637 90234567 1303 Disconnect Request with Framed-IP-Address: 1305 0: xxxx xxxx xxxx xxxx xxxx 2801 001a 0bda .B....."2.(..... 1306 16: 33fe 765b 05f0 fd9c c32a 2f6b 5182 0806 3.v[.....*/kQ... 1307 32: 0a00 0203 1309 8. References 1311 8.1. Normative References 1313 [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, 1314 April 1992. 1316 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1317 Requirement Levels", RFC 2119, March 1997. 1319 [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange (IKE)", 1320 RFC 2409, November 1998. 1322 [RFC2865] Rigney, C., Rubens, A., Simpson, W. and S. Willens, "Remote 1323 Authentication Dial In User Service (RADIUS)", RFC 2865, June 1324 2000. 1326 [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000. 1328 [RFC2869] Rigney, C., Willats W. and P. Calhoun, "RADIUS Extensions", 1329 RFC 2869, June 2000. 1331 [RFC3162] Aboba, B., Zorn, G. and D. Mitton, "RADIUS and IPv6", RFC 1332 3162, August 2001. 1334 [RFC3280] Housley, R., Polk, W., Ford, W. and D. Solo, "Internet X.509 1335 Public Key Infrastructure Certificate and Certificate 1336 Revocation List (CRL) Profile", RFC 3280, April 2002. 1338 [RFC3575] Aboba, B., "IANA Considerations for RADIUS", RFC 3575, July 1339 2003. 1341 [RFC3579] Aboba, B. and P. Calhoun, "RADIUS Support for Extensible 1342 Authentication Protocol (EAP)", RFC 3579, September 2003. 1344 [RFC4282] Aboba, B., Beadles, M., Arkko, J. and P. Eronen, "The Network 1345 Access Identifier", RFC 4282, December 2005. 1347 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet 1348 Protocol", RFC 4301, December 2005. 1350 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, 1351 December 2005. 1353 8.2. Informative References 1355 [RFC2868] Zorn, G., Leifer, D., Rubens, A., Shriver, J., Holdrege, M. 1356 and I. Goyret, "RADIUS Attributes for Tunnel Protocol 1357 Support", RFC 2868, June 2000. 1359 [RFC2983] Black, D. "Differentiated Services and Tunnels", RFC 2983, 1360 October 2000. 1362 [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and 1363 Accounting Transport Profile", RFC 3539, June 2003. 1365 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G. and J. 1366 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 1368 [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D. and B. Aboba, 1369 "Dynamic Authorization Extensions to Remote Authentication 1370 Dial In User Service (RADIUS)", RFC 3576, July 2003. 1372 [RFC4005] Calhoun, P., Zorn, G., Spence, D. and D. Mitton, "Diameter 1373 Network Access Server Application", RFC 4005, August 2005. 1375 [RFC4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 for 1376 IPv4, IPv6 and OSI", RFC 4330, January 2006. 1378 [RFC4372] Adrangi, F., Lior, A., Korhonen, J. and J. Loughney, 1379 "Chargeable User Identity", RFC 4372, January 2006. 1381 [RFC4675] Congdon, P., Sanchez, M. and B. Aboba, "RADIUS Attributes for 1382 Virtual LAN and Priority Support", RFC 4675, September 2006. 1384 [RFC4818] Salowey, J. and R. Droms, "RADIUS Delegated-IPv6-Prefix 1385 Attribute", RFC 4818, April 2007. 1387 [RFCFilter] 1388 Congdon, P., Sanchez, M. and B. Aboba, "RADIUS Filter Rule 1389 Attribute", draft-ietf-radext-filter-08.txt, Internet draft 1390 (work in progress), January 2007. 1392 [MD5Attack] 1393 Dobbertin, H., "The Status of MD5 After a Recent Attack", 1394 CryptoBytes Vol.2 No.2, Summer 1996. 1396 Acknowledgments 1398 This protocol was first developed and distributed by Ascend 1399 Communications. Example code was distributed in their free server 1400 kit. 1402 The authors would like to acknowledge the valuable suggestions and 1403 feedback from the following people: 1405 Avi Lior , 1406 Randy Bush , 1407 Steve Bellovin 1408 Glen Zorn , 1409 Mark Jones , 1410 Claudio Lapidus , 1411 Anurag Batta , 1412 Kuntal Chowdhury 1413 Tim Moore 1414 Russ Housley 1415 Joe Salowey 1417 Authors' Addresses 1419 Murtaza Chiba 1420 Cisco Systems, Inc. 1421 170 West Tasman Dr. 1422 San Jose CA, 95134 1424 EMail: mchiba@cisco.com 1425 Phone: +1 408 525 7198 1427 Gopal Dommety 1428 Cisco Systems, Inc. 1429 170 West Tasman Dr. 1430 San Jose, CA 95134 1432 EMail: gdommety@cisco.com 1433 Phone: +1 408 525 1404 1435 Mark Eklund 1436 Cisco Systems, Inc. 1437 170 West Tasman Dr. 1438 San Jose, CA 95134 1440 EMail: meklund@cisco.com 1441 Phone: +1 865 671 6255 1443 David Mitton 1444 RSA Security, Inc. 1445 174 Middlesex Turnpike 1446 Bedford, MA 01730 1448 EMail: dmitton@circularnetworks.com 1450 Bernard Aboba 1451 Microsoft Corporation 1452 One Microsoft Way 1453 Redmond, WA 98052 1455 EMail: bernarda@microsoft.com 1456 Phone: +1 425 706 6605 1457 Fax: +1 425 936 7329 1459 Appendix A - Changes from RFC 3576 1461 This Appendix lists the major changes between [RFC3576] and this 1462 document. Minor changes, including style, grammar, spelling, and 1463 editorial changes are not mentioned here. 1465 o Added details relating to handling of the Proxy-State Attribute. 1466 Added requirement for duplicate detection on the RADIUS client 1467 (Section 2.3). 1469 o Added Chargeable-User-Identity as a session identification 1470 attribute (Section 3). 1472 o Added requirements for inclusion of the State Attribute in CoA- 1473 Request packets with a Service-Type of "Authorize Only" (Section 1474 3.1). 1476 o Added clarification on the calculation of the Message-Authenticator 1477 Attribute (Section 3.2). 1479 o Added statement that support for "Authorize Only" Service-Type is 1480 optional (Section 3.4). 1482 o Updated CoA-Request Attribute Table to include Filter-Rule, 1483 Delegated-IPv6-Prefix, Egress-VLANID, Ingress-Filters, Egress-VLAN- 1484 Name and User-Priority attributes (Section 3.4). 1486 o Added the Chargeable-User-Identity Attribute to both the CoA- 1487 Request and Disconnect-Request Attribute Table (Section 3.4). 1489 o Added note relating to use of Service-Type="Authorize Only" for 1490 renumbering (Section 3.4). 1492 o Use of a Service-Type Attribute within a Disconnect-Request is 1493 prohibited (Sections 3.4, 4). 1495 o Added Diameter Considerations (Section 5). 1497 o Changed the text to indicate that the Event-Timestamp Attribute 1498 should not be recalculated on retransmission. The implications for 1499 replay and duplicate detection are discussed (Section 6.4). 1501 Full Copyright Statement 1503 Copyright (C) The IETF Trust (2007). 1505 This document is subject to the rights, licenses and restrictions 1506 contained in BCP 78, and except as set forth therein, the authors 1507 retain all their rights. 1509 This document and the information contained herein are provided on an 1510 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 1511 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 1512 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 1513 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 1514 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 1515 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 1517 Intellectual Property 1519 The IETF takes no position regarding the validity or scope of any 1520 Intellectual Property Rights or other rights that might be claimed to 1521 pertain to the implementation or use of the technology described in 1522 this document or the extent to which any license under such rights 1523 might or might not be available; nor does it represent that it has 1524 made any independent effort to identify any such rights. 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