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MUST This word, or the adjecti...' RFC 2119 keyword, line 182: '... MUST NOT This phrase means that th...' RFC 2119 keyword, line 185: '... SHOULD This word, or the adjecti...' RFC 2119 keyword, line 191: '... MAY This word, or the adjecti...' RFC 2119 keyword, line 193: '...h does not include this option MUST be...' (113 more instances...) Miscellaneous warnings: ---------------------------------------------------------------------------- == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: This Attribute is available to allow vendors to support their own extended Attributes not suitable for general usage. 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'1') ** Obsolete normative reference: RFC 1700 (ref. '3') (Obsoleted by RFC 3232) -- Possible downref: Non-RFC (?) normative reference: ref. '4' -- Possible downref: Non-RFC (?) normative reference: ref. '6' ** Obsolete normative reference: RFC 1717 (ref. '7') (Obsoleted by RFC 1990) ** Downref: Normative reference to an Historic RFC: RFC 1352 (ref. '8') Summary: 14 errors (**), 0 flaws (~~), 4 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 RADIUS Working Group C Rigney 2 INTERNET-DRAFT Livingston 3 A Rubens 4 Merit 5 W A Simpson 6 Daydreamer 7 S Willens 8 Livingston 9 expires in six months June 1996 11 Remote Authentication Dial In User Service (RADIUS) 12 draft-ietf-radius-radius-04.txt 14 Status of this Memo 16 This document is a submission to the RADIUS Working Group of the 17 Internet Engineering Task Force (IETF). Comments should be submitted 18 to the ietf-radius@livingston.com mailing list. 20 Distribution of this memo is unlimited. 22 This document is an Internet-Draft. Internet-Drafts are working 23 documents of the Internet Engineering Task Force (IETF), its areas, 24 and its working groups. Note that other groups may also distribute 25 working documents as Internet-Drafts. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as ``work in progress.'' 32 To learn the current status of any Internet-Draft, please check the 33 ``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow 34 Directories on on ftp.is.co.za (Africa), nic.nordu.net (Europe), 35 munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or 36 ftp.isi.edu (US West Coast). 38 Abstract 40 This document describes a protocol for carrying authentication, 41 authorization, and configuration information between a Network Access 42 Server which desires to authenticate its links and a shared 43 Authentication Server. 45 Table of Contents 47 1. Introduction .......................................... 1 48 1.1 Specification of Requirements ................... 2 49 1.2 Terminology ..................................... 2 51 2. Operation ............................................. 3 52 2.1 Challenge/Response .............................. 4 53 2.2 Interoperation with PAP and CHAP ................ 5 54 2.3 Why UDP? ........................................ 6 56 3. Packet Format ......................................... 8 58 4. Packet Types .......................................... 12 59 4.1 Access-Request .................................. 12 60 4.2 Access-Accept ................................... 13 61 4.3 Access-Reject ................................... 14 62 4.4 Access-Challenge ................................ 15 64 5. Attributes ............................................ 18 65 5.1 User-Name ....................................... 20 66 5.2 User-Password ................................... 21 67 5.3 CHAP-Password ................................... 22 68 5.4 NAS-IP-Address .................................. 23 69 5.5 NAS-Port ........................................ 24 70 5.6 Service-Type .................................... 25 71 5.7 Framed-Protocol ................................. 27 72 5.8 Framed-IP-Address ............................... 28 73 5.9 Framed-IP-Netmask ............................... 28 74 5.10 Framed-Routing .................................. 29 75 5.11 Filter-Id ....................................... 30 76 5.12 Framed-MTU ...................................... 31 77 5.13 Framed-Compression .............................. 32 78 5.14 Login-IP-Host ................................... 32 79 5.15 Login-Service ................................... 33 80 5.16 Login-TCP-Port .................................. 34 81 5.17 (unassigned) .................................... 35 82 5.18 Reply-Message ................................... 35 83 5.19 Callback-Number ................................. 36 84 5.20 Callback-Id ..................................... 37 85 5.21 (unassigned) .................................... 38 86 5.22 Framed-Route .................................... 38 87 5.23 Framed-IPX-Network .............................. 39 88 5.24 State ........................................... 40 89 5.25 Class ........................................... 41 90 5.26 Vendor-Specific ................................. 42 91 5.27 Session-Timeout ................................. 43 92 5.28 Idle-Timeout .................................... 44 93 5.29 Termination-Action .............................. 45 94 5.30 Called-Station-Id ............................... 46 95 5.31 Calling-Station-Id .............................. 46 96 5.32 NAS-Identifier .................................. 47 97 5.33 Proxy-State ..................................... 48 98 5.34 Login-LAT-Service ............................... 49 99 5.35 Login-LAT-Node .................................. 50 100 5.36 Login-LAT-Group ................................. 51 101 5.37 Framed-AppleTalk-Link ........................... 52 102 5.38 Framed-AppleTalk-Network ........................ 53 103 5.39 Framed-AppleTalk-Zone ........................... 54 104 5.40 CHAP-Challenge .................................. 55 105 5.41 NAS-Port-Type ................................... 55 106 5.42 Port-Limit ...................................... 56 107 5.43 Login-LAT-Port .................................. 57 108 5.44 Table of Attributes ............................. 58 110 6. Examples .............................................. 60 111 6.1 User Telnet to Specified Host ................... 60 112 6.2 Framed User Authenticating with CHAP ............ 60 113 6.3 User with Challenge-Response card ............... 61 115 SECURITY CONSIDERATIONS ...................................... 64 117 REFERENCES ................................................... 65 119 ACKNOWLEDGEMENTS ............................................. 65 121 CHAIR'S ADDRESS .............................................. 66 123 AUTHOR'S ADDRESS ............................................. 66 125 1. Introduction 127 Managing dispersed serial line and modem pools for large numbers of 128 users can create the need for significant administrative support. 129 Since modem pools are by definition a link to the outside world, they 130 require careful attention to security, authorization and accounting. 131 This can be best achieved by managing a single "database" of users, 132 which allows for authentication (verifying user name and password) as 133 well as configuration information detailing the type of service to 134 deliver to the user (for example, SLIP, PPP, telnet, rlogin). 136 Key features of RADIUS are: 138 Client/Server Model 140 A Network Access Server (NAS) operates as a client of RADIUS. The 141 client is responsible for passing user information to designated 142 RADIUS servers, and then acting on the response which is returned. 144 RADIUS servers are responsible for receiving user connection 145 requests, authenticating the user, and then returning all 146 configuration information necessary for the client to deliver 147 service to the user. 149 A RADIUS server can act as a proxy client to other RADIUS servers 150 or other kinds of authentication servers. 152 Network Security 154 Transactions between the client and RADIUS server are 155 authenticated through the use of a shared secret, which is never 156 sent over the network. In addition, any user passwords are sent 157 encrypted between the client and RADIUS server, to eliminate the 158 possibility that someone snooping on an unsecure network could 159 determine a user's password. 161 Flexible Authentication Mechanisms 163 The RADIUS server can support a variety of methods to authenticate 164 a user. When it is provided with the user name and original 165 password given by the user, it can support PPP PAP or CHAP, UNIX 166 login, and other authentication mechanisms. 168 Extensible Protocol 170 All transactions are comprised of variable length Attribute- 171 Length-Value 3-tuples. New attribute values can be added without 172 disturbing existing implementations of the protocol. 174 1.1. Specification of Requirements 176 In this document, several words are used to signify the requirements 177 of the specification. These words are often capitalized. 179 MUST This word, or the adjective "required", means that the 180 definition is an absolute requirement of the specification. 182 MUST NOT This phrase means that the definition is an absolute 183 prohibition of the specification. 185 SHOULD This word, or the adjective "recommended", means that there 186 may exist valid reasons in particular circumstances to 187 ignore this item, but the full implications must be 188 understood and carefully weighed before choosing a 189 different course. 191 MAY This word, or the adjective "optional", means that this 192 item is one of an allowed set of alternatives. An 193 implementation which does not include this option MUST be 194 prepared to interoperate with another implementation which 195 does include the option. 197 1.2. Terminology 199 This document frequently uses the following terms: 201 service The NAS provides a service to the dial-in user, such as PPP 202 or Telnet. 204 session Each service provided by the NAS to a dial-in user 205 constitutes a session, with the beginning of the session 206 defined as the point where service is first provided and 207 the end of the session defined as the point where service 208 is ended. A user may have multiple sessions in parallel or 209 series if the NAS supports that. 211 silently discard 212 This means the implementation discards the packet without 213 further processing. The implementation SHOULD provide the 214 capability of logging the error, including the contents of 215 the silently discarded packet, and SHOULD record the event 216 in a statistics counter. 218 2. Operation 220 When a client is configured to use RADIUS, any user of the client 221 presents authentication information to the client. This might be 222 with a customizable login prompt, where the user is expected to enter 223 their username and password. Alternatively, the user might use a 224 link framing protocol such as the Point-to-Point Protocol (PPP), 225 which has authentication packets which carry this information. 227 Once the client has obtained such information, it may choose to 228 authenticate using RADIUS. To do so, the client creates an "Access- 229 Request" containing such Attributes as the user's name, the user's 230 password, the ID of the client and the Port ID which the user is 231 accessing. When a password is present, it is hidden using a method 232 based on the RSA Message Digest Algorithm MD5 [1]. 234 The Access-Request is submitted to the RADIUS server via the network. 235 If no response is returned within a length of time, the request is 236 re-sent a number of times. The client can also forward requests to 237 an alternate server or servers in the event that the primary server 238 is down or unreachable. An alternate server can be used either after 239 a number of tries to the primary server fail, or in a round-robin 240 fashion. Retry and fallback algorithms are the topic of current 241 research and are not specified in detail in this document. 243 Once the RADIUS server receives the request, it validates the sending 244 client. A request from a client for which the RADIUS server does not 245 have a shared secret should be silently discarded. If the client is 246 valid, the RADIUS server consults a database of users to find the 247 user whose name matches the request. The user entry in the database 248 contains a list of requirements which must be met to allow access for 249 the user. This always includes verification of the password, but can 250 also specify the client(s) or port(s) to which the user is allowed 251 access. 253 The RADIUS server MAY make requests of other servers in order to 254 satisfy the request, in which case it acts as a client. 256 If any condition is not met, the RADIUS server sends an "Access- 257 Reject" response indicating that this user request is invalid. If 258 desired, the server MAY include a text message in the Access-Reject 259 which MAY be displayed by the client to the user. No other 260 Attributes are permitted in an Access-Reject. 262 If all conditions are met and the RADIUS server wishes to issue a 263 challenge to which the user must respond, the RADIUS server sends an 264 "Access-Challenge" response. It MAY include a text message to be 265 displayed by the client to the user prompting for a response to the 266 challenge, and MAY include a State attribute. If the client receives 267 an Access-Challenge and supports challenge/response it MAY display 268 the text message, if any, to the user, and then prompt the user for a 269 response. The client then re-submits its original Access-Request 270 with a new request ID, with the User-Password Attribute replaced by 271 the response (encrypted), and including the State Attribute from the 272 Access-Challenge, if any. Only 0 or 1 instances of the State 273 Attributes should be present in a request. The server can respond to 274 this new Access-Request with either an Access-Accept, an Access- 275 Reject, or another Access-Challenge. 277 If all conditions are met, the list of configuration values for the 278 user are placed into an "Access-Accept" response. These values 279 include the type of service (for example: SLIP, PPP, Login User) and 280 all necessary values to deliver the desired service. For SLIP and 281 PPP, this may include values such as IP address, subnet mask, MTU, 282 desired compression, and desired packet filter identifiers. For 283 character mode users, this may include values such as desired 284 protocol and host. 286 2.1. Challenge/Response 288 In challenge/response authentication, the user is given an 289 unpredictable number and challenged to encrypt it and give back the 290 result. Authorized users are equipped with special devices such as 291 smart cards or software that facilitate calculation of the correct 292 response with ease. Unauthorized users, lacking the appropriate 293 device or software and lacking knowledge of the secret key necessary 294 to emulate such a device or software, can only guess at the response. 296 The Access-Challenge packet typically contains a Reply-Message 297 including a challenge to be displayed to the user, such as a numeric 298 value unlikely ever to be repeated. Typically this is obtained from 299 an external server that knows what type of authenticator should be in 300 the possession of the authorized user and can therefore choose a 301 random or non-repeating pseudorandom number of an appropriate radix 302 and length. 304 The user then enters the challenge into his device (or software) and 305 it calculates a response, which the user enters into the client which 306 forwards it to the RADIUS server via a second Access-Request. If the 307 response matches the expected response the RADIUS server replies with 308 an Access-Accept, otherwise an Access-Reject. 310 Example: The NAS sends an Access-Request packet to the RADIUS Server 311 with NAS-Identifier, NAS-Port, User-Name, User-Password (which may 312 just be a fixed string like "challenge" or ignored). The server 313 sends back an Access-Challenge packet with State and a Reply-Message 314 along the lines of "Challenge 12345678, enter your response at the 315 prompt" which the NAS displays. The NAS prompts for the response and 316 sends a NEW Access-Request to the server (with a new ID) with NAS- 317 Identifier, NAS-Port, User-Name, User-Password (the response just 318 entered by the user, encrypted), and the same State Attribute that 319 came with the Access-Challenge. The server then sends back either an 320 Access-Accept or Access-Reject based on whether the response matches 321 what it should be, or it can even send another Access-Challenge. 323 2.2. Interoperation with PAP and CHAP 325 For PAP, the NAS takes the PAP ID and password and sends them in an 326 Access-Request packet as the User-Name and User-Password. The NAS MAY 327 include the Attributes Service-Type = Framed-User and Framed-Protocol 328 = PPP as a hint to the RADIUS server that PPP service is expected. 330 For CHAP, the NAS generates a random challenge (preferably 16 octets) 331 and sends it to the user, who returns a CHAP response along with a 332 CHAP ID and CHAP username. The NAS then sends an Access-Request 333 packet to the RADIUS server with the CHAP username as the User-Name 334 and with the CHAP ID and CHAP response as the CHAP-Password 335 (Attribute 3). The random challenge can either be included in the 336 CHAP-Challenge attribute or, if it is 16 octets long, it can be 337 placed in the Request Authenticator field of the Access-Request 338 packet. The NAS MAY include the Attributes Service-Type = Framed- 339 User and Framed-Protocol = PPP as a hint to the RADIUS server that 340 PPP service is expected. 342 The RADIUS server looks up a password based on the User-Name, 343 encrypts the challenge using MD5 on the CHAP ID octet, that password, 344 and the CHAP challenge (from the CHAP-Challenge attribute if present, 345 otherwise from the Request Authenticator), and compares that result 346 to the CHAP-Password. If they match, the server sends back an 347 Access-Accept, otherwise it sends back an Access-Reject. 349 If the RADIUS server is unable to perform the requested 350 authentication it should return an Access-Reject. For example, CHAP 351 requires that the user's password be available in cleartext to the 352 server so that it can encrypt the CHAP challenge and compare that to 353 the CHAP response. If the password is not available in cleartext to 354 the RADIUS server then the server MUST send an Access-Reject to the 355 client. 357 2.3. Why UDP? 359 A frequently asked question is why RADIUS uses UDP instead of TCP as 360 a transport protocol. UDP was chosen for strictly technical reasons. 362 There are a number of issues which must be understood. RADIUS is a 363 transaction based protocol which has several interesting 364 characteristics: 366 1. If the request to a primary Authentication server fails, a 367 secondary server must be queried. 369 To meet this requirement, a copy of the request must be kept 370 above the transport layer to allow for alternate transmission. 371 This means that retransmission timers are still required. 373 2. The timing requirements of this particular protocol are 374 significantly different than TCP provides. 376 At one extreme, RADIUS does not require a "responsive" detection 377 of lost data. The user is willing to wait several seconds for 378 the authentication to complete. The generally aggressive TCP 379 retransmission (based on average round trip time) is not 380 required, nor is the acknowledgement overhead of TCP. 382 At the other extreme, the user is not willing to wait several 383 minutes for authentication. Therefore the reliable delivery of 384 TCP data two minutes later is not useful. The faster use of an 385 alternate server allows the user to gain access before giving 386 up. 388 3. The stateless nature of this protocol simplifies the use of UDP. 390 Clients and servers come and go. Systems are rebooted, or are 391 power cycled independently. Generally this does not cause a 392 problem and with creative timeouts and detection of lost TCP 393 connections, code can be written to handle anomalous events. 394 UDP however completely eliminates any of this special handling. 395 Each client and server can open their UDP transport just once 396 and leave it open through all types of failure events on the 397 network. 399 4. UDP simplifies the server implementation. 401 In the earliest implementations of RADIUS, the server was single 402 threaded. This means that a single request was received, 403 processed, and returned. This was found to be unmanageable in 404 environments where the back-end security mechanism took real 405 time (1 or more seconds). The server request queue would fill 406 and in environments where hundreds of people were being 407 authenticated every minute, the request turn-around time 408 increased to longer that users were willing to wait (this was 409 especially severe when a specific lookup in a database or over 410 DNS took 30 or more seconds). The obvious solution was to make 411 the server multi-threaded. Achieving this was simple with UDP. 412 Separate processes were spawned to serve each request and these 413 processes could respond directly to the client NAS with a simple 414 UDP packet to the original transport of the client. 416 It's not all a panacea. As noted, using UDP requires one thing which 417 is built into TCP: with UDP we must artificially manage 418 retransmission timers to the same server, although they don't require 419 the same attention to timing provided by TCP. This one penalty is a 420 small price to pay for the advantages of UDP in this protocol. 422 Without TCP we would still probably be using tin cans connected by 423 string. But for this particular protocol, UDP is a better choice. 425 3. Packet Format 427 Exactly one RADIUS packet is encapsulated in the UDP Data field [2], 428 where the UDP Destination Port field indicates 1645 (decimal). 430 When a reply is generated, the source and destination ports are 431 reversed. 433 A summary of the RADIUS data format is shown below. The fields are 434 transmitted from left to right. 436 0 1 2 3 437 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 1 438 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 439 | Code | Identifier | Length | 440 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 441 | | 442 | Authenticator | 443 | | 444 | | 445 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 446 | Attributes ... 447 +-+-+-+-+-+-+-+-+-+-+-+-+- 449 Code 451 The Code field is one octet, and identifies the type of RADIUS 452 packet. When a packet is received with an invalid Code field, it is 453 silently discarded. 455 RADIUS Codes (decimal) are assigned as follows: 457 1 Access-Request 458 2 Access-Accept 459 3 Access-Reject 460 4 Accounting-Request 461 5 Accounting-Response 462 11 Access-Challenge 463 12 Status-Server (experimental) 464 13 Status-Client (experimental) 465 255 Reserved 467 Codes 4 and 5 will be covered in the RADIUS Accounting Internet- 468 Draft, and are not further mentioned here. Codes 12 and 13 are 469 reserved for possible use, but are not further mentioned here. 471 Identifier 473 The Identifier field is one octet, and aids in matching requests and 474 replies. 476 Length 478 The Length field is two octets. It indicates the length of the 479 packet including the Code, Identifier, Length, Authenticator and 480 Attribute fields. Octets outside the range of the Length field 481 should be treated as padding and should be ignored on reception. If 482 the packet is shorter than the Length field indicates, it should be 483 silently discarded. The minimum length is 20 and maximum length is 484 4096. 486 Authenticator 488 The Authenticator field is sixteen (16) octets. The most significant 489 octet is transmitted first. This value is used to authenticate the 490 reply from the RADIUS server, and is used in the password hiding 491 algorithm. 493 Request Authenticator 495 In Access-Request Packets, the Authenticator value is a 16 octet 496 random number, called the Request Authenticator. The value SHOULD 497 be unpredictable and unique over the lifetime of a secret (the 498 password shared between the client and the RADIUS server), since 499 repetition of a request value in conjunction with the same secret 500 would permit an attacker to reply with a previously intercepted 501 response. Since it is expected that the same secret MAY be used 502 to authenticate with servers in disparate geographic regions, the 503 Request Authenticator field SHOULD exhibit global and temporal 504 uniqueness. 506 The Request Authenticator value in an Access-Request packet SHOULD 507 also be unpredictable, lest an attacker trick a server into 508 responding to a predicted future request, and then use the 509 response to masquerade as that server to a future Access-Request. 511 Although protocols such as RADIUS are incapable of protecting 512 against theft of an authenticated session via realtime active 513 wiretapping attacks, generation of unique unpredictable requests 514 can protect against a wide range of active attacks against 515 authentication. 517 The NAS and RADIUS server share a secret. That shared secret 518 followed by the Request Authenticator is put through a one-way MD5 519 hash to create a 16 octet digest value which is xored with the 520 password entered by the user, and the xored result placed in the 521 User-Password attribute in the Access-Request packet. See the 522 entry for User-Password in the section on Attributes for a more 523 detailed description. 525 Response Authenticator 527 The value of the Authenticator field in Access-Accept, Access- 528 Reject, and Access-Challenge packets is called the Response 529 Authenticator, and contains a one-way MD5 hash calculated over a 530 stream of octets consisting of: the RADIUS packet, beginning with 531 the Code field, including the Identifier, the Length, the Request 532 Authenticator field from the Access-Request packet, and the 533 response Attributes, followed by the shared secret. That is, 534 ResponseAuth = MD5(Code+ID+Length+RequestAuth+Attributes+Secret) 535 where + denotes concatenation. 537 Administrative Note 539 The secret (password shared between the client and the RADIUS server) 540 SHOULD be at least as large and unguessable as a well-chosen 541 password. It is preferred that the secret be at least 16 octets. 542 This is to ensure a sufficiently large range for the secret to 543 provide protection against exhaustive search attacks. A RADIUS 544 server SHOULD use the source IP address of the RADIUS UDP packet to 545 decide which shared secret to use, so that RADIUS requests can be 546 proxied. 548 When using a forwarding proxy, the proxy must be able to alter the 549 packet as it passes through in each direction - when the proxy 550 forwards the request, the proxy can add a Proxy-State Attribute, and 551 when the proxy forwards a response, it removes the Proxy-State 552 Attribute. Since Access-Accept and Access-Reject replies are 553 authenticated on the entire packet contents, the stripping of the 554 Proxy-State attribute would invalidate the signature in the packet - 555 so the proxy has to re-sign it. 557 Further details of RADIUS proxy implementation are outside the scope 558 of this document. 560 Attributes 562 Many Attributes may have multiple instances, in such a case the order 563 of Attributes of the same Type SHOULD be preserved. The order of 564 Attributes of different Types is not required to be preserved. 566 In the section below on "Attributes" where the text refers to which 567 packets an attribute is allowed in, only packets with Codes 1, 2, 3 568 and 11 and attributes defined in this document are covered in this 569 document. A summary table is provided at the end of the "Attributes" 570 section. To determine which Attributes are allowed in packets with 571 codes 4 and 5 refer to the RADIUS Accounting Internet-Draft. 573 4. Packet Types 575 The RADIUS Packet type is determined by the Code field in the first 576 octet of the Packet. 578 4.1. Access-Request 580 Description 582 Access-Request packets are sent to a RADIUS server, and convey 583 information used to determine whether a user is allowed access to 584 a specific NAS, and any special services requested for that user. 585 An implementation wishing to authenticate a user MUST transmit a 586 RADIUS packet with the Code field set to 1 (Access-Request). 588 Upon receipt of an Access-Request from a valid client, an 589 appropriate reply MUST be transmitted. 591 An Access-Request MUST contain a User-Name attribute. It SHOULD 592 contain either a NAS-IP-Address attribute or NAS-Identifier 593 attribute (or both, although that is not recommended). It MUST 594 contain either a User-Password attribute or CHAP-Password 595 attribute. It SHOULD contain a NAS-Port or NAS-Port-Type 596 attribute or both unless the type of access being requested does 597 not involve a port or the NAS does not distinguish among its 598 ports. 600 An Access-Request MAY contain additional attributes as a hint to 601 the server, but the server is not required to honor the hint. 603 When a User-Password is present, it is hidden using a method based 604 on the RSA Message Digest Algorithm MD5 [1]. 606 A summary of the Access-Request packet format is shown below. The 607 fields are transmitted from left to right. 609 0 1 2 3 610 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 1 611 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 612 | Code | Identifier | Length | 613 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 614 | | 615 | Request Authenticator | 616 | | 617 | | 618 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 619 | Attributes ... 620 +-+-+-+-+-+-+-+-+-+-+-+-+- 622 Code 624 1 for Access-Request. 626 Identifier 628 The Identifier field MUST be changed whenever the content of the 629 Attributes field changes, and whenever a valid reply has been 630 received for a previous request. For retransmissions, the 631 Identifier MUST remain unchanged. 633 Request Authenticator 635 The Request Authenticator value MUST be changed each time a new 636 Identifier is used. 638 Attributes 640 The Attribute field is variable in length, and contains the list 641 of Attributes that are required for the type of service, as well 642 as any desired optional Attributes. 644 4.2. Access-Accept 646 Description 648 Access-Accept packets are sent by the RADIUS server, and provide 649 specific configuration information necessary to begin delivery of 650 service to the user. If all Attribute values received in an 651 Access-Request are acceptable then the RADIUS implementation MUST 652 transmit a packet with the Code field set to 2 (Access-Accept). 654 On reception of an Access-Accept, the Identifier field is matched 655 with a pending Access-Request. Additionally, the Response 656 Authenticator field MUST contain the correct response for the 657 pending Access-Request. Invalid packets are silently discarded. 659 A summary of the Access-Accept packet format is shown below. The 660 fields are transmitted from left to right. 662 0 1 2 3 663 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 1 664 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 665 | Code | Identifier | Length | 666 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 667 | | 668 | Response Authenticator | 669 | | 670 | | 671 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 672 | Attributes ... 673 +-+-+-+-+-+-+-+-+-+-+-+-+- 675 Code 677 2 for Access-Accept. 679 Identifier 681 The Identifier field is a copy of the Identifier field of the 682 Access-Request which caused this Access-Accept. 684 Response Authenticator 686 The Response Authenticator value is calculated from the Access- 687 Request value, as described earlier. 689 Attributes 691 The Attribute field is variable in length, and contains a list of 692 zero or more Attributes. 694 4.3. Access-Reject 696 Description 698 If any value of the received Attributes is not acceptable, then 699 the RADIUS server MUST transmit a packet with the Code field set 700 to 3 (Access-Reject). It MAY include one or more Reply-Message 701 Attributes with a text message which the NAS MAY display to the 702 user. 704 A summary of the Access-Reject packet format is shown below. The 705 fields are transmitted from left to right. 707 0 1 2 3 708 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 1 709 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 710 | Code | Identifier | Length | 711 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 712 | | 713 | Response Authenticator | 714 | | 715 | | 716 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 717 | Attributes ... 718 +-+-+-+-+-+-+-+-+-+-+-+-+- 720 Code 722 3 for Access-Reject. 724 Identifier 726 The Identifier field is a copy of the Identifier field of the 727 Access-Request which caused this Access-Reject. 729 Response Authenticator 731 The Response Authenticator value is calculated from the Access- 732 Request value, as described earlier. 734 Attributes 736 The Attribute field is variable in length, and contains a list of 737 zero or more Attributes. 739 4.4. Access-Challenge 741 Description 743 If the RADIUS server desires to send the user a challenge 744 requiring a response, then the RADIUS server MUST respond to the 745 Access-Request by transmitting a packet with the Code field set to 746 11 (Access-Challenge). 748 The Attributes field MAY have one or more Reply-Message 749 Attributes, and MAY have a single State Attribute, or none. No 750 other Attributes are permitted in an Access-Challenge. 752 On receipt of an Access-Challenge, the Identifier field is matched 753 with a pending Access-Request. Additionally, the Response 754 Authenticator field MUST contain the correct response for the 755 pending Access-Request. Invalid packets are silently discarded. 757 If the NAS does not support challenge/response, it MUST treat an 758 Access-Challenge as though it had received an Access-Reject 759 instead. 761 If the NAS supports challenge/response, receipt of a valid 762 Access-Challenge indicates that a new Access-Request SHOULD be 763 sent. The NAS MAY display the text message, if any, to the user, 764 and then prompt the user for a response. It then sends its 765 original Access-Request with a new request ID and Request 766 Authenticator, with the User-Password Attribute replaced by the 767 user's response (encrypted), and including the State Attribute 768 from the Access-Challenge, if any. Only 0 or 1 instances of the 769 State Attribute can be present in an Access-Request. 771 A NAS which supports PAP MAY forward the Reply-Message to the 772 dialin client and accept a PAP response which it can use as though 773 the user had entered the response. If the NAS cannot do so, it 774 should treat the Access-Challenge as though it had received an 775 Access-Reject instead. 777 A summary of the Access-Challenge packet format is shown below. The 778 fields are transmitted from left to right. 780 0 1 2 3 781 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 1 782 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 783 | Code | Identifier | Length | 784 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 785 | | 786 | Response Authenticator | 787 | | 788 | | 789 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 790 | Attributes ... 791 +-+-+-+-+-+-+-+-+-+-+-+-+- 792 Code 794 11 for Access-Challenge. 796 Identifier 798 The Identifier field is a copy of the Identifier field of the 799 Access-Request which caused this Access-Challenge. 801 Response Authenticator 803 The Response Authenticator value is calculated from the Access- 804 Request value, as described earlier. 806 Attributes 808 The Attributes field is variable in length, and contains a list of 809 zero or more Attributes. 811 5. Attributes 813 RADIUS Attributes carry the specific authentication, authorization, 814 information and configuration details for the request and reply. 816 Some Attributes MAY be included more than once. The effect of this 817 is Attribute specific, and is specified in each Attribute 818 description. 820 The end of the list of Attributes is indicated by the Length of the 821 RADIUS packet. 823 A summary of the Attribute format is shown below. The fields are 824 transmitted from left to right. 826 0 1 2 827 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 828 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 829 | Type | Length | Value ... 830 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 832 Type 834 The Type field is one octet. Up-to-date values of the RADIUS Type 835 field are specified in the most recent "Assigned Numbers" RFC [3]. 836 Values 192-223 are reserved for experimental use, values 224-240 837 are reserved for implementation-specific use, and values 241-255 838 are reserved and should not be used. This specification concerns 839 the following values: 841 A RADIUS server MAY ignore Attributes with an unknown Type. 843 A RADIUS client MAY ignore Attributes with an unknown Type. 845 1 User-Name 846 2 User-Password 847 3 CHAP-Password 848 4 NAS-IP-Address 849 5 NAS-Port 850 6 Service-Type 851 7 Framed-Protocol 852 8 Framed-IP-Address 853 9 Framed-IP-Netmask 854 10 Framed-Routing 855 11 Filter-Id 856 12 Framed-MTU 857 13 Framed-Compression 858 14 Login-IP-Host 859 15 Login-Service 860 16 Login-TCP-Port 861 17 (unassigned) 862 18 Reply-Message 863 19 Callback-Number 864 20 Callback-Id 865 21 (unassigned) 866 22 Framed-Route 867 23 Framed-IPX-Network 868 24 State 869 25 Class 870 26 Vendor-Specific 871 27 Session-Timeout 872 28 Idle-Timeout 873 29 Termination-Action 874 30 Called-Station-Id 875 31 Calling-Station-Id 876 32 NAS-Identifier 877 33 Proxy-State 878 34 Login-LAT-Service 879 35 Login-LAT-Node 880 36 Login-LAT-Group 881 37 Framed-AppleTalk-Link 882 38 Framed-AppleTalk-Network 883 39 Framed-AppleTalk-Zone 884 40-59 (reserved for accounting) 885 60 CHAP-Challenge 886 61 NAS-Port-Type 887 62 Port-Limit 888 63 Login-LAT-Port 890 Length 892 The Length field is one octet, and indicates the length of this 893 Attribute including the Type, Length and Value fields. If an 894 Attribute is received in an Access-Request but with an invalid 895 Length, an Access-Reject SHOULD be transmitted. If an Attribute 896 is received in an Access-Accept, Access-Reject or Access-Challenge 897 packet with an invalid length, the packet MUST either be treated 898 as an Access-Reject or else silently discarded. 900 Value 902 The Value field is zero or more octets and contains information 903 specific to the Attribute. The format and length of the Value 904 field is determined by the Type and Length fields. 906 Note that a "string" in RADIUS does not require termination by an 907 ASCII NUL because the Attribute already has a length field. 909 The format of the value field is one of four data types. 911 string 0-253 octets 913 address 32 bit value, most significant octet first. 915 integer 32 bit value, most significant octet first. 917 time 32 bit value, most significant octet first -- seconds 918 since 00:00:00 GMT, January 1, 1970. The standard 919 Attributes do not use this data type but it is presented 920 here for possible use within Vendor-Specific attributes. 922 5.1. User-Name 924 Description 926 This Attribute indicates the name of the user to be authenticated. 927 It is only used in Access-Request packets. 929 A summary of the User-Name Attribute format is shown below. The 930 fields are transmitted from left to right. 932 0 1 2 933 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 934 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 935 | Type | Length | String ... 936 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 938 Type 940 1 for User-Name. 942 Length 944 >= 3 946 String 948 The String field is one or more octets. The NAS may limit the 949 maximum length of the User-Name but the ability to handle at least 950 63 octets is recommended. 952 The format of the username MAY be one of several forms: 954 monolithic Consisting only of alphanumeric characters. This 955 simple form might be used to locally manage a NAS. 957 simple Consisting only of printable ASCII characters. 959 name@fqdn SMTP address. The Fully Qualified Domain Name (with or 960 without trailing dot) indicates the realm in which the 961 name part applies. 963 distinguished name 964 A name in ASN.1 form used in Public Key authentication 965 systems. 967 5.2. User-Password 969 Description 971 This Attribute indicates the password of the user to be 972 authenticated, or the user's input following an Access-Challenge. 973 It is only used in Access-Request packets. 975 On transmission, the password is hidden. The password is first 976 padded at the end with nulls to a multiple of 16 octets. A one- 977 way MD5 hash is calculated over a stream of octets consisting of 978 the shared secret followed by the Request Authenticator. This 979 value is XORed with the first 16 octet segment of the password and 980 placed in the first 16 octets of the String field of the User- 981 Password Attribute. 983 If the password is longer than 16 characters, a second one-way MD5 984 hash is calculated over a stream of octets consisting of the 985 shared secret followed by the result of the first xor. That hash 986 is XORed with the second 16 octet segment of the password and 987 placed in the second 16 octets of the String field of the User- 988 Password Attribute. 990 If necessary, this operation is repeated, with each xor result 991 being used along with the shared secret to generate the next hash 992 to xor the next segment of the password, to no more than 128 993 characters. 995 The method is taken from the book "Network Security" by Kaufman, 996 Perlman and Speciner [4] pages 109-110. A more precise 997 explanation of the method follows: 999 Call the shared secret S and the pseudo-random 128-bit Request 1000 Authenticator RA. Break the password into 16-octet chunks p1, p2, 1001 etc. with the last one padded at the end with nulls to a 16-octet 1002 boundary. Call the ciphertext blocks c(1), c(2), etc. We'll need 1003 intermediate values b1, b2, etc. 1005 b1 = MD5(S + RA) c(1) = p1 xor b1 1006 b2 = MD5(S + c(1)) c(2) = p2 xor b2 1007 . . 1008 . . 1009 . . 1010 bi = MD5(S + c(i-1)) c(i) = pi xor bi 1012 The String will contain c(1)+c(2)+...+c(i) where + denotes 1013 concatenation. 1015 On receipt, the process is reversed to yield the original 1016 password. 1018 A summary of the User-Password Attribute format is shown below. The 1019 fields are transmitted from left to right. 1021 0 1 2 1022 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1023 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1024 | Type | Length | String ... 1025 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1027 Type 1029 2 for User-Password. 1031 Length 1033 At least 18 and no larger than 130. 1035 String 1037 The String field is between 16 and 128 octets long, inclusive. 1039 5.3. CHAP-Password 1041 Description 1042 This Attribute indicates the response value provided by a PPP 1043 Challenge-Handshake Authentication Protocol (CHAP) user in 1044 response to the challenge. It is only used in Access-Request 1045 packets. 1047 The CHAP challenge value is found in the CHAP-Challenge Attribute 1048 (60) if present in the packet, otherwise in the Request 1049 Authenticator field. 1051 A summary of the CHAP-Password Attribute format is shown below. The 1052 fields are transmitted from left to right. 1054 0 1 2 1055 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 1056 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1057 | Type | Length | CHAP Ident | String ... 1058 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1060 Type 1062 3 for CHAP-Password. 1064 Length 1066 19 1068 CHAP Ident 1070 This field is one octet, and contains the CHAP Identifier from the 1071 user's CHAP Response. 1073 String 1075 The String field is 16 octets, and contains the CHAP Response from 1076 the user. 1078 5.4. NAS-IP-Address 1080 Description 1082 This Attribute indicates the identifying IP Address of the NAS 1083 which is requesting authentication of the user. It is only used 1084 in Access-Request packets. Either NAS-IP-Address or NAS- 1085 Identifier SHOULD be present in an Access-Request packet. 1087 A summary of the NAS-IP-Address Attribute format is shown below. The 1088 fields are transmitted from left to right. 1090 0 1 2 3 1091 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 1092 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1093 | Type | Length | Address 1094 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1095 Address (cont) | 1096 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1098 Type 1100 4 for NAS-IP-Address. 1102 Length 1104 6 1106 Address 1108 The Address field is four octets. 1110 5.5. NAS-Port 1112 Description 1114 This Attribute indicates the physical port number of the NAS which 1115 is authenticating the user. It is only used in Access-Request 1116 packets. Note that this is using "port" in its sense of a 1117 physical connection on the NAS, not in the sense of a TCP or UDP 1118 port number. Either NAS-Port or NAS-Port-Type (61) or both SHOULD 1119 be present in an Access-Request packet, if the NAS differentiates 1120 among its ports. 1122 A summary of the NAS-Port Attribute format is shown below. The 1123 fields are transmitted from left to right. 1125 0 1 2 3 1126 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 1127 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1128 | Type | Length | Value 1129 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1130 Value (cont) | 1131 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1132 Type 1134 5 for NAS-Port. 1136 Length 1138 6 1140 Value 1142 The Value field is four octets. Despite the size of the field, 1143 values range from 0 to 65535. 1145 5.6. Service-Type 1147 Description 1149 This Attribute indicates the type of service the user has 1150 requested, or the type of service to be provided. It MAY be used 1151 in both Access-Request and Access-Accept packets. A NAS is not 1152 required to implement all of these service types, and MUST treat 1153 unknown or unsupported Service-Types as though an Access-Reject 1154 had been received instead. 1156 A summary of the Service-Type Attribute format is shown below. The 1157 fields are transmitted from left to right. 1159 0 1 2 3 1160 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 1161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1162 | Type | Length | Value 1163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1164 Value (cont) | 1165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1167 Type 1169 6 for Service-Type. 1171 Length 1173 6 1175 Value 1177 The Value field is four octets. 1179 1 Login 1180 2 Framed 1181 3 Callback Login 1182 4 Callback Framed 1183 5 Outbound 1184 6 Administrative 1185 7 NAS Prompt 1186 8 Authenticate Only 1187 9 Callback NAS Prompt 1189 The service types are defined as follows when used in an Access- 1190 Accept. When used in an Access-Request, they should be considered 1191 to be a hint to the RADIUS server that the NAS has reason to 1192 believe the user would prefer the kind of service indicated, but 1193 the server is not required to honor the hint. 1195 Login The user should be connected to a host. 1197 Framed A Framed Protocol should be started for the 1198 User, such as PPP or SLIP. 1200 Callback Login The user should be disconnected and called 1201 back, then connected to a host. 1203 Callback Framed The user should be disconnected and called 1204 back, then a Framed Protocol should be started 1205 for the User, such as PPP or SLIP. 1207 Outbound The user should be granted access to outgoing 1208 devices. 1210 Administrative The user should be granted access to the 1211 administrative interface to the NAS from which 1212 privileged commands can be executed. 1214 NAS Prompt The user should be provided a command prompt 1215 on the NAS from which non-privileged commands 1216 can be executed. 1218 Authenticate Only Only Authentication is requested, and no 1219 authorization information needs to be returned 1220 in the Access-Accept (typically used by proxy 1221 servers rather than the NAS itself). 1223 Callback NAS Prompt The user should be disconnected and called 1224 back, then provided a command prompt on the 1225 NAS from which non-privileged commands can be 1226 executed. 1228 5.7. Framed-Protocol 1230 Description 1232 This Attribute indicates the framing to be used for framed access. 1233 It MAY be used in both Access-Request and Access-Accept packets. 1235 A summary of the Framed-Protocol Attribute format is shown below. 1236 The fields are transmitted from left to right. 1238 0 1 2 3 1239 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 1240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1241 | Type | Length | Value 1242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1243 Value (cont) | 1244 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1246 Type 1248 7 for Framed-Protocol. 1250 Length 1252 6 1254 Value 1256 The Value field is four octets. 1258 1 PPP 1259 2 SLIP 1260 3 AppleTalk Remote Access Protocol (ARAP) 1261 4 Gandalf proprietary SingleLink/MultiLink protocol 1262 5 Xylogics proprietary IPX/SLIP 1264 5.8. Framed-IP-Address 1266 Description 1268 This Attribute indicates the address to be configured for the 1269 user. It MAY be used in Access-Accept packets. It MAY be used in 1270 an Access-Request packet as a hint by the NAS to the server that 1271 it would prefer that address, but the server is not required to 1272 honor the hint. 1274 A summary of the Framed-IP-Address Attribute format is shown below. 1275 The fields are transmitted from left to right. 1277 0 1 2 3 1278 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 1279 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1280 | Type | Length | Address 1281 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1282 Address (cont) | 1283 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1285 Type 1287 8 for Framed-IP-Address. 1289 Length 1291 6 1293 Address 1295 The Address field is four octets. The value 0xFFFFFFFF indicates 1296 that the NAS should allow the user to select an address (e.g. 1297 Negotiated). The value 0xFFFFFFFE indicates that the NAS should 1298 select an address for the user (e.g. Assigned from a pool of 1299 addresses kept by the NAS). Other valid values indicate that the 1300 NAS should use that value as the user's IP address. 1302 5.9. Framed-IP-Netmask 1304 Description 1306 This Attribute indicates the IP netmask to be configured for the 1307 user when the user is a router to a network. It MAY be used in 1308 Access-Accept packets. It MAY be used in an Access-Request packet 1309 as a hint by the NAS to the server that it would prefer that 1310 netmask, but the server is not required to honor the hint. 1312 A summary of the Framed-IP-Netmask Attribute format is shown below. 1313 The fields are transmitted from left to right. 1315 0 1 2 3 1316 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 1317 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1318 | Type | Length | Address 1319 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1320 Address (cont) | 1321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1323 Type 1325 9 for Framed-IP-Netmask. 1327 Length 1329 6 1331 Address 1333 The Address field is four octets specifying the IP netmask of the 1334 user. 1336 5.10. Framed-Routing 1338 Description 1340 This Attribute indicates the routing method for the user, when the 1341 user is a router to a network. It is only used in Access-Accept 1342 packets. 1344 A summary of the Framed-Routing Attribute format is shown below. The 1345 fields are transmitted from left to right. 1347 0 1 2 3 1348 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 1349 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1350 | Type | Length | Value 1351 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1352 Value (cont) | 1353 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1354 Type 1356 10 for Framed-Routing. 1358 Length 1360 6 1362 Value 1364 The Value field is four octets. 1366 0 None 1367 1 Send routing packets 1368 2 Listen for routing packets 1369 3 Send and Listen 1371 5.11. Filter-Id 1373 Description 1375 This Attribute indicates the name of the filter list for this 1376 user. Zero or more Filter-Id attributes MAY be sent in an 1377 Access-Accept packet. 1379 Identifying a filter list by name allows the filter to be used on 1380 different NASes without regard to filter-list implementation 1381 details. 1383 A summary of the Filter-Id Attribute format is shown below. The 1384 fields are transmitted from left to right. 1386 0 1 2 1387 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1388 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1389 | Type | Length | String ... 1390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1392 Type 1394 11 for Filter-Id. 1396 Length 1398 >= 3 1400 String 1402 The String field is one or more octets, and its contents are 1403 implementation dependent. It is intended to be human readable and 1404 MUST NOT affect operation of the protocol. It is recommended that 1405 the message contain displayable ASCII characters from the range 32 1406 through 126 decimal. 1408 5.12. Framed-MTU 1410 Description 1412 This Attribute indicates the Maximum Transmission Unit to be 1413 configured for the user, when it is not negotiated by some other 1414 means (such as PPP). It is only used in Access-Accept packets. 1416 A summary of the Framed-MTU Attribute format is shown below. The 1417 fields are transmitted from left to right. 1419 0 1 2 3 1420 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 1421 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1422 | Type | Length | Value 1423 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1424 Value (cont) | 1425 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1427 Type 1429 12 for Framed-MTU. 1431 Length 1433 6 1435 Value 1437 The Value field is four octets. Despite the size of the field, 1438 values range from 64 to 65535. 1440 5.13. Framed-Compression 1442 Description 1444 This Attribute indicates a compression protocol to be used for the 1445 link. It MAY be used in Access-Accept packets. It MAY be used in 1446 an Access-Request packet as a hint to the server that the NAS 1447 would prefer to use that host, but the server is not required to 1448 honor the hint. 1450 More than one compression protocol Attribute MAY be sent. It is 1451 the responsibility of the NAS to apply the proper compression 1452 protocol to appropriate link traffic. 1454 A summary of the Framed-Compression Attribute format is shown below. 1455 The fields are transmitted from left to right. 1457 0 1 2 3 1458 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 1459 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1460 | Type | Length | Value 1461 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1462 Value (cont) | 1463 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1465 Type 1467 13 for Framed-Compression. 1469 Length 1471 6 1473 Value 1475 The Value field is four octets. 1477 0 None 1478 1 VJ TCP/IP header compression [5] 1479 2 IPX header compression 1481 5.14. Login-IP-Host 1483 Description 1484 This Attribute indicates the system with which to connect the 1485 user, when the Login-Service Attribute is included. It MAY be 1486 used in Access-Accept packets. It MAY be used in an Access- 1487 Request packet as a hint to the server that the NAS would prefer 1488 to use that host, but the server is not required to honor the 1489 hint. 1491 A summary of the Login-IP-Host Attribute format is shown below. The 1492 fields are transmitted from left to right. 1494 0 1 2 3 1495 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 1496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1497 | Type | Length | Address 1498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1499 Address (cont) | 1500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1502 Type 1504 14 for Login-IP-Host. 1506 Length 1508 6 1510 Address 1512 The Address field is four octets. The value 0xFFFFFFFF indicates 1513 that the NAS SHOULD allow the user to select an address. The 1514 value 0 indicates that the NAS SHOULD select a host to connect the 1515 user to. Other values indicate the address the NAS SHOULD connect 1516 the user to. 1518 5.15. Login-Service 1520 Description 1522 This Attribute indicates the service which should be used to 1523 connect the user to the login host. It is only used in Access- 1524 Accept packets. 1526 A summary of the Login-Service Attribute format is shown below. The 1527 fields are transmitted from left to right. 1529 0 1 2 3 1530 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 1531 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1532 | Type | Length | Value 1533 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1534 Value (cont) | 1535 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1537 Type 1539 15 for Login-Service. 1541 Length 1543 6 1545 Value 1547 The Value field is four octets. 1549 0 Telnet 1550 1 Rlogin 1551 2 TCP Clear 1552 3 PortMaster (proprietary) 1553 4 LAT 1555 5.16. Login-TCP-Port 1557 Description 1559 This Attribute indicates the TCP port with which the user is to be 1560 connected, when the Login-Service Attribute is also present. It 1561 is only used in Access-Accept packets. 1563 A summary of the Login-TCP-Port Attribute format is shown below. The 1564 fields are transmitted from left to right. 1566 0 1 2 3 1567 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 1568 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1569 | Type | Length | Value 1570 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1571 Value (cont) | 1572 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1574 Type 1576 16 for Login-TCP-Port. 1578 Length 1580 6 1582 Value 1584 The Value field is four octets. Despite the size of the field, 1585 values range from 0 to 65535. 1587 5.17. (unassigned) 1589 Description 1591 ATTRIBUTE TYPE 17 HAS NOT BEEN ASSIGNED. 1593 5.18. Reply-Message 1595 Description 1597 This Attribute indicates text which MAY be displayed to the user. 1599 When used in an Access-Accept, it is the success message. 1601 When used in an Access-Reject, it is the failure message. It MAY 1602 indicate a dialog message to prompt the user before another 1603 Access-Request attempt. 1605 When used in an Access-Challenge, it MAY indicate a dialog message 1606 to prompt the user for a response. 1608 Multiple Reply-Message's MAY be included and if any are displayed, 1609 they MUST be displayed in the same order as they appear in the 1610 packet. 1612 A summary of the Reply-Message Attribute format is shown below. The 1613 fields are transmitted from left to right. 1615 0 1 2 1616 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1617 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1618 | Type | Length | String ... 1619 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1621 Type 1623 18 for Reply-Message. 1625 Length 1627 >= 3 1629 String 1631 The String field is one or more octets, and its contents are 1632 implementation dependent. It is intended to be human readable, 1633 and MUST NOT affect operation of the protocol. It is recommended 1634 that the message contain displayable ASCII characters from the 1635 range 10, 13, and 32 through 126 decimal. Mechanisms for 1636 extension to other character sets are beyond the scope of this 1637 specification. 1639 5.19. Callback-Number 1641 Description 1643 This Attribute indicates a dialing string to be used for callback. 1644 It MAY be used in Access-Accept packets. It MAY be used in an 1645 Access-Request packet as a hint to the server that a Callback 1646 service is desired, but the server is not required to honor the 1647 hint. 1649 A summary of the Callback-Number Attribute format is shown below. 1650 The fields are transmitted from left to right. 1652 0 1 2 1653 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1654 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1655 | Type | Length | String ... 1656 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1658 Type 1660 19 for Callback-Number. 1662 Length 1664 >= 3 1666 String 1668 The String field is one or more octets. The actual format of the 1669 information is site or application specific, and a robust 1670 implementation SHOULD support the field as undistinguished octets. 1672 The codification of the range of allowed usage of this field is 1673 outside the scope of this specification. 1675 5.20. Callback-Id 1677 Description 1679 This Attribute indicates the name of a place to be called, to be 1680 interpreted by the NAS. It MAY be used in Access-Accept packets. 1682 A summary of the Callback-Id Attribute format is shown below. The 1683 fields are transmitted from left to right. 1685 0 1 2 1686 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1687 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1688 | Type | Length | String ... 1689 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1691 Type 1693 20 for Callback-Id. 1695 Length 1697 >= 3 1699 String 1701 The String field is one or more octets. The actual format of the 1702 information is site or application specific, and a robust 1703 implementation SHOULD support the field as undistinguished octets. 1705 The codification of the range of allowed usage of this field is 1706 outside the scope of this specification. 1708 5.21. (unassigned) 1710 Description 1712 ATTRIBUTE TYPE 21 HAS NOT BEEN ASSIGNED. 1714 5.22. Framed-Route 1716 Description 1718 This Attribute provides routing information to be configured for 1719 the user on the NAS. It is used in the Access-Accept packet and 1720 can appear multiple times. 1722 A summary of the Framed-Route Attribute format is shown below. The 1723 fields are transmitted from left to right. 1725 0 1 2 1726 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 1727 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1728 | Type | Length | String... 1729 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1731 Type 1733 22 for Framed-Route. 1735 Length 1737 >= 3 1739 String 1741 The String field is one or more octets, and its contents are 1742 implementation dependent. It is intended to be human readable and 1743 MUST NOT affect operation of the protocol. It is recommended that 1744 the message contain displayable ASCII characters from the range 32 1745 through 126 decimal. 1747 For IP routes, it SHOULD contain a destination prefix in dotted 1748 quad form optionally followed by a slash and a decimal specifier 1749 stating how many high order bits of the prefix should be used. 1750 That is followed by a space, a gateway address in dotted quad 1751 form, a space, and one or more metrics separated by spaces. For 1752 example, "192.168.1.0/24 192.168.1.1 1 2 -1 3 400". The length 1753 specifier may be omitted in which case it should default to 8 bits 1754 for class A prefixes, 16 bits for class B prefixes, and 24 bits 1755 for class C prefixes. For example, "192.168.1.0 192.168.1.1 1". 1757 Whenever the gateway address is specified as "0.0.0.0" the IP 1758 address of the user SHOULD be used as the gateway address. 1760 5.23. Framed-IPX-Network 1762 Description 1764 This Attribute indicates the IPX Network number to be configured 1765 for the user. It is used in Access-Accept packets. 1767 A summary of the Framed-IPX-Network Attribute format is shown below. 1768 The fields are transmitted from left to right. 1770 0 1 2 3 1771 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 1772 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1773 | Type | Length | Value 1774 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1775 Value (cont) | 1776 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1778 Type 1780 23 for Framed-IPX-Network. 1782 Length 1784 6 1786 Value 1788 The Value field is four octets. The value 0xFFFFFFFE indicates 1789 that the NAS should select an IPX network for the user (e.g. 1790 assigned from a pool of one or more IPX networks kept by the NAS). 1791 Other values should be used as the IPX network for the link to the 1792 user. 1794 5.24. State 1796 Description 1798 This Attribute is available to be sent by the server to the client 1799 in an Access-Challenge and MUST be sent unmodified from the client 1800 to the server in the new Access-Request reply to that challenge, 1801 if any. 1803 This Attribute is available to be sent by the server to the client 1804 in an Access-Request that also includes a Termination-Action 1805 Attribute with the value of RADIUS-Request. If the NAS performs 1806 the Termination-Action by sending a new Access-Request upon 1807 termination of the current session, it MUST include the State 1808 attribute unchanged in that Access-Request. 1810 In either usage, no interpretation by the client should be made. 1811 A packet may have only one State Attribute. Usage of the State 1812 Attribute is implementation dependent. 1814 A summary of the State Attribute format is shown below. The fields 1815 are transmitted from left to right. 1817 0 1 2 1818 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1819 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1820 | Type | Length | String ... 1821 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1823 Type 1825 24 for State. 1827 Length 1829 >= 3 1831 String 1833 The String field is one or more octets. The actual format of the 1834 information is site or application specific, and a robust 1835 implementation SHOULD support the field as undistinguished octets. 1837 The codification of the range of allowed usage of this field is 1838 outside the scope of this specification. 1840 5.25. Class 1842 Description 1844 This Attribute is available to be sent by the server to the client 1845 in an Access-Accept and should be sent unmodified by the client to 1846 the accounting server as part of the Accounting-Request packet if 1847 accounting is supported. No interpretation by the client should 1848 be made. 1850 A summary of the Class Attribute format is shown below. The fields 1851 are transmitted from left to right. 1853 0 1 2 1854 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1855 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1856 | Type | Length | String ... 1857 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1859 Type 1861 25 for Class. 1863 Length 1865 >= 3 1867 String 1869 The String field is one or more octets. The actual format of the 1870 information is site or application specific, and a robust 1871 implementation SHOULD support the field as undistinguished octets. 1873 The codification of the range of allowed usage of this field is 1874 outside the scope of this specification. 1876 5.26. Vendor-Specific 1878 Description 1880 This Attribute is available to allow vendors to support their own 1881 extended Attributes not suitable for general usage. It MUST not 1882 affect the operation of the RADIUS protocol. 1884 Servers not equipped to interpret the vendor-specific information 1885 sent by a client MUST ignore it (although it may be reported). 1886 Clients which do not receive desired vendor-specific information 1887 SHOULD make an attempt to operate without it, although they may do 1888 so (and report they are doing so) in a degraded mode. 1890 A summary of the Vendor-Specific Attribute format is shown below. 1891 The fields are transmitted from left to right. 1893 0 1 2 3 1894 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 1895 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1896 | Type | Length | Vendor-Id 1897 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1898 Vendor-Id (cont) | String... 1899 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1901 Type 1903 26 for Vendor-Specific. 1905 Length 1907 >= 7 1909 Vendor-Id 1911 The high-order octet is 0 and the low-order 3 octets are the SMI 1912 Network Management Private Enterprise Code of the Vendor in 1913 network byte order, as defined in the Assigned Numbers RFC [2]. 1915 String 1917 The String field is one or more octets. The actual format of the 1918 information is site or application specific, and a robust 1919 implementation SHOULD support the field as undistinguished octets. 1921 The codification of the range of allowed usage of this field is 1922 outside the scope of this specification. 1924 It SHOULD be encoded as a sequence of vendor type / vendor length 1925 / value fields, as follows. The Attribute-Specific field is 1926 dependent on the vendor's definition of that attribute. An 1927 example encoding of the Vendor-Specific attribute using this 1928 method follows: 1930 0 1 2 3 1931 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 1932 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1933 | Type | Length | Vendor-Id 1934 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1935 Vendor-Id (cont) | Vendor type | Vendor length | 1936 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1937 | Attribute-Specific... 1938 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 1940 5.27. Session-Timeout 1942 Description 1944 This Attribute sets the maximum number of seconds of service to be 1945 provided to the user before termination of the session or prompt. 1946 This Attribute is available to be sent by the server to the client 1947 in an Access-Accept or Access-Challenge. 1949 A summary of the Session-Timeout Attribute format is shown below. 1950 The fields are transmitted from left to right. 1952 0 1 2 3 1953 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 1954 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1955 | Type | Length | Value 1956 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1957 Value (cont) | 1958 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1959 Type 1961 27 for Session-Timeout. 1963 Length 1965 6 1967 Value 1969 The field is 4 octets, containing a 32-bit unsigned integer with 1970 the maximum number of seconds this user should be allowed to 1971 remain connected by the NAS. 1973 5.28. Idle-Timeout 1975 Description 1977 This Attribute sets the maximum number of consecutive seconds of 1978 idle connection allowed to the user before termination of the 1979 session or prompt. This Attribute is available to be sent by the 1980 server to the client in an Access-Accept or Access-Challenge. 1982 A summary of the Idle-Timeout Attribute format is shown below. The 1983 fields are transmitted from left to right. 1985 0 1 2 3 1986 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 1987 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1988 | Type | Length | Value 1989 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1990 Value (cont) | 1991 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1993 Type 1995 28 for Idle-Timeout. 1997 Length 1999 6 2001 Value 2003 The field is 4 octets, containing a 32-bit unsigned integer with 2004 the maximum number of consecutive seconds of idle time this user 2005 should be permitted before being disconnected by the NAS. 2007 5.29. Termination-Action 2009 Description 2011 This Attribute indicates what action the NAS should take when the 2012 specified service is completed. It is only used in Access-Accept 2013 packets. 2015 A summary of the Termination-Action Attribute format is shown below. 2016 The fields are transmitted from left to right. 2018 0 1 2 3 2019 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 2020 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2021 | Type | Length | Value 2022 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2023 Value (cont) | 2024 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2026 Type 2028 29 for Termination-Action. 2030 Length 2032 6 2034 Value 2036 The Value field is four octets. 2038 0 Default 2039 1 RADIUS-Request 2041 If the Value is set to RADIUS-Request, upon termination of the 2042 specified service the NAS MAY send a new Access-Request to the 2043 RADIUS server, including the State attribute if any. 2045 5.30. Called-Station-Id 2047 Description 2049 This Attribute allows the NAS to send in the Access-Request packet 2050 the phone number that the user called, using DNIS or similar 2051 technology. Note that this may be different from the phone number 2052 the call comes in on. It is only used in Access-Request packets. 2054 A summary of the Called-Station-Id Attribute format is shown below. 2055 The fields are transmitted from left to right. 2057 0 1 2 2058 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2059 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2060 | Type | Length | String ... 2061 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2063 Type 2065 30 for Called-Station-Id. 2067 Length 2069 >= 3 2071 String 2073 The String field is one or more octets, containing the phone 2074 number that the user's call came in on. 2076 The actual format of the information is site or application 2077 specific. Printable ASCII is recommended, but a robust 2078 implementation SHOULD support the field as undistinguished octets. 2080 The codification of the range of allowed usage of this field is 2081 outside the scope of this specification. 2083 5.31. Calling-Station-Id 2085 Description 2087 This Attribute allows the NAS to send in the Access-Request packet 2088 the phone number that the call came from, using ANI or similar 2089 technology. It is only used in Access-Request packets. 2091 A summary of the Calling-Station-Id Attribute format is shown below. 2092 The fields are transmitted from left to right. 2094 0 1 2 2095 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2096 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2097 | Type | Length | String ... 2098 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2100 Type 2102 31 for Calling-Station-Id. 2104 Length 2106 >= 3 2108 String 2110 The String field is one or more octets, containing the phone 2111 number that the user placed the call from. 2113 The actual format of the information is site or application 2114 specific. Printable ASCII is recommended, but a robust 2115 implementation SHOULD support the field as undistinguished octets. 2117 The codification of the range of allowed usage of this field is 2118 outside the scope of this specification. 2120 5.32. NAS-Identifier 2122 Description 2124 This Attribute contains a string identifying the NAS originating 2125 the Access-Request. It is only used in Access-Request packets. 2126 Either NAS-IP-Address or NAS-Identifier SHOULD be present in an 2127 Access-Request packet. 2129 A summary of the NAS-Identifier Attribute format is shown below. The 2130 fields are transmitted from left to right. 2132 0 1 2 2133 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2134 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2135 | Type | Length | String ... 2136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2138 Type 2140 32 for NAS-Identifier. 2142 Length 2144 >= 3 2146 String 2148 The String field is one or more octets, and should be unique to 2149 the NAS within the scope of the RADIUS server. For example, a 2150 fully qualified domain name would be suitable as a NAS-Identifier. 2152 The actual format of the information is site or application 2153 specific, and a robust implementation SHOULD support the field as 2154 undistinguished octets. 2156 The codification of the range of allowed usage of this field is 2157 outside the scope of this specification. 2159 5.33. Proxy-State 2161 Description 2163 This Attribute is available to be sent by a proxy server to 2164 another server when forwarding an Access-Request and MUST be 2165 returned unmodified in the Access-Accept, Access-Reject or 2166 Access-Challenge. This attribute should be removed by the proxy 2167 server before the response is forwarded to the NAS. 2169 Usage of the Proxy-State Attribute is implementation dependent. A 2170 description of its function is outside the scope of this 2171 specification. 2173 A summary of the Proxy-State Attribute format is shown below. The 2174 fields are transmitted from left to right. 2176 0 1 2 2177 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2179 | Type | Length | String ... 2180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2182 Type 2184 33 for Proxy-State. 2186 Length 2188 >= 3 2190 String 2192 The String field is one or more octets. The actual format of the 2193 information is site or application specific, and a robust 2194 implementation SHOULD support the field as undistinguished octets. 2196 The codification of the range of allowed usage of this field is 2197 outside the scope of this specification. 2199 5.34. Login-LAT-Service 2201 Description 2203 This Attribute indicates the system with which the user is to be 2204 connected by LAT. It MAY be used in Access-Accept packets, but 2205 only when LAT is specified as the Login-Service. It MAY be used 2206 in an Access-Request packet as a hint to the server, but the 2207 server is not required to honor the hint. 2209 Administrators use the service attribute when dealing with 2210 clustered systems, such as a VAX or Alpha cluster. In such an 2211 environment several different time sharing hosts share the same 2212 resources (disks, printers, etc.), and administrators often 2213 configure each to offer access (service) to each of the shared 2214 resources. In this case, each host in the cluster advertises its 2215 services through LAT broadcasts. 2217 Sophisticated users often know which service providers (machines) 2218 are faster and tend to use a node name when initiating a LAT 2219 connection. Alternately, some administrators want particular 2220 users to use certain machines as a primitive form of load 2221 balancing (although LAT knows how to do load balancing itself). 2223 A summary of the Login-LAT-Service Attribute format is shown below. 2224 The fields are transmitted from left to right. 2226 0 1 2 2227 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2229 | Type | Length | String ... 2230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2232 Type 2234 34 for Login-LAT-Service. 2236 Length 2238 >= 3 2240 String 2242 The String field is one or more octets, and contains the identity 2243 of the LAT service to use. The LAT Architecture allows this 2244 string to contain $ (dollar), - (hyphen), . (period), _ 2245 (underscore), numerics, upper and lower case alphabetics, and the 2246 ISO Latin-1 character set extension [6]. All LAT string 2247 comparisons are case insensitive. 2249 5.35. Login-LAT-Node 2251 Description 2253 This Attribute indicates the Node with which the user is to be 2254 automatically connected by LAT. It MAY be used in Access-Accept 2255 packets, but only when LAT is specified as the Login-Service. It 2256 MAY be used in an Access-Request packet as a hint to the server, 2257 but the server is not required to honor the hint. 2259 A summary of the Login-LAT-Node Attribute format is shown below. The 2260 fields are transmitted from left to right. 2262 0 1 2 2263 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2265 | Type | Length | String ... 2266 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2268 Type 2270 35 for Login-LAT-Node. 2272 Length 2274 >= 3 2276 String 2278 The String field is one or more octets, and contains the identity 2279 of the LAT Node to connect the user to. The LAT Architecture 2280 allows this string to contain $ (dollar), - (hyphen), . (period), 2281 _ (underscore), numerics, upper and lower case alphabetics, and 2282 the ISO Latin-1 character set extension. All LAT string 2283 comparisons are case insensitive. 2285 5.36. Login-LAT-Group 2287 Description 2289 This Attribute contains a string identifying the LAT group codes 2290 which this user is authorized to use. It MAY be used in Access- 2291 Accept packets, but only when LAT is specified as the Login- 2292 Service. It MAY be used in an Access-Request packet as a hint to 2293 the server, but the server is not required to honor the hint. 2295 LAT supports 256 different group codes, which LAT uses as a form 2296 of access rights. LAT encodes the group codes as a 256 bit 2297 bitmap. 2299 Administrators can assign one or more of the group code bits at 2300 the LAT service provider; it will only accept LAT connections that 2301 have these group codes set in the bit map. The administrators 2302 assign a bitmap of authorized group codes to each user; LAT gets 2303 these from the operating system, and uses these in its requests to 2304 the service providers. 2306 A summary of the Login-LAT-Group Attribute format is shown below. 2307 The fields are transmitted from left to right. 2309 0 1 2 2310 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2311 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2312 | Type | Length | String ... 2313 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2315 Type 2317 36 for Login-LAT-Group. 2319 Length 2321 34 2323 String 2325 The String field is a 32 octet bit map, most significant octet 2326 first. A robust implementation SHOULD support the field as 2327 undistinguished octets. 2329 The codification of the range of allowed usage of this field is 2330 outside the scope of this specification. 2332 5.37. Framed-AppleTalk-Link 2334 Description 2336 This Attribute indicates the AppleTalk network number which should 2337 be used for the serial link to the user, which is another 2338 AppleTalk router. It is only used in Access-Accept packets. It 2339 is never used when the user is not another router. 2341 A summary of the Framed-AppleTalk-Link Attribute format is shown 2342 below. The fields are transmitted from left to right. 2344 0 1 2 3 2345 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 2346 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2347 | Type | Length | Value 2348 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2349 Value (cont) | 2350 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2351 Type 2353 37 for Framed-AppleTalk-Link. 2355 Length 2357 6 2359 Value 2361 The Value field is four octets. Despite the size of the field, 2362 values range from 0 to 65535. The special value of 0 indicates 2363 that this is an unnumbered serial link. A value of 1-65535 means 2364 that the serial line between the NAS and the user should be 2365 assigned that value as an AppleTalk network number. 2367 5.38. Framed-AppleTalk-Network 2369 Description 2371 This Attribute indicates the AppleTalk Network number which the 2372 NAS should probe to allocate an AppleTalk node for the user. It 2373 is only used in Access-Accept packets. It is never used when the 2374 user is another router. Multiple instances of this Attribute 2375 indicate that the NAS may probe using any of the network numbers 2376 specified. 2378 A summary of the Framed-AppleTalk-Network Attribute format is shown 2379 below. The fields are transmitted from left to right. 2381 0 1 2 3 2382 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 2383 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2384 | Type | Length | Value 2385 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2386 Value (cont) | 2387 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2389 Type 2391 38 for Framed-AppleTalk-Network. 2393 Length 2395 6 2397 Value 2399 The Value field is four octets. Despite the size of the field, 2400 values range from 0 to 65535. The special value 0 indicates that 2401 the NAS should assign a network for the user, using its default 2402 cable range. A value between 1 and 65535 (inclusive) indicates 2403 the AppleTalk Network the NAS should probe to find an address for 2404 the user. 2406 5.39. Framed-AppleTalk-Zone 2408 Description 2410 This Attribute indicates the AppleTalk Default Zone to be used for 2411 this user. It is only used in Access-Accept packets. Multiple 2412 instances of this attribute in the same packet are not allowed. 2414 A summary of the Framed-AppleTalk-Zone Attribute format is shown 2415 below. The fields are transmitted from left to right. 2417 0 1 2 2418 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 2419 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2420 | Type | Length | String ... 2421 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2423 Type 2425 39 for Framed-AppleTalk-Zone. 2427 Length 2429 >= 3 2431 String 2433 The name of the Default AppleTalk Zone to be used for this user. 2434 A robust implementation SHOULD support the field as 2435 undistinguished octets. 2437 The codification of the range of allowed usage of this field is 2438 outside the scope of this specification. 2440 5.40. CHAP-Challenge 2442 Description 2444 This Attribute contains the CHAP Challenge sent by the NAS to a 2445 PPP Challenge-Handshake Authentication Protocol (CHAP) user. It 2446 is only used in Access-Request packets. 2448 If the CHAP challenge value is 16 octets long it MAY be placed in 2449 the Request Authenticator field instead of using this attribute. 2451 A summary of the CHAP-Challenge Attribute format is shown below. The 2452 fields are transmitted from left to right. 2454 0 1 2 2455 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 2456 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2457 | Type | Length | String... 2458 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2460 Type 2462 60 for CHAP-Challenge. 2464 Length 2466 >= 7 2468 String 2470 The String field contains the CHAP Challenge. 2472 5.41. NAS-Port-Type 2474 Description 2476 This Attribute indicates the type of the physical port of the NAS 2477 which is authenticating the user. It can be used instead of or in 2478 addition to the NAS-Port (5) attribute. It is only used in 2479 Access-Request packets. Either NAS-Port (5) or NAS-Port-Type or 2480 both SHOULD be present in an Access-Request packet, if the NAS 2481 differentiates among its ports. 2483 A summary of the NAS-Port-Type Attribute format is shown below. The 2484 fields are transmitted from left to right. 2486 0 1 2 3 2487 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 2488 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2489 | Type | Length | Value 2490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2491 Value (cont) | 2492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2494 Type 2496 61 for NAS-Port-Type. 2498 Length 2500 6 2502 Value 2504 The Value field is four octets. "Virtual" refers to a connection 2505 to the NAS via some transport protocol, instead of through a 2506 physical port. For example, if a user telnetted into a NAS to 2507 authenticate himself as an Outbound-User, the Access-Request might 2508 include NAS-Port-Type = Virtual as a hint to the RADIUS server 2509 that the user was not on a physical port. 2511 0 Async 2512 1 Sync 2513 2 ISDN Sync 2514 3 ISDN Async V.120 2515 4 ISDN Async V.110 2516 5 Virtual 2518 5.42. Port-Limit 2520 Description 2522 This Attribute sets the maximum number of ports to be provided to 2523 the user by the NAS. This Attribute MAY be sent by the server to 2524 the client in an Access-Accept packet. It is intended for use in 2525 conjunction with Multilink PPP [7] or similar uses. It MAY also 2526 be sent by the NAS to the server as a hint that that many ports 2527 are desired for use, but the server is not required to honor the 2528 hint. 2530 A summary of the Port-Limit Attribute format is shown below. The 2531 fields are transmitted from left to right. 2533 0 1 2 3 2534 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 2535 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2536 | Type | Length | Value 2537 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2538 Value (cont) | 2539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2541 Type 2543 62 for Port-Limit. 2545 Length 2547 6 2549 Value 2551 The field is 4 octets, containing a 32-bit unsigned integer with 2552 the maximum number of ports this user should be allowed to connect 2553 to on the NAS. 2555 5.43. Login-LAT-Port 2557 Description 2559 This Attribute indicates the Port with which the user is to be 2560 connected by LAT. It MAY be used in Access-Accept packets, but 2561 only when LAT is specified as the Login-Service. It MAY be used 2562 in an Access-Request packet as a hint to the server, but the 2563 server is not required to honor the hint. 2565 A summary of the Login-LAT-Port Attribute format is shown below. The 2566 fields are transmitted from left to right. 2568 0 1 2 2569 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2570 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2571 | Type | Length | String ... 2572 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 2573 Type 2575 63 for Login-LAT-Port. 2577 Length 2579 >= 3 2581 String 2583 The String field is one or more octets, and contains the identity 2584 of the LAT port to use. The LAT Architecture allows this string 2585 to contain $ (dollar), - (hyphen), . (period), _ (underscore), 2586 numerics, upper and lower case alphabetics, and the ISO Latin-1 2587 character set extension. All LAT string comparisons are case 2588 insensitive. 2590 5.44. Table of Attributes 2592 The following table provides a guide to which attributes may be found 2593 in which kinds of packets, and in what quantity. 2595 Request Accept Reject Challenge # Attribute 2596 1 0 0 0 1 User-Name 2597 0-1 0 0 0 2 User-Password [Note 1] 2598 0-1 0 0 0 3 CHAP-Password [Note 1] 2599 0-1 0 0 0 4 NAS-IP-Address 2600 0-1 0 0 0 5 NAS-Port 2601 0-1 0-1 0 0 6 Service-Type 2602 0-1 0-1 0 0 7 Framed-Protocol 2603 0-1 0-1 0 0 8 Framed-IP-Address 2604 0-1 0-1 0 0 9 Framed-IP-Netmask 2605 0 0-1 0 0 10 Framed-Routing 2606 0 0+ 0 0 11 Filter-Id 2607 0 0-1 0 0 12 Framed-MTU 2608 0+ 0+ 0 0 13 Framed-Compression 2609 0+ 0+ 0 0 14 Login-IP-Host 2610 0 0-1 0 0 15 Login-Service 2611 0 0-1 0 0 16 Login-TCP-Port 2612 0 0+ 0+ 0+ 18 Reply-Message 2613 0-1 0-1 0 0 19 Callback-Number 2614 0 0-1 0 0 20 Callback-Id 2615 0 0+ 0 0 22 Framed-Route 2616 0 0-1 0 0 23 Framed-IPX-Network 2617 0-1 0-1 0 0-1 24 State 2618 0 0+ 0 0 25 Class 2619 0+ 0+ 0 0+ 26 Vendor-Specific 2620 0 0-1 0 0-1 27 Session-Timeout 2621 0 0-1 0 0-1 28 Idle-Timeout 2622 0 0-1 0 0 29 Termination-Action 2623 0-1 0 0 0 30 Called-Station-Id 2624 0-1 0 0 0 31 Calling-Station-Id 2625 0-1 0 0 0 32 NAS-Identifier 2626 0+ 0+ 0+ 0+ 33 Proxy-State 2627 0-1 0-1 0 0 34 Login-LAT-Service 2628 0-1 0-1 0 0 35 Login-LAT-Node 2629 0-1 0-1 0 0 36 Login-LAT-Group 2630 0 0-1 0 0 37 Framed-AppleTalk-Link 2631 0 0+ 0 0 38 Framed-AppleTalk-Network 2632 0 0-1 0 0 39 Framed-AppleTalk-Zone 2633 0-1 0 0 0 60 CHAP-Challenge 2634 0-1 0 0 0 61 NAS-Port-Type 2635 0-1 0-1 0 0 62 Port-Limit 2636 0-1 0-1 0 0 63 Login-LAT-Port 2637 Request Accept Reject Challenge # Attribute 2639 [Note 1] An Access-Request MUST contain either a User-Password or a 2640 CHAP-Password, and MUST NOT contain both. 2642 The following table defines the meaning of the above table entries. 2644 0 This attribute MUST NOT be present in packet. 2645 0+ Zero or more instances of this attribute MAY be present in packet. 2646 0-1 Zero or one instance of this attribute MAY be present in packet. 2647 1 Exactly one instance of this attribute MUST be present in packet. 2649 6. Examples 2651 A few examples are presented to illustrate the flow of packets and 2652 use of typical attributes. These examples are not intended to be 2653 exhaustive, many others are possible. 2655 6.1. User Telnet to Specified Host 2657 The NAS at 192.168.1.16 sends an Access-Request UDP packet to the 2658 RADIUS Server for a user named nemo logging in on port 3. 2660 Code = 1 (Access-Request) 2661 ID = 0 2662 Request Authenticator = {16 octet random number} 2663 Attributes: 2664 User-Name = "nemo" 2665 User-Password = {16 octets of Password padded at end with nulls, 2666 XORed with MD5(shared secret|Request Authenticator)} 2667 NAS-IP-Address = 192.168.1.16 2668 NAS-Port = 3 2670 The RADIUS server authenticates nemo, and sends an Access-Accept UDP 2671 packet to the NAS telling it to telnet nemo to host 192.168.1.3. 2673 Code = 2 (Access-Accept) 2674 ID = 0 (same as in Access-Request) 2675 Response Authenticator = {16-octet MD-5 checksum of the code (2), 2676 id (0), the Request Authenticator from above, the 2677 attributes in this reply, and the shared secret} 2678 Attributes: 2679 Service-Type = Login-User 2680 Login-Service = Telnet 2681 Login-Host = 192.168.1.3 2683 6.2. Framed User Authenticating with CHAP 2685 The NAS at 192.168.1.16 sends an Access-Request UDP packet to the 2686 RADIUS Server for a user named flopsy logging in on port 20 with PPP, 2687 authenticating using CHAP. The NAS sends along the Service-Type and 2688 Framed-Protocol attributes as a hint to the RADIUS server that this 2689 user is looking for PPP, although the NAS is not required to do so. 2691 Code = 1 (Access-Request) 2692 ID = 1 2693 Request Authenticator = {16 octet random number also used as 2694 CHAP challenge} 2695 Attributes: 2696 User-Name = "flopsy" 2697 CHAP-Password = {1 octet CHAP ID followed by 16 octet 2698 CHAP response} 2699 NAS-IP-Address = 192.168.1.16 2700 NAS-Port = 20 2701 Service-Type = Framed-User 2702 Framed-Protocol = PPP 2704 The RADIUS server authenticates flopsy, and sends an Access-Accept 2705 UDP packet to the NAS telling it to start PPP service and assign an 2706 address for the user out of its dynamic address pool. 2708 Code = 2 (Access-Accept) 2709 ID = 1 (same as in Access-Request) 2710 Response Authenticator = {16-octet MD-5 checksum of the code (2), 2711 id (1), the Request Authenticator from above, the 2712 attributes in this reply, and the shared secret} 2713 Attributes: 2714 Service-Type = Framed-User 2715 Framed-Protocol = PPP 2716 Framed-IP-Address = 255.255.255.254 2717 Framed-Routing = None 2718 Framed-Compression = 1 (VJ TCP/IP Header Compression) 2719 Framed-MTU = 1500 2721 6.3. User with Challenge-Response card 2723 The NAS at 192.168.1.16 sends an Access-Request UDP packet to the 2724 RADIUS Server for a user named mopsy logging in on port 7. 2726 Code = 1 (Access-Request) 2727 ID = 2 2728 Request Authenticator = {16 octet random number} 2729 Attributes: 2730 User-Name = "mopsy" 2731 User-Password = {16 octets of Password padded at end with nulls, 2732 XORed with MD5(shared secret|Request Authenticator)} 2733 NAS-IP-Address = 192.168.1.16 2734 NAS-Port = 7 2736 The RADIUS server decides to challenge mopsy, sending back a 2737 challenge string and looking for a response. The RADIUS server 2738 therefore and sends an Access-Challenge UDP packet to the NAS. 2740 Code = 11 (Access-Challenge} 2741 ID = 2 (same as in Access-Request) 2742 Response Authenticator = {16-octet MD-5 checksum of the code (11), 2743 id (2), the Request Authenticator from above, the 2744 attributes in this reply, and the shared secret} 2745 Attributes: 2746 Reply-Message = "Challenge 32769430. Enter response at prompt." 2747 State = {Magic Cookie to be returned along with user's response} 2749 The user enters his response, and the NAS send a new Access-Request 2750 with that response, and includes the State Attribute. 2752 Code = 1 (Access-Request) 2753 ID = 3 (Note that this changes) 2754 Request Authenticator = {NEW 16 octet random number} 2755 Attributes: 2756 User-Name = "mopsy" 2757 User-Password = {16 octets of Response padded at end with 2758 nulls, XORed with MD5 checksum of shared secret 2759 plus above Request Authenticator} 2760 NAS-IP-Address = 192.168.1.16 2761 NAS-Port = 7 2762 State = {Magic Cookie from Access-Challenge packet, unchanged} 2764 The Response was incorrect, so the RADIUS server tells the NAS to 2765 reject the login attempt. 2767 Code = 3 (Access-Reject) 2768 ID = 3 (same as in Access-Request) 2769 Response Authenticator = {16-octet MD-5 checksum of the code (3), 2770 id (3), the Request Authenticator from above, the 2771 attributes in this reply if any, and the shared 2772 secret} 2773 Attributes: 2774 (none, although a Reply-Message could be sent) 2776 Security Considerations 2778 Security issues are the primary topic of this document. 2780 In practice, within or associated with each RADIUS server, there is a 2781 database which associates "user" names with authentication 2782 information ("secrets"). It is not anticipated that a particular 2783 named user would be authenticated by multiple methods. This would 2784 make the user vulnerable to attacks which negotiate the least secure 2785 method from among a set. Instead, for each named user there should 2786 be an indication of exactly one method used to authenticate that user 2787 name. If a user needs to make use of different authentication 2788 methods under different circumstances, then distinct user names 2789 SHOULD be employed, each of which identifies exactly one 2790 authentication method. 2792 Passwords and other secrets should be stored at the respective ends 2793 such that access to them is as limited as possible. Ideally, the 2794 secrets should only be accessible to the process requiring access in 2795 order to perform the authentication. 2797 The secrets should be distributed with a mechanism that limits the 2798 number of entities that handle (and thus gain knowledge of) the 2799 secret. Ideally, no unauthorized person should ever gain knowledge 2800 of the secrets. It is possible to achieve this with SNMP Security 2801 Protocols [8], but such a mechanism is outside the scope of this 2802 specification. 2804 Other distribution methods are currently undergoing research and 2805 experimentation. The SNMP Security document [8] also has an 2806 excellent overview of threats to network protocols. 2808 References 2810 [1] Rivest, R., and S. Dusse, "The MD5 Message-Digest Algorithm", 2811 RFC 1321, MIT Laboratory for Computer Science, RSA Data 2812 Security Inc., April 1992. 2814 [2] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 2815 USC/Information Sciences Institute, August 1980. 2817 [3] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC 2818 1700, USC/Information Sciences Institute, October 1994. 2820 [4] Kaufman, C., Perlman, R., and Speciner, M., "Network Security: 2821 Private Communications in a Public World", Prentice Hall, March 2822 1995, ISBN 0-13-061466-1. 2824 [5] Jacobson, V., "Compressing TCP/IP headers for low-speed serial 2825 links", RFC 1144, Lawrence Berkeley Laboratory, February 1990. 2827 [6] ISO 8859. International Standard -- Information Processing -- 2828 8-bit Single-Byte Coded Graphic Character Sets -- Part 1: Latin 2829 Alphabet No. 1, ISO 8859-1:1987. 2830 2832 [7] Sklower, K., Lloyd, B., McGregor, G., and Carr, D., "The PPP 2833 Multilink Protocol (MP)", RFC 1717, University of California 2834 Berkeley, Lloyd Internetworking, Newbridge Networks 2835 Corporation, November 1994. 2837 [8] Galvin, J., McCloghrie, K., and J. Davin, "SNMP Security 2838 Protocols", RFC 1352, Trusted Information Systems, Inc., Hughes 2839 LAN Systems, Inc., MIT Laboratory for Computer Science, July 2840 1992. 2842 Acknowledgments 2844 RADIUS was originally developed by Livingston Enterprises for their 2845 PortMaster series of Network Access Servers. 2847 Chair's Address 2849 The working group can be contacted via the current chair: 2851 Carl Rigney 2852 Livingston Enterprises 2853 6920 Koll Center Parkway, Suite 220 2854 Pleasanton, California 94566 2856 Phone: +1 510 426 0770 2857 E-Mail: cdr@livingston.com 2859 Author's Address 2861 Questions about this memo can also be directed to: 2863 Carl Rigney 2864 Livingston Enterprises 2865 6920 Koll Center Parkway, Suite 220 2866 Pleasanton, California 94566 2868 Phone: +1 510 426 0770 2869 E-Mail: cdr@livingston.com 2871 Allan C. Rubens 2872 Merit Network, Inc. 2873 4251 Plymouth Road 2874 Ann Arbor, Michigan 48105-2785 2876 E-Mail: acr@merit.edu 2878 William Allen Simpson 2879 Daydreamer 2880 Computer Systems Consulting Services 2881 1384 Fontaine 2882 Madison Heights, Michigan 48071 2884 E-Mail: wsimpson@greendragon.com 2886 Steve Willens 2887 Livingston Enterprises 2888 6920 Koll Center Parkway, Suite 220 2889 Pleasanton, California 94566 2891 E-Mail: steve@livingston.com