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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group T. Kause 3 Internet-Draft Tectia 4 Updates: 4210 (if approved) M. Peylo 5 Intended status: Standards Track NSN 6 Expires: January 1, 2012 June 30, 2011 8 Internet X.509 Public Key Infrastructure -- HTTP Transport for CMP 9 draft-ietf-pkix-cmp-transport-protocols-13.txt 11 Abstract 13 This document describes how to layer the Certificate Management 14 Protocol over HTTP. It is the "CMPtrans" document referenced in RFC 15 4210 and therefore updates the reference given therein. 17 Status of this Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at http://datatracker.ietf.org/drafts/current/. 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 This Internet-Draft will expire on January 1, 2012. 34 Copyright Notice 36 Copyright (c) 2011 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (http://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 This document may contain material from IETF Documents or IETF 50 Contributions published or made publicly available before November 51 10, 2008. The person(s) controlling the copyright in some of this 52 material may not have granted the IETF Trust the right to allow 53 modifications of such material outside the IETF Standards Process. 54 Without obtaining an adequate license from the person(s) controlling 55 the copyright in such materials, this document may not be modified 56 outside the IETF Standards Process, and derivative works of it may 57 not be created outside the IETF Standards Process, except to format 58 it for publication as an RFC or to translate it into languages other 59 than English. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 4 65 3. HTTP-Based Protocol . . . . . . . . . . . . . . . . . . . . . 5 66 3.1. HTTP Versions . . . . . . . . . . . . . . . . . . . . . . 5 67 3.2. Persistent Connections . . . . . . . . . . . . . . . . . . 5 68 3.3. General Form . . . . . . . . . . . . . . . . . . . . . . . 5 69 3.4. Media Type . . . . . . . . . . . . . . . . . . . . . . . . 5 70 3.5. Communication Workflow . . . . . . . . . . . . . . . . . . 6 71 3.6. HTTP Request-URI . . . . . . . . . . . . . . . . . . . . . 6 72 3.7. Pushing of Announcements . . . . . . . . . . . . . . . . . 7 73 3.8. HTTP Considerations . . . . . . . . . . . . . . . . . . . 8 74 4. Compatibility Issues with Legacy Implementations . . . . . . . 9 75 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 76 6. Information Security Considerations . . . . . . . . . . . . . 11 77 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 78 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 79 8.1. Normative References . . . . . . . . . . . . . . . . . . . 13 80 8.2. Informative References . . . . . . . . . . . . . . . . . . 13 81 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 14 82 Appendix B. Registration of the application/pkixcmp Media Type . 15 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 85 1. Introduction 87 The Certificate Management Protocol (CMP) [RFC4210] requires well 88 defined transport mechanisms to enable End Entities, RAs and CAs to 89 pass PKIMessage sequences between them. This document defines the 90 transport mechanisms which were removed from the main CMP 91 specification with the second release and referred to be in a 92 separate document. 94 The first version of the CMP specification [RFC2510] included a brief 95 description of a simple transport protocol layer on top of TCP. Its 96 features was simple transport level error-handling and a mechanism to 97 poll for outstanding PKI messages. Additionally it was mentioned 98 that PKI messages could also be conveyed using file-, E-mail- and 99 HTTP-based transport, but those were not specified in detail. 101 The current version of the CMP specification incorporated an own 102 polling mechanism and thus the need for a transport protocol 103 providing this functionality vanished. The remaining features CMP 104 requires from its transport protocols are connection- and error- 105 handling. 107 During the long time it existed as draft, this RFC was undergoing 108 drastic changes. The TCP-based transport protocol was enhanced and a 109 TCP-Messages-over-HTTP transport specification appeared. As both 110 proved to be needless and cumbersome, implementers preferred to use 111 plain HTTP transport. This document now reflects that by exclusively 112 describing HTTP as transport protocol for CMP. 114 HTTP transport is generally easy to implement, traverses network 115 borders utilizing ubiquitous proxies and is already commonly found in 116 existing implementations. 118 2. Requirements 120 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 121 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 122 document are to be interpreted as described in [RFC2119]. 124 3. HTTP-Based Protocol 126 For direct interaction between two entities, where a reliable 127 transport protocol like TCP is available, HTTP SHOULD be utilized for 128 conveying CMP messages. 130 With its status codes HTTP provides needed error reporting 131 capabilities. General problems on the server side as well as those 132 directly caused by the respective request can be reported to the 133 client. 135 As CMP implements a transaction ID, identifying transactions spanning 136 over more than just a single request/response pair, the statelessness 137 of HTTP is not blocking its usage as transport protocol for CMP 138 messages. 140 3.1. HTTP Versions 142 Either HTTP/1.0 as described in [RFC1945] or HTTP/1.1 as in [RFC2616] 143 MAY be used. Both server and client SHOULD be able to interact with 144 counterparts utilizing either HTTP protocol version. 146 3.2. Persistent Connections 148 HTTP permits to reuse a connection for subsequent requests. 149 Implementations may use this functionality for messages within the 150 same transaction but MUST NOT rely on that, as e.g. intermediate HTTP 151 proxies might terminate the connection after each request/response 152 pair. 154 3.3. General Form 156 An ASN.1 DER-encoded PKIMessage is sent as the entity-body of an HTTP 157 POST request. If this HTTP request is successful, the server returns 158 the CMP reply in the body of the HTTP response. The response status 159 code in this case MUST be 200; other 2xx codes MUST NOT be used for 160 this purpose. HTTP responses with empty message body to pushed CMP 161 Announcement messages utilize the status codes 201, 202 and 204 to 162 identify whether the received information was processed. 164 All applicable 4xx or 5xx status codes may be used to inform the 165 client about errors. 167 3.4. Media Type 169 The Internet Media Type "application/pkixcmp" MUST be set in the HTTP 170 header when conveying a PKIMessage. 172 3.5. Communication Workflow 174 In CMP most communication is initiated by the end entities where 175 every CMP request triggers a CMP response message from the CA or RA. 177 The CMP Announcement messages described in Section 3.7 are an 178 exception. Their creation may be triggered by certain events or done 179 on a regular basis by a CA. The recipient of the Announcement only 180 replies with an HTTP status code acknowledging the receipt or 181 indicating an error but not with a CMP response. 183 If the receipt of an HTTP request is not confirmed by receiving an 184 HTTP response, it MUST be assumed that the transported CMP message 185 was not successfully delivered to its destination. 187 3.6. HTTP Request-URI 189 The Request-URI is formed as specified in [RFC3986]. 191 Client requests containing a PKI message MUST be directed to an 192 Request-URI depicting a directory. A server implementation MUST 193 handle Request-URIs with or without a trailing slash as identical. 194 The following list contains all such CMP message types. The prefixed 195 numbers reflect the ASN.1 numbering of the respective element. 197 [0] Initialization Request 198 [2] Certification Request 199 [4] PKCS-10 Request 200 [6] pop Response 201 [7] Key Update Request 202 [9] Key Recovery Request 203 [11] Revocation Request 204 [13] Cross-Certification Request 205 [15] CA Key Update Announcement 206 [16] Certificate Announcement 207 [17] Revocation Announcement 208 [18] CRL Announcement 209 [20] Nested Message 210 [21] General Message 211 [23] Error Message 212 [24] Certificate Confirmation 213 [25] Polling Request 215 An example of a Request-Line and a Host header field in an HTTP/1.1 216 header, sending a CMP request to a server, located in the "/cmp" 217 directory of the host example.com, would be 218 POST /cmp HTTP/1.1 219 Host: example.com 221 or in the absoluteURI form 223 POST http://example.com/cmp/ HTTP/1.1 224 Host: example.com 226 A CMP server may be logically located either inside the root- or 227 within subdirectories of an HTTP server domain. 229 3.7. Pushing of Announcements 231 A CMP server may create event-triggered announcements or generate 232 them on a regular basis. It MAY also utilize HTTP transport to 233 convey them to a suitable recipient. No request message for is 234 specified, so they can only be pushed to the recipient. If an EE 235 wants to poll for a potential CA Key Update Announcement or the 236 current CRL, a PKI Information Request using a General Message as 237 described in E.5 of [RFC4210] can be used. 239 When pushing Annocements, ASN.1 encoded structures are sent as the 240 entity-body of an HTTP POST request. 242 Suitable recipients for CMP announcements might e.g. be repositories 243 storing the announced information such as directory services. Those 244 listen for incoming messages, utilizing the same HTTP Request-URI 245 scheme as defined in Section 3.6. 247 The following PKIMessages are announcements that may be pushed by a 248 CA. The prefixed numbers reflect ASN.1 numbering of the respective 249 element. 251 [15] CA Key Update Announcement 252 [16] Certificate Announcement 253 [17] Revocation Announcement 254 [18] CRL Announcement 256 CMP Announcement messages do not require any CMP response. However, 257 the recipient MUST acknowledge receipt with a HTTP response having an 258 appropriate status code and an empty body. When not receiving such 259 response it MUST be assumed that the delivery was not successful and 260 if applicable the sending side may retry sending the Announcement 261 after waiting for an appropriate time span. 263 If the announced issue was successfully stored in a database or was 264 already present, the answer MUST be an HTTP response with a "201 265 Created" or "204 No Content" status code and empty message body. 267 In case the announced information was only accepted for further 268 processing, the status code of the returned HTTP response MAY also be 269 "202 Accepted". After an appropriate delay, the server may then try 270 to send the Announcement again and may repeat this until it receives 271 a confirmation that it had been successfully stored. The appropriate 272 duration of the delay and the option to increase it between 273 consecutive attempts should be carefully considered. 275 A receiver MUST answer with a suitable 4xx or 5xx HTTP error code 276 when a problem occurs. 278 3.8. HTTP Considerations 280 In general CMP messages are not cachable. HTTP headers of requests 281 and responses MUST include "Cache-Control: no-cache" and, in case of 282 HTTP/1.0, additionally "Pragma: no-cache" to protect the client from 283 getting cached responses. 285 Connection management is based on the HTTP provided mechanisms 286 ("Connection" and "Proxy-Connection" header fields). 288 While an implementation MAY make use of all defined features of the 289 HTTP protocol, it SHOULD keep the protocol utilization as simple as 290 possible. 292 There is no need for the clients to send an "Expect" request-header 293 field with the "100-continue" expectation and wait for a "100 294 Continue" status as described in chapter 8.2.3 of [RFC2616]. The CMP 295 payload sent by a client is relatively small, so having extra 296 messages exchanged is more inefficient as the server will anyway only 297 seldomly reject a message without evaluating the body. 299 Content codings MAY be applied. 301 4. Compatibility Issues with Legacy Implementations 303 As this document was subject of multiple changes during the long 304 period of time it was created in, implementations using a different 305 approach for HTTP transport may exist. While only those 306 implementations according to this specification are compliant, 307 implementers should to be aware that there might be existing ones 308 which behave differently. 310 Legacy implementations might also use an unregistered "application/ 311 pkixcmp-poll" MIME type as it was specified in earlier drafts of this 312 document. Here, the entity-body of an HTTP POST request contains the 313 DER-encoded PKIMessage prefixed by an additional "TCP-Messaging" 314 protocol. TCP-Messaging was described in draft versions of this 315 document but was removed. 317 5. Security Considerations 319 The following aspects need to be considered by server side 320 implementers: 322 1. There is the risk for denial of service attacks through resource 323 consumption by opening many connections. Therefore idle 324 connections should be terminated after an appropriate timeout, 325 maybe also depending on the available free resources. After 326 sending a CMP Error Message, the server should close the 327 connection even if the CMP transaction is not yet fully 328 completed. 330 2. There is no security at the HTTP protocol level (unless tunneled 331 via TLS) and thus information from the HTTP protocol SHOULD NOT 332 be used to change state of the transaction. Change of state 333 SHOULD be triggered by signed PKIMessages only. Likewise, the 334 clients SHOULD NOT support the 301 HTTP status code which could 335 otherwise be used by an man-in-the-middle attacker to barr them 336 permanently from contacting the correct server. 338 6. Information Security Considerations 340 CMP provides inbuilt integrity protection and authentication. Due to 341 the nature of a PKI, from a security perspective the information 342 communicated unencrypted does not contain sensitive information. 344 However, it might be possible for an interceptor to utilize the 345 available information to gather confidential technical or business 346 critical information. Therefore users of the HTTP CMP transport 347 might want to use HTTP over TLS according to [RFC2818] or should 348 consider to use virtual private networks created e.g. by utilizing 349 Internet Protocol Security according to [RFC4301]. 351 7. IANA Considerations 353 The IANA has already registered TCP and UDP port 829 for "PKIX-3 354 CA/RA" and the MIME media type "application/pkixcmp" for identifying 355 CMP sequences. 357 No further action by the IANA is necessary for this document or any 358 anticipated updates. 360 8. References 362 8.1. Normative References 364 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 365 Requirement Levels", BCP 14, RFC 2119, March 1997. 367 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 368 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 369 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 371 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 372 Resource Identifier (URI): Generic Syntax", STD 66, 373 RFC 3986, January 2005. 375 [RFC4210] Adams, C., Farrell, S., Kause, T., and T. Mononen, 376 "Internet X.509 Public Key Infrastructure Certificate 377 Management Protocol (CMP)", RFC 4210, September 2005. 379 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 380 Housley, R., and W. Polk, "Internet X.509 Public Key 381 Infrastructure Certificate and Certificate Revocation List 382 (CRL) Profile", RFC 5280, May 2008. 384 [RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, 385 October 2008. 387 [RFC5646] Phillips, A. and M. Davis, "Tags for Identifying 388 Languages", BCP 47, RFC 5646, September 2009. 390 8.2. Informative References 392 [RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext 393 Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996. 395 [RFC2482] Whistler, K. and G. Adams, "Language Tagging in Unicode 396 Plain Text", RFC 2482, January 1999. 398 [RFC2510] Adams, C. and S. Farrell, "Internet X.509 Public Key 399 Infrastructure Certificate Management Protocols", 400 RFC 2510, March 1999. 402 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. 404 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 405 Internet Protocol", RFC 4301, December 2005. 407 Appendix A. Acknowledgments 409 Until the fifth draft version of this document, released in November 410 24th 2000, the sole authors were Amit Kapoor and Ronald Tschlaer from 411 Certicom. Up to this point the now removed TCP-Based transport was 412 described in detail. They are not available for this working on this 413 document anymore at the time it is entering the "Authors Final Review 414 state AUTH48". As they therefore cannot approve this document as it 415 would be necessary, their names were moved to this section. Their 416 contact data, as originally stated by them, is as follows: 418 Amit Kapoor 419 Certicom 420 25801 Industrial Blvd 421 Hayward, CA 422 US 423 Email: amit@trustpoint.com 425 Ronald Tschalaer 426 Certicom 427 25801 Industrial Blvd 428 Hayward, CA 429 US 430 Email: ronald@trustpoint.com 432 The authors gratefully acknowledge the contributions of various 433 members of the IETF PKIX Working Group and the ICSA CA-talk mailing 434 list (a list solely devoted to discussing CMP interoperability 435 efforts). 437 By providing ideas, giving hints and doing invaluable review work, 438 the following individuals, listed alphabetically, have significantly 439 contributed to this document: 441 Tomas Gustavsson, Primekey 442 Peter Gutmann, University of Auckland 443 Wolf-Dietrich Moeller, Nokia Siemens Networks 445 Appendix B. Registration of the application/pkixcmp Media Type 446 To: ietf-types@iana.org 447 Subject: Registration of MIME media type application/pkixcmp 449 MIME media type name: application 451 MIME subtype name: pkixcmp 453 Required parameters: - 455 Optional parameters: - 457 Encoding considerations: 459 Content may contain arbitrary octet values (the ASN.1 DER encoding 460 of a PKIMessage sequence, as defined in the IETF PKIX Working Group 461 specifications). base64 encoding is required for MIME e-mail; no 462 encoding is necessary for HTTP. 464 Security considerations: 466 This MIME type may be used to transport Public-Key Infrastructure 467 (PKI) messages between PKI entities. These messages are defined by 468 the IETF PKIX Working Group and are used to establish and maintain 469 an Internet X.509 PKI. There is no requirement for specific 470 security mechanisms to be applied at this level if the PKI messages 471 themselves are protected as defined in the PKIX specifications. 473 Interoperability considerations: - 475 Published specification: this document 477 Applications which use this media type: Applications using 478 certificate management, operational, or ancillary protocols (as 479 defined by the IETF PKIX Working Group) to send PKI messages via 480 E-Mail or HTTP. 482 Additional information: 484 Magic number (s): - 485 File extension (s): ".PKI" 486 Macintosh File Type Code (s): - 488 Person and email address to contact for further information: 489 Martin Peylo, martin.peylo@nsn.com 491 Intended usage: COMMON 493 Author/Change controller: Martin Peylo 495 Authors' Addresses 497 Tomi Kause 498 Tectia Corporation 499 Fredrikinkatu 42 500 Helsinki 00100 501 Finland 503 Email: toka@tectia.com 505 Martin Peylo 506 Nokia Siemens Networks 507 Linnoitustie 6 508 Espoo 02600 509 Finland 511 Email: martin.peylo@nsn.com