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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ACE P. van der Stok 3 Internet-Draft Consultant 4 Intended status: Standards Track P. Kampanakis 5 Expires: January 19, 2019 Cisco Systems 6 S. Kumar 7 Philips Lighting Research 8 M. Richardson 9 SSW 10 M. Furuhed 11 Nexus Group 12 S. Raza 13 RISE SICS 14 July 18, 2018 16 EST over secure CoAP (EST-coaps) 17 draft-ietf-ace-coap-est-05 19 Abstract 21 Enrollment over Secure Transport (EST) is used as a certificate 22 provisioning protocol over HTTPS. Low-resource devices often use the 23 lightweight Constrained Application Protocol (CoAP) for message 24 exchanges. This document defines how to transport EST payloads over 25 secure CoAP (EST-coaps), which allows low-resource constrained 26 devices to use existing EST functionality for provisioning 27 certificates. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at https://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on January 19, 2019. 46 Copyright Notice 48 Copyright (c) 2018 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (https://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 3. Conformance to RFC7925 profiles . . . . . . . . . . . . . . . 3 66 4. Protocol Design . . . . . . . . . . . . . . . . . . . . . . . 4 67 4.1. Payload format . . . . . . . . . . . . . . . . . . . . . 5 68 4.1.1. Content Format application/multipart-core . . . . . . 6 69 4.2. Message Bindings . . . . . . . . . . . . . . . . . . . . 6 70 4.3. CoAP response codes . . . . . . . . . . . . . . . . . . . 6 71 4.4. Delayed Responses . . . . . . . . . . . . . . . . . . . . 7 72 4.5. Server-side Key Generation . . . . . . . . . . . . . . . 9 73 4.6. Message fragmentation . . . . . . . . . . . . . . . . . . 10 74 4.7. Deployment limits . . . . . . . . . . . . . . . . . . . . 11 75 5. Discovery and URI . . . . . . . . . . . . . . . . . . . . . . 11 76 6. DTLS Transport Protocol . . . . . . . . . . . . . . . . . . . 13 77 7. HTTPS-CoAPS Registrar . . . . . . . . . . . . . . . . . . . . 14 78 8. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 16 79 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 80 9.1. Content-Format Registry . . . . . . . . . . . . . . . . . 17 81 9.2. Resource Type registry . . . . . . . . . . . . . . . . . 18 82 10. Security Considerations . . . . . . . . . . . . . . . . . . . 18 83 10.1. EST server considerations . . . . . . . . . . . . . . . 18 84 10.2. HTTPS-CoAPS Registrar considerations . . . . . . . . . . 19 85 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 86 12. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 20 87 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 88 13.1. Normative References . . . . . . . . . . . . . . . . . . 21 89 13.2. Informative References . . . . . . . . . . . . . . . . . 22 90 Appendix A. EST messages to EST-coaps . . . . . . . . . . . . . 24 91 A.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 25 92 A.2. csrattrs . . . . . . . . . . . . . . . . . . . . . . . . 29 93 A.3. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 29 94 A.4. serverkeygen . . . . . . . . . . . . . . . . . . . . . . 32 95 Appendix B. EST-coaps Block message examples . . . . . . . . . . 34 96 B.1. cacerts block example . . . . . . . . . . . . . . . . . . 34 97 B.2. enroll block example . . . . . . . . . . . . . . . . . . 37 98 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38 100 1. Introduction 102 "Classical" Enrollment over Secure Transport (EST) [RFC7030] is used 103 for authenticated/authorized endpoint certificate enrollment (and 104 optionally key provisioning) through a Certificate Authority (CA) or 105 Registration Authority (RA). EST messages run over HTTPS. 107 This document defines a new transport for EST based on the 108 Constrained Application Protocol (CoAP) since some Internet of Things 109 (IoT) devices use CoAP instead of HTTP. Therefore, this 110 specification utilizes DTLS [RFC6347], CoAP [RFC7252], and UDP 111 instead of TLS [RFC5246], HTTP [RFC7230] and TCP. 113 EST messages may be relatively large and for this reason this 114 document also uses CoAP Block-Wise Transfer [RFC7959] to offer a 115 fragmentation mechanism of EST messages at the CoAP layer. 117 This specification also profiles the use of EST to only support 118 certificate-based client Authentication. HTTP Basic or Digest 119 authentication (as described in Section 3.2.3 of [RFC7030] are not 120 supported. 122 2. Terminology 124 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 125 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 126 document are to be interpreted as described in [RFC2119]. 128 Many of the concepts in this document are taken over from [RFC7030]. 129 Consequently, much text is directly traceable to [RFC7030]. The same 130 document structure is followed to point out the differences and 131 commonalities between EST and EST-coaps. 133 3. Conformance to RFC7925 profiles 135 This section shows how EST-coaps fits into the profiles of low- 136 resource devices described in [RFC7925]. 138 EST-coaps can transport certificates and private keys. Certificates 139 are responses to (re-)enrollment requests or request for a trusted 140 certificate list. Private keys can be transported as responses to a 141 request to a server-side keygeneration as described in section 4.4 of 142 [RFC7030] and discussed in Section 4.5 of this document. 144 As per [RFC7925] section 3.3 and section 4.4, the mandatory cipher 145 suite for DTLS in EST-coaps is TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 146 defined in [RFC7251], and the curve secp256r1 MUST be supported 147 [RFC4492]; this curve is equivalent to the NIST P-256 curve. Crypto 148 agility is important, and the recommendations in [RFC7925] section 149 4.4 and any updates to RFC7925 concerning Curve25519 and other CFRG 150 curves also applies. 152 DTLS1.2 implementations MUST use the Supported Elliptic Curves and 153 Supported Point Formats Extensions [RFC4492]. Uncompressed point 154 format MUST also be supported. [RFC6090] can be used as summary of 155 the ECC algorithms. DTLS 1.3 implementations differ from DTLS 1.2 156 because they do not support point format negotiation in favor of a 157 single point format for each curve and thus support for DTLS 1.3 does 158 not mandate point formation extensions and negotiation. 160 The EST-coaps client MUST be configured with at least an implicit TA 161 database from its manufacturer. The authentication of the EST-coaps 162 server by the EST-coaps client is based on certificate authentication 163 in the DTLS handshake. 165 The authentication of the EST-coaps client is based on a client 166 certificate in the DTLS handshake. This can either be 168 o a previously issued client certificate (e.g., an existing 169 certificate issued by the EST CA); this could be a common case for 170 simple re-enrollment of clients; 172 o a previously installed certificate (e.g., manufacturer-installed 173 certificate or a certificate issued by some other party); the 174 server is expected to trust the manufacturer's root CA certificate 175 in this case. 177 4. Protocol Design 179 EST-coaps uses CoAP to transfer EST messages, aided by Block-Wise 180 Transfer [RFC7959] to transport CoAP messages in blocks thus avoiding 181 (excessive) fragmentation of UDP datagrams. The use of "Block" for 182 the transfer of larger EST messages is specified in Section 4.6. The 183 Figure 1 below shows the layered EST-coaps architecture. 185 +------------------------------------------------+ 186 | EST request/response messages | 187 +------------------------------------------------+ 188 | CoAP for message transfer and signalling | 189 +------------------------------------------------+ 190 | DTLS for transport security | 191 +------------------------------------------------+ 192 | UDP for transport | 193 +------------------------------------------------+ 195 Figure 1: EST-coaps protocol layers 197 The EST-coaps protocol design follows closely the EST design. The 198 actions supported by EST-coaps are identified by their message types: 200 o CA certificate retrieval, needed to receive the complete set of CA 201 certificates. 203 o Simple enroll and reenroll, for CA to sign public client-identity 204 key. 206 o Certificate Signing Request (CSR) Attributes request messages, 207 informs the client of the fields to include in generated CSR. 209 o Server-side key generation messages, to provide a private client- 210 identity key when the client choses for an external entity to 211 generate its private key. 213 4.1. Payload format 215 The content-format (media type equivalent) of the CoAP message 216 determines which EST message is transported in the CoAP payload. The 217 media types specified in the HTTP Content-Type header (section 3.2.2 218 of [RFC7030]) are in EST-coaps specified by the Content-Format Option 219 (12) of CoAP. The combination of URI path and content-format used 220 for CoAP MUST map to an allowed combination of URI and media type as 221 defined for EST. The required content-formats for these requests and 222 response messages are defined in Section 9. The CoAP response codes 223 are defined in Section 4.3. 225 EST-coaps is designed for use between low-resource devices and hence 226 does not need to send base64-encoded data. Simple binary is more 227 efficient (30% smaller payload) and well supported by CoAP. 228 Therefore, the content formats specification in Section 4.1.1 229 specifies that the binary payload is transported as a CBOR major type 230 2, a byte string, for all EST-coaps Content-Formats. In the examples 231 of Appendix A, the base16 diagnostic notation is used for CBOR major 232 type 2, where h'450aafbb' represents an example binary payload. 234 4.1.1. Content Format application/multipart-core 236 A representation with content format ID TBD8 contains a collection of 237 representations along with their respective content format. The 238 content-format identifies the media-type application/multipart-core 239 specified in [I-D.fossati-core-multipart-ct]. 241 The collection is encoded as a CBOR array [RFC7049] with an even 242 number of elements. The second, fourth, sixth, etc. element is a 243 binary string containing a representation. The first, third, fifth, 244 etc. element is an unsigned integer specifying the content format ID 245 of the following representation. 247 For example, a collection containing two representations, one with 248 content format ID TBD5 and one with content format ID TBD2, looks 249 like this in diagnostic CBOR notation: 250 [TBD5,h'0123456789abcdef',TBD2,h'fedcba9876543210']. An example is 251 shown in Appendix A.4. 253 4.2. Message Bindings 255 The general EST CoAP message characteristics are: 257 o All EST-coaps messages expect a response from the server, thus the 258 client MUST send the requests over confirmable CON COAP messages. 260 o The Ver, TKL, Token, and Message ID values of the CoAP header are 261 not affected by EST. 263 o The CoAP options used are Uri-Host, Uri-Path, Uri-Port, Content- 264 Format, and Location-Path in CoAP. These CoAP Options are used to 265 communicate the HTTP fields specified in the EST REST messages. 267 o EST URLs are HTTPS based (https://), in CoAP these will be assumed 268 to be transformed to coaps (coaps://) 270 Appendix A includes some practical examples of EST messages 271 translated to CoAP. 273 4.3. CoAP response codes 275 Section 5.9 of [RFC7252] specifies the mapping of HTTP response codes 276 to CoAP response codes. Every time the HTTP response code 200 is 277 specified in [RFC7030] in response to a GET request, in EST-coaps the 278 equivalent CoAP response code 2.05 or 2.03 MUST be used. Similarly, 279 2.01, 2.02 or 2.04 MUST be used in response to POST EST requests. 280 Response code HTTP 202 has no equivalent in CoAP. In Section 4.4 it 281 is specified how EST requests over CoAP handle delayed messages. 283 All other HTTP 2xx response codes are not used by EST. For the 284 following HTTP 4xx error codes that may occur: 400, 401, 403, 404, 285 405, 406, 412, 413, 415; the equivalent CoAP response code for EST- 286 coaps is 4.xx. For the HTTP 5xx error codes: 500, 501, 502, 503, 504 287 the equivalent CoAP response code is 5.xx. 289 4.4. Delayed Responses 291 Appendix B.2 shows an example of a server response that comes 292 immediately after a client request. The example shows the flows of 293 blocks as the large messages require fragmentation. But server 294 responses can sometimes be delayed. 296 According to section 5.2.2 of [RFC7252], a slow server can 297 acknowledge the request and respond later with the requested resource 298 representation. In particular, a slow server can respond to a enroll 299 request with an empty ACK with code 0.00, before sending the 300 certificate to the server after a short delay. Consecutively, the 301 server will need more than one "Block2" blocks to respond if the 302 certificate is large. This situation is shown in Figure 2 where a 303 client sends an enrollment request that uses more than one "Block1" 304 blocks. The server uses an empty 0.00 ACK to announce the response 305 which will be provided later with 2.04 messages containing "Block2" 306 options. Having received the first 128 bytes in the first "block2" 307 block, the client asks for a block reduction to 128 bytes in all 308 following "block2" blocks, starting with the second block (NUM=1). 310 POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256) {CSR req} --> 311 <-- (ACK) (1:0/1/256) (2.31 Continue) 312 POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256) {CSR req} --> 313 <-- (ACK) (1:1/1/256) (2.31 Continue) 314 . 315 . 316 . 317 POST [2001:db8::2:1]:61616/est/sen (CON)(1:N1/0/256){CSR req} --> 318 <-- (0.00 empty ACK) 319 | 320 ...... short delay before certificate is ready....... 321 | 322 <-- (CON) (1:N1/0/256)(2:0/1/256)(2.04 Changed) {Cert resp} 323 (ACK) --> 324 POST [2001:db8::2:1]:61616/est/sen (CON)(2:1/0/128) --> 325 <-- (ACK) (2:1/1/128) (2.04 Changed) {Cert resp} 326 . 327 . 328 . 329 POST [2001:db8::2:1]:61616/est/sen (CON)(2:N2/0/128) --> 330 <-- (ACK) (2:N2/0/128) (2.04 Changed) {Cert resp} 332 Figure 2: EST-COAP enrolment with short wait 334 If the server is very slow providing the response (say minutes, 335 possible when a manual intervention is wanted), the server SHOULD 336 respond with an ACK containing response code 5.03 (Service 337 unavailable) and a Max-Age option to indicate the time the client 338 SHOULD wait to request the content later. After a delay of Max-Age, 339 the client SHOULD resend the identical CSR to the server. As long as 340 the server responds with response code 5.03 (Service Unavailable), 341 the client can resend the enrolment request until the server responds 342 with the certificate or the client abandons for other reasons. 344 To demonstrate this situation, Figure 3 shows a client sending an 345 enrolment request that will use more than one "Block1" block to send 346 the CSR to the server. The server needs more than one "Block2" 347 blocks to respond, but also needs to take a long delay (minutes) to 348 provide the response. Consequently, the server will use a 5.03 ACK 349 for the response. The client can be requested to wait multiple times 350 for a period of Max-Age. Note that in the example below the server 351 asks for a decrease in the block size when acknowledging the first 352 Block2. 354 Figure 5 can be compared with Figure 3 to see the extra requests 355 after a Max-Age wait. 357 POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256) {CSR req} --> 358 <-- (ACK) (1:0/1/256) (2.31 Continue) 359 POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256) {CSR req} --> 360 <-- (ACK) (1:1/1/256) (2.31 Continue) 361 . 362 . 363 POST [2001:db8::2:1]:61616/est/sen (CON)(1:N1/0/256){CSR req} --> 364 <-- (ACK) (1:N1/0/256) (2:0/0/128) (5.03 Service Unavailable) 365 (Max-Age) 366 | 367 | 368 Client tries one or more times after Max-Age with identical payload 369 | 370 | 371 POST [2001:db8::2:1]:61616/est/sen (CON)(1:N1/0/256){CSR req} --> 372 <-- (ACK) (1:N1/0/256) (2:0/1/128) (2.04 Changed){Cert resp} 373 POST [2001:db8::2:1]:61616/est/sen (CON)(2:1/0/128) --> 374 <-- (ACK) (2:1/1/128) (2.04 Changed) {Cert resp} 375 . 376 . 377 . 378 POST [2001:db8::2:1]:61616/est/sen (CON)(2:N2/0/128) --> 379 <-- (ACK) (2:N2/0/128) (2.04 Changed) {Cert resp} 381 Figure 3: EST-COAP enrolment with long wait 383 4.5. Server-side Key Generation 385 Constrained devices sometimes do not have the necessary hardware to 386 generate statistically random numbers for private keys and DTLS 387 ephemeral keys. Past experience has shown that low-resource 388 endpoints sometimes generate numbers which could allow someone to 389 decrypt the communication or guess the private key and impersonate as 390 the device. Studies have shown that the same keys are generated by 391 the same model devices deployed on-line. 393 Additionally, random number key generation is costly, thus energy 394 draining. Even though the random numbers that constitute the 395 identity/cert do not get generated often, an endpoint may not want to 396 spend time and energy generating keypairs, and just ask for one from 397 the server. 399 In these scenarios, server-side key generation can be used. The 400 client asks for the server or proxy to generate the private key and 401 the certificate which is transferred back to the client in the 402 server-side key generation response. 404 [RFC7030] recommends for the private key returned by the server to be 405 encrypted. The specification provides two methods to encrypt the 406 generated key, symmetric and asymmetric. The methods are signalled 407 by the client by using the relevant attributes (SMIMECapabilities and 408 DecryptKeyIdentifier or AsymmetricDecryptKeyIdentifier) in the CSR 409 request. In the symmetric key case, the key can be established out- 410 of-band or alternatively derived by the established TLS connection as 411 described in [RFC5705]. 413 The sever-side key generation response is returned using a CBOR array 414 Section 4.1.1. The certificate part exactly matches the response 415 from a enrollment response. The private key is placed inside of a 416 CMS SignedData. The SignedData is signed by the party that generated 417 the private key, which may or may not be the EST server or the EST 418 CA. The SignedData is further protected by placing it inside of a 419 CMS EnvelopedData as explained in Section 4.4.2 of [RFC7030]. 421 4.6. Message fragmentation 423 DTLS defines fragmentation only for the handshake part and not for 424 secure data exchange (DTLS records). [RFC6347] states that to avoid 425 using IP fragmentation, which involves error-prone datagram 426 reconstitution, invokers of the DTLS record layer SHOULD size DTLS 427 records so that they fit within any Path MTU estimates obtained from 428 the record layer. In addition, invokers residing on a 6LoWPAN over 429 IEEE 802.15.4 network SHOULD attempt to size CoAP messages such that 430 each DTLS record will fit within one or two IEEE 802.15.4 frames. 432 That is not always possible. Even though ECC certificates are small 433 in size, they can vary greatly based on signature algorithms, key 434 sizes, and OID fields used. For 256-bit curves, common ECDSA cert 435 sizes are 500-1000 bytes which could fluctuate further based on the 436 algorithms, OIDs, SANs and cert fields. For 384-bit curves, ECDSA 437 certs increase in size and can sometimes reach 1.5KB. Additionally, 438 there are times when the EST cacerts response from the server can 439 include multiple certs that amount to large payloads. Section 4.6 of 440 CoAP [RFC7252] describes the possible payload sizes: "if nothing is 441 known about the size of the headers, good upper bounds are 1152 bytes 442 for the message size and 1024 bytes for the payload size". 443 Section 4.6 of [RFC7252] also suggests that IPv4 implementations may 444 want to limit themselves to more conservative IPv4 datagram sizes 445 such as 576 bytes. From [RFC0791] follows that the absolute minimum 446 value of the IP MTU for IPv4 is as low as 68 bytes, which would leave 447 only 40 bytes minus security overhead for a UDP payload. Thus, even 448 with ECC certs, EST-coaps messages can still exceed sizes in MTU of 449 1280 for IPv6 or 60-80 bytes for 6LoWPAN [RFC4919] as explained in 450 section 2 of [RFC7959]. EST-coaps needs to be able to fragment EST 451 messages into multiple DTLS datagrams. Fine-grained fragmentation of 452 EST messages is essential. 454 To perform fragmentation in CoAP, [RFC7959] specifies the "Block1" 455 option for fragmentation of the request payload and the "Block2" 456 option for fragmentation of the return payload of a CoAP flow. 458 The BLOCK draft defines SZX in the Block1 and Block2 option fields. 459 These are used to convey the size of the blocks in the requests or 460 responses. 462 The CoAP client MAY specify the Block1 size and MAY also specify the 463 Block2 size. The CoAP server MAY specify the Block2 size, but not 464 the Block1 size. As explained in Section 1 of [RFC7959]), blockwise 465 transfers SHOULD be used in Confirmable CoAP messages to avoid the 466 exacerbation of lost blocks. 468 The Size1 response MAY be parsed by the client as a size indication 469 of the Block2 resource in the server response or by the server as a 470 request for a size estimate by the client. Similarly, Size2 option 471 defined in BLOCK should be parsed by the server as an indication of 472 the size of the resource carried in Block1 options and by the client 473 as a maximum size expected in the 4.13 (Request Entity Too Large) 474 response to a request. 476 Examples of fragmented messages are shown in Appendix B. 478 4.7. Deployment limits 480 Although EST-coaps paves the way for the utilization of EST for 481 constrained devices on constrained networks, some devices will not 482 have enough resources to handle the large payloads that come with 483 EST-coaps. The specification of EST-coaps is intended to ensure that 484 EST works for networks of constrained devices that choose to limit 485 their communications stack to UDP/CoAP. It is up to the network 486 designer to decide which devices execute the EST protocol and which 487 do not. 489 5. Discovery and URI 491 EST-coaps is targeted to low-resource networks with small packets. 492 Saving header space is important and an additional EST-coaps URI is 493 specified that is shorter than the EST URI. 495 In the context of CoAP, the presence and location of (path to) the 496 management data are discovered by sending a GET request to "/.well- 497 known/core" including a resource type (RT) parameter with the value 498 "ace.est" [RFC6690]. Upon success, the return payload will contain 499 the root resource of the EST resources. It is up to the 500 implementation to choose its root resource; throughout this document 501 the example root resource /est is used. 503 The individual EST-coaps server URIs differ from the EST URI by 504 replacing the scheme https by coaps and by specifying shorter 505 resource path names: 507 coaps://www.example.com/.well-known/est/ArbitraryLabel/. 509 The ArbitraryLabel Path-Segment SHOULD be of the shortest length 510 possible. 512 Figure 5 in section 3.2.2 of [RFC7030] enumerates the operations and 513 corresponding paths which are supported by EST. Table 1 provides the 514 mapping from the EST URI path to the shorter EST-coaps URI path. 516 +------------------+-----------+ 517 | EST | EST-coaps | 518 +------------------+-----------+ 519 | /cacerts | /crts | 520 | /simpleenroll | /sen | 521 | /simplereenroll | /sren | 522 | /csrattrs | /att | 523 | /serverkeygen | /skg | 524 +------------------+-----------+ 526 Table 1 528 The short resource URIs MUST be supported. The corresponding longer 529 URIs specified in [RFC7030] MAY be supported. 531 When discovering the root path for the EST resources, the server MAY 532 return all available resource paths and the used content types. This 533 is useful when multiple content types are specified for EST-coaps 534 server. The example below shows the discovery of the presence and 535 location of management data. 537 REQ: GET /.well-known/core?rt=ace.est 539 RES: 2.05 Content 540 ; rt="ace.est" 541 ;ct=TBD2 542 ;ct=TBD2 TBD7 543 ;ct=TBD2 TBD7 544 ;ct=TBD6 545 ;ct=TBD1 TBD7 TBD8 546 The first line of the discovery response MUST be returned. The five 547 consecutive lines MAY be returned. The return of the content-types 548 in the last four lines allows the client to choose the most 549 appropriate one from multiple content types. 551 6. DTLS Transport Protocol 553 EST-coaps depends on a secure transport mechanism over UDP that can 554 secure (confidentiality, authenticity) the exchanged CoAP messages. 556 DTLS is one such secure protocol. When "TLS" is referred to in the 557 context of EST, it is understood that in EST-coaps, security is 558 provided using DTLS instead. No other changes are necessary (all 559 provisional modes etc. are the same as for TLS). 561 CoAP was designed to avoid fragmentation. DTLS is used to secure 562 CoAP messages. However, fragmentation is still possible at the DTLS 563 layer during the DTLS handshake when using ECC ciphersuites. If 564 fragmentation is necessary, "DTLS provides a mechanism for 565 fragmenting a handshake message over several records, each of which 566 can be transmitted separately, thus avoiding IP fragmentation" 567 [RFC6347]. 569 CoAP and DTLS can provide proof of identity for EST-coaps clients and 570 server with simple PKI messages conformant to section 3.1 of 571 [RFC5272]. EST-coaps supports the certificate types and Trust 572 Anchors (TA) that are specified for EST in section 3 of [RFC7030]. 574 Channel-binding information for linking proof-of-identity with 575 connection-based proof-of-possession is optional for EST-coaps. When 576 proof-of-possession is desired, a set of actions are required 577 regarding the use of tls-unique, described in section 3.5 in 578 [RFC7030]. The tls-unique information translates to the contents of 579 the first "Finished" message in the (D)TLS handshake between server 580 and client [RFC5929]. The client is then supposed to add this 581 "Finished" message as a ChallengePassword in the attributes section 582 of the PKCS#10 Request Info to prove that the client is indeed in 583 control of the private key at the time of the TLS session when 584 performing a /simpleenroll, for example. In the case of EST-coaps, 585 the same operations can be performed during the DTLS handshake. For 586 DTLS 1.2, in the event of handshake message fragmentation, the Hash 587 of the handshake messages used in the MAC calculation of the Finished 588 message 590 PRF(master_secret, finished_label, Hash(handshake_messages)) 591 [0..verify_data_length-1]; 593 MUST be computed as if each handshake message had been sent as a 594 single fragment [RFC6347]. Similarly, for DTLS 1.3, the Finished 595 message 597 HMAC(finished_key, 598 Transcript-Hash(Handshake Context, 599 Certificate*, CertificateVerify*)) 601 * Only included if present. 603 MUST be computed as if each handshake message had been sent as a 604 single fragment following the algorithm described in 4.4.4 of 605 [I-D.ietf-tls-tls13]. 607 In a constrained CoAP environment, endpoints can't afford to 608 establish a DTLS connection for every EST transaction. 609 Authenticating and negotiating DTLS keys requires resources on low- 610 end endpoints and consumes valuable bandwidth. The DTLS connection 611 SHOULD remain open for persistent EST connections. For example, an 612 EST cacerts request that is followed by a simpleenroll request can 613 use the same authenticated DTLS connection. Given that after a 614 successful enrollment, it is more likely that a new EST transaction 615 will take place after a significant amount of time, the DTLS 616 connections SHOULD only be kept alive for EST messages that are 617 relatively close to each other. In some cases, such as NAT 618 rebinding, keeping the state of a connection is not possible when 619 devices sleep for extended periods of time. In such occasions, 620 [I-D.rescorla-tls-dtls-connection-id] negotiates a connection ID that 621 can eliminate the need for new handshake and its additional cost. 623 7. HTTPS-CoAPS Registrar 625 In real-world deployments, the EST server will not always reside 626 within the CoAP boundary. The EST-server can exist outside the 627 constrained network in a non-constrained network that supports TLS/ 628 HTTP. In such environments EST-coaps is used by the client within 629 the CoAP boundary and TLS is used to transport the EST messages 630 outside the CoAP boundary. A Registrar at the edge is required to 631 operate between the CoAP environment and the external HTTP network. 632 The EST coaps-to-HTTPS Registrar MUST terminate EST-coaps and 633 authenticate the client downstream and initiate EST connections over 634 TLS upstream. 636 The Registrar SHOULD authenticate the client downstream and it should 637 be authenticated by the EST server or CA upstream. The Registration 638 Authority (re-)creates the secure connection from DTLS to TLS and 639 vice versa. A trust relationship SHOULD be pre-established between 640 the Registrar and the EST servers to be able to proxy these 641 connections on behalf of various clients. 643 When enforcing Proof-of-Possession (POP), the (D)TLS tls-unique value 644 of the (D)TLS session needs to be used to prove that the private key 645 corresponding to the public key is in the possession of and can be 646 used by an end-entity or client. In other words, the CSR the client 647 is using needs to include information from the DTLS connection the 648 client establishes with the server. In EST, that information is the 649 (D)TLS tls-unique value of the (D)TLS session. In the presence of 650 ESTcoaps-to-HTTPS Registrar, the EST-coaps client MUST be 651 authenticated and authorized by the Registrar and the Registrar MUST 652 be authenticated as an EST Registrar client to the EST server. Thus 653 the POP information is lost between the EST-coaps client and the EST 654 server. The EST server becomes aware of the presence of an EST 655 Registrar from its TLS client certificate that includes id-kp-cmcRA 656 [RFC6402] extended key usage extension. As explained in Section 3.7 657 of [RFC7030], the EST server SHOULD apply an authorization policy 658 consistent with a Registrar client. For example, it could be 659 configured to accept POP linking information that does not match the 660 current TLS session because the authenticated EST client Registrar 661 has verified this information when acting as an EST server. 663 One possible use-case, shown in one figure below, is expected to be 664 deployed in practice: 666 Constrained Network 667 .---------. .----------------------------. 668 | CA | |.--------------------------.| 669 '---------' || || 670 | || || 671 .------. HTTP .-----------------. CoAPS .-----------. || 672 | EST |<------->|ESTcoaps-to-HTTPS|<-------->| EST Client| || 673 |Server|over TLS | Registrar | '-----------' || 674 '------' '-----------------' || 675 || || 676 |'--------------------------'| 677 '----------------------------' 679 ESTcoaps-to-HTTPS Registrar at the CoAP boundary. 681 Table 1 contains the URI mapping between the EST-coaps and EST the 682 Registrar SHOULD adhere to. Section 7 of [RFC8075] and Section 4.3 683 define the mapping between EST-coaps and HTTP response codes, that 684 determines how the Registrar translates CoAP response codes from/to 685 HTTP status codes. The mapping from Content-Type to media type is 686 defined in Section 9. The conversion from CBOR major type 2 to 687 base64 encoding needs to be done in the Registrar. Conversion is 688 possible because a TLS link exists between EST-coaps-to-HTTP 689 Registrar and EST server and a corresponding DTLS link exists between 690 EST-coaps-to-HTTP Registrar and EST client. 692 Due to fragmentation of large messages into blocks, an EST-coaps-to- 693 HTTP Registrar SHOULD reassemble the BLOCKs before translating the 694 binary content to Base-64, and consecutively relay the message 695 upstream. 697 For the discovery of the EST server by the EST client in the coap 698 environment, the EST-coaps-to-HTTP Registrar MUST announce itself 699 according to the rules of Section 5. The available actions of the 700 Registrars MUST be announced with as many resource paths. The 701 discovery of EST server in the http environment follow the rules 702 specified in [RFC7030]. 704 When server-side key generation is used, if the private key is 705 protected using symmetric keys then the Registrar needs to encrypt 706 the private key down to the client with one symmetric key and decrypt 707 it from the server with another. If no private key encryption takes 708 place the Registrar will be able to see the key as it establishes a 709 separate connection to the server. In the case of asymmetrically 710 encrypted private key, the Registrar may not be able to decrypt it if 711 the server encrypted it with a public key that corresponds to a 712 private key that belongs to the client. 714 8. Parameters 716 THis section addresses transmission parameters described in sections 717 4.7 and 4.8 of the CoAP document [RFC7252]. 719 ACK_TIMEOUT | 2 seconds | 720 ACK_RANDOM_FACTOR | 1.5 | 721 MAX_RETRANSMIT | 4 | 722 NSTART | 1 | 723 DEFAULT_LEISURE | 5 seconds | 724 PROBING_RATE | 1 byte/second | 726 Figure 4: EST-COAP protocol parameters 728 EST does not impose any unique parameters that affect the CoAP 729 parameters in Table 2 and 3 in the CoAP draft but the ones in CoAP 730 could be affecting EST. For example, the processing delay of CAs 731 could be less then 2s, but in this case they should send a CoAP ACK 732 every 2s while processing. 734 The main recommendation, based on experiments using Nexus Certificate 735 Manager with Californium for CoAP support, communicating with a 736 ContikiOS and tinyDTLS based client, from RISE SICS, is to start with 737 the default CoAP configuration parameters. 739 However, depending on the implementation scenario, resending and 740 timeouts can also occur on other networking layers, governed by other 741 configuration parameters. 743 Some further comments about some specific parameters, mainly from 744 Table 2 in [RFC7252]: 746 o DEFAULT_LEISURE: This setting is only relevant in multicast 747 scenarios, outside the scope of the EST-coaps draft. 749 o NSTART: Limit the number of simultaneous outstanding interactions 750 that a client maintains to a given server. The default is one, 751 hence is the risk of congestion or out-of-order messages already 752 limited. 754 o PROBING_RATE: A parameter which specifies the rate of re-sending 755 non-confirmable messages. The EST messages are defined to be sent 756 as CoAP confirmable messages, hence the PROBING_RATE setting is 757 not applicable. 759 Finally, the Table 3 parameters are mainly derived from the more 760 basic Table 2 parameters. If the CoAP implementation allows setting 761 them directly, they might need to be updated if the table 2 762 parameters are changed. 764 9. IANA Considerations 766 9.1. Content-Format Registry 768 Additions to the sub-registry "CoAP Content-Formats", within the 769 "CoRE Parameters" registry are specified in Table 2. These can be 770 registered either in the Expert Review range (0-255) or IETF Review 771 range (256-9999). 773 +-----------------------------------+----------+------+-------------+ 774 | Media type | Encoding | ID | Reference | 775 +-----------------------------------+----------+------+-------------+ 776 | application/pkcs7-mime; smime- | - | TBD1 | [RFC5751] | 777 | type=server-generated-key | | | [RFC7030] | 778 | application/pkcs7-mime; smime- | - | TBD2 | [RFC5751] | 779 | type=certs-only | | | | 780 | application/pkcs7-mime; smime- | - | TBD3 | [RFC5751] | 781 | type=CMC-request | | | [RFC5273] | 782 | application/pkcs7-mime; smime- | - | TBD4 | [RFC5751] | 783 | type=CMC-response | | | [RFC5273] | 784 | application/pkcs8 | - | TBD5 | [RFC5751] | 785 | | | | [RFC5958] | 786 | application/csrattrs | - | TBD6 | [RFC7030] | 787 | | | | [RFC7231] | 788 | application/pkcs10 | - | TBD7 | [RFC5751] | 789 | | | | [RFC5967] | 790 +-----------------------------------+----------+------+-------------+ 792 Table 2: New CoAP Content-Formats 794 9.2. Resource Type registry 796 Additions to the sub-registry "CoAP Resource Type", within the "CoRE 797 Parameters" registry are needed for a new resource type. 799 o rt="ace.est" needs registration with IANA. 801 10. Security Considerations 803 10.1. EST server considerations 805 The security considerations of Section 6 of [RFC7030] are only 806 partially valid for the purposes of this document. As HTTP Basic 807 Authentication is not supported, the considerations expressed for 808 using passwords do not apply. 810 Given that the client has only limited resources and may not be able 811 to generate sufficiently random keys to encrypt its identity, it is 812 possible that the client uses server generated private/public keys to 813 encrypt its certificate. The transport of these keys is inherently 814 risky. A full probability analysis MUST be done to establish whether 815 server side key generation enhances or decreases the probability of 816 identity stealing. 818 When a client uses the Implicit TA database for certificate 819 validation, the client cannot verify that the implicit database can 820 act as an RA. It is RECOMMENDED that such clients include "Linking 821 Identity and POP Information" Section 6 in requests (to prevent such 822 requests from being forwarded to a real EST server by a man in the 823 middle). It is RECOMMENDED that the Implicit Trust Anchor database 824 used for EST server authentication be carefully managed to reduce the 825 chance of a third-party CA with poor certification practices from 826 being trusted. Disabling the Implicit Trust Anchor database after 827 successfully receiving the Distribution of CA certificates response 828 (Section 4.1.3 of [RFC7030]) limits any risk to the first DTLS 829 exchange. 831 In accordance with [RFC7030], TLS cipher suites that include 832 "_EXPORT_" and "_DES_" in their names MUST NOT be used. More 833 information about recommendations of TLS and DTLS are included in 834 [RFC7525]. 836 As described in CMC, Section 6.7 of [RFC5272], "For keys that can be 837 used as signature keys, signing the certification request with the 838 private key serves as a POP on that key pair". The inclusion of tls- 839 unique in the certification request links the proof-of-possession to 840 the TLS proof-of-identity. This implies but does not prove that the 841 authenticated client currently has access to the private key. 843 Regarding the Certificate Signing Request (CSR), an adversary could 844 exclude attributes that a server may want, include attributes that a 845 server may not want, and render meaningless other attributes that a 846 server may want. The CA is expected to be able to enforce policies 847 to recover from improper CSR requests. 849 Interpreters of ASN.1 structures should be aware of the use of 850 invalid ASN.1 length fields and should take appropriate measures to 851 guard against buffer overflows, stack overruns in particular, and 852 malicious content in general. 854 10.2. HTTPS-CoAPS Registrar considerations 856 The Registrar proposed in Section 7 must be deployed with care, and 857 only when the recommended connections are impossible. When POP is 858 used the Registrar terminating the TLS connection establishes a new 859 one with the upstream CA. Thus, it is impossible for POP to be 860 enforced throughout the EST transaction. The EST server could be 861 configured to accept POP linking information that does not match the 862 current TLS session because the authenticated EST Registrar client 863 has verified this information when acting as an EST server. The 864 introduction of an EST-coaps-to-HTTP Registrar assumes the client can 865 trust the registrar using its implicit or explicit TA database. It 866 also assumes the Registrar has a trust relationship with the upstream 867 EST server in order to act on behalf of the clients. 869 In a server-side key generation case, depending on the private key 870 encryption method, the Registrar may be able see the private key as 871 it acts as a man-in-the-middle. Thus, the clients puts its trust on 872 the Registrar not exposing the private key. 874 For some use cases, clients that leverage server-side key generation 875 might prefer for the enrolled keys to be generated by the Registrar 876 if the CA does not support server-side key generation. In these 877 cases the Registrar must support the random number generation using 878 proper entropy. Since the client has no knowledge if the Registrar 879 will be generating the keys and enrolling the certificates with the 880 CA or if the CA will be responsible for generating the keys, the 881 existence of a Registrar requires the client to put its trust on the 882 registrar doing the right thing if it is generating they private 883 keys. 885 11. Acknowledgements 887 The authors are very grateful to Klaus Hartke for his detailed 888 explanations on the use of Block with DTLS and his support for the 889 content-format specification. The authors would like to thank Esko 890 Dijk and Michael Verschoor for the valuable discussions that helped 891 in shaping the solution. They would also like to thank Peter 892 Panburana for his feedback on technical details of the solution. 893 Constructive comments were received from Benjamin Kaduk, Eliot Lear, 894 Jim Schaad, Hannes Tschofenig, Julien Vermillard, and John Manuel. 896 12. Change Log 898 -04: 900 TBD8 removed from C-F registration, to be done CT draft 902 -03: 904 Removed observe and simplified long waits 906 Repaired content-format specification 908 -02: 910 Added parameter discussion in section 8 912 Concluded content-format specification using multipart-ct draft 914 examples updated 916 -01: 918 Editorials done. 920 Redefinition of proxy to Registrar in Section 7. Explained better 921 the role of https-coaps Registrar, instead of "proxy" 923 Provide "observe" option examples 925 extended block message example. 927 inserted new server key generation text in Section 4.5 and 928 motivated server key generation. 930 Broke down details for DTLS 1.3 932 New media type uses CBOR array for multiple content-format 933 payloads 935 provided new content format tables 937 new media format for IANA 939 -00 941 copied from vanderstok-ace-coap-04 943 13. References 945 13.1. Normative References 947 [I-D.fossati-core-multipart-ct] 948 Bormann, C., "Multipart Content-Format for CoAP", draft- 949 fossati-core-multipart-ct-05 (work in progress), June 950 2018. 952 [I-D.ietf-tls-tls13] 953 Rescorla, E., "The Transport Layer Security (TLS) Protocol 954 Version 1.3", draft-ietf-tls-tls13-28 (work in progress), 955 March 2018. 957 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 958 Requirement Levels", BCP 14, RFC 2119, 959 DOI 10.17487/RFC2119, March 1997, 960 . 962 [RFC5272] Schaad, J. and M. Myers, "Certificate Management over CMS 963 (CMC)", RFC 5272, DOI 10.17487/RFC5272, June 2008, 964 . 966 [RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet 967 Mail Extensions (S/MIME) Version 3.2 Message 968 Specification", RFC 5751, DOI 10.17487/RFC5751, January 969 2010, . 971 [RFC5967] Turner, S., "The application/pkcs10 Media Type", RFC 5967, 972 DOI 10.17487/RFC5967, August 2010, 973 . 975 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 976 Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, 977 January 2012, . 979 [RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link 980 Format", RFC 6690, DOI 10.17487/RFC6690, August 2012, 981 . 983 [RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed., 984 "Enrollment over Secure Transport", RFC 7030, 985 DOI 10.17487/RFC7030, October 2013, 986 . 988 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 989 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 990 October 2013, . 992 [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained 993 Application Protocol (CoAP)", RFC 7252, 994 DOI 10.17487/RFC7252, June 2014, 995 . 997 [RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in 998 the Constrained Application Protocol (CoAP)", RFC 7959, 999 DOI 10.17487/RFC7959, August 2016, 1000 . 1002 [RFC8075] Castellani, A., Loreto, S., Rahman, A., Fossati, T., and 1003 E. Dijk, "Guidelines for Mapping Implementations: HTTP to 1004 the Constrained Application Protocol (CoAP)", RFC 8075, 1005 DOI 10.17487/RFC8075, February 2017, 1006 . 1008 13.2. Informative References 1010 [I-D.rescorla-tls-dtls-connection-id] 1011 Rescorla, E., Tschofenig, H., Fossati, T., and T. Gondrom, 1012 "The Datagram Transport Layer Security (DTLS) Connection 1013 Identifier", draft-rescorla-tls-dtls-connection-id-02 1014 (work in progress), November 2017. 1016 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1017 DOI 10.17487/RFC0791, September 1981, 1018 . 1020 [RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B. 1021 Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites 1022 for Transport Layer Security (TLS)", RFC 4492, 1023 DOI 10.17487/RFC4492, May 2006, 1024 . 1026 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 1027 over Low-Power Wireless Personal Area Networks (6LoWPANs): 1028 Overview, Assumptions, Problem Statement, and Goals", 1029 RFC 4919, DOI 10.17487/RFC4919, August 2007, 1030 . 1032 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1033 (TLS) Protocol Version 1.2", RFC 5246, 1034 DOI 10.17487/RFC5246, August 2008, 1035 . 1037 [RFC5273] Schaad, J. and M. Myers, "Certificate Management over CMS 1038 (CMC): Transport Protocols", RFC 5273, 1039 DOI 10.17487/RFC5273, June 2008, 1040 . 1042 [RFC5705] Rescorla, E., "Keying Material Exporters for Transport 1043 Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705, 1044 March 2010, . 1046 [RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings 1047 for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010, 1048 . 1050 [RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958, 1051 DOI 10.17487/RFC5958, August 2010, 1052 . 1054 [RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic 1055 Curve Cryptography Algorithms", RFC 6090, 1056 DOI 10.17487/RFC6090, February 2011, 1057 . 1059 [RFC6402] Schaad, J., "Certificate Management over CMS (CMC) 1060 Updates", RFC 6402, DOI 10.17487/RFC6402, November 2011, 1061 . 1063 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1064 Protocol (HTTP/1.1): Message Syntax and Routing", 1065 RFC 7230, DOI 10.17487/RFC7230, June 2014, 1066 . 1068 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1069 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 1070 DOI 10.17487/RFC7231, June 2014, 1071 . 1073 [RFC7251] McGrew, D., Bailey, D., Campagna, M., and R. Dugal, "AES- 1074 CCM Elliptic Curve Cryptography (ECC) Cipher Suites for 1075 TLS", RFC 7251, DOI 10.17487/RFC7251, June 2014, 1076 . 1078 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 1079 "Recommendations for Secure Use of Transport Layer 1080 Security (TLS) and Datagram Transport Layer Security 1081 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 1082 2015, . 1084 [RFC7925] Tschofenig, H., Ed. and T. Fossati, "Transport Layer 1085 Security (TLS) / Datagram Transport Layer Security (DTLS) 1086 Profiles for the Internet of Things", RFC 7925, 1087 DOI 10.17487/RFC7925, July 2016, 1088 . 1090 Appendix A. EST messages to EST-coaps 1092 This section takes all examples from Appendix A of [RFC7030], changes 1093 the payload from Base64 to binary and replaces the http headers by 1094 their CoAP equivalents. 1096 The corresponding CoAP headers are only shown in Appendix A.1. 1097 Creating CoAP headers are assumed to be generally known. 1099 Binary payload is a CBOR major type 2 (byte array), that is shown 1100 with a base16 (hexadecimal) CBOR diagnostic notation. 1102 [EDNOTE: The payloads of the examples need to be re-generated with 1103 appropriate tools and example certificates.] 1105 A.1. cacerts 1107 These examples assume that the resource discovery, returned a short 1108 URL of "/est". 1110 In EST-coaps, a coaps cacerts IPv4 message can be: 1112 GET coaps://192.0.2.1:8085/est/crts 1114 The corresponding CoAP header fields are shown below. The use of 1115 block and DTLS are worked out in Appendix B. 1117 Ver = 1 1118 T = 0 (CON) 1119 Code = 0x01 (0.01 is GET) 1120 Token = 0x9a (client generated) 1121 Options 1122 Option1 (Uri-Host) [optional] 1123 Option Delta = 0x3 (option nr = 3) 1124 Option Length = 0x9 1125 Option Value = 192.0.2.1 1126 Option2 (Uri-Port) [optional] 1127 Option Delta = 0x4 (option nr = 3+4=7) 1128 Option Length = 0x4 1129 Option Value = 8085 1130 Option3 (Uri-Path) 1131 Option Delta = 0x4 (option nr = 7+4= 11) 1132 Option Length = 0x5 1133 Option Value = "est" 1134 Option4 (Uri-Path) 1135 Option Delta = 0x0 (option nr = 11+0= 11) 1136 Option Length = 0x6 1137 Option Value = "crts" 1138 Option5 (Max-Age) 1139 Option Delta = 0x3 (option nr = 11+3= 14) 1140 Option Length = 0x1 1141 Option Value = 0x1 (1 minute) 1142 Payload = [Empty] 1144 A 2.05 Content response with a cert in EST-coaps will then be: 1146 2.05 Content (Content-Format: TBD2) 1147 {payload} 1149 with CoAP fields 1151 Ver = 1 1152 T = 2 (ACK) 1153 Code = 0x45 (2.05 Content) 1154 Token = 0x9a (copied by server) 1155 Options 1156 Option1 (Content-Format) 1157 Option Delta = 0xC (option nr =12) 1158 Option Length = 0x2 1159 Option Value = TBD2 (defined in this document) 1161 Payload = 1162 h'30233906092a6206734107028c2a3023260201013100300b06092a6206734107018 1163 c0c3020bb302063c20102020900a61e75193b7acc0d06092a620673410105050030 1164 1b31193017060355040313106573744578616d706c654341204f774f301e170d313 1165 3303530393033353333315a170d3134303530393033353333315a301b3119301706 1166 0355040313106573744578616d706c654341204f774f302062300d06092a6206734 1167 10101050003204f0030204a022041003a923a2968bae4aae136ca4e2512c5200680 1168 358482ac39d6f640e4574e654ea35f48b1e054c5da3372872f7a1e429f4edf39584 1169 32efb2106591d3eb783c1034709f251fc86566bda2d541c792389eac4ec9e181f4b 1170 9f596e5ef2679cc321542b11337f90a44df3c85f1516561fa968a1914f265bc0b82 1171 76ebe3106a790d97d34c8c37c74fe1c30b396424664ac426284a9f6022e02693843 1172 6880adfcd95c98ca1dfc2e6d75319b85d0458de28a9d13fb16d620fff7541f6a25d 1173 7daf004355020301000130b040300f0603551d130101f10530030101fc1d0603551 1174 d0e04160414084d321ca0135e77217a486b686b334b00e0603551d0f0101f104030 1175 20106300d06092a62067341010505000320410023703b965746a0c2c978666d787a 1176 94f89b495a11f0d369b28936ec2475c0f0855c8e83f823f2b871a1d92282f323c45 1177 904ba008579216cf5223b8b1bc425a0677262047f7700240631c17f3035d1c3780b 1178 2385241cba1f4a6e98e6be6820306b3a786de5a557795d1893822347b5f825d34a7 1179 ad2876f8feba4d525b31066f6505796f71530003431a3e6bbfe788b4565029a7e20 1180 a51107677552586152d051e8eebf383e92288983421d5c5652a4870c3af74b9bdbe 1181 d6b462e2263d30f6d3020c330206bc20102020101300d06092a6206734101050500 1182 301b31193017060355040313106573744578616d706c654341204f774f301e170d3 1183 133303530393033353333325a170d3134303530393033353333325a301b31193017 1184 060355040313106573744578616d706c654341204e774f302062300d06092a62067 1185 3410101050003204f0030204a02204100ef6b677a3247c1fc03d2b9baf113e5e7e1 1186 1f49e0421120e6b8384160f2bf02630ef544d5fd0d5623b35713c79a7229283a790 1187 8751a634aa420a3e2a4b1f10519d046f02f5a5dd6d760c2a842356e067b7bd94338 1188 d1faa3b3ddd4813060a207b0a097067007e45b052b60fdbae4656e11562c4f5abb7 1189 b0cf87a79d221f1127313c53371ce1245d63db45a1203a23340ba08042c768d03b8 1190 076a028d3a51d87d2ef107bbd6f2305ce5e67668724002fb726df9c14476c37de0f 1191 55033f192a5ad21f9a2a71c20301000134b050300e0603551d0f0101f104030204c 1192 1d0603551d0e04160414112966e304761732fbfe6a2c823c301f0603551d2304183 1193 0165084d321ca0135e77217a486b686b334b00d06092a6206734101050500032041 1194 00b382ba3355a50e287bae15758b3beff63d34d3e357b90031495d018868e49589b 1195 9faf46a4ad49b1d35b06ef380106677440934663c2cc111c183655f4dc41c0b3401 1196 123d35387389db91f1e1b4131b16c291d35730b3f9b33c7475124851555fe5fc647 1197 e8fd029605367c7e01281bf6617110021b0d10847dce0e9f0ca6c764b6334784055 1198 172c3983d1e3a3a82301a54fcc9b0670c543a1c747164619101ff23b240b2a26394 1199 c1f7d38d0e2f4747928ece5c34627a075a8b3122011e9d9158055c28f020c330206 1200 bc20102020102300d06092a6206734101050500301b311930170603550403131065 1201 73744578616d706c654341204e774e301e170d3133303530393033353333325a170 1202 d3134303530393033353333325a301b31193017060355040313106573744578616d 1203 706c654341204f774e302062300d06092a620673410101050003204f0030204a022 1204 041003a923a2968bae4aae136ca4e2512c5200680358482ac39d6f640e4574e654e 1205 a35f48b1e054c5da3372872f7a1e429f4edf3958432efb2106591d3eb783c103470 1206 9f251fc86566bda2d541c792389eac4ec9e181f4b9f596e5ef2679cc321542b1133 1207 7f90a44df3c85f1516561fa968a1914f265bc0b8276ebe3106a790d97d34c8c37c7 1208 4fe1c30b396424664ac426284a9f6022e026938436880adfcd95c98ca1dfc2e6d75 1209 319b85d0458de28a9d13fb16d620fff7541f6a25d7daf004355020301000134b050 1210 300e0603551d0f0101f104030204c1d0603551d0e04160414084d321ca0135e7721 1211 7a486b686b334b01f0603551d230418301653112966e304761732fbfe6a2c823c30 1212 0d06092a6206734101050500032041002e106933a443070acf5594a3a584d08af7e 1213 06c295059370a06639eff9bd418d13bc25a298223164a6cf1856b11a81617282e4a 1214 410d82ef086839c6e235690322763065455351e4c596acc7c016b225dec094706c2 1215 a10608f403b10821984c7c152343b18a768c2ad30238dc45dd653ee6092b0d5cd4c 1216 2f7d236043269357f76d13f95fb5f00d0e19263c6833948e1ba612ce8197af650e2 1217 5d882c12f4b6b9b67252c608ef064aca3f9bc867d71172349d510bb7651cd438837 1218 73d927deb41c4673020bb302063c201020209009b9dda3324700d06092a62067341 1219 01050500301b31193017060355040313106573744578616d706c654341204e774e3 1220 01e170d3133303530393033353333325a170d3134303530393033353333325a301b 1221 31193017060355040313106573744578616d706c654341204e774e302062300d060 1222 92a620673410101050003204f0030204a02204100ef6b677a3247c1fc03d2b9baf1 1223 13e5e7e11f49e0421120e6b8384160f2bf02630ef544d5fd0d5623b35713c79a722 1224 9283a7908751a634aa420a3e2a4b1f10519d046f02f5a5dd6d760c2a842356e067b 1225 7bd94338d1faa3b3ddd4813060a207b0a097067007e45b052b60fdbae4656e11562 1226 c4f5abb7b0cf87a79d221f1127313c53371ce1245d63db45a1203a23340ba08042c 1227 768d03b8076a028d3a51d87d2ef107bbd6f2305ce5e67668724002fb726df9c1447 1228 6c37de0f55033f192a5ad21f9a2a71c20301000130b040300f0603551d130101f10 1229 530030101fc1d0603551d0e04160414112966e304761732fbfe6a2c823c300e0603 1230 551d0f0101f10403020106300d06092a620673410105050003204100423f06d4b76 1231 0f4b42744a279035571696f272a0060f1325a40898509601ad14004f652db6312a1 1232 475c4d7cd50f4b269035585d7856c5337765a66b38462d5bdaa7778aab24bbe2815 1233 e37722cd10e7166c50e75ab75a1271324460211991e7445a2960f47351a1a629253 1234 34119794b90e320bc730d6c1bee496e7ac125ce9a1eca595a3a4c54a865e6b623c9 1235 247bfd0a7c19b56077392555c955e233642bec643ae37c166c5e221d797aea3748f 1236 0391c8d692a5cf9bb71f6d0e37984d6fa673a30d0c006343116f58403100' 1238 The hexadecimal dump of the CBOR payload looks like: 1240 59 09CD # bytes(2509) 1241 30233906092A6206734107028C2A3023260201013100300B06092A62067341070 1242 18C0C3020BB302063C20102020900A61E75193B7ACC0D06092A62067341010505 1243 00301B31193017060355040313106573744578616D706C654341204F774F301E1 1244 70D3133303530393033353333315A170D3134303530393033353333315A301B31 1245 193017060355040313106573744578616D706C654341204F774F302062300D060 1246 92A620673410101050003204F0030204A022041003A923A2968BAE4AAE136CA4E 1247 2512C5200680358482AC39D6F640E4574E654EA35F48B1E054C5DA3372872F7A1 1248 E429F4EDF3958432EFB2106591D3EB783C1034709F251FC86566BDA2D541C7923 1249 89EAC4EC9E181F4B9F596E5EF2679CC321542B11337F90A44DF3C85F1516561FA 1250 968A1914F265BC0B8276EBE3106A790D97D34C8C37C74FE1C30B396424664AC42 1251 6284A9F6022E026938436880ADFCD95C98CA1DFC2E6D75319B85D0458DE28A9D1 1252 3FB16D620FFF7541F6A25D7DAF004355020301000130B040300F0603551D13010 1253 1F10530030101FC1D0603551D0E04160414084D321CA0135E77217A486B686B33 1254 4B00E0603551D0F0101F10403020106300D06092A620673410105050003204100 1255 23703B965746A0C2C978666D787A94F89B495A11F0D369B28936EC2475C0F0855 1256 C8E83F823F2B871A1D92282F323C45904BA008579216CF5223B8B1BC425A06772 1257 62047F7700240631C17F3035D1C3780B2385241CBA1F4A6E98E6BE6820306B3A7 1258 86DE5A557795D1893822347B5F825D34A7AD2876F8FEBA4D525B31066F6505796 1259 F71530003431A3E6BBFE788B4565029A7E20A51107677552586152D051E8EEBF3 1260 83E92288983421D5C5652A4870C3AF74B9BDBED6B462E2263D30F6D3020C33020 1261 6BC20102020101300D06092A6206734101050500301B311930170603550403131 1262 06573744578616D706C654341204F774F301E170D313330353039303335333332 1263 5A170D3134303530393033353333325A301B31193017060355040313106573744 1264 578616D706C654341204E774F302062300D06092A620673410101050003204F00 1265 30204A02204100EF6B677A3247C1FC03D2B9BAF113E5E7E11F49E0421120E6B83 1266 84160F2BF02630EF544D5FD0D5623B35713C79A7229283A7908751A634AA420A3 1267 E2A4B1F10519D046F02F5A5DD6D760C2A842356E067B7BD94338D1FAA3B3DDD48 1268 13060A207B0A097067007E45B052B60FDBAE4656E11562C4F5ABB7B0CF87A79D2 1269 21F1127313C53371CE1245D63DB45A1203A23340BA08042C768D03B8076A028D3 1270 A51D87D2EF107BBD6F2305CE5E67668724002FB726DF9C14476C37DE0F55033F1 1271 92A5AD21F9A2A71C20301000134B050300E0603551D0F0101F104030204C1D060 1272 3551D0E04160414112966E304761732FBFE6A2C823C301F0603551D2304183016 1273 5084D321CA0135E77217A486B686B334B00D06092A62067341010505000320410 1274 0B382BA3355A50E287BAE15758B3BEFF63D34D3E357B90031495D018868E49589 1275 B9FAF46A4AD49B1D35B06EF380106677440934663C2CC111C183655F4DC41C0B3 1276 401123D35387389DB91F1E1B4131B16C291D35730B3F9B33C7475124851555FE5 1277 FC647E8FD029605367C7E01281BF6617110021B0D10847DCE0E9F0CA6C764B633 1278 4784055172C3983D1E3A3A82301A54FCC9B0670C543A1C747164619101FF23B24 1279 0B2A26394C1F7D38D0E2F4747928ECE5C34627A075A8B3122011E9D9158055C28 1280 F020C330206BC20102020102300D06092A6206734101050500301B31193017060 1281 355040313106573744578616D706C654341204E774E301E170D31333035303930 1282 33353333325A170D3134303530393033353333325A301B3119301706035504031 1283 3106573744578616D706C654341204F774E302062300D06092A62067341010105 1284 0003204F0030204A022041003A923A2968BAE4AAE136CA4E2512C520068035848 1285 2AC39D6F640E4574E654EA35F48B1E054C5DA3372872F7A1E429F4EDF3958432E 1286 FB2106591D3EB783C1034709F251FC86566BDA2D541C792389EAC4EC9E181F4B9 1287 F596E5EF2679CC321542B11337F90A44DF3C85F1516561FA968A1914F265BC0B8 1288 276EBE3106A790D97D34C8C37C74FE1C30B396424664AC426284A9F6022E02693 1289 8436880ADFCD95C98CA1DFC2E6D75319B85D0458DE28A9D13FB16D620FFF7541F 1290 6A25D7DAF004355020301000134B050300E0603551D0F0101F104030204C1D060 1291 3551D0E04160414084D321CA0135E77217A486B686B334B01F0603551D2304183 1292 01653112966E304761732FBFE6A2C823C300D06092A6206734101050500032041 1293 002E106933A443070ACF5594A3A584D08AF7E06C295059370A06639EFF9BD418D 1294 13BC25A298223164A6CF1856B11A81617282E4A410D82EF086839C6E235690322 1295 763065455351E4C596ACC7C016B225DEC094706C2A10608F403B10821984C7C15 1296 2343B18A768C2AD30238DC45DD653EE6092B0D5CD4C2F7D236043269357F76D13 1297 F95FB5F00D0E19263C6833948E1BA612CE8197AF650E25D882C12F4B6B9B67252 1298 C608EF064ACA3F9BC867D71172349D510BB7651CD43883773D927DEB41C467302 1299 0BB302063C201020209009B9DDA3324700D06092A6206734101050500301B3119 1300 3017060355040313106573744578616D706C654341204E774E301E170D3133303 1301 530393033353333325A170D3134303530393033353333325A301B311930170603 1302 55040313106573744578616D706C654341204E774E302062300D06092A6206734 1303 10101050003204F0030204A02204100EF6B677A3247C1FC03D2B9BAF113E5E7E1 1304 1F49E0421120E6B8384160F2BF02630EF544D5FD0D5623B35713C79A7229283A7 1305 908751A634AA420A3E2A4B1F10519D046F02F5A5DD6D760C2A842356E067B7BD9 1306 4338D1FAA3B3DDD4813060A207B0A097067007E45B052B60FDBAE4656E11562C4 1307 F5ABB7B0CF87A79D221F1127313C53371CE1245D63DB45A1203A23340BA08042C 1308 768D03B8076A028D3A51D87D2EF107BBD6F2305CE5E67668724002FB726DF9C14 1309 476C37DE0F55033F192A5AD21F9A2A71C20301000130B040300F0603551D13010 1310 1F10530030101FC1D0603551D0E04160414112966E304761732FBFE6A2C823C30 1311 0E0603551D0F0101F10403020106300D06092A620673410105050003204100423 1312 F06D4B760F4B42744A279035571696F272A0060F1325A40898509601AD14004F6 1313 52DB6312A1475C4D7CD50F4B269035585D7856C5337765A66B38462D5BDAA7778 1314 AAB24BBE2815E37722CD10E7166C50E75AB75A1271324460211991E7445A2960F 1315 47351A1A62925334119794B90E320BC730D6C1BEE496E7AC125CE9A1ECA595A3A 1316 4C54A865E6B623C9247BFD0A7C19B56077392555C955E233642BEC643AE37C166 1317 C5E221D797AEA3748F0391C8D692A5CF9BB71F6D0E37984D6FA673A30D0C00634 1318 3116F58403100 1320 A.2. csrattrs 1322 In the following valid /csrattrs exchange, the EST-coaps client 1323 authenticates itself with a certificate issued by the connected CA. 1325 The initial DTLS handshake is identical to the enrollment example. 1326 The IPv6 CoAP GET request looks like: 1328 REQ: 1329 GET coaps://[2001:db8::2:1]:61616/est/att 1330 (Content-Format: TBD6) 1332 A 2.05 Content response contains attributes which are relevant for 1333 the authenticated client. In this example, the EST-coaps server 1334 returns two attributes that the client can ignore when they are 1335 unknown to him. 1337 A.3. enroll / reenroll 1339 During the Enroll/Reenroll exchange, the EST-coaps client uses a CSR 1340 (Content-Format TBD7) request in the POST request payload. 1342 After verification of the CSR by the server, a 2.05 Content response 1343 with the issued certificate will be returned to the client. As 1344 described in Section 4.4, if the server is not able to provide a 1345 response immediately, it sends an empty ACK with response code 5.03 1346 (Service Unavailabel) and the Max-Age option. See Figure 3 for an 1347 example exchange. 1349 [EDNOTE: When redoing this example, given that proof of possession 1350 (POP) is also used, make sure it is obvious that the 1351 ChallengePassword attribute in the CSR is valid HMAC output. HMAC- 1352 REAL.] 1353 POST [2001:db8::2:1]:61616/est/sen 1354 (token 0x45) 1355 (Content-Format: TBD7) 1356 h'30208530206d020100301f311d301b0603550403131464656d6f7374657034203 1357 1333638313431333532302062300d06092a620673410101050003204f0030204a 1358 022041005d9f4dffd3c5949f646a9584367778560950b355c35b8e34726dd3764 1359 54231734795b4c09b9c6d75d408311307a81f7adef7f5d241f7d5be85620c5d44 1360 38bbb4242cf215c167f2ccf36c364ea2618a62f0536576369d6304e6a96877224 1361 7d86824f079faac7a6f694cfda5b84c42087dc062d462190c525813f210a036a7 1362 37b4f30d8891f4b75559fb72752453146332d51c937557716ccec624f5125c3a4 1363 447ad3115020048113fef54ad554ee88af09a2583aac9024075113db4990b1786 1364 b871691e0f02030100018701f06092a620673410907311213102b72724369722f 1365 372b45597535305434300d06092a620673410105050003204100441b40177a3a6 1366 5501487735a8ad5d3827a4eaa867013920e2afcda87aa81733c7c0353be47e1bf 1367 a7cda5176e7ccc6be22ae03498588d5f2de3b143f2b1a6175ec544e8e7625af6b 1368 836fd4416894c2e55ea99c6606f69075d6d53475d410729aa6d806afbb9986caf 1369 7b844b5b3e4545f19071865ada007060cad6db26a592d4a7bda7d586b68110962 1370 17071103407553155cddc75481e272b5ed553a8593fb7e25100a6f7605085dab4 1371 fc7e0731f0e7fe305703791362d5157e92e6b5c2e3edbcadb40' 1373 RET: 1374 (Content-Format: TBD2)(token =0x45) 1375 2.01 Created 1376 h'3020f806092a62067341070283293020e50201013100300b06092a62067341070 1377 1830b3020c730206fc20102020115300d06092a6206734101050500301b311930 1378 17060355040313106573744578616d706c654341204e774e301e170d313330353 1379 0393233313535335a170d3134303530393233313535335a301f311d301b060355 1380 0403131464656d6f73746570342031333638313431333532302062300d06092a6 1381 20673410101050003204f0030204a022041005d9f4dffd3c5949f646a95843677 1382 78560950b355c35b8e34726dd376454231734795b4c09b9c6d75d408311307a81 1383 f7adef7f5d241f7d5be85620c5d4438bbb4242cf215c167f2ccf36c364ea2618a 1384 62f0536576369d6304e6a968772247d86824f079faac7a6f694cfda5b84c42087 1385 dc062d462190c525813f210a036a737b4f30d8891f4b75559fb72752453146332 1386 d51c937557716ccec624f5125c3a4447ad3115020048113fef54ad554ee88af09 1387 a2583aac9024075113db4990b1786b871691e0f020301000134b050300e060355 1388 1d0f0101f104030204c1d0603551d0e04160414e81d0788aa2710304c5ecd4d1e 1389 065701f0603551d230418301653112966e304761732fbfe6a2c823c300d06092a 1390 6206734101050500032041002910d86f2ffeeb914c046816871de601567d291b4 1391 3fabee0f0e8ff81cea27302a7133e20e9d04029866a8963c7d14e26fbe8a0ab1b 1392 77fbb1214bbcdc906fbc381137ec1de685f79406c3e416b8d82f97174bc691637 1393 5a4e1c4bf744c7572b4b2c6bade9fb35da786392ee0d95e3970542565f3886ad6 1394 7746d1b12484bb02616e63302dc371dc6006e431fb7c457598dd204b367b0b3d3 1395 258760a303f1102db26327f929b7c5a60173e1799491b69150248756026b80553 1396 171e4733ad3d13c0103100' 1398 A.4. serverkeygen 1400 During this valid /serverkeygen exchange, the EST-coaps client 1401 authenticates itself using the certificate provided by the connected 1402 CA. 1404 The initial DTLS handshake is identical to the enrollment example. 1405 The CoAP GET request looks like: 1407 [EDNOTE: same comment as HMAC-REAL above applies.] 1409 [EDNOTE: Suggestion to have only one example with complete encrypted 1410 payload (the short one) and point out the different fields. Update 1411 this example according to the agreed upon solution from Section 4.5. 1412 ] 1414 POST coaps://192.0.2.1:8085/est/skg 1415 (token 0xa5) 1416 (Content-Format: TBD7)(Max-Age=120) 1418 h'302081302069020100305b313e303c060355040313357365727665724b6579476 1419 56e2072657120627920636c69656e7420696e2064656d6f207374657020313220 1420 3133363831343139353531193017060355040513105049443a576964676574205 1421 34e3a3130302062300d06092a620673410101050003204f0030204a02204100f4 1422 dfa6c03f7f2766b23776c333d2c0f9d1a7a6ee36d01499bbe6f075d1e38a57e98 1423 ecc197f51b75228454b7f19652332de5e52e4a974c6ae34e1df80b33f15f47d3b 1424 cbf76116bb0e4d3e04a9651218a476a13fc186c2a255e4065ff7c271cff104e47 1425 31fad53c22b21a1e5138bf9ad0187314ac39445949a48805392390e78c7659621 1426 6d3e61327a534f5ea7721d2b1343c7362b37da502717cfc2475653c7a3860c5f4 1427 0612a5db6d33794d755264b6327e3a3263b149628585b85e57e42f6b3277591b0 1428 2030100018701f06092a6206734109073112131064467341586d4a6e6a6f6b427 1429 4447672300d06092a620673410105050003204100472d11007e5a2b2c2023d47a 1430 6d71d046c307701d8ebc9e47272713378390b4ee321462a3dbe54579f5a514f6f 1431 4050af497f428189b63655d03a194ef729f101743e5d03fbc6ae1e84486d1300a 1432 f9288724381909188c851fa9a5059802eb64449f2a3c9e441353d136768da27ff 1433 4f277651d676a6a7e51931b08f56135a2230891fd184960e1313e7a1a9139ed19 1434 28196867079a456cd2266cb754a45151b7b1b939e381be333fea61580fe5d25bf 1435 4823dbd2d6a98445b46305c10637e202856611' 1437 RET: 1438 2.01 Content (Content-Format: TBD8) 1439 (token=0xa5) 1441 [TBD5, 1442 h'30213e020100300d06092a6206734101010500042128302124020100022041003 1443 c0bc2748f2003e3e8ea15f746f2a71e83f585412b92cf6f8e64de02e056153274 1444 dd01c95dd9cff3112aa141774ab655c3d56359c3b3df055294692ed848e7e30a1 1445 1bf14e47e0693d93017022b4cdb3e6d40325356152b213c8b535851e681a7074c 1446 0c6d2b60e7c32fc0336b28e743eba4e5921074d47195d3c05e43c527526e692d5 1447 45e562578d2d4b5f2191bff89d3eef0222764a2674637a1f99257216647df6704 1448 efec5adbf54dab24231844eb595875795000e673dd6862310a146ad7e31083010 1449 001022041004e6b3f78b7791d6377f33117c17844531c81111fb8000282816264 1450 915565bc7c3f3f643b537a2c69140a31c22550fa97e5132c61b74166b68626704 1451 260620333050f510096b6570f5880e7e1c15dc0ca6ce2b5f187e2325da14ab705 1452 ad004717f3b2f779127b5c535e0cee6a343b502722f2397a26126e0af606b5aa7 1453 f96313511c0b7eb26354f91b82269de62757e3def807a6afdf83ddcbb0614bb7c 1454 542e6975d6456554e7bd9988fbd1930cd44d0e01ee9182ca54539418653150254 1455 1ad1a2a11e5021040bfce554b642c29131e7d65455e83c5406d76771912f758f5 1456 ee3ee36af386f38ffa313c0f661880c5a2b0970485d36f528e7f77a2e55b4ad76 1457 1242d1c2f75939c8061217d31491d305d3e07d6161c43e26f7de4477b1811de92 1458 33dc75b426302104015bf48ac376f52887813461fc54635517bcb67293837053e 1459 8ce1a33da7a35565a75a370dc14555b5316cb55742380350774d769d151ff0456 1460 0214389a232a2258326163167504cfce44cd316f63bb8a52da53a4cb74fd87194 1461 c0844881f791f23b0813ea0921325edd14459d41c8a1593f04316388e40b35fef 1462 7d2a195a5930fa54774427ac821eee2c62790d2c17bd192af794c611011506557 1463 83d4efe22185cbd83368786f2b1e68a5a27067e321066f0217b4b6d7971a3c21a 1464 241366b7907187583b511102103369047e5cce0b65012200df5ec697b5827575c 1465 db6821ff299d6a69574b31ddf0fbe9245ea2f74396c24b3a7565067e41366423b 1466 5bdd2b2a78194094dbe333f493d159b8e07722f2280d48388db7f1c9f0633bb0e 1467 173de2c3aa1f200af535411c7090210401421e2ea217e37312dcc606f453a6634 1468 f3df4dc31a9e910614406412e70eec9247f10672a500947a64356c015a845a7d1 1469 50e2e3911a2b3b61070a73247166da10bb45474cc97d1ec2bc392524307f35118 1470 f917438f607f18181684376e13a39e07', 1471 TBD2, 1472 h'3020c506092a62067341070283363020f20201013100300b06092a62067341070 1473 183183020d430207cc20102020116300d06092a6206734101050500301b311930 1474 17060355040313106573744578616d706c654341204e774e301e170d313330353 1475 0393233323535365a170d3134303530393233323535365a302c312a3028060355 1476 0403132173657276657273696465206b65792067656e657261746564207265737 1477 06f6e7365302062300d06092a620673410101050003204f0030204a022041003c 1478 0bc2748f2003e3e8ea15f746f2a71e83f585412b92cf6f8e64de02e056153274d 1479 d01c95dd9cff3112aa141774ab655c3d56359c3b3df055294692ed848e7e30a11 1480 bf14e47e0693d93017022b4cdb3e6d40325356152b213c8b535851e681a7074c0 1481 c6d2b60e7c32fc0336b28e743eba4e5921074d47195d3c05e43c527526e692d54 1482 5e562578d2d4b5f2191bff89d3eef0222764a2674637a1f99257216647df6704e 1483 fec5adbf54dab24231844eb595875795000e673dd6862310a146ad7e310830100 1484 0134b050300e0603551d0f0101f104030204c1d0603551d0e04160414764b1bd5 1485 e69935626e476b195a1a8c1f0603551d230418301653112966e304761732fbfe6 1486 a2c823c300d06092a620673410105050003204100474e5100a9cdaaa813b30f48 1487 40340fb17e7d6d6063064a5a7f2162301c464b5a8176623dfb1a4a484e618de1c 1488 3c3c5927cf590f4541233ff3c251e772a9a3f2c5fc6e5ef2fe155e5e385deb846 1489 b36eb4c3c7ef713f2d137ae8be4c022715fd033a818d55250f4e6077718180755 1490 a4fa677130da60818175ca4ab2af1d15563624c51e13dfdcf381881b72327e2f4 1491 9b7467e631a27b5b5c7d542bd2edaf78c0ac294f3972278996bdf673a334ff74c 1492 84aa7d65726310252f6a4f41281ec10ca2243864e3c5743103100'] 1493 Without the DecryptKeyIdentifier attribute, the response has no 1494 additional encryption beyond DTLS. 1496 The response contains first a preamble that can be ignored. The EST- 1497 coaps server can use the preamble to include additional explanations, 1498 like ownership or support information 1500 Appendix B. EST-coaps Block message examples 1502 Two examples are presented: (1) a cacerts exchange shows the use of 1503 Block2 and the block headers, and (2) a enroll exchange shows the 1504 Block1 and Block2 size negotiation for request and response payloads. 1506 B.1. cacerts block example 1508 This section provides a detailed example of the messages using DTLS 1509 and BLOCK option Block2. The minimum PMTU is 1280 bytes, which is 1510 the example value assumed for the DTLS datagram size. The example 1511 block length is taken as 64 which gives an SZX value of 2. 1513 The following is an example of a valid /cacerts exchange over DTLS. 1514 The content length of the cacerts response in appendix A.1 of 1515 [RFC7030] is 4246 bytes using base64. This leads to a length of 2509 1516 bytes in binary. The CoAP message adds around 10 bytes, the DTLS 1517 record 29 bytes. To avoid IP fragmentation, the CoAP block option is 1518 used and an MTU of 127 is assumed to stay within one IEEE 802.15.4 1519 packet. To stay below the MTU of 127, the payload is split in 39 1520 packets with a payload of 64 bytes each, followed by a packet of 13 1521 bytes. The client sends an IPv6 packet containing the UDP datagram 1522 with the DTLS record that encapsulates the CoAP Request 40 times. 1523 The server returns an IPv6 packet containing the UDP datagram with 1524 the DTLS record that encapsulates the CoAP response. The CoAP 1525 request-response exchange with block option is shown below. Block 1526 option is shown in a decomposed way (block-option:NUM/M/size) 1527 indicating the kind of Block option (2 in this case because used in 1528 the response) followed by a colon, and then the block number (NUM), 1529 the more bit (M = 0 in lock2 response means last block), and block 1530 size with exponent (2**(SZX+4)) separated by slashes. The Length 64 1531 is used with SZX= 2 to avoid IP fragmentation. The CoAP Request is 1532 sent with confirmable (CON) option and the content format of the 1533 Response is /application/cacerts. 1535 GET /192.0.2.1:8085/est/crts (2:0/0/64) --> 1536 <-- (2:0/1/64) 2.05 Content 1537 GET /192.0.2.1:8085/est/crts (2:1/0/64) --> 1538 <-- (2:1/1/64) 2.05 Content 1539 | 1540 | 1541 | 1542 GET /192.0.2.1:8085/est/crts (2:39/0/64) --> 1543 <-- (2:39/0/64) 2.05 Content 1545 40 blocks have been sent with partially filled block NUM=39 as last 1546 block. 1548 For further detailing the CoAP headers, the first two blocks are 1549 written out. 1551 The header of the first GET looks like: 1553 Ver = 1 1554 T = 0 (CON) 1555 Code = 0x01 (0.1 GET) 1556 Token = 0x9a (client generated) 1557 Options 1558 Option1 (Uri-Host) [optional] 1559 Option Delta = 0x3 (option nr = 3) 1560 Option Length = 0x9 1561 Option Value = 192.0.2.1 1562 Option2 (Uri-Port) [optional] 1563 Option Delta = 0x4 (option nr = 3+4=7) 1564 Option Length = 0x4 1565 Option Value = 8085 1566 Option3 (Uri-Path) 1567 Option Delta = 0x4 (option nr = 7+4=11) 1568 Option Length = 0x5 1569 Option Value = "est" 1570 Option4 (Uri-Path) 1571 Option Delta = 0x0 (option nr = 11+0=11) 1572 Option Length = 0x6 1573 Option Value = "crts" 1574 Payload = [Empty] 1576 The header of the first response looks like: 1578 Ver = 1 1579 T = 2 (ACK) 1580 Code = 0x45 (2.05 Content) 1581 Token = 0x9a (copied by server) 1582 Options 1583 Option1 (Content-Format) 1584 Option Delta = 0xC (option nr =12) 1585 Option Length = 0x2 1586 Option Value = TBD2 1587 Option2 (Block2) 1588 Option Delta = 0xB (option 23 = 12 + 11) 1589 Option Length = 0x1 1590 Option Value = 0x0A (block number = 0, M=1, SZX=2) 1591 Payload = 1592 h'30233906092a6206734107028c2a3023260201013100300b06092a6206734107018 1593 c0c3020bb302063c20102020900a61e75193b7acc0d06092a6206734101' 1595 The second Block2: 1597 Ver = 1 1598 T = 2 (means ACK) 1599 Code = 0x45 (2.05 Content) 1600 Token = 0x9a (copied by server) 1601 Options 1602 Option1 (Content-Format) 1603 Option Delta = 0xC (option nr =12) 1604 Option Length = 0x2 1605 Option Value = TBD2 1606 Option2 (Block2) 1607 Option Delta = 0xB (option 23 = 12 + 11) 1608 Option Length = 0x1 1609 Option Value = 0x1A (block number = 1, M=1, SZX=2) 1610 Payload = 1611 h'05050030 1612 1b31193017060355040313106573744578616d706c654341204f774f301e170d313 1613 3303530393033353333315a170d3134303530393033353333315a' 1615 The 40th and final Block2: 1617 Ver = 1 1618 T = 2 (means ACK) 1619 Code = 0x45 (2.05 Content) 1620 Token = 0x9a (copied by server) 1621 Options 1622 Option1 (Content-Format) 1623 Option Delta = 0xC (option nr =12) 1624 Option Length = 0x2 1625 Option Value = TBD2 1626 Option2 (Block2) 1627 Option Delta = 0xB (option 23 = 12 + 11) 1628 Option Length = 0x2 1629 Option Value = 0x272 (block number = 39, M=0, SZX=2) 1630 Payload = h'73a30d0c006343116f58403100' 1632 B.2. enroll block example 1634 In this example the requested block2 size of 256 bytes, required by 1635 the client, is transferred to the server in the very first request 1636 message. The request/response consists of two parts: part1 1637 containing the CSR transferred to the server, and part2 contains the 1638 certificate transferred back to the client. The block size 1639 256=(2**(SZX+4)) which gives SZX=4. The notation for block numbering 1640 is the same as in Appendix B.1. It is assumed that CSR takes N1+1 1641 blocks and Cert response takes N2+1 blocks. The header fields and 1642 the payload are omitted to show the block exchange. The type of 1643 payload is shown within curly brackets. 1645 POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256) {CSR req} --> 1646 <-- (ACK) (1:0/1/256) (2.31 Continue) 1647 POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256) {CSR req} --> 1648 <-- (ACK) (1:1/1/256) (2.31 Continue) 1649 . 1650 . 1651 . 1652 POST [2001:db8::2:1]:61616/est/sen (CON)(1:N1/0/256){CSR req} --> 1653 <-- (ACK) (1:N1/0/256) (2:0/1/256) (2.04 Changed){Cert resp} 1654 POST [2001:db8::2:1]:61616/est/sen (CON)(2:1/0/256) --> 1655 <-- (ACK) (2:1/1/256) (2.04 Changed) {Cert resp} 1656 . 1657 . 1658 . 1659 POST [2001:db8::2:1]:61616/est/sen (CON)(2:N2/0/256) --> 1660 <-- (ACK) (2:N2/0/256) (2.04 Changed) {Cert resp} 1662 Figure 5: EST-COAP enrolment with multiple blocks 1664 N1+1 blocks have been transferred from client to server and N2+1 1665 blocks have been transferred from server to client. 1667 Authors' Addresses 1669 Peter van der Stok 1670 Consultant 1672 Email: consultancy@vanderstok.org 1674 Panos Kampanakis 1675 Cisco Systems 1677 Email: pkampana@cisco.com 1679 Sandeep S. Kumar 1680 Philips Lighting Research 1681 High Tech Campus 7 1682 Eindhoven 5656 AE 1683 NL 1685 Email: ietf@sandeep.de 1686 Michael C. Richardson 1687 Sandelman Software Works 1689 Email: mcr+ietf@sandelman.ca 1690 URI: http://www.sandelman.ca/ 1692 Martin Furuhed 1693 Nexus Group 1695 Email: martin.furuhed@nexusgroup.com 1697 Shahid Raza 1698 RISE SICS 1699 Isafjordsgatan 22 1700 Kista, Stockholm 16440 1701 SE 1703 Email: shahid@sics.se