draft-ietf-ace-coap-est-00.txt   draft-ietf-ace-coap-est-01.txt 
ACE P. van der Stok ACE P. van der Stok
Internet-Draft Consultant Internet-Draft Consultant
Intended status: Standards Track P. Kampanakis Intended status: Standards Track P. Kampanakis
Expires: September 1, 2018 Cisco Systems Expires: December 8, 2018 Cisco Systems
S. Kumar S. Kumar
Philips Lighting Research Philips Lighting Research
M. Richardson M. Richardson
SSW SSW
M. Furuhed M. Furuhed
Nexus Group Nexus Group
S. Raza S. Raza
RISE SICS RISE SICS
February 28, 2018 June 6, 2018
EST over secure CoAP (EST-coaps) EST over secure CoAP (EST-coaps)
draft-ietf-ace-coap-est-00 draft-ietf-ace-coap-est-01
Abstract Abstract
Enrollment over Secure Transport (EST) [RFC7030] is used as a Enrollment over Secure Transport (EST) is used as a certificate
certificate management protocol over HTTPS. provisioning protocol over HTTPS. Low-resource devices often use the
lightweight Constrained Application Protocol (CoAP) for message
Low-resource devices often use the lightweight Constrained exchanges. This document defines how to transport EST payloads over
Application Protocol (CoAP) [RFC7252] for message exchanges. This secure CoAP (EST-coaps), which allows low-resource constrained
document defines how to transport EST payloads over secure CoAP (EST- devices to use existing EST functionality for provisioning
coaps). This allows low-resource constrained devices to re-use certificates.
existing EST functionality. Example low-resource use cases for EST
are: secure bootstrapping and certificate enrollment.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 1, 2018. This Internet-Draft will expire on December 8, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. EST operational differences . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 3. Conformance to RFC7925 profiles . . . . . . . . . . . . . . . 3
2. Conformance to RFC7925 profiles . . . . . . . . . . . . . . . 4 4. Protocol Design . . . . . . . . . . . . . . . . . . . . . . . 4
3. Protocol Design and Layering . . . . . . . . . . . . . . . . 5 4.1. Payload format . . . . . . . . . . . . . . . . . . . . . 5
3.1. Payload format . . . . . . . . . . . . . . . . . . . . . 6 4.2. Message Bindings . . . . . . . . . . . . . . . . . . . . 6
3.2. Message Bindings . . . . . . . . . . . . . . . . . . . . 6 4.3. CoAP response codes . . . . . . . . . . . . . . . . . . . 6
3.3. CoAP response codes . . . . . . . . . . . . . . . . . . . 6 4.4. Delayed Results . . . . . . . . . . . . . . . . . . . . . 6
3.4. Message fragmentation . . . . . . . . . . . . . . . . . . 7 4.5. Server-side Key Generation . . . . . . . . . . . . . . . 7
3.5. Deployment limits . . . . . . . . . . . . . . . . . . . . 8 4.6. Message fragmentation . . . . . . . . . . . . . . . . . . 8
4. Discovery and URI . . . . . . . . . . . . . . . . . . . . . . 8 4.7. Deployment limits . . . . . . . . . . . . . . . . . . . . 9
5. DTLS Transport Protocol . . . . . . . . . . . . . . . . . . . 10 5. Discovery and URI . . . . . . . . . . . . . . . . . . . . . . 9
6. Proxying . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6. DTLS Transport Protocol . . . . . . . . . . . . . . . . . . . 10
7. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 12 7. HTTPS-CoAPS Registrar . . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 8. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Content-Format registry . . . . . . . . . . . . . . . . . 12 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8.2. Resource Type registry . . . . . . . . . . . . . . . . . 14 9.1. Media-Type Registry . . . . . . . . . . . . . . . . . . . 14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 15 9.2. Content-Format Registry . . . . . . . . . . . . . . . . . 15
9.1. proxy considerations . . . . . . . . . . . . . . . . . . 15 9.2.1. Content Format application/multict . . . . . . . . . 16
9.2. EST server considerations . . . . . . . . . . . . . . . . 15 9.3. Resource Type registry . . . . . . . . . . . . . . . . . 17
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16 10. Security Considerations . . . . . . . . . . . . . . . . . . . 17
11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 16 10.1. EST server considerations . . . . . . . . . . . . . . . 17
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 10.2. HTTPS-CoAPS Registrar considerations . . . . . . . . . . 18
12.1. Normative References . . . . . . . . . . . . . . . . . . 16 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18
12.2. Informative References . . . . . . . . . . . . . . . . . 17 12. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 19
Appendix A. EST messages to EST-coaps . . . . . . . . . . . . . 19 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
A.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 20 13.1. Normative References . . . . . . . . . . . . . . . . . . 19
A.2. csrattrs . . . . . . . . . . . . . . . . . . . . . . . . 22 13.2. Informative References . . . . . . . . . . . . . . . . . 21
A.3. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 22 Appendix A. EST messages to EST-coaps . . . . . . . . . . . . . 22
A.4. serverkeygen . . . . . . . . . . . . . . . . . . . . . . 24 A.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 23
Appendix B. Encoding for server side key generation . . . . . . 26 A.2. csrattrs . . . . . . . . . . . . . . . . . . . . . . . . 26
Appendix C. EST-coaps Block message examples . . . . . . . . . . 26 A.3. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28 A.4. serverkeygen . . . . . . . . . . . . . . . . . . . . . . 29
Appendix B. EST-coaps Block message examples . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35
1. Introduction 1. Introduction
Enrollment over Secure Transport (EST) [RFC7030] is used for "Classical" Enrollment over Secure Transport (EST) [RFC7030] is used
authenticated/authorized endpoint certificate enrollment (and for authenticated/authorized endpoint certificate enrollment (and
optionally key provisioning) through a Certificate Authority (CA) or optionally key provisioning) through a Certificate Authority (CA) or
Registration Authority (RA). This functionality is also needed for Registration Authority (RA). EST messages run over HTTPS.
low resource devices.
"Classical" EST uses HTTPS and this specification defines a new
transport for EST using CoAP. It also profiles the use of EST to a
smaller subset.
IPv6 over Low-power Wireless Personal Area Networks (6LoWPANs)
[RFC4944] on IEEE 802.15.4 [ieee802.15.4] wireless networks are
becoming common in many industry application domains such as lighting
controls. Although IEEE 802.15.4 defines how security can be enabled
between nodes within a single mesh network, it does not specify the
provisioning and management of the keys. Therefore, securing a
6LoWPAN network with devices from multiple manufacturers with
different provisioning techniques is often tedious and time
consuming. An example use case is the application of Bootstrapping
of Remote Secure Infrastructures (BRSKI)
[I-D.ietf-anima-bootstrapping-keyinfra]. The low resource aspects
are detailed for 6tisch in [I-D.ietf-6tisch-minimal-security] and
[I-D.ietf-6tisch-dtsecurity-secure-join].
Constrained networks use DTLS [RFC6347], CoAP [RFC7252], and UDP
instead of TLS [RFC5246], HTTP [RFC7230] and TCP. EST-coaps replaces
the invocations of TLS and HTTP by DTLS and CoAP invocations thus
enabling EST for CoAP-based low-resource devices.
Because the relatively large EST messages cannot be readily
transported over constrained (6LoWPAN, LLN) wireless networks, this
document specifies the use of CoAP Block-Wise Transfer ("Block")
[RFC7959] to fragment EST messages at the application layer.
1.1. EST operational differences
Only the differences to EST with respect to operational scenarios are
described in this section. EST-coaps server differs from EST server
as follows:
o Replacement of TLS by DTLS and HTTP by CoAP, resulting in:
* DTLS-secured CoAP sessions between EST-coaps client and EST-
coaps server.
o Only certificate-based client authentication is supported, which This document defines a new transport for EST based on the
results in: Constrained Application Protocol (CoAP) since some Internet of Things
(IoT) devices use CoAP instead of HTTP. Therefore, this
specification utilizes DTLS [RFC6347], CoAP [RFC7252], and UDP
instead of TLS [RFC5246], HTTP [RFC7230] and TCP.
* The EST-coaps client does not support HTTP Basic authentication EST messages may be relatively large and for this reason this
(as described in Section 3.2.3 of [RFC7030]). document also uses CoAP Block-Wise Transfer [RFC7959] to offer a
fragmentation mechanism of EST messages at the CoAP layer. COAP
Observe options [RFC7641] are also used to convey delayed EST
responses to clients.
* The EST-coaps client does not support authentication at the This specification also profiles the use of EST to only support
application layer (as described in Section 3.2.3 of [RFC7030]). certificate-based client Authentication. HTTP Basic or Digest
authentication (as described in Section 3.2.3 of [RFC7030] are not
supported.
1.2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
Many of the concepts in this document are taken over from [RFC7030]. Many of the concepts in this document are taken over from [RFC7030].
Consequently, much text is directly traceable to [RFC7030]. The same Consequently, much text is directly traceable to [RFC7030]. The same
document structure is followed to point out the differences and document structure is followed to point out the differences and
commonalities between EST and EST-coaps. commonalities between EST and EST-coaps.
2. Conformance to RFC7925 profiles 3. Conformance to RFC7925 profiles
This section shows how EST-coaps fits into the profiles of low- This section shows how EST-coaps fits into the profiles of low-
resource devices as described in [RFC7925]. resource devices described in [RFC7925].
EST-coaps can transport certificates and private keys. Private keys EST-coaps can transport certificates and private keys. Certificates
can be transported as response to a request to a server-side key are responses to (re-)enrollment requests or request for a trusted
generation as described in section 4.4 of [RFC7030]. certificate list. Private keys can be transported as responses to a
request to a server-side keygeneration as described in section 4.4 of
[RFC7030] and discussed in Section 4.5 of this document.
The mandatory cipher suite for DTLS is The mandatory cipher suite for DTLS in EST-coaps is
TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 defined in [RFC7251] which is the TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 defined in [RFC7251] which is the
mandatory-to-implement cipher suite in CoAP. Additionally, the curve mandatory-to-implement cipher suite in CoAP. Additionally, the curve
secp256r1 MUST be supported [RFC4492]; this curve is equivalent to secp256r1 MUST be supported [RFC4492]; this curve is equivalent to
the NIST P-256 curve. The hash algorithm is SHA-256. DTLS the NIST P-256 curve. [Q-EDNOTE: the NIST P-256 curve is a MUST-
implementations MUST use the Supported Elliptic Curves and Supported according to the terminology of RFC8247, and Curve25519 is a
Point Formats Extensions [RFC4492]; the uncompressed point format SHOULD+].
MUST be supported; [RFC6090] can be used as an implementation method.
The EST-coaps client MUST be configured with an explicit TA database DTLS1.2 implementations MUST use the Supported Elliptic Curves and
or at least an implicit TA database from its manufacturer. The Supported Point Formats Extensions [RFC4492]. Uncompressed point
authentication of the EST-coaps server by the EST-coaps client is format MUST also be supported. [RFC6090] can be used as summary of
based on Certificate authentication in the DTLS handshake. the ECC algorithms. DTLS 1.3 implementations differ from DTLS 1.2
because they do not support point format negotiation in favor of a
single point format for each curve and thus support for DTLS 1.3 does
not mandate point formation extensions and negotiation.
The authentication of the EST-coaps client is based on client The EST-coaps client MUST be configured with at least an implicit TA
database from its manufacturer. The authentication of the EST-coaps
server by the EST-coaps client is based on certificate authentication
in the DTLS handshake.
The authentication of the EST-coaps client is based on a client
certificate in the DTLS handshake. This can either be certificate in the DTLS handshake. This can either be
o DTLS with a previously issued client certificate (e.g., an
existing certificate issued by the EST CA); this could be a common
case for simple re-enrollment of clients;
o DTLS with a previously installed certificate (e.g., manufacturer- o a previously issued client certificate (e.g., an existing
installed certificate or a certificate issued by some other certificate issued by the EST CA); this could be a common case for
party); simple re-enrollment of clients;
3. Protocol Design and Layering o a previously installed certificate (e.g., manufacturer-installed
certificate or a certificate issued by some other party); the
server is expected to trust the manufacturer's root CA certificate
in this case.
4. Protocol Design
EST-coaps uses CoAP to transfer EST messages, aided by Block-Wise EST-coaps uses CoAP to transfer EST messages, aided by Block-Wise
Transfer [RFC7959] to transport CoAP messages in blocks thus avoiding Transfer [RFC7959] to transport CoAP messages in blocks thus avoiding
(excessive) 6LoWPAN fragmentation of UDP datagrams. The use of (excessive) fragmentation of UDP datagrams. The use of "Block" for
"Block" for the transfer of larger EST messages is specified in the transfer of larger EST messages is specified in Section 4.6. The
Section 3.4. The Figure 1 below shows the layered EST-coaps Figure 1 below shows the layered EST-coaps architecture.
architecture.
+------------------------------------------------+ +------------------------------------------------+
| EST request/response messages | | EST request/response messages |
+------------------------------------------------+ +------------------------------------------------+
| CoAP for message transfer and signaling | | CoAP for message transfer and signaling |
+------------------------------------------------+ +------------------------------------------------+
| DTLS for transport security | | DTLS for transport security |
+------------------------------------------------+ +------------------------------------------------+
| UDP for transport | | UDP for transport |
+------------------------------------------------+ +------------------------------------------------+
Figure 1: EST-coaps protocol layers Figure 1: EST-coaps protocol layers
The EST-coaps protocol design follows closely the EST design. The The EST-coaps protocol design follows closely the EST design. The
parts supported by EST-coaps are identified by their message types: actions supported by EST-coaps are identified by their message types:
o Simple enroll and reenroll, for CA to sign public client-identity
key.
o CA certificate retrieval, needed to receive the complete set of CA o CA certificate retrieval, needed to receive the complete set of CA
certificates. certificates.
o CSR Attributes request messages, informs the client of the fields o Simple enroll and reenroll, for CA to sign public client-identity
to include in generated CSR. key.
o Certificate Signing Request (CSR) Attributes request messages,
informs the client of the fields to include in generated CSR.
o Server-side key generation messages, to provide a private client- o Server-side key generation messages, to provide a private client-
identity key when the client is too restricted or because of lack identity key when the client choses for an external entity to
of an entropy source. [EDNOTE: Encrypting these keys is generate its private key.
important. RFC7030 specifies how the private key can be encrypted
with CMS using symmetric or asymmetric keys. Mention how
symmetric key can be derived for EST server side key generation
from the TLS KEM draft.]
3.1. Payload format 4.1. Payload format
The content-format (media type equivalent) of the CoAP message The content-format (media type equivalent) of the CoAP message
determines which EST message is transported in the CoAP payload. The determines which EST message is transported in the CoAP payload. The
media types specified in the HTTP Content-Type header (see section media types specified in the HTTP Content-Type header (section 3.2.2
3.2.2 of [RFC7030]) are in EST-coaps specified by the Content-Format of [RFC7030]) are in EST-coaps specified by the Content-Format Option
Option (12) of CoAP. The combination of URI path-suffix and content- (12) of CoAP. The combination of URI path and content-format used
format used for CoAP MUST map to an allowed combination of path- for CoAP MUST map to an allowed combination of URI and media type as
suffix and media type as defined for EST. The required content- defined for EST. The required content-formats for these requests and
formats for these request and response messages are defined in response messages are defined in Section 9. The CoAP response codes
Section 8. The CoAP response codes are defined in Section 3.3. are defined in Section 4.3.
EST-coaps is designed for use between low-resource devices using CoAP EST-coaps is designed for use between low-resource devices and hence
and hence does not need to send base64-encoded data. Simple binary does not need to send base64-encoded data. Simple binary is more
is more efficient (30% less payload compared to base64) and well efficient (30% smaller payload) and well supported by CoAP.
supported by CoAP. Therefore, the content formats specification in Therefore, the content formats specification in Section 9 specifies
Section 8 requires the use of binary for all EST-coaps Content- that the binary payload is transported as a CBOR major type 2, a byte
Formats. string, for all EST-coaps Content-Formats. In the examples of
Appendix A, the base16 diagnostic notation is used for CBOR major
type 2, where h'450aafbb' represents an example binary payload.
3.2. Message Bindings 4.2. Message Bindings
This section describes the general EST CoAP message characteristics. The general EST CoAP message characteristics are:
It is RECOMMENDED to use CoAP CON messages. This recommendation does o All EST-coaps messages expect a response from the server, thus the
not influence the communication efficiency because all EST-coaps client MUST send the requests over confirmable CON COAP messages.
messages expect a response.
The Ver, TKL, Token, and Message ID values of the CoAP header are not o The Ver, TKL, Token, and Message ID values of the CoAP header are
influenced by EST. not affected by EST.
CoAP options are used to convey Uri-Host, Uri-Path, Uri-Port, o The CoAP options used are Uri-Host, Uri-Path, Uri-Port, Content-
Content-Format and more in CoAP. The CoAP Options are used to Format, and Location-Path in CoAP. These CoAP Options are used to
communicate the HTTP fields specified in the EST REST messages. communicate the HTTP fields specified in the EST REST messages.
EST URLs are HTTPS based (https://), in CoAP these will be assumed to o EST URLs are HTTPS based (https://), in CoAP these will be assumed
be transformed to coaps (coaps://) to be transformed to coaps (coaps://)
Appendix A includes some practical examples of EST messages Appendix A includes some practical examples of EST messages
translated to CoAP. translated to CoAP.
3.3. CoAP response codes 4.3. CoAP response codes
Section 5.9 of [RFC7252] specifies the mapping of HTTP response codes Section 5.9 of [RFC7252] specifies the mapping of HTTP response codes
to CoAP response codes. Every time the HTTP response code 200 is to CoAP response codes. Every time the HTTP response code 200 is
specified in [RFC7030] in response to a GET (POST) request, in EST- specified in [RFC7030] in response to a GET request, in EST-coaps the
coaps the equivalent CoAP response code 2.05 (2.01) MUST be used. equivalent CoAP response code 2.05 or 2.03 MUST be used. Similarly,
Response code HTTP 202 in EST is mapped to CoAP _.__. In 2.01, 2.02 or 2.04 MUST be used in response to POST EST requests.
[I-D.hartke-core-pending] it is specified how multiple concurrently Response code HTTP 202 has no equivalent in CoAP. In Section 4.4 it
open requests may be handled. All other HTTP 2xx response codes are is specified how EST requests over CoAP handle delayed messages.
not used by EST. For the following HTTP 4xx error codes that may
occur: 400, 401, 403, 404, 405, 406, 412, 413, 415; the equivalent
CoAP response code for EST-coaps is 4.xx. For the HTTP 5xx error
codes: 500, 501, 502, 503, 504 the equivalent CoAP response code is
5.xx.
3.4. Message fragmentation All other HTTP 2xx response codes are not used by EST. For the
following HTTP 4xx error codes that may occur: 400, 401, 403, 404,
405, 406, 412, 413, 415; the equivalent CoAP response code for EST-
coaps is 4.xx. For the HTTP 5xx error codes: 500, 501, 502, 503, 504
the equivalent CoAP response code is 5.xx.
4.4. Delayed Results
It is possible that responses are not always directly available by
the server, and may even require manual intervention to generate the
certificate for the server response. Delays of minutes to hours are
possible. Therefore, each GET request MUST be accompanied by the
observe option. When the result is directly available, the client
receives the result and forgets about the observe as specified in
section 3.6 of [RFC7641]. When a POST response is delayed, the POST
returns a 2.01 (Created) response code, having put a value in the
Location-Path option. After reception of 2.01 the client does a GET
request with the observe option to the newly returned location. Once
the delayed result is notified by the server, the client forgets
about the observe.
Next to the observe option the server MUST specify the Max-Age option
that indicates the maximum waiting time in minutes.
4.5. Server-side Key Generation
Constrained devices sometimes do not have the necessary hardware to
generate statistically random numbers for private keys and DTLS
ephemeral keys. Past experience has shown that low-resource
endpoints sometimes generate numbers which could allow someone to
decrypt the communication or guess the private key and impersonate as
the device. Studies have shown that the same keys are generated by
the same model devices deployed on-line.
Additionally, random number key generation is costly, thus energy
draining. Even though the random numbers that constitute the
identity/cert do not get generated often, an endpoint may not want to
spend time and energy generating keypairs, and just ask for one from
the server.
In these scenarios, server-side key generation can be used. The
client asks for the server or proxy to generate the private key and
the certificate which is transferred back to the client in the
server-side key generation response.
[RFC7030] recommends for the private key returned by the server to be
encrypted. The specification provides two methods to encrypt the
generated key, symmetric and asymmetric. The methods are signalled
by the client by using the relevant attributes (SMIMECapabilities and
DecryptKeyIdentifier or AsymmetricDecryptKeyIdentifier) in the CSR
request. In the symmetric key case, the key can be established out-
of-band or alternatively derived by the established TLS connection as
described in [RFC5705].
The sever-side key generation response is returned using a CBOR array
Section 9.2.1. The certificate part exactly matches the response
from a enrollment response. The private key is placed inside of a
CMS SignedData. The SignedData is signed by the party that generated
the private key, which may or may not be the EST server or the EST
CA. The SignedData is further protected by placing it inside of a
CMS EnvelopedData as explained in Section 4.4.2 of [RFC7030].
4.6. Message fragmentation
DTLS defines fragmentation only for the handshake part and not for DTLS defines fragmentation only for the handshake part and not for
secure data exchange (DTLS records). [RFC6347] states that to avoid secure data exchange (DTLS records). [RFC6347] states that to avoid
using IP fragmentation, which involves error-prone datagram using IP fragmentation, which involves error-prone datagram
reconstitution, invokers of the DTLS record layer SHOULD size DTLS reconstitution, invokers of the DTLS record layer SHOULD size DTLS
records so that they fit within any Path MTU estimates obtained from records so that they fit within any Path MTU estimates obtained from
the record layer. In addition, invokers residing on a 6LoWPAN over the record layer. In addition, invokers residing on a 6LoWPAN over
IEEE 802.15.4 network SHOULD attempt to size CoAP messages such that IEEE 802.15.4 network SHOULD attempt to size CoAP messages such that
each DTLS record will fit within one or two IEEE 802.15.4 frames. each DTLS record will fit within one or two IEEE 802.15.4 frames.
skipping to change at page 8, line 19 skipping to change at page 9, line 13
exacerbation of lost blocks. exacerbation of lost blocks.
The Size1 response MAY be parsed by the client as a size indication The Size1 response MAY be parsed by the client as a size indication
of the Block2 resource in the server response or by the server as a of the Block2 resource in the server response or by the server as a
request for a size estimate by the client. Similarly, Size2 option request for a size estimate by the client. Similarly, Size2 option
defined in BLOCK should be parsed by the server as an indication of defined in BLOCK should be parsed by the server as an indication of
the size of the resource carried in Block1 options and by the client the size of the resource carried in Block1 options and by the client
as a maximum size expected in the 4.13 (Request Entity Too Large) as a maximum size expected in the 4.13 (Request Entity Too Large)
response to a request. response to a request.
Examples of fragmented messages are shown in Appendix C. Examples of fragmented messages are shown in Appendix B.
3.5. Deployment limits 4.7. Deployment limits
Although EST-coaps paves the way for the utilization of EST for Although EST-coaps paves the way for the utilization of EST for
constrained devices on constrained networks, some devices will not constrained devices on constrained networks, some devices will not
have enough resources to handle the large payloads that come with have enough resources to handle the large payloads that come with
EST-coaps. The specification of EST-coaps is intended to ensure that EST-coaps. The specification of EST-coaps is intended to ensure that
EST works for networks of constrained devices that choose to limit EST works for networks of constrained devices that choose to limit
their communications stack to UDP/CoAP. It is up to the network their communications stack to UDP/CoAP. It is up to the network
designer to decide which devices execute the EST protocol and which designer to decide which devices execute the EST protocol and which
not. do not.
4. Discovery and URI 5. Discovery and URI
EST-coaps is targeted to low-resource networks with small packets. EST-coaps is targeted to low-resource networks with small packets.
Saving header space is important and an additional EST-coaps URI is Saving header space is important and an additional EST-coaps URI is
specified that is shorter than the EST URI. specified that is shorter than the EST URI.
In the context of CoAP, the presence and location of (path to) the In the context of CoAP, the presence and location of (path to) the
management data are discovered by sending a GET request to "/.well- management data are discovered by sending a GET request to "/.well-
known/core" including a resource type (RT) parameter with the value known/core" including a resource type (RT) parameter with the value
"ace.est" [RFC6690]. Upon success, the return payload will contain "ace.est" [RFC6690]. Upon success, the return payload will contain
the root resource of the EST resources. It is up to the the root resource of the EST resources. It is up to the
implementation to choose its root resource; throughout this document implementation to choose its root resource; throughout this document
the example root resource /est is used. The example below shows the the example root resource /est is used.
discovery of the presence and location of management data.
REQ: GET /.well-known/core?rt=ace.est
RES: 2.05 Content The individual EST-coaps server URIs differ from the EST URI by
</est>; rt="ace.est" replacing the scheme https by coaps and by specifying shorter
The additional EST-coaps server URIs differ from the EST URI by
replacing the scheme https by coaps and by specifying a shorter
resource path names: resource path names:
coaps://www.example.com/est/short-name coaps://www.example.com/.well-known/est/ArbitraryLabel/<short-est>.
The CoAP short URI exists next to the URI defined in [RFC7030].
coaps://www.example.com/.well-known/est/est-name The ArbitraryLabel Path-Segment SHOULD be of the shortest length
OR possible.
coaps://www.example.com/.well-known/est/ArbitraryLabel/est-name
Figure 5 in section 3.2.2 of [RFC7030] enumerates the operations and Figure 5 in section 3.2.2 of [RFC7030] enumerates the operations and
corresponding paths which are supported by EST. Table 1 provides the corresponding paths which are supported by EST. Table 1 provides the
mapping from the EST URI path to the shorter EST-coaps URI path. mapping from the EST URI path to the shorter EST-coaps URI path.
+------------------+-----------+ +------------------+-----------+
| EST | EST-coaps | | EST | EST-coaps |
+------------------+-----------+ +------------------+-----------+
| /cacerts | /crts | | /cacerts | /crts |
| /simpleenroll | /sen | | /simpleenroll | /sen |
| /simplereenroll | /sren | | /simplereenroll | /sren |
| /csrattrs | /att | | /csrattrs | /att |
| /serverkeygen | /skg | | /serverkeygen | /skg |
+------------------+-----------+ +------------------+-----------+
Table 1 Table 1
The short resource URIs MUST be supported. The corresponding longer
URIs specified in [RFC7030] MAY be supported.
When discovering the root path for the EST resources, the server MAY When discovering the root path for the EST resources, the server MAY
return the full resource paths and the used content types. This is return all available resource paths and the used content types. This
useful when multiple content types are specified for EST-coaps is useful when multiple content types are specified for EST-coaps
server. For example, the following more complete response is server. The example below shows the discovery of the presence and
possible. location of management data.
REQ: GET /.well-known/core?rt=ace.est REQ: GET /.well-known/core?rt=ace.est
RES: 2.05 Content RES: 2.05 Content
</est>; rt="ace.est" </est>; rt="ace.est"
</est/crts>; rt="ace.est";ct=TBD1 </est/crts>;ct=TBD2
</est/sen>; rt="ace.est";ct=TBD1 TBD4 </est/sen>;ct=TBD2 TBD7
</est/sren>; rt="ace.est";ct=TBD1 TBD4 </est/sren>;ct=TBD2 TBD7
</est/att>; rt="ace.est";ct=TBD4 </est/att>;ct=TBD6
</est/skg>; rt="ace.est";ct=TBD1 TBD4 TBD2 </est/skg>;ct=TBD1 TBD7 TBD8
The return of the content-types allows the client to choose the most The first line of the discovery response MUST be returned. The five
consecutive lines MAY be returned. The return of the content-types
in the last four lines allows the client to choose the most
appropriate one from multiple content types. appropriate one from multiple content types.
5. DTLS Transport Protocol 6. DTLS Transport Protocol
EST-coaps depends on a secure transport mechanism over UDP that can EST-coaps depends on a secure transport mechanism over UDP that can
secure (confidentiality, authenticity) the CoAP messages exchanged. secure (confidentiality, authenticity) the exchanged CoAP messages.
DTLS is one such secure protocol. When "TLS" is referred to in the DTLS is one such secure protocol. When "TLS" is referred to in the
context of EST, it is understood that in EST-coaps, security is context of EST, it is understood that in EST-coaps, security is
provided using DTLS instead. No other changes are necessary (all provided using DTLS instead. No other changes are necessary (all
provisional modes etc. are the same as for TLS). provisional modes etc. are the same as for TLS).
CoAP was designed to avoid fragmentation. DTLS is used to secure CoAP was designed to avoid fragmentation. DTLS is used to secure
CoAP messages. However, fragmentation is still possible at the DTLS CoAP messages. However, fragmentation is still possible at the DTLS
layer during the DTLS handshake when using ECC ciphersuites. If layer during the DTLS handshake when using ECC ciphersuites. If
fragmentation is necessary, "DTLS provides a mechanism for fragmentation is necessary, "DTLS provides a mechanism for
fragmenting a handshake message over a number of records, each of fragmenting a handshake message over several records, each of which
which can be transmitted separately, thus avoiding IP fragmentation" can be transmitted separately, thus avoiding IP fragmentation"
[RFC6347]. [RFC6347].
CoAP and DTLS can provide proof of identity for EST-coaps clients and CoAP and DTLS can provide proof of identity for EST-coaps clients and
server with simple PKI messages conformant to section 3.1 of server with simple PKI messages conformant to section 3.1 of
[RFC5272]. EST-coaps supports the certificate types and Trust [RFC5272]. EST-coaps supports the certificate types and Trust
Anchors (TA) that are specified for EST in section 3 of [RFC7030]. Anchors (TA) that are specified for EST in section 3 of [RFC7030].
Channel-binding information for linking proof-of-identity with Channel-binding information for linking proof-of-identity with
connection-based proof-of-possession is optional for EST-coaps. When connection-based proof-of-possession is optional for EST-coaps. When
proof-of-possession is desired, a set of actions are required proof-of-possession is desired, a set of actions are required
regarding the use of tls-unique, described in section 3.5 in regarding the use of tls-unique, described in section 3.5 in
[RFC7030]. The tls-unique information translates to the contents of [RFC7030]. The tls-unique information translates to the contents of
the first "Finished" message in the TLS handshake between server and the first "Finished" message in the (D)TLS handshake between server
client [RFC5929]. The client is then supposed to add this "Finished" and client [RFC5929]. The client is then supposed to add this
message as a ChallengePassword in the attributes section of the "Finished" message as a ChallengePassword in the attributes section
PKCS#10 Request Info to prove that the client is indeed in control of of the PKCS#10 Request Info to prove that the client is indeed in
the private key at the time of the TLS session when performing a control of the private key at the time of the TLS session when
/simpleenroll, for example. In the case of EST-coaps, the same performing a /simpleenroll, for example. In the case of EST-coaps,
operations can be performed during the DTLS handshake. In the event the same operations can be performed during the DTLS handshake. For
of handshake message fragmentation, the Hash of the handshake DTLS 1.2, in the event of handshake message fragmentation, the Hash
messages used in the MAC calculation of the Finished message of the handshake messages used in the MAC calculation of the Finished
message
PRF(master_secret, finished_label, Hash(handshake_messages)) PRF(master_secret, finished_label, Hash(handshake_messages))
[0..verify_data_length-1]; [0..verify_data_length-1];
MUST be computed as if each handshake message had been sent as a MUST be computed as if each handshake message had been sent as a
single fragment [RFC6347]. single fragment [RFC6347]. Similarly, for DTLS 1.3, the Finished
message
HMAC(finished_key,
Transcript-Hash(Handshake Context,
Certificate*, CertificateVerify*))
* Only included if present.
MUST be computed as if each handshake message had been sent as a
single fragment following the algorithm described in 4.4.4 of
[I-D.ietf-tls-tls13].
In a constrained CoAP environment, endpoints can't afford to In a constrained CoAP environment, endpoints can't afford to
establish a DTLS connection for every EST transaction. establish a DTLS connection for every EST transaction.
Authenticating and negotiating DTLS keys requires resources on low- Authenticating and negotiating DTLS keys requires resources on low-
end endpoints and consumes valuable bandwidth. The DTLS connection end endpoints and consumes valuable bandwidth. The DTLS connection
SHOULD remain open for persistent EST connections. For example, an SHOULD remain open for persistent EST connections. For example, an
EST cacerts request that is followed by a simpleenroll request can EST cacerts request that is followed by a simpleenroll request can
use the same authenticated DTLS connection. Given that after a use the same authenticated DTLS connection. Given that after a
successful enrollment, it is more likely that a new EST transaction successful enrollment, it is more likely that a new EST transaction
will take place after a significant amount of time, the DTLS will take place after a significant amount of time, the DTLS
connections SHOULD only be kept alive for EST messages that are connections SHOULD only be kept alive for EST messages that are
relatively close to each other. relatively close to each other. In some cases, such as NAT
rebinding, keeping the state of a connection is not possible when
devices sleep for extended periods of time. In such occasions,
[I-D.rescorla-tls-dtls-connection-id] negotiates a connection ID that
can eliminate the need for new handshake and its additional cost.
Support for Observe CoAP options [RFC7641] is out-of-scope for this Support for Observe CoAP options [RFC7641] is compulsory. The
document. Observe options could be used by the server to notify necessity of Observer for long delays (minutes - hours)is explained
clients about a change in the cacerts or csr attributes (resources) in Section 4.4. Observe options could also be used by the server to
and might be an area of future work. notify clients about a change in the cacerts or csr attributes
(resources) and might be an area of future work.
6. Proxying 7. HTTPS-CoAPS Registrar
In real-world deployments, the EST server will not always reside In real-world deployments, the EST server will not always reside
within the CoAP boundary. The EST-server can exist outside the within the CoAP boundary. The EST-server can exist outside the
constrained network in a non-constrained network that supports TLS/ constrained network in a non-constrained network that supports TLS/
HTTP. In such environments EST-coaps is used by the client within HTTP. In such environments EST-coaps is used by the client within
the CoAP boundary and TLS is used to transport the EST messages the CoAP boundary and TLS is used to transport the EST messages
outside the CoAP boundary. A proxy entity at the edge is required to outside the CoAP boundary. A Registrar at the edge is required to
operate between the CoAP environment and the external HTTP network. operate between the CoAP environment and the external HTTP network.
The ESTcoaps-to-HTTPS proxy SHOULD terminate EST-coaps downstream and The EST coaps-to-HTTPS Registrar MUST terminate EST-coaps and
initiate EST connections over TLS upstream. authenticate the client downstream and initiate EST connections over
TLS upstream.
The Registrar SHOULD authenticate the client downstream and it should
be authenticated by the EST server or CA upstream. The Registration
Authority (re-)creates the secure connection from DTLS to TLS and
vice versa. A trust relationship SHOULD be pre-established between
the Registrar and the EST servers to be able to proxy these
connections on behalf of various clients.
When enforcing Proof-of-Possession (POP), the (D)TLS tls-unique value
of the (D)TLS session needs to be used to prove that the private key
corresponding to the public key is in the possession of and can be
used by an end-entity or client. In other words, the CSR the client
is using needs to include information from the DTLS connection the
client establishes with the server. In EST, that information is the
(D)TLS tls-unique value of the (D)TLS session. In the presence of
ESTcoaps-to-HTTPS Registrar, the EST-coaps client MUST be
authenticated and authorized by the Registrar and the Registrar MUST
be authenticated as an EST Registrar client to the EST server. Thus
the POP information is lost between the EST-coaps client and the EST
server. The EST server becomes aware of the presence of an EST
Registrar from its TLS client certificate that includes id-kp-cmcRA
[RFC6402] extended key usage extension. As explained in Section 3.7
of [RFC7030], the EST server SHOULD apply an authorization policy
consistent with a Registrar client. For example, it could be
configured to accept POP linking information that does not match the
current TLS session because the authenticated EST client Registrar
has verified this information when acting as an EST server.
One possible use-case, shown in one figure below, is expected to be One possible use-case, shown in one figure below, is expected to be
deployed in practice: deployed in practice:
o A proxy between any EST-client and EST-server
Constrained Network Constrained Network
.---------. .----------------------------. .---------. .----------------------------.
| RA | |.--------------------------.| | CA | |.--------------------------.|
'---------' || || '---------' || ||
| || || | || ||
.------. HTTP .-----------------. CoAPS .-----------. || .------. HTTP .-----------------. CoAPS .-----------. ||
| EST |<------->|ESTcoaps-to-HTTPS|<-------->| EST Client| || | EST |<------->|ESTcoaps-to-HTTPS|<-------->| EST Client| ||
|Server|over TLS | Proxy | '-----------' || |Server|over TLS | Registrar | '-----------' ||
'------' '-----------------' || '------' '-----------------' ||
|| || || ||
|'--------------------------'| |'--------------------------'|
'----------------------------' '----------------------------'
ESTcoaps-to-HTTPS proxy at the CoAP boundary. ESTcoaps-to-HTTPS Registrar at the CoAP boundary.
Table 1 contains the URI mapping between the EST-coaps and EST the Table 1 contains the URI mapping between the EST-coaps and EST the
proxy SHOULD adhere to. Section 7 of [RFC8075] and Section 3.3 Registrar SHOULD adhere to. Section 7 of [RFC8075] and Section 4.3
define the mapping between EST-coaps and HTTP response codes, that define the mapping between EST-coaps and HTTP response codes, that
determines how a proxy translates CoAP response codes from/to HTTP determines how the Registrar translates CoAP response codes from/to
status codes. The mapping from Content-Type to media type is defined HTTP status codes. The mapping from Content-Type to media type is
in Section 8. The conversion from binary to BSD64 needs to be done defined in Section 9. The conversion from CBOR major type 2 to
in the proxy. Conversion is possible because a TLS link exists base64 encoding needs to be done in the Registrar. Conversion is
between EST-coaps-to-HTTP proxy and EST server and a corresponding possible because a TLS link exists between EST-coaps-to-HTTP
DTLS linked exists between EST-coaps-to-HTTP proxy and EST client. Registrar and EST server and a corresponding DTLS link exists between
EST-coaps-to-HTTP Registrar and EST client.
Due to fragmentation of large messages into blocks, an EST-coaps-to- Due to fragmentation of large messages into blocks, an EST-coaps-to-
HTTP proxy SHOULD reassemble the BLOCKs before translating the binary HTTP Registrar SHOULD reassemble the BLOCKs before translating the
content to BSD64, and consecutively relay the message upstream into binary content to Base-64, and consecutively relay the message
the HTTP environment. upstream.
For the discovery of the EST server by the EST client in the coap For the discovery of the EST server by the EST client in the coap
environment, the EST-coaps-to-HTTP proxy MUST announce itself environment, the EST-coaps-to-HTTP Registrar MUST announce itself
according to the rules of Section 4. The available functions of the according to the rules of Section 5. The available actions of the
proxies MUST be announced with as many resource paths. The discovery Registrars MUST be announced with as many resource paths. The
of EST server in the http environment follow the rules specified in discovery of EST server in the http environment follow the rules
[RFC7030]. specified in [RFC7030].
[ EDNOTE: PoP will be addressed here. ]
A proxy SHOULD authenticate the client downstream and it should be
authenticated by the EST server or CA upstream. The Registration
Authority (RA) is necessary to (re-)create the secure connection from
DTLS to TLS and vice versa. A trust relationship needs to be pre-
established between the proxy and the EST servers to be able to proxy
these connections on behalf of various clients.
[EDNOTE: To add more details about trust relations in this section. ] When server-side key generation is used, if the private key is
protected using symmetric keys then the Registrar needs to encrypt
the private key down to the client with one symmetric key and decrypt
it from the server with another. If no private key encryption takes
place the Registrar will be able to see the key as it establishes a
separate connection to the server. In the case of asymmetrically
encrypted private key, the Registrar may not be able to decrypt it if
the server encrypted it with a public key that corresponds to a
private key that belongs to the client.
7. Parameters 8. Parameters
[EDNOTE: This section to be populated. It will address transmission [EDNOTE: This section to be populated. It will address transmission
parameters described in sections 4.7 and 4.8 of the CoAP draft. EST parameters described in sections 4.7 and 4.8 of the CoAP draft. EST
does not impose any unique parameters that affect the CoAP parameters does not impose any unique parameters that affect the CoAP parameters
in Table 2 and 3 in the CoAP draft but the ones in CoAP could be in Table 2 and 3 in the CoAP draft but the ones in CoAP could be
affecting EST. For example, the processing delay of CAs could be affecting EST. For example, the processing delay of CAs could be
less then 2s, but in this case they should send a CoAP ACK every 2s less then 2s, but in this case they should send a CoAP ACK every 2s
while processing.] while processing.]
8. IANA Considerations 9. IANA Considerations
8.1. Content-Format registry
Additions to the sub-registry "CoAP Content-Formats", within the
"CoRE Parameters" registry are needed for the below media types.
These can be registered either in the Expert Review range (0-255) or
IETF Review range (256-9999).
1.
* application/pkcs7-mime
* Type name: application
* Subtype name: pkcs7-mime
* ID: TBD1
* Required parameters: None
* Optional parameters: None
* Encoding considerations: binary
* Security considerations: As defined in this specification
* Published specification: [RFC5751]
* Applications that use this media type: EST
2.
* application/pkcs8
* Type name: application
* Subtype name: pkcs8
* ID: TBD2
* Required parameters: None
* Optional parameters: None
* Encoding considerations: binary
* Security considerations: As defined in this specification
* Published specification: [RFC5958]
* Applications that use this media type: EST
3.
* application/csrattrs
* Type name: application
* Subtype name: csrattrs
* ID: TBD3
* Required parameters: None
* Optional parameters: None
* Encoding considerations: binary
* Security considerations: As defined in this specification
* Published specification: [RFC7030]
* Applications that use this media type: EST 9.1. Media-Type Registry
4. This section registers the 'application/multict' media type in the
"Media Types" registry. This media type is used to indicate that the
payload is composed of multiple content formats.
* application/pkcs10 Type name: application
Subtype name: multict
Required parameters: none
Optional parameters: none
Encoding considerations: CBOR array of content-format.
Security considerations: See Security Considerations Section
Interoperability considerations: The format is designed to be
broadly interoperable.
Published specification: THIS RFC <xref target="cborpair"/>.
Applications that use this media type: ACE, ANIMA, 6tisch,
and other low-resource EST applications.
Additional information:
Magic number(s): None
File extension(s): .cbor
Macintosh file type code(s): none
Person & email address to contact for further information: IETF
ACE WG
Intended usage: LIMITED
Restrictions on usage: NONE
Author: ACE WG
Change controller: IETF
Provisional registration? (standards tree only): NO
* Type name: application 9.2. Content-Format Registry
* Subtype name: pkcs10 Additions to the sub-registry "CoAP Content-Formats", within the
"CoRE Parameters" registry are specified in Table 2. These can be
registered either in the Expert Review range (0-255) or IETF Review
range (256-9999).
* ID: TBD4 +---------------------------------+----------+------+---------------+
| Media type | Encoding | ID | Reference |
+---------------------------------+----------+------+---------------+
| application/pkcs7-mime; smime- | - | TBD1 | [RFC5751] |
| type=server-generated-key | | | [RFC7030] |
| application/pkcs7-mime; smime- | - | TBD2 | [RFC5751] |
| type=certs-only | | | |
| application/pkcs7-mime; smime- | - | TBD3 | [RFC5751] |
| type=CMC-request | | | [RFC5273] |
| application/pkcs7-mime; smime- | - | TBD4 | [RFC5751] |
| type=CMC-response | | | [RFC5273] |
| application/pkcs8 | - | TBD5 | [RFC5751] |
| | | | [RFC5958] |
| application/csrattrs | - | TBD6 | [RFC7030] |
| | | | [RFC7231] |
| application/pkcs10 | - | TBD7 | [RFC5751] |
| | | | [RFC5967] |
| application/multict | - | TBD8 | Section 9.2.1 |
+---------------------------------+----------+------+---------------+
* Required parameters: None Table 2: New CoAP Content-Formats
* Optional parameters: None 9.2.1. Content Format application/multict
* Encoding considerations: binary A representation with content format ID TBD8 contains a collection of
representations along with their respective content format.
* Security considerations: As defined in this specification The collection is encoded as a CBOR array [RFC7049] with an even
number of elements. The second, fourth, sixth, etc. element is a
binary string containing a representation. The first, third, fifth,
etc. element is an unsigned integer specifying the content format ID
of the following representation.
* Published specification: [RFC5967] For example, a collection containing two representations, one with
content format ID TBD5 and one with content format ID TBD2, looks
like this in diagnostic CBOR notation:
[TBD5,h'0123456789abcdef',TBD2,h'fedcba9876543210']. An example is
shown in Appendix A.4.
* Applications that use this media type: EST [EDNOTE: the intention is that this text is replaced by draft-
fossati-core-multipart-ct, which has yet to be adopted. The above
text is a copy of the critical text, in the event that the CORE WG
does not adopt the document]
8.2. Resource Type registry 9.3. Resource Type registry
Additions to the sub-registry "CoAP Resource Type", within the "CoRE Additions to the sub-registry "CoAP Resource Type", within the "CoRE
Parameters" registry are needed for a new resource type. Parameters" registry are needed for a new resource type.
o rt="ace.est" needs registration with IANA. o rt="ace.est" needs registration with IANA.
9. Security Considerations 10. Security Considerations
9.1. proxy considerations
The proxy proposed in Section 6 must be deployed with great care, and
only when the recommended connections are impossible.
[EDNOTE: To add more details about trust relations through proxies in
this section. ]
9.2. EST server considerations 10.1. EST server considerations
The security considerations of section 6 of [RFC7030] are only The security considerations of Section 6 of [RFC7030] are only
partially valid for the purposes of this document. As HTTP Basic partially valid for the purposes of this document. As HTTP Basic
Authentication is not supported, the considerations expressed for Authentication is not supported, the considerations expressed for
using passwords do not apply. using passwords do not apply.
Given that the client has only limited resources and may not be able Given that the client has only limited resources and may not be able
to generate sufficiently random keys to encrypt its identity, it is to generate sufficiently random keys to encrypt its identity, it is
possible that the client uses server generated private/public keys to possible that the client uses server generated private/public keys to
encrypt its certificate. The transport of these keys is inherently encrypt its certificate. The transport of these keys is inherently
risky. A full probability analysis MUST be done to establish whether risky. A full probability analysis MUST be done to establish whether
server side key generation enhances or decreases the probability of server side key generation enhances or decreases the probability of
identity stealing. identity stealing.
When a client uses the Implicit TA database for certificate When a client uses the Implicit TA database for certificate
validation, the client cannot verify that the implicit data base can validation, the client cannot verify that the implicit database can
act as an RA. It is RECOMMENDED that such clients include "Linking act as an RA. It is RECOMMENDED that such clients include "Linking
Identity and POP Information" Section 5 in requests (to prevent such Identity and POP Information" Section 6 in requests (to prevent such
requests from being forwarded to a real EST server by a man in the requests from being forwarded to a real EST server by a man in the
middle). It is RECOMMENDED that the Implicit Trust Anchor database middle). It is RECOMMENDED that the Implicit Trust Anchor database
used for EST server authentication be carefully managed to reduce the used for EST server authentication be carefully managed to reduce the
chance of a third-party CA with poor certification practices from chance of a third-party CA with poor certification practices from
being trusted. Disabling the Implicit Trust Anchor database after being trusted. Disabling the Implicit Trust Anchor database after
successfully receiving the Distribution of CA certificates response successfully receiving the Distribution of CA certificates response
(Section 4.1.3 of [RFC7030]) limits any vulnerability to the first (Section 4.1.3 of [RFC7030]) limits any risk to the first DTLS
DTLS exchange. exchange.
In accordance with [RFC7030], TLS cipher suites that include In accordance with [RFC7030], TLS cipher suites that include
"_EXPORT_" and "_DES_" in their names MUST NOT be used. More "_EXPORT_" and "_DES_" in their names MUST NOT be used. More
information about recommendations of TLS and DTLS are included in information about recommendations of TLS and DTLS are included in
[RFC7525]. [RFC7525].
As described in CMC, Section 6.7 of [RFC5272], "For keys that can be As described in CMC, Section 6.7 of [RFC5272], "For keys that can be
used as signature keys, signing the certification request with the used as signature keys, signing the certification request with the
private key serves as a POP on that key pair". The inclusion of tls- private key serves as a POP on that key pair". The inclusion of tls-
unique in the certification request links the proof-of-possession to unique in the certification request links the proof-of-possession to
the TLS proof-of-identity. This implies but does not prove that the the TLS proof-of-identity. This implies but does not prove that the
authenticated client currently has access to the private key. authenticated client currently has access to the private key.
Regarding the CSR attributes that the CA may list for inclusion in an Regarding the Certificate Signing Request (CSR), an adversary could
enrollment request, an adversary could exclude attributes that a exclude attributes that a server may want, include attributes that a
server may want, include attributes that a server may not want, and server may not want, and render meaningless other attributes that a
render meaningless other attributes that a server may want. The CA server may want. The CA is expected to be able to enforce policies
is expected to be able to enforce policies to recover from improper to recover from improper CSR requests.
CSR requests.
Interpreters of ASN.1 structures should be aware of the use of Interpreters of ASN.1 structures should be aware of the use of
invalid ASN.1 length fields and should take appropriate measures to invalid ASN.1 length fields and should take appropriate measures to
guard against buffer overflows, stack overruns in particular, and guard against buffer overflows, stack overruns in particular, and
malicious content in general. malicious content in general.
10. Acknowledgements 10.2. HTTPS-CoAPS Registrar considerations
The Registrar proposed in Section 7 must be deployed with care, and
only when the recommended connections are impossible. When POP is
used the Registrar terminating the TLS connection establishes a new
one with the upstream CA. Thus, it is impossible for POP to be
enforced throughout the EST transaction. The EST server could be
configured to accept POP linking information that does not match the
current TLS session because the authenticated EST Registrar client
has verified this information when acting as an EST server. The
introduction of an EST-coaps-to-HTTP Registrar assumes the client can
trust the registrar using its implicit or explicit TA database. It
also assumes the Registrar has a trust relationship with the upstream
EST server in order to act on behalf of the clients.
In a server-side key generation case, depending on the private key
encryption method, the Registrar may be able see the private key as
it acts as a man-in-the-middle. Thus, the clients puts its trust on
the Registrar not exposing the private key.
For some use cases, clients that leverage server-side key generation
might prefer for the enrolled keys to be generated by the Registrar
if the CA does not support server-side key generation. In these
cases the Registrar must support the random number generation using
proper entropy. Since the client has no knowledge if the Registrar
will be generating the keys and enrolling the certificates with the
CA or if the CA will be responsible for generating the keys, the
existence of a Registrar requires the client to put its trust on the
registrar doing the right thing if it is generating they private
keys.
11. Acknowledgements
The authors are very grateful to Klaus Hartke for his detailed The authors are very grateful to Klaus Hartke for his detailed
explanations on the use of Block with DTLS. The authors would like explanations on the use of Block with DTLS and his support for the
to thank Esko Dijk and Michael Verschoor for the valuable discussions content-format specification. The authors would like to thank Esko
that helped in shaping the solution. They would also like to thank Dijk and Michael Verschoor for the valuable discussions that helped
Peter Panburana from Cisco for his feedback on technical details of in shaping the solution. They would also like to thank Peter
the solution. Constructive comments were received from Eliot Lear, Panburana from Cisco for his feedback on technical details of the
Jim Schaad, Hannes Tschofenig, and Julien Vermillard. solution. Constructive comments were received from Benjamin Kaduk,
Eliot Lear, Jim Schaad, Hannes Tschofenig, and Julien Vermillard.
11. Change Log 12. Change Log
-00: -01:
copied from vanderstok-ace-coap-est-04 Editorials done.
12. References Redefinition of proxy to Registrar in Section 7. Explained better
the role of https-coaps Registrar, instead of "proxy"
12.1. Normative References Provide "observe" option examples
inserted new server key generation text in Section 4.5 and
motivated server key generation.
Broke down details for DTLS 1.3
New media type uses CBOR array for multiple content-format
payloads
provided new content format tables
new media format for IANA
-00
copied from vanderstok-ace-coap-04
13. References
13.1. Normative References
[I-D.ietf-tls-tls13]
Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", draft-ietf-tls-tls13-28 (work in progress),
March 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5272] Schaad, J. and M. Myers, "Certificate Management over CMS [RFC5272] Schaad, J. and M. Myers, "Certificate Management over CMS
(CMC)", RFC 5272, DOI 10.17487/RFC5272, June 2008, (CMC)", RFC 5272, DOI 10.17487/RFC5272, June 2008,
<https://www.rfc-editor.org/info/rfc5272>. <https://www.rfc-editor.org/info/rfc5272>.
skipping to change at page 17, line 22 skipping to change at page 20, line 31
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link [RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, DOI 10.17487/RFC6690, August 2012, Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
<https://www.rfc-editor.org/info/rfc6690>. <https://www.rfc-editor.org/info/rfc6690>.
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed., [RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030, "Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013, DOI 10.17487/RFC7030, October 2013,
<https://www.rfc-editor.org/info/rfc7030>. <https://www.rfc-editor.org/info/rfc7030>.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/info/rfc7049>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252, Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014, DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>. <https://www.rfc-editor.org/info/rfc7252>.
[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in [RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959, the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016, DOI 10.17487/RFC7959, August 2016,
<https://www.rfc-editor.org/info/rfc7959>. <https://www.rfc-editor.org/info/rfc7959>.
[RFC8075] Castellani, A., Loreto, S., Rahman, A., Fossati, T., and [RFC8075] Castellani, A., Loreto, S., Rahman, A., Fossati, T., and
E. Dijk, "Guidelines for Mapping Implementations: HTTP to E. Dijk, "Guidelines for Mapping Implementations: HTTP to
the Constrained Application Protocol (CoAP)", RFC 8075, the Constrained Application Protocol (CoAP)", RFC 8075,
DOI 10.17487/RFC8075, February 2017, DOI 10.17487/RFC8075, February 2017,
<https://www.rfc-editor.org/info/rfc8075>. <https://www.rfc-editor.org/info/rfc8075>.
12.2. Informative References 13.2. Informative References
[I-D.hartke-core-pending]
Stok, P. and K. Hartke, ""Pending" Responses for the
Constrained Application Protocol (CoAP)", draft-hartke-
core-pending-02 (work in progress), February 2018.
[I-D.ietf-6tisch-dtsecurity-secure-join]
Richardson, M., "6tisch Secure Join protocol", draft-ietf-
6tisch-dtsecurity-secure-join-01 (work in progress),
February 2017.
[I-D.ietf-6tisch-minimal-security]
Vucinic, M., Simon, J., Pister, K., and M. Richardson,
"Minimal Security Framework for 6TiSCH", draft-ietf-
6tisch-minimal-security-04 (work in progress), October
2017.
[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M., Behringer, M., Bjarnason,
S., and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
keyinfra-11 (work in progress), February 2018.
[ieee802.15.4] [I-D.rescorla-tls-dtls-connection-id]
Institute of Electrical and Electronics Engineers, "IEEE Rescorla, E., Tschofenig, H., Fossati, T., and T. Gondrom,
Standard 802.15.4-2006", 2006. "The Datagram Transport Layer Security (DTLS) Connection
Identifier", draft-rescorla-tls-dtls-connection-id-02
(work in progress), November 2017.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981, DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>. <https://www.rfc-editor.org/info/rfc791>.
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B. [RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
for Transport Layer Security (TLS)", RFC 4492, for Transport Layer Security (TLS)", RFC 4492,
DOI 10.17487/RFC4492, May 2006, DOI 10.17487/RFC4492, May 2006,
<https://www.rfc-editor.org/info/rfc4492>. <https://www.rfc-editor.org/info/rfc4492>.
[RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
over Low-Power Wireless Personal Area Networks (6LoWPANs): over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals", Overview, Assumptions, Problem Statement, and Goals",
RFC 4919, DOI 10.17487/RFC4919, August 2007, RFC 4919, DOI 10.17487/RFC4919, August 2007,
<https://www.rfc-editor.org/info/rfc4919>. <https://www.rfc-editor.org/info/rfc4919>.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<https://www.rfc-editor.org/info/rfc4944>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>. <https://www.rfc-editor.org/info/rfc5246>.
[RFC5273] Schaad, J. and M. Myers, "Certificate Management over CMS
(CMC): Transport Protocols", RFC 5273,
DOI 10.17487/RFC5273, June 2008,
<https://www.rfc-editor.org/info/rfc5273>.
[RFC5705] Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705,
March 2010, <https://www.rfc-editor.org/info/rfc5705>.
[RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings [RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings
for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010, for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010,
<https://www.rfc-editor.org/info/rfc5929>. <https://www.rfc-editor.org/info/rfc5929>.
[RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958, [RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958,
DOI 10.17487/RFC5958, August 2010, DOI 10.17487/RFC5958, August 2010,
<https://www.rfc-editor.org/info/rfc5958>. <https://www.rfc-editor.org/info/rfc5958>.
[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic [RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
Curve Cryptography Algorithms", RFC 6090, Curve Cryptography Algorithms", RFC 6090,
DOI 10.17487/RFC6090, February 2011, DOI 10.17487/RFC6090, February 2011,
<https://www.rfc-editor.org/info/rfc6090>. <https://www.rfc-editor.org/info/rfc6090>.
[RFC6402] Schaad, J., "Certificate Management over CMS (CMC)
Updates", RFC 6402, DOI 10.17487/RFC6402, November 2011,
<https://www.rfc-editor.org/info/rfc6402>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing", Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014, RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>. <https://www.rfc-editor.org/info/rfc7230>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
[RFC7251] McGrew, D., Bailey, D., Campagna, M., and R. Dugal, "AES- [RFC7251] McGrew, D., Bailey, D., Campagna, M., and R. Dugal, "AES-
CCM Elliptic Curve Cryptography (ECC) Cipher Suites for CCM Elliptic Curve Cryptography (ECC) Cipher Suites for
TLS", RFC 7251, DOI 10.17487/RFC7251, June 2014, TLS", RFC 7251, DOI 10.17487/RFC7251, June 2014,
<https://www.rfc-editor.org/info/rfc7251>. <https://www.rfc-editor.org/info/rfc7251>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer "Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>. 2015, <https://www.rfc-editor.org/info/rfc7525>.
skipping to change at page 19, line 50 skipping to change at page 23, line 8
Appendix A. EST messages to EST-coaps Appendix A. EST messages to EST-coaps
This section takes all examples from Appendix A of [RFC7030], changes This section takes all examples from Appendix A of [RFC7030], changes
the payload from Base64 to binary and replaces the http headers by the payload from Base64 to binary and replaces the http headers by
their CoAP equivalents. their CoAP equivalents.
The corresponding CoAP headers are only shown in Appendix A.1. The corresponding CoAP headers are only shown in Appendix A.1.
Creating CoAP headers are assumed to be generally known. Creating CoAP headers are assumed to be generally known.
Binary payload is a CBOR major type 2 (byte array), that is shown
with a base16 (hexadecimal) CBOR diagnostic notation.
[EDNOTE: The payloads of the examples need to be re-generated with [EDNOTE: The payloads of the examples need to be re-generated with
appropriate tools and example certificates.] appropriate tools and example certificates.]
A.1. cacerts A.1. cacerts
These examples assume that the resource discovery, returned a short
URL of "/est".
In EST-coaps, a coaps cacerts IPv4 message can be: In EST-coaps, a coaps cacerts IPv4 message can be:
GET coaps://[192.0.2.1:8085]/est/crts GET coaps://192.0.2.1:8085/est/crts
The corresponding CoAP header fields are shown below. The use of The corresponding CoAP header fields are shown below. The use of
block and DTLS are worked out in Appendix C. block and DTLS are worked out in Appendix B.
Ver = 1 Ver = 1
T = 0 (CON) T = 0 (CON)
Code = 0x01 (0.01 is GET) Code = 0x01 (0.01 is GET)
Token = 0x9a (client generated)
Options Options
Option1 (Uri-Host) Option1 (Uri-Host) [optional]
Option Delta = 0x3 (option nr = 3) Option Delta = 0x3 (option nr = 3)
Option Length = 0x9 Option Length = 0x9
Option Value = 192.0.2.1 Option Value = 192.0.2.1
Option2 (Uri-Port) Option2 (Observe)
Option Delta = 0x4 (option nr = 4+3=7) Option Delta = 0x1 (option nr = 3+3=6)
Option Length = 0x1
Option Value = 0 (register)
Option3 (Uri-Port) [optional]
Option Delta = 0x1 (option nr = 6+1=7)
Option Length = 0x4 Option Length = 0x4
Option Value = 8085 Option Value = 8085
Option3 (Uri-Path) Option4 (Uri-Path)
Option Delta = 0x4 (option nr = 7+4= 11) Option Delta = 0x4 (option nr = 7+4= 11)
Option Length = 0x9 Option Length = 0x5
Option Value = /est/crts Option Value = "est"
Option5 (Uri-Path)
Option Delta = 0x0 (option nr = 11+0= 11)
Option Length = 0x6
Option Value = "crts"
Option6 (Max-Age)
Option Delta = 0x3 (option nr = 11+3= 14)
Option Length = 0x1
Option Value = 0x1 (1 minute)
Payload = [Empty] Payload = [Empty]
A 2.05 Content response with a cert in EST-coaps will then be: A 2.05 Content response with a cert in EST-coaps will then be:
2.05 Content (Content-Format: application/pkcs7-mime) 2.05 Content (Content-Format: TBD2)
{payload} {payload}
with CoAP fields with CoAP fields
Ver = 1 Ver = 1
T = 2 (ACK) T = 2 (ACK)
Code = 0x45 (2.05 Content) Code = 0x45 (2.05 Content)
Token = 0x9a (copied by server)
Options Options
Option1 (Content-Format) Option1 (Observe)
Option Delta = 0xC (option nr = 12) Option Delta = 0x6 (option nr =6)
Option Length = 0x1
Option Value = 12 ( 12 > 0)
Option2 (Content-Format)
Option Delta = 0xC (option nr = 6+6 =12)
Option Length = 0x2 Option Length = 0x2
Option Value = TBD1 (defined in this document) Option Value = TBD2 (defined in this document)
Payload = Payload =
30233906092a6206734107028c2a3023260201013100300b06092a6206734107018 h'30233906092a6206734107028c2a3023260201013100300b06092a6206734107018
c0c3020bb302063c20102020900a61e75193b7acc0d06092a620673410105050030 c0c3020bb302063c20102020900a61e75193b7acc0d06092a620673410105050030
1b31193017060355040313106573744578616d706c654341204f774f301e170d313 1b31193017060355040313106573744578616d706c654341204f774f301e170d313
3303530393033353333315a170d3134303530393033353333315a301b3119301706 3303530393033353333315a170d3134303530393033353333315a301b3119301706
0355040313106573744578616d706c654341204f774f302062300d06092a6206734 0355040313106573744578616d706c654341204f774f302062300d06092a6206734
10101050003204f0030204a022041003a923a2968bae4aae136ca4e2512c5200680 10101050003204f0030204a022041003a923a2968bae4aae136ca4e2512c5200680
358482ac39d6f640e4574e654ea35f48b1e054c5da3372872f7a1e429f4edf39584 358482ac39d6f640e4574e654ea35f48b1e054c5da3372872f7a1e429f4edf39584
32efb2106591d3eb783c1034709f251fc86566bda2d541c792389eac4ec9e181f4b 32efb2106591d3eb783c1034709f251fc86566bda2d541c792389eac4ec9e181f4b
9f596e5ef2679cc321542b11337f90a44df3c85f1516561fa968a1914f265bc0b82 9f596e5ef2679cc321542b11337f90a44df3c85f1516561fa968a1914f265bc0b82
76ebe3106a790d97d34c8c37c74fe1c30b396424664ac426284a9f6022e02693843 76ebe3106a790d97d34c8c37c74fe1c30b396424664ac426284a9f6022e02693843
6880adfcd95c98ca1dfc2e6d75319b85d0458de28a9d13fb16d620fff7541f6a25d 6880adfcd95c98ca1dfc2e6d75319b85d0458de28a9d13fb16d620fff7541f6a25d
skipping to change at page 22, line 26 skipping to change at page 26, line 35
c4f5abb7b0cf87a79d221f1127313c53371ce1245d63db45a1203a23340ba08042c c4f5abb7b0cf87a79d221f1127313c53371ce1245d63db45a1203a23340ba08042c
768d03b8076a028d3a51d87d2ef107bbd6f2305ce5e67668724002fb726df9c1447 768d03b8076a028d3a51d87d2ef107bbd6f2305ce5e67668724002fb726df9c1447
6c37de0f55033f192a5ad21f9a2a71c20301000130b040300f0603551d130101f10 6c37de0f55033f192a5ad21f9a2a71c20301000130b040300f0603551d130101f10
530030101fc1d0603551d0e04160414112966e304761732fbfe6a2c823c300e0603 530030101fc1d0603551d0e04160414112966e304761732fbfe6a2c823c300e0603
551d0f0101f10403020106300d06092a620673410105050003204100423f06d4b76 551d0f0101f10403020106300d06092a620673410105050003204100423f06d4b76
0f4b42744a279035571696f272a0060f1325a40898509601ad14004f652db6312a1 0f4b42744a279035571696f272a0060f1325a40898509601ad14004f652db6312a1
475c4d7cd50f4b269035585d7856c5337765a66b38462d5bdaa7778aab24bbe2815 475c4d7cd50f4b269035585d7856c5337765a66b38462d5bdaa7778aab24bbe2815
e37722cd10e7166c50e75ab75a1271324460211991e7445a2960f47351a1a629253 e37722cd10e7166c50e75ab75a1271324460211991e7445a2960f47351a1a629253
34119794b90e320bc730d6c1bee496e7ac125ce9a1eca595a3a4c54a865e6b623c9 34119794b90e320bc730d6c1bee496e7ac125ce9a1eca595a3a4c54a865e6b623c9
247bfd0a7c19b56077392555c955e233642bec643ae37c166c5e221d797aea3748f 247bfd0a7c19b56077392555c955e233642bec643ae37c166c5e221d797aea3748f
0391c8d692a5cf9bb71f6d0e37984d6fa673a30d0c006343116f58403100 0391c8d692a5cf9bb71f6d0e37984d6fa673a30d0c006343116f58403100'
After reception of the 2.05 response, the client can forget the
observe.
A.2. csrattrs A.2. csrattrs
In the following valid /csrattrs exchange, the EST-coaps client In the following valid /csrattrs exchange, the EST-coaps client
authenticates itself with a certificate issued by the connected CA. authenticates itself with a certificate issued by the connected CA.
The initial DTLS handshake is identical to the enrollment example. The initial DTLS handshake is identical to the enrollment example.
The IPv6 CoAP GET request looks like: The IPv6 CoAP GET request looks like:
REQ: REQ:
GET coaps://[2001:db8::2:1]:61616/est/att GET coaps://[2001:db8::2:1]:61616/est/att
(Content-Format: TBD6)(observe =0)(Max-Age =1)
A 2.05 Content response contains attributes which are relevant for A 2.05 Content response contains attributes which are relevant for
the authenticated client. In this example, the EST-coaps server two the authenticated client. In this example, the EST-coaps server
attributes that the client can ignore when they are unknown to him.: returns two attributes that the client can ignore when they are
unknown to him.
A.3. enroll / reenroll A.3. enroll / reenroll
[EDNOTE: We might need a new Option for the Retry-After response
message. We might need a new Option for the WWW-Authenticate
response.]
During the Enroll/Reenroll exchange, the EST-coaps client uses a CSR During the Enroll/Reenroll exchange, the EST-coaps client uses a CSR
(PKCS#10) request in the POST request payload. (Content-Format TBD7) request in the POST request payload.
After verification of the certificate by the server, a 2.05 Content After verification of the CSR by the server, a 2.05 Content response
response with the issued certificate will be returned. with the issued certificate will be returned to the client. As
described in Section 4.4, if the server is not able to provide a
response, then it ACKs the GET (with no payload), and the payload
will be sent later as part of the OBSERVE processing.
[EDNOTE: When redoing this example, given that proof of possession
(POP) is also used, make sure it is obvious that the
ChallengePassword attribute in the CSR is valid HMAC output. HMAC-
REAL.]
POST [2001:db8::2:1]:61616/est/sen POST [2001:db8::2:1]:61616/est/sen
(Content-Format: application/pkcs10) (token 0x45)
30208530206d020100301f311d301b0603550403131464656d6f7374657034203 (Content-Format: TBD7)(observe 0)
h'30208530206d020100301f311d301b0603550403131464656d6f7374657034203
1333638313431333532302062300d06092a620673410101050003204f0030204a 1333638313431333532302062300d06092a620673410101050003204f0030204a
022041005d9f4dffd3c5949f646a9584367778560950b355c35b8e34726dd3764 022041005d9f4dffd3c5949f646a9584367778560950b355c35b8e34726dd3764
54231734795b4c09b9c6d75d408311307a81f7adef7f5d241f7d5be85620c5d44 54231734795b4c09b9c6d75d408311307a81f7adef7f5d241f7d5be85620c5d44
38bbb4242cf215c167f2ccf36c364ea2618a62f0536576369d6304e6a96877224 38bbb4242cf215c167f2ccf36c364ea2618a62f0536576369d6304e6a96877224
7d86824f079faac7a6f694cfda5b84c42087dc062d462190c525813f210a036a7 7d86824f079faac7a6f694cfda5b84c42087dc062d462190c525813f210a036a7
37b4f30d8891f4b75559fb72752453146332d51c937557716ccec624f5125c3a4 37b4f30d8891f4b75559fb72752453146332d51c937557716ccec624f5125c3a4
447ad3115020048113fef54ad554ee88af09a2583aac9024075113db4990b1786 447ad3115020048113fef54ad554ee88af09a2583aac9024075113db4990b1786
b871691e0f02030100018701f06092a620673410907311213102b72724369722f b871691e0f02030100018701f06092a620673410907311213102b72724369722f
372b45597535305434300d06092a620673410105050003204100441b40177a3a6 372b45597535305434300d06092a620673410105050003204100441b40177a3a6
5501487735a8ad5d3827a4eaa867013920e2afcda87aa81733c7c0353be47e1bf 5501487735a8ad5d3827a4eaa867013920e2afcda87aa81733c7c0353be47e1bf
a7cda5176e7ccc6be22ae03498588d5f2de3b143f2b1a6175ec544e8e7625af6b a7cda5176e7ccc6be22ae03498588d5f2de3b143f2b1a6175ec544e8e7625af6b
836fd4416894c2e55ea99c6606f69075d6d53475d410729aa6d806afbb9986caf 836fd4416894c2e55ea99c6606f69075d6d53475d410729aa6d806afbb9986caf
7b844b5b3e4545f19071865ada007060cad6db26a592d4a7bda7d586b68110962 7b844b5b3e4545f19071865ada007060cad6db26a592d4a7bda7d586b68110962
17071103407553155cddc75481e272b5ed553a8593fb7e25100a6f7605085dab4 17071103407553155cddc75481e272b5ed553a8593fb7e25100a6f7605085dab4
fc7e0731f0e7fe305703791362d5157e92e6b5c2e3edbcadb40 fc7e0731f0e7fe305703791362d5157e92e6b5c2e3edbcadb40'
RET: RET:
2.05 Content (Content-Format: application/pkcs7-mime) (Content-Format: TBD2)(token =0x45)(observe =12)
3020f806092a62067341070283293020e50201013100300b06092a62067341070 2.01 Created
h'3020f806092a62067341070283293020e50201013100300b06092a62067341070
1830b3020c730206fc20102020115300d06092a6206734101050500301b311930 1830b3020c730206fc20102020115300d06092a6206734101050500301b311930
17060355040313106573744578616d706c654341204e774e301e170d313330353 17060355040313106573744578616d706c654341204e774e301e170d313330353
0393233313535335a170d3134303530393233313535335a301f311d301b060355 0393233313535335a170d3134303530393233313535335a301f311d301b060355
0403131464656d6f73746570342031333638313431333532302062300d06092a6 0403131464656d6f73746570342031333638313431333532302062300d06092a6
20673410101050003204f0030204a022041005d9f4dffd3c5949f646a95843677 20673410101050003204f0030204a022041005d9f4dffd3c5949f646a95843677
78560950b355c35b8e34726dd376454231734795b4c09b9c6d75d408311307a81 78560950b355c35b8e34726dd376454231734795b4c09b9c6d75d408311307a81
f7adef7f5d241f7d5be85620c5d4438bbb4242cf215c167f2ccf36c364ea2618a f7adef7f5d241f7d5be85620c5d4438bbb4242cf215c167f2ccf36c364ea2618a
62f0536576369d6304e6a968772247d86824f079faac7a6f694cfda5b84c42087 62f0536576369d6304e6a968772247d86824f079faac7a6f694cfda5b84c42087
dc062d462190c525813f210a036a737b4f30d8891f4b75559fb72752453146332 dc062d462190c525813f210a036a737b4f30d8891f4b75559fb72752453146332
d51c937557716ccec624f5125c3a4447ad3115020048113fef54ad554ee88af09 d51c937557716ccec624f5125c3a4447ad3115020048113fef54ad554ee88af09
a2583aac9024075113db4990b1786b871691e0f020301000134b050300e060355 a2583aac9024075113db4990b1786b871691e0f020301000134b050300e060355
1d0f0101f104030204c1d0603551d0e04160414e81d0788aa2710304c5ecd4d1e 1d0f0101f104030204c1d0603551d0e04160414e81d0788aa2710304c5ecd4d1e
065701f0603551d230418301653112966e304761732fbfe6a2c823c300d06092a 065701f0603551d230418301653112966e304761732fbfe6a2c823c300d06092a
6206734101050500032041002910d86f2ffeeb914c046816871de601567d291b4 6206734101050500032041002910d86f2ffeeb914c046816871de601567d291b4
3fabee0f0e8ff81cea27302a7133e20e9d04029866a8963c7d14e26fbe8a0ab1b 3fabee0f0e8ff81cea27302a7133e20e9d04029866a8963c7d14e26fbe8a0ab1b
77fbb1214bbcdc906fbc381137ec1de685f79406c3e416b8d82f97174bc691637 77fbb1214bbcdc906fbc381137ec1de685f79406c3e416b8d82f97174bc691637
5a4e1c4bf744c7572b4b2c6bade9fb35da786392ee0d95e3970542565f3886ad6 5a4e1c4bf744c7572b4b2c6bade9fb35da786392ee0d95e3970542565f3886ad6
7746d1b12484bb02616e63302dc371dc6006e431fb7c457598dd204b367b0b3d3 7746d1b12484bb02616e63302dc371dc6006e431fb7c457598dd204b367b0b3d3
258760a303f1102db26327f929b7c5a60173e1799491b69150248756026b80553 258760a303f1102db26327f929b7c5a60173e1799491b69150248756026b80553
171e4733ad3d13c0103100 171e4733ad3d13c0103100'
[EDNOTE: If POP is used, make sure tls-unique in the CSR is a valid After reception of the 2.01 response the client can forget the
HMAC output. ] observe registration
The same example when delays occur (omitting the payloads in the
examples) has a different behavior. The response to the POST is an
empty payload with response code 2.01 (Created) that also returns the
resource to query. The client issues a GET with an observe and a new
token value, and waits for the notification after possibly receiving
an empty payload first.
POST [2001:db8::2:1]:61616/est/sen
(token 0x45)(observe = 0)
(Content-Format: TBD7)(Max-Age=120)
[payload]
RET:
(token =0x45)(observe =12)(Location-Path=/est/1245)
2.01 Created
[empty payload]
GET [2001:db8::2:1]:61616/est/1245
(token 0x53)
(observe =0)(Max-Age=120)
RET:
(token =0x53)(observe = 5)
2.01 Created
[empty payload]
RET:
(token =0x53)(observe = 6)
(Content-Format: TBD2)
2.04 Changed
[payload]
A.4. serverkeygen A.4. serverkeygen
During this valid /serverkeygen exchange, the EST-coaps client During this valid /serverkeygen exchange, the EST-coaps client
authenticates itself using the certificate provided by the connected authenticates itself using the certificate provided by the connected
CA. CA.
[EDNOTE: the client incudes a CSR with a public key that the server
should ignore, so we need a content-format here. ]
[EDNote: If POP is used, make sure tls-unique in the CSR is a valid
HMAC output. ]
The initial DTLS handshake is identical to the enrollment example. The initial DTLS handshake is identical to the enrollment example.
The CoAP GET request looks like: The CoAP GET request looks like:
POST coaps://[192.0.2.1:8085]/est/skg [EDNOTE: same comment as HMAC-REAL above applies.]
302081302069020100305b313e303c060355040313357365727665724b6579476
[EDNOTE: Suggestion to have only one example with complete encrypted
payload (the short one) and point out the different fields. Update
this example according to the agreed upon solution from Section 4.5.
]
POST coaps://192.0.2.1:8085/est/skg
(token 0xa5)(observe = 0)
(Content-Format: TBD7)(Max-Age=120)
h'302081302069020100305b313e303c060355040313357365727665724b6579476
56e2072657120627920636c69656e7420696e2064656d6f207374657020313220 56e2072657120627920636c69656e7420696e2064656d6f207374657020313220
3133363831343139353531193017060355040513105049443a576964676574205 3133363831343139353531193017060355040513105049443a576964676574205
34e3a3130302062300d06092a620673410101050003204f0030204a02204100f4 34e3a3130302062300d06092a620673410101050003204f0030204a02204100f4
dfa6c03f7f2766b23776c333d2c0f9d1a7a6ee36d01499bbe6f075d1e38a57e98 dfa6c03f7f2766b23776c333d2c0f9d1a7a6ee36d01499bbe6f075d1e38a57e98
ecc197f51b75228454b7f19652332de5e52e4a974c6ae34e1df80b33f15f47d3b ecc197f51b75228454b7f19652332de5e52e4a974c6ae34e1df80b33f15f47d3b
cbf76116bb0e4d3e04a9651218a476a13fc186c2a255e4065ff7c271cff104e47 cbf76116bb0e4d3e04a9651218a476a13fc186c2a255e4065ff7c271cff104e47
31fad53c22b21a1e5138bf9ad0187314ac39445949a48805392390e78c7659621 31fad53c22b21a1e5138bf9ad0187314ac39445949a48805392390e78c7659621
6d3e61327a534f5ea7721d2b1343c7362b37da502717cfc2475653c7a3860c5f4 6d3e61327a534f5ea7721d2b1343c7362b37da502717cfc2475653c7a3860c5f4
0612a5db6d33794d755264b6327e3a3263b149628585b85e57e42f6b3277591b0 0612a5db6d33794d755264b6327e3a3263b149628585b85e57e42f6b3277591b0
2030100018701f06092a6206734109073112131064467341586d4a6e6a6f6b427 2030100018701f06092a6206734109073112131064467341586d4a6e6a6f6b427
4447672300d06092a620673410105050003204100472d11007e5a2b2c2023d47a 4447672300d06092a620673410105050003204100472d11007e5a2b2c2023d47a
6d71d046c307701d8ebc9e47272713378390b4ee321462a3dbe54579f5a514f6f 6d71d046c307701d8ebc9e47272713378390b4ee321462a3dbe54579f5a514f6f
4050af497f428189b63655d03a194ef729f101743e5d03fbc6ae1e84486d1300a 4050af497f428189b63655d03a194ef729f101743e5d03fbc6ae1e84486d1300a
f9288724381909188c851fa9a5059802eb64449f2a3c9e441353d136768da27ff f9288724381909188c851fa9a5059802eb64449f2a3c9e441353d136768da27ff
4f277651d676a6a7e51931b08f56135a2230891fd184960e1313e7a1a9139ed19 4f277651d676a6a7e51931b08f56135a2230891fd184960e1313e7a1a9139ed19
28196867079a456cd2266cb754a45151b7b1b939e381be333fea61580fe5d25bf 28196867079a456cd2266cb754a45151b7b1b939e381be333fea61580fe5d25bf
4823dbd2d6a98445b46305c10637e202856611 4823dbd2d6a98445b46305c10637e202856611'
RET: RET:
2.05 Content (Content-Format: application/pkcs8) 2.01 Content (Content-Format: TBD8)
30213e020100300d06092a6206734101010500042128302124020100022041003 (observe = 5)(token=0xa5)
[TBD5,
h'30213e020100300d06092a6206734101010500042128302124020100022041003
c0bc2748f2003e3e8ea15f746f2a71e83f585412b92cf6f8e64de02e056153274 c0bc2748f2003e3e8ea15f746f2a71e83f585412b92cf6f8e64de02e056153274
dd01c95dd9cff3112aa141774ab655c3d56359c3b3df055294692ed848e7e30a1 dd01c95dd9cff3112aa141774ab655c3d56359c3b3df055294692ed848e7e30a1
1bf14e47e0693d93017022b4cdb3e6d40325356152b213c8b535851e681a7074c 1bf14e47e0693d93017022b4cdb3e6d40325356152b213c8b535851e681a7074c
0c6d2b60e7c32fc0336b28e743eba4e5921074d47195d3c05e43c527526e692d5 0c6d2b60e7c32fc0336b28e743eba4e5921074d47195d3c05e43c527526e692d5
45e562578d2d4b5f2191bff89d3eef0222764a2674637a1f99257216647df6704 45e562578d2d4b5f2191bff89d3eef0222764a2674637a1f99257216647df6704
efec5adbf54dab24231844eb595875795000e673dd6862310a146ad7e31083010 efec5adbf54dab24231844eb595875795000e673dd6862310a146ad7e31083010
001022041004e6b3f78b7791d6377f33117c17844531c81111fb8000282816264 001022041004e6b3f78b7791d6377f33117c17844531c81111fb8000282816264
915565bc7c3f3f643b537a2c69140a31c22550fa97e5132c61b74166b68626704 915565bc7c3f3f643b537a2c69140a31c22550fa97e5132c61b74166b68626704
260620333050f510096b6570f5880e7e1c15dc0ca6ce2b5f187e2325da14ab705 260620333050f510096b6570f5880e7e1c15dc0ca6ce2b5f187e2325da14ab705
ad004717f3b2f779127b5c535e0cee6a343b502722f2397a26126e0af606b5aa7 ad004717f3b2f779127b5c535e0cee6a343b502722f2397a26126e0af606b5aa7
skipping to change at page 25, line 21 skipping to change at page 31, line 12
0214389a232a2258326163167504cfce44cd316f63bb8a52da53a4cb74fd87194 0214389a232a2258326163167504cfce44cd316f63bb8a52da53a4cb74fd87194
c0844881f791f23b0813ea0921325edd14459d41c8a1593f04316388e40b35fef c0844881f791f23b0813ea0921325edd14459d41c8a1593f04316388e40b35fef
7d2a195a5930fa54774427ac821eee2c62790d2c17bd192af794c611011506557 7d2a195a5930fa54774427ac821eee2c62790d2c17bd192af794c611011506557
83d4efe22185cbd83368786f2b1e68a5a27067e321066f0217b4b6d7971a3c21a 83d4efe22185cbd83368786f2b1e68a5a27067e321066f0217b4b6d7971a3c21a
241366b7907187583b511102103369047e5cce0b65012200df5ec697b5827575c 241366b7907187583b511102103369047e5cce0b65012200df5ec697b5827575c
db6821ff299d6a69574b31ddf0fbe9245ea2f74396c24b3a7565067e41366423b db6821ff299d6a69574b31ddf0fbe9245ea2f74396c24b3a7565067e41366423b
5bdd2b2a78194094dbe333f493d159b8e07722f2280d48388db7f1c9f0633bb0e 5bdd2b2a78194094dbe333f493d159b8e07722f2280d48388db7f1c9f0633bb0e
173de2c3aa1f200af535411c7090210401421e2ea217e37312dcc606f453a6634 173de2c3aa1f200af535411c7090210401421e2ea217e37312dcc606f453a6634
f3df4dc31a9e910614406412e70eec9247f10672a500947a64356c015a845a7d1 f3df4dc31a9e910614406412e70eec9247f10672a500947a64356c015a845a7d1
50e2e3911a2b3b61070a73247166da10bb45474cc97d1ec2bc392524307f35118 50e2e3911a2b3b61070a73247166da10bb45474cc97d1ec2bc392524307f35118
f917438f607f18181684376e13a39e07 f917438f607f18181684376e13a39e07',
--estServerExampleBoundary TBD2,
3020c506092a62067341070283363020f20201013100300b06092a62067341070 h'3020c506092a62067341070283363020f20201013100300b06092a62067341070
183183020d430207cc20102020116300d06092a6206734101050500301b311930 183183020d430207cc20102020116300d06092a6206734101050500301b311930
17060355040313106573744578616d706c654341204e774e301e170d313330353 17060355040313106573744578616d706c654341204e774e301e170d313330353
0393233323535365a170d3134303530393233323535365a302c312a3028060355 0393233323535365a170d3134303530393233323535365a302c312a3028060355
0403132173657276657273696465206b65792067656e657261746564207265737 0403132173657276657273696465206b65792067656e657261746564207265737
06f6e7365302062300d06092a620673410101050003204f0030204a022041003c 06f6e7365302062300d06092a620673410101050003204f0030204a022041003c
0bc2748f2003e3e8ea15f746f2a71e83f585412b92cf6f8e64de02e056153274d 0bc2748f2003e3e8ea15f746f2a71e83f585412b92cf6f8e64de02e056153274d
d01c95dd9cff3112aa141774ab655c3d56359c3b3df055294692ed848e7e30a11 d01c95dd9cff3112aa141774ab655c3d56359c3b3df055294692ed848e7e30a11
bf14e47e0693d93017022b4cdb3e6d40325356152b213c8b535851e681a7074c0 bf14e47e0693d93017022b4cdb3e6d40325356152b213c8b535851e681a7074c0
c6d2b60e7c32fc0336b28e743eba4e5921074d47195d3c05e43c527526e692d54 c6d2b60e7c32fc0336b28e743eba4e5921074d47195d3c05e43c527526e692d54
5e562578d2d4b5f2191bff89d3eef0222764a2674637a1f99257216647df6704e 5e562578d2d4b5f2191bff89d3eef0222764a2674637a1f99257216647df6704e
fec5adbf54dab24231844eb595875795000e673dd6862310a146ad7e310830100 fec5adbf54dab24231844eb595875795000e673dd6862310a146ad7e310830100
0134b050300e0603551d0f0101f104030204c1d0603551d0e04160414764b1bd5 0134b050300e0603551d0f0101f104030204c1d0603551d0e04160414764b1bd5
e69935626e476b195a1a8c1f0603551d230418301653112966e304761732fbfe6 e69935626e476b195a1a8c1f0603551d230418301653112966e304761732fbfe6
a2c823c300d06092a620673410105050003204100474e5100a9cdaaa813b30f48 a2c823c300d06092a620673410105050003204100474e5100a9cdaaa813b30f48
40340fb17e7d6d6063064a5a7f2162301c464b5a8176623dfb1a4a484e618de1c 40340fb17e7d6d6063064a5a7f2162301c464b5a8176623dfb1a4a484e618de1c
3c3c5927cf590f4541233ff3c251e772a9a3f2c5fc6e5ef2fe155e5e385deb846 3c3c5927cf590f4541233ff3c251e772a9a3f2c5fc6e5ef2fe155e5e385deb846
b36eb4c3c7ef713f2d137ae8be4c022715fd033a818d55250f4e6077718180755 b36eb4c3c7ef713f2d137ae8be4c022715fd033a818d55250f4e6077718180755
a4fa677130da60818175ca4ab2af1d15563624c51e13dfdcf381881b72327e2f4 a4fa677130da60818175ca4ab2af1d15563624c51e13dfdcf381881b72327e2f4
9b7467e631a27b5b5c7d542bd2edaf78c0ac294f3972278996bdf673a334ff74c 9b7467e631a27b5b5c7d542bd2edaf78c0ac294f3972278996bdf673a334ff74c
84aa7d65726310252f6a4f41281ec10ca2243864e3c5743103100 84aa7d65726310252f6a4f41281ec10ca2243864e3c5743103100']
Without the DecryptKeyIdentifier attribute, the response has no Without the DecryptKeyIdentifier attribute, the response has no
additional encryption beyond DTLS. [EDNOTE: Add comment about additional encryption beyond DTLS.
deriving symmetric keys by using the TLS KEM draft. ]
The response contains first a preamble that can be ignored. The EST- The response contains first a preamble that can be ignored. The EST-
coaps server can use the preamble to include additional explanations, coaps server can use the preamble to include additional explanations,
like ownership or support information like ownership or support information
Appendix B. Encoding for server side key generation Appendix B. EST-coaps Block message examples
Sever side key generation for CoAP can be implemented efficiently
using multipart encoding
[EDNOTE: text to be written.]
Appendix C. EST-coaps Block message examples
This section provides a detailed example of the messages using DTLS This section provides a detailed example of the messages using DTLS
and BLOCK option Block2. The minimum PMTU is 1280 bytes, which is and BLOCK option Block2. The minimum PMTU is 1280 bytes, which is
the example value assumed for the DTLS datagram size. The example the example value assumed for the DTLS datagram size. The example
block length is taken as 64 which gives an SZX value of 2. block length is taken as 64 which gives an SZX value of 2.
The following is an example of a valid /cacerts exchange over DTLS. The following is an example of a valid /cacerts exchange over DTLS.
The content length of the cacerts response in appendix A.1 of The content length of the cacerts response in appendix A.1 of
[RFC7030] is 4246 bytes using base64. This leads to a length of 2509 [RFC7030] is 4246 bytes using base64. This leads to a length of 2509
bytes in binary. The CoAP message adds around 10 bytes, the DTLS bytes in binary. The CoAP message adds around 10 bytes, the DTLS
record 29 bytes. To avoid IP fragmentation, the CoAP block option is record 29 bytes. To avoid IP fragmentation, the CoAP block option is
used and an MTU of 127 is assumed to stay within one IEEE 802.15.4 used and an MTU of 127 is assumed to stay within one IEEE 802.15.4
packet. To stay below the MTU of 127, the payload is split in 39 packet. To stay below the MTU of 127, the payload is split in 39
packets with a payload of 64 bytes each, followed by a packet of 13 packets with a payload of 64 bytes each, followed by a packet of 13
bytes. The client sends an IPv6 packet containing the UDP datagram bytes. The client sends an IPv6 packet containing the UDP datagram
with the DTLS record that encapsulates the CoAP Request 40 times. with the DTLS record that encapsulates the CoAP Request 40 times.
The server returns an IPv6 packet containing the UDP datagram with The server returns an IPv6 packet containing the UDP datagram with
the DTLS record that encapsulates the CoAP response. The CoAP the DTLS record that encapsulates the CoAP response. The CoAP
skipping to change at page 26, line 41 skipping to change at page 32, line 25
request-response exchange with block option is shown below. Block request-response exchange with block option is shown below. Block
option is shown in a decomposed way indicating the kind of Block option is shown in a decomposed way indicating the kind of Block
option (2 in this case because used in the response) followed by a option (2 in this case because used in the response) followed by a
colon, and then the block number (NUM), the more bit (M = 0 means colon, and then the block number (NUM), the more bit (M = 0 means
last block), and block size exponent (2**(SZX+4)) separated by last block), and block size exponent (2**(SZX+4)) separated by
slashes. The Length 64 is used with SZX= 2 to avoid IP slashes. The Length 64 is used with SZX= 2 to avoid IP
fragmentation. The CoAP Request is sent with confirmable (CON) fragmentation. The CoAP Request is sent with confirmable (CON)
option and the content format of the Response is /application/ option and the content format of the Response is /application/
cacerts. cacerts.
GET [192.0.2.1:8085]/est/crts --> GET /192.0.2.1:8085/est/crts -->
<-- (2:0/1/39) 2.05 Content <-- (2:0/1/39) 2.05 Content
GET URI (2:1/1/39) --> GET URI (2:1/1/39) -->
<-- (2:1/1/39) 2.05 Content <-- (2:1/1/39) 2.05 Content
| |
| |
| |
GET URI (2:65/1/39) --> GET URI (2:65/1/39) -->
<-- (2:65/0/39) 2.05 Content <-- (2:65/0/39) 2.05 Content
For further detailing the CoAP headers of the first two blocks are For further detailing the CoAP headers of the first two blocks are
written out. written out.
The header of the first GET looks like: The header of the first GET looks like:
Ver = 1 Ver = 1
T = 0 (CON) T = 0 (CON)
Code = 0x01 (0.1 GET) Code = 0x01 (0.1 GET)
Token = 0x9a (client generated)
Options Options
Option1 (Uri-Host) Option1 (Uri-Host) [optional]
Option Delta = 0x3 (option nr = 3) Option Delta = 0x3 (option nr = 3)
Option Length = 0x9 Option Length = 0x9
Option Value = 192.0.2.1 Option Value = 192.0.2.1
Option2 (Uri-Port) Option2 (Observe)
Option Delta = 0x3 (option nr = 3+3=6)
Option Length = 0x1
Option Value = 0 (register)
Option3 (Uri-Port) [optional]
Option Delta = 0x4 (option nr = 3+4=7) Option Delta = 0x4 (option nr = 3+4=7)
Option Length = 0x4 Option Length = 0x4
Option Value = 8085 Option Value = 8085
Option3 (Uri-Path) Option4 (Uri-Path)
Option Delta = 0x4 (option nr = 7+4=11) Option Delta = 0x4 (option nr = 7+4=11)
Option Length = 0x9 Option Length = 0x5
Option Value = /est/crts Option Value = "est"
Option5 (Uri-Path)
Option Delta = 0x0 (option nr = 11+0=11)
Option Length = 0x6
Option Value = "crts"
Option6 (Max-Age)
Option Delta = 0x3 (option nr = 11+3=14)
Option Length = 0x1
Option Value = 0x1 ( 1 minute)
Payload = [Empty] Payload = [Empty]
The header of the first response looks like: The header of the first response looks like:
Ver = 1 Ver = 1
T = 2 (ACK) T = 2 (ACK)
Code = 0x45 (2.05 Content.) Code = 0x45 (2.05 Content)
Token = 0x9a (copied by server)
Options Options
Option1 (Content-Format) Option1 (Observe)
Option Delta = 0xC (option 12) Option Delta = 0x6 (option nr=6)
Option Length = 0x1
Option Value = 12 (12 > 0)
Option2 (Content-Format)
Option Delta = 0xC (option nr =6+6=12)
Option Length = 0x2 Option Length = 0x2
Option Value = TBD1 Option Value = TBD2
Option2 (Block2) Option2 (Block2)
Option Delta = 0xB (option 23 = 12 + 11) Option Delta = 0xB (option 23 = 12 + 11)
Option Length = 0x1 Option Length = 0x1
Option Value = 0x0A (block number = 0, M=1, SZX=2) Option Value = 0x0A (block number = 0, M=1, SZX=2)
Payload = Payload =
30233906092a6206734107028c2a3023260201013100300b06092a6206734107018 h'30233906092a6206734107028c2a3023260201013100300b06092a6206734107018
c0c3020bb302063c20102020900a61e75193b7acc0d06092a6206734101 c0c3020bb302063c20102020900a61e75193b7acc0d06092a6206734101'
The second Block2: The second Block2:
Ver = 1 Ver = 1
T = 2 (means ACK) T = 2 (means ACK)
Code = 0x45 (2.05 Content.) Code = 0x45 (2.05 Content)
Token = 0x9a (copied by server)
Options Options
Option1 (Content-Format) Option1 (Observe)
Option Delta = 0xC (option 12) Option Delta = 0x6 (option nr=6)
Option Length = 0x1
Option Value = 16 (16 > 12)
Option2 (Content-Format)
Option Delta = 0xC (option nr =6+6=12)
Option Length = 0x2 Option Length = 0x2
Option Value = TBD1 Option Value = TBD2
Option2 (Block2) Option2 (Block2)
Option Delta = 0xB (option 23 = 12 + 11) Option Delta = 0xB (option 23 = 12 + 11)
Option Length = 0x1 Option Length = 0x1
Option Value = 0x1A (block number = 1, M=1, SZX=2) Option Value = 0x1A (block number = 1, M=1, SZX=2)
Payload = Payload =
05050030 h'05050030
1b31193017060355040313106573744578616d706c654341204f774f301e170d313 1b31193017060355040313106573744578616d706c654341204f774f301e170d313
3303530393033353333315a170d3134303530393033353333315a 3303530393033353333315a170d3134303530393033353333315a'
The 40th and final Block2: The 40th and final Block2:
Ver = 1 Ver = 1
T = 2 (means ACK) T = 2 (means ACK)
Code = 0x21 Code = 0x45 (2.05 Content)
Token = 0x9a (copied by server)
Options Options
Option1 (Content-Format) Option1 (Observe)
Option Delta = 0xC (option 12) Option Delta = 0x6 (option nr=6)
Option Length = 0x1
Option Value = 55 (55 > 12)
Option2 (Content-Format)
Option Delta = 0xC (option nr =6+6=12)
Option Length = 0x2 Option Length = 0x2
Option Value = TBD1 Option Value = TBD2
Option2 (Block2) Option2 (Block2)
Option Delta = 0xB (option 23 = 12 + 11) Option Delta = 0xB (option 23 = 12 + 11)
Option Length = 0x2 Option Length = 0x2
Option Value = 0x272 (block number = 39, M=0, SZX=2) Option Value = 0x272 (block number = 39, M=0, SZX=2)
Payload = 73a30d0c006343116f58403100 Payload = h'73a30d0c006343116f58403100'
Authors' Addresses Authors' Addresses
Peter van der Stok Peter van der Stok
Consultant Consultant
Email: consultancy@vanderstok.org Email: consultancy@vanderstok.org
Panos Kampanakis Panos Kampanakis
Cisco Systems Cisco Systems
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