draft-ietf-ace-coap-est-05.txt   draft-ietf-ace-coap-est-06.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: January 19, 2019 Cisco Systems Expires: April 11, 2019 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
July 18, 2018 October 8, 2018
EST over secure CoAP (EST-coaps) EST over secure CoAP (EST-coaps)
draft-ietf-ace-coap-est-05 draft-ietf-ace-coap-est-06
Abstract Abstract
Enrollment over Secure Transport (EST) is used as a certificate Enrollment over Secure Transport (EST) is used as a certificate
provisioning protocol over HTTPS. Low-resource devices often use the provisioning protocol over HTTPS. Low-resource devices often use the
lightweight Constrained Application Protocol (CoAP) for message lightweight Constrained Application Protocol (CoAP) for message
exchanges. This document defines how to transport EST payloads over exchanges. This document defines how to transport EST payloads over
secure CoAP (EST-coaps), which allows low-resource constrained secure CoAP (EST-coaps), which allows low-resource constrained
devices to use existing EST functionality for provisioning devices to use existing EST functionality for provisioning
certificates. certificates.
skipping to change at page 1, line 45 skipping to change at page 1, line 45
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 19, 2019. This Internet-Draft will expire on April 11, 2019.
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.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Conformance to RFC7925 profiles . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Protocol Design . . . . . . . . . . . . . . . . . . . . . . . 4 4. Conformance to RFC7925 profiles . . . . . . . . . . . . . . . 5
4.1. Payload format . . . . . . . . . . . . . . . . . . . . . 5 5. Protocol Design . . . . . . . . . . . . . . . . . . . . . . . 6
4.1.1. Content Format application/multipart-core . . . . . . 6 5.1. Mandatory/optional EST Functions . . . . . . . . . . . . 7
4.2. Message Bindings . . . . . . . . . . . . . . . . . . . . 6 5.2. Payload format . . . . . . . . . . . . . . . . . . . . . 7
4.3. CoAP response codes . . . . . . . . . . . . . . . . . . . 6 5.2.1. Content Format application/multipart-core . . . . . . 8
4.4. Delayed Responses . . . . . . . . . . . . . . . . . . . . 7 5.3. Message Bindings . . . . . . . . . . . . . . . . . . . . 8
4.5. Server-side Key Generation . . . . . . . . . . . . . . . 9 5.4. CoAP response codes . . . . . . . . . . . . . . . . . . . 9
4.6. Message fragmentation . . . . . . . . . . . . . . . . . . 10 5.5. Delayed Responses . . . . . . . . . . . . . . . . . . . . 9
4.7. Deployment limits . . . . . . . . . . . . . . . . . . . . 11 5.6. Server-side Key Generation . . . . . . . . . . . . . . . 11
5. Discovery and URI . . . . . . . . . . . . . . . . . . . . . . 11 5.7. Message fragmentation . . . . . . . . . . . . . . . . . . 12
6. DTLS Transport Protocol . . . . . . . . . . . . . . . . . . . 13 5.8. Deployment limits . . . . . . . . . . . . . . . . . . . . 13
7. HTTPS-CoAPS Registrar . . . . . . . . . . . . . . . . . . . . 14 6. Discovery and URI . . . . . . . . . . . . . . . . . . . . . . 13
8. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 16 7. DTLS Transport Protocol . . . . . . . . . . . . . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 8. HTTPS-CoAPS Registrar . . . . . . . . . . . . . . . . . . . . 17
9.1. Content-Format Registry . . . . . . . . . . . . . . . . . 17 9. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.2. Resource Type registry . . . . . . . . . . . . . . . . . 18 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
10. Security Considerations . . . . . . . . . . . . . . . . . . . 18 10.1. Content-Format Registry . . . . . . . . . . . . . . . . 20
10.1. EST server considerations . . . . . . . . . . . . . . . 18 10.2. Resource Type registry . . . . . . . . . . . . . . . . . 20
10.2. HTTPS-CoAPS Registrar considerations . . . . . . . . . . 19 11. Security Considerations . . . . . . . . . . . . . . . . . . . 21
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 11.1. EST server considerations . . . . . . . . . . . . . . . 21
12. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 20 11.2. HTTPS-CoAPS Registrar considerations . . . . . . . . . . 22
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22
13.1. Normative References . . . . . . . . . . . . . . . . . . 21 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
13.2. Informative References . . . . . . . . . . . . . . . . . 22 13.1. Normative References . . . . . . . . . . . . . . . . . . 23
Appendix A. EST messages to EST-coaps . . . . . . . . . . . . . 24 13.2. Informative References . . . . . . . . . . . . . . . . . 24
A.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 25 Appendix A. EST messages to EST-coaps . . . . . . . . . . . . . 26
A.2. csrattrs . . . . . . . . . . . . . . . . . . . . . . . . 29 A.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 26
A.3. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 29 A.2. csrattrs . . . . . . . . . . . . . . . . . . . . . . . . 31
A.4. serverkeygen . . . . . . . . . . . . . . . . . . . . . . 32 A.3. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 31
Appendix B. EST-coaps Block message examples . . . . . . . . . . 34 A.4. serverkeygen . . . . . . . . . . . . . . . . . . . . . . 33
B.1. cacerts block example . . . . . . . . . . . . . . . . . . 34 Appendix B. EST-coaps Block message examples . . . . . . . . . . 35
B.2. enroll block example . . . . . . . . . . . . . . . . . . 37 B.1. cacerts block example . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38 B.2. enroll block example . . . . . . . . . . . . . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39
1. Introduction 1. Change Log
EDNOTE: Remove this section before publication
-06:
clarified discovery section, by specifying that no discovery may
be needed for /.well-known/est URI.
added resource type values for IANA
added list of compulsory to implement and optional functions.
Fixed issues pointed out by the idnits tool.
Updated COAP response codes section with more mappings between EST
HTTP codes and EST-coaps COAP codes.
Minor updates to the MTI EST Functions section.
Moved Change Log section higher.
-05:
repaired again
TBD8 removed from C-F registration, to be done in CT draft.
-04:
Updated Delayed response section to reflect short and long delay
options.
-03:
Removed observe and simplified long waits
Repaired content-format specification
-02:
Added parameter discussion in section 8
Concluded content-format specification using multipart-ct draft
examples updated
-01:
Editorials done.
Redefinition of proxy to Registrar in Section 8. Explained better
the role of https-coaps Registrar, instead of "proxy"
Provide "observe" option examples
extended block message example.
inserted new server key generation text in Section 5.6 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
2. Introduction
"Classical" Enrollment over Secure Transport (EST) [RFC7030] is used "Classical" Enrollment over Secure Transport (EST) [RFC7030] is used
for 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). EST messages run over HTTPS. Registration Authority (RA). EST messages run over HTTPS.
This document defines a new transport for EST based on the This document defines a new transport for EST based on the
Constrained Application Protocol (CoAP) since some Internet of Things Constrained Application Protocol (CoAP) since some Internet of Things
(IoT) devices use CoAP instead of HTTP. Therefore, this (IoT) devices use CoAP instead of HTTP. Therefore, this
specification utilizes DTLS [RFC6347], CoAP [RFC7252], and UDP specification utilizes DTLS [RFC6347], CoAP [RFC7252], and UDP
instead of TLS [RFC5246], HTTP [RFC7230] and TCP. instead of TLS [RFC8446], HTTP [RFC7230] and TCP.
EST messages may be relatively large and for this reason this EST messages may be relatively large and for this reason this
document also uses CoAP Block-Wise Transfer [RFC7959] to offer a document also uses CoAP Block-Wise Transfer [RFC7959] to offer a
fragmentation mechanism of EST messages at the CoAP layer. fragmentation mechanism of EST messages at the CoAP layer.
This specification also profiles the use of EST to only support This specification also profiles the use of EST to only support
certificate-based client Authentication. HTTP Basic or Digest certificate-based client Authentication. HTTP Basic or Digest
authentication (as described in Section 3.2.3 of [RFC7030] are not authentication (as described in Section 3.2.3 of [RFC7030] are not
supported. supported.
2. Terminology 3. 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.
3. Conformance to RFC7925 profiles 4. 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 described in [RFC7925]. resource devices described in [RFC7925].
EST-coaps can transport certificates and private keys. Certificates EST-coaps can transport certificates and private keys. Certificates
are responses to (re-)enrollment requests or request for a trusted are responses to (re-)enrollment requests or request for a trusted
certificate list. Private keys can be transported as responses to a certificate list. Private keys can be transported as responses to a
request to a server-side keygeneration as described in section 4.4 of request to a server-side keygeneration as described in section 4.4 of
[RFC7030] and discussed in Section 4.5 of this document. [RFC7030] and discussed in Section 5.6 of this document.
As per [RFC7925] section 3.3 and section 4.4, the mandatory cipher As per [RFC7925] section 3.3 and section 4.4, the mandatory cipher
suite for DTLS in EST-coaps is TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 suite for DTLS in EST-coaps is TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8
defined in [RFC7251], and the curve secp256r1 MUST be supported defined in [RFC7251], and the curve secp256r1 MUST be supported
[RFC4492]; this curve is equivalent to the NIST P-256 curve. Crypto [RFC8422]; this curve is equivalent to the NIST P-256 curve. Crypto
agility is important, and the recommendations in [RFC7925] section agility is important, and the recommendations in [RFC7925] section
4.4 and any updates to RFC7925 concerning Curve25519 and other CFRG 4.4 and any updates to RFC7925 concerning Curve25519 and other CFRG
curves also applies. curves also apply.
DTLS1.2 implementations MUST use the Supported Elliptic Curves and DTLS1.2 implementations MUST use the Supported Elliptic Curves and
Supported Point Formats Extensions [RFC4492]. Uncompressed point Supported Point Formats Extensions [RFC8422]. Uncompressed point
format MUST also be supported. [RFC6090] can be used as summary of format MUST also be supported. [RFC6090] can be used as summary of
the ECC algorithms. DTLS 1.3 implementations differ from DTLS 1.2 the ECC algorithms. DTLS 1.3 implementations differ from DTLS 1.2
because they do not support point format negotiation in favor of a 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 single point format for each curve and thus support for DTLS 1.3 does
not mandate point formation extensions and negotiation. not mandate point formation extensions and negotiation.
The EST-coaps client MUST be configured with at least an implicit TA The EST-coaps client MUST be configured with at least an implicit TA
database from its manufacturer. The authentication of the EST-coaps database from its manufacturer. The authentication of the EST-coaps
server by the EST-coaps client is based on certificate authentication server by the EST-coaps client is based on certificate authentication
in the DTLS handshake. in the DTLS handshake.
The authentication of the EST-coaps client is based on a client 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 a previously issued client certificate (e.g., an existing o a previously issued client certificate (e.g., an existing
certificate issued by the EST CA); this could be a common case for certificate issued by the EST CA); this could be a common case for
simple re-enrollment of clients; simple reenrollment of clients;
o a previously installed certificate (e.g., manufacturer-installed o a previously installed certificate (e.g., manufacturer-installed
certificate or a certificate issued by some other party); the certificate or a certificate issued by some other party); the
server is expected to trust the manufacturer's root CA certificate server is expected to trust the manufacturer's root CA certificate
in this case. in this case.
4. Protocol Design 5. 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) fragmentation of UDP datagrams. The use of "Block" for (excessive) fragmentation of UDP datagrams. The use of "Block" for
the transfer of larger EST messages is specified in Section 4.6. The the transfer of larger EST messages is specified in Section 5.7. The
Figure 1 below shows the layered EST-coaps architecture. Figure 1 below shows the layered EST-coaps architecture.
+------------------------------------------------+ +------------------------------------------------+
| EST request/response messages | | EST request/response messages |
+------------------------------------------------+ +------------------------------------------------+
| CoAP for message transfer and signalling | | CoAP for message transfer and signalling |
+------------------------------------------------+ +------------------------------------------------+
| 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
actions supported by EST-coaps are identified by their message types: actions supported by EST-coaps are identified by their message types:
skipping to change at page 5, line 33 skipping to change at page 7, line 9
o Simple enroll and reenroll, for CA to sign public client-identity o Simple enroll and reenroll, for CA to sign public client-identity
key. key.
o Certificate Signing Request (CSR) Attributes request messages, o Certificate Signing Request (CSR) Attributes request messages,
informs the client of the fields to include in generated CSR. 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 choses for an external entity to identity key when the client choses for an external entity to
generate its private key. generate its private key.
4.1. Payload format 5.1. Mandatory/optional EST Functions
This specification contains a set of required-to-implement functions,
optional functions, and not specified functions. The latter ones are
deemed too expensive for low-resource devices in payload and
calculation times.
Table 1 specifies the mandatory-to-implement or optional
implementation of the est-coaps functions.
+------------------+--------------------------+
| EST Functions | EST-coaps implementation |
+------------------+--------------------------+
| /cacerts | Mandatory |
| /simpleenroll | Mandatory |
| /simplereenroll | Mandatory |
| /fullcmc | Not specified |
| /serverkeygen | Optional |
| /csrattrs | Optional |
+------------------+--------------------------+
Table 1: list of EST -coaps fuctions
5.2. 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 (section 3.2.2 media types specified in the HTTP Content-Type header (section 3.2.2
of [RFC7030]) are in EST-coaps specified by the Content-Format Option of [RFC7030]) are in EST-coaps specified by the Content-Format Option
(12) of CoAP. The combination of URI path and content-format used (12) of CoAP. The combination of URI path and content-format used
for CoAP MUST map to an allowed combination of URI and media type as for CoAP MUST map to an allowed combination of URI and media type as
defined for EST. The required content-formats for these requests and defined for EST. The required content-formats for these requests and
response messages are defined in Section 9. The CoAP response codes response messages are defined in Section 10. The CoAP response codes
are defined in Section 4.3. are defined in Section 5.4.
EST-coaps is designed for use between low-resource devices and hence EST-coaps is designed for use between low-resource devices and hence
does not need to send base64-encoded data. Simple binary is more does not need to send base64-encoded data. Simple binary is more
efficient (30% smaller payload) and well supported by CoAP. efficient (30% smaller payload) and well supported by CoAP.
Therefore, the content formats specification in Section 4.1.1
specifies that the binary payload is transported as a CBOR major type
2, a byte 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.
4.1.1. Content Format application/multipart-core The payload for a given media type follows the ASN.1 structure of the
media-type and is transported as straight binary coding instead of
the base64-encoded. The binary is wrapped in a CBOR major type 2
using h'xxx' notation (to assure compatibility with multipart).
EDNote: suggestion to remove CBOR wrapping for not multipart.
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. The content formats specification in Section 5.2.1
specifies the payload structure when multiple media types are present
in the payload.
5.2.1. Content Format application/multipart-core
A representation with content format ID TBD8 contains a collection of A representation with content format ID TBD8 contains a collection of
representations along with their respective content format. The representations along with their respective content format. The
content-format identifies the media-type application/multipart-core content-format identifies the media-type application/multipart-core
specified in [I-D.fossati-core-multipart-ct]. specified in [I-D.ietf-core-multipart-ct].
The collection is encoded as a CBOR array [RFC7049] with an even The collection is encoded as a CBOR array [RFC7049] with an even
number of elements. The second, fourth, sixth, etc. element is a number of elements. The second, fourth, sixth, etc. element is a
binary string containing a representation. The first, third, fifth, binary string containing a representation. The first, third, fifth,
etc. element is an unsigned integer specifying the content format ID etc. element is an unsigned integer specifying the content format ID
of the following representation. of the following representation.
For example, a collection containing two representations, one with For example, a collection containing two representations in response
content format ID TBD5 and one with content format ID TBD2, looks to a server-side key generation, could include a private key in
like this in diagnostic CBOR notation: PKCS#8 with content format ID 284 and a certificate with content
[TBD5,h'0123456789abcdef',TBD2,h'fedcba9876543210']. An example is format ID 281, looks like this in diagnostic CBOR notation:
shown in Appendix A.4. [284,h'0123456789abcdef',281,h'fedcba9876543210']. The PKCS#8 key
and the X.509 certificate representations will be ASN.1 encoded in
binary format. An example is shown in Appendix A.4.
4.2. Message Bindings 5.3. Message Bindings
The general EST CoAP message characteristics are: The general EST CoAP message characteristics are:
o All EST-coaps messages expect a response from the server, thus the o All EST-coaps messages expect a response from the server, thus the
client MUST send the requests over confirmable CON COAP messages. client MUST send the requests over confirmable CON COAP messages.
o The Ver, TKL, Token, and Message ID values of the CoAP header are o The Ver, TKL, Token, and Message ID values of the CoAP header are
not affected by EST. not affected by EST.
o The CoAP options used are Uri-Host, Uri-Path, Uri-Port, Content- o The CoAP options used are Uri-Host, Uri-Path, Uri-Port, Content-
Format, and Location-Path in CoAP. These 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.
o EST URLs are HTTPS based (https://), in CoAP these will be assumed o EST URLs are HTTPS based (https://), in CoAP these will be assumed
to 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.
4.3. CoAP response codes 5.4. 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 request, in EST-coaps the specified in [RFC7030] in response to a GET request, in EST-coaps the
equivalent CoAP response code 2.05 or 2.03 MUST be used. Similarly, equivalent CoAP response code 2.05 or 2.03 MUST be used. Similarly,
2.01, 2.02 or 2.04 MUST be used in response to POST EST requests. 2.01, 2.02 or 2.04 MUST be used in response to POST EST requests.
Response code HTTP 202 has no equivalent in CoAP. In Section 4.4 it Response code HTTP 202 has no equivalent in CoAP. Section 5.5
is specified how EST requests over CoAP handle delayed messages. specifies how EST requests over CoAP handle delayed messages.
All other HTTP 2xx response codes are not used by EST. For the Other HTTP response codes EST makes use of, are 204 and 404 when a
following HTTP 4xx error codes that may occur: 400, 401, 403, 404, resource is not available for the client. The equivalent COAP error
405, 406, 412, 413, 415; the equivalent CoAP response code for EST- code to use in an EST-coaps response is 4.04. Additionally, EST's
coaps is 4.xx. For the HTTP 5xx error codes: 500, 501, 502, 503, 504 401 error translates to 4.01 in EST-coaps. Other HTTP error messages
the equivalent CoAP response code is 5.xx. commonly used in EST are 400, 423 and 503. Their equivalent COAP
errors are 4.00, 4.03 and 5.03 respectively.
4.4. Delayed Responses 5.5. Delayed Responses
Appendix B.2 shows an example of a server response that comes Appendix B.2 shows an example of a server response that comes
immediately after a client request. The example shows the flows of immediately after a client request. The example shows the flows of
blocks as the large messages require fragmentation. But server blocks as the large messages require fragmentation. But server
responses can sometimes be delayed. responses can sometimes be delayed.
According to section 5.2.2 of [RFC7252], a slow server can According to section 5.2.2 of [RFC7252], a slow server can
acknowledge the request and respond later with the requested resource acknowledge the request and respond later with the requested resource
representation. In particular, a slow server can respond to a enroll representation. In particular, a slow server can respond to a enroll
request with an empty ACK with code 0.00, before sending the request with an empty ACK with code 0.00, before sending the
skipping to change at page 9, line 31 skipping to change at page 11, line 31
POST [2001:db8::2:1]:61616/est/sen (CON)(2:1/0/128) --> POST [2001:db8::2:1]:61616/est/sen (CON)(2:1/0/128) -->
<-- (ACK) (2:1/1/128) (2.04 Changed) {Cert resp} <-- (ACK) (2:1/1/128) (2.04 Changed) {Cert resp}
. .
. .
. .
POST [2001:db8::2:1]:61616/est/sen (CON)(2:N2/0/128) --> POST [2001:db8::2:1]:61616/est/sen (CON)(2:N2/0/128) -->
<-- (ACK) (2:N2/0/128) (2.04 Changed) {Cert resp} <-- (ACK) (2:N2/0/128) (2.04 Changed) {Cert resp}
Figure 3: EST-COAP enrolment with long wait Figure 3: EST-COAP enrolment with long wait
4.5. Server-side Key Generation 5.6. Server-side Key Generation
Constrained devices sometimes do not have the necessary hardware to Constrained devices sometimes do not have the necessary hardware to
generate statistically random numbers for private keys and DTLS generate statistically random numbers for private keys and DTLS
ephemeral keys. Past experience has shown that low-resource ephemeral keys. Past experience has shown that low-resource
endpoints sometimes generate numbers which could allow someone to endpoints sometimes generate numbers which could allow someone to
decrypt the communication or guess the private key and impersonate as decrypt the communication or guess the private key and impersonate as
the device. Studies have shown that the same keys are generated by the device. Studies have shown that the same keys are generated by
the same model devices deployed on-line. the same model devices deployed on-line.
EDNote: Is there a reference for these studies?
Additionally, random number key generation is costly, thus energy Additionally, random number key generation is costly, thus energy
draining. Even though the random numbers that constitute the draining. Even though the random numbers that constitute the
identity/cert do not get generated often, an endpoint may not want to 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 spend time and energy generating keypairs, and just ask for one from
the server. the server.
In these scenarios, server-side key generation can be used. The In these scenarios, server-side key generation can be used. The
client asks for the server or proxy to generate the private key and client asks for the server or proxy to generate the private key and
the certificate which is transferred back to the client in the the certificate which is transferred back to the client in the
server-side key generation response. server-side key generation response.
skipping to change at page 10, line 15 skipping to change at page 12, line 17
[RFC7030] recommends for the private key returned by the server to be [RFC7030] recommends for the private key returned by the server to be
encrypted. The specification provides two methods to encrypt the encrypted. The specification provides two methods to encrypt the
generated key, symmetric and asymmetric. The methods are signalled generated key, symmetric and asymmetric. The methods are signalled
by the client by using the relevant attributes (SMIMECapabilities and by the client by using the relevant attributes (SMIMECapabilities and
DecryptKeyIdentifier or AsymmetricDecryptKeyIdentifier) in the CSR DecryptKeyIdentifier or AsymmetricDecryptKeyIdentifier) in the CSR
request. In the symmetric key case, the key can be established out- request. In the symmetric key case, the key can be established out-
of-band or alternatively derived by the established TLS connection as of-band or alternatively derived by the established TLS connection as
described in [RFC5705]. described in [RFC5705].
The sever-side key generation response is returned using a CBOR array The sever-side key generation response is returned using a CBOR array
Section 4.1.1. The certificate part exactly matches the response Section 5.2.1. The certificate part exactly matches the response
from a enrollment response. The private key is placed inside of a from an enrollment response. The private key is placed inside of a
CMS SignedData. The SignedData is signed by the party that generated 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 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 CA. The SignedData is further protected by placing it inside of a
CMS EnvelopedData as explained in Section 4.4.2 of [RFC7030]. CMS EnvelopedData as explained in Section 4.4.2 of [RFC7030].
4.6. Message fragmentation 5.7. 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 11, line 31 skipping to change at page 13, line 33
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 B. Examples of fragmented messages are shown in Appendix B.
4.7. Deployment limits 5.8. 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
do not. do not.
5. Discovery and URI 6. 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 a short EST-coaps URI (see
specified that is shorter than the EST URI. Table 2) is specified that is shorter than the EST URI specified in
[RFC7030]. The individual EST-coaps well-known server URIs differ
from the EST URI by replacing the scheme https by coaps and by
specifying shorter resource path names:
coaps://example.com:<port>/.well-known/est/<short-est>
coaps://example.com:<port>/.well-known/est/ArbitraryLabel/<short-est>
The ArbitraryLabel Path-Segment, if used, SHOULD be of the shortest
length possible (See sections 3.1 and 3.2.2 of [RFC7030]. Following
[RFC7030] discovery is not needed when the client is preconfigured
with the /.well-known/est server URI and the coaps port 5684.
The additional EST-coaps server URIs, obtained through discovery of
the EST root resource(s) as shown below, are of the form:
coaps://example.com:<port>/<root-resource>/<short-est>
coaps://example.com:<port>/<root-resource>/ArbitraryLabel/<short-est>
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 root resource /est is used.
The individual EST-coaps server URIs differ from the EST URI by The optional additional EST-coaps server URIs, obtained through
replacing the scheme https by coaps and by specifying shorter discovery of the EST root resource(s) as shown below, are of the
resource path names: form:
coaps://www.example.com/.well-known/est/ArbitraryLabel/<short-est>.
The ArbitraryLabel Path-Segment SHOULD be of the shortest length coaps://example.com:<port>/<root-resource>/<short-est>
possible. coaps://example.com:<port>/<root-resource>/ArbitraryLabel/<short-est>
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 2 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 2: Short EST-coaps URI path
The short resource URIs MUST be supported. The corresponding longer The short resource URIs MUST be supported. The corresponding longer
URIs specified in [RFC7030] MAY be supported. 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 all available resource paths and the used content types. This return all available resource paths and the used content types. This
is useful when multiple content types are specified for EST-coaps is useful when multiple content types are specified for EST-coaps
server. The example below shows the discovery of the presence and server and optional functions are available. The example below shows
location of management data. the discovery of the presence and location of EST-coaps resources.
Linefeeds are included only for readability.
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>;ct=TBD2 </est/crts>;rt="ace.est.crts";ct=281,
</est/sen>;ct=TBD2 TBD7 </est/sen>;rt="ace.est.sen"ct=281 286,
</est/sren>;ct=TBD2 TBD7 </est/sren>;rt="ace.est.sren"ct=281 286,
</est/att>;ct=TBD6 </est/att>;rt="ace.est.att"ct=285,
</est/skg>;ct=TBD1 TBD7 TBD8 </est/skg>;rt="ace.est.skg"ct=280 286 TBD8
The first line of the discovery response MUST be returned. The five The first line of the discovery response MUST be returned. The five
consecutive lines MAY be returned. The return of the content-types consecutive lines MAY be returned. The return of the content-types
in the last four lines allows the client to choose the most in the last four lines allows the client to choose the most
appropriate one from multiple content types. appropriate one from multiple content types.
6. DTLS Transport Protocol Port numbers, not returned in the example, are assumed to be the
default numbers 5683 and 5684 for coap and coaps respectively
(sections 12.6 and 12.7 of [RFC7252]. Discoverable port numbers MAY
be returned in the <href> of the payload.
7. 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 exchanged CoAP messages. 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
skipping to change at page 14, line 17 skipping to change at page 16, line 39
message message
HMAC(finished_key, HMAC(finished_key,
Transcript-Hash(Handshake Context, Transcript-Hash(Handshake Context,
Certificate*, CertificateVerify*)) Certificate*, CertificateVerify*))
* Only included if present. * Only included if present.
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 following the algorithm described in 4.4.4 of single fragment following the algorithm described in 4.4.4 of
[I-D.ietf-tls-tls13]. [RFC8446].
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. In some cases, such as NAT relatively close to each other. In some cases, such as NAT
rebinding, keeping the state of a connection is not possible when rebinding, keeping the state of a connection is not possible when
devices sleep for extended periods of time. In such occasions, devices sleep for extended periods of time. In such occasions,
[I-D.rescorla-tls-dtls-connection-id] negotiates a connection ID that [I-D.rescorla-tls-dtls-connection-id] negotiates a connection ID that
can eliminate the need for new handshake and its additional cost. can eliminate the need for new handshake and its additional cost.
7. HTTPS-CoAPS Registrar 8. 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 Registrar 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 EST coaps-to-HTTPS Registrar MUST terminate EST-coaps and The EST coaps-to-HTTPS Registrar MUST terminate EST-coaps and
authenticate the client downstream and initiate EST connections over authenticate the client downstream and initiate EST connections over
TLS upstream. TLS upstream.
The Registrar SHOULD authenticate the client downstream and it should The Registrar SHOULD authenticate the client downstream and it should
be authenticated by the EST server or CA upstream. The Registration be authenticated by the EST server or CA upstream. The Registration
Authority (re-)creates the secure connection from DTLS to TLS and Authority (re-)creates the secure connection from DTLS to TLS and
vice versa. A trust relationship SHOULD be pre-established between vice versa. A trust relationship SHOULD be pre-established between
the Registrar and the EST servers to be able to proxy these the Registrar and the EST servers to be able to proxy these
connections on behalf of various clients. connections on behalf of various clients.
When enforcing Proof-of-Possession (POP), the (D)TLS tls-unique value When enforcing Proof-of-Possession (POP) linking, the (D)TLS tls-
of the (D)TLS session needs to be used to prove that the private key unique value of the (D)TLS session needs to be used to prove that the
corresponding to the public key is in the possession of and can be private key corresponding to the public key is in the possession of
used by an end-entity or client. In other words, the CSR the client and was used to establish the connection by an end-entity or client.
is using needs to include information from the DTLS connection the To do that the CSR the client is using needs to include information
client establishes with the server. In EST, that information is the from the DTLS connection the client establishes with the server. In
(D)TLS tls-unique value of the (D)TLS session. In the presence of EST, that information is the (D)TLS tls-unique value of the (D)TLS
ESTcoaps-to-HTTPS Registrar, the EST-coaps client MUST be session. In the presence of ESTcoaps-to-HTTPS Registrar, the EST-
authenticated and authorized by the Registrar and the Registrar MUST coaps client MUST be authenticated and authorized by the Registrar
be authenticated as an EST Registrar client to the EST server. Thus and the Registrar MUST be authenticated as an EST Registrar client to
the POP information is lost between the EST-coaps client and the EST the EST server. Thus the POP linking information is lost between the
server. The EST server becomes aware of the presence of an EST EST-coaps client and the EST server. The EST server becomes aware of
Registrar from its TLS client certificate that includes id-kp-cmcRA the presence of an EST Registrar from its TLS client certificate that
[RFC6402] extended key usage extension. As explained in Section 3.7 includes id-kp-cmcRA [RFC6402] extended key usage extension. As
of [RFC7030], the EST server SHOULD apply an authorization policy explained in Section 3.7 of [RFC7030], the EST server SHOULD apply an
consistent with a Registrar client. For example, it could be authorization policy consistent with a Registrar client. For
configured to accept POP linking information that does not match the example, it could be configured to accept POP linking information
current TLS session because the authenticated EST client Registrar that does not match the current TLS session because the authenticated
has verified this information when acting as an EST server. EST client Registrar has verified this information when acting as an
EST server.
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 and is responsible for generating a new CSR signed by
a new key which will be returned to the client along with the
certificate from the CA.
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:
Constrained Network Constrained Network
.---------. .----------------------------. .------. .----------------------------.
| CA | |.--------------------------.| | CA | |.--------------------------.|
'---------' || || '------' || ||
| || || | || ||
.------. HTTP .-----------------. CoAPS .-----------. || .------. HTTP .-----------------. CoAPS .-----------. ||
| EST |<------->|ESTcoaps-to-HTTPS|<-------->| EST Client| || | EST |<------->|ESTcoaps-to-HTTPS|<-------->| EST Client| ||
|Server|over TLS | Registrar | '-----------' || |Server|over TLS | Registrar | '-----------' ||
'------' '-----------------' || '------' '-----------------' ||
|| || || ||
|'--------------------------'| |'--------------------------'|
'----------------------------' '----------------------------'
ESTcoaps-to-HTTPS Registrar 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 2 contains the URI mapping between the EST-coaps and EST the
Registrar SHOULD adhere to. Section 7 of [RFC8075] and Section 4.3 Registrar SHOULD adhere to. Section 7 of [RFC8075] and Section 5.4
define the mapping between EST-coaps and HTTP response codes, that define the mapping between EST-coaps and HTTP response codes, that
determines how the Registrar translates CoAP response codes from/to determines how the Registrar translates CoAP response codes from/to
HTTP status codes. The mapping from Content-Type to media type is HTTP status codes. The mapping from Content-Type to media type is
defined in Section 9. The conversion from CBOR major type 2 to defined in Section 10. The conversion from CBOR major type 2 to
base64 encoding needs to be done in the Registrar. Conversion is base64 encoding needs to be done in the Registrar. Conversion is
possible because a TLS link exists between EST-coaps-to-HTTP possible because a TLS link exists between EST-coaps-to-HTTP
Registrar and EST server and a corresponding DTLS link exists between Registrar and EST server and a corresponding DTLS link exists between
EST-coaps-to-HTTP Registrar and EST client. 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 Registrar SHOULD reassemble the BLOCKs before translating the HTTP Registrar MUST reassemble the BLOCKs before translating the
binary content to Base-64, and consecutively relay the message binary content to Base-64, and consecutively relay the message
upstream. 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 Registrar MUST announce itself environment, the EST-coaps-to-HTTP Registrar MUST announce itself
according to the rules of Section 5. The available actions of the according to the rules of Section 6. The available actions of the
Registrars MUST be announced with as many resource paths. The Registrars MUST be announced with as many resource paths. The
discovery of EST server in the http environment follow the rules discovery of EST server in the http environment follow the rules
specified in [RFC7030]. specified in [RFC7030].
When server-side key generation is used, if the private key is 9. Parameters
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.
8. Parameters
THis section addresses transmission parameters described in sections This section addresses transmission parameters described in sections
4.7 and 4.8 of the CoAP document [RFC7252]. 4.7 and 4.8 of the CoAP document [RFC7252].
ACK_TIMEOUT | 2 seconds | ACK_TIMEOUT | 2 seconds |
ACK_RANDOM_FACTOR | 1.5 | ACK_RANDOM_FACTOR | 1.5 |
MAX_RETRANSMIT | 4 | MAX_RETRANSMIT | 4 |
NSTART | 1 | NSTART | 1 |
DEFAULT_LEISURE | 5 seconds | DEFAULT_LEISURE | 5 seconds |
PROBING_RATE | 1 byte/second | PROBING_RATE | 1 byte/second |
Figure 4: EST-COAP protocol parameters Figure 4: EST-COAP protocol parameters
EST does not impose any unique parameters that affect the CoAP EST 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 parameters 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 could be less then 2s, but in this case they should send a CoAP ACK
every 2s while processing. every 2s while processing.
The main recommendation, based on experiments using Nexus Certificate The main recommendation, based on experiments using Nexus Certificate
skipping to change at page 17, line 32 skipping to change at page 20, line 7
o PROBING_RATE: A parameter which specifies the rate of re-sending o PROBING_RATE: A parameter which specifies the rate of re-sending
non-confirmable messages. The EST messages are defined to be sent non-confirmable messages. The EST messages are defined to be sent
as CoAP confirmable messages, hence the PROBING_RATE setting is as CoAP confirmable messages, hence the PROBING_RATE setting is
not applicable. not applicable.
Finally, the Table 3 parameters are mainly derived from the more Finally, the Table 3 parameters are mainly derived from the more
basic Table 2 parameters. If the CoAP implementation allows setting basic Table 2 parameters. If the CoAP implementation allows setting
them directly, they might need to be updated if the table 2 them directly, they might need to be updated if the table 2
parameters are changed. parameters are changed.
9. IANA Considerations 10. IANA Considerations
9.1. Content-Format Registry 10.1. Content-Format Registry
Additions to the sub-registry "CoAP Content-Formats", within the Additions to the sub-registry "CoAP Content-Formats", within the
"CoRE Parameters" registry are specified in Table 2. These can be "CoRE Parameters" registry are specified in Table 3. These have been
registered either in the Expert Review range (0-255) or IETF Review registered temporarily in the Expert Review range (0-255).
range (256-9999).
+-----------------------------------+----------+------+-------------+ +--------------------------+--------+-----+-------------------------+
| Media type | Encoding | ID | Reference | | HTTP Media-Type | Encodi | ID | Reference |
+-----------------------------------+----------+------+-------------+ | | ng | | |
| application/pkcs7-mime; smime- | - | TBD1 | [RFC5751] | +--------------------------+--------+-----+-------------------------+
| type=server-generated-key | | | [RFC7030] | | application/pkcs7-mime; | - | 280 | [I-D.ietf-lamps-rfc5751 |
| application/pkcs7-mime; smime- | - | TBD2 | [RFC5751] | | smime-type=server- | | | -bis] [RFC7030] |
| type=certs-only | | | | | generated-key | | | |
| application/pkcs7-mime; smime- | - | TBD3 | [RFC5751] | | application/pkcs7-mime; | - | 281 | [I-D.ietf-lamps-rfc5751 |
| type=CMC-request | | | [RFC5273] | | smime-type=certs-only | | | -bis] |
| application/pkcs7-mime; smime- | - | TBD4 | [RFC5751] | | application/pkcs7-mime; | - | 282 | [I-D.ietf-lamps-rfc5751 |
| type=CMC-response | | | [RFC5273] | | smime-type=CMC-request | | | -bis] [RFC5273] |
| application/pkcs8 | - | TBD5 | [RFC5751] | | application/pkcs7-mime; | - | 283 | [I-D.ietf-lamps-rfc5751 |
| | | | [RFC5958] | | smime-type=CMC-response | | | -bis] [RFC5273] |
| application/csrattrs | - | TBD6 | [RFC7030] | | application/pkcs8 | - | 284 | [I-D.ietf-lamps-rfc5751 |
| | | | [RFC7231] | | | | | -bis] [RFC5958] |
| application/pkcs10 | - | TBD7 | [RFC5751] | | application/csrattrs | - | 285 | [RFC7030] [RFC7231] |
| | | | [RFC5967] | | application/pkcs10 | - | 286 | [I-D.ietf-lamps-rfc5751 |
+-----------------------------------+----------+------+-------------+ | | | | -bis] [RFC5967] |
+--------------------------+--------+-----+-------------------------+
Table 2: New CoAP Content-Formats Table 3: New CoAP Content-Formats
9.2. Resource Type registry 10.2. Resource Type registry
Additions to the sub-registry "CoAP Resource Type", within the "CoRE This memo registers a new Resource Type (rt=) Link Target Attributes
Parameters" registry are needed for a new resource type. in the "Resource Type (rt=) Link Target Attribute Values" subregistry
under the "Constrained RESTful Environments (CoRE) Parameters"
registry.
o rt="ace.est" needs registration with IANA. o rt="ace.est". This EST resource is used to query and return the
supported EST resources of a CoAP server.
10. Security Considerations o rt="ace.est.crts". This resource depicts the support of EST get
cacerts.
10.1. EST server considerations o rt="ace.est.sen". This resource depicts the support of EST simple
enroll.
o rt="ace.est.sren". This resource depicts the support of EST
simple reenroll.
o rt="ace.est.att". This resource depicts the support of EST CSR
attributes.
o rt="ace.est.skg". This resource depicts the support of EST
server-side key generation.
11. Security Considerations
11.1. 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 database 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 6 in requests (to prevent such Identity and POP Information" Section 7 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 risk to the first DTLS (Section 4.1.3 of [RFC7030]) limits any risk to the first DTLS
exchange. exchange.
In accordance with [RFC7030], TLS cipher suites that include In accordance with [RFC7030], TLS cipher suites that include
skipping to change at page 19, line 37 skipping to change at page 22, line 18
exclude attributes that a server may want, include attributes that a exclude attributes that a server may want, include attributes that a
server may not want, and render meaningless other attributes that a server may not want, and render meaningless other attributes that a
server may want. The CA is expected to be able to enforce policies server may want. The CA is expected to be able to enforce policies
to recover from improper CSR requests. to recover from improper 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.
10.2. HTTPS-CoAPS Registrar considerations 11.2. HTTPS-CoAPS Registrar considerations
The Registrar proposed in Section 7 must be deployed with care, and The Registrar proposed in Section 8 must be deployed with care, and
only when the recommended connections are impossible. When POP is only when the recommended connections are impossible. When POP
used the Registrar terminating the TLS connection establishes a new linking is used the Registrar terminating the TLS connection
one with the upstream CA. Thus, it is impossible for POP to be establishes a new one with the upstream CA. Thus, it is impossible
enforced throughout the EST transaction. The EST server could be for POP linking to be enforced end-to-end for the EST transaction.
configured to accept POP linking information that does not match the The EST server could be configured to accept POP linking information
current TLS session because the authenticated EST Registrar client that does not match the current TLS session because the authenticated
has verified this information when acting as an EST server. The EST Registrar client has verified this information when acting as an
introduction of an EST-coaps-to-HTTP Registrar assumes the client can EST server. The introduction of an EST-coaps-to-HTTP Registrar
trust the registrar using its implicit or explicit TA database. It assumes the client can trust the registrar using its implicit or
also assumes the Registrar has a trust relationship with the upstream explicit TA database. It also assumes the Registrar has a trust
EST server in order to act on behalf of the clients. 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 In a server-side key generation case, if no end-to-end encryption is
encryption method, the Registrar may be able see the private key as used, the Registrar may be able see the private key as it acts as a
it acts as a man-in-the-middle. Thus, the clients puts its trust on man-in-the-middle. Thus, the clients puts its trust on the Registrar
the Registrar not exposing the private key. not exposing the private key.
For some use cases, clients that leverage server-side key generation Clients that leverage server-side key generation have no knowledge if
might prefer for the enrolled keys to be generated by the Registrar the Registrar will be generating the keys and enrolling the
if the CA does not support server-side key generation. In these certificates with the CA or if the CA will be responsible for
cases the Registrar must support the random number generation using generating the keys, the existence of a Registrar requires the client
proper entropy. Since the client has no knowledge if the Registrar to put its trust on the registrar doing the right thing if it is
will be generating the keys and enrolling the certificates with the generating they private keys.
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 12. 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 and his support for the explanations on the use of Block with DTLS and his support for the
content-format specification. The authors would like to thank Esko content-format specification. The authors would like to thank Esko
Dijk and Michael Verschoor for the valuable discussions that helped Dijk and Michael Verschoor for the valuable discussions that helped
in shaping the solution. They would also like to thank Peter in shaping the solution. They would also like to thank Peter
Panburana for his feedback on technical details of the solution. Panburana for his feedback on technical details of the solution.
Constructive comments were received from Benjamin Kaduk, Eliot Lear, Constructive comments were received from Benjamin Kaduk, Eliot Lear,
Jim Schaad, Hannes Tschofenig, Julien Vermillard, and John Manuel. Jim Schaad, Hannes Tschofenig, Julien Vermillard, and John Manuel.
12. Change Log
-04:
TBD8 removed from C-F registration, to be done CT draft
-03:
Removed observe and simplified long waits
Repaired content-format specification
-02:
Added parameter discussion in section 8
Concluded content-format specification using multipart-ct draft
examples updated
-01:
Editorials done.
Redefinition of proxy to Registrar in Section 7. Explained better
the role of https-coaps Registrar, instead of "proxy"
Provide "observe" option examples
extended block message example.
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. References
13.1. Normative References 13.1. Normative References
[I-D.fossati-core-multipart-ct] [I-D.ietf-core-multipart-ct]
Bormann, C., "Multipart Content-Format for CoAP", draft- Fossati, T., Hartke, K., and C. Bormann, "Multipart
fossati-core-multipart-ct-05 (work in progress), June Content-Format for CoAP", draft-ietf-core-multipart-ct-02
2018. (work in progress), August 2018.
[I-D.ietf-tls-tls13] [I-D.ietf-lamps-rfc5751-bis]
Rescorla, E., "The Transport Layer Security (TLS) Protocol Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Version 1.3", draft-ietf-tls-tls13-28 (work in progress), Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
March 2018. Message Specification", draft-ietf-lamps-rfc5751-bis-12
(work in progress), September 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>.
[RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
Mail Extensions (S/MIME) Version 3.2 Message
Specification", RFC 5751, DOI 10.17487/RFC5751, January
2010, <https://www.rfc-editor.org/info/rfc5751>.
[RFC5967] Turner, S., "The application/pkcs10 Media Type", RFC 5967, [RFC5967] Turner, S., "The application/pkcs10 Media Type", RFC 5967,
DOI 10.17487/RFC5967, August 2010, DOI 10.17487/RFC5967, August 2010,
<https://www.rfc-editor.org/info/rfc5967>. <https://www.rfc-editor.org/info/rfc5967>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>. January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[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,
skipping to change at page 22, line 47 skipping to change at page 24, line 25
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>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
13.2. Informative References 13.2. Informative References
[I-D.rescorla-tls-dtls-connection-id] [I-D.rescorla-tls-dtls-connection-id]
Rescorla, E., Tschofenig, H., Fossati, T., and T. Gondrom, Rescorla, E., Tschofenig, H., Fossati, T., and T. Gondrom,
"The Datagram Transport Layer Security (DTLS) Connection "The Datagram Transport Layer Security (DTLS) Connection
Identifier", draft-rescorla-tls-dtls-connection-id-02 Identifier", draft-rescorla-tls-dtls-connection-id-02
(work in progress), November 2017. (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.
Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
for Transport Layer Security (TLS)", RFC 4492,
DOI 10.17487/RFC4492, May 2006,
<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>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5273] Schaad, J. and M. Myers, "Certificate Management over CMS [RFC5273] Schaad, J. and M. Myers, "Certificate Management over CMS
(CMC): Transport Protocols", RFC 5273, (CMC): Transport Protocols", RFC 5273,
DOI 10.17487/RFC5273, June 2008, DOI 10.17487/RFC5273, June 2008,
<https://www.rfc-editor.org/info/rfc5273>. <https://www.rfc-editor.org/info/rfc5273>.
[RFC5705] Rescorla, E., "Keying Material Exporters for Transport [RFC5705] Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705, Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705,
March 2010, <https://www.rfc-editor.org/info/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
skipping to change at page 24, line 36 skipping to change at page 26, line 5
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>.
[RFC7925] Tschofenig, H., Ed. and T. Fossati, "Transport Layer [RFC7925] Tschofenig, H., Ed. and T. Fossati, "Transport Layer
Security (TLS) / Datagram Transport Layer Security (DTLS) Security (TLS) / Datagram Transport Layer Security (DTLS)
Profiles for the Internet of Things", RFC 7925, Profiles for the Internet of Things", RFC 7925,
DOI 10.17487/RFC7925, July 2016, DOI 10.17487/RFC7925, July 2016,
<https://www.rfc-editor.org/info/rfc7925>. <https://www.rfc-editor.org/info/rfc7925>.
[RFC8422] Nir, Y., Josefsson, S., and M. Pegourie-Gonnard, "Elliptic
Curve Cryptography (ECC) Cipher Suites for Transport Layer
Security (TLS) Versions 1.2 and Earlier", RFC 8422,
DOI 10.17487/RFC8422, August 2018,
<https://www.rfc-editor.org/info/rfc8422>.
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 Binary payload is a CBOR major type 2 (byte array), that is shown
skipping to change at page 25, line 46 skipping to change at page 27, line 34
Option Length = 0x6 Option Length = 0x6
Option Value = "crts" Option Value = "crts"
Option5 (Max-Age) Option5 (Max-Age)
Option Delta = 0x3 (option nr = 11+3= 14) Option Delta = 0x3 (option nr = 11+3= 14)
Option Length = 0x1 Option Length = 0x1
Option Value = 0x1 (1 minute) 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: TBD2) 2.05 Content (Content-Format: 281)
{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) Token = 0x9a (copied by server)
Options Options
Option1 (Content-Format) Option1 (Content-Format)
Option Delta = 0xC (option nr =12) Option Delta = 0xC (option nr =12)
Option Length = 0x2 Option Length = 0x2
Option Value = TBD2 (defined in this document) Option Value = 281 (defined in this document)
Payload = Payload =
h'30233906092a6206734107028c2a3023260201013100300b06092a6206734107018 h'30233906092a6206734107028c2a3023260201013100300b06092a6206734107018
c0c3020bb302063c20102020900a61e75193b7acc0d06092a620673410105050030 c0c3020bb302063c20102020900a61e75193b7acc0d06092a620673410105050030
1b31193017060355040313106573744578616d706c654341204f774f301e170d313 1b31193017060355040313106573744578616d706c654341204f774f301e170d313
3303530393033353333315a170d3134303530393033353333315a301b3119301706 3303530393033353333315a170d3134303530393033353333315a301b3119301706
0355040313106573744578616d706c654341204f774f302062300d06092a6206734 0355040313106573744578616d706c654341204f774f302062300d06092a6206734
10101050003204f0030204a022041003a923a2968bae4aae136ca4e2512c5200680 10101050003204f0030204a022041003a923a2968bae4aae136ca4e2512c5200680
358482ac39d6f640e4574e654ea35f48b1e054c5da3372872f7a1e429f4edf39584 358482ac39d6f640e4574e654ea35f48b1e054c5da3372872f7a1e429f4edf39584
32efb2106591d3eb783c1034709f251fc86566bda2d541c792389eac4ec9e181f4b 32efb2106591d3eb783c1034709f251fc86566bda2d541c792389eac4ec9e181f4b
skipping to change at page 29, line 39 skipping to change at page 31, line 27
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) (Content-Format: 285)
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 the authenticated client. In this example, the EST-coaps server
returns two attributes that the client can ignore when they are returns two attributes that the client can ignore when they are
unknown to him. unknown to him.
A.3. enroll / reenroll A.3. enroll / reenroll
During the Enroll/Reenroll exchange, the EST-coaps client uses a CSR During the Enroll/Reenroll exchange, the EST-coaps client uses a CSR
(Content-Format TBD7) request in the POST request payload. (Content-Format 286) request in the POST request payload.
After verification of the CSR by the server, a 2.05 Content response After verification of the CSR by the server, a 2.05 Content response
with the issued certificate will be returned to the client. As 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 described in Section 5.5, if the server is not able to provide a
response immediately, it sends an empty ACK with response code 5.03 response immediately, it sends an empty ACK with response code 5.03
(Service Unavailabel) and the Max-Age option. See Figure 3 for an (Service Unavailabel) and the Max-Age option. See Figure 3 for an
example exchange. example exchange.
[EDNOTE: When redoing this example, given that proof of possession [EDNOTE: When redoing this example, given that POP linking is also
(POP) is also used, make sure it is obvious that the used, make sure it is obvious that the ChallengePassword attribute in
ChallengePassword attribute in the CSR is valid HMAC output. HMAC- the CSR is valid HMAC output. HMAC-REAL.]
REAL.]
POST [2001:db8::2:1]:61616/est/sen POST [2001:db8::2:1]:61616/est/sen
(token 0x45) (token 0x45)
(Content-Format: TBD7) (Content-Format: 286)
h'30208530206d020100301f311d301b0603550403131464656d6f7374657034203 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:
(Content-Format: TBD2)(token =0x45) (Content-Format: 281)(token =0x45)
2.01 Created 2.01 Created
h'3020f806092a62067341070283293020e50201013100300b06092a62067341070 h'3020f806092a62067341070283293020e50201013100300b06092a62067341070
1830b3020c730206fc20102020115300d06092a6206734101050500301b311930 1830b3020c730206fc20102020115300d06092a6206734101050500301b311930
17060355040313106573744578616d706c654341204e774e301e170d313330353 17060355040313106573744578616d706c654341204e774e301e170d313330353
0393233313535335a170d3134303530393233313535335a301f311d301b060355 0393233313535335a170d3134303530393233313535335a301f311d301b060355
0403131464656d6f73746570342031333638313431333532302062300d06092a6 0403131464656d6f73746570342031333638313431333532302062300d06092a6
20673410101050003204f0030204a022041005d9f4dffd3c5949f646a95843677 20673410101050003204f0030204a022041005d9f4dffd3c5949f646a95843677
78560950b355c35b8e34726dd376454231734795b4c09b9c6d75d408311307a81 78560950b355c35b8e34726dd376454231734795b4c09b9c6d75d408311307a81
f7adef7f5d241f7d5be85620c5d4438bbb4242cf215c167f2ccf36c364ea2618a f7adef7f5d241f7d5be85620c5d4438bbb4242cf215c167f2ccf36c364ea2618a
62f0536576369d6304e6a968772247d86824f079faac7a6f694cfda5b84c42087 62f0536576369d6304e6a968772247d86824f079faac7a6f694cfda5b84c42087
skipping to change at page 32, line 18 skipping to change at page 33, line 18
authenticates itself using the certificate provided by the connected authenticates itself using the certificate provided by the connected
CA. CA.
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:
[EDNOTE: same comment as HMAC-REAL above applies.] [EDNOTE: same comment as HMAC-REAL above applies.]
[EDNOTE: Suggestion to have only one example with complete encrypted [EDNOTE: Suggestion to have only one example with complete encrypted
payload (the short one) and point out the different fields. Update payload (the short one) and point out the different fields. Update
this example according to the agreed upon solution from Section 4.5. this example according to the agreed upon solution from Section 5.6.
] ]
POST coaps://192.0.2.1:8085/est/skg POST coaps://192.0.2.1:8085/est/skg
(token 0xa5) (token 0xa5)
(Content-Format: TBD7)(Max-Age=120) (Content-Format: 286)(Max-Age=120)
h'302081302069020100305b313e303c060355040313357365727665724b6579476 h'302081302069020100305b313e303c060355040313357365727665724b6579476
56e2072657120627920636c69656e7420696e2064656d6f207374657020313220 56e2072657120627920636c69656e7420696e2064656d6f207374657020313220
3133363831343139353531193017060355040513105049443a576964676574205 3133363831343139353531193017060355040513105049443a576964676574205
34e3a3130302062300d06092a620673410101050003204f0030204a02204100f4 34e3a3130302062300d06092a620673410101050003204f0030204a02204100f4
dfa6c03f7f2766b23776c333d2c0f9d1a7a6ee36d01499bbe6f075d1e38a57e98 dfa6c03f7f2766b23776c333d2c0f9d1a7a6ee36d01499bbe6f075d1e38a57e98
ecc197f51b75228454b7f19652332de5e52e4a974c6ae34e1df80b33f15f47d3b ecc197f51b75228454b7f19652332de5e52e4a974c6ae34e1df80b33f15f47d3b
cbf76116bb0e4d3e04a9651218a476a13fc186c2a255e4065ff7c271cff104e47 cbf76116bb0e4d3e04a9651218a476a13fc186c2a255e4065ff7c271cff104e47
31fad53c22b21a1e5138bf9ad0187314ac39445949a48805392390e78c7659621 31fad53c22b21a1e5138bf9ad0187314ac39445949a48805392390e78c7659621
6d3e61327a534f5ea7721d2b1343c7362b37da502717cfc2475653c7a3860c5f4 6d3e61327a534f5ea7721d2b1343c7362b37da502717cfc2475653c7a3860c5f4
skipping to change at page 32, line 48 skipping to change at page 33, line 48
4050af497f428189b63655d03a194ef729f101743e5d03fbc6ae1e84486d1300a 4050af497f428189b63655d03a194ef729f101743e5d03fbc6ae1e84486d1300a
f9288724381909188c851fa9a5059802eb64449f2a3c9e441353d136768da27ff f9288724381909188c851fa9a5059802eb64449f2a3c9e441353d136768da27ff
4f277651d676a6a7e51931b08f56135a2230891fd184960e1313e7a1a9139ed19 4f277651d676a6a7e51931b08f56135a2230891fd184960e1313e7a1a9139ed19
28196867079a456cd2266cb754a45151b7b1b939e381be333fea61580fe5d25bf 28196867079a456cd2266cb754a45151b7b1b939e381be333fea61580fe5d25bf
4823dbd2d6a98445b46305c10637e202856611' 4823dbd2d6a98445b46305c10637e202856611'
RET: RET:
2.01 Content (Content-Format: TBD8) 2.01 Content (Content-Format: TBD8)
(token=0xa5) (token=0xa5)
[TBD5, [284,
h'30213e020100300d06092a6206734101010500042128302124020100022041003 h'30213e020100300d06092a6206734101010500042128302124020100022041003
c0bc2748f2003e3e8ea15f746f2a71e83f585412b92cf6f8e64de02e056153274 c0bc2748f2003e3e8ea15f746f2a71e83f585412b92cf6f8e64de02e056153274
dd01c95dd9cff3112aa141774ab655c3d56359c3b3df055294692ed848e7e30a1 dd01c95dd9cff3112aa141774ab655c3d56359c3b3df055294692ed848e7e30a1
1bf14e47e0693d93017022b4cdb3e6d40325356152b213c8b535851e681a7074c 1bf14e47e0693d93017022b4cdb3e6d40325356152b213c8b535851e681a7074c
0c6d2b60e7c32fc0336b28e743eba4e5921074d47195d3c05e43c527526e692d5 0c6d2b60e7c32fc0336b28e743eba4e5921074d47195d3c05e43c527526e692d5
45e562578d2d4b5f2191bff89d3eef0222764a2674637a1f99257216647df6704 45e562578d2d4b5f2191bff89d3eef0222764a2674637a1f99257216647df6704
efec5adbf54dab24231844eb595875795000e673dd6862310a146ad7e31083010 efec5adbf54dab24231844eb595875795000e673dd6862310a146ad7e31083010
001022041004e6b3f78b7791d6377f33117c17844531c81111fb8000282816264 001022041004e6b3f78b7791d6377f33117c17844531c81111fb8000282816264
915565bc7c3f3f643b537a2c69140a31c22550fa97e5132c61b74166b68626704 915565bc7c3f3f643b537a2c69140a31c22550fa97e5132c61b74166b68626704
260620333050f510096b6570f5880e7e1c15dc0ca6ce2b5f187e2325da14ab705 260620333050f510096b6570f5880e7e1c15dc0ca6ce2b5f187e2325da14ab705
skipping to change at page 33, line 29 skipping to change at page 34, line 29
c0844881f791f23b0813ea0921325edd14459d41c8a1593f04316388e40b35fef c0844881f791f23b0813ea0921325edd14459d41c8a1593f04316388e40b35fef
7d2a195a5930fa54774427ac821eee2c62790d2c17bd192af794c611011506557 7d2a195a5930fa54774427ac821eee2c62790d2c17bd192af794c611011506557
83d4efe22185cbd83368786f2b1e68a5a27067e321066f0217b4b6d7971a3c21a 83d4efe22185cbd83368786f2b1e68a5a27067e321066f0217b4b6d7971a3c21a
241366b7907187583b511102103369047e5cce0b65012200df5ec697b5827575c 241366b7907187583b511102103369047e5cce0b65012200df5ec697b5827575c
db6821ff299d6a69574b31ddf0fbe9245ea2f74396c24b3a7565067e41366423b db6821ff299d6a69574b31ddf0fbe9245ea2f74396c24b3a7565067e41366423b
5bdd2b2a78194094dbe333f493d159b8e07722f2280d48388db7f1c9f0633bb0e 5bdd2b2a78194094dbe333f493d159b8e07722f2280d48388db7f1c9f0633bb0e
173de2c3aa1f200af535411c7090210401421e2ea217e37312dcc606f453a6634 173de2c3aa1f200af535411c7090210401421e2ea217e37312dcc606f453a6634
f3df4dc31a9e910614406412e70eec9247f10672a500947a64356c015a845a7d1 f3df4dc31a9e910614406412e70eec9247f10672a500947a64356c015a845a7d1
50e2e3911a2b3b61070a73247166da10bb45474cc97d1ec2bc392524307f35118 50e2e3911a2b3b61070a73247166da10bb45474cc97d1ec2bc392524307f35118
f917438f607f18181684376e13a39e07', f917438f607f18181684376e13a39e07',
TBD2, 281,
h'3020c506092a62067341070283363020f20201013100300b06092a62067341070 h'3020c506092a62067341070283363020f20201013100300b06092a62067341070
183183020d430207cc20102020116300d06092a6206734101050500301b311930 183183020d430207cc20102020116300d06092a6206734101050500301b311930
17060355040313106573744578616d706c654341204e774e301e170d313330353 17060355040313106573744578616d706c654341204e774e301e170d313330353
0393233323535365a170d3134303530393233323535365a302c312a3028060355 0393233323535365a170d3134303530393233323535365a302c312a3028060355
0403132173657276657273696465206b65792067656e657261746564207265737 0403132173657276657273696465206b65792067656e657261746564207265737
06f6e7365302062300d06092a620673410101050003204f0030204a022041003c 06f6e7365302062300d06092a620673410101050003204f0030204a022041003c
0bc2748f2003e3e8ea15f746f2a71e83f585412b92cf6f8e64de02e056153274d 0bc2748f2003e3e8ea15f746f2a71e83f585412b92cf6f8e64de02e056153274d
d01c95dd9cff3112aa141774ab655c3d56359c3b3df055294692ed848e7e30a11 d01c95dd9cff3112aa141774ab655c3d56359c3b3df055294692ed848e7e30a11
bf14e47e0693d93017022b4cdb3e6d40325356152b213c8b535851e681a7074c0 bf14e47e0693d93017022b4cdb3e6d40325356152b213c8b535851e681a7074c0
c6d2b60e7c32fc0336b28e743eba4e5921074d47195d3c05e43c527526e692d54 c6d2b60e7c32fc0336b28e743eba4e5921074d47195d3c05e43c527526e692d54
skipping to change at page 36, line 13 skipping to change at page 37, line 13
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) Token = 0x9a (copied by server)
Options Options
Option1 (Content-Format) Option1 (Content-Format)
Option Delta = 0xC (option nr =12) Option Delta = 0xC (option nr =12)
Option Length = 0x2 Option Length = 0x2
Option Value = TBD2 Option Value = 281
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 =
h'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) Token = 0x9a (copied by server)
Options Options
Option1 (Content-Format) Option1 (Content-Format)
Option Delta = 0xC (option nr =12) Option Delta = 0xC (option nr =12)
Option Length = 0x2 Option Length = 0x2
Option Value = TBD2 Option Value = 281
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 =
h'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 = 0x45 (2.05 Content) Code = 0x45 (2.05 Content)
Token = 0x9a (copied by server) Token = 0x9a (copied by server)
Options Options
Option1 (Content-Format) Option1 (Content-Format)
Option Delta = 0xC (option nr =12) Option Delta = 0xC (option nr =12)
Option Length = 0x2 Option Length = 0x2
Option Value = TBD2 Option Value = 281
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 = h'73a30d0c006343116f58403100' Payload = h'73a30d0c006343116f58403100'
B.2. enroll block example B.2. enroll block example
In this example the requested block2 size of 256 bytes, required by In this example the requested block2 size of 256 bytes, required by
the client, is transferred to the server in the very first request the client, is transferred to the server in the very first request
 End of changes. 93 change blocks. 
300 lines changed or deleted 394 lines changed or added

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