draft-ietf-ace-coap-est-08.txt   draft-ietf-ace-coap-est-09.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: August 10, 2019 Cisco Systems Expires: August 31, 2019 Cisco Systems
M. Richardson M. Richardson
SSW SSW
S. Raza S. Raza
RISE SICS RISE SICS
February 6, 2019 February 27, 2019
EST over secure CoAP (EST-coaps) EST over secure CoAP (EST-coaps)
draft-ietf-ace-coap-est-08 draft-ietf-ace-coap-est-09
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 constrained devices to use secure CoAP (EST-coaps), which allows constrained devices to use
existing EST functionality for provisioning certificates. existing EST functionality for provisioning certificates.
skipping to change at page 1, line 40 skipping to change at page 1, line 40
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 August 10, 2019. This Internet-Draft will expire on August 31, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Conformance to RFC7925 profiles . . . . . . . . . . . . . . . 6 4. DTLS and conformance to RFC7925 profiles . . . . . . . . . . 6
5. Protocol Design . . . . . . . . . . . . . . . . . . . . . . . 7 5. Protocol Design . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Discovery and URIs . . . . . . . . . . . . . . . . . . . 8 5.1. Discovery and URIs . . . . . . . . . . . . . . . . . . . 9
5.2. Mandatory/optional EST Functions . . . . . . . . . . . . 10 5.2. Mandatory/optional EST Functions . . . . . . . . . . . . 11
5.3. Payload formats . . . . . . . . . . . . . . . . . . . . . 10 5.3. Payload formats . . . . . . . . . . . . . . . . . . . . . 12
5.4. Message Bindings . . . . . . . . . . . . . . . . . . . . 12 5.4. Message Bindings . . . . . . . . . . . . . . . . . . . . 13
5.5. CoAP response codes . . . . . . . . . . . . . . . . . . . 13 5.5. CoAP response codes . . . . . . . . . . . . . . . . . . . 14
5.6. Message fragmentation . . . . . . . . . . . . . . . . . . 13 5.6. Message fragmentation . . . . . . . . . . . . . . . . . . 14
5.7. Delayed Responses . . . . . . . . . . . . . . . . . . . . 14 5.7. Delayed Responses . . . . . . . . . . . . . . . . . . . . 15
5.8. Server-side Key Generation . . . . . . . . . . . . . . . 16 5.8. Server-side Key Generation . . . . . . . . . . . . . . . 17
6. DTLS Transport Protocol . . . . . . . . . . . . . . . . . . . 18 6. HTTPS-CoAPS Registrar . . . . . . . . . . . . . . . . . . . . 19
7. HTTPS-CoAPS Registrar . . . . . . . . . . . . . . . . . . . . 19 7. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 20
8. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 21 8. Deployment limitations . . . . . . . . . . . . . . . . . . . 21
9. Deployment limitations . . . . . . . . . . . . . . . . . . . 21 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 9.1. Content-Format Registry . . . . . . . . . . . . . . . . . 21
10.1. Content-Format Registry . . . . . . . . . . . . . . . . 22 9.2. Resource Type registry . . . . . . . . . . . . . . . . . 22
10.2. Resource Type registry . . . . . . . . . . . . . . . . . 22 10. Security Considerations . . . . . . . . . . . . . . . . . . . 23
11. Security Considerations . . . . . . . . . . . . . . . . . . . 23 10.1. EST server considerations . . . . . . . . . . . . . . . 23
11.1. EST server considerations . . . . . . . . . . . . . . . 23 10.2. HTTPS-CoAPS Registrar considerations . . . . . . . . . . 24
11.2. HTTPS-CoAPS Registrar considerations . . . . . . . . . . 25 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 25
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 25 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 13.1. Normative References . . . . . . . . . . . . . . . . . . 26
14.1. Normative References . . . . . . . . . . . . . . . . . . 26 13.2. Informative References . . . . . . . . . . . . . . . . . 27
14.2. Informative References . . . . . . . . . . . . . . . . . 28
Appendix A. EST messages to EST-coaps . . . . . . . . . . . . . 30 Appendix A. EST messages to EST-coaps . . . . . . . . . . . . . 30
A.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 31 A.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 30
A.2. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 33 A.2. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 32
A.3. serverkeygen . . . . . . . . . . . . . . . . . . . . . . 35 A.3. serverkeygen . . . . . . . . . . . . . . . . . . . . . . 34
A.4. csrattrs . . . . . . . . . . . . . . . . . . . . . . . . 37 A.4. csrattrs . . . . . . . . . . . . . . . . . . . . . . . . 36
Appendix B. EST-coaps Block message examples . . . . . . . . . . 38 Appendix B. EST-coaps Block message examples . . . . . . . . . . 37
B.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 38 B.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 37
B.2. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 42 B.2. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 41
Appendix C. Message content breakdown . . . . . . . . . . . . . 43 Appendix C. Message content breakdown . . . . . . . . . . . . . 42
C.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 43 C.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 42
C.2. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 45 C.2. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 44
C.3. serverkeygen . . . . . . . . . . . . . . . . . . . . . . 46 C.3. serverkeygen . . . . . . . . . . . . . . . . . . . . . . 45
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 48
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 47
1. Change Log 1. Change Log
EDNOTE: Remove this section before publication EDNOTE: Remove this section before publication
-09
WGLC comments taken into account
consensus about discovery of content-format
added additional path for content-format selection
merged DTLS sections
-08 -08
added application/pkix-cert Content-Format TBD287. added application/pkix-cert Content-Format TBD287.
discovery text clarified
Removed text on ct negotiation in connection to multipart-core
removed text that duplicates or contradicts RFC7252 (thanks Klaus)
Stated that well-known/est is compulsory Stated that well-known/est is compulsory
Use of response codes clarified. Use of response codes clarified.
removed bugs: Max-Age and Content-Format Options in Request removed bugs: Max-Age and Content-Format Options in Request
Accept Option explained for est/skg and added in enroll example Accept Option explained for est/skg and added in enroll example
Persistenc of DTLS connection clarified. Added second URI /skc for server-side key gen and a simple cert
(not PKCS#7)
Persistence of DTLS connection clarified.
Minor text fixes. Minor text fixes.
-07: -07:
redone examples from scratch with openssl redone examples from scratch with openssl
Updated authors. Updated authors.
Added CoAP RST as a MAY for an equivalent to an HTTP 204 message. Added CoAP RST as a MAY for an equivalent to an HTTP 204 message.
skipping to change at page 5, line 7 skipping to change at page 5, line 26
Added parameter discussion in section 8 Added parameter discussion in section 8
Concluded Content-Format specification using multipart-ct draft Concluded Content-Format specification using multipart-ct draft
examples updated examples updated
-01: -01:
Editorials done. Editorials done.
Redefinition of proxy to Registrar in Section 7. Explained better Redefinition of proxy to Registrar in Section 6. Explained better
the role of https-coaps Registrar, instead of "proxy" the role of https-coaps Registrar, instead of "proxy"
Provide "observe" Option examples Provide "observe" Option examples
extended block message example. extended block message example.
inserted new server key generation text in Section 5.8 and inserted new server key generation text in Section 5.8 and
motivated server key generation. motivated server key generation.
Broke down details for DTLS 1.3 Broke down details for DTLS 1.3
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2. Introduction 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 transports messages over HTTPS. Registration Authority (RA). EST transports messages 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 instead specification utilizes DTLS [RFC6347] and CoAP [RFC7252] instead of
of TLS [RFC8446], HTTP [RFC7230] and TCP. TLS [RFC8446] and HTTP [RFC7230].
EST responses can be relatively large and for this reason this EST responses can be relatively large and for this reason this
specification also uses CoAP Block-Wise Transfer [RFC7959] to offer a specification 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 document also profiles the use of EST to only support This document 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.
3. 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", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
Many of the concepts in this document are taken from [RFC7030]. Many of the concepts in this document are taken from [RFC7030].
Consequently, much text is directly traceable to [RFC7030]. Consequently, much text is directly traceable to [RFC7030].
4. Conformance to RFC7925 profiles 4. DTLS and conformance to RFC7925 profiles
This section describes how EST-coaps fits into the profiles of low- This section describes how EST-coaps fits into the profiles of low-
resource devices described in [RFC7925]. EST-coaps can transport resource devices described in [RFC7925]. EST-coaps can transport
certificates and private keys. Certificates are responses to certificates and private keys. Certificates are responses to
(re-)enrollment requests or requests for a trusted certificate list. (re-)enrollment requests or requests for a trusted certificate list.
Private keys can be transported as responses to a server-side key Private keys can be transported as responses to a server-side key
generation request as described in section 4.4 of [RFC7030] and generation request as described in Section 4.4 of [RFC7030] and
discussed in Section 5.8 of this document. discussed in Section 5.8 of this document.
As per Sections 3.3 and 4.4 of [RFC7925], the mandatory cipher suite EST-coaps depends on a secure transport mechanism that secures the
exchanged CoAP messages. DTLS is one such secure protocol. No other
changes are necessary regarding the secure transport of EST messages.
+------------------------------------------------+
| EST request/response messages |
+------------------------------------------------+
| CoAP for message transfer and signaling |
+------------------------------------------------+
| Secure Transport |
+------------------------------------------------+
Figure 1: EST-coaps protocol layers
As per sections 3.3 and 4.4 of [RFC7925], the mandatory cipher suite
for DTLS in EST-coaps is TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 for DTLS in EST-coaps is TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8
[RFC7251]. Curve secp256r1 MUST be supported [RFC8422]; this curve [RFC7251]. Curve secp256r1 MUST be supported [RFC8422]; this curve
is equivalent to the NIST P-256 curve. Crypto agility is important, is equivalent to the NIST P-256 curve. Additionally, crypto agility
and the recommendations in [RFC7925] section 4.4 and any updates to is important, and the recommendations in Section 4.4 of [RFC7925] and
RFC7925 concerning Curve25519 and other CFRG curves also apply. any updates to it concerning Curve25519 and other curves also apply.
DTLS1.2 implementations MUST use the Supported Elliptic Curves and DTLS 1.2 implementations must use the Supported Elliptic Curves and
Supported Point Formats Extensions [RFC8422]. Uncompressed point Supported Point Formats Extensions in [RFC8422]. Uncompressed point
format MUST also be supported. [RFC6090] is a summary of the ECC format must also be supported. DTLS 1.3 [I-D.ietf-tls-dtls13]
algorithms. DTLS 1.3 [I-D.ietf-tls-dtls13] implementations differ implementations differ from DTLS 1.2 because they do not support
from DTLS 1.2 because they do not support point format negotiation in point format negotiation in favor of a single point format for each
favor of a single point format for each curve. Thus, support for curve. Thus, support for DTLS 1.3 does not mandate point format
DTLS 1.3 does not mandate point formation extensions and negotiation. extensions and negotiation.
CoAP was designed to avoid IP fragmentation. DTLS is used to secure
CoAP messages. However, fragmentation is still possible at the DTLS
layer during the DTLS handshake when using ECC ciphersuites. If
fragmentation is necessary, "DTLS provides a mechanism for
fragmenting a handshake message over several records, each of which
can be transmitted separately, thus avoiding IP fragmentation"
[RFC6347].
The authentication of the EST-coaps server by the EST-coaps client is The authentication of the EST-coaps server by the EST-coaps client is
based on certificate authentication in the DTLS handshake. The EST- based on certificate authentication in the DTLS handshake. The EST-
coaps client MUST be configured with at least an Implicit TA database coaps client MUST be configured with at least an Implicit TA database
from its manufacturer which will enable the authentication of the which will enable the authentication of the server the first time
server the first time before updating its trust anchor (Explicit TA) before updating its trust anchor (Explicit TA) [RFC7030].
[RFC7030].
The authentication of the EST-coaps client MUST be with a client The authentication of the EST-coaps client MUST be with 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 re-enrollment of clients.
o a previously installed certificate (e.g., manufacturer IDevID o a previously installed certificate (e.g., manufacturer IDevID
[ieee802.1ar] or a certificate issued by some other party); the [ieee802.1ar] or a certificate issued by some other party); the
server is expected to trust that certificate. IDevID's are server is expected to trust that certificate. IDevID's are
expected to have a very long life, as long as the device, but expected to have a very long life, as long as the device, but
under some conditions could expire. In that case, the server MAY under some conditions could expire. In that case, the server MAY
want to authenticate a client certificate against its trust store want to authenticate a client certificate against its trust store
skipping to change at page 7, line 14 skipping to change at page 8, line 8
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 re-enrollment of clients.
o a previously installed certificate (e.g., manufacturer IDevID o a previously installed certificate (e.g., manufacturer IDevID
[ieee802.1ar] or a certificate issued by some other party); the [ieee802.1ar] or a certificate issued by some other party); the
server is expected to trust that certificate. IDevID's are server is expected to trust that certificate. IDevID's are
expected to have a very long life, as long as the device, but expected to have a very long life, as long as the device, but
under some conditions could expire. In that case, the server MAY under some conditions could expire. In that case, the server MAY
want to authenticate a client certificate against its trust store want to authenticate a client certificate against its trust store
although the certificate is expired (Section 11). although the certificate is expired (Section 10).
5. Protocol Design EST-coaps supports the certificate types and Trust Anchors (TA) that
are specified for EST in Section 3 of [RFC7030].
EST-coaps uses CoAP to transfer EST messages, aided by Block-Wise CoAP and DTLS can provide proof-of-identity for EST-coaps clients and
Transfer [RFC7959] to avoid (excessive) fragmentation of UDP servers with simple PKI messages as described in Section 3.1 of
datagrams. The use of Blocks for the transfer of larger EST messages [RFC5272]. Moreover, channel-binding information for linking proof-
is specified in Section 5.6. Figure 1 below shows the layered EST- of-identity with connection-based proof-of-possession is OPTIONAL for
coaps architecture. EST-coaps. When proof-of-possession is desired, a set of actions are
required regarding the use of tls-unique, described in Section 3.5 in
[RFC7030]. The tls-unique information consists of the contents of
the first "Finished" message in the (D)TLS handshake between server
and client [RFC5929]. The client adds the "Finished" message as a
ChallengePassword in the attributes section of the PKCS#10 Request
[RFC5967] to prove that the client is indeed in control of the
private key at the time of the (D)TLS session establishment.
+------------------------------------------------+ In the case of EST-coaps, the same operations can be performed during
| EST request/response messages | the DTLS handshake. For DTLS 1.2, in the event of handshake message
+------------------------------------------------+ fragmentation, the Hash of the handshake messages used in the MAC
| CoAP for message transfer and signaling | calculation of the Finished message must be computed as if each
+------------------------------------------------+ handshake message had been sent as a single fragment (Section 4.2.6
| DTLS for transport security | of [RFC6347]). The Finished message is calculated as shown in
+------------------------------------------------+ Section 7.4.9 of [RFC5246]. Similarly, for DTLS 1.3, the Finished
| UDP for transport | message must be computed as if each handshake message had been sent
+------------------------------------------------+ as a single fragment (Section 5.8 of [I-D.ietf-tls-dtls13]) following
the algorithm described in 4.4.4 of [RFC8446].
Figure 1: EST-coaps protocol layers In a constrained CoAP environment, endpoints can't always afford to
establish a DTLS connection for every EST transaction.
Authenticating and negotiating DTLS keys requires resources on low-
end endpoints and consumes valuable bandwidth. To alleviate this
situation, an EST-coaps DTLS connection MAY remain open for
sequential EST transactions. For example, an EST csrattrs request
that is followed by a simpleenroll request can use the same
authenticated DTLS connection. However, when a cacerts request is
included in the set of sequential EST transactions, some additional
security considerations apply regarding the use of the Implicit and
Explicit TA database as explained in Section 10.1.
Given that after a successful enrollment, it is more likely that a
new EST transaction will take place after a significant amount of
time, the DTLS connections SHOULD only be kept alive for EST messages
that are relatively close to each other. In some cases, like NAT
rebinding, keeping the state of a connection is not possible when
devices sleep for extended periods of time. In such occasions,
[I-D.ietf-tls-dtls-connection-id] negotiates a connection ID that can
eliminate the need for new handshake and its additional cost.
5. Protocol Design
EST-coaps uses CoAP to transfer EST messages, aided by Block-Wise
Transfer [RFC7959] to avoid IP fragmentation. The use of Blocks for
the transfer of larger EST messages is specified in Section 5.6.
Figure 1 shows the layered EST-coaps architecture.
The EST-coaps protocol design follows closely the EST design. The The EST-coaps protocol design follows closely the EST design. The
supported message types in EST-coaps are: supported message types in EST-coaps are:
o CA certificate retrieval, needed to receive the complete set of CA o CA certificate retrieval needed to receive the complete set of CA
certificates. certificates.
o Simple enroll and reenroll, for a CA to sign public client- o Simple enroll and re-enroll for a CA to sign public client
identity key. identity key.
o Certificate Signing Request (CSR) Attributes messages that informs o Certificate Signing Request (CSR) attribute messages that inform
the client of the fields to include in generated CSR. the client of the fields to include in a 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 so. identity key when the client choses so.
5.1. Discovery and URIs 5.1. Discovery and URIs
EST-coaps is targeted for low-resource networks with small packets. EST-coaps is targeted for low-resource networks with small packets.
Saving header space is important and short EST-coaps URIs are Saving header space is important and short EST-coaps URIs are
specified in this document. These URIs are shorter than the ones in specified in this document. These URIs are shorter than the ones in
[RFC7030]. Two example EST-coaps resource path names are: [RFC7030]. Two example EST-coaps resource path names are:
coaps://est-coaps.example.ietf.org:<port>/.well-known/est/<short-est> coaps://est-coaps.example.org:<port>/.well-known/est/<short-est>
coaps://est-coaps.example.ietf.org:<port>/.well-known/est/ coaps://est-coaps.example.org:<port>/.well-known/est/
ArbitraryLabel/<short-est> ArbitraryLabel/<short-est>
The short-est strings are defined in Table 1. The ArbitraryLabel The short-est strings are defined in Table 1. The ArbitraryLabel
path-segment, if used, SHOULD be of the shortest length possible path-segment, if used, SHOULD be of the shortest length possible
(Sections 3.1 and 3.2.2 of [RFC7030]. Arbitrary Labels are usually (Sections 3.1 and 3.2.2 of [RFC7030]. Arbitrary Labels are usually
defined and used by EST CAs in order to route client requests to the defined and used by EST CAs in order to route client requests to the
appropriate certificate profile. appropriate certificate profile.
The EST-coaps server URIs, obtained through discovery of the EST- The EST-coaps server URIs, obtained through discovery of the EST-
coaps root resource(s) as shown below, are of the form: coaps root resource(s) as shown below, are of the form:
coaps://est-coaps.example.ietf.org:<port>/<root-resource>/<short-est> coaps://est-coaps.example.org:<port>/<root-resource>/<short-est>
coaps://est-coaps.example.ietf.org:<port>/<root-resource>/ coaps://est-coaps.example.org:<port>/<root-resource>/
ArbitraryLabel/<short-est> 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 1 provides the
mapping from the EST URI path to the shorter EST-coaps URI path. mapping from the EST URI path to the shorter EST-coaps URI path.
+------------------+-----------+ +------------------+-------------------------------+
| EST | EST-coaps | | EST | EST-coaps |
+------------------+-----------+ +------------------+-------------------------------+
| /cacerts | /crts | | /cacerts | /crts |
| /simpleenroll | /sen | | /simpleenroll | /sen |
| /simplereenroll | /sren | | /simplereenroll | /sren |
| /csrattrs | /att | | /csrattrs | /att |
| /serverkeygen | /skg | | /serverkeygen | /skg (PKCS#7) |
+------------------+-----------+ | /serverkeygen | /skc (application/pkix-cert) |
+------------------+-------------------------------+
Table 1: Table 1: Short EST-coaps URI path Table 1: Short EST-coaps URI path
Clients and servers MUST support the short resource URIs. The The /skg message is the EST /serverkeygen equivalent where the client
corresponding longer URIs from [RFC7030] MAY be supported. requests for a certificate in PKCS#7 format and a private key. If
the client prefers a single application/pkix-cert certificate instead
of PKCS#7, he will make an /skc request.
Clients and servers MUST support the short resource URIs.
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. The example below shows the the root resource of the EST resources. The example below shows the
discovery of the presence and location of EST-coaps resources. discovery of the presence and location of EST-coaps resources.
Linefeeds are included only for readability. 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/crts>;rt="ace.est.crts";ct="281 TBD287", </est/crts>;rt="ace.est.crts";ct="281 TBD287",
</est/sen>;rt="ace.est.sen";ct="281 TBD287", </est/sen>;rt="ace.est.sen";ct="281 TBD287",
</est/sren>;rt="ace.est.sren";ct="281 TBD287", </est/sren>;rt="ace.est.sren";ct="281 TBD287",
</est/att>;rt="ace.est.att";ct=285, </est/att>;rt="ace.est.att";ct=285,
</est/skg>;rt="ace.est.skg";ct="62 280 284 281 TBD287" </est/skg>;rt="ace.est.skg";ct=62,
</est/skc>;rt="ace.est.skc";ct=62
The first line of the discovery response above MUST be included. The The first three lines of the discovery response above MUST be
five consecutive lines after the first MAY be included. The return returned if the server supports resource discovery. The last three
of the content types allows the client to choose the most appropriate lines are only included if the corresponding EST functions are
one. implemented. The Content-Formats in the response allow the client to
request one that is supported by the server.
Port numbers, not returned in the example, are assumed to be the Discoverable port numbers can be returned in the response payload.
default numbers 5683 and 5684 for CoAP and CoAPS respectively An example response payload for non-default CoAPS server port 61617
(Sections 12.6 and 12.7 of [RFC7252]). Discoverable port numbers MAY follows below. Linefeeds were included only for readability.
be returned in the <href> of the payload
[I-D.ietf-core-resource-directory]. An example response payload for
non-default CoAPS server port 61617 follows below. Linefeeds were
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
<coap://[2001:db8:3::123]:61617/est>;rt="ace.est"; <coaps://[2001:db8:3::123]:61617/est/crts>;rt="ace.est.crts";
anchor="coap://[2001:db8:3::123]:61617", ct="281 TBD287",
<coap://[2001:db8:3::123]:61617/est/crts>;rt="ace.est.crts"; <coaps://[2001:db8:3::123]:61617/est/sen>;rt="ace.est.sen";
ct="281 TBD287";anchor="coap://[2001:db8:3::123]:61617", ct="281 TBD287",
<coap://[2001:db8:3::123]:61617/est/sen>;rt="ace.est.sen"; <coaps://[2001:db8:3::123]:61617/est/sren>;rt="ace.est.sren";
ct="281 TBD287";anchor="coap://[2001:db8:3::123]:61617", ct="281 TBD287",
<coap://[2001:db8:3::123]:61617/est/sren>;rt="ace.est.sren"; <coaps://[2001:db8:3::123]:61617/est/att>;rt="ace.est.att";
ct="281 TBD287";anchor="coap://[2001:db8:3::123]:61617", ct=285,
<coap://[2001:db8:3::123]:61617/est/att>;rt="ace.est.att"; <coaps://[2001:db8:3::123]:61617/est/skg>;rt="ace.est.skg";
ct="285";anchor="coap://[2001:db8:3::123]:61617", ct=62,
<coap://[2001:db8:3::123]:61617/est/skg>;rt="ace.est.skg"; <coaps://[2001:db8:3::123]:61617/est/skc>;rt="ace.est.skc";
ct="62 280 284 281 TBD287";anchor="coap://[2001:db8:3::123]:61617" ct=62
The server MUST support the default /.well-known/est server root The server MUST support the default /.well-known/est root resource.
resource and port 5684. Resource discovery is necessary when the IP The server SHOULD support resource discovery when he supports non-
address of the server is unknown to the client. Resource discovery default URIs (like /est or /est/ArbitraryLabel) or ports. The client
SHOULD be employed when non-default URIs (like /est or /est/ SHOULD use resource discovery when /.well-known/est fails or when the
ArbitraryLabel) or ports are supported by the server, when the client client is unaware of the available EST-coaps resources.
is unaware of what EST-coaps resources are available or if the client
considers sending two Uri-Path Options to convey the resource is
wasteful.
It is up to the implementation to choose its root resource; It is up to the implementation to choose its root resource;
throughout this document the example root resource /est is used. throughout this document the example root resource /est is used.
5.2. Mandatory/optional EST Functions 5.2. Mandatory/optional EST Functions
This specification contains a set of required-to-implement functions, This specification contains a set of required-to-implement functions,
optional functions, and not specified functions. The latter ones are optional functions, and not specified functions. The latter ones are
deemed too expensive for low-resource devices in payload and deemed too expensive for low-resource devices in payload and
calculation times. calculation times.
Table 2 specifies the mandatory-to-implement or optional Table 2 specifies the mandatory-to-implement or optional
implementation of the est-coaps functions. implementation of the EST-coaps functions. Discovery of the
existence of optional functions is described in Section 5.1.
+------------------+--------------------------+ +------------------+--------------------------+
| EST Functions | EST-coaps implementation | | EST Functions | EST-coaps implementation |
+------------------+--------------------------+ +------------------+--------------------------+
| /cacerts | MUST | | /cacerts | MUST |
| /simpleenroll | MUST | | /simpleenroll | MUST |
| /simplereenroll | MUST | | /simplereenroll | MUST |
| /fullcmc | Not specified |
| /serverkeygen | OPTIONAL |
| /csrattrs | OPTIONAL | | /csrattrs | OPTIONAL |
| /serverkeygen | OPTIONAL |
| /fullcmc | Not specified |
+------------------+--------------------------+ +------------------+--------------------------+
Table 2: Table 2: List of EST-coaps functions Table 2: List of EST-coaps functions
While [RFC7030] permits a number of these functions to be used While [RFC7030] permits a number of these functions to be used
without authentication, this specification requires that the client without authentication, this specification requires that the client
MUST be authenticated for all functions. MUST be authenticated for all functions.
5.3. Payload formats 5.3. Payload formats
EST-coaps is designed for low-resource devices and hence does not
need to send Base64-encoded data. Simple binary is more efficient
(30% smaller payload) and well supported by CoAP. Thus, the payload
for a given Media-Type follows the ASN.1 structure of the Media-Type
and is transported in binary format.
The Content-Format (HTTP Media-Type equivalent) of the CoAP message The Content-Format (HTTP 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 specified by the Content-Format Option (12) of
(12) of CoAP. The combination of URI-Path and Content-Format in EST- CoAP. The combination of URI-Path and Content-Format in EST-coaps
coaps MUST map to an allowed combination of URI and Media-Type in MUST map to an allowed combination of URI and Media-Type in EST. The
EST. The required Content-Formats for these requests and response required Content-Formats for these requests and response messages are
messages are defined in Section 10.1. The CoAP response codes are defined in Section 9.1. The CoAP response codes are defined in
defined in Section 5.5. Section 5.5.
Content-Format TBD287 can be used in place of 281 to carry a single Content-Format TBD287 can be used in place of 281 to carry a single
certificate instead of a PKCS#7 container in a /crts, /sen, /sren or certificate instead of a PKCS#7 container in a /crts, /sen, /sren or
/skg response. Content-Format 281 MUST be supported by EST-coaps /skg response. Content-Format 281 MUST be supported by EST-coaps
servers. Servers MAY also support Content-Format TBD287. It is up servers. Servers MAY also support Content-Format TBD287. It is up
to the client to support only Content-Format 281, TBD287 or both. to the client to support only Content-Format 281, TBD287 or both.
The client is expected to use an COAP Accept Option in the request to The client will use a COAP Accept Option in the request to express
express the preferred response Content-Format. If an Accept Option the preferred response Content-Format. If an Accept Option is not
is not included in the request, the client is not expressing any included in the request, the client is not expressing any preference
preference and the server SHOULD choose format 281. If the preferred and the server SHOULD choose format 281.
Content-Format cannot be returned, the server MUST send a 4.06 (Not
Acceptable) response, unless another error code takes precedence for
the response [RFC7252].
Content-Format 286 is used in /sen, /sren and /skg requests and 285 Content-Format 286 is used in /sen, /sren and /skg requests and 285
in /att responses. in /att responses.
EST-coaps is designed for low-resource devices and hence does not
need to send Base64-encoded data. Simple binary is more efficient
(30% smaller payload) and well supported by CoAP. Thus, the payload
for a given Media-Type follows the ASN.1 structure of the Media-Type
and is transported in binary format.
*application/multipart-core*
A representation with Content-Format identifier 62 contains a A representation with Content-Format identifier 62 contains a
collection of representations along with their respective Content- collection of representations along with their respective Content-
Format. The Content-Format identifies the Media-Type application/ Format. The Content-Format identifies the Media-Type application/
multipart-core specified in [I-D.ietf-core-multipart-ct]. multipart-core specified in [I-D.ietf-core-multipart-ct]. For
example, a collection, containing two representations in response to
The collection is encoded as a CBOR array [RFC7049] with an even a EST-coaps server-side key generation /skg request, could include a
number of elements. The second, fourth, sixth, etc. element is a private key in PKCS#8 [RFC5958] with Content-Format identifier 284
binary string containing a representation. The first, third, fifth, (0x011C) and a single certificate in a PKCS#7 container with Content-
etc. element is an unsigned integer specifying the Content-Format Format identifier 281 (0x0119). Such a collection would look like
identifier of the consecutive representation. For example, a
collection containing two representations in response to a EST-coaps
server-side key generation request, could include a private key in
PKCS#8 [RFC5958] with Content-Format identifier 284 (0x011C) and a
single certificate in a PKCS#7 container with Content-Format
identifier 281 (0x0119). Such a collection would look like
[284,h'0123456789abcdef', 281,h'fedcba9876543210'] in diagnostic CBOR [284,h'0123456789abcdef', 281,h'fedcba9876543210'] in diagnostic CBOR
notation. The serialization of such CBOR content would be notation. The serialization of such CBOR content would be
84 # array(4) 84 # array(4)
19 011C # unsigned(284) 19 011C # unsigned(284)
48 # bytes(8) 48 # bytes(8)
0123456789ABCDEF # "\x01#Eg\x89\xAB\xCD\xEF" 0123456789ABCDEF # "\x01#Eg\x89\xAB\xCD\xEF"
19 0119 # unsigned(281) 19 0119 # unsigned(281)
48 # bytes(8) 48 # bytes(8)
FEDCBA9876543210 # "\xFE\xDC\xBA\x98vT2\x10" FEDCBA9876543210 # "\xFE\xDC\xBA\x98vT2\x10"
Multipart /skg response serialization Multipart /skg response serialization
skipping to change at page 12, line 14 skipping to change at page 13, line 27
84 # array(4) 84 # array(4)
19 011C # unsigned(284) 19 011C # unsigned(284)
48 # bytes(8) 48 # bytes(8)
0123456789ABCDEF # "\x01#Eg\x89\xAB\xCD\xEF" 0123456789ABCDEF # "\x01#Eg\x89\xAB\xCD\xEF"
19 0119 # unsigned(281) 19 0119 # unsigned(281)
48 # bytes(8) 48 # bytes(8)
FEDCBA9876543210 # "\xFE\xDC\xBA\x98vT2\x10" FEDCBA9876543210 # "\xFE\xDC\xBA\x98vT2\x10"
Multipart /skg response serialization Multipart /skg response serialization
When the returned certificate is a single X.509 certificate (not a When the client makes an /skc request the certificate returned with
PKCS#7 container) the Content-Format identifier is TBD287 (0x011F) the private key is a single X.509 certificate (not a PKCS#7
instead of 281. In cases where the private key is encrypted with CMS container) with Content-Format identifier TBD287 (0x011F) instead of
(as explained in Section 5.8) the Content-Format identifier is 280 281. In cases where the private key is encrypted with CMS (as
explained in Section 5.8) the Content-Format identifier is 280
(0x0118) instead of 284. The key and certificate representations are (0x0118) instead of 284. The key and certificate representations are
ASN.1 encoded in binary format. An example is shown in Appendix A.3. ASN.1 encoded in binary format. An example is shown in Appendix A.3.
5.4. Message Bindings 5.4. Message Bindings
The general EST-coaps message characteristics are: The general EST-coaps message characteristics are:
o All EST-coaps messages expect a response from the server, thus the o All EST-coaps request messages expect an acknowledgement (with a
client MUST send the requests over confirmable CON CoAP messages. response payload); EST-coaps requests are confirmable CON CoAP
messages.
o The Ver, TKL, Token, and Message ID values of the CoAP header are
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, Accept and Location-Path. These CoAP Options are used to Format, Block, Accept and Location-Path. These CoAP Options are
communicate the HTTP fields specified in the EST REST messages. used to communicate the HTTP fields specified in the EST REST
The Uri-Host and Uri-Port Options are optional. They are usually messages. The URI-host and Uri-Port Options can be omitted from
omitted as the DTLS destination and port are sufficient. Explicit the COAP message sent on the wire. When omitted, they are
Uri-Host and Uri-Port Options are typically used when an endpoint logically assumed to be the transport protocol destination address
hosts multiple virtual servers and uses the Options to route the and port respectively. Explicit Uri-Host and Uri-Port Options are
requests accordingly. Alternatively, if a UDP port to a server is typically used when an endpoint hosts multiple virtual servers and
blocked, someone could send the DTLS packets to a known open port uses the Options to route the requests accordingly. Other COAP
on the server and use the Uri-Port to convey the intended port he Options should be handled in accordance with [RFC7252].
is attempting to reach.
o EST URLs are HTTPS based (https://), in CoAP these are assumed to o EST URLs are HTTPS based (https://), in CoAP these are assumed to
be translated to CoAPS (coaps://) be translated to CoAPS (coaps://)
Table 1 provides the mapping from the EST URI path to the EST-coaps Table 1 provides the mapping from the EST URI path to the EST-coaps
URI path. Appendix A includes some practical examples of EST URI path. Appendix A includes some practical examples of EST
messages translated to CoAP. messages translated to CoAP.
5.5. CoAP response codes 5.5. CoAP response codes
Section 5.9 of [RFC7252] and Section 7 of [RFC8075] specify the Section 5.9 of [RFC7252] and Section 7 of [RFC8075] specify the
mapping of HTTP response codes to CoAP response codes. Every time mapping of HTTP response codes to CoAP response codes. Every time
the HTTP response code 200 is specified in [RFC7030] in response to a the HTTP response code 200 is specified in [RFC7030] in response to a
GET request (/cacerts, /csrattrs), in EST-coaps the equivalent CoAP GET request (/cacerts, /csrattrs), the equivalent CoAP response code
response code 2.05 or 2.03 MUST be used. Similarly, 2.01, 2.02 or 2.05 or 2.03 MUST be used in EST-coaps. Similarly, 2.01, 2.02 or
2.04 MUST be used in response to EST POST requests (/simpleenroll, 2.04 MUST be used in response to EST POST requests (/simpleenroll,
/simplereenroll, /serverkeygen). /simplereenroll, /serverkeygen).
Response code HTTP 202 Retry-After that existed in EST has no HTTP response code 202 with a Retry-After header in [RFC7030] has no
equivalent in CoAP. Retry-After is used in EST for delayed server equivalent in CoAP. Retry-After is used in EST for delayed server
responses. Section 5.7 specifies how EST-coaps handles delayed responses. Section 5.7 specifies how EST-coaps handles delayed
messages. messages.
EST makes use of HTTP 204 and 404 responses when a resource is not EST makes use of HTTP 204 and 404 responses when a resource is not
available for the client. The equivalent CoAP codes to use in an available for the client. The equivalent CoAP codes to use in an
EST-coaps responses are 2.04 and 4.04. Additionally, EST's HTTP 401 EST-coaps responses are 2.04 and 4.04. Additionally, EST's HTTP 401
error translates to 4.01 in EST-coaps. Other EST HTTP error messages error translates to 4.01 in EST-coaps. Other EST HTTP error messages
are 400, 423 and 503. Their equivalent CoAP errors are 4.00, 4.03 are 400, 423 and 503. Their equivalent CoAP errors are 4.00, 4.03
and 5.03 respectively. In case a CoAP Option is unrecognized and and 5.03 respectively. In case a CoAP Option is unrecognized and
critical, the server is expected to return a 4.02 (Bad Option). critical, the server is expected to return a 4.02 (Bad Option).
Moreover, if the Content-Format requested in the client Accept
Option, is not supported the server MUST return a 4.06 (Not
Acceptable), unless another error code takes precedence for the
response.
5.6. Message fragmentation 5.6. Message fragmentation
DTLS defines fragmentation only for the handshake and not for secure DTLS defines fragmentation only for the handshake and not for secure
data exchange (DTLS records). [RFC6347] states that to avoid using data exchange (DTLS records). [RFC6347] states that to avoid using
IP fragmentation, which involves error-prone datagram reconstitution, IP fragmentation, which involves error-prone datagram reconstitution,
invokers of the DTLS record layer SHOULD size DTLS records so that invokers of the DTLS record layer should size DTLS records so that
they fit within any Path MTU estimates obtained from the record they fit within any Path MTU estimates obtained from the record
layer. In addition, invokers residing on a 6LoWPAN over IEEE layer. In addition, invokers residing on a 6LoWPAN over IEEE
802.15.4 [ieee802.15.4] network SHOULD attempt to size CoAP messages 802.15.4 [ieee802.15.4] network should attempt to size CoAP messages
such that each DTLS record will fit within one or two IEEE 802.15.4 such that each DTLS record will fit within one or two IEEE 802.15.4
frames. frames.
That is not always possible in EST-coaps. Even though ECC That is not always possible in EST-coaps. Even though ECC
certificates are small in size, they can vary greatly based on certificates are small in size, they can vary greatly based on
signature algorithms, key sizes, and Object Identifier (OID) fields signature algorithms, key sizes, and Object Identifier (OID) fields
used. For 256-bit curves, common ECDSA cert sizes are 500-1000 bytes used. For 256-bit curves, common ECDSA cert sizes are 500-1000 bytes
which could fluctuate further based on the algorithms, OIDs, Subject which could fluctuate further based on the algorithms, OIDs, Subject
Alternative Names (SAN) and cert fields. For 384-bit curves, ECDSA Alternative Names (SAN) and cert fields. For 384-bit curves, ECDSA
certificates increase in size and can sometimes reach 1.5KB. certificates increase in size and can sometimes reach 1.5KB.
skipping to change at page 14, line 30 skipping to change at page 15, line 36
supported for EST-coaps enrollment requests that exceed the Path MTU. supported for EST-coaps enrollment requests that exceed the Path MTU.
[RFC7959] also defines Size1 and Size2 Options to provide size [RFC7959] also defines Size1 and Size2 Options to provide size
information about the resource representation in a request and information about the resource representation in a request and
response. EST-client and server MAY support Size1 and Size2 Options. response. EST-client and server MAY support Size1 and Size2 Options.
Examples of fragmented EST-coaps messages are shown in Appendix B. Examples of fragmented EST-coaps messages are shown in Appendix B.
5.7. Delayed Responses 5.7. Delayed Responses
Server responses can sometimes be delayed. According to section Server responses can sometimes be delayed. According to
5.2.2 of [RFC7252], a slow server can acknowledge the request and Section 5.2.2 of [RFC7252], a slow server can acknowledge the request
respond later with the requested resource representation. In and respond later with the requested resource representation. In
particular, a slow server can respond to an EST-coaps enrollment particular, a slow server can respond to an EST-coaps enrollment
request with an empty ACK with code 0.00, before sending the request with an empty ACK with code 0.00, before sending the
certificate to the server after a short delay. If the certificate certificate to the client after a short delay. If the certificate
response is large, the server will need more than one Block2 blocks response is large, the server will need more than one Block2 blocks
to transfer it. This situation is shown in Figure 2. The client to transfer it.
sends an enrollment request that uses N1+1 Block1 blocks. The server
uses an empty 0.00 ACK to announce the delayed response which is This situation is shown in Figure 2. The client sends an enrollment
provided later with 2.04 messages containing N2+1 Block2 Options. request that uses N1+1 Block1 blocks. The server uses an empty 0.00
The first 2.04 is a confirmable message that is acknowledged by the ACK to announce the delayed response which is provided later with
client with an ACK. Onwards, having received the first 256 bytes in 2.04 messages containing N2+1 Block2 Options. The first 2.04 is a
the first Block2 block, the client asks for a block reduction to 128 confirmable message that is acknowledged by the client. Onwards,
bytes in a confirmable enrollment request Uri-Path and acknowledges having received the first 256 bytes in the first Block2 block, the
the Block2 blocks sent up to that point. client asks for a block reduction to 128 bytes in a confirmable
enrollment request and acknowledges the Block2 blocks sent up to that
point.
POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256) {CSR req} --> POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256) {CSR req} -->
<-- (ACK) (1:0/1/256) (2.31 Continue) <-- (ACK) (1:0/1/256) (2.31 Continue)
POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256) {CSR req} --> POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256) {CSR req} -->
<-- (ACK) (1:1/1/256) (2.31 Continue) <-- (ACK) (1:1/1/256) (2.31 Continue)
. .
. .
. .
POST [2001:db8::2:1]:61616/est/sen (CON)(1:N1/0/256){CSR req} --> POST [2001:db8::2:1]:61616/est/sen (CON)(1:N1/0/256){CSR req} -->
<-- (0.00 empty ACK) <-- (0.00 empty ACK)
skipping to change at page 15, line 30 skipping to change at page 16, line 32
<-- (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 2: EST-COAP enrollment with short wait Figure 2: EST-COAP enrollment with short wait
If the server is very slow (i.e. minutes) in providing the response If the server is very slow (i.e. minutes) in providing the response
(i.e. when a manual intervention is needed), the server SHOULD (i.e. when a manual intervention is needed), he SHOULD respond with
respond with an ACK containing response code 5.03 (Service an ACK containing response code 5.03 (Service unavailable) and a Max-
unavailable) and a Max-Age Option to indicate the time the client Age Option to indicate the time the client SHOULD wait to request the
SHOULD wait to request the content later. After a delay of Max-Age, content later. After a delay of Max-Age, the client SHOULD resend
the client SHOULD resend the identical CSR to the server. As long as the identical CSR to the server. As long as the server responds with
the server responds with response code 5.03 (Service Unavailable) response code 5.03 (Service Unavailable) with a Max-Age Option, the
with a Max-Age Option, the client SHOULD keep resending the client SHOULD keep resending the enrollment request until the server
enrollment request until the server responds with the certificate or responds with the certificate or the client abandons for other
the client abandons for other reasons. reasons.
To demonstrate this scenario, Figure 3 shows a client sending an To demonstrate this scenario, Figure 3 shows a client sending an
enrollment request that uses N1+1 Block1 blocks to send the CSR to enrollment request that uses N1+1 Block1 blocks to send the CSR to
the server. The server needs N2+1 Block2 blocks to respond, but also the server. The server needs N2+1 Block2 blocks to respond, but also
needs to take a long delay (minutes) to provide the response. needs to take a long delay (minutes) to provide the response.
Consequently, the server uses a 5.03 ACK response with a Max-Age Consequently, the server uses a 5.03 ACK response with a Max-Age
Option. The client waits for a period of Max-Age as many times as he Option. The client waits for a period of Max-Age as many times as he
receives the same 5.03 response and retransmits the enrollment receives the same 5.03 response and retransmits the enrollment
request until he receives a certificate in a fragmented 2.01 request until he receives a certificate in a fragmented 2.01
response. Note that the server asks for a decrease in the block size response. Note that the server asks for a decrease in the block size
skipping to change at page 17, line 7 skipping to change at page 18, line 11
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 are transferred back to the client in the the certificate which are transferred back to the client in the
server-side key generation response. In all respects, the server server-side key generation response. In all respects, the server
SHOULD treat the CSR as it would treat any enroll or re-enroll CSR; SHOULD treat the CSR as it would treat any enroll or re-enroll CSR;
the only distinction here is that the server MUST ignore the public the only distinction here is that the server MUST ignore the public
key values and signature in the CSR. These are included in the key values and signature in the CSR. These are included in the
request only to allow re-use of existing codebases for generating and request only to allow re-use of existing codebases for generating and
parsing such requests. parsing such requests.
The client /skg request needs to communicate to the server the The client /skg request is for a certificate in a PKCS#7 container
Content-Format of the application/multipart-core elements. The key and private key in two application/multipart-core elements.
Content-Format requested by the client is depicted in the PKCS#10 Respectively, an /skc request is for a single application/pkix-cert
request. If the request contains SMIMECapabilities the client is certificate and a private key. The private key Content-Format
expecting Content-Format 280. Otherwise he expects a PKCS#8 key in requested by the client is depicted in the PKCS#10 CSR request. If
Content-Format 284. The client expresses the preferred certificate the request contains SMIMECapabilities and DecryptKeyIdentifier or
Content-Format in his /skg request by using an Accept Option. The AsymmetricDecryptKeyIdentifier the client is expecting Content-Format
Accept Option is 281 when preferring a certificate in a PKCS#7 280 for the private key. Then the private key is encrypted
container or TBD287 when preferring a single X.509 certificate. symmetrically or asymmetrically as per [RFC7030]. The symmetric key
or the asymmetric keypair establishment method is out of scope of the
[RFC7030] provides two methods, symmetric and asymmetric, to specification. A /skg or /skc request with a CSR without
optionally encrypt the generated key. The methods are signaled by SMIMECapabilities expects an application/multipart-core with an
the client by using the relevant attributes (SMIMECapabilities and unencrypted PKCS#8 private key with Content-Format 284.
DecryptKeyIdentifier or AsymmetricDecryptKeyIdentifier) in the CSR
request. The symmetric key or the asymmetric keypair establishment
method is out of scope of the specification.
The EST-coaps server-side key generation response is returned with The EST-coaps server-side key generation response is returned with
Content-Format application/multipart-core Content-Format application/multipart-core
[I-D.ietf-core-multipart-ct] containing a CBOR array with four items [I-D.ietf-core-multipart-ct] containing a CBOR array with four items
Section 5.3. The certificate part exactly matches the response from (Section 5.3) . The two representations (each consisting of two CBOR
an enrollment response. The private key can be in unprotected PKCS#8 array items) do not have to be in a particular order since each
[RFC5958] format (Content-Format 284) or protected inside of CMS representation is preceded by its Content-Format ID. The private key
SignedData (Content-Format 280). The SignedData is signed by the can be in unprotected PKCS#8 [RFC5958] format (Content-Format 284) or
party that generated the private key, which may be the EST server or protected inside of CMS SignedData (Content-Format 280). The
the EST CA. The SignedData is further protected by placing it inside SignedData is signed by the party that generated the private key,
of a CMS EnvelopedData as explained in Section 4.4.2 of [RFC7030]. which may be the EST server or the EST CA. The SignedData is further
In summary, the symmetrically encrypted key is included in the protected by placing it inside of a CMS EnvelopedData as explained in
encryptedKey attribute in a KEKRecipientInfo structure. In the case Section 4.4.2 of [RFC7030]. In summary, the symmetrically encrypted
where the asymmetric encryption key is suitable for transport key key is included in the encryptedKey attribute in a KEKRecipientInfo
operations the generated private key is encrypted with a symmetric structure. In the case where the asymmetric encryption key is
suitable for transport key operations the generated private key is
encrypted with a symmetric key which is encrypted by the client
defined (in the CSR) asymmetric public key and is carried in an
encryptedKey attribute in a KeyTransRecipientInfo structure.
Finally, if the asymmetric encryption key is suitable for key
agreement, the generated private key is encrypted with a symmetric
key which is encrypted by the client defined (in the CSR) asymmetric key which is encrypted by the client defined (in the CSR) asymmetric
public key and is carried in an encryptedKey attribute in a public key and is carried in an recipientEncryptedKeys attribute in a
KeyTransRecipientInfo structure. Finally, if the asymmetric KeyAgreeRecipientInfo.
encryption key is suitable for key agreement, the generated private
key is encrypted with a symmetric key which is encrypted by the
client defined (in the CSR) asymmetric public key and is carried in
an recipientEncryptedKeys attribute in a KeyAgreeRecipientInfo.
[RFC7030] recommends the use of additional encryption of the returned [RFC7030] recommends the use of additional encryption of the returned
private key. For the context of this specification, clients and private key. For the context of this specification, clients and
servers that choose to support server-side key generation MUST servers that choose to support server-side key generation MUST
support unprotected (PKCS#8) private keys (Content-Format 284). support unprotected (PKCS#8) private keys (Content-Format 284).
Symmetric or asymmetric encryption of the private key (CMS Symmetric or asymmetric encryption of the private key (CMS
EnvelopedData, Content-Format 280) SHOULD be supported for EnvelopedData, Content-Format 280) SHOULD be supported for
deployments where end-to-end encryption needs to be provided between deployments where end-to-end encryption needs to be provided between
the client and a server. Such cases could include architectures the client and a server. Such cases could include architectures
where an entity between the client and the CA terminates the DTLS where an entity between the client and the CA terminates the DTLS
connection (Registrar in Figure 4). connection (Registrar in Figure 4).
6. DTLS Transport Protocol 6. HTTPS-CoAPS Registrar
EST-coaps depends on a secure transport mechanism over UDP that
secures the exchanged CoAP messages. DTLS is one such secure
protocol. EST depended in TLS. No other changes are necessary
regarding the secure transport of EST messages.
CoAP was designed to avoid fragmentation. DTLS is used to secure
CoAP messages. However, fragmentation is still possible at the DTLS
layer during the DTLS handshake when using ECC ciphersuites. If
fragmentation is necessary, "DTLS provides a mechanism for
fragmenting a handshake message over several records, each of which
can be transmitted separately, thus avoiding IP fragmentation"
[RFC6347].
The DTLS handshake is authenticated by using certificates. EST-coaps
supports the certificate types and Trust Anchors (TA) that are
specified for EST in Section 3 of [RFC7030].
CoAP and DTLS can provide proof-of-identity for EST-coaps clients and
servers with simple PKI messages as described in Section 3.1 of
[RFC5272]. Moreover, channel-binding information for linking proof-
of-identity with connection-based proof-of-possession is OPTIONAL for
EST-coaps. When proof-of-possession is desired, a set of actions are
required regarding the use of tls-unique, described in section 3.5 in
[RFC7030]. The tls-unique information consists of the contents of
the first "Finished" message in the (D)TLS handshake between server
and client [RFC5929]. The client adds the "Finished" message as a
ChallengePassword in the attributes section of the PKCS#10 Request
[RFC5967] to prove that the client is indeed in control of the
private key at the time of the (D)TLS session establishment.
In the case of EST-coaps, the same operations can be performed during
the DTLS handshake. For DTLS 1.2, in the event of handshake message
fragmentation, the Hash of the handshake messages used in the MAC
calculation of the Finished message MUST be computed as if each
handshake message had been sent as a single fragment (Section 4.2.6
of [RFC6347]). The Finished message is calculated as shown in
Section 7.4.9 of [RFC5246]. Similarly, for DTLS 1.3, the Finished
message MUST be computed as if each handshake message had been sent
as a single fragment (Section 5.8 of [I-D.ietf-tls-dtls13]) following
the algorithm described in 4.4.4 of [RFC8446].
In a constrained CoAP environment, endpoints can't always afford to
establish a DTLS connection for every EST transaction.
Authenticating and negotiating DTLS keys requires resources on low-
end endpoints and consumes valuable bandwidth. To alleviate this
situation, an EST-coaps DTLS connection MAY remain open for
sequential EST transactions. For example, an EST csrattrs request
that is followed by a simpleenroll request can use the same
authenticated DTLS connection. However, when a cacerts request is
included in the set of sequential EST transactions, some additional
security considerations apply regarding the use of the Implicit and
Explicit TA database as explained in Section 11.1.
Given that after a successful enrollment, it is more likely that a
new EST transaction will take place after a significant amount of
time, the DTLS connections SHOULD only be kept alive for EST messages
that are relatively close to each other. In some cases, like NAT
rebinding, keeping the state of a connection is not possible when
devices sleep for extended periods of time. In such occasions,
[I-D.ietf-tls-dtls-connection-id] negotiates a connection ID that can
eliminate the need for new handshake and its additional cost.
7. HTTPS-CoAPS Registrar
In real-world deployments, the EST server will not always reside In real-world deployments, the EST server will not always reside
within the CoAP boundary. The EST server can exist outside the within the CoAP boundary. The EST server can exist outside the
constrained network in which case it will support TLS/HTTP instead of constrained network in which case it will support TLS/HTTP instead of
CoAPS. In such environments EST-coaps is used by the client within CoAPS. 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 as operate between the CoAP environment and the external HTTP network as
shown in Figure 4. shown in Figure 4.
skipping to change at page 20, line 15 skipping to change at page 19, line 48
The EST-coaps-to-HTTPS Registrar MUST terminate EST-coaps downstream The EST-coaps-to-HTTPS Registrar MUST terminate EST-coaps downstream
and initiate EST connections over TLS upstream. The Registrar MUST and initiate EST connections over TLS upstream. The Registrar MUST
authenticate and OPTIONALLY authorize the clients and it MUST be authenticate and OPTIONALLY authorize the clients and it MUST be
authenticated by the EST server or CA. The trust relationship authenticated by the EST server or CA. The trust relationship
between the Registrar and the EST server SHOULD be pre-established between the Registrar and the EST server SHOULD be pre-established
for the Registrar to proxy these connections on behalf of various for the Registrar to proxy these connections on behalf of various
clients. clients.
When enforcing Proof-of-Possession (POP) linking, the DTLS tls-unique When enforcing Proof-of-Possession (POP) linking, the DTLS tls-unique
value of the (D)TLS session is used to prove that the private key value of the (D)TLS session is used to prove that the private key
corresponding to the public key is in the possession of and was used corresponding to the public key is in the possession of the client
to establish the connection by the client as explained in Section 6). and was used to establish the connection as explained in Section 4.
The POP linking information is lost between the EST-coaps client and The POP linking information is lost between the EST-coaps client and
the EST server when a Registrar is present. The EST server becomes the EST server when a Registrar is present. The EST server becomes
aware of the presence of a Registrar from its TLS client certificate aware of the presence of a Registrar from its TLS client certificate
that includes id-kp-cmcRA [RFC6402] extended key usage extension that includes id-kp-cmcRA [RFC6402] extended key usage extension
(EKU). As explained in Section 3.7 of [RFC7030], the EST server (EKU). As explained in Section 3.7 of [RFC7030], the EST server
SHOULD apply an authorization policy consistent with a Registrar SHOULD apply an authorization policy consistent with a Registrar
client. For example, it could be configured to accept POP linking client. For example, it could be configured to accept POP linking
information that does not match the current TLS session because the information that does not match the current TLS session because the
authenticated EST client Registrar has verified this information when authenticated EST client Registrar has verified this information when
acting as an EST server. acting as an EST server.
For some use cases, clients that leverage server-side key generation For some use cases, clients that leverage server-side key generation
might prefer for the enrolled keys to be generated by the Registrar might prefer for the enrolled keys to be generated by the Registrar
if the CA does not support server-side key generation. In these if the CA does not support server-side key generation. Such
cases, the Registrar MUST support random number generation using Registrar is responsible for generating a new CSR signed by a new key
proper entropy. Such Registrar is responsible for generating a new which will be returned to the client along with the certificate from
CSR signed by a new key which will be returned to the client along the CA. In these cases, the Registrar MUST support random number
with the certificate from the CA. generation using proper entropy.
Table 1 contains the URI mappings between EST-coaps and EST that the Table 1 contains the URI mappings between EST-coaps and EST that the
Registrar MUST adhere to. Section 5.5 of this specification and Registrar MUST adhere to. Section 5.5 of this specification and
Section 7 of [RFC8075] define the mappings between EST-coaps and HTTP Section 7 of [RFC8075] define the mappings between EST-coaps and HTTP
response codes, that determine how the Registrar MUST translate CoAP response codes, that determine how the Registrar MUST translate CoAP
response codes from/to HTTP status codes. The mapping from CoAP response codes from/to HTTP status codes. The mapping from CoAP
Content-Format to HTTP Media-Type is defined in Section 10.1. Content-Format to HTTP Media-Type is defined in Section 9.1.
Additionally, a conversion from CBOR major type 2 to Base64 encoding Additionally, a conversion from CBOR major type 2 to Base64 encoding
MUST take place at the Registrar when server-side key generation is MUST take place at the Registrar when server-side key generation is
supported. If CMS end-to-end encryption is employed for the private supported. If CMS end-to-end encryption is employed for the private
key, the encrypted CMS EnvelopedData blob MUST be converted to binary key, the encrypted CMS EnvelopedData blob MUST be converted to binary
in CBOR type 2 downstream to the client. in CBOR type 2 downstream to the 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 MUST reassemble the BLOCKs before translating the HTTP Registrar MUST reassemble the BLOCKs before translating the
binary content to Base64, and consecutively relay the message binary content to Base64, and consecutively relay the message
upstream. upstream.
For the discovery of the EST server by the EST client in the CoAP If necessary, the EST-coaps-to-HTTP Registrar will support resouce
environment, the EST-coaps-to-HTTP Registrar MUST announce itself discovery according to the rules in Section 5.1.
according to the rules in Section 5.1. The available actions of the
Registrars MUST be announced with as many resource paths necessary.
8. Parameters 7. Parameters
This section addresses transmission parameters described in sections This section addresses transmission parameters described in sections
4.7 and 4.8 of [RFC7252]. EST does not impose any unique values on 4.7 and 4.8 of [RFC7252]. EST does not impose any unique values on
the CoAP parameters in [RFC7252], but the EST parameter values need the CoAP parameters in [RFC7252], but the EST parameter values need
to be tuned to the CoAP parameter values. to be tuned to the CoAP parameter values.
It is RECOMMENDED, based on experiments, to follow the default CoAP It is RECOMMENDED, based on experiments, to follow the default CoAP
configuration parameters ([RFC7252]). However, depending on the configuration parameters ([RFC7252]). However, depending on the
implementation scenario, retransmissions and timeouts can also occur implementation scenario, retransmissions and timeouts can also occur
on other networking layers, governed by other configuration on other networking layers, governed by other configuration
parameters. A change in a server parameter MUST ensure the adjusted parameters. A change in a server parameter MUST ensure the adjusted
value is also available to all the endpoints with which these value is also available to all the endpoints with which these
adjusted values are to be used to communicate. adjusted values are to be used to communicate.
Some further comments about some specific parameters, mainly from Some further comments about some specific parameters, mainly from
Table 2 in [RFC7252]: Table 2 in [RFC7252]:
o NSTART: Limit the number of simultaneous outstanding interactions o NSTART: A parameter that controls the number of simultaneous
that a client maintains to a given server. EST-coaps clients outstanding interactions that a client maintains to a given
SHOULD use 1, which is the default. A EST-coaps client is not server. An EST-coaps client is not expected to interact with more
expected to interact with more than one servers at the same time. than one servers at the same time, which is the default NSTART
value defined in [RFC7252].
o DEFAULT_LEISURE: This setting is only relevant in multicast o DEFAULT_LEISURE: This setting is only relevant in multicast
scenarios, outside the scope of EST-coaps. scenarios, outside the scope of EST-coaps.
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 this setting is not as CoAP confirmable messages, hence this setting is not
applicable. applicable.
Finally, the Table 3 parameters in [RFC7252] are mainly derived from Finally, the Table 3 parameters in [RFC7252] are mainly derived from
Table 2. Directly changing parameters on one table would affect Table 2. Directly changing parameters on one table would affect
parameters on the other. parameters on the other.
9. Deployment limitations 8. Deployment limitations
Although EST-coaps paves the way for the utilization of EST by Although EST-coaps paves the way for the utilization of EST by
constrained devices in constrained networks, some classes of devices constrained devices in constrained networks, some classes of devices
[RFC7228] will not have enough resources to handle the large payloads [RFC7228] will not have enough resources to handle the payloads that
that come with EST-coaps. The specification of EST-coaps is intended come with EST-coaps. The specification of EST-coaps is intended to
to ensure that EST works for networks of constrained devices that ensure that EST works for networks of constrained devices that choose
choose to limit their communications stack to UDP/DTLS/CoAP. It is to limit their communications stack to DTLS/CoAP. It is up to the
up to the network designer to decide which devices execute the EST network designer to decide which devices execute the EST protocol and
protocol and which do not. which do not.
10. IANA Considerations 9. IANA Considerations
10.1. Content-Format Registry 9.1. 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 [COREparams] are specified in Table 3. "CoRE Parameters" registry [COREparams] are specified in Table 3.
These have been registered provisionally in the Expert Review range These have been registered provisionally in the Expert Review range
(0-255). (0-255).
+------------------------------+-------+----------------------------+ +------------------------------+-------+----------------------------+
| HTTP Media-Type | ID | Reference | | HTTP Media-Type | ID | Reference |
+------------------------------+-------+----------------------------+ +------------------------------+-------+----------------------------+
| application/pkcs7-mime; | 280 | [RFC7030] [I-D.ietf-lamps- | | application/pkcs7-mime; | 280 | [RFC7030] [I-D.ietf-lamps- |
| smime-type=server-generated- | | rfc5751-bis] | | smime-type=server-generated- | | rfc5751-bis] |
| key | | | | key | | |
| application/pkcs7-mime; | 281 | [I-D.ietf-lamps-rfc5751-bi | | application/pkcs7-mime; | 281 | [I-D.ietf-lamps-rfc5751-bi |
| smime-type=certs-only | | s] | | smime-type=certs-only | | s] |
| application/pkcs7-mime; | 282 | [RFC5273] [I-D.ietf-lamps- |
| smime-type=CMC-request | | rfc5751-bis] |
| application/pkcs7-mime; | 283 | [RFC5273] [I-D.ietf-lamps- |
| smime-type=CMC-response | | rfc5751-bis] |
| application/pkcs8 | 284 | [RFC5958] [I-D.ietf-lamps- | | application/pkcs8 | 284 | [RFC5958] [I-D.ietf-lamps- |
| | | rfc5751-bis] | | | | rfc5751-bis] |
| application/csrattrs | 285 | [RFC7030] [RFC7231] | | application/csrattrs | 285 | [RFC7030] [RFC7231] |
| application/pkcs10 | 286 | [RFC5967] [I-D.ietf-lamps- | | application/pkcs10 | 286 | [RFC5967] [I-D.ietf-lamps- |
| | | rfc5751-bis] | | | | rfc5751-bis] |
| application/pkix-cert | TBD28 | [RFC2585] | | application/pkix-cert | TBD28 | [RFC2585] |
| | 7 | | | | 7 | |
+------------------------------+-------+----------------------------+ +------------------------------+-------+----------------------------+
Table 3: Table 3: New CoAP Content-Formats Table 3: New CoAP Content-Formats
The Content-Formats 281 to 286 have been the subject of an earlier It is suggested that 287 is allocated to TBD287.
temporary allocation. It is suggested that 287 is allocated to
TBD287.
10.2. Resource Type registry 9.2. Resource Type registry
This memo registers a new Resource Type (rt=) Link Target Attributes This memo registers new Resource Type (rt=) Link Target Attributes in
in the "Resource Type (rt=) Link Target Attribute Values" subregistry the "Resource Type (rt=) Link Target Attribute Values" subregistry
under the "Constrained RESTful Environments (CoRE) Parameters" under the "Constrained RESTful Environments (CoRE) Parameters"
registry. registry.
o rt="ace.est". This EST resource is used to query and return the
supported EST resources of a CoAP server.
o rt="ace.est.crts". This resource depicts the support of EST get o rt="ace.est.crts". This resource depicts the support of EST get
cacerts. cacerts.
o rt="ace.est.sen". This resource depicts the support of EST simple o rt="ace.est.sen". This resource depicts the support of EST simple
enroll. enroll.
o rt="ace.est.sren". This resource depicts the support of EST o rt="ace.est.sren". This resource depicts the support of EST
simple reenroll. simple reenroll.
o rt="ace.est.att". This resource depicts the support of EST CSR o rt="ace.est.att". This resource depicts the support of EST CSR
attributes. attributes.
o rt="ace.est.skg". This resource depicts the support of EST o rt="ace.est.skg". This resource depicts the support of EST
server-side key generation. server-side key generation with the returned certificate in a
PKCS#7 container.
11. Security Considerations o rt="ace.est.skc". This resource depicts the support of EST
server-side key generation with the returned certificate in
application/pkix-cert format.
11.1. EST server considerations 10. Security Considerations
10.1. EST server considerations
The security considerations of Section 6 of [RFC7030] are only The security considerations of Section 6 of [RFC7030] are only
partially valid for the purposes of this document. As HTTP Basic partially valid for the purposes of this document. As HTTP Basic
Authentication is not supported, the considerations expressed for Authentication is not supported, the considerations expressed for
using passwords do not apply. using passwords do not apply.
Given that the client has only limited resources and may not be able Given that the client has only limited resources and may not be able
to generate sufficiently random keys to encrypt its identity, it is to generate sufficiently random keys to encrypt its identity, it is
possible that the client uses server generated private/public keys. possible that the client uses server generated private/public keys.
The transport of these keys is inherently risky. Analysis SHOULD be The transport of these keys is inherently risky. Analysis SHOULD be
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It is also RECOMMENDED that the Implicit Trust Anchor database used It is also RECOMMENDED that the Implicit Trust Anchor database used
for EST server authentication is carefully managed to reduce the for EST server authentication is carefully managed to reduce the
chance of a third-party CA with poor certification practices chance of a third-party CA with poor certification practices
jeopardizing authentication. Disabling the Implicit Trust Anchor jeopardizing authentication. Disabling the Implicit Trust Anchor
database after successfully receiving the Distribution of CA database after successfully receiving the Distribution of CA
certificates response (Section 4.1.3 of [RFC7030]) limits any risk to certificates response (Section 4.1.3 of [RFC7030]) limits any risk to
the first DTLS exchange. Alternatively, in a case where a /sen the first DTLS exchange. Alternatively, in a case where a /sen
request immediately follows a /crt, a client MAY choose to keep the request immediately follows a /crt, a client MAY choose to keep the
connection authenticated by the Implicit TA open for efficiency connection authenticated by the Implicit TA open for efficiency
reasons (Section 6). A client that pipelines EST-coaps /crt request reasons (Section 4). A client that pipelines EST-coaps /crt request
with other requests in the same DTLS connection SHOULD revalidate the with other requests in the same DTLS connection SHOULD revalidate the
server certificate chain against the updated Explicit TA from the server certificate chain against the updated Explicit TA from the
/crt response before proceeding with the subsequent requests. If the /crt response before proceeding with the subsequent requests. If the
server certificate chain does not authenticate against the database, server certificate chain does not authenticate against the database,
the client SHOULD close the connection without completing the rest of the client SHOULD close the connection without completing the rest of
the requests. The updated Explicit TA MUST continue to be used in the requests. The updated Explicit TA MUST continue to be used in
new DTLS connections. new DTLS connections.
In cases where the IDevID used to authenticate the client is expired In cases where the IDevID used to authenticate the client is expired
the server MAY still authenticate the client because IDevIDs are the server MAY still authenticate the client because IDevIDs are
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binding is in use. The attack was possible because of certain (D)TLS binding is in use. The attack was possible because of certain (D)TLS
implementation imperfections. In the context of this specification, implementation imperfections. In the context of this specification,
an attacker could invalidate the purpose of the POP linking an attacker could invalidate the purpose of the POP linking
ChallengePassword in the client request by resuming an EST-coaps ChallengePassword in the client request by resuming an EST-coaps
connection. Even though the practical risk of such an attack to EST- connection. Even though the practical risk of such an attack to EST-
coaps is not devastating, we would rather use a more secure channel coaps is not devastating, we would rather use a more secure channel
binding mechanism. Such a mechanism could include an updated tls- binding mechanism. Such a mechanism could include an updated tls-
unique value generation like the tls-unique-prf defined in unique value generation like the tls-unique-prf defined in
[I-D.josefsson-sasl-tls-cb] by using a TLS exporter [RFC5705] in TLS [I-D.josefsson-sasl-tls-cb] by using a TLS exporter [RFC5705] in TLS
1.2 or TLS 1.3's updated exporter (Section 7.5 of [RFC8446]). Such 1.2 or TLS 1.3's updated exporter (Section 7.5 of [RFC8446]). Such
mechanism has not been standardized yet. Adopting in this document a mechanism has not been standardized yet. Adopting a channel binding
channel binding value generated from an exporter would break value generated from an exporter would break backwards compatibility.
backwards compatibility. Thus, in this specification we still depend Thus, in this specification we still depend in the tls-unique
in the tls-unique mechanism defined in [RFC5929], especially since mechanism defined in [RFC5929], especially since the practicality of
the practicality of such an attack would not expose any messages such an attack would not expose any messages exchanged with EST-
exchanged with EST-coaps. coaps.
Regarding the Certificate Signing Request (CSR), a CA is expected to Regarding the Certificate Signing Request (CSR), a CA is expected to
be able to enforce policies to recover from improper CSR requests. be able to enforce policies 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.
11.2. HTTPS-CoAPS Registrar considerations 10.2. HTTPS-CoAPS Registrar considerations
The Registrar proposed in Section 7 must be deployed with care, and The Registrar proposed in Section 6 must be deployed with care, and
only when the recommended connections are impossible. When POP only when the recommended connections are impossible. When POP
linking is used the Registrar terminating the TLS connection linking is used the Registrar terminating the TLS connection
establishes a new one with the upstream CA. Thus, it is impossible establishes a new one with the upstream CA. Thus, it is impossible
for POP linking to be enforced end-to-end for the EST transaction. for POP linking to be enforced end-to-end for the EST transaction.
The EST server could be configured to accept POP linking information The EST server could be configured to accept POP linking information
that does not match the current TLS session because the authenticated that does not match the current TLS session because the authenticated
EST Registrar client has verified this information when acting as an EST Registrar client has verified this information when acting as an
EST server. EST server.
The introduction of an EST-coaps-to-HTTP Registrar assumes the client The introduction of an EST-coaps-to-HTTP Registrar assumes the client
skipping to change at page 25, line 19 skipping to change at page 25, line 4
linking is used the Registrar terminating the TLS connection linking is used the Registrar terminating the TLS connection
establishes a new one with the upstream CA. Thus, it is impossible establishes a new one with the upstream CA. Thus, it is impossible
for POP linking to be enforced end-to-end for the EST transaction. for POP linking to be enforced end-to-end for the EST transaction.
The EST server could be configured to accept POP linking information The EST server could be configured to accept POP linking information
that does not match the current TLS session because the authenticated that does not match the current TLS session because the authenticated
EST Registrar client has verified this information when acting as an EST Registrar client has verified this information when acting as an
EST server. EST server.
The introduction of an EST-coaps-to-HTTP Registrar assumes the client The introduction of an EST-coaps-to-HTTP Registrar assumes the client
can trust the registrar using its implicit or explicit TA database. can trust the registrar using its implicit or explicit TA database.
It also assumes the Registrar has a trust relationship with the It also assumes the Registrar has a trust relationship with the
upstream EST server in order to act on behalf of the clients. When a upstream EST server in order to act on behalf of the clients. When a
client uses the Implicit TA database for certificate validation, he client uses the Implicit TA database for certificate validation, he
SHOULD confirm if the server is acting as an RA by the presence of SHOULD confirm if the server is acting as an RA by the presence of
the id-kp-cmcRA [RFC6402] EKU in the server certificate. If the the id-kp-cmcRA EKU [RFC6402] in the server certificate.
server certificate does not include the EKU, it is RECOMMENDED that
the client includes "Linking Identity and POP Information"
(Section 6) in requests.
In a server-side key generation case, if no end-to-end encryption is In a server-side key generation case, if no end-to-end encryption is
used, the Registrar may be able see the private key as it acts as a used, the Registrar may be able see the private key as it acts as a
man-in-the-middle. Thus, the client puts its trust on the Registrar man-in-the-middle. Thus, the client puts its trust on the Registrar
not exposing the private key. not exposing the private key.
Clients that leverage server-side key generation without end-to-end Clients that leverage server-side key generation without end-to-end
encryption of the private key (Section 5.8) have no knowledge if the encryption of the private key (Section 5.8) have no knowledge if the
Registrar will be generating the private key and enrolling the Registrar will be generating the private key and enrolling the
certificates with the CA or if the CA will be responsible for certificates with the CA or if the CA will be responsible for
generating the key. In such cases, the existence of a Registrar generating the key. In such cases, the existence of a Registrar
requires the client to put its trust on the registrar doing the right requires the client to put its trust on the registrar doing the right
thing if it is generating the private key. thing if it is generating the private key.
12. Contributors 11. Contributors
Martin Furuhed contributed to the EST-coaps specification by Martin Furuhed contributed to the EST-coaps specification by
providing feedback based on the Nexus EST over CoAPS server providing feedback based on the Nexus EST over CoAPS server
implementation that started in 2015. Sandeep Kumar kick-started this implementation that started in 2015. Sandeep Kumar kick-started this
specification and was instrumental in drawing attention to the specification and was instrumental in drawing attention to the
importance of the subject. importance of the subject.
13. 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, John Manuel, Oliver Jim Schaad, Hannes Tschofenig, Julien Vermillard, John Manuel, Oliver
Pfaff and Pete Beal. Pfaff, Pete Beal and Carsten Bormann.
Interop tests were done by Oliver Pfaff, Thomas Werner, Oskar Interop tests were done by Oliver Pfaff, Thomas Werner, Oskar
Camezind, Bjorn Elmers and Joel Hoglund. Camezind, Bjorn Elmers and Joel Hoglund.
Robert Moskowitz provided code to create the examples. Robert Moskowitz provided code to create the examples.
14. References 13. References
14.1. Normative References 13.1. Normative References
[I-D.ietf-core-multipart-ct] [I-D.ietf-core-multipart-ct]
Fossati, T., Hartke, K., and C. Bormann, "Multipart Fossati, T., Hartke, K., and C. Bormann, "Multipart
Content-Format for CoAP", draft-ietf-core-multipart-ct-02 Content-Format for CoAP", draft-ietf-core-multipart-ct-02
(work in progress), August 2018. (work in progress), August 2018.
[I-D.ietf-tls-dtls13] [I-D.ietf-tls-dtls13]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version Datagram Transport Layer Security (DTLS) Protocol Version
1.3", draft-ietf-tls-dtls13-30 (work in progress), 1.3", draft-ietf-tls-dtls13-30 (work in progress),
skipping to change at page 27, line 22 skipping to change at page 27, line 5
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link [RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, DOI 10.17487/RFC6690, August 2012, Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
<https://www.rfc-editor.org/info/rfc6690>. <https://www.rfc-editor.org/info/rfc6690>.
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed., [RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030, "Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013, DOI 10.17487/RFC7030, October 2013,
<https://www.rfc-editor.org/info/rfc7030>. <https://www.rfc-editor.org/info/rfc7030>.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/info/rfc7049>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252, Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014, DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>. <https://www.rfc-editor.org/info/rfc7252>.
[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in [RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959, the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016, DOI 10.17487/RFC7959, August 2016,
<https://www.rfc-editor.org/info/rfc7959>. <https://www.rfc-editor.org/info/rfc7959>.
skipping to change at page 28, line 5 skipping to change at page 27, line 29
<https://www.rfc-editor.org/info/rfc8075>. <https://www.rfc-editor.org/info/rfc8075>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>. <https://www.rfc-editor.org/info/rfc8446>.
14.2. Informative References 13.2. Informative References
[COREparams] [COREparams]
IANA, "Constrained RESTful Environments (CoRE) IANA, "Constrained RESTful Environments (CoRE)
Parameters", <https://www.iana.org/assignments/core- Parameters", <https://www.iana.org/assignments/core-
parameters/core-parameters.xhtml>. parameters/core-parameters.xhtml>.
[I-D.ietf-core-resource-directory]
Shelby, Z., Koster, M., Bormann, C., Stok, P., and C.
Amsuess, "CoRE Resource Directory", draft-ietf-core-
resource-directory-19 (work in progress), January 2019.
[I-D.ietf-lamps-rfc5751-bis] [I-D.ietf-lamps-rfc5751-bis]
Schaad, J., Ramsdell, B., and S. Turner, "Secure/ Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Multipurpose Internet Mail Extensions (S/MIME) Version 4.0 Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
Message Specification", draft-ietf-lamps-rfc5751-bis-12 Message Specification", draft-ietf-lamps-rfc5751-bis-12
(work in progress), September 2018. (work in progress), September 2018.
[I-D.ietf-tls-dtls-connection-id] [I-D.ietf-tls-dtls-connection-id]
Rescorla, E., Tschofenig, H., Fossati, T., and T. Gondrom, Rescorla, E., Tschofenig, H., Fossati, T., and T. Gondrom,
"Connection Identifiers for DTLS 1.2", draft-ietf-tls- "Connection Identifiers for DTLS 1.2", draft-ietf-tls-
dtls-connection-id-02 (work in progress), October 2018. dtls-connection-id-02 (work in progress), October 2018.
skipping to change at page 29, line 15 skipping to change at page 28, line 33
[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>.
[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>.
[RFC5273] Schaad, J. and M. Myers, "Certificate Management over CMS
(CMC): Transport Protocols", RFC 5273,
DOI 10.17487/RFC5273, June 2008,
<https://www.rfc-editor.org/info/rfc5273>.
[RFC5705] Rescorla, E., "Keying Material Exporters for Transport [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
for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010, for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010,
<https://www.rfc-editor.org/info/rfc5929>. <https://www.rfc-editor.org/info/rfc5929>.
[RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958, [RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958,
DOI 10.17487/RFC5958, August 2010, DOI 10.17487/RFC5958, August 2010,
<https://www.rfc-editor.org/info/rfc5958>. <https://www.rfc-editor.org/info/rfc5958>.
[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
Curve Cryptography Algorithms", RFC 6090,
DOI 10.17487/RFC6090, February 2011,
<https://www.rfc-editor.org/info/rfc6090>.
[RFC6402] Schaad, J., "Certificate Management over CMS (CMC) [RFC6402] Schaad, J., "Certificate Management over CMS (CMC)
Updates", RFC 6402, DOI 10.17487/RFC6402, November 2011, Updates", RFC 6402, DOI 10.17487/RFC6402, November 2011,
<https://www.rfc-editor.org/info/rfc6402>. <https://www.rfc-editor.org/info/rfc6402>.
[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228, Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC7228, May 2014, DOI 10.17487/RFC7228, May 2014,
<https://www.rfc-editor.org/info/rfc7228>. <https://www.rfc-editor.org/info/rfc7228>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
skipping to change at page 30, line 51 skipping to change at page 30, line 10
Fournet, Alfredo Pironti, Pierre-Yves Strub, "Triple Fournet, Alfredo Pironti, Pierre-Yves Strub, "Triple
Handshakes and Cookie Cutters: Breaking and Fixing Handshakes and Cookie Cutters: Breaking and Fixing
Authentication over TLS", IEEE Security and Privacy ISBN Authentication over TLS", IEEE Security and Privacy ISBN
978-1-4799-4686-0, May 2014. 978-1-4799-4686-0, May 2014.
Appendix A. EST messages to EST-coaps Appendix A. EST messages to EST-coaps
This section shows similar examples to the ones presented in This section shows similar examples to the ones presented in
Appendix A of [RFC7030]. The payloads in the examples are the hex Appendix A of [RFC7030]. The payloads in the examples are the hex
encoded binary, generated with 'xxd -p', of the PKI certificates encoded binary, generated with 'xxd -p', of the PKI certificates
created following [I-D.moskowitz-ecdsa-pki]. The payloads are shown created following [I-D.moskowitz-ecdsa-pki]. Hex is used for
unencrypted. In practice the message content would be binary visualization purposes because a binary representation cannot be
formatted and transferred over an encrypted DTLS tunnel. The rendered well in text. The hexadecimal representations would not be
hexadecimal representations in the examples below would NOT be transported in hex, but in binary. The payloads are shown
transported in hex, but in binary. Hex is used for visualization unencrypted. In practice the message content would be transferred
purposes because a binary representation cannot be rendered well in over an encrypted DTLS tunnel.
text.
The certificate responses included in the examples contain Content- The certificate responses included in the examples contain Content-
Format 281 (application/pkcs7). If the client had requested Content- Format 281 (application/pkcs7). If the client had requested Content-
Format TBD287 (application/pkix-cert) with an Accept Option, the Format TBD287 (application/pkix-cert) by querying /est/skc, the
server would respond a single DER binary certificate. server would respond with a single DER binary certificate.
These examples assume that the resource discovery, returned a short These examples assume a short root resource path of "/est".
base path of "/est".
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 is assumed to be generally understood. Creating CoAP headers is assumed to be generally understood.
The message content breakdown is presented in Appendix C. The message content breakdown is presented in Appendix C.
A.1. cacerts A.1. cacerts
In EST-coaps, a cacerts message can be: In EST-coaps, a cacerts message can be:
GET coaps://est-coaps.example.ietf.org:9085/est/crts GET coaps://est-coaps.example.org:9085/est/crts
(Accept: 281) (Accept: 281)
The corresponding CoAP header fields are shown below. The use of The corresponding CoAP header fields are shown below. The use of
block and DTLS are worked out in Appendix B. block and DTLS are worked out in Appendix B.
Ver = 1 Ver = 1
T = 0 (CON) T = 0 (CON)
Code = 0x01 (0.01 is GET) Code = 0x01 (0.01 is GET)
Token = 0x9a (client generated) Token = 0x9a (client generated)
Options Options
Option (Uri-Host) [optional] Option (Uri-Host)
Option Delta = 0x3 (option# 3) Option Delta = 0x3 (option# 3)
Option Length = 0x9 Option Length = 0x9
Option Value = est-coaps.example.ietf.org Option Value = est-coaps.example.org
Option (Uri-Port) [optional] Option (Uri-Port)
Option Delta = 0x4 (option# 3+4=7) Option Delta = 0x4 (option# 3+4=7)
Option Length = 0x4 Option Length = 0x4
Option Value = 9085 Option Value = 9085
Option (Uri-Path) Option (Uri-Path)
Option Delta = 0x4 (option# 7+4=11) Option Delta = 0x4 (option# 7+4=11)
Option Length = 0x5 Option Length = 0x5
Option Value = "est" Option Value = "est"
Option (Uri-Path) Option (Uri-Path)
Option Delta = 0x0 (option# 11+0=11) Option Delta = 0x0 (option# 11+0=11)
Option Length = 0x6 Option Length = 0x6
Option Value = "crts" Option Value = "crts"
Option (Accept) Option (Accept)
Option Delta = 0x6 (option# 11+6=17) Option Delta = 0x6 (option# 11+6=17)
Option Length = 0x2 Option Length = 0x2
Option Value = 281 Option Value = 281
Payload = [Empty] Payload = [Empty]
The Uri-Host and Uri-Port Options are optional. They are usually The Uri-Host and Uri-Port Options can be omitted if they coincide
omitted as the DTLS destination and port are sufficient. Explicit with the transport protocol destination address and port
Uri-Host and Uri-Port Options are typically used when an endpoint respectively. Explicit Uri-Host and Uri-Port Options are typically
hosts multiple virtual servers and uses the Options to route the used when an endpoint hosts multiple virtual servers and uses the
requests accordingly. Alternatively, if a UDP port to a server is Options to route the requests accordingly.
blocked, someone could send the DTLS packets to a known open port on
the server and use the Uri-Port to convey the intended port he is
attempting to reach.
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: 281) 2.05 Content (Content-Format: 281)
{payload with certificate in binary format} {payload with certificate in binary format}
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)
skipping to change at page 33, line 51 skipping to change at page 32, line 51
The breakdown of the payload is shown in Appendix C.1. The breakdown of the payload is shown in Appendix C.1.
A.2. enroll / reenroll A.2. enroll / reenroll
During the (re-)enroll exchange the EST-coaps client uses a CSR During the (re-)enroll exchange the EST-coaps client uses a CSR
(Content-Format 286) request in the POST request payload. The Accept (Content-Format 286) request in the POST request payload. The Accept
option tells the server that the client is expecting Content-Format option tells the server that the client is expecting Content-Format
281 (PKCS#7) in the response. As shown in Appendix C.2, the CSR 281 (PKCS#7) in the response. As shown in Appendix C.2, the CSR
contains a ChallengePassword which is used for POP linking contains a ChallengePassword which is used for POP linking
(Section 6). (Section 4).
POST [2001:db8::2:1]:61616/est/sen POST [2001:db8::2:1]:61616/est/sen
(Token: 0x45) (Token: 0x45)
(Accept: 281) (Accept: 281)
(Content-Format: 286) (Content-Format: 286)
[ The hexadecimal representation below would NOT be transported [ The hexadecimal representation below would NOT be transported
in hex, but in binary. Hex is used because a binary representation in hex, but in binary. Hex is used because a binary representation
cannot be rendered well in text. ] cannot be rendered well in text. ]
skipping to change at page 35, line 37 skipping to change at page 34, line 37
041496600d8716bf7fd0e752d0ac760777ad665d02a0301f0603551d2304 041496600d8716bf7fd0e752d0ac760777ad665d02a0301f0603551d2304
183016801468d16551f951bfc82a431d0d9f08bc2d205b1160300e060355 183016801468d16551f951bfc82a431d0d9f08bc2d205b1160300e060355
1d0f0101ff0404030205a0302a0603551d1104233021a01f06082b060105 1d0f0101ff0404030205a0302a0603551d1104233021a01f06082b060105
05070804a013301106092b06010401b43b0a01040401020304300a06082a 05070804a013301106092b06010401b43b0a01040401020304300a06082a
8648ce3d0403020349003046022100c0d81996d2507d693f3c48eaa5ee94 8648ce3d0403020349003046022100c0d81996d2507d693f3c48eaa5ee94
91bda6db214099d98117c63b361374cd86022100a774989f4c321a5cf25d 91bda6db214099d98117c63b361374cd86022100a774989f4c321a5cf25d
832a4d336a08ad67df20f1506421188a0ade6d349236a1003100 832a4d336a08ad67df20f1506421188a0ade6d349236a1003100
The breakdown of the request and response is shown in Appendix C.2. The breakdown of the request and response is shown in Appendix C.2.
As described in Section 5.7, if the server is not able to provide a
response immediately, it sends an empty ACK with response code 5.03
(Service Unavailable) and the Max-Age Option. See Figure 3 for an
example exchange.
A.3. serverkeygen A.3. serverkeygen
In a serverkeygen exchange the CoAP POST request looks like In a serverkeygen exchange the CoAP POST request looks like
POST coaps://192.0.2.1:8085/est/skg POST coaps://192.0.2.1:8085/est/skg
(Token: 0xa5) (Token: 0xa5)
(Accept: 281) (Accept: 62)
(Content-Format: 286) (Content-Format: 286)
[ The hexadecimal representation below would NOT be transported [ The hexadecimal representation below would NOT be transported
in hex, but in binary. Hex is used because a binary representation in hex, but in binary. Hex is used because a binary representation
cannot be rendered well in text. ] cannot be rendered well in text. ]
3081cf3078020100301631143012060355040a0c0b736b67206578616d70 3081cf3078020100301631143012060355040a0c0b736b67206578616d70
6c653059301306072a8648ce3d020106082a8648ce3d030107034200041b 6c653059301306072a8648ce3d020106082a8648ce3d030107034200041b
b8c1117896f98e4506c03d70efbe820d8e38ea97e9d65d52c8460c5852c5 b8c1117896f98e4506c03d70efbe820d8e38ea97e9d65d52c8460c5852c5
1dd89a61370a2843760fc859799d78cd33f3c1846e304f1717f8123f1a28 1dd89a61370a2843760fc859799d78cd33f3c1846e304f1717f8123f1a28
skipping to change at page 38, line 22 skipping to change at page 37, line 22
in hex, but in binary. Hex is used because a binary representation in hex, but in binary. Hex is used because a binary representation
cannot be rendered well in text. ] cannot be rendered well in text. ]
307c06072b06010101011630220603883701311b131950617273652053455 307c06072b06010101011630220603883701311b131950617273652053455
420617320322e3939392e31206461746106092a864886f70d010907302c06 420617320322e3939392e31206461746106092a864886f70d010907302c06
0388370231250603883703060388370413195061727365205345542061732 0388370231250603883703060388370413195061727365205345542061732
0322e3939392e32206461746106092b240303020801010b06096086480165 0322e3939392e32206461746106092b240303020801010b06096086480165
03040202 03040202
A 2.05 Content response should contain attributes which are relevant A 2.05 Content response should contain attributes which are relevant
for the authenticated client. This example is copied from section for the authenticated client. This example is copied from
A.2 in [RFC7030], where the base64 representation is replaced with a Section A.2 in [RFC7030], where the base64 representation is replaced
hexadecimal representation of the equivalent binary format. The EST- with a hexadecimal representation of the equivalent binary format.
coaps server returns attributes that the client can ignore if they The EST-coaps server returns attributes that the client can ignore if
are unknown to him. they are unknown to him.
Appendix B. EST-coaps Block message examples Appendix B. EST-coaps Block message examples
Two examples are presented in this section: Two examples are presented in this section:
1. a cacerts exchange shows the use of Block2 and the block headers 1. a cacerts exchange shows the use of Block2 and the block headers
2. an enroll exchange shows the Block1 and Block2 size negotiation 2. an enroll exchange shows the Block1 and Block2 size negotiation
for request and response payloads. for request and response payloads.
The payloads are shown unencrypted. In practice the message contents The payloads are shown unencrypted. In practice the message contents
would be binary formatted and transferred over an encrypted DTLS would be binary formatted and transferred over an encrypted DTLS
tunnel. The corresponding CoAP headers are only shown in tunnel. The corresponding CoAP headers are only shown in
Appendix B.1. Creating CoAP headers are assumed to be generally Appendix B.1. Creating CoAP headers is assumed to be generally
known. known.
B.1. cacerts B.1. cacerts
This section provides a detailed example of the messages using DTLS This section provides a detailed example of the messages using DTLS
and BLOCK option Block2. The minimum PMTU is 1280 bytes, which is and BLOCK option Block2. The minimum PMTU is 1280 bytes, which is
the example value assumed for the DTLS datagram size. The example the example value assumed for the DTLS datagram size. The example
block length is taken as 64 which gives an SZX value of 2. block length is taken as 64 which gives an SZX value of 2.
The following is an example of a cacerts exchange over DTLS. The The following is an example of a cacerts exchange over DTLS. The
skipping to change at page 39, line 25 skipping to change at page 38, line 25
option:NUM/M/size) indicating the kind of Block Option (2 in this option:NUM/M/size) indicating the kind of Block Option (2 in this
case) followed by a colon, and then the block number (NUM), the more case) followed by a colon, and then the block number (NUM), the more
bit (M = 0 in Block2 response means it is last block), and block size bit (M = 0 in Block2 response means it is last block), and block size
with exponent (2**(SZX+4)) separated by slashes. The Length 64 is with exponent (2**(SZX+4)) separated by slashes. The Length 64 is
used with SZX=2 to avoid IP fragmentation. The CoAP Request is sent used with SZX=2 to avoid IP fragmentation. The CoAP Request is sent
confirmable (CON) and the Content-Format of the response, even though confirmable (CON) and the Content-Format of the response, even though
not shown, is 281 (application/pkcs7-mime; smime-type=certs-only). not shown, is 281 (application/pkcs7-mime; smime-type=certs-only).
The transfer of the 10 blocks with partially filled block NUM=9 is The transfer of the 10 blocks with partially filled block NUM=9 is
shown below shown below
GET coaps://est-coaps.example.ietf.org:9085/est/crts (2:0/0/64) --> GET coaps://est-coaps.example.org:9085/est/crts (2:0/0/64) -->
<-- (2:0/1/64) 2.05 Content <-- (2:0/1/64) 2.05 Content
GET coaps://est-coaps.example.ietf.org:9085/est/crts (2:1/0/64) --> GET coaps://est-coaps.example.org:9085/est/crts (2:1/0/64) -->
<-- (2:1/1/64) 2.05 Content <-- (2:1/1/64) 2.05 Content
| |
| |
| |
GET coaps://est-coaps.example.ietf.org:9085/est/crts (2:9/0/64) --> GET coaps://est-coaps.example.org:9085/est/crts (2:9/0/64) -->
<-- (2:9/0/64) 2.05 Content <-- (2:9/0/64) 2.05 Content
The header of the GET request looks like The header of the GET request looks like
Ver = 1 Ver = 1
T = 0 (CON) T = 0 (CON)
Code = 0x01 (0.1 GET) Code = 0x01 (0.1 GET)
Token = 0x9a (client generated) Token = 0x9a (client generated)
Options Options
Option (Uri-Host) [optional] Option (Uri-Host)
Option Delta = 0x3 (option# 3) Option Delta = 0x3 (option# 3)
Option Length = 0x9 Option Length = 0x9
Option Value = est-coaps.example.ietf.org Option Value = est-coaps.example.org
Option (Uri-Port) [optional] Option (Uri-Port)
Option Delta = 0x4 (option# 3+4=7) Option Delta = 0x4 (option# 3+4=7)
Option Length = 0x4 Option Length = 0x4
Option Value = 9085 Option Value = 9085
Option (Uri-Path) Option (Uri-Path)
Option Delta = 0x4 (option# 7+4=11) Option Delta = 0x4 (option# 7+4=11)
Option Length = 0x5 Option Length = 0x5
Option Value = "est" Option Value = "est"
Option (Uri-Path)Uri-Path) Option (Uri-Path)Uri-Path)
Option Delta = 0x0 (option# 11+0=11) Option Delta = 0x0 (option# 11+0=11)
Option Length = 0x6 Option Length = 0x6
Option Value = "crts" Option Value = "crts"
Option (Accept) Option (Accept)
Option Delta = 0x6 (option# 11+6=17) Option Delta = 0x6 (option# 11+6=17)
Option Length = 0x2 Option Length = 0x2
Option Value = 281 Option Value = 281
Payload = [Empty] Payload = [Empty]
The Uri-Host and Uri-Port Options are optional. They are usually The Uri-Host and Uri-Port Options can be omitted if they coincide
omitted as the DTLS destination and port are sufficient. Explicit with the transport protocol destination address and port
Uri-Host and Uri-Port Options are typically used when an endpoint respectively. Explicit Uri-Host and Uri-Port Options are typically
hosts multiple virtual servers and uses the Options to route the used when an endpoint hosts multiple virtual servers and uses the
requests accordingly. Alternatively, if a UDP port to a server is Options to route the requests accordingly.
blocked, someone could send the DTLS packets to a known open port on
the server and use the Uri-Port to convey the intended port he is
attempting to reach.
For further detailing the CoAP headers, the first two and the last For further detailing the CoAP headers, the first two and the last
blocks are written out below. The header of the first Block2 blocks are written out below. The header of the first Block2
response looks like 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 from request by server) Token = 0x9a (copied from request by server)
Options Options
Option Option
skipping to change at page 42, line 31 skipping to change at page 41, line 31
in hex, but in binary. Hex is used because a binary representation in hex, but in binary. Hex is used because a binary representation
cannot be rendered well in text. ] cannot be rendered well in text. ]
Payload = Payload =
2ec0b4af52d46f3b7ecc9687ddf267bcec368f7b7f1353272f022047a28a 2ec0b4af52d46f3b7ecc9687ddf267bcec368f7b7f1353272f022047a28a
e5c7306163b3c3834bab3c103f743070594c089aaa0ac870cd13b902caa1 e5c7306163b3c3834bab3c103f743070594c089aaa0ac870cd13b902caa1
003100 003100
B.2. enroll / reenroll B.2. enroll / reenroll
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
message. The block size 256=(2**(SZX+4)) which gives SZX=4. The message. The block size 256=(2**(SZX+4)) which gives SZX=4. The
notation for block numbering is the same as in Appendix B.1. It is notation for block numbering is the same as in Appendix B.1. The
assumed that CSR takes N1+1 blocks and the cert response takes N2+1 header fields and the payload are omitted for brevity.
blocks. The header fields and the payload are omitted for brevity.
POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256) {CSR req} --> POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256) {CSR req} -->
<-- (ACK) (1:0/1/256) (2.31 Continue) <-- (ACK) (1:0/1/256) (2.31 Continue)
POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256) {CSR req} --> POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256) {CSR req} -->
<-- (ACK) (1:1/1/256) (2.31 Continue) <-- (ACK) (1:1/1/256) (2.31 Continue)
. .
. .
. .
POST [2001:db8::2:1]:61616/est/sen (CON)(1:N1/0/256){CSR req} --> POST [2001:db8::2:1]:61616/est/sen (CON)(1:N1/0/256){CSR req} -->
<-- (ACK) (1:N1/0/256)(2:0/1/256)(2.04 Changed){Cert resp} <-- (ACK) (1:N1/0/256)(2:0/1/256)(2.04 Changed){Cert resp}
skipping to change at page 43, line 34 skipping to change at page 42, line 34
N1+1 blocks have been transferred from client to the server and N2+1 N1+1 blocks have been transferred from client to the server and N2+1
blocks have been transferred from server to client. blocks have been transferred from server to client.
Appendix C. Message content breakdown Appendix C. Message content breakdown
This appendix presents the breakdown of the hexadecimal dumps of the This appendix presents the breakdown of the hexadecimal dumps of the
binary payloads shown in Appendix A. binary payloads shown in Appendix A.
C.1. cacerts C.1. cacerts
Breakdown of cacerts response containing one root CA certificate. The breakdown of cacerts response containing one root CA certificate
is
Certificate: Certificate:
Data: Data:
Version: 3 (0x2) Version: 3 (0x2)
Serial Number: Serial Number:
91:89:bc:df:9c:99:24:4b 91:89:bc:df:9c:99:24:4b
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
Issuer: C=US, ST=CA, L=LA, O=Example Inc, Issuer: C=US, ST=CA, L=LA, O=Example Inc,
OU=certification, CN=Root CA OU=certification, CN=Root CA
Validity Validity
Not Before: Jan 7 10:40:41 2019 GMT Not Before: Jan 7 10:40:41 2019 GMT
skipping to change at page 45, line 7 skipping to change at page 44, line 7
X509v3 Subject Alternative Name: X509v3 Subject Alternative Name:
email:certify@example.com email:certify@example.com
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
30:45:02:21:00:da:e3:7c:96:f1:54:c3:2e:c0:b4:af:52:d4: 30:45:02:21:00:da:e3:7c:96:f1:54:c3:2e:c0:b4:af:52:d4:
6f:3b:7e:cc:96:87:dd:f2:67:bc:ec:36:8f:7b:7f:13:53:27: 6f:3b:7e:cc:96:87:dd:f2:67:bc:ec:36:8f:7b:7f:13:53:27:
2f:02:20:47:a2:8a:e5:c7:30:61:63:b3:c3:83:4b:ab:3c:10: 2f:02:20:47:a2:8a:e5:c7:30:61:63:b3:c3:83:4b:ab:3c:10:
3f:74:30:70:59:4c:08:9a:aa:0a:c8:70:cd:13:b9:02:ca 3f:74:30:70:59:4c:08:9a:aa:0a:c8:70:cd:13:b9:02:ca
C.2. enroll / reenroll C.2. enroll / reenroll
The breakdown of the request is The breakdown of the enrollment request is
Certificate Request: Certificate Request:
Data: Data:
Version: 0 (0x0) Version: 0 (0x0)
Subject: C=US, ST=CA, L=LA, O=example Inc, Subject: C=US, ST=CA, L=LA, O=example Inc,
OU=IoT/serialNumber=Wt1234 OU=IoT/serialNumber=Wt1234
Subject Public Key Info: Subject Public Key Info:
Public Key Algorithm: id-ecPublicKey Public Key Algorithm: id-ecPublicKey
Public-Key: (256 bit) Public-Key: (256 bit)
pub: pub:
skipping to change at page 45, line 37 skipping to change at page 44, line 37
Requested Extensions: Requested Extensions:
X509v3 Subject Alternative Name: X509v3 Subject Alternative Name:
othername:<unsupported> othername:<unsupported>
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
30:45:02:21:00:92:56:3a:54:64:63:bd:9e:cf:f1:70:d0:fd: 30:45:02:21:00:92:56:3a:54:64:63:bd:9e:cf:f1:70:d0:fd:
1f:2e:f0:d3:d0:12:16:0e:5e:e9:0c:ff:ed:ab:ec:9b:9a:38: 1f:2e:f0:d3:d0:12:16:0e:5e:e9:0c:ff:ed:ab:ec:9b:9a:38:
92:02:20:17:9f:10:a3:43:61:09:05:1a:ba:d1:75:90:a0:9b: 92:02:20:17:9f:10:a3:43:61:09:05:1a:ba:d1:75:90:a0:9b:
c8:7c:4d:ce:54:53:a6:fc:11:35:a1:e8:4e:ed:75:43:77 c8:7c:4d:ce:54:53:a6:fc:11:35:a1:e8:4e:ed:75:43:77
The CSR contained a ChallengePassword which is used for POP linking The CSR contained a ChallengePassword which is used for POP linking
(Section 6). (Section 4).
The breakdown of the issued certificate response is The breakdown of the issued certificate is
Certificate: Certificate:
Data: Data:
Version: 3 (0x2) Version: 3 (0x2)
Serial Number: 9112578475118446130 (0x7e7661d7b54e4632) Serial Number: 9112578475118446130 (0x7e7661d7b54e4632)
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
Issuer: C=US, ST=CA, O=Example Inc, OU=certification, Issuer: C=US, ST=CA, O=Example Inc, OU=certification,
CN=802.1AR CA CN=802.1AR CA
Validity Validity
Not Before: Jan 31 11:29:16 2019 GMT Not Before: Jan 31 11:29:16 2019 GMT
Not After : Dec 31 23:59:59 9999 GMT Not After : Dec 31 23:59:59 9999 GMT
skipping to change at page 46, line 49 skipping to change at page 45, line 49
X509v3 Subject Alternative Name: X509v3 Subject Alternative Name:
othername:<unsupported> othername:<unsupported>
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
30:46:02:21:00:c0:d8:19:96:d2:50:7d:69:3f:3c:48:ea:a5: 30:46:02:21:00:c0:d8:19:96:d2:50:7d:69:3f:3c:48:ea:a5:
ee:94:91:bd:a6:db:21:40:99:d9:81:17:c6:3b:36:13:74:cd: ee:94:91:bd:a6:db:21:40:99:d9:81:17:c6:3b:36:13:74:cd:
86:02:21:00:a7:74:98:9f:4c:32:1a:5c:f2:5d:83:2a:4d:33: 86:02:21:00:a7:74:98:9f:4c:32:1a:5c:f2:5d:83:2a:4d:33:
6a:08:ad:67:df:20:f1:50:64:21:18:8a:0a:de:6d:34:92:36 6a:08:ad:67:df:20:f1:50:64:21:18:8a:0a:de:6d:34:92:36
C.3. serverkeygen C.3. serverkeygen
The following is the breakdown of the request example used. The following is the breakdown of the server-side key generation
request.
Certificate Request: Certificate Request:
Data: Data:
Version: 0 (0x0) Version: 0 (0x0)
Subject: O=skg example Subject: O=skg example
Subject Public Key Info: Subject Public Key Info:
Public Key Algorithm: id-ecPublicKey Public Key Algorithm: id-ecPublicKey
Public-Key: (256 bit) Public-Key: (256 bit)
pub: pub:
04:1b:b8:c1:11:78:96:f9:8e:45:06:c0:3d:70:ef: 04:1b:b8:c1:11:78:96:f9:8e:45:06:c0:3d:70:ef:
skipping to change at page 47, line 28 skipping to change at page 46, line 28
ASN1 OID: prime256v1 ASN1 OID: prime256v1
NIST CURVE: P-256 NIST CURVE: P-256
Attributes: Attributes:
a0:00 a0:00
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
30:44:02:20:38:7c:d4:e9:cf:62:8d:4a:f7:7f:92:eb:ed:48: 30:44:02:20:38:7c:d4:e9:cf:62:8d:4a:f7:7f:92:eb:ed:48:
90:d9:d1:41:dc:a8:6c:d2:75:7d:d1:4c:bd:59:cd:f6:96:18: 90:d9:d1:41:dc:a8:6c:d2:75:7d:d1:4c:bd:59:cd:f6:96:18:
02:20:2f:24:5e:82:8c:77:75:43:78:b6:66:60:a4:97:7f:11: 02:20:2f:24:5e:82:8c:77:75:43:78:b6:66:60:a4:97:7f:11:
3c:ac:da:a0:cc:7b:ad:7d:14:74:a7:fd:15:5d:09:0d 3c:ac:da:a0:cc:7b:ad:7d:14:74:a7:fd:15:5d:09:0d
The following is the breakdown of the private key content of the Following is the breakdown of the private key content of the server-
server-side key generation response payload. side key generation response.
Private-Key: (256 bit) Private-Key: (256 bit)
priv: priv:
0b:9a:67:78:5b:65:e0:73:60:b6:d2:8c:fc:1d:3f: 0b:9a:67:78:5b:65:e0:73:60:b6:d2:8c:fc:1d:3f:
39:25:c0:75:57:99:de:ec:a7:45:37:2b:01:69:7b: 39:25:c0:75:57:99:de:ec:a7:45:37:2b:01:69:7b:
d8:a6 d8:a6
pub: pub:
04:1b:b8:c1:11:78:96:f9:8e:45:06:c0:3d:70:ef: 04:1b:b8:c1:11:78:96:f9:8e:45:06:c0:3d:70:ef:
be:82:0d:8e:38:ea:97:e9:d6:5d:52:c8:46:0c:58: be:82:0d:8e:38:ea:97:e9:d6:5d:52:c8:46:0c:58:
52:c5:1d:d8:9a:61:37:0a:28:43:76:0f:c8:59:79: 52:c5:1d:d8:9a:61:37:0a:28:43:76:0f:c8:59:79:
9d:78:cd:33:f3:c1:84:6e:30:4f:17:17:f8:12:3f: 9d:78:cd:33:f3:c1:84:6e:30:4f:17:17:f8:12:3f:
1a:28:4c:c9:9f 1a:28:4c:c9:9f
ASN1 OID: prime256v1 ASN1 OID: prime256v1
NIST CURVE: P-256 NIST CURVE: P-256
The following is the breakdown of the certificate of the second part The following is the breakdown of the certificate in the server-side
of the server-side key generation response payload. key generation response payload.
Certificate: Certificate:
Data: Data:
Version: 3 (0x2) Version: 3 (0x2)
Serial Number: 1327972925857878603 (0x126de8571518524b) Serial Number: 1327972925857878603 (0x126de8571518524b)
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
Issuer: O=skg example Issuer: O=skg example
Validity Validity
Not Before: Jan 9 08:57:08 2019 GMT Not Before: Jan 9 08:57:08 2019 GMT
Not After : Jan 4 08:57:08 2039 GMT Not After : Jan 4 08:57:08 2039 GMT
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