Clarification of RFC7030 CSR Attributes definition
draft-ietf-lamps-rfc7030-csrattrs-03
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| Authors | Michael Richardson , Owen Friel , David von Oheimb , Dan Harkins | ||
| Last updated | 2023-06-15 (Latest revision 2023-04-08) | ||
| Replaces | draft-richardson-lamps-rfc7030-csrattrs | ||
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draft-ietf-lamps-rfc7030-csrattrs-03
LAMPS Working Group M. Richardson, Ed.
Internet-Draft Sandelman Software Works
Intended status: Standards Track O. Friel
Expires: 17 December 2023 Cisco
D. von Oheimb
Siemens
D. Harkins
The Industrial Lounge
15 June 2023
Clarification of RFC7030 CSR Attributes definition
draft-ietf-lamps-rfc7030-csrattrs-03
Abstract
The Enrollment over Secure Transport (EST, RFC7030) is ambiguous in
its specification of the CSR Attributes Response. This has resulted
in implementation challenges and implementor confusion.
This document updates RFC7030 (EST) and clarifies how the CSR
Attributes Response can be used by an EST server to specify both CSR
attribute OIDs and also CSR attribute values, in particular X.509
extension values, that the server expects the client to include in
subsequent CSR request.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 17 December 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. CSR Attributes Handling . . . . . . . . . . . . . . . . . . . 3
3.1. Extensions to RFC 7030 section 2.6. . . . . . . . . . . . 3
3.2. Extensions to RFC 7030 section 4.5.2. . . . . . . . . . . 4
4. Co-existence with existing implementations . . . . . . . . . 5
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. RFC8994/ACP subjectAltName with specific otherName . . . 5
5.1.1. Base64 encoded example . . . . . . . . . . . . . . . 5
5.1.2. ASN.1 DUMP output . . . . . . . . . . . . . . . . . . 5
5.2. RFC7030 original example . . . . . . . . . . . . . . . . 6
5.2.1. Base64 encoded example . . . . . . . . . . . . . . . 6
5.2.2. ASN.1 DUMP output . . . . . . . . . . . . . . . . . . 6
5.3. EST server requires a specific subjectAltName
extension . . . . . . . . . . . . . . . . . . . . . . . . 8
5.3.1. Base64 encoded example . . . . . . . . . . . . . . . 8
5.3.2. ASN.1 DUMP output . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6.1. Identity and Privacy Considerations . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
9. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Raw DER for examples . . . . . . . . . . . . . . . . 11
A.1. Raw RFC8994/ACP subjectAltName with specific otherName . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Enrollment over Secure Transport [RFC7030] (EST) has been used in a
wide variety of applications. In particular, [RFC8994] and [RFC8995]
describe a way to use it in order to build out an autonomic control
plane (ACP) [RFC8368].
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The ACP requires that each node be given a very specific
subjectAltName. In the ACP specification, the solution was for the
EST server to use section 2.6 of [RFC7030] to convey to the EST
client the actual subjectAltName that will end up in its certificate.
As a result of some implementation challenges, it came to light that
this particular way of using the CSR attributes was not universally
agreed upon, and it was suggested that it went contrary to section
2.6.
Section 2.6 says that the CSR attributes "can provide additional
descriptive information that the EST server cannot access itself".
This is extended to mention also values that the EST server demands
to use.
After significant discussion, it has been determined that Section 4.5
of [RFC7030] specification is sufficiently difficult to read and
ambiguous to interpret that clarification is needed.
This document motivates the different use cases, and provides
additional worked out examples.
Also, section 4.5.2 is extended to clarify the use of the existing
ASN.1 syntax. This covers all uses and is fully backward compatible
with the existing use.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. CSR Attributes Handling
3.1. Extensions to RFC 7030 section 2.6.
Replace the second paragraph with the following text:
These attributes can provide additional descriptive information that
the EST server cannot access itself, such as the Media Access Control
(MAC) address of an interface of the EST client. The EST server can also
provide concrete values that it tells the client to include in the CSR,
such as a specific X.509 Subject Alternative Name extension. Moreover,
these attributes can indicate the kind of enrollment request, such as
a specific elliptic curve or a specific hash function that the client
is expected to use when generating the CSR.
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3.2. Extensions to RFC 7030 section 4.5.2.
The ASN.1 for CSR Attributes as defined in EST section 4.5.2 is as
follows:
CsrAttrs ::= SEQUENCE SIZE (0..MAX) OF AttrOrOID
AttrOrOID ::= CHOICE (oid OBJECT IDENTIFIER, attribute Attribute }
Attribute { ATTRIBUTE:IOSet } ::= SEQUENCE {
type ATTRIBUTE.&id({IOSet}),
values SET SIZE(1..MAX) OF ATTRIBUTE.&Type({IOSet}{@type}) }
This remains unchanged, such that bits-on-the-wire compatibility is
maintained.
Key parts that were unclear were which OID to use in the 'type' field
and that the 'values' field can contain an entire sequence of X.509
extensions.
The OID to use for such attributes in the 'type' field MUST be
extensionRequest, which has the numerical value
1.2.840.113549.1.9.14. There MUST be only one such
The 'values' field of this attribute MUST contain a set with exactly
one element, and this element MUST by of type Extensions, as per
Section 4.1 of [RFC5280]:
Extensions ::= SEQUENCE SIZE (1..MAX) OF Extension
Extension ::= SEQUENCE {
extnID OBJECT IDENTIFIER,
critical BOOLEAN DEFAULT FALSE,
extnValue OCTET STRING
-- contains the DER encoding of an ASN.1 value
-- corresponding to the extension type identified
-- by extnID
}
In each such Extensions sequence, an extnID OID MUST appear at most
once.
An Extension comprises of the OID of the specific X.509 extension
(extnID), optionally the 'critical' bit, and the extension value
(extnValue).
With this understanding, the needs of [RFC8994] and [RFC8995] are
satisfied with no change to the bits on the wire.
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4. Co-existence with existing implementations
5. Examples
Each example has a high-level (english) explanation of what is
expected. Some mapping back to the Attribute and Extension
definitions above are included. The base64 encode DER is then shown.
The output of "dumpasn1" is then provided to detail what the contents
are.
5.1. RFC8994/ACP subjectAltName with specific otherName
A single subjectAltName extension is specified in a single Extension
attribute. This is what might be created by an [RFC8995] Registrar
that is asking for [RFC8994] AcpNodeName format otherNames.
5.1.1. Base64 encoded example
<CODE BEGINS>
MGQwYgYJKoZIhvcNAQkOMVUwUwYDVR0RAQH/BEmgRzBFBggr
BgEFBQcICgw5cmZjODk5NCtmZDczOWZjMjNjMzQ0MDExMjIz
MzQ0NTUwMDAwMDAwMCtAYWNwLmV4YW1wbGUuY29t
<CODE ENDS>
5.1.2. ASN.1 DUMP output
There is a single subjectAltName Extension with an Attribute with
Extension type.
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<30 64>
0 100: SEQUENCE {
<30 62>
2 98: SEQUENCE {
<06 09>
4 9: OBJECT IDENTIFIER extensionRequest (1 2 840 113549 1 9 14)
: (PKCS #9 via CRMF)
<31 55>
15 85: SET {
<30 53>
17 83: SEQUENCE {
<06 03>
19 3: OBJECT IDENTIFIER subjectAltName (2 5 29 17)
: (X.509 extension)
<01 01>
24 1: BOOLEAN TRUE
<04 49>
27 73: OCTET STRING
: A0 47 30 45 06 08 2B 06 .G0E..+.
: 01 05 05 07 08 0A 0C 39 .......9
: 72 66 63 38 39 39 34 2B rfc8994+
: 66 64 37 33 39 66 63 32 fd739fc2
: 33 63 33 34 34 30 31 31 3c344011
: 32 32 33 33 34 34 35 35 22334455
: 30 30 30 30 30 30 30 30 00000000
: 2B 40 61 63 70 2E 65 78 +@acp.ex
: 61 6D 70 6C 65 2E 63 6F ample.co
: 6D m
: }
: }
: }
: }
5.2. RFC7030 original example
In this example, taken from [RFC7030], a few different attributes are
included.
5.2.1. Base64 encoded example
<CODE BEGINS>
MEEGCSqGSIb3DQEJBzASBgcqhkjOPQIBMQcGBSuBBAAiMBYG
CSqGSIb3DQEJDjEJBgcrBgEBAQEWBggqhkjOPQQDAw==
<CODE ENDS>
5.2.2. ASN.1 DUMP output
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1. The challengePassword attribute is included to indicate that the
CSR should included this value.
2. An ecPublicKey attribute is provided with the value secp384r1 to
indicate what kind of key should be submitted.
3. An extensionRequest container with an OID 1.3.6.1.1.1.1.22
(macAddress), but without a value, to indicate that the CSR
should include an extensionRequest with this value.
4. The ecdsaWithSHA384 OID is included to indicate what kind of hash
is expected to be used with the ecPublicKey provided.
<30 41>
0 65: SEQUENCE {
<06 09>
2 9: OBJECT IDENTIFIER challengePassword (1 2 840 113549 1 9 7)
: (PKCS #9)
<30 12>
13 18: SEQUENCE {
<06 07>
15 7: OBJECT IDENTIFIER ecPublicKey (1 2 840 10045 2 1)
: (ANSI X9.62 public key type)
<31 07>
24 7: SET {
<06 05>
26 5: OBJECT IDENTIFIER secp384r1 (1 3 132 0 34)
: (SECG (Certicom) named elliptic curve)
: }
: }
<30 16>
33 22: SEQUENCE {
<06 09>
35 9: OBJECT IDENTIFIER extensionRequest (1 2 840 113549 1 9 14)
: (PKCS #9 via CRMF)
<31 09>
46 9: SET {
<06 07>
48 7: OBJECT IDENTIFIER '1 3 6 1 1 1 1 22'
: }
: }
<06 08>
57 8: OBJECT IDENTIFIER ecdsaWithSHA384 (1 2 840 10045 4 3 3)
: (ANSI X9.62 ECDSA algorithm with SHA384)
: }
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5.3. EST server requires a specific subjectAltName extension
A single subjectAltName extension is specified in a single Extension
attribute.
5.3.1. Base64 encoded example
<CODE BEGINS>
MGYGCSqGSIb3DQEJBzASBgcqhkjOPQIBMQcGBSuBBAAiMDsG
CSqGSIb3DQEJDjEuMCwGA1UdEQEB/wQioCAwHgYIKwYBBQUH
CAoMEnBvdGF0b0BleGFtcGxlLmNvbQYIKoZIzj0EAwM=
<CODE ENDS>
5.3.2. ASN.1 DUMP output
1. The challengePassword attribute is included to indicate that the
CSR should included this value.
2. An ecPublicKey attribute is provided with the value secp384r1 to
indicate what kind of key should be submitted.
3. An extensionRequest container with a subjectAltName value
containing the name potato@example.com
4. The ecdsaWithSHA384 OID is included to indicate what kind of hash
is expected to be used with the ecPublicKey provided.
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<30 66>
0 102: SEQUENCE {
<06 09>
2 9: OBJECT IDENTIFIER challengePassword (1 2 840 113549 1 9 7)
: (PKCS #9)
<30 12>
13 18: SEQUENCE {
<06 07>
15 7: OBJECT IDENTIFIER ecPublicKey (1 2 840 10045 2 1)
: (ANSI X9.62 public key type)
<31 07>
24 7: SET {
<06 05>
26 5: OBJECT IDENTIFIER secp384r1 (1 3 132 0 34)
: (SECG (Certicom) named elliptic curve)
: }
: }
<30 3B>
33 59: SEQUENCE {
<06 09>
35 9: OBJECT IDENTIFIER extensionRequest (1 2 840 113549 1 9 14)
: (PKCS #9 via CRMF)
<31 2E>
46 46: SET {
<30 2C>
48 44: SEQUENCE {
<06 03>
50 3: OBJECT IDENTIFIER subjectAltName (2 5 29 17)
: (X.509 extension)
<01 01>
55 1: BOOLEAN TRUE
<04 22>
58 34: OCTET STRING
: A0 20 30 1E 06 08 2B 06 . 0...+.
: 01 05 05 07 08 0A 0C 12 ........
: 70 6F 74 61 74 6F 40 65 potato@e
: 78 61 6D 70 6C 65 2E 63 xample.c
: 6F 6D om
: }
: }
: }
<06 08>
94 8: OBJECT IDENTIFIER ecdsaWithSHA384 (1 2 840 10045 4 3 3)
: (ANSI X9.62 ECDSA algorithm with SHA384)
: }
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6. Security Considerations
The security considerations from EST [RFC7030] section 6 are
unchanged.
6.1. Identity and Privacy Considerations
An EST server may use this mechanism to instruct the EST client about
the identities it should include in the CSR it sends as part of
enrollment. The client may only be aware of its IDevID Subject,
which includes a manufacturer serial number. The EST server can use
this mechanism to tell the client to include a specific fully
qualified domain name in the CSR in order to complete domain
ownership proofs required by the CA. Additionally, the EST server
may deem the manufacturer serial number in an IDevID as personally
identifiable information, and may want to specify a new random opaque
identifier that the pledge should use in its CSR. This may be
desirable if the CA and EST server have different operators.
7. IANA Considerations
No requests are made to IANA.
8. Acknowledgements
TODO
9. Changelog
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/rfc/rfc5280>.
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013,
<https://www.rfc-editor.org/rfc/rfc7030>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8994] Eckert, T., Ed., Behringer, M., Ed., and S. Bjarnason, "An
Autonomic Control Plane (ACP)", RFC 8994,
DOI 10.17487/RFC8994, May 2021,
<https://www.rfc-editor.org/rfc/rfc8994>.
[RFC8995] Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructure (BRSKI)", RFC 8995, DOI 10.17487/RFC8995,
May 2021, <https://www.rfc-editor.org/rfc/rfc8995>.
10.2. Informative References
[RFC8368] Eckert, T., Ed. and M. Behringer, "Using an Autonomic
Control Plane for Stable Connectivity of Network
Operations, Administration, and Maintenance (OAM)",
RFC 8368, DOI 10.17487/RFC8368, May 2018,
<https://www.rfc-editor.org/rfc/rfc8368>.
Appendix A. Raw DER for examples
This section contains Base64 versions of all examples that were
decoded.
A.1. Raw RFC8994/ACP subjectAltName with specific otherName
example in Section 5.1
MGQwYgYJKoZIhvcNAQkOMVUwUwYDVR0RAQH/BEmgRzBFBggrBgEFBQcICgw5cmZjODk5NCtmZDcz
OWZjMjNjMzQ0MDExMjIzMzQ0NTUwMDAwMDAwMCtAYWNwLmV4YW1wbGUuY29t
Authors' Addresses
Michael Richardson (editor)
Sandelman Software Works
Email: mcr+ietf@sandelman.ca
Owen Friel
Cisco
Email: ofriel@cisco.com
Dr. David von Oheimb
Siemens
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Email: dev@ddvo.net
Dan Harkins
The Industrial Lounge
Email: dharkins@lounge.org
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