Internet DRAFT - draft-reddy-lamps-jose-eku
draft-reddy-lamps-jose-eku
LAMPS WG T. Reddy
Internet-Draft J. Ekman
Intended status: Standards Track Nokia
Expires: 19 October 2023 D. Migault
Ericsson
17 April 2023
X.509 Certificate Extended Key Usage (EKU) for (JOSE) and CBOR Object
Signing and Encryption (COSE)
draft-reddy-lamps-jose-eku-02
Abstract
RFC 5280 specifies several extended key purpose identifiers
(KeyPurposeIds) for X.509 certificates. This document defines JSON
Web Signature (JWS), JSON Web Encryption (JWE), CBOR Object Web
Signature (CWS) and CBOR Object Web Encryption (CWE) KeyPurposeIds
inclusion in the Extended Key Usage (EKU) extension of X.509 public
key certificates. An application processing JWS, JWE, CWS or CWE may
require that the EKU extension be present and that a JWS, JWE, CWS or
CWE KeyPurposeId be indicated in order for the certificate to be
acceptable to validate the JWS or CWS signature or to encrypt a key
in JWE or CWE.
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
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This Internet-Draft will expire on 19 October 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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Extended Key Purpose for JWS, JWE, CWS and CWE . . . . . . . 4
4. Including the Extended KeyPurpose for JWS and JWE in
Certificates . . . . . . . . . . . . . . . . . . . . . . 5
5. Implications for a Certification Authority . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
11.1. Normative References . . . . . . . . . . . . . . . . . . 7
11.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
[RFC5280] specifies several extended key purpose identifiers
(KeyPurposeIds) for X.509 certificates. In addition, the IANA
repository "SMI Security for PKIX Extended Key Purpose" [RFC7299]
includes a number of KeyPurposeIds. While usage of the
anyExtendedKeyUsage KeyPurposeId is bad practice - especially but not
only for for publicly trusted certificates (multi-purpose or single-
purpose) - there are no extended key purpose identifiers explicitly
assigned for JSON Web Signature (JWS) [RFC7515] JSON Web Encryption
(JWE) [RFC7516] or their CBOR Object Signing and Encryption (COSE)
[RFC9052] counterparts defined as CBOR Object Web Signature (CWS) and
CBOR Object Web Encryption (CWE).
JSON Web Signature (JWS) and CBOR Object Web Signature (CWS)
represents content secured with digital signatures or Message
Authentication Codes (MACs) using JSON-based [RFC7159] data
structures and CBOR-based [RFC8949] data structures. The JWS and CWS
cryptographic mechanisms provide integrity protection for an
arbitrary sequence of octets.
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JSON Web Encryption (JWE) and CBOR Object Web Encryption (CWE)
represents encrypted content using JSON-based data structures and
CBOR-based data structures. The JWE and CWE cryptographic mechanisms
encrypt and provide integrity protection for an arbitrary sequence of
octets. The cryptographic algorithms and identifiers to be used with
the JSON Web Signature (JWS) and JSON Web Encryption (JWE), CBOR
Object Web Signature (CWS) and CBOR Object Web Encryption (CWE) are
defined in [RFC7518] and [RFC9052].
Network Functions (NFs) as part of the service-based architecture
within the 5G System [TS23.501]. The Operators of 5G systems make
use of an internal PKI to generate X.509 PKI certificates for the NFs
in a 5G system. The certificates are used for the following
purposes:
* Client and Server certificates for NFs in 5GC Service Based
Architecture (Section 6.1.3c of [TS33.310])
* Certificates for signing Client Credentials Assertion (CCA) tokens
using JWS (Section 13.3.8.2 of [TS33.501])
* Certificates for encrypting JSON objects in HTTP messages between
Security Edge Protection Proxies (SEPPs) using JWE
(Section 13.2.4.4 of [TS33.501]) and Section 6.3.2 of [TS33.210])
* Certificates for signing the OAuth 2.0 access tokens for service
authorization to grant temporary access to resources provided by
NF producers using JWS (Section 13.4.1 of [TS33.501])
If the purpose of the issued certificates is not restricted, i.e.,
the type of operations for which a public key contained in the
certificate can be used are not specified, those certificates could
be used for another purpose than intended, violating the CA policies,
and increasing the risk of cross-protocol attacks. Failure to ensure
proper segregation of duties means that a NF who generates the
public/private keys and applies for a certificate to the operator CA,
could obtain a certificate which can be misused for tasks that this
NF is not entitled to perform. For example, a NF service consumer
could impersonate NF service producers using its certificate.
Another example, if the purpose of the certificate is for the NF
service consumer is to use it as a client certificate, the NF with
this client certificate and corresponding private key must not be
allowed to sign the CCA. When a NF service producer receives the
signed CCA from the NF service consumer, the NF would accept the
token even if CCA is signed with a certificate not issued for this
purpose.
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The KeyPurposeId id-kp-serverAuth (Section 4.2.1.12 of [RFC5280]) can
be used to identify that the certificate is for a server (e.g., NF
service producer), and the KeyPurposeId id-kp-clientAuth
(Section 4.2.1.12 of [RFC5280]) can be used to identify that the
certificate is for a client (e.g., NF service consumer). However,
there is no KeyPurposeIds to identify whether the certificate can be
used to generate JWS, JWE, CWS or CWE.
Vendor-defined KeyPurposeIds that are used in a PKI governed by the
vendor or a group of vendors pose no interoperability concern.
Appropriating, or misappropriating as the case may be, KeyPurposeIds
for use outside of their originally intended vendor or group of
vendors controlled environment can introduce problems, the impact of
which is difficult to determine. Therefore, it is not favorable to
use vendor-defined KeyPurposeIds for JWS, JWE, CWS and CWE in
deployments that are not governed by the vendor.
This document defines extended key purpose identifiers for JWS, JWE,
CWS and CWE.
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.
CBOR Object Web Signature (CWS): Signing Object of a CBOR Object
Signing and Encryption (COSE) defined in Section 4 of [RFC9052].
CBOR Object Web Encryption (CWE): Encryption Object of a CBOR Object
Signing and Encryption (COSE) defined in Section 4 of [RFC9052].
3. Extended Key Purpose for JWS, JWE, CWS and CWE
This specification defines the KeyPurposeIds id-kp-json, id-kp-cbor.
As described in [RFC5280], "[i]f the [Extended Key Usage] extension
is present, then the certificate MUST only be used for one of the
purposes indicated." [RFC5280] also notes that "[i]f multiple [key]
purposes are indicated the application need not recognize all
purposes indicated, as long as the intended purpose is present."
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Applications processing JWS, JWE, CWS or CWE MAY require the CBOR
format or the JSON format be specified by the EKU extention id-kp-
cbor or id-kp-json. In addition, such application MUST require the
keyUsage extension be set to nonRepudiation (also designated as
contentCommitment) for the signature calculation and/or to
keyEncipherment for encryption of the secret key.
4. Including the Extended KeyPurpose for JWS and JWE in Certificates
[RFC5280] specifies the EKU X.509 certificate extension for use on
end entity certificates. The extension indicates one or more
purposes for which the certified public key is valid. The EKU
extension can be used in conjunction with the key usage extension,
which indicates the set of basic cryptographic operations for which
the certified key may be used. The EKU extension syntax is repeated
here for convenience:
ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId
KeyPurposeId ::= OBJECT IDENTIFIER
As described in [RFC5280], the EKU extension may, at the option of
the certificate issuer, be either critical or non-critical. This
specification defines the KeyPurposeIds id-kp-json and id-kp-cbor.
Inclusion of KeyPurposeId id-kp-json in a certificate indicates that
the public key encoded in the certificate has been certified to be
used for validating the JWS or that the public key encoded in the
certificate has been certified to be used for encrypting the Content
Encryption Key (CEK) in JWE (for example, encrypt the CEK with the
recipient's public key using the RSAES-OAEP algorithm to produce the
JWE Encrypted Key). The distinction between JWS and JWE is performed
via the KU that is set to nonRepudiation for JWS and dataEncipherment
for JWE.
Similarly, inclusion of KeyPurposeId id-kp-cbor in a certificate
indicates that the public key encoded in the certificate has been
certified to be used for validating the CWS or that the public key
encoded in the certificate has been certified to be used for
encrypting the CEK in CWE. The distinction between CWS and CWE is
performed via the KU that is set to nonRepudiation for CWS and
dataEncipherment for CWE.
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id-kp OBJECT IDENTIFIER ::= {
iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) kp(3) }
id-kp-json OBJECT IDENTIFIER ::= { id-kp TBD1 }
id-kp-cbor OBJECT IDENTIFIER ::= { id-kp TBD2 }
5. Implications for a Certification Authority
The procedures and practices employed by a certification authority
MUST ensure that the correct values for the EKU extension as well as
the KU extension are inserted in each certificate that is issued.
The inclusion of the id-kp-json, id-kp-cbor KeyPurposeIds does not
preclude the inclusion of other KeyPurposeIds.
6. Security Considerations
The Security Considerations of [RFC5280] are applicable to this
document. This extended key purpose does not introduce new security
risks but instead reduces existing security risks by providing means
to identify if the certificate is generated to process JWS or CWS
signature or to encrypt the CEK in JWE or CWE.
To reduce the risk of specific cross-protocol attacks, the relying
party or the relying party software may additionally prohibit use of
specific combinations of KeyPurposeIds. The procedure of using
Excluded KeyPurposeId and Permitted KeyPurposeId by an relying party
to permit or prohibit combinations of KeyPurposeIds is defined in
Section 4 of [RFC9336]. Examples of Excluded KeyPurposeId include
the presence of the anyExtendedKeyUsage KeyPurposeId or the complete
absence of the EKU extension in a certificate. Examples of Permitted
KeyPurposeId include the presence of JWS, JWE, CWS or CWE
KeyPurposeId.
7. Privacy Considerations
In some security protocols, such as TLS 1.2 [RFC5246], certificates
are exchanged in the clear. In other security protocols, such as TLS
1.3 [RFC8446], the certificates are encrypted. The inclusion of EKU
extension can help an observer determine the purpose of the
certificate. In addition, If the certificate is issued by a public
certification authority, the inclusion of EKU extension can help an
attacker to monitor the Certificate Transparency logs [RFC9162] to
identify the purpose of the certificate.
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8. IANA Considerations
IANA is requested to register the following OIDs in the "SMI Security
for PKIX Extended Key Purpose" registry (1.3.6.1.5.5.7.3). This OID
is defined in Section 4.
+=========+=======================+============+
| Decimal | Description | References |
+=========+=======================+============+
| TBD1 | id-kp-json | This-RFC |
+---------+-----------------------+------------+
| TBD2 | id-kp-cbor | This-RFC |
+---------+-----------------------+------------+
Figure 1: Table 1
IANA is also requested to register the following ASN.1[X.680] module
OID in the "SMI Security for PKIX Module Identifier" registry
(1.3.6.1.5.5.7.0). This OID is defined in Appendix A.
+=========+====================+============+
| Decimal | Description | References |
+=========+==========================+============+
| TBD5 | id-mod-jose-and-cose-eku | This-RFC |
+---------+--------------------------+------------+
Figure 2: Table 2
9. Contributors
The following individuals have contributed to this document:
German Peinado
Nokia
Email: german.peinado@nokia.com
10. Acknowledgments
We would like to thank Corey Bonnell, Ilari Liusvaara, Carl Wallace
and Russ Housley for their useful feedback.
11. References
11.1. Normative References
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[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/info/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/info/rfc5280>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <https://www.rfc-editor.org/info/rfc7159>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/info/rfc7515>.
[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<https://www.rfc-editor.org/info/rfc7516>.
[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/info/rfc8174>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/info/rfc8949>.
[RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/info/rfc9052>.
11.2. Informative References
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC7299] Housley, R., "Object Identifier Registry for the PKIX
Working Group", RFC 7299, DOI 10.17487/RFC7299, July 2014,
<https://www.rfc-editor.org/info/rfc7299>.
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[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<https://www.rfc-editor.org/info/rfc7518>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC9162] Laurie, B., Messeri, E., and R. Stradling, "Certificate
Transparency Version 2.0", RFC 9162, DOI 10.17487/RFC9162,
December 2021, <https://www.rfc-editor.org/info/rfc9162>.
[RFC9336] Ito, T., Okubo, T., and S. Turner, "X.509 Certificate
General-Purpose Extended Key Usage (EKU) for Document
Signing", RFC 9336, DOI 10.17487/RFC9336, December 2022,
<https://www.rfc-editor.org/info/rfc9336>.
[TS23.501] "3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects; System
architecture for the 5G System (5GS); Stage 2 (Release
18), 3GPP TS 23.501 V18.0.0 Dec 2022,",
<https://www.3gpp.org/ftp/Specs/
archive/23_series/23.501/23501-i00.zip>.
[TS33.210] "3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects;Network
Domain Security (NDS); IP network layer security (Release
17), 3GPP TS 33.210 V17.1.0 Sept 2022,",
<https://www.3gpp.org/ftp/Specs/
archive/33_series/33.210/33210-h10.zip>.
[TS33.310] "3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects; Network
Domain Security (NDS); Authentication Framework (AF)
(Release 17), 3GPP 33.310 V17.4.0, Sept 2022,",
<https://www.3gpp.org/ftp/Specs/
archive/33_series/33.310/33310-h40.zip>.
[TS33.501] "3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects; Security
architecture and procedures for 5G system (Release 17), ,
3GPP TS:33.501 V17.7.0, Sept 2022,",
<https://www.3gpp.org/ftp/Specs/
archive/33_series/33.501/33501-h70.zip>.
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[X.680] "ITU-T, "Information technology - Abstract Syntax Notation
One (ASN.1): Specification of basic notation", ITU-T
Recommendation X.680, February 2021.",
<https://www.itu.int/rec/T-REC-X.680>.
[X.690] "ITU-T, "Information technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", ITU-T Recommendation X.690, February 2021,",
<https://www.itu.int/rec/T-REC-X.690>.
Appendix A. ASN.1 Module
The following module adheres to ASN.1 specifications [X.680] and
[X.690].
<CODE BEGINS>
JOSE-EKU
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-jose-eku(TBD4) }
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
-- OID Arc
id-kp OBJECT IDENTIFIER ::=
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) kp(3) }
-- Extended Key Usage Values
id-kp-json OBJECT IDENTIFIER ::= { id-kp TBD1 }
id-kp-cbor OBJECT IDENTIFIER ::= { id-kp TBD2 }
END
<CODE ENDS>
Authors' Addresses
Tirumaleswar Reddy
Nokia
India
Email: kondtir@gmail.com
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Jani Ekman
Nokia
Finland
Email: jani.ekman@nokia.com
Daniel Migault
Ericsson
Canada
Email: daniel.migault@ericsson.com
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