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Versions: 00
Internet Engineering Task Force H. Brockhaus
Internet-Draft Siemens
Updates: 4210 (if approved) July 7, 2019
Intended status: Standards Track
Expires: January 8, 2020
CMP Updates
draft-brockhaus-lamps-cmp-updates-00
Abstract
This document contains a set of updates to the base syntax of
Certificate Management Protocol (CMP) version 2. This document
updates RFC 4210.
Specifically, the CMP services updated in this document comprise:
Enable protection of server-side key generation using elliptic curve
algorithms and the definition of an extended key usage to identify
certificates of CMP endpoints on registration authorities and
certification authorities.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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 January 8, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Convention and Terminology . . . . . . . . . . . . . . . 3
2. Updates to RFC 4210 - Certificate Management Protocol (CMP) . 3
2.1. New Section 1.1. - Changes since RFC 4210 . . . . . . . . 3
2.2. Replace Section 5.2.2. - Encrypted Values . . . . . . . . 4
2.3. Update Section 5.3.4. - Certification Response . . . . . 5
2.4. Update Section 5.3.19.9. - Revocation Passphrase . . . . 5
2.5. Update Appendix B - The Use of Revocation Passphrase . . 6
2.6. Update Appendix C - Request Message Behavioral
Clarifications . . . . . . . . . . . . . . . . . . . . . 7
2.7. Update Appendix D.4. - Request Message Behavioral
Clarifications . . . . . . . . . . . . . . . . . . . . . 7
2.8. Insert section for EKUs like kp-id-cmpRA definition at an
appropriate location. . . . . . . . . . . . . . . . . . . 7
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. Normative References . . . . . . . . . . . . . . . . . . 8
6.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. ASN.1 Modules . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
While using CMP [RFC4210] in industrial and IoT environments and
developing the Lightweight CMP Profile
[I-D.brockhaus-lamps-industrial-cmp-profile] some limitations were
identified in the original CMP specification. This document updates
RFC 4210 [RFC4210] to overcome these limitations.
In general this document aims to improve the crypto agility of CMP to
be flexible to react on future advances in cryptography.
This document also introduces a new extended key usage to identify
CMP services on registration and certification authorities.
< TBD: While implementing CMP we identified some wording that could
be more precise. It can be discussed if such wording issued need to
be addressed in the context of this document or not. >
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1.1. Convention and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying significance described in RFC 2119.
Technical terminology is used in conformance with RFC 4210 [RFC4210],
RFC 4211 [RFC4211], and RFC 5280 [RFC5280]. The following key words
are used:
CA: Certification authority, which issues certificates.
RA: Registration authority, an optional system component to which
a CA delegates certificate management functions such as
authorization checks.
EE: End entity, a user or device or service that holds a PKI
certificate. An identifier for the EE is given as the
subject of the certificate.
2. Updates to RFC 4210 - Certificate Management Protocol (CMP)
2.1. New Section 1.1. - Changes since RFC 4210
The following subsections describe feature updates to RFC 4210
[RFC4210]. They are always related to the base specification. Hence
references to the original sections in RFC 4210 are used whenever
possible.
Insert this section at the end of the current Section 1.
The following updates were made since RFC 4210:
o Offering envelopedData as another choice next to EncryptedValue to
extend crypto agility in CMP. . Note that according to RFC 4211
[RFC4211] section 2.1.9 the use of the EncryptedValue structure
has been deprecated in favor of the EnvelopedData structure. For
reasons of completeness and consistency the exchange of
EncryptedValue with EncryptedKey is performed not only where
required for the needed crypto agility for protection of centrally
generated private key, but also for other purposes like encryption
of revocation passphrases.
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o Add new extended key usages for different CMP server types, e.g.
Registration authority and certification authority.
2.2. Replace Section 5.2.2. - Encrypted Values
Section 5.2.2 of RFC 4210 [RFC4210] describes the usage of
EncryptedValue to transport encrypted data.
Replace the text of the section with the following text.
Where encrypted data (restricted, in this specification, to be either
private keys, certificates or passwords) are sent in PKI messages,
the EncryptedKey data structure is used.
EncryptedKey ::= CHOICE {
encryptedValue EncryptedValue, -- deprecated
envelopedData [0] EnvelopedData }
See CRMF [RFC4211] for EncryptedKey and EncryptedValue syntax.
Using this data structure, it offers the choice to either use
EncryptedValue or EnvelopedData. As EncryptedValue offers only key
transport, e.g. using RSA or symmetic encryption, EnvelopedData
offers further key management techniques, e.g. key agreement, and
more crypto agility. Note that according to RFC 4211 [RFC4211]
section 2.1.9 the use of the EncryptedValue structure has been
deprecated in favor of the EnvelopedData structure. Therefore, it is
recommended to use EnvelopedData.
See CMS [RFC5652] for EnvelopedData syntax.
Using envelopedData within CMP contains only one recepientInfo
structure because the content is encrypted only for one recipient.
< TBD: Explain the detailed usage of the different key management
techniques (e.g. key transport, key agreement, and previously
distributed symmetric key-encryption keys) for encryption of the
respective private key, certificate or revocation passphrase as
specified for EnvelopedData in section 6 in CMS [RFC5652]. >
Use of either EnvelopedData or EncryptedValue (for backward
compatibility only) requires that the creator and intended recipient
be able to encrypt and decrypt, respectively. Typically, this will
mean that the sender and recipient have, or are able to generate, a
shared secret key.
< TBD: Description of EnvelopedData structure parts which are used
and filled to support application in CMP >
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If EncryptedValue is used by the sender and the recipient of the
PKIMessage already possesses a private key usable for decryption,
then the encSymmKey field MAY contain a session key encrypted using
the recipient's public key.
2.3. Update Section 5.3.4. - Certification Response
Section 5.3.4 of RFC 4210 [RFC4210] describes the Certification
Response. This document updates the syntax by using EncryptedKey
instead of EncryptedValue as described in Section 2.1 above.
Replace the ASN.1 syntax of CertifiedKeyPair and CertorEncCert with
the following text.
CertifiedKeyPair ::= SEQUENCE {
certOrEncCert CertOrEncCert,
privateKey [0] EncryptedKey OPTIONAL,
-- see [CRMF] for comment on encoding
publicationInfo [1] PKIPublicationInfo OPTIONAL
}
CertOrEncCert ::= CHOICE {
certificate [0] Certificate,
encryptedCert [1] EncryptedKey
}
< Question to Jim Schaad: Simply exchanging EncryptedValue with
EncryptedKey is what I understood from our discussion back in April.
Is it completely backwards compatible to current ASN.1 Syntax of
RFC4210? >
Add the following paragraphs to the end of the section.
In case EnvelopedData is the choice used for EncryptedKey, the
encrypted private key or certificate MUST be placed in the
envelopedData encryptedContentInfo encryptedContent OCTET STRING.
Note that according to RFC 4211 [RFC4211] section 2.1.9 the use of
the EncryptedValue structure has been deprecated in favor of the
EnvelopedData structure.
2.4. Update Section 5.3.19.9. - Revocation Passphrase
Section 5.3.19.9 of RFC 4210 [RFC4210] describes the provisioning of
a revocation passphrase for authenticating a later revocation
request. This document updates the handling by using EncryptedKey
instead of EncryptedValue to transport this information as described
in Section 2.1 above.
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Replace the text of the section with the following text.
The revocation passphrase MAY be used by the EE to send a passphrase
to a CA/RA for the purpose of authenticating a later revocation
request (in the case that the appropriate signing private key is no
longer available to authenticate the request). See Appendix B for
further details on the use of this mechanism.
GenMsg: {id-it 12}, EncryptedKey
GenRep: {id-it 12}, < absent >
In case EnvelopedData is the choice used for EncryptedKey, the
encrypted revocation passphrase MUST be placed in the envelopedData
encryptedContentInfo encryptedContent OCTET STRING. Note that
according to RFC 4211 [RFC4211] section 2.1.9 the use of the
EncryptedValue structure has been deprecated in favor of the
EnvelopedData structure.
2.5. Update Appendix B - The Use of Revocation Passphrase
Appendix B of RFC 4210 [RFC4210] describes the usage of the
revocation passphrases. As this document updates RFC 4210 [RFC4210]
to utilize EncryptedKey in favor of EncryptedValue as described in
Section 2.1 above, the description is updated accordingly.
Replace the first bullet point of this section with the following
text.
o The OID and value specified in Section 5.3.19.9 of RFC 4210
[RFC4210] MAY be sent in a GenMsg message at any time, or MAY be
sent in the generalInfo field of the PKIHeader of any PKIMessage
at any time. (In particular, the EncryptedKey may be sent in the
header of the certConf message that confirms acceptance of
certificates requested in an initialization request or certificate
request message.) This conveys a revocation passphrase chosen by
the entity (i.e., and for use of EnvelopedData this is in the
decrypted bytes of encryptedContent of the EnvelopedData structure
and for use of EncryptedValue this is in the decrypted bytes of
the encValue field) to the relevant CA/RA; furthermore, the
transfer is accomplished with appropriate confidentiality
characteristics. Note that according to RFC 4211 [RFC4211]
section 2.1.9 the use of the EncryptedValue structure has been
deprecated in favor of the EnvelopedData structure.
Replace the third bullet point of this section with the following
text.
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o When using EnvelopedData the contentType of EncryptedContentInfo
and when using EncryptedValue the valueHint field MAY contain a
key identifier (chosen by the entity, along with the passphrase
itself) to assist in later retrieval of the correct passphrase
(e.g., when the revocation request is constructed by the entity
and received by the CA/RA).
2.6. Update Appendix C - Request Message Behavioral Clarifications
Appendix C of [RFC4210] provides clarifications to the request
message behavior. As this document updates [RFC4210] to utilize
EncryptedKey in favor of EncryptedValue as described in Section 2.1
above, the description is updated accordingly.
Replace the note coming after the ASN.1 syntax of POPOPrivKey of this
section with the following text.
-- **********
-- * the type of "thisMessage" is given as BIT STRING in RFC 4211
-- * [RFC4211]; it should be "EncryptedKey" (in accordance with
-- * Section 5.2.2, "Encrypted Values", of this specification).
-- * Therefore, this document makes the behavioral clarification of
-- * specifying that the contents of "thisMessage" MUST be encoded
-- * either as EnvelopedData or EncryptedValue (only for backward
-- * compatibility) and then wrapped in a BIT STRING. This allows
-- * the necessary conveyance and protection of the private key
-- * while maintaining bits-on-the-wire compatibility with RFC 4211
-- * [RFC4211].
-- **********
2.7. Update Appendix D.4. - Request Message Behavioral Clarifications
< TBD, add further details on crc[1].certifiedKeyPair, e.g. refer to
usage of EncryptedValue protected with the pre-shared symmetric
MACing key using SYM_PENC_ALG. >
2.8. Insert section for EKUs like kp-id-cmpRA definition at an
appropriate location.
< Details need to be defined later >
3. IANA Considerations
<Add any IANA considerations>
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4. Security Considerations
No changes are made to the existing security considerations of
RFC 4210 [RFC4210].
5. Acknowledgements
We would like to thank the various reviewers of this document.
6. References
6.1. 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/info/rfc2119>.
[RFC4210] Adams, C., Farrell, S., Kause, T., and T. Mononen,
"Internet X.509 Public Key Infrastructure Certificate
Management Protocol (CMP)", RFC 4210,
DOI 10.17487/RFC4210, September 2005,
<https://www.rfc-editor.org/info/rfc4210>.
[RFC4211] Schaad, J., "Internet X.509 Public Key Infrastructure
Certificate Request Message Format (CRMF)", RFC 4211,
DOI 10.17487/RFC4211, September 2005,
<https://www.rfc-editor.org/info/rfc4211>.
[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>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/rfc5652>.
[RFC6712] Kause, T. and M. Peylo, "Internet X.509 Public Key
Infrastructure -- HTTP Transfer for the Certificate
Management Protocol (CMP)", RFC 6712,
DOI 10.17487/RFC6712, September 2012,
<https://www.rfc-editor.org/info/rfc6712>.
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6.2. Informative References
[I-D.brockhaus-lamps-industrial-cmp-profile]
Brockhaus, H., Fries, S., and D. Oheimb, "Lightweight
Industrial CMP Profile", draft-brockhaus-lamps-industrial-
cmp-profile-00 (work in progress), March 2019.
Appendix A. ASN.1 Modules
Changes to the following parts are needed
o Import from PKIKXCRMF-2005
CertTemplate, PKIPublicationInfo, EncryptedKey, CertId,
CertReqMessages
FROM PKIXCRMF-2005 {iso(1) identified-organization(3)
dod(6) internet(1) security(5) mechanisms(5) pkix(7)
id-mod(0) id-mod-crmf2005(36)}
o In CertifiedKeyPair, CertOrEncCert and id-it-revPassphrase
CertifiedKeyPair ::= SEQUENCE {
certOrEncCert CertOrEncCert,
privateKey [0] EncryptedKey OPTIONAL,
-- see [CRMF] for comment on encoding
publicationInfo [1] PKIPublicationInfo OPTIONAL
}
CertOrEncCert ::= CHOICE {
certificate [0] CMPCertificate,
encryptedCert [1] EncryptedKey
}
-- id-it-revPassphrase OBJECT IDENTIFIER ::= {id-it 12}
-- RevPassphraseValue ::= EncryptedKey
< TBD: If needed the complete ASN.1 Module from RFC 4210 section
needs to be copied here to be changed. >
Author's Address
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Hendrik Brockhaus
Siemens AG
Otto-Hahn-Rin 6
Munich 81739
Germany
Email: hendrik.brockhaus@siemens.com
URI: http://www.siemens.com/
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