--- 1/draft-ietf-lamps-hash-of-root-key-cert-extn-05.txt 2019-06-28 11:13:06.730759663 -0700 +++ 2/draft-ietf-lamps-hash-of-root-key-cert-extn-06.txt 2019-06-28 11:13:06.754760269 -0700 @@ -1,18 +1,18 @@ Network Working Group R. Housley Internet-Draft Vigil Security -Intended status: Informational January 31, 2019 -Expires: August 4, 2019 +Intended status: Informational June 28, 2019 +Expires: December 30, 2019 Hash Of Root Key Certificate Extension - draft-ietf-lamps-hash-of-root-key-cert-extn-05 + draft-ietf-lamps-hash-of-root-key-cert-extn-06 Abstract This document specifies the Hash Of Root Key certificate extension. This certificate extension is carried in the self-signed certificate for a trust anchor, which is often called a Root Certification Authority (CA) certificate. This certificate extension unambiguously identifies the next public key that will be used at some point in the future as the next Root CA certificate, eventually replacing the current one. @@ -25,21 +25,21 @@ 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 August 4, 2019. + This Internet-Draft will expire on December 30, 2019. 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 @@ -54,24 +54,24 @@ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 1.2. ASN.1 . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Hash Of Root Key Certificate Extension . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 5. Operational Considerations . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 8.1. Normative References . . . . . . . . . . . . . . . . . . 7 - 8.2. Informative References . . . . . . . . . . . . . . . . . 8 - Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 8 - Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 + 8.2. Informative References . . . . . . . . . . . . . . . . . 9 + Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 9 + Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction This document specifies the Hash Of Root Key X.509 version 3 certificate extension. The extension is an optional addition to the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile [RFC5280]. The certificate extension facilitates the orderly transition from one Root Certification Authority (CA) public key to the next. It does so by publishing the hash value of the next generation public key in the current self- @@ -89,23 +89,22 @@ 1.1. 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. 1.2. ASN.1 - Certificates [RFC5280] are generated using ASN.1 [X680]; certificates - are always encoded with the Distinguished Encoding Rules (DER) - [X690]. + Certificates [RFC5280] use ASN.1 [X680]; Distinguished Encoding Rules + (DER) [X690] are REQUIRED for certificate signing and validation. 2. Overview Before the initial deployment of the Root CA, the following are generated: R1 = The initial Root key pair R2 = The second generation Root key pair H2 = Thumbprint (hash) of the public key of R2 C1 = Self-signed certificate for R1, which also contains H2 @@ -156,21 +155,21 @@ The following ASN.1 [X680][X690] syntax defines the HashOfRootKey certificate extension: ext-HashOfRootKey EXTENSION ::= { -- Only in Root CA certificates SYNTAX HashedRootKey IDENTIFIED BY id-ce-hashOfRootKey CRITICALITY {FALSE} } HashedRootKey ::= SEQUENCE { - hashAlg AlgorithmIdentifier, -- Hash algorithm used + hashAlg HashAlgorithm, -- Hash algorithm used hashValue OCTET STRING } -- Hash of DER-encoded -- SubjectPublicKeyInfo id-ce-hashOfRootKey ::= OBJECT IDENTIFIER { 1 3 6 1 4 1 51483 2 1 } The definitions of EXTENSION and HashAlgorithm can be found in [RFC5912]. The hashAlg indicates the one-way hash algorithm that was used to compute the hash value. @@ -189,43 +188,57 @@ available in Section 4.4 of [RFC4210]. In particular, the oldWithNew and newWithOld advice ensures that relying parties are able to validate certificates issued under the current Root CA certificate and the next generation Root CA certificate throughout the transition. The notAfter field in the oldWithNew certificate MUST cover the validity period of all unexpired certificates issued under the old Root CA private key. Further, this advice SHOULD be followed by Root CAs to avoid the need for all relying parties to make the transition at the same time. - After issuing the oldWithNew and newWithOld certificates, the Root CA - MUST stop using the old private key to sign certificates. + After issuing the newWithOld certificate, the Root CA MUST stop using + the old private key to sign certificates. Some enterprise and application-specific environments offer a directory service or certificate repository to make certificate and CRLs available to relying parties. Section 3 in [RFC5280] describes a certificate repository. When a certificate repository is available, the oldWithNew and newWithOld certificates SHOULD be published before the successor to the current Root CA self-signed certificate is released. Recipients that are able to obtain the oldWithNew certificate SHOULD immediately remove the old Root CA self-signed certificate from the trust anchor store. + In environments without such a directory service or repository, like + the Web PKI, recipients need a way to obtain the oldWithNew and + newWithOld certificates. The Root CA SHOULD include the subject + information access extension [RFC5280] with the accessMethod set to + id-ad-caRepository and the assessLocation set to the HTTP URL that + can be used to fetch a DER-encoded "certs-only" (simple PKI response) + message as specified in [RFC5272] in all of their self-signed + certificates. The Root CA SHOULD publish the "certs-only" message + with the oldWithNew certificate and the newWithOld certificate before + the subsequent Root CA self-signed certificate is released. The + "certs-only" message format allows certificates to be added and + removed from the bag of certificates over time, so the same HTTP URL + can be used throughout the lifetime of the Root CA. + In environments without such a directory service or repository, recipients SHOULD keep both the old and replacement Root CA self- - signed certificate in the trust anchor store for some amount of time + signed certificates in the trust anchor store for some amount of time to ensure that all end-entity certificates can be validated until they expire. The recipient MAY keep the old Root CA self-signed certificate until all of the certificates in the local cache that are subordinate to it have expired. - Certification path construction is more complex when multiple self- - signed certificates in the trust anchor store have the same + Certification path construction is more complex when the trust anchor + store contains multiple self-signed certificates with the same distinguished name. For this reason, the replacement Root CA self- signed certificate SHOULD contain a different distinguished name than the one it is replacing. One approach is to include a number as part of the name that is incremented with each generation, such as "Example CA", "Example CA G2", "Example CA G3", and so on. Changing names from one generation to another can lead to confusion when reviewing the history of a trust anchor store. To assist with such review, a recipient MAY create an audit entry to capture the old and replacement self-signed certificates. @@ -270,51 +283,60 @@ preimage attacks [RFC4270]. A first-preimage attack against the hash function would allow an attacker to find another input that results published hash value. For the attack to be successful, the input would have to be a valid SubjectPublicKeyInfo that contains a public key that corresponds to a private key known to the attacker. A second-preimage attack becomes possible once the Root CA releases the next generation public key, which makes the input to the hash function available to the attacker and everyone else. Again, the attacker needs to find a valid SubjectPublicKeyInfo that contains the public key that corresponds to a private key known to the attacker. + If the employed hash function is broken after the Root CA publishes + the self-signed certificate with the HashOfRootKey certificate + extension, an attacker would be able to trick the recipient into + installing the incorrect next generation certificate in the trust + anchor store. If an early release of the next generation public key occurs and the Root CA is concerned that attackers were given too much lead time to analyze that public key, then the Root CA can transition to a freshly generated key pair by rapidly performing two transitions. The first transition takes the Root CA to the key pair that suffered the early release, and it causes the Root CA to generate the subsequent Root key pair. The second transition occurs when the Root CA is confident that the population of relying parties have completed the first transition, and it takes the Root CA to the freshly generated key pair. Of course, the second transition also causes the Root CA to - generate another key pair that is reserved for future use. + generate another key pair that is reserved for future use. Queries + for the CRLs associated with certificates that are subordinate to the + self-signed certificate can give some indication for the number of + relying parties that are still actively using the self-signed + certificates. 7. Acknowledgements The Secure Electronic Transaction (SET) [SET] specification published by MasterCard and VISA in 1997 includes a very similar certificate extension. The SET certificate extension has essentially the same semantics, but the syntax fairly different. - CTIA - The Wireless Association is developing a public key + CTIA - The Wireless Association - is developing a public key infrastructure that will make use of the certificate extension - described in this document. + described in this document, and the object identifiers used in the + ASN.1 module were assigned by CTIA. Many thanks to Stefan Santesson, Jim Schaad, Daniel Kahn Gillmor, - Joel Halpern, Paul Hoffman, and Rich Salz. Their review and comments - have greatly improved the document, especially the Operational - Considerations and Security Considerations sections. + Joel Halpern, Paul Hoffman, Rich Salz, and Ben Kaduk. Their review + and comments have greatly improved the document, especially the + Operational Considerations and Security Considerations sections. 8. References - 8.1. 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, . [RFC4210] Adams, C., Farrell, S., Kause, T., and T. Mononen, "Internet X.509 Public Key Infrastructure Certificate Management Protocol (CMP)", RFC 4210, @@ -319,20 +341,24 @@ "Internet X.509 Public Key Infrastructure Certificate Management Protocol (CMP)", RFC 4210, DOI 10.17487/RFC4210, September 2005, . [RFC4270] Hoffman, P. and B. Schneier, "Attacks on Cryptographic Hashes in Internet Protocols", RFC 4270, DOI 10.17487/RFC4270, November 2005, . + [RFC5272] Schaad, J. and M. Myers, "Certificate Management over CMS + (CMC)", RFC 5272, DOI 10.17487/RFC5272, June 2008, + . + [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, . [RFC5912] Hoffman, P. and J. Schaad, "New ASN.1 Modules for the Public Key Infrastructure Using X.509 (PKIX)", RFC 5912, DOI 10.17487/RFC5912, June 2010, . @@ -363,25 +389,25 @@ HashedRootKeyCertExtn { 1 3 6 1 4 1 51483 0 1 } DEFINITIONS IMPLICIT TAGS ::= BEGIN -- EXPORTS All IMPORTS - AlgorithmIdentifier{}, DIGEST-ALGORITHM - FROM AlgorithmInformation-2009 -- [RFC5912] + HashAlgorithm + FROM PKIX1-PSS-OAEP-Algorithms-2009 -- [RFC5912] { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) - id-mod-algorithmInformation-02(58) } + id-mod-pkix1-rsa-pkalgs-02(54) } EXTENSION FROM PKIX-CommonTypes-2009 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-pkixCommon-02(57) } ; -- -- Expand the certificate extensions list in [RFC5912] -- @@ -392,21 +418,21 @@ -- -- HashOfRootKey Certificate Extension -- ext-HashOfRootKey EXTENSION ::= { -- Only in Root CA certificates SYNTAX HashedRootKey IDENTIFIED BY id-ce-hashOfRootKey CRITICALITY {FALSE} } HashedRootKey ::= SEQUENCE { - hashAlg HashAlgorithmId, -- Hash algorithm used + hashAlg HashAlgorithm, -- Hash algorithm used hashValue OCTET STRING } -- Hash of DER-encoded -- SubjectPublicKeyInfo HashAlgorithmId ::= AlgorithmIdentifier {DIGEST-ALGORITHM,{ ... }} id-ce-hashOfRootKey OBJECT IDENTIFIER ::= { 1 3 6 1 4 1 51483 2 1 } END Author's Address