PKCS #15 Updates
draft-gutmann-pkcs15-00

Network Working Group                                         P. Gutmann
Internet-Draft                                    University of Auckland
Intended status: Informational                           6 December 2023
Expires: 8 June 2024

                            PKCS #15 Updates
                        draft-gutmann-pkcs15-00

Abstract

   This document describes updates to the PKCS #15 standard made since
   the original publication of the standard.

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   material may not have granted the IETF Trust the right to allow
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  ValidFrom/ValidTo Dates . . . . . . . . . . . . . . . . . . .   2
   3.  Key Identifiers . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Authenticated-Enveloped-Data  . . . . . . . . . . . . . . . .   4
   5.  Public/Private Key Binding  . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   After the publication of the original PKCS #15 standard it saw minor
   updates that were only published as drafts and circulated informally
   among implementers, but never finalised due to the dissolution of the
   organisation that published the standards.  Since the standard,
   including the updates, remains in active use today, this document
   gathers the updates in a single location for reference by
   implementers.

   The updates cover the extension of the original PKCS #15 identifiers
   to handle validFrom/validTo dates for certificates and PGP/OpenPGP
   keys and email addresses, the addition of support for CMS
   Authenticated-Enveloped-Data, and support for cryptographic binding
   of public-key components to private-key ones.

   Since names and definitions have changed across the different drafts
   (for example v1.0 used PKCS15XXXAttributes while v1.1 and later used
   XXXXAttributes), this document uses the v1.1 ASN.1 module pkcs-
   15v1_1.asn as its baseline.

2.  ValidFrom/ValidTo Dates

   PKCS #15 v1.0 didn't support the validFrom/validTo dates that are
   required for certificates, these were added in the PKCS #15 v1.2
   draft and extend the CommonCertificateAttributes to add:

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           validFrom               GeneralisedTime OPTIONAL,
           validTo         [4] GeneralisedTime OPTIONAL,

   For context, the full CommonCertificateAttributes are then:

        CommonCertificateAttributes ::= SEQUENCE {
                iD                      Identifier,
                authority       BOOLEAN DEFAULT FALSE,
                identifier      CredentialIdentifier {{KeyIdentifiers}} OPTIONAL,
                certHash        [0] OOBCertHash OPTIONAL,
                ...,
                trustedUsage [1] Usage OPTIONAL,
                identifiers     [2] SEQUENCE OF CredentialIdentifier{{KeyIdentifiers}} OPTIONAL,
                implicitTrust [3] BOOLEAN DEFAULT FALSE
                validFrom       GeneralisedTime OPTIONAL,
                validTo         [4] GeneralisedTime OPTIONAL,
                }

3.  Key Identifiers

   PKCS #15 v1.0, designed for use with smart cards, didn't support PGP/
   OpenPGP or email use, making it difficult to implement PKCS #11 with
   PKCS #15 as the storage format.  The PKCS #15 v1.2 draft extended
   CredentialIdentifier to include these additional IDs, which extend
   the existing KeyIdentifiers values to add pgp, openPGP, and uri
   identifiers:

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        KeyIdentifiers KEY-IDENTIFIER ::= {
                issuerAndSerialNumber |
                issuerAndSerialNumberHash |
                subjectKeyId |
                subjectKeyHash |
                issuerKeyHash |
                issuerNameHash |
                subjectNameHash |
                pgp |
                openPGP |
                uri
                ...
        }

        pgp KEY-IDENTIFIER ::=
                {SYNTAX OCTET STRING SIZE(8) IDENTIFIED BY 8}
                -- RFC 4880 V3 (PGP 2.x) key ID

        openPGP KEY-IDENTIFIER ::=
                {SYNTAX OCTET STRING SIZE(8) IDENTIFIED BY 9}
                -- RFC 4880 V4 key ID

        uri KEY-IDENTIFIER ::=
                {SYNTAX UTF8String IDENTIFIED BY 10}
                -- Typically email address but may be a more general URI

4.  Authenticated-Enveloped-Data

   PKCS #15 v1.0 predates the existence of CMS Authenticated-Enveloped-
   Data, which was added in the PKCS #15 v1.2 draft by extending the
   ObjectValue/ PathOrObjects CHOICE to include a new content type
   AuthEnvelopedData alongside the existing EnvelopedData.  For
   ObjectValue this is:

           direct-protected-auth [4] AuthEnvelopedData {Type},

   For PathOrObjects this is:

        direct-protected-auth [4] AuthEnvelopedData {SEQUENCE OF ObjectType},

   Note that the tags jump from the v1.1 'direct-protected [2]
   EnvelopedData' to 'direct-protected-auth [4] AuthEnvelopedData', the
   [3] tag was used for another object type whose purpose is now lost.
   For context, the full ObjectValue / PathOrObjects are then:

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        ObjectValue { Type } ::= CHOICE {
                indirect                        ReferencedValue {Type},
                direct                          [0] Type,
                indirect-protected      [1] ReferencedValue {EnvelopedData {Type}},
                direct-protected        [2] EnvelopedData {Type},
                direct-protected-auth [4] AuthEnvelopedData {Type}
                }

        PathOrObjects {ObjectType} ::= CHOICE {
                path                            Path,
                objects                         [0] SEQUENCE OF ObjectType,
                ...,
                indirect-protected      [1] ReferencedValue {EnvelopedData {SEQUENCE OF ObjectType}},
                direct-protected        [2] EnvelopedData {SEQUENCE OF ObjectType}
                direct-protected-auth [4] AuthEnvelopedData {SEQUENCE OF ObjectType},
                }

5.  Public/Private Key Binding

   An update to the PKCS #15 v1.2 draft provided for cryptographic
   binding between the private key and public key data.  This protects
   the otherwise typically unprotected public-key objects from
   undetectable manipulation.  This cryptographic binding is added by
   extending the existing privateXXXKey types with new privateXXXKeyExt
   types that include the cryptographic binding:

        PrivateKeyType ::= CHOICE {
                privateRSAKey   PrivateKeyObject {PrivateRSAKeyAttributes},
                privateECKey    [0] PrivateKeyObject {PrivateECKeyAttributes},
                privateDHKey    [1] PrivateKeyObject {PrivateDHKeyAttributes},
                privateDSAKey   [2] PrivateKeyObject {PrivateDSAKeyAttributes},
                privateKEAKey   [3] PrivateKeyObject {PrivateKEAKeyAttributes},
                privateRSAKeyExt [4] PrivateKeyObject {PrivateRSAKeyAttributesExt},
                privateECKeyExt [5] PrivateKeyObject {PrivateECKeyAttributesExt},
                privateDSAKeyExt [6] PrivateKeyObject {PrivateDSAKeyAttributesExt},
                ...
                }

   The Ext variants wrap the original XXXPrivateKeyObject in an
   additional SEQUENCE that adds an [ESSCertIDv2] field, with the
   ESSCertIDv2 restricted to contain only a SHA-2 hash of the public key
   data in SubjectPublicKeyInfo form.  In other words the ESSCertIDv2:

        ESSCertIDv2 ::= SEQUENCE {
                hashAlgorithm   AlgorithmIdentifier DEFAULT {algorithm id-sha256},
                certHash                Hash,
                issuerSerial    IssuerSerial OPTIONAL
                }

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   is present as:

           ESSCertIDv2 ::=  SEQUENCE {
                   certHash                OCTET STRING SIZE(32),
                   }

   The resulting XXXPrivateKeyObject is then, in an ASN.1-like notation:

           XXXPrivateKeyObject ::= SEQUENCE {
                   spkiHash                ESSCertIDv2,
                   -- Original PrivateXXXKeyObject
                   }

   For example for an ECC private key the original:

           ECPrivateKey ::= INTEGER

   would become in extended form with cryptographic binding:

           ECPrivateKeyExt ::= SEQUENCE {
                   spkiHash                ESSCertIDv2,
                   value                   INTEGER
                   }

   For an RSA private key the original:

        RSAPrivateKeyObject ::= SEQUENCE {
                modulus                 [0] INTEGER OPTIONAL, -- n
                ...
                coefficient             [7] INTEGER OPTIONAL -- inv(q) mod p
                }

   would become in extended form with cryptographic binding:

        RSAPrivateKeyObjectExt ::= SEQUENCE {
                spkiHash                ESSCertIDv2,
                value                   SEQUENCE {
                        modulus         [0] INTEGER OPTIONAL, -- n
                        ...
                        coefficient     [7] INTEGER OPTIONAL -- inv(q) mod p
                        }
                }

6.  IANA Considerations

   This document has no IANA actions.

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7.  Security Considerations

   This document serves to document minor updates to the original PKCS
   #15 standard, there are no security considerations present beyond
   those in the original standard.

8.  Normative References

   [ESSCertIDv2]
              Schaad, J., "Enhanced Security Services (ESS) Update:
              Adding CertID Algorithm Agility", RFC 5035, August 2007,
              <http://www.ietf.org/rfc/rfc5035.txt>.

Author's Address

   Peter Gutmann
   University of Auckland
   Department of Computer Science
   Auckland
   New Zealand
   Email: pgut001@cs.auckland.ac.nz

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