Network Working Group J. Schaad
Internet-Draft Soaring Hawk Consulting
Expires: October 19, 2006 April 17, 2006
ESS Update: Adding CertID Algorithm Agility
draft-ietf-smime-escertid-01.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on October 19, 2006.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
In the original Enhanced Security Services for S/MIME draft, a
structure for cryptographically linking the certificate to be used in
validation with the signature was introduced, this structure was
hardwired to use SHA-1. This document allows for the structure to
have algorithm agility and defines new attributes to deal with the
updating.
Schaad Expires October 19, 2006 [Page 1]
Internet-Draft ESSCertID Update April 2006
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notation . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Replace Section 5.4 Signing Certificate Attribute
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Insert new section 5.4.1 . . . . . . . . . . . . . . . . . . . 5
4. Insert new section 5.4.1.1 . . . . . . . . . . . . . . . . . . 7
5. Insert new section 5.4.2 . . . . . . . . . . . . . . . . . . . 9
6. Renumber Section 5.4.1 Certificate Identification . . . . . . 11
7. Normative References . . . . . . . . . . . . . . . . . . . . . 11
Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . . . 18
Schaad Expires October 19, 2006 [Page 2]
Internet-Draft ESSCertID Update April 2006
1. Introduction
In the original Enhanced Security Services (ESS) for S/MIME draft
[ESS], a structure for cryptographically linking the certificate to
be used in validation with the signature was defined. This
structure, called ESSCertID was hardwired to use a SHA-1 hash value.
The recent attacks on SHA-1 require that we change define a new
attribute which allows for the use of a different algorithm. This
document performs that task.
This document defines the structure ESSCertIDv2 along with a new
attribute SigningCertificateV2 which uses the updated structure.
This document allows for the structure to have algorithm agility and
defines new attributes to deal with the updating.
1.1. Notation
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 [RFC2119].
Schaad Expires October 19, 2006 [Page 3]
Internet-Draft ESSCertID Update April 2006
2. Replace Section 5.4 Signing Certificate Attribute Definitions
The signing certificate attribute is designed to prevent simple
substitution and re-issue attacks, and to allow for a restricted set
of authorization certificates to be used in verifying a signature.
Two different attributes exist for this due to a flaw in the original
design. The only substantial difference between the two attributes
is that SigningCertificateV2 allows for hash algorithm agility, while
SigningCertificate forces the use of the SHA-1 hash algorithm. With
the recent advances in the ability to create hash collisions for
SHA-1 it is deemed wise to move forward sooner rather than later.
When the SHA-1 hash function is used, the SigningCertificate
attribute MUST be used. The SigningCertificateV2 attribute MUST be
used if any algorithm other than SHA-1 is used and SHOULD NOT be used
for SHA-1. Applications SHOULD recognize both attributes as long as
they consider SHA-1 to be sufficiently descriminating.
Schaad Expires October 19, 2006 [Page 4]
Internet-Draft ESSCertID Update April 2006
3. Insert new section 5.4.1
5.4.1 Signing Certificate Attribute Definition
The signing certificate attribute is designed to prevent the simple
substitution and re-issue attacks, and to allow for a restricted set
of authorization certificates to be used in verifying a signature.
The definition of SigningCertificateV2 is
SigningCertificateV2 ::= SEQUENCE {
certs SEQUENCE OF ESSCertIDv2,
policies SEQUENCE OF PolicyInformation OPTIONAL
}
id-aa-signingCertificateV2 OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-aa(2) XX }
certs contains the list of certificates that are to be used in
validating the message. The first certificate identified in the
sequence of certificate identifiers MUST be the certificate used
to verify the signature. The encoding of the ESSCertIDv2 for this
certificate SHOULD include the issuerSerial field. If other
constraints ensure that issuerAndSerialNumber will be present in
the SignerInfo, the issuerSerial field MAY be omitted. The
certificate identified is used during the signature verification
process. If the hash of the certificate does not match the
certificate used to verify the signature, the signature MUST be
considered invalid.
If more than one certificate is present, subsequent certificates
limit the set of authorization certificates that are used during
signature validation. Authorization certificates can be either
attribute certificates or normal certificates. The issuerSerial
field (in the ESSCertIDv2 structure) SHOULD be present for these
certificates, unless the client who is validating the signature is
expected to have easy access to all the certificates required for
validation. If only the signing certificate is present in the
sequence, there are no restrictions on the set of authorization
certificates used in validating the signature.
policies contains a sequence of policy information terms that
identify those certificate policies that the signer asserts apply
to the certificate, and under which the certificate should be
relied upon. This value suggests a policy value to be used in the
relying party's certification path validation. The definition of
PolicyInformation can be found in [PKIXCERT].
Schaad Expires October 19, 2006 [Page 5]
Internet-Draft ESSCertID Update April 2006
If present, the SigningCertificateV2 attribute MUST be a signed
attribute; it MUST NOT be an unsigned attribute. CMS defines
SignedAttributes as a SET OF Attribute. A SignerInfo MUST NOT
include multiple instances of the SigningCertificate attribute. CMS
defines the ASN.1 syntax for the signed attributes to include
attrValues SET OF AttributeValue. A SigningCertificate attribute
MUST include only a single instance of AttributeValue. There MUST
NOT be zero or multiple instances of AttributeValue present in the
attrValues SET OF AttributeValue.
Schaad Expires October 19, 2006 [Page 6]
Internet-Draft ESSCertID Update April 2006
4. Insert new section 5.4.1.1
Insert the following text as a new section
5.4.1.1 Certificate Identification
The best way to identify certificates is an often-discussed issue.
The ESSCertIDV2 structure supplies two different fields that are used
for this purpose.
The hash of the entire certificate allows for a verifier to check
that the certificate used in the verification process was the same as
the signer intended to be used. Hashes are convient in that they are
frequently used by certificate stores as a method of indexing and
retrieving certificates as well. The use of the hash is required by
this structure since the detection of substitued certificates is
based on the fact they would map to different hash values.
The issuer/serial number pair is the method of identification of
certificates used in [PKIXCERT]. That document imposes a restriction
for certificates that the issuer DN must be present. The issuer/
serial number pair would therefore normally be sufficient to identify
the correct signing certificate. (This assumes the same issuer name
is not re-used from the set of trust anchors.) The issuer/serial
number pair can be stored in the sid field of the SignerInfo object.
However the sid field is not covered by the signature. In the cases
where the issuer/serial number pair is not used in the sid or the
issuer/serial number need to be signed, they should be placed in the
issuerSerial field of the ESSCertIDv2 structure.
Attribute certificates and additional public key certificates
containing authorization information do not have an issuer/serial
number pair represented anywhere in a SignerInfo object. When an
attribute certificate or an additional public key certificate is not
included in the SignedData object, it becomes much more difficult to
get the correct set of certificates based only on a hash of the
certificate. For this reason, these certificates SHOULD be
identified by the IssuerSerial object.
This document defines a certificate identifier as:
Schaad Expires October 19, 2006 [Page 7]
Internet-Draft ESSCertID Update April 2006
ESSCertIDv2 ::= SEQUENCE {
hashAlg AlgorithmIdentifier DEFAULT {id-sha256}
certHash Hash,
issuerSerial IssuerSerial OPTIONAL
}
Hash ::= OCTET STRING
IssuerSerial ::= SEQUENCE {
issuer GeneralNames,
serialNumber CertificateSerialNumber
}
The fields of ESSCertIDv2 are defined as follows:
certHash is computed over the entire DER encoded certificate
including the signature. The issuerSerial would normally be
present unless the value can be inferred from other information.
hashAlg contains the identifier of the algorithm used in computing
certHash.
issuerSerial holds the identification of the certificate.
The fields of IssuerSerial are defined as follows:
issuer contains the issuer name of the certificate. For non-
attribute certificates, the issuer MUST contain only the issuer
name from the certificate encoded in the directoryName choice of
GeneralNames. For attribute certificates, the issuer MUST contain
the issuer name field from the attribute certificate.
serialNumber holds the serial number that uniquely identifies the
certificate.
Schaad Expires October 19, 2006 [Page 8]
Internet-Draft ESSCertID Update April 2006
5. Insert new section 5.4.2
5.4.2 Signing Certificate Attribute Definition with SHA-1
The signing certificate attribute is designed to prevent the simple
substitution and re-issue attacks, and to allow for a restricted set
of authorization certificates to be used in verifying a signature.
The definition of SigningCertificate is
SigningCertificate ::= SEQUENCE {
certs SEQUENCE OF ESSCertID,
policies SEQUENCE OF PolicyInformation OPTIONAL
}
id-aa-signingCertificate OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-aa(2) 12 }
The first certificate identified in the sequence of certificate
identifiers MUST be the certificate used to verify the signature.
The encoding of the ESSCertID for this certificate SHOULD include the
issuerSerial field. If other constraints ensure that
issuerAndSerialNumber will be present in the SignerInfo, the
issuerSerial field MAY be omitted. The certificate identified is
used during the signature verification process. If the hash of the
certificate does not match the certificate used to verify the
signature, the signature MUST be considered invalid.
If more than one certificate is present in the sequence of
ESSCertIDs, the certificates after the first one limit the set of
authorization certificates that are used during signature validation.
Authorization certificates can be either attribute certificates or
normal certificates. The issuerSerial field (in the ESSCertID
structure) SHOULD be present for these certificates, unless the
client who is validating the signature is expected to have easy
access to all the certificates required for validation. If only the
signing certificate is present in the sequence, there are no
restrictions on the set of authorization certificates used in
validating the signature.
The sequence of policy information terms identifies those certificate
policies that the signer asserts apply to the certificate, and under
which the certificate should be relied upon. This value suggests a
policy value to be used in the relying party's certification path
validation.
If present, the SigningCertificate attribute MUST be a signed
Schaad Expires October 19, 2006 [Page 9]
Internet-Draft ESSCertID Update April 2006
attribute; it MUST NOT be an unsigned attribute. CMS defines
SignedAttributes as a SET OF Attribute. A SignerInfo MUST NOT
include multiple instances of the SigningCertificate attribute. CMS
defines the ASN.1 syntax for the signed attributes to include
attrValues SET OF AttributeValue. A SigningCertificate attribute
MUST include only a single instance of AttributeValue. There MUST
NOT be zero or multiple instances of AttributeValue present in the
attrValues SET OF AttributeValue.
Schaad Expires October 19, 2006 [Page 10]
Internet-Draft ESSCertID Update April 2006
6. Renumber Section 5.4.1 Certificate Identification
Change the number on this section from 5.4.1 to 5.4.2.1
Change the title on this section to "Certificate Identification with
SHA-1".
7. Normative References
[ESS] Hoffman, P., "Enhanced Security Services for S/MIME",
RFC 2634, June 1999.
[PKIXCERT]
Housley, R., Ford, W., Polk, W., and D. Solo, "Internet
X.509 Public Key Infrastructure Certificate and
Certificate Revocation List (CRL) Profile", RFC 3280,
April 2002.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997.
Schaad Expires October 19, 2006 [Page 11]
Internet-Draft ESSCertID Update April 2006
Appendix A. ASN.1 Module
ExtendedSecurityServices-2006
{ iso(1) member-body(2) us(840) rsadsi(113549)
pkcs(1) pkcs-9(9) smime(16) modules(0) ess-2006(TBD) }
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
IMPORTS
-- Cryptographic Message Syntax (CMS)
ContentType, IssuerAndSerialNumber, SubjectKeyIdentifier,
AlgorithmIdentifier
FROM CryptographicMessageSyntax { iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) modules(0) cms(1)}
-- PKIX Certificate and CRL Profile, Sec A.2 Implicitly Tagged Module,
-- 1988 Syntax
PolicyInformation, CertificateSerialNumber, GeneralNames FROM
PKIX1Implicit88 {iso(1)
identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7)id-mod(0) id-pkix1-implicit(19)};
-- Extended Security Services
-- The construct "SEQUENCE SIZE (1..MAX) OF" appears in several ASN.1
-- constructs in this module. A valid ASN.1 SEQUENCE can have zero or
-- more entries. The SIZE (1..MAX) construct constrains the SEQUENCE to
-- have at least one entry. MAX indicates the upper bound is unspecified.
-- Implementations are free to choose an upper bound that suits their
-- environment.
UTF8String ::= [UNIVERSAL 12] IMPLICIT OCTET STRING
-- The contents are formatted as described in [UTF8]
-- Section 2.7
ReceiptRequest ::= SEQUENCE {
signedContentIdentifier ContentIdentifier,
receiptsFrom ReceiptsFrom,
receiptsTo SEQUENCE SIZE (1..ub-receiptsTo) OF GeneralNames }
ub-receiptsTo INTEGER ::= 16
id-aa-receiptRequest OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 1}
ContentIdentifier ::= OCTET STRING
Schaad Expires October 19, 2006 [Page 12]
Internet-Draft ESSCertID Update April 2006
id-aa-contentIdentifier OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 7}
ReceiptsFrom ::= CHOICE {
allOrFirstTier [0] AllOrFirstTier,
-- formerly "allOrNone [0]AllOrNone"
receiptList [1] SEQUENCE OF GeneralNames }
AllOrFirstTier ::= INTEGER { -- Formerly AllOrNone
allReceipts (0),
firstTierRecipients (1) }
-- Section 2.8
Receipt ::= SEQUENCE {
version ESSVersion,
contentType ContentType,
signedContentIdentifier ContentIdentifier,
originatorSignatureValue OCTET STRING }
id-ct-receipt OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-ct(1) 1}
ESSVersion ::= INTEGER { v1(1) }
-- Section 2.9
ContentHints ::= SEQUENCE {
contentDescription UTF8String (SIZE (1..MAX)) OPTIONAL,
contentType ContentType }
id-aa-contentHint OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 4}
-- Section 2.10
MsgSigDigest ::= OCTET STRING
id-aa-msgSigDigest OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 5}
-- Section 2.11
ContentReference ::= SEQUENCE {
contentType ContentType,
signedContentIdentifier ContentIdentifier,
originatorSignatureValue OCTET STRING }
Schaad Expires October 19, 2006 [Page 13]
Internet-Draft ESSCertID Update April 2006
id-aa-contentReference OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 10 }
-- Section 3.2
ESSSecurityLabel ::= SET {
security-policy-identifier SecurityPolicyIdentifier,
security-classification SecurityClassification OPTIONAL,
privacy-mark ESSPrivacyMark OPTIONAL,
security-categories SecurityCategories OPTIONAL }
id-aa-securityLabel OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 2}
SecurityPolicyIdentifier ::= OBJECT IDENTIFIER
SecurityClassification ::= INTEGER {
unmarked (0),
unclassified (1),
restricted (2),
confidential (3),
secret (4),
top-secret (5) } (0..ub-integer-options)
ub-integer-options INTEGER ::= 256
ESSPrivacyMark ::= CHOICE {
pString PrintableString (SIZE (1..ub-privacy-mark-length)),
utf8String UTF8String (SIZE (1..MAX))
}
ub-privacy-mark-length INTEGER ::= 128
SecurityCategories ::= SET SIZE (1..ub-security-categories) OF
SecurityCategory
ub-security-categories INTEGER ::= 64
SecurityCategory ::= SEQUENCE {
type [0] OBJECT IDENTIFIER,
value [1] ANY DEFINED BY type -- defined by type
}
--Note: The aforementioned SecurityCategory syntax produces identical
--hex encodings as the following SecurityCategory syntax that is
--documented in the X.411 specification:
--
--SecurityCategory ::= SEQUENCE {
Schaad Expires October 19, 2006 [Page 14]
Internet-Draft ESSCertID Update April 2006
-- type [0] SECURITY-CATEGORY,
-- value [1] ANY DEFINED BY type }
--
--SECURITY-CATEGORY MACRO ::=
--BEGIN
--TYPE NOTATION ::= type | empty
--VALUE NOTATION ::= value (VALUE OBJECT IDENTIFIER)
--END
-- Section 3.4
EquivalentLabels ::= SEQUENCE OF ESSSecurityLabel
id-aa-equivalentLabels OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 9}
-- Section 4.4
MLExpansionHistory ::= SEQUENCE
SIZE (1..ub-ml-expansion-history) OF MLData
id-aa-mlExpandHistory OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 3}
ub-ml-expansion-history INTEGER ::= 64
MLData ::= SEQUENCE {
mailListIdentifier EntityIdentifier,
expansionTime GeneralizedTime,
mlReceiptPolicy MLReceiptPolicy OPTIONAL }
EntityIdentifier ::= CHOICE {
issuerAndSerialNumber IssuerAndSerialNumber,
subjectKeyIdentifier SubjectKeyIdentifier }
MLReceiptPolicy ::= CHOICE {
none [0] NULL,
insteadOf [1] SEQUENCE SIZE (1..MAX) OF GeneralNames,
inAdditionTo [2] SEQUENCE SIZE (1..MAX) OF GeneralNames }
-- Section 5.4
SigningCertificate ::= SEQUENCE {
certs SEQUENCE OF ESSCertID,
policies SEQUENCE OF PolicyInformation OPTIONAL
}
Schaad Expires October 19, 2006 [Page 15]
Internet-Draft ESSCertID Update April 2006
id-aa-signingCertificate OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-aa(2) 12 }
SigningCertificateV2 ::= SEQUENCE {
certs SEQUENCE OF ESSCertIDv2,
policies SEQUENCE OF PolicyInformation OPTIONAL
}
id-aa-signingCertificateV2 OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-aa(2) XX }
id-sha256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101)
csor(3) nistalgorithm(4) hashalgs(2) 1 }
ESSCertIDv2 ::= SEQUENCE {
certHash Hash,
hashAlgorithm AlgorithmIdentifier DEFAULT {algorithm
id-sha256 parameters NULL}
issuerSerial IssuerSerial OPTIONAL
}
ESSCertID ::= SEQUENCE {
certHash Hash,
issuerSerial IssuerSerial OPTIONAL
}
Hash ::= OCTET STRING -- SHA1 hash of entire certificate
IssuerSerial ::= SEQUENCE {
issuer GeneralNames,
serialNumber CertificateSerialNumber
}
END -- of ExtendedSecurityServices-2006
Schaad Expires October 19, 2006 [Page 16]
Internet-Draft ESSCertID Update April 2006
Author's Address
Jim Schaad
Soaring Hawk Consulting
PO Box 675
Gold Bar, WA 98251
Phone: (425) 785-1031
Email: jimsch@exmsft.com
Schaad Expires October 19, 2006 [Page 17]
Internet-Draft ESSCertID Update April 2006
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Schaad Expires October 19, 2006 [Page 18]
