Network Working Group J. Schaad
Internet-Draft Soaring Hawk Consulting
Expires: September 3, 2006 M. Myers
TraceRoute Security, Inc.
March 2, 2006
Certificate Management Messages over CMS
draft-ietf-pkix-2797-bis-04.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 September 3, 2006.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document defines the base syntax for CMC, a Certificate
Management protocol using CMS (Cryptographic Message Syntax). This
protocol addresses two immediate needs within the Internet PKI
community:
1. The need for an interface to public key certification products
and services based on CMS and PKCS #10 (Public Key Crytpography
Schaad & Myers Expires September 3, 2006 [Page 1]
Internet-Draft CMS: Structures March 2006
Standard), and
2. The need in S/MIME (Secure MIME) for a certificate enrollment
protocol for DSA-signed certificates with Diffie-Hellman public
keys.
CMC also requires the use of the transport document and the
requirements usage document along with this document for a full
definition.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Protocol Requirements . . . . . . . . . . . . . . . . . . 4
1.2. Notation . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
2.2. Protocol Flow Charts . . . . . . . . . . . . . . . . . . . 8
3. Protocol Elements . . . . . . . . . . . . . . . . . . . . . . 10
3.1. PKIData Object . . . . . . . . . . . . . . . . . . . . . . 10
3.2. ResponseBody Object . . . . . . . . . . . . . . . . . . . 11
3.3. Certification Requests (PKCS10/CRMF) . . . . . . . . . . . 12
3.3.1. PKCS10 Request Body . . . . . . . . . . . . . . . . . 12
3.3.2. CRMF Request Body . . . . . . . . . . . . . . . . . . 13
3.3.3. Production of Diffie-Hellman Public Key
Certification Requests . . . . . . . . . . . . . . . . 14
3.4. Body Part Identifiers . . . . . . . . . . . . . . . . . . 15
3.5. Control Attributes . . . . . . . . . . . . . . . . . . . . 15
3.6. Content Info objects . . . . . . . . . . . . . . . . . . . 16
3.6.1. Signed Data . . . . . . . . . . . . . . . . . . . . . 17
3.6.2. Enveloped Data . . . . . . . . . . . . . . . . . . . . 17
3.6.3. Authenticated Data . . . . . . . . . . . . . . . . . . 17
3.7. Other Message Bodies . . . . . . . . . . . . . . . . . . . 18
3.8. Unsigned Attributes . . . . . . . . . . . . . . . . . . . 18
4. PKI Messages . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.1. Simple Enrollment Request . . . . . . . . . . . . . . . . 20
4.2. Full PKI Request . . . . . . . . . . . . . . . . . . . . . 20
4.3. Simple Enrollment Response . . . . . . . . . . . . . . . . 21
4.4. Full PKI Response . . . . . . . . . . . . . . . . . . . . 22
4.5. Application of Encryption to a PKI Message . . . . . . . . 22
5. Control Attributes . . . . . . . . . . . . . . . . . . . . . . 24
5.1. CMC Status Info Control Attributes . . . . . . . . . . . . 24
5.1.1. Extended CMC Status Info Control Attribute . . . . . . 25
5.1.2. CMC Status Info Control Attribute . . . . . . . . . . 26
5.1.3. CMCStatus values . . . . . . . . . . . . . . . . . . . 27
5.1.4. CMCFailInfo . . . . . . . . . . . . . . . . . . . . . 27
5.2. Identification and IdentityProof Control Attributes . . . 28
Schaad & Myers Expires September 3, 2006 [Page 2]
Internet-Draft CMS: Structures March 2006
5.2.1. Hardware Shared Secret Token Generation . . . . . . . 30
5.3. Linking Identity and POP Information . . . . . . . . . . . 30
5.3.1. Witness values derived from the shared-secret . . . . 30
5.3.2. Shared-secret/subject DN matching . . . . . . . . . . 31
5.3.3. Renewal and Re-Key Messages . . . . . . . . . . . . . 32
5.4. Data Return Control Attribute . . . . . . . . . . . . . . 32
5.5. RA Certificate Modification Controls . . . . . . . . . . . 33
5.5.1. Modify Certificate Request Control . . . . . . . . . . 33
5.5.2. Add Extensions Control . . . . . . . . . . . . . . . . 34
5.6. Transaction Management Control Attributes . . . . . . . . 36
5.7. Proof-of-possession (POP) for encryption-only keys . . . . 36
5.8. LRA POP Witnesses Control Attribute . . . . . . . . . . . 40
5.9. Get Certificate Control Attribute . . . . . . . . . . . . 40
5.10. Get CRL Control Attribute . . . . . . . . . . . . . . . . 41
5.11. Revocation Request Control Attribute . . . . . . . . . . . 42
5.12. Registration and Response Information Control
Attributes . . . . . . . . . . . . . . . . . . . . . . . . 43
5.13. Query Pending Control Attribute . . . . . . . . . . . . . 43
5.14. Confirm Certificate Acceptance . . . . . . . . . . . . . . 44
5.15. Publish Trust Roots . . . . . . . . . . . . . . . . . . . 45
5.16. Provide Autenticated Data . . . . . . . . . . . . . . . . 46
5.17. Batch Process Identification . . . . . . . . . . . . . . . 46
5.18. Publication Information Control . . . . . . . . . . . . . 46
5.19. Control Processed . . . . . . . . . . . . . . . . . . . . 47
6. Local Registration Authorities . . . . . . . . . . . . . . . . 48
6.1. Encryption Removal . . . . . . . . . . . . . . . . . . . . 49
6.2. Signature Layer Removal . . . . . . . . . . . . . . . . . 49
7. Security Considerations . . . . . . . . . . . . . . . . . . . 50
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 52
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 53
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 54
10.1. Normative References . . . . . . . . . . . . . . . . . . . 54
10.2. Informational References . . . . . . . . . . . . . . . . . 54
Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 56
Appendix B. Enrollment Message Flows . . . . . . . . . . . . . . 64
Appendix B.1. Request of a Signing Certificate . . . . . . . . . . 64
Appendix B.2. Single Certificate Request, But Modified by RA . . . 65
Appendix B.3. Indirect POP for an RSA certificate . . . . . . . . 68
Appendix C. Change History . . . . . . . . . . . . . . . . . . . 73
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 74
Intellectual Property and Copyright Statements . . . . . . . . . . 75
Schaad & Myers Expires September 3, 2006 [Page 3]
Internet-Draft CMS: Structures March 2006
1. Introduction
This document defines the base syntax for CMC, a Certificate
Management protocol using CMS (Cryptographic Message Syntax). This
protocol addresses two immediate needs within the Internet PKI
community:
1. The need for an interface to public key certification products
and services based on CMS and the PKCS #10 (Public Key
Cryptography Standard), and
2. The need in S/MIME (Secure MIME) for a certificate enrollment
protocol for DSA-signed certificates with Diffie-Hellman public
keys.
A small number of additional services are defined to supplement the
core certificate request service.
Throughout this specification the term CMS is used to refer to both
[CMS] and [PKCS7]. For both signedData and envelopedData, CMS is a
superset of the PKCS7. In general, the use of PKCS7 in this document
is aligned to the Cryptographic Message Syntax [CMS] that provides a
superset of the PKCS7 syntax. The term CMC refers to this
specification.
1.1. Protocol Requirements
o The protocol is to be based as much as possible on the existing
CMS, PKCS#10 and CRMF specifications.
o The protocol must support the current industry practice of a
PKCS#10 request followed by a PKCS#7 response as a subset of the
protocol.
o The protocol needs to easily support the multi-key enrollment
protocols required by S/MIME and other groups.
o The protocol must supply a way of doing all operations in a
single-round trip. When this is not possible the number of round
trips is to be minimized.
o The protocol will be designed such that all key generation can
occur on the client.
o The mandatory algorithms must superset the required algorithms for
S/MIME.
Schaad & Myers Expires September 3, 2006 [Page 4]
Internet-Draft CMS: Structures March 2006
o The protocol will contain POP methods. Optional provisions for
multiple-round trip POP will be made if necessary.
o The protocol will support deferred and pending responses to
certificate request for cases where external procedures are
required to issue a certificate.
o The protocol needs to support arbitrary chains of local
registration authorities as intermediaries between certificate
requesters and issuers.
1.2. 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 & Myers Expires September 3, 2006 [Page 5]
Internet-Draft CMS: Structures March 2006
2. Protocol Overview
An enrollment transaction in this specification is generally composed
of a single round trip of messages. In the simplest case an
enrollment request is sent from the client to the server and an
enrollment response is then returned from the server to the client.
In some more complicated cases, such as delayed certificate issuance
and polling for responses, more than one round trip is required.
This specification supports two different request messages and two
different response messages.
Public key certification requests can be based on either the PKCS10
or CRMF object. The two different request messages are (a) the bare
PKCS10 (in the event that no other services are needed), and (b) the
PKCS10 or CRMF message wrapped in a CMS encapsulation as part of a
PKIData object.
Public key certification responses are based on the CMS signedData
object. The response may be either (a) a degenerate CMS signedData
object (in the event no other services are needed), or (b) a
ResponseBody object wrapped in a CMS signedData object.
No special services are provided for doing either renewal (new
certificates with the same key) or re-keying (new certificates on new
keys) of clients. Instead a renewal/re-key message looks the same as
any enrollment message, with the identity proof being supplied by
existing certificates from the CA.
No special services are provided to distinguish between doing a re-
keying operation and obtaining a new certificate (generally for a new
purpose). A control to unpublish a certificate would normally be
included in a replacement operation, and be omitted if a new
certificate was desired. CAs or other publishing agents are also
expected to have policies for removing certificates from publication
either based on new certificates being added or the expiration or
revocation of a certificate.
A provision exists for Local Registration Authorities (LRAs) to
participate in the protocol by taking client enrollment messages,
wrapping them in a second layer of enrollment message with additional
requirements or statements from the LRA and then passing this new
expanded request on to the Certification Authority.
This specification makes no assumptions about the underlying
transport mechanism. The use of CMS is not meant to imply an email-
based transport.
Schaad & Myers Expires September 3, 2006 [Page 6]
Internet-Draft CMS: Structures March 2006
Optional services available through this specification are
transaction management, replay detection (through nonces), deferred
certificate issuance, certificate revocation requests and
certificate/CRL retrieval.
2.1. Terminology
There are several different terms, abbreviations and acronyms used in
this document that we define here for convenience and consistency of
usage:
End-Entity (EE) refers to the entity that owns a key pair and for
whom a certificate is issued.
LRA or "RA" refers to a (Local) Registration Authority. A
registration authority acts as an intermediary between an End-
Entity and a Certification Authority. Multiple RAs can exist
between the End-Entity and the Certification Authority.
CA refers to a Certification Authority. A Certification Authority is
the entity that performs the actual issuance of a certificate.
Client refers to an entity that creates a PKI request. In this
document both RAs and End-Entities can be clients.
Server refers to the entities that process PKI requests and create
PKI responses. CAs and RAs can be servers in this document.
PKCS#10 refers the Public Key Cryptography Standard #10. This is one
of a set of standards defined by RSA Laboratories in the 1980s.
PKCS#10 defines a Certificate Request Message syntax.
CRMF refers to the Certificate Request Message Format RFC [CRMF]. We
are using certificate request message format defined in this
document as part of our management protocol.
CMS refers to the Cryptographic Message Syntax RFC [CMS]. This
document provides for basic cryptographic services including
encryption and signing with and without key management.
POP is an acronym for "Proof of Possession". POP refers to a value
that can be used to prove that the private key corresponding to a
public key is in the possession and can be used by an end-entity.
Transport wrapper refers to the outermost CMS wrapping layer.
Schaad & Myers Expires September 3, 2006 [Page 7]
Internet-Draft CMS: Structures March 2006
2.2. Protocol Flow Charts
Figure 1 shows the Simple Enrollment Request and Response messages.
The contents of these messages are detailed in Sections 4.1 and 4.3
below.
Simple PKI Request Simple PKI Response
------------------------- --------------------------
+----------+ +------------------+
| PKCS #10 | | CMS "certs-only" |
+----------+--------------+ | message |
| | +------------------+------+
| Certificate Request | | |
| | | CMS Signed Data, |
| Subject Name | | no signerInfo |
| Subject Public Key Info | | |
| (K_PUB) | | signedData contains one |
| Attributes | | or more certificates in |
| | | the "certificates" |
+-----------+-------------+ | portion of the |
| signed with | | signedData. |
| matching | | |
| K_PRIV | | encapsulatedContentInfo |
+-------------+ | is empty. |
| |
+--------------+----------+
| unsigned |
+----------+
Figure 1: Simple PKI Request and Response Messages
Schaad & Myers Expires September 3, 2006 [Page 8]
Internet-Draft CMS: Structures March 2006
Full PKI Request Full PKI Response
----------------------- ------------------------
+----------------+ +----------------+
| CMS signedData | | CMS signedData |
| object | | object |
+----------------+--------+ +----------------+--------+
| | | |
| PKIData object | | ResponseBody object |
| | | |
| Sequence of: | | Sequence of: |
| <enrollment attribute>* | | <enrollment attribute>* |
| <certification request>*| | <CMS object>* |
| <CMS objects>* | | <other message>* |
| <other message>* | | |
| | | where * == zero or more |
| where * == zero or more | | |
| | | All certificates issued |
| Certificate requests | | as part of the response |
| are CRMF or PKCS#10 | | are included in the |
| objects. Attributes are | | "certificates" portion |
| (OID, ANY defined by | | of the signedData. |
| OID) pairs. | | Relevant CA certs and |
| | | CRLs can be included as |
+-------+-----------------+ | well. |
| signed (keypair | | |
| used may be pre-| +---------+---------------+
| existing or | | signed by the |
| identified in | | CA or an LRA |
| the request) | +---------------+
+-----------------+
Figure 2: Full PKI Request and Response Messages
Figure 2 shows the Full Enrollment Request and Response messages.
The contents of these messages are detailed in Sections 4.2 and 4.4
below.
Schaad & Myers Expires September 3, 2006 [Page 9]
Internet-Draft CMS: Structures March 2006
3. Protocol Elements
This section covers each of the different elements that may be used
to construct enrollment request and enrollment response messages.
Section 4 will cover how to build the enrollment request and response
messages.
3.1. PKIData Object
The new content object PKIData has been defined for this protocol.
This new object is used as the body of the full PKI request message.
The new body is identified by:
id-cct-PKIData ::= {id-pkix id-cct(12) 2 }
The ASN.1 structure corresponding to this new content type is:
PKIData ::= SEQUENCE {
controlSequence SEQUENCE SIZE(0..MAX) OF TaggedAttribute,
reqSequence SEQUENCE SIZE(0..MAX) OF TaggedRequest,
cmsSequence SEQUENCE SIZE(0..MAX) OF TaggedContentInfo,
otherMsgSequence SEQUENCE SIZE(0..MAX) OF OtherMsg
}
controlSequence consists of a sequence of control attributes. The
control attributes defined in this document are found in section
5. As control sequences are defined by OIDs, other parties can
define additional control attributes. Unrecognized OIDs MUST
result in no part of the request being successfully processed.
reqSequence consists of a sequence of requests. The requests can be
a CertificateRequest (PKCS10 request), a CertReqMsg or an
externally defined request (orm). Details on the first two
request types are found in sections 3.3.1 and 3.3.2 respectively.
If an externally defined request message is present, but the
server does not understand the request (or will not process it), a
CMCStatus of noSupport MUST be returned for the request item and
no requests processed.
cmsSequence consists of a sequence of [CMS] message objects. This
protocol uses EnvelopedData, SignedData, EncryptedData and
AuthenticatedData. See section 3.6 for more details.
otherMsgSequence allows for other arbitrary data items to be placed
into the enrollment protocol. The {OID, any} pair of values
allows for arbitrary definition of material. Data objects are
placed here while control objects are placed in the
controlSequence field. See section 3.7 for more details.
Schaad & Myers Expires September 3, 2006 [Page 10]
Internet-Draft CMS: Structures March 2006
Processing of this object by a recipient is as follows:
1. All control attributes should be examined and processed in an
appropriate manner. The appropriate processing may be either to
do complete processing at this time, ignore the control attribute
or to place the control attribute on a to-do list for later
processing.
2. An implicit control attribute is then processed for each item in
the reqSequence. Again this may be either immediate processing
or addition to a to-do list for later processing.
No processing is required for cmsSequence or otherMsgSequence members
of the element. If items are present and are not referenced by a
control sequence, they are to be ignored.
3.2. ResponseBody Object
The new content object ResponseBody has been defined for this
protocol. This new object is used as the body of the full PKI
response message. The new body is identified by:
id-cct-PKIResponse ::= {id-pkix id-cct(12) 3 }
The ASN.1 structure corresponding to this body content type is:
ResponseBody ::= SEQUENCE {
controlSequence SEQUENCE SIZE(0..MAX) OF TaggedAttribute,
cmsSequence SEQUENCE SIZE(0..MAX) OF TaggedContentInfo,
otherMsgSequence SEQUENCE SIZE(0..MAX) OF OtherMsg
}
controlSequence consists of a sequence of control attributes. The
control attributes defined in this document are found in section
3.5. Other parties can define additional control attributes.
cmsSequence consists of a sequence of [CMS] message objects. This
protocol only uses EnvelopedData, SignedData, EncryptedData and
AuthenticatedData. See section 3.6 for more details.
otherMsgSequence allows for other arbitrary items to be placed into
the enrollment protocol. The {OID, any} pair of values allows for
arbitrary definition of material. Data objects are placed here
while control objects are placed in the controlSequence field.
See section 3.7 for more details.
Processing of this object by a recipient is as follows:
Schaad & Myers Expires September 3, 2006 [Page 11]
Internet-Draft CMS: Structures March 2006
1. All control attributes should be examined and processed in an
appropriate manner. The appropriate processing may be either to
do complete processing at this time, ignore the control attribute
or to place the control attribute on a to-do list for later
processing.
2. Additional processing of non-element items includes the saving of
certificates and CRLs present in wrapping layers. This type of
processing is based on the consumer of the element and should not
be relied on by generators.
No processing is required for cmsSequence or otherMsgSequence members
of the element. If items are present and are not referenced by a
control sequence, they are to be ignored.
3.3. Certification Requests (PKCS10/CRMF)
Certification Requests are based on either PKCS10 or CRMF messages.
Section 3.3.1 specifies mandatory and optional requirements for
clients and servers dealing with PKCS10 request messages. Section
3.3.2 specifies mandatory and optional requirements for clients and
servers dealing with CRMF request messages.
All certificate requests directly encoded into a single PKIData
object SHOULD be for the same identity. RAs that batch processing
are expected to place the signed PKIData sequences received into the
cmsSequence of the PKIData object it generates.
3.3.1. PKCS10 Request Body
Servers MUST be able to understand and process PKCS10 request bodies.
Clients MUST produce a PKCS10 request body when using the Simple
Enrollment Request message. Clients MAY produce a PKCS10 request
body when using the Full Enrollment Request message.
When producing a PKCS10 request body, clients MUST produce a PKCS10
message body containing a subject name and public key. Some
certification products are operated using a central repository of
information to assign subject names upon receipt of a public key for
certification. To accommodate this mode of operation, the subject
name in a CertificationRequest MAY be NULL, but MUST be present. CAs
that receive a CertificationRequest with a NULL subject name MAY
reject such requests. If rejected and a response is returned, the CA
MUST respond with the failInfo attribute of badRequest.
The client MAY incorporate one or more standard X.509 v3 extensions
in any PKCS10 request as an ExtensionReq attribute. An ExtensionReq
attribute is defined as
Schaad & Myers Expires September 3, 2006 [Page 12]
Internet-Draft CMS: Structures March 2006
ExtensionReq ::= SEQUENCE OF Extension
where Extension is imported from [PKIXCERT] and ExtensionReq is
identified by {pkcs-9 14}.
Servers MUST be able to process all extensions defined, but not
prohibited, in [PKIXCERT]. Servers are not required to be able to
process other V3 X.509 extensions transmitted using this protocol,
nor are they required to be able to process other, private
extensions. Servers are not required to put all client-requested
extensions into a certificate. Servers are permitted to modify
client-requested extensions. Servers MUST NOT alter an extension so
as to invalidate the original intent of a client-requested extension.
(For example, changing key usage from key exchange to signing.) If a
certification request is denied due to the inability to handle a
requested extension and a response is returned, the server MUST
respond with the failInfo attribute of unsupportedExt.
3.3.2. CRMF Request Body
Servers MUST be able to understand and process CRMF request body.
Clients MAY produce a CRMF message body when using the Full
Enrollment Request message.
This memo imposes the following additional changes on the
construction and processing of CRMF messages:
o When CRMF message bodies are used in the Full Enrollment Request
message, each CRMF message MUST include both the subject and
publicKey fields in the CertTemplate. As in the case of PKCS10
requests, the subject may be encoded as NULL, but MUST be present.
o When both CRMF and CMC controls exist with equivalent
functionality, the CMC control SHOULD be used. The CMC control
MUST override the CRMF control.
o The regInfo field MUST NOT be used on a CRMF message. Equivalent
functionality is provided in the regInfo control attribute
(section 5.12).
o The indirect method of proving POP is not supported in this
protocol. One of the other methods (including the direct method
described in this document) MUST be used instead if POP is
desired. The value of encrCert in SubsequentMessage MUST NOT be
used.
o Since the subject and publicKeyValues are always present, the
POPOSigningKeyInput MUST NOT be used when computing the value for
Schaad & Myers Expires September 3, 2006 [Page 13]
Internet-Draft CMS: Structures March 2006
POPSigningKey.
A server is not required to use all of the values suggested by the
client in the certificate template. Servers MUST be able to process
all extensions defined, but not prohibited in [PKIXCERT]. Servers
are not required to be able to process other V3 X.509 extension
transmitted using this protocol, nor are they required to be able to
process other, private extensions. Servers are permitted to modify
client-requested extensions. Servers MUST NOT alter an extension so
as to invalidate the original intent of a client-requested extension.
(For example change key usage from key exchange to signing.) If a
certificate request is denied due to the inability to handle a
requested extension, the server MUST respond with a failInfo
attribute of unsupportedExt.
3.3.3. Production of Diffie-Hellman Public Key Certification Requests
Part of a certification request is a signature over the request;
Diffie-Hellman is a key agreement algorithm and cannot be used to
directly produce the required signature object. [DH-POP] provides
two ways to produce the necessary signature value. This document
also defines a signature algorithm that does not provide a POP value,
but can be used to produce the necessary signature value.
3.3.3.1. No-Signature Signature Mechanism
Key management (encryption/decryption) private keys cannot always be
used to produce some type of signature value as they can be in a
decrypt only device. Certification requests require that the
signature field be populated. This section provides a signature
algorithm specifically for that purposes. The following object
identifier and signature value are used to identify this signature
type:
id-alg-noSignature OBJECT IDENTIFIER ::= {id-pkix id-alg(6) 2}
NoSignatureValue ::= OCTET STRING
The parameters for id-alg-noSignature MUST be present and MUST be
encoded as NULL. NoSignatureValue contains the hash of the
certification request. It is important to realize that there is no
security associated with this signature type. If this signature type
is on a certification request and the Certification Authority policy
requires proof-of-possession of the private key, the POP mechanism
defined in section 5.7 MUST be used.
Schaad & Myers Expires September 3, 2006 [Page 14]
Internet-Draft CMS: Structures March 2006
3.3.3.2. Diffie-Hellman POP Discrete Logarithm Signature
CMC compliant implementations MUST support section 4 of [DH-POP].
3.3.3.3. Diffie-Hellman MAC signature
CMC compliant implementations MAY support section 3 of [DH-POP].
3.4. Body Part Identifiers
Each element of a PKIData or PKIResponse message has an associated
body part identifier. The body part identifier is a 4-octet integer
encoded in the certReqIds field for CertReqMsg objects (in a
TaggedRequest) or in the bodyPartID field of the other objects. The
body part identifier MUST be unique within a single PKIData or
PKIResponse object. Body part identifiers can be duplicated in
different layers (for example a CMC message embedded within another).
The body part Identifier of zero is reserved to designate the current
PKIData object. This value is used in control attributes such as the
Add Extensions Control in the pkiDataReference field to refer to a
request in the current PKIData object.
Some control attribute, such as the CMC Status Info attribute, will
also use body part identifiers to refer to elements in the previous
message. This allows an error to be explicit about the attribute or
request to which the error applies.
3.5. Control Attributes
The overall control flow of how a message is processed in this
document is based on the control attributes. Each control attribute
consists of an object identifier and a value based on the object
identifier.
The final server MUST fail the processing of an entire PKIData
message if any included control attribute is not recognized and that
control is not already marked as processed by id-cmc-
controlProcessed. The response MUST be the error badRequest and
bodyList MUST contain the bodyPartID of the invalid or unrecognized
control attribute(s). A server is the final server if and only if
(1) it is not generating a error response for another reason and (2)
it is not going to process and pass the request on to another server
for processing.
The syntax of a control attribute is
Schaad & Myers Expires September 3, 2006 [Page 15]
Internet-Draft CMS: Structures March 2006
TaggedAttribute ::= SEQUENCE {
bodyPartID BodyPartID,
attrType OBJECT IDENTIFIER,
attrValues SET OF AttributeValue
}
bodyPartID is a unique integer that is used to reference this control
attribute. The id of 0 is reserved for use as the reference to
the current PKIData object.
attrType is the OID defining the associated data in attrValues
attrValues contains the set of data values used in processing the
control attribute.
The set of control attributes that are defined by this memo are found
in section 5.
3.6. Content Info objects
The cmsSequence field of the PKIRequest and PKIResponse messages
contains zero or more tagged content info objects. The syntax for
this structure is
TaggedContentInfo ::= SEQUENCE {
bodyPartID BodyPartID,
contentInfo ContentInfo
}
bodyPartID is a unique integer that is used to reference this content
info object. The id of 0 is reserved for use as the reference to
the current PKIData object.
contentInfo contains a ContentInfo object (defined in [CMS]).
The four contents used in this location are SignedData,
EnvelopedData, AuthenticatedData and Data.
EnvelopedData provides for shrouding of data.
Data allows for general transport of unstructured data.
SignedData object from [CMS] is also used in this specification to
provide for authentication as well as serving as the general
transport wrapper of requests and responses.
Schaad & Myers Expires September 3, 2006 [Page 16]
Internet-Draft CMS: Structures March 2006
AuthenticatedData provides a method of doing pass phrase based
validation of data being sent between two parties. Unlike
SignedData it does not specify which party actually generated the
information.
3.6.1. Signed Data
The signedData object is used in two different locations when
constructing enrollment messages. The signedData object is used as a
wrapper for a PKIData as part of the enrollment request message. The
signedData object is also used as the outer part of an enrollment
response message.
As part of processing a message the signature(s) MUST be verified.
If the signature does not verify, and the body contains anything
other than a status response, a new message containing a status
response MUST be returned using a CMCFailInfo with a value of
badMessageCheck and a bodyPart of 0.
For the enrollment response the signedData wrapper allows the server
to sign the returning data, if any exists, and to carry the
certificates and CRLs for the enrollment request. If no data is
being returned beyond the certificates, no signerInfo objects are
placed in the signedData object.
3.6.2. Enveloped Data
EnvelopedData is the primary method of providing confidentiality for
sensitive information in this protocol. The protocol currently uses
EnvelopedData to provide encryption of an entire request (see section
4.5). The envelopedData object would also be used to wrap private
key material for key archival. If the decryption on an envelopedData
failes, the response is a CMCFailInfo with a value of badMessageCheck
and a bodyPart of 0.
Servers MUST implement envelopedData according to [CMS]. There is an
ambiguity (about encrypting content types other than id-data) in the
PKCS7 specification that has lead to non-interoperability.
3.6.3. Authenticated Data
AuthenticatedData is used for providing origination authentication in
those circumstances where a shared-secret exists, but a PKI trust
anchor has not yet been established. This is currently only used for
the id-cmc-authData control (section 5.2.16). This control is uses
the PKIData body so that new controls with additional policy type
information could be included as well.
Schaad & Myers Expires September 3, 2006 [Page 17]
Internet-Draft CMS: Structures March 2006
3.7. Other Message Bodies
The other message body portion of the message allows for arbitrary
data objects to be carried as part of a message. This is intended to
contain data that is not already wrapped in a CMS contentInfo object.
The data is ignored unless a control attribute references the data by
bodyPartID.
OtherMsg ::= SEQUENCE {
bodyPartID BodyPartID,
otherMsgType OBJECT IDENTIFIER,
otherMsgValue ANY DEFINED BY otherMsgType }
bodyPartID contains the unique id of this object
otherMsgType contains the OID defining both the usage of this body
part and the syntax of the value associated with this body part
otherMsgValue contains the data associated with the message body
part.
3.8. Unsigned Attributes
There is sometimes a need to include data in an enrollment message
designed to be removed during processing. An example of this is the
inclusion of an encrypted private key, where a key archive agent
removes the encrypted private key before sending it on to the CA.
One side effect of this desire is the fact that every RA which
encapsulates this information needs to move the data so that it is
not covered by the RA signature. (A client request, encapsulated by
an RA cannot have the unsigned attribute removed by the key archive
agent without breaking the RA's signature.) This attribute addresses
that problem.
This attribute is used to contain the information that is not
directly signed by a user. When an RA finds a message that has this
attribute in the unsigned or unauthenticated attribute fields of the
CMS objects it is aggregating, they are removed from the embedded CMS
objects and propagated up to the RA CMS object.
id-aa-cmc-unsignedData OBJECT IDENTIFIER ::= {id-aa 34}
CMCUnsignedData ::= SEQUENCE {
bodyPartPath SEQUENCE SIZE (1..MAX) OF BodyPartID,
identifier OBJECT IDENTIFIER,
content ANY DEFINED BY identifier
}
Schaad & Myers Expires September 3, 2006 [Page 18]
Internet-Draft CMS: Structures March 2006
There MUST be at most one CMCUnsignedData attribute in the
UnsignedAttribute sequence of a SignerInfo structure. The attribute
can have any number of attribute values greater than zero. If the
attribute appears in one SignerInfo in a sequence, it MUST appear the
same in all SignerInfo items and MUST have the same value(s).
Schaad & Myers Expires September 3, 2006 [Page 19]
Internet-Draft CMS: Structures March 2006
4. PKI Messages
This section discusses the details of putting together the different
enrollment request and response messages.
4.1. Simple Enrollment Request
The simplest form of an enrollment request is a plain PKCS10 message.
If this form of enrollment request is used for a private key that is
capable of generating a signature, the PKCS10 MUST be signed with
that private key. If this form of the enrollment request is used for
a D-H key, then the D-H POP mechanism described in [DH-POP] MUST be
used.
Servers MUST support the Simple Enrollment Request message. If the
Simple Enrollment Request message is used, servers MUST return the
Simple Enrollment Response message (see Section 4.3) if the
enrollment request is granted. If the enrollment request fails, the
Full Enrollment Response MAY be returned or no response MAY be
returned.
The Simple Enrollment Request message MUST NOT be used if a proof-of-
identity needs to be included.
Many advanced services specified in this memo are not supported by
the Simple Enrollment Request message.
4.2. Full PKI Request
The Full Enrollment Request provides the most functionality and
flexibility. Clients SHOULD use the Full Enrollment Request message
when enrolling. Servers MUST support the Full Enrollment Request
message. An enrollment response (full or simple as appropriate) MUST
be returned to all Full Enrollment Requests.
The Full Enrollment Request message consists of a PKIData object
wrapped in a signedData CMS object. The objects in the PKIData are
ordered as follows:
1. All Control Attributes,
2. All certification requests,
3. All CMS objects,
4. All other messages.
Each object in the PKIData sequence is identified by a Body Part
Schaad & Myers Expires September 3, 2006 [Page 20]
Internet-Draft CMS: Structures March 2006
Identifier. If duplicate ids are found, the server MUST return the
error badRequest with a bodyPartID of 0.
The signedData object wrapping the PKIData may be signed either by
the private key material of the signature certification request, or
by a previously certified signature key. If the private key of a
signature certification request is being used, then:
the certification request containing the corresponding public key
MUST include a Subject Key Identifier extension,
the subjectKeyIdentifier form of signerInfo MUST be used, and
the value of the subjectKeyIdentifier form of signerInfo MUST be
the Subject Key Identifier specified in the corresponding
certification request.
(The subjectKeyIdentifier form of signerInfo is used here because no
certificates have yet been issued for the signing key.) If the
request key is used for signing, there MUST be only one signerInfo
object in the signedData object.
When creating a message to renew a certificate, the following should
be taken into consideration:
1. The identification and identityProof control statements are not
required. The same information is provided by the use of an
existing certificate from the CA when signing the enrollment
message.
2. CAs and LRAs may impose additional restrictions on the signing
certificate used. They may require that the most recently issued
signing certificate for an entity be used.
3. A renewal message may occur either by creating a new set of keys,
or by re-using an existing set of keys. Some CAs may prevent re-
use of keys by policy. In this case the CA MUST return
NOKEYREUSE as the failure code.
4.3. Simple Enrollment Response
Servers SHOULD use the simple enrollment response message whenever
possible. Clients MUST be able to process the simple enrollment
response message. The simple enrollment response message consists of
a signedData object with no signerInfo objects on it. The
certificates requested are returned in the certificate bag of the
signedData object.
Schaad & Myers Expires September 3, 2006 [Page 21]
Internet-Draft CMS: Structures March 2006
Clients MUST NOT assume the certificates are in any order. Servers
SHOULD include all intermediate certificates needed to form complete
chains to one or more trust anchors, not just the newly issued
certificate(s). The server MAY additionally return CRLs in the CRL
bag. Servers MAY include the self-signed certificates. Clients MUST
NOT implicitly trust included self-signed certificate(s) merely due
to its presence in the certificate bag. In the event clients receive
a new self-signed certificate from the server, clients SHOULD provide
a mechanism to enable the user to explicitly trust the certificate.
4.4. Full PKI Response
Servers MUST return full PKI response messages if a) a full PKI
request message failed or b) additional services other than returning
certificates are required. Servers MAY return full PKI responses
with failure information for simple PKI requests. Following section
4.3 above, servers returning only certificates and a success status
to the client SHOULD use the simple PKI response message.
Clients MUST be able to process a full PKI response message.
The full enrollment response message consists of a signedData object
encapsulating a responseBody object. In a responseBody object all
Control Attributes MUST precede all CMS objects. The certificates
granted in an enrollment response are returned in the certificates
field of the immediately encapsulating signedData object.
Clients MUST NOT assume the certificates are in any order. Servers
SHOULD include all intermediate certificates needed to form complete
chains one or more trust anchors, not just the newly issued
certificate(s). The server MAY additionally return CRLs in the CRL
bag. Servers MAY include the self-signed certificates. Clients MUST
NOT implicitly trust included self-signed certificate(s) merely due
to its presence in the certificate bag. In the event clients receive
a new self-signed certificate from the server, clients SHOULD provide
a mechanism to enable the user to explicitly trust the certificate.
(The publish trust root control exists for the purpose of allowing
for distribution of root certificates. If a trusted root publishes a
new trusted root, this is one case where automated trust of the new
root could be allowed.)
4.5. Application of Encryption to a PKI Message
There are occasions where a PKI request or response message must be
encrypted in order to prevent any information about the enrollment
from being accessible to unauthorized entities. This section
describes the means used to encrypt a PKI message. This section is
not applicable to a simple enrollment message.
Schaad & Myers Expires September 3, 2006 [Page 22]
Internet-Draft CMS: Structures March 2006
Confidentiality is provided by wrapping the PKI message (a signedData
object) in a CMS EnvelopedData object. The nested content type in
the EnvelopedData is id-signedData. Note that this is different from
S/MIME where there is a MIME layer placed between the encrypted and
signed data objects. It is recommended that if an enveloped data
layer is applied to a PKI message, a second signing layer be placed
outside of the enveloped data layer. The following figure shows how
this nesting would be done:
Normal Option 1 Option 2
------ -------- --------
SignedData EnvelopedData SignedData
PKIData SignedData EnvelopedData
PKIData SignedData
PKIData
Options 1 and 2 provide the benefit of preventing leakage of
sensitive data by encrypting the information. LRAs can remove the
enveloped data wrapping, and replace or forward without further
processing. Section 6 contains more information about LRA
processing.
PKI Messages MAY be encrypted or transmitted in the clear. Servers
MUST provided support for all three versions.
Alternatively, an authenticated, secure channel could exist between
the parties requiring encryption. Clients and servers MAY use such
channels instead of the technique described above to provide secure,
private communication of PKI request and response messages.
Schaad & Myers Expires September 3, 2006 [Page 23]
Internet-Draft CMS: Structures March 2006
5. Control Attributes
Control attributes are carried as part of both PKI requests and
responses. Each control attribute is encoded as a unique Object
Identifier followed by that data for the control attribute. The
encoding of the data is based on the control attribute object
identifier. Processing systems would first detect the OID and
process the corresponding attribute value prior to processing the
message body.
The following table lists the names, OID and syntactic structure for
each of the control attributes documented in this memo.
Control Attribute OID Syntax
----------------- ---------- --------------
id-cmc-statusInfo id-cmc 1 CMCStatusInfo
id-cmc-identification id-cmc 2 UTF8String
id-cmc-identityProof id-cmc 3 OCTET STRING
id-cmc-dataReturn id-cmc 4 OCTET STRING
id-cmc-transactionId id-cmc 5 INTEGER
id-cmc-senderNonce id-cmc 6 OCTET STRING
id-cmc-recipientNonce id-cmc 7 OCTET STRING
id-cmc-addExtensions id-cmc 8 AddExtensions
id-cmc-encryptedPOP id-cmc 9 EncryptedPOP
id-cmc-decryptedPOP id-cmc 10 DecryptedPOP
id-cmc-lraPOPWitness id-cmc 11 LraPOPWitness
id-cmc-getCert id-cmc 15 GetCert
id-cmc-getCRL id-cmc 16 GetCRL
id-cmc-revokeRequest id-cmc 17 RevokeRequest
id-cmc-regInfo id-cmc 18 OCTET STRING
id-cmc-responseInfo id-cmc 19 OCTET STRING
id-cmc-queryPending id-cmc 21 OCTET STRING
id-cmc-popLinkRandom id-cmc 22 OCTET STRING
id-cmc-popLinkWitness id-cmc 23 OCTET STRING
id-cmc-confirmCertAcceptance id-cmc 24 CMCCertId
id-cmc-statusInfoEx id-cmc 25 CMCStatusInfoEx
id-cmc-trustedRoots id-cmc 26 PublishTrustRoots
id-cmc-authData id-cmc 27 AuthPublish
id-cmc-batchRequests id-cmc 28 BodyPartList
id-cmc-batchResponses id-cmc 29 BodyPartList
id-cmc-publishCert id-cmc 30 CMCPublicationInfo
id-cmc-modCertTemplate id-cmc 31 ModCertTemplate
id-cmc-controlProcessed id-cmc 32 ControlsProcessed
5.1. CMC Status Info Control Attributes
The CMC status info control is used in full PKI Response messages to
return information about the processing of a client request. Two
Schaad & Myers Expires September 3, 2006 [Page 24]
Internet-Draft CMS: Structures March 2006
controls are described in this section. The first is the preferred
control; the second is included for backwards compatibility with RFC
2797.
Servers MAY emit multiple CMC status info controls referring to a
single body part. Clients MUST be able to deal with multiple CMC
status info controls in a response message. Servers MUST use the
CMCStatusInfoEx control, but MAY additionally use the CMCStatusInfo
control. Clients MUST be able to process the CMCStatusInfoEx
control.
5.1.1. Extended CMC Status Info Control Attribute
This control uses the following ASN.1 definition:
CMCStatusInfoEx ::= SEQUENCE {
cMCStatus CMCStatus,
bodyList SEQUENCE SIZE (1..MAX) OF
BodyPartReference,
statusString UTF8String OPTIONAL,
otherInfo CHOICE {
failInfo CMCFailInfo,
pendInfo PendInfo,
extendedFailInfo SEQUENCE {
failInfoOID OBJECT IDENTIFIER,
failInfoValue AttributeValue }
} OPTIONAL
}
BodyPartReference ::= CHOICE {
bodyPartID BodyPartID,
bodyPartPath SEQUENCE SIZE (1..MAX) OF BodyPartID
}
PendInfo ::= SEQUENCE {
pendToken OCTET STRING,
pendTime GeneralizedTime
}
cMCStatus is described in section 5.1.3
bodyList contains the list of references to body parts in the request
message to which this status information applies. If an error is
being returned for a simple enrollment message, body list will
contain a single integer of value '1'.
Schaad & Myers Expires September 3, 2006 [Page 25]
Internet-Draft CMS: Structures March 2006
statusString contains a string with additional description
information. This string is human readable.
failInfo is described in section 5.1.4. It provides a detailed error
on what the failure was. This choice is present only if cMCStatus
is failed.
extendedFailInfo is provided for other users of the enrollment
protocol to provided their own error codes. This choice is
present only if cMCStatus is failed. Caution should be used in
defining new values as they may not be correctly recognized by all
clients and servers. The failInfo value of internalCA error may
be assumed if the extended error is not recognized.
pendToken is the token to be used in the queryPending control
attribute.
pendTime contains the suggested time the server wants to be queried
about the status of the request.
If the cMCStatus field is success, the CMC Status Info Control MAY be
omitted unless it is only item in the response message. If no status
exists for a certificate request or other item requiring processing,
then the value of success is to be assumed.
5.1.2. CMC Status Info Control Attribute
The CMC status info control is used in full PKI Response messages to
return information on a client request. Servers MAY emit multiple
CMC status info controls referring to a single body part. Clients
MUST be able to deal with multiple CMC status info controls in a
response message. This statement uses the following ASN.1
definition:
CMCStatusInfo ::= SEQUENCE {
cMCStatus CMCStatus,
bodyList SEQUENCE SIZE (1..MAX) OF BodyPartID,
statusString UTF8String OPTIONAL,
otherInfo CHOICE {
failInfo CMCFailInfo,
pendInfo PendInfo } OPTIONAL
}
cMCStatus is described in section 5.1.3
Schaad & Myers Expires September 3, 2006 [Page 26]
Internet-Draft CMS: Structures March 2006
bodyList contains the list of body parts in the request message to
which this status information applies. If an error is being
returned for a simple enrollment message, body list will contain a
single integer of value '1'.
statusString contains a string with additional description
information. This string is human readable.
failInfo is described in section 5.1.4. It provides a detailed error
on what the failure was. This choice is present only if cMCStatus
is failed.
If the cMCStatus field is success, the CMC Status Info Control MAY be
omitted unless it is only item in the response message. If no status
exists for a certificate request or other item requiring processing,
then the value of success is to be assumed.
5.1.3. CMCStatus values
CMCStatus is a field in the CMCStatusInfo structure. This field
contains a code representing the success or failure of a specific
operation. CMCStatus has the ASN.1 structure of:
CMCStatus ::= INTEGER {
success (0),
-- request was granted
-- reserved (1),
-- not used, defined where the original structure was defined
failed (2),
-- you don't get what you want, more information elsewhere in the
message
pending (3),
-- the request body part has not yet been processed,
-- requester is responsible to poll back on this
-- pending may only be return for certificate request operations.
noSupport (4),
-- the requested operation is not supported
confirmRequired (5),
-- conformation using the confirmCertAcceptance control is
required
-- before use of certificate
popRequired (6)
-- A certificate requires an indirect POP operation.
-- Info for the indirect POP in this message.
}
5.1.4. CMCFailInfo
CMCFailInfo conveys information relevant to the interpretation of a
failure condition. The CMCFailInfo has the following ASN.1
Schaad & Myers Expires September 3, 2006 [Page 27]
Internet-Draft CMS: Structures March 2006
structure:
CMCFailInfo ::= INTEGER {
badAlg (0),
-- Unrecognized or unsupported algorithm
badMessageCheck (1),
-- integrity check failed
badRequest (2),
-- transaction not permitted or supported
badTime (3),
-- Message time field was not sufficiently close to the system
time
badCertId (4),
-- No certificate could be identified matching the provided
criteria
unsuportedExt (5),
-- A requested X.509 extension is not supported by the recipient
CA.
mustArchiveKeys (6),
-- Private key material must be supplied
badIdentity (7),
-- Identification Attribute failed to verify
popRequired (8),
-- Server requires a POP proof before issuing certificate
popFailed (9),
-- POP processing failed
noKeyReuse (10),
-- Server policy does not allow key re-use
internalCAError (11),
tryLater (12),
authDataFail (13)
-- Failure occurred during processing of authenticated data
}
Additional failure reasons MAY be defined for closed environments
with a need. If additional failure reasons are needed, this SHOULD
be done by using an Extended Fail Info item in the CMCStatusInfoEx
structure.
5.2. Identification and IdentityProof Control Attributes
Some CAs and LRAs require that a proof of identity be included in a
certification request. Many different ways of doing this exist with
different degrees of security and reliability. Most people are
familiar with the request of a bank to provide your mother's maiden
name as a form of identity proof.
CMC provides one method of proving the client's identity based on a
shared secret between the certificate requestor and the verifying
authority. If clients support full request messages, clients MUST
implement this method of identity proof. Servers MUST provide this
Schaad & Myers Expires September 3, 2006 [Page 28]
Internet-Draft CMS: Structures March 2006
method and MAY also have bilateral methods of similar strength
available.
The CMC method starts with an out-of-band transfer of a token (the
shared secret). The shared-secret should be generated in a random
manner. The distribution of this token is beyond the scope of this
document. The client then uses this token for an identity proof as
follows:
1. The reqSequence field of the PKIData object (encoded exactly as
it appears in the request message including the sequence type and
length) is the value to be validated.
2. A SHA1 hash of the token is computed.
3. An HMAC-SHA1 value is then computed over the value produced in
Step 1, as described in [HMAC], using the hash of the token from
Step 2 as the shared secret value.
4. The 160-bit HMAC-SHA1 result from Step 3 is then encoded as the
value of the identityProof attribute.
When the server verifies the identityProof attribute, it computes the
HMAC-SHA1 value in the same way and compares it to the identityProof
attribute contained in the enrollment request.
If a server fails the verification of an identityProof attribute and
the server returns a response message, the failInfo attribute MUST be
present in the response and MUST have a value of badIdentity. Reuse
of the shared-secret on enrollment retries makes it easier for the
client and to prevent getting out of sync. However, reuse of the
shared-secret can potentially open the door for some types of
attacks.
Optionally, servers MAY require the inclusion of the unprotected
identification attribute with an identification attribute. The
identification attribute is intended to contain either a text string
or a numeric quantity, such as a random number, which assists the
server in locating the shared secret needed to validate the contents
of the identityProof attribute. Numeric values MUST be converted to
text string representations prior to encoding as UTF8-STRINGs in this
attribute. If the identification control attribute is included in
the message, the derivation of the shared secret in step 2 is altered
so that the hash of the concatenation of the token and the UTF8
encoded (without the type and length bytes) identity value are hashed
rather than just the token.
Schaad & Myers Expires September 3, 2006 [Page 29]
Internet-Draft CMS: Structures March 2006
5.2.1. Hardware Shared Secret Token Generation
The shared secret between the end-entity and the identity verify is
sometimes transferred using a hardware device that generates a series
of tokens based on some shared secret value. The user can therefore
prove their identity by transferring this token in plain text along
with a name string. The above protocol can be used with a hardware
shared-secret token generation device by the following modifications:
1. The identification attribute MUST be included and MUST contain
the hardware-generated token.
2. The shared secret value used above is the same hardware-generated
token.
3. All certification requests MUST have a subject name and the
subject name MUST contain the fields required to identify the
holder of the hardware token device.
5.3. Linking Identity and POP Information
In a PKI Full Request message identity information about the creator/
author of the message is carried in the signature of the CMS
SignedData object containing all of the certificate requests. Proof-
of-possession information for key pairs requesting certification,
however, is carried separately for each PKCS#10 or CRMF message.
(For keys capable of generating a digital signature, the POP is
provided by the signature on the PKCS#10 or CRMF request. For
encryption-only keys the controls described in Section 5.7 below are
used.) In order to prevent substitution-style attacks we must
guarantee that the same entity generated both the POP and proof-of-
identity information.
This section describes two mechanisms for linking identity and POP
information: witness values cryptographically derived from the
shared-secret (Section 5.3.1) and shared-secret/subject DN matching
(Section 5.3.2). Clients and servers MUST support the witness value
technique. Clients and servers MAY support shared-secret/subject DN
matching or other bilateral techniques of similar strength. The idea
behind both mechanisms is to force the client to sign some data into
each certificate request that can be directly associated with the
shared-secret; this will defeat attempts to include certificate
requests from different entities in a single Full PKI Request
message.
5.3.1. Witness values derived from the shared-secret
The first technique for doing identity-POP linking works by forcing
Schaad & Myers Expires September 3, 2006 [Page 30]
Internet-Draft CMS: Structures March 2006
the client to include a piece of information cryptographically-
derived from the shared-secret token as a signed extension within
each certificate request (PKCS#10 or CRMF) message. This technique
is useful if null subject DNs are used (because, for example, the
server can generate the subject DN for the certificate based only on
the shared secret). Processing begins when the client receives the
shared-secret token out-of-band from the server. The client then
computes the following values:
1. The client generates a random byte-string, R, which SHOULD be at
least 512 bits in length.
2. A SHA1 hash of the token is computed.
3. An HMAC-SHA1 value is then computed over the random value
produced in Step 1, as described in [HMAC], using the hash of the
token from Step 2 as the shared secret.
4. The random value produced in Step 1 is encoded as the value of a
popLinkRandom control attribute. This control attribute MUST be
included in the Full PKI Request message.
5. The 160-bit HMAC-SHA1 result from Step 3 is encoded as the value
of a popLinkWitness extension to the certificate request.
1. For CRMF, popLinkWitness is included in the controls section
of the CertRequest structure.
2. For PKCS#10, popLinkWitness is included in the attributes
section of the CertificationRequest structure.
Upon receipt, servers MUST verify that each certificate request
contains a copy of the popLinkWitness and that its value was derived
in the specified manner from the shared secret and the random string
included in the popLinkRandom control attribute.
5.3.2. Shared-secret/subject DN matching
The second technique for doing identity-POP linking is to link a
particular subject distinguished name (subject DN) to the shared-
secrets that are distributed out-of-band and to require that clients
using the shared-secret to prove identity include that exact subject
DN in every certificate request. It is expected that many client-
server connections using shared-secret based proof-of-identity will
use this mechanism. (It is common not to omit the subject DN
information from the certificate request messages.)
When the shared secret is generated and transferred out-of-band to
Schaad & Myers Expires September 3, 2006 [Page 31]
Internet-Draft CMS: Structures March 2006
initiate the registration process (Section 5.2), a particular subject
DN is also associated with the shared secret and communicated to the
client. (The subject DN generated MUST be unique per entity in
accordance with CA policy; a null subject DN cannot be used. A
common practice could be to place the identification value as part of
the subject DN.) When the client generates the Full PKI Request
message, it MUST use these two pieces of information as follows:
1. The client MUST include the specific subject DN that it received
along with the shared secret as the subject name in every
certificate request (PKCS#10 and/or CRMF) in the Full PKI
Request. The subject names in the requests MUST NOT be null.
2. The client MUST include the identityProof control attribute
(Section 5.2), derived from the shared secret, in the Full PKI
Request.
The server receiving this message MUST (a) validate the identityProof
control attribute and then, (b) check that the subject DN included in
each certificate request matches that associated with the shared
secret. If either of these checks fails the certificate request MUST
be rejected.
5.3.3. Renewal and Re-Key Messages
In a renewal or re-key message, the subject DN in (a) the certificate
referenced by the CMS SignerInfo object, and (b) all certificate
requests within the request message MUST match according to the
standard name match rules described in [PKIXCERT].
5.4. Data Return Control Attribute
The data return control attribute allows clients to send arbitrary
data (usually some type of internal state information) to the server
and to have the data returned as part of the enrollment response
message. Data placed in a data return statement is considered to be
opaque to the server. The same control is used for both requests and
responses. If the data return statement appears in an enrollment
message, the server MUST return it as part of the enrollment response
message.
In the event that the information in the data return statement needs
to be confidential, it is expected that the client would apply some
type of encryption to the contained data, but the details of this are
outside the scope of this specification.
An example of using this feature is for a client to place an
identifier marking the exact source of the private key material.
Schaad & Myers Expires September 3, 2006 [Page 32]
Internet-Draft CMS: Structures March 2006
This might be the identifier of a hardware device containing the
private key.
5.5. RA Certificate Modification Controls
These extensions exist for RAs/LRAs to be able to modify the contents
of a requestors certificate. This might be necessary for various
reasons. The addition of extensions dealing with policies and
correcting naming information for subject and alternative subject
names are two such reasons.
Two controls exist for this purpose. The first Modify Certificate
Template has the full control for allowing modification of any field
in the certificate. The second Add Extensions control only allows
for the addition of extensions.
5.5.1. Modify Certificate Request Control
The Modify Certificate Request control is used by LRAs/RAs in order
to change various fields in an EE requested certificate. This
control allows for the specification of fields in the certificate
other than extensions. This attribute uses the following ASN.1
definition:
ModCertTemplate ::= SEQUENCE {
pkiDataReference BodyPartList,
certReferences SEQUENCE OF BodyPartID,
replace BOOLEAN DEFAULT TRUE,
certTemplate CertTemplate
}
pkiDataReference field contains the list of body part ids that define
the path of the embedded request message.
certReferences field is a list of references to one or more of the
payloads contained within a PKIData element. Each element of the
certReferences sequence MUST be equal to either the bodyPartID of
a TaggedCertificationRequest or the certReqId of the CertRequest
within a CertReqMsg. By definition, the listed extensions are to
be applied to every element referenced in the certReferences
sequence. If a request corresponding to bodyPartID cannot be
found, the error badRequest is returned referencing this control
attribute.
replace specifies if the data is to be replace with what is here, or
if the fields in the original certificate request are to be
removed. If replace is FALSE, any field defined in the
certTemplate field is removed from proposed certificate. For the
Schaad & Myers Expires September 3, 2006 [Page 33]
Internet-Draft CMS: Structures March 2006
extensions field, only those extensions which are defined in the
template certificate are removed. The use of the replace field
set to FALSE is be considered to be a rare event as generally the
field would just be replaced with a correct value.
certTemplate contains a certificate template object. Items are to be
omitted from the certificate template unless the value present is
to replace the value found the in the requested certificate
template. If a field is present in the extensions field of the
template, that extension would either replace the same existing
extension or be added to the set of extensions in the requested
certificate.
Servers MUST be able to process all extensions defined, but not
prohibited, in [PKIXCERT]. Servers are not required to be able to
process every V3 X.509 extension transmitted using this protocol, nor
are they required to be able to process other, private extensions.
Servers are not required to put all LRA-requested extensions into a
certificate. Servers are permitted to modify LRA-requested
extensions. Servers MUST NOT alter an extension so as to reverse the
meaning of a client-requested extension. If a certification request
is denied due to the inability to handle a requested extension and a
response is returned, the server MUST return a failInfo attribute
with the value of unsupportedExt.
If multiple Modify Certificate Template controls exist in an
enrollment message, the exact behavior is left up to the certificate
issuer policy. However it is recommended that the following policy
be used. These rules would be applied to individual extensions
within an Add Extensions control attribute (as opposed to an "all or
nothing" approach).
1. If the conflict is within a single PKIData object, the
certificate request would be rejected with an error of
badRequest.
2. If the conflict is between different PKIData objects, the
outermost version of the extension would be used (allowing an LRA
to override the extension requested by the end-entity).
5.5.2. Add Extensions Control
The Add Extensions control has been depreciated in favor of the
Modify Certificate Template control. It was replaced so that fields
in the certificate template other than extensions could be modified.
The Add Extensions control attribute is used by LRAs in order to
specify additional extensions that are to be placed on certificates.
Schaad & Myers Expires September 3, 2006 [Page 34]
Internet-Draft CMS: Structures March 2006
This attribute uses the following ASN.1 definition:
AddExtensions ::= SEQUENCE {
pkiDataReference BodyPartID
certReferences SEQUENCE OF BodyPartID,
extensions SEQUENCE OF Extension
}
pkiDataReference field contains the body part id of the embedded
request message.
certReferences field is a list of references to one or more of the
payloads contained within a PKIData. Each element of the
certReferences sequence MUST be equal to either the bodyPartID of
a TaggedCertificationRequest or the certReqId of the CertRequest
within a CertReqMsg. By definition, the listed extensions are to
be applied to every element referenced in the certReferences
sequence. If a request corresponding to bodyPartID cannot be
found, the error badRequest is returned referencing this control
attribute.
extensions field contains the sequence of extensions to be applied to
the referenced certificate requests.
Servers MUST be able to process all extensions defined, but not
prohibited, in [PKIXCERT]. Servers are not required to be able to
process every V3 X.509 extension transmitted using this protocol, nor
are they required to be able to process other, private extensions.
Servers are not required to put all LRA-requested extensions into a
certificate. Servers are permitted to modify LRA-requested
extensions. Servers MUST NOT alter an extension so as to reverse the
meaning of a client-requested extension If a certification request is
denied due to the inability to handle a requested extension and a
response is returned, the server MUST return a failInfo attribute
with the value of unsupportedExt.
If multiple Add Extensions statements exist in an enrollment message,
the exact behavior is left up to the certificate issuer policy.
However it is recommended that the following policy be used. These
rules would be applied to individual extensions within an Add
Extensions control attribute (as opposed to an "all or nothing"
approach).
1. If the conflict is within a single PKIData object, the
certificate request would be rejected with an error of
badRequest.
Schaad & Myers Expires September 3, 2006 [Page 35]
Internet-Draft CMS: Structures March 2006
2. If the conflict is between different PKIData objects, the
outermost version of the extension would be used (allowing an LRA
to override the extension requested by the end-entity).
5.6. Transaction Management Control Attributes
Transactions are identified and tracked using a transaction
identifier. If used, clients generate transaction identifiers and
retain their value until the server responds with a message that
completes the transaction. Servers correspondingly include received
transaction identifiers in the response.
The transactionId attribute identifies a given transaction. It is
used between client and server to manage the state of an operation.
Clients MAY include a transactionID attribute in request messages.
If the original request contains a transactionID attribute, all
subsequent request and response messages MUST include the same
transactionID attribute. A server MUST use only transactionIds in
the outermost PKIdata object. TransactionIds on inner PKIdata
objects are for intermediate entities.
Replay protection can be supported through the use of sender and
recipient nonces. If nonces are used, in the first message of a
transaction, no recipientNonce is transmitted; a senderNonce is
instantiated by the message originator and retained for later
reference. The recipient of a sender nonce reflects this value back
to the originator as a recipientNonce and includes it's own
senderNonce. Upon receipt by the transaction originator of this
message, the originator compares the value of recipientNonce to its
retained value. If the values match, the message can be accepted for
further security processing. The received value for senderNonce is
also retained for inclusion in the next message associated with the
same transaction.
The senderNonce and recipientNonce attribute can be used to provide
application-level replay prevention. Clients MAY include a
senderNonce in the initial request message. Originating messages
include only a value for senderNonce. If a message includes a
senderNonce, the response MUST include the transmitted value of the
previously received senderNonce as recipientNonce and include new
value for senderNonce. A server MUST use only nonces in the
outermost PKIdata object. Nonces on inner PKIdata objects are for
intermediate entities.
5.7. Proof-of-possession (POP) for encryption-only keys
Everything described in this section is optional to implement, for
both servers and clients. Servers MAY require this POP method be
Schaad & Myers Expires September 3, 2006 [Page 36]
Internet-Draft CMS: Structures March 2006
used only if another POP method is unavailable. Servers SHOULD
reject all requests contained within a PKIData if any required POP is
missing for any element within the PKIData.
Many servers require proof that an entity requesting a certificate
for a public key actually possesses the corresponding private
component of the key pair. For keys that can be used as signature
keys, signing the certification request with the private key serves
as a POP on that key pair. With keys that can only be used for
encryption operations, POP MUST be performed by forcing the client to
decrypt a value. See Section 5 of [CRMF] for a detailed discussion
of POP.
By necessity, POP for encryption-only keys cannot be done in one
round-trip, since there are four distinct phases:
1. Client tells the server about the public component of a new
encryption key pair.
2. Server sends the client a POP challenge, encrypted with the
presented public encryption key, which the client must decrypt.
3. Client decrypts the POP challenge and sends it back to the
server.
4. Server validates the decrypted POP challenge and continues
processing the certificate request.
CMC defines two different attributes. The first deals with the
encrypted challenge sent from the server to the user in step 2. The
second deals with the decrypted challenge sent from the client to the
server in step 3.
The encryptedPOP attribute is used to send the encrypted challenge
from the server to the client. As such, it is encoded as a tagged
attribute within the controlSequence of a ResponseBody. (Note that
we assume that the message sent in Step 1 above is an enrollment
request and that the response in step 2 is a Full Enrollment Response
including a failureInfo specifying that a POP is explicitly required,
and providing the POP challenge in the encryptedPOP attribute.)
Schaad & Myers Expires September 3, 2006 [Page 37]
Internet-Draft CMS: Structures March 2006
EncryptedPOP ::= SEQUENCE {
request TaggedRequest,
cms contentInfo,
thePOPAlgID AlgorithmIdentifier,
witnessAlgID AlgorithmIdentifier,
witness OCTET STRING
}
DecryptedPOP ::= SEQUENCE {
bodyPartID BodyPartID,
thePOPAlgID AlgorithmIdentifier,
thePOP OCTET STRING
}
The encrypted POP algorithm works as follows:
1. The server generates a random value y and associates it with the
request.
2. The server returns the encrypted pop with the following fields
set:
1. request is the certificate request in the original request
message (it is included here so the client need not key a
copy of the request),
2. cms is an EnvelopedData object, the content type being id-
data and the content being the value y. If the certificate
request contains a subject key identifier (SKI) extension,
then the recipient identifier SHOULD be the SKI. If the
issuerAndSerialNumber form is used, the IsserName MUST be
encoded as NULL and the SerialNumber as the bodyPartID of the
certificate request,
3. thePOPAlgID contains the algorithm to be used in computing
the return POP value,
4. witnessAlgID contains the hash algorithm used on y to create
the field witness,
5. witness contains the hashed value of y.
3. The client decrypts the cms field to obtain the value y. The
client computes H(y) using the witnessAlgID and compares to the
value of witness. If the values do not compare or the decryption
is not successful, the client MUST abort the enrollment process.
The client aborts the process by sending a request message
containing a CMCStatusInfo control attribute with failInfo value
Schaad & Myers Expires September 3, 2006 [Page 38]
Internet-Draft CMS: Structures March 2006
of popFailed.
4. The client creates the decryptedPOP as part of a new PKIData
message. The fields in the decryptedPOP are:
1. bodyPartID refers to the certificate request in the new
enrollment message,
2. thePOPAlgID is copied from the encryptedPOP,
3. thePOP contains the possession proof. This value is computed
by thePOPAlgID using the value y and request referenced in
(4a).
5. The server then re-computes the value of thePOP from its cached
value of y and the request and compares to the value of thePOP.
If the values do not match, the server MUST NOT issue the
certificate. The server MAY re-issue a new challenge or MAY fail
the request altogether.
When defining the algorithms for thePOPAlgID and witnessAlgID care
must be taken to ensure that the result of witnessAlgID is not a
useful value to shortcut the computation with thePOPAlgID. Clients
MUST implement SHA-1 for witnessAlgID. Clients MUST implement HMAC-
SHA1 for thePOPAlgID. The value of y is used as the secret value in
the HMAC algorithm and the request referenced in (4a) is used as the
data. If y is greater than 64 bytes, only the first 64 bytes of y
are used as the secret.
One potential problem with the algorithm above is the amount of state
that a CA needs to keep in order to verify the returned POP value.
This describes one of many possible ways of addressing the problem by
reducing the amount of state kept on the CA to a single (or small
set) of values.
1. Server generates random seed x, constant across all requests.
(The value of x would normally be altered on a regular basis and
kept for a short time afterwards.)
2. For certificate request R, server computes y = F(x,R). F can be,
for example, HMAC-SHA1(x,R). All that's important for
statelessness is that y be consistently computable with only
known state constant x and function F, other inputs coming from
the cert request structure. y should not be predictable based on
knowledge of R, thus the use of a OWF like HMAC-SHA1.
Schaad & Myers Expires September 3, 2006 [Page 39]
Internet-Draft CMS: Structures March 2006
5.8. LRA POP Witnesses Control Attribute
In an enrollment scenario involving an LRAs the CA may allow (or
require) the LRA to perform the POP protocol with the entity
requesting certification. In this case the LRA needs a way to inform
the CA it has done the POP. This control attribute has been created
to address this issue.
The ASN.1 structure for the LRA POP witness is as follows:
LraPopWitness ::= SEQUENCE {
pkiDataBodyid BodyPartID,
bodyIds SEQUENCE of BodyPartID
}
pkiDataBodyid field contains the body part id of the nested CMS body
object containing the client's full request message. pkiDataBodyid
is set to 0 if the request is in the current PKIRequest body.
bodyIds contains a list of certificate requests for which the LRA has
performed an out-of-band authentication. The method of
authentication could be archival of private key material,
challenge-response or other means.
If a certificate server does not allow for an LRA to do the POP
verification, it returns an error of POPFAILURE. The CA MUST NOT
start a challenge-response to re-verify the POP itself.
5.9. Get Certificate Control Attribute
Everything described in this section is optional to implement.
The get certificate control attribute is used to retrieve previously
issued certificates from a repository of certificates. A Certificate
Authority, an LRA or an independent service may provide this
repository. The clients expected to use this facility are those
operating in a resource-constrained environment. (An example of a
resource-constrained client would be a low-end IP router that does
not retain its own certificate in non-volatile memory.)
The get certificate control attribute has the following ASN.1
structure:
GetCert ::= SEQUENCE {
issuerName GeneralName,
serialNumber INTEGER }
The service responding to the request will place the requested
Schaad & Myers Expires September 3, 2006 [Page 40]
Internet-Draft CMS: Structures March 2006
certificate in the certificates field of a SignedData object. If the
get certificate attribute is the only control in a Full PKI Request
message, the response would be a Simple Enrollment Response.
5.10. Get CRL Control Attribute
Everything described in this section is optional to implement.
The get CRL control attribute is used to retrieve CRLs from a
repository of CRLs. A Certification Authority, an LRA or an
independent service may provide this repository. The clients
expected to use this facility are those where a fully deployed
directory is either infeasible or undesirable.
The get CRL control attribute has the following ASN.1 structure:
GetCRL ::= SEQUENCE {
issuerName Name,
cRLName GeneralName OPTIONAL,
time GeneralizedTime OPTIONAL,
reasons ReasonFlags OPTIONAL }
The fields in a GetCRL have the following meanings:
issuerName is the name of the CRL issuer.
cRLName may be the value of CRLDistributionPoints in the subject
certificate or equivalent value in the event the certificate does
not contain such a value.
time is used by the client to specify from among potentially several
issues of CRL that one whose thisUpdate value is less than but
nearest to the specified time. In the absence of a time
component, the CA always returns with the most recent CRL.
reasons is used to specify from among CRLs partitioned by revocation
reason. Implementers should bear in mind that while a specific
revocation request has a single CRLReason code--and consequently
entries in the CRL would have a single CRLReason code value--a
single CRL can aggregate information for one or more reasonFlags.
A service responding to the request will place the requested CRL in
the crls field of a SignedData object. If the get CRL attribute is
the only control in a full enrollment message, the response would be
a simple enrollment response.
Schaad & Myers Expires September 3, 2006 [Page 41]
Internet-Draft CMS: Structures March 2006
5.11. Revocation Request Control Attribute
The revocation request control attribute is used to request that a
certificate be revoked.
The revocation request control attribute has the following ASN.1
syntax:
RevokeRequest ::= SEQUENCE {
issuerName Name,
serialNumber INTEGER,
reason CRLReason,
invalidityDate GeneralizedTime OPTIONAL,
sharedSecret OCTET STRING OPTIONAL,
comment UTF8string OPTIONAL }
issuerName contains the issuerName of the certificate to be revoked.
serialNumber contains the serial number of the certificate to be
revoked
reason contains the suggested CRLReason code for why the certificate
is being revoked. The CA can use this value at its discretion in
building the CRL.
invalidityDate contains the suggested value for the Invalidity Date
CRL Extension. The CA can use this value at its discretion in
building the CRL.
sharedSecret contains a secret value registered by the EE when the
certificate was obtained to allow for revocation of a certificate
in the event of key loss.
comment contains a human readable comment.
For a revocation request to become a reliable object in the event of
a dispute, a strong proof of originator authenticity is required.
However, in the instance when an end-entity has lost use of its
signature private key, it is impossible for the end-entity to produce
a digital signature (prior to the certification of a new signature
key pair). The RevokeRequest provides for the optional transmission
from the end-entity to the CA of a shared secret that may be used as
an alternative authenticator in the instance of loss of use. The
acceptability of this practice is a matter of local security policy.
(Note that in some situations a Registration Authority may be
delegated authority to revoke certificates on behalf of some
population within its scope control. In these situations the CA
Schaad & Myers Expires September 3, 2006 [Page 42]
Internet-Draft CMS: Structures March 2006
would accept the LRA's digital signature on the request to revoke a
certificate, independent of whether the end entity still had access
to the private component of the key pair.)
Clients MUST provide the capability to produce a digitally signed
revocation request control attribute. Clients SHOULD be capable of
producing an unsigned revocation request containing the end-entity's
shared secret. (The unsigned message consisting of a CMS signedData
object with no signatures.) If a client provides shared secret based
self-revocation, the client MUST be capable of producing a revocation
request containing the shared secret. Servers MUST be capable of
accepting both forms of revocation requests.
The structure of an unsigned, shared secret based revocation request
is a matter of local implementation. The shared secret does not need
to be encrypted when sent in a revocation request. The shared secret
has a one-time use, that of causing the certificate to be revoked,
and public knowledge of the shared secret after the certificate has
been revoked is not a problem. Clients need to inform users that the
same shared secret SHOULD NOT be used for multiple certificates.
A full response message MUST be returned for a revocation request.
5.12. Registration and Response Information Control Attributes
The regInfo control attribute is for clients and LRAs to pass
additional information as part a PKI request. The regInfo control
attribute uses the ASN.1 structure:
RegInfo ::= OCTET STRING
The content of this data is based on bilateral agreement between the
client and server.
If a server (or LRA) needs to return information back to a requestor
in response to data submitted in a regInfo attribute, then that data
is returned as a responseInfo control attribute. The content of the
OCTET STRING for response information is based on bilateral agreement
between the client and server.
5.13. Query Pending Control Attribute
In some environments, process requirements for manual intervention or
other identity checking can cause a delay in returning the
certificate related to a certificate request. The query pending
attribute allows for a client to query a server about the state of a
pending certificate request. The server returns a token as part of
the CMCStatusInfo attribute (in the otherInfo field). The client
Schaad & Myers Expires September 3, 2006 [Page 43]
Internet-Draft CMS: Structures March 2006
puts the token into the query pending attribute to identify the
correct request to the server. The server can also return a
suggested time for the client to query for the state of a pending
certificate request.
The ASN.1 structure used by the query pending control attribute is:
QueryPending ::= OCTET STRING
If a server returns a pending state (the transaction is still
pending), the otherInfo MAY be omitted. If it is not omitted then
the same value MUST be returned (the token MUST NOT change during the
request).
5.14. Confirm Certificate Acceptance
Some Certification Authorities require that clients give a positive
conformation that the certificates issued to it are acceptable. The
Confirm Certificate Acceptance control attribute is used for that
purpose. If the CMCStatusInfo on a certificate response is
confirmRequired, then the client MUST return a Confirm Certificate
attribute contained in a full enrollment response message.
Clients SHOULD wait for the response from the server that the
conformation has been received before using the certificate for any
purpose.
The confirm certificate acceptance structure is:
CMCCertId ::= IssuerAndSerialNumber
CMCCertId contains the issuer and serial number of the certificate
being accepted.
Servers MUST return a full enrollment response for a confirm
certificate acceptance control.
Note that if the Certification Authority includes this attribute,
there will be two full round trips of messages.
1. The client sends the request to the CA.
2. The CA returns the certificate and this attribute.
3. The client sends a response message to the CA with a
CMCStatusInfoEx control either accepting or rejecting the
certificate.
Schaad & Myers Expires September 3, 2006 [Page 44]
Internet-Draft CMS: Structures March 2006
4. The CA sends a response message to the client with a
CMCStatusInfoEx of success.
5.15. Publish Trust Roots
This control allows for distribution of trust roots from a central
authority to an end-entity.
What is included in the control as data is the set of certificates
that are to be treated as trusted roots, and a set of certificates
that are no longer to be treated as trusted roots.
Prior to accepting the change in trust roots, a client MUST do the at
least following: Validate the signature on the message to a current
trusted root, check with policy to ensure that the signer is
permitted to use the attribute, validate that the authenticated
publish time in the signature is near to the current time and
validate the sequence number is greater than the previously used one.
This attribute uses the following ASN.1 definition:
PublishTrustRoots ::= SEQUENCE {
seqNumber INTEGER,
rootHashes SEQUENCE OF OCTET STRING
}
seqNumber contains an increasing integer specifying where in the
sequence of updates this item is.
rootHashes contains the hashes for the certificates that are to be
treated as trust roots by the client.
While it is recommended that the sender places the certificates that
are to be trusted in the message, it is not required as the
certificates should be obtainable using normal discovery techniques.
In the event that multiple agents publish a set of trust lists, it is
up to local policy to determine how the different trust lists should
be combined. Clients SHOULD be able to handle the update of trust
lists multiple trust list independently.
NOTE: Clients which handle this attribute must use extreme care in
validating that the operation is permissible. Incorrect handling of
this attribute allows for an attacker to change the set of trusted
roots on the client.
Schaad & Myers Expires September 3, 2006 [Page 45]
Internet-Draft CMS: Structures March 2006
5.16. Provide Autenticated Data
This control allows for an authority to provide data back to the user
in an authenticated manner. In general, one would expect that the
same passphrase used in the identity proof operation. This attribute
uses the following ASN.1 definition:
AuthPublish ::= BodyPartID
The bodyPartID refers to a member of the cmsSequence either a
ResponseBody or PKIData sequence. The element within the is an
AuthenticatedData structure with a id-cct-PKIData content. Only the
id-Publish-Roots control is currently expected to be in this
sequence.
If the authentication operation fails, the error authDataFail is
returned.
5.17. Batch Process Identification
With the processing rules on message bodies, items which have been
batched together must be identified as such. Additionally the
returned batched responses must also be identified as such.
The batchRequests control attribute is used to identify the elements
in the cmsSequence section that contain batched up requests to be
processed.
The batchResponses control attribute is used to identify the set of
elements in the cmsSequence which correspond to batched responses.
When a server processes a batchRequests control, it may return the
items being processed either as individual messages or in a batched
response (identifying the elements with a batchResponses control).
The preferable behavior is to batch the responses back to the client
submitting the batched request. If only partial responses can be
generated at this time, the server SHOULD generate a batchResponse
with complete responses where available and QueryPending responses
where a complete response is not ready. A QueryPending responses on
the entire request SHOULD only be returned if processing based on the
top level message itself (or on the status of the requestor) is
involved in the pending processing.
5.18. Publication Information Control
This control allows for modifying publication of already issued
certificates, both for publishing and removal from publication. A
common usage for this control is to remove an existing certificate
Schaad & Myers Expires September 3, 2006 [Page 46]
Internet-Draft CMS: Structures March 2006
from publication during a re-key operation. This control should
always be processed after the issuance of new certificates and
revocation requests. This control should not be processed if a
certificate failed to be issued.
The attribute uses the following ASN.1 definition:
CMCPublicationInfo ::= SEQUENCE {
certHashes SEQUENCE of OCTET STRING,
pubInfo PKIPublicationInfo
}
certHashes contains the hashes of the certificates for which
publication is to change
pubInfo contains the information how where and how the certificates
should be published. The action dontPublish has the added
connotation of remove from publication if the certificate is
already published.
A single certificate SHOULD NOT appear in more than one
CMCPublicationInfo attribute. The behavior is undefined in the event
that it does.
The PKIPublicationInfo control is used to control publication of
certificates at the time of issue.
5.19. Control Processed
This control exists to allow an RA to single to subsequent processors
of the control sections that a specific control has already been
processed. This permits an RA in the middle of a processing stream
to process a control defined either in a local context or in a
subsequent document. This control uses the following ASN.1
definition::
ControlList ::= SEQUENCE {
bodyList SEQUENCE SIZE (1..MAX) OF
BodyPartReference
|
bodyList contains a series of body part identifiers that form a path
to each of the controls that were processed by the RA. This
control is only needed for those controls which are not part of
this standard and thus would cause an error condition of a server
attempting to deal with a control which is not defined in this
document. No error status is needed since an error causes the RA
to return the request to the client with the error rather than
passing the request on to the next server in the processing list.
Schaad & Myers Expires September 3, 2006 [Page 47]
Internet-Draft CMS: Structures March 2006
6. Local Registration Authorities
This specification permits the use of Local Registration Authorities
(LRAs). An LRA sits between the end-entity and the Certification
Authority. From the end-entity's perspective, the LRA appears to be
the Certification Authority and from the server the LRA appears to be
a client. LRAs receive the enrollment messages, perform local
processing and then forward onto Certificate Authorities. Some of
the types of local processing that an LRA can perform include:
o batching multiple enrollment messages together,
o challenge/response POP proofs,
o addition of private or standardized certificate extensions to all
requests,
o archival of private key material,
o routing of requests to different CAs.
When an LRA receives an enrollment message it has three options: it
may forward the message without modification, it may add a new
wrapping layer to the message, or it may remove one or more existing
layers and add a new wrapping layer.
When an LRA adds a new wrapping layer to a message it creates a new
PKIData object. The new layer contains any control attributes
required (for example if the LRA does the POP proof for an encryption
key or the addExtension control attribute to modify an enrollment
request) and the client enrollment message. The client enrollment
message is placed in the cmsSequence if it is a Full Enrollment
message and in the reqSequence if it is a Simple Enrollment message.
If an LRA is batching multiple client messages together, then each
client enrollment message is placed into the appropriate location in
the LRA's PKIData object along with all relevant control attributes.
(If multiple LRAs are in the path between the end-entity and the
Certification Authority, this will lead to multiple wrapping layers
on the message.)
In processing an enrollment message, an LRA MUST NOT alter any
certificate request body (PKCS #10 or CRMF) as any alteration would
invalidate the signature on the request and thus the POP for the
private key.
An example of how this would look is illustrated by the following
figure:
Schaad & Myers Expires September 3, 2006 [Page 48]
Internet-Draft CMS: Structures March 2006
SignedData (by LRA)
PKIData
controlSequence
LRA added control statements
reqSequence
Zero or more Simple CertificationRequests from clients
cmsSequence
Zero or more Full PKI messages from clients
SignedData (by client)
PKIData
Under some circumstances an LRA is required to remove wrapping
layers. The following sections look at the processing required if
encryption layers and signing layers need to be removed.
6.1. Encryption Removal
There are two cases that require an LRA to remove or change
encryption in an enrollment message. In the first case the
encryption was applied for the purposes of protecting the entire
enrollment request from unauthorized entities. If the CA does not
have a recipient info entry in the encryption layer, the LRA MUST
remove the encryption layer. The LRA MAY add a new encryption layer
with or without adding a new signing layer.
The second change of encryption that may be required is to change the
encryption inside of a signing layer. In this case the LRA MUST
remove all signing layers containing the encryption. All control
statements MUST be merged according to local policy rules as each
signing layer is removed and the resulting merged controls MUST be
placed in a new signing layer provided by the LRA. If the signing
layer provided by the end-entity needs to be removed to the LRA can
remove the layer.
6.2. Signature Layer Removal
Only two instances exist where an LRA should remove a signature layer
on a Full Enrollment message. If an encryption needs to be modified
within the message, or if a Certificate Authority will not accept
secondary delegation (i.e. multiple LRA signatures). In all other
situations LRAs SHOULD NOT remove a signing layer from a message.
If an LRA removes a signing layer from a message, all control
statements MUST be merged according to local policy rules. The
resulting merged control statements MUST be placed in a new signing
layer provided by the LRA.
Schaad & Myers Expires September 3, 2006 [Page 49]
Internet-Draft CMS: Structures March 2006
7. Security Considerations
Initiation of a secure communications channel between an end-entity
and a CA or LRA (and, similarly, between an LRA and another LRA or
CA) necessarily requires an out-of-band trust initiation mechanism.
For example, a secure channel may be constructed between the end-
entity and the CA via IPSEC or TLS. Many such schemes exist and the
choice of any particular scheme for trust initiation is outside the
scope of this document. Implementers of this protocol are strongly
encouraged to consider generally accepted principles of secure key
management when integrating this capability within an overall
security architecture.
Mechanisms for thwarting replay attacks may be required in particular
implementations of this protocol depending on the operational
environment. In cases where the CA maintains significant state
information, replay attacks may be detectable without the inclusion
of the optional nonce mechanisms. Implementers of this protocol need
to carefully consider environmental conditions before choosing
whether or not to implement the senderNonce and recipientNonce
attributes described in section 5.6. Developers of state-constrained
PKI clients are strongly encouraged to incorporate the use of these
attributes.
Under no circumstances should a signing key be archived. Doing so
allows the archiving entity to potentially use the key for forging
signatures.
Due care must be taken prior to archiving keys. Once a key is given
to an archiving entity, the archiving entity could use the keys in a
way not conducive to the archiving entity. Users should be made
especially aware that proper verification is made of the certificate
used to encrypt the private key material.
Clients and servers need to do some checks on cryptographic
parameters prior to issuing certificates to make sure that weak
parameters are not used. A description of the small subgroup attack
is provided in [X942]. Methods of avoiding the small subgroup attack
can be found in [SMALL-GROUP]. CMC implementations ought to be aware
of this attack when doing parameter validations.
When using a shared-secret for authentication purposes, the shared-
secret should be generated using good random number techniques. User
selection of the secret allows for dictionary attacks to be mounted.
Extreme care must be used when processing the Publish Trust Roots
attribute. Incorrect processing can lead to the practice of slamming
where an attacker changes the set of trusted roots in order to weaken
Schaad & Myers Expires September 3, 2006 [Page 50]
Internet-Draft CMS: Structures March 2006
security.
Schaad & Myers Expires September 3, 2006 [Page 51]
Internet-Draft CMS: Structures March 2006
8. IANA Considerations
This document defines a number of control objects. These are
identified by Object Identifiers (OIDs). The objects are defined
from an arc delegated by IANA to the PKIX Working Group. No further
action by IANA is necessary for this document or any anticipated
updates.
Schaad & Myers Expires September 3, 2006 [Page 52]
Internet-Draft CMS: Structures March 2006
9. Acknowledgments
The authors and the Working Group are greatful for the participation
of Xiaoui Lui and Jeff Weinstein in helping to author the original
versions of this document.
The authors would like to thank Brian LaMacchia for his work in
developing and writing up many of the concepts presented in this
document. The authors would also like to thank Alex Deacon and Barb
Fox for their contributions.
Schaad & Myers Expires September 3, 2006 [Page 53]
Internet-Draft CMS: Structures March 2006
10. References
10.1. Normative References
[CMS] Housley, R., "Cryptographic Message Syntax (CMS)",
RFC 3852, July 2004.
[CRMF] Schaad, J., "Internet X.509 Certificate Request message
Format", RFC 4211, January 2005.
[DH-POP] Prafullchandra, H. and J. Schaad, "Diffie-Hellman Proof-
of-Possession Algorithms", RFC 2875, June 2000.
[HMAC] Krawczyk, H., Bellare, M., and R. Canetti, "Diffie-Hellman
Proof-of-Possession Algorithms", RFC 2104, February 1997.
[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.
10.2. Informational References
[DH] Kaliski, B., "PKCS 3: Diffie-Hellman Key Agreement v1.4",
Lost 1900.
[PKCS1] Kaliski, B., "PKCS #1: RSA Encryption, Version 1.5",
PKCS #1, March 1998.
[PKCS7] Kaliski, B., "PKCS #7: Cryptographic Message Syntax v1.5",
RFC 2315, October 1997.
[PKCS8] Laboratories, RSA., "PKCS#8: Private-Key Information
Syntax Standard, Version 1.2", November 1993.
[PKCS10] Kaliski, B., "PKCS #10: Certification Request Syntax
v1.5", RFC 2314, October 1997.
[SMALL-GROUP]
Zuccherato, R., "Methods for Avoiding the "Small-Subgroup"
Attacks on the Diffie-Hellman Key Agreement Method for
S/MIME", RFC 2785, March 2000.
[SMIMEV2] Dusse, S., Hoffman, P., Ramsdell, B., Lundblade, L., and
Schaad & Myers Expires September 3, 2006 [Page 54]
Internet-Draft CMS: Structures March 2006
L. Repka, "S/MIME Version 2 Message Specification",
RFC 2311, March 1998.
[SMIMEV3] Ramsdell, B., "S/MIME Version 3 Message Specification",
RFC 2633, June 1999.
[X942] Rescorla, E., "Diffie-Hellman Key Agreement Method",
RFC 2631, June 1999.
Schaad & Myers Expires September 3, 2006 [Page 55]
Internet-Draft CMS: Structures March 2006
Appendix A. ASN.1 Module
EnrollmentMessageSyntax
{ iso(1) identified-organization(3) dod(4) internet(1)
security(5) mechansims(5) pkix(7) id-mod(0) id-mod-cmc2002(23) }
DEFINITIONS IMPLICIT TAGS :: BEGIN
-- EXPORTS All --
-- The types and values defined in this module are exported for use
-- in the other ASN.1 modules. Other applications may use them for
-- their own purposes.
IMPORTS
-- PKIX Part 1 - Implicit From [PKIXCERT]
CertificateSerialNumber, GeneralName, CRLReason, ReasonFlags
FROM PKIX1Implicit88 {iso(1) identified-organization(3) dod(6)
internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
id-pkix1-implicit(19)}
-- PKIX Part 1 - Explicit From [PKIXCERT]
AlgorithmIdentifier, Extension, Name
FROM PKIX1Explicit88 {iso(1) identified-organization(3) dod(6)
internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
id-pkix1-explicit(18)}
-- Cryptographic Message Syntax FROM [CMS]
ContentInfo, Attribute, IssuerAndSerialNumber
FROM CryptographicMessageSyntax2004 { 1 2 840 113549 1 9 16 0 24}
-- CRMF FROM [CRMF]
CertReqMsg, PKIPublicationInfo
FROM PKIXCRMF {iso(1) identified-organization(3) dod(6)
internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-crmf(5)};
-- Global Types
UTF8String ::= [UNIVERSAL 12] IMPLICIT OCTET STRING
-- The content of this type conforms to RFC 2279.
id-pkix OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
dod(6) internet(1) security(5) mechanisms(5) pkix(7) }
id-cmc OBJECT IDENTIFIER ::= {id-pkix 7} -- CMC controls
id-cct OBJECT IDENTIFIER ::= {id-pkix 12} -- CMC content types
Schaad & Myers Expires September 3, 2006 [Page 56]
Internet-Draft CMS: Structures March 2006
-- The following controls have the type OCTET STRING
id-cmc-identityProof OBJECT IDENTIFIER ::= {id-cmc 3}
id-cmc-dataReturn OBJECT IDENTIFIER ::= {id-cmc 4}
id-cmc-regInfo OBJECT IDENTIFIER ::= {id-cmc 18}
id-cmc-responseInfo OBJECT IDENTIFIER ::= {id-cmc 19}
id-cmc-queryPending OBJECT IDENTIFIER ::= {id-cmc 21}
id-cmc-popLinkRandom OBJECT IDENTIFIER ::= {id-cmc 22}
id-cmc-popLinkWitness OBJECT IDENTIFIER ::= {id-cmc 23}
-- The following controls have the type UTF8String
id-cmc-identification OBJECT IDENTIFIER ::= {id-cmc 2}
-- The following controls have the type INTEGER
id-cmc-transactionId OBJECT IDENTIFIER ::= {id-cmc 5}
-- The following controls have the type OCTET STRING
id-cmc-senderNonce OBJECT IDENTIFIER ::= {id-cmc 6}
id-cmc-recipientNonce OBJECT IDENTIFIER ::= {id-cmc 7}
-- This is the content type used for a request message in the protocol
id-cct-PKIData OBJECT IDENTIFIER ::= { id-cct 2 }
PKIData ::= SEQUENCE {
controlSequence SEQUENCE SIZE(0..MAX) OF TaggedAttribute,
reqSequence SEQUENCE SIZE(0..MAX) OF TaggedRequest,
cmsSequence SEQUENCE SIZE(0..MAX) OF TaggedContentInfo,
otherMsgSequence SEQUENCE SIZE(0..MAX) OF OtherMsg
}
bodyIdMax INTEGER ::= 4294967295
BodyPartID ::= INTEGER(0..bodyIdMax)
TaggedAttribute ::= SEQUENCE {
bodyPartID BodyPartID,
attrType OBJECT IDENTIFIER,
attrValues SET OF AttributeValue
}
AttributeValue ::= ANY
Schaad & Myers Expires September 3, 2006 [Page 57]
Internet-Draft CMS: Structures March 2006
TaggedRequest ::= CHOICE {
tcr [0] TaggedCertificationRequest,
crm [1] CertReqMsg,
orm [2] SEQUENCE {
bodyPartID BodyPartID,
requestMessageType OBJECT IDENTIFIER,
requestMessageValue ANY DEFINED BY requestMessageType
}
}
TaggedCertificationRequest ::= SEQUENCE {
bodyPartID BodyPartID,
certificationRequest CertificationRequest
}
CertificationRequest ::= SEQUENCE {
certificationRequestInfo SEQUENCE {
version INTEGER,
subject Name,
subjectPublicKeyInfo SEQUENCE {
algorithm AlgorithmIdentifier,
subjectPublicKey BIT STRING },
attributes [0] IMPLICIT SET OF Attribute },
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING
}
TaggedContentInfo ::= SEQUENCE {
bodyPartID BodyPartID,
contentInfo ContentInfo
}
OtherMsg ::= SEQUENCE {
bodyPartID BodyPartID,
otherMsgType OBJECT IDENTIFIER,
otherMsgValue ANY DEFINED BY otherMsgType }
-- This defines the response message in the protocol
id-cct-PKIResponse OBJECT IDENTIFIER ::= { id-cct 3 }
ResponseBody ::= SEQUENCE {
controlSequence SEQUENCE SIZE(0..MAX) OF TaggedAttribute,
cmsSequence SEQUENCE SIZE(0..MAX) OF TaggedContentInfo,
otherMsgSequence SEQUENCE SIZE(0..MAX) OF OtherMsg
}
-- Used to return status state in a response
Schaad & Myers Expires September 3, 2006 [Page 58]
Internet-Draft CMS: Structures March 2006
id-cmc-statusInfo OBJECT IDENTIFIER ::= {id-cmc 1}
CMCStatusInfo ::= SEQUENCE {
cMCStatus CMCStatus,
bodyList SEQUENCE SIZE (1..MAX) OF BodyPartID,
statusString UTF8String OPTIONAL,
otherInfo CHOICE {
failInfo CMCFailInfo,
pendInfo PendInfo } OPTIONAL
}
PendInfo ::= SEQUENCE {
pendToken OCTET STRING,
pendTime GeneralizedTime
}
CMCStatus ::= INTEGER {
success (0),
-- you got exactly what you asked for
-- reserved (1), -- use is deprecated.
failed (2),
-- you don't get it, more information elsewhere in the message
pending (3),
-- the request body part has not yet been processed,
-- requester is responsible to poll back on this
noSupport (4),
-- the requested operation is not supported
confirmRequired (5),
-- confirmation using the confirmCertAcceptance control is
-- required
popRequired (6)
-- A certificate request requires an indirect POP operation.
-- Info for the indirect POP in this message.
}
CMCFailInfo ::= INTEGER {
badAlg (0),
-- Unrecognized or unsupported algorithm
badMessageCheck (1),
-- integrity check failed
badRequest (2),
-- transaction not permitted or supported
badTime (3),
-- Message time field was not sufficiently close to the systemtime
badCertId (4),
-- No certificate could be identified matching the provided criteria
unsuportedExt (5),
-- A requested X.509 extension is not supported by the recipient CA.
Schaad & Myers Expires September 3, 2006 [Page 59]
Internet-Draft CMS: Structures March 2006
mustArchiveKeys (6),
-- Private key material must be supplied
badIdentity (7),
-- Identification Attribute failed to verify
popRequired (8),
-- Server requires a POP proof before issuing certificate
popFailed (9),
-- Server failed to get an acceptable POP for the request
noKeyReuse (10),
-- Server policy does not allow key re-use
internalCAError (11),
tryLater (12),
authDataFail (13)
-- Failure occurred during processing of authenticated data
}
-- Used for LRAs to add extensions to certificate requests
id-cmc-addExtensions OBJECT IDENTIFIER ::= {id-cmc 8}
AddExtensions ::= SEQUENCE {
pkiDataReference BodyPartID,
certReferences SEQUENCE OF BodyPartID,
extensions SEQUENCE OF Extension
}
id-cmc-encryptedPOP OBJECT IDENTIFIER ::= {id-cmc 9}
id-cmc-decryptedPOP OBJECT IDENTIFIER ::= {id-cmc 10}
EncryptedPOP ::= SEQUENCE {
request TaggedRequest,
cms ContentInfo,
thePOPAlgID AlgorithmIdentifier,
witnessAlgID AlgorithmIdentifier,
witness OCTET STRING
}
DecryptedPOP ::= SEQUENCE {
bodyPartID BodyPartID,
thePOPAlgID AlgorithmIdentifier,
thePOP OCTET STRING
}
id-cmc-lraPOPWitness OBJECT IDENTIFIER ::= {id-cmc 11}
LraPopWitness ::= SEQUENCE {
pkiDataBodyid BodyPartID,
bodyIds SEQUENCE OF BodyPartID
Schaad & Myers Expires September 3, 2006 [Page 60]
Internet-Draft CMS: Structures March 2006
}
--
id-cmc-getCert OBJECT IDENTIFIER ::= {id-cmc 15}
GetCert ::= SEQUENCE {
issuerName GeneralName,
serialNumber INTEGER }
id-cmc-getCRL OBJECT IDENTIFIER ::= {id-cmc 16}
GetCRL ::= SEQUENCE {
issuerName Name,
cRLName GeneralName OPTIONAL,
time GeneralizedTime OPTIONAL,
reasons ReasonFlags OPTIONAL }
id-cmc-revokeRequest OBJECT IDENTIFIER ::= {id-cmc 17}
RevokeRequest ::= SEQUENCE {
issuerName Name,
serialNumber INTEGER,
reason CRLReason,
invalidityDate GeneralizedTime OPTIONAL,
passphrase OCTET STRING OPTIONAL,
comment UTF8String OPTIONAL }
id-cmc-confirmCertAcceptance OBJECT IDENTIFIER ::= {id-cmc 24}
CMCCertId ::= IssuerAndSerialNumber
-- The following is used to request V3 extensions be added to a
certificate
id-ExtensionReq OBJECT IDENTIFIER ::= {iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs-9(9) 14}
ExtensionReq ::= SEQUENCE OF Extension
-- The following exists to allow Diffie-Hellman Certificate Requests
Messages to be
-- well-formed
id-alg-noSignature OBJECT IDENTIFIER ::= {id-pkix id-alg(6) 2}
NoSignatureValue ::= OCTET STRING
-- Unauthenticated attribute to carry removable data.
Schaad & Myers Expires September 3, 2006 [Page 61]
Internet-Draft CMS: Structures March 2006
-- This will be used in the key archive draft among others.
id-aa OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2)}
id-aa-cmc-unsignedData OBJECT IDENTIFIER ::= {id-aa 34}
CMCUnsignedData ::= SEQUENCE {
bodyPartPath SEQUENCE SIZE (1..MAX) OF BodyPartID,
identifier OBJECT IDENTIFIER,
content ANY DEFINED BY identifier
}
-- Replaces CMC Status Info
--
id-cmc-statusInfoEx OBJECT IDENTIFIER ::= {id-cmc 25}
CMCStatusInfoEx ::= SEQUENCE {
cMCStatus CMCStatus,
bodyList SEQUENCE SIZE (1..MAX) OF
BodyPartReference,
statusString UTF8String OPTIONAL,
otherInfo CHOICE {
failInfo CMCFailInfo,
pendInfo PendInfo,
extendedFailInfo SEQUENCE {
failInfoOID OBJECT IDENTIFIER,
failInfoValue AttributeValue
}
} OPTIONAL
}
BodyPartReference ::= CHOICE {
bodyPartID BodyPartID,
bodyPartPath SEQUENCE SIZE (1..MAX) OF BodyPartID
}
-- Allow for distribution of trust roots
--
id-cmc-trustedRoots OBJECT IDENTIFIER ::= {id-cmc 26}
PublishTrustRoots ::= SEQUENCE {
seqNumber INTEGER,
rootHashes SEQUENCE OF OCTET STRING
}
id-cmc-authData OBJECT IDENTIFIER ::= {id-cmc 27}
Schaad & Myers Expires September 3, 2006 [Page 62]
Internet-Draft CMS: Structures March 2006
AuthPublish ::= BodyPartID
-- These two items use BodyPartList
id-cmc-batchRequests OBJECT IDENTIFIER ::= {id-cmc 28}
id-cmc-batchResponses OBJECT IDENTIFIER ::= {id-cmc 29}
BodyPartList ::= SEQUENCE OF BodyPartID
--
id-cmc-publishCert OBJECT IDENTIFIER ::= {id-cmc 30}
CMCPublicationInfo ::= SEQUENCE {
certHashes SEQUENCE of OCTET STRING,
pubInfo PKIPublicationInfo
}
id-cmc-modCertTemplate OBJECT IDENTIFIER ::= {id-cmc 31}
ModCertTemplate ::= SEQUENCE {
pkiDataReference BodyPartList,
certReferences SEQUENCE OF BodyPartID,
replace BOOLEAN DEFAULT TRUE,
certTemplate CertTemplate
}
-- Inform follow on servers that one or more controls have already been
processed
id-cmc-controlProcessed OBJECT IDENTIFIER ::= {id-cmc 32}
ControlsProcessed ::= SEQUENCE {
bodyList SEQUENCE SIZE(1..MAX) OF BodyPartReference
}
END
Schaad & Myers Expires September 3, 2006 [Page 63]
Internet-Draft CMS: Structures March 2006
Appendix B. Enrollment Message Flows
This section is informational. The purpose of this section is to
present, in an abstracted version, the messages that would flow
between the client and server for several different common cases.
Appendix B.1. Request of a Signing Certificate
This section looks at the messages that would flow in the event that
an enrollment is occurring for a signing only key. If the
certificate was designed for both signing and encryption, the only
difference would be the key usage extension in the certificate
request.
Message from client to server:
ContentInfo.contentType = id-SignedData
ContentInfo.content
SignedData.encapContentInfo
eContentType = id-ct-PKIData
eContent
controlSequence
{102, id-cmc-identityProof, computed value}
{103, id-cmc-senderNonce, 10001}
reqSequence
certRequest
certReqId = 201
certTemplate
subject = My Proposed DN
publicKey = My Public Key
extensions
{id-ce-subjectPublicKeyIdentifier, 1000}
{id-ce-keyUsage, digitalSignature}
SignedData.SignerInfos
SignerInfo
sid.subjectKeyIdentifier = 1000
Response from server to client:
Schaad & Myers Expires September 3, 2006 [Page 64]
Internet-Draft CMS: Structures March 2006
ContentInfo.contentType = id-SignedData
ContentInfo.content
SignedData.encapContentInfo
eContentType = id-ct-PKIResponse
eContent
controlSequence
{102, id-cmc-statusInfoEx, {success, 201}}
{103, id-cmc-senderNonce, 10005}
{104, id-cmc-recipientNonce, 10001}
certificates
Newly issued certificate
Other certificates
SignedData.SignerInfos
Signed by CA
Appendix B.2. Single Certificate Request, But Modified by RA
This section looks at the messages that would flow in the event that
an enrollment is has one RA in the middle of the data flow. That RA
will modify the certificate request before passing it on the CA.
Message from client to RA:
ContentInfo.contentType = id-SignedData
ContentInfo.content
SignedData.encapContentInfo
eContentType = id-ct-PKIData
eContent
controlSequence
{102, id-cmc-identityProof, computed value}
{103, id-cmc-senderNonce, 10001}
reqSequence
certRequest
certReqId = 201
certTemplate
subject = My Proposed DN
publicKey = My Public Key
extensions
{id-ce-subjectPublicKeyIdentifier, 1000}
{id-ce-keyUsage, digitalSignature}
SignedData.SignerInfos
SignerInfo
sid.subjectKeyIdentifier = 1000
Message from RA to CA:
Schaad & Myers Expires September 3, 2006 [Page 65]
Internet-Draft CMS: Structures March 2006
ContentInfo.contentType = id-SignedData
ContentInfo.content
SignedData.encapContentInfo
eContentType = id-ct-PKIData
eContent
controlSequence
{ 102, id-cmc-batchRequests, { 1, 2} }
{ 103, id-cmc-addExtensions,
{ {1, 201, {id-ce-certificatePolicies, anyPolicy}}
{1, 201, {id-ce-subjectAltName, {extension data}}
{2, XXX, {id-ce-subjectAltName, {extension data}}}
cmsSequence
{ 1, <Message from client to RA #1> }
{ 2, <Message from client to RA #2> }
SignedData.SignerInfos
SignerInfo
sid = RA key.
Response from the CA to the RA:
Schaad & Myers Expires September 3, 2006 [Page 66]
Internet-Draft CMS: Structures March 2006
ContentInfo.contentType = id-SignedData
ContentInfo.content
SignedData.encapContentInfo
eContentType = id-ct-PKIResponse
eContent
controlSequence
{102, id-cmc-BatchResponse, {999, 998}}
{102, id-cmc-statusInfoEx, {failed, 2, badIdentity}}
cmsSequence
{ bodyPartID = 999
contentInfo
ContentInfo.contentType = id-SignedData
ContentInfo.content
SignedData.encapContentInfo
eContentType = id-ct-PKIResponse
eContent
controlSequence
{102, id-cmc-statusInfoEx, {success, 201}}
certificates
Newly issued certificate
Other certificates
SignedData.SignerInfos
Signed by CA
}
{ bodyPartID = 998,
contentInfo
ContentInfo.contentType = id-SignedData
ContentInfo.content
SignedData.encapContentInfo
eContentType = id-ct-PKIResponse
eContent
controlSequence
{102, id-cmc-statusInfoEx, {failure, badAlg}}
certificates
Newly issued certificate
Other certificates
SignedData.SignerInfos
Signed by CA
}
SignedData.SignerInfos
Signed by CA
Response from RA to client:
Schaad & Myers Expires September 3, 2006 [Page 67]
Internet-Draft CMS: Structures March 2006
ContentInfo.contentType = id-SignedData
ContentInfo.content
SignedData.encapContentInfo
eContentType = id-ct-PKIResponse
eContent
controlSequence
{102, id-cmc-statusInfoEx, {success, 201}}
certificates
Newly issued certificate
Other certificates
SignedData.SignerInfos
Signed by CA
Appendix B.3. Indirect POP for an RSA certificate
This section looks at the messages that would flow in the event that
an enrollment is done for an encryption only certificate using an
indirect POP method. For simplicity it is assumed that the
certificate requestor already has a signing only certificate
The fact that a second round trip is required is implicit rather than
explicit. The server determines this based on fact that no other POP
exists for the certificate request.
Message #1 from client to server:
Schaad & Myers Expires September 3, 2006 [Page 68]
Internet-Draft CMS: Structures March 2006
ContentInfo.contentType = id-SignedData
ContentInfo.content
SignedData.encapContentInfo
eContentType = id-ct-PKIData
eContent
controlSequence
{102, id-cmc-transactionID, 10132985123483401}
{103, id-cmc-senderNonce, 10001}
{104, id-cmc-dataRetrun, <packet of binary data identifying
where the key in question is.>}
reqSequence
certRequest
certReqId = 201
certTemplate
subject = <My DN from my signing cert>
publicKey = My Public Key
extensions
{id-ce-keyUsage, keyEncipherment}
popo
keyEncipherment
subsequentMessage
SignedData.SignerInfos
SignerInfo
Signed by requestor's signing cert
Response #1 from server to client:
Schaad & Myers Expires September 3, 2006 [Page 69]
Internet-Draft CMS: Structures March 2006
ContentInfo.contentType = id-SignedData
ContentInfo.content
SignedData.encapContentInfo
eContentType = id-ct-PKIResponse
eContent
controlSequence
{101, id-cmc-statusInfoEx, {failed, 201, popRequired}}
{102, id-cmc-transactionID, 10132985123483401}
{103, id-cmc-senderNonce, 10005}
{104, id-cmc-recipientNonce, 10001}
{105, id-cmc-encryptedPOP, {
request {
certRequest
certReqId = 201
certTemplate
subject = <My DN from my signing cert>
publicKey = My Public Key
extensions
{id-ce-keyUsage, keyEncipherment}
popo
keyEncipherment
subsequentMessage
}
cms
contentType = id-envelopedData
content
recipipentInfos.riid.issuerSerialNumber = <NULL, 201>
encryptedContentInfo
eContentType = id-data
eContent = <Encrypted value of 'y'>
thePOPAlgID = HMAC-SHA1
witnessAlgID = SHA-1
witness <hashed value of 'y'>}}
{106, id-cmc-dataReturn, <packet of binary data identifying
where the key in question is.>}
certificates
Newly issued certificate
Other certificates
SignedData.SignerInfos
Signed by CA
Schaad & Myers Expires September 3, 2006 [Page 70]
Internet-Draft CMS: Structures March 2006
ContentInfo.contentType = id-SignedData
ContentInfo.content
SignedData.encapContentInfo
eContentType = id-ct-PKIData
eContent
controlSequence
{102, id-cmc-transactionID, 10132985123483401}
{103, id-cmc-senderNonce, 100101}
{104, id-cmc-dataRetrun, <packet of binary data identifying
where the key in question is.>}
{105, id-cmc-recipientNonce, 10005}
{107, id-cmc-decryptedPOP, {
bodyPartID 201,
thePOPAlgID HMAC-SHA1,
thePOP <HMAC computed value goes here>}}
reqSequence
certRequest
certReqId = 201
certTemplate
subject = <My DN from my signing cert>
publicKey = My Public Key
extensions
{id-ce-keyUsage, keyEncipherment}
popo
keyEncipherment
subsequentMessage
SignedData.SignerInfos
SignerInfo
Signed by requestor's signing cert
Response from server to client:
ContentInfo.contentType = id-SignedData
ContentInfo.content
SignedData.encapContentInfo
eContentType = id-ct-PKIResponse
eContent
controlSequence
{101, id-cmc-transactionID, 10132985123483401}
{102, id-cmc-statusInfoEx, {success, 201}}
{103, id-cmc-senderNonce, 10019}
{104, id-cmc-recipientNonce, 100101}
{104, id-cmc-dataReturn, <packet of binary data identifying
where the key in question is.>}
certificates
Newly issued certificate
Other certificates
SignedData.SignerInfos
Schaad & Myers Expires September 3, 2006 [Page 71]
Internet-Draft CMS: Structures March 2006
Signed by CA
Schaad & Myers Expires September 3, 2006 [Page 72]
Internet-Draft CMS: Structures March 2006
Appendix C. Change History
RFC 27XX to -00
1. Addition of CMCStatusInfoEx
From -00 to -01
1. Removal of Transport section to a new document.
2. Removal of Compliance section to a new document.
From -01 to -02
1. Add processing rules for PKIData and PKIResponse processing.
2. Add unsigned attribute for holding data (to be used by key
archival).
3. Add trust root identification control.
4. Add Server to Client identity proof method.
5. Add controls to identify batch processing, needed by rules added
in item 1.
From -02 to -03
1. Add unpublish control
2. Added use of AuthenticatedData structure from CMS
3. Insert Appendix B - Enrollment Message Flows
4. Add Modify Certificate Request control
From -03 to -04
1. Change author list.
2. Add IANA Considerations section
3. Correct module names in ASN.1
4. Add id-cmc-controlProcessed control with associated changes.
Schaad & Myers Expires September 3, 2006 [Page 73]
Internet-Draft CMS: Structures March 2006
Authors' Addresses
Jim Schaad
Soaring Hawk Consulting
PO Box 675
Gold Bar, WA 98251
Phone: (425) 785-1031
Email: jimsch@exmsft.com
Michael Myers
TraceRoute Security, Inc.
Email: myers@coastside.inc
Schaad & Myers Expires September 3, 2006 [Page 74]
Internet-Draft CMS: Structures March 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 & Myers Expires September 3, 2006 [Page 75]
