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Keywords: PKIX, digital security, ocsp
Internet Engineering Task Force (IETF) S. Santesson
Request for Comments: 6960 3xA Security
Obsoletes: 2560, 6277 M. Myers
Updates: 5912 TraceRoute Security
Category: Standards Track R. Ankney
ISSN: 2070-1721
A. Malpani
CA Technologies
S. Galperin
A9
C. Adams
University of Ottawa
June 2013
X.509 Internet Public Key Infrastructure
Online Certificate Status Protocol - OCSP
Abstract
This document specifies a protocol useful in determining the current
status of a digital certificate without requiring Certificate
Revocation Lists (CRLs). Additional mechanisms addressing PKIX
operational requirements are specified in separate documents. This
document obsoletes RFCs 2560 and 6277. It also updates RFC 5912.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6960.
Santesson, et al. Standards Track [Page 1]
RFC 6960 PKIX OCSP June 2013
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................4
1.1. Requirements Language ......................................5
2. Protocol Overview ...............................................5
2.1. Request ....................................................5
2.2. Response ...................................................6
2.3. Exception Cases ............................................8
2.4. Semantics of thisUpdate, nextUpdate, and producedAt ........9
2.5. Response Pre-Production ....................................9
2.6. OCSP Signature Authority Delegation .......................10
2.7. CA Key Compromise .........................................10
3. Functional Requirements ........................................10
3.1. Certificate Content .......................................10
3.2. Signed Response Acceptance Requirements ...................10
4. Details of the Protocol ........................................11
4.1. Request Syntax ............................................11
4.1.1. ASN.1 Specification of the OCSP Request ............11
4.1.2. Notes on OCSP Requests .............................13
4.2. Response Syntax ...........................................14
4.2.1. ASN.1 Specification of the OCSP Response ...........14
4.2.2. Notes on OCSP Responses ............................16
4.2.2.1. Time ......................................16
4.2.2.2. Authorized Responders .....................16
4.2.2.2.1. Revocation Checking of
an Authorized Responder ........17
4.2.2.3. Basic Response ............................18
4.3. Mandatory and Optional Cryptographic Algorithms ...........19
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RFC 6960 PKIX OCSP June 2013
4.4. Extensions ................................................19
4.4.1. Nonce ..............................................20
4.4.2. CRL References .....................................20
4.4.3. Acceptable Response Types ..........................20
4.4.4. Archive Cutoff .....................................21
4.4.5. CRL Entry Extensions ...............................21
4.4.6. Service Locator ....................................22
4.4.7. Preferred Signature Algorithms .....................22
4.4.7.1. Extension Syntax ..........................23
4.4.7.2. Responder Signature Algorithm Selection ...24
4.4.7.2.1. Dynamic Response ...............24
4.4.7.2.2. Static Response ................25
4.4.8. Extended Revoked Definition ........................25
5. Security Considerations ........................................26
5.1. Preferred Signature Algorithms ............................27
5.1.1. Use of Insecure Algorithms .........................27
5.1.2. Man-in-the-Middle Downgrade Attack .................27
5.1.3. Denial-of-Service Attack ...........................28
6. IANA Considerations ............................................28
7. References .....................................................28
7.1. Normative References ......................................28
7.2. Informative References ....................................29
8. Acknowledgements ...............................................29
Appendix A. OCSP over HTTP ........................................30
A.1. Request ....................................................30
A.2. Response ...................................................30
Appendix B. ASN.1 Modules .........................................30
B.1. OCSP in ASN.1 - 1998 Syntax ................................31
B.2. OCSP in ASN.1 - 2008 Syntax ................................34
Appendix C. MIME Registrations ....................................39
C.1. application/ocsp-request ...................................39
C.2. application/ocsp-response ..................................40
Santesson, et al. Standards Track [Page 3]
RFC 6960 PKIX OCSP June 2013
1. Introduction
This document specifies a protocol useful in determining the current
status of a digital certificate without requiring CRLs. Additional
mechanisms addressing PKIX operational requirements are specified in
separate documents.
This specification obsoletes [RFC2560] and [RFC6277]. The primary
reason for the publication of this document is to address ambiguities
that have been found since the publication of RFC 2560. This
document differs from RFC 2560 in only a few areas:
o Section 2.2 extends the use of the "revoked" response to allow
this response status for certificates that have never been issued.
o Section 2.3 extends the use of the "unauthorized" error response,
as specified in [RFC5019].
o Sections 4.2.1 and 4.2.2.3 state that a response may include
revocation status information for certificates that were not
included in the request, as permitted in [RFC5019].
o Section 4.2.2.2 clarifies when a responder is considered an
Authorized Responder.
o Section 4.2.2.3 clarifies that the ResponderID field corresponds
to the OCSP responder signer certificate.
o Section 4.3 changes the set of cryptographic algorithms that
clients must support and the set of cryptographic algorithms that
clients should support as specified in [RFC6277].
o Section 4.4.1 specifies, for the nonce extension, ASN.1 syntax
that was missing in RFC 2560.
o Section 4.4.7 specifies a new extension that may be included in a
request message to specify signature algorithms the client would
prefer the server use to sign the response as specified in
[RFC6277].
o Section 4.4.8 specifies a new extension that indicates that the
responder supports the extended use of the "revoked" response for
non-issued certificates defined in Section 2.2.
o Appendix B.2 provides an ASN.1 module using the 2008 syntax of
ASN.1, which updates [RFC5912].
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RFC 6960 PKIX OCSP June 2013
An overview of the protocol is provided in Section 2. Functional
requirements are specified in Section 3. Details of the protocol are
discussed in Section 4. We cover security issues with the protocol
in Section 5. Appendix A defines OCSP over HTTP, Appendix B provides
ASN.1 syntactic elements, and Appendix C specifies the MIME types for
the messages.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. Protocol Overview
In lieu of, or as a supplement to, checking against a periodic CRL,
it may be necessary to obtain timely information regarding the
revocation status of certificates (cf. [RFC5280], Section 3.3).
Examples include high-value funds transfers or large stock trades.
The Online Certificate Status Protocol (OCSP) enables applications to
determine the (revocation) state of identified certificates. OCSP
may be used to satisfy some of the operational requirements of
providing more timely revocation information than is possible with
CRLs and may also be used to obtain additional status information.
An OCSP client issues a status request to an OCSP responder and
suspends acceptance of the certificates in question until the
responder provides a response.
This protocol specifies the data that needs to be exchanged between
an application checking the status of one or more certificates and
the server providing the corresponding status.
2.1. Request
An OCSP request contains the following data:
- protocol version
- service request
- target certificate identifier
- optional extensions, which MAY be processed by the OCSP responder
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Upon receipt of a request, an OCSP responder determines if:
1. the message is well formed,
2. the responder is configured to provide the requested service, and
3. the request contains the information needed by the responder.
If any one of these conditions is not met, the OCSP responder
produces an error message; otherwise, it returns a definitive
response.
2.2. Response
OCSP responses can be of various types. An OCSP response consists of
a response type and the bytes of the actual response. There is one
basic type of OCSP response that MUST be supported by all OCSP
servers and clients. The rest of this section pertains only to this
basic response type.
All definitive response messages SHALL be digitally signed. The key
used to sign the response MUST belong to one of the following:
- the CA who issued the certificate in question
- a Trusted Responder whose public key is trusted by the requestor
- a CA Designated Responder (Authorized Responder, defined in
Section 4.2.2.2) who holds a specially marked certificate issued
directly by the CA, indicating that the responder may issue OCSP
responses for that CA
A definitive response message is composed of:
- version of the response syntax
- identifier of the responder
- time when the response was generated
- responses for each of the certificates in a request
- optional extensions
- signature algorithm OID
- signature computed across a hash of the response
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The response for each of the certificates in a request consists of:
- target certificate identifier
- certificate status value
- response validity interval
- optional extensions
This specification defines the following definitive response
indicators for use in the certificate status value:
- good
- revoked
- unknown
The "good" state indicates a positive response to the status inquiry.
At a minimum, this positive response indicates that no certificate
with the requested certificate serial number currently within its
validity interval is revoked. This state does not necessarily mean
that the certificate was ever issued or that the time at which the
response was produced is within the certificate's validity interval.
Response extensions may be used to convey additional information on
assertions made by the responder regarding the status of the
certificate, such as a positive statement about issuance, validity,
etc.
The "revoked" state indicates that the certificate has been revoked,
either temporarily (the revocation reason is certificateHold) or
permanently. This state MAY also be returned if the associated CA
has no record of ever having issued a certificate with the
certificate serial number in the request, using any current or
previous issuing key (referred to as a "non-issued" certificate in
this document).
The "unknown" state indicates that the responder doesn't know about
the certificate being requested, usually because the request
indicates an unrecognized issuer that is not served by this
responder.
NOTE: The "revoked" status indicates that a certificate with the
requested serial number should be rejected, while the "unknown"
status indicates that the status could not be determined by
this responder, thereby allowing the client to decide whether
it wants to try another source of status information (such as a
Santesson, et al. Standards Track [Page 7]
RFC 6960 PKIX OCSP June 2013
CRL). This makes the "revoked" response suitable for
non-issued certificates (as defined above) where the intention
of the responder is to cause the client to reject the
certificate rather than trying another source of status
information. The "revoked" status is still optional for
non-issued certificates in order to maintain backwards
compatibility with deployments of RFC 2560. For example, the
responder may not have any knowledge about whether a requested
serial number has been assigned to any issued certificate, or
the responder may provide pre-produced responses in accordance
with RFC 5019 and, for that reason, is not capable of providing
a signed response for all non-issued certificate serial
numbers.
When a responder sends a "revoked" response to a status request for a
non-issued certificate, the responder MUST include the extended
revoked definition response extension (Section 4.4.8) in the
response, indicating that the OCSP responder supports the extended
definition of the "revoked" state to also cover non-issued
certificates. In addition, the SingleResponse related to this
non-issued certificate:
- MUST specify the revocation reason certificateHold (6),
- MUST specify the revocationTime January 1, 1970, and
- MUST NOT include a CRL references extension (Section 4.4.2) or any
CRL entry extensions (Section 4.4.5).
2.3. Exception Cases
In case of errors, the OCSP responder may return an error message.
These messages are not signed. Errors can be of the following types:
- malformedRequest
- internalError
- tryLater
- sigRequired
- unauthorized
A server produces the "malformedRequest" response if the request
received does not conform to the OCSP syntax.
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The response "internalError" indicates that the OCSP responder
reached an inconsistent internal state. The query should be retried,
potentially with another responder.
In the event that the OCSP responder is operational but unable to
return a status for the requested certificate, the "tryLater"
response can be used to indicate that the service exists but is
temporarily unable to respond.
The response "sigRequired" is returned in cases where the server
requires that the client sign the request in order to construct a
response.
The response "unauthorized" is returned in cases where the client is
not authorized to make this query to this server or the server is not
capable of responding authoritatively (cf. [RFC5019], Section 2.2.3).
2.4. Semantics of thisUpdate, nextUpdate, and producedAt
Responses defined in this document can contain four times --
thisUpdate, nextUpdate, producedAt, and revocationTime. The
semantics of these fields are:
thisUpdate The most recent time at which the status being
indicated is known by the responder to have been
correct.
nextUpdate The time at or before which newer information will be
available about the status of the certificate.
producedAt The time at which the OCSP responder signed this
response.
revocationTime The time at which the certificate was revoked or
placed on hold.
2.5. Response Pre-Production
OCSP responders MAY pre-produce signed responses specifying the
status of certificates at a specified time. The time at which the
status was known to be correct SHALL be reflected in the thisUpdate
field of the response. The time at or before which newer information
will be available is reflected in the nextUpdate field, while the
time at which the response was produced will appear in the producedAt
field of the response.
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2.6. OCSP Signature Authority Delegation
The key that signs a certificate's status information need not be the
same key that signed the certificate. A certificate's issuer
explicitly delegates OCSP signing authority by issuing a certificate
containing a unique value for the extended key usage extension
(defined in [RFC5280], Section 4.2.1.12) in the OCSP signer's
certificate. This certificate MUST be issued directly to the
responder by the cognizant CA. See Section 4.2.2.2 for details.
2.7. CA Key Compromise
If an OCSP responder knows that a particular CA's private key has
been compromised, it MAY return the "revoked" state for all
certificates issued by that CA.
3. Functional Requirements
3.1. Certificate Content
In order to convey to OCSP clients a well-known point of information
access, CAs SHALL provide the capability to include the authority
information access extension (defined in [RFC5280], Section 4.2.2.1)
in certificates that can be checked using OCSP. Alternatively, the
accessLocation for the OCSP provider may be configured locally at the
OCSP client.
CAs that support an OCSP service, either hosted locally or provided
by an Authorized Responder, MUST provide for the inclusion of a value
for a Uniform Resource Identifier (URI) [RFC3986] accessLocation and
the OID value id-ad-ocsp for the accessMethod in the
AccessDescription SEQUENCE.
The value of the accessLocation field in the subject certificate
defines the transport (e.g., HTTP) used to access the OCSP responder
and may contain other transport-dependent information (e.g., a URL).
3.2. Signed Response Acceptance Requirements
Prior to accepting a signed response for a particular certificate as
valid, OCSP clients SHALL confirm that:
1. The certificate identified in a received response corresponds to
the certificate that was identified in the corresponding request;
2. The signature on the response is valid;
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3. The identity of the signer matches the intended recipient of the
request;
4. The signer is currently authorized to provide a response for the
certificate in question;
5. The time at which the status being indicated is known to be
correct (thisUpdate) is sufficiently recent;
6. When available, the time at or before which newer information will
be available about the status of the certificate (nextUpdate) is
greater than the current time.
4. Details of the Protocol
The ASN.1 syntax imports terms defined in [RFC5280]. For signature
calculation, the data to be signed is encoded using the ASN.1
distinguished encoding rules (DER) [X.690].
ASN.1 EXPLICIT tagging is used as a default unless specified
otherwise.
The terms imported from elsewhere are Extensions,
CertificateSerialNumber, SubjectPublicKeyInfo, Name,
AlgorithmIdentifier, and CRLReason.
4.1. Request Syntax
This section specifies the ASN.1 specification for a confirmation
request. The actual formatting of the message could vary, depending
on the transport mechanism used (HTTP, SMTP, LDAP, etc.).
4.1.1. ASN.1 Specification of the OCSP Request
The ASN.1 structure corresponding to the OCSPRequest is:
OCSPRequest ::= SEQUENCE {
tbsRequest TBSRequest,
optionalSignature [0] EXPLICIT Signature OPTIONAL }
TBSRequest ::= SEQUENCE {
version [0] EXPLICIT Version DEFAULT v1,
requestorName [1] EXPLICIT GeneralName OPTIONAL,
requestList SEQUENCE OF Request,
requestExtensions [2] EXPLICIT Extensions OPTIONAL }
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Signature ::= SEQUENCE {
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING,
certs [0] EXPLICIT SEQUENCE OF Certificate
OPTIONAL}
Version ::= INTEGER { v1(0) }
Request ::= SEQUENCE {
reqCert CertID,
singleRequestExtensions [0] EXPLICIT Extensions OPTIONAL }
CertID ::= SEQUENCE {
hashAlgorithm AlgorithmIdentifier,
issuerNameHash OCTET STRING, -- Hash of issuer's DN
issuerKeyHash OCTET STRING, -- Hash of issuer's public key
serialNumber CertificateSerialNumber }
The fields in OCSPRequest have the following meanings:
o tbsRequest is the optionally signed OCSP request.
o optionalSignature contains the algorithm identifier and any
associated algorithm parameters in signatureAlgorithm; the
signature value in signature; and, optionally, certificates the
server needs to verify the signed response (normally up to but not
including the client's root certificate).
The contents of TBSRequest include the following fields:
o version indicates the version of the protocol, which for this
document is v1(0).
o requestorName is OPTIONAL and indicates the name of the OCSP
requestor.
o requestList contains one or more single certificate status
requests.
o requestExtensions is OPTIONAL and includes extensions applicable
to the requests found in reqCert. See Section 4.4.
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The contents of Request include the following fields:
o reqCert contains the identifier of a target certificate.
o singleRequestExtensions is OPTIONAL and includes extensions
applicable to this single certificate status request. See
Section 4.4.
The contents of CertID include the following fields:
o hashAlgorithm is the hash algorithm used to generate the
issuerNameHash and issuerKeyHash values.
o issuerNameHash is the hash of the issuer's distinguished name
(DN). The hash shall be calculated over the DER encoding of the
issuer's name field in the certificate being checked.
o issuerKeyHash is the hash of the issuer's public key. The hash
shall be calculated over the value (excluding tag and length) of
the subject public key field in the issuer's certificate.
o serialNumber is the serial number of the certificate for which
status is being requested.
4.1.2. Notes on OCSP Requests
The primary reason to use the hash of the CA's public key in addition
to the hash of the CA's name to identify the issuer is that it is
possible that two CAs may choose to use the same Name (uniqueness in
the Name is a recommendation that cannot be enforced). Two CAs will
never, however, have the same public key unless the CAs either
explicitly decided to share their private key or the key of one of
the CAs was compromised.
Support for any specific extension is OPTIONAL. The critical flag
SHOULD NOT be set for any of them. Section 4.4 suggests several
useful extensions. Additional extensions MAY be defined in
additional RFCs. Unrecognized extensions MUST be ignored (unless
they have the critical flag set and are not understood).
The requestor MAY choose to sign the OCSP request. In that case, the
signature is computed over the tbsRequest structure. If the request
is signed, the requestor SHALL specify its name in the requestorName
field. Also, for signed requests, the requestor MAY include
certificates that help the OCSP responder verify the requestor's
signature in the certs field of Signature.
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4.2. Response Syntax
This section specifies the ASN.1 specification for a confirmation
response. The actual formatting of the message could vary, depending
on the transport mechanism used (HTTP, SMTP, LDAP, etc.).
4.2.1. ASN.1 Specification of the OCSP Response
An OCSP response at a minimum consists of a responseStatus field
indicating the processing status of the prior request. If the value
of responseStatus is one of the error conditions, the responseBytes
field is not set.
OCSPResponse ::= SEQUENCE {
responseStatus OCSPResponseStatus,
responseBytes [0] EXPLICIT ResponseBytes OPTIONAL }
OCSPResponseStatus ::= ENUMERATED {
successful (0), -- Response has valid confirmations
malformedRequest (1), -- Illegal confirmation request
internalError (2), -- Internal error in issuer
tryLater (3), -- Try again later
-- (4) is not used
sigRequired (5), -- Must sign the request
unauthorized (6) -- Request unauthorized
}
The value for responseBytes consists of an OBJECT IDENTIFIER and a
response syntax identified by that OID encoded as an OCTET STRING.
ResponseBytes ::= SEQUENCE {
responseType OBJECT IDENTIFIER,
response OCTET STRING }
For a basic OCSP responder, responseType will be id-pkix-ocsp-basic.
id-pkix-ocsp OBJECT IDENTIFIER ::= { id-ad-ocsp }
id-pkix-ocsp-basic OBJECT IDENTIFIER ::= { id-pkix-ocsp 1 }
OCSP responders SHALL be capable of producing responses of the
id-pkix-ocsp-basic response type. Correspondingly, OCSP clients
SHALL be capable of receiving and processing responses of the
id-pkix-ocsp-basic response type.
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The value for response SHALL be the DER encoding of
BasicOCSPResponse.
BasicOCSPResponse ::= SEQUENCE {
tbsResponseData ResponseData,
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING,
certs [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL }
The value for signature SHALL be computed on the hash of the DER
encoding of ResponseData. The responder MAY include certificates in
the certs field of BasicOCSPResponse that help the OCSP client verify
the responder's signature. If no certificates are included, then
certs SHOULD be absent.
ResponseData ::= SEQUENCE {
version [0] EXPLICIT Version DEFAULT v1,
responderID ResponderID,
producedAt GeneralizedTime,
responses SEQUENCE OF SingleResponse,
responseExtensions [1] EXPLICIT Extensions OPTIONAL }
ResponderID ::= CHOICE {
byName [1] Name,
byKey [2] KeyHash }
KeyHash ::= OCTET STRING -- SHA-1 hash of responder's public key
(excluding the tag and length fields)
SingleResponse ::= SEQUENCE {
certID CertID,
certStatus CertStatus,
thisUpdate GeneralizedTime,
nextUpdate [0] EXPLICIT GeneralizedTime OPTIONAL,
singleExtensions [1] EXPLICIT Extensions OPTIONAL }
CertStatus ::= CHOICE {
good [0] IMPLICIT NULL,
revoked [1] IMPLICIT RevokedInfo,
unknown [2] IMPLICIT UnknownInfo }
RevokedInfo ::= SEQUENCE {
revocationTime GeneralizedTime,
revocationReason [0] EXPLICIT CRLReason OPTIONAL }
UnknownInfo ::= NULL
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4.2.2. Notes on OCSP Responses
4.2.2.1. Time
Responses can contain four times -- thisUpdate, nextUpdate,
producedAt, and revocationTime. The semantics of these fields are
defined in Section 2.4. The format for GeneralizedTime is as
specified in Section 4.1.2.5.2 of [RFC5280].
The thisUpdate and nextUpdate fields define a recommended validity
interval. This interval corresponds to the {thisUpdate, nextUpdate}
interval in CRLs. Responses whose nextUpdate value is earlier than
the local system time value SHOULD be considered unreliable.
Responses whose thisUpdate time is later than the local system time
SHOULD be considered unreliable.
If nextUpdate is not set, the responder is indicating that newer
revocation information is available all the time.
4.2.2.2. Authorized Responders
The key that signs a certificate's status information need not be the
same key that signed the certificate. It is necessary, however, to
ensure that the entity signing this information is authorized to do
so. Therefore, a certificate's issuer MUST do one of the following:
- sign the OCSP responses itself, or
- explicitly designate this authority to another entity
OCSP signing delegation SHALL be designated by the inclusion of
id-kp-OCSPSigning in an extended key usage certificate extension
included in the OCSP response signer's certificate. This certificate
MUST be issued directly by the CA that is identified in the request.
The CA SHOULD use the same issuing key to issue a delegation
certificate as that used to sign the certificate being checked for
revocation. Systems relying on OCSP responses MUST recognize a
delegation certificate as being issued by the CA that issued the
certificate in question only if the delegation certificate and the
certificate being checked for revocation were signed by the same key.
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Note: For backwards compatibility with RFC 2560 [RFC2560], it is not
prohibited to issue a certificate for an Authorized Responder
using a different issuing key than the key used to issue the
certificate being checked for revocation. However, such a
practice is strongly discouraged, since clients are not
required to recognize a responder with such a certificate as an
Authorized Responder.
id-kp-OCSPSigning OBJECT IDENTIFIER ::= {id-kp 9}
Systems or applications that rely on OCSP responses MUST be capable
of detecting and enforcing the use of the id-kp-OCSPSigning value as
described above. They MAY provide a means of locally configuring one
or more OCSP signing authorities and specifying the set of CAs for
which each signing authority is trusted. They MUST reject the
response if the certificate required to validate the signature on the
response does not meet at least one of the following criteria:
1. Matches a local configuration of OCSP signing authority for the
certificate in question, or
2. Is the certificate of the CA that issued the certificate in
question, or
3. Includes a value of id-kp-OCSPSigning in an extended key usage
extension and is issued by the CA that issued the certificate in
question as stated above.
Additional acceptance or rejection criteria may apply to either the
response itself or to the certificate used to validate the signature
on the response.
4.2.2.2.1. Revocation Checking of an Authorized Responder
Since an authorized OCSP responder provides status information for
one or more CAs, OCSP clients need to know how to check that an
Authorized Responder's certificate has not been revoked. CAs may
choose to deal with this problem in one of three ways:
- A CA may specify that an OCSP client can trust a responder for the
lifetime of the responder's certificate. The CA does so by
including the extension id-pkix-ocsp-nocheck. This SHOULD be a
non-critical extension. The value of the extension SHALL be NULL.
CAs issuing such a certificate should realize that a compromise of
the responder's key is as serious as the compromise of a CA key
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used to sign CRLs, at least for the validity period of this
certificate. CAs may choose to issue this type of certificate with
a very short lifetime and renew it frequently.
id-pkix-ocsp-nocheck OBJECT IDENTIFIER ::= { id-pkix-ocsp 5 }
- A CA may specify how the responder's certificate is to be checked
for revocation. This can be done by using CRL Distribution Points
if the check should be done using CRLs, or by using Authority
Information Access if the check should be done in some other way.
Details for specifying either of these two mechanisms are available
in [RFC5280].
- A CA may choose not to specify any method of revocation checking
for the responder's certificate, in which case it would be up to
the OCSP client's local security policy to decide whether that
certificate should be checked for revocation or not.
4.2.2.3. Basic Response
The basic response type contains:
o the version of the response syntax, which MUST be v1 (value is 0)
for this version of the basic response syntax;
o either the name of the responder or a hash of the responder's
public key as the ResponderID;
o the time at which the response was generated;
o responses for each of the certificates in a request;
o optional extensions;
o a signature computed across a hash of the response; and
o the signature algorithm OID.
The purpose of the ResponderID information is to allow clients to
find the certificate used to sign a signed OCSP response. Therefore,
the information MUST correspond to the certificate that was used to
sign the response.
The responder MAY include certificates in the certs field of
BasicOCSPResponse that help the OCSP client verify the responder's
signature.
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The response for each of the certificates in a request consists of:
o an identifier of the certificate for which revocation status
information is being provided (i.e., the target certificate);
o the revocation status of the certificate (good, revoked, or
unknown); if revoked, it indicates the time at which the
certificate was revoked and, optionally, the reason why it was
revoked;
o the validity interval of the response; and
o optional extensions.
The response MUST include a SingleResponse for each certificate in
the request. The response SHOULD NOT include any additional
SingleResponse elements, but, for example, OCSP responders that
pre-generate status responses might include additional SingleResponse
elements if necessary to improve response pre-generation performance
or cache efficiency (according to [RFC5019], Section 2.2.1).
4.3. Mandatory and Optional Cryptographic Algorithms
Clients that request OCSP services SHALL be capable of processing
responses signed using RSA with SHA-256 (identified by the
sha256WithRSAEncryption OID specified in [RFC4055]). Clients SHOULD
also be capable of processing responses signed using RSA with SHA-1
(identified by the sha1WithRSAEncryption OID specified in [RFC3279])
and the Digital Signature Algorithm (DSA) with SHA-1 (identified by
the id-dsa-with-sha1 OID specified in [RFC3279]). Clients MAY
support other algorithms.
4.4. Extensions
This section defines some standard extensions, based on the extension
model employed in X.509 version 3 certificates (see [RFC5280]).
Support for all extensions is optional for both clients and
responders. For each extension, the definition indicates its syntax,
processing performed by the OCSP responder, and any extensions that
are included in the corresponding response.
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4.4.1. Nonce
The nonce cryptographically binds a request and a response to prevent
replay attacks. The nonce is included as one of the
requestExtensions in requests, while in responses it would be
included as one of the responseExtensions. In both the request and
the response, the nonce will be identified by the object identifier
id-pkix-ocsp-nonce, while the extnValue is the value of the nonce.
id-pkix-ocsp OBJECT IDENTIFIER ::= { id-ad-ocsp }
id-pkix-ocsp-nonce OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 }
Nonce ::= OCTET STRING
4.4.2. CRL References
It may be desirable for the OCSP responder to indicate the CRL on
which a revoked or onHold certificate is found. This can be useful
where OCSP is used between repositories, and also as an auditing
mechanism. The CRL may be specified by a URL (the URL at which the
CRL is available), a number (CRL number), or a time (the time at
which the relevant CRL was created). These extensions will be
specified as singleExtensions. The identifier for this extension
will be id-pkix-ocsp-crl, while the value will be CrlID.
id-pkix-ocsp-crl OBJECT IDENTIFIER ::= { id-pkix-ocsp 3 }
CrlID ::= SEQUENCE {
crlUrl [0] EXPLICIT IA5String OPTIONAL,
crlNum [1] EXPLICIT INTEGER OPTIONAL,
crlTime [2] EXPLICIT GeneralizedTime OPTIONAL }
For the choice crlUrl, the IA5String will specify the URL at which
the CRL is available. For crlNum, the INTEGER will specify the value
of the CRL number extension of the relevant CRL. For crlTime, the
GeneralizedTime will indicate the time at which the relevant CRL was
issued.
4.4.3. Acceptable Response Types
An OCSP client MAY wish to specify the kinds of response types it
understands. To do so, it SHOULD use an extension with the OID
id-pkix-ocsp-response and the value AcceptableResponses. This
extension is included as one of the requestExtensions in requests.
The OIDs included in AcceptableResponses are the OIDs of the various
response types this client can accept (e.g., id-pkix-ocsp-basic).
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id-pkix-ocsp-response OBJECT IDENTIFIER ::= { id-pkix-ocsp 4 }
AcceptableResponses ::= SEQUENCE OF OBJECT IDENTIFIER
As noted in Section 4.2.1, OCSP responders SHALL be capable of
responding with responses of the id-pkix-ocsp-basic response type.
Correspondingly, OCSP clients SHALL be capable of receiving and
processing responses of the id-pkix-ocsp-basic response type.
4.4.4. Archive Cutoff
An OCSP responder MAY choose to retain revocation information beyond
a certificate's expiration. The date obtained by subtracting this
retention interval value from the producedAt time in a response is
defined as the certificate's "archive cutoff" date.
OCSP-enabled applications would use an OCSP archive cutoff date to
contribute to a proof that a digital signature was (or was not)
reliable on the date it was produced even if the certificate needed
to validate the signature has long since expired.
OCSP servers that provide support for such a historical reference
SHOULD include an archive cutoff date extension in responses. If
included, this value SHALL be provided as an OCSP singleExtensions
extension identified by id-pkix-ocsp-archive-cutoff and of syntax
GeneralizedTime.
id-pkix-ocsp-archive-cutoff OBJECT IDENTIFIER ::= {id-pkix-ocsp 6}
ArchiveCutoff ::= GeneralizedTime
To illustrate, if a server is operated with a 7-year retention
interval policy and status was produced at time t1, then the value
for ArchiveCutoff in the response would be (t1 - 7 years).
4.4.5. CRL Entry Extensions
All the extensions specified as CRL entry extensions -- in
Section 5.3 of [RFC5280] -- are also supported as singleExtensions.
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4.4.6. Service Locator
An OCSP server may be operated in a mode whereby the server receives
a request and routes it to the OCSP server that is known to be
authoritative for the identified certificate. The serviceLocator
request extension is defined for this purpose. This extension is
included as one of the singleRequestExtensions in requests.
id-pkix-ocsp-service-locator OBJECT IDENTIFIER ::= {id-pkix-ocsp 7}
ServiceLocator ::= SEQUENCE {
issuer Name,
locator AuthorityInfoAccessSyntax OPTIONAL }
Values for these fields are obtained from the corresponding fields in
the subject certificate.
4.4.7. Preferred Signature Algorithms
Since algorithms other than the mandatory-to-implement algorithms are
allowed, and since a client currently has no mechanism to indicate
its algorithm preferences, there is always a risk that a server
choosing a non-mandatory algorithm will generate a response that the
client may not support.
While an OCSP responder may apply rules for algorithm selection,
e.g., using the signature algorithm employed by the CA for signing
CRLs and certificates, such rules may fail in common situations:
o The algorithm used to sign the CRLs and certificates may not be
consistent with the key pair being used by the OCSP responder to
sign responses.
o A request for an unknown certificate provides no basis for a
responder to select from among multiple algorithm options.
The last criterion cannot be resolved through the information
available from in-band signaling using the RFC 2560 [RFC2560]
protocol without modifying the protocol.
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In addition, an OCSP responder may wish to employ different signature
algorithms than the one used by the CA to sign certificates and CRLs
for two reasons:
o The responder may employ an algorithm for certificate status
response that is less computationally demanding than for signing
the certificate itself.
o An implementation may wish to guard against the possibility of a
compromise resulting from a signature algorithm compromise by
employing two separate signature algorithms.
This section describes:
o An extension that allows a client to indicate the set of preferred
signature algorithms.
o Rules for signature algorithm selection that maximize the
probability of successful operation in the case that no supported
preferred algorithm(s) are specified.
4.4.7.1. Extension Syntax
A client MAY declare a preferred set of algorithms in a request by
including a preferred signature algorithms extension in
requestExtensions of the OCSPRequest.
id-pkix-ocsp-pref-sig-algs OBJECT IDENTIFIER ::= { id-pkix-ocsp 8 }
PreferredSignatureAlgorithms ::= SEQUENCE OF
PreferredSignatureAlgorithm
PreferredSignatureAlgorithm ::= SEQUENCE {
sigIdentifier AlgorithmIdentifier,
pubKeyAlgIdentifier SMIMECapability OPTIONAL
}
The syntax of AlgorithmIdentifier is defined in Section 4.1.1.2 of
RFC 5280 [RFC5280]. The syntax of SMIMECapability is defined in
RFC 5751 [RFC5751].
sigIdentifier specifies the signature algorithm the client prefers,
e.g., algorithm=ecdsa-with-sha256. Parameters are absent for most
common signature algorithms.
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pubKeyAlgIdentifier specifies the subject public key algorithm
identifier the client prefers in the server's certificate used to
validate the OCSP response, e.g., algorithm=id-ecPublicKey and
parameters= secp256r1.
pubKeyAlgIdentifier is OPTIONAL and provides a means to specify
parameters necessary to distinguish among different usages of a
particular algorithm, e.g., it may be used by the client to specify
what curve it supports for a given elliptic curve algorithm.
The client MUST support each of the specified preferred signature
algorithms, and the client MUST specify the algorithms in the order
of preference, from the most preferred to the least preferred.
Section 4.4.7.2 of this document describes how a server selects an
algorithm for signing OCSP responses to the requesting client.
4.4.7.2. Responder Signature Algorithm Selection
RFC 2560 [RFC2560] did not specify a mechanism for deciding the
signature algorithm to be used in an OCSP response. This does not
provide a sufficient degree of certainty as to the algorithm selected
to facilitate interoperability.
4.4.7.2.1. Dynamic Response
A responder MAY maximize the potential for ensuring interoperability
by selecting a supported signature algorithm using the following
order of precedence, as long as the selected algorithm meets all
security requirements of the OCSP responder, where the first
selection mechanism has the highest precedence:
1. Select an algorithm specified as a preferred signature algorithm
in the client request.
2. Select the signature algorithm used to sign a certificate
revocation list (CRL) issued by the certificate issuer providing
status information for the certificate specified by CertID.
3. Select the signature algorithm used to sign the OCSPRequest.
4. Select a signature algorithm that has been advertised as being the
default signature algorithm for the signing service using an
out-of-band mechanism.
5. Select a mandatory or recommended signature algorithm specified
for the version of OCSP in use.
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A responder SHOULD always apply the lowest-numbered selection
mechanism that results in the selection of a known and supported
algorithm that meets the responder's criteria for cryptographic
algorithm strength.
4.4.7.2.2. Static Response
For purposes of efficiency, an OCSP responder is permitted to
generate static responses in advance of a request. The case may not
permit the responder to make use of the client request data during
the response generation; however, the responder SHOULD still use the
client request data during the selection of the pre-generated
response to be returned. Responders MAY use the historical client
requests as part of the input to the decisions of what different
algorithms should be used to sign the pre-generated responses.
4.4.8. Extended Revoked Definition
This extension indicates that the responder supports the extended
definition of the "revoked" status to also include non-issued
certificates according to Section 2.2. One of its main purposes is
to allow audits to determine the responder's type of operation.
Clients do not have to parse this extension in order to determine the
status of certificates in responses.
This extension MUST be included in the OCSP response when that
response contains a "revoked" status for a non-issued certificate.
This extension MAY be present in other responses to signal that the
responder implements the extended revoked definition. When included,
this extension MUST be placed in responseExtensions, and it MUST NOT
appear in singleExtensions.
This extension is identified by the object identifier
id-pkix-ocsp-extended-revoke.
id-pkix-ocsp-extended-revoke OBJECT IDENTIFIER ::= {id-pkix-ocsp 9}
The value of the extension SHALL be NULL. This extension MUST NOT be
marked critical.
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5. Security Considerations
For this service to be effective, certificate-using systems must
connect to the certificate status service provider. In the event
such a connection cannot be obtained, certificate-using systems could
implement CRL processing logic as a fall-back position.
A vulnerability to denial of service is evident with respect to a
flood of queries. The production of a cryptographic signature
significantly affects response generation cycle time, thereby
exacerbating the situation. Unsigned error responses open up the
protocol to another denial-of-service attack, where the attacker
sends false error responses.
The use of precomputed responses allows replay attacks in which an
old (good) response is replayed prior to its expiration date but
after the certificate has been revoked. Deployments of OCSP should
carefully evaluate the benefit of precomputed responses against the
probability of a replay attack and the costs associated with its
successful execution.
Requests do not contain the responder they are directed to. This
allows an attacker to replay a request to any number of OCSP
responders.
The reliance of HTTP caching in some deployment scenarios may result
in unexpected results if intermediate servers are incorrectly
configured or are known to possess cache management faults.
Implementors are advised to take the reliability of HTTP cache
mechanisms into account when deploying OCSP over HTTP.
Responding with a "revoked" state to a certificate that has never
been issued may enable someone to obtain a revocation response for a
certificate that is not yet issued, but soon will be issued, if the
certificate serial number of the certificate that will be issued can
be predicted or guessed by the requestor. Such a prediction is easy
for a CA that issues certificates using sequential certificate serial
number assignment. This risk is handled in the specification by
requiring compliant implementations to use the certificateHold reason
code, which avoids permanently revoking the serial number. For CAs
that support "revoked" responses to status requests for non-issued
certificates, one way to completely avoid this issue is to assign
random certificate serial number values with high entropy.
Santesson, et al. Standards Track [Page 26]
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5.1. Preferred Signature Algorithms
The mechanism used to choose the response signing algorithm MUST be
considered to be sufficiently secure against cryptanalytic attack for
the intended application.
In most applications, it is sufficient for the signing algorithm to
be at least as secure as the signing algorithm used to sign the
original certificate whose status is being queried. However, this
criterion may not hold in long-term archival applications, in which
the status of a certificate is being queried for a date in the
distant past, long after the signing algorithm has ceased being
considered trustworthy.
5.1.1. Use of Insecure Algorithms
It is not always possible for a responder to generate a response that
the client is expected to understand and that meets contemporary
standards for cryptographic security. In such cases, an OCSP
responder operator MUST balance the risk of employing a compromised
security solution and the cost of mandating an upgrade, including the
risk that the alternative chosen by end users will offer even less
security or no security.
In archival applications, it is quite possible that an OCSP responder
might be asked to report the validity of a certificate on a date in
the distant past. Such a certificate might employ a signing method
that is no longer considered acceptably secure. In such
circumstances, the responder MUST NOT generate a signature using a
signing mechanism that is not considered acceptably secure.
A client MUST accept any signing algorithm in a response that it
specified as a preferred signing algorithm in the request. It
follows, therefore, that a client MUST NOT specify as a preferred
signing algorithm any algorithm that is either not supported or not
considered acceptably secure.
5.1.2. Man-in-the-Middle Downgrade Attack
The mechanism to support client indication of preferred signature
algorithms is not protected against a man-in-the-middle downgrade
attack. This constraint is not considered to be a significant
security concern, since the OCSP responder MUST NOT sign OCSP
responses using weak algorithms even if requested by the client. In
addition, the client can reject OCSP responses that do not meet its
own criteria for acceptable cryptographic security no matter what
mechanism is used to determine the signing algorithm of the response.
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5.1.3. Denial-of-Service Attack
Algorithm agility mechanisms defined in this document introduce a
slightly increased attack surface for denial-of-service attacks where
the client request is altered to require algorithms that are not
supported by the server. Denial-of-service considerations as
discussed in RFC 4732 [RFC4732] are relevant for this document.
6. IANA Considerations
This document includes media type registrations (in Appendix C) for
ocsp-request and ocsp-response that were registered when RFC 2560 was
published. Because this document obsoletes RFC 2560, IANA has
updated the references in the "Application Media Types" registry for
ocsp-request and ocsp-response to point to this document.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and
Identifiers for the Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 3279, April 2002.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional
Algorithms and Identifiers for RSA Cryptography for use in
the Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile", RFC 4055,
June 2005.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
Santesson, et al. Standards Track [Page 28]
RFC 6960 PKIX OCSP June 2013
[RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
Mail Extensions (S/MIME) Version 3.2 Message
Specification", RFC 5751, January 2010.
[RFC6277] Santesson, S. and P. Hallam-Baker, "Online Certificate
Status Protocol Algorithm Agility", RFC 6277, June 2011.
[X.690] ITU-T Recommendation X.690 (2008) | ISO/IEC 8825-1:2008,
"Information Technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", November 2008.
7.2. Informative References
[RFC2560] Myers, M., Ankney, R., Malpani, A., Galperin, S., and C.
Adams, "X.509 Internet Public Key Infrastructure Online
Certificate Status Protocol - OCSP", RFC 2560, June 1999.
[RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
Denial-of-Service Considerations", RFC 4732,
December 2006.
[RFC5019] Deacon, A. and R. Hurst, "The Lightweight Online
Certificate Status Protocol (OCSP) Profile for High-Volume
Environments", RFC 5019, September 2007.
[RFC5912] Hoffman, P. and J. Schaad, "New ASN.1 Modules for the
Public Key Infrastructure Using X.509 (PKIX)", RFC 5912,
June 2010.
8. Acknowledgements
Development of this document has been made possible thanks to
extensive inputs from members of the PKIX working group.
Jim Schaad provided valuable support by compiling and checking the
ASN.1 modules of this specification.
Santesson, et al. Standards Track [Page 29]
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Appendix A. OCSP over HTTP
This section describes the formatting that will be done to the
request and response to support HTTP [RFC2616].
A.1. Request
HTTP-based OCSP requests can use either the GET or the POST method to
submit their requests. To enable HTTP caching, small requests (that
after encoding are less than 255 bytes) MAY be submitted using GET.
If HTTP caching is not important or if the request is greater than
255 bytes, the request SHOULD be submitted using POST. Where privacy
is a requirement, OCSP transactions exchanged using HTTP MAY be
protected using either Transport Layer Security/Secure Socket Layer
(TLS/SSL) or some other lower-layer protocol.
An OCSP request using the GET method is constructed as follows:
GET {url}/{url-encoding of base-64 encoding of the DER encoding of
the OCSPRequest}
where {url} may be derived from the value of the authority
information access extension in the certificate being checked for
revocation, or other local configuration of the OCSP client.
An OCSP request using the POST method is constructed as follows: The
Content-Type header has the value "application/ocsp-request", while
the body of the message is the binary value of the DER encoding of
the OCSPRequest.
A.2. Response
An HTTP-based OCSP response is composed of the appropriate HTTP
headers, followed by the binary value of the DER encoding of the
OCSPResponse. The Content-Type header has the value
"application/ocsp-response". The Content-Length header SHOULD
specify the length of the response. Other HTTP headers MAY be
present and MAY be ignored if not understood by the requestor.
Appendix B. ASN.1 Modules
This appendix includes the ASN.1 modules for OCSP. Appendix B.1
includes an ASN.1 module that conforms to the 1998 version of ASN.1
for all syntax elements of OCSP, including the preferred signature
algorithms extension that was defined in [RFC6277]. This module
replaces the modules in Appendix B of [RFC2560] and Appendix A.2 of
[RFC6277]. Appendix B.2 includes an ASN.1 module, corresponding to
the module present in B.1, that conforms to the 2008 version of
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ASN.1. This module replaces the modules in Section 12 of [RFC5912]
and Appendix A.1 of [RFC6277]. Although a 2008 ASN.1 module is
provided, the module in Appendix B.1 remains the normative module as
per the policy of the PKIX working group.
B.1. OCSP in ASN.1 - 1998 Syntax
OCSP-2013-88
{iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-ocsp-2013-88(81)}
DEFINITIONS EXPLICIT TAGS ::=
BEGIN
IMPORTS
-- PKIX Certificate Extensions
AuthorityInfoAccessSyntax, CRLReason, GeneralName
FROM PKIX1Implicit88 { iso(1) identified-organization(3)
dod(6) internet(1) security(5) mechanisms(5) pkix(7)
id-mod(0) id-pkix1-implicit(19) }
Name, CertificateSerialNumber, Extensions,
id-kp, id-ad-ocsp, Certificate, AlgorithmIdentifier
FROM PKIX1Explicit88 { iso(1) identified-organization(3)
dod(6) internet(1) security(5) mechanisms(5) pkix(7)
id-mod(0) id-pkix1-explicit(18) };
OCSPRequest ::= SEQUENCE {
tbsRequest TBSRequest,
optionalSignature [0] EXPLICIT Signature OPTIONAL }
TBSRequest ::= SEQUENCE {
version [0] EXPLICIT Version DEFAULT v1,
requestorName [1] EXPLICIT GeneralName OPTIONAL,
requestList SEQUENCE OF Request,
requestExtensions [2] EXPLICIT Extensions OPTIONAL }
Signature ::= SEQUENCE {
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING,
certs [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL }
Version ::= INTEGER { v1(0) }
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Request ::= SEQUENCE {
reqCert CertID,
singleRequestExtensions [0] EXPLICIT Extensions OPTIONAL }
CertID ::= SEQUENCE {
hashAlgorithm AlgorithmIdentifier,
issuerNameHash OCTET STRING, -- Hash of issuer's DN
issuerKeyHash OCTET STRING, -- Hash of issuer's public key
serialNumber CertificateSerialNumber }
OCSPResponse ::= SEQUENCE {
responseStatus OCSPResponseStatus,
responseBytes [0] EXPLICIT ResponseBytes OPTIONAL }
OCSPResponseStatus ::= ENUMERATED {
successful (0), -- Response has valid confirmations
malformedRequest (1), -- Illegal confirmation request
internalError (2), -- Internal error in issuer
tryLater (3), -- Try again later
-- (4) is not used
sigRequired (5), -- Must sign the request
unauthorized (6) -- Request unauthorized
}
ResponseBytes ::= SEQUENCE {
responseType OBJECT IDENTIFIER,
response OCTET STRING }
BasicOCSPResponse ::= SEQUENCE {
tbsResponseData ResponseData,
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING,
certs [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL }
ResponseData ::= SEQUENCE {
version [0] EXPLICIT Version DEFAULT v1,
responderID ResponderID,
producedAt GeneralizedTime,
responses SEQUENCE OF SingleResponse,
responseExtensions [1] EXPLICIT Extensions OPTIONAL }
ResponderID ::= CHOICE {
byName [1] Name,
byKey [2] KeyHash }
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KeyHash ::= OCTET STRING -- SHA-1 hash of responder's public key
-- (i.e., the SHA-1 hash of the value of the
-- BIT STRING subjectPublicKey [excluding
-- the tag, length, and number of unused
-- bits] in the responder's certificate)
SingleResponse ::= SEQUENCE {
certID CertID,
certStatus CertStatus,
thisUpdate GeneralizedTime,
nextUpdate [0] EXPLICIT GeneralizedTime OPTIONAL,
singleExtensions [1] EXPLICIT Extensions OPTIONAL }
CertStatus ::= CHOICE {
good [0] IMPLICIT NULL,
revoked [1] IMPLICIT RevokedInfo,
unknown [2] IMPLICIT UnknownInfo }
RevokedInfo ::= SEQUENCE {
revocationTime GeneralizedTime,
revocationReason [0] EXPLICIT CRLReason OPTIONAL }
UnknownInfo ::= NULL
ArchiveCutoff ::= GeneralizedTime
AcceptableResponses ::= SEQUENCE OF OBJECT IDENTIFIER
ServiceLocator ::= SEQUENCE {
issuer Name,
locator AuthorityInfoAccessSyntax }
CrlID ::= SEQUENCE {
crlUrl [0] EXPLICIT IA5String OPTIONAL,
crlNum [1] EXPLICIT INTEGER OPTIONAL,
crlTime [2] EXPLICIT GeneralizedTime OPTIONAL }
PreferredSignatureAlgorithms ::= SEQUENCE OF PreferredSignatureAlgorithm
PreferredSignatureAlgorithm ::= SEQUENCE {
sigIdentifier AlgorithmIdentifier,
certIdentifier AlgorithmIdentifier OPTIONAL }
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-- Object Identifiers
id-kp-OCSPSigning OBJECT IDENTIFIER ::= { id-kp 9 }
id-pkix-ocsp OBJECT IDENTIFIER ::= { id-ad-ocsp }
id-pkix-ocsp-basic OBJECT IDENTIFIER ::= { id-pkix-ocsp 1 }
id-pkix-ocsp-nonce OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 }
id-pkix-ocsp-crl OBJECT IDENTIFIER ::= { id-pkix-ocsp 3 }
id-pkix-ocsp-response OBJECT IDENTIFIER ::= { id-pkix-ocsp 4 }
id-pkix-ocsp-nocheck OBJECT IDENTIFIER ::= { id-pkix-ocsp 5 }
id-pkix-ocsp-archive-cutoff OBJECT IDENTIFIER ::= { id-pkix-ocsp 6 }
id-pkix-ocsp-service-locator OBJECT IDENTIFIER ::= { id-pkix-ocsp 7 }
id-pkix-ocsp-pref-sig-algs OBJECT IDENTIFIER ::= { id-pkix-ocsp 8 }
id-pkix-ocsp-extended-revoke OBJECT IDENTIFIER ::= { id-pkix-ocsp 9 }
END
B.2. OCSP in ASN.1 - 2008 Syntax
OCSP-2013-08
{iso(1) identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) id-mod(0) id-mod-ocsp-2013-08(82)}
DEFINITIONS EXPLICIT TAGS ::=
BEGIN
IMPORTS
Extensions{}, EXTENSION, ATTRIBUTE
FROM PKIX-CommonTypes-2009 -- From [RFC5912]
{iso(1) identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) id-mod(0) id-mod-pkixCommon-02(57)}
AlgorithmIdentifier{}, DIGEST-ALGORITHM, SIGNATURE-ALGORITHM, PUBLIC-KEY
FROM AlgorithmInformation-2009 -- From [RFC5912]
{iso(1) identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) id-mod(0)
id-mod-algorithmInformation-02(58)}
AuthorityInfoAccessSyntax, GeneralName, CrlEntryExtensions
FROM PKIX1Implicit-2009 -- From [RFC5912]
{iso(1) identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-implicit-02(59)}
Name, CertificateSerialNumber, id-kp, id-ad-ocsp, Certificate
FROM PKIX1Explicit-2009 -- From [RFC5912]
{iso(1) identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-explicit-02(51)}
Santesson, et al. Standards Track [Page 34]
RFC 6960 PKIX OCSP June 2013
sa-dsaWithSHA1, sa-rsaWithMD2, sa-rsaWithMD5, sa-rsaWithSHA1
FROM PKIXAlgs-2009 -- From [RFC5912]
{iso(1) identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) id-mod(0)
id-mod-pkix1-algorithms2008-02(56)};
OCSPRequest ::= SEQUENCE {
tbsRequest TBSRequest,
optionalSignature [0] EXPLICIT Signature OPTIONAL }
TBSRequest ::= SEQUENCE {
version [0] EXPLICIT Version DEFAULT v1,
requestorName [1] EXPLICIT GeneralName OPTIONAL,
requestList SEQUENCE OF Request,
requestExtensions [2] EXPLICIT Extensions {{re-ocsp-nonce |
re-ocsp-response, ...,
re-ocsp-preferred-signature-algorithms}} OPTIONAL }
Signature ::= SEQUENCE {
signatureAlgorithm AlgorithmIdentifier
{ SIGNATURE-ALGORITHM, {...}},
signature BIT STRING,
certs [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL }
Version ::= INTEGER { v1(0) }
Request ::= SEQUENCE {
reqCert CertID,
singleRequestExtensions [0] EXPLICIT Extensions
{ {re-ocsp-service-locator,
...}} OPTIONAL }
CertID ::= SEQUENCE {
hashAlgorithm AlgorithmIdentifier
{DIGEST-ALGORITHM, {...}},
issuerNameHash OCTET STRING, -- Hash of issuer's DN
issuerKeyHash OCTET STRING, -- Hash of issuer's public key
serialNumber CertificateSerialNumber }
OCSPResponse ::= SEQUENCE {
responseStatus OCSPResponseStatus,
responseBytes [0] EXPLICIT ResponseBytes OPTIONAL }
Santesson, et al. Standards Track [Page 35]
RFC 6960 PKIX OCSP June 2013
OCSPResponseStatus ::= ENUMERATED {
successful (0), -- Response has valid confirmations
malformedRequest (1), -- Illegal confirmation request
internalError (2), -- Internal error in issuer
tryLater (3), -- Try again later
-- (4) is not used
sigRequired (5), -- Must sign the request
unauthorized (6) -- Request unauthorized
}
RESPONSE ::= TYPE-IDENTIFIER
ResponseSet RESPONSE ::= {basicResponse, ...}
ResponseBytes ::= SEQUENCE {
responseType RESPONSE.
&id ({ResponseSet}),
response OCTET STRING (CONTAINING RESPONSE.
&Type({ResponseSet}{@responseType}))}
basicResponse RESPONSE ::=
{ BasicOCSPResponse IDENTIFIED BY id-pkix-ocsp-basic }
BasicOCSPResponse ::= SEQUENCE {
tbsResponseData ResponseData,
signatureAlgorithm AlgorithmIdentifier{SIGNATURE-ALGORITHM,
{sa-dsaWithSHA1 | sa-rsaWithSHA1 |
sa-rsaWithMD5 | sa-rsaWithMD2, ...}},
signature BIT STRING,
certs [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL }
ResponseData ::= SEQUENCE {
version [0] EXPLICIT Version DEFAULT v1,
responderID ResponderID,
producedAt GeneralizedTime,
responses SEQUENCE OF SingleResponse,
responseExtensions [1] EXPLICIT Extensions
{{re-ocsp-nonce, ...,
re-ocsp-extended-revoke}} OPTIONAL }
ResponderID ::= CHOICE {
byName [1] Name,
byKey [2] KeyHash }
KeyHash ::= OCTET STRING -- SHA-1 hash of responder's public key
-- (excluding the tag and length fields)
Santesson, et al. Standards Track [Page 36]
RFC 6960 PKIX OCSP June 2013
SingleResponse ::= SEQUENCE {
certID CertID,
certStatus CertStatus,
thisUpdate GeneralizedTime,
nextUpdate [0] EXPLICIT GeneralizedTime OPTIONAL,
singleExtensions [1] EXPLICIT Extensions{{re-ocsp-crl |
re-ocsp-archive-cutoff |
CrlEntryExtensions, ...}
} OPTIONAL }
CertStatus ::= CHOICE {
good [0] IMPLICIT NULL,
revoked [1] IMPLICIT RevokedInfo,
unknown [2] IMPLICIT UnknownInfo }
RevokedInfo ::= SEQUENCE {
revocationTime GeneralizedTime,
revocationReason [0] EXPLICIT CRLReason OPTIONAL }
UnknownInfo ::= NULL
ArchiveCutoff ::= GeneralizedTime
AcceptableResponses ::= SEQUENCE OF RESPONSE.&id({ResponseSet})
ServiceLocator ::= SEQUENCE {
issuer Name,
locator AuthorityInfoAccessSyntax }
CrlID ::= SEQUENCE {
crlUrl [0] EXPLICIT IA5String OPTIONAL,
crlNum [1] EXPLICIT INTEGER OPTIONAL,
crlTime [2] EXPLICIT GeneralizedTime OPTIONAL }
PreferredSignatureAlgorithms ::= SEQUENCE OF PreferredSignatureAlgorithm
PreferredSignatureAlgorithm ::= SEQUENCE {
sigIdentifier AlgorithmIdentifier{SIGNATURE-ALGORITHM, {...}},
certIdentifier AlgorithmIdentifier{PUBLIC-KEY, {...}} OPTIONAL
}
-- Certificate Extensions
ext-ocsp-nocheck EXTENSION ::= { SYNTAX NULL IDENTIFIED
BY id-pkix-ocsp-nocheck }
Santesson, et al. Standards Track [Page 37]
RFC 6960 PKIX OCSP June 2013
-- Request Extensions
re-ocsp-nonce EXTENSION ::= { SYNTAX OCTET STRING IDENTIFIED
BY id-pkix-ocsp-nonce }
re-ocsp-response EXTENSION ::= { SYNTAX AcceptableResponses IDENTIFIED
BY id-pkix-ocsp-response }
re-ocsp-service-locator EXTENSION ::= { SYNTAX ServiceLocator
IDENTIFIED BY
id-pkix-ocsp-service-locator }
re-ocsp-preferred-signature-algorithms EXTENSION ::= {
SYNTAX PreferredSignatureAlgorithms
IDENTIFIED BY id-pkix-ocsp-pref-sig-algs }
-- Response Extensions
re-ocsp-crl EXTENSION ::= { SYNTAX CrlID IDENTIFIED BY
id-pkix-ocsp-crl }
re-ocsp-archive-cutoff EXTENSION ::= { SYNTAX ArchiveCutoff
IDENTIFIED BY
id-pkix-ocsp-archive-cutoff }
re-ocsp-extended-revoke EXTENSION ::= { SYNTAX NULL IDENTIFIED BY
id-pkix-ocsp-extended-revoke }
-- Object Identifiers
id-kp-OCSPSigning OBJECT IDENTIFIER ::= { id-kp 9 }
id-pkix-ocsp OBJECT IDENTIFIER ::= id-ad-ocsp
id-pkix-ocsp-basic OBJECT IDENTIFIER ::= { id-pkix-ocsp 1 }
id-pkix-ocsp-nonce OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 }
id-pkix-ocsp-crl OBJECT IDENTIFIER ::= { id-pkix-ocsp 3 }
id-pkix-ocsp-response OBJECT IDENTIFIER ::= { id-pkix-ocsp 4 }
id-pkix-ocsp-nocheck OBJECT IDENTIFIER ::= { id-pkix-ocsp 5 }
id-pkix-ocsp-archive-cutoff OBJECT IDENTIFIER ::= { id-pkix-ocsp 6 }
id-pkix-ocsp-service-locator OBJECT IDENTIFIER ::= { id-pkix-ocsp 7 }
id-pkix-ocsp-pref-sig-algs OBJECT IDENTIFIER ::= { id-pkix-ocsp 8 }
id-pkix-ocsp-extended-revoke OBJECT IDENTIFIER ::= { id-pkix-ocsp 9 }
END
Santesson, et al. Standards Track [Page 38]
RFC 6960 PKIX OCSP June 2013
Appendix C. MIME Registrations
C.1. application/ocsp-request
To: ietf-types@iana.org
Subject: Registration of MIME media type application/ocsp-request
MIME media type name: application
MIME subtype name: ocsp-request
Required parameters: None
Optional parameters: None
Encoding considerations: binary
Security considerations: Carries a request for information. This
request may optionally be cryptographically signed.
Interoperability considerations: None
Published specification: IETF PKIX Working Group document on the
Online Certificate Status Protocol - OCSP
Applications which use this media type: OCSP clients
Additional information:
Magic number(s): None
File extension(s): .ORQ
Macintosh File Type Code(s): none
Person & email address to contact for further information:
Stefan Santesson <sts@aaa-sec.com>
Intended usage: COMMON
Author/Change controller: IETF
Santesson, et al. Standards Track [Page 39]
RFC 6960 PKIX OCSP June 2013
C.2. application/ocsp-response
To: ietf-types@iana.org
Subject: Registration of MIME media type application/ocsp-response
MIME media type name: application
MIME subtype name: ocsp-response
Required parameters: None
Optional parameters: None
Encoding considerations: binary
Security considerations: Carries a cryptographically signed response.
Interoperability considerations: None
Published specification: IETF PKIX Working Group document on the
Online Certificate Status Protocol - OCSP
Applications which use this media type: OCSP servers
Additional information:
Magic number(s): None
File extension(s): .ORS
Macintosh File Type Code(s): none
Person & email address to contact for further information:
Stefan Santesson <sts@aaa-sec.com>
Intended usage: COMMON
Author/Change controller: IETF
Santesson, et al. Standards Track [Page 40]
RFC 6960 PKIX OCSP June 2013
Authors' Addresses
Stefan Santesson
3xA Security AB
Scheelev. 17
223 70 Lund
Sweden
EMail: sts@aaa-sec.com
Michael Myers
TraceRoute Security
EMail: mmyers@fastq.com
Rich Ankney
Ambarish Malpani
CA Technologies
455 West Maude Ave. Suite 210
Sunnyvale, CA 94085
United States
EMail: ambarish@gmail.com
Slava Galperin
A9.com Inc.
130 Lytton Ave. Suite 300
Palo Alto, CA 94301
United States
EMail: slava.galperin@gmail.com
Carlisle Adams
University of Ottawa
800 King Edward Avenue
Ottawa ON K1N 6N5
Canada
EMail: cadams@eecs.uottawa.ca
Santesson, et al. Standards Track [Page 41]