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draft-ietf-pkix-ocsp-03.txt --> draft-ietf-pkix-ocsp-04.txt

Expires in 6 months March June 1998

X.509 Internet Public Key Infrastructure
Online Certificate Status Protocol - OCSP
<draft-ietf-pkix-ocsp-03.txt>
<draft-ietf-pkix-ocsp-04.txt>

Status of this Memo

This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
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ftp.isi.edu (US West Coast).

1. Abstract

This document specifies a protocol useful in determining the current
status of a digital certificate without the use of requiring CRLs. Additional
mechanisms addressing PKIX operational requirements are specified in
separate documents.

Section 2 provides an overview of the protocol. Section 3 goes establishes
functional requirements, while section 4 provides the details of the
protocol. In section 5 we cover security issues with the
protocol. Appendix A demonstrates OCSP over HTTP and appendix B
accumulates ASN.1 syntactic elements.

2. Protocol Overview

In lieu of or as a supplement to checking against a periodic CRL, it
may be necessary to obtain timely status regarding a certificate’s certificate's
revocation state (cf. PKIX Part 1, Section 3.3). Examples include
high- value funds transfer or the compromise of a highly sensitive key. large stock trades.

The Online Certificate Status Protocol (OCSP) enables applications to
determine the revocation state of an identified certificate. OCSP may

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be used to satisfy some of the operational requirements of providing
more timely revocation information than is possible with CRLs. An
OCSP client issues a status request to an OCSP responder and suspends
acceptance of the certificate in question until the responder provides
a response.

This protocol specifies the data that needs to be exchanged between an
application checking the revocation status of a certificate and the
server providing that status.

2.1 Request

An OCSP request contains the following data:

- protocol version
- service request
- target certificate identifier or a single end-entity certificate
- optional extensions which MAY be processed by the OCSP Responder

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, service and 3) the responder can perform request contains the requested
service for information needed
by the subject certificate. responder. If any one of the prior conditions are 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. However, there is one basic
type of OCSP response that MUST be supported by all OCSP servers and
clients. The rest of this section only describes this basic response
type.

An OCSP response consists of a response type and the bytes of the
actual response. 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 requester
- a CA Designated Responder (Authorized Responder) who holds a special
certificate issued by the CA indicating that it may issue OCSP responses
for that CA

A definitive response message is composed of:

- response type identifier (to allow for different response types)
- version of the response
- name of the responder
- responses for each of the certificates in a request
- optional extensions
- signature algorithm OID
- signature computed across hash of the response

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:

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- notRevoked
- revoked
- onHold
- expired unknown

The notRevoked state indicates that the certificate is not revoked. It
does not necessarily mean that the certificate was ever issued. Nor
does it mean that the certificate is in its validity interval. A
notRevoked state by an OCSP responder DOES NOT absolve the application
of the responsibility of checking that the certificate is in its
validity period and has been correctly signed. For example, it is
quite possible that an OCSP responder returns the notRevoked state if
a certificate was revoked, but has since expired (equivalent to a
serial number being dropped from the CRL).

The revoked state indicates that the certificate has been revoked.

The onHold state corresponds to valid certificates that are
operationally suspended in accordance with PKIX Part 1.

A request that returns an expired unknown state indicates that the validity of
the subject certificate has expired. Applications SHOULD check responder doesn't know about the
validity interval of a
certificate and not perform an OCSP request if
the certificate’s validity has expired. being requested.

2.3 Exception Cases

In case of errors, the OCSP Responder may return an error message.
Errors can be of the following types:

- malformedRequest
- internalError
- tryLater
- notFound
- certRequired
- noCRL sigRequired

A server produces the malformedRequest response if the request
received does not conform to the OCSP syntax.

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.

A recipient of a request may not be able to resolve a reference to the
subject certificate; a value of notFound is returned in such a case.
This value should not be taken as confirmation of the certificate's
existence.

The response certRequired is returned in cases where the server
requires the client to supply the certificate data itself in order to
construct a response.

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An extension is defined to enable delivery of CRLs with OCSP responses.
However, there

The response sigRequired is no requirement to list certificates on a CRL returned in cases where the server
requires the client sign the request in order to use OCSP to acquire revocation status on those certificates. The
error value noCRL is defined for this instance. construct a response.

2.4 Response Pre-production

The response validity interval noted Semantics of thisUpdate, nextUpdate and producedAt

Responses can contain three times in them - thisUpdate, nextUpdate and
producedAt. The semantics of these fields are:

- thisUpdate: the prior section time at which the status being indicated is composed of
a {thisUpdate, nextUpdate} pair of elements in
known to be correct
- nextUpdate: the response syntax.
Section 4.2 provides details time at or before which newer information will
be available about the status of the response syntax. certificate
- producedAt: the time at which the OCSP responder signed this
response.

If nextUpdate is not set, the responder is indicating that newer
revocation information is available all the time.

2.5 Response Pre-production

OCSP responders MAY pre-produce signed responses specifying the current status
of certificates at the time the response was produced. a specified time. The time at which the response status was produced
known to be correct SHALL be reflected in the thisUpdate field of the
response.

If responses are pre-produced, then for a given certificate, the
periodicity of this pre-production SHOULD match the response validity
interval of the most recently produced response.

[need to resolve the above statement with The time at or before which newer information will be
available is reflected in the following RCSP assertions,
esp. with respect to positive responses. Question put to nextUpdate field, while the list.]

The time at
which the response was known to be correct SHALL
be specified produced will appear in the producedAt field of
the response. This time is

2.6 OCSP Signature Authority Delegation

The key that signs a certificate's revocation information need not
necessarily be
the same as the time at which the response was produced -
e.g. if key that signed the responder obtains certificate. A certificate's issuer
explicitly delegates OCSP signing authority by issuing a CRL from certificate
containing a CA and creates pre-produced
responses, the thisUpdate time should specify the thisUpdate time unique value for extendedKeyUsage in the CRL.

The producer OCSP signer's
certificate.

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 response MAY include a value for nextUpdate. The
exact interval between thisUpdate and nextUpdate for given response is
a matter of local security and operational policy. If the nextUpdate
field is not present, the response is is known to be correct at the
thisUpdate time. Equivalently, the nextUpdate field is considered to be
the same as the thisUpdate field.

No assertions are being made about the current state of the certificate,
nor are any recommendations being made as to when the requestor should
check again with the responder. If the value of nextUpdate is set, it
is just a hint, not a guarantee, of when the responder expects to have
new information about that certificate's status.

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 capability to include the
AuthorityInfoAccess extension (defined in PKIX Part 1, 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.

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CAs that support an OCSP service, either hosted locally or provided by
an Authorized Responder, MAY provide a value for a
uniformResourceIndicator (URI) 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
corresponds
defines the transport (e.g. HTTP) used to access the URL placed into an OCSP request.

3.3 responder
and may contain other transport dependent information (e.g. a URL).

3.2 Error Responses

Upon receipt of a request which fails to parse, the receiving OCSP
responder SHALL respond with an error message. Error responses MAY be
signed.

3.5

3.3 Signed Response Acceptance Requirements

Prior to accepting a signed response as valid, OCSP clients SHALL
confirm that:

a. The certificate identified in a received response corresponds to
that which was identified in the corresponding request;

2.
b. The signature on the response is valid;

3.
c. The identity of the signer matches the intended recipient of the
request.
d. The signer is currently authorized to sign the response.
e. The response is in its validity period.

4. Detailed Protocol

The ASN.1 syntax imports terms defined in the X.509 Certificate and
CRL Profile Internet Draft. 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: Version, Extensions,
CertificateSerialNumber, SubjectPublicKeyInfo, Name,
AlgorithmIdentifier, GeneralizedTime CRLReason

4.1 Requests

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 Request Syntax

OCSPRequest ::= SEQUENCE {
tbsRequest TBSRequest
optionalSignature [0] Signature OPTIONAL }

TBSRequest ::= SEQUENCE {
version [0] EXPLICIT Version DEFAULT v1,
hashAlgorithm AlgorithmIdentifier,
requestList SEQUENCE OF Request,
requestExtensions [1] EXPLICIT Extensions OPTIONAL }

Signature ::= SEQUENCE {
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING,
certs [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL
}

Version ::= INTEGER { v1(0) }

Request ::= SEQUENCE {
reqCert RequestedCert,
singleRequestExtensions [0] EXPLICIT Extensions OPTIONAL }

RequestedCert ::= CHOICE {
certID [0] EXPLICIT CertID,
cert [1] EXPLICIT Certificate }

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CertID ::= SEQUENCE {
issuerNameAndKeyHash Hash,
hashAlgorithm AlgorithmIdentifier,
issuerNameHash OCTET STRING, -- Hash of Issuer's DN
issuerKeyHash OCTET STRING, -- Hash of Issuers public key
serialNumber CertificateSerialNumber }

IssuerNameAndKey ::= SEQUENCE {
issuer Name,
issuerPublicKey SubjectPublicKeyInfo }

Hash ::= OCTET STRING --hash

issuerNameHash is the hash of IssuerNameAndKey--

3.2 Response Syntax

This section specifies the ASN.1 specification Issuer's distinguished name. The
hash shall be calculated over the DER encoding of the issuer's name
field in the certificate being checked. issuerKeyHash is the hash of
the Issuer's public key. The hash shall be calculated over the the
value (excluding tag and length) of the subject public key field in
the issuer's certificate.

4.1.2 Notes on the Request Syntax

The primary reason to use both the name and the public key 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.

While it is possible to identify a certificate by sending over either
the entire certificate or just a CertID, it is recommended that
clients use just the CertID to reduce the size of the request.
However, certain OCSP responders MAY require the entire certificate
whose status is to be determined.

Support for extensions is OPTIONAL. The critical flag SHOULD NOT be
set for any of them. This standard suggests several useful extensions
in Section 4.5. Additional extensions MAY be defined in additional
RFCs. Unrecognized extensions SHOULD be ignored.

Requests may be signed or unsigned. For signed requests, the
optionalSignature field is present, while it is absent for unsigned
requests.

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, (HTTP, SMTP, LDAP, etc.).

3.2.1

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, responseBytes are
not set.

OCSPResponse ::= SEQUENCE {
responseStatus OCSPResponseStatus,
responseBytes [0] EXPLICIT ResponseBytes OPTIONAL }

OCSPResponseStatus ::= ENUMERATED {
successful (0), --Response has valid confirmations confirmations--
malformedRequest (1), --Illegal confirmation request request--
internalError (2), --Internal error in issuer issuer--
tryLater (3), --Try again later
notFound (4), --Certificate not on record later--
certRequired (5) (4), --Must supply certificate
sigRequired (5) --Must sign the request-- }

3.2.1.1 BasicResponse

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,
where:

id-pkix-ocsp OBJECT IDENTIFIER ::= { id-ad-ocsp }
id-pkix-ocsp-basic OBJECT IDENTIFIER ::= { id-pkix-ocsp 1 }

OCSP responders SHALL be capable of recognizing and responding to the
id-pkix-ocsp-basic response type. Correspondingly, OCSP clients SHALL
be capable of receiving and processing 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 [1] EXPLICIT SEQUENCE OF Certificate OPTIONAL }

The value for signature SHALL be computed on the hash of the DER
encoding ResponseData.

3.2.1.2 ResponseData

ResponseData ::= SEQUENCE {
version [0] EXPLICIT Version DEFAULT v1,
reponderID
responderID ResponderID,
producedAt GeneralizedTime,
responses SEQUENCE OF SingleResponse,
responseExtensions [1] EXPLICIT Extensions OPTIONAL }

ResponderID ::= CHOICE {
byName [0] Name,
byKey [1] KeyHash }

KeyHash ::= KeyIdentifier –-SHA-1 OCTET STRING --SHA-1 hash as defined in PKIX Part.1

3.2.1.3 SingleResponse

[note: question put to of responder's public key
(excluding the list regarding bandwidth issues associated
with sending certificates back; could just use certID directly since
requester already has certificates in question.] tag and length fields)

SingleResponse ::= SEQUENCE {
request Request,
certID certID,
certStatus CertStatus,
producedAt
thisUpdate GeneralizedTime,
nextUpdate [0] EXPLICIT GeneralizedTime OPTIONAL,
singleExtensions [2] [1] EXPLICIT Extensions OPTIONAL }

CertStatus ::= CHOICE {
certStatusType
notRevoked [0] EXPLICIT CertStatusType (notRevoked | onHold),
statusWithTime IMPLICIT NULL,
revoked [1] EXPLICIT StatusWithTime IMPLICIT RevokedInfo,
unknown [2] IMPLICIT UnknownInfo }

StatusWithTime

RevokedInfo ::= SEQUENCE {
certStatusType CertStatusType (revoked),
time GeneralizedTime
revocationTime GeneralizedTime,
revocationReason [0] EXPLICIT CRLReason OPTIONAL }

CertStatusType

UnknownInfo ::= ENUMERATED {
notRevoked (0), --This serial number is not revoked
revoked (1), --Serial number was revoked
onHold (2), --Cert is on hold
expired (3) NULL -- this can be replaced with an enumeration

4.2.2 Notes on OCSP Responses

4.2.2.1 Identification of the target certificate in a response

In responses, the certificate whose status is expired }

Applications SHOULD determine being returned, is always
identified by observation of the certificate’s certID, even if the query was specified using the full
certificate.

4.2.2.2 Time

The thisUpdate and nextUpdate fields define a recommended validity
interval. This interval that 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 earlier than the local system time SHOULD be
considered unreliable. Responses where the nextUpdate value is not
set are equivalent to a certificate CRL with no time for nextUpdate (see section
2.3).

The producedAt time is expired. the time at which this response was signed.

4.2.2.3 Authorized Responders

The expired value of

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CertStatusType defines key that signs a certificate's revocation information need not be
the same key that signed the certificate. A certificate's issuer MAY
explicitly delegate OCSP signing authority by issuing a certificate
including an extendedKeyUsage extension in the OCSP signer's
certificate containing the value id-kp-OCSPSigning.

id-kp-OCSPSigning OBJECT IDENTIFIER ::= {id-kp ?}

4.2.2.3.1 Revocation Checking of an Authorized Responder

[Note: The requirement of the following mechanism to return when actively inhibit a request is received
revocation check of an Authorized Responder's certificate needs review
and
comment by the list.]

Since an Authorized OCSP responder provides revocation information for
a subject CA, OCSP clients need to know how to check that an authorized
responder's certificate in has not been revoked. CAs may choose to deal
with this state.

3.2.2 Notes on problem in one of three ways:

- A CA may specify that an OCSP Responses

If client can trust a responder for the certStatusType is revoked, onHold or expired,
lifetime of the time field responder's authorization 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 should be NULL. CAs
issuing such a certificate should realized that a compromise of
StatusWithTime the
responder's key, is as serious as the time compromise of revocation, suspension or expiration
respectively. The date returned for expiration should match the
notAfter date of CA's key, at
least for the certificate’s validity interval.

The thisUpdate and nextUpdate fields define period of this certificate. CA's may choose to
issue this type of certificate with a recommended validity
interval. very short lifetime and renew it
frequently.
- A CA may specify how the responder's certificate be checked for
revocation. This interval corresponds to can be done using CRL Distribution Points if the {thisUpdate, nextUpdate}
interval in CRLs. Responses whose nextUpdate value is earlier
than
check should be done using CRLs or CRL Distribution Points, or
Authority Information Access if the local system time value SHOULD check should be considered unreliable.
Responses whose thusUpdate time is earlier than done in some other
way. Details for specifying either of these two mechanisms are
available in PKIX Part 1.
- A CA may choose not to specify any method of revocation checking for
the local system time
SHOULD responder's certificate, in which case, it would be considered unreliable. Responses where up to the nextUpdate value
is not set are equivalant OCSP
client's local security policy to a CRL with no time decide whether that certificate
should be checked for nextUpdate (see
section 2.3).

3.3 revocation or not.

4.3 Mandatory and Optional Cryptographic Algorithms

Clients that request OCSP services SHALL be capable of processing
responses signed used DSA keys identified by the DSA sig-alg-oid
specified in section 7.2.2 of PKIX Part 1. Clients SHOULD also be
capable of processing RSA signatures as specified in section 7.2.1 of
PKIX Part 1. OCSP responders SHALL support the SHA1 hash hashing
algorithm.

3.4

4.4 Extensions

This section defines some standard extensions. Support for all
extensions is OPTIONAL. For each extension, the definition indicates
its syntax, processing performed by the OCSP Responder, and any
extensions which are included in the corresponding response.

3.4.1

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-nonce OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 }

3.4.2 Signed Requests

This extension allows the requester to sign a request. The requestor
includes an extension that has the signatureIdentifier, the actual bits
of the signature and a sequence of certificates to allow the OCSP
responder to verify the signature. The data to be signed is just the
basic request (none of the extensions). The OCSP Responder can verify
the signature, potentially using certificates that have been included

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with the extension. The signature on a request will be identified by id-
pkix-ocsp-signature, while the value will be SignatureData, where:

id-pkix-ocsp-signature OBJECT IDENTIFIER ::= { id-pkix-ocsp 5 }

SignatureData OBJECT IDENTIFIER ::= SEQUENCE {
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING,
certs [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL id-pkix-ocsp 2 }

3.4.3

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 4 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.

Note: There is no requirement to list certificates on a CRL in order to
use OCSP to acquire revocation status on those certificates. Therefore
inclusion of this extension in a request may yield no CRL information.
The error value noCRL is defined for this instance.

3.4.4

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. The OIDs
included in AcceptableResponses are the OIDs of the various response
types this client can accept (e.g., id-pkix-ocsp-basic).

id-pkix-ocsp-response OBJECT IDENTIFIER ::= { id-pkix-ocsp 3 4 }

AcceptableResponses ::= SEQUENCE OF { id OBJECT IDENTIFIER }

As noted in section 3.3, OCSP responders SHALL be capable of
recognizing and responding to the id-pkix-ocsp-basic response
type. Correspondingly,

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processing the id-pkix- ocsp-basic response type.

3.4.5

4.4.4 Other Extensions

CRL Entry Extensions - specified in Section 5.3 of PKIX part I - are
also supported as singleExtensions.

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 denial of service vulnerability is evident with respect to a flood
of
queries constructed to produce error responses. queries. The production of a cryptographic signature significantly
affects response generation cycle time, thereby exacerbating the
situation.

Unsigned error responses can be produced more rapidly and thus reduce
the danger of this attack. However, 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
(notRevoked) 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 its successful
execution.

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.

6. References

[HTTP] Hypertext Transfer Protocol -- HTTP/1.0. T. Berners-Lee, HTTP/1.1. R. Fielding & Fielding,
J. Gettys, J. Mogul, H. Frystyk, RFC 1945, May 1996.

[ABNF] Augmented BNF for Syntax Specifications: ABNF. D. Crocker,
P. Overell, Frystyk and T. Berners-Lee, RFC 2234, November 2068, January
1997.

[MUSTSHOULD] Key words for use in RFCs to Indicate Requirement Levels,
S. Bradner, RFC 2119, March 1997.

[URL] Uniform Resource Locators (URL), T. Berners-Lee, L. Masinter, M.
McCahill, RFC 1738, December 1994.

7. Author’s Author's Address

Michael Myers
VeriSign, Inc.
1390 Shorebird Way
Mountain View, CA 94019
mmyers@verisign.com

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Rich Ankney
CertCo, LLC
13506 King Charles Dr.
Chantilly, VA 20151
rankney@erols.com

Ambarish Malpani
ValiCert, Inc.
3160 W. Bayshore Drive
Palo Alto, CA 94303
ambarish@valicert.com
650.849.9880

Slava Galperin
Netscape Communications Corp.
MV-068
501 E. Middlefield Rd.
Mountain View,
Teknowledge Corporation
1810 Embarcadero Road
Palo Alto, CA 94043
galperin@netscape.com
galperin@teknowledge.com

Carlisle Adams
Entrust Technologies
750 Heron Road, Suite E08
Ottawa, Ontario
K1V 1A7
Canada
cadams@entrust.com

Appendix A

A.1 OCSP over HTTP

This section describes the formatting that will be done to the request
and response to support HTTP.

A.1.1 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 the request is greater than
255 bytes, the request should be submitted using POST.

A.1.1.1 Requests using GET
An OCSP request using the GET method, is an HTTP 1.0 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 AuthorityInfoAccess or
other local configuration of the OCSP client.

A.1.1.2 Requests using POST

An OCSP request using the POST method. method, is constructed as follows: The
Content-Type header has the value "application/ocsp-request" while the
body of the message is the DER encoding of the OCSPRequest.

A.1.2 Response

An HTTP-based OCSP response is composed of the appropriate HTTP
headers, followed by 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.

Myers, Ankney, Malpani, Galperin, Adams [Page 11]
INTERNET DRAFT March 1998

Appendix B: OCSP in ASN.1

OCSP1 DEFINITIONS EXPLICIT TAGS::=

BEGIN

OCSPRequest ::= SEQUENCE {
tbsRequest TBSRequest
optionalSignature [0] Signature OPTIONAL }

TBSRequest ::= SEQUENCE {
version [0] EXPLICIT Version DEFAULT v1,
hashAlgorithm AlgorithmIdentifier,
requestList SEQUENCE OF Request,
requestExtensions [1] EXPLICIT Extensions OPTIONAL }

Signature ::= SEQUENCE {
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING,
certs [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL
}

Version ::= INTEGER { v1(0) }

Request ::= SEQUENCE {
reqCert RequestedCert,
singleRequestExtensions [0] EXPLICIT Extensions OPTIONAL }

RequestedCert ::= CHOICE {
certID [0] EXPLICIT CertID,
cert [1] EXPLICIT Certificate }

CertID ::= SEQUENCE {
issuerNameAndKeyHash Hash,
serialNumber CertificateSerialNumber }

IssuerNameAndKey ::= SEQUENCE {
issuer Name,
issuerPublicKey SubjectPublicKeyInfo }
hashAlgorithm AlgorithmIdentifier,
issuerNameHash OCTET STRING, -- Hash ::= of Issuer's DN
issuerKeyHash OCTET STRING --hash STRING, -- Hash of IssuerNameAndKey-- Issuers public key
serialNumber CertificateSerialNumber }

OCSPResponse ::= SEQUENCE {
responseStatus OCSPResponseStatus,
responseBytes [0] EXPLICIT ResponseBytes OPTIONAL }

ResponseBytes ::= SEQUENCE {
responseType OBJECT IDENTIFIER,
response OCTET STRING }

id-pkix-ocsp OBJECT IDENTIFIER ::= { id-ad-ocsp }
id-pkix-ocsp-basic OBJECT IDENTIFIER ::= { id-pkix-ocsp 1 }

BasicOCSPResponse ::= SEQUENCE {
tbsResponseData ResponseData,
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING,
certs [1] EXPLICIT SEQUENCE OF Certificate OPTIONAL }

ResponderID ::= CHOICE {
byName [0] Name,
byKey [1] KeyHash }

KeyHash ::= KeyIdentifier –-SHA-1 OCTET STRING --SHA-1 hash as defined in PKIX Part.1

Myers, Ankney, Malpani, Galperin, Adams [Page 12]
INTERNET DRAFT March 1998 of responder's public key
--(excluding the tag and length fields)

CertStatus ::= CHOICE {
certStatusType [0] EXPLICIT CertStatusType (notRevoked | onHold),
statusWithTime [1] EXPLICIT StatusWithTime }

StatusWithTime ::= SEQUENCE {
certStatusType CertStatusType (revoked),
time GeneralizedTime }

CertStatusType ::= ENUMERATED {
notRevoked (0), --This serial number is not revoked
revoked (1), --Serial number was [0] IMPLICIT NULL,
revoked
onHold (2), --Cert is on hold
expired (3) -- certificate is expired [1] IMPLICIT RevokedInfo,
unknown [2] IMPLICIT UnknownInfo }

--Extensions

SignatureData

RevokedInfo ::= SEQUENCE {
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING,
certs
revocationTime GeneralizedTime,
revocationReason [0] EXPLICIT SEQUENCE OF Certificate CRLReason OPTIONAL }

AcceptableResponses ::= SEQUENCE OF { id OBJECT IDENTIFIER }

CrlID

UnknownInfo ::= SEQUENCE {
crlUrl [0] EXPLICIT IA5String OPTIONAL,
crlNum [1] EXPLICIT INTEGER OPTIONAL,
crlTime [2] EXPLICIT GeneralizedTime OPTIONAL } NULL -- Object Identifiers

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-response OBJECT IDENTIFIER ::= { id-pkix-ocsp 3 }
id-pkix-ocsp-crl OBJECT IDENTIFIER ::= { id-pkix-ocsp 4 }
id-pkix-ocsp-signature OBJECT IDENTIFIER ::= { id-pkix-ocsp 5 }

Myers, Ankney, Malpani, Galperin, Adams [Page 13] this can be replaced with an enumeration

END

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: will be none for 8-bit transports and most
likely
Base64 for SMTP or other 7-bit transports

Security considerations: Carries a cryptographically signed request
for
information

Interoperability considerations: None

Published specification: This document

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:
Ambarish Malpani <ambarish@valicert.com>

Intended usage: COMMON

Author/Change controller:
Ambarish Malpani <ambarish@valicert.com>

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: will be none for 8-bit transports and most
likely
Base64 for SMTP or other 7-bit transports

Security considerations: Carries a cryptographically signed
response

Interoperability considerations: None

Published specification: This document

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:
Ambarish Malpani <ambarish@valicert.com>

Intended usage: COMMON

Author/Change controller:
Ambarish Malpani <ambarish@valicert.com>

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