rfc8954xml2.original.xml   rfc8954.xml 
<?xml version='1.0' encoding='utf-8'?> <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [ <!DOCTYPE rfc SYSTEM "rfc2629-xhtml.ent">
<!ENTITY RFC2119 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RF
C.2119.xml"> <rfc xmlns:xi="http://www.w3.org/2001/XInclude" submissionType="IETF"
<!ENTITY RFC3279 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RF category="std" consensus="true" docName="draft-ietf-lamps-ocsp-nonce-05"
C.3279.xml"> number="8954" ipr="trust200902" updates="6960" obsoletes=""
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<!ENTITY RFC5019 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RF <!-- Generated by id2xml 1.5.0 on 2020-03-02T06:24:23Z -->
C.5019.xml"> <front>
<!ENTITY RFC5912 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RF
C.5912.xml"> <title abbrev="OCSP Nonce Extension">Online Certificate Status Protocol
<!ENTITY RFC6960 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RF (OCSP) Nonce Extension</title>
C.6960.xml"> <seriesInfo name="RFC" value="8954"/>
<!ENTITY RFC5280 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RF <author initials="M." surname="Sahni" fullname="Mohit Sahni" role="editor">
C.5280.xml">
<!ENTITY RFC4086 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RF
C.4086.xml">
]>
<rfc submissionType="IETF" docName="draft-ietf-lamps-ocsp-nonce-05" category="st
d" ipr="trust200902" updates="6960">
<!-- Generated by id2xml 1.5.0 on 2020-03-02T06:24:23Z -->
<?rfc compact="yes"?>
<?rfc text-list-symbols="*o+-"?>
<?rfc subcompact="no"?>
<?rfc sortrefs="no"?>
<?rfc symrefs="yes"?>
<?rfc strict="yes"?>
<?rfc toc="yes"?>
<front>
<title>OCSP Nonce Extension</title>
<author initials="M." surname="Sahni" fullname="Mohit Sahni" role="ed
itor">
<organization>Palo Alto Networks</organization> <organization>Palo Alto Networks</organization>
<address> <address>
<postal> <postal>
<street>3000 Tannery Way</street> <street>3000 Tannery Way</street>
<city>Santa Clara</city> <city>Santa Clara</city>
<region>CA</region> <region>CA</region>
<code>95054</code> <code>95054</code>
<country>US</country> <country>United States of America</country>
</postal> </postal>
<email>msahni@paloaltonetworks.com</email> <email>msahni@paloaltonetworks.com</email>
</address> </address>
</author> </author>
<date month="November" year="2020"/>
<workgroup>LAMPS</workgroup>
<date day="10" month="September" year="2020"/> <keyword>OCSP Nonce Length</keyword>
<workgroup>LAMPS</workgroup> <keyword>OCSP Nonce Randomness</keyword>
<abstract><t>
<abstract>
<t>
This document specifies the updated format of the Nonce extension in the This document specifies the updated format of the Nonce extension in the
Online Certificate Status Protocol (OCSP) request and response Online Certificate Status Protocol (OCSP) request and response
messages. OCSP is used to check the status of a certificate and messages. OCSP is used to check the status of a certificate, and
the Nonce extension is used to cryptographically bind an OCSP the Nonce extension is used to cryptographically bind an OCSP
response message to a particular OCSP request message. This document updates RFC 6960.</t> response message to a particular OCSP request message. This document updates RFC 6960.</t>
</abstract> </abstract>
</front> </front>
<middle>
<middle> <section anchor="sect-1" numbered="true" toc="default">
<section title="Introduction" anchor="sect-1"><t> <name>Introduction</name>
<t>
This document updates the usage and format of the Nonce extension This document updates the usage and format of the Nonce extension
used in OCSP request and response messages. This extension was in OCSP request and response messages. This extension was
previously defined in section 4.4.1 of <xref target="RFC6960"/>. <xref target previously defined in <xref target="RFC6960"
="RFC6960"/> sectionFormat="of" section="4.4.1"/>. <xref target="RFC6960" format="default"
does not mention any minimum and maximum length of nonce in the Nonce />
extension. Lacking limits on the length of nonce in the Nonce extension, an O does not mention any minimum or maximum length of the nonce in the Nonce
CSP responders that follow <xref target="RFC6960"/> may be extension.
vulnerable to various attacks like Denial of Service attacks <xref target="RF
C4732"/>, chosen
prefix attacks to get a desired signature, and
possible evasions using the Nonce extension data. This
document specifies a lower limit of 1 and an upper limit of 32 to the
length of nonce in the Nonce extension. This document updates <xref target="R
FC6960"/>.</t>
<section title="Terminology" anchor="sect-1.1"><t>
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONA
L" in this
document are to be interpreted as described in BCP 14 <xref target="RFC2119"
format="default"/> <xref target="RFC8174" format="default"/> when, and only when
, they appear in all capitals, as shown here.</t>
</section>
</section>
<section title="OCSP Extensions" anchor="sect-2"><t> Lacking limits on the length of the nonce in the Nonce extension, OCSP
The message format for OCSP request and response is defined in responders that follow <xref target="RFC6960" format="default"/> may be
<xref target="RFC6960"/>. <xref target="RFC6960"/> also defines the standard vulnerable to various attacks, like Denial-of-Service attacks <xref
extensions for OCSP target="RFC4732" format="default"/> or chosen-prefix attacks (to get a desire
d signature), and
possible evasions using the Nonce extension data. This
document specifies a lower limit of 1 and an upper limit of 32 for the
length of the nonce in the Nonce extension. This document updates <xref
target="RFC6960" format="default"/>.</t>
<section anchor="sect-1.1" numbered="true" toc="default">
<name>Terminology</name>
<t>
The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
"<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
"<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to
be interpreted as
described in BCP&nbsp;14 <xref target="RFC2119"/> <xref target="RFC8174"/>
when, and only when, they appear in all capitals, as shown here.
</t>
</section>
</section>
<section anchor="sect-2" numbered="true" toc="default">
<name>OCSP Extensions</name>
<t>
The message formats for OCSP requests and responses are defined in
<xref target="RFC6960" format="default"/>. <xref target="RFC6960"
format="default"/> also defines the standard extensions for OCSP
messages based on the extension model employed in X.509 version 3 messages based on the extension model employed in X.509 version 3
certificates (see <xref target="RFC5280"/>). This document only specifies the certificates (see <xref target="RFC5280" format="default"/>). This document
new format for Nonce extension and only specifies the new format for the Nonce extension and
does not change specification of any of the other standard extensions defined does not change the specifications of any of the other standard extensions
in <xref target="RFC6960"/>.</t> defined in <xref target="RFC6960" format="default"/>.</t>
<section anchor="sect-2.1" numbered="true" toc="default">
<section title="Nonce Extension" anchor="sect-2.1"> <t> <name>Nonce Extension</name>
This section replaces the entirety of the Section 4.4.1 of <xref target="RFC6 <t>This section replaces the entirety of <xref target="RFC6960"
960"/> which describes the OCSP Nonce extension. sectionFormat="of" section="4.4.1"/>, which describes the OCSP Nonce
</t><t> extension.</t>
<t>
The nonce cryptographically binds a request and a response to The nonce cryptographically binds a request and a response to
prevent replay attacks. The nonce is included as one of the prevent replay attacks. The nonce is included as one of the
requestExtensions in requests, while in responses it would be requestExtensions in requests; in responses, it would be
included as one of the responseExtensions. In both the request and included as one of the responseExtensions. In both the request and
the response, the nonce will be identified by the object identifier 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, while the extnValue is the value of the nonce.
If Nonce extension is present then the length of nonce MUST be at If the Nonce extension is present, then the length of the nonce <bcp14>MUST</ bcp14> be at
least 1 octet and can be up to 32 octets. least 1 octet and can be up to 32 octets.
</t> </t>
<t> <t>A server <bcp14>MUST</bcp14> reject any OCSP request that has a nonce
A server MUST reject any OCSP request having a nonce in the Nonce extension w in the Nonce extension with a length of either 0 octets or more than 32 o
ith ctets
length of 0 octets or more than 32 octets with the malformedRequest with the malformedRequest OCSPResponseStatus, as described in <xref
OCSPResponseStatus as described in section 4.2.1 of <xref target="RFC6960"/>. target="RFC6960" sectionFormat="of" section="4.2.1"/>.</t>
</t> <t>
<t> The value of the nonce <bcp14>MUST</bcp14> be generated using a cryptographic
The value of the nonce MUST be generated using a cryptographically ally
strong pseudorandom number generator (see <xref target="RFC4086"/>). strong pseudorandom number generator (see <xref target="RFC4086" format="defa
ult"/>).
The minimum nonce length of 1 octet is defined to provide The minimum nonce length of 1 octet is defined to provide
backward compatibility with older clients that follow [RFC6960]. backward compatibility with older clients that follow <xref
Newer OCSP clients that support this document MUST use a target="RFC6960" format="default"/>.
length of 32 octets for the nonce in Nonce extension. OCSP responders Newer OCSP clients that support this document <bcp14>MUST</bcp14> use a
MUST accept lengths of at least 16 octets, and MAY choose to length of 32 octets for the nonce in the Nonce extension. OCSP responders
ignore the Nonce extension for requests where the length of the nonce is less <bcp14>MUST</bcp14> accept lengths of at least 16 octets and <bcp14>MAY</bcp
than 16 octets 14> choose to
</t> ignore the Nonce extension for requests where the length of the nonce is less
than 16 octets.
</t>
<figure><artwork><![CDATA[ <sourcecode type="asn.1"><![CDATA[
id-pkix-ocsp OBJECT IDENTIFIER ::= { id-ad-ocsp } id-pkix-ocsp OBJECT IDENTIFIER ::= { id-ad-ocsp }
id-pkix-ocsp-nonce OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 } id-pkix-ocsp-nonce OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 }
Nonce ::= OCTET STRING(SIZE(1..32)) Nonce ::= OCTET STRING(SIZE(1..32))
]]></artwork> ]]></sourcecode>
</figure> </section>
</section> </section>
<section anchor="sect-3" numbered="true" toc="default">
</section> <name>Security Considerations</name>
<section title="Security Considerations" anchor="sect-3">
<t> <t>
The security considerations of OCSP, in general, are described in The security considerations of OCSP, in general, are described in
<xref target="RFC6960"/>. During the interval in which the previous OCSP r <xref target="RFC6960" format="default"/>. During the interval in which
esponse for a the previous OCSP response for a
certificate is not expired but the responder has a changed status for certificate is not expired but the responder has a changed status for
that certificate, a copy of that OCSP response can be used to indicate tha that certificate, a copy of that OCSP response can be used to indicate
t the status of the certificate is still valid. that the status of the certificate is still valid.
Including client's Nonce value in the OCSP Including a client's nonce value in the OCSP
response makes sure that the response is the latest response from response makes sure that the response is the latest response from
the server and not an old copy. the server and not an old copy.
</t> </t>
<section anchor="sect-3-1" numbered="true" toc="default">
<section title="Replay Attack" anchor="sect-3-1"> <name>Replay Attack</name>
<t> <t>
The Nonce extension is used to avoid replay attacks. Since the OCSP The Nonce extension is used to avoid replay attacks. Since the OCSP
responder may choose to not send the Nonce extension in the OCSP responder may choose not to send the Nonce extension in the OCSP
response even if the client has sent the Nonce extension in the response even if the client has sent the Nonce extension in the
request <xref target="RFC5019"/>, an on-path attacker can intercept the OCSP request request <xref target="RFC5019" format="default"/>, an on-path attacker can in tercept the OCSP request
and respond with an earlier response from the server without the and respond with an earlier response from the server without the
Nonce extension. This can be mitigated by configuring the server to Nonce extension. This can be mitigated by configuring the server to
use a short time interval between the thisUpdate and nextUpdate fields in use a short time interval between the thisUpdate and nextUpdate fields in
the OCSP response. the OCSP response.
</t> </t>
</section> </section>
<section title="Nonce Collision" anchor="sect-3-2"> <section anchor="sect-3-2" numbered="true" toc="default">
<t> <name>Nonce Collision</name>
If the value of nonce used by a client in OCSP request is <t>
If the value of the nonce used by a client in the OCSP request is
predictable, then an attacker may prefetch responses with the predictable, then an attacker may prefetch responses with the
predicted nonce and can replay them, thus defeating the purpose of predicted nonce and can replay them, thus defeating the purpose of
using nonce. Therefore the value of Nonce extension in the OCSP using the nonce. Therefore, the value of the Nonce extension in the OCSP
request MUST contain cryptographically strong randomness and MUST be request <bcp14>MUST</bcp14> contain cryptographically strong randomness and <
freshly generated at the time of creating the OCSP request. Also bcp14>MUST</bcp14> be
if the length of nonce is too small e.g. 1 octet then freshly generated at the time of the creation of the OCSP request. Also,
if the length of the nonce is too small (e.g., 1 octet), then
an on-path attacker can prefetch responses with all the possible an on-path attacker can prefetch responses with all the possible
values of nonce and replay a matching nonce. values of the nonce and replay a matching nonce.
</t> </t>
</section> </section>
</section> </section>
<section anchor="sect-4" numbered="true" toc="default">
<section title="IANA Considerations" anchor="sect-4"> <name>IANA Considerations</name>
<t>This document does not call for any IANA actions.</t> <t>This document has no IANA actions.</t>
</section> </section>
<section title="Changes to Appendix B. of RFC 6960" anchor="sect-5"> <section anchor="sect-5" numbered="true" toc="default">
<t> <name>Changes to Appendix B of RFC 6960</name>
This section updates the ASN.1 definitions of the OCSP Nonce extension in <t>
Appendix B.1 and Appendix B.2 of <xref target="RFC6960"/> This section updates the ASN.1 definitions of the OCSP Nonce extension
The Appendix B.1 defines OCSP using ASN.1 - 1998 Syntax and Appendix B.2 in Appendices <xref target="RFC6960"
defines OCSP using ASN.1 - 2008 Syntax section="B.1" sectionFormat="bare"/> and <xref target="RFC6960"
</t> section="B.2" sectionFormat="bare"/> of <xref target="RFC6960"/>.
<section title="Changes to Appendix B.1. OCSP in ASN.1 - 1998 Syntax" anc Appendix <xref target="RFC6960" section="B.1" sectionFormat="bare"/>
hor="sect-5-1"> defines OCSP using ASN.1 - 1998 Syntax; Appendix <xref
<t>OLD Syntax: </t> target="RFC6960" section="B.2" sectionFormat="bare"/> defines OCSP
<t>The definition of OCSP Nonce Extension is not provided in Appendix B.1 using ASN.1 - 2008 Syntax.</t>
of <xref target="RFC6960"/> for the ASN.1 - 1998 Syntax.</t> <section anchor="sect-5-1" numbered="true" toc="default">
<t>NEW Syntax: </t> <name>Changes to Appendix B.1 OCSP in ASN.1 - 1998 Syntax</name>
<figure><artwork><![CDATA[ <t>OLD Syntax: </t>
<t>The definition of OCSP Nonce extension is not provided in <xref
target="RFC6960" sectionFormat="of" section="B.1"/> for the ASN.1 -
1998 Syntax.</t>
<t>NEW Syntax: </t>
<sourcecode type="asn.1"><![CDATA[
Nonce ::= OCTET STRING(SIZE(1..32)) Nonce ::= OCTET STRING(SIZE(1..32))
]]></artwork> ]]></sourcecode>
</figure> </section>
</section> <section anchor="sect-5-2" numbered="true" toc="default">
<section title="Changes to Appendix B.2 OCSP in ASN.1 - 2008 Syntax" anc <name>Changes to Appendix B.2 OCSP in ASN.1 - 2008 Syntax</name>
hor="sect-5-2"> <t>OLD Syntax: </t>
<t>OLD Syntax: </t> <sourcecode type="asn.1"><![CDATA[
<figure><artwork><![CDATA[
re-ocsp-nonce EXTENSION ::= { SYNTAX OCTET STRING IDENTIFIED re-ocsp-nonce EXTENSION ::= { SYNTAX OCTET STRING IDENTIFIED
BY id-pkix-ocsp-nonce } BY id-pkix-ocsp-nonce }
]]></sourcecode>
]]></artwork> <t>NEW Syntax: </t>
</figure> <sourcecode type="asn.1"><![CDATA[
<t>NEW Syntax: </t>
<figure><artwork><![CDATA[
re-ocsp-nonce EXTENSION ::= { SYNTAX OCTET STRING(SIZE(1..32)) re-ocsp-nonce EXTENSION ::= { SYNTAX OCTET STRING(SIZE(1..32))
IDENTIFIED BY id-pkix-ocsp-nonce } IDENTIFIED BY id-pkix-ocsp-nonce }
]]></artwork> ]]></sourcecode>
</figure> </section>
</section> </section>
</section> </middle>
</middle> <back>
<references>
<back> <name>References</name>
<references title="Normative References"> <references>
<reference anchor="RFC2119" target="http://www.rfc-editor.org/info/rfc211
9"><front>
<title>Key words for use in RFCs to Indicate Requirement Levels</title>
<author fullname="S. Bradner" initials="S." surname="Bradner">
</author>
<date month="March" year="1997"/>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="2119"/>
<seriesInfo name="DOI" value="10.17487/RFC2119"/>
</reference>
<reference anchor="RFC8174" target="https://www.rfc-editor.org/info/rfc81
74">
<front>
<title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</ti
tle>
<author initials="B." surname="Leiba" fullname="B. Leiba">
</author>
<date year="2017" month="May"/>
</front>
<seriesInfo name="DOI" value="10.17487/RFC8174"/>
<seriesInfo name="RFC" value="8174"/>
<seriesInfo name="BCP" value="14"/>
</reference>
&RFC5280;
&RFC6960;
</references>
<references title="Informative References">
&RFC4086;
&RFC4732;
&RFC5019;
</references>
</back>
</rfc> <name>Normative References</name>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.2119.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.8174.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.5280.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.6960.xml"/>
</references>
<references>
<name>Informative References</name>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.4086.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.4732.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.5019.xml"/>
</references>
</references>
</back>
</rfc>
 End of changes. 27 change blocks. 
211 lines changed or deleted 175 lines changed or added

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