rfc8705xml2.original.xml   rfc8705.xml 
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<?rfc tocdepth="4"?> <rfc number="8705" xmlns:xi="http://www.w3.org/2001/XInclude" category="std"
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<rfc category="std" docName="draft-ietf-oauth-mtls-17" ipr="trust200902">
<front> <front>
<title abbrev="OAuth Mutual TLS">OAuth 2.0 Mutual-TLS Client Authentication <title abbrev="OAuth Mutual TLS">OAuth 2.0 Mutual-TLS Client
and Certificate-Bound Access&nbsp;Tokens</title> Authentication and Certificate-Bound Access&nbsp;Tokens</title>
<seriesInfo name="RFC" value="8705" />
<author fullname="Brian Campbell" initials="B." surname="Campbell"> <author fullname="Brian Campbell" initials="B." surname="Campbell">
<organization>Ping Identity</organization> <organization>Ping Identity</organization>
<address><email>brian.d.campbell@gmail.com</email></address> <address>
<email>brian.d.campbell@gmail.com</email>
</address>
</author> </author>
<author fullname="John Bradley" initials="J." surname="Bradley"> <author fullname="John Bradley" initials="J." surname="Bradley">
<organization>Yubico</organization> <organization>Yubico</organization>
<address> <address>
<email>ve7jtb@ve7jtb.com</email> <email>ve7jtb@ve7jtb.com</email>
<uri>http://www.thread-safe.com/</uri> <uri>http://www.thread-safe.com/</uri>
</address> </address>
</author> </author>
<author fullname="Nat Sakimura" initials="N." surname="Sakimura"> <author fullname="Nat Sakimura" initials="N." surname="Sakimura">
<organization>Nomura Research Institute</organization> <organization>Nomura Research Institute</organization>
<address> <address>
<email>n-sakimura@nri.co.jp</email> <email>n-sakimura@nri.co.jp</email>
<uri>https://nat.sakimura.org/</uri> <uri>https://nat.sakimura.org/</uri>
</address> </address>
</author> </author>
<author fullname="Torsten Lodderstedt" initials="T." surname="Lodderstedt"> <author fullname="Torsten Lodderstedt" initials="T." surname="Lodderstedt">
<organization>YES.com AG</organization> <organization>YES.com AG</organization>
<address> <address>
<email>torsten@lodderstedt.net</email> <email>torsten@lodderstedt.net</email>
</address> </address>
</author> </author>
<date month="February" year="2020" />
<date />
<area>Security</area> <area>Security</area>
<workgroup>OAuth Working Group</workgroup> <workgroup>OAuth Working Group</workgroup>
<keyword>JSON Web Token</keyword> <keyword>JSON Web Token</keyword>
<keyword>JWT</keyword> <keyword>JWT</keyword>
<keyword>MTLS</keyword> <keyword>MTLS</keyword>
<keyword>Mutual TLS</keyword> <keyword>Mutual TLS</keyword>
<keyword>proof-of-possession</keyword> <keyword>proof-of-possession</keyword>
<keyword>proof-of-possession access token</keyword> <keyword>proof-of-possession access token</keyword>
<keyword>key confirmed access token</keyword> <keyword>key confirmed access token</keyword>
<keyword>certificate-bound access token</keyword> <keyword>certificate-bound access token</keyword>
<keyword>client certificate</keyword> <keyword>client certificate</keyword>
<keyword>X.509 Client Certificate Authentication</keyword> <keyword>X.509 Client Certificate Authentication</keyword>
skipping to change at line 67 skipping to change at line 61
<keyword>proof-of-possession</keyword> <keyword>proof-of-possession</keyword>
<keyword>proof-of-possession access token</keyword> <keyword>proof-of-possession access token</keyword>
<keyword>key confirmed access token</keyword> <keyword>key confirmed access token</keyword>
<keyword>certificate-bound access token</keyword> <keyword>certificate-bound access token</keyword>
<keyword>client certificate</keyword> <keyword>client certificate</keyword>
<keyword>X.509 Client Certificate Authentication</keyword> <keyword>X.509 Client Certificate Authentication</keyword>
<keyword>key confirmation</keyword> <keyword>key confirmation</keyword>
<keyword>confirmation method</keyword> <keyword>confirmation method</keyword>
<keyword>holder-of-key</keyword> <keyword>holder-of-key</keyword>
<keyword>OAuth</keyword> <keyword>OAuth</keyword>
<abstract> <abstract>
<t> <t>
This document describes OAuth client authentication and certificate-bound acce This document describes OAuth client authentication and certificate-bound
ss and refresh tokens using access and refresh tokens using mutual Transport Layer Security (TLS)
mutual Transport Layer Security (TLS) authentication with X.509 certificates. authentication with X.509 certificates. OAuth clients are provided a
OAuth clients are provided a mechanism for authentication to the authorization mechanism for authentication to the authorization server using mutual TLS,
server using mutual TLS, based on either self-signed certificates or public ke based on either self-signed certificates or public key infrastructure (PKI).
y infrastructure (PKI). OAuth authorization servers are provided a mechanism for binding access
OAuth authorization servers are provided a mechanism for binding access tokens tokens to a client's mutual-TLS certificate, and OAuth protected resources
to a client's are provided a method for ensuring that such an access token presented to it
mutual-TLS certificate, and OAuth protected resources are provided a method fo was issued to the client presenting the token.
r ensuring
that such an access token presented to it was issued to the client presenting
the token.
</t> </t>
</abstract> </abstract>
</front> </front>
<middle> <middle>
<section anchor="Introduction" title="Introduction"> <section anchor="Introduction" numbered="true" toc="default">
<t> <name>Introduction</name>
The OAuth 2.0 Authorization Framework <xref target="RFC6749"/> enables third-p <t>
arty The OAuth 2.0 Authorization Framework <xref target="RFC6749" format="default"/
> enables third-party
client applications to obtain delegated access to protected resources. client applications to obtain delegated access to protected resources.
In the prototypical abstract OAuth flow, illustrated in <xref target="protocol -flow-figure"/>, In the prototypical abstract OAuth flow, illustrated in <xref target="protocol -flow-figure" format="default"/>,
the client obtains an access token from an entity known as an the client obtains an access token from an entity known as an
authorization server and then uses that token when accessing protected resourc es, authorization server and then uses that token when accessing protected resourc es,
such as HTTPS APIs. such as HTTPS APIs.
</t> </t>
<t> <figure anchor="protocol-flow-figure">
<figure title='Abstract OAuth 2.0 Protocol Flow' anchor='protocol-flow-figure' <name>Abstract OAuth 2.0 Protocol Flow</name>
> <artwork name="" type="" align="left" alt=""><![CDATA[
<artwork><![CDATA[
+--------+ +---------------+ +--------+ +---------------+
| | | | | | | |
| |<--(A)-- Get an access token --->| Authorization | | |<--(A)-- Get an access token --->| Authorization |
| | | Server | | | | Server |
| | | | | | | |
| | +---------------+ | | +---------------+
| | ^ | | ^
| | | | | |
| | | |
| | (C) | | | (C) |
skipping to change at line 118 skipping to change at line 112
| | | | | |
| | v | | v
| | +---------------+ | | +---------------+
| | | (C) | | | | (C) |
| | | | | | | |
| |<--(B)-- Use the access token -->| Protected | | |<--(B)-- Use the access token -->| Protected |
| | | Resource | | | | Resource |
| | | | | | | |
+--------+ +---------------+ +--------+ +---------------+
]]></artwork> ]]></artwork>
</figure> </figure>
<t>
The flow illustrated in <xref target="protocol-flow-figure" format="default"/>
includes the following steps:
</t> </t>
<t> <ol spacing="normal" type="(%C)" indent="5">
The flow illustrated in <xref target="protocol-flow-figure"/> includes the fol <li>
lowing steps: The client makes an HTTPS <tt>POST</tt> request to
<list style='format (%C)'>
<t>
The client makes an HTTPS <spanx style='verb'>POST</spanx> request to
the authorization server and presents the authorization server and presents
a credential representing the authorization grant. For a credential representing the authorization grant. For
certain types of clients (those that have been issued or otherwise establi shed certain types of clients (those that have been issued or otherwise establi shed
a set of client credentials) the request must be authenticated. a set of client credentials) the request must be authenticated.
In the response, the authorization server issues an access token to the cl ient. In the response, the authorization server issues an access token to the cl ient.
</t> </li>
<t> <li>
The client includes the access token when making a request to access a pro tected resource. The client includes the access token when making a request to access a pro tected resource.
</t> </li>
<t> <li>
The protected resource validates the access token in order to authorize th e request. The protected resource validates the access token in order to authorize th e request.
In some cases, such as when the token is self-contained and cryptographica lly secured, In some cases, such as when the token is self-contained and cryptographica lly secured,
the validation can be done locally by the protected resource. Other cases require the validation can be done locally by the protected resource. Other cases require
that the protected resource call out to the authorization server to determ ine the state that the protected resource call out to the authorization server to determ ine the state
of the token and obtain meta-information about it. of the token and obtain metainformation about it.
</t> </li>
</list> </ol>
</t> <t>
<t> Layering on the abstract flow above, this document standardizes enhanced
Layering on the abstract flow above, security options for OAuth 2.0 utilizing client-certificate-based mutual
this document standardizes enhanced security options for OAuth 2.0 utilizing c TLS. <xref target="mtlsca" format="default"/> provides options for
lient-certificate-based mutual TLS. authenticating the request in Step
<xref target="mtlsca"/> provides options for authenticating the request in ste (A). Step (C) is supported with semantics
p (A). Step (C) is supported to express the binding of the token to the client certificate for both local
with semantics to express the binding of the token to the client certificate f and remote processing in Sections <xref target="x5t" format="counter"/> and
or both local and remote processing <xref target="introspect" format="counter"/>, respectively. This ensures
in <xref target="x5t"/> and <xref target="introspect"/> respectively. This ens that, as described in <xref target="CertificateBoundAccessTokens"
ures that, as format="default"/>, protected resource access in Step
described in <xref target="CertificateBoundAccessTokens"/>, protected resource (B) is only possible by the legitimate client using a
access in step (B) is only possible by the legitimate client using a certifica certificate-bound token and holding the private key corresponding to the
te-bound token and certificate.
holding the private key corresponding to the certificate.
</t> </t>
<t> <t>
OAuth 2.0 OAuth 2.0
defines a shared-secret method of client authentication but also defines a shared-secret method of client authentication but also
allows for definition and use of additional client authentication mechanisms allows for defining and using additional client authentication mechanisms
when interacting directly with the authorization server. when interacting directly with the authorization server.
This document describes an additional mechanism of client authentication utili zing This document describes an additional mechanism of client authentication utili zing
mutual-TLS certificate-based authentication, which provides mutual-TLS certificate-based authentication that provides
better security characteristics than shared secrets. better security characteristics than shared secrets.
While <xref target="RFC6749"/> documents client authentication for requests to While <xref target="RFC6749" format="default"/> documents client authenticatio
the token endpoint, n for requests to the token endpoint,
extensions to OAuth 2.0 (such as <xref target="RFC7662">Introspection</xref>, extensions to OAuth 2.0 (such as Introspection <xref target="RFC7662" format="
<xref target="RFC7009">Revocation</xref>, and the Backchannel Authentication E default"></xref>,
ndpoint Revocation <xref target="RFC7009" format="default"></xref>, and the Backchanne
in <xref target="OpenID.CIBA"/>) define endpoints that also utilize client aut l Authentication Endpoint
hentication in <xref target="OpenID.CIBA" format="default"/>) define endpoints that also u
and the mutual TLS methods defined herein are applicable to those endpoints as tilize client authentication,
well. and the mutual-TLS methods defined herein are applicable to those endpoints as
well.
</t> </t>
<t>
<t>
Mutual-TLS certificate-bound access tokens ensure that Mutual-TLS certificate-bound access tokens ensure that
only the party in possession of the only the party in possession of the
private key corresponding to the certificate can utilize the token to private key corresponding to the certificate can utilize the token to
access the associated resources. Such a constraint is access the associated resources. Such a constraint is
sometimes referred to as key confirmation, proof-of-possession, or holder-of-k ey sometimes referred to as key confirmation, proof-of-possession, or holder-of-k ey
and is unlike the case of the and is unlike the case of the
bearer token described in <xref target="RFC6750"/>, where any party in bearer token described in <xref target="RFC6750" format="default"/>, where any party in
possession of the access token can use it to access the associated resources. possession of the access token can use it to access the associated resources.
Binding an access token to the client's certificate Binding an access token to the client's certificate
prevents the use of stolen access tokens or replay of access tokens prevents the use of stolen access tokens or replay of access tokens
by unauthorized parties. by unauthorized parties.
</t> </t>
<t> <t>
Mutual-TLS certificate-bound access tokens and mutual-TLS client authenticatio n Mutual-TLS certificate-bound access tokens and mutual-TLS client authenticatio n
are distinct mechanisms, which are complementary but don't necessarily need to be deployed or used together. are distinct mechanisms that are complementary but don't necessarily need to b e deployed or used together.
</t> </t>
<t> <t>
Additional client metadata parameters are introduced by this document in suppo rt of Additional client metadata parameters are introduced by this document in suppo rt of
certificate-bound access tokens and mutual-TLS client authentication. certificate-bound access tokens and mutual-TLS client authentication.
The authorization server can obtain client metadata via the The authorization server can obtain client metadata via the
<xref target="RFC7591">Dynamic Client Registration Protocol</xref>, Dynamic Client Registration Protocol <xref target="RFC7591"
which defines mechanisms for dynamically registering format="default"></xref>, which defines mechanisms for dynamically registering
OAuth 2.0 client metadata with authorization servers. OAuth 2.0 client metadata with authorization servers.
Also the metadata defined by RFC7591, and registered extensions to Also the metadata defined by <xref target="RFC7591" format="default"></xref>, and registered extensions to
it, imply a general data model for clients that is useful for it, imply a general data model for clients that is useful for
authorization server implementations even when the Dynamic Client authorization server implementations, even when the Dynamic Client
Registration Protocol isn't in play. Such implementations will typically have Registration Protocol isn't in play. Such implementations will typically have
some sort of user interface available for managing client configuration. some sort of user interface available for managing client configuration.
</t> </t>
<section anchor="RNC" title="Requirements Notation and Conventions"> <section anchor="RNC" numbered="true" toc="default">
<t> <name>Requirements Notation and Conventions</name>
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL
"
in this document are to be interpreted as described in
BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/>
when, and only when, they appear in all capitals, as shown here.
</t>
</section>
<section anchor="Terminology" title="Terminology"> <t>
<t> The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQU
IRED</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 anchor="Terminology" numbered="true" toc="default">
<name>Terminology</name>
<t>
Throughout this document the term "mutual TLS" refers to the process whereby, in addition to the normal TLS Throughout this document the term "mutual TLS" refers to the process whereby, in addition to the normal TLS
server authentication with a certificate, a client presents its X.509 certific ate server authentication with a certificate, a client presents its X.509 certific ate
and proves possession of the corresponding private key to a server when negoti ating a TLS session. and proves possession of the corresponding private key to a server when negoti ating a TLS session.
In contemporary versions of TLS <xref target="RFC8446"/> <xref target="RFC5246 "/> this requires that the client send In contemporary versions of TLS <xref target="RFC5246" format="default"/> <xre f target="RFC8446" format="default"/>, this requires that the client send
the Certificate and CertificateVerify messages during the handshake and the Certificate and CertificateVerify messages during the handshake and
for the server to verify the CertificateVerify and Finished messages. for the server to verify the CertificateVerify and Finished messages.
</t> </t>
</section>
</section> </section>
<section anchor="mtlsca" numbered="true" toc="default">
</section> <name>Mutual TLS for OAuth Client Authentication</name>
<section anchor="mtlsca" title="Mutual TLS for OAuth Client Authentication"> <t>
<t>
This section defines, as an extension of This section defines, as an extension of
<xref target="RFC6749">OAuth 2.0, Section 2.3</xref>, two distinct methods of using <xref target="RFC6749" sectionFormat="of" section="2.3">OAuth 2.0</xref>, two distinct methods of using
mutual-TLS X.509 client certificates as client credentials. mutual-TLS X.509 client certificates as client credentials.
The requirement of mutual TLS for client authentication is determined by the a
The requirement of mutual TLS for client authentication is determined by the a uthorization server,
uthorization server
based on policy or configuration for the given client (regardless of whether t he client was dynamically based on policy or configuration for the given client (regardless of whether t he client was dynamically
registered, statically configured, or otherwise established). registered, statically configured, or otherwise established).
</t> </t>
<t> <t>
In order to utilize TLS for OAuth client authentication, the TLS In order to utilize TLS for OAuth client authentication, the TLS
connection between the client and the authorization server MUST have been esta blished or reestablished connection between the client and the authorization server <bcp14>MUST</bcp14> have been established or re-established
with mutual-TLS X.509 certificate authentication with mutual-TLS X.509 certificate authentication
(i.e. the Client Certificate and Certificate Verify messages are sent during t (i.e., the client Certificate and CertificateVerify messages are sent during
he TLS Handshake). the TLS handshake).
</t>
<t>
For all requests to the authorization server utilizing mutual-TLS client authe
ntication,
the client MUST include the <spanx style='verb'>client_id</spanx> parameter,
described in <xref target="RFC6749">OAuth 2.0, Section 2.2</xref>.
The presence of the <spanx style='verb'>client_id</spanx>
parameter enables the authorization server to easily identify the
client independently from the content of the certificate. The authorization se
rver
can locate the client configuration using the client identifier and check the
certificate
presented in the TLS Handshake against the expected credentials for that clien
t.
The authorization server MUST enforce the
binding between client and certificate as described in either <xref target="pk
i_method"/> or
<xref target="self_signed_method"/> below.
If no certificate is presented or that which is presented doesn't match that w
hich is expected for the given <spanx style='verb'>client_id</spanx>,
the authorization server returns a normal OAuth 2.0 error response per <xref t
arget="RFC6749"> Section 5.2 of RFC6749</xref>
with the <spanx style='verb'>invalid_client</spanx> error code to indicate fai
led client authentication.
</t>
<section anchor="pki_method" title="PKI Mutual-TLS Method"> </t>
<t> <t>
For all requests to the authorization server utilizing mutual-TLS client
authentication, the client <bcp14>MUST</bcp14> include the
<tt>client_id</tt> parameter described in <xref target="RFC6749"
sectionFormat="of" section="2.2">OAuth 2.0</xref>. The presence of the
<tt>client_id</tt> parameter enables the authorization server to easily
identify the client independently from the content of the certificate. The
authorization server can locate the client configuration using the client
identifier and check the certificate presented in the TLS handshake against
the expected credentials for that client. The authorization server
<bcp14>MUST</bcp14> enforce the binding between client and certificate, as
described in either Section <xref target="pki_method" format="counter"/> or <x
ref
target="self_signed_method" format="counter"/> below. If no certificate is
presented, or that which is presented doesn't match that which is expected
for the given <tt>client_id</tt>, the authorization server returns a normal
OAuth 2.0 error response per <xref target="RFC6749" sectionFormat="of"
section="5.2"></xref> with the <tt>invalid_client</tt> error code to
indicate failed client authentication.
</t>
<section anchor="pki_method" numbered="true" toc="default">
<name>PKI Mutual-TLS Method</name>
<t>
The PKI (public key infrastructure) method of mutual-TLS OAuth client au thentication The PKI (public key infrastructure) method of mutual-TLS OAuth client au thentication
adheres to the way in which X.509 certificates are traditionally used adheres to the way in which X.509 certificates are traditionally used
for authentication. It relies on a validated certificate chain <xref tar get="RFC5280"/> for authentication. It relies on a validated certificate chain <xref tar get="RFC5280" format="default"/>
and a single subject distinguished name (DN) or a single and a single subject distinguished name (DN) or a single
subject alternative name (SAN) to authenticate the client. subject alternative name (SAN) to authenticate the client.
Only one subject name value of any type is used for each client. Only one subject name value of any type is used for each client.
The TLS handshake is utilized to validate the client's possession The TLS handshake is utilized to validate the client's possession
of the private key corresponding to the public key in the certificate an d to of the private key corresponding to the public key in the certificate an d to
validate the corresponding certificate chain. The client is successfully authenticated validate the corresponding certificate chain. The client is successfully authenticated
if the subject information in the certificate matches the single expecte d subject configured or if the subject information in the certificate matches the single expecte d subject configured or
registered for that particular client registered for that particular client
(note that a predictable treatment of DN values, such as the distinguish edNameMatch (note that a predictable treatment of DN values, such as the distinguish edNameMatch
rule from <xref target="RFC4517"/>, is needed in comparing the rule from <xref target="RFC4517" format="default"/>, is needed in compar ing the
certificate's subject DN to the client's registered DN). certificate's subject DN to the client's registered DN).
Revocation checking is possible with the PKI method but if and how to ch eck a certificate's Revocation checking is possible with the PKI method but if and how to ch eck a certificate's
revocation status is a deployment decision at the discretion of the auth orization server. revocation status is a deployment decision at the discretion of the auth orization server.
Clients can rotate their X.509 certificates Clients can rotate their X.509 certificates
without the need to modify the respective authentication data at the aut horization without the need to modify the respective authentication data at the aut horization
server by obtaining a new certificate with the same subject from a trust ed certificate authority (CA). server by obtaining a new certificate with the same subject from a trust ed certificate authority (CA).
</t> </t>
<section anchor="metadata_auth_value_pki" numbered="true" toc="default">
<section anchor="metadata_auth_value_pki" title="PKI Method Metadata Value <name>PKI Method Metadata Value</name>
"> <t>
<t>
For the PKI method of mutual-TLS client authentication, this specifica tion For the PKI method of mutual-TLS client authentication, this specifica tion
defines and registers the following authentication method metadata defines and registers the following authentication method metadata
value into the "OAuth Token Endpoint Authentication Methods" registry value into the "OAuth Token Endpoint Authentication Methods" registry
<xref target="IANA.OAuth.Parameters"/>. <xref target="IANA.OAuth.Parameters" format="default"/>.
</t> </t>
<t> <dl newline="true" spacing="normal">
<list style="hanging"> <dt>tls_client_auth</dt>
<t hangText="tls_client_auth"> <dd>
<vspace/>
Indicates that client authentication to the authorization server w ill occur with Indicates that client authentication to the authorization server w ill occur with
mutual TLS utilizing the PKI method of associating a certificate t o a client. mutual TLS utilizing the PKI method of associating a certificate t o a client.
</t> </dd>
</list> </dl>
</t> </section>
</section> <section anchor="client_metadata_pki" numbered="true" toc="default">
<name>Client Registration Metadata</name>
<section anchor="client_metadata_pki" title="Client Registration Metadata" <t>
>
<t>
In order to convey the expected subject of the certificate, In order to convey the expected subject of the certificate,
the following metadata the following metadata
parameters are introduced for the parameters are introduced for the
<xref target="RFC7591">OAuth 2.0 Dynamic Client Registration Protocol< /xref> in support of OAuth 2.0 Dynamic Client Registration Protocol <xref target="RFC7591" format="default"></xref> in support of
the PKI method of mutual-TLS client authentication. the PKI method of mutual-TLS client authentication.
A client using the <spanx style="verb">tls_client_auth</spanx> authent ication method MUST use A client using the <tt>tls_client_auth</tt> authentication method <bcp 14>MUST</bcp14> use
exactly one of the below metadata parameters to indicate the certifica te subject value that exactly one of the below metadata parameters to indicate the certifica te subject value that
the authorization server is to expect when authenticating the respecti ve client. the authorization server is to expect when authenticating the respecti ve client.
<list style="hanging"> </t>
<t hangText="tls_client_auth_subject_dn"><vspace/> <dl newline="true" spacing="normal">
An <xref target="RFC4514"/> string representation of the expected <dt>tls_client_auth_subject_dn</dt>
subject distinguished <dd>
name of the certificate, which the OAuth client will use in mutual A string representation -- as defined in <xref target="RFC4514" fo
-TLS authentication. rmat="default"/> -- of the expected subject distinguished
</t> name of the certificate that the OAuth client will use in mutual-T
LS authentication.
<t hangText="tls_client_auth_san_dns"><vspace/> </dd>
<dt>tls_client_auth_san_dns</dt>
<dd>
A string containing the value of an expected dNSName SAN entry A string containing the value of an expected dNSName SAN entry
in the certificate, which the OAuth client will use in mutual-TLS in the certificate that the OAuth client will use in mutual-TLS
authentication. authentication.
</t> </dd>
<dt>tls_client_auth_san_uri</dt>
<t hangText="tls_client_auth_san_uri"><vspace/> <dd>
A string containing the value of an expected A string containing the value of an expected
uniformResourceIdentifier SAN entry in the certificate, which uniformResourceIdentifier SAN entry in the certificate that
the OAuth client will use in mutual-TLS authentication. the OAuth client will use in mutual-TLS authentication.
</t> </dd>
<dt>tls_client_auth_san_ip</dt>
<t hangText="tls_client_auth_san_ip"><vspace/> <dd>
A string representation of an IP address in either dotted decimal A string representation of an IP address in either dotted
notation (for IPv4) or colon-delimited hexadecimal (for IPv6, as decimal notation (for IPv4) or colon-delimited hexadecimal (for
defined in <xref target="RFC5952"/>) that is expected to be presen IPv6, as defined in <xref target="RFC5952" format="default"/>)
t that is expected to be present as an iPAddress SAN entry in the
as an iPAddress SAN entry in the certificate, which the OAuth certificate that the OAuth client will use in mutual-TLS
client will use in mutual-TLS authentication. Per section 8 of <xr authentication. Per <xref target="RFC5952"
ef target="RFC5952"/> sectionFormat="of" section="8"/>, the IP address comparison of the
the IP address comparison of the value in this parameter and the S value in
AN entry in the this parameter and the SAN entry in the certificate is to be
certificate is to be done in binary format. done in binary format.
</t> </dd>
<dt>tls_client_auth_san_email</dt>
<t hangText="tls_client_auth_san_email"><vspace/> <dd>
A string containing the value of an expected rfc822Name SAN A string containing the value of an expected rfc822Name SAN
entry in the certificate, which the OAuth client will use in entry in the certificate that the OAuth client will use in
mutual-TLS authentication. mutual-TLS authentication.
</t> </dd>
</list> </dl>
</t> </section>
</section> </section>
<section anchor="self_signed_method" numbered="true" toc="default">
</section> <name>Self-Signed Certificate Mutual-TLS Method</name>
<t>
<section anchor="self_signed_method" title="Self-Signed Certificate Mutual-T
LS Method">
<t>
This method of mutual-TLS OAuth client authentication This method of mutual-TLS OAuth client authentication
is intended to support client authentication using self-signed certifica tes. is intended to support client authentication using self-signed certifica tes.
As a prerequisite, the client registers its X.509 certificates As a prerequisite, the client registers its X.509 certificates
(using <spanx style="verb">jwks</spanx> defined in <xref target="RFC7591 (using <tt>jwks</tt> defined in <xref target="RFC7591" format="default"/
"/>) or a reference to a trusted source >) or a reference to a trusted source
for its X.509 certificates (using <spanx style="verb">jwks_uri</spanx> f for its X.509 certificates (using <tt>jwks_uri</tt> from <xref target="R
rom <xref target="RFC7591"/>) FC7591" format="default"/>)
with the authorization server. During authentication, with the authorization server. During authentication,
TLS is utilized to validate the client's possession of the private key TLS is utilized to validate the client's possession of the private key
corresponding to the public key presented within the certificate in the respective TLS handshake. In corresponding to the public key presented within the certificate in the respective TLS handshake. In
contrast to the PKI method, the client's certificate chain is not valida ted by the server in this case. contrast to the PKI method, the client's certificate chain is not valida ted by the server in this case.
The client is successfully authenticated if the The client is successfully authenticated if the
certificate that it presented during the handshake matches one of the ce rtificates certificate that it presented during the handshake matches one of the ce rtificates
configured or registered for that particular client. configured or registered for that particular client.
The Self-Signed Certificate method allows the use of mutual TLS to authe nticate clients without The Self-Signed Certificate method allows the use of mutual TLS to authe nticate clients without
the need to maintain a PKI. When used in conjunction with a <spanx style ="verb">jwks_uri</spanx> for the the need to maintain a PKI. When used in conjunction with a <tt>jwks_uri </tt> for the
client, it also allows the client to rotate its X.509 certificates witho ut the client, it also allows the client to rotate its X.509 certificates witho ut the
need to change its respective authentication data directly with the auth orization server. need to change its respective authentication data directly with the auth orization server.
</t> </t>
<section anchor="metadata_auth_value_self_signed" title="Self-Signed Metho <section anchor="metadata_auth_value_self_signed" numbered="true" toc="d
d Metadata Value"> efault">
<t> <name>Self-Signed Method Metadata Value</name>
<t>
For the Self-Signed Certificate method of mutual-TLS client authentica tion, this specification For the Self-Signed Certificate method of mutual-TLS client authentica tion, this specification
defines and registers the following authentication method metadata defines and registers the following authentication method metadata
value into the "OAuth Token Endpoint Authentication Methods" registry value into the "OAuth Token Endpoint Authentication Methods" registry
<xref target="IANA.OAuth.Parameters"/>. <xref target="IANA.OAuth.Parameters" format="default"/>.
</t> </t>
<t> <dl newline="true" spacing="normal">
<list style="hanging"> <dt>self_signed_tls_client_auth</dt>
<t hangText="self_signed_tls_client_auth"> <dd>
<vspace/>
Indicates that client authentication to the authorization server w ill occur using Indicates that client authentication to the authorization server w ill occur using
mutual TLS with the client utilizing a self-signed certificate. mutual TLS with the client utilizing a self-signed certificate.
</t> </dd>
</list> </dl>
</t> </section>
</section> <section anchor="client_metadata_self_signed" numbered="true" toc="defau
lt">
<name>Client Registration Metadata</name>
<section anchor="client_metadata_self_signed" title="Client Registration M <t>
etadata"> For the Self-Signed Certificate method of binding a certificate with
<t> a client using mutual-TLS client authentication, the existing
For the Self-Signed Certificate method of binding a certificate with a <tt>jwks_uri</tt> or <tt>jwks</tt> metadata parameters from <xref
client using mutual target="RFC7591" format="default"/> are used to convey the client's
TLS client authentication, the existing certificates via JSON Web Key (JWK) in a JWK Set <xref
<spanx style="verb">jwks_uri</spanx> or <spanx style="verb">jwks</span target="RFC7517" format="default"/>. The <tt>jwks</tt> metadata
x> parameter is a JWK Set containing the client's public keys as an
metadata parameters from <xref target="RFC7591"/> are used to convey t array of JWKs, while the <tt>jwks_uri</tt> parameter is a URL that
he client's references a client's JWK Set. A certificate is represented with
certificates via JSON Web Key (JWK) in a JWK Set (JWKS) <xref target=" the <tt>x5c</tt> parameter of an individual JWK within the set.
RFC7517"/>. Note that the members of the JWK representing the public key
The <spanx style="verb">jwks</spanx> metadata parameter is a (e.g., "n" and "e" for RSA, "x" and "y" for Elliptic Curve (EC)) are r
JWK Set containing the client's public keys as an array of JWKs while equired
the <spanx style="verb">jwks_uri</spanx> parameter is a URL that refer parameters per <xref target="RFC7518" format="default"/> so will be
ences a client's JWK Set. present even though they are not utilized in this context. Also note
A certificate is represented with the <spanx style="verb">x5c</spanx> that <xref target="RFC7517" sectionFormat="of"
parameter of an individual JWK within section="4.7"/> requires that the key in the first certificate of
the set. the <tt>x5c</tt> parameter match the public key represented by those
Note that the members of the JWK representing the public key (e.g. "n" other members of the JWK.
and "e" for RSA, </t>
"x" and "y" for EC) are required parameters per <xref target="RFC7518" </section>
/> so will be present
even though they are not utilized in this context. Also note that
that Section 4.7 of <xref target="RFC7517"/> requires that the key
in the first certificate of the <spanx style="verb">x5c</spanx> parame
ter match the public
key represented by those other members of the JWK.
</t>
</section> </section>
</section> </section>
<section anchor="CertificateBoundAccessTokens" numbered="true" toc="default"
</section> >
<name>Mutual-TLS Client Certificate-Bound Access Tokens</name>
<section anchor="CertificateBoundAccessTokens" title="Mutual-TLS Client Cert <t>
ificate-Bound Access Tokens">
<t>
When mutual TLS is used by the client on the connection to the token endpoint, When mutual TLS is used by the client on the connection to the token endpoint,
the authorization server is able to bind the issued access token to the client certificate. the authorization server is able to bind the issued access token to the client certificate.
Such a binding is accomplished by associating the certificate with the token i n Such a binding is accomplished by associating the certificate with the token i n
a way that can be accessed by the protected resource, such as embedding the ce rtificate a way that can be accessed by the protected resource, such as embedding the ce rtificate
hash in the issued access token directly, using the syntax described in <xref hash in the issued access token directly, using the syntax described in <xref
target="x5t"/>, target="x5t" format="default"/>,
or through token introspection as described in <xref target="introspect"/>. or through token introspection as described in <xref target="introspect" forma
t="default"/>.
Binding the access token to the client certificate in that fashion has the ben efit of Binding the access token to the client certificate in that fashion has the ben efit of
decoupling that binding from the client's authentication with the decoupling that binding from the client's authentication with the
authorization server, which enables mutual TLS during protected resource acces s to authorization server, which enables mutual TLS during protected resource acces s to
serve purely as a proof-of-possession mechanism. serve purely as a proof-of-possession mechanism.
Other methods of associating a certificate with an access token are possible, Other methods of associating a certificate with an access token are possible,
per agreement by the authorization server and the protected resource, but are per agreement by the authorization server and the protected resource, but are
beyond the scope of this specification. beyond the scope of this specification.
</t> </t>
<t> <t>
In order for a resource server to use certificate-bound access tokens, it In order for a resource server to use certificate-bound access tokens, it
must have advance knowledge that mutual TLS is to be used for some or all must have advance knowledge that mutual TLS is to be used for some or all
resource accesses. In particular, the access token itself resource accesses.
cannot be used as input to the decision of whether or not to request mutual TL
S, In particular, the access token
since from the TLS perspective those are "Application Data", only exchanged itself cannot be used as input to the decision of whether or not to
after the TLS handshake has been completed, and the initial request mutual TLS because (from the TLS perspective) it is
CertificateRequest occurs during the handshake, before the Application Data "Application Data", only exchanged after the TLS handshake has been
is available. Although subsequent opportunities for a TLS client to completed, and the initial CertificateRequest occurs during the
handshake, before the Application Data is available.
Although subsequent opportunities for a TLS client to
present a certificate may be available, e.g., via TLS 1.2 renegotiation present a certificate may be available, e.g., via TLS 1.2 renegotiation
<xref target="RFC5246"/> or TLS 1.3 post-handshake authentication <xref target ="RFC8446"/>, this document <xref target="RFC5246" format="default"/> or TLS 1.3 post-handshake authentica tion <xref target="RFC8446" format="default"/>, this document
makes no provision for their usage. It is expected to be common that a makes no provision for their usage. It is expected to be common that a
mutual-TLS-using resource server will require mutual TLS for all resources hos ted mutual-TLS-using resource server will require mutual TLS for all resources hos ted
thereupon, or will serve mutual-TLS-protected and regular resources on separat thereupon or will serve mutual-TLS-protected and regular resources on separate
e hostname and port combinations, though other workflows are possible.
hostname+port combinations, though other workflows are possible. How
resource server policy is synchronized with the AS is out of scope for this How
resource server policy is synchronized with the authorization server (AS) is o
ut of scope for this
document. document.
</t> </t>
<t> <t>
Within the scope of an mutual-TLS-protected resource-access flow, Within the scope of a mutual-TLS-protected resource-access flow,
the client makes protected resource requests as described in <xref target="RFC the client makes protected resource requests, as described in <xref target="RF
6750"/>, C6750" format="default"/>,
however, those requests MUST be made over a mutually authenticated TLS connect however, those requests <bcp14>MUST</bcp14> be made over a mutually authentica
ion ted TLS connection
using the same certificate that was used for mutual TLS at the token endpoint. using the same certificate that was used for mutual TLS at the token endpoint.
</t> </t>
<t> <t>
The protected resource MUST obtain, from its TLS implementation layer, the cli The protected resource <bcp14>MUST</bcp14> obtain, from its TLS implementation
ent certificate layer, the client certificate
used for mutual TLS used for mutual TLS
and MUST verify that the certificate matches the and <bcp14>MUST</bcp14> verify that the certificate matches the
certificate associated with the access token. If they do not match, certificate associated with the access token. If they do not match,
the resource access attempt MUST be rejected with an error per <xref target="R the resource access attempt <bcp14>MUST</bcp14> be rejected with an error, per
FC6750"/> <xref target="RFC6750" format="default"/>,
using an HTTP 401 status code and the <spanx style="verb">invalid_token</spanx using an HTTP 401 status code and the <tt>invalid_token</tt> error code.
> error code.
</t> </t>
<t> <t>
Metadata to convey server and client capabilities for mutual-TLS client certif icate-bound access tokens Metadata to convey server and client capabilities for mutual-TLS client certif icate-bound access tokens
is defined in <xref target="server_metadata_at"/> and <xref target="client_met adata_at"/> respectively. is defined in Sections <xref target="server_metadata_at" format="counter"/> an d <xref target="client_metadata_at" format="counter"/>, respectively.
</t> </t>
<section anchor="x5t" numbered="true" toc="default">
<section anchor="x5t" title="JWT Certificate Thumbprint Confirmation Metho <name>JWT Certificate Thumbprint Confirmation Method</name>
d"> <t>
<t> When access tokens are represented as JSON Web Tokens (JWT) <xref target="RF
When access tokens are represented as JSON Web Tokens (JWT)<xref target="RFC C7519" format="default"/>,
7519"/>, the certificate hash information <bcp14>SHOULD</bcp14> be represented using
the certificate hash information SHOULD be represented using the <tt>x5t#S256</tt> confirmation method member defined herein.
the <spanx style="verb">x5t#S256</spanx> confirmation method member defined </t>
herein. <t>
</t> To represent the hash of a certificate in a JWT, this specification
<t> defines the new JWT Confirmation Method <xref target="RFC7800"
To represent the hash of a certificate in a JWT, format="default"></xref> member <tt>x5t#S256</tt> for the X.509
this specification defines the new <xref target="RFC7800">JWT Confirmation M Certificate SHA-256 Thumbprint. The value of the <tt>x5t#S256</tt> member
ethod</xref> is a base64url-encoded <xref target="RFC4648" format="default"/> SHA-256
member <spanx style="verb">x5t#S256</spanx> for the X.509 Certificate SHA-25 <xref target="SHS" format="default"/> hash (a.k.a., thumbprint, fingerprint,
6 Thumbprint. or digest) of the DER encoding <xref target="X690" format="default"/> of
The value of the <spanx style="verb">x5t#S256</spanx> member is a base64url- the X.509 certificate <xref target="RFC5280" format="default"/>. The
encoded <xref target="RFC4648"/> base64url-encoded value <bcp14>MUST</bcp14> omit all trailing pad '='
SHA-256 <xref target="SHS"/> hash (a.k.a. thumbprint, fingerprint or digest) characters and <bcp14>MUST NOT</bcp14> include any line breaks,
of the DER encoding <xref target="X690"/> of the X.509 certificate whitespace, or other additional characters.
<xref target="RFC5280"/>. The base64url-encoded value MUST omit all trailing </t>
pad '=' characters <t>
and MUST NOT include any line breaks, whitespace, or other additional charac The following is an example of a JWT payload containing an <tt>x5t#S256</tt>
ters. certificate thumbprint
</t> confirmation method. The new JWT content introduced by this specification is
<t> the <tt>cnf</tt>
The following is an example of a JWT payload containing an <spanx style="ver
b">x5t#S256</spanx> certificate thumbprint
confirmation method. The new JWT content introduced by this specification is
the <spanx style="verb">cnf</spanx>
confirmation method claim at the bottom of the example that has confirmation method claim at the bottom of the example that has
the <spanx style="verb">x5t#S256</spanx> confirmation method member containi ng the value that is the hash the <tt>x5t#S256</tt> confirmation method member containing the value that i s the hash
of the client certificate to which the access token is bound. of the client certificate to which the access token is bound.
</t> </t>
<figure anchor="eg_x5ts256jwt">
<figure anchor="eg_x5ts256jwt" title="Example JWT Claims Set with an X.509 Cer <name>Example JWT Claims Set with an X.509 Certificate Thumbprint Conf
tificate Thumbprint Confirmation Method"> irmation Method</name>
<artwork><![CDATA[ <sourcecode type="json"><![CDATA[
{ {
"iss": "https://server.example.com", "iss": "https://server.example.com",
"sub": "ty.webb@example.com", "sub": "ty.webb@example.com",
"exp": 1493726400, "exp": 1493726400,
"nbf": 1493722800, "nbf": 1493722800,
"cnf":{ "cnf":{
"x5t#S256": "bwcK0esc3ACC3DB2Y5_lESsXE8o9ltc05O89jdN-dg2" "x5t#S256": "bwcK0esc3ACC3DB2Y5_lESsXE8o9ltc05O89jdN-dg2"
} }
}]]> }
</artwork> ]]></sourcecode>
</figure> </figure>
</section> </section>
<section anchor="introspect" numbered="true" toc="default">
<section anchor="introspect" title="Confirmation Method for Token Introspe <name>Confirmation Method for Token Introspection</name>
ction">
<t> <t>
<xref target="RFC7662">OAuth 2.0 Token Introspection</xref> defines a OAuth 2.0 Token Introspection <xref target="RFC7662" format="default"> </xref> defines a
method for a protected resource to query method for a protected resource to query
an authorization server about the active state of an an authorization server about the active state of an
access token as well as to determine meta-information about the token. access token as well as to determine metainformation about the token.
</t> </t>
<t> <t>
For a mutual-TLS client certificate-bound access token, the hash of th e For a mutual-TLS client certificate-bound access token, the hash of th e
certificate to which the token is bound certificate to which the token is bound
is conveyed to the protected resource as meta-information is conveyed to the protected resource as metainformation
in a token introspection response. The hash is conveyed using the same in a token introspection response. The hash is conveyed using the same
<spanx style="verb">cnf</spanx> with <spanx style="verb">x5t#S256</spa nx> member structure as the <tt>cnf</tt> with <tt>x5t#S256</tt> member structure as the
certificate SHA-256 thumbprint confirmation method, described in certificate SHA-256 thumbprint confirmation method, described in
<xref target="x5t"/>, as a top-level member of the introspection respo nse JSON. <xref target="x5t" format="default"/>, as a top-level member of the in trospection response JSON.
The protected resource compares The protected resource compares
that certificate hash to a hash of the client certificate used for that certificate hash to a hash of the client certificate used for
mutual-TLS authentication mutual-TLS authentication
and rejects the request, if they do not match. and rejects the request if they do not match.
</t> </t>
<t> <t>
The following is an example of an introspection response for an active token with The following is an example of an introspection response for an active token with
an <spanx style="verb">x5t#S256</spanx> certificate thumbprint an <tt>x5t#S256</tt> certificate thumbprint
confirmation method. The new introspection response content introduced confirmation method. The new introspection response content introduced
by this specification is the <spanx style="verb">cnf</spanx> by this specification is the <tt>cnf</tt>
confirmation method at the bottom of the example that has confirmation method at the bottom of the example that has
the <spanx style="verb">x5t#S256</spanx> confirmation method member co ntaining the value that is the hash the <tt>x5t#S256</tt> confirmation method member containing the value that is the hash
of the client certificate to which the access token is bound. of the client certificate to which the access token is bound.
</t> </t>
<figure anchor="eg_x5ts256intro">
<figure anchor="eg_x5ts256intro" title="Example Introspection Response f <name>Example Introspection Response for a Certificate-Bound Access To
or a Certificate-Bound Access Token"> ken</name>
<artwork><![CDATA[ <artwork name="" type="" align="left" alt=""><![CDATA[
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
{ {
"active": true, "active": true,
"iss": "https://server.example.com", "iss": "https://server.example.com",
"sub": "ty.webb@example.com", "sub": "ty.webb@example.com",
"exp": 1493726400, "exp": 1493726400,
"nbf": 1493722800, "nbf": 1493722800,
"cnf":{ "cnf":{
"x5t#S256": "bwcK0esc3ACC3DB2Y5_lESsXE8o9ltc05O89jdN-dg2" "x5t#S256": "bwcK0esc3ACC3DB2Y5_lESsXE8o9ltc05O89jdN-dg2"
} }
}]]> }
</artwork> ]]></artwork>
</figure> </figure>
</section> </section>
<section anchor="server_metadata_at" numbered="true" toc="default">
<name>Authorization Server Metadata</name>
<t>This document introduces the following new authorization server
metadata <xref target="RFC8414" format="default"/> parameter to sign
al the server's capability to issue certificate-bound access tokens:
<section anchor="server_metadata_at" title="Authorization Server Metadata" </t>
> <dl newline="true" spacing="normal">
<t>This document introduces the following new authorization server <dt>tls_client_certificate_bound_access_tokens</dt>
metadata <xref target="RFC8414"/> parameter to signal the server's c <dd>
apability to issue certificate <bcp14>OPTIONAL</bcp14>. Boolean value indicating server support
bound access tokens: for
<list style="hanging">
<t hangText="tls_client_certificate_bound_access_tokens"><vspace/>
OPTIONAL. Boolean value indicating server support for
mutual-TLS client certificate-bound access tokens. If omitted, t he mutual-TLS client certificate-bound access tokens. If omitted, t he
default value is <spanx style="verb">false</spanx>. default value is <tt>false</tt>.
</t> </dd>
</list> </dl>
</t> </section>
</section> <section anchor="client_metadata_at" numbered="true" toc="default">
<name>Client Registration Metadata</name>
<section anchor="client_metadata_at" title="Client Registration Metadata">
<t>The following new client <t>The following new client
metadata parameter is introduced to convey the client's intention to u metadata parameter is introduced to convey the client's intention to u
se certificate se certificate-bound access tokens:
bound access tokens:
<list style="hanging"> </t>
<t hangText="tls_client_certificate_bound_access_tokens"><vspace/> <dl newline="true" spacing="normal">
OPTIONAL. Boolean value used to indicate the client's intention <dt>tls_client_certificate_bound_access_tokens</dt>
<dd>
<bcp14>OPTIONAL</bcp14>. Boolean value used to indicate the client
's intention
to use mutual-TLS client certificate-bound access tokens. to use mutual-TLS client certificate-bound access tokens.
If omitted, the default value is <spanx style="verb">false</spanx> If omitted, the default value is <tt>false</tt>.
. </dd>
</t> </dl>
</list> <t>
Note that, if a client that has indicated the intention to use mutual- TLS client certificate-bound tokens Note that if a client that has indicated the intention to use mutual-T LS client certificate-bound tokens
makes a request to the token endpoint over a non-mutual-TLS connection , makes a request to the token endpoint over a non-mutual-TLS connection ,
it is at the authorization server's discretion as to whether to return an error or issue an unbound token. it is at the authorization server's discretion as to whether to return an error or issue an unbound token.
</t> </t>
</section>
</section> </section>
</section>
<section anchor="PubClient" title="Public Clients and Certificate-Bound Toke <section anchor="PubClient" numbered="true" toc="default">
ns"> <name>Public Clients and Certificate-Bound Tokens</name>
<t> <t>
Mutual-TLS OAuth client authentication and certificate-bound access toke ns Mutual-TLS OAuth client authentication and certificate-bound access toke ns
can be used independently of each other. can be used independently of each other.
Use of certificate-bound access tokens without mutual-TLS OAuth client a uthentication, for example, Use of certificate-bound access tokens without mutual-TLS OAuth client a uthentication, for example,
is possible in support of binding access tokens to a TLS client certific ate for public clients (those without is possible in support of binding access tokens to a TLS client certific ate for public clients (those without
authentication credentials associated with the <spanx style="verb">clien t_id</spanx>). authentication credentials associated with the <tt>client_id</tt>).
The authorization server would configure the TLS stack in the same manne r as for the Self-Signed Certificate method The authorization server would configure the TLS stack in the same manne r as for the Self-Signed Certificate method
such that it does not verify that the certificate presented by the clien t during the handshake is such that it does not verify that the certificate presented by the clien t during the handshake is
signed by a trusted CA. Individual instances of a client would create a self-signed signed by a trusted CA. Individual instances of a client would create a self-signed
certificate for mutual TLS with both the authorization server and resour ce server. The authorization certificate for mutual TLS with both the authorization server and resour ce server. The authorization
server would not use the mutual-TLS certificate to authenticate the clie nt at the OAuth layer server would not use the mutual-TLS certificate to authenticate the clie nt at the OAuth layer
but would bind the issued access token but would bind the issued access token
to that certificate, for which the client has proven possession of the c orresponding private key. to the certificate for which the client has proven possession of the cor responding private key.
The access token is then bound to the certificate and can only be used b y the client The access token is then bound to the certificate and can only be used b y the client
possessing the certificate and corresponding private key and utilizing t hem to negotiate mutual TLS on possessing the certificate and corresponding private key and utilizing t hem to negotiate mutual TLS on
connections to the resource server. connections to the resource server.
When the authorization server issues a refresh token to such a client, i When the authorization server issues a refresh token to such a client, i
t SHOULD also bind the refresh token t <bcp14>SHOULD</bcp14> also bind the refresh token
to the respective certificate. And check the binding when the refresh to to the respective certificate and check the binding when the refresh tok
ken is presented to get new en is presented to get new
access tokens. access tokens.
The implementation details of the binding the refresh token are at the d iscretion of the authorization The implementation details of the binding of the refresh token are at th e discretion of the authorization
server. server.
</t> </t>
</section> </section>
<section anchor="endpointAliases" numbered="true" toc="default">
<section anchor="endpointAliases" title="Metadata for Mutual-TLS Endpoint Al <name>Metadata for Mutual-TLS Endpoint Aliases</name>
iases">
<t> <t>
The process of negotiating client certificate-based mutual TLS involves a TLS server requesting a certificate The process of negotiating client certificate-based mutual TLS involves a TLS server requesting a certificate
from the TLS client (the client does not provide one unsolicited). Altho ugh a server can be configured from the TLS client (the client does not provide one unsolicited). Altho ugh a server can be configured
such that client certificates are optional, meaning that the connection is allowed to continue when the client such that client certificates are optional, meaning that the connection is allowed to continue when the client
does not provide a certificate, the act of a server requesting a certifi cate can result in undesirable does not provide a certificate, the act of a server requesting a certifi cate can result in undesirable
behavior from some clients. This is particularly true of web browsers as TLS clients, which will typically behavior from some clients. This is particularly true of web browsers as TLS clients, which will typically
present the end-user with an intrusive certificate selection interface w hen the server requests a certificate. present the end user with an intrusive certificate selection interface w hen the server requests a certificate.
</t> </t>
<t> <t>
Authorization servers supporting both clients using mutual TLS and conve ntional clients MAY chose to Authorization servers supporting both clients using mutual TLS and conve ntional clients <bcp14>MAY</bcp14> chose to
isolate the server side mutual-TLS behavior to only clients intending to do mutual TLS, thus isolate the server side mutual-TLS behavior to only clients intending to do mutual TLS, thus
avoiding any undesirable effects it might have on conventional clients. The following authorization server avoiding any undesirable effects it might have on conventional clients. The following authorization server
metadata parameter is introduced to facilitate such separation: metadata parameter is introduced to facilitate such separation:
</t> </t>
<t> <dl newline="true" spacing="normal">
<list style="hanging"> <dt>mtls_endpoint_aliases</dt>
<t hangText="mtls_endpoint_aliases"> <dd><bcp14>OPTIONAL</bcp14>.
<vspace/>OPTIONAL.
A JSON object containing alternative authorization server endpoints that, A JSON object containing alternative authorization server endpoints that,
when present, an OAuth client intending to do mutual TLS when present, an OAuth client intending to do mutual TLS
uses in preference to the conventional endpoints. uses in preference to the conventional endpoints.
The parameter value itself consists of one or more endpoint paramete rs, The parameter value itself consists of one or more endpoint paramete rs,
such as <spanx style="verb">token_endpoint</spanx>, such as <tt>token_endpoint</tt>,
<spanx style="verb">revocation_endpoint</spanx>, <tt>revocation_endpoint</tt>,
<spanx style="verb">introspection_endpoint</spanx>, etc., convention <tt>introspection_endpoint</tt>, etc., conventionally defined for th
ally defined for the e
top-level of authorization server metadata. top level of authorization server metadata.
An OAuth client intending to do mutual TLS An OAuth client intending to do mutual TLS
(for OAuth client authentication and/or to acquire or use certificat e-bound tokens) (for OAuth client authentication and/or to acquire or use certificat e-bound tokens)
when making a request directly to the authorization server MUST when making a request directly to the authorization server <bcp14>MU
use the alias URL of the endpoint within the <spanx style="verb">mtl ST</bcp14>
s_endpoint_aliases</spanx>, when present, use the alias URL of the endpoint within the <tt>mtls_endpoint_alias
in preference to the endpoint URL of the same name at top-level of m es</tt>, when present,
etadata. in preference to the endpoint URL of the same name at the top level
of metadata.
When an endpoint is not present in When an endpoint is not present in
<spanx style="verb">mtls_endpoint_aliases</spanx>, then the client u <tt>mtls_endpoint_aliases</tt>, then the client uses the conventiona
ses the conventional endpoint URL l endpoint URL
defined at the top-level of the authorization server metadata. Metad defined at the top level of the authorization server metadata. Metad
ata parameters within ata parameters within
<spanx style="verb">mtls_endpoint_aliases</spanx> that do not define <tt>mtls_endpoint_aliases</tt> that do not define
endpoints to which an OAuth client makes a direct request have no me endpoints to which an OAuth client makes a direct request have no me
aning and SHOULD be ignored. aning and <bcp14>SHOULD</bcp14> be ignored.
</t> </dd>
</list> </dl>
</t>
<t> <t>
Below is an example of an authorization server metadata document with th e Below is an example of an authorization server metadata document with th e
<spanx style="verb">mtls_endpoint_aliases</spanx> parameter, which indic ates aliases for the <tt>mtls_endpoint_aliases</tt> parameter, which indicates aliases for th e
token, revocation, and introspection endpoints that an OAuth client inte nding to do mutual TLS token, revocation, and introspection endpoints that an OAuth client inte nding to do mutual TLS
would in preference to the conventional token, revocation, and introspec would use in preference to the conventional token, revocation, and
tion endpoints. introspection endpoints.
Note that the endpoints in <spanx style="verb">mtls_endpoint_aliases</sp Note that the endpoints in <tt>mtls_endpoint_aliases</tt> use a differen
anx> use a different t
host than their conventional counterparts, which allows the authorizatio n server host than their conventional counterparts, which allows the authorizatio n server
(via TLS <spanx style="verb">server_name</spanx> extension <xref target= "RFC6066"/> or actual distinct hosts) to differentiate its TLS behavior as appro priate. (via TLS <tt>server_name</tt> extension <xref target="RFC6066" format="d efault"/> or actual distinct hosts) to differentiate its TLS behavior as appropr iate.
<figure title='Example Authorization Server Metadata with Mutual-TLS End </t>
point Aliases' anchor='as-meta'> <figure anchor="as-meta">
<artwork><![CDATA[ <name>Example Authorization Server Metadata with Mutual-TLS Endpoint Ali
ases</name>
<sourcecode type="json"><![CDATA[
{ {
"issuer": "https://server.example.com", "issuer": "https://server.example.com",
"authorization_endpoint": "https://server.example.com/authz", "authorization_endpoint": "https://server.example.com/authz",
"token_endpoint": "https://server.example.com/token", "token_endpoint": "https://server.example.com/token",
"introspection_endpoint": "https://server.example.com/introspect", "introspection_endpoint": "https://server.example.com/introspect",
"revocation_endpoint": "https://server.example.com/revo", "revocation_endpoint": "https://server.example.com/revo",
"jwks_uri": "https://server.example.com/jwks", "jwks_uri": "https://server.example.com/jwks",
"response_types_supported": ["code"], "response_types_supported": ["code"],
"response_modes_supported": ["fragment","query","form_post"], "response_modes_supported": ["fragment","query","form_post"],
"grant_types_supported": ["authorization_code", "refresh_token"], "grant_types_supported": ["authorization_code", "refresh_token"],
"token_endpoint_auth_methods_supported": "token_endpoint_auth_methods_supported":
["tls_client_auth","client_secret_basic","none"], ["tls_client_auth","client_secret_basic","none"],
"tls_client_certificate_bound_access_tokens": true "tls_client_certificate_bound_access_tokens": true,
"mtls_endpoint_aliases": { "mtls_endpoint_aliases": {
"token_endpoint": "https://mtls.example.com/token", "token_endpoint": "https://mtls.example.com/token",
"revocation_endpoint": "https://mtls.example.com/revo", "revocation_endpoint": "https://mtls.example.com/revo",
"introspection_endpoint": "https://mtls.example.com/introspect" "introspection_endpoint": "https://mtls.example.com/introspect"
} }
} }
]]></artwork> ]]></sourcecode>
</figure> </figure>
</t>
</section> </section>
<section anchor="Impl" numbered="true" toc="default">
<section anchor="Impl" title="Implementation Considerations"> <name>Implementation Considerations</name>
<section anchor="ImplAS" title="Authorization Server"> <section anchor="ImplAS" numbered="true" toc="default">
<t>The authorization server needs to set up its TLS configuration appropriat <name>Authorization Server</name>
ely <t>The authorization server needs to set up its TLS configuration approp
riately
for the OAuth client authentication methods it supports.</t> for the OAuth client authentication methods it supports.</t>
<t>An authorization server that supports mutual-TLS client authentication <t>An authorization server that supports mutual-TLS client authenticatio n
and other client authentication methods or public clients in parallel would make mutual TLS and other client authentication methods or public clients in parallel would make mutual TLS
optional (i.e. allowing a handshake to continue after the server requests a client certificate optional (i.e., allowing a handshake to continue after the server requests a client certificate
but the client does not send one).</t> but the client does not send one).</t>
<t>In order to support the Self-Signed Certificate method alone, the authori zation server <t>In order to support the Self-Signed Certificate method alone, the aut horization server
would configure the TLS stack in such a way that it does not verify whether the would configure the TLS stack in such a way that it does not verify whether the
certificate presented by the client during the handshake is signed by a trus ted CA certificate presented by the client during the handshake is signed by a trus ted CA
certificate.</t> certificate.</t>
<t>As described in <xref target="CertificateBoundAccessTokens"/>, the author ization server <t>As described in <xref target="CertificateBoundAccessTokens" format="d efault"/>, the authorization server
binds the issued access token to the TLS client certificate, which means tha t it binds the issued access token to the TLS client certificate, which means tha t it
will only issue certificate-bound tokens for a will only issue certificate-bound tokens for a
certificate which the client has proven possession of the corresponding priv certificate that the client has proven possession of the corresponding priva
ate key.</t> te key.</t>
<t>The authorization server may also consider hosting the token endpoint, <t>The authorization server may also consider hosting the token endpoint
and other endpoints requiring client authentication, on and other endpoints requiring client authentication on
a separate host name or port in order to prevent unintended impact on the TL S behavior of a separate host name or port in order to prevent unintended impact on the TL S behavior of
its other endpoints, e.g. the authorization endpoint. As described in <xref target="endpointAliases"/>, its other endpoints, e.g., the authorization endpoint. As described in <xref target="endpointAliases" format="default"/>,
it may further isolate any potential impact of the server requesting client certificates by it may further isolate any potential impact of the server requesting client certificates by
offering a distinct set of endpoints on a separate host or port, which are a liases for offering a distinct set of endpoints on a separate host or port, which are a liases for
the originals that a client intending to do mutual TLS will use in preferenc e to the conventional endpoints.</t> the originals that a client intending to do mutual TLS will use in preferenc e to the conventional endpoints.</t>
</section> </section>
<section anchor="ImplRS" title="Resource Server"> <section anchor="ImplRS" numbered="true" toc="default">
<t> <name>Resource Server</name>
<t>
OAuth divides the roles and responsibilities such that the resource server relies OAuth divides the roles and responsibilities such that the resource server relies
on the authorization server to perform client authentication and obtain re source owner (end-user) on the authorization server to perform client authentication and obtain re source-owner (end-user)
authorization. The resource server makes authorization decisions based on the access token authorization. The resource server makes authorization decisions based on the access token
presented by the client but does not directly authenticate the client per se. presented by the client but does not directly authenticate the client per se.
The manner in which an access token is bound to the client certificate and how a protected resource verifies the proof-of-possession The manner in which an access token is bound to the client certificate and how a protected resource verifies the proof-of-possession
decouples that from the specific method that the client used to authentica te with the decouples that from the specific method that the client used to authentica te with the
authorization server. Mutual TLS during protected resource access can ther efore authorization server. Mutual TLS during protected resource access can, the refore,
serve purely as a proof-of-possession mechanism. serve purely as a proof-of-possession mechanism.
As such, it is not necessary for the resource server to validate As such, it is not necessary for the resource server to validate
the trust chain of the client's certificate in any of the methods the trust chain of the client's certificate in any of the methods
defined in this document. defined in this document.
The resource server would therefore configure the TLS stack The resource server would, therefore, configure the TLS stack
in a way that it does not verify whether the certificate presented by the client in a way that it does not verify whether the certificate presented by the client
during the handshake is signed by a trusted CA certificate. during the handshake is signed by a trusted CA certificate.
</t> </t>
</section> </section>
<section anchor="ImplExp" title="Certificate Expiration and Bound Access Tok <section anchor="ImplExp" numbered="true" toc="default">
ens"> <name>Certificate Expiration and Bound Access Tokens</name>
<t> <t>
As described in <xref target="CertificateBoundAccessTokens"/>, As described in <xref target="CertificateBoundAccessTokens" format="defa
ult"/>,
an access token is bound to a specific client certificate, which means t hat an access token is bound to a specific client certificate, which means t hat
the same certificate must be used for mutual TLS on protected resource a ccess. the same certificate must be used for mutual TLS on protected resource a ccess.
It also implies that access tokens are invalidated when a client updates the certificate, It also implies that access tokens are invalidated when a client updates the certificate,
which can be handled similar to expired access tokens where the client which can be handled similarly to expired access tokens where the client
requests a new access token (typically with a refresh token) and retries the protected resource requests a new access token (typically with a refresh token) and retries the protected resource
request. request.
</t> </t>
</section> </section>
<section anchor="ImplImplicit" title="Implicit Grant Unsupported"> <section anchor="ImplImplicit" numbered="true" toc="default">
<t> <name>Implicit Grant Unsupported</name>
<t>
This document describes binding an access token to the This document describes binding an access token to the
client certificate presented on the TLS connection from the client to the client certificate presented on the TLS connection from the client to the
authorization server's token endpoint, authorization server's token endpoint,
however, such binding of access tokens issued directly from the authorizat ion however, such binding of access tokens issued directly from the authorizat ion
endpoint via the implicit grant flow is explicitly out of scope. endpoint via the implicit grant flow is explicitly out of scope.
End users interact directly with the authorization endpoint using a web br owser End users interact directly with the authorization endpoint using a web br owser,
and the use of client certificates in user's browsers bring operational an d and the use of client certificates in user's browsers bring operational an d
usability issues, which make it undesirable to support certificate-bound a ccess usability issues that make it undesirable to support certificate-bound acc ess
tokens issued in the implicit grant flow. Implementations wanting to emplo y tokens issued in the implicit grant flow. Implementations wanting to emplo y
certificate-bound access tokens should utilize grant types certificate-bound access tokens should utilize grant types
that involve the client making an access token request directly to the tok en endpoint that involve the client making an access token request directly to the tok en endpoint
(e.g. the authorization code and refresh token grant types). (e.g., the authorization code and refresh token grant types).
</t> </t>
</section> </section>
<section anchor="TTRP" title="TLS Termination"> <section anchor="TTRP" numbered="true" toc="default">
<t> <name>TLS Termination</name>
An authorization server or resource server MAY choose to terminate TLS con <t>
nections at a load balancer, An authorization server or resource server <bcp14>MAY</bcp14> choose to te
rminate TLS connections at a load balancer,
reverse proxy, or other network intermediary. How the client certificate m etadata is securely reverse proxy, or other network intermediary. How the client certificate m etadata is securely
communicated between the intermediary and the application server in this c communicated between the intermediary and the application server, in this
ase is out of scope of this specification. case, is out of scope of this specification.
</t> </t>
</section> </section>
</section> </section>
<section anchor="Security" numbered="true" toc="default">
<section anchor="Security" title="Security Considerations"> <name>Security Considerations</name>
<section title="Certificate-Bound Refresh Tokens"> <section numbered="true" toc="default">
<t>The OAuth 2.0 Authorization Framework <xref target="RFC6749"/> requir <name>Certificate-Bound Refresh Tokens</name>
es that an authorization server <t>The OAuth 2.0 Authorization Framework <xref target="RFC6749"
format="default"/> requires that an authorization server (AS)
bind refresh tokens to the client to which they were issued and that c onfidential clients bind refresh tokens to the client to which they were issued and that c onfidential clients
(those having established authentication credentials with the authoriz ation server) authenticate to (those having established authentication credentials with the AS) auth enticate to
the AS when presenting a refresh token. As a result, refresh tokens ar e indirectly certificate-bound by way of the the AS when presenting a refresh token. As a result, refresh tokens ar e indirectly certificate-bound by way of the
client ID and the associated requirement for (certificate-based) authe client ID and the associated requirement for (certificate-based) authe
ntication to the authorization server when ntication to the AS when
issued to clients utilizing the <spanx style="verb">tls_client_auth</s issued to clients utilizing the <tt>tls_client_auth</tt> or
panx> or <tt>self_signed_tls_client_auth</tt> methods of client authentication.
<spanx style="verb">self_signed_tls_client_auth</spanx> methods of cli <xref target="PubClient" format="default"/> describes certificate-boun
ent authentication. d refresh tokens issued to public clients (those without
<xref target="PubClient"/> describes certificate-bound refresh tokens authentication credentials associated with the <tt>client_id</tt>).
issued to public clients (those without
authentication credentials associated with the <spanx style="verb">cli
ent_id</spanx>).
</t> </t>
</section> </section>
<section title="Certificate Thumbprint Binding"> <section numbered="true" toc="default">
<name>Certificate Thumbprint Binding</name>
<t> <t>
The binding between the certificate and access token specified in <xre f target="x5t"/> uses The binding between the certificate and access token specified in <xre f target="x5t" format="default"/> uses
a cryptographic hash of the certificate. It relies on the hash functio n having sufficient a cryptographic hash of the certificate. It relies on the hash functio n having sufficient
second-preimage resistance so as to make it computationally infeasible to second-preimage resistance so as to make it computationally infeasible to
find or create another certificate that produces to the same hash outp ut value. find or create another certificate that produces to the same hash outp ut value.
The SHA-256 hash function was used because it meets the aforementioned requirement while being widely available. The SHA-256 hash function was used because it meets the aforementioned requirement while being widely available.
If, in the future, certificate thumbprints need to be computed using If, in the future, certificate thumbprints need to be computed using
hash function(s) other than SHA-256, it is suggested that additional hash function(s) other than SHA-256, it is suggested that, for additio
related JWT confirmation methods members be defined for that purpose nal
related JWT confirmation methods, members be defined for that purpose
and registered in the IANA "JWT Confirmation Methods" registry and registered in the IANA "JWT Confirmation Methods" registry
<xref target="IANA.JWT.Claims"/> <xref target="IANA.JWT.Claims" format="default"/>
for JWT <spanx style="verb">cnf</spanx> member values. for JWT <tt>cnf</tt> member values.
</t> </t>
<t> <t>
Community knowledge about the strength of various algorithms and Community knowledge about the strength of various algorithms and
feasible attacks can change suddenly, and experience shows that a feasible attacks can change suddenly, and experience shows that a
document about security is a point-in-time document about security is a point-in-time
statement. Readers are advised to seek out any errata or updates statement. Readers are advised to seek out any errata or updates
that apply to this document. that apply to this document.
</t> </t>
</section> </section>
<section anchor="TLSV" title="TLS Versions and Best Practices"> <section anchor="TLSV" numbered="true" toc="default">
<name>TLS Versions and Best Practices</name>
<t> <t>
In the abstract this document is applicable with any TLS version suppo This document is applicable with any TLS version supporting certificat
rting certificate-based client authentication. e-based client authentication.
Both <xref target="RFC8446">TLS 1.3</xref> and <xref target="RFC5246"> Both <xref target="RFC8446" format="default">TLS 1.3</xref> and <xref
TLS 1.2</xref> are cited herein because, target="RFC5246" format="default">TLS 1.2</xref> are cited herein, because,
at the time of writing, 1.3 is the newest version while 1.2 is the mos at the time of writing, 1.3 is the newest version, while 1.2 is the mo
t widely deployed. st widely deployed.
General implementation and security considerations for TLS, including version recommendations, General implementation and security considerations for TLS, including version recommendations,
can be found in <xref target="BCP195"/>. can be found in <xref target="BCP195" format="default"/>.
</t> </t>
<t> <t>
TLS certificate validation TLS certificate validation
(for both client and server certificates) requires a local database of (for both client and server certificates) requires a local database of
trusted certificate authorities (CAs). Decisions about what CAs to tr ust trusted certificate authorities (CAs). Decisions about what CAs to tru st
and how to make such a determination of trust are out of scope for thi s and how to make such a determination of trust are out of scope for thi s
document. document.
</t> </t>
</section> </section>
<section anchor="certspoofing" title="X.509 Certificate Spoofing"> <section anchor="certspoofing" numbered="true" toc="default">
<name>X.509 Certificate Spoofing</name>
<t> <t>
If the PKI method of client authentication is used, an attacker could try to impersonate a client using If the PKI method of client authentication is used, an attacker could try to impersonate a client using
a certificate with the same subject (DN or SAN) but issued by a differ a certificate with the same subject (DN or SAN) but issued by a
ent CA, which the authorization server trusts. different CA that the authorization server trusts.
To cope with that threat, the authorization server SHOULD only accept To cope with that threat, the authorization server <bcp14>SHOULD</bcp1
as trust anchors 4> only accept, as trust anchors,
a limited number of CAs whose certificate issuance policy meets its se curity requirements. a limited number of CAs whose certificate issuance policy meets its se curity requirements.
There is an assumption then that the client and server agree out of ba nd on the set There is an assumption then that the client and server agree out of ba nd on the set
of trust anchors that the server uses to create and validate the of trust anchors that the server uses to create and validate the
certificate chain. Without this assumption the use of a subject certificate chain. Without this assumption the use of a subject
to identify the client certificate would open the server up to to identify the client certificate would open the server up to
certificate spoofing attacks. certificate spoofing attacks.
</t> </t>
</section> </section>
<section title="X.509 Certificate Parsing and Validation Complexity"> <section numbered="true" toc="default">
<name>X.509 Certificate Parsing and Validation Complexity</name>
<t> <t>
Parsing and validation of X.509 certificates and certificate chains is Parsing and validation of X.509 certificates and certificate chains
complex and implementation is complex, and implementation
mistakes have previously exposed security vulnerabilities. mistakes have previously exposed security vulnerabilities.
Complexities of validation include (but are not limited to) Complexities of validation include (but are not limited to)
<xref target="CX5P"/> <xref target="DCW"/> <xref target="RFC5280"/>: <xref target="CX5P" format="default"/> <xref target="DCW" format="defa ult"/> <xref target="RFC5280" format="default"/>:
</t> </t>
<ul spacing="normal">
<li>checking of basic constraints, basic and extended key usage constr
aints, validity periods, and critical extensions;</li>
<li>handling of embedded NUL bytes in ASN.1 counted-length strings and
non-canonical or non-normalized string representations in subject names;</li>
<li>handling of wildcard patterns in subject names;</li>
<li>recursive verification of certificate chains and checking certific
ate revocation.</li>
</ul>
<t> <t>
<list style="symbols"> For these reasons, implementors <bcp14>SHOULD</bcp14> use an establish
<t>checking of Basic Constraints, basic and extended Key Usage constra ed and well-tested X.509 library
ints, validity periods, and critical extensions;</t>
<t>handling of embedded NUL bytes in ASN.1 counted-length strings, and
non-canonical or non-normalized string representations in subject names;</t>
<t>handling of wildcard patterns in subject names;</t>
<t>recursive verification of certificate chains and checking certifica
te revocation.</t>
</list>
</t><t>
For these reasons, implementors SHOULD use an established and well-tes
ted X.509 library
(such as one used by an established TLS library) for validation of X.5 09 certificate chains (such as one used by an established TLS library) for validation of X.5 09 certificate chains
and SHOULD NOT attempt to write their own X.509 certificate validation procedures. and <bcp14>SHOULD NOT</bcp14> attempt to write their own X.509 certifi cate validation procedures.
</t> </t>
</section> </section>
</section> </section>
<section anchor="Privacy" numbered="true" toc="default">
<section anchor="Privacy" title="Privacy Considerations"> <name>Privacy Considerations</name>
<t> <t>
In TLS versions prior to 1.3, the client's certificate is sent unencrypt ed in the initial handshake and In TLS versions prior to 1.3, the client's certificate is sent unencrypt ed in the initial handshake and
can potentially be used by third parties to monitor, track, and correlat e client activity. can potentially be used by third parties to monitor, track, and correlat e client activity.
This is likely of little concern for clients that act on behalf of a sig This is likely of little concern for clients that act on behalf of a
nificant number of end-users because significant number of end users because
individual user activity will not be discernible amidst the client activ ity as a whole. individual user activity will not be discernible amidst the client activ ity as a whole.
However, clients that act on behalf of a single end-user, such as a nati ve application on a mobile device, However, clients that act on behalf of a single end user, such as a nati ve application on a mobile device,
should use TLS version 1.3 whenever possible or consider the potential p rivacy implications of using mutual TLS on should use TLS version 1.3 whenever possible or consider the potential p rivacy implications of using mutual TLS on
earlier versions. earlier versions.
</t> </t>
</section> </section>
<section anchor="IANA" numbered="true" toc="default">
<section anchor="IANA" title="IANA Considerations"> <name>IANA Considerations</name>
<section numbered="true" toc="default">
<section title="JWT Confirmation Methods Registration"> <name>JWT Confirmation Methods Registration</name>
<t> <t>
This specification requests registration of the following value Per this specification, the following value has been registered
in the IANA "JWT Confirmation Methods" registry in the IANA "JWT Confirmation Methods" registry
<xref target="IANA.JWT.Claims"/> <xref target="IANA.JWT.Claims" format="default"/>
for JWT <spanx style="verb">cnf</spanx> member values for JWT <tt>cnf</tt> member values
established by <xref target="RFC7800"/>. established by <xref target="RFC7800" format="default"/>.
</t>
<t>
<?rfc subcompact="yes"?>
<list style='symbols'>
<t>Confirmation Method Value: <spanx style="verb">x5t#S256</spanx></
t>
<t>Confirmation Method Description: X.509 Certificate SHA-256 Thumbp
rint</t>
<t>Change Controller: IESG</t>
<t>Specification Document(s): <xref target="x5t"/> of [[ this specif
ication ]]</t>
</list>
<?rfc subcompact="no"?>
</t> </t>
</section>
<section title="Authorization Server Metadata Registration"> <dl spacing="compact">
<dt>Confirmation Method Value:</dt><dd><tt>x5t#S256</tt></dd>
<dt>Confirmation Method Description:</dt><dd>X.509 Certificate SHA-256
Thumbprint</dd>
<dt>Change Controller:</dt><dd>IESG</dd>
<dt>Specification Document(s):</dt><dd><xref target="x5t" format="defa
ult"/>
of RFC 8705</dd>
</dl>
</section>
<section numbered="true" toc="default">
<name>Authorization Server Metadata Registration</name>
<t> <t>
This specification requests registration of the following values Per this specification, the following values have been registered
in the IANA "OAuth Authorization Server Metadata" registry in the IANA "OAuth Authorization Server Metadata" registry
<xref target="IANA.OAuth.Parameters"/> established by <xref target="RF <xref target="IANA.OAuth.Parameters" format="default"/> established by
C8414"/>. <xref target="RFC8414" format="default"/>.
</t>
<t>
<?rfc subcompact="yes"?>
<list style='symbols'>
<t>Metadata Name: <spanx style="verb">tls_client_certificate_bound_a
ccess_tokens</spanx></t>
<t>Metadata Description: Indicates authorization server support for
mutual-TLS client certificate-bound
access tokens.</t>
<t>Change Controller: IESG</t>
<t>Specification Document(s): <xref target="server_metadata_at"/> of
[[ this specification ]]</t>
</list>
<?rfc subcompact="no"?>
</t>
<t>
<?rfc subcompact="yes"?>
<list style='symbols'>
<t>Metadata Name: <spanx style="verb">mtls_endpoint_aliases</spanx><
/t>
<t>Metadata Description: JSON object containing alternative authoriz
ation server endpoints, which a client
intending to do mutual TLS will use in preference to the conventio
nal endpoints.</t>
<t>Change Controller: IESG</t>
<t>Specification Document(s): <xref target="endpointAliases"/> of [[
this specification ]]</t>
</list>
<?rfc subcompact="no"?>
</t> </t>
</section>
<section title="Token Endpoint Authentication Method Registration"> <dl spacing="compact">
<dt>Metadata Name:</dt><dd><tt>tls_client_certificate_bound_access_tok
ens</tt></dd>
<dt>Metadata Description:</dt><dd>Indicates authorization server
support for mutual-TLS client certificate-bound access tokens.</dd>
<dt>Change Controller:</dt><dd>IESG</dd>
<dt>Specification Document(s):</dt><dd><xref target="server_metadata_a
t"
format="default"/> of RFC 8705</dd>
</dl>
<dl spacing="compact">
<dt>Metadata Name:</dt><dd><tt>mtls_endpoint_aliases</tt></dd>
<dt>Metadata Description:</dt><dd>JSON object containing alternative
authorization server endpoints, which a client
intending to do mutual TLS will use in preference to the conventio
nal endpoints.</dd>
<dt>Change Controller:</dt><dd>IESG</dd>
<dt>Specification Document(s):</dt><dd><xref target="endpointAliases"
format="default"/> of RFC 8705</dd>
</dl>
</section>
<section numbered="true" toc="default">
<name>Token Endpoint Authentication Method Registration</name>
<t> <t>
This specification requests registration of the following values Per this specification, the following values have been registered
in the IANA "OAuth Token Endpoint Authentication Methods" registry in the IANA "OAuth Token Endpoint Authentication Methods" registry
<xref target="IANA.OAuth.Parameters"/> established by <xref target="RF <xref target="IANA.OAuth.Parameters" format="default"/> established by
C7591"/>. <xref target="RFC7591" format="default"/>.
</t>
<t>
<?rfc subcompact="yes"?>
<list style='symbols'>
<t>Token Endpoint Authentication Method Name: <spanx style="verb">tl
s_client_auth</spanx></t>
<t>Change Controller: IESG</t>
<t>Specification Document(s): <xref target="metadata_auth_value_pki"
/> of [[ this specification ]]</t>
</list>
<?rfc subcompact="no"?>
</t>
<t>
<?rfc subcompact="yes"?>
<list style='symbols'>
<t>Token Endpoint Authentication Method Name: <spanx style="verb">se
lf_signed_tls_client_auth</spanx></t>
<t>Change Controller: IESG</t>
<t>Specification Document(s): <xref target="metadata_auth_value_self
_signed"/> of [[ this specification ]]</t>
</list>
<?rfc subcompact="no"?>
</t> </t>
</section>
<section title="Token Introspection Response Registration"> <dl spacing="compact">
<dt>Token Endpoint Authentication Method Name:</dt><dd><tt>tls_client_
auth</tt></dd>
<dt>Change Controller:</dt><dd>IESG</dd>
<dt>Specification Document(s):</dt><dd><xref
target="metadata_auth_value_pki" format="default"/> of RFC 8705</dd>
</dl>
<dl spacing="compact">
<dt>Token Endpoint Authentication Method Name:</dt><dd><tt>self_signed
_tls_client_&zwsp;auth</tt></dd>
<dt>Change Controller:</dt><dd>IESG</dd>
<dt>Specification Document(s):</dt><dd><xref
target="metadata_auth_value_self_signed" format="default"/> of RFC 8705
</dd>
</dl>
</section>
<section numbered="true" toc="default">
<name>Token Introspection Response Registration</name>
<t> <t>
<xref target="RFC7800">Proof-of-Possession Key Semantics for JSON Web "Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)" <xref t
Tokens</xref> defined the arget="RFC7800" format="default"></xref> defined the
<spanx style="verb">cnf</spanx> (confirmation) claim, which enables <tt>cnf</tt> (confirmation) claim that enables
confirmation key information to be carried in a JWT. confirmation key information to be carried in a JWT.
However, the same proof-of-possession semantics are also useful for in trospected access tokens However, the same proof-of-possession semantics are also useful for in trospected access tokens
whereby the protected resource obtains the confirmation key data as me ta-information whereby the protected resource obtains the confirmation key data as me tainformation
of a token introspection response and uses that information in verifyi ng proof-of-possession. of a token introspection response and uses that information in verifyi ng proof-of-possession.
Therefore this specification defines and registers proof-of-possession Therefore, this specification defines and registers proof-of-possessio
semantics for n semantics for
<xref target="RFC7662">OAuth 2.0 Token Introspection</xref> using the OAuth 2.0 Token Introspection <xref target="RFC7662" format="default">
<spanx style="verb">cnf</spanx> </xref> using the <tt>cnf</tt>
structure. structure.
When included as a top-level member of an OAuth token introspection re When included as a top-level member of an OAuth token introspection re
sponse, <spanx style="verb">cnf</spanx> sponse, <tt>cnf</tt>
has the same semantics and format as the claim of the same name define has the same semantics and format as the claim of the same name define
d in <xref target="RFC7800"/>. d in <xref target="RFC7800" format="default"/>.
While this specification only explicitly uses the <spanx style="verb"> While this specification only explicitly uses the <tt>x5t#S256</tt>
x5t#S256</spanx> confirmation method member (see <xref target="introspect" format="defa
confirmation method member (see <xref target="introspect"/>), it needs ult"/>), it needs to define and register
to define and register the higher-level <tt>cnf</tt>
the higher level <spanx style="verb">cnf</spanx>
structure as an introspection response member in order to define and u se the more specific structure as an introspection response member in order to define and u se the more specific
certificate thumbprint confirmation method. certificate thumbprint confirmation method.
</t> </t>
<t> <t>
As such, this specification requests registration of the following val ue As such, the following values have been registered
in the IANA "OAuth Token Introspection Response" registry in the IANA "OAuth Token Introspection Response" registry
<xref target="IANA.OAuth.Parameters"/> <xref target="IANA.OAuth.Parameters" format="default"/>
established by <xref target="RFC7662"/>. established by <xref target="RFC7662" format="default"/>.
</t>
<t>
<?rfc subcompact="yes"?>
<list style='symbols'>
<t>Claim Name: <spanx style="verb">cnf</spanx></t>
<t>Claim Description: Confirmation</t>
<t>Change Controller: IESG</t>
<t>Specification Document(s): <xref target="RFC7800"/> and [[ this s
pecification ]]</t>
</list>
<?rfc subcompact="no"?>
</t> </t>
</section>
<section title="Dynamic Client Registration Metadata Registration"> <dl spacing="compact">
<t> <dt>Claim Name:</dt><dd><tt>cnf</tt></dd>
This specification requests registration of the following client metad <dt>Claim Description:</dt><dd>Confirmation</dd>
ata definitions <dt>Change Controller:</dt><dd>IESG</dd>
in the IANA "OAuth Dynamic Client Registration Metadata" registry <dt>Specification Document(s):</dt><dd><xref target="RFC7800"
<xref target="IANA.OAuth.Parameters"/> format="default"/> and RFC 8705</dd>
established by <xref target="RFC7591"/>: </dl>
</t>
<t> </section>
<?rfc subcompact="yes"?> <section numbered="true" toc="default">
<list style="symbols"> <name>Dynamic Client Registration Metadata Registration</name>
<t>
Client Metadata Name: <spanx style="verb">tls_client_certificate_b
ound_access_tokens</spanx>
</t>
<t>
Client Metadata Description:
Indicates the client's intention to use mutual-TLS client certific
ate-bound
access tokens.
</t>
<t>
Change Controller: IESG
</t>
<t>
Specification Document(s): <xref target="client_metadata_at"/> of
[[ this specification ]]
</t>
</list>
</t>
<t>
<list style="symbols">
<t>
Client Metadata Name: <spanx style="verb">tls_client_auth_subject_
dn</spanx>
</t>
<t>
Client Metadata Description:
String value specifying the expected subject DN of the client cert
ificate.
</t>
<t>
Change Controller: IESG
</t>
<t>
Specification Document(s): <xref target="client_metadata_pki"/> of
[[ this specification ]]
</t>
</list>
</t>
<t>
<list style="symbols">
<t>
Client Metadata Name: <spanx style="verb">tls_client_auth_san_dns<
/spanx>
</t>
<t>
Client Metadata Description:
String value specifying the expected dNSName SAN entry in the clie
nt certificate.
</t>
<t>
Change Controller: IESG
</t>
<t>
Specification Document(s): <xref target="client_metadata_pki"/> of
[[ this specification ]]
</t>
</list>
</t>
<t>
<list style="symbols">
<t>
Client Metadata Name: <spanx style="verb">tls_client_auth_san_uri<
/spanx>
</t>
<t>
Client Metadata Description:
String value specifying the expected uniformResourceIdentifier SAN
entry in the client certificate.
</t>
<t>
Change Controller: IESG
</t>
<t>
Specification Document(s): <xref target="client_metadata_pki"/> of
[[ this specification ]]
</t>
</list>
</t>
<t>
<list style="symbols">
<t>
Client Metadata Name: <spanx style="verb">tls_client_auth_san_ip</
spanx>
</t>
<t>
Client Metadata Description:
String value specifying the expected iPAddress SAN entry in the cl
ient certificate.
</t>
<t>
Change Controller: IESG
</t>
<t>
Specification Document(s): <xref target="client_metadata_pki"/> of
[[ this specification ]]
</t>
</list>
</t>
<t> <t>
<list style="symbols"> Per this specification, the following client metadata definitions
<t> have been registered in the IANA "OAuth Dynamic Client Registration Me
Client Metadata Name: <spanx style="verb">tls_client_auth_san_emai tadata" registry
l</spanx> <xref target="IANA.OAuth.Parameters" format="default"/>
</t> established by <xref target="RFC7591" format="default"/>:
<t>
Client Metadata Description:
String value specifying the expected rfc822Name SAN entry in the c
lient certificate.
</t>
<t>
Change Controller: IESG
</t>
<t>
Specification Document(s): <xref target="client_metadata_pki"/> of
[[ this specification ]]
</t>
</list>
<?rfc subcompact="no"?>
</t> </t>
<dl spacing="compact">
<dt>
Client Metadata Name:</dt><dd><tt>tls_client_certificate_bound_acc
ess_tokens</tt>
</dd>
<dt>
Client Metadata Description:</dt><dd>Indicates the client's
intention to use mutual-TLS client certificate-bound access
tokens.
</dd>
<dt>
Change Controller:</dt><dd>IESG
</dd>
<dt>
Specification Document(s):</dt><dd><xref target="client_metadata_a
t"
format="default"/> of RFC 8705
</dd>
</dl>
<dl spacing="compact">
<dt>
Client Metadata Name:</dt><dd><tt>tls_client_auth_subject_dn</tt>
</dd>
<dt>
Client Metadata Description:</dt><dd>String value specifying
the expected subject DN of the client certificate.
</dd>
<dt>
Change Controller:</dt><dd>IESG
</dd>
<dt>
Specification Document(s):</dt><dd><xref target="client_metadata_p
ki"
format="default"/> of RFC 8705
</dd>
</dl>
<dl spacing="compact">
<dt>
Client Metadata Name:</dt><dd><tt>tls_client_auth_san_dns</tt>
</dd>
<dt>
Client Metadata Description:</dt><dd>String value specifying
the expected dNSName SAN entry in the client certificate.
</dd>
<dt>
Change Controller:</dt><dd>IESG
</dd>
<dt>
Specification Document(s):</dt><dd><xref target="client_metadata_p
ki"
format="default"/> of RFC 8705
</dd>
</dl>
<dl spacing="compact">
<dt>
Client Metadata Name:</dt><dd><tt>tls_client_auth_san_uri</tt>
</dd>
<dt>
Client Metadata Description:</dt><dd>String value specifying
the expected uniformResourceIdentifier SAN entry in the client
certificate.
</dd>
<dt>
Change Controller:</dt><dd>IESG
</dd>
<dt>
Specification Document(s):</dt><dd><xref target="client_metadata_p
ki"
format="default"/> of RFC 8705
</dd>
</dl>
<dl spacing="compact">
<dt>
Client Metadata Name:</dt><dd><tt>tls_client_auth_san_ip</tt>
</dd>
<dt>
Client Metadata Description:</dt><dd>String value specifying
the expected iPAddress SAN entry in the client certificate.
</dd>
<dt>
Change Controller:</dt><dd>IESG
</dd>
<dt>
Specification Document(s):</dt><dd><xref target="client_metadata_p
ki"
format="default"/> of RFC 8705
</dd>
</dl>
<dl spacing="compact">
<dt>
Client Metadata Name:</dt><dd><tt>tls_client_auth_san_email</tt>
</dd>
<dt>
Client Metadata Description:</dt><dd>String value specifying
the expected rfc822Name SAN entry in the client certificate.
</dd>
<dt>
Change Controller:</dt><dd>IESG
</dd>
<dt>
Specification Document(s):</dt><dd><xref target="client_metadata_p
ki"
format="default"/> of RFC 8705
</dd>
</dl>
</section> </section>
</section> </section>
</middle> </middle>
<back> <back>
<references title="Normative References">
<?rfc include='reference.RFC.2119'?>
<?rfc include='reference.RFC.4514'?> <!-- LDAP: String Representation of D
istinguished Names -->
<?rfc include='reference.RFC.4648'?> <!-- base64 -->
<?rfc include='reference.RFC.5246'?> <!-- TLS 1.2 -->
<?rfc include='reference.RFC.5280'?> <!-- X.509 Public Key Infrastructure
Certificate ... -->
<?rfc include='reference.RFC.6749'?> <!-- OAuth 2.0 Authorization Framewor
k -->
<?rfc include='reference.RFC.6750'?> <!-- OAuth 2.0 Authorization Framewor
k: Bearer Token Usage -->
<?rfc include='reference.RFC.7517'?> <!-- JWK -->
<?rfc include='reference.RFC.7519'?> <!-- JWT -->
<?rfc include='reference.RFC.7591'?> <!-- Dynamic Client Registration -->
<?rfc include='reference.RFC.7662'?> <!-- introspection -->
<?rfc include='reference.RFC.7800'?>
<?rfc include='reference.RFC.8174'?>
<?rfc include='reference.RFC.8414'?> <!-- OAuth AS metadata -->
<?rfc include='reference.RFC.8446'?> <!-- TLS 1.3 --> <displayreference target="I-D.ietf-oauth-token-binding" to="TOKEN"/>
<reference anchor="BCP195" target="http://www.rfc-editor.org/info/bcp195">
<front>
<title>Recommendations for Secure Use of Transport Layer Security (TLS
) and Datagram Transport Layer Security (DTLS)</title>
<author initials="Y." surname="Sheffer" fullname="Y. Sheffer">
<organization/>
</author>
<author initials="R." surname="Holz" fullname="R. Holz">
<organization/>
</author>
<author initials="P." surname="Saint-Andre" fullname="P. Saint-Andre">
<organization/>
</author>
<date year="2015" month="May"/>
<abstract>
<t>Transport Layer Security (TLS) and Datagram Transport Layer Secur
ity (DTLS) are widely used to protect data exchanged over application protocols
such as HTTP, SMTP, IMAP, POP, SIP, and XMPP. Over the last
few years, several serious attacks on TLS have emerged, including
attacks on its most commonly used cipher suites and their modes of operation. Th
is document provides recommendations for improving the
security of deployed services that use TLS and DTLS. The recommend
ations are applicable to the majority of use cases.
</t>
</abstract>
</front>
<seriesInfo name="BCP" value="195"/>
<seriesInfo name="RFC" value="7525"/>
<seriesInfo name="DOI" value="10.17487/RFC7525"/>
</reference>
<reference anchor="SHS" target="http://csrc.nist.gov/publications/fips/fip <references>
s180-4/fips-180-4.pdf"> <name>References</name>
<front> <references>
<title>Secure Hash Standard (SHS)</title> <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.4514.xml"/>
<!-- LDAP: String Representation of Distinguished Names -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.4648.xml"/>
<!-- base64 -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.5246.xml"/>
<!-- TLS 1.2 -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.5280.xml"/>
<!-- X.509 Public Key Infrastructure Certificate ... -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.6749.xml"/>
<!-- OAuth 2.0 Authorization Framework -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.6750.xml"/>
<!-- OAuth 2.0 Authorization Framework: Bearer Token Usage -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.7517.xml"/>
<!-- JWK -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.7519.xml"/>
<!-- JWT -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.7591.xml"/>
<!-- Dynamic Client Registration -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.7662.xml"/>
<!-- introspection -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.7800.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.8414.xml"/>
<!-- OAuth AS metadata -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.8446.xml"/>
<!-- TLS 1.3 -->
<author> <reference anchor='BCP195' target='https://www.rfc-editor.org/info/bcp195'>
<organization>National Institute of Standards and <front>
Technology</organization> <title>Recommendations for Secure Use of Transport Layer Security (TLS) and Data
</author> gram Transport Layer Security (DTLS)</title>
<author initials='Y.' surname='Sheffer' fullname='Y. Sheffer'><organization /></
author>
<author initials='R.' surname='Holz' fullname='R. Holz'><organization /></author
>
<author initials='P.' surname='Saint-Andre' fullname='P. Saint-Andre'><organizat
ion /></author>
<date year='2015' month='May' />
</front>
<seriesInfo name='BCP' value='195'/>
<seriesInfo name='RFC' value='7525'/>
</reference>
<date month="March" year="2012" /> <reference anchor="SHS" target="https://nvlpubs.nist.gov/nistpubs/FIPS/N
</front> IST.FIPS.180-4.pdf">
<seriesInfo name="FIPS" value="PUB 180-4" /> <front>
<format target="http://csrc.nist.gov/publications/fips/fips180-4/fips-18 <title>Secure Hash Standard (SHS)</title>
0-4.pdf" type="PDF" /> <author>
</reference> <organization>National Institute of Standards and
Technology (NIST)</organization>
</author>
<date month="August" year="2015"/>
</front>
<seriesInfo name="FIPS" value="PUB 180-4"/>
<seriesInfo name="DOI" value="10.6028/NIST.FIPS.180-4" />
</reference>
<reference anchor="X690"> <reference anchor="X690">
<front> <front>
<title> <title>
ASN.1 encoding rules: Specification of basic encoding Rules (BER Information Technology - ASN.1 encoding rules:
), Specification of Basic Encoding Rules (BER), Canonical
Canonical encoding rules (CER) and Distinguished encoding rules Encoding Rules (CER) and Distinguished Encoding Rules (DER)
(DER)
</title> </title>
<seriesInfo name="ITU-T" value="Recommendation X.690"/>
<author> <author>
<organization> <organization>ITU-T</organization>
International Telephone and Telegraph Consultative Committee
</organization>
</author> </author>
<date month="July" year="2015"/> <date month="August" year="2015"/>
</front> </front>
<seriesInfo name="CCITT" value="Recommendation X.690"/> </reference>
</reference>
</references>
<references title="Informative References"> </references>
<reference anchor="IANA.OAuth.Parameters" target="http://www.iana.org/assi
gnments/oauth-parameters">
<front>
<title>OAuth Parameters</title>
<author>
<organization>IANA</organization>
</author>
<date/>
</front>
</reference>
<reference anchor="IANA.JWT.Claims" target="http://www.iana.org/assignment
s/jwt">
<front>
<title>JSON Web Token Claims</title>
<author>
<organization>IANA</organization>
</author>
<date/>
</front>
</reference>
<?rfc include='reference.RFC.4517'?> <references>
<?rfc include='reference.RFC.5952'?> <!-- IPv6 text rep --> <name>Informative References</name>
<?rfc include='reference.RFC.6066'?> <reference anchor="IANA.OAuth.Parameters" target="https://www.iana.org/a
<?rfc include='reference.RFC.7009'?> <!-- revocation --> ssignments/oauth-parameters">
<?rfc include='reference.RFC.7518'?> <!-- JWA --> <front>
<title>OAuth Parameters</title>
<author>
<organization>IANA</organization>
</author>
</front>
</reference>
<reference anchor="IANA.JWT.Claims" target="https://www.iana.org/assignm
ents/jwt">
<front>
<title>JSON Web Token Claims</title>
<author>
<organization>IANA</organization>
</author>
</front>
</reference>
<?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml3/reference. <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
I-D.draft-ietf-oauth-token-binding-06.xml'?> FC.4517.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.5952.xml"/>
<!-- IPv6 text rep -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.6066.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.7009.xml"/>
<!-- revocation -->
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.7518.xml"/>
<!-- JWA -->
<reference anchor="CX5P" target="https://www.cryptologie.net/article/374/c <!-- ietf-oauth-token-binding Expired -->
ommon-x509-certificate-validationcreation-pitfalls">
<front>
<title>Common x509 certificate validation/creation pitfalls</title>
<author fullname="David Wong" initials="D." surname="Wong"><organizati
on/></author>
<date month="September" year="2016"/>
</front>
</reference>
<reference anchor="DCW" target="http://www.cs.utexas.edu/~shmat/shmat_ccs1 <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.
2.pdf"> I-D.ietf-oauth-token-binding.xml"/>
<front> <reference anchor="CX5P" target="https://www.cryptologie.net/article/374
<title>The Most Dangerous Code in the World: Validating SSL Certificat /common-x509-certificate-validationcreation-pitfalls">
es in Non-Browser Software</title> <front>
<author fullname="Martin Georgiev" initials="M." surname="Georgiev"><o <title>Common x509 certificate validation/creation pitfalls</title>
rganization/></author> <author fullname="David Wong" initials="D." surname="Wong">
<author fullname="Subodh Iyengar" initials="S." surname="Iyengar"><org <organization/>
anization/></author> </author>
<author fullname="Suman Jana" initials="S." surname="Jana"><organizati <date month="September" year="2016"/>
on/></author> </front>
<author fullname="Rishita Anubhai" initials="R." surname="Anubhai"><or </reference>
ganization/></author>
<author fullname="Dan Boneh" initials="D." surname="Boneh"><organizati
on/></author>
<author fullname="Vitaly Shmatikov" initials="V." surname="Shmatikov">
<organization/></author>
<date/>
</front>
</reference>
<reference anchor="OpenID.CIBA" <reference anchor="DCW" target="http://www.cs.utexas.edu/~shmat/shmat_cc
target="https://openid.net/specs/openid-client-initiated-backchannel- s12.pdf">
authentication-core-1_0.html"> <front>
<front> <title>The Most Dangerous Code in the World: Validating SSL Certific
<title abbrev="CIBA">OpenID Connect Client Initiated Backchannel Authe ates in Non-Browser Software</title>
ntication Flow - Core 1.0</title> <author fullname="Martin Georgiev" initials="M." surname="Georgiev">
<author fullname="Gonzalo Fernandez Rodriguez" initials="G." surname=" <organization/>
Fernandez"> </author>
<organization abbrev="Telefonica">Telefonica I+D</organization> <author fullname="Subodh Iyengar" initials="S." surname="Iyengar">
<address> <organization/>
<email>gonzalo.fernandezrodriguez@telefonica.com</email> </author>
</address> <author fullname="Suman Jana" initials="S." surname="Jana">
</author> <organization/>
<author fullname="Florian Walter" initials="F." surname="Walter"> </author>
<organization abbrev="">Deutsche Telekom AG</organization> <author fullname="Rishita Anubhai" initials="R." surname="Anubhai">
<address> <organization/>
<email>F.Walter@telekom.de</email> </author>
</address> <author fullname="Dan Boneh" initials="D." surname="Boneh">
</author> <organization/>
<author fullname="Axel Nennker" initials="A." surname="Nennker"> </author>
<organization abbrev="">Deutsche Telekom AG</organization> <author fullname="Vitaly Shmatikov" initials="V." surname="Shmatikov
<address> ">
<email>axel.nennker@telekom.de</email> <organization/>
</address> </author>
</author> <date month="October" year="2012"/>
<author fullname="Dave Tonge" initials="D." surname="Tonge"> </front>
<organization abbrev="Moneyhub">Moneyhub</organization> <seriesInfo name="DOI" value="10.1145/2382196.2382204"/>
<address> </reference>
<email>dave.tonge@moneyhub.com</email>
</address>
</author>
<author fullname="Brian Campbell" initials="B." surname="Campbell">
<organization abbrev="Ping Identity">Ping Identity</organization>
<address>
<email>bcampbell@pingidentity.com</email>
</address>
</author>
<date day="16" month="January" year="2019"/>
</front>
</reference>
<reference anchor="OpenID.CIBA" target="https://openid.net/specs/openid-
client-initiated-backchannel-authentication-core-1_0.html">
<front>
<title abbrev="CIBA">OpenID Connect Client Initiated Backchannel Aut
hentication Flow - Core 1.0</title>
<author fullname="Gonzalo Fernandez Rodriguez" initials="G." surname
="Fernandez">
<organization abbrev="Telefonica">Telefonica I+D</organization>
<address>
<email>gonzalo.fernandezrodriguez@telefonica.com</email>
</address>
</author>
<author fullname="Florian Walter" initials="F." surname="Walter">
<organization abbrev="">Deutsche Telekom AG</organization>
<address>
<email>F.Walter@telekom.de</email>
</address>
</author>
<author fullname="Axel Nennker" initials="A." surname="Nennker">
<organization abbrev="">Deutsche Telekom AG</organization>
<address>
<email>axel.nennker@telekom.de</email>
</address>
</author>
<author fullname="Dave Tonge" initials="D." surname="Tonge">
<organization abbrev="Moneyhub">Moneyhub</organization>
<address>
<email>dave.tonge@moneyhub.com</email>
</address>
</author>
<author fullname="Brian Campbell" initials="B." surname="Campbell">
<organization abbrev="Ping Identity">Ping Identity</organization>
<address>
<email>bcampbell@pingidentity.com</email>
</address>
</author>
<date day="16" month="January" year="2019"/>
</front>
</reference>
</references>
</references> </references>
<section title='Example "cnf" Claim, Certificate and JWK' anchor="example"> <section anchor="example" numbered="true" toc="default">
<name>Example "cnf" Claim, Certificate, and JWK</name>
<t> <t>
For reference, an <spanx style="verb">x5t#S256</spanx> value and the X.5 For reference, an <tt>x5t#S256</tt> value and the X.509 certificate
09 Certificate from which it was from which it was calculated are provided in the following examples,
calculated are provided in the following examples, <xref target="cnf"/> Figures <xref target="cnf" format="counter"/> and <xref target="pem"
and <xref target="pem"/> respectively. format="counter"/>, respectively. A JWK representation of the
A JWK representation of the certificate's public certificate's public key along with the <tt>x5c</tt> member is also
key along with the <spanx style="verb">x5c</spanx> member is also provid provided in <xref target="jwk" format="default"/>.
ed in <xref target="jwk"/>.
<figure title="x5t#S256 Confirmation Claim" anchor="cnf"> </t>
<artwork><![CDATA["cnf":{"x5t#S256":"A4DtL2JmUMhAsvJj5tKyn64SqzmuXbMrJ <figure anchor="cnf">
a0n761y5v0"} <name>x5t#S256 Confirmation Claim</name>
]]></artwork> <sourcecode type="json"><![CDATA[
</figure> "cnf":{"x5t#S256":"A4DtL2JmUMhAsvJj5tKyn64SqzmuXbMrJa0n761y5v0"}
]]></sourcecode>
</figure>
<figure title="PEM Encoded Self-Signed Certificate" anchor="pem"> <figure anchor="pem">
<artwork><![CDATA[-----BEGIN CERTIFICATE----- <name>PEM Encoded Self-Signed Certificate</name>
<artwork name="" type="" align="left" alt=""><![CDATA[
-----BEGIN CERTIFICATE-----
MIIBBjCBrAIBAjAKBggqhkjOPQQDAjAPMQ0wCwYDVQQDDARtdGxzMB4XDTE4MTAx MIIBBjCBrAIBAjAKBggqhkjOPQQDAjAPMQ0wCwYDVQQDDARtdGxzMB4XDTE4MTAx
ODEyMzcwOVoXDTIyMDUwMjEyMzcwOVowDzENMAsGA1UEAwwEbXRsczBZMBMGByqG ODEyMzcwOVoXDTIyMDUwMjEyMzcwOVowDzENMAsGA1UEAwwEbXRsczBZMBMGByqG
SM49AgEGCCqGSM49AwEHA0IABNcnyxwqV6hY8QnhxxzFQ03C7HKW9OylMbnQZjjJ SM49AgEGCCqGSM49AwEHA0IABNcnyxwqV6hY8QnhxxzFQ03C7HKW9OylMbnQZjjJ
/Au08/coZwxS7LfA4vOLS9WuneIXhbGGWvsDSb0tH6IxLm8wCgYIKoZIzj0EAwID /Au08/coZwxS7LfA4vOLS9WuneIXhbGGWvsDSb0tH6IxLm8wCgYIKoZIzj0EAwID
SQAwRgIhAP0RC1E+vwJD/D1AGHGzuri+hlV/PpQEKTWUVeORWz83AiEA5x2eXZOV SQAwRgIhAP0RC1E+vwJD/D1AGHGzuri+hlV/PpQEKTWUVeORWz83AiEA5x2eXZOV
bUlJSGQgjwD5vaUaKlLR50Q2DmFfQj1L+SY= bUlJSGQgjwD5vaUaKlLR50Q2DmFfQj1L+SY=
-----END CERTIFICATE-----]]></artwork> -----END CERTIFICATE-----]]></artwork>
</figure> </figure>
<figure title="JSON Web Key" anchor="jwk"> <figure anchor="jwk">
<artwork><![CDATA[ <name>JSON Web Key</name>
<sourcecode type="json"><![CDATA[
{ {
"kty":"EC", "kty":"EC",
"x":"1yfLHCpXqFjxCeHHHMVDTcLscpb07KUxudBmOMn8C7Q", "x":"1yfLHCpXqFjxCeHHHMVDTcLscpb07KUxudBmOMn8C7Q",
"y":"8_coZwxS7LfA4vOLS9WuneIXhbGGWvsDSb0tH6IxLm8", "y":"8_coZwxS7LfA4vOLS9WuneIXhbGGWvsDSb0tH6IxLm8",
"crv":"P-256", "crv":"P-256",
"x5c":[ "x5c":[
"MIIBBjCBrAIBAjAKBggqhkjOPQQDAjAPMQ0wCwYDVQQDDARtdGxzMB4XDTE4MTA "MIIBBjCBrAIBAjAKBggqhkjOPQQDAjAPMQ0wCwYDVQQDDARtdGxzMB4XDTE4MTA
xODEyMzcwOVoXDTIyMDUwMjEyMzcwOVowDzENMAsGA1UEAwwEbXRsczBZMBMGBy xODEyMzcwOVoXDTIyMDUwMjEyMzcwOVowDzENMAsGA1UEAwwEbXRsczBZMBMGBy
qGSM49AgEGCCqGSM49AwEHA0IABNcnyxwqV6hY8QnhxxzFQ03C7HKW9OylMbnQZ qGSM49AgEGCCqGSM49AwEHA0IABNcnyxwqV6hY8QnhxxzFQ03C7HKW9OylMbnQZ
jjJ/Au08/coZwxS7LfA4vOLS9WuneIXhbGGWvsDSb0tH6IxLm8wCgYIKoZIzj0E jjJ/Au08/coZwxS7LfA4vOLS9WuneIXhbGGWvsDSb0tH6IxLm8wCgYIKoZIzj0E
AwIDSQAwRgIhAP0RC1E+vwJD/D1AGHGzuri+hlV/PpQEKTWUVeORWz83AiEA5x2 AwIDSQAwRgIhAP0RC1E+vwJD/D1AGHGzuri+hlV/PpQEKTWUVeORWz83AiEA5x2
eXZOVbUlJSGQgjwD5vaUaKlLR50Q2DmFfQj1L+SY=" eXZOVbUlJSGQgjwD5vaUaKlLR50Q2DmFfQj1L+SY="
] ]
}]]></artwork> }]]></sourcecode>
</figure> </figure>
</t>
</section> </section>
<section anchor="relation" numbered="true" toc="default">
<section anchor="relation" title="Relationship to Token Binding"> <name>Relationship to Token Binding</name>
<t> <t>
<xref target="I-D.ietf-oauth-token-binding">OAuth 2.0 Token Binding</xre f> OAuth 2.0 Token Binding <xref target="I-D.ietf-oauth-token-binding" form at="default"></xref>
enables the application of Token Binding to the various artifacts and to kens employed throughout OAuth. enables the application of Token Binding to the various artifacts and to kens employed throughout OAuth.
That includes binding of an access token to a Token Binding key, which b ears some similarities in motivation That includes binding of an access token to a Token Binding key, which b ears some similarities in motivation
and design to the mutual-TLS client certificate-bound access tokens defi ned in this document. and design to the mutual-TLS client certificate-bound access tokens defi ned in this document.
Both documents define what is often called a proof-of-possession securit y mechanism Both documents define what is often called a proof-of-possession securit y mechanism
for access tokens, whereby a client must demonstrate possession of crypt ographic keying for access tokens, whereby a client must demonstrate possession of crypt ographic keying
material when accessing a protected resource. The details differ somewha t between the two documents but both material when accessing a protected resource. The details differ somewha t between the two documents but both
have the authorization server bind the access token that it issues to an asymmetric key pair have the authorization server bind the access token that it issues to an asymmetric key pair
held by the client. The client then proves possession of the private key from that pair held by the client. The client then proves possession of the private key from that pair
with respect to the TLS connection over which the protected resource is accessed. with respect to the TLS connection over which the protected resource is accessed.
</t> </t>
<t> <t>
Token Binding uses bare keys that are generated on the client, Token Binding uses bare keys that are generated on the client,
which avoids many of the difficulties of creating, distributing, and man aging certificates which avoids many of the difficulties of creating, distributing, and man aging certificates
used in this specification. However, at the time of used in this specification. However, at the time of
writing, Token Binding is fairly new and there is relatively little supp ort for it in available writing, Token Binding is fairly new, and there is relatively little sup port for it in available
application development platforms and tooling. Until better support for the underlying application development platforms and tooling. Until better support for the underlying
core Token Binding specifications exists, practical implementations of O Auth 2.0 Token Binding core Token Binding specifications exists, practical implementations of O Auth 2.0 Token Binding
are infeasible. are infeasible.
Mutual TLS, on the other hand, has been around for some time and enjoys Mutual TLS, on the other hand, has been around for some time and enjoys
widespread support in web servers and development platforms. As a conse quence, OAuth 2.0 Mutual-TLS widespread support in web servers and development platforms. As a conseq uence, OAuth 2.0 Mutual-TLS
Client Authentication and Certificate-Bound Access Tokens can be Client Authentication and Certificate-Bound Access Tokens can be
built and deployed now using existing platforms and tools. built and deployed now using existing platforms and tools.
In the future, the two specifications are likely to be In the future, the two specifications are likely to be
deployed in parallel for solving similar problems in different environme nts. deployed in parallel for solving similar problems in different environme nts.
Authorization servers may even support both specifications simultaneousl y using different Authorization servers may even support both specifications simultaneousl y using different
proof-of-possession mechanisms for tokens issued to different clients. proof-of-possession mechanisms for tokens issued to different clients.
</t> </t>
</section> </section>
<section anchor="Acknowledgements" numbered="false" toc="default">
<section anchor="Acknowledgements" title="Acknowledgements"> <name>Acknowledgements</name>
<t> <t>
Scott "not Tomlinson" Tomilson and Matt Peterson were involved in Scott "not Tomlinson" Tomilson and <contact fullname="Matt Peterson"/> w ere involved in
design and development work on a mutual-TLS OAuth client authentication design and development work on a mutual-TLS OAuth client authentication
implementation, which predates this document. Experience and learning fr om that work implementation that predates this document. Experience and learning from that work
informed some of the content of this document. informed some of the content of this document.
</t> </t>
<t> <t>
This specification was developed within the OAuth Working Group This specification was developed within the OAuth Working Group
under the chairmanship of Hannes Tschofenig under the chairmanship of <contact fullname="Hannes Tschofenig"/>
and Rifaat Shekh-Yusef with Eric Rescorla, Benjamin Kaduk, and Roman Dan and <contact fullname="Rifaat Shekh-Yusef"/> with <contact fullname="Eri
yliw c Rescorla"/>,
serving as Security Area Directors. Additionally, the following <contact fullname="Benjamin Kaduk"/>, and
<contact fullname="Roman Danyliw"/>
serving as Security Area Directors. Additionally, the following
individuals contributed ideas, feedback, and wording individuals contributed ideas, feedback, and wording
that helped shape this specification: that helped shape this specification:
Vittorio Bertocci,
Sergey Beryozkin,
Ralph Bragg,
Sophie Bremer,
Roman Danyliw,
Vladimir Dzhuvinov,
Samuel Erdtman,
Evan Gilman,
Leif Johansson,
Michael Jones,
Phil Hunt,
Benjamin Kaduk,
Takahiko Kawasaki,
Sean Leonard,
Kepeng Li,
Neil Madden,
James Manger,
Jim Manico,
Nov Matake,
Sascha Preibisch,
Eric Rescorla,
Justin Richer,
Vincent Roca,
Filip Skokan,
Dave Tonge,
and
Hannes Tschofenig.
</t>
</section>
<section anchor="History" title="Document(s) History"> <contact fullname="Vittorio Bertocci"/>,
<?rfc subcompact="yes"?> <contact fullname="Sergey Beryozkin"/>,
<t> <contact fullname="Ralph Bragg"/>,
[[ to be removed by the RFC Editor before publication as an RFC ]] <contact fullname="Sophie Bremer"/>,
</t> <contact fullname="Roman Danyliw"/>,
<t> <contact fullname="Vladimir Dzhuvinov"/>,
draft-ietf-oauth-mtls-17 <contact fullname="Samuel Erdtman"/>,
<list style='symbols'> <contact fullname="Evan Gilman"/>,
<t>Updates from IESG ballot position comments.</t> <contact fullname="Leif Johansson"/>,
</list> <contact fullname="Michael Jones"/>,
</t> <contact fullname="Phil Hunt"/>,
<t> <contact fullname="Benjamin Kaduk"/>,
draft-ietf-oauth-mtls-16 <contact fullname="Takahiko Kawasaki"/>,
<list style='symbols'> <contact fullname="Sean Leonard"/>,
<t>Editorial updates from last call review.</t> <contact fullname="Kepeng Li"/>,
</list> <contact fullname="Neil Madden"/>,
</t> <contact fullname="James Manger"/>,
<t> <contact fullname="Jim Manico"/>,
draft-ietf-oauth-mtls-15 <contact fullname="Nov Matake"/>,
<list style='symbols'> <contact fullname="Sascha Preibisch"/>,
<t>Editorial updates from second AD review.</t> <contact fullname="Eric Rescorla"/>,
</list> <contact fullname="Justin Richer"/>,
</t> <contact fullname="Vincent Roca"/>,
<t> <contact fullname="Filip Skokan"/>,
draft-ietf-oauth-mtls-14 <contact fullname="Dave Tonge"/>,
<list style='symbols'> and
<t>Editorial clarifications around there being only a single subject r <contact fullname="Hannes Tschofenig"/>.
egistered/configured per client
for the tls_client_auth method.</t>
<t>Add a brief explanation about how, with tls_client_auth and self_si
gned_tls_client_auth,
refresh tokens are certificate-bound indirectly via the client authe
ntication.</t>
<t>Add mention of refresh tokens in the abstract.</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-13
<list style='symbols'>
<t>Add an abstract protocol flow and diagram to serve as an overview o
f OAuth in general and
baseline to describe the various ways
in which the mechanisms defined herein are intended to be used.</t>
<t>A little bit less of that German influence.</t>
<t>Rework the TLS references a bit and, in the Terminology section, cl
ean up the description
of what messages are sent and verified in the handshake to do 'mutua
l TLS'.</t>
<t>Move the explanation about "cnf" introspection registration
into the IANA Considerations.</t>
<t>Add CIBA as an informational reference and additional example of an
OAuth extension that
defines an endpoint that utilizes client authentication.</t>
<t>Shorten a few of the section titles.</t>
<t>Add new client metadata values to allow for the use of a SAN in the
PKI MTLS client authentication method.</t>
<t>Add privacy considerations attempting to discuss the implications o
f the client cert being sent in
the clear in TLS 1.2.</t>
<t>Changed the 'Certificate Bound Access Tokens Without Client Authent
ication' section to
'Public Clients and Certificate-Bound Tokens' and moved it up to be
a top level section
while adding discussion of binding refresh tokens for public clients
.</t>
<t>Reword/restructure the main PKI method section somewhat to (hopeful
ly) improve readability.</t>
<t>Reword/restructure the Self-Signed method section a bit to (hopeful
ly) make it more comprehensible.</t>
<t>Reword the AS and RS Implementation Considerations somewhat to (hop
efully) improve readability.</t>
<t>Clarify that the protected resource obtains the client certificate
used for mutual TLS from its TLS implementation layer.</t>
<t>Add Security Considerations section about the certificate thumbprin
t binding that includes the hash algorithm agility recommendation.</t>
<t>Add an "mtls_endpoint_aliases" AS metadata parameter that is a JSON
object containing alternative authorization
server endpoints, which a client intending to do mutual TLS will use
in preference to the conventional endpoints.</t>
<t>Minor editorial updates.</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-12
<list style='symbols'>
<t>Add an example certificate, JWK, and confirmation method claim.</t>
<t>Minor editorial updates based on implementer feedback.</t>
<t>Additional Acknowledgements.</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-11
<list style='symbols'>
<t>Editorial updates.</t>
<t>Mention/reference TLS 1.3 RFC8446 in the TLS Versions and Best Prac
tices section.</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-10
<list style='symbols'>
<t>Update draft-ietf-oauth-discovery reference to RFC8414</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-09
<list style='symbols'>
<t>Change "single certificates" to "self-signed certificates" in the A
bstract</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-08
<list style='symbols'>
<t>Incorporate clarifications and editorial improvements from Justin R
icher's WGLC review</t>
<t>Drop the use of the "sender constrained" terminology per WGLC feedb
ack from Neil Madden (including changing
the metadata parameters from mutual_tls_sender_constrained_access_toke
ns
to tls_client_certificate_bound_access_tokens)</t>
<t>Add a new security considerations section on X.509 parsing and vali
dation
per WGLC feedback from Neil Madden and Benjamin Kaduk</t>
<t>Note that a server can terminate TLS at a load balancer, reverse pr
oxy, etc. but how the
client certificate metadata is securely communicated to the backend
is out of scope per WGLC feedback</t>
<t>Note that revocation checking is at the discretion of the AS per WG
LC feedback</t>
<t>Editorial updates and clarifications</t>
<t>Update draft-ietf-oauth-discovery reference to -10 and draft-ietf-o
auth-token-binding to -06</t>
<t>Add folks involved in WGLC feedback to the acknowledgements list</t
>
</list>
</t>
<t>
draft-ietf-oauth-mtls-07
<list style='symbols'>
<t>Update to use the boilerplate from RFC 8174</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-06
<list style='symbols'>
<t>Add an appendix section describing the relationship of this documen
t to OAuth Token Binding as
requested during the Singapore meeting
https://datatracker.ietf.org/doc/minutes-100-oauth/</t>
<t>Add an explicit note that the implicit flow is not supported for ob
taining certificate
bound access tokens as discussed at the Singapore meeting
https://datatracker.ietf.org/doc/minutes-100-oauth/</t>
<t>Add/incorporate text to the Security Considerations on Certificate
Spoofing as
suggested https://mailarchive.ietf.org/arch/msg/oauth/V26070X-6OtbVS
eUz_7W2k94vCo</t>
<t>Changed the title to be more descriptive</t>
<t>Move the Security Considerations section to before the IANA Conside
rations</t>
<t>Elaborated on certificate-bound access tokens a bit more in the Abs
tract</t>
<t>Update draft-ietf-oauth-discovery reference to -08</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-05
<list style='symbols'>
<t>Editorial fixes</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-04
<list style='symbols'>
<t>Change the name of the 'Public Key method' to the more accurate 'Se
lf-Signed Certificate method' and
also change the associated authentication method metadata value to "
self_signed_tls_client_auth".</t>
<t>Removed the "tls_client_auth_root_dn" client metadata field as disc
ussed in
https://mailarchive.ietf.org/arch/msg/oauth/swDV2y0be6o8czGKQi1eJV-g
8qc</t>
<t>Update draft-ietf-oauth-discovery reference to -07</t>
<t>Clarify that MTLS client authentication isn't exclusive to the toke
n endpoint
and can be used with other endpoints, e.g. RFC 7009 revocation and 7
662 introspection,
that utilize client authentication as discussed in
https://mailarchive.ietf.org/arch/msg/oauth/bZ6mft0G7D3ccebhOxnEYUv4
puI</t>
<t>Reorganize the document somewhat in an attempt to more clearly make
a distinction between
mTLS client authentication and certificate-bound access tokens as we
ll as a more clear
delineation between the two (PKI/Public key) methods for client auth
entication</t>
<t>Editorial fixes and clarifications</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-03
<list style='symbols'>
<t>Introduced metadata and client registration parameter to publish an
d request
support for mutual TLS sender constrained access tokens</t>
<t>Added description of two methods of binding the cert and client, PK
I and Public Key.</t>
<t>Indicated that the "tls_client_auth" authentication method is for t
he PKI method and
introduced "pub_key_tls_client_auth" for the Public Key method</t>
<t>Added implementation considerations, mainly regarding TLS stack con
figuration
and trust chain validation, as well as how to to do binding of access
tokens to a TLS client
certificate for public clients, and considerations around certificate-
bound access tokens</t>
<t>Added new section to security considerations on cert spoofing</t>
<t>Add text suggesting that a new cnf member be defined in the future,
if hash function(s) other than SHA-256 need to be used for certifica
te thumbprints</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-02
<list style='symbols'>
<t>Fixed editorial issue https://mailarchive.ietf.org/arch/msg/oauth/U
46UMEh8XIOQnvXY9pHFq1MKPns</t>
<t>Changed the title (hopefully "Mutual TLS Profile for OAuth 2.0" is
better than "Mutual TLS Profiles for OAuth Clients").</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-01
<list style='symbols'>
<t>Added more explicit details of using RFC 7662 token introspection w
ith mutual TLS sender constrained access tokens.</t>
<t>Added an IANA OAuth Token Introspection Response Registration reque
st for "cnf".</t>
<t>Specify that tls_client_auth_subject_dn and tls_client_auth_root_dn
are RFC 4514 String Representation of Distinguished Names.</t>
<t>Changed tls_client_auth_issuer_dn to tls_client_auth_root_dn.</t>
<t>Changed the text in the <xref target="CertificateBoundAccessTokens"
/> to not be specific about using a hash of the cert.</t>
<t>Changed the abbreviated title to 'OAuth Mutual TLS' (previously was
the acronym MTLSPOC).</t>
</list>
</t>
<t>
draft-ietf-oauth-mtls-00
<list style='symbols'>
<t>Created the initial working group version from draft-campbell-oauth
-mtls</t>
</list>
</t>
<t>
draft-campbell-oauth-mtls-01
<list style='symbols'>
<t>Fix some typos.</t>
<t>Add to the acknowledgements list.</t>
</list>
</t>
<t>
draft-campbell-oauth-mtls-00
<list style='symbols'>
<t>
Add a Mutual TLS sender constrained protected resource access method
and a x5t#S256 cnf method for JWT access tokens
(concepts taken in part from draft-sakimura-oauth-jpop-04).
</t>
<t>
Fixed "token_endpoint_auth_methods_supported" to "token_endpoint_aut
h_method" for client metadata.
</t>
<t>
Add "tls_client_auth_subject_dn" and "tls_client_auth_issuer_dn" cli
ent metadata parameters and
mention using "jwks_uri" or "jwks".
</t>
<t>
Say that the authentication method is determined by client policy re
gardless of whether the client
was dynamically registered or statically configured.
</t>
<t>Expand acknowledgements to those that participated in discussions a
round
draft-campbell-oauth-tls-client-auth-00</t>
<t>
Add Nat Sakimura and Torsten Lodderstedt to the author list.
</t>
</list>
</t>
<t>
draft-campbell-oauth-tls-client-auth-00
<list style='symbols'>
<t>
Initial draft.
</t>
</list>
</t> </t>
<?rfc subcompact="no"?>
</section> </section>
</back> </back>
</rfc> </rfc>
 End of changes. 222 change blocks. 
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