One document matched: draft-wouters-tls-oob-pubkey-02.xml
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<rfc category="std" docName="draft-wouters-tls-oob-pubkey-02" ipr="trust200902">
<front>
<!-- The abbreviated title is used in the page header - it is only necessary if the
full title is longer than 39 characters -->
<title abbrev="TLS oob pubkey">TLS out-of-band public key validation</title>
<!-- add 'role="editor"' below for the editors if appropriate -->
<!-- Another author who claims to be an editor -->
<author fullname="Paul Wouters" initials="P." surname="Wouters">
<organization>Xelerance</organization>
<address>
<postal>
<street>4130 Ramsayville Road</street>
<city>Ottawa</city>
<region>On</region>
<code>K1G 3N4</code>
<country>Canada</country>
</postal>
<phone>+1-647-722-5653</phone>
<email>paul@xelerance.com</email>
<uri>https://www.xelerance.com/</uri>
</address>
</author>
<author fullname="John Gilmore" initials="J." surname="Gilmore">
<organization />
<address>
<postal>
<street>PO Box 170608</street>
<city>San Francisco</city>
<region>California</region>
<code>94117</code>
<country>USA</country>
</postal>
<phone>+1 415 221 6524</phone>
<email>gnu@toad.com</email>
<uri>https://www.toad.com/</uri>
</address>
</author>
<author fullname="Samuel Weiler" initials="S." surname="Weiler">
<organization>SPARTA, Inc.</organization>
<address>
<postal>
<street>7110 Samuel Morse Drive</street>
<city>Columbia, Maryland</city>
<code>21046</code>
<country>US</country>
</postal>
<email>weiler@tislabs.com</email>
</address>
</author>
<author initials="T." surname="Kivinen" fullname="Tero Kivinen">
<organization>AuthenTec</organization>
<address>
<postal>
<street>Eerikinkatu 28</street>
<city>HELSINKI</city>
<code>FI-00180</code>
<country>FI</country>
</postal>
<email>kivinen@iki.fi</email>
</address>
</author>
<author initials="H." surname="Tschofenig" fullname="Hannes Tschofenig">
<organization>Nokia Siemens Networks</organization>
<address>
<postal>
<street>Linnoitustie 6</street>
<city>Espoo</city>
<code>02600</code>
<country>Finland</country>
</postal>
<phone>+358 (50) 4871445</phone>
<email>Hannes.Tschofenig@gmx.net</email>
<uri>http://www.tschofenig.priv.at</uri>
</address>
</author>
<date year="2011" />
<!-- If the month and year are both specified and are the current ones, xml2rfc will fill
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purpose of calculating the expiry date). With drafts it is normally sufficient to
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<!-- Meta-data Declarations -->
<area>Applications</area>
<workgroup>IETF</workgroup>
<!-- WG name at the upperleft corner of the doc,
IETF is fine for individual submissions.
If this element is not present, the default is "Network Working Group",
which is used by the RFC Editor as a nod to the history of the IETF. -->
<keyword>TLS</keyword>
<keyword>DNSSEC</keyword>
<keyword>DANE</keyword>
<!-- Keywords will be incorporated into HTML output
files in a meta tag but they have no effect on text or nroff
output. If you submit your draft to the RFC Editor, the
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<abstract>
<t>
This document specifies a new TLS certificate type for exchanging
raw public keys in Transport Layer Security (TLS)
and Datagram Transport Layer Security (DTLS) for use with out-of-band
authentication. Currently, TLS authentication can only occur via PKIX
or OpenPGP certificates. By specifying a minimum resource for raw
public key exchange, implementations can use alternative authentication
methods.
</t>
<t>
One such method is using DANE Resource Records secured by DNSSEC, Another
use case is to provide authentication functionality when used with
devices in a constrained environment that use whitelists and blacklists, as is the case with sensors and other
embedded devices that are constrained by memory, computational, and
communication limitations where the usage of PKIX is not feasible.
</t>
<t>
The new certificate type specified can also be used to reduce the latency
of a TLS client that is already in possession of a validated public key
of the TLS server before it starts a (non-resumed) TLS handshake.
</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<section title="Motivation" anchor="motivation">
<t>Traditionally, TLS server public keys are obtained in PKIX containers
in-band using the TLS connection and validated using trust anchors
based on a <xref target='PKIX'/> certification authority (CA). This
method can add a complicated trust relationship that is difficult
to validate. Examples of such complexity can be seen in
<xref target='Defeating-SSL'/>.</t>
<t>Alternative methods are available that allow a TLS client to obtain
the TLS server public key:</t>
<t><list style="symbols">
<t>The TLS server public key is obtained from a DNSSEC secured RRset
using <xref target='DANE'/></t>
<t>The TLS server public key is obtained from a <xref target='PKIX'/>
certificate chain from an <xref target="LDAP"/> server</t>
<t>The TLS server public key is provisioned by the operating system
and updated via software updates</t>
<t>A TLS client has connected to the TLS server before and has cached
the TLS server certificate chain or TLS server public key for re-use</t>
</list>
</t>
<t><xref target='RFC5246'/> does not provide a mechanism for a TLS client
to tell the TLS server it is already in possession of the authenticated
public key. Therefore, a TLS server must always send a list of trusted
CA keys and its EE certificate containing its public key, even when
the TLS client does not require or desire that data for authentication.</t>
<t><xref target='RFC6066'/> allows suppression of the certificate trust
anchor chain, but not suppression of the PKIX EE certificate container.
These certificate chains are large opaque blocks of data containing
much more than the public key of the TLS server. Since the TLS client
might only be able to validate the PKIX SubjectPublicKeyInfo via an
out-of-band method such as [DANE], it has to ignore any additional
information received that was sent by the server that it could not
validate. Furthermore, information that comes in via these certificate
chains could contain contradicting or additional information that the
TLS client cannot validate or trust, such as an expiry date that
conflicts with information obtained from DNS or LDAP. This document
specifies a method to suppress sending this additional information.</t>
<t>Some small embedded devices use the UDP based <xref target='CoAP'/>, a
specialized
constrained networks and nodes for machine-to-machine applications.
These devices interact with a Web server to upload data such as
temperature sensor readings at a regular intervals. Constrained Application Protocol (CoAP)
<xref target="CoAP"/> can utilize
DTLS for its communication security. As part of the provisioning procedure,
the embeded device is configured with the address and public key of a
dedicated CoAP server to upload sensor data. Receiving PKIX information <xref target='PKIX'/>
from a webserver would be an unneccesarry burden on a sensor networking
deployment environment that requires pre-configured client-server
public keys. These devices often also lack a real-time clock to perform
any PKIX epixry checks.
</t>
</section>
<section title="Applicability" anchor="applicability">
<t>The Transport Layer Security (TLS) Protocol Version 1.2 is specified
in <xref target="RFC5246"/> and provides
a framework for extensions to TLS as well as considerations for
designing such extensions. <xref target="RFC6066"/>
defines several new TLS extensions. This document extends the
specifications of those RFCs with one new TLS Certificate Type to facilitate
suppressing unneeded <xref target='PKIX'/> information from being sent
during the TLS handshake when this information is not required
to authenticate the TLS server.</t>
</section>
<section title="Terminology" anchor="terminology">
<t>Most security-related terms in this document are to be understood in the
sense defined in <xref target="SECTERMS"/>; such terms include, but are
not limited to, "attack", "authentication", "authorization",
"certification authority", "certification path", "certificate",
"credential", "identity", "self-signed certificate", "trust",
"trust anchor", "trust chain", "validate", and "verify".</t>
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in <xref target="RFC2119">RFC 2119</xref>.</t>
</section>
</section>
<section title="Changes to the Handshake Message Contents">
<t>
This section describes the changes to the TLS handshake message
contents when raw public keys are to be used for authentication.
<xref target="flow"/> illustrates the exchange of messages as
described in the sub-sections below. The new "RawPublicKey" value
in the cert_type extension indicates the ability and desire to
exchange raw public keys, which are then exchanged as part of the
certificate payloads.
</t>
<t>
<figure anchor="flow" title="Example Message Flow">
<artwork>
<![CDATA[
client_hello,
cert_type="RawPublicKey" ->
<- server_hello,
cert_type="RawPublicKey",
certificate,
server_key_exchange,
certificate_request,
server_hello_done
certificate,
client_key_exchange,
certificate_verify,
change_cipher_spec,
finished ->
<- change_cipher_spec,
finished
Application Data <-------> Application Data
]]>
</artwork>
</figure>
</t>
<section title="Client Hello">
<t>
In order to indicate the support of out-of-bound raw public keys,
clients MUST include an extension of type "cert_type" to the extended
client hello message. The "cert_type" TLS extension, which is defined
in <xref target="RFC6091"/>, is assigned the
value of 9 from the TLS ExtensionType registry. This value is used
as the extension number for the extensions in both the client hello
message and the server hello message. The hello extension mechanism
is described in <xref target="RFC5246"/>.
</t>
<t>
The "cert_type" TLS extension carries a list of supported certificate types the
client can use, sorted by client preference. This extension MUST be
omitted if the client only supports X.509 certificates. The
"extension_data" field of this extension contains a
CertificateTypeExtension structure. Note that the
CertificateTypeExtension structure is being used both by the client
and the server, even though the structure is only specified once in
this document.
</t>
<t>The <xref target="RFC6091"/> defined CertificateTypeExtension is extended
as follows:
<figure>
<artwork>
<![CDATA[
enum { client, server } ClientOrServerExtension;
enum { X.509(0), OpenPGP(1),
RawPublicKey([TBD]),
(255) } CertificateType;
struct {
select(ClientOrServerExtension)
case client:
CertificateType certificate_types<1..2^8-1>;
case server:
CertificateType certificate_type;
}
} CertificateTypeExtension;
]]>
</artwork>
</figure>
</t>
<t>No new cipher suites are required to use raw public keys. All
existing cipher suites that support a key exchange method compatible
with the defined extension can be used.</t>
</section>
<section title="Server Hello">
<t>If the server receives a client hello that contains the "cert_type"
extension and chooses a cipher suite then two outcomes are possible.
The server MUST either select a certificate type from the certificate_types
field in the extended client hello or terminate the session with a
fatal alert of type "unsupported_certificate".</t>
<t>The certificate type selected by the server is encoded in a
CertificateTypeExtension structure, which is included in the extended
server hello message using an extension of type "cert_type". Servers
that only support X.509 certificates MAY omit including the
"cert_type" extension in the extended server hello.
</t>
<t>If the negotiated certificate type is RawPublicKey the TLS server MUST
send a CertificateTypeExtension structure with a PKIX <xref target='PKIX'/> certificate
containing ONLY the SubjectPublicKeyInfo. The public key MUST match the
selected key exchange algorithm.</t>
</section>
<section title="Certificate Request">
<t>
The semantics of this message remain the same as in the TLS
specification. However, if this message is sent, and the negotiated
certificate type is RawPublicKey, the
"certificate_authorities" list MUST be empty.
</t>
</section>
<section title="Other Handshake Messages">
<t>All the other handshake messages are identical to the TLS
specification.</t>
</section>
</section>
<section title="Security Considerations" anchor="security">
<t>The TLS cert_type extension defined here lets a TLS client attempt to supress
the sending of server certificate as well as the certification chain
for that certificate.</t>
<t>A client using this cert_type needs to be confident in the
authenticity of the public key it is using. Since those
public keys were obtained out-of-band extension), the authentication must also be out-of-band.</t>
<t>Depending on exactly how the public keys were obtained, it may be
appropriate to use authentication mechanisms tied to the public key
transport. For example, if public keys were obtained using <xref target="DANE"/>
it is appropriate to use DNSSEC to authenticate the public keys.</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>We request that IANA assign a TLS cert_type value for RawPublicKey.</t>
</section>
<section title="Contributors" anchor="contributors">
<t>The following individuals made important contributions to this document: Paul Hoffman.</t>
</section>
<section title="Acknowledgements" anchor="acknowledgements">
<t>This document is based on material from RFC 6066 for which the
author is Donald Eastlake 3rd. Contributions to that document
also include Joseph Salowey, Alexey Melnikov, Peter Saint-Andre,
and Adrian Farrel.</t>
<t>The second version of this document was made after feedback from the TLS working group at IETF#81.
The support for hashes of public keys has been removed after the discussions at the IETF#82 meeting.
</t>
</section>
</middle>
<!-- *****BACK MATTER ***** -->
<back>
<!-- References split into informative and normative -->
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<references title="Normative References">
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.5246.xml"?>
<reference anchor='PKIX'>
<front>
<title>Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile</title>
<author initials='D.' surname='Cooper' fullname='D. Cooper'>
<organization /></author>
<author initials='S.' surname='Santesson' fullname='S. Santesson'>
<organization /></author>
<author initials='S.' surname='Farrell' fullname='S. Farrell'>
<organization /></author>
<author initials='S.' surname='Boeyen' fullname='S. Boeyen'>
<organization /></author>
<author initials='R.' surname='Housley' fullname='R. Housley'>
<organization /></author>
<author initials='W.' surname='Polk' fullname='W. Polk'>
<organization /></author>
<date year='2008' month='May' />
<abstract>
<t>This memo profiles the X.509 v3 certificate and X.509 v2 certificate revocation list (CRL) for use in the Internet. An overview of this approach and model is provided as an introduction. The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms. Standard certificate extensions are described and two Internet-specific extensions are defined. A set of required certificate extensions is specified. The X.509 v2 CRL format is described in detail along with standard and Internet-specific extensions. An algorithm for X.509 certification path validation is described. An ASN.1 module and examples are provided in the appendices. [STANDARDS TRACK]</t></abstract></front>
<seriesInfo name='RFC' value='5280' />
<format type='TXT' octets='352580' target='ftp://ftp.isi.edu/in-notes/rfc5280.txt' />
</reference>
<reference anchor='SECTERMS'>
<front>
<title>Internet Security Glossary, Version 2</title>
<author initials='R.' surname='Shirey' fullname='R. Shirey'>
<organization /></author>
<date year='2007' month='August' />
<abstract>
<t>This Glossary provides definitions, abbreviations, and
explanations of terminology for information system security.
The 334 pages of entries offer recommendations to improve the
comprehensibility of written material that is generated in the
Internet Standards Process (RFC 2026). The recommendations
follow the principles that such writing should (a) use the same
term or definition whenever the same concept is mentioned; (b)
use terms in their plainest, dictionary sense; (c) use terms that
are already well-established in open publications; and (d) avoid
terms that either favor a particular vendor or favor a particular
technology or mechanism over other, competing techniques
that already exist or could be developed. This memo provides
information for the Internet community.</t>
</abstract>
</front>
<seriesInfo name='RFC' value='4949' />
<format type='TXT' octets='867626' target='ftp://ftp.isi.edu/in-notes/rfc4949.txt' />
</reference>
</references>
<references title="Informative References">
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.6066.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.6091.xml"?>
<reference anchor='LDAP'>
<front>
<title>Lightweight Directory Access Protocol (LDAP): The Protocol</title>
<author initials='J.' surname='Sermersheim' fullname='J. Sermersheim'>
<organization /></author>
<date year='2006' month='June' />
<abstract>
<t>This document describes the protocol elements, along with
their semantics and encodings, of the Lightweight Directory
Access Protocol (LDAP). LDAP provides access to distributed
directory services that act in accordance with X.500 data
and service models. These protocol elements are based
on those described in the X.500 Directory Access Protocol
(DAP). [STANDARDS TRACK]</t>
</abstract>
</front>
<seriesInfo name='RFC' value='4511' />
<format type='TXT' octets='150116' target='ftp://ftp.isi.edu/in-notes/rfc4511.txt' />
</reference>
<reference anchor='DANE'>
<front>
<title>Using Secure DNS to Associate Certificates with Domain Names For TLS</title>
<author initials='P' surname='Hoffman' fullname='Paul Hoffman'>
<organization />
</author>
<author initials='J' surname='Schlyter' fullname='J. Schlyter'>
<organization />
</author>
<date month='September' day='27' year='2011' />
<abstract><t>TLS and DTLS use certificates for authenticating the server. Users
want their applications to verify that the certificate provided by
the TLS server is in fact associated with the domain name they
expect. DNSSEC provides a mechanism for a zone operator to sign DNS
information directly. This way, bindings of keys to domains are
asserted not by external entities, but by the entities that operate
the DNS. This document describes how to use secure DNS to associate
the TLS server's certificate with the intended domain name.</t></abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-ietf-dane-protocol-12' />
<format type='TXT'
target='http://www.ietf.org/internet-drafts/draft-ietf-dane-protocol-12.txt' />
</reference>
<reference anchor='CoAP'>
<front>
<title>Constrained Application Protocol</title>
<author initials='Z' surname='Shelby' fullname='Z. Shelby'>
<organization>Sensinode</organization>
</author>
<author initials='K' surname='Hartke' fullname='K. Hartke'>
<organization />
</author>
<author initials='C' surname='Bormann' fullname='C. Bormann'>
<organization>Universitaet Bremen TZI</organization>
</author>
<author initials='B' surname='Frank' fullname='B. Frank'>
<organization>SkyFoundry</organization>
</author>
<date month='July' day='8' year='2011' />
<abstract><t>
This document specifies the Constrained Application Protocol (CoAP),
a specialized web transfer protocol for use with constrained networks
and nodes for machine-to-machine applications such as smart energy
and building automation. These constrained nodes often have 8-bit
microcontrollers with small amounts of ROM and RAM, while networks
such as 6LoWPAN often have high packet error rates and a typical
throughput of 10s of kbit/s. CoAP provides a method/response
interaction model between application end-points, supports built-in
resource discovery, and includes key web concepts such as URIs and
content-types. CoAP easily translates to HTTP for integration with
the web while meeting specialized requirements such as multicast
support, very low overhead and simplicity for constrained
environments.
</t></abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-ietf-core-coap-07' />
<format type='TXT'
target='http://www.ietf.org/internet-drafts/draft-ietf-core-coap-07.txt' />
</reference>
<reference anchor='Defeating-SSL' target='http://www.blackhat.com/presentations/bh-dc-09/Marlinspike/BlackHat-DC-09-Marlinspike-Defeating-SSL.pdf'>
<front>
<title>New Tricks for Defeating SSL in Practice</title>
<author initials='M.' surname='Marlinspike' fullname='Moxie Marlinspike'>
<organization /></author>
<date year='2009' month='February' />
</front>
<format type='PDF' target='http://www.blackhat.com/presentations/bh-dc-09/Marlinspike/BlackHat-DC-09-Marlinspike-Defeating-SSL.pdf' />
</reference>
</references>
</back>
</rfc>
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