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version-01.xml
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version-01.xml
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<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
<?rfc toc="yes"?>
<?rfc tocompact="yes"?>
<?rfc tocdepth="3"?>
<?rfc tocindent="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc comments="no"?>
<?rfc inline="yes"?>
<?rfc compact="yes"?>
<?rfc subcompact="no"?>
<rfc xmlns:xi="http://www.w3.org/2001/XInclude" category="std" docName="draft-ietf-raviolli-trusted-domain-srv6"
ipr="trust200902"
obsoletes="" submissionType="IETF" updates="" xml:lang="en">
<front>
<title abbrev="draft-ietf-raviolli-trusted-domain-srv6">
Trusted Domain SRv6
</title>
<author fullname="Andrew Alston" initials="A." surname="Alston">
<organization>Liquid Intelligent Technologies</organization>
<address>
<email>[email protected]
</email>
<uri/>
</address>
</author>
<author fullname="Tom Hill" initials="T." surname="Hill">
<organization>British Telecom</organization>
<address>
<email>[email protected]
</email>
<uri/>
</address>
</author>
<author fullname="Tony Przygienda" initials="A." surname="Przygienda">
<organization>Juniper</organization>
<address>
<postal>
<street>1137 Innovation Way
</street>
<city>Sunnyvale</city>
<region>CA
</region>
<code/>
<country>USA
</country>
</postal>
<phone/>
<facsimile/>
<email>[email protected]
</email>
<uri/>
</address>
</author>
<date year="2023"/>
<abstract>
<t>
</t>
</abstract>
<note title="Requirements Language">
<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 format="default"
pageno="false" target="RFC2119">RFC 2119</xref>.
</t>
</note>
</front>
<middle>
<section title="Description" >
<t>
SRv6 as designed has evoked interest from various parties,
though its deployment is being limited by known security problems
in its architecture. This document specifies a standard to create a
solution that closes some of the major security concerns,
while retaining the basis of the SRv6 protocol.
</t>
</section>
<section title="Glossary" >
<dl newline="true" spacing="normal">
<dt>Fail-Closed Domain:</dt>
<dd>
synonymous with a Trusted Domain.
</dd>
<dt>
Trusted Domain (TD):
</dt>
<dd>
A domain that prevents processing of a protocol without explicit configuration, defined
in detail in <xref target="fcpd"/>.
</dd>
<dt>
Fail-Closed Protocol (FPC):
</dt>
<dd>
A protocol that can be deployed by establishing a fail closed domain.
</dd>
<dt>
TD-SRv6:
</dt>
<dd>
SRv6 modified to become a FPC and with that allowing for easy deployment in
a TD.
</dd>
</dl>
</section>
<section title="The SRv6 Security Problem">
<t>
SRv6 relies in its architecture on the concept of limited domain which
as a concept suffers from lack of security that is deployable in
economical, scalable fashion easily.
</t>
<t>
Limited domains without very careful deployment will invariably leak beyond
the domain and allow untrusted traffic to enter the domain and terminate
on any arbitrary node.
</t>
<t>
As
per <xref format="default" pageno="false" target="RFC8402">RFC 8402</xref>RFC8402 Section 8,
SRv6 that leaks beyond the border of a trusted domain creates a security violation.
</t>
<t>
The proper solution is to create a trusted
domain that has a default fail-closed approach and a well-defined
red-black boundary.
</t>
<t> Examples of fail closed protocols currently include:</t>
<ul>
<li>mpls</li>
<li>clns</li>
<li>lldp</li>
<li>bier</li>
</ul>
</section>
<section title="Characteristics of a Fail-Closed Protocol Domain" anchor="fcpd">
<t>
A fail closed protocol domain is determined by following properties:
</t>
<t>
Processing of the protocol packet on an interface requires explicit configuration with a
default drop behavior.</t>
<t>
Leaking according protocol packets beyond the boundary of fail-closed domain requires
explicit config.
</t>
<t>
Fail closed protocols are easily identifiable by their top level
(e.g. link layer) encoding
early in the packet formats and often by fields at fixed offset.
In another words either their encoding or encapsulation allows to
distinguish it easily from other traffic.
</t>
<t>
Classification of the protocol packets is completely deterministic.
</t>
<t>
Confining the protocol to the trusted domaim does not require complex processing in
either hardware or software to allow for scalability and economical deployment.
</t>
<t>
The boundary of a trusted domain consists of a set of interfaces that exhibit default
behavior.
</t>
</section>
<section title="SRv6 in the context of a trusted domain - an objective analysis">
<t>
It is currently impossible to differentiate SRv6 and IPv6 at the link-layer or
easily at network layer by e.g. a reserved protocol number as IPSec does.
</t>
<t>
In the event of a packet being sent into a trusted domain, either accidentally
or by a malicious actor,
it is possible to send the frame to a node binding the specific SID,
and have the packet processed,
irrespective of the content of the underlying (encapsulated) packet.
</t>
<t>
The current security proposals in RFC8402 section 8.2, security is
based on the application of
filters preventing ingress traffic at the boundary routers destined
towards a SID within the domain.
Such filtering is prone to configuration errors and in addition,
has significant impact on TCAM utilization
on devices that have large numbers of ingress points into the domain.
The matching itself, due to the complexity and numerous possibilities
of expressing a set of SIDs will likely necessitate a complete semantic
parsing of such list to guarantee fully precise matching including
wildcarding in different forms.
</t>
<t>
In the context of a trusted domain, anything outside of the
operators control should not be considered
trusted. This means applying filters to prevent
leakage into the domain at every customer port,
every server, and every cloud stack.
The scale and complexity of maintaining such a "shorewall" is daunting
and at large scale will not be likely to keep up with the
timing necessary in case of attacks mounted and metamorphosing in
short time intervals. An attack avoiding the filter wall may evade
discovery for a long time in case of lack of sophisticated
traffic analyis and analytics tools.
</t>
</section>
<section title="Trusted-Domain Implementation">
<t>
To implement SRv6 in the context of a trusted domain, it is necessary
to modify it to allow deployment in a fail-closed boundary efficiently.
This requires changes to the protocol encapsulation at both the boundary
routers and the transit nodes.
This document introduces a distinct ethertype to be used for td-srv6
</t>
<section title="Boundary routers">
<t>
Trusted Domain boundary routers form the point at which the new
ethertype is imposed.
Imposition of the ethertype happens on packet ingress,
at the same point as SRv6 header imposition
is performed.
</t>
<t>
Boundary interfaces will, by default behavior, drop packets already
containing the srv6-td ethertype.
</t>
</section>
<section title="Transit and egress routers">
<t>
In the case of a transit or egress router, should a frame not
be marked with the srv6-td ethertype, the
frame will be treated as a standard IPv6 packet for the
purposes of handling and forwarding.
</t>
<t>
Only frames marked with the srv6-td ethertype will be
processed as SRv6 packets.
</t>
<t>
A router configured to process TD-SRv6 MUST drop packets
containing an SRH if received on any ethertype except srv6-td.
</t>
</section>
</section>
<section anchor="registry" title="Registry Considerations">
<section anchor="IANA" title="IANA Considerations" toc="default">
<t>
No IANA Considerations
</t>
</section>
<section anchor="IEEE" title="IEEE Considerations" toc="default">
<t>
TD-SRv6 Ethertype: TBD0
</t>
</section>
</section>
<section title="Security Considerations">
<t>
This draft enhances the security mechanisms required by section 8 of RFC8402, and does not
impose any further security considerations of its own.
</t>
</section>
<section title="Contributors">
<t>
Weiqiang Cheng
</t>
<t>
</t>
</section>
</middle>
<back>
<references title="Informative References">
</references>
<references title="Normative References">
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8402.xml"/>
</references>
</back>
</rfc>