Internet DRAFT - draft-intarea-raviolli-trusted-domain-srv6
draft-intarea-raviolli-trusted-domain-srv6
Network Working Group A. Alston
Internet-Draft Liquid Intelligent Technologies
Intended status: Standards Track T. Hill
Expires: 26 September 2023 British Telecom
A. Przygienda
Juniper
25 March 2023
Trusted Domain SRv6
draft-intarea-raviolli-trusted-domain-srv6-00
Abstract
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.
Requirements Language
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 RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 26 September 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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Table of Contents
1. Description . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. The SRv6 Security Problem . . . . . . . . . . . . . . . . . . 3
4. Characteristics of a Fail-Closed Protocol Domain . . . . . . 3
5. SRv6 in the context of a trusted domain - an objective
analysis . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Trusted-Domain Implementation . . . . . . . . . . . . . . . . 5
6.1. Boundary routers . . . . . . . . . . . . . . . . . . . . 5
6.2. Transit and egress routers . . . . . . . . . . . . . . . 5
7. Registry Considerations . . . . . . . . . . . . . . . . . . . 5
7.1. IANA Considerations . . . . . . . . . . . . . . . . . . . 5
7.2. IEEE Considerations . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Informative References . . . . . . . . . . . . . . . . . 6
10.2. Normative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Description
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.
2. Glossary
Fail-Closed Domain:
synonymous with a Trusted Domain.
Trusted Domain (TD):
A domain that prevents processing of a protocol without explicit
configuration, defined in detail in Section 4.
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Fail-Closed Protocol (FPC):
A protocol that can be deployed by establishing a fail closed
domain.
TD-SRv6:
SRv6 modified to become a FPC and with that allowing for easy
deployment in a TD.
3. The SRv6 Security Problem
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.
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.
As per RFC 8402 [RFC8402]RFC8402 Section 8, SRv6 that leaks beyond
the border of a trusted domain creates a security violation.
The proper solution is to create a trusted domain that has a default
fail-closed approach and a well-defined trusted/untrusted boundary.
Examples of fail closed protocols currently include:
* mpls
* clns
* lldp
* bier
4. Characteristics of a Fail-Closed Protocol Domain
A fail closed protocol domain is determined by following properties:
Processing of the protocol packet on an interface requires explicit
configuration with a default drop behavior.
Leaking according protocol packets beyond the boundary of fail-closed
domain requires explicit config.
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.
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Classification of the protocol packets is completely deterministic.
Confining the protocol to the trusted domaim does not require complex
processing in either hardware or software to allow for scalability
and economical deployment.
The boundary of a trusted domain consists of a set of interfaces that
exhibit default behavior.
5. SRv6 in the context of a trusted domain - an objective analysis
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.
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.
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.
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.
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6. Trusted-Domain Implementation
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
6.1. Boundary routers
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.
Boundary interfaces will, by default behavior, drop packets already
containing the srv6-td ethertype.
6.2. Transit and egress routers
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.
Only frames marked with the srv6-td ethertype will be processed as
SRv6 packets.
A router configured to process TD-SRv6 MUST drop packets containing
an SRH if received on any ethertype except srv6-td.
7. Registry Considerations
7.1. IANA Considerations
No IANA Considerations
7.2. IEEE Considerations
TD-SRv6 Ethertype: TBD0
8. Security Considerations
This draft enhances the security mechanisms required by section 8 of
RFC8402, and does not impose any further security considerations of
its own.
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9. Contributors
Weiqiang Cheng
chengweiqiang@chinamobile.com
Anthony Somerset
anthony.somerset@liquid.tech
10. References
10.1. Informative References
10.2. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
Authors' Addresses
Andrew Alston
Liquid Intelligent Technologies
Email: andrew-ietf@liquid.tech
Tom Hill
British Telecom
Email: tom@ninjabadger.net
Tony Przygienda
Juniper
1137 Innovation Way
Sunnyvale, CA
United States of America
Email: prz@juniper.net
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