257 lines
9 KiB
XML
257 lines
9 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
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<?rfc comments="yes"?>
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<?rfc compact="yes"?>
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<?rfc subcompact="no"?>
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<?rfc inline="yes"?>
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<?rfc sortrefs="yes"?>
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<?rfc symrefs="yes"?>
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<?rfc toc="yes"?>
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<?rfc tocdepth="6"?>
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<?rfc tocindent="yes"?>
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<?rfc tocompact="yes"?>
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<rfc category="std" docName="draft-ymbk-lsvr-l3dl-signing-00" ipr="trust200902">
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<front>
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<title>Layer 3 Discovery and Liveness Signing</title>
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<author fullname="Randy Bush" initials="R." surname="Bush">
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<organization>Arrcus & IIJ</organization>
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<address>
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<postal>
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<street>5147 Crystal Springs</street>
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<city>Bainbridge Island</city>
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<region>WA</region>
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<code>98110</code>
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<country>United States of America</country>
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</postal>
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<email>randy@psg.com</email>
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</address>
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</author>
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<!--
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<author fullname="Russ Housley" initials="R" surname="Housley">
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<organization abbrev="Vigil Security">Vigil Security, LLC</organization>
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<address>
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<postal>
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<street>918 Spring Knoll Drive</street>
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<city>Herndon</city>
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<region>VA</region>
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<code>20170</code>
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<country>USA</country>
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</postal>
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<email>housley@vigilsec.com</email>
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</address>
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</author>
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-->
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<author initials="R." surname="Austein" fullname="Rob Austein">
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<organization abbrev="Arrcus">Arrcus, Inc.</organization>
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<address>
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<email>sra@hactrn.net</email>
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</address>
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</author>
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<date />
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<abstract>
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<t>The Layer 3 Discovery and Liveness protocol OPEN PDU contains a
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key which can be used to verify signatures on subsequent PDUs. This
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document describes two mechanisms based on digital signatures, one
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that is Trust On First Use (TOFU), and one that uses certificates to
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provide authentication as well as session integrity.</t>
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</abstract>
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<note title="Requirements Language">
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<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
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"OPTIONAL" in this document are to be interpreted as described in
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BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when,
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and only when, they appear in all capitals, as shown here.</t>
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</note>
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</front>
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<middle>
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<section anchor="intro" title="Introduction">
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<t>The Layer 3 Discovery and Liveness protocol [old ref because new
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draft not yet pushed] <xref target="I-D.ietf-lsvr-lsoe"/> OPEN PDU
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contains an algorithm specifier and a key which can be used to
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verify signatures on subsequent PDUs. This document describes two
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methods of key generation and signing for use by L3DL, Trust On
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First Use (TOFU) and a PKI-based mechanism to provide authentication
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as well as session integrity.</t>
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<t>The Key in the OPEN PDU SHOULD be the public key of an asymmetric
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key pair. The sender signs with the private key, of course. The
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device sending the OPEN may use one key for all links, a different
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key for each link, or some aggregation(s) thereof.</t>
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<t>In the TOFU method the OPEN key is generated on the sending
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device, believed without question by the receiver, and used to
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verify all subsequent PDUs from the same sender with the same Key
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Type.</t>
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<t>With the PKI-mechanism, an enrollment step is performed. The
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public key and an identifier of the subject are put into a
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certificate, which is signed by the the operational environment's
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trust anchor. In this way, the relying party can be confident that
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the public key is under control of the identified L3DL protocol
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entity.</t>
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<t>To the receiver verifying signatures on PDUs, the two methods are
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indistinguishable; the key provided in the OPEN PDU is used to
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verify the signatures of subsequent PDUs. The difference that
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PKI-based keys may be verified against the trust anchor when the
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OPEN PDU is received.</t>
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<t>In the PKI method the OPEN key MUST be verified against the trust
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anchor for the operational domain. It is then used to verify all
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subsequent PDUs from the same peer with the same Key Type.</t>
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</section>
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<section anchor="tofu" title="Trust On First Use Method">
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</section>
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<section anchor="pki" title="Public Key Infrastructure Method">
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</section>
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<section anchor="roll" title="NEWKEY, Key Roll">
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<t>Modern key management allows for agility in 'rolling' to a new
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key or even algorithm in case of key expiry, key compromise, or
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merely prudence. Declaring a new key with an L3DL OPEN PDU would
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cause serious churn in topology as a new OPEN causes a withdraw of
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previously announced encapsulations. Therefore, a gentler rekeying
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is needed.</t>
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<!--
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protocol "Type = 8:8,Payload Length:16,New Key Type:8,New Key Length:16,New Key ...:40,Old Sig Type:8,Old Signature Length:16,Old Signature ...:40"
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-->
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<figure>
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<artwork>
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Type = 8 | Payload Length | New Key Type |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| New Key Length | ~
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
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~ New Key ... | Old Sig Type |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Old Signature Length | ~
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
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~ Old Signature ... |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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</artwork>
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</figure>
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<t>The New Key Type, New Key Length, and New Key fields declare the
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replacement algorithm suite and key.</t>
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<t>The NEWKEY PDU is signed using the current (soon to be old)
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algorithm suite and key.</t>
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<t>The sender and the receiver should be cautious of algorithm suite
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downgrade attacks.</t>
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<t>To avoid possible race conditions, the receiver SHOULD accept
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signatures using either the new or old key for a configurable time
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(default 30 seconds). This is intended to accommodate situations
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such as senders with high peer out-degree and a single per-device
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asymmetric key.</t>
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<t>If the sender does not receive an ACK in the normal window,
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including retransmission, then the sender MAY choose to allow a
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session reset by either issuing a new OPEN or by letting the
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receiver eventually have a signature failure (error code 3) on a
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PDU.</t>
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</section>
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<section anchor="security" title="Security Considerations">
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<t>The TOFU method requires a leap of faith to accept the key in the
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OPEN PDU, as it can not be verified against any authority. Hence it
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is jokingly referred to as Married On First Date. The assurance it
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does provide is that subsequent signed PDUs are from the same peer.
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And data integrity is a positive side effect of the signature.</t>
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<t>The PKI-based method offers assurance that the certificate, and
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hence the keying material, provided in the OPEN PDU are authorized
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by a central authority, e.g. the Clos's network security team. The
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onward assurance of talking to the same peer and data integrity are
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the same as in the TOFU method.</t>
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<t>With the PKI-based method, automated device provisioning could
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restrict which subsidiary certificates were allowed from which peers
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on a per interface basis. This would complicate key rolls. Where
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one draws the line between rigidity, flexibility, and security
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varies.</t>
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<t>The REKEY PDU is open to abuse to create an algorithm suite
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downgrade attack.</t>
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</section>
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<section anchor="iana" title="IANA Considerations">
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<t>This document requests the IANA create a new entry in the L3DL PDU
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Type registry as follows:</t>
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<figure>
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<artwork>
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PDU
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Code PDU Name
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---- -------------------
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8 NEWKEY
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</artwork>
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</figure>
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<t>This document requests the IANA add a registry entry for "TOFU -
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Trust On First Use" to the L3DL-Signature-Type registry as follows:</t>
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<figure>
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<artwork>
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Number Name
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------ -------------------
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1 TOFU - Trust On First Use
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2 PKI
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</artwork>
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</figure>
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</section>
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<section anchor="acks" title="Acknowledgments">
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<t>The authors than Russ Housley for advice and review.</t>
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</section>
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</middle>
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<back>
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<references title="Normative References">
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<?rfc include="reference.RFC.2119"?>
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<?rfc include="reference.RFC.8174"?>
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<?rfc include="reference.I-D.ietf-lsvr-lsoe"?>
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</references>
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<!--
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<references title="Informative References">
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</references>
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-->
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</back>
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</rfc>
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