wdiff draft-ietf-sidr-roa-validation-03.txt draft-ietf-sidr-roa-validation-04.txt

Secure Inter-Domain Routing (SIDR) G. Huston
Internet-Draft G. Michaelson
Intended status: Informational APNIC
Expires: February 7, September 4, 2010 March 3, 2010 August 6, 2009

Validation of Route Origination in BGP using the Resource Certificate PKI and
ROAs
draft-ietf-sidr-roa-validation-03.txt
draft-ietf-sidr-roa-validation-04.txt

Abstract

This document defines the semantics of a Route Origin Authorization
in terms of the context of an application of the Resource Public Key
Infrastructure to validate the origination of routes advertised in
the Border Gateway Protocol.

Status of this Memo

This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.

The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.

This Internet-Draft will expire on February 7, September 4, 2010.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document (http://trustee.ietf.org/license-info). document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document.

Abstract

This Code Components extracted from this document defines an application of the Resource Public Key
Infrastructure to validate the origination of routes advertised must
include Simplified BSD License text as described in Section 4.e of
the Border Gateway Protocol. The proposed application is intended to
fit within the requirement for adding security to inter-domain
routing, including the ability to support incremental and piecemeal
deployment, Trust Legal Provisions and does not require any changes to are provided without warranty as
described in the specification of
BGP. BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. ROA Validation Outcomes of for a BGP Route Object . . . . . . . . . . 3
3. Applying Validation Outcomes to BGP Route Selection . . . . . 4
4. Further Considerations . . . . . . . . . . . . . . . . . . . . 6
4.1. Partial Deployment Considerations . . . . . . . . . . . . 6
4.2. 5
4. Disavowal of Routing Origination . . . . . . . . . . . . . 7
4.3. BGP Considerations . . . . . . . . . . . . . . . . . . . . 8 6
5. Security Considerations . . . . Route Object Validation Lifetime . . . . . . . . . . . . . . . 8 7
6. IANA Security Considerations . . . . . . . . . . . . . . . . . . . . . 9 7
7. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Changes -02 to -03 . . . . . . . . . . . . . . . . . . IANA Considerations . . 9
7.2. Changes -01 to -02 . . . . . . . . . . . . . . . . . . . . 10 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8
8.1. Normative References . . . . . . . . . . . . . . . . . . . 10 8
8.2. Informative References . . . . . . . . . . . . . . . . . . 11 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 8

1. Introduction

This document defines the semantics of a Route Origin Authorization
(ROA) in terms of the context of an application of the Resource
Public Key Infrastructure (RPKI) [I-D.ietf-sidr-arch] to validate the
origination of routes advertised in the Border Gateway Protocol (BGP)
[RFC4271].

The RPKI is based on a hierarchy of Resource Certificates that are
aligned to the Internet number resource allocation structure.
Resource Certificates are X.509 certificates that conform to the PKIX
profile [RFC5280], and to the extensions for IP addresses and AS
identifiers [RFC3779]. A Resource Certificate describes an action by
an issuer that binds a list of IP address blocks and Autonomous
System (AS) numbers to the Subject of a certificate, identified by
the unique association of the Subject's private key with the public
key contained in the Resource Certificate. The RPKI is structured
such that each current Resource Certificate matches a current
resource allocation or assignment. This is further described in
[I-D.ietf-sidr-arch].

Route Origin Authorizations (ROAs)

ROAs are digitally signed objects that bind an address to an AS
number, signed by the address holder. A ROA provides a means of
verifying that an IP address block holder has authorized an a particular
AS to originate route objects in the inter-domain routing environment
for that address block. ROAs are described in
[I-D.ietf-sidr-roa-format]. ROAs are intended to fit within the
requirements for adding security to inter-domain routing.

This document describes the semantic interpretation of a valid ROA, with
particular reference to application in BGP inter-domain routing relating
to the origination of route objects.

This proposed application of validation of ROAs does not require any
changes to objects, and the specification of BGP protocol elements. The outcomes
of ROA validation may be used as part intended scope of BGP's local route selection
procedure [RFC4271]. the
authority that is conveyed in the ROA.

2. ROA Validation Outcomes of for a BGP Route Object

A BGP "route object" is an address prefix and an associated set of
routing attributes. In terms of validation of the route object in
the context of BGP [RFC4271]the address prefix value and the "origin
AS" are used in the ROA validation operation. The route object's
origin AS is the final element of the route object's AS_PATH
attribute. If the final AS_PATH element is an AS Set, indicating
that the route object is an aggregate, then the origin AS is taken as
the AS component of the AGGREGATOR attribute [RFC4271].

A BGP route object does not refer to a specific ROA

It is assumed here that should be
used by a Relying Party (RP) has access to validate the origination information
contained in a local
cache of the complete set of valid ROAs when performing validation of
a route object. (Valid ROAs are defined as ROAs that are determined
to be syntactically correct and are signed using a signature that can
be verified using the RPKI, as described in
[I-D.ietf-sidr-roa-format].) The RP needs to match a route object to
one or more candidate valid ROAs in order to determine a validation
outcome, which, in turn, can be used to determine the appropriate
local actions to perform on the route object. Valid ROAs
are defined as ROAs that are determined

This approach to be syntactically correct
and are signed using route object origination validation uses a signature model of
"positive" attestations, where route objects that can cannot be verified using validated
within the RPKI, RPKI framework would conventionally be treated by a RP as described in [I-D.ietf-sidr-roa-format]. The outcome
"invalid". However, the considerations of accommodating environments
of partial adoption of the use of ROAs, where only a subset of
validly advertised address prefixes have associated published ROAs
within the structure of the RPKI, imply some modification to this ROA
model of positive attestation. In the context of route object
validation function it is assumed that either the RP has determined once an address prefix is described in
a ROA, then this ROA speifically encompasses all address prefixes
that are more specific than that described in the ROA. Thus, any
route object for more specific address prefix than that described by
any valid ROA that does not itself have a matching valid ROA is
considered to be "invalid". However, routes objects for address
prefixes that are not fully described by any single ROA, i.e., those
route objects whose address prefixes may be an aggregate of address
prefixes described in a valid ROA, or have address prefixes where
there is no intersection with any ROA, and are not matched by any ROA
and are not a more specific of any ROA cannot be reliably classified
as "invalid" in the context a partial deployment scenario. Such route objects
have a validation outcome of the RPKI, or the "unknown".

The validation condition of a route object with a prefix and an
origin AS when using single ROA for validation is invalid, summarized in which
case the
following table:

In an environment of a collection of ROAs, a route object is not
considered to be used by the RP. "valid" if any ROA provides a "valid" outcome. It
is assumed here that considered to be "invalid" if one (or more) ROAs are managed and distributed
independently of the operation of BGP itself, provide an
"invalid" outcome and that no ROAs provide a local BGP
speaker has access "valid" outcome. It is
considered to a local cache of the complete set of valid ROAs be "unknown" when performing no ROA produces either a route object validation operation. "valid" or
an "invalid" outcome.

Route object validation is defined by the following procedure:

1. Select all valid ROAs that include a ROAIPAddress value that
either matches, or is a covering aggregate of, the address
prefix in the route object.

2. If the set of candidate ROAs is empty then the validation
procedure stops with an outcome of "unknown".

3. If any ROA of the selected ROAs has an asID value that matches the
origin AS in the route object, and either the route object's
address prefix precisely matches a ROAIPAddress in the ROA, or
the route object's address prefix is a more specific prefix of
a
ROAIPAddress ROAIPAddress, and the route object's prefix length value is
less than or equal to the ROAIPAddress' maxLength value, then
the validation procedure stops with an outcome of "valid".

4. Otherwise, the validation procedure stops with an outcome of
"invalid".

3. Applying Validation Outcomes to BGP Route Selection

Within the framework of the abstract model of the operation of inter-
domain routing using BGP operation, [RFC4271], a received prefix announcement
from a BGP speaking routing peer is compared to all announcements for this prefix
received from other BGP routing peers and a route selection procedure is
used to select the "best" route object from this candidate set. This route object is then used locally by
installing it in the loc-RIB [RFC4271], and is announced to peers as
the local "best" route.

The route object validation outcome, described in Section 2, of
"unknown", "valid" or "invalid" may be used as part of the
determination of the local degree of preference as defined preference, in section
9.1.1 of which case the BGP specification [RFC4271]. The
local degree order of preference is as follows:
"valid" is to be preferred over
"unknown", which itself is to be preferred over
"invalid".

This preference ranking is performed prior to the steps described in
section 9.1.1 of [RFC4271].

It is a matter of local BGP selection routing policy as to the actions to be
undertaken by a BGP instance routing entity in processing route objects with
"unknown" validation outcomes. Due to considerations of partial use
of ROAs in heterogeneous environments, such as in the public
Internet, it is advised that local policy settings should not result
in "unknown" validation outcomes being considered as sufficient
grounds to reject a route object outright from further consideration
as a local "best" route.

It is a matter of local BGP selection routing policy as to whether "invalid" route
objects are considered to be ineligible for further consideration in the
a route selection process. The A possible consideration here is one of
potential circularity of dependence. If the authoritative
publication point of the repository of ROAs, or that of any
certificate used in relation to an address prefix, is located at an
address that lies within the address prefix described in a ROA, then
the repository can only be accessed by the RP once a route for the
prefix has been accepted by the RP's local routing domain. It is
also noted that the propagation time of RPKI objects may be different
to the propagation time of route objects in BGP, objects, and that route objects may
be received before the RP's local repository cache picks up the
associated ROAs and recognises them as valid within the RPKI.

A local policy setting may be considered such that "invalid"
validation outcomes would be sufficient grounds to reject the route
object. However, due to these considerations of circular dependence
and differing propagation times of ROAs and route objects, an
alternate local policy setting may be considered that would involve
the use of a local timer to accept the route object as feasible for
an interim period of time, until there is an acceptable level of
assurance that all reasonable efforts to obtain a valid ROA for the
route object have been undertaken.

4. Further Considerations

4.1. Partial Deployment Considerations

This approach to route object origination validation uses a model of
"positive security" attestations, where information that cannot be
validated within the RPKI framework is intended to interpreted by a
RP as invalid information.

However, the considerations of accommodating environments of partial
adoption, where only a subset of valid route objects have associated
ROAs within the structure of the RPKI, imply some modification to
this model of positive security. Here it is assumed that once an
address prefix is described in a ROA, then this ROA encompasses all
address prefixes that are more specific than that described in the
ROA. Thus, any more specific address prefix and originating AS
combination of a valid ROA, that does not have a matching valid ROA
is considered to be "invalid".

Routes objects that describe address prefixes that are not fully
described by any single ROA, i.e., those address prefixes that may be
an aggregate of a ROA, or have no intersection with any ROA, and are
not matched by any ROA and are not a more specific of any ROA cannot
be reliably classified as "invalid" in a partial deployment scenario,
and are therefore described as "unknown".

The match condition of a route object against a single ROA is
summarized in the following table:

In an environment of a collection of ROAs, a route object is
considered to be "valid" if any ROA provides a "valid" outcome, and
"invalid" if one or more ROAs provide an "invalid" outcome and no
ROAs provide a "valid" outcome. The "unknown" outcome occurs when no
ROA produces either a "valid" or an "invalid" outcome.

4.2. Disavowal of Routing Origination

A ROA is a positive attestation that a prefix holder has authorized
an AS to originate a route for this prefix into the inter-domain
routing system. It is possible for a prefix holder to attest that construct an
authorization where no valid AS has been granted any such authority
to originate a route object for an address prefix. This is acheived
by using a ROA where the ROA'S ROA's subject AS is one that will not must never be
used in a any routing context. Specifically, AS 0 is reserved by the
IANA such that it "may be use [sic] to identify non-routed networks"
[IANA.AS-Registry].

A ROA with a subject of AS 0 is an attestation by the holder of a
prefix that the prefix described in the ROA, and any more specific
prefix, should not SHOULD NOT be used in a routing context.

The route object validation procedure, described in Section 2, will
provide a "valid" outcome if any ROA matches the address prefix and
origin AS, even if other valid ROAs would provide an "invalid"
validation outcome if used in isolation. Consequently, an AS0 AS 0 ROA
has a lower preference than any other ROA that has a routeable AS as
its subject. This allows a prefix holder to use an AS0 AS 0 ROA to
declare a default condition that any route object that is equal to,
or more specific than the prefix to be considered to be invalid,
while also allowing other concurrently issued ROAs to describe valid
origination authorizations for more specific prefixes.

For example, the holder of prefix 203.0.113.0/24 may wish to
authorise the origination of a route object of 203.0.113.196/26 by
64496, and explicitly declare that all other use of prefixes from
this block should be considered invalid. This could be achieved
through the issuing of a ROA for Address=203.0.113.0/24,
maxLength=32, AS = 0 and a second ROA for Address=203.0.113.196/26,
maxLength=26, AS=64496.

By convention, an AS 0 ROA should SHOULD have a maxLength value of 32 for
IPv4 addresses and 128 for IPv6 addresses, although in terms of route
object validation the same outcome would be achieved with any valid
maxLength value, or even if the maxLength element were to be omitted
from the ROA.

Also by convention, an AS 0 ROA should SHOULD be the only ROA issued for a
given address prefix, although again this is not a strict
requirement. An AS 0 ROA can coexist with ROAs that have different
subject AS values, although in such cases the presence of the AS 0
ROA does not alter the route object validation outcome in any way.

4.3. BGP Considerations

This document provides a description of how ROAs could be used by a
BGP speaker.

It is noted that the proposed procedure requires no changes to the
operation of BGP. However, there are a number of considerations
about this approach to origination validation that are relevant to
the operation of a BGP speaker that are not specified here.

These considerations include:

* It is not specified when validation of an advertised prefix
should be performed by a BGP speaker. It is considered to be a
matter of local policy whether it is strictly required to
perform validation at a point prior to loading the object into
the Adj-RIB-In structure [RFC4271], or once the object has been
loaded into Adj-RIB-In, or at a later time that is determined
by a local configuration setting. It is also not specified
whether origination validation should be performed each time a
route object is updated by a peer even when the origin AS has
not altered.

5. Route Object Validation Lifetime

The lifetime "lifetime" of a validation outcome is not specified here.
This specifically refers to the time period
during which the original validation outcome can be still applied, at applied.
The implicit assumption here is that when the
expiration of which validation lifetime
expires the routing object should SHOULD be re-tested for validity. It is

The validation lifetime for a matter of local policy setting as ROA is controlled by the Valid times
specified in the End Entity (EE) Certificate used to whether
a validation outcome be regarded as sign the ROA,
and the valid until times of those certificates in the route
object is withdrawn or further updated, or whether certification path
used to validate the EE Certificate. A ROA validation "expires" at
the Validity To field of a route object should occur the signing EE certificate, or at more frequent intervals.

* It is such a matter of local configuration as to whether ROA
validation
time when there is performed on a per-AS basis rather than no certification path that can validate the ROA.
A ROA issuer may prematurely invalidate a per-BGP
speaker, and ROA by revoking the appropriate mechanisms EE
certificate that was used to support a de-coupled
framework of validation of ROAs and sign the loading of outcomes
into BGP speakers are not considered here.

5. ROA.

6. Security Considerations

ROA issuers should be aware of the validation implication in issuing
a ROA, in that a ROA will implicitly invalidate invalidates all route objects for that
have more specific prefixes with a prefix length greater than
maxLength, and all originating AS's other than the AS listed in the
collection of ROAs. ROAs for this prefix.

A conservative operational practice would be to ensure the issuing of
ROAs for all more specific prefixes with distinct origination AS's
prior to the issuing of ROAs for larger encompassing address blocks,
in order to avoid inadvertent invalidation of valid route objects
during ROA generation.

ROA issuers should also be aware that if they generate a ROA for one
origin AS, then if the prefix is authorised by holder authorises multiple AS's then
ROAs should be generated for all such authorized AS's.

6. IANA Considerations

Dear IANA,

The AS number registry [IANA.AS-Registry] contains the following
annotation against AS 0: "may be use to identify non-routed
networks." Could you please add a 'd' as appropriate to this text?

Thank you,

the authors.

7. Change Log

Note: This section is NOT to be included in final version of this
document.

7.1. Changes -02 to -03

Further Considerations section now has a subsection describing the
assumptions that ROA validation is making about the precise nature of
partial deployment, noting that a ROA has an implicit scope of
application for all prefixes that are equal to or more specific than
the prefix listed in the ROA

Moved the table of validation outcomes from the Security
Considerations section to the section on Further Considerations.

Added consideration about disavowal and the use of an AS 0 ROA and
its interpretation in the context of validation of
originate route objects, and
proposed conventions of use of an AS 0 ROA.

Noted hierarchical dependence of ROA issuance in the Security
Considerations section.

7.2. Changes -01 to -02

Following WG review of the means of specification of denial in
routing authorizations in the context of the RPKI at IETF 74 and IETF
75, objects it appears that there is no general WG support necessary for the use of an
explicit denial object (termed a 'BOA'). The alternative approach,
explored in previous iterations of this draft, used a more restricted
interpretation of a ROA that yielded only "valid" or "unknown"
outcomes (by using "unknown" where "invalid" is used in this revision
of the document). To allow for "invalid" outcomes the draft used the
BOA to undertake the role of a 'disavow' constraint, where a route
object was considered to be "invalid" if it was the subject of a
valid BOA and was not considered to be "valid" by any valid ROA. The
reasons advanced to support the dropping of the BOA was the increased
complexity of RP systems through the use of a second object in route
validation, a potentially confusing mismatch in the interpretation
scope between the ROA and the BOA, where the ROAs scope was limited
to set of prefixes described in the ROA, while the BOA's scope
included all possible more specifics of the prefixes listed in the
BOA, and the ability to reconstruct the semantic equivalent of a BOA
through the use of a ROA that used a restricted-use AS as its asID.
Accordingly, this draft has been revised to remove all references to
the use of an explicit denial object and uses the implicit semantics
of denial in a ROA object.

There appears to be generated for
every such authorized AS.

7. IANA Considerations

[There are no WG interest in consideration of validation in
a "linked" model, where a ROA is bound to the route object that it is
intended to validate. Accordingly this section of the text has also
been dropped from this version. IANA Considerations.]

8. References

8.1. Normative References

[I-D.ietf-sidr-arch]
Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", draft-ietf-sidr-arch (work in
progress), July October 2009.

[I-D.ietf-sidr-roa-format]
Lepinski, M., Kent, S., and D. Kong, "An Infrastructure to
Support Secure Internet Routing",
draft-ietf-sidr-roa-format (work in progress), July
October 2009.

[RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
Addresses and AS Identifiers", RFC 3779, June 2004.

[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.

[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.

8.2. Informative References

[IANA.AS-Registry]
IANA, "IANA Autonomous System Number Registry",
August 2009.
March 2010.

Authors' Addresses

Geoff Huston
Asia Pacific Network Information Centre

Email: gih@apnic.net
George Michaelson
Asia Pacific Network Information Centre

Email: ggm@apnic.net