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

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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 of this ROA
validation function is that either
"invalid". However, the RP has determined that considerations of accommodating environments
of partial adoption of the ROA
is valid in use of ROAs, where only a subset of
validly advertised address prefixes have associated published ROAs
within the context structure of the RPKI, or the ROA is invalid, in which
case the ROA is not imply some modification to be used by the RP.

It is assumed here that ROAs are managed and distributed
independently this
model of positive attestation. In the operation context of BGP itself, and route object
validation it is assumed that once an address prefix is described in
a local BGP
speaker has access to a local cache of ROA, then this ROA speifically encompasses all address prefixes
that are more specific than that described in the complete set of valid ROAs
when performing a ROA. Thus, any
route object validation operation.

Route object validation is defined for more specific address prefix than that described by the following procedure:

1. Select all
any valid ROAs ROA that include does not itself have a ROAIPAddress value that
either matches, or matching valid ROA is a covering aggregate of, the
considered to be "invalid". However, routes objects for address
prefix in the
prefixes that are not fully described by any single ROA, i.e., those
route object.

2. If the set of candidate ROAs is empty then the validation
procedure stops with objects whose address prefixes may be an outcome aggregate of "unknown".

3. If any ROA 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
prefixes described in the a valid ROA, or the route
object's have address prefix prefixes where
there is no intersection with any ROA, and are not matched by any ROA
and are not a more specific prefix of any ROA cannot be reliably classified
as "invalid" in a
ROAIPAddress and the partial deployment scenario. Such route object's prefix length value is
less than or equal to the ROAIPAddress' maxLength value, then
the objects
have a validation procedure stops with an outcome of "valid".

4. Otherwise, the "unknown".

The validation procedure stops with an outcome of
"invalid".

3. Applying Validation Outcomes to BGP Route Selection

Within the framework of the abstract model condition of BGP operation, a
received prefix announcement from route object with a BGP speaking peer is compared to
all announcements for this prefix received from other BGP 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 in section
9.1.1 of the BGP specification [RFC4271]. The local degree 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 policy as to the actions to be
undertaken by a BGP instance 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 policy as to whether "invalid"
route objects are considered to be ineligible for further
consideration in the route selection process. The 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 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, 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 no
AS has been granted any such authority by prefix and an
origin AS when using a single ROA where the ROA'S
subject AS for validation is one that will not be used summarized in a 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
following table:

Prefix matching non-matching
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 be used in a routing context.

In an AS0 ROA to
declare environment of a collection of ROAs, 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 "valid" if any ROA provides 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 "valid" outcome. It
is considered invalid. This could to be achieved
through the issuing of a ROA for Address=203.0.113.0/24,
maxLength=32, AS = 0 "invalid" if one (or more) ROAs provide an
"invalid" outcome and no ROAs provide a second ROA for Address=203.0.113.196/26,
maxLength=26, AS=64496.

By convention, an AS 0 "valid" outcome. It is
considered to be "unknown" when no ROA should have produces either a maxLength value of 32 for
IPv4 addresses and 128 for IPv6 addresses, although in terms of route "valid" or
an "invalid" outcome.

Route object validation is defined by the same outcome would be achieved with any following procedure:

1. Select all valid
maxLength value, ROAs that include a ROAIPAddress value that
either matches, or even if is a covering aggregate of, the maxLength element were to be omitted
from address
prefix in the ROA. Also by convention, an AS 0 ROA should be route object.

2. If the only ROA
issued for a given address prefix, although again this set of candidate ROAs is not a
strict requirement. An AS 0 ROA can coexist empty then the validation
procedure stops with an outcome of "unknown".

3. If any of the selected ROAs has an asID value that have
different subject matches the
origin AS values, although in such cases the presence of the AS 0 ROA does not alter route object, and either the route object validation outcome object's
address prefix precisely matches a ROAIPAddress in
any way.

4.3. BGP Considerations

This document provides the ROA, or
the route object's address prefix is a description more specific prefix of how ROAs could be used by
a
BGP speaker.

It ROAIPAddress, and the route object's prefix length value is noted that
less than or equal to the ROAIPAddress' maxLength value, then
the validation procedure stops with an outcome of "valid".

4. Otherwise, the proposed validation procedure requires no changes stops with an outcome of
"invalid".

3. Applying Validation Outcomes to Route Selection

Within the
operation framework of BGP. However, there are a number the abstract model of considerations
about this approach to origination validation that are relevant to the operation of a inter-
domain routing using BGP speaker that are not specified here.

These considerations include:

* It is not specified when validation of an advertised [RFC4271], a received prefix
should be performed by announcement
from a BGP speaker. It routing peer is considered compared to be all announcements for this prefix
received from other routing peers and a
matter of local policy whether it route selection procedure is strictly required to
perform validation at a point prior
used to loading select the "best" route object into
the Adj-RIB-In structure [RFC4271], or once the from this candidate set.

The route 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 outcome, described in Section 2, of
"unknown", "valid" or "invalid" may be performed each time a
route object is updated by a peer even when used as part of the origin AS has
not altered.

* The lifetime
determination of a validation outcome is not specified here.
This specifically refers to the time period during local degree of preference, in which case the
original validation outcome can be still applied, at the
expiration
local order of preference is as follows:
"valid" is to be preferred over
"unknown", which the routing object should itself is to be re-tested for
validity. preferred over
"invalid".

It is a matter of local routing policy as to the actions to be
undertaken by a 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 setting settings should not result
in "unknown" validation outcomes being considered as sufficient
grounds to whether reject a validation outcome be regarded as valid until the route object is withdrawn or outright from further updated, or whether validation
of consideration
as a route object should occur at more frequent intervals.

* local "best" route.

It is a matter of local configuration routing policy as to whether ROA
validation is performed on a per-AS basis rather than a per-BGP
speaker, and the appropriate mechanisms "invalid" route
objects are considered to support be ineligible for further consideration in
a de-coupled
framework route selection process. A possible consideration here is one of validation
potential circularity of ROAs and dependence. If the loading authoritative
publication point of outcomes
into BGP speakers are not considered here.

5. Security Considerations

ROA issuers should be aware 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 validation implication address prefix described in issuing a ROA, in that then
the repository can only be accessed by the RP once a ROA will implicitly invalidate all route objects for
more specific prefixes with a the
prefix length greater than maxLength,
and all originating AS's other than has been accepted by the AS listed in RP's local routing domain. It is
also noted that the collection propagation time of ROAs.

A conservative operational practice would RPKI objects may be different
to ensure the issuing propagation time of route objects, and that route objects may
be received before the RP's local repository cache picks up the
associated ROAs for all more specific prefixes with distinct origination AS's
prior and recognises them as valid within the RPKI.

4. 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 issuing of ROAs inter-domain
routing system. It is possible for larger encompassing address blocks,
in order a prefix holder to avoid inadvertent invalidation of construct an
authorization where no valid AS has been granted any such authority
to originate a route objects
during ROA generation.

ROA issuers should also be aware that if they generate object for an address prefix. This is acheived
by using a ROA for one
origin AS, then if where the prefix ROA's subject AS is authorised by multiple AS's then
ROAs should one that must never be generated for all such authorized AS's.

6. IANA Considerations

Dear IANA,

The
used in any routing context. Specifically, AS number registry [IANA.AS-Registry] contains 0 is reserved by the following
annotation against AS 0:
IANA such that it "may be use [sic] to identify non-routed
networks." Could you please add networks"
[IANA.AS-Registry].

A ROA with a 'd' as appropriate to this text?

Thank you,

the authors.

7. Change Log

Note: This section 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 to be included used in final version of this
document.

7.1. Changes -02 to -03

Further Considerations section now has a subsection describing the
assumptions that ROA routing context.

The route object validation is making about procedure, described in Section 2, will
provide a "valid" outcome if any ROA matches the precise nature of
partial deployment, noting that address prefix and
origin AS, even if other valid ROAs would provide an "invalid"
validation outcome if used in isolation. Consequently, an 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 implicit scope of
application for all prefixes AS 0 ROA to
declare a default condition that are 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 or describe valid
origination authorizations for 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 prefixes.

By convention, an AS 0 ROA SHOULD have a maxLength value of 32 for
IPv4 addresses and
its interpretation 128 for IPv6 addresses, although in the context of validation terms of route objects, and
proposed conventions of use of
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.

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 SHOULD be the RPKI at IETF 74 and IETF
75, it appears that there is no general WG support only ROA issued for the use of an
explicit denial object (termed a 'BOA'). The alternative approach,
explored in previous iterations of
given address prefix, although again this draft, used a more restricted
interpretation of is not a strict
requirement. An AS 0 ROA can coexist with ROAs that yielded only "valid" or "unknown"
outcomes (by using "unknown" where "invalid" is used have different
subject AS values, although in this revision
of the document). To allow for "invalid" outcomes such cases the draft used presence of the
BOA to undertake AS 0
ROA does not alter 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 validation outcome in any valid ROA. way.

5. Route Object Validation Lifetime

The
reasons advanced to support the dropping "lifetime" of a validation outcome refers to the BOA was time period
during which the increased
complexity of RP systems through original validation outcome can be still applied.
The implicit assumption here is that when the use of a second validation lifetime
expires the routing object in route
validation, SHOULD be re-tested for validity.

The validation lifetime for a potentially confusing mismatch ROA is controlled by the Valid times
specified in the interpretation
scope between End Entity (EE) Certificate used to sign the ROA ROA,
and the BOA, where the ROAs scope was limited
to set valid times of prefixes described those certificates in the ROA, while certification path
used to validate the BOA's scope
included all possible more specifics EE Certificate. A ROA validation "expires" at
the Validity To field of the prefixes listed in signing EE certificate, or at such a
time when there is no certification path that can validate the
BOA, and ROA.
A ROA issuer may prematurely invalidate a ROA by revoking the ability EE
certificate that was used to reconstruct sign the semantic equivalent ROA.

6. Security Considerations

ROA issuers should be aware of a BOA
through the use of validation implication in issuing
a ROA, in that a ROA implicitly invalidates all route objects that used
have more specific prefixes with a restricted-use prefix length greater than
maxLength, and all originating AS's other than the AS as its asID.
Accordingly, listed in the
collection of ROAs for this draft has been revised to remove all references prefix.

A conservative operational practice would be to ensure the use issuing of an explicit denial object and uses
ROAs for all more specific prefixes with distinct origination AS's
prior to the implicit semantics issuing of denial ROAs for larger encompassing address blocks,
in a ROA object.

There appears order to be no WG interest in consideration avoid inadvertent invalidation of validation in
a "linked" model, where valid route objects
during ROA generation.

ROA issuers should also be aware that if they generate a ROA is bound to for one
origin AS, then if the prefix holder authorises multiple AS's to
originate route object that objects it is
intended to validate. Accordingly this section of the text has also
been dropped from this version. necessary for a ROA be generated for
every such authorized AS.

7. IANA Considerations

[There are no 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