Internet DRAFT - draft-ietf-sidr-as-migration
draft-ietf-sidr-as-migration
SIDR W. George
Internet-Draft
Intended status: Standards Track S. Murphy
Expires: June 10, 2017 SPARTA, Inc., a Parsons Company
December 7, 2016
BGPSec Considerations for AS Migration
draft-ietf-sidr-as-migration-06
Abstract
This document discusses considerations and methods for supporting and
securing a common method for AS-Migration within the BGPSec protocol.
Status of This Memo
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Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
1.2. Documentation note . . . . . . . . . . . . . . . . . . . 3
2. General Scenario . . . . . . . . . . . . . . . . . . . . . . 3
3. RPKI Considerations . . . . . . . . . . . . . . . . . . . . . 3
3.1. Origin Validation . . . . . . . . . . . . . . . . . . . . 4
3.2. Path Validation . . . . . . . . . . . . . . . . . . . . . 5
3.2.1. Outbound announcements (PE-->CE) . . . . . . . . . . 5
3.2.2. Inbound announcements (CE-->PE) . . . . . . . . . . . 6
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Outbound (PE->CE) . . . . . . . . . . . . . . . . . . . . 8
5.2. Inbound (CE->PE) . . . . . . . . . . . . . . . . . . . . 8
5.3. Other considerations . . . . . . . . . . . . . . . . . . 9
5.4. Example . . . . . . . . . . . . . . . . . . . . . . . . . 9
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. Note for RFC Editor . . . . . . . . . . . . . . . . . . . . . 14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1. Normative References . . . . . . . . . . . . . . . . . . 14
10.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
A method of managing a BGP Autonomous System Number (ASN) migration
is described in RFC7705 [RFC7705]. Since it concerns the handling of
AS_PATH attributes, it is necessary to ensure that the process and
features are properly supported in BGPSec
[I-D.ietf-sidr-bgpsec-protocol], because BGPSec is explicitly
designed to protect against changes in the BGP AS_PATH, whether by
choice, by misconfiguration, or by malicious intent. It is critical
that the BGPSec protocol framework is able to support this
operationally necessary tool without creating an unacceptable
security risk or exploit in the process.
1.1. 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].
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1.2. Documentation note
This document uses Autonomous System Numbers (ASNs) from the range
reserved for documentation as described in RFC 5398 [RFC5398]. In
the examples used here, they are intended to represent Globally
Unique ASNs, not ASNs reserved for private use as documented in RFC
1930 [RFC1930] section 10.
2. General Scenario
This document assumes that the reader has read and understood the ASN
migration method discussed in RFC7705 [RFC7705] including its
examples (see section 2 of the referenced document), as they will be
heavily referenced here. The use case being discussed in the
referenced document is as follows: For whatever the reason, a
provider is in the process of merging two or more ASes, where
eventually one subsumes the other(s). BGP AS Confederations RFC 5065
[RFC5065] is not enabled between the ASes, but a mechanism is being
used to modify BGP's default behavior and allow the migrating
Provider Edge router (PE) to masquerade as the old ASN for the
Provider Edge to Customer Edge (PE-CE) eBGP session, or to manipulate
the AS_PATH, or both. While BGPSec [I-D.ietf-sidr-bgpsec-protocol]
does have a method to handle standard confederation implementations,
it is not applicable in this exact case. This migration requires a
slightly different solution in BGPSec than for a standard
confederation because unlike in a confederation, eBGP peers may not
be peering with the "correct" external ASN, and the forward-signed
updates are for a public ASN, rather than a private one, so there is
no expectation that the BGP speaker would strip the affected
signatures before propagating the route to its eBGP neighbors.
In the following examples (section 5.4) (Section 5.4), AS64510 is
being subsumed by AS64500, and both ASNs represent a Service Provider
(SP) network (see Figures 1 & 2 in RFC7705 [RFC7705]). AS64496 and
64499 represent end customer networks. References to PE, CE, and P
routers mirror the diagrams and references in the above cited draft.
3. RPKI Considerations
The methods and implementation discussed in RFC7705 [RFC7705] are
widely used during network integrations resulting from mergers and
acquisitions, as well as network redesigns, and therefore it is
necessary to support this capability on any BGPSec-enabled routers/
ASNs. What follows is a discussion of the potential issues to be
considered regarding how ASN-migration and BGPSec
[I-D.ietf-sidr-bgpsec-protocol] validation might interact.
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One of the primary considerations for this document and migration is
that service providers (SPs) rarely stop after one
merger/acquisition/divestiture, and end up accumulating several
legacy ASNs over time. Since they are using methods to migrate that
are transparent to and therefore do not require coordination with
customers, they do not have a great deal of control over the length
of the transition period as they might with something completely
under their administrative control (e.g. a key roll). Because they
are not forcing a simultaneous migration (i.e. both ends switch to
the new ASN at an agreed-upon time), there is no incentive for a
given customer to complete the move from the old ASN to the new.
This leaves many SPs with multiple legacy ASNs which don't go away
very quickly, if at all. As solutions were being proposed for RPKI
implementations to solve this transition case, the WG carefully
considered operational complexity and hardware scaling issues
associated with maintaining multiple legacy ASN keys on routers
throughout the combined network. While SPs who choose to remain in
this transition phase indefinitely invite added risks because of the
operational complexity and scaling considerations associated with
maintaining multiple legacy ASN keys on routers throughout the
combined network, saying "don't do this" is of limited utility as a
solution. As a result, this solution attempts to minimize the
additional complexity during the transition period, on the assumption
that it will likely be protracted. Note: While this document
primarily discusses service provider considerations, it is not solely
applicable to SPs, as enterprises often migrate between ASNs using
the same functionality. What follows is a discussion of origin and
path validation functions and how they interact with ASN migrations.
3.1. Origin Validation
Route Origin Validation as defined by RFC 6480 [RFC6480] does not
modification to enable AS migration, as the existing protocol and
procedure allows for a solution. In the scenario discussed in RFC
7705 [RFC7705], AS64510 is being replaced by AS64500. If there are
any existing routes originated by AS64510 on the router being moved
into the new ASN, this simply requires generating new Route
Origination Authorizations (ROAs) for the routes with the new ASN and
treating them as new routes to be added to AS64500. However, we also
need to consider the situation where one or more other PEs are still
in AS64510, and are originating one or more routes that may be
distinct from any that the router under migration is originating.
PE1 (which is now a part of AS64500 and instructed to use Replace Old
AS as defined in RFC 7705 [RFC7705] to remove AS64510 from the path)
needs to be able to properly handle routes originated from AS64510.
If the route now shows up as originating from AS64500, any downstream
peers' validation check will fail unless a ROA is *also* available
for AS64500 as the origin ASN. In addition to generating a ROA for
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65400 for any prefixes originated by the router being moved, it may
be necessary to generate ROAs for 65400 for prefixes that are
originating on routers still in 65410, since the AS replacement
function will change the origin AS in some cases. This means that
there will be multiple ROAs showing different ASes authorized to
orignate the same prefixes until all routers originating prefixes
from AS64510 are migrated to AS64500. Multiple ROAs of this type are
permissible per RFC 6480 [RFC6480] section 3.2, and so managing
origin validation during a migration like this is merely applying the
defined case where a set of prefixes are originated from more than
one ASN. Therefore, for each ROA that authorizes the old ASN (e.g.
AS64510) to originate a prefix, a new ROA MUST also be created that
authorizes the replacing ASN (e.g. AS64500) to originate the same
prefix.
3.2. Path Validation
BGPSec Path Validation requires that each router in the AS Path
cryptographically sign its update to assert that "Every AS on the
path of ASes listed in the update message has explicitly authorized
the advertisement of the route to the subsequent AS in the path."
(see intro of [I-D.ietf-sidr-bgpsec-protocol]) Since the referenced
AS migration technique is explicitly modifying the AS_PATH between
two eBGP peers who are not coordinating with one another (are not in
the same administrative domain), no level of trust can be assumed,
and therefore it may be difficult to identify legitimate manipulation
of the AS_PATH for migration activities when compared to manipulation
due to misconfiguration or malicious intent.
3.2.1. Outbound announcements (PE-->CE)
When PE1 is moved from AS64510 to AS64500, it will be provisioned
with the appropriate keys for AS64500 to allow it to forward-sign
routes using AS64500. However, there is no guidance in the BGPSec
protocol specification [I-D.ietf-sidr-bgpsec-protocol] on whether or
not the forward-signed ASN value is required to match the configured
remote AS to validate properly. That is, if CE1's BGP session is
configured as "remote AS 64510", the presence of "local AS 64510" on
PE1 will ensure that there is no ASN mismatch on the BGP session
itself, but if CE1 receives updates from its remote neighbor (PE1)
forward-signed from AS64500, there is no guidance as to whether the
BGPSec validator on CE1 still considers those valid by default.
RFC4271 [RFC4271] section 6.3 mentions this match between the ASN of
the peer and the AS_PATH data, but it is listed as an optional
validation, rather than a requirement. We cannot assume that this
mismatch will be allowed by vendor implementations and thus using it
as a means to solve this migration case is likely to be problematic.
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3.2.2. Inbound announcements (CE-->PE)
Inbound is more complicated, because the CE doesn't know that PE1 has
changed ASNs, so it is forward-signing all of its routes with
AS64510, not AS64500. The BGPSec speaker cannot manipulate previous
signatures, and therefore cannot manipulate the previous AS Path
without causing a mismatch that will invalidate the route. If the
updates are simply left intact, the ISP would still need to publish
and maintain valid and active public-keys for AS 64510 if it is to
appear in the BGPSec_Path_Signature in order that receivers can
validate the BGPSEC_Path_Signature arrived intact/whole. However, if
the updates are left intact, this will cause the AS Path length to be
increased, which is unacceptable as discussed in RFC7705 [RFC7705].
4. Requirements
In order to be deployable, any solution to the described problem
needs to consider the following requirements, listed in no particular
order. BGPSec:
o MUST support AS Migration for both inbound and outbound route
announcements (see Section 3.2.1 and 3.2.2) without reducing
BGPSec's protections for route path
o MUST NOT require any reconfiguration on the remote eBGP neighbor
(CE)
o SHOULD NOT require global (i.e. network-wide) configuration
changes to support migration. The goal is to limit required
configuration changes to the devices (PEs) being migrated.
o MUST NOT lengthen AS Path during migration
o MUST operate within existing trust boundaries e.g. can't expect
remote side to accept pCount=0 (see Section 4.2 of
[I-D.ietf-sidr-bgpsec-protocol]) from untrusted/non-confed
neighbor
5. Solution
As noted in [I-D.ietf-sidr-bgpsec-protocol], section 4.2, BGPSec
already has a solution for hiding ASNs where increasing the AS Path
length is undesirable. So a simple solution would be to retain the
keys for AS64510 on PE1, and forward-sign towards CE1 with AS64510
and pCount=0. However, this would mean passing a pCount=0 between
two ASNs that are in different administrative and trust domains such
that it could represent a significant attack vector to manipulate
BGPSec-signed paths. The expectation for legitimate instances of
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pCount=0 (to make a route-server that is not part of the transit path
invisible) is that there is some sort of existing trust relationship
between the operators of the route-server and the downstream peers
such that the peers could be explicitly configured by policy to
accept pCount=0 announcements only on the sessions where they are
expected. For the same reason that things like "Local AS" [RFC7705]
are used for ASN migration without end customer coordination, it is
unrealistic to assume any sort of coordination between the SP and the
administrators of CE1 to ensure that they will by policy accept
pCount=0 signatures during the transition period, and therefore this
is not a workable solution.
A better solution presents itself when considering how to handle
routes coming from the CE toward the PE, where the routes are
forward-signed to AS64510, but will eventually need to show AS64500
in the outbound route announcement. Because both AS64500 and AS64510
are in the same administrative domain, a signature from AS64510
forward-signed to AS64500 with pCount=0 would be acceptable as it
would be within the appropriate trust boundary so that each BGP
speaker could be explicitly configured to accept pCount=0 where
appropriate between the two ASNs. At the very simplest, this could
potentially be used at the eBGP boundary between the two ASNs during
migration. Since the AS_PATH manipulation described above usually
happens at the PE router on a per-session basis, and does not happen
network-wide simultaneously, it is not generally appropriate to apply
this AS hiding technique across all routes exchanged between the two
ASNs, as it may result in routing loops and other undesirable
behavior. Therefore the most appropriate place to implement this is
on the local PE that still has eBGP sessions with peers expecting to
peer with AS64510 (using the transition mechanisms detailed in
RFC7705 [RFC7705]). Since that PE has been moved to AS64500, it is
not possible for it to forward-sign AS64510 with pCount=0 without
some minor changes to the BGPSec behavior to address this use case.
AS migration is using AS_PATH and remote AS manipulation to act as if
a PE under migration exists simultaneously in both ASNs even though
it is only configured with one global ASN. This document describes
applying a similar technique to the BGPSec signatures generated for
routing updates processed through this migration machinery. Each
routing update that is received from or destined to an eBGP neighbor
that is still using the old ASN (64510) will be signed twice, once
with the ASN to be hidden and once with the ASN that will remain
visible. In essence, we are treating the update as if the PE had an
internal BGP hop and the update was passed across an eBGP session
between AS64500 and AS64510, configured to use and accept pCount=0,
while eliminating the processing and storage overhead of creating an
actual eBGP session between the two ASNs within the PE router. This
will result in a properly secured AS Path in the affected route
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updates, because the PE router will be provisioned with valid keys
for both AS64500 and AS64510. An important distinction here is that
while AS migration under standard BGP4 is manipulating the AS_PATH
attribute, BGPSec uses an attribute called the Secure_Path (see
Section 3.1 of [I-D.ietf-sidr-bgpsec-protocol]), and BGPSec capable
neighbors do not exchange AS_PATH information in their route
announcements. However, a BGPSec neighbor peering with a non-BGPSec-
capable neighbor will use the information found in Secure_Path to
reconstruct a standard AS_PATH for updates sent to that neighbor.
Unlike in Secure_Path where the ASN to be hidden is still present,
but ignored when considering AS Path (due to pCount=0), when
reconstructing an AS_PATH for a non-BGPSec neighbor, the pCount=0
ASNs will not appear in the AS_PATH at all (see section 4.4 of the
[I-D.ietf-sidr-bgpsec-protocol]). This document is not changing
existing AS_PATH reconstruction behavior, merely highlighting it for
clarity.
The procedure to support AS Migration in BGPSec is slightly different
depending on whether the PE under migration is receiving the routes
from one of its eBGP peers ("inbound" as in section 3.2.2) or
destined toward the eBGP peers ("outbound" as in section 3.2.1).
5.1. Outbound (PE->CE)
When a PE router receives an update destined for an eBGP neighbor
that is locally configured with AS-migration mechanisms as discussed
in RFC7705 [RFC7705], it MUST generate a valid BGPSec signature as
defined in [I-D.ietf-sidr-bgpsec-protocol] for _both_ configured
ASNs. It MUST generate a signature from the new (global) ASN forward
signing to the old (local) ASN with pCount=0, and then it MUST
generate a forward signature from the old (local) ASN to the target
eBGP ASN with pCount=1 as normal.
5.2. Inbound (CE->PE)
When a PE router receives an update from an eBGP neighbor that is
locally configured with AS-migration mechanisms (i.e. the opposite
direction of the previous route flow), it MUST generate a signature
from the old (local) ASN forward signing to the new (global) ASN with
pCount=0. It is not necessary to generate the second signature from
the new (global) ASN because the Autonomous System Border Router
(ASBR) will generate that when it forward signs towards its eBGP
peers as defined in normal BGPSec operation. Note that a signature
is not normally added when a routing update is sent across an iBGP
session. The requirement to sign updates in iBGP represents a change
to the normal behavior for this specific AS-migration scenario only.
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5.3. Other considerations
In this case, the PE is adding BGPSec attributes to routes received
from or destined to an iBGP neighbor, and using pCount=0 to mask
them. While this is not prohibited by BGPSec
[I-D.ietf-sidr-bgpsec-protocol], BGPSec-capable routers that receive
updates from BGPSec-enabled iBGP neighbors MUST accept updates with
new (properly-formed) BGPSec attributes, including the presence of
pCount=0 on a previous signature, or they will interfere with this
method. In similar fashion, any BGPSec-capable route-reflectors in
the path of these updates MUST reflect them transparently to their
BGPSec-capable clients.
In order to secure this set of signatures, the PE router MUST be
provisioned with valid keys for _both_ configured ASNs (old and new),
and the key for the old ASN MUST be kept valid until all eBGP
sessions are migrated to the new ASN. Downstream neighbors will see
this as a valid BGPSec path, as they will simply trust that their
upstream neighbor accepted pCount=0 because it was explicitly
configured to do so based on a trust relationship and business
relationship between the upstream and its neighbor (the old and new
ASNs).
Additionally, section 4 of RFC7705 [RFC7705] discusses methods in
which AS migrations can be completed for iBGP peers such that a
session between two routers will be treated as iBGP even if the
neighbor ASN is not the same ASN on each peer's global configuration.
As far as BGPSec is concerned, this requires the same procedure as
when the routers migrating are applying AS migration mechanisms to
eBGP peers, but the router functioning as the "ASBR" between old and
new ASN is different. In eBGP, the router being migrated has direct
eBGP sessions to the old ASN and signs from old ASN to new with
pCount=0 before passing the update along to additional routers in its
global (new) ASN. In iBGP, the router being migrated is receiving
updates (that may have originated either from eBGP neighbors or other
iBGP neighbors) from its downstream neighbors in the old ASN, and
MUST sign those updates from old ASN to new with pCount=0 before
sending them on to other peers.
5.4. Example
The following example will illustrate the method being used above.
As with previous examples, PE1 is the router being migrated, AS64510
is the old ASN, which is being subsumed by AS64500, the ASN to be
permanently retained. 64505 is another external peer, used to
demonstrate what the announcements will look like to a third party
peer that is not part of the migration. Some additional notation is
used to delineate the details of each signature as follows:
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The origin BGPSEC signature attribute takes the form: sig(<Target
ASN>, Origin ASN, pCount, NLRI Prefix) key
Intermediate BGPSEC signature attributes take the form: sig(<Target
ASN>, Signer ASN, pCount, <most recent sig field>) key
Equivalent AS_PATH refers to what the AS_PATH would look like if it
was reconstructed to be sent to a non-BGPSec peer, while Secure_Path
shows the AS Path as represented between BGPSec peers.
Note: The representation of signature attribute generation is being
simplified here somewhat for the sake of brevity; the actual details
of the signing process are as described Sections 4.1 and 4.2 in
[I-D.ietf-sidr-bgpsec-protocol]. For example, what is covered by the
signature also includes Flags, Algorithm Suite ID, NLRI length, etc.
Also, the key is not carried in the update, instead the SKI is
carried.
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Before Merger
64505
|
ISP B ISP A
CE-1 <--- PE-1 <------------------- PE-2 <--- CE-2
64496 Old_ASN: 64510 Old_ASN: 64500 64499
CE-2 to PE-2: sig(<64500>, O=64499, pCount=1, N)K_64499-CE2 [sig1]
Equivalent AS_PATH=(64499)
Secure_Path=(64499)
length=sum(pCount)=1
PE-2 to 64505: sig(<64505>, 64500, pCount=1, <sig1>)K_64500-PE2 [sig2]
sig(<64500>, 64499, pCount=1, N)K_64499-CE2 [sig1]
Equivalent AS_PATH=(64500,64499)
Secure_Path=(64500,64499)
length=sum(pCount)=2
PE-2 to PE-1: sig(<64510>, 64500, pCount=1, <sig1>)K_64500-PE2 [sig3]
sig(<64500>, 64499, pCount=1, N)K_64499-CE2 [sig1]
Equivalent AS_PATH=(64500,64499)
Secure_Path=(64500,64499)
length=sum(pCount)=2
PE-1 to CE-1: sig(<64496>, 64510, pCount=1, <sig3>)K_64510-PE1 [sig4]
sig(<64510>, 64500, pCount=1, <sig1>)K_64500-PE2 [sig3]
sig(<64500>, 64499, pCount=1, N)K_64499-CE2 [sig1]
Equivalent AS_PATH= (64510,64500,64499)
Secure_Path=(64510,64500,64499)
length=sum(pCount)=3
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Migrating, route flow outbound PE-1 to CE-1
64505
|
ISP A' ISP A'
CE-1 <--- PE-1 <------------------- PE-2 <--- CE-2
64496 Old_ASN: 64510 Old_ASN: 64500 64499
New_ASN: 64500 New_ASN: 64500
CE-2 to PE-2: sig(<64500>, 64499, pCount=1, N)K_64499-CE2 [sig11]
Equivalent AS_PATH=(64499)
Secure_Path=(64499)
length=sum(pCount)=1
PE-2 to 64505: sig(<64505>, 64500, pCount=1, <sig11>)K_64500-PE2 [sig12]
sig(<64500>, 64499, pCount=1, N)K_64499-CE2 [sig11]
Equivalent AS_PATH=(64500,64499)
Secure_Path=(64500,64499)
length=sum(pCount)=2
PE-2 to PE-1: sig(<64500>, 64499, pCount=1, N)K_64499-CE2 [sig11]
Equivalent AS_PATH=(64499)
Secure_Path=(64499)
length=sum(pCount)=1
#PE-2 sends to PE-1 (in iBGP) the exact same update
#as received from AS64499.
PE-1 to CE-1: sig(<64496>, 64510, pCount=1, <sig13>)K_64510-PE1 [sig14]
sig(<64510>, 64500, pCount=0, <sig11>)K_64500-PE2 [sig13]
sig(<64500>, 64499, pCount=1, N)K_64499-CE2 [sig11]
Equivalent AS_PATH=(64510,64499)
Secure_Path=(64510, 64500(pCount=0),64499)
length=sum(pCount)=2 (length is NOT 3)
#PE1 adds [sig13] acting as AS64500
#PE1 accepts [sig13] with pCount=0 acting as AS64510,
#as it would if it received sig13 from an eBGP peer
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Migrating, route flow inbound CE-1 to PE-1
64505
|
ISP A' ISP A'
CE-1 ---> PE-1 -------------------> PE-2 ---> CE-2
64496 Old_ASN: 64510 Old_ASN: 64500 64499
New_ASN: 64500 New_ASN: 64500
CE-1 to PE-1: sig(<64510>, 64496, pCount=1, N)K_64496-CE1 [sig21]
Equivalent AS_PATH=(64496)
Secure_Path=(64496)
length=sum(pCount)=1
PE-1 to PE-2: sig(<64500>, 64510, pCount=0, <sig21>)K_64510-PE1 [sig22]
sig(<64510>, 64496, pCount=1, N)K_64496-CE1 [sig21]
Equivalent AS_PATH=(64496)
Secure_Path=(64510 (pCount=0),64496)
length=sum(pCount)=1 (length is NOT 2)
#PE1 adds [sig22] acting as AS64510
#PE1 accepts [sig22] with pCount=0 acting as AS64500,
#as it would if it received sig22 from an eBGP peer
PE-2 to 64505: sig(<64505>, 64500, pCount=1, <sig22>)K_64500-PE2 [sig23]
sig(<64500>, 64510, pCount=0, <sig21>)K_64510-PE1 [sig22]
sig(<64510>, 64496, pCount=1, N)K_64496-CE1 [sig21]
Equivalent AS_PATH=(64500,64496)
Secure_Path=(64500,64510 (pCount=0), 64496)
length=sum(pCount)=2 (length is NOT 3)
PE-2 to CE-2: sig(<64499>, 64500, pCount=1, <sig22>)K_64500-PE2 [sig24]
sig(<64500>, 64510, pCount=0, <sig21>)K_64510-PE1 [sig22]
sig(<64510>, 64496, pCount=1, N)K_64496-CE1 [sig21]
Equivalent AS_PATH=(64500,64496)
Secure_Path=(64500, 64510 (pCount=0), 64496)
length=sum(pCount)=2 (length is NOT 3)
6. Acknowledgements
Thanks to Kotikalapudi Sriram, Shane Amante, Warren Kumari, Terry
Manderson, Keyur Patel, Alia Atlas, and Alvaro Retana for their
review comments.
Additionally, the solution presented in this document is an amalgam
of several SIDR interim meeting discussions plus a discussion at
IETF85, collected and articulated thanks to Sandy Murphy.
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Internet-Draft BGPSec-as-migration December 2016
7. IANA Considerations
This memo includes no request to IANA.
8. Note for RFC Editor
This section can be removed prior to publication.
RFC Editor - this document updates draft-ietf-sidr-bgpsec-protocol,
but the normal Updates= metadata method cannot be used until an RFC
number is assigned to the document being updated. Please ensure that
the metadata is corrected when the bgpsec-protocol document has been
assigned an RFC number.
9. Security Considerations
RFC7705 [RFC7705] discusses a process by which one ASN is migrated
into and subsumed by another. Because this process involves
manipulating the AS_Path in a BGP route to make it deviate from the
actual path that it took through the network, this migration process
is attempting to do exactly what BGPSec is working to prevent.
BGPSec MUST be able to manage this legitimate use of AS_Path
manipulation without generating a vulnerability in the RPKI route
security infrastructure, and this document was written to define the
method by which the protocol can meet this need.
The solution discussed above is considered to be reasonably secure
from exploitation by a malicious actor because it requires both
signatures to be secured as if they were forward-signed between two
eBGP neighbors. This requires any router using this solution to be
provisioned with valid keys for both the migrated and subsumed ASN so
that it can generate valid signatures for each of the two ASNs it is
adding to the path. If the AS's keys are compromised, or zero-length
keys are permitted, this does potentially enable an AS_PATH
shortening attack, but these are existing security risks for BGPSec.
10. References
10.1. Normative References
[I-D.ietf-sidr-bgpsec-protocol]
Lepinski, M. and K. Sriram, "BGPsec Protocol
Specification", draft-ietf-sidr-bgpsec-protocol-20 (work
in progress), December 2016.
George & Murphy Expires June 10, 2017 [Page 14]
Internet-Draft BGPSec-as-migration December 2016
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC7705] George, W. and S. Amante, "Autonomous System Migration
Mechanisms and Their Effects on the BGP AS_PATH
Attribute", RFC 7705, DOI 10.17487/RFC7705, November 2015,
<http://www.rfc-editor.org/info/rfc7705>.
10.2. Informative References
[RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation,
selection, and registration of an Autonomous System (AS)",
BCP 6, RFC 1930, DOI 10.17487/RFC1930, March 1996,
<http://www.rfc-editor.org/info/rfc1930>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<http://www.rfc-editor.org/info/rfc4271>.
[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
System Confederations for BGP", RFC 5065,
DOI 10.17487/RFC5065, August 2007,
<http://www.rfc-editor.org/info/rfc5065>.
[RFC5398] Huston, G., "Autonomous System (AS) Number Reservation for
Documentation Use", RFC 5398, DOI 10.17487/RFC5398,
December 2008, <http://www.rfc-editor.org/info/rfc5398>.
[RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480,
February 2012, <http://www.rfc-editor.org/info/rfc6480>.
Authors' Addresses
Wesley George
Email: wesgeorge@puck.nether.net
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Sandy Murphy
SPARTA, Inc., a Parsons Company
7110 Samuel Morse Drive
Columbia, MD 21046
US
Phone: +1 443-430-8000
Email: sandy@tislabs.com
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