One document matched: draft-ietf-sidr-as-migration-04.txt
Differences from draft-ietf-sidr-as-migration-03.txt
SIDR W. George
Internet-Draft Time Warner Cable
Intended status: Standards Track S. Murphy
Expires: April 18, 2016 SPARTA, Inc., a Parsons Company
October 16, 2015
BGPSec Considerations for AS Migration
draft-ietf-sidr-as-migration-04
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
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on April 18, 2016.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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described in the Simplified BSD License.
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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. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
A method of managing a BGP Autonomous System Number (ASN) migration
was just recently described in draft-ietf-idr-as-migration
[I-D.ietf-idr-as-migration]. 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 private ASNs 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 draft-ietf-idr-as-migration
[I-D.ietf-idr-as-migration] 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 ASNs, where eventually one subsumes the other(s).
BGP AS Confederations RFC 5065 [RFC5065] is not enabled between the
ASNs, but configuration knobs are 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. The reason that this migration requires a slightly
different solution in BGPSec than for a standard confederation is
that 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 draft-ietf-idr-as-migration
[I-D.ietf-idr-as-migration]). 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 draft-ietf-idr-as-
migration [I-D.ietf-idr-as-migration] 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
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ASN-migration and BGPSec [I-D.ietf-sidr-bgpsec-protocol] validation
might interact.
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
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). 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,
operational complexity and hardware scaling considerations associated
with maintaining multiple legacy ASN keys on routers throughout the
combined network have been carefully considered. While SPs SHOULD
NOT remain in this transition phase indefinitely because of the
operational complexity and scaling considerations associated with
maintaining multiple legacy ASN keys on routers throughout the
combined network, this is of limited utility as a solution, and so
every effort has been made to keep the additional complexity during
the transition period to a minimum, 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.
3.1. Origin Validation
Route Origin Validation as defined by RFC 6480 [RFC6480] does not
need a unique solution to enable migration, as the existing protocol
and procedure allows for a solution. In the scenario discussed,
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 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-as as defined in RFC 6480 [RFC6480] 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 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
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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 AS64510 to originate a prefix, a new ROA MUST also be
created that authorizes 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 currently no guidance in the
BGPSec protocol specification [I-D.ietf-sidr-bgpsec-protocol] on
whether or not the forward-signed ASN value MUST 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. Assuming that this mismatch
will be allowed by vendor implementations and 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 undesirable as discussed in draft-ietf-idr-as-
migration [I-D.ietf-idr-as-migration].
4. Requirements
In order to be deployable, any solution to the described problem
needs to consider the following requirements, listed in no particular
order:
o BGPSec MUST support AS Migration for both inbound and outbound
route announcements (see Section 3.2.1 and 3.2.2). It SHOULD do
this without reducing BGPSec's protections for route path
o MUST NOT require any reconfiguration on the remote eBGP neighbor
(CE)
o SHOULD confine configuration changes to the migrating PEs e.g.
can't require global configuration changes to support migration
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 3 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"
[I-D.ietf-idr-as-migration] 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 knobs detailed in draft-ietf-
idr-as-migration [I-D.ietf-idr-as-migration]). 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
implementation 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 proposes
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
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will result in a properly secured AS Path in the affected route
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 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
above-referenced draft). 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 knobs as discussed in
draft-ietf-idr-as-migration [I-D.ietf-idr-as-migration], 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 knobs (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 implementation
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], routers that receive updates from
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 implementation. In
similar fashion, any route-reflectors in the path of these updates
MUST reflect them transparently to their 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 draft-ietf-idr-as-migration
[I-D.ietf-idr-as-migration] 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 knobs 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 AS, which is being subsumed by AS64500, the "keep" AS.
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.
George & Murphy Expires April 18, 2016 [Page 13]
Internet-Draft BGPSec-as-migration October 2015
7. IANA Considerations
This memo includes no request to IANA.
8. Security Considerations
This document 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.
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 this is not fundamentally altering the
existing security risks for BGPSec.
9. References
9.1. Normative References
[I-D.ietf-idr-as-migration]
George, W. and S. Amante, "Autonomous System Migration
Mechanisms and Their Effects on the BGP AS_PATH
Attribute", draft-ietf-idr-as-migration-06 (work in
progress), July 2015.
[I-D.ietf-sidr-bgpsec-protocol]
Lepinski, M., "BGPsec Protocol Specification", draft-ietf-
sidr-bgpsec-protocol-13 (work in progress), July 2015.
[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>.
George & Murphy Expires April 18, 2016 [Page 14]
Internet-Draft BGPSec-as-migration October 2015
9.2. 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
Time Warner Cable
13820 Sunrise Valley Drive
Herndon, VA 20171
US
Phone: +1 703-561-2540
Email: wesley.george@twcable.com
Sandy Murphy
SPARTA, Inc., a Parsons Company
7110 Samuel Morse Drive
Columbia, MD 21046
US
Phone: +1 443-430-8000
Email: sandy@tislabs.com
George & Murphy Expires April 18, 2016 [Page 15]
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