One document matched: draft-white-sobgparchitecture-00.txt
Network Working Group Russ White
Internet Draft (editor)
Expiration Date: October 2004 Cisco Systems
File Name: draft-white-sobgparchitecture-00.txt April 2004
Architecture and Deployment Considerations for Secure Origin BGP (soBGP)
draft-white-sobgparchitecture-00.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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. Internet Drafts may be updated, replaced, or obsoleted by
other documents at any time. It is not appropriate to use Internet
Drafts as reference material or to cite them other than as a "working
draft" or "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.
Abstract
There is a great deal of concern over the security of the Border
Gateway Protocol, which is used to provide routing information to the
Internet and other large internetworks. This draft provides an
architecture for a secure distributed registry of routing information
to address these concerns. The draft begins with an overview of the
operation of this system, and then follows with various deployment
scenerios, starting with what we believe will be the most common
deployment option.
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1. Background
There are two fundamental pieces of a routing system that need to be
secured:
o Adjacencies between devices running the routing protocol
o Information carried within the routing protocol.
While security between BGP [BGP] speakers has been addressed in a
number of ways, including cryptographic authentication [BGP-MD5] and
limiting the attack radius through TTL mechanisms [GTSH], security
for the information carried within BGP is not considered a solved
problem.
This draft proposes a possible solution to securing the information
within BGP, using the certificates and protocol extensions proposed
in [SOBGP-BGPTRANSPORT], [SOBGP-CERTIFICATE], and [SOBGP-RADIUS].
A large number of people contributed to this draft; we've tried to
include all of them here (but might have missed a few): James Ng, Tim
Gage, Alvaro Retana, Dave Cook, Brian Weis, and Iljitsch van Beijnum.
2. General Theory
soBGP provides a secure registry mechanism against which a BGP
speaker can check:
o The authorization of the AS listed as the originating AS in any
received update to advertise reachability to the prefix listed
in the update.
o The validity of the AS Path contained in the update.
We use the term validity in reference to the AS Path, in this docu-
ment, to indicate the plausibility of the AS Path listed. As shown in
[PATH-CONSIDER], it isn't possible to communicate authorization
through an AS Path; only the existence or nonexistance of the AS Path
listed can be proven.
soBGP operates by distributing a set of signed certificates,
described in [SOBGP-CERTIFICATE], containing the information required
to validate the two pieces of information given above. These certifi-
cates MAY be distributed using the mechanisms described in [SOBGP-
BGPTRANSPORT], or some other mechanism. Once these certificates have
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been received and processed (signatures validated, etc, as described
in [SOBGP-CERTIFICATE], they form a database containing:
o A listing of IP address blocks and the AS authorized to ori-
ginate them.
o Policies related to specific prefixes and blocks of addresses.
o A list of autonomous systems connected to each autonomous system
within the internetwork. This connection list is used to build a
graph of AS interconnectivity within the internetwork, as
described in the section Building the AS Connectivity Graph,
below.
This effectively forms a secure registry of routing information which
can be used to check the validity of routing information received
from BGP peers. This database is termed the "authorization database."
No assumption about the location of the authorization database is
made within this document.
When soBGP is supported, a BGP speaker MUST have access to the
authorization database. Possible methods of access include:
o Have a local copy of this authorization database, and perform
the checkes described later in this document against that local
database.
o Pass received routing information to a locally maintained server
for validation against that server's copy of the authorization
database.
o Accept filters built from a copy of the authorization database
contained on a locally maintained server.
As BGP updates are processed, a security preference is assigned to
each prefix, as described further in the Security Preference section
of this document. BGP update processing is described in the Receiving
and Processing Updates section of this document.
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3. soBGP Operation
Each section below provides detailed information on some aspect of
soBGP operation.
3.1. The Security Preference
Rather than simply noting a given prefix should be dropped (not
trusted) or retained (trusted), soBGP extends the concept of locally
generated and maintained policy in BGP by assigning each prefix a
Security Preference. This allows the local operator to drop prefixes
not meeting certain security criteria, while simply lowering their
preference for prefixes meeting some security criteria. This allows
operators some flexibility in their implementation of security poli-
cies, especially as the security system is being tested, or while the
security system isn't fully deployed.
While the amount by which the Security Preference is increased or
decreased for any operation described in this draft is locally signi-
ficant to the autonomous system. All devices processing routes
against soBGP information MUST use the same mechanisms and values of
the Security Preference to ensure consistent routing within the auto-
nomous system.
If the Security Preference is set to a value precluding a route from
further consideration in the decision process, the route should be
discarded at that point, rather than continuing with the decision
process.
The Security Preference value may be used to select among different
routes for the same prefix; the higher value MUST be preferred. Any
of the following methods may be used:
A Consider the Security Preference prior to calculating the degree
of preference [BGP] for a prefix.
B Assign the value of the Security Preference to any of the attri-
butes used in the Decision Process [BGP]. Care must be taken
with attributes for which the lower value is preferred.
C Use a Cost Community [COST] and its associated methods to con-
sider the Security Preference at any step in the Decision Pro-
cess [BGP] without overloading other attributes. Care must be
taken as the lowest value in a Cost Community is preferred.
The method selected MUST be consistent through the local Autonomous
System.
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3.2. Building the AS Connectivity Graph
Each ASPolicyCert advertised by a member of the internetwork contains
a list of the autonomous systems the advertising AS is connected to,
along with possible policy information about that connection. From
this information, a graph of AS connectivity within the internetwork
is built.
Any AS can be used as the starting point for building this graph,
thus multiple disconnected graphs (representing section of the inter-
network running soBGP and providing interconnection information) are
possible. If every AS within the internetwork is providing intercon-
nection information, one graph can be built containing all the
internetwork's interconnections.
The process of creating this graph is:
o Examine the list of connected autonomous systems advertised by
the current AS.
o Examine the ASPolicyCert of each AS the current AS is advertis-
ing as connected, and determine if that AS is advertising a con-
nection back to the current AS. This is termed the two way con-
nectivity check.
o If the two way connectivity check passes, the connection SHOULD
be added to the interconnection graph, and marked as trustable.
o If the two way connectivity check fails, the connection MAY be
added to the interconnection graph, but marked so a lower secu-
rity preference will be assigned to AS_PATHs traversing this
link.
o Repeat this process for each ASPolicyCert in the authorization
database.
The resulting graph is called the internetwork graph.
3.3. Validating Routing Information
For each prefix within a given BGP UPDATE message:
o The local authorization database is examined, and the AuthCert
with the longest prefix length encompassing the range of
addresses described by the prefix is chosen.
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o If there is no entry in the local authorization database which
encompasses the range of addresses described by the prefix, then
the route is said to be unverified, and should be handled
according to local policy (either discarded, or have its secu-
rity preference lowered). The rest of this process is ignored in
these cases.
o The second hop in the AS_PATH attribute is examined.
o If the second hop in the AS_PATH is advertised as connected
by the originating AS, the Security Preference for this pre-
fix SHOULD be increased.
o If the second hop in the AS_PATH is not advertised as con-
nected by the originating AS, the Security Preference for
this prefix SHOULD be decreased.
o If the second hop in the AS_PATH is not advertised as con-
nected by the originating AS and the originator's policy
indicates the second hop MUST be validated, the prefix should
be removed from further consideration.
o The AS_PATH attribute is compared to the internetwork graph.
o If the AS_PATH described is contained within the internetwork
graph, the Security Preference SHOULD be increased.
o If the AS_PATH described is not contained within the inter-
network graph, the Security Preference SHOULD be decreased.
o If the AS_PATH traverses a connection which is only described
by one of the two autonomous systems, this is a one way con-
nection. Local policy may be used to determine if the secu-
rity preference should be increased in this case.
o If the AS_PATH described is not contained within the inter-
network graph, and the originator indicated the AS_PATH MUST
be checked, the prefix should be removed from further con-
sideration.
o The AuthCert chosen at the first step is examined.
o If the authorized AS in the AuthCert matches the originating
AS in the AS_PATH, the Security Preference SHOULD be
increased.
o If the authorized AS in the AuthCert does not mathc the ori-
ginating AS in the AS_PATH, the Security Preference SHOULD be
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set low enough to cause the route to be discarded.
o Other policies contained in the local authorization database
should be applied as directed by the policy.
3.4. Validating Received BGP UPDATES
As BGP UPDATES are received, they may be processed in one of several
ways:
o Each prefix may be validated according to the process outlined
in Validating Routing Information before they are installed in
the ADj-RIB-IN.
o Each prefix may be validated according to the process outlined
in Validating Routing Information after they are installed in
the Adj-RIB-In, but before they are considered in the BGP Best
Path calculation.
o Each prefix may be validated according to the process outlined
in Validating Routing Information after they are run through the
Best Path algorithm, but before they are installed in the local
RIB.
o Routes may be installed in the local RIB, and then validated
using the process outlined in Validating Routing Information.
Once validation is accomplished, adjustments to the local RIB
and routes advertised to BGP peers may need to be adjusted.
3.5. Aggregation
Aggregation is a difficult problem with any method which attempts to
verify the origin of any given prefix, since aggregation removes the
relationship between prefixes originated and originators. Prefixes
may only be aggregated by an entity which is otherwise authorized to
advertise the aggregated prefix.
3.6. Requirements for Systems Running soBGP
This section describes requirements for autonomous systems running
soBGP, requirements for BGP speakers forming external adjacencies
from within such autonomous systems, and devices exchanging soBGP
certificates.
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o Any peering session along the border of an autonomous system
running soBGP SHOULD be authenticated through some means such as
[BGP-MD5], IPsec ([ESP], [AH]), or through some other current,
effective means of protecting BGP sessions from being hijacked,
or otherwise abused.
o Any peering session along which soBGP certificates are exchanged
SHOULD be authenticated through some means such as [BGP-MD5],
IPsec ([ESP, [AH]), or through some other current, effective
means of protecting BGP sessions from being hijacked, or other-
wise abused.
o The AS_PATH of any routing information received from any BGP
peer outside the autonomous system MUST be checked to validate
the next hop AS is the AS the update was received from. If the
next hop AS in any received update does not match the configured
AS the route is learned from, the update MUST be discarded.
4. soBGP Deployment
This section begins by describing what we believe to be the most
practical deployment of this secure registry of routing information.
Following sections describe some other deployment options that may
prove useful in some situations, or may prove to be more practical
than the deployment outlined in this section.
4.1. Deploying soBGP on Distributed Registry Servers
This deployment scenerio works within three constraints:
o It may not be not desirable to combine routing and cryptographic
processing of soBGP certificates on the same device.
o The system should be distributed, using as few centralized
resources as possible.
o Trust relationships should be based on existing business and
working relationships, rather than building new relationships
specifically for securing the routing system.
Assume we have a small internetwork, as shown below:
S1 - - - - - - - - - - -S2 - - - -S3
10.1.1.0/24---A---B-----C---D-----E---F
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| AS65000 | AS65001 | AS65002
In this network, we assume each AS has an soBGP server locally within
their AS, marked as S1, S2, and S3, above. These servers are inter-
connected in a way similar to eBGP peering between AS65000, AS65001,
and AS65002; S1 and S2 are using the mechanisms described in [SOBGP-
BGPEXT] to distribute the certificates described in [SOBGP-
CERTIFICATE] between them.
Each server then processes the certificates as described in [SOBGP-
CERTIFICATE], and either provides a set of filters or a mechanism
through which the eBGP peering routers can authenticate routing
information, such as described in [SOBGP-RADIUS]. This deployment
technique provides BGP route validation that is:
o Fully Distributed: Local server (or set of servers) which builds
the required databases based on received certificates, and dis-
tributes certificates throughout the routing system.
o Locally Controlled: Each local server (or set of server) is
maintained and managed by autonomous systems participating in
the internetwork.
o Based on Existing Business Relationships: Peering autonomous
systems also peer their soBGP servers, so the system uses exist-
ing business relationships to provide the deployment and long
term maintenance of the system.
o Very Little Impact on the Existing Routing System: The current
processing and distribution of routing information through [BGP]
isn't impacted in any way. The only additional requirements on
existing equipment are to compare the routing information to the
database results provided by the local servers (i.e., receiving
and processing filter lists, or through [SOBGP-RADIUS]).
4.2. Certificate Processing on Edge Peering Routers
soBGP can also be deployed entirely within BGP speakers at the edge
of an Autonomous System (AS).
+-(eBGP)-+ +-(eBGP)-+
| | | |
v v v V
A--------B-----C-----D--------E
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^ ^
| |
+--(iBGP)---+
In this network, A is sending certificates it has learned from other
sources to B using the mechanisms described in [SOBGP-BGPEXT]. It is
passing these certificates to D via iBGP, and D is passing these cer-
tificates to E via eBGP. Each edge router, B and D, process these
certificates locally, building the databases required to validate
received routing information from them.
4.3. Multihoming Deployment
Multihoming presents a special challenge to the deployment of soBGP
within a large scale internetwork.
(---------) (---------)
( AS65401 ) ( AS65402 )
( ) ( )
( ) ( )
(---A---) (---B---)
| |
\ /
\-----+ +-----/
| |
(--C------D--)
( )
( No-AS )
(----------)
Assume No-AS has obtained a block of addresses, 10.1.1.0/24, from
AS65401, and would like to advertise that same block of addresses
through AS65402. Since No-AS has no AS number, it cannot generate any
soBGP certificates, and must rely on its upstream providers to work
out the security impact in some way. The simplest solution would be,
of course, for NOAS to obtain an AS number, and fully participate in
soBGP, but barring that, what other solutions are there?
AS65401 could issue a certificate allowing AS65402 to originate just
the prefix in question, 10.1.1.0/24, or AS65401 could simply list
AS65402 in the certificate covering 10.1.1.0/24 as an authorized ori-
ginator for this address space (as multiple authorized originators
are allowed).
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4.4. Proxy Advertisement of Certificates
Note there is no requirement for a given entity which originates
routes into the routing system to actually originate the correspond-
ing certificates required for the correct origination of the route to
be validated, and the AS Path attached to the route to be verified.
(-----------------)
( Other Third Party )
(---------------)
/ \
/ \
(---------) (---------)
( AS65401 ) ( AS65402 )
( ) ( )
( ) ( )
(---A---) (---B---)
| |
\ /
\-----+ +-----/
| |
(--C------D--)
( )
( AS65403 )
(----------)
In this case, AS65401, AS65402, or some other third part may actually
advertise the certificates necessary for AS65403 to originate vali-
dated routes.
5. Other Deployment Considerations
In this section, we move from specific deployment scenerios to other
deployment considerations, such as key generation and protection, and
memory utilization/impact.
5.1. Certificate Generation and Private Key Protection
There is only one private/public key pair per autonomous system; cer-
tificates are generated as determined by local policy and as required
to account for changes in the network. Since the entity's private key
is not used in any part of the operations verifying received informa-
tion, or in generating information to transmit to other devices,
these certificates could be generated on some secure central system
in the AS, and the results, containing only public keys, can be
transmitted throughout the network.
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Securing the private key of each entity should be relatively easy in
this environment, since the location of the private key can be care-
fully constrained; no device other than the system which generates
the required certificates needs use of the private key.
5.2. Impact on Performance and Memory Utilization
Detailed performance and memory utilization characteristics of soBGP
will be the subject of future investigation. However, as this is an
important area of consideration, we present some suggested analysis
below. (In other words, this is a guess).
In terms of memory, each device running sobGP will need to store:
o Each of the Entitycerts Received. The maximum number of Enti-
tycerts within the routing system would be the number partici-
pating autonomous systems multiplied by the number of outstand-
ing Entitycerts from each autonomous system.
o Each of the ASPolicycerts Received. The number of ASPolicycerts
within the system will probably be similar to the number of
Entitycerts within the system.
o Each of the PrefixPolicycerts Received. The number of PrefixPol-
icyCerts within the system will depend on the number of address
blocks each participant in the routing system advertises, and
could double during key rollover.
Performance will depend on the cryptographic processing requirements
imposed by the certificate signature methods, as described in
[SOBGP-CERTIFICATE]. However, all of this additional memory and pro-
cessing would most likely be required on a distributed soBGP server,
rather than on routers themselves.
The primary impact on routers and routing protocol convergence will
be the memory and processing requirements added from the additional
route filters or processing as required by the deployment technique
used.
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6. Normative References
[BGP] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 (BGP-4)",
RFC 1771, March 1995.
[SOBGP-BGPEXT]
Ng J (editor), "Extensions to BGP to Support Secure Origin BGP
(soBGP)", draft-ng-sobgp-bgp-extensions-01.txt, April 2004
[SOBGP-CERTIFICATE]
Weis, Brian (editor), "Secure Origin BGP (soBGP) Certificates",
draft-weis-sobgp-certificates-01.txt, October 2003
7. Informative References
[SOBGP-RADIUS]
Lovnick, C, "RADIUS Attributes for soBGP Support", draft-lonvick-
sobgp-radius-04.txt, February 2004
[PATH-CONSIDER]
White, Russ, "Considerations in Validating the Path in Routing Pro-
tocols", draft-white-pathconsiderations-02.txt, April 2004
[COST]
Retana, A., White, R., "BGP Custom Decision Process", draft-
retana-bgp-custom-decision-00, October 2002.
8. Editor's Address
Russ White
Cisco Systems
7025 Kit Creek Road
Research Triangle Park, NC 27709
riw@cisco.com
White, et. all [Page 13]
Network Working Group James Ng
Internet Draft (editor)
Expiration Date: October 2004 Cisco Systems
File Name: draft-ng-sobgp-bgpextensions-00.txt April 2004
Extensions to BGP Transport soBGP Certificates
draft-ng-sobgp-bgpextensions-00.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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. Internet Drafts may be updated, replaced, or obsoleted by
other documents at any time. It is not appropriate to use Internet
Drafts as reference material or to cite them other than as a "working
draft" or "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.
1. Contributors
A large number of people contributed to or provided valuable feedback
on this document; we've tried to include all of them here (in no
particular order), but might have missed a few: Russ White, Alvaro
Retana, Dave Cook, John Scudder, David Ward, Martin Djernaes, Chris
Lonvick, Brian Weis, Tim Gage, Scott Fanning, Barry Friedman, Jim
Duncan, Yi Yang, Robert Adams, Tony Tauber, Iljitsch van Beijnum, and
Jonathan Natale.
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2. Abstract
There is a great deal of concern over the security of routing systems
within the Internet, particularly in relation to the Border Gateway
Protocol [BGP], which is used to provide routing information between
autonomous systems. This document proposes a system where the origin
of any advertisement within BGP can be verified and authenticated,
preventing the advertisement of prefix blocks by unauthorized
networks, verifying that the final destination in the path is
actually within the autonomous system to which the packets are being
routed, and proving the validity of the AS Path contained in the
update.
This document does not:
o Attempt to provide information on how such a security system
could or should be deployed; readers are referenced to [SOBGP-
ARCH] for this discussion.
o Attempt to determine what sorts of keys should be used within
such a system, nor how any sort of trust relationship can or
should be built between the entities cooperating within the
routing system. These are considered in [SOBGP-CERTIFICATE].
o Attempt to analyse the performance, memory utilization, or other
impacts on devices running this protocol; these are addressed in
[SOBGP-ARCH].
o Attempt to analyze the security protection provided by the pro-
posed security system. This may be address in a future draft.
This document primarily focuses on extensions to the BGP protocol
itself to support such a security system through the transport of the
certificates described in [SOBGP-CERTIFICATE].
The IETF has been notified of intellectual property rights claimed in
regard to some or all of the specification contained in this docu-
ment. For more information consult the online list of claimed rights.
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3. Definitions
o Entity: A participant in the internetwork routing system.
4. The Security Message
This document proposes a new message type, the SECURITY message,
which is to be used for carrying security information within the BGP
protocol. The SECURITY message is type [TBD]. The SECURITY message is
used to transport the certificates described in [SOBGP-CERTIFICATE].
4.1. Negotiating Security Capability
The ability to exchange SECURITY messages MAY be negotiated at ses-
sion startup, as described in [CAPABILITY]. The capability code is
<to be assigned by IANA>.
o Speakers MAY negotiate the exchange of SECURITY information only
or SECURITY and NLRIs.
o If the exchange of SECURITY messages is negotiated, the SECURITY
option message MUST be exchanged before any other SECURITY mes-
sages are exchanged. The option bits in this message determine
if SECURITY messages or NLRIs will be exchanged first.
o If two BGP speakers have negotiated to exchange SECURITY mes-
sages, they SHOULD exchange the soBGP certificates contained in
their local databases.
4.2. The Security Message Format
The SECURITY message is formatted as described in [BGP], with a type
code of [TBD]. Within each message is a series of TLVs, or security
message blocks, formatted as:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-------------------------------+-------------------------------+
| Type | Length |
+-------------------------------+-------------------------------+
| Data |
+---------
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o Type: A two octet unsigned integer describing the type of infor-
mation contained within the data field.
o Length: A two octet unsigned integer describing the length of
the data field, in octets.
o Data: The data, as described within this and other documents
which describe information to be carried within the SECURITY
message type.
Two TLVs are currently defined within the SECURITY message.
Further TLVs are defined for carrying certificates in [SOBGP-
CERTIFICATE].
4.2.1. The SECURITY Option TLV
The SECURITY Option TLV provides a way for exchanging speakers to
inform their peers about local configurations which may pertain to
the peering session. SECURITY Option TLVs are encapsulated within a
TLV Type 1, and transmitted within the SECURITY message type.
If SECURITY Option TLVs are transmitted, they MUST be transmitted
before the transmission of any other SECURITY data.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| Options |
+---------------------------------------------------------------+
o TLV type: (2 octets), 1 (0x0001)
o Length: (2 octets), set to 2
o Options: (4 octets), a bitfield, described below
The options field is a 32 bit bitfield, allowing up to 32 different
options to be specified.
o Bit 0: If set, indicates that SECURITY information should be
sent before NLRI information on this session; if cleared, indi-
cates that NLRI information should be sent before SECURITY
information.
o Bit 1: If set, indicates that this peer will only transmit
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validated certificates of any type along this session. This bit
MUST NOT be used for eBGP sessions.
o Bit 2: If set, indicates that this peer will only accept vali-
dated certificates of any type along this session (valid only on
iBGP sessions).
Bit 0 in the option field allows the operator to configure the local
device so it receives all prefixes first, decreasing convergence to
the minimum time, or receives all SECURITY information first, allow-
ing all prefixes to be validated before they are installed.
Bits 1 and 2 allow peers along an iBGP session to trust the certifi-
cations they receive without validating them. If bit 1 is set on the
transmitting peer, bit 2 is set on the receiving peer, and the BGP
peering session is an authenticated or encrypted iBGP session, the
receiving peer may accept all received certificates from the
transmitting peer as already validated. This is called a trusted
peering relationship.
4.2.2. The Request TLV
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| Request Type | Length |
+-------------------------------+-------------------------------+
| Request Indicator SubTV .... |
+---------------------------
| Request Type | Length |
+-------------------------------+-------------------------------+
| Request Indicator SubTV .... |
+---------------------------
o TLV type: (2 octets), 2
o Length: (2 octets), set to the total length of the request in
octets.
o Request Type: (2 octets), treated as an unsigned integer indi-
cating the type of information requested.
o Length: (2 octets), set to the number of requests of the request
type included in this request.
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o Reserved: (2 octets), set to 0x0000.
o Request Indicator: The information indicated by the request type
bit field.
The Request Type field indicates the type of certificates requested.
Four request types are defined in this document.
1 Any certificate matching the Request Indicator are requested.
2 EntityCerts matching the Request Indicator are requested.
3 ASPolicyCerts matching the Request Indicator are requested.
4 PrefixPolicyCerts matching the Request Indicator are requested.
Request indicator SubTVs restrict the set of certificates returned;
there may be one or more request indicator SubTVs included in a
request. Each SubTV consists of a two octet type field, treated as an
unsigned integer, and a fixed length field containing the request
indicator.
o Type 1: A four octet origin/authorized AS Number; two octet AS
numbers shall be right justified within this field (placed in
the two least significant octets).
o Type 2: A four octet signer/authorizer AS Number; two octet AS
numbers shall be right justified within this field (placed in
the two least significant octets).
o Type 3: A four octet IPv4 address is included in the request
indicator.
o Type 4: A sixteen octet IPv6 address is included in the request
indicator.
o Type 5: An eight octet starting serial number is included in the
request indicator.
o Type 6: An eight octet ending serial number is included in the
request indicator.
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4.2.3. The Cluster List TLV
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| Cluster ID |
+-------------------------------+-------------------------------+
| .... |
+---------------------------
o TLV type: (2 octets), 3
o Length: (2 octets), set to the number of cluster IDs in the TLV
The use of the Cluster List TLV is described in the Reflecting SECU-
RITY messages section below.
5. Receiving and Processing SECURITY messages
Each section below describes the receipt and processing of SECURITY
messages.
5.1. Processing SECURITY Messages Containing a Certificate
For each certificate received, the BGP speaker MUST:
o Examine the certificate to determine if a copy of this certifi-
cate already exists in the local database. Any certificate
which is found to already be held locally MUST be discarded.
o If the certificate is received through an untrusted peering
relationship, place the certificate in a local certificate data-
base and process according to [SOBGP-CERTIFICATE].
o If the certificate is received through a trusted peering rela-
tionship, place certificate in a local certificate database,
treating it as if it is already validated according to [SOBGP-
CERTIFICATE].
o If a received certificate is sucessfully validated using the
process described in [SOBGP-CERTIFICATE], it should be readver-
tised to all peers outside the local autonomous system (eBGP
peers). If the peering relationship is trusted, the certificate
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INTERNET DRAFT Secure Origin BGP (soBGP) April 2004
should be advertised as validated by marking it as indicated in
[SOBGP-CERTIFICATE].
5.2. Reflecting SECURITY Messages
A BGP speaker MAY be configured to reflect received SECURITY mes-
sages, with or without processing them, in a way similar to the way
BGP routing information is reflected among iBGP speakers, described
in [BGP-REFLECTION]. When reflecting SECURITY messages, a BGP speaker
MUST:
o Examine the SECURITY message for the presence of a Cluster List
TLV.
o If a Cluster List TLV exists, and the local router ID is con-
tained in the list of Cluster IDs, discard the SECURITY mes-
sage.
o If a Cluster List TLV exists, and the local router ID is not
contained in the list of Cluster IDs, add the local router ID
to the list and retransmit the SECURITY message to all BGP
peers which have negotiated receipt of SECURITY messages.
o If a Cluster List TLV does not exist, add a new Cluster List
TLV to the SECURITY message, including the local router ID in
the new TLV.
5.3. Filtering of Certificates
A BGP speaker may, for reasons of policy, filter soBGP certificates
received from a peer.
o If a BGP speaker is part of a transit AS, it SHOULD NOT filter
soBGP certificates.
o A BGP speaker MAY discard soBGP certificates which describe the
authorization of address space which is being filtered out of
the local routing information.
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5.4. Receiving and Processing Requests
If a device receives a Request TLV, as described in the section "The
Security Message," above, it should:
o Examine the request to ensure it is logically consistent. For
instance, requesting an Entitycert based on an IPv4 address
range is not logically consistent, since these certificates only
contain an AS and a Signer AS. If the request is not logically
consistent, discard it.
o If the request is logically consistent, examine its local data-
bases, and transmit the certificates requested which fulfill the
conditions supplied in the request indicator SubTVs.
o If more than one of the same request indicator is included in a
request message, they shall be treated as an OR condition; if
any of the conditions match, the certificate shall match the
set.
6. Security Considerations
This document defines extensions to BGP that address specific secu-
rity concerns for the protocol. While it adds functionality, the
flexibility allows it to not introduce any new security concerns.
7. IANA Considerations
This document defines the Security Message for BGP, which contains a
series of TLVs. IANA is expected to maintain a registry of all the
values defined, as follows:
The SECURITY message Type field :
o Type value 0 is reserved.
o Type values 1 through 3 are assigned in this document.
o Type values 4 through 16575 MUST be assigned using the "IETF
Consensus" policy defined in RFC2434 [RFC2434].
o Type values 16576 through 32895 SHOULD be assigned using the
"Specification Required" policy defined in RFC2434 [RFC2434].
o Type values 32896 through 65535 are for "Private Use" as defined
in RFC2434 [RFC2434].
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Request TLV Request Type Field:
o Types 1 through 3 are assigned in this document.
o Types 4 thru 16575 MUST be assigned using the "IETF Consensus"
policy defined in RFC2434 [RFC2434].
o Type values 16576 through 32895 SHOULD be assigned using the
"Specification Required" policy defined in RFC2434 [RFC2434].
o Type values 32896 through 65535 are for "Private Use" as defined
in RFC2434 [RFC2434].
8. Normative References
[BGP] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 (BGP-4)",
RFC 1771, March 1995.
[MULTIPROTOCOL-BGP]
Bates, T., Chandra, R., Katz, D., and Rekhter, Y., "Multiproto-
col Extensions for BGP-4", RFC 2858, June 2000
[CAPABILITY]
Chandra, R., Scudder, J., "Capabilities Advertisement with BGP-
4", RFC2842, May 2000
[SOBGP-ARCH]
White, R. (editor), "Architecture and Deployment Considerations
for Secure Origin BGP (soBGP)", draft-white-sobgp-deployment-03,
April 2004
[SOBGP-CERTIFICATE]
Weis, Brian (editor), "Secure Origin BGP (soBGP) Certificates",
draft-weis-sobgp-certificates-01.txt, October 2003
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9. Informative References
[RFC2434]
Narten, T., Alvestrand, H., "Guidelines for Writing an IANA Con-
siderations Section in RFCs", RFC 2434, October 1998.
[BGP-MD5]
Heffernan, A., "Protection of BGP Sessions via the TCP MD5 Signa-
ture Option", RFC2385, August 1998
[ESP] Kent, S., and R. Atkinson, "IP Encapsulating Security Payload",
RFC 2406, November 1998.
[AH] Kent, S., and R. Atkinson, "IP Authentication Header", RFC 2402,
November 1998.
[SOBGP-RADIUS]
Lovnick, C, "RADIUS Attributes for soBGP Support", draft-lonvick-
sobgp-radius-04.txt, February 2004
[BGP-REFLECTION]
Bates, T, et al, "BGP Route Reflection - An Alternative to Full
Mesh IBGP", draft-ietf-idr-rfc2796bis-00.txt, March 2004
10. Editor's Address
James Ng (Editor)
Cisco Systems
7025 Kit Creek Road
Research Triangle Park, NC 27709
jamng@cisco.com
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