One document matched: draft-weis-sobgp-certificates-01.txt
Differences from draft-weis-sobgp-certificates-00.txt
Internet Engineering Task Force Brian Weis, Editor
INTERNET-DRAFT Cisco Systems
draft-weis-sobgp-certificates-01.txt
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Secure Origin BGP (soBGP) Certificates
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
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This document describes the format of digital certificates that are
used by the Secure Origin BGP (soBGP) extensions to BGP, as well as
acceptable use of those certificates. Included are certificates
providing authentication, authorization, and policy distribution.
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Table of Contents
1.0 Introduction......................................................3
1.1 Key Words.......................................................3
1.2 Terminology.....................................................3
2.0 Overview..........................................................4
2.1 Digital Signature Algorithms....................................5
3.0 Entity Certificate (Entitycert)...................................5
3.1 Format..........................................................6
3.2 Creation........................................................7
3.3 Distribution....................................................8
3.4 Validation......................................................8
3.5 Revocation and Expiration......................................10
4.0 Authorization Certificates (Authcert)............................10
4.1 Format.........................................................11
4.2 Creation.......................................................15
4.3 Distribution...................................................16
4.4 Validation.....................................................16
4.5 Revocation.....................................................17
5.0 Prefix Policy Certificates (PrefixPolicycert)....................17
5.1 Format.........................................................17
5.2 Creation.......................................................22
5.3 Distribution...................................................23
5.4 Validation.....................................................23
5.5 Revocation.....................................................23
6.0 AS Policy Certificates (ASPolicycert)............................24
6.1 Format.........................................................24
6.2 Creation.......................................................31
6.3 Distribution...................................................32
6.4 Validation.....................................................32
6.5 Revocation.....................................................32
7.0 Security Considerations..........................................33
7.1 Entitycerts....................................................33
7.2 Authcerts......................................................33
7.3 PrefixPolicycerts..............................................34
7.4 ASPolicycerts..................................................34
7.5 Entitycert Uniform Resource Locators...........................34
8.0 IANA Considerations..............................................34
8.1 Authorization Certificate......................................35
8.2 Prefix Policy Certificate......................................35
8.3 AS Policy Certificate..........................................36
9.0 Acknowledgments..................................................37
10.0 References......................................................37
10.1 Normative References..........................................37
10.2 Informative References........................................38
Editor's Address.....................................................38
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1.0 Introduction
There is a great deal of concern over the security of routing systems
within the Internet. This is particularly true in relation to the
Border Gateway Protocol [BGP], the protocol used to provide routing
information between Autonomous Systems (ASes). Source Origin BGP
(soBGP) provides a method that ASes can use to determine the
correctness of BGP messages received by their BGP routers. It also
provides a method for ASes to detect implausible routes reported in a
BGP Update AS_PATH, and acts as an aid in detecting misconfigured
routers advertising incorrect routes.
Source Origin BGP does not define changes to BGP Updates. Rather, it
provides authorization and path policy "out-of-band" from the BGP
Updates. An AS compares the information claimed in BGP Updates to the
soBGP policy, and makes judgments to the fitness of the claim.
Source Origin BGP distributes authorization and policy as digitally
signed objects, which can be distributed in many ways. To aid
interoperability, extensions have been defined in [SOBGP-BGP] that
support distribution of the digitally signed soBGP objects within BGP
itself..
Source Origin BGP deployment models are discussed in [SOBGP-DEPLOY].
Extensions to RADIUS to support soBGP are defined in [SOBGP-RADIUS].
This document defines the format of the digitally signed objects used
by soBGP, as well as the operations to be performed on those objects.
1.1 Key Words
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 [RFC2119].
1.2 Terminology
This document frequently uses the following terms:
AS Policy Certificate (ASPolicycert)
A digital certificate that asserts routing policy for an
Autonomous System.
Authorization Certificates (Authcerts)
A digital certificate that asserts that an Autonomous System is
authorized to advertise a particular prefix.
Entity
Participants within the routing system. These include Regional
Internet Registry (RIR) authorities, Local Internet Registry
(LIR) authorities, Internet Service Providers (ISPs), and other
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organizations participating in soBGP. An Entity must have an
Autonomous System (AS) number assigned to it as a unique
identity, even if it does not source routes within the routing
system.
Entity Certificate (Entitycert)
An X.509 certificate that asserts a mapping between an Autonomous
System identifier and a public key.
Prefix Policy Certificate (Prefixpolicycert)
A digital certificate mapping usage policy to one or more
prefixes.
Regional Internet Registry (RIR)
An entity recognized by IANA and tasked with managing IP address
space within a wide geographical area. RIRs allocate address
space to Local Internet Registries and other entities.
Local Internet Registry (LIR)
An entity that allocates address space to the users of the
network services that it provides.
2.0 Overview
Source Origin BGP refers to participants within the routing system
as entities. Each entity must have an Autonomous System (AS)
number, issued from an authorized entity (e.g., Regional Internet
Registry), to participate in soBGP. Entities may have one or more
roles within soBGP. They may act as a trusted signer, an authorizer
of address blocks, and/or as a route originator.
Source Origin BGP provides a method of verifying that an AS is
authorized to advertise certain prefixes. The authorization to
advertise prefixes or a given address space is validated through
Authorization Certificates (Authcerts). Authcerts are issued by
entities (e.g., ISP) that allocate prefixes.
An AS given an Authcert (e.g., ISP customer) may assign local policy
to be used with the prefixes listed in the Authcert using a Prefix
Policy Certificate (PrefixPolicycert).
Policies specific to an Autonomous System are provided through AS
Policy Certificates (ASPolicycerts). This policy enables another
entity to develop a database of plausible paths through the routing
system, and aids in detecting impossible and fraudulent paths.
Authcerts, PrefixPolicycerts, and ASPolicycerts are verified using
public keys embedded in Entity Certificates (Entitycerts).
Entitycerts are X.509 certificates as specified by [RFC3280].
Figure 1 illustrates the relationship between soBGP certificates for
a single AS. AS 1 allocates a prefix to AS 2. AS 1 also issues an
Authcert to AS 2 proving that AS 2 may legitimately use that prefix.
In this example, AS 1 also acts as an Entitycert issuer for AS 2. AS
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2 then creates two policy certificates: one specifying particular
policy for the authorized prefix, and one specifying particular
policy for the AS.
+-----+------+
| AS 1 |
+-------| Entitycert |
/ +------------+
/ |
+ |
| |
v v
+-------+--+ +-----+------+ +------------------+
| AS 2 | | AS 2 | | AS 2 |
| Authcert | | Entitycert |-------> | PrefixPolicycert |
+----------+ +------------+ +------------------+
|
| +------------------+
| | AS 2 |
+---------> | ASPolicycert |
+------------------+
Figure 1. Relationship between soBGP certificates
Each of the soBGP certificates is discussed in detail in subsequent
sections of this document.
2.1 Digital Signature Algorithms
The RSA Public Key Algorithm [RSA] is a widely deployed public key
algorithm commonly used for digital signatures. Compared to other
public key algorithms, signature verification is relatively quick.
This property is useful considering the large number of signature
verifications that will be done on soBGP certificates. The RSA
Algorithm is commonly supported in hardware, and is no longer
encumbered by intellectual property claims.
All soBGP implementations MUST support a digital signature of a SHA1
digest encrypted with the RSA algorithm. An implementation MAY
support other signature methods, but any AS using alternate signature
methods run the risk of their signatures not being universally
verifiable.
3.0 Entity Certificate (Entitycert)
Entitycerts provide authentication, providing a binding of an
identity (i.e., autonomous system number) to a public key. The
authenticity of the binding is verified with a digital signature,
where the public key of the certificate issuer has been previously
accepted by an receiver as valid. Issuer public keys can either be
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manually configured, or are verified through the use of another
issuer's trusted public key in a "web of trust" built by the
receiver.
Entitycerts are used to verify, through a trust model, the existence
of an entity within the routing system, and the value of that
entity's public key for use in the routing system. Each entity
within the routing system participating in soBGP MUST generate a
public/private key pair. The public key portion of this pair is then
signed, verifying that anyone using this public key is actually the
entity in question. This signature may be provided by various other
trusted parties within the routing system, including (but not
limited to):
- The authority that issued the autonomous system number.
- An external commercial authority that provides authentication
certificates for other commercial transactions.
- Any other trusted party within the domain of Internet routing,
such as a well known Service Provider.
- Self-signed if the entity is well known within the routing system.
A public key is used to verify the validity of other messages
transmitted by this entity within the routing system.The public key,
along with other verifying information, is formatted into an
Entitycert, as described in the next section.
3.1 Format
An Entitycert MUST be formatted as an X.509 authentication
certificate, as defined in [RFC3280]. The Entitycert MUST be
generated with a signature of type sha1withRSAEncryption [RFC3279].
The primary identity in soBGP is the autonomous system number.
Because of this, each entity that issues Entitycerts MUST be
assigned an AS number, even if they do not originate routes into the
internetwork. In accordance with Section 4.2.1.7 of [RFC3280],
issuers MUST verify all parts of the subject alternative name,
including the AS number, before issuing the certificate.
An Entitycert MUST have a subjectAltname critical extension, which
MUST contain the AS number of the subject as an otherName choice.
The AS number is encoded with the OID defined in Section 3.2.1 of
[ADDR-EXT].
An Entitycert MUST have an issuerAltname critical extension, which
MUST contain the AS number of the subject as an otherName choice.
The AS number is encoded with the OID defined in Section 3.2.1 of
[ADDR-EXT].
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The X.509 Issuer and Subject distinguished names are not used by
soBGP. In accordance with Section 4.2.1.7 of [RFC3280], when
subjectAltName is required, the Subject field MAY be empty.
3.2 Creation
An Entitycert is usually created with the following steps:
- The entity requesting an Entitycert generates a signature key pair
- The entity forwards its identity (including its AS number) and the
public key to an Entitycert issuer using the certificate
registration mechanism supported by the issuer.
- The issuing autonomous system verifies that the identity of the
receiving autonomous system, generates an Entitycert including
that identity, and signs it with its own private key.
- The issuing autonomous system returns the Entitycert to the
receiving autonomous system.
3.2.1 Certificate Uniqueness
Digital certificates are created as uniquely named objects, which
allows them to be uniquely identified. For the purposes of soBGP, the
pair of CertificateSerialNumber and IssuerAltName values uniquely
identifies entity Certificates. Note that although RFC 3280 contains
an X.509v3 IssuerName, it is not used elsewhere within soBGP.
3.2.2 Certificate Encoding
Entitycerts distributed in [SOBGP-BGP] use their native DER [X.690]
form. If Entitycerts are manually distributed (e.g., through
electronic mail) they may need to be base64 encoded into ASCII as
described in Section 4.3 of [RFC1421].
3.2.3 Multiplicity of Entitycerts
An autonomous system MAY enroll with more than one issuer, which
results in multiple Entitycerts. An AS holding certificates from
different well-known issuing entities within the routing system may
result in a greater number of other autonomous systems accepting
their public key. Or, it may simply result in other autonomous
systems accepting their public key faster, which increases BGP
convergence times.
If an entity detects that an autonomous system has valid Entitycerts
from different issuers, the entity SHOULD treat the various
Entitycerts as independent. Revocation from one issuer does not
necessarily imply that Entitycerts from other issuers are invalid.
An issuer may revoke a certificate for reasons other than private
key compromise or loss.
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However, even if an issuer states key compromise as the reason for
revocation, a receiving entity SHOULD treat this state as specific
to the issuer. Note that if the state of one issuer were instead
considered transitive, the erroneous revocation of a single issuer
would result in a denial of service attack on the victim autonomous
system.
In the face of inconsistent state from different issuers, a receiver
MAY choose to trust one issuer over another. For example, a receiver
may choose to prefer the result of an issuer they directly trust to
an issuer that was verified further away in the "web of trust".
3.3 Distribution
Entitycerts may be distributed using any number of methods, for
example:
- maintained in a directory maintained by the issuing autonomous
system,
- distributed via some out of band mechanism, and/or
- distributed within BGP using extensions defined in [SOBGP-BGP].
To ensure interoperability, the receiving autonomous system SHOULD
distribute its Entitycert within BGP.
3.4 Validation
Any device receiving an Entitycert can verify it by validating the
signature on the certificate, along with the verifying information.
If a Certificate Revocation List (CRL) is available for that issuer,
it MUST be consulted to verify that this certificate has not been
revoked. Once validation is complete, the public key contained in
this certificate may be used to verify messages purportedly sent by
this entity.
3.4.1 Web of Trust
An soBGP entity uses the "web of trust" paradigm for purposes of
Entitycert validation, where the entity learns the validity of
public keys over time. An entity follows the following procedure for
validating Entitycerts in the web of trust.
- A small number of Entitycerts are manually configured and copied
to a device's local configuration. These are implicitly trusted as
being previously verified and authenticated.
- When the entity receives a new Entitycert, it checks to see if it
has the public key of the issuing autonomous system in its
configuration. If so, it attempts to validate the Entitycert,
using the previously known public key, and any revocation material
that is available from the issuer.
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- If the new Entitycert proves valid, it is added to the device's
local configuration and may be used to validate subsequently
received Entitycerts.
- If the new Entitycert cannot be validated because the issuer?s
public key is not yet available, local policy dictates as to
whether or not the certificate is held awaiting the issuer?s
certificate.
Figure 2 shows an example web of trust. In this example, Entitycerts
for AS 1 and AS 5 would be manually copied to the local
configuration on the box. Other Entitycerts would be validated using
the usual PKI path validation techniques.
+------------+ +------------+
| AS 1 | | AS 5 |
| Entitycert | | Entitycert |
+-----+------+ +---+----+---+
| / \
| / \
| + +
| | |
V V V
+------------+ +------------+ +------------+
| AS 2 | | AS 6 | | AS 7 |
| Entitycert | | Entitycert | | Entitycert |
+---+----+---+ +------------+ +-----+------+
/ \ |
/ \ V
+ + +------------+
| | | AS 8 |
V V | Entitycert |
+------------+ +------------+ +-----+------+
| AS 3 | | AS 4 | |
| Entitycert | | Entitycert | V
+------------+ +------------+ +------------+
| AS 9 |
| Entitycert |
+------------+
Figure 2. Example Web of Trust
An autonomous system may define local policy to restrict the scope
of the web of trust. However it should be noted that any local
policy restricting the web of trust reduces the value of soBGP
authorization and path validation.
One type of local policy would be to accept only a certain "depth"
of Entitycert issuers. For example, consider if AS 6 in Figure 2
only accepted two levels of issuers. AS 6 would only trust ASes
1,2,5,6 and 7 to issue Entitycerts. It would never validate the
Entitycert from ASes 3, 4, 8, and 9.
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3.4.2 Self-signed Entitycerts
Entitycerts MAY be self-signed, but SHOULD only be accepted from
autonomous systems when an alternative method exists of validating
that the self-signed certificate is genuine. For example,
distribution out-of-band using a trusted delivery procedure would be
acceptable.
Typical users of a self-signed Entitycert would be:
- A commercial authority in the business of providing authentication
certificates for many types of commercial transactions
- An Entitycert issuer that is at the top of a hierarchy of issuers
- A well-known trusted party within the domain of Internet routing
3.5 Revocation and Expiration
Any entity issuing an Entitycert may have need to revoke it. The
entity MAY use any form for propagating that revocation list, but
SHOULD also send it as part of an AS Policy Certificate (distributed
using [SOBGP-BGP]). This allows autonomous systems that cannot route
to the issuing autonomous system to verify that the Entitycert has
not been revoked.
If an Entitycert is discarded due to revocation, the Authcert and
Policy databases should be examined. Any Authcerts and Policy
certificates that were validated using the discarded certificate
should be removed from the database.
X.509 certificates contain expiration dates. Any device validating
Entitycerts MUST have a time of day clock that is close to real time
in order to properly deal with expired certificates
If an Entitycert is discarded due to expiration, an Authcerts or
Policy certificates validated using the discarded certificate remain
valid if another valid Entitycert for the AS can be found containing
the same public key.
4.0 Authorization Certificates (Authcert)
Authcerts prove the right of an entity to advertise particular
address spaces. They are generated in a hierarchical manner
following the order of address space allocation (i.e., from RIR, to
LIR or ISP, to customer), and are distributed along with the address
space allocation. Receivers use the Authcert to validate
announcements received in BGP UPDATE messages.
The authorization certificate binds one or more prefix blocks to a
particular autonomous system. It is typically provided by an entity
issuing a prefix block to an autonomous system, and is digitally
signed by the issuing autonomous system. The Authcert can be thought
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of as an "Attribute Certificate" in the spirit of RFC 3281, although
it does not follow the syntax of that document.
The authenticity of Authcerts is verified with a digital signature
provided by the issuing autonomous system. Authcerts do not contain
public keys. Rather, they bind an address space to a particular
identity (i.e., autonomous system).
4.1 Format
The Authcert is defined as a header block followed by a set of
Type/Length/Value attributes, as identified in the following
sections. Each Authcert TLV includes a type, which is treated as a
16 bit (two octet) unsigned integer. The TLVs described must be
placed within the Authcert in type order; every Authcert should
begin with a TLV type 1 (Autonomous System and Options). All TLVs
are REQUIRED to be in an Authcert unless otherwise noted.
4.1.1 Authcert Header
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
+---------------+---------------+-------------------------------+
| Cert. Marker | Type Id | Length |
+---------------+---------------+-------------------------------+
| TLVs
+----------------
o Certificate Marker: "162(0xa2), identifying this as an soBGP
certificate.
o Type ID: "1(0x01), identifying this as an Authcert.
o Length: Set to the length of the TLVs.
o TLVs: The Type/Length/Value attributes making up an Authcert.
4.1.2 The Authorizing 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
+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| Autonomous System |
+---------------------------------------------------------------+
o TLV type: 1 (0x0001)
o Length: Set to 4.
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o AS: (4 octets), the autonomous system authorizing other
entities to advertise prefixes within this block. AS numbers
containing only two octets should be placed in the least
significant octets of this four-octet field (the two rightmost
octets).
Each authorizing entity MUST have an autonomous system number, used
as a unique identifier, even though they may not advertise prefixes
into the routing system.
4.1.3 Authorized Originator
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 |
+-------------------------------+-------------------------------+
| Autonomous System |
+---------------------------------------------------------------+
o TLV type: 2 (0x0002)
o Length: Set to 4.
o AS: (4 octets), the autonomous system of an entity authorized
to advertise prefixes within this block. AS numbers containing
only two octets should be placed in the least significant
octets of this four-octet field (the two rightmost octets).
Multiple authorized originator TLVs may be included in the Authcert.
4.1.4 The Serial Number 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 |
+-------------------------------+-------------------------------+
| Serial Number |
+---------------------------------------------------------------+
o TLV type: 3 (0x0003)
o Length: Set to 4.
o Serial Number: (4 octets), unsigned integer taken from a number
space maintained by the Authorizing AS indicating the serial
number of this Authorization certificate. The Authorizing AS
MUST manage the number space as a monotonically increasing
value so that a relative ordering of Authcerts is maintained.
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4.1.5 Authorizing AS Entitycert Uniform Resource Locator
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 |
+-------------------------------+-------------------------------+
| URL |
+----------------
o TLV type: 4 (0x0004)
o Length: Denotes the length of the URL in octets.
o URL: A uniform resource locator indicating a location where the
Authorizing AS?s Entitycert can be found.
An Authcert may omit this TLV. However, an implementation is
REQUIRED to correctly parse them if they are present. A receiving
device MAY choose to ignore the URL TLV.
4.1.6 Authorizing AS Validation List Uniform Resource Locator
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 |
+-------------------------------+-------------------------------+
| URL |
+----------------
o TLV type: 5 (0x0005)
o Length: Denotes the length of the URL in octets.
o URL: A uniform resource locator indicating a location where the
Authorizing AS?s Validation List can be found.
An Authcert may omit this TLV. However, an implementation is
REQUIRED to correctly parse them if they are present. A receiving
device MAY choose to ignore the URL TLV.
4.1.7 The Address Prefix TLV
The address prefix TLV shall define blocks of address within which
the authorized AS' are allowed to advertise prefixes (or routes).
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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 |
+-------------------------------+---------------+---------------+
| Address Family Identifier | RESERVED | Subsequent AFI|
+-------------------------------+---------------+---------------+
| NLRI Data |
+----------------
o TLV Type: 14 (0x000D)
o Length (2 octets), set to 4 + the length of the NLRI Data.
o Address Family Identifier: This field carries the identity of
the Network Layer protocol associated with the Network Address
that follows. Presently defined values for this field are
specified in RFC 1700 (see the Address Family Numbers section).
o RESERVED: Set to 0.
o Subsequent AFI: This field provides additional information
about the type of the Network Layer Reachability Information
carried in the attribute.
o NLRI Data: An address prefix as described in Section 4 of
[RFC2858].
4.1.8 Signature
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 |
+-------------------------------+-------------------------------+
| Signature Type | Number of Issuers |
+-------------------------------+-------------------------------+
| Entity Certificate Issuer Autonomous System |
+-------------------------------+-------------------------------+
| Entity Certificate Serial Number |
+-------------------------------+-------------------------------+
| ... |
+---------------------------------------------------------------+
| Signature |
+------------------
o TLV type: 65535 (0xFFFF)
o Length: (2 octets), unsigned integer denoting the length of the
payload bytes which follow.
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o Signature Type: (2 octets), unsigned integer denoting the type
of signature (the algorithm used to build this signature). Each
possible signing algorithm is assigned an integer from this
field. Signature type 1 is defined as an RSA encryption of a
SHA1 digest.
o Number of Issuers (2 octets): The number of Entitycert
references included in the signature payload. If more than one
Entitycert reference follows, all Entitycerts MUST contain the
same public key for the same authorizing autonomous system.
o Entity Certificate Issuer Autonomous System: (4 octets), the
autonomous system of the entity that provided the Entitycert to
the Authorizing AS. AS numbers containing only two octets
should be placed in the least significant octets of this four-
octet field (the two rightmost octets).
o Entity Certificate Serial Number: (4 octets), the Entitycert
serial number containing the public key of the Authorizing AS.
o Signature: The signature itself.
The signature is calculated using the private key of the authorizing
entity across all the TLVs within the Authcert. The Signature TLV
MUST be appended as the last TLV in the Authcert after the signature
has been computed.
4.2 Creation
An Authcert is usually created by the authorizing autonomous system
with the following steps:
- Allocate a prefix block to the receiving autonomous system.
- Build an Authcert by adding TLVs containing its own AS number, the
receiving (authorized) AS number, the prefix block, a unique
sequence number, and any other information (e.g., URL pointing to
the Entitycert that signed this Authcert.).
- Sign the Authcert by hashing and encrypting the Authcert TLVs.
Place the signature (and other required) information in a
Signature TLV, and append it to the Authcert.
4.2.1 Certificate Uniqueness
Digital certificates are created as uniquely named objects, which
allows them to be uniquely identified. An Authcert is uniquely
identified by the pair of Authorized Originator and Serial Number
TLV values.
4.2.2 Certificate Encoding
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Authcerts distributed in [SOBGP-BGP] are distributed in TLV form.
However if they are manually distributed (e.g., through electronic
mail) they may need to be base64 encoded into ASCII as described in
Section 4.3 of [RFC1421].
4.3 Distribution
Authcerts are distributed as part of a Prefix Policy Certificate, so
that an autonomous system can reliably match distribution policy to
the prefix block.
4.4 Validation
The Authcert is validated using the following steps.
- Identify the Entitycert that signed the Authcert. The correct
Entitycert is uniquely identified with the Entity Certificate
Issuer Autonomous System and Entity Certificate Serial Number
contained in the Signature TLV. The Entity Certificate Issuer
Autonomous System is compared with the AS number in the Entitycert
IssuerAltName field. The Entity Certificate Serial Number is
compared with the Entitycert CertificateSerialNumber.
- Obtain the Entitycert that signed the Authcert, and validate it.
The Entitycert may be in a local cache (already received via BGP
extensions), retrieved using the URL in the Authcert, or through
other means. If an entity does not have the validating public key
it MUST NOT assume the Authcert is valid.
- Verify that the autonomous system identifier in SubjectAltname
matches the Authorized Originator TLV value of the Authcert.
- If an Authorization Certificate Validity List is available,
validate that the issuer of the Entitycert has not invalidated the
Authcert. Validity lists may be distributed in the signers
ASPolicycert, or a pointer to the list may be distributed in the
Authcert in an Authorizing AS Validation List URL. If no
Authorization Certificate Validity List is available, an entity
MAY accept the certificate. However if a validation list is
received later, the entity MUST check the validity of all
certificates that had been previously accepted.
- Hash the Authcert TLVs.
- Extract the signature from the Authcert.
- Extract the public key from the Entitycert, and use it to decrypt
the signature.
- Accept the Authcert as valid if the computed hash matches the
decrypted hash. If the hashes do not match, the Authcert MUST be
discarded.
4.4.1 Self-generated Authcerts
Self-generated Authcerts are dangerous, because a responsible third
party does not assign the authorization. Trusting an autonomous
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system to declare its own address space nullifies most of the
protections outlined in this document.
However, the autonomous systems at the highest level of allocation
(e.g. Regional Internet Registries (RIRs) or Local Internet
Registries (LIRs)) may not be able to find a responsible third party
to sign their Authcerts. In this case, self-generated Authcerts may
be unavoidable.
Authcerts MAY be self-generated, but MUST only be accepted from
autonomous systems that have been explicitly authorized and locally
configured. For example, a device may be configured to accept
Authcerts for the RIR autonomous systems.
4.5 Revocation
An entity issuing an Authcert MUST keep an Authcert revocation list.
The entity MAY use any form for propagating that revocation list.
Because BGP routers do not necessarily have synchronized clocks,
Authcerts do not carry expiration times, and thus do not expire.
Revocation is only method of invalidating an Authcert.
Revocation information may be represented as a "validation list". A
validation list includes lists of both valid and invalid (i.e.,
revoked) certificates. Any number not appearing in the list MUST be
considered invalid. Validation list may be more efficient than a
pure revocation list for Authcerts in the case where a large number
of serial numbers have been revoked by an issuer.
An autonomous system SHOULD include an Authcert validation list in
their AS Policy Certificate (distributed using [SOBGP-BGP]). This
allows autonomous systems that cannot route to the issuing
autonomous system to verify that the Entitycert has not been
revoked.
5.0 Prefix Policy Certificates (PrefixPolicycert)
The PrefixPolicycert carries policy information sourced from route
originators. It provides a specific set of policy regarding one or
more prefix blocks. The owner of the prefix block creates it. There
is only one valid PrefixPolicycert for each prefix block at any
given time.
PrefixPolicycerts are verified with a digital signature provided by
the autonomous system generating the policy. It does not contain a
public key. Rather, it binds a particular policy to a particular
identity (i.e., autonomous system).
5.1 Format
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This certificate is formatted as a series of TLVs. Each TLV will
include a type, which is treated as a 16 bit (two octet) unsigned
integer, a length, which is also two octets, and a variable length
data field. TLVs MUST be placed in the PrefixPolicycert in type
order.
5.1.1 PrefixPolicycert Header
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+---------------+---------------+-------------------------------+
| Cert. Marker | Type Id | Length |
+---------------+---------------+-------------------------------+
| TLVs
+----------------
o Certificate Marker: "162(0xa2), identifying this as an soBGP
certificate.
o Type ID: "2(0x02), identifying this as an PrefixPolicycert.
o Length: Set to the length of the TLVs.
o TLVs: The Type/Length/Value attributes making up an
PrefixPolicycert.
5.1.2 The Originating Autonomous System
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+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| Originating Autonomous System |
+---------------------------------------------------------------+
o TLV type: 1 (0x0001)
o Length: Set to 4.
o Originating Autonomous System: (4 octets), the autonomous
system which originated this certificate. AS numbers containing
only two octets should be placed in the least significant
octets of this four-octet field (the two rightmost octets).
5.1.3 The Serial Number
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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 |
+-------------------------------+-------------------------------+
| Serial Number |
+---------------------------------------------------------------+
o TLV type: 2 (0x0002)
o Length: Set to 4.
o Serial Number: (4 octets), A serial number which identifies
this PrefixPolicycert, taken from a 32 bit number space.
5.1.4 Authorizing AS Entitycert Uniform Resource Locator
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+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| URL |
+----------------
o TLV type: 3 (0x0003)
o Length: Denotes the length of the URL in octets.
o URL: A uniform resource locator indicating a location where the
Authorizing AS?s Entitycert can be found.
An PrefixPolicycert may omit this TLV. However, an implementation is
REQUIRED to correctly parse them if they are present. A receiving
device MAY choose to ignore the URL TLV.
5.1.5 Authcert
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+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| Authentication Certificate |
+----------------
o TLV type: 4 (0x0004)
o Length: Set to the length of the Authentication Certificate.
o Authentication Certificate containing a prefix block for which
the PrefixPolicycert applies.
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One or more Authcert TLVs MUST be included in the PrefixPolicycert.
5.1.6 Policies
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+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| Options | SubTVs
+-------------------------------+--------------
o TLV type: 5 (0x0005)
o Length: Set to the sum of the Options size (2) and the length
of the SubTVs.
o Options: (2 octets), a bit field describing various policies
which should be applied to the prefixes indicated.
o SubTVs: (variable length), zero or more fields, the length of
which is determined by the type, as described below.
5.1.6.1 Option bits
The options bit field describes policies that should be applied
to the address prefix described in the TLV. These options are:
o Bit 0: Path Check. If this bit is set, the receiver should not
accept any prefix for which the path cannot be verified as
described in the section Verifying the Path, below.
o Bit 1: Second Hop Check. If this bit is set, the receiver
should not accept any prefix for which the second entry in the
AS PATH cannot be verified as described in the section
Verifying the Second Hop, below.
o Bits 2-15: Reserved for future use.
5.1.6.2 SubTVs
The Authcert Policy subTVs provide optional policy information for
the block of addresses included in the Authcert indicated; each
subTV is of a fixed length, as determined by its type.
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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
+-------------------------------+------------------------------+
| TV Type | Data....
+-------------------------------+-------------------------
o TV Type: (2 octets), An unsigned integer indicating the type of
subTV
Types defined within this specification are:
- Type 1: Must Include AS, 4 octets of data, an AS which must be
included in the AS path of any prefix falling within this block
of addresses.
- Type 2: OR Include AS, 4 octets of data, at least one of the
included OR Include AS' must be included in the AS path of any
prefix falling within this block of addresses.
- Type 3: Maximum Prefix Length, 1 octet of data, the maximum
length of any prefix allowed within this block of prefixes.
5.1.7 Signature
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+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| Signature Type | Number of Issuers |
+-------------------------------+-------------------------------+
| Entity Certificate Issuer Autonomous System |
+-------------------------------+-------------------------------+
| Entity Certificate Serial Number |
+-------------------------------+-------------------------------+
| ... |
+---------------------------------------------------------------+
| Signature |
+------------------
o TLV type: 65535 (0xFFFF)
o Length: (2 octets), unsigned integer denoting the length of the
payload bytes which follow.
o Signature Type: (2 octets), unsigned integer denoting the type
of signature (the algorithm used to build this signature). Each
possible signing algorithm is assigned an integer from this
field. Signature type 1 is defined as an RSA encryption of a
SHA1 digest.
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o Number of Issuers (2 octets): The number of Entitycert
references included in the signature payload. If more than one
Entitycert reference follows, all Entitycerts MUST contain the
same public key for the same authorizing autonomous system.
o Entity Certificate Issuer Autonomous System: (4 octets), the
autonomous system of the entity that provided the Entitycert to
the AS issuing the PrefixPolicycert. AS numbers containing only
two octets should be placed in the least significant octets of
this four-octet field (the two rightmost octets).
o Entity Certificate Serial Number: (4 octets), the Entitycert
serial number containing the public key of the AS issuing the
PrefixPolicycert.
o Signature: The signature itself.
The signature is calculated using the private key of the authorizing
entity across all the TLVs within the PrefixPolicycert. The
Signature TLV MUST be appended as the last TLV in the
PrefixPolicycert after the signature has been computed.
5.2 Creation
An PrefixPolicycert is created by an autonomous system for prefix
blocks that it owns. An autonomous system creates it with the
following steps:
- Build an PrefixPolicycert by adding TLVs containing its own AS
number, a unique sequence number, policy related to one or more
prefix blocks, and the Authcert or Authcerts defining the prefix
blocks to which this policy applies.
- Sign the PrefixPolicycert by hashing and encrypting the
PrefixPolicycert TLVs. Place the signature (and other required)
information in a Signature TLV, and append it to the
PrefixPolicycert.
5.2.1 Certificate Uniqueness
Digital certificates are created as uniquely named objects, which
allows them to be uniquely identified. A PrefixPolicycert is
uniquely identified by the pair of Authorized Originator and Serial
Number TLV values.
5.2.2 Certificate Encoding
PrefixPolicycert distributed in [SOBGP-BGP] are distributed in TLV
form. However if they are manually distributed (e.g., through
electronic mail) they may need to be encoded into ASCII.
PrefixPolicycert SHOULD be base64 encoded as described in Section
4.3 of [RFC1421].
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5.3 Distribution
PrefixPolicycerts may be distributed using any number of methods,
for example:
- maintained in a directory maintained by the issuing autonomous
system,
- distributed via some out of band mechanism, or
- distributed within BGP using extensions defined in [SOBGP-BGP].
To ensure interoperability, an autonomous system SHOULD distribute
its PrefixPolicycerts within BGP.
5.4 Validation
The Authcert included in the Authcert TLV MUST be validated as
correct before the Policy TLV can be accepted. Thus, the Authcert
should be extracted from the PrefixPolicycert and validated before
the PrefixPolicycert is validated.
The PrefixPolicycert is validated using the following steps.
- Identify the Entitycert that signed the PrefixPolicycert. The
correct Entitycert is uniquely identified with the Entity
Certificate Issuer Autonomous System and Entity Certificate Serial
Number contained in the Signature TLV. The Entity Certificate
Issuer Autonomous System is compared with the AS number in the
Entitycert IssuerAltName field. The Entity Certificate Serial
Number is compared with the Entitycert CertificateSerialNumber.
- Obtain the Entitycert that signed the Authcert, and validate it.
The Entitycert may be in a local cache (already received via BGP
extensions), retrieved using the URL in the Authcert, or through
other means. If an entity does not have the validating public key
it MUST NOT assume the PrefixPolicycert is valid.
- Verify that the autonomous system identifier in SubjectAltname
matches the Authorized Originator TLV value of the
PrefixPolicycert.
- Hash the PrefixPolicycert TLVs.
- Extract the signature from the PrefixPolicycert.
- Extract the public key from the Entitycert, and use it to decrypt
the signature.
- Validate that the computed hash matches the decrypted hash. If the
hashes do not match, the PrefixPolicycert MUST be discarded.
Once a PrefixPolicycert has been validated, any PrefixPolicycert
that matches the following criteria MUST be discarded:
- has a lower serial number from the same originating AS, and
- includes an Authcert with the same prefix block
5.5 Revocation
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Any entity issuing an PrefixPolicycert MUST keep a revocation list.
The entity MAY use any form for propagating that revocation list.
Because BGP routers do not necessarily have synchronized clocks,
PrefixPolicycert do not carry expiration times, and thus do not
expire. Revocation is only method of invalidating an
PrefixPolicycert.
Revocation information may be represented as a "validation list". A
validation list includes lists of both valid and invalid (i.e.,
revoked) certificates. Any number not appearing in the list MUST be
considered invalid. Validation list may be more efficient than a
pure revocation list for PrefixPolicycerts in the case where a large
number of serial numbers have been revoked by an issuer.
An autonomous system SHOULD include an PrefixPolicycert validation
list in their AS Policy Certificate (distributed using [SOBGP-BGP]).
This allows autonomous systems that cannot route to the issuing
autonomous system to verify that the Entitycert has not been
revoked.
6.0 AS Policy Certificates (ASPolicycert)
The ASPolicycert provides a specific set of policy relating to an
autonomous system. An administrative entity within the autonomous
system creates it. There is only one valid ASPolicycert for each
autonomous system at any given time.
ASPolicycerts are verified with a digital signature from the
autonomous system generating the policy. It does not contain a
public key. Rather, it binds a particular policy to a particular
identity (i.e., autonomous system).
6.1 Format
This certificate is formatted as a series of TLVs. Each TLV will
include a type, which is treated as a 16 bit (two octet) unsigned
integer, a length, which is also two octets, and a variable length
data field. TLVs MUST be placed in the ASPolicycert in type order.
6.1.1 ASPolicycert Header
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+---------------+---------------+-------------------------------+
| Cert. Marker | Type Id | Length |
+---------------+---------------+-------------------------------+
| TLVs
+----------------
o Certificate Marker: "162(0xa2), identifying this as an soBGP
certificate.
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o Type ID: "3(0x03), identifying this as an ASPolicycert.
o Length: Set to the length of the TLVs.
o TLVs: The Type/Length/Value attributes making up an
ASPolicycert.
6.1.2 The Originating Autonomous System
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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 |
+-------------------------------+-------------------------------+
| Originating Autonomous System |
+---------------------------------------------------------------+
o TLV type: 1 (0x0001)
o Length: Set to 4.
o Originating Autonomous System: (4 octets), the autonomous
system which originated this certificate. AS numbers containing
only two octets should be placed in the least significant
octets of this four-octet field (the two rightmost octets).
6.1.3 The Serial Number
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+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| Serial Number |
+---------------------------------------------------------------+
o TLV type: 2 (0x0002)
o Length: Set to 4.
o Serial Number: (4 octets), A serial number which identifies
this ASPolicycert, taken from a 32 bit number space.
6.1.4 Authorizing AS Entitycert Uniform Resource Locator
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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 |
+-------------------------------+-------------------------------+
| URL |
+----------------
o TLV type: 3 (0x0003)
o Length: Denotes the length of the URL in octets.
o URL: A uniform resource locator indicating a location where the
Authorizing AS?s Entitycert can be found.
An PrefixPolicycert may omit this TLV. However, an implementation is
REQUIRED to correctly parse them if they are present. A receiving
device MAY choose to ignore the URL TLV.
6.1.5 Attached Transit Autonomous Systems
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+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+---------------+---------------+
| Address Family Identifier | RESERVED | Subsequent AFI |
+-------------------------------+---------------+---------------+
| Autonomous Systems |
+-----------------
o TLV type: 4 (0x0004)
o Length: Set to 4 + 4 octets for each autonomous system in the
list.
o Address Family Identifier: This field carries the identity a
the Network Layer protocol. Presently defined values for this
field are specified in RFC 1700 (see the Address Family Numbers
section).
o RESERVED: Set to 0.
o Subsequent AFI: This field provides additional information
about the type of the Network Layer protocol.
o Autonomous Systems: List of autonomous systems which are
connected to the originating autonomous system through some
form of peering arrangement and which may transit traffic from
the origin AS. Each AS number takes four octets. AS number
values containing only two octets should be placed in the least
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significant octets of this four-octet field (the two rightmost
octets).
One or more Attached Transit AS TLVs may be included in the Policy
Certificate. Each type 4 TLV indicates an AS which is connected to
the AS which originates this ASPolicycert through a BGP peering
relationship.
6.1.6 Attached Non-transit Autonomous Systems
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+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+---------------+---------------+
| Address Family Identifier | RESERVED | Subsequent AFI|
+-------------------------------+---------------+---------------+
| Autonomous Systems |
+------------------
o TLV type: 5 (0x0005)
o Length: Set to 4 + 4 octets for each autonomous system in the
list.
o Address Family Identifier: This field carries the identity a
the Network Layer protocol. Presently defined values for this
field are specified in RFC 1700 (see the Address Family Numbers
section).
o RESERVED: Set to 0.
o Subsequent AFI: This field provides additional information
about the type of the Network Layer protocol.
o Autonomous Systems: List of autonomous systems which are
connected to the originating autonomous system through some
form of peering arrangement and which may not transit traffic
from the origin AS. Each AS number takes four octets. AS number
values containing only two octets should be placed in the least
significant octets of this four-octet field (the two rightmost
octets).
One or more Attached Non-Transit AS TLVs may be included in the
ASPolicycert. Each type 5 TLV indicates an AS which is connected to
the AS which originates this ASPolicycert through a BGP peering
relationship.
6.1.7 Revoked Entity Certificate List
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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 |
+-------------------------------+-------------------------------+
| Entity Certificate Revocation List
+----------------
o TLV type: 6 (0x0006)
o Length: (2 octets), length of TLV data (the list of revoked
Entity Certificates) in octets
o Entity Certificate Revocation List: A revocation list created
by the autonomous system, which includes a list of revoked
Entity Certificates issued by this autonomous system. The
format of the revocation list MUST be as defined in [RFC3280].
A single Revoked Entity Certificate List TLV MAY be included in an
ASPolicycert, or it may be omitted.
When an Entity Certificate Revocation List is received, all
currently held Entitycerts from this issuer MUST be checked against
the validity list. Entitycerts found to be invalid MUST be deleted.
6.1.8 Authorization Certificate Validity List
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+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| Validity Ranges
+----------------
o TLV type: 7 (0x0007)
o Length: (2 octets), length of TLV data (the list of revoked
Authorization Certificates) in octets
o Validity Ranges: A list of validity subTVs defining which
serial numbers are valid and invalid. Validity ranges are
interpreted in order until a match is found. For more
information on validity lists, see Section 4.5.
A single TLV of this type MAY be included in an ASPolicycert, or it
may be omitted.
When an Authorization Certificate Validity List is received, all
currently held Authcerts from this issuer MUST be checked against
the validity list. Authcerts found to be invalid MUST be deleted.
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6.1.8.1 Validity Ranges
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+-------------------------------+-------------------------------+
| subTV Type | Size of Range |
+-------------------------------+-------------------------------+
| Lowest Authorization Serial Number |
+---------------------------------------------------------------+
o subTV type: (2 octets).
SubTV type Value
---------- -----
VALID 0
INVALID 1
o Size of Range: (2 octets). Number of contiguous serial numbers
defining a range.
o Lowest Authorization Serial Number (4 octets). The lowest value
in the range.
6.1.9 Prefix Policy Certificate Validity List
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+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| Validity Ranges
+----------------
o TLV type: 8 (0x0008)
o Length: (2 octets), length of TLV data (the list of revoked
Authorization Certificates) in octets
o Validity Ranges: A list of validity subTVs (as defined in the
previous section) defining which PrefixPolicycert serial
numbers are valid and invalid. Validity ranges are interpreted
in order until a match is found.. For more information on
validity lists, see Section 5.5.
A single TLV of this type MAY be included in an ASPolicycert, or it
may be omitted.
When an Prefix Policy Validity List is received, all currently held
PrefixPolicycerts from this issuer MUST be checked against the
validity list. PrefixPolicycerts found to be invalid MUST be
deleted.
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6.1.10 Most Recent AS Policy Certificate Uniform Resource Locator
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+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| URL |
+----------------
o TLV type: 9 (0x0009)
o Length: Denotes the length of the URL in octets.
o URL: A uniform resource locator indicating a location where the
most recent AS Policy Certificate can be found. This is useful
for a receiver to verify that they have the most recent AS
Policy Certificate for an AS.
An PrefixPolicycert may omit this TLV. However, an implementation is
REQUIRED to correctly parse them if they are present. A receiving
device MAY choose to ignore the URL TLV.
6.1.11 Signature
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+-------------------------------+-------------------------------+
| TLV Type | Length |
+-------------------------------+-------------------------------+
| Signature Type | Number of Issuers |
+-------------------------------+-------------------------------+
| Entity Certificate Issuer Autonomous System |
+-------------------------------+-------------------------------+
| Entity Certificate Serial Number |
+-------------------------------+-------------------------------+
| ... |
+---------------------------------------------------------------+
| Signature |
+------------------
o TLV type: 65535 (0xFFFF)
o Length: (2 octets), unsigned integer denoting the length of the
payload bytes which follow.
o Signature Type: (2 octets), unsigned integer denoting the type
of signature (the algorithm used to build this signature). Each
possible signing algorithm is assigned an integer from this
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field. Signature type 1 is defined as an RSA encryption of a
SHA1 digest.
o Number of Issuers (2 octets): The number of Entitycert
references included in the signature payload. If more than one
Entitycert reference follows, all Entitycerts MUST contain the
same public key for the same authorizing autonomous system.
o Entity Certificate Issuer Autonomous System: (4 octets), the
autonomous system of the entity that provided the Entitycert to
the AS issuing the PrefixPolicycert. AS numbers containing only
two octets should be placed in the least significant octets of
this four-octet field (the two rightmost octets).
o Entity Certificate Serial Number: (4 octets), the Entitycert
serial number containing the public key of the AS issuing the
PrefixPolicycert.
o Signature: The signature itself.
The signature is calculated using the private key of the authorizing
entity across all the TLVs within the ASPolicycert. The Signature
TLV MUST be appended as the last TLV in the ASPolicycert after the
signature has been computed.
6.2 Creation
An ASPolicycert is created by an autonomous system in order to relay
its own policy. An autonomous system creates it with the following
steps:
- Build an ASPolicycert by adding TLVs containing its own AS number,
a unique sequence number, and policy related to the autonomous
system.
- Sign the ASPolicycert by hashing and encrypting the ASPolicycert
TLVs. Place the signature (and other required) information in a
Signature TLV, and append it to the ASPolicycert.
6.2.1 Certificate Uniqueness
Digital certificates are created as uniquely named objects, which
allows them to be uniquely identified. An ASPolicycert is uniquely
identified by the pair of Authorized Originator and Serial Number
TLV values.
6.2.2 Certificate Encoding
ASPolicycert distributed in [SOBGP-BGP] are distributed in TLV form.
However if they are manually distributed (e.g., through electronic
mail) they may need to be encoded into ASCII. ASPolicycert SHOULD be
base64 encoded following Section 4.3 of [RFC1421].
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6.3 Distribution
ASPolicycert may be distributed using any number of methods, for
example:
- maintained in a directory maintained by the issuing autonomous
system,
- distributed via some out of band mechanism, or
- distributed within BGP using extensions defined in [SOBGP-BGP].
To ensure interoperability, an autonomous system SHOULD distribute
its ASPolicycert within BGP.
6.4 Validation
The ASPolicycert is validated using the following steps.
- Identify the Entitycert that signed the ASPolicycert. The correct
Entitycert is uniquely identified with the Entity Certificate
Issuer Autonomous System and Entity Certificate Serial Number
contained in the Signature TLV. The Entity Certificate Issuer
Autonomous System is compared with the AS number in the Entitycert
IssuerAltName field. The Entity Certificate Serial Number is
compared with the Entitycert CertificateSerialNumber.
- Obtain the Entitycert that signed the ASPolicycert, and validate
it. The Entitycert may be in a local cache (already received via
BGP extensions), retrieved using the URL in the Authcert, or
through other means. If an entity does not have the validating
public key it MUST NOT assume the ASPolicycert is valid.
- Verify that the autonomous system identifier in SubjectAltname
matches the Authorized Originator TLV value of the ASPolicycert.
- Hash the ASPolicycert TLVs.
- Extract the signature from the ASPolicycert.
- Extract the public key from the Entitycert, and use it to decrypt
the signature.
- Validate that the computed hash matches the decrypted hash. If the
hashes do not match, the ASPolicycert MUST be discarded.
Once an ASPolicycert has been validated, any ASPolicycert with a
lower serial number from the same originating AS MUST be discarded.
6.5 Revocation
Each ASPolicycert issued by an autonomous system overrides any
previously issued ASPolicycerts from this autonomous system.
Therefore, revocation is not required.
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If present, a receiver has the opportunity of using the Most Recent
AS Policy Certificate URL in the ASPolicycert to verify that they
have the most recent policy certificate.
7.0 Security Considerations
This document describes the format of authentication, authorization,
and policy certificates used to with [SOBGP-BGP]. Each certificate
type is digitally signed, and therefore requires no external
protection to ensure its integrity. There are no restrictions on how
they may be distributed. Revocation schemes are defined for all
certificate types.
The following sections describe the security considerations of each
of those objects.
7.1 Entitycerts
Entitycerts provide authentication, providing a binding of an
identity (i.e., autonomous system number) to a public key. The
authenticity of the binding is verified with a digital signature,
where the public key of the certificate issuer has been previously
accepted as valid. Issuer public keys can either be manually
configured, or are verified through the use of another issuer's
trusted public key in a "web of trust" built by the receiver.
Certificate issuers MUST maintain certificate revocation lists
(CRLs). Entities verifying Entitycerts SHOULD reference the
certificate revocation lists whenever possible. (Mandating the
consultation of a CRL as part of the verification process is not
possible, because the CRL may not be available at the time
verification is performed. For example, if the issuer maintains the
CRL on a directory server to which routing is not yet setup.)
Issuers SHOULD distribute their CRLs within their AS Policy
Certificates to increase the likelihood of a receiver having the CRL
available.
Self-signed Entitycerts may be necessary in order to start a chain
of trust. However self-signed Entitycerts MUST be manually validated
as accurate before the enclosed public key is used, else the "web of
trust" breaks down.
7.2 Authcerts
Authcerts provide authorization, where the issuer of a prefix block
certifies that it has given that prefix block to a specific
autonomous system. Receivers use the Authcert to validate
announcements received in BGP UPDATE messages.
The authenticity of Authcerts is verified with a digital signature,
where the public key of the certificate issuer is distributed in an
Entitycert. Before a receiver can verify the Authcert, they MUST
first check that the verifying Entitycert is authentic.
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The Authcert issuer MUST keep an Authcert validation list describing
which certificates are valid, and which are invalid. The receivers
of an Authcert SHOULD consult the Authcert validation list to ensure
that the authorization has not been revoked.
Autonomous systems may need to authorize their own use of prefix
blocks if the autonomous system that issued their prefix blocks does
not issue them an Authcert. However, such self-generated Authcerts
are dangerous, since unrestricted use of self-signed Authcerts
defeats the goal of authorization. Thus an entity MUST accept self-
generated Authcerts only from autonomous systems that have been
explicitly configured as trusted to claim authorization without the
confirmation of a third party.
7.3 PrefixPolicycerts
PrefixPolicycerts bind policy generated by an autonomous system for
prefix blocks that they advertise. This policy is bound to a
particular Authcert, which verifies that they are authorized to
advertise those prefix blocks.
PrefixPolicycerts are verified with a digital signature, where the
public key of the certificate issuer is distributed in an
Entitycert. Before a receiver can verify the PrefixPolicycert, they
MUST first verify that the verifying Entitycert is authentic.
7.4 ASPolicycerts
ASPolicycerts contain policy generated by an autonomous system, and
contain policy about the autonomous system itself. The policy
includes its neighbor autonomous systems, which can be used by other
entities to validate valid inter-connections. The policy can also
include revocation and validation lists (Authcert,
PrefixPolicycert).
ASPolicycerts are verified with a digital signature, where the
public key of the certificate issuer is distributed in an
Entitycert. Before a receiver can verify the ASPolicycerts, they
MUST first verify that the verifying Entitycert is authentic.
7.5 Entitycert Uniform Resource Locators
Authcerts, PrefixPolicycerts, and ASPolicycerts may contain a URL
that references the Entitycert used to validate it. Care should be
taken in evaluating the URL since it is not yet known to be valid
and could be used to propagate a denial of service attack.
8.0 IANA Considerations
This document defines three certificate types, each of which contains
a series of TLVs. IANA is expected to maintain a registry of all the
values defined, according to the following sections.
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8.1 Authorization Certificate
The Authorization Certificate Type Field:
o Type values 1 through 4, 14 and 65535 are assigned in this
document.
o Type values 5 through 13 and 15 through 16575 MUST be assigned
using the "IETF Consensus" policy defined in RFC 2434
[RFC2434].
o Type values 16576 through 32895 SHOULD be assigned using the
"Specification Required" policy defined in RFC 2434 [RFC2434].
o Type values 32896 through 65534 are for "Private Use" as defined
in RFC 2434 [RFC2434].
8.1.1 Signature Type
The Signature TLV Signature Type field:
o Type values 1 is assigned in this document.
o Type values 2 through 16575 MUST be assigned using the "IETF
Consensus" policy defined in RFC 2434 [RFC2434].
o Type values 16576 through 32895 SHOULD be assigned using the
"Specification Required" policy defined in RFC 2434 [RFC2434].
o Type values 32896 through 65534 are for "Private Use" as defined
in RFC 2434 [RFC2434].
8.2 Prefix Policy Certificate
o Type values 1 through 5, 14 and 65535 are assigned in this
document.
o Type values 6 through 13 and 15 through 16575 MUST be assigned
using the "IETF Consensus" policy defined in RFC 2434
[RFC2434].
o Type values 16576 through 32895 SHOULD be assigned using the
"Specification Required" policy defined in RFC 2434 [RFC2434].
o Type values 32896 through 65534 are for "Private Use" as defined
in RFC 2434 [RFC2434].
8.2.1 Policies Type
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The Policies Type has two name spaces: Options flags and SubTVs.
The Options Field:
o Bits 0 and 1 are assigned in this document.
o Bits 2 thru 7 MUST be assigned using the "IETF Consensus"
policy defined in RFC 2434 [RFC2434].
o Bits 8 thru 15 are for "Private Use" as defined in RFC 2434
[RFC2434].
The subTV TV Type field:
o TV Type values 1 through 3 are assigned in this document.
o TV Type values 4 through 16575 MUST be assigned using the "IETF
Consensus" policy defined in RFC 2434 [RFC2434].
o TV Type values 16576 through 32895 SHOULD be assigned using the
"Specification Required" policy defined in RFC 2434 [RFC2434].
o TV Type values 32896 through 65534 are for "Private Use" as
defined in RFC 2434 [RFC2434].
8.2.2 Signature Type
The Signature TLV Signature Type field:
o Type values 1 is assigned in this document.
o Type values 2 through 16575 MUST be assigned using the "IETF
Consensus" policy defined in RFC 2434 [RFC2434].
o Type values 16576 through 32895 SHOULD be assigned using the
"Specification Required" policy defined in RFC 2434 [RFC2434].
o Type values 32896 through 65534 are for "Private Use" as defined
in RFC 2434 [RFC2434].
8.3 AS Policy Certificate
o Type values 1 through 9, 14 and 65535 are assigned in this
document.
o Type values 10 through 16575 MUST be assigned using the "IETF
Consensus" policy defined in RFC 2434 [RFC2434].
o Type values 16576 through 32895 SHOULD be assigned using the
"Specification Required" policy defined in RFC 2434 [RFC2434].
o Type values 32896 through 65534 are for "Private Use" as defined
in RFC 2434 [RFC2434].
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8.3.1 Validity Ranges
o Type values 1 through 2 are assigned in this document.
o Type values 3 through 16575 MUST be assigned using the "IETF
Consensus" policy defined in RFC 2434 [RFC2434].
o Type values 16576 through 32895 SHOULD be assigned using the
"Specification Required" policy defined in RFC 2434 [RFC2434].
o Type values 32896 through 65534 are for "Private Use" as defined
in RFC 2434 [RFC2434].
8.3.2 Signature Type
The Signature TLV Signature Type field:
o Type values 1 is assigned in this document.
o Type values 2 through 16575 MUST be assigned using the "IETF
Consensus" policy defined in RFC 2434 [RFC2434].
o Type values 16576 through 32895 SHOULD be assigned using the
"Specification Required" policy defined in RFC 2434 [RFC2434].
o Type values 32896 through 65534 are for "Private Use" as defined
in RFC 2434 [RFC2434].
9.0 Acknowledgments
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: James Ng, Russ White,
Alvaro Retana, Dave Cook, John Scudder, David Ward, Martin Djernaes,
Max Pritikin, Chris Lonvick, Tim Gage, Scott Fanning, Barry Friedman,
Jim Duncan, Yi Yang, Robert Adams, Tony Tauber, Iljitsch van Beijnum,
Ed Lewis, and Jonathan Natale.
10.0 References
10.1 Normative References
[ADDR-EXT] Lynn, C., Kent, S. and K. Seo, "X.509 Extensions for IP
Addresses and AS Identifiers", draft-ietf-pkix-x509-ipaddr-as-extn-
03.txt, September 2003.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Level", BCP 14, RFC 2119, March 1997.
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[RFC2434] Narten, T., and H. Alvestrand,, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 2434, October 1998.
[RFC2858] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 2858, June 2000.
[RFC3279] Polk, T., et. al., " Algorithms and Identifiers for the
Internet X.509 Public Key Infrastructure Certificate and Certificate
Revocation List (CRL) Profile", RFC 3279, April 2002.
[RFC3280] Housley, R., et. al., "Internet X.509 Public Key
Infrastructure Certificate and CRL Profile", RFC 3280, April 2002.
[SOBGP-BGP] Ng, J. (editor), "Extensions to BGP to Support Secure
Origin BGP (soBGP)", draft-ng-sobgp-extensions-01.txt, June 2003.
[SOBGP-DEPLOY] White, R. (editor), ?Deployment Considerations for
Secure Origin BGP (soBGP)?, draft-white-sobgp-bgp-deployment-01.txt,
June 2003.
[SOBGP-RADIUS] Lonvick, C., ?RADIUS Attributes for soBGP Support?,
draft-lonvick-sobgp-radius-03.txt, August 19, 2003.
[X.690] International Telecommunication Union, "ITU-T Recommendation
X.660 Information Technology - ASN.1 encoding rules: Specification
of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER), 1997.
10.2 Informative References
[IAB-SC] Rescorla, E., B. Korver, and the Internet Architecture
Board, "Guidelines for Writing RFC Text on Security Considerations",
http://www.ietf.org/internet-drafts/draft-iab-sec-cons-03.txt, Work
in progress, 2003.
[RFC3281] Farrell, S., and R. Housley, " An Internet Attribute
Certificate Profile for Authorization", RFC 3281, April 2002.
Editor's Address
Brian Weis
Cisco Systems
170 W. Tasman Drive,
San Jose, CA 95134-1706, USA
(408) 526-4796
bew@cisco.com
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| PAFTECH AB 2003-2026 | 2026-04-22 13:35:39 |