Individual Submission G. Huston
Internet-Draft T. Manderson
Intended status: Standards Track G. Michaelson
Expires: February 8, 2009 APNIC
August 7, 2008
A Profile for Bogon Origin Attestations (BOAs)
draft-ietf-sidr-bogons-00.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document defines a standard profile for Bogon Origin
Attestations (BOAs). A BOA is a digitally signed object that
provides a means of verifying that an IP address block holder has not
authorized any Autonomous System (AS) to originate routes that are
equivalent to any of the addresses listed in the BOA, and also
provides a means of verifying that BGP speaker is not using an AS as
a BGP speaker without appropriate authority to use that AS. The
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proposed application of BOAs is intended to fit within the
requirements for adding security measures to inter-domain routing,
including the ability to support incremental and piecemeal deployment
of such measures, and does not require any changes to the
specification of BGP.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Basic Format . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Signed-Data Content Type . . . . . . . . . . . . . . . . . 4
2.1.1. version . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.2. digestAlgorithms . . . . . . . . . . . . . . . . . . . 4
2.1.3. encapContentInfo . . . . . . . . . . . . . . . . . . . 4
2.1.4. certificates . . . . . . . . . . . . . . . . . . . . . 6
2.1.5. crls . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.6. signerInfo . . . . . . . . . . . . . . . . . . . . . . 6
3. BOA Validation . . . . . . . . . . . . . . . . . . . . . . . . 9
4. BOA Use Practices . . . . . . . . . . . . . . . . . . . . . . 11
5. BOA Interpretation . . . . . . . . . . . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
9. Normative References . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
Intellectual Property and Copyright Statements . . . . . . . . . . 15
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1. Introduction
This document defines an application of the Resource Public Key
Infrastructure (RPKI) to validate the attestations of Internet
Registries that certain addresses are currently neither allocated nor
assigned to any party, and any appearance of such addresses or ASes
in a routing advertisement in the Border Gateway Protocol (BGP)
[RFC4271] should be considered an invalid use of such addresses or
ASes.
The RPKI is based on Resource Certificates. Resource Certificates
are X.509 certificates that conform to the PKIX profile [RFC5280],
and to the extensions for IP addresses and AS identifiers [RFC3779].
A Resource Certificate describes an action by an Issuer that binds a
list of IP address blocks and Autonomous System (AS) numbers to the
Subject of a certificate, identified by the unique association of the
Subject's private key with the public key contained in the Resource
Certificate. The RPKI is structured such that each current Resource
Certificate matches a current resource allocation or assignment.
This is described in [ID.ietf-sidr-arch].
BOAs can be regarded as a logical opposite of a Route Origin
Authorization (ROA) [ID.ietf-sidr-roa-format], and allows a resource
holder to explicitly list those IP addresses and ASes that are
denoted by the holder as not validly appearing in any routing
advertisement, and to make this attestation in a manner that a
relying party can validate under the framework of the RPKI.
A BOA is a digitally signed object that makes use of Cryptographic
Message Syntax (CMS) [RFC3852] as a standard encapsulation format.
CMS was chosen to take advantage of existing open source software
available for processing messages in this format.
2. Basic Format
Using CMS syntax, a BOA is a type of signed-data object. The general
format of a CMS object is:
ContentInfo ::= SEQUENCE {
contentType ContentType,
content [0] EXPLICIT ANY DEFINED BY contentType }
ContentType ::= OBJECT IDENTIFIER
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2.1. Signed-Data Content Type
According to the CMS specification, The signed-data content type
shall have ASN.1 type SignedData:
SignedData ::= SEQUENCE {
version CMSVersion,
digestAlgorithms DigestAlgorithmIdentifiers,
encapContentInfo EncapsulatedContentInfo,
certificates [0] IMPLICIT CertificateSet OPTIONAL,
crls [1] IMPLICIT RevocationInfoChoices OPTIONAL,
signerInfos SignerInfos }
DigestAlgorithmIdentifiers ::= SET OF DigestAlgorithmIdentifier
SignerInfos ::= SET OF SignerInfo
2.1.1. version
The version is the syntax version number. It MUST be 3,
corresponding to the signerInfo structure having version number 3.
2.1.2. digestAlgorithms
The digestAlgorithms set MUST include only SHA-256, the OID for which
is 2.16.840.1.101.3.4.2.1. [RFC4055] It MUST NOT contain any other
algorithms.
2.1.3. encapContentInfo
encapContentInfo is the signed content, consisting of a content type
identifier and the content itself.
EncapsulatedContentInfo ::= SEQUENCE {
eContentType ContentType,
eContent [0] EXPLICIT OCTET STRING OPTIONAL }
ContentType ::= OBJECT IDENTIFIER
2.1.3.1. eContentType
The ContentType for a BOA is defined as id-ct-rpkiBOA, and has the
numerical value of 1.2.840.113549.1.9.16.1.[TBD]. [This value has to
be assigned via an OID registration.]
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id-smime OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs9(9) 16 }
id-ct OBJECT INDENTIFIER ::= { id-smime 1 }
id-ct-rpkiBOA OBJECT IDENTIFIER ::= { id-ct [TBD] }
2.1.3.2. eContent
The content of a BOA identifies a list of one or more ASes and a list
of one or more IP address prefixes that are asserted to be "bogons"
and, accordingly, BOAs are intended to act as a constraint on the
routing system to signal that no route object that that relates to
these ASes or IP addresses should be interpreted as representing a
valid routing attestation. A BOA is formally defined as:
id-ct-rpkiBOA ::= {
version [0] INTEGER DEFAULT 0,
asIDs SEQUENCE OF asIdsOrRange,
ipAddrBlocks SEQUENCE OF BOAIPAddressFamily }
ASIdOrRange ::= CHOICE {
id ASId,
range ASRange }
ASRange ::= SEQUENCE {
min ASId,
max ASId }
ASId ::= INTEGER
BOAIPAddressFamily ::= SEQUENCE {
addressFamily OCTET STRING (SIZE (2..3)),
addresses SEQUENCE OF IPAddress }
IPAddress ::= BIT STRING
2.1.3.2.1. version
The version number of the BogonOriginAttestation MUST be 0.
2.1.3.2.2. asIDs
The asIDs field contains the AS numbers that are to be regarded as
Bogon ASes. The set of AS numbers may be explicitly listed, or
specified as a continuous range of values. The field is to be
formatted as per the canonical format specified in [RFC3779].
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2.1.3.2.3. BOAIPAddressFamily
The BOAIPAddressFamily field encodes the set of IP address prefixes
that are to be regarded as Bogon IP addresses that are to be
constrained from appearing in any routing advertisement. The
intended semantics of an address prefix in a BOA is that any route
object that has the same address prefix as that listed as a Bogon IP
address, or is a more specific prefix of a Bogon IP address can be
regarded as a Bogon route object.
The syntax of the addres prefixes listed in a BOA uses a subset of
the IP Address Delegation extension defined in [RFC3779]. The
BOAIPAddressFamily cannot contain arbitrary address ranges, but in
all other respects uses the same canonical format as the IP Address
Delegation Extension.
Within the BOAIPAddressFamily structure, addressFamily contains the
Address Family Identifier (AFI) of an IP address family. This
specification only supports IPv4 and IPv6. Therefore, addressFamily
MUST be either 0001 or 0002. The addresses field represents prefixes
as a sequence of type IPAddress, as defined in[RFC3779].
2.1.4. certificates
The certificates field MUST be included, and MUST contain only the
end entity (EE) certificate needed to validate this BOA.
2.1.5. crls
The crls field MUST be omitted.
2.1.6. signerInfo
SignerInfo is defined under CMS as:
SignerInfo ::= SEQUENCE {
version CMSVersion,
sid SignerIdentifier,
digestAlgorithm DigestAlgorithmIdentifier,
signedAttrs [0] IMPLICIT SignedAttributes OPTIONAL,
signatureAlgorithm SignatureAlgorithmIdentifier,
signature SignatureValue,
unsignedAttrs [1] IMPLICIT UnsignedAttributes OPTIONAL }
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2.1.6.1. version
The version number MUST be 3, corresponding with the choice of
SubjectKeyIdentifier for the sid.
2.1.6.2. sid
The sid is defined as:
SignerIdentifier ::= CHOICE {
issuerAndSerialNumber IssuerAndSerialNumber,
subjectKeyIdentifier [0] SubjectKeyIdentifier }
For a BOA, the sid MUST be a SubjectKeyIdentifier.
2.1.6.3. digestAlgorithm
The digestAlgorithm MUST be SHA-256, the OID for which is
2.16.840.1.101.3.4.2.1. [RFC4055]
2.1.6.4. signedAttrs
Signed Attributes are defined as:
SignedAttributes ::= SET SIZE (1..MAX) OF Attribute
Attribute ::= SEQUENCE {
attrType OBJECT IDENTIFIER,
attrValues SET OF AttributeValue }
AttributeValue ::= ANY
The signedAttr element MUST be present and MUST include the content-
type and message-digest attributes. The signer MAY also include the
signing-time signed attribute, the binary-signing-time signed
attribute, or both signed attributes. Other signed attributes that
are deemed appropriate MAY also be included. The intent is to allow
additional signed attributes to be included if a future need is
identified. This does not cause an interoperability concern because
unrecognized signed attributes are ignored by the relying party.
The signedAttr MUST include only a single instance of any particular
attribute. Additionally, even though the syntax allows for a SET OF
AttributeValue, in a BOA the attrValues must consist of only a single
AttributeValue.
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2.1.6.4.1. Content-Type Attribute
The ContentType attribute MUST be present. The attrType OID for the
ContentType attribute is 1.2.840.113549.1.9.3.
The attrValues for the ContentType attribute in a ROA MUST be
1.2.840.113549.1.9.16.1.[TBD] (matching the eContentType in the
EncapsulatedContentInfo).
2.1.6.4.2. Message-Digest Attribute
The MessageDigest Attribute MUST be present. The attrType OID for
the MessageDigest Attribute is 1.2.840.113549.1.9.4.
The attrValues for the MessageDigest attribute contains the output of
the digest algorithm applied to the content being signed, as
specified in Section 11.1 of[RFC3852].
2.1.6.4.3. Signing-Time Attribute
The SigningTime Attribute MAY be present in a BOA. If it is present
it MUST be ignored by the relying party. The presence of absence of
the SigningTime attribute in no way affects the validation of the BOA
(as specified in Section 3). The attrType OID for the SigningTime
attribute is 1.2.840.113549.1.9.5.
The SigningTime attribute is defined as:
id-signingTime OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs9(9) 5 }
SigningTime ::= Time
Time ::= CHOICE {
utcTime UTCTime,
generalizedTime GeneralizedTime }
The Time element specifies the time, based on the local system clock,
at which the digital signature was applied to the content.
2.1.6.4.4. BinarySigningTime Attribute
The BinarySigningTime Attribute MAY be present. If it is present it
MUST be ignored by the relying party. The presence of absence of the
BinarySigningTime attribute in no way affects the validation of the
ROA (as specified in Section 3). The attrType OID for the
BinarySigningTime attribute is 1.2.840.113549.1.9.16.2.46.
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The VinarySigningTime attribute is defined as:
id-aa-binarySigningTime OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) aa(2) 46 }
BinarySigningTime ::= BinaryTime
BinaryTime ::= INTEGER (0..MAX)
The BinaryTime element specifies the time, based on the local system
clock, at which the digital signature was applied to the content.
2.1.6.5. signatureAlgorithm
The signatureAlgorithm MUST be RSA (rsaEncryption), the OID for which
is 1.2.840.113549.1.1.1.
2.1.6.6. signature
The signature value is defined as:
SignatureValue ::= OCTET STRING
The signature characteristics are defined by the digest and signature
algorithms.
2.1.6.7. unsignedAttrs
unsignedAttrs MUST be omitted.
3. BOA Validation
Before a relying party can use a BOA as a constrictor of a routing
announcement, the relying party must use the RPKI to validate the
BOA. To do this the relying party performs the following steps:
1. Verify that the BOA syntax complies with this specification. In
particular, verify the following:
1.a The contentType of the CMS object is SignedData (OID
1.2.840.113549.1.7.2)
1.b The eContentType of the CMS object is id-ct-rpkiBOA (OID
1.2.840.113549.1.9.16.1.[TBD])
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1.c The version of the SignedData object is 3.
1.d The digestAlgorithm in the SignedData object is SHA-256 (OID
2.16.840.1.101.3.4.2.1).
1.e The certificates field in the SignedData object is present
and contains an EE certificate whose Subject Key Identifier
(SKI) matches the sid field of the SignerInfo object.
1.f The crls field in the SignedData object is omitted.
1.g The eContentType in the EncapsulatedContentInfo is rid-ct-
rpkiBOA (OID 1.2.840.113549.1.9.16.1.[TBD])
1.h The version of the BOA is 0.
1.i The addressFamily in the BOAIPAddressFamily is either IPv4
or IPv6 (0001 and 0002, respectively).
1.j The version of the SignerInfo is 3.
1.k The digestAlgorithm in the SignerInfo object is SHA-256 (OID
2.16.840.1.101.3.4.2.1).
1.l The signatureAlgorithm in the SignerInfo object is RSA (OID
1.2.840.113549.1.1.1).
1.m The signedAttrs field in the SignerInfo object is present
and contains both the ContentType attribute (OID
1.2.840.113549.1.9.3) and the MessageDigest attribute (OID
1.2.840.113549.1.9.4). .
1.n The unsignedAttrs field in the SignerInfo object is omitted.
2. Use the public key in the EE certificate to verify the signature
on the BOA.
3. Verify that the EE certificate has an IP Address Delegation
extension [RFC3779] and that the IP address prefixes in that
extension exactly match the IP address prefixes in the BOA, and
the AS numbers in that extension exactly match the AS numbers in
the BOA.
4. Verify that the EE certificate is a valid end-entity certificate
in the resource PKI by constructing a valid certificate path to a
trust anchor. (See [ID.ietf-sidr-res-certs] for more details.)
Note that requiring an exact match between the IP address prefixes
and ASes in a BOA and the IP address prefixes and ASes in the
corresponding EE certificate does not place any limitations on BOA
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use. Since each EE certificate in the RPKI architecture is used to
verify only a single BOA, it is natural to have the IP address
prefixes in the certificate match those in the corresponding BOA.
4. BOA Use Practices
BOAs are intended to allow relying parties a means of validating
whether route origination information as described in a route
advertisement refers to an IP address or AS number that has not been
validly allocated for use in the routing system.
Any party with a validly assigned Internet resource set and a CA
certificate that describes this delegation can publish a BOA,
independently of the actions of the actions of the party that
assigned the resource set.
BOAs are not hierarchically related.
An Internet Registry SHOULD maintain a single BOA in relation to each
parent registry that has assigned resources to this registry.
An Internet Registry SHOULD maintain a regular issuance cycle for
BOAs.
For registries that operate on a day-to-day basis in terms of
resource transactions, it is suggested that a local BOA management
practice would be that a new BOA should be issued on a regular 24
hour basis. The corresponding EE certificate should have a validity
period of no more than 72 hours from the time of issuance. Each time
a new EE certificate for a BOA is issued the previous BOA's EE
certificate should be revoked and the previous BOA removed from the
publication repository.
Parties that operate a local cache of RPKI objects should ensure that
they refresh BOA objects at intervals 24 hours to ensure that they
have the current BOA in the local cache.
5. BOA Interpretation
A BOA can be used to check a route object to determine if the
origination information in the route object refers to invalid IP
addresses or an invalid AS number.
If a route object has an AS origination that refers to an AS number
that is included in a valid BOA then the route object can be regarded
as a Bogon object, and local policies that apply to Bogon ASes can be
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applied to the object. This holds whether or not the address prefix
of the route object is described by a valid ROA or not.
If a route object has an address prefix that is equal to, or is a
more specific prefix of an IP address that is included in a valid BOA
then the route object can be regarded as a Bogon object, and local
policies that apply to Bogon ASes can be applied to the object,
unless the address prefix and AS origination of the route object is
also described by a valid ROA, in which case the BOA is to be
disregarded. In other words a valid ROA SHOULD infer a higher trust
preference than a ROA if a valid ROA and BOA exist for the same
address prefix and AS number.
6. Security Considerations
There is no assumption of confidentiality for the data in a BOA; it
is anticipated that BOAs will be stored in repositories that are
accessible to all ISPs, and perhaps to all Internet users. There is
no explicit authentication associated with a BOA, since the RPKI used
for BOA validation provides authorization but not authentication.
Although the BOA is a signed, application layer object, there is no
intent to convey non-repudiation via a BOA.
The purpose of a BOA is to convey an attestation by an address holder
that there is no authority for the generation of a route object that
refers to specified addresses or origination from specified ASes.
The integrity of a BOA must be established in order to validate the
authority of the Bogon Attestation. The BOA makes use of the CMS
signed message format for integrity, and thus inherits the security
considerations associated with that data structure. The right of the
BOA signer to authorize the attestation of specified IP addresses and
ASes as Bogons is established through use of the address space and AS
number PKI described in [ID.ietf-sidr-arch]. Specifically, a relying
party must verify the signature on the BOA using an X.509 certificate
issued under this PKI, and check that the prefix(es) in the BOA match
those in the address space extension in the certificate.
7. IANA Considerations
[None]
8. Acknowledgments
The authors are indebted to the authors of Route Origin Authorization
(ROA) [ID.ietf-sidr-roa-format], M. Lepinski, S. Kent and D. Kong, as
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much of the text used to define a BOA has been borrowed from the ROA
format specification, and Russ Housley for clarification on the CMS
profile.
9. Normative References
[ID.ietf-sidr-arch]
Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", draft-ietf-sidr-arch (work in
progress), February 2008.
[ID.ietf-sidr-res-certs]
Huston, G., Michaleson, G., and R. Loomans, "A Profile for
X.509 PKIX Resource Certificates", Internet
Draft draft-ietf-sidr-res-certs, August 2008.
[ID.ietf-sidr-roa-format]
Lepinski, M., Kent, S., and D. Kong, "An Infrastructure to
Support Secure Internet Routing",
draft-ietf-sidr-roa-format (work in progress), July 2008.
[RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
Addresses and AS Identifiers", RFC 3779, June 2004.
[RFC3852] Housley, R., "Cryptographic Message Syntax (CMS)",
RFC 3852, July 2004.
[RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional
Algorithms and Identifiers for RSA Cryptography for use in
the Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile", RFC 4055,
June 2005.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
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Authors' Addresses
Geoff Huston
Asia Pacific Network Information Centre
Email: gih@apnic.net
URI: http://www.apnic.net
Terry Manderson
Asia Pacific Network Information Centre
Email: terry@apnic.net
URI: http://www.apnic.net
George Michaelson
Asia Pacific Network Information Centre
Email: ggm@apnic.net
URI: http://www.apnic.net
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