Individual Submission G. Huston
Internet-Draft G. Michaelson
Intended status: BCP APNIC
Expires: November 9, 2010 May 8, 2010
A Profile for AS Adjacency Attestation Objects
draft-huston-sidr-aao-profile-03.txt
Abstract
This document describes a profile for AS Adjacency Attestation
Objects (AAOs). An AAO is a digitally signed object that provides a
means of verifying that an AS holder has made an attestation that it
has a inter-domain routing adjacency with one or more other AS's,
with the associated inference that this AS is prepared to announce or
receive routes with these adjacent AS's in the inter-domain domain
environment.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on November 9, 2010.
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Semantic Interpretation of an AAO . . . . . . . . . . . . . . 3
3. Basic Format . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Signed-Data Content Type . . . . . . . . . . . . . . . . . 5
3.1.1. version . . . . . . . . . . . . . . . . . . . . . . . 5
3.1.2. digestAlgorithms . . . . . . . . . . . . . . . . . . . 5
3.1.3. encapContentInfo . . . . . . . . . . . . . . . . . . . 5
3.1.4. CertificateSet . . . . . . . . . . . . . . . . . . . . 7
3.1.5. certificates . . . . . . . . . . . . . . . . . . . . . 7
3.1.6. crls . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1.7. signerInfos . . . . . . . . . . . . . . . . . . . . . 7
4. AAO Validation . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
The primary purpose of the Internet IP Address and AS Number Resource
Public Key Infrastructure (RPKI) system [ID.ietf-sidr-arch] is to
improve routing security. As part of this security framework, a
mechanism is defined here to allow entities to verify that an AS
holder attests that is adjacent to one or more other AS's, with the
inference that it is prepared to announce routes to these adjacent
AS's in the inter-domain routing environment. An AS Adjacency
Attestation Object (AAO) provides this function.
An AAO is a digitally signed object that makes use of Cryptographic
Message Syntax (CMS) [RFC5652] as a standard encapsulation format.
CMS was chosen to take advantage of existing open source software
available for processing messages in this format.
The AAO is an attestation, made and issued by the local AS holder,
that the local AS is an inter-domain routing peer with each of the
AS's that are enumerated in an associated AS list contained in the
AAO. An AAO is a two part structure, containing the local AS and a
list of adjacent AS's. The AAO is signed by a an End Entity (EE)
Resource Certificate that has the local AS as the value of its
[RFC3779] AS number resource extension.
1.1. Terminology
It is assumed that the reader is familiar with the terms and concepts
described in "Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile" [RFC5280], "X.509
Extensions for IP Addresses and AS Identifiers" [RFC3779], and BGP-4
[RFC4271]
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
2. Semantic Interpretation of an AAO
An AAO is an attestation on the part of a AS holder that it supports
currently active inter-domain routing adjacencies to each of the AS's
listed in the AAO. The AAO does not list any prefixes that may be
announced to the adjacent AS's either directly or indirectly. The
AAO also does not list any local routing policies that have been
applied to the routes that are advertised across this adjacency, nor
any routing policies that may be applied to routes that are learned
from this adjacency.
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The AAO is intended to provide "closure" with respect to
interpretation of the AAO by relying parties, to the extent that if a
valid AAO exists for a local AS, then from the perspective of that
local AS all adjacencies with those AS's listed in the valid AAO can
be regarded as "valid" and any other adjacency from the perspective
of the local AS can be regarded as potentially "invalid". In other
words an AAO is an attestation of adjacency with the AS's listed in
the AAO and an implicit attestation of the denial of adjacency with
all other AS's.
Where an AS holder has published two or more valid AAO's, the set of
"valid" adjacent AS's refers to the union of the lists of adjacent
AS's and all other AS's can be regarded as "invalid" from the
perspective of the local AS.
A relying party may infer from a valid AAO that the signing AS holder
may have the intent to advertise route objects across this inter-AS
routing adjacency, and may be prepared to learn route objects that
are passed to it from the adjacent AS. The AAO does not described
which routes may be announced across a corresponding inter-AS routing
adjacency.
It is noted that an AAO is an asymmetric assertion, where one AS is
asserting that an inter-domain routing adjacency with another AS
exists. It should also be noted that this assertion is not
explicitly acknowledged by the remote AS in the context of a single
issued AAO. Relying parties may elect to place greater levels of
confidence in the existence of an inter-domain routing adjacency when
both AS's have signed and published AAO objects that contain mutual
references.
It is also noted that there is a subtle distinction that could be
drawn here between the appropriate semantic interpretation a pair of
unilateral assertions of adjacency using two AAOs and a combined
assertion of adjacency where both AS's sign a single attestation of
the existence of an inter-domain routing adjacency between these
AS's. Such a combined approach, using a single assertion with two
digital signatures, is not defined in this document.
3. Basic Format
Using CMS syntax, an AAO is a type of signed-data object. The
general format of a CMS object is:
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ContentInfo ::= SEQUENCE {
contentType ContentType,
content [0] EXPLICIT ANY DEFINED BY contentType }
ContentType ::= OBJECT IDENTIFIER
As a AAO is a signed-data object, it uses the corresponding OID,
1.2.840.113549.1.7.2. [RFC5652]
3.1. Signed-Data Content Type
According to the CMS standard, 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
3.1.1. version
The version is the syntax version number. It MUST be 3,
corresponding to the signerInfo structure having version number 3.
3.1.2. digestAlgorithms
The digestAlgorithms set contains the OIDs of the digest algorithm(s)
used in signing the encapsulated content. This set MUST conform to
the RPKI Algorithms and Key Size Profile specification
[ID.sidr-rpki-algs].
3.1.3. 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
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3.1.3.1. eContentType
The ContentType for a AAO is defined as id-ct-ASAdjancyAttest and has
the numerical value of 1.2.840.113549.1.9.16.1.32.
id-smime OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs9(9) 16 }
id-ct OBJECT IDENTIFIER ::= { id-smime 1 }
id-ct-ASAdjacencyAttest OBJECT IDENTIFIER ::= { id-ct 32 }
3.1.3.2. eContent
The content of an AAO identifies one or more AS's that the signing AS
holder is attesting the existence of a routing adjacency.
The AAO contains no routing policy qualifications, nor does it
reference any address prefixes that may be announced or received
within the context of any routing adjacency.
An AAO is defined as:
id-ct-ASAdjacencyAttest ::= SEQUENCE {
version [0] INTEGER DEFAULT 0,
ASIdentifiers ::= SEQUENCE OF ASIdOrRange,
localASNum ASId}
ASIdOrRange ::= CHOICE {
id ASId,
range ASRange }
ASRange ::= SEQUENCE {
min ASId,
max ASId }
ASId ::= INTEGER
3.1.3.2.1. version
The version number of the ASAdjacencyAttestation MUST be 0.
3.1.3.2.2. ASIdentifiers
The ASIdentifiers element is a SEQUENCE containing AS numbers for
which the localASnum AS is attesting the existence of a routing
adjacency. Any pair of items in the asIdentifiers SEQUENCE MUST NOT
overlap. Any contiguous series of AS identifiers MUST be combined
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into a single range whenever possible. The AS identifiers in the
asIdentifiers element MUST be sorted by increasing numeric value.
3.1.3.2.2.1. ASIdOrRange
The ASIdOrRange type is a CHOICE of either a single integer (ASId) or
a single sequence (ASRange).
3.1.3.2.2.2. ASRange
The ASRange type is a SEQUENCE consisting of a min and a max element,
and is used to specify a range of AS identifier values.
3.1.3.2.2.2.1. min and max
The min and max elements have type ASId. The min element is used to
specify the value of the minimum AS identifier in the range, and the
max element specifies the value of the maximum AS identifier in the
range.
3.1.3.2.2.3. ASId
The ASId type is an INTEGER.
3.1.3.2.3. localASNum
The localASNum field contains the AS that is making the attestation
of routing adjacency to each of the AS's listed in the ASIdentifiers
element.
3.1.4. CertificateSet
The CertificateSet type is defined in section 10 of [RFC5652]
3.1.5. certificates
The certificates element MUST be included and MUST contain only the
single EE resource certificate needed to validate this AAO.
3.1.6. crls
The crls element MUST be omitted.
3.1.7. signerInfos
SignerInfo is defined under CMS as:
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SignerInfo ::= SEQUENCE {
version CMSVersion,
sid SignerIdentifier,
digestAlgorithm DigestAlgorithmIdentifier,
signedAttrs [0] IMPLICIT SignedAttributes OPTIONAL,
signatureAlgorithm SignatureAlgorithmIdentifier,
signature SignatureValue,
unsignedAttrs [1] IMPLICIT UnsignedAttributes OPTIONAL }
3.1.7.1. version
The version number MUST be 3, corresponding with the choice of
SubjectKeyIdentifier for the sid.
3.1.7.2. sid
The sid is defined as:
SignerIdentifier ::= CHOICE {
issuerAndSerialNumber IssuerAndSerialNumber,
subjectKeyIdentifier [0] SubjectKeyIdentifier }
For a AAO, the sid MUST be a SubjectKeyIdentifier.
3.1.7.3. digestAlgorithm
The digestAlgorithm MUST consist of the OID of a digest algorithm
that conforms to the RPKI Algorithms and Key Size Profile
specification [ID.sidr-rpki-algs].
3.1.7.4. signedAttrs
The signedAttrs is 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 signed 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 by the signer MAY also be included. The
intent is to allow additional signed attributes to be included if a
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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 AAO the attrValues must consist of only a single
AttributeValue
3.1.7.4.1. ContentType 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 AAO MUST be
1.2.840.113549.1.9.16.1.24 (matching the eContentType in the
EncapsulatedContentInfo).
3.1.7.4.2. MessageDigest 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 [RFC5652].
3.1.7.4.3. SigningTime Attribute
The SigningTime attribute MAY be present. 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 AAO (as
specified in Section 4). The attrType OID for the SigningTime
attribute is 1.2.840.113549.1.9.5.
The attrValues for the SigningTime attribute is defined as:
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.
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3.1.7.4.4. BinarySigningTimeAttribute
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
AAO (as specified in Section 3). The attrType OID for the
SigningTime attribute is 1.2.840.113549.1.9.16.2.46.
The attrValues for the SigningTime attribute is defined as:
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.
3.1.7.5. signatureAlgorithm
The signatureAlgorithm MUST consist of the OID of a signature
algorithm that conforms RPKI Algorithms and Key Size Profile
specification [ID.sidr-rpki-algs].
3.1.7.6. signature
The signature value is defined as:
SignatureValue ::= OCTET STRING
The signature characteristics are defined by the digest and signature
algorithms.
3.1.7.7. unsignedAttrs
unsignedAttrs MUST be omitted.
4. AAO Validation
Before a relying party can use an AAO, the relying party must first
use the RPKI to validate the AAO by performing the following steps.
1. Verify that the AAO syntax complies with this specification. In
particular, verify the following:
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a. The contentType of the CMS object is SignedData (OID
1.2.840.113549.1.7.2).
b. The version of the SignedData object is 3.
c. 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.
d. The crls field in the SignedData object is omitted.
e. The eContentType in the EncapsulatedContentInfo is id-ct-
ADAdjacencyAttest (OID 1.2.840.113549.1.9.16.1.32)
f. The version of the id-ct-ASAdjacencyAttest is 0.
g. The version of the SignerInfo is 3.
h. 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).
i. The unsignedAttrs field in the SignerInfo object is omitted.
j. The digestAlgorithm in the SignedData and SignerInfo objects
as well as the signatureAlgorithm in the SignerInfo object
conform to the RPKI Algorithms and Key Size Profile
specification [ID.sidr-rpki-algs].
2. The public key in the EE certificate (contained within the AAO)
can be used to successfully verify the signature on the AAO.
3. The EE certificate has an Autonomous System Identifier Delegation
Extension [RFC3779] and that the Autonomous System Identifier in
that extension exactly matches the Autonomous System Identifier
in the localASNum element of the AAO.
4. The EE certificate is a valid end-entity certificate in the
Resource PKI as specified by [ID.ietf-sidr-res-certs]. (in
particular, there exists a valid certification path from a trust
anchor to the EE certificate.)
5. Security Considerations
There is no assumption of confidentiality for the data in a AAO; it
is anticipated that AAOs will be stored in public repositories that
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are accessible to all ISPs, and potentially to all Internet users.
There is no explicit authentication associated with a AAO, since the
RPKI that is used for AAO validation provides authorization but not
authentication. Although the AAO is a signed, application layer
object, there is no intent to convey non-repudiation via a AAO.
The purpose of a AAO is to convey a unilateral statement of routing
capability that an AS has the capability to announce route objects
via a routing adjacency with another AS and has the capability to
listen for route objects that are passed to it over a routing
adjacency. This should not be interpreted as an authority, nor is a
relying party justified in assuming that such a routing adjacency
exists, nor that any valid routing announcements that are passed
across this routing adjacency.
A relying party may be able to place greater confidence in the
inferred existence of a routing adjacency in the case where both AS
holders have issued current AAO objects that nominate each other as
an adjacent AS.
The AAO object does not convey any information relating to route
policies that may be applied to the adjacency by either party to a
route adjacency, nor what prefixes may be advertised across that
adjacency, nor any attributes that may be associated with such
advertisements.
6. IANA Considerations
[Note to IANA, to be removed prior to publication: there are no IANA
considerations stated in this version of the document.]
7. Acknowledgements
The authors would like to acknowledge the work of Matt Lepinski,
Stephen Kent and Derrick Kong, whose work on the Route Origin
Attestation Profile was used as the starting point for this document.
8. References
8.1. 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), March 2009.
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[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, February 2009.
[ID.sidr-rpki-algs]
Huston, G., "A Profile for Algorithms and Key Sizes for
use in the Resource Public Key Infrastructure", Work in
progress: Internet
Drafts draft-ietf-sidr-rpki-algs-00.txt, August 2009.
[RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
Addresses and AS Identifiers", RFC 3779, June 2004.
[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.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)",
RFC 5652, September 2009.
8.2. Informative References
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
Authors' Addresses
Geoff Huston
Email: gih@apnic.net
URI: http://www.apnic.net
George Michaelson
Email: ggm@apnic.net
URI: http://www.apnic.net
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