Secure Inter-Domain Routing (SIDR) T. Manderson
Internet-Draft May 25, 2009
Intended status: Standards Track
Expires: November 26, 2009
A Profile for Bogon Origin Attestations (BOAs)
draft-ietf-sidr-bogons-03.txt
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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
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authorised any Autonomous System (AS) to originate routes that are
equivalent to any of the addresses listed in the BOA. A BOA also
provides a means of verifying that a BGP speaker is not using an AS
without appropriate authority. The 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 the Border Gateway Protocol.
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 . . . . . . . . . . . . . . . . . . . . . . . 13
9. Normative References . . . . . . . . . . . . . . . . . . . . . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Introduction
This document defines an application of the Resource Public Key
Infrastructure (RPKI) to validate the attestations of resource
holders and Internet Registries that certain addresses are currently
neither allocated to any party, nor in use by any party, and any
appearance of such addresses or AS's in a routing advertisement in
the Border Gateway Protocol (BGP) [RFC4271] should be considered an
invalid use of such addresses or Autonomous System Numbers.
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 [I-D.ietf-sidr-arch].
BOAs can be regarded as a logical opposite of a Route Origin
Authorization (ROA) [I-D.ietf-sidr-roa-format], however are not
contradictory to a ROA and allows a resource holder to explicitly
list those IP addresses and AS's 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 unambiguously
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 needs
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 IDENTIFIER ::= { 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 AS's and 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 AS's
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 AS's. 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 address 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 BinarySigningTime 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:
a. The contentType of the CMS object is SignedData (OID
1.2.840.113549.1.7.2)
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b. The eContentType of the CMS object is id-ct-rpkiBOA (OID
1.2.840.113549.1.9.16.1.[TBD])
c. The version of the SignedData object is 3.
d. The digestAlgorithm in the SignedData object is SHA-256 (OID
2.16.840.1.101.3.4.2.1).
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.
f. The crls field in the SignedData object is omitted.
g. The eContentType in the EncapsulatedContentInfo is rid-ct-
rpkiBOA (OID 1.2.840.113549.1.9.16.1.[TBD])
h. The version of the BOA is 0.
i. The addressFamily in the BOAIPAddressFamily is either IPv4 or
IPv6 (0001 and 0002, respectively).
j. The version of the SignerInfo is 3.
k. The digestAlgorithm in the SignerInfo object is SHA-256 (OID
2.16.840.1.101.3.4.2.1).
l. The signatureAlgorithm in the SignerInfo object is RSA (OID
1.2.840.113549.1.1.1).
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). .
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 cover the IP address prefixes in the BOA, and the AS
numbers in that extension cover the AS numbers in the BOA.
4. Verify that no valid ROA exists which also covers any more or
less specific prefixes, or any AS numbers. In the case that a
ROA does exist which overlaps the BOA in any way, the BOA MUST be
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considered invalid.
5. 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 [I-D.ietf-sidr-res-certs] for more details.)
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 allocation can publish a BOA,
independently of the actions of the actions of the party that
assigned the resource set.
An Internet Registry SHOULD maintain a single BOA in relation to each
parent registry that has assigned resources to this registry.
BOAs are not hierarchically related however they are subordinate to
the CA certificate that describes the immediate allocations assigned.
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 an inter-domain routing advertisement
("route") to determine if the origination information in the route
object refers to invalid IP addresses or an invalid AS number.
If a route has an AS origination that refers to an AS number that is
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listed in a valid BOA, then the route can be regarded as a Bogon, and
local policies that apply to Bogon AS's can be applied to the route.
However if the AS number of this route is described in a valid ROA
whose EE certificate lists the AS number, the BOA MUST be considered
invalid
If a route 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 can be regarded as a Bogon, and local policies that apply
to Bogon prefixes can be applied to the route. However if the
address prefix of the route is described (either more or less
specific) by a valid ROA, the BOA MUST be considered invalid.
BOA interpretation in the context of validation of origination of
route objects is described in [I-D.ietf-sidr-roa-validation].
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 that refers
to specified addresses or origination from specified AS's. 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
AS's as Bogons is established through use of the address space and AS
number PKI described in [I-D.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, or are covered by those in the address space extension
in the certificate.
7. IANA Considerations
It would be anticipated that the IANA maintain a BOA for all
unallocated space or reserved space (IPv4, IPv6 and ASNs) not
intended for public use.
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8. Acknowledgments
The authors are indebted to the authors of Route Origin Authorization
(ROA) [I-D.ietf-sidr-roa-format], M. Lepinski, S. Kent and D. Kong,
as 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.
Further the authors wish to thank many security people, too many to
name, for clarifying that negative attestations are a valid and
useful security construct.
Lastly, without the orginal thoughts and words from George Michaelson
and Geoff Huston this document would not exist. Their hands helped
form the concepts of why we need BOAs in the RPKI and historically
were two of the original three authors of this document.
9. Normative References
[I-D.ietf-sidr-arch]
Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", draft-ietf-sidr-arch-06 (work in
progress), March 2009.
[I-D.ietf-sidr-res-certs]
Huston, G., Michaelson, G., and R. Loomans, "A Profile for
X.509 PKIX Resource Certificates",
draft-ietf-sidr-res-certs-16 (work in progress),
February 2009.
[I-D.ietf-sidr-roa-format]
Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
Origin Authorizations (ROAs)",
draft-ietf-sidr-roa-format-04 (work in progress),
November 2008.
[I-D.ietf-sidr-roa-validation]
Huston, G. and G. Michaelson, "Validation of Route
Origination in BGP using the Resource Certificate PKI",
draft-ietf-sidr-roa-validation-01 (work in progress),
October 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.
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[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.
Author's Address
Terry Manderson
Email: terry@terrym.net
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