Secure Inter-Domain Routing (sidr) M. Lepinski
Internet Draft S. Kent
Expires: April 26, 2010 D. Kong
Intended Status: Proposed Standard BBN Technologies
October 26, 2009
A Profile for Route Origin Authorizations (ROAs)
draft-ietf-sidr-roa-format-06.txt
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Abstract
This document defines a standard profile for Route Origin
Authorizations (ROAs). A ROA is a digitally signed object that
provides a means of verifying that an IP address block holder has
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authorized an Autonomous System (AS) to originate routes to that one
or more prefixes within the address block.
Table of Contents
1. Introduction...................................................2
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
2.1.3.1. eContentType....................................4
2.1.3.2. eContent........................................5
2.1.3.2.1. version....................................5
2.1.3.2.2. asID.......................................5
2.1.3.2.3. ipAddrBlocks...............................5
2.1.4. certificates.........................................6
2.1.5. crls.................................................6
2.1.6. signerInfos..........................................7
2.1.6.1. version.........................................7
2.1.6.2. sid.............................................7
2.1.6.3. digestAlgorithm.................................7
2.1.6.4. signedAttrs.....................................7
2.1.6.4.1. ContentType Attribute......................8
2.1.6.4.2. MessageDigest Attribute....................8
2.1.6.4.3. SigningTime Attribute......................8
2.1.6.4.4. BinarySigningTimeAttribute.................9
2.1.6.5. signatureAlgorithm..............................9
2.1.6.6. signature......................................10
2.1.6.7. unsignedAttrs..................................10
3. ROA Validation................................................10
4. Security Considerations.......................................11
5. IANA Considerations...........................................12
6. Acknowledgments...............................................12
7. References....................................................13
7.1. Normative References.....................................13
7.2. Informative References...................................13
Authors' Addresses...............................................14
Intellectual Property Statement..................................14
Disclaimer of Validity...........................................14
Copyright Statement..............................................14
1. Introduction
The primary purpose of the Internet IP Address and AS Number Resource
Public Key Infrastructure (RPKI) system is to improve routing
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security. As part of this system, a mechanism is needed to allow
entities to verify that an AS has been given permission by an IP
address block holder to advertise routes to one or more prefixes
within that block. A ROA provides this function.
A ROA 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.
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] and "X.509
Extensions for IP Addresses and AS Identifiers" [RFC3779].
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 [RFC2119].
1.2. Note on Algorithms
Cryptographic Message Syntax is a general format capable of
accommodating a wide variety of signature and digest algorithms. This
specification takes no stand with regards to the signature and digest
algorithms that are appropriate for use in a ROA. Appropriate
algorithms and associated key sizes are specified in a separate
document [ALGS].
2. Basic Format
Using CMS syntax, a ROA 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
As a ROA is a signed-data object, it uses the corresponding OID,
1.2.840.113549.1.7.2. [RFC3852]
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2.1. 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
Additionally, the SignerInfos set must contain only a single
SignerInfo object.
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 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 [ALGS].
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 ROA is defined as routeOriginAttestation and
has the numerical value of 1.2.840.113549.1.9.16.1.24.
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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 }
routeOriginAttestion OBJECT IDENTIFIER ::= { id-ct 24 }
2.1.3.2. eContent
The content of a ROA identifies a single AS that has been authorized
by the address space holder to originate routes and a list of one or
more IP address prefixes that will be advertised. If the address
space holder needs to authorize multiple ASes to advertise the same
set of address prefixes, the holder issues multiple ROAs, one per AS
number. A ROA is formally defined as:
RouteOriginAttestation ::= SEQUENCE {
version [0] INTEGER DEFAULT 0,
asID ASID,
ipAddrBlocks SEQUENCE OF ROAIPAddressFamily }
ASID ::= INTEGER
ROAIPAddressFamily ::= SEQUENCE {
addressFamily OCTET STRING (SIZE (2..3)),
addresses SEQUENCE OF ROAIPAddress }
ROAIPAddress ::= SEQUENCE {
address IPAddress,
maxLength INTEGER OPTIONAL }
IPAddress ::= BIT STRING
2.1.3.2.1. version
The version number of the RouteOriginAttestation MUST be 0.
2.1.3.2.2. asID
The asID field contains the AS number that is authorized to originate
routes to the given IP address prefixes.
2.1.3.2.3. ipAddrBlocks
The ipAddrBlocks field encodes the set of IP address prefixes to
which the AS is authorized to originate routes. Note that the syntax
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here is more restrictive than that used in the IP Address Delegation
extension defined in RFC 3779. That extension can represent arbitrary
address ranges, whereas ROAs need to represent only prefixes.
Within the ROAIPAddressFamily 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.
Within a ROAIPAddress structure, the addresses field represents
prefixes as a sequence of type IPAddress. (See [RFC3779] for more
details). If present, the maxLength must be an integer greater than
or equal to the length of the accompanying prefix and less than or
equal to the length (in bits) of an IP address in the address family
(32 for IPv4 and 128 for IPv6). When present, the maxLength specifies
the maximum length of IP address prefix that the AS is authorized to
advertise. (For example, if the IP Address prefix is 10.0/16 and the
maxLength is 24, the AS is authorized to advertise any more specific
prefix having length at most 24. That is, in this example, the AS
would be authorized to advertise 10.0/16, 10.0.128/20, or
10.0.255/24, but not 10.0.255.0/25.) When the maxLength is not
present, the AS is only authorized to advertise exactly the prefix
specified in the ROA.
Note that a valid ROA may contain an IP Address prefix (within a
ROAIPAddress element) that is encompassed by another IP Address
prefix (within a separate ROAIPAddress element). For example, a ROA
may contain the prefix 10.0/16 with maxLength 18, as well as the
prefix 10.0.0/24 with maxLength 24. (Such a ROA would authorize the
indicated AS to advertise any prefix beginning with 10.0 with length
at least 16 and no greater than 18, as well as the specific prefix
10.0.0/24.) Additionally, a ROA MAY contain two ROAIPAddress elements
where the IP Address prefix is identical in both cases. However, this
is NOT RECOMMENDED as in such a case the ROAIPAddress with the
shorter maxLength grants no additional privileges to the indicated AS
and thus can be omitted without changing the meaning of the ROA.
2.1.4. certificates
The certificates field MUST be included and MUST contain only the end
entity certificate needed to validate this ROA.
2.1.5. crls
The crls field MUST be omitted.
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2.1.6. signerInfos
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 }
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 ROA, the sid MUST be a SubjectKeyIdentifier.
2.1.6.3. digestAlgorithm
The digestAlgorithm MUST consist of the OID of a digest algorithm
that conforms to the RPKI Algorithms and Key Size Profile
specification [ALGS].
2.1.6.4. signedAttrs
The signedAttrs is defined as:
SignedAttributes ::= SET SIZE (1..MAX) OF Attribute
Attribute ::= SEQUENCE {
attrType OBJECT IDENTIFIER,
attrValues SET OF AttributeValue }
AttributeValue ::= ANY
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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 ROA the attrValues must consist of only a single
AttributeValue.
2.1.6.4.1. 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 ROA MUST be
1.2.840.113549.1.9.16.1.24 (matching the eContentType in the
EncapsulatedContentInfo).
2.1.6.4.2. 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 RFC 3852.
2.1.6.4.3. 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 ROA (as
specified in Section 3). The attrType OID for the SigningTime
attribute is 1.2.840.113549.1.9.5.
The attrValues for the SigningTime attribute is defined as:
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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.
The definition of Time matches the one specified in the 1997 version
of X.509. Additional information regarding the use of UTCTime and
GeneralizedTime can we found in [RFC3852].
2.1.6.4.4. 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
ROA (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. The
precise definition of the BinaryTime element can be found in
[RFC4049].
2.1.6.5. signatureAlgorithm
The signatureAlgorithm MUST consist of the OID of a signature
algorithm that conforms RPKI Algorithms and Key Size Profile
specification [ALGS].
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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. ROA Validation
Before a relying party can use a ROA to validate a routing
announcement, the relying party must first validate the ROA by
verifying that all of the following conditions hold. (Note that a
relying party may perform these checks in any order.)
1. The ROA syntax complies with this specification. In particular,
that each of the following is true:
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
routeOriginAttestation (OID 1.2.840.113549.1.9.16.1.24)
f. The version of the RouteOriginAttestation is 0.
g. The addressFamily in the ROAIPAddressFamily is either IPv4 or
IPv6 (0001 and 0002, respectively).
h. The version of the SignerInfo is 3.
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i. 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).
j. The unsignedAttrs field in the SignerInfo object is omitted.
k. 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 [ALGS].
2. The public key of the end-entity certificate (contained within the
ROA) can be used to successfully verify the signature on the ROA.
3. The IP Address Delegation extension [RFC3779] is present in the EE
certificate (contained within the ROA) and each IP address
prefix(es) in ROA is contained within the set of IP addresses
specified by the EE certificate's IP address delegation extension.
4. The EE certificate (contained within the ROA) is a valid end-
entity certificate in the resource PKI as specified by [RESCERT].
(In particular, there exists a valid certification path from a
trust anchor to the EE certificate.)
4. Security Considerations
There is no assumption of confidentiality for the data in a ROA; it
is anticipated that ROAs 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 ROA, since the PKI used
for ROA validation provides authorization but not authentication.
Although the ROA is a signed, application layer object, there is no
intent to convey non-repudiation via a ROA.
The purpose of a ROA is to convey authorization for an AS to
originate a route to the prefix(es) in the ROA. Thus the integrity of
a ROA must be established. The ROA 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
ROA signer to authorize the target AS to originate routes to the
prefix(es) is established through use of the address space and AS
number PKI described in [ARCH]. Specifically one must verify the
signature on the ROA using an X.509 certificate issued under this
PKI, and check that the prefix(es) in the ROA match those in the
address space extension in the certificate.
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5. IANA Considerations
None.
6. Acknowledgments
The authors wish to thank Charles Gardiner and Russ Housley for their
help and contributions. Additionally, the authors would like to thank
Danny McPherson and Roque Gagliano for their careful reviews and
helpful comments.
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7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3852] Housley, R., "Cryptographic Message Syntax", RFC 3852, July
2004.
[RFC3779] Lynn, C., Kent, S., and Seo, K., "X.509 Extensions for IP
Addresses and AS Identifiers", RFC 3779, June 2004.
[ALGS] Huston, G., "A Profile for Algorithms and Key Sizes for use
in the Resource Public Key Infrastructure", draft-ietf-
sidr-rpki-algs-00, August 2009
7.2. Informative References
[ARCH] Lepinski, M. and Kent, S., "An Infrastructure to Support
Secure Internet Routing," draft-ietf-sidr-arch-09, October
2009.
[CP] Seo, K., et. al., "A Certificate Policy for the Resource
PKI," draft-ietf-sidr-cp-07, October 2009.
[RESCERT] Huston, G., Michaelson, G., and Loomans, R., "A Profile for
X.509 PKIX Resource Certificates," draft-ietf-sidr-res-
certs-17, August 2009.
[RFC4049] Housley, R., "BinaryTime: An Alternative Format for
Representing Time in ASN.1," RFC 4049, April 2005.
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Authors' Addresses
Matt Lepinski
BBN Technologies
10 Moulton Street
Cambridge MA 02138
Email: mlepinski@bbn.com
Stephen Kent
BBN Technologies
10 Moulton Street
Cambridge MA 02138
Email: skent@bbn.com
Derrick Kong
BBN Technologies
10 Moulton Street
Cambridge MA 02138
Email: dkong@bbn.com
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