Secure Inter-Domain Routing (sidr) M. Lepinski
Internet Draft S. Kent
Expires: January 2009 D. Kong
Intended Status: Proposed Standard BBN Technologies
July 7, 2008
A Profile for Route Origin Authorizations (ROAs)
draft-ietf-sidr-roa-format-03.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
authorized an Autonomous System (AS) to originate routes to that one
or more prefixes within the address block.
Conventions used in this document
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].
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Table of Contents
1. Introduction...................................................2
2. Basic Format...................................................3
2.1. Signed-Data Content Type..................................3
2.1.1. version..............................................3
2.1.2. digestAlgorithms.....................................4
2.1.3. encapContentInfo.....................................4
2.1.3.1. eContentType....................................4
2.1.3.2. eContent........................................4
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..........................................6
2.1.6.1. version.........................................6
2.1.6.2. sid.............................................6
2.1.6.3. digestAlgorithm.................................6
2.1.6.4. signedAttrs.....................................6
2.1.6.4.1. ContentType Attribute......................7
2.1.6.4.2. MessageDigest Attribute....................7
2.1.6.4.3. SigningTime Attribute......................7
2.1.6.4.4. BinarySigningTimeAttribute.................8
2.1.6.5. signatureAlgorithm..............................8
2.1.6.6. signature.......................................8
2.1.6.7. unsignedAttrs...................................9
3. ROA Validation.................................................9
4. Security Considerations.......................................10
5. IANA Considerations...........................................11
6. Acknowledgments...............................................11
7. References....................................................12
7.1. Normative References.....................................12
7.2. Informative References...................................12
Authors' Addresses...............................................13
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
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
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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.
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]
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
2.1.1. version
The version is the syntax version number. It MUST be 3,
corresponding to the signerInfo structure having version number 3.
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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 ROA is defined as routeOriginAttestation and
has the numerical value of 1.2.840.113549.1.9.16.1.24.
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 {
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addressFamily OCTET STRING (SIZE (2..3)),
addresses SEQUENCE OF ROAIPAddress }
ROAIPAddress ::= SEQUENCE {
address IPAdress,
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
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.
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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.
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 be SHA-256, the OID for which is
2.16.840.1.101.3.4.2.1. [RFC4055]
2.1.6.4. signedAttrs
The signedAttrs is defined as:
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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 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
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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:
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. 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.
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.
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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 use the resource PKI to
validate the ROA by performing the following steps.
1. Verify that the ROA 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)
b. The version of the SignedData object is 3.
c. The digestAlgorithm in the SignedData object is SHA-256 (OID
2.16.840.1.101.3.4.2.1).
d. 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.
e. The crls field in the SignedData object is omitted.
f. The eContentType in the EncapsulatedContentInfo is
routeOriginAttestation (OID 1.2.840.113549.1.9.16.1.24)
g. The version of the RouteOriginAttestation is 0.
h. The addressFamily in the ROAIPAddressFamily is either IPv4 or
IPv6 (0001 and 0002, respectively).
i. The version of the SignerInfo is 3.
j. The digestAlgorithm in the SignerInfo object is SHA-256 (OID
2.16.840.1.101.3.4.2.1).
k. The signatureAlgorithm in the SignerInfo object is RSA (OID
1.2.840.113549.1.1.1).
l. 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).
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m. The unsignedAttrs field in the SignerInfo object is omitted.
2. Use the public key in the EE certificate to verify the signature
on the ROA.
3. Verify that the EE certificate has an IP Address Delegation
extension [RFC3779] and that the IP address prefix(es) in that
extension exactly matches the IP address prefix(es) in the ROA.
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 [RESCERT] for more details.)
Note that requiring an exact match between the IP address prefix(es)
in a ROA and the IP address prefix(es) in the corresponding EE
certificate does not place any limitations on ROA use. Indeed, since
each EE certificate in the resource RPKI architecture is used to
verify only a single ROA, it is natural to have the IP address
prefixes in the certificate match those in the corresponding ROA.
When the issuer of a ROA does not require an exact match between the
IP address prefix(es) in the ROA and the prefix(es) advertised by the
AS (when it originates routes for the prefix), the issuer includes
the maxLength element within the ROAIPAddress to indicate that the AS
is authorized to advertise more specific prefixes than those
indicated in the ROA (up to the specified maxLength values).
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.
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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.
[RFC4055] Schaad, J., Kaliski, B., and Housley, R., "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.
[RFC3779] Lynn, C., Kent, S., and Seo, K., "X.509 Extensions for IP
Addresses and AS Identifiers", RFC 3779, June 2004.
7.2. Informative References
[RSA] Rivest, R., Shamir, A., and Adelman, L. M. 1978. A method
for obtaining digital signatures and public-key
cryptosystems. Commun. ACM 21, 2 (Feb.), 120-126.
[ARCH] Lepinski, M., Kent, S., and Barnes, R., "An Infrastructure
to Support Secure Internet Routing," draft-ietf-sidr-arch-
03.txt, February, 2008 (work in progress).
[RESCERT] Huston, G., Michaelson, G., and Loomans, R., "A Profile for
X.509 PKIX Resource Certificates," draft-ietf-sidr-res-
certs-10.txt, June, 2008 (work in progress).
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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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