Secure Inter-Domain Routing R. Austein
Internet-Draft ISC
Intended status: Standards Track G. Huston
Expires: February 7, 2009 APNIC
S. Kent
M. Lepinski
BBN
August 6, 2008
Manifests for the Resource Public Key Infrastructure
draft-ietf-sidr-rpki-manifests-02.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document defines a "manifest" for use in the Resource Public Key
Infrastructure. A "manifest" is a signed object that contains a
listing of all the signed objects in the repository publication point
associated with an authority responsible for publishing in the
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repository. For each certificate, or other forms of signed objects
issued by the authority that are published at this repository
publication point, the manifest contains both the name of the file
containing the object, and a hash of the file content. Manifests are
intended to expose potential attacks against relying parties of the
RPKI, such as a man-in-the middle withholding repository data or
replaying stale repository data.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Manifest Scope and Syntax . . . . . . . . . . . . . . . . . . 4
2.1. Manifest Scope . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Manifest Syntax . . . . . . . . . . . . . . . . . . . . . 4
2.2.1. Signed-Data Content Type . . . . . . . . . . . . . . . 4
2.2.2. ASN.1 . . . . . . . . . . . . . . . . . . . . . . . . 10
3. Manifest Generation . . . . . . . . . . . . . . . . . . . . . 12
3.1. CA Manifest Generation . . . . . . . . . . . . . . . . . . 12
3.2. End Entity Manifest Generation . . . . . . . . . . . . . . 13
3.3. Common Considerations for Manifest Generation . . . . . . 14
4. Processing Certificate Requests . . . . . . . . . . . . . . . 15
5. Manifest Validation . . . . . . . . . . . . . . . . . . . . . 16
6. Relying Party Use of Manifests . . . . . . . . . . . . . . . . 17
6.1. Tests for Determining Manifest State . . . . . . . . . . . 17
6.2. Missing Manifests . . . . . . . . . . . . . . . . . . . . 18
6.3. Invalid Manifests . . . . . . . . . . . . . . . . . . . . 19
6.4. Stale Manifests . . . . . . . . . . . . . . . . . . . . . 19
6.5. Files Not on Manifests (or Missing from a Publication
Point) . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.6. Hash Values Not Matching Manifests . . . . . . . . . . . . 21
7. Publication Repositories . . . . . . . . . . . . . . . . . . . 21
8. Security Considerations . . . . . . . . . . . . . . . . . . . 22
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
11. Normative References . . . . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
Intellectual Property and Copyright Statements . . . . . . . . . . 25
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1. Introduction
The Resource PKI (RPKI) [ID.SIDR-ARCH] makes use of a distributed
repository system [ID.SIDR-REPOSITORY] to make available a variety of
objects needed by relying parties (RPs) such as Internet service
providers (ISPs). Because all of the objects stored in the
repository system are digitally signed by the entities that created
them, attacks that modify these objects are detectable by RPs.
However, digital signatures provide no protection against attacks
that substitute "stale" versions of signed objects (i.e., objects
that were valid but have since been superceded) or attacks that
remove an object that should be present in the repository. To assist
in the detection of such attacks, the RPKI repository system will
make use of a new signed object called a "manifest."
A manifest is an object that lists of all of the other signed objects
issued by the authority responsible for a publication point in the
repository system. For each certificate, Certificate Revocation List
(CRL), or other signed object, such as a Route Origination Authority
(ROA), issued by the authority, the manifest contains both the name
of the file containing the object, and a hash of the file content.
Manifests allow a RP to obtain sufficient information to detect
whether the retrieval of objects from an RPKI repository has been
compromised by unauthorized object removal, or by the substitution of
"stale" versions of objects. Manifests are designed to be used both
for Certification Authority (CA) publication points in repositories,
that contain subordinate certificates, CRLs and other signed objects,
and End Entity (EE) publication points in repositories that contain
signed objects.
Manifests are modelled on CRLs, as the issues involved in detecting
stale manifests, and detection of potential attacks using manifest
replays, etc are similar to those for CRLs. The syntax of the
manifest payload differs from CRLs, since RPKI repositories can
contain objects not covered by CRLs, such as digitally signed
objects, such as ROAs.
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.
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2. Manifest Scope and Syntax
2.1. Manifest Scope
In the case of a CA's manifest of its associated publication
repository in the scope of the Resource Certificate PKI (RPKI), the
manifest contains the current published certificates issued by this
CA, the most recent CRLs that are associated with the CA's non-
revoked keypairs, and all objects that are signed using a "single-
use" EE certificate, where the EE certificate was issued by this CA.
In the case where an EE has a defined publication repository, the
EE's manifest contains all published objects that have been signed by
the EE's key pair.
2.2. Manifest Syntax
A manifest is a Cryptographic Message Syntax (CMS) [RFC3852] 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
A Manifest is a signed-data object. The ContentType used is the
signed-data type of id-data, namely the id-signedData OID,
1.2.840.113549.1.7.2. [RFC3852]
2.2.1. Signed-Data Content Type
According to the CMS specification, signed-data content types shall
have the 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
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2.2.1.1. version
The version is the syntax version number. It MUST be 3,
corresponding to the signerInfo structure having version number 3.
2.2.1.2. 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.
2.2.1.3. 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
2.2.1.3.1. eContentType
The eContentType for a Manifest is defined as id-ct-rpkiManifest, and
has the numerical value of 1.2.840.113549.1.9.16.1.26.
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-rpkiManifest OBJECT IDENTIFIER ::= { id-ct 26 }
2.2.1.3.2. eContent
The content of a Manifest is defined as follows:
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Manifest ::= SEQUENCE {
version [0] INTEGER DEFAULT 0,
manifestNumber INTEGER,
thisUpdate GeneralizedTime,
nextUpdate GeneralizedTime,
fileHashAlg OBJECT IDENTIFIER,
fileList SEQUENCE OF (SIZE 0..MAX) FileAndHash
}
FileAndHash ::= SEQUENCE {
file IA5String
hash BIT STRING
}
2.2.1.3.2.1. Manifest
The manifestNumber, thisUpdate, and nextUpdate fields are modelled
after the corresponding fields in X.509 CRLs (see [RFC5280]).
Analogous to CRLS, a manifest is nominally valid until the time
specified in nextUpdate or until a manifest is issued with a greater
manifest number, whichever comes first. The revoked EE certificate
for the previous manifest's signature will be removed from the CRL
when it expires.
To prevent needless growth of CRLs, it is RECOMMENDED that the EE
certificate used to issue a manifest have an validity period that
coincides with the interval from thisUpdate to nextUpdate.
2.2.1.3.2.1.1. version
The version number of the rpkiManifest MUST be 0.
2.2.1.3.2.1.2. manifestNumber
The manifestNumber field is a sequence number that is incremented
each time a new manifest is issued for a given publication point.
This field is used to allow a RP to detect gaps in a sequence of
published manifest.
2.2.1.3.2.1.3. thisUpdate
The thisUpdate field contains the time when the manifest was created.
2.2.1.3.2.1.4. nextUpdate
The nextUpdate field contains the time at which the next scheduled
manifest will be issued. The value of nextUpdate MUST be later than
the value of thisUpdate. If the authority alters any of the items in
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the repository publication point, then the authority MUST issue a new
manifest before the nextUpdate time. In such a case, when the
authority issues the new manifest, it MUST also issue a new CRL that
includes the EE certificate corresponding to the old manifest.
2.2.1.3.2.1.5. fileHashAlg
The fileHashAlg field contains the OID of the hash algorithm used to
hash the files that the authority has placed into the repository.
The mandatory to implement hash algorithm is SHA-256 and its OID is
2.16.840.1.101.3.4.2.1. [RFC4055].
2.2.1.3.2.1.6. fileList
The fileList field contains a sequence of FileAndHash pairs, one for
each currently valid signed object that has been issued by the
authority. Each FileAndHash pair contains the name of the file in
the repository that contains the object in question, and a hash of
the file's contents.
2.2.1.4. certificates
The certificates field MUST be included, and MUST contain the RPKI
end entity certificate needed to validate this Manifest in the
context of the RPKI.
2.2.1.5. crls
This field MUST be omitted.
2.2.1.6. signerInfos
Signer Infos is defined as a SignerInfo, which 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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2.2.1.6.1. version
The version number MUST be 3, corresponding with the choice of
SubjectKeyIdentifier for the sid.
2.2.1.6.2. sid
The sid is defined as:
SignerIdentifier ::= CHOICE {
issuerAndSerialNumber IssuerAndSerialNumber,
subjectKeyIdentifier [0] SubjectKeyIdentifier }
For a Manifest, the sid MUST be a SubjectKeyIdentifier.
2.2.1.6.3. digestAlgorithm
The digestAlgorithm MUST be SHA-256, the OID for which is
2.16.840.1.101.3.4.2.1. [RFC4055]
2.2.1.6.4. signedAttrs
The signedAttrs is defined as signedAttributes:
SignedAttributes ::= SET SIZE (1..MAX) OF Attribute
UnsignedAttributes ::= 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 signing-time 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 Manifest the attrValues MUST consist of only a
single AttributeValue.
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2.2.1.6.4.1. 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 Manifest MUST be
1.2.840.113549.1.9.16.1.26, matching the eContentType in the
EncapsulatedContentInfo.
2.2.1.6.4.2. 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].
2.2.1.6.4.3. SigningTime Attribute
The SigningTime attribute MAY be present. The presence of absence of
the SigningTime attribute in no way affects the validation of the
Manifest (as specified in Section 5).
The attrType OID for the SigningTime attribute is
1.2.840.113549.1.9.5.
The attrValues for 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.
2.2.1.6.4.4. BinarySigningTime Attribute
The signer MAY include a BinarySigningTime attribute, specifying the
time at which the digital signature was applied to the content. If
both the BinarySigningTime and SigningTime attributes are present,
the time that is represented by the binary-signing-time attribute
MUST represent the same time value as the signing-time attribute.
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The presence or absence of the Binary-SigningTime attribute in no way
affects the validation of the Manifest (as specified in Section 5).
The binary-signing-time attribute is defined in [RFC4049] 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)
2.2.1.6.5. signatureAlgorithm
The signatureAlgorithm MUST be RSA (rsaEncryption), the OID for which
is 1.2.840.113549.1.1.1.
2.2.1.6.6. signature
The signature value is defined as:
SignatureValue ::= OCTET STRING
The signature characteristics are defined by the digest and signature
algorithms.
2.2.1.6.7. unsignedAttrs
unsignedAttrs MUST be omitted.
2.2.2. ASN.1
The following is the ASN.1 specification of the CMS-signed Manifest.
ContentInfo ::= SEQUENCE {
contentType ContentType,
content [0] EXPLICIT ANY DEFINED BY contentType }
ContentType ::= OBJECT IDENTIFIER
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-rpkiManifest OBJECT IDENTIFIER ::= { id-ct 26 }
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Manifest ::= SEQUENCE {
version [0] INTEGER DEFAULT 0,
manifestNumber INTEGER,
thisUpdate GeneralizedTime,
nextUpdate GeneralizedTime,
fileHashAlg OBJECT IDENTIFIER,
fileList SEQUENCE OF (SIZE 0..MAX) FileAndHash}
FileAndHash ::= SEQUENCE {
file IA5String
hash BIT STRING}
id-signedData OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs7(7) 2 }
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
SignerInfo ::= SEQUENCE {
version CMSVersion,
sid SignerIdentifier,
digestAlgorithm DigestAlgorithmIdentifier,
signedAttrs [0] IMPLICIT SignedAttributes OPTIONAL,
signatureAlgorithm SignatureAlgorithmIdentifier,
signature SignatureValue,
unsignedAttrs [1] IMPLICIT UnsignedAttributes OPTIONAL }
SignerIdentifier ::= CHOICE {
issuerAndSerialNumber IssuerAndSerialNumber,
subjectKeyIdentifier [0] SubjectKeyIdentifier }
SignedAttributes ::= SET SIZE (1..MAX) OF Attribute
UnsignedAttributes ::= SET SIZE (1..MAX) OF Attribute
Attribute ::= SEQUENCE {
attrType OBJECT IDENTIFIER,
attrValues SET OF AttributeValue }
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AttributeValue ::= ANY
SignatureValue ::= OCTET STRING
id-contentType OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs9(9) 3 }
ContentType ::= OBJECT IDENTIFIER
id-messageDigest OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs9(9) 4 }
MessageDigest ::= OCTET STRING
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 }
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)
3. Manifest Generation
3.1. CA Manifest Generation
Each CA in the RPKI publishes the certificates and CRLs it issues at
a publication point in the RPKI repository system. To create a
manifest, each CA MUST perform the following steps:
1. Generate a key pair.
2. Issue a "single use" EE certificate for this key pair to enable
relying parties to verify the signature on the manifest.
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* This EE certificate has an SIA extension access description
field with an accessMethod OID value of id-ad-signedobject
where the associated accessLocation references the publication
point of the manifest as an object URL.
* This EE certificate SHOULD describe its IP number resources
using the "inherit" attribute rather than explicit description
of a resource set.
* The validity times of the EE certificate SHOULD exactly match
the thisUpdate and nextUpdate times of the manifest, and MUST
encompass the interval from thisUpdate to nextUpdate.
3. The EE certificate SHOULD NOT be published in the authority's
repository publication point.
4. Construct the Manifest content. Note that the manifest does not
include a self reference (i.e., its own file name and hash),
since it would be impossible to compute the hash of the manifest
itself prior to it being signed.
5. Encapsulate the Manifest content using the CMS SignedData content
type (as specified in Section 2), sign the manifest using the EE
certificate, and publish the manifest in repository system
publication point that is described by the manifest.
6. The private key associated with the EE certificate SHOULD now be
destroyed.
3.2. End Entity Manifest Generation
EE repository publication points are only used in conjunction with
"multi-use" EE Certificates. In this case the EE Certificate has two
accessMethods specified in its SIA field. The id-ad-
signedObjectRepository accessMethod has an associated accessLocation
that points to the repository publication point of the objects signed
by this EE certificate, as specified in [ID.SIDR-CERTPROFILE]. The
id-ad-rpkiManifest accessMethod has an associated access location
that points to the manifest object as an object URL, that is
associated with this repository publication point. This manifest
describes all the signed objects that are to be found in that
publication point that have been signed by this EE certificate, and
the hash value of each product (excluding the manifest itself).
To create a manifest, each "multi-use" EE MUST perform the following
steps:.
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o Construct the Manifest content. Note that the manifest does not
include a self reference (i.e., its own file name and hash), since
it would be impossible to compute the hash of the manifest itself
prior to it being signed.
o Encapsulate the Manifest content using the CMS SignedData content
type (as specified in Section 2), sign the manifest using the EE
certificate, and publish the manifest in repository system
publication point that is described by the manifest.
"Single Use" EE certificates do not have repository publication
points. The object signed by the "Single Use" EE certificate is
published in the repository publication point of the CA certificate
that issued the EE certificate, and is listed in the corresponding
manifest for this CA certificate.
3.3. Common Considerations for Manifest Generation
o A new manifest MUST be issued on or before the nextUpdate time.
o An authority MUST issue a new manifest in conjunction with the
finalization of changes made to objects in the publication point.
An authority MAY perform a number of object operations on a
publication repository within the scope of a repository change
before issuing a single manifest that covers all the operations
within the scope of this change. Repository operators SHOULD
implement some form of synchronization function on the repository
to ensure that relying parties who are performing retrieval
operations on the repository are not exposed to intermediate
states during changes to the repository and the associated
manifest.
o Since the manifest object URL is included in the SIA of issued
certificates then a new manifest MUST NOT invalidate the manifest
object URL of previously issued certificates. This implies that
the manifest's publication name in the repository, in the form of
an object URL, is one that is unchanged across manifest generation
cycles.
o As the manifest scope is all signed objects associated with an
authority responsible for a publication point, the manifest must
persist across key rollover events. This implies that this
persistent repository publication name cannot be derived from the
authority's current public key value in any way.
o In the case of a CA publication point manifest, when the CA is
performing a key rollover, the CA will use its new private key to
sign an EE certificate for a new manifest. The new manifest will
list all products of the CA that have been signed with the new
private key. The new manifest will start a new serial number
sequence. As long as there are published products that have been
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signed with the to-be-retired key, the old CA associated with this
to-be-retired key will continue to generate manifests that
describe all published products of the to-be-retired key and
associated CA certificate. There is no manifest overlap.
o In the case of a EE publication point manifest, when the EE
certificate is re-keyed, a new publication point is established.
A new EE certificate for manifest validation will be generated by
the CA that issues the new EE certificate associated with the new
publication point. In this case there is no manifest overlap, as
the new repository publication point will have a distinct
manifest.
4. Processing Certificate Requests
When an EE certificate is intended for use in verifying multiple
objects, the certificate request for the EE certificate MUST include
in the SIA of the request an access method OID of id-ad-
signedObjectRepository where the associated access location refers to
the publication point for objects signed by this EE certificate, and
MUST include in the SIA of the request an access method OID of id-ad-
rpkiManifest, where the associated access location refers to the
publication point of the manifest that is associated with published
objects that are verified using this EE certificate
[ID.SIDR-CERTPROFILE]. The issuer SHOULD honour these values in the
issued certificate or MUST reject the Certificate Request.
When an EE certificate is used to sign a single object, the
certificate request for the EE certificate MUST include in the SIA of
the request an access method OID of id-ad-signedObject, where the
associated access location refers to the publication point of the
single object that is verified using this EE certificate. The
certificate request MUST NOT include in the SIA of the request the
access method OID of id-ad-rpkiManifest. The issuer SHOULD honour
these values in the issued certificate or MUST reject the Certificate
Request.
In accordance with the provisions of [ID.SIDR-CERTPROFILE], all
certificate issuance requests for a CA certificate SHOULD include in
the SIA of the request the id-ad-caRepository access method, and also
the id-ad-rpkiManifest access method that references the intended
publication point of the manifest in the associated access location
in the request. The issuer SHOULD honour these values in the issued
certificate or MUST reject the Certificate Request.
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5. Manifest Validation
To determine whether a manifest is valid, the relying party must
perform the following checks:
1. Verify that the Manifest 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 id-ad-
rpkiManifest (OID 1.2.840.113549.1.9.16.1.26).
G. The version of the rpkiManifest is 0.
H. In the rpkiManifest, thisUpdate precedes nextUpdate.
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).
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 Manifest.
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3. 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.RESCERT] for more details.)
If the above procedure indicates that the manifest is invalid, then
the manifest MUST be discarded and treated as though no manifest were
present.
6. Relying Party Use of Manifests
The goal of the relying party is to determine which signed objects to
use for routing-related tasks, (e.g. which ROAs to use in the
construction of route filters). Ultimately, this is a matter of
local policy. However, in the following sections, we describe a
sequence of tests that the relying party should perform to determine
the manifest state of the given publication point. We then discuss
the risks associated with using signed objects in the publication
point, given the manifest state; and provide suitable warning text
that should placed in a user-accessible log file. It is the
responsibility of the relying party to weigh these risks against the
risk of routing failure that could occur if valid data is rejected,
and construct a suitable local policy. Note that if a certificate is
deemed unfit for use do to local policy, then any descendent object
that is validated using this certificate should also be deemed unfit
for use (regardless of the status of the manifest at its own
publication point).
6.1. Tests for Determining Manifest State
For a given publication point, the relying party should perform the
following tests to determine the manifest state of the publication
point:
1. Select the manifest having highest manifestNumber among all valid
manifests (where manifest validity is defined in Section 5).
* If the publication point does not contain a valid manifest,
see Section 6.2. (Lacking a valid manifest, the following
tests cannot be performed).
2. Check that the current time is between thisUpdate and nextUpdate.
* If the current time does not lie in this interval then see
Section 6.4 (but still continue with the following tests).
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3. Check that every file at the publication point appears on the
manifest, and that every file on the manifest appears at the
publication point.
* If there exists files at the publication point that do not
appear on the manifest, or files on the manifest that do not
appear at the publication point then see Section 6.5 (but
still continue with the following test).
4. Check that the hash of every file listed on the manifest matches
the value obtained by hashing the file in at the publication
point.
* If there exist files at the publication point whose hash does
not match the hash value listed in the manifest, then see
Section 6.6.
For a particular signed object, if (A) the manifest for its
publication passes all of the above checks; (B) the signed object is
valid; and (C) the manifests for every certificate on the certificate
path used to validate the signed object pass all of the above checks;
then the relying party can conclude that no attack against the
repository system has compromised the given signed object and the
signed object MUST be treated as valid.
6.2. Missing Manifests
The absence of a valid manifest at a publication could occur due to
an error by the publisher or due to (malicious or accidental)
deletion or corruption of all valid manifests.
When no valid manifest is available, there is no protection against
attacks that delete signed objects or replay old versions of signed
objects. All signed objects at the publication point, and all
descendent objects that are validated using a certificate at this
publication point should be viewed as somewhat suspect, but may be
used by the relying party as per local policy.
The primary risk in using signed objects at this publication point is
that a deleted CRL causes the relying party to improperly treat a
revoked certificate as valid. This risk is somewhat mitigated if the
CRL for this publication point has a short time between thisUpdate
and nextUpdate (and the current time is within this interval). The
risk in discarding signed objects at this publication point is that
the relying party may incorrectly discard a large number of valid
objects. This gives significant power to an adversary that is able
to corrupt all manifests at the publication point.
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Regardless of whether signed objects from this publication are deemed
fit for use by the relying party, this situation should result in a
warning to the effect that: "No manifest is available for <pub point
name>, and thus there may have been undetected deletions from the
publication point."
6.3. Invalid Manifests
The presence of invalid manifests at a publication point could occur
due to an error by the publisher or due to (malicious or accidental)
corruption of a valid manifest. An invalid manifest MUST never be
used even if the manifestNumber is greater than that on valid
manifests.
There are no risks associated with using signed objects at a
publication point containing an invalid manifest, provided that a
valid manifest is also present.
If an invalid manifest is present at a publication point that also
contains one or more valid manifests, this situation should result in
a warning to the effect that: "An invalid manifest was found at <pub
point name>, this indicates an attack against the publication point
or an error by the publisher. Processing for this publication point
will continue using the most recent valid manifest."
6.4. Stale Manifests
A manifest is considered stale if the current time is after the
nextUpdate time for the manifest. This could be due to publisher
failure to promptly publish a new manifest, or due to (malicious or
accidental) corruption of a more recent manifest.
All signed objects at the publication point, and all descendent
objects that are validated using a certificate at this publication
point should be viewed as somewhat suspect, but may be used by the
relying party as per local policy.
The primary risk in using signed objects at this publication point is
that a newer manifest exists that, if present, would indicate that
certain objects are have been removed or replaced. (E.g. the new
manifest if present might show the existence of a newer CRL and the
removal of several revoked certificates). Thus use of objects on a
stale manifest may cause the relying party to incorrectly treat
several invalid objects as valid. The risk is that a stale CRL
causes the relying party to improperly treat a revoked certificate as
valid. This risk is somewhat mitigated if the time between the
nextUpdate field of the manifest and the current time is short. The
risk in discarding signed objects at this publication point is that
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the relying party may incorrectly discard a large number of valid
objects. This gives significant power to an adversary that is able
to prevent the publication of a new manifest at a given publication
point.
Regardless of whether signed objects from this publication are deemed
fit for use by the relying party, this situation should result in a
warning to the effect that: "The manifest for <pub point name> is no
longer current. It is possible that undetected deletions have
occurred at this publication point."
Note that there is also a less common case where the current time is
before the thisUpdate time for the manifest. This case is
necessarily due to publisher error and in such a case this situation
should result in a warning to the effect that: "The manifest found at
<pub point name> has an incorrect thisUpdate field. This is due to
publisher error, and processing for this publication point will
continue using this otherwise valid manifest."
6.5. Files Not on Manifests (or Missing from a Publication Point)
If there exist otherwise valid signed objects that do not appear on
any manifest, then provided the manifest is not stale (see Section
6.4) it is likely that their omission is an error by the publisher.
(If the objects were intended to be invalid, then they should have
been revoked using whatever revocation mechanism is appropriate for
the signed object in question.) Therefore, there is little risk in
using such signed objects. If the manifest in question is stale,
then there is a greater risk that the objects in question were
revoked with a missing CRL (whose absence is undetectable since the
manifest is stale). In any case, the use of signed objects not
present on a manifest (or descendent objects that are validated using
such signed objects) is a matter of local policy.
Regardless of whether objects not appearing on a manifest are deemed
fit for use by the relying party, this situation should result in a
warning to the effect that: "The following files are present in the
repository at <pub point name>, but are not on the manifest <file
list>."
If there exist files listed on the manifest that do not appear in the
repository, then these objects are likely to have been improperly
(via malice or accident) deleted from the manifest. A primary
purpose of manifests is to detect such deletions. Therefore, in such
a case this situation should result in a warning to the effect that:
"The following files that should have been present in the repository
at <pub point name>, are missing <file list>. This indicates an
attack against this publication point, or the repository, or an error
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by the publisher."
6.6. Hash Values Not Matching Manifests
A file appearing on a manifest with an incorrect hash value could
occur because of publisher error, but it is likely to indicate that a
serious error has occurred.
If an object appeared on a previous valid manifest with a correct
hash value and now appears with an invalid hash value, then it is
likely that the object has been superceded by a new (unavailable)
version of the object. If the object is used there is a risk that
the relying party will be treating a stale object as valid. This
risk is more significant if the object in question is a CRL.
Assuming that the object is validated in the RPKI, the use of these
objects is a matter of local policy.
If an object appears on a manifest with an invalid hash and has never
previously appeared on a manifest, then it is unclear whether the
available version of the object is more or less recent than the
version whose hash appears in the manifest. If the manifest is stale
(see Section 6.4) then it becomes more likely that the available
version is more recent that the version indicated on the manifest,
but this is never certain. Whether to use such objects is a matter
of local policy. However, in general, it is better to use a possibly
outdated version of the object, then to discard the object
completely.
Regardless of whether objects with incorrect hashes are deemed fit
for use by the relying party, this situation should result in a
warning to the effect that: "The following files at the repository
<pub point name> appear on a manifest with incorrect hash values
<file list>. It is likely that these objects have been superseded by
a more recent version. It is very likely that this problem is due to
an attack on the publication point, although it could be due to a
publisher error."
7. Publication Repositories
The RPKI publication system model requires that every publication
point be associated with a CA or an EE, and be non-empty. Upon
creation of the publication point associated with a CA, the CA MUST
create and publish a manifest as well as a CRL. The manifest will
contain at least one entry, the CRL issued by the CA upon repository
creation. Upon the creation of the publication point associated with
an EE, the EE MUST create and publish a manifest. The manifest in an
otherwise empty repository publication point associated with an EE
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will contain no entries in the manifest's fileList sequence (i.e. a
sequence of length zero). [ID.SIDR-REPOSITORY]
For signed objects EE certificate used in the verification of such
objects is either a single-use certificate, used to verify a single
signed object, or a multiple-use certificate. In the case of a
single-use EE certificate, the signed object is published in the
repository publication point of the CA that issued the single use EE
certificate, and is listed in the manifest associated with that CA
certificate. In the case where the EE certificate is used to verify
multiple objects, signed object is published in the EE certificate's
repository publication point and listed in the manifest associated
with the EE certificate.
8. Security Considerations
Manifests provide an additional level of protection for users of the
repository system. Manifests can assist the user to determine if
repository objects have been occluded or other removed from view, and
to determine if an older version of an object has been substituted
for the current object.
Manifests cannot repair the effects of such forms of attempted
corruption of repository retrieval operations, but are capable of
allowing the user to determine if a locally maintained copy of a
repository is a complete and up to date copy, even when the
repository retrieval operation is conduction over an insecure
channel. In those cases where the manifest and the retrieved
repository contents differ, the manifest can assist in determining
which repository objects form the difference set in terms of missing,
extraneous or older objects.
The signing structure of a manifest and the use of next update times
allows the user to determine if the manifest itself is the subject of
attempted alteration. The requirement for all repositories to
contain manifests allows the user to determine is the manifest itself
has been occluded from view. Such attacks against the manifest are
detectable within the timeframe of the regular schedule of manifest
updates. Forms of replay attack within finer-grained timeframes are
not necessarily detectable by the manifest structure.
9. IANA Considerations
[Note to IANA, to be removed prior to publication: there are no IANA
considerations stated in this version of the document.]
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10. Acknowledgements
The authors would like to acknowledge the contributions from George
Michaelson and Randy Bush in the preparation of the manifest
specification. Additionally, the authors would like to thank Mark
Reynolds and Christopher Small for assistance in clarifying manifest
validation and relying party behavior.
11. Normative References
[ID.SIDR-ARCH]
Lepinski, M., Kent, S., and R. Barnes, "An Infrastructure
to Support Secure Internet Routing", Work in progress:
Internet Drafts draft-ietf-sidr-arch-03.txt,
February 2008.
[ID.SIDR-CERTPROFILE]
Huston, G., Michaleson, G., and R. Loomans, "A Profile for
X.509 PKIX Resource Certificates", Work in progress:
Internet Drafts draft-ietf-sidr-res-certs-10.txt,
June 2008.
[ID.SIDR-REPOSITORY]
Huston, G., Loomans, R., and G. Michaleson, "A Profile for
Resource Certificate Repository Structure", Work in
progress: Internet
Drafts draft-huston-sidr-repos-struct-02.txt, June 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.
[RFC4049] Housley, R., "BinaryTime: An Alternate Format for
Representing Date and Time in ASN.1", RFC 4049,
April 2005.
[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.
[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
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(CRL) Profile", RFC 5280, May 2008.
Authors' Addresses
Rob Austein
Internet Systems Consortium
950 Charter St.
Redwood City, CA 94063
USA
Email: sra@isc.org
Geoff Huston
Asia Pacific Network Information Centre
33 park Rd.
Milton, QLD 4064
Australia
Email: gih@apnic.net
URI: http://www.apnic.net
Stephen Kent
BBN Technologies
10 Moulton St.
Cambridge, MA 02138
USA
Email: kent@bbn.com
Matt Lepinski
BBN Technologies
10 Moulton St.
Cambridge, MA 02138
USA
Email: mlepinski@bbn.com
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Full Copyright Statement
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