One document matched: draft-ietf-sidr-repos-struct-04.txt
Differences from draft-ietf-sidr-repos-struct-03.txt
Secure Inter-Domain Routing G. Huston
Internet-Draft R. Loomans
Intended status: BCP G. Michaelson
Expires: November 16, 2010 APNIC
May 15, 2010
A Profile for Resource Certificate Repository Structure
draft-ietf-sidr-repos-struct-04.txt
Abstract
This document defines a profile for the structure of repository
publication points that contain X.509 / PKIX Resource Certificates,
Certificate Revocation Lists and signed objects. This profile
contains the proposed object naming scheme, the contents of
repository publication points, the contents of publication point
manifests and a suggested internal structure of a local repository
cache that is intended to facilitate synchronisation across a
distributed collection of repository publication points and
facilitate certification path construction.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 16, 2010.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
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publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. RPKI Repository Publication Point Content and Structure . . . 3
2.1. Manifests . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. CA Repository Publication Point . . . . . . . . . . . . . 6
2.3. EE Repository Publication Point . . . . . . . . . . . . . 8
3. Resource Certificate Publication Repository Considerations . . 9
4. Certificate Reissuance and Repositories . . . . . . . . . . . 10
5. Synchronising Repositories . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Normative References . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
To validate attestations made in the context of the Resource Public
Key Infrastructure (RPKI) [I-D.sidr-arch] Relying Parties (RPs) need
access to all the X.509 / PKIX Resource Certificates, Certificate
Revocation Lists (CRLs), and signed objects that collectively define
the RPKI.
Each issuer of a certificate, CRL or a signed object makes it
available for download to RPs through the publication of the object
in a RPKI repository.
The repository system is the central clearing-house for all signed
objects that must be globally accessible to all RPs. When
certificates, CRLs and signed objects are created, they are uploaded
to a repository publication point, from whence they can be downloaded
for use by RPs.
This document defines a profile for the structure of RPKI
repositories. This profile contains the proposed object naming
scheme, the contents of repository publication points, the contents
of publication point manifests and a possible internal structure of a
Repository Cache that is intended to facilitate synchronisation
across a distributed collection of repositories and facilitate
certificate path construction.
A Resource Certificate describes an attestation by an Issuer that
binds a list of IP address blocks and 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.
1.1. Terminology
It is assumed that the reader is familiar with the terms and concepts
described in "Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile" [RFC5280], "X.509
Extensions for IP Addresses and AS Identifiers" [RFC3779], and
related regional Internet registry address management policy
documents.
2. RPKI Repository Publication Point Content and Structure
The RPKI does not use a single repository publication point to
publish RPKI objects. Instead, the RPKI repository system is
comprised of multiple repository publication points. Each repository
publication point is associated with one or more RPKI certificates'
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publication points, as defined in the certificate's Subject
Information Authority (SIA) extension.
This section describes the collection of objects (RPKI certificates,
CRLs, manifests and signed objects) held in repository publication
points.
For every certificate in the PKI, there will be a corresponding
repository publication point file system directory that is the
authoritative publication point for all objects signed by the private
key part of the key pair whose public key part is the subject public
key of this certificate.
Objects are added to the publication point when issued by the
associated CA, or when signed by the private key part of a key pair
whose subject public key is described in an EE certificate that is
associated with the repository publication point, and are removed
when expired or revoked.
The certificate's Subject Information Authority (SIA) extension
provides a URI that references this repository publication point and
supported repository access mechanisms. Additionally, a
certificate's Authority Information Authority (AIA) extension
contains a URI that references the authoritative location for the
Certification Authority (CA) certificate under which the given
certificate was issued. That is, if the subject of certificate A has
issued certificate B, then the AIA extension of certificate B points
to certificate A, and the SIA extension of certificate A points to a
repository publication point file system directory containing
certificate B (see Figure 1).
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+--------+
+--------->| Cert A |<----+
| | CRLDP | |
| | AIA | |
| +--------- SIA | |
| | +--------+ |
| | |
| | |
| | |
| | +-------------------|------------------+
| | | | |
| +->| +--------+ | +--------+ |
| | | Cert B | | | Cert C | |
| | | CRLDP ----+ | | CRLDP -+-+ |
+----------- AIA | | +----- AIA | | |
| | SIA | | | SIA | | |
| +--------+ | +--------+ | |
| V | |
| +---------+ | |
| | A's CRL |<-----------+ |
| +---------+ |
| A's Repository Publication Directory |
+--------------------------------------+
Figure 1: Example Repository Structure.
In the example shown in Figure 1, certificates B and C are issued by
CA A. Therefore, the AIA extensions of certificates B and C point to
the object publication point where Certificate A is published, and
the SIA extension of certificate A points to the repository
publication point of CA A's subordinate products, including
certificates B and C, as well as A's CRL.
The general intent of this distributed repository structure is that
an instance of a CA's repository publication point contains all the
signed products of that CA, and an End Entity's (EE's) repository
publication point contains all the objects that have been signed by
the private key part of a key pair whose public key is described in
the subject public key of the associated EE certificate.
2.1. Manifests
All CA's and all EE's that have repository publication points
("multi-use" EE certificates, as defined in [I-D.sidr-res-certs])
MUST maintain a manifest [I-D.sidr-rpki-manifests] of their published
subordinate products. The manifest contains a list of the names of
all objects issued by that CA, or signed by the private key part of a
key pair whose public key is the subject public key of the associated
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EE certificate, and published in a repository publication point file
system directory, as well as the hash value of each object's
contents.
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 synchronisation 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.
2.2. CA Repository Publication Point
A CA Certificate has two accessMethod elements specified in its SIA
field. The id-ad-caRepository accessMethod element has an associated
accessLocation element that points to the repository publication
point of the products of this CA, as specified in
[I-D.sidr-res-certs]. The id-ad-rpkiManifest accessMethod element
has an associated accessLocation element that points to the manifest
object, as an object URL, that is associated with this CA.
In the case of a CA's publication repository in the scope of the
RPKI, the repository contains the current unrevoked certificates
issued by this CA, the most recent CRL that is associated with the
CA's non-revoked key pairs, the current unrevoked manifest, and all
current objects that are signed using the private key of a key pair
whose public key is the subject public key of a current unrevoked
"single-use" EE certificate, where the EE certificate was issued by
this CA.
The CA's manifest describes all the current unrevoked objects that
are to be found in that publication point that were issued by this
CA, and all published objects signed using the private key of a key
pair whose public key is the subject public key of a current
unrevoked "single-use" EE certificate that has been issued by this
CA, and the hash value of each object (excluding the manifest itself)
[I-D.sidr-rpki-manifests].
Because an instance of a CA is associated with a single key pair, an
entity performs the equivalent of a key rollover operation by
generating a new CA instance as well as a new key pair. In such
cases the entity may chose to continue the use of a single repository
publication point for both CA instances. In such cases the
repository publication point will contain the CRL, manifest,
subordinate certificates and signed objects of both CA instances.
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Some guidelines for naming objects in a CA's repository publication
point are as follows:
CRL: The scope of a CRL in the RPKI is all objects issued by a CA,
implying that publication of successive instances of a CA's CRL
should overwrite previous instances of CRLs signed by the same
CA's private key in the publication repository. It is consistent
with this objective that the name chosen for the CRL in the
publication repository be a value derived from the public key part
of the CA's key pair whose private key was used to sign the CRL.
One such method of generating a CRL publication name is described
in section 2.1 of [RFC4387], converting the 160-bit hash of the
CA's public key value into a 27-character string using a modified
form of Base64 encoding, with an additional modification as
proposed in section 5, table 2, of [RFC4648]. A CRL MAY use a
filesystem name extension of ".crl" to denote the object as a CRL.
Manifest: When a new instance of a manifest is published by the CA,
there is no requirement within the RPKI for any RP to have
continuing access to older instances of the CA's manifest. When
multiple CA's share a common repository publication point their
respective manifests must be distinct. It is consistent with this
objective that the name chosen for the manifest in the publication
repository be a value derived from the public key part of the CA's
key pair, using the algorithm described above for CRL object
names. A manifest MAY use a filesystem name extension of ".mft"
to denote the object as a manifest.
Certificates: Within the RPKI framework it is possible that a CA may
issue a series of certificates for the same subject name, the same
subject public key, and the same resource collection. Within the
context of each such series of certificates a RP has an interest
only in the most recently published current certificate. The
publication repository object name scheme for the CA may use a
unique name for each such series of certificates, thereby ensuring
that each successive issued certificate in such a series
effectively overwrites the previous instance of the certificate in
the publication repository. If the CA adopts a local policy that
each subject uses a unique key pair for each unique instance of a
certified resource collection then the CA can use a certificate
object name scheme that is derived from the subject's public key,
applying the algorithm described above for CRL object names to the
subject's public key value. A certificate MAY use a filesystem
name extension of ".cer" to denote the object as a certificate.
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Signed Objects: Within the RPKI framework there are two kinds of EE
certificates that are used in conjunction with digital
certificates: "single-use" EE certificates, where the private key
of the key pair whose public key is the subject public key of the
EE certificate is used to sign a single object, and "multi-use" EE
Certificates, whose private key of the key pair whose public key
is the subject public key of the EE certificate may be used to
sign multiple objects. In the case of "single-use" EE
certificates, the single signed object is to be published in the
same repository publication point as the associated EE
certificate. The signed object name scheme for such objects can
be derived from the associated EE certificate's subject public
key, applying the algorithm described above for CRL object names
to the EE certificates's subject public key value. The signed
object is listed in the manifest associated with this repository
publication point. In the case of "multi-use" EE certificates the
repository publication point is described in the following
section.
2.3. EE Repository Publication Point
EE repository publication points are used in conjunction with "multi-
use" EE Certificates. In this case the EE Certificate has two
accessMethod elements specified in its SIA field. The id-ad-
signedObjectRepository accessMethod element has an associated
accessLocation element that points to the repository publication
point of the objects signed by the private key of a key pair whose
public key is the subject public key of this EE certificate, as
specified in [I-D.sidr-res-certs]. The id-ad-rpkiManifest
accessMethod element has an associated accessLocation element 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 the private key of a key pair whose public
key is the subject public key of this EE certificate, and the hash
value of each product (excluding the manifest itself)
[I-D.sidr-rpki-manifests].
In the case of an EE's publication repository in the scope of the
RPKI, the repository contains objects that have been signed by the
private key of the key pair whose public key is the subject public
key of the EE certificate, and a manifest of all such signed objects.
The objects published in a EE repository publication point do not
form a logical sequence, and must be named uniquely in the context of
the publication repository.
It is consistent with this specification, but not recommended
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practice, that all subordinate EE's of a given CA share a common
publication repository. In this case the repository publication
point would contain multiple manifest objects, one for each EE that
has placed objects into this common publication point. Each manifest
is limited in scope to listing the objects signed by the EE
certificate. The implication is that all objects signed by the
private key of a key pair whose public key is the subject key of a
single EE certificate, including the EE's manifest, share a base name
element that is generated from the public key of the EE certificate.
The choice of whether to use a common single publication repository
or a dedicated publication repository for each EE certificate is an
implementation choice.
3. Resource Certificate Publication Repository Considerations
Each issuer may publish their issued certificates and CRL in any
location of their choice. However, there are a number of
considerations which guide the choice of a suitable repository
publication structure.
o The publication repository SHOULD be hosted on a highly available
service and high capacity publication platform.
o The publication repository MUST be available using RSYNC
[RFC5781][I-D.sidr-res-certs] Support of additional retrieval
mechanisms is the choice of the repository operator. The
supported retrieval mechanisms should be consistent with the
accessMethod element value(s) specified in the SIA of the
associated CA or EE.
o Each CA repository publication point file system directory in the
publication repository should contain the products of this CA,
including those objects signed by single-use EE certificates that
have been issued by this CA. The signed products of related CA's
that are operated by the same entity may share the CA repository
publication point file system directory. Aside from
subdirectories, no other objects should be placed in a repository
publication point file system directory.
Any such subdirectory should be the repository publication point
file system directory of a CA or EE certificate that is contained
in the CA's repository publication point file system directory.
There are no constraints on the name of a repository publication
point file system subdirectory. These considerations also apply
recursively to subdirectories of these repository publication
point file system subdirectories directories.
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o Signed Objects are published in the location indicated by the SIA
field of the EE certificate that has certified the public key part
of the key pair whose private key part was used to sign the
object. The choice of the repository publication point is
determined by the nature of the signing EE certificate. In the
case of "multi-use" EE certificates the signed object is published
in an EE repository publication point as referenced by the SIA
extension of the EE certificate. In the case of "single-use" EE
certificates the signed object is published in the repository
publication point of the CA certificate that issued the EE
certificate, and the SIA extension of the single use EE
certificate references this object rather than the repository
publication point file system directory[I-D.sidr-res-certs].
4. Certificate Reissuance and Repositories
If a CA certificate is reissued, it should not be necessary to
reissue all certificates signed by the certificate being reissued.
Therefore, a CA SHOULD use a persistent naming scheme for the
certificate's repository publication point that is persistent across
certificate re-issuance events. That is, reissued certificates
SHOULD use the same repository publication point as previously issued
certificates having the same subject and subject public key, and
SHOULD overwrite previously issued certificates within the repository
publication point file system directory.
5. Synchronising Repositories
It is possible to perform the validation-related task of certificate
path construction using retrieval of individual certificates and
certificate revocation lists using online retrieval of individual
certificates, sets of candidate certificates and certificate
revocation lists based on the Authority Information Access, Subject
Information Access and CRL Distribution Points certificate fields.
This is not recommended in circumstances where speed and efficiency
are relevant considerations. Where an efficient validation operation
is required, it is RP MAY maintain a local repository containing a
synchronised copy of all current valid certificates, current
certificate revocation lists, and all related signed objects,
maintained as a local current copy of the complete distributed RPKI
repository collection.
The general approach to repository synchronisation is one of a "top-
down" walk of the distributed repository structure, commencing with
the initial configured trust anchor certificates, and then populating
the local repository cache will all valid certificates that have been
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issued by these issuers, and then recursively applying the same
approach to each of these subordinate certificates. Such a
repository traversal process would need to support some locally
configured maximal chain length from the initial trust anchors to the
current working validation point in order to ensure that the process
does not follow a loop or a non-terminating certificate chain.
6. Security Considerations
Repositories are not "protected" structures, and repository retrieval
operations are vulnerable to various forms of "man-in-the-middle"
attacks. Corruption of retrieved objects is detectable by a RP
through the RPKI validation of the retrieved object. Insertion of
older objects is detectable by the CRL, assuming that the older
object has been revoked by the issuer. However, certain forms of
substitution and removal attacks are not directly detectable. For
this reason all published RPKI objects are described in a manifest
[I-D.sidr-rpki-manifests]. The manifest can improve the level of
assurance that a RP is receiving an authentic copy of the repository,
and that the set of retrieved objects is complete.
7. IANA Considerations
[There are no IANA considerations in this document.]
8. Normative References
[I-D.sidr-arch]
Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", draft-ietf-sidr-arch-08.txt
(work in progress), July 2009.
[I-D.sidr-res-certs]
Huston, G., Michaelson, G., and R. Loomans, "A Profile for
X.509 PKIX Resource Certificates",
draft-ietf-sidr-res-certs-16.txt (work in progress),
February 2008.
[I-D.sidr-rpki-manifests]
Austein, R., Huston, G., Kent, S., and M. Lepinski,
"Manifests for the Resource Public Key Infrastructure",
draft-ietf-sidr-rpki-manifests (work in progress),
August 2009.
[RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
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Addresses and AS Identifiers", RFC 3779, June 2004.
[RFC4387] Gutmann, P., "Internet X.509 Public Key Infrastructure
Operational Protocols: Certificate Store Access via HTTP",
RFC 4387, February 2006.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 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.
[RFC5781] Weiler, S., Ward, D., and R. Housley, "The rsync URI
Scheme", RFC 5781, February 2010.
Authors' Addresses
Geoff Huston
Asia Pacific Network Information Centre
Email: gih@apnic.net
URI: http://www.apnic.net
Robert Loomans
Asia Pacific Network Information Centre
Email: robertl@apnic.net
URI: http://www.apnic.net
George Michaelson
Asia Pacific Network Information Centre
Email: ggm@apnic.net
URI: http://www.apnic.net
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