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Secure Inter-Domain Routing                                   R. Austein
Internet-Draft                                                       ISC
Intended status: Standards Track                               G. Huston
Expires: April 18, 2011                                            APNIC
                                                                 S. Kent
                                                             M. Lepinski
                                                                     BBN
                                                        October 15, 2010


          Manifests for the Resource Public Key Infrastructure
                 draft-ietf-sidr-rpki-manifests-08.txt

Abstract

   This document defines a "manifest" for use in the Resource Public Key
   Infrastructure (RPKI).  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
   repository.  For each certificate, Certificate Revocation List (CRL),
   or other type 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 enable a relying party (RP)
   to detect certain forms of attacks against a repository.
   Specifically, if a RP checks a manifest's contents against the signed
   objects retrieved from a repository publication point, then the RP
   can detect "stale" (valid) data and deletion of signed objects.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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 April 18, 2011.

Copyright Notice




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   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Manifest Scope . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Manifest Signing . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Manifest Definition  . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  eContentType . . . . . . . . . . . . . . . . . . . . . . .  5
     4.2.  eContent . . . . . . . . . . . . . . . . . . . . . . . . .  5
       4.2.1.  Manifest . . . . . . . . . . . . . . . . . . . . . . .  5
     4.3.  ContentType Attribute  . . . . . . . . . . . . . . . . . .  7
     4.4.  Manifest Validation  . . . . . . . . . . . . . . . . . . .  7
   5.  Manifest Generation  . . . . . . . . . . . . . . . . . . . . .  7
     5.1.  CA Manifest Generation . . . . . . . . . . . . . . . . . .  8
     5.2.  End Entity Manifest Generation . . . . . . . . . . . . . .  9
     5.3.  Common Considerations for Manifest Generation  . . . . . . 10
   6.  Relying Party Use of Manifests . . . . . . . . . . . . . . . . 10
     6.1.  Tests for Determining Manifest State . . . . . . . . . . . 11
     6.2.  Missing Manifests  . . . . . . . . . . . . . . . . . . . . 12
     6.3.  Invalid Manifests  . . . . . . . . . . . . . . . . . . . . 13
     6.4.  Stale Manifests  . . . . . . . . . . . . . . . . . . . . . 13
     6.5.  Mismatch between Manifest and Publication Point  . . . . . 14
     6.6.  Hash Values Not Matching Manifests . . . . . . . . . . . . 15
   7.  Publication Repositories . . . . . . . . . . . . . . . . . . . 16
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 17
     11.2. Informative References . . . . . . . . . . . . . . . . . . 18
   Appendix A.  ASN.1 Module  . . . . . . . . . . . . . . . . . . . . 19
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19





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1.  Introduction

   The Resource Public Key Infrastructure (RPKI) [ID.ietf-sidr-arch]
   makes use of a distributed repository system
   [ID.ietf-sidr-repos-struct] to make available a variety of objects
   needed by relying parties (RPs).  Because all of the objects stored
   in the repository system are digitally signed by the entities that
   created them, attacks that modify these published 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 and have not expired, but have since
   been superseded) 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 can make use of a signed object
   called a "manifest".

   A manifest is a signed object that enumerates all the signed objects
   in the repository publication point that are associated with an
   authority responsible for publishing at that publication point.  Each
   manifest contains both the name of the file containing the object,
   and a hash of the file content, for every signed object issued by an
   authority that is published at the authority's repository publication
   point.  A manifest is intended to allow an RP to detect unauthorized
   object removal, or the substitution of "stale" versions of objects at
   a publication point.  A manifest also intended to allow an RP to
   detect similar outcomes that may result from a man-in-the middle
   attack on the retrieval of objects from the repository.  Manifests
   are intended to be used both in Certification Authority (CA)
   publication points in repositories (containing subordinate
   certificates, Certificate Revocation Lists (CRLs) and other signed
   objects) and in End Entity (EE) publication points in repositories
   (containing only 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 contain
   objects not covered by CRLs,e.g., digitally signed objects, such as
   Route Origination Authorizations (ROAs).

1.1.  Terminology

   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

   A manifest associated with a CA's repository publication point
   contains:

      *  the set of (non-expired, non-revoked) certificates issued and
         published by this CA,
      *  the most recent CRL issued by this CA, and
      *  all signed objects that are verifiable using a "single-use" EE
         certificate [I-D.sidr-res-certs], issued by this CA.

   Where multiple CA instances share a common publication point, as can
   occur when an entity performs a key-rollover operation
   [ID.sidr-keyroll], the repository publication point will contain
   multiple manifests.  In this case, each manifest describes only the
   collection of published products of its associated CA instance.

   A manifest associated with a "multi-use" EE certificate
   [I-D.sidr-res-certs] where an EE has a defined repository publication
   point (i.e., the SIA extension of the EE certificate has an
   accessMethod OID of id-ad-signedObjectRepository), contains all
   published objects that are verifiable using this EE certificate, and
   the accessMethod id-as-rpkiManifest points to the publication point
   of the EE's manifest.


3.  Manifest Signing

   A CA's manifest is verified using an EE certificate that is
   designated in [I-D.sidr-res-certs] as a "single-use" EE certificate.
   The SIA field of the "single-use" EE certificate contains the access
   method OID of id-ad-signedObject.

   The CA MAY chose to sign only one manifest with the private key of
   the EE certificate, and generate a new EE certificate for each new
   version of the manifest.  This form of use of a "single-use" EE
   certificate is termed a "one-time-use" EE certificate.

   Alternatively, the CA MAY chose to use the same EE certificate's
   private key to sign a sequence of manifests.  Because only a single
   manifest (issued under a single CA instance) is current at any point
   in time, the EE certificate is used to verify only a single object at
   a time.  As long as the sequence of objects verified by this EE
   certificate are published using the same file name, then this
   sequential, multiple use of this "single-use" EE certificate is also
   valid.  This form of use of a "single-use" EE certificate is termed a
   "sequential-use" EE certificate.




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   A "multi-use" EE's manifest of it's publication repository is signed
   with the EE's private key.


4.  Manifest Definition

   A manifest is a RPKI signed object, as specified in
   [ID.sidr-signed-object].  The RPKI signed object template requires
   specification of the following data elements in the context of the
   manifest structure.

4.1.  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 }

4.2.  eContent

   The content of a Manifest is defined as follows:

     Manifest ::= SEQUENCE {
      version     [0] INTEGER DEFAULT 0,
      manifestNumber  INTEGER (0..MAX),
      thisUpdate      GeneralizedTime,
      nextUpdate      GeneralizedTime,
      fileHashAlg     OBJECT IDENTIFIER,
      fileList        SEQUENCE (SIZE 0..MAX) OF FileAndHash
      }

    FileAndHash ::=     SEQUENCE {
      file            IA5String,
      hash            BIT STRING
      }

4.2.1.  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 current until the time
   specified in nextUpdate or until a manifest is issued with a greater
   manifest number, whichever comes first.



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   If a "one-time-use" EE certificate is employed to verify a manifest,
   the EE certificate MUST have an validity period that coincides with
   the interval from thisUpdate to nextUpdate, to prevent needless
   growth of the CA's CRL.

   If a "sequential-use" EE certificate is employed to verify a
   manifest, the EE certificate's validity period needs to be no shorter
   than the nextUpdate time of the current manifest.  The extended
   validity time raises the possibility of a substitution attack using a
   stale manifest, as described in Section 6.4.

   The data elements of the Manifest structure are defined as follows:

   version:
      The version number of this version of the manifest specification
      MUST be 0.

   manifestNumber:
      This field is an integer that is incremented each time a new
      manifest is issued for a given publication point.  This field
      allows a RP to detect gaps in a sequence of published manifest.

      As the manifest is modelled on the CRL specification, the
      ManifestNumber is analogous to the CRLNumber, and the guidance in
      [RFC5280] for CRLNumber values is appropriate as to the range of
      number values that can be used for the manifestNumber.  Manifest
      numbers can be expected to contain long integers.  Manifest
      verifiers MUST be able to handle number values up to 20 octets.
      Conforming Manifest issuers MUST NOT use number values longer than
      20 octets

   thisUpdate:
      This field contains the time when the manifest was created.  This
      field has the same format constraints as specified in [RFC5280]
      for the CRL field of the same name.

   nextUpdate:
      This 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.  The specification of the GeneralizedTime
      value is the same as required for the thisUpdate field.

      If the authority alters any of the items that it has published in
      the repository publication point, then the authority MUST issue a
      new manifest before the nextUpdate time.  If a manifest
      encompasses a CRL, the nextUpdate field of the manifest MUST match
      that of the CRL's nextUpdate field, as the manifest will be
      reissued when a new CRL is published.  If a "one-time-use" EE



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      certificate is used to verify the manifest, then when a new
      manifest is issued before the time specified in nextUpdate of the
      current manifest, the CA MUST also issue a new CRL that includes
      the EE certificate corresponding to the old manifest.

   fileHashAlg:
      This field contains the OID of the hash algorithm used to hash the
      files that the authority has placed into the repository.  The hash
      algorithm used MUST conform to the RPKI Algorithms and Key Size
      Profile specification [ID.ietf-sidr-rpki-algs].

   fileList:
      This field is a sequence of FileAndHash objects.  There is one
      FileAndHash entry for each currently valid signed object that has
      been published by the authority (at this publication point).  Each
      FileAndHash is an ordered pair consisting of the name of the file
      in the repository that contains the object in question, and a hash
      of the file's contents.


4.3.  ContentType Attribute

   The mandatory Content-Type Attribute MUST have its attrValues field
   set to the same OID as eContentType.  This OID is id-ct-rpkiManifest,
   and has the numerical value of 1.2.840.113549.1.9.16.1.26.

4.4.  Manifest Validation

   To determine whether a manifest is valid, the RP MUST perform the
   following checks in addition to those specified in
   [ID.sidr-signed-object]:

   1.  The eContentType in the EncapsulatedContentInfo is id-ad-
       rpkiManifest (OID 1.2.840.113549.1.9.16.1.26).

   2.  The version of the rpkiManifest is 0.

   3.  In the rpkiManifest, thisUpdate precedes nextUpdate.


   If the above procedure indicates that the manifest is invalid, then
   the manifest MUST be discarded and treated as though no manifest were
   present.


5.  Manifest Generation





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5.1.  CA Manifest Generation

   For a CA publication point in the RPKI repository system, a CA MUST
   perform the following steps to generate a manifest:

   1.  If no key pair exists, or if using a "one-time-use" EE
       certificate with a new key pair, generate a key pair.

   2.  If using a "one-time-use" EE certificate, or if a key pair was
       generated in step 1, issue a "single-use" EE certificate for this
       key pair.

          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 MUST describe its Internet Number
          Resources (INRs) using the "inherit" attribute, rather than
          explicit description of a resource set (see [RFC3779]).

          In the case of a "one-time-use" EE certificate, the validity
          times of the EE certificate MUST exactly match the thisUpdate
          and nextUpdate times of the manifest.

          In the case of a "sequential-use" EE certificate the validity
          times of the EE certificate MUST encompass the time interval
          from thisUpdate to nextUpdate.

   3.  The EE certificate MUST 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.  The manifest content is
       described in Section 4.2.1.  The manifest's fileList includes the
       file name and hash pair for each object issued by this CA that
       has been published at this repository publication point.  The
       collection of objects to be included in the manifest includes all
       certificates issued by this CA that are published at the CA's
       repository publication point, the most recent CRL issued by the
       CA, and all objects verified by "single-use" EE certificates that
       were issued by this CA that are published at this repository
       publication point.






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   5.  Encapsulate the Manifest content using the CMS SignedData content
       type (as specified Section 4), sign the manifest using the
       private key corresponding to the subject key contained in the EE
       certificate, and publish the manifest in repository system
       publication point that is described by the manifest.

   6.  In the case of a key pair that is to be used only once, in
       conjunction with a "one-time-use" EE certificate, the private key
       associated with this key pair SHOULD now be destroyed.


5.2.  End Entity Manifest Generation

   EE repository publication points are used only in conjunction with
   "multi-use" EE Certificates.  In this case the EE Certificate has two
   accessMethods specified in its SIA field.  The accessDescription
   element that contains an accessMethod value of id-ad-
   signedObjectRepository has an associated accessLocation directory URL
   that points to the repository publication point of the objects
   verifiable using this EE certificate, as specified in
   [I-D.sidr-res-certs].  The accessDescription element that contains an
   accessMethod value of id-ad-rpkiManifest has an associated
   accessLocation that points to the EE's published manifest object as
   an object URL.  This manifest enumerates every signed object to be
   found in that publication point (that can be verified using this EE
   certificate), and the hash value of each object (excluding the
   manifest itself).

   To create a manifest, each "multi-use" EE MUST perform the following
   steps:.

   1.  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.  The manifest content is
       described in Section 4.2.1.  The manifest's fileList includes the
       file names and hash pair for each object that is verifiable using
       that EE certificate that has been published at this repository
       publication point.

   2.  Encapsulate the Manifest content using the CMS SignedData content
       type (as specified in Section 4), sign the manifest using the
       private key corresponding to the subject key contained in the EE
       certificate, and publish the manifest in repository system
       publication point that is described by the manifest.


   "Single Use" EE certificates (EE certificates with an SIA



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   accessMethod OID of id-as-signedObject) do not have repository
   publication points.  The object that is verifiable using 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.

5.3.  Common Considerations for Manifest Generation

   A new manifest MUST be issued on or before the nextUpdate time.

   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
   repository update procedure that mitigates, to the extent possible,
   the risk that RPs who are performing retrieval operations on the
   repository are exposed to inconsistent transient intermediate states
   during updates to the repository and the associated manifest.

   Since the manifest object URL is included in the SIA of issued
   Certificates, 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 unchanged across manifest generation cycles.

   In the case of a CA publication point manifest, when the CA entity is
   performing a key rollover, the entity MAY chose to have two CAs
   instances simultaneously publishing at the same publication point.
   In this case there will be one manifest associated with each active
   CA instance that is publishing into the common repository publication
   point.

   In the case of an EE publication point, the manifest lists all
   published objects verified using that EE certificate.  Multiple EEs
   MAY share a common repository publication point, in which case there
   will be one manifest associated with each active EE that is
   publishing into the common repository publication point.


6.  Relying Party Use of Manifests

   The goal of an RP is to determine which signed objects to use for
   validating assertions about INRs and their use (e.g., which ROAs to
   use in the construction of route filters).  Ultimately, this
   selection is a matter of local policy.  However, in the following
   sections, we describe a sequence of tests that the RP SHOULD perform



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   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; we also provide suitable
   warning text that SHOULD be placed in a user-accessible log file.  It
   is the responsibility of the RP to weigh these risks against the risk
   of routing failure that could occur if valid data is rejected, and to
   implement a suitable local policy.  Note that if a certificate is
   deemed unfit for use due to local policy, then any signed object that
   is validatable using this certificate also SHOULD 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 RP SHOULD perform the following
   tests to determine the manifest state of the publication point:

   1.  For each entity using this publication point, select the entity's
       current manifest (The "current" manifest is the manifest issued
       by this CA having highest manifestNumber among all valid
       manifests, and where manifest validity is defined in
       Section 4.4).

       1.  If the publication point does not contain a valid manifest,
           see Section Section 6.2.  Lacking a valid manifest, the
           following tests cannot be performed.

   2.  Check that the current time (translated to UTC) is between
       thisUpdate and nextUpdate.

       1.  If the current time does not lie within this interval then
           see Section 6.4, but still continue with the following tests.

   3.  Check that every file at the publication point appears in one and
       only one current manifest, and that every file listed in each
       current manifest that is published at this publication point also
       is published at the publication point.

       1.  If there exist files at the publication point that do not
           appear on any manifest, or files listed in a manifest that do
           not appear at the publication point then see Section 6.5, but
           still continue with the following test.

   4.  Verify that listed hash value of every file listed in each
       manifest matches the value obtained by hashing the file at the
       publication point.





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       1.  If the computed hash value of a file listed on the manifest
           does not match the hash value contained in the manifest, then
           see Section 6.6.

   5.  Check that the contents of each current manifest conforms to the
       manifest's scope constraints, as specified in Section 2.

       1.  If a current manifest contains entries for objects that are
           not within the scope of the manifest, then the out-of-scope
           entries SHOULD be disregarded in the context of this
           manifest.  If there is no other current manifest that
           describes these objects within that other manifest's scope,
           then see Section 6.2.


   For each signed object, if all of the following conditions hold:

      *  the manifest for its publication, and the associated
         publication point, pass all of the above checks;
      *  the signed object is valid; and
      *  the manifests for every certificate on the certification path
         used to validate the signed object, and the associated
         publication points, pass all of the above checks;
   then the RP 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 current manifest at a publication point 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
   descendant objects that are validated using a certificate at this
   publication point SHOULD be viewed as suspect, but MAY be used by the
   RP, as per local policy.

   The primary risk in using signed objects at this publication point is
   that a superseded (but not stale) CRL would cause an RP to improperly
   accept a revoked certificate as valid (and thus rely upon signed
   objects that are validated using that certificate).  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 an RP may incorrectly discard a large



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   number of valid objects.  This gives significant power to an
   adversary that is able to delete a manifest at the publication point.

   Regardless of whether signed objects from this publication are deemed
   fit for use by an RP, 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 or replay substitutions
   from the publication point."

   In the case where an RP has access to a local cache of previously
   issued manifests that are valid, the RP MAY use the most recently
   previously issued valid manifests for this RPKI repository
   publication collection in this case for each entity that publishes at
   his publication point.

6.3.  Invalid Manifests

   The presence of an invalid manifest 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 of
   other valid manifests.

   There are no risks associated with using signed objects at a
   publication point containing an invalid manifest, provided that valid
   manifests that collectively cover all the signed objects are 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(s)."

   In the case where the RP has access to a local cache of previously
   issued (valid) manifests, an RP MAY make use of that locally cached
   data.  Specifically, the RP use use the locally cached, most recent,
   previously issued. valid manifest issued by the entity that (appears
   to have) issued the invalid 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 or suppression of a more recent manifest.




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   All signed objects at the publication point issued by the entity that
   has published the stale manifest, and all descendant signed objects
   that are validated using a certificate issued by the entity that has
   published the stale manifest at this publication point SHOULD be
   viewed as somewhat suspect, but MAY be used by the RP as per local
   policy.

   The primary risk in using such signed objects is that a newer
   manifest exists that, if present, would indicate that certain objects
   are have been removed or replaced.  (For example, the new manifest
   might show the existence of a newer CRL and the removal of one or
   more revoked certificates).  Thus, the use of objects from a stale
   manifest may cause an RP to incorrectly treat invalid objects as
   valid.  The risk is that the CRL covered by the stale manifest has
   been superseded, and thus an RP will to improperly treat 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 the RP 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 an RP, this situation SHOULD result in a warning to
   the effect that: "A manifest found at <pub point name> is no longer
   current.  It is possible that undetected deletions have occurred at
   this publication point."

   Note that there is also the potential for the current time to be
   before the thisUpdate time for the manifest.  This case could be due
   to publisher error, or a local clock error, and in such a case this
   situation SHOULD result in a warning to the effect that: "A manifest
   found at <pub point name> has an incorrect thisUpdate field.  This
   could be due to publisher error, or a local clock error, and
   processing for this publication point will continue using this
   otherwise valid manifest."

6.5.  Mismatch between Manifest and Publication Point

   If there exist valid signed objects that do not appear in 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.  It is
   also possible that this state could be the result of a (malicious or
   accidental) replacement of a current manifest with an older, but
   still valid manifest.  However, regarding the appropriate
   interpretation such objects, it remains the case that if the objects
   were intended to be invalid, then they should have been revoked using



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   whatever revocation mechanism is appropriate for the signed object in
   question.)  Therefore, there is little risk in using such signed
   objects.  If the publication point contains a stale manifest, then
   there is a greater risk that the objects in question were revoked,
   along with a missing Certificate Revocation List (CRL), the absence
   of which is undetectable since the manifest is stale.  In any case,
   the use of signed objects not present on a manifest, or descendant
   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 RP, 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 listed on any manifest <file list>
   for <pub point name>."

   If there exists 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 repository.  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
   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 also may indicate that an
   attack has occurred.

   If an object appeared on a previous valid manifest with a correct
   hash value, and it now appears with an invalid hash value, then it is
   likely that the object has been superseded by a new (unavailable)
   version of the object.  If the object is used, there is a risk that
   the RP will be treating a stale object as valid.  This risk is more
   significant if the object in question is a CRL.  If the object can be
   validated using 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 indicated by 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



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   policy.  However, in general, it is better to use a possibly outdated
   version of the object than to discard the object completely.

   While it is a matter of local policy, in the case of CRLs, an RP
   SHOULD endeavour to use the most recently issued valid CRL, even
   where the hash value in the manifest matches an older CRL, or does
   not match any available CRL for a CA instance.  The thisUpdate field
   of the CRL can be used to establish the most recent CRL in the case
   where an RP has more than one valid CRL for a CA instance.

   Regardless of whether objects with incorrect hashes are deemed fit
   for use by the RP, 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
   possible 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 also could be due to a publisher
   error."


7.  Publication Repositories

   The RPKI publication system model requires that every publication
   point be associated with one or more CAs or one or more EEs, 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 will contain no entries in the manifest's
   fileList sequence (i.e., the ASN.1 SEQUENCE will have a length of
   zero) [ID.ietf-sidr-repos-struct].

   For each signed object, the EE certificate used to verify the
   object's signature is either a single-use certificate, or a multi-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 an
   EE certificate is used to verify multiple objects, each 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 RPKI RPs.



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   Manifests can assist a RP to determine if a repository object has
   been deleted, occluded or otherwise removed from view, or if a
   publication of a newer version of an object has been suppressed (and
   an older version of the object has been substituted).

   Manifests cannot repair the effects of such forms of corruption of
   repository retrieval operations.  However, a manifest enables an RP
   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 conducted over an insecure channel.  In 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 superseded objects.

   The signing structure of a manifest and the use of the nextUpdate
   value allows an RP to determine if the manifest itself is the subject
   of attempted alteration.  The requirement for every repository
   publication point to contain at least one manifest allows a RP to
   determine is the manifest itself has been occluded from view.  Such
   attacks against the manifest are detectable within the time frame of
   the regular schedule of manifest updates.  Forms of replay attack
   within finer-grained time frames 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.]


10.  Acknowledgements

   The authors would like to acknowledge the contributions from George
   Michelson 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 RP behaviour.  The authors also wish to thank Sean
   Turner for his helpful of this document.


11.  References

11.1.  Normative References

   [I-D.sidr-res-certs]
              Huston, G., Michaleson, G., and R. Loomans, "A Profile for
              X.509 PKIX Resource Certificates",



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              draft-ietf-sidr-res-certs-16.txt (work in progress),
              February 2009.

   [ID.ietf-sidr-repos-struct]
              Huston, G., Loomans, R., and G. Michaleson, "A Profile for
              Resource Certificate Repository Structure",
              draft-ietf-sidr-repos-struct-04.txt (work in progress),
              May 2010.

   [ID.ietf-sidr-rpki-algs]
              Huston, G., "A Profile for Algorithms and Key Sizes for
              use in the Resource Public Key Infrastructure",
              draft-huston-sidr-rpki-algs-00.txt (work in progress),
              July 2009.

   [ID.sidr-signed-object]
              Lepinski, M., Chi, A., and S. Kent, "Signed Object
              Template for the Resource Public Key Infrastructure",
              draft-ietf-sidr-signed-object-01.txt (work in progress),
              October 2010.

   [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.

11.2.  Informative References

   [ID.ietf-sidr-arch]
              Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", draft-ietf-sidr-arch-11.txt
              (work in progress), September 2010.

   [ID.sidr-keyroll]
              Huston, G., Michaelson, G., and S. Kent, "CA Key Rollover
              in the RPKI", draft-ietf-sidr-keyroll-02.txt (work in
              progress), October 2010.

   [RFC3779]  Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
              Addresses and AS Identifiers", RFC 3779, June 2004.











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Appendix A.  ASN.1 Module

   RPKIManifest { iso(1) identified-organization(3)
    dod(6) internet(1) security(5) mechanisms(5) smime(7)
    mod(0) TBD }

   DEFINITIONS EXPLICIT TAGS ::=

   BEGIN

   -- EXPORTS ALL --

   -- IMPORTS NOTHING --

   -- Manifest Content Type: OID

   yid-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 }

   -- Manifest Content Type: eContent

   Manifest ::= SEQUENCE {
    version        [0] INTEGER DEFAULT 0,
    manifestNumber     INTEGER (0..MAX),
    thisUpdate         GeneralizedTime,
    nextUpdate         GeneralizedTime,
    fileHashAlg        OBJECT IDENTIFIER,
    fileList           SEQUENCE SIZE (0..MAX) OF FileAndHash
   }

   FileAndHash ::= SEQUENCE {
    file  IA5String,
    hash  BIT STRING
   }

   END











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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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