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Internet Engineering Task Force (IETF)                    T. BruijnzeelsRequest for Comments: 8182                                  O. MuravskiyCategory: Standards Track                                       RIPE NCCISSN: 2070-1721                                                 B. Weber                                                                Cobenian                                                              R. Austein                                                    Dragon Research Labs                                                               July 2017The RPKI Repository Delta Protocol (RRDP)Abstract   In the Resource Public Key Infrastructure (RPKI), Certificate   Authorities (CAs) publish certificates, including end-entity   certificates, Certificate Revocation Lists (CRLs), and RPKI signed   objects to repositories.  Relying Parties retrieve the published   information from those repositories.  This document specifies a new   RPKI Repository Delta Protocol (RRDP) for this purpose.  RRDP was   specifically designed for scaling.  It relies on an Update   Notification File which lists the current Snapshot and Delta Files   that can be retrieved using HTTPS (HTTP over Transport Layer Security   (TLS)), and it enables the use of Content Distribution Networks   (CDNs) or other caching infrastructures for the retrieval of these   files.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc8182.Bruijnzeels, et al.          Standards Track                    [Page 1]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017Copyright Notice   Copyright (c) 2017 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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 Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .32.  Requirements Notation . . . . . . . . . . . . . . . . . . . .43.  RPKI Repository Delta Protocol Implementation . . . . . . . .43.1.  Informal Overview . . . . . . . . . . . . . . . . . . . .43.2.  Certificate Authority Use . . . . . . . . . . . . . . . .53.3.  Repository Server Use . . . . . . . . . . . . . . . . . .63.3.1.  Initialization  . . . . . . . . . . . . . . . . . . .63.3.2.  Publishing Updates  . . . . . . . . . . . . . . . . .63.4.  Relying Party Use . . . . . . . . . . . . . . . . . . . .73.4.1.  Processing the Update Notification File . . . . . . .73.4.2.  Processing Delta Files  . . . . . . . . . . . . . . .93.4.3.  Processing a Snapshot File  . . . . . . . . . . . . .103.4.4.  Polling the Update Notification File  . . . . . . . .10       3.4.5.  Considerations Regarding Operational Failures in RRDP  113.5.  File Definitions  . . . . . . . . . . . . . . . . . . . .113.5.1.  Update Notification File  . . . . . . . . . . . . . .113.5.2.  Snapshot File . . . . . . . . . . . . . . . . . . . .133.5.3.  Delta File  . . . . . . . . . . . . . . . . . . . . .153.5.4.  XML Schema  . . . . . . . . . . . . . . . . . . . . .174.  Operational Considerations  . . . . . . . . . . . . . . . . .184.1.  Compatibility with previous standards . . . . . . . . . .184.2.  Distribution Considerations . . . . . . . . . . . . . . .194.3.  HTTPS Considerations  . . . . . . . . . . . . . . . . . .195.  Security Considerations . . . . . . . . . . . . . . . . . . .206.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .217.  References  . . . . . . . . . . . . . . . . . . . . . . . . .227.1.  Normative References  . . . . . . . . . . . . . . . . . .227.2.  Informative References  . . . . . . . . . . . . . . . . .23   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .24   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .24Bruijnzeels, et al.          Standards Track                    [Page 2]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 20171.  Introduction   In the Resource Public Key Infrastructure (RPKI), Certificate   Authorities publish certificates [RFC6487], RPKI signed objects   [RFC6488], manifests [RFC6486], and CRLs to repositories.  CAs may   have an embedded mechanism to publish to these repositories, or they   may use a separate Repository Server and publication protocol.  RPKI   repositories are currently accessible using the rsync protocol   [RSYNC], allowing Relying Parties to synchronize a local copy of the   RPKI repository used for validation with the remote repositories   [RFC6481].   rsync [RSYNC] has proven valuable in the early deployment of RPKI,   because it allowed operators to gain experience without the need to   invent a custom protocol.  However, operational experience has   brought concerns to light that we wish to address here:   o  rsync [RSYNC] is designed to limit the amount of data that needs      to be transferred between client and server.  However, the server      needs to spend significant resources in terms of CPU and memory      for every connection.  This is a problem in an envisioned RPKI      deployment where thousands of Relying Parties query a small number      of central repositories, and it makes these repositories weak to      denial-of-service attacks.   o  A secondary concern is the lack of supported rsync server and      client libraries.  In practice, all implementations have to make      system calls to an rsync binary.  This is inefficient; it      introduces fragility with regards to updates of this binary, makes      it difficult to catch and report problems to operators, and      complicates software development and testing.   This document specifies an alternative repository access protocol   based on Update Notification, Snapshot, and Delta Files that a   Relying Party can retrieve over the HTTPS protocol.  This allows   Relying Parties to either perform a full (re-)synchronization of   their local copy of the repository using Snapshot Files or use Delta   Files to keep their local repository updated after initial   synchronization.  We call this the RPKI Repository Delta Protocol, or   RRDP in short.   RRDP was designed to support scaling in RPKI's asymmetric deployment.   It is consistent (in terms of data structures) with the publication   protocol [RFC8181] and treats publication events of one or more   repository objects as discrete events that can be communicated to   Relying Parties.  This approach helps to minimize the amount of data   that traverses the network and thus helps minimize the amount of time   until repository convergence occurs.  RRDP also provides a standards-Bruijnzeels, et al.          Standards Track                    [Page 3]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017   based way to obtain consistent, point-in-time views of a single   repository, eliminating a number of consistency-related issues.   Finally, this approach allows these discrete events to be   communicated as immutable files.  This enables Repository Servers to   pre-calculate these files only once for all clients, thus limiting   the CPU and memory investments required, and enables the use of a   caching infrastructure to reduce the load on a Repository Server when   a large number of Relying Parties are querying it.   This document allows the use of RRDP as an additional repository   distribution mechanism for RPKI.  In time, RRDP may replace rsync   [RSYNC] as the only mandatory-to-implement repository distribution   mechanism.  However, this transition is outside of the scope of this   document.2.  Requirements Notation   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and   "OPTIONAL" in this document are to be interpreted as described inBCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all   capitals, as shown here.3.  RPKI Repository Delta Protocol Implementation3.1.  Informal Overview   Certification Authorities in the RPKI use a Repository Server to   publish their RPKI products, such as manifests, CRLs, signed   certificates, and RPKI-signed objects.  This Repository Server may be   remote or embedded in the Certificate Authority engine itself.   Certificates in the RPKI that use a Repository Server that supports   RRDP include a special Subject Information Access (SIA) pointer   referring to an Update Notification File.   The Update Notification File includes a globally unique session_id in   the form of a version 4 Universally Unique IDentifier (UUID)   [RFC4122] and serial number that can be used by the Relying Party to   determine if it and the repository are synchronized.  Furthermore, it   includes a link to the most recent complete snapshot of current   objects that are published by the Repository Server, and a list of   links to Delta Files, for each revision starting at a point   determined by the Repository Server, up to the current revision of   the repository.   A Relying Party that learns about an Update Notification File   location for the first time can download it and then proceed to   download the latest Snapshot File, thus creating a local copy of theBruijnzeels, et al.          Standards Track                    [Page 4]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017   repository that is in sync with the Repository Server.  The Relying   Party records the location of this Update Notification File, the   session_id, and the current serial number.   Relying Parties are encouraged to re-fetch this Update Notification   File at regular intervals, but not more often than once per minute.   After re-fetching the Update Notification File, the Relying Party may   find that there are one or more Delta Files available that allow it   to synchronize its local repository with the current state of the   Repository Server.  If no contiguous chain of deltas from the Relying   Party's serial to the latest repository serial is available, or if   the session_id has changed, the Relying Party performs a full   resynchronization instead.   As soon as the Relying Party fetches new content in this way, it   could start a validation process.  An example of a reason why a   Relying Party may not choose to do this immediately is because it has   learned of more than one notification location, and it prefers to   complete all its updates before validating.   The Repository Server could use a caching infrastructure to reduce   its load, particularly because snapshots and deltas for any given   session_id and serial number contain an immutable record of the state   of the Repository Server at a certain point in time.  For this   reason, these files can be cached indefinitely.  Update Notification   Files are polled by Relying Parties to discover if updates exist; for   this reason, Update Notification Files may not be cached for longer   than one minute.3.2.  Certificate Authority Use   Certificate Authorities that use RRDP MUST include an instance of an   SIA AccessDescription extension in resource certificates they   produce, in addition to the ones defined in [RFC6487]:             AccessDescription ::= SEQUENCE {               accessMethod OBJECT IDENTIFIER,               accessLocation GeneralName }   This extension MUST use an accessMethod of id-ad-rpkiNotify; seeSection 6:     id-pkix OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)       dod(6) internet(1) security(5) mechanisms(5) pkix(7) }     id-ad OBJECT IDENTIFIER ::= { id-pkix 48 }     id-ad-rpkiNotify OBJECT IDENTIFIER ::= { id-ad 13 }Bruijnzeels, et al.          Standards Track                    [Page 5]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017   The accessLocation MUST be an HTTPS URI as defined in [RFC7230] that   will point to the Update Notification File for the Repository Server   that publishes the products of this Certificate Authority   certificate.3.3.  Repository Server Use3.3.1.  Initialization   When the Repository Server initializes, it performs the following   actions:   o  The server MUST generate a new random version 4 UUID (seeSection 4.1.3 of [RFC4122]) to be used as the session_id.   o  The server MUST then generate a Snapshot File for serial number      ONE for this new session that includes all currently known      published objects that the Repository Server is responsible for.      Note that this Snapshot File may contain zero publish elements at      this point if no objects have been submitted for publication yet.   o  This Snapshot File MUST be made available at a URL that is unique      to this session_id and serial number, so that it can be cached      indefinitely.  The format and caching concerns for Snapshot Files      are explained in more detail inSection 3.5.2.   o  After the Snapshot File has been published, the Repository Server      MUST publish a new Update Notification File that contains the new      session_id, has serial number ONE, has one reference to the      Snapshot File that was just published, and contains no delta      references.  The format and caching concerns for Update      Notification Files are explained in more detail inSection 3.5.1.3.3.2.  Publishing Updates   Whenever the Repository Server receives updates from a Certificate   Authority, it MUST generate new snapshot and Delta Files within one   minute.  If a Repository Server services a large number of   Certificate Authorities, it MAY choose to combine updates from   multiple CAs.  If a Repository Server combines updates in this way,   it MUST ensure that publication never postponed for longer than one   minute for any of the CAs involved.   Updates are processed as follows:   o  The new repository serial number MUST be one greater than the      current repository serial number.Bruijnzeels, et al.          Standards Track                    [Page 6]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017   o  A new Delta File MUST be generated for this new serial.  This      Delta File MUST include all new, replaced, and withdrawn objects      for multiple CAs, if applicable, as a single change set.   o  This Delta File MUST be made available at a URL that is unique to      the current session_id and serial number, so that it can be cached      indefinitely.   o  The format and caching concerns for Delta Files are explained in      more detail inSection 3.5.3.   o  The Repository Server MUST also generate a new Snapshot File for      this new serial.  This file MUST contain all "publish" elements      for all current objects.   o  The Snapshot File MUST be made available at a URL that is unique      to this session and new serial, so that it can be cached      indefinitely.   o  The format and caching concerns for Snapshot Files are explained      in more detail inSection 3.5.2.   o  Any older Delta Files that, when combined with all more recent      Delta Files, will result in the total size of deltas exceeding the      size of the snapshot MUST be excluded to avoid that Relying      Parties download more data than necessary.   o  A new Update Notification File MUST now be created by the      Repository Server.  This new Update Notification File MUST include      a reference to the new Snapshot File and all Delta Files selected      in the previous steps.   o  The format and caching concerns for Update Notification Files are      explained in more detail inSection 3.5.1.   If the Repository Server is not capable of performing the above for   some reason, then it MUST perform a full re-initialization, as   explained above inSection 3.3.1.3.4.  Relying Party Use3.4.1.  Processing the Update Notification File   When a Relying Party performs RPKI validation and learns about a   valid certificate with an SIA entry for the RRDP protocol, it SHOULD   use this protocol as follows.Bruijnzeels, et al.          Standards Track                    [Page 7]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017   The Relying Party MUST download the Update Notification File, unless   an Update Notification File was already downloaded and processed from   the same location in this validation run or a polling strategy was   used (seeSection 3.4.4).   It is RECOMMENDED that the Relying Party uses a "User-Agent" header   explained inSection 5.5.3. of [RFC7231] to identify the name and   version of the Relying Party software used.  It is useful to track   capabilities of Relying Parties in the event of changes to the RPKI   standards.   When the Relying Party downloads an Update Notification File, it MUST   verify the file format and validation steps described inSection 3.5.1.3.  If this verification fails, the file MUST be   rejected and RRDP cannot be used.  SeeSection 3.4.5 for   considerations.   The Relying Party MUST verify whether the session_id matches the last   known session_id for this Update Notification File location.  Note   that even though the session_id is a random UUID value, it alone MUST   NOT be used by a Relying Party as a unique identifier of a session   but always together with the location of the Update Notification   File.  The reason for this is that a malicious server can use an   existing session_id from another Repository Server.   If the session_id matches the last known session_id, then a Relying   Party MAY download and process missing Delta Files as described inSection 3.4.2, provided that all Delta Files for serial numbers   between the last processed serial number and the current serial   number in the Update Notification File can be processed this way.   If the session_id matches the last known session_id, but Delta Files   were not used, then the Relying Party MUST download and process the   Snapshot File on the Update Notification File as described inSection 3.4.3.   If the session_id does not match the last known session_id, the   Relying Party MUST update its last known session_id to the value   specified in the downloaded Update Notification File.  The Relying   Party MUST then download and process the Snapshot File specified in   the downloaded Update Notification File as described inSection 3.4.3.Bruijnzeels, et al.          Standards Track                    [Page 8]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 20173.4.2.  Processing Delta Files   If an Update Notification File contains a contiguous chain of links   to Delta Files from the last processed serial number to the current   serial number, then Relying Parties MUST attempt to download and   process all Delta Files in order of serial number as follows.   When the Relying Party downloads a Delta File, it MUST verify the   file format and perform validation steps described inSection 3.5.3.3.  If this verification fails, the file MUST be   rejected.   Furthermore, the Relying Party MUST verify that the hash of the   contents of this file matches the hash on the Update Notification   File that referenced it.  In case of a mismatch of this hash, the   file MUST be rejected.   If a Relying Party retrieved a Delta File that is valid according to   the above criteria, it performs the following actions:   o  The Relying Party MUST verify that the session_id matches the      session_id of the Update Notification File.  If the session_id      values do not match, the file MUST be rejected.   o  The Relying Party MUST verify that the serial number of this Delta      File is exactly one greater than the last processed serial number      for this session_id, and if not, this file MUST be rejected.   o  The Relying Party SHOULD add all publish elements to a local      storage and update its last processed serial number to the serial      number of this Delta File.   o  When a Relying Party encounters a "withdraw" element, or a      "publish" element where an object is replaced, in a delta that it      retrieves from a Repository Server, it MUST verify that the object      to be withdrawn or replaced was retrieved from this same      Repository Server before applying the appropriate action.  Failing      to do so will leave the Relying Party vulnerable to malicious      Repository Servers instructing it to delete or change arbitrary      objects.   If any Delta File is rejected, Relying Parties MUST process the   current Snapshot File instead, as described inSection 3.4.3.Bruijnzeels, et al.          Standards Track                    [Page 9]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 20173.4.3.  Processing a Snapshot File   Snapshot Files MUST only be used if Delta Files are unavailable or   were rejected; for a description of the process, seeSection 3.4.1.   When the Relying Party downloads a Snapshot File, it MUST verify the   file format and validation steps described inSection 3.5.2.3.  If   this verification fails, the file MUST be rejected.   Furthermore, the Relying Party MUST verify that the hash of the   contents of this file matches the hash on the Update Notification   File that referenced it.  In case of a mismatch of this hash, the   file MUST be rejected.   If a Relying Party retrieved a Snapshot File that is valid according   to the above criteria, it performs the following actions:   o  The Relying Party MUST verify that the session_id matches the      session_id of the Update Notification File.  If the session_id      values do not match, the file MUST be rejected.   o  The Relying Party MUST verify that the serial number of this      Snapshot File is greater than the last processed serial number for      this session_id.  If this fails, the file MUST be rejected.   o  The Relying Party SHOULD then add all publish elements to a local      storage and update its last processed serial number to the serial      number of this Snapshot File.   If a Snapshot File is rejected, it means that RRDP cannot be used.   SeeSection 3.4.5 for considerations.3.4.4.  Polling the Update Notification File   Once a Relying Party has learned about the location, session_id, and   last processed serial number of the repository that uses the RRDP   protocol, the Relying Party MAY start polling the Repository Server   for updates.  However, the Relying Party MUST NOT poll for updates   more often than once every 1 minute, and in order to reduce data   usage, Relying Parties MUST use the "If-Modified-Since" header   explained inSection 3.3 of [RFC7232] in requests.   If a Relying Party finds that updates are available, it SHOULD   download and process the file as described inSection 3.4.1 and   initiate a new RPKI object validation process.  However, a detailed   description of the RPKI object validation process itself is out of   scope of this document.Bruijnzeels, et al.          Standards Track                   [Page 10]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 20173.4.5.  Considerations Regarding Operational Failures in RRDP   If a Relying Party experiences any issues with retrieving or   processing any of the files used in this protocol, it will be unable   to retrieve new RPKI data from the affected Repository Server.   Relying Parties could attempt to use alternative repository access   mechanisms, if they are available, according to the accessMethod   element value(s) specified in the SIA of the associated certificate   (seeSection 4.8.8 of [RFC6487]).   Furthermore, Relying Parties may wish to employ re-try strategies   while fetching RRDP files.  Relying Parties are also advised to keep   old objects in their local cache so that validation can be done using   old objects.   It is also recommendable that re-validation and retrieval is   performed pro-actively before manifests or CRLs go stale, or   certificates expire, to ensure that problems on the side of the   Relying Party can be identified and resolved before they cause major   concerns.3.5.  File Definitions3.5.1.  Update Notification File3.5.1.1.  Purpose   The Update Notification File is used by Relying Parties to discover   whether any changes exist between the state of the repository and the   Relying Party's cache.  It describes the location of the files   containing the snapshot and incremental deltas, which can be used by   the Relying Party to synchronize with the repository.3.5.1.2.  Cache Concerns   A Repository Server MAY use caching infrastructure to cache the   Update Notification File and reduce the load of HTTPS requests.   However, since this file is used by Relying Parties to determine   whether any updates are available, the Repository Server SHOULD   ensure that this file is not cached for longer than 1 minute.  An   exception to this rule is that it is better to serve a stale Update   Notification File rather than no Update Notification File.   How this is achieved exactly depends on the caching infrastructure   used.  In general, a Repository Server may find certain HTTP headers   to be useful, such as: "Cache-Control: max-age=60" (seeSection 5.2   of [RFC7234]).  Another approach can be to have the Repository ServerBruijnzeels, et al.          Standards Track                   [Page 11]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017   push out new versions of the Update Notification File to the caching   infrastructure when appropriate.   In case of a high load on a Repository Server or its distribution   network, the Cache-Control HTTP header, or a similar mechanism, MAY   be used to suggest an optimal (for the Repository Server) poll   interval for Relying Parties.  However, setting it to an interval   longer than 1 hour is NOT RECOMMENDED.  Relying parties SHOULD align   the suggested interval with their operational practices and the   expected update frequency of RPKI repository data and MAY discard the   suggested value.3.5.1.3.  File Format and Validation   Example Update Notification File:     <notification xmlns="http://www.ripe.net/rpki/rrdp"           version="1"           session_id="9df4b597-af9e-4dca-bdda-719cce2c4e28"           serial="3">       <snapshot uri="https://host/9d-8/3/snapshot.xml" hash="AB"/>       <delta serial="3" uri="https://host/9d-8/3/delta.xml" hash="CD"/>       <delta serial="2" uri="https://host/9d-8/2/delta.xml" hash="EF"/>     </notification>   Note: URIs and hash values in this example are shortened because of   formatting.   The following validation rules MUST be observed when creating or   parsing Update Notification Files:   o  A Relying Party MUST reject any Update Notification File that is      not well-formed or does not conform to the RELAX NG schema      outlined inSection 3.5.4 of this document.   o  The XML namespace MUST be "http://www.ripe.net/rpki/rrdp".   o  The encoding MUST be "US-ASCII".   o  The version attribute in the notification root element MUST be      "1".   o  The session_id attribute MUST be a random version 4 UUID      [RFC4122], unique to this session.   o  The serial attribute MUST be an unbounded, unsigned positive      integer in decimal format indicating the current version of the      repository.Bruijnzeels, et al.          Standards Track                   [Page 12]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017   o  The Update Notification File MUST contain exactly one 'snapshot'      element for the current repository version.   o  If delta elements are included, they MUST form a contiguous      sequence of serial numbers starting at a revision determined by      the Repository Server, up to the serial number mentioned in the      notification element.  Note that the elements may not be ordered.   o  The hash attribute in snapshot and delta elements MUST be the      hexadecimal encoding of the SHA-256 [SHS] hash of the referenced      file.  The Relying Party MUST verify this hash when the file is      retrieved and reject the file if the hash does not match.3.5.2.  Snapshot File3.5.2.1.  Purpose   A snapshot is intended to reflect the complete and current contents   of the repository for a specific session and version.  Therefore, it   MUST contain all objects from the repository current as of the time   of the publication.3.5.2.2.  Cache Concerns   A snapshot reflects the content of the repository at a specific point   in time; for that reason, it can be considered immutable data.   Snapshot Files MUST be published at a URL that is unique to the   specific session and serial.   Because these files never change, they MAY be cached indefinitely.   However, in order to prevent these files from using a lot of space in   the caching infrastructure, it is RECOMMENDED that a limited interval   is used in the order of hours or days.   To avoid race conditions where a Relying Party downloads an Update   Notification File moments before it's updated, Repository Servers   SHOULD retain old Snapshot Files for at least 5 minutes after a new   Update Notification File is published.Bruijnzeels, et al.          Standards Track                   [Page 13]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 20173.5.2.3.  File Format and Validation   Example Snapshot File:      <snapshot xmlns="http://www.ripe.net/rpki/rrdp"             version="1"             session_id="9df4b597-af9e-4dca-bdda-719cce2c4e28"             serial="2">        <publish uri="rsync://rpki.ripe.net/Alice/Bob.cer">          ZXhhbXBsZTE=        </publish>        <publish uri="rsync://rpki.ripe.net/Alice/Alice.mft">          ZXhhbXBsZTI=        </publish>        <publish uri="rsync://rpki.ripe.net/Alice/Alice.crl">          ZXhhbXBsZTM=        </publish>      </snapshot>   The following rules MUST be observed when creating or parsing   Snapshot Files:   o  A Relying Party MUST reject any Snapshot File that is not well-      formed or does not conform to the RELAX NG schema outlined inSection 3.5.4 of this document.   o  The XML namespace MUST be "http://www.ripe.net/rpki/rrdp".   o  The encoding MUST be "US-ASCII".   o  The version attribute in the notification root element MUST be      "1".   o  The session_id attribute MUST match the expected session_id in the      reference in the Update Notification File.   o  The serial attribute MUST match the expected serial in the      reference in the Update Notification File.   o  Note that the publish element is similar to the publish element      defined in the publication protocol [RFC8181].  However, the "tag"      attribute is not used here because it is not relevant to Relying      Parties.  The "hash" attribute is not used here because this file      represents a complete current state of the repository; therefore,      it is not relevant to know which existing RPKI object (if any) is      updated.Bruijnzeels, et al.          Standards Track                   [Page 14]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 20173.5.3.  Delta File3.5.3.1.  Purpose   An incremental Delta File contains all changes for exactly one serial   increment of the Repository Server.  In other words, a single delta   will typically include all the new objects, updated objects, and   withdrawn objects that a Certification Authority sent to the   Repository Server.  In its simplest form, the update could concern   only a single object, but it is RECOMMENDED that CAs send all changes   for one of their key pairs (updated objects as well as a new manifest   and CRL) as one atomic update message.3.5.3.2.  Cache Concerns   Deltas reflect the difference between two consecutive versions of a   repository for a given session.  For that reason, deltas can be   considered immutable data.  Delta Files MUST be published at a URL   that is unique to the specific session and serial.   Because these files never change, they MAY be cached indefinitely.   However, in order to prevent these files from using a lot of space in   the caching infrastructure, it is RECOMMENDED that a limited interval   is used in the order of hours or days.   To avoid race conditions where a Relying Party downloads an Update   Notification File moments before it's updated, Repository Servers   SHOULD retain old Delta Files for at least 5 minutes after they are   no longer included in the latest Update Notification File.Bruijnzeels, et al.          Standards Track                   [Page 15]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 20173.5.3.3.  File Format and Validation   Example Delta File:     <delta xmlns="http://www.ripe.net/rpki/rrdp"            version="1"            session_id="9df4b597-af9e-4dca-bdda-719cce2c4e28"            serial="3">       <publish uri="rsync://rpki.ripe.net/repo/Alice/Alice.mft"                hash="50d8...545c">         ZXhhbXBsZTQ=       </publish>       <publish uri="rsync://rpki.ripe.net/repo/Alice/Alice.crl"                hash="5fb1...6a56">         ZXhhbXBsZTU=       </publish>       <withdraw uri="rsync://rpki.ripe.net/repo/Alice/Bob.cer"                 hash="caeb...15c1"/>     </delta>   Note that a formal RELAX NG specification of this file format is   included later in this document.  A Relying Party MUST NOT process   any Delta File that is incomplete or not well-formed.   The following validation rules MUST be observed when creating or   parsing Delta Files:   o  A Relying Party MUST reject any Delta File that is not well-formed      or does not conform to the RELAX NG schema outlined inSection 3.5.4 of this document.   o  The XML namespace MUST be "http://www.ripe.net/rpki/rrdp".   o  The encoding MUST be "US-ASCII".   o  The version attribute in the delta root element MUST be "1".   o  The session_id attribute MUST be a random version 4 UUID unique to      this session.   o  The session_id attribute MUST match the expected session_id in the      reference in the Update Notification File.   o  The serial attribute MUST match the expected serial in the      reference in the Update Notification File.Bruijnzeels, et al.          Standards Track                   [Page 16]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017   o  Note that the publish element is similar to the publish element      defined in the publication protocol [RFC8181].  However, the "tag"      attribute is not used here because it is not relevant to Relying      Parties.3.5.4.  XML Schema   The following is a RELAX NG compact form schema describing version 1   of this protocol.   #   # RELAX NG schema for the RPKI Repository Delta Protocol (RRDP).   #   default namespace = "http://www.ripe.net/rpki/rrdp"   version = xsd:positiveInteger   { maxInclusive="1" }   serial  = xsd:positiveInteger   uri     = xsd:anyURI   uuid    = xsd:string            { pattern = "[\-0-9a-fA-F]+" }   hash    = xsd:string            { pattern = "[0-9a-fA-F]+" }   base64  = xsd:base64Binary   # Notification File: lists current snapshots and deltas.   start |= element notification {     attribute version    { version },     attribute session_id { uuid },     attribute serial     { serial },     element snapshot {       attribute uri  { uri },       attribute hash { hash }     },     element delta {       attribute serial { serial },       attribute uri    { uri },       attribute hash   { hash }     }*   }   # Snapshot segment: think DNS AXFR.   start |= element snapshot {     attribute version    { version },     attribute session_id { uuid },     attribute serial     { serial },     element publish      {       attribute uri { uri },Bruijnzeels, et al.          Standards Track                   [Page 17]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017       base64     }*   }   # Delta segment: think DNS IXFR.   start |= element delta {     attribute version    { version },     attribute session_id { uuid },     attribute serial     { serial },     delta_element+   }   delta_element |= element publish  {     attribute uri  { uri },     attribute hash { hash }?,     base64   }   delta_element |= element withdraw {     attribute uri  { uri },     attribute hash { hash }   }   # Local Variables:   # indent-tabs-mode: nil   # comment-start: "# "   # comment-start-skip: "#[ \t]*"   # End:4.  Operational Considerations4.1.  Compatibility with previous standards   This protocol has been designed to replace rsync as a distribution   mechanism of an RPKI repository.  However, it is also designed to   coexist with existing implementations based on rsync, to enable   smooth transition from one distribution mechanism to another.   For every repository object listed in the Snapshot and Delta Files,   both the hash of the object's content and the rsync URI [RFC5781] of   its location in the repository are listed.  This makes it possible to   distribute the same RPKI repository, represented by a set of files on   a filesystem, using both rsync and RRDP.  It also enables Relying   Parties tools to query, combine, and consequently validate objects   from repositories of different types.Bruijnzeels, et al.          Standards Track                   [Page 18]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 20174.2.  Distribution Considerations   One of the design goals of RRDP was to minimize load on a Repository   Server while serving clients.  To achieve this, neither the content   nor the URLs of the Snapshot and Delta Files are modified after they   have been published in the Update Notification File.  This allows   their effective distribution by using either a single HTTP server or   a CDN.   The RECOMMENDED way for Relying Parties to keep up with the   repository updates is to poll the Update Notification File for   changes.  The content of that file is updated with every new serial   version of a repository (while its URL remains stable).  To   effectively implement distribution of the Update Notification File,   an "If-Modified-Since" HTTP request header is required to be present   in all requests for the Update Notification File (seeSection 3.4.4).   Therefore, it is RECOMMENDED that Relying Party tools implement a   mechanism to keep track of a previous successful fetch of an Update   Notification File.   Implementations of RRDP should also take care of not producing new   versions of the repository (and subsequently, new Update   Notification, Snapshot, and Delta Files) too often.  Usually the   maintenance of the RPKI repository includes regular updates of   manifest and CRL objects performed on a schedule.  This often results   in bursts of repository updates during a short period of time.  Since   the Relying Parties are required to poll for the Update Notification   File not more often than once per minute (Section 3.4.4), it is not   practical to generate new serial versions of the repository much more   often than 1 per minute.  It is allowed to combine multiple updates,   possibly from different CAs, into a new serial repository version   (Section 3.3.2).  This will significantly shorten the size of the   Update Notification File and total amount of data distributed to all   Relying Parties.4.3.  HTTPS Considerations   Note that a Man in the Middle (MITM) cannot produce validly signed   RPKI data but can perform withhold or replay attacks targeting a   Relying Party and keep the Relying Party from learning about changes   in the RPKI.  Because of this, Relying Parties SHOULD do TLS   certificate and host name validation when they fetch from an RRDP   Repository Server.   Relying Party tools SHOULD log any TLS certificate or host name   validation issues found, so that an operator can investigate the   cause.  However, such validation issues are often due to   configuration errors or a lack of a common TLS trust anchor.  InBruijnzeels, et al.          Standards Track                   [Page 19]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017   these cases, it is better if the Relying Party retrieves the signed   RPKI data regardless and performs validation on it.  Therefore, the   Relying Party MUST continue to retrieve the data in case of errors.   The Relying Party MAY choose to log encountered issues only when   fetching the Update Notification File, but not when it subsequently   fetches Snapshot or Delta Files from the same host.  Furthermore, the   Relying Party MAY provide a way for operators to accept untrusted   connections for a given host, after the cause has been identified.   It is RECOMMENDED that Relying Parties and Repository Servers follow   the Best Current Practices outlined in [RFC7525] on the use of HTTP   over TLS (HTTPS) [RFC7230].  Relying Parties SHOULD do TLS   certificate and host name validation using subjectAltName dNSName   identities as described in [RFC6125].  The rules and guidelines   defined in [RFC6125] apply here, with the following considerations:   o  Relying Parties and Repository Servers SHOULD support the DNS-ID      identifier type.  The DNS-ID identifier type SHOULD be present in      Repository Server certificates.   o  DNS names in Repository Server certificates SHOULD NOT contain the      wildcard character "*".   o  A Common Name (CN) field may be present in a Repository Server      certificate's subject name but SHOULD NOT be used for      authentication within the rules described in [RFC6125].   o  This protocol does not require the use of SRV-IDs.   o  This protocol does not require the use of URI-IDs.   Note, however, that this validation is done on a best-effort basis   and serves to highlight potential issues, but RPKI object security   does not depend on this.  Therefore, Relying Parties MAY deviate from   the validation steps listed above.5.  Security Considerations   RRDP deals exclusively with the transfer of RPKI objects from a   Repository Server to a Relying Party.  The trust relation between a   Certificate Authority and its Repository Server is out of scope for   this document.  However, it should be noted that from a Relying Party   point of view, all RPKI objects (certificates, CRLs, and objects   wrapped in Cryptographic Message Syntax (CMS)) are already covered by   object security mechanisms including signed manifests.  This allows   validation of these objects even though the Repository Server itself   is not trusted.  This document makes no change to RPKI validation   procedures per se.Bruijnzeels, et al.          Standards Track                   [Page 20]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017   The original RPKI transport protocol is rsync, which offers no   channel security mechanism.  RRDP replaces the use of rsync by HTTPS;   while the channel security mechanism underlying RRDP (HTTPS) is not a   cure-all, it does make some forms of denial-of-service attacks more   difficult for the attacker.  HTTPS issues are discussed in more   detail inSection 4.3.   Supporting both RRDP and rsync necessarily increases the number of   opportunities for a malicious RPKI Certificate Authority to perform   denial-of-service attacks on Relying Parties, by expanding the number   of URIs which the Relying Party may need to contact in order to   complete a validation run.  However, other than the relative cost of   HTTPS versus rsync, adding RRDP to the mix does not change this   picture significantly: with either RRDP or rsync a malicious   Certificate Authority can supply an effectively infinite series of   URIs for the Relying Party to follow.  The only real solution to this   is for the Relying Party to apply some kind of bound to the amount of   work it is willing to do.  Note also that the attacker in this   scenario must be an RPKI Certificate Authority; otherwise, the normal   RPKI object security checks would reject the malicious URIs.   Processing costs for objects retrieved using RRDP may be somewhat   different from the same objects retrieved using rsync: because RRDP   treats an entire set of changes as a unit (one "delta"), it may not   be practical to start processing any of the objects in the delta   until the entire delta has been received.  With rsync, by contrast,   incremental processing may be easy, but the overall cost of transfer   may be higher, as may be the number of corner cases in which the   Relying Party retrieves some but not all of the updated objects.   Overall, RRDP's behavior is closer to a proper transactional system,   which (probably) leads to an overall reliability increase.   RRDP is designed to scale much better than rsync.  In particular,   RRDP is designed to allow use of an HTTPS caching infrastructure to   reduce load on primary Repository Servers and increase resilience   against denial-of-service attacks on the RPKI publication service.6.  IANA Considerations   IANA has updated the reference for id-ad-rpkiNotify to point to this   document in the "SMI Security for PKIX Access Descriptor" registry   [IANA-AD-NUMBERS].Bruijnzeels, et al.          Standards Track                   [Page 21]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 20177.  References7.1.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119,              DOI 10.17487/RFC2119, March 1997,              <http://www.rfc-editor.org/info/rfc2119>.   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally              Unique IDentifier (UUID) URN Namespace",RFC 4122,              DOI 10.17487/RFC4122, July 2005,              <http://www.rfc-editor.org/info/rfc4122>.   [RFC5781]  Weiler, S., Ward, D., and R. Housley, "The rsync URI              Scheme",RFC 5781, DOI 10.17487/RFC5781, February 2010,              <http://www.rfc-editor.org/info/rfc5781>.   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and              Verification of Domain-Based Application Service Identity              within Internet Public Key Infrastructure Using X.509              (PKIX) Certificates in the Context of Transport Layer              Security (TLS)",RFC 6125, DOI 10.17487/RFC6125, March              2011, <http://www.rfc-editor.org/info/rfc6125>.   [RFC6481]  Huston, G., Loomans, R., and G. Michaelson, "A Profile for              Resource Certificate Repository Structure",RFC 6481,              DOI 10.17487/RFC6481, February 2012,              <http://www.rfc-editor.org/info/rfc6481>.   [RFC6487]  Huston, G., Michaelson, G., and R. Loomans, "A Profile for              X.509 PKIX Resource Certificates",RFC 6487,              DOI 10.17487/RFC6487, February 2012,              <http://www.rfc-editor.org/info/rfc6487>.   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer              Protocol (HTTP/1.1): Message Syntax and Routing",RFC 7230, DOI 10.17487/RFC7230, June 2014,              <http://www.rfc-editor.org/info/rfc7230>.   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer              Protocol (HTTP/1.1): Semantics and Content",RFC 7231,              DOI 10.17487/RFC7231, June 2014,              <http://www.rfc-editor.org/info/rfc7231>.Bruijnzeels, et al.          Standards Track                   [Page 22]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017   [RFC7232]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer              Protocol (HTTP/1.1): Conditional Requests",RFC 7232,              DOI 10.17487/RFC7232, June 2014,              <http://www.rfc-editor.org/info/rfc7232>.   [RFC7234]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,              Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",RFC 7234, DOI 10.17487/RFC7234, June 2014,              <http://www.rfc-editor.org/info/rfc7234>.   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,              "Recommendations for Secure Use of Transport Layer              Security (TLS) and Datagram Transport Layer Security              (DTLS)",BCP 195,RFC 7525, DOI 10.17487/RFC7525, May              2015, <http://www.rfc-editor.org/info/rfc7525>.   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase inRFC2119 Key Words",BCP 14,RFC 8174, DOI 10.17487/RFC8174,              May 2017, <http://www.rfc-editor.org/info/rfc8174>.   [RFC8181]  Weiler, S., Sonalker, A., and R. Austein, "A Publication              Protocol for the Resource Public Key Infrastructure              (RPKI)", DOI 10.17487/RFC8181, July 2017,              <http://www.rfc-editor.org/info/rfc8181>.   [SHS]      National Institute of Standards and Technology, "Secure              Hash Standard (SHS)", FIPS PUB 180-4,              DOI 10.6028/NIST.FIPS.180-4, August 2015,              <http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf>.7.2.  Informative References   [IANA-AD-NUMBERS]              IANA, "Structure of Management Information (SMI) Numbers              (MIB Module Registrations)",              <http://www.iana.org/assignments/smi-numbers>.   [RFC6486]  Austein, R., Huston, G., Kent, S., and M. Lepinski,              "Manifests for the Resource Public Key Infrastructure              (RPKI)",RFC 6486, DOI 10.17487/RFC6486, February 2012,              <http://www.rfc-editor.org/info/rfc6486>.   [RFC6488]  Lepinski, M., Chi, A., and S. Kent, "Signed Object              Template for the Resource Public Key Infrastructure              (RPKI)",RFC 6488, DOI 10.17487/RFC6488, February 2012,              <http://www.rfc-editor.org/info/rfc6488>.Bruijnzeels, et al.          Standards Track                   [Page 23]

RFC 8182        The RPKI Repository Delta Protocol (RRDP)      July 2017   [RSYNC]    "rsync", <https://rsync.samba.org>.Acknowledgements   The authors would like to thank David Mandelberg for reviewing this   document.Authors' Addresses   Tim Bruijnzeels   RIPE NCC   Email: tim@ripe.net   Oleg Muravskiy   RIPE NCC   Email: oleg@ripe.net   Bryan Weber   Cobenian   Email: bryan@cobenian.com   Rob Austein   Dragon Research Labs   Email: sra@hactrn.netBruijnzeels, et al.          Standards Track                   [Page 24]