RPKI Repository Delta Protocol
draft-ietf-sidr-delta-protocol-06
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8182.
|
|
|---|---|---|---|
| Authors | Tim Bruijnzeels , Oleg Muravskiy , Bryan Weber , Rob Austein | ||
| Last updated | 2017-02-10 | ||
| Replaces | draft-tbruijnzeels-sidr-delta-protocol | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
GENART Last Call review
by Orit Levin
Ready w/nits
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Chris Morrow | ||
| Shepherd write-up | Show Last changed 2016-10-26 | ||
| IESG | IESG state | Became RFC 8182 (Proposed Standard) | |
| Consensus boilerplate | Yes | ||
| Telechat date |
(None)
Needs a YES. Needs 10 more YES or NO OBJECTION positions to pass. |
||
| Responsible AD | Alvaro Retana | ||
| Send notices to | "Chris Morrow" <morrowc@ops-netman.net>, aretana@cisco.com | ||
| IANA | IANA review state | Version Changed - Review Needed |
draft-ietf-sidr-delta-protocol-06
Network Working Group T. Bruijnzeels
Internet-Draft O. Muravskiy
Updates: 6480,6481,7730 (if approved) RIPE NCC
Intended status: Standards Track B. Weber
Expires: August 14, 2017 Cobenian
R. Austein
Dragon Research Labs
February 10, 2017
RPKI Repository Delta Protocol
draft-ietf-sidr-delta-protocol-06
Abstract
In the Resource Public Key Infrastructure (RPKI), certificate
authorities publish certificates, including end entity certificates,
Certificate Revocation Lists (CRL), and RPKI signed objects to
repositories. Relying Parties (RP) retrieve the published
information from those repositories. This document specifies a
protocol which provides relying parties with a mechanism to query a
repository for incremental updates using the HTTP Over TLS (HTTPS)
[RFC2818] protocol, thus enabling the RP to keep its state in sync
with the repository using a secure transport channel. This document
updates [RFC6480], [RFC6481], and [RFC7730], to remove the dependency
on [rsync] as the only mandatory RPKI repository distribution
mechanism.
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 August 14, 2017.
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Copyright Notice
Copyright (c) 2017 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. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. RPKI Repository Delta Protocol Implementation . . . . . . . . 4
3.1. Informal Overview . . . . . . . . . . . . . . . . . . . . 4
3.2. Certificate Authority Use . . . . . . . . . . . . . . . . 5
3.3. Repository Server Use . . . . . . . . . . . . . . . . . . 5
3.3.1. Initialisation . . . . . . . . . . . . . . . . . . . 5
3.3.2. Publishing Updates . . . . . . . . . . . . . . . . . 6
3.4. Relying Party Use . . . . . . . . . . . . . . . . . . . . 7
3.4.1. Processing the Update Notification File . . . . . . . 7
3.4.2. Processing Delta Files . . . . . . . . . . . . . . . 8
3.4.3. Processing a Snapshot File . . . . . . . . . . . . . 9
3.4.4. Polling the Update Notification File . . . . . . . . 9
3.4.5. Considerations Regarding Operational Failures in RRDP 10
3.5. File Definitions . . . . . . . . . . . . . . . . . . . . 10
3.5.1. Update Notification File . . . . . . . . . . . . . . 10
3.5.2. Snapshot File . . . . . . . . . . . . . . . . . . . . 12
3.5.3. Delta File . . . . . . . . . . . . . . . . . . . . . 13
3.5.4. XML Schema . . . . . . . . . . . . . . . . . . . . . 15
4. Updates . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1. Updates to RFC6480 . . . . . . . . . . . . . . . . . . . 17
4.1.1. Update in Section 4.3, Access Protocols . . . . . . . 17
4.1.2. Update in Section 11.1, Normative References . . . . 17
4.1.3. Update in Section 11.2, Informative References . . . 17
4.2. Updates to RFC6481 . . . . . . . . . . . . . . . . . . . 18
4.2.1. Update in Section 3, Resource Certificate Publication
Repository Considerations . . . . . . . . . . . . . . 18
4.2.2. Update in Section 9.1, Normative References . . . . . 18
4.2.3. Update in Section 9.2, Informative References . . . . 18
4.3. Updates to RFC7730 . . . . . . . . . . . . . . . . . . . 18
4.3.1. Update in Section 2.1, Trust Anchor Locator Format . 18
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4.3.2. Update in Section 2.2, TAL and Trust Anchor
Certificate Considerations . . . . . . . . . . . . . 19
4.3.3. Update in Section 5.1, Normative References . . . . . 19
5. Operational Considerations . . . . . . . . . . . . . . . . . 19
5.1. Compatibility with previous standards . . . . . . . . . . 19
5.2. Distribution considerations . . . . . . . . . . . . . . . 20
5.3. HTTPS considerations . . . . . . . . . . . . . . . . . . 20
6. Security Considerations . . . . . . . . . . . . . . . . . . . 21
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
9.1. Normative References . . . . . . . . . . . . . . . . . . 22
9.2. Informative References . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Requirements notation
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 [RFC2119].
2. Introduction
In the Resource Public Key Infrastructure (RPKI), Certificate
Authorities (CAs) 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,
allowing Relying Parties (RPs) to synchronise a local copy of the
RPKI repository used for validation with the remote repositories
[RFC6481].
This document specifies an alternative repository access protocol
based on notification, snapshot and delta files that a RP can
retrieve over the HTTPS protocol. This allows RPs to perform either
a full (re-)synchronisation of their local copy of the repository
using snapshot files, or use delta files to keep their local
repository updated after initial synchronisation. We call this the
RPKI Repository Delta Protocol, or RRDP in short.
This protocol is designed to be consistent (in terms of data
structures) with the publication protocol [I-D.ietf-sidr-publication]
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. This protocol also provides a standards based
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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, so that caching infrastructure can be used to reduce the load
on a repository server when a large number of relying parties are
querying it.
In order to facilitate transition to this new protocol, this document
updates the texts of [RFC6480], [RFC6481], and [RFC7730], removing
the dependency on [rsync] as the only mandatory RPKI repository
distribution mechanism, and allowing use of a non-rsync URI in a
Trust Anchor Locator file.
3. RPKI Repository Delta Protocol Implementation
3.1. Informal Overview
Certification Authorities (CA) 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 CA engine itself. Certificates in the
RPKI that use a repository server that supports this delta protocol
include a special Subject Information Access (SIA) pointer referring
to a notification file.
The notification file includes a globally unique session_id in the
form of a version 4 UUID ([RFC4122]), and serial number that can be
used by the Relying Party (RP) to determine if it and the repository
are synchronised. 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 RP that learns about a notification file location for the first
time can download it, and then proceed to download the latest
snapshot file, and thus create a local copy of the repository that is
in sync with the repository server. The RP records the location of
this notification file, the session_id and current serial number.
RPs are encouraged to re-fetch this notification file at regular
intervals, but not more often than once per minute. After re-
fetching the notification file, the RP may find that there are one or
more delta files available that allow it to synchronise its local
repository with the current state of the repository server. If no
contiguous chain of deltas from RP's serial to the latest repository
serial is available, or if the session_id has changed, the RP
performs a full resynchronisation instead.
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As soon as the RP fetches new content in this way it could start a
validation process. An example of a reason why a RP may not 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 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. Notification files are
polled by RPs to discover if updates exist, and for this reason
notification files may not be cached for longer than one minute.
3.2. Certificate Authority Use
Certificate Authorities that use this delta protocol 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, see
Section 7:
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 }
The accessLocation MUST be an HTTPS URI as defined in [RFC2818], that
will point to the update notification file for the repository server
that publishes the products of this CA certificate.
3.3. Repository Server Use
3.3.1. Initialisation
When the repository server initialises it performs the following
actions:
o The server MUST generate a new random version 4 UUID to be used as
the session_id
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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 in Section 3.5.2.
o After the snapshot file has been published the repository server
MUST publish a new notification file that contains the new
session_id, has serial number ONE, has one reference to the
snapshot file that was just published, and that contains no delta
references. The format and caching concerns for update
notification files are explained in more detail in Section 3.5.1.
3.3.2. Publishing Updates
Whenever the repository server receives updates from a CA it MUST
generate new snapshot and delta files within one minute. If a
publication server services a large number of CAs it MAY choose to
combine updates from multiple CAs. If a publication 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.
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 in Section 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.
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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 in Section 3.5.2.
o Any older delta files that, when combined with all more recent
delta files, will result in total size of deltas exceeding the
size of the snapshot, MUST be excluded to avoid that RPs download
more data than necessary.
o A new notification file MUST now be created by the repository
server. This new 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 in Section 3.5.1.
If the repository server is not capable of performing the above for
some reason, then it MUST perform a full re-initialisation, as
explained above in Section 3.3.1.
3.4. Relying Party Use
3.4.1. Processing the Update Notification File
When a Relying Party (RP) performs RPKI validation and learns about a
valid certificate with an SIA entry for the RRDP protocol, it SHOULD
use this protocol as follows.
The RP 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 because a polling strategy was
used (see Section 3.4.4).
It is RECOMMENDED that RP uses a "User-Agent" header explained in
section 5.5.3. of [RFC7231] to identify the name and version of the
RP software used. It is useful to track capabilities of Relying
Parties in the event of changes to the RPKI standards.
When the RP downloads an update notification file it MUST verify the
file format and validation steps described in section
Section 3.5.1.3. If this verification fails, the file MUST be
rejected and RRDP cannot be used. See Section 3.4.5 for
considerations.
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The RP MUST verify whether the session_id in this update notification
file matches the last known session_id for this update notification
file location. If the session_id matches the last known session_id,
then an RP MAY download and process missing delta files as described
in section Section 3.4.2, provided that all delta files for serial
numbers between the last processed serial number and the current
serial number in the notification file can be processed this way.
If the session_id was not previously known, or if delta files could
not be used, then the RP MUST update its last known session_id to
this session_id and download and process snapshot file on the update
notification file as described in section Section 3.4.3.
3.4.2. 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 RPs MUST attempt to download and process all
delta files in order of serial number as follows.
When the RP downloads a delta file it MUST verify the file format and
perform validation steps described in Section 3.5.3.3. If this
verification fails, the file MUST be rejected.
Furthermore the RP 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 an RP retrieved a delta file that is valid according to the above
criteria, it performs the following actions:
The RP MUST verify that the session_id matches the session_id of
the notification file. If the session_id values do not match the
file MUST be rejected.
The RP 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.
The RP SHOULD add all publish elements to a local storage and
update its last processed serial number to the serial number of
this delta file.
The RP SHOULD NOT remove objects from its local storage solely
because it encounters a "withdraw" element, because this would
enable a publication server to withdraw any object without the
signing Certificate Authority consent. The RP could use
additional strategies to determine if an object is still relevant
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for validation before removing it from its local storage. In
particular objects should not be removed if they are included in a
current validated manifest.
If any delta file is rejected RPs MUST process the current Snapshot
File instead, as described in Section 3.4.3.
3.4.3. Processing a Snapshot File
Snapshot Files MUST only be used if Delta Files are unavailable, or
were rejected. As is ensured, if the process described in
Section 3.4.1 is followed.
When the RP downloads a snapshot file it MUST verify the file format
and validation steps described in Section 3.5.2.3. If this
verification fails, the file MUST be rejected.
Furthermore the RP 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 an RP retrieved a snapshot file that is valid according to the
above criteria, it performs the following actions:
The RP MUST verify that the session_id matches the session_id of
the notification file. If the session_id values do not match the
file MUST be rejected.
The RP 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.
The RP 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 that means that RRDP cannot be used.
See Section 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 repository that uses the RRDP
protocol, the RP MAY start polling the repository server for updates.
However the RP MUST NOT poll for updates more often than once every 1
minute, and in order to reduce data usage RPs MUST use the "If-
Modified-Since" header explained in section 3.3 of [RFC7232] in
requests.
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If an RP finds that updates are available it SHOULD download and
process the file as described in Section 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.
3.4.5. Considerations Regarding Operational Failures in RRDP
If an RP 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 publication 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
(see Section 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 RP
can be identified and resolved before they cause major concerns.
3.5. File Definitions
3.5.1. Update Notification File
3.5.1.1. Purpose
The update notification file is used by RPs to discover whether any
changes exist between the state of the repository and the RP's cache.
It describes the location of the files containing the snapshot and
incremental deltas which can be used by the RP to synchronise with
the repository.
3.5.1.2. Cache Concerns
A repository server MAY use caching infrastructure to cache the
notification file and reduce the load of HTTPS requests. However,
since this file is used by RPs 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 notification file, than no notification
file.
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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" (see Section 5.2
of [RFC7234]). Another approach can be to have the repository server
push out new versions of the 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
suggested value.
3.5.1.3. File Format and Validation
Example 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 notification files:
o A RP MUST reject any update notification file that is not well-
formed, or which does not conform to the RELAX NG schema outlined
in Section 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
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o The serial attribute MUST be an unbounded, unsigned positive
integer in decimal format indicating the current version of the
repository.
o The 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 hash of the referenced file.
The RP MUST verify this hash when the file is retrieved and reject
the file if the hash does not match.
3.5.2. Snapshot File
3.5.2.1. 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, and for that reason 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 that these files use a lot of space in
caching infrastructure it is RECOMMENDED that a limited interval is
used in the order of hours or days.
To avoid race conditions where an RP downloads a notification file
moments before it's updated, Repository Servers SHOULD retain old
snapshot files for at least 5 minutes after a new notification file
is published.
3.5.2.3. File Format and Validation
Example snapshot file:
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<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 RP MUST reject any snapshot file that is not well-formed, or
which does not conform to the RELAX NG schema outlined in
Section 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 notification file.
o The serial attribute MUST match the expected serial in the
reference in the notification file.
o Note that the publish element is similar to the publish element
defined in the publication protocol [I-D.ietf-sidr-publication].
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, and therefore it is not relevant to know which
existing RPKI object (if any) is updated.
3.5.3. Delta File
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3.5.3.1. 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
caching infrastructure it is RECOMMENDED that a limited interval is
used in the order of hours or days.
To avoid race conditions where an RP downloads a 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 notification file.
3.5.3.3. 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>
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Note that a formal RELAX NG specification of this file format is
included later in this document. A RP 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 RP MUST reject any delta file that is not well-formed, or which
does not conform to the RELAX NG schema outlined in Section 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 notification file.
o The serial attribute MUST match the expected serial in the
reference in the notification file.
o Note that the publish element is similar to the publish element
defined in the publication protocol [I-D.ietf-sidr-publication].
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.
#
# RelaxNG schema for 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
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# 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 },
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 }
}
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# Local Variables:
# indent-tabs-mode: nil
# comment-start: "# "
# comment-start-skip: "#[ \t]*"
# End:
4. Updates
This section provides updates to several paragraphs in [RFC6480],
[RFC6481], and [RFC7730]. For clarity, the original text and the
replacement text are shown.
4.1. Updates to RFC6480
4.1.1. Update in Section 4.3, Access Protocols
OLD:
To ensure all relying parties are able to acquire all RPKI signed
objects, all publication points MUST be accessible via rsync (see
[RFC5781] and [RSYNC]), although other download protocols MAY also
be supported. A repository publication point may provide
update/change/delete functionality via (set of) access protocols
that it desires, provided that the supported protocols are clearly
communicated to all certification authorities publishing data at a
given publication point.
NEW:
To ensure all relying parties are able to acquire all RPKI signed
objects, all publication points MUST be accessible using retrieval
mechanism(s) consistent with the accessMethod element value(s).
Multiple retrieval mechanisms MAY be supported at the repository
operator's discretion. A repository publication point may provide
update/change/delete functionality via (set of) access protocols
that it desires, provided that the supported protocols are clearly
communicated to all certification authorities publishing data at a
given publication point.
4.1.2. Update in Section 11.1, Normative References
Remove the reference to RFC5781, "The rsync URI Scheme".
4.1.3. Update in Section 11.2, Informative References
Remove the reference to rsync, "rsync web pages".
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4.2. Updates to RFC6481
4.2.1. Update in Section 3, Resource Certificate Publication Repository
Considerations
OLD:
The publication repository MUST be available using rsync [RFC5781]
[RSYNC]. Support of additional retrieval mechanisms is the choice
of the repository operator. The supported retrieval mechanisms
MUST be consistent with the accessMethod element value(s)
specified in the SIA of the associated CA or EE certificate.
NEW:
The publication repository MUST be available using retrieval
mechanism(s) consistent with the accessMethod element value(s)
specified in the SIA of the associated CA or EE certificate.
Support of multiple retrieval mechanisms is the choice of the
repository operator.
4.2.2. Update in Section 9.1, Normative References
Remove the reference to RFC5781, "The rsync URI Scheme".
4.2.3. Update in Section 9.2, Informative References
Remove the reference to rsync, "rsync web pages".
4.3. Updates to RFC7730
4.3.1. Update in Section 2.1, Trust Anchor Locator Format
OLD:
where the URI section is comprised of one of more of the ordered
sequence of:
1.1) an rsync URI [RFC5781],
1.2) a <CRLF> or <LF> line break.
NEW:
where the URI section is comprised of one of more of the ordered
sequence of:
1.1) a URI [RFC3986],
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1.2) a <CRLF> or <LF> line break.
4.3.2. Update in Section 2.2, TAL and Trust Anchor Certificate
Considerations
OLD:
Each rsync URI in the TAL MUST reference a single object. It MUST
NOT reference a directory or any other form of collection of
objects.
...
Where the TAL contains two or more rsync URIs, then the same self-
signed CA certificate MUST be found at each referenced location.
NEW:
Each URI in the TAL MUST reference a single object. It MUST NOT
reference a directory or any other form of collection of objects.
...
Where the TAL contains two or more URIs, then the same self-signed
CA certificate MUST be found at each referenced location.
4.3.3. Update in Section 5.1, Normative References
Remove the reference to RFC5781, "The rsync URI Scheme".
Add a reference to RFC3986, "Uniform Resource Identifier (URI):
Generic Syntax".
5. Operational Considerations
5.1. 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 co-
exist 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
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from repositories of different types. (For an example of such
implementation see [I-D.ietf-sidrops-rpki-tree-validation].)
5.2. Distribution considerations
One of the design goals of RRDP was to minimise 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 notification file. This allows their
effective distribution, either by a single HTTP server, or using a
Content Distribution Network (CDN).
The RECOMMENDED way for RPs 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 notification file, an "If-Modified-Since" HTTP
request header is required to be present in all requests for
notification file (see Section 3.4.4.) Therefore it is RECOMMENDED
that RP tools implement a mechanism to keep track of a previous
successful fetch of a notification file.
Implementations of RRDP should also take care of not producing new
versions of the repository (and subsequently, new 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 RPs 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 RPs.
5.3. HTTPS considerations
It is RECOMMENDED that Relying Parties and Publication Servers follow
the Best Current Practices outlined in [RFC7525] on the use of HTTP
over TLS (HTTPS) [RFC2818].
Note that a Man-in-the-Middle (MITM) cannot produce validly signed
RPKI data, but they can perform withhold or replay attacks targeting
an RP, and keep the RP from learning about changes in the RPKI.
Because of this RPs SHOULD do TLS certificate and host name
validation when they fetch from an RRDP Publication Server.
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RP tools SHOULD log any TLS certificate or host name validation
issues they find, 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. In these cases it is
better if the RP retrieves the signed RPKI data regardless, and
performs validation on it. Therefore RP MUST continue to retrieve
the data in case of errors. The RP MAY choose to log encountered
issues only when fetching the notification update file, but not when
it subsequently fetches snapshot or delta files from the same host.
Furthermore the RP MAY provide a way for operators to accept
untrusted connections for a given host, after the cause has been
identified.
6. Security Considerations
RRDP deals exclusively with transfer of RPKI objects from a
repository server to a relying party. The trust relation between a
CA 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 CMS-wrapped objects) 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.
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 attack more
difficult for the attacker. HTTPS issues are discussed in more
detail in Section 5.3.
Supporting both RRDP and rsync necessarily increases the number of
opportunities for a malicious RPKI CA to perform denial of service
attacks on relying parties, by expanding the number of URIs which the
RP 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 CA can supply an effectively
infinite series of URIs for the RP to follow. The only real solution
to this is for the RP 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 CA, since 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
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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 RP
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 HTTPS caching infrastructure to
reduce load on primary publication servers and increase resilience
against denial of service attacks on the RPKI publication service.
7. IANA Considerations
IANA is requested to update the reference for id-ad-rpkiNotify to
this document in the PKIX Access Descriptor registry
[IANA-AD-NUMBERS].
8. Acknowledgements
The authors would like to thank David Mandelberg for reviewing this
document.
9. References
9.1. Normative References
[I-D.ietf-sidr-publication]
Weiler, S., Sonalker, A., and R. Austein, "A Publication
Protocol for the Resource Public Key Infrastructure
(RPKI)", draft-ietf-sidr-publication-10 (work in
progress), January 2017.
[IANA-AD-NUMBERS]
"SMI Security for PKIX Access Descriptor",
<http://www.iana.org/assignments/smi-numbers/
smi-numbers.xhtml#smi-numbers-1.3.6.1.5.5.7.48>.
[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>.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000,
<http://www.rfc-editor.org/info/rfc2818>.
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[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>.
[RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480,
February 2012, <http://www.rfc-editor.org/info/rfc6480>.
[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>.
[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>.
[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>.
[RFC7730] Huston, G., Weiler, S., Michaelson, G., and S. Kent,
"Resource Public Key Infrastructure (RPKI) Trust Anchor
Locator", RFC 7730, DOI 10.17487/RFC7730, January 2016,
<http://www.rfc-editor.org/info/rfc7730>.
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9.2. Informative References
[I-D.ietf-sidrops-rpki-tree-validation]
Muravskiy, O. and T. Bruijnzeels, "RPKI Certificate Tree
Validation by the RIPE NCC RPKI Validator", draft-ietf-
sidrops-rpki-tree-validation-00 (work in progress),
January 2017.
[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>.
[rsync] "Rsync home page", <https://rsync.samba.org>.
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.net
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