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Internet Engineering Task Force (IETF) J. Field
Request for Comments: 8322 Pivotal
Category: Standards Track S. Banghart
ISSN: 2070-1721 D. Waltermire
NIST
February 2018
Resource-Oriented Lightweight Information Exchange (ROLIE)
Abstract
This document defines a resource-oriented approach for security
automation information publication, discovery, and sharing. Using
this approach, producers may publish, share, and exchange
representations of software descriptors, security incidents, attack
indicators, software vulnerabilities, configuration checklists, and
other security automation information as web-addressable resources.
Furthermore, consumers and other stakeholders may access and search
this security information as needed, establishing a rapid and
on-demand information exchange network for restricted internal use or
public access repositories. This specification extends the Atom
Publishing Protocol and Atom Syndication Format to transport and
share security automation resource representations.
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 in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8322.
Field, et al. Standards Track [Page 1]
RFC 8322 ROLIE February 2018
Copyright Notice
Copyright (c) 2018 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
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
2. Terminology .....................................................4
3. XML-Related Conventions .........................................5
3.1. XML Namespaces .............................................5
3.2. RELAX NG Compact Schema ....................................5
4. Background and Motivation .......................................5
5. ROLIE Requirements for the Atom Publishing Protocol .............7
5.1. AtomPub Service Documents ..................................7
5.1.1. Use of the "app:workspace" Element ..................8
5.1.2. Use of the "app:collection" Element .................8
5.1.3. Service Document Discovery ..........................9
5.2. Category Documents .........................................9
5.3. Transport Layer Security ..................................10
5.4. User Authentication and Authorization .....................10
5.5. "/" (Forward Slash) Resource URL ..........................11
5.6. HTTP Methods ..............................................11
6. ROLIE Requirements for the Atom Syndication Format .............11
6.1. Use of the "atom:feed" Element ............................11
6.1.1. Use of the "atom:category" Element .................13
6.1.2. Use of the "atom:link" Element .....................14
6.1.3. Use of the "atom:updated" Element ..................15
6.2. Use of the "atom:entry" Element ...........................16
6.2.1. Use of the "atom:content" Element ..................17
6.2.2. Use of the "atom:link" Element .....................17
6.2.3. Use of the "rolie:format" Element ..................18
6.2.4. Use of the "rolie:property" Element ................19
6.2.5. Requirements for a Standalone Entry ................20
Field, et al. Standards Track [Page 2]
RFC 8322 ROLIE February 2018
7. Available Extension Points Provided by ROLIE ...................21
7.1. The Category Extension Point ..............................21
7.1.1. General Use of the "atom:category" Element .........22
7.1.2. Identification of Security Automation
Information Types ..................................22
7.2. The "rolie:format" Extension Point ........................24
7.3. The Link Relation Extension Point .........................24
7.4. The "rolie:property" Extension Point ......................24
8. IANA Considerations ............................................26
8.1. XML Namespaces and Schema URNs ............................26
8.2. ROLIE URN Sub-namespace ...................................26
8.3. ROLIE URN Parameters ......................................27
8.4. ROLIE Information Types Registry ..........................29
9. Security Considerations ........................................29
10. Privacy Considerations ........................................31
11. References ....................................................32
11.1. Normative References .....................................32
11.2. Informative References ...................................34
Appendix A. RELAX NG Compact Schema for ROLIE .....................37
Appendix B. Examples of Use .......................................37
B.1. Service Discovery ..........................................37
B.2. Feed Retrieval .............................................40
B.3. Entry Retrieval ............................................42
Acknowledgements ..................................................43
Authors' Addresses ................................................43
1. Introduction
This document defines a resource-oriented approach to security
automation information sharing that follows the Representational
State Transfer (REST) architectural style [REST]. In this approach,
computer security resources are maintained in web-accessible
repositories structured as Atom Syndication Format [RFC4287] Feeds.
Within a given Feed, which may be requested by the consumer,
representations of specific types of security automation information
are organized, categorized, and described. Furthermore, all
collections available to a given user are discoverable, allowing the
consumer to search all available content they are authorized to view,
and to locate and request the desired information resources. Through
the use of granular authentication and access controls, only
authorized consumers may be permitted the ability to read or write to
a given Feed.
The goal of this approach is to increase the communication and
sharing of security information between providers and consumers that
can be used to automate security processes (e.g., incident reports,
vulnerability assessments, configuration checklists, and other
security automation information). Such sharing allows human
Field, et al. Standards Track [Page 3]
RFC 8322 ROLIE February 2018
operators and computer systems to leverage this standardized
communication system to gather information that supports the
automation of security processes.
To support new types of security automation information being used as
time goes on, this specification defines a number of extension points
that can be used either privately or globally. These global
extensions are IANA-registered by Resource-Oriented Lightweight
Information Exchange (ROLIE) extension specifications and provide
enhanced interoperability for new use cases and domains. Sections 5
and 6 of this document define the requirements for XML
representations of ROLIE; other equivalent representations (e.g.
JSON) may be described by other documents. An overview of the
extension system is provided in Section 7. Implementers seeking to
provide support for specific security automation information types
should refer to the specification for that domain as described by the
IANA registry found in Section 8.4.
2. Terminology
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 in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
The previous key words are used in this document to define only the
requirements for implementations of this specification and are not
used for recommendations or requirements for the usage of ROLIE. (In
other words, a programmer of a ROLIE server MUST implement a given
feature, but a user of that ROLIE server needn't use that feature.)
Definitions for some of the common computer-security-related
terminology used in this document can be found in Section 2 of
[RFC7970].
The following term is unique to this specification:
Information Type: A class of security automation information having
one or more associated data models. Often, such security
automation information is used in the automation of a security
process. See Section 7.1.2 for more information.
Field, et al. Standards Track [Page 4]
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3. XML-Related Conventions
3.1. XML Namespaces
This specification uses XML namespaces [W3C.REC-xml-names-20091208]
to uniquely identify XML element names. It uses the following
namespace prefix mappings for the indicated namespace URI:
o "app" is used for the "https://www.w3.org/2007/app" namespace
defined in [RFC5023].
o "atom" is used for the "https://www.w3.org/2005/Atom" namespace
defined in [RFC4287].
o "rolie" is used for the "urn:ietf:params:xml:ns:rolie:1.0"
namespace defined in Section 8.1 of this specification.
3.2. RELAX NG Compact Schema
Some sections of this specification are illustrated with fragments of
a non-normative RELAX NG Compact Schema [RELAX-NG]. The text of this
specification provides the definition of conformance. Schema for the
"https://www.w3.org/2007/app" and "https://www.w3.org/2005/Atom"
namespaces appear in Appendix B of [RFC5023] and Appendix B of
[RFC4287], respectively.
A complete informative RELAX NG Compact Schema for the new elements
introduced by ROLIE is provided in Appendix A of this document.
4. Background and Motivation
In order to automate security processes, tools need access to
sufficient sources of structured security information that can be
used to drive security processes. Thus, security information sharing
is one of the core components of automating security processes.
Vulnerabilities, configurations, software identification, security
incidents, and patch data are just a few of the classes of
information that are shared today to enable effective security on a
wide scale. However, as the scale of defense broadens as networks
become larger and more complex, and the volume of information to
process makes humans-in-the-loop difficult to scale, the need for
automation and machine-to-machine communication becomes increasingly
critical.
Field, et al. Standards Track [Page 5]
RFC 8322 ROLIE February 2018
ROLIE seeks to address this need by providing four major information-
sharing benefits:
Extensible information type categories and format agnosticism: ROLIE
is not bound to any given data format or category of information.
Instead, information categories are extensible, and Entries
declare the format of the referenced data. In cases where several
formats or serializations are available, ROLIE can use link
relations to communicate how a consumer can access these formats.
For example, clients may request that a given resource
representation be returned as XML, JSON, or in some other format
or serialization. This approach allows the provider to support
multiple isomorphic formats, allowing the consumer to select the
most suitable version.
Open and distributed information sharing: Using the Atom Publishing
Protocol (AtomPub), ROLIE Feeds can easily aggregate Feeds and
accept information posted to them from other sources. Webs of
communicating ROLIE servers form ad hoc sharing communities,
increasing data availability and the ability to correlate linked
data across sources for participating consumers. ROLIE servers
needn't be distributed, however, as large ROLIE repositories can
function as a central collection or federated collections.
Stateless communication model: ROLIE, as a RESTful system, is
stateless. That is, the server doesn't keep track of client
sessions but rather uses link relations for state transitions. In
practice, this means that any consumer can find and share
information at any organizational level and at any time without
needing to execute a long series of requests.
Information discovery and navigation: ROLIE provides a number of
mechanisms to allow clients to programmatically discover and
navigate collections of information in order to dynamically
discover new or revised content. Extensible information types and
other categories provide one way of determining content that is
desirable. Link elements, each with a target URI and an
established relationship type, provide a means for ROLIE providers
to link other information that is relevant to the current Entry
or Feed.
These benefits result in an information-sharing protocol that is
lightweight, interactive, open, and, most importantly, machine
readable.
The requirements in this specification are broken into two major
sections: extensions to AtomPub [RFC5023] and extensions to the Atom
Syndication Format [RFC4287]. All normative requirements in AtomPub
Field, et al. Standards Track [Page 6]
RFC 8322 ROLIE February 2018
and Atom Syndication are inherited from their respective
specifications and apply here unless the requirement is explicitly
overridden in this document. In this way, this document may upgrade
the requirement (e.g., make a "SHOULD" a "MUST") but will never
downgrade a given requirement (e.g., make a "MUST" a "SHOULD").
5. ROLIE Requirements for the Atom Publishing Protocol
This section describes a number of restrictions of, and extensions
to, AtomPub [RFC5023] that define the use of AtomPub in the context
of a ROLIE-based solution. The normative requirements in this
section are generally oriented towards client and server
implementations. An understanding of the AtomPub specification
[RFC5023] is helpful to understand the requirements in this section.
5.1. AtomPub Service Documents
As described in Section 8 of [RFC5023], a Service Document is an
XML-based document format that allows a client to dynamically
discover the Collections provided by a publisher. A Service Document
consists of one or more "app:workspace" elements that may each
contain a number of "app:collection" elements.
The general structure of a Service Document is as follows (from
Section 4.2 of [RFC5023]):
Service
o- Workspace
| |
| o- Collection
| | |
| | o- URI, categories, media types
| |
| o- ...
|
o- Workspace
| |
| o- Collection
| | |
| | o- URI, categories, media types
| |
| o- ...
|
o- ...
Note that the Internationalized Resource Identifiers (IRIs) in the
original diagram have been replaced with URIs.
Field, et al. Standards Track [Page 7]
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5.1.1. Use of the "app:workspace" Element
In AtomPub, a workspace, represented by the "app:workspace" element,
describes a group of one or more Collections. Building on the
AtomPub concept of a workspace, in ROLIE a workspace represents an
aggregation of Collections pertaining to security automation
information resources. This specification does not restrict the
number of workspaces that may be in a Service Document or the
specific Collections to be provided within a given workspace.
A ROLIE implementation can host Collections containing both public
and private information Entries. It is suggested that
implementations segregate Collections into different "app:workspace"
elements by their client access requirements. With proper naming of
workspaces, this reduces the amount of trial and error a human user
would need to utilize to discover accessible Collections.
5.1.2. Use of the "app:collection" Element
In AtomPub, a Collection in a Service Document, represented by the
"app:collection" element, provides metadata that can be used to point
to a specific Atom Feed that contains information Entries that may be
of interest to a client. The association between a Collection and a
Feed is provided by the "href" attribute of the "app:collection"
element. Building on the AtomPub concept of a Collection, in ROLIE a
Collection represents a pointer to a group of security automation
information resources pertaining to a given type of security
automation information. Collections are represented as Atom Feeds as
per RFC 5023. Requirements specific to Atom Feed are defined in
Section 6.1.
ROLIE defines specialized data requirements for Collections, Feeds,
and Entries containing data related to security automation. The
difference between a ROLIE Collection and a non-ROLIE Collection
defined in a Service Document can be determined as follows:
ROLIE Collection: An app:collection is considered a ROLIE Collection
when it contains an "app:categories" element that contains only
one "atom:category" element with a "scheme" attribute value of
"urn:ietf:params:rolie:category:information-type". Further, this
category has an appropriate "term" attribute value as defined in
Section 7.1.1. This ensures that a given Collection corresponds
to a specific type of security automation information.
Non-ROLIE Collection: An app:collection is considered a non-ROLIE
Collection when it does not contain an "atom:category" element
with a "scheme" attribute value of
"urn:ietf:params:rolie:category:information-type".
Field, et al. Standards Track [Page 8]
RFC 8322 ROLIE February 2018
By distinguishing between ROLIE and non-ROLIE Collections in this
way, implementations supporting ROLIE can host Collections pertaining
to security automation information alongside Collections of other
non-ROLIE information within the same AtomPub instance.
The following are additional requirements on the use of the
"app:collection" element for a ROLIE Collection:
o The child "atom:category" elements contained in the
"app:categories" element MUST be the same set of "atom:category"
elements used in the Atom Feed resource referenced by the
"app:collection" element's "href" attribute value. This ensures
that the category metadata associated with the Collection and the
associated Feed is discoverable in both of these resources.
o The "app:categories" element in an app:collection MAY include
additional "atom:category" elements using a scheme other than
"urn:ietf:params:rolie:category:information-type". This allows
other category metadata to be included.
5.1.3. Service Document Discovery
The Service Document serves as the "head" of a given ROLIE
repository: from the Service Document, all other repository content
can be discovered. A client will need to determine the URL of this
Service Document to discover the Collections provided by the
repository. The client might determine the URL from a web page,
based on out-of-band communication, or through a "service" link
relation in a Feed or Entry Document that the client has already
retrieved. The latter is a typical scenario if the client learns of
a specific Feed or Entry through an out-of-band mechanism and wishes
to discover additional information provided by the repository.
This document does not provide a fully automated discovery mechanism.
A mechanism may be defined in the future that allows automated
clients to discover the URL to use to retrieve a ROLIE Service
Document representing the head of the ROLIE repository.
5.2. Category Documents
As described in Section 7 of [RFC5023], a Category Document is an
XML-based document format that allows a client to dynamically
discover the categories used within AtomPub Service Documents, Atom
Syndication Feeds, and Entry Documents provided by a publisher. A
Category Document consists of one "app:categories" element that
contains a number of inline "atom:category" elements, or a URI
referencing a Category Document.
Field, et al. Standards Track [Page 9]
RFC 8322 ROLIE February 2018
5.3. Transport Layer Security
ROLIE is intended to be handled with Transport Layer Security (TLS).
TLS version 1.2 MUST be supported. TLS 1.2 SHOULD be implemented
according to all recommendations and best practices presented in
[RFC7525].
It is RECOMMENDED that the most recent published version of TLS be
supported. If this version is TLS 1.3 [TLS-1.3], it is suggested
that 0-RTT (Zero Round-Trip Time Resumption) not be used, in order to
prevent replay attacks. Replay attacks on PUT, POST, or DELETE
requests can disrupt repository operation by modifying data
unexpectedly.
For example, an automated ROLIE repository that updates very
frequently may receive a PUT request against a given resource a few
times an hour (or more). An attacker may store an early PUT request,
and at the end of the resumption window replay the PUT request,
reverting the resource to an old version. Not only could an attacker
be doing this replay continuously to cause havoc on the server, but
the client is completely unaware of the attack taking place.
Given the potentially sensitive nature of data handled by ROLIE, all
appropriate precautions should be taken at the transport layer to
protect forward secrecy and user privacy.
The server MUST implement certificate-based client authentication.
This MAY be enabled on a workspace-by-workspace basis.
5.4. User Authentication and Authorization
Implementations MUST support user authentication. However, a given
implementation MAY allow user authentication to be disabled on a
Feed-by-Feed or workspace-by-workspace basis.
It is recommended that servers participating in an information-
sharing consortium and supporting interactive user logins by members
of the consortium support client authentication via a federated
identity scheme.
This document does not mandate the use of any specific user
authorization mechanisms. However, service implementers SHOULD
support appropriate authorization checking for all resource accesses,
including individual Atom Entries, Atom Feeds, and Atom Service
Documents.
Field, et al. Standards Track [Page 10]
RFC 8322 ROLIE February 2018
5.5. "/" (Forward Slash) Resource URL
The "/" resource MAY be supported for compatibility with existing
deployments that are using [RFC6546] ("Transport of Real-time
Inter-network Defense (RID) Messages over HTTP/TLS"). The following
requirements apply only to implementations that support both RFC 6546
and the "/" resource as described above:
o Consistent with Erratum ID 3267 [Err3267] for [RFC6546], a client
requesting a GET on the "/" resource SHOULD receive an HTTP status
code 405 ("Method Not Allowed").
o An implementation MAY provide full support for [RFC6546] such that
a POST to the "/" resource containing a recognized RID message is
handled correctly as a RID request. Alternatively, a client
requesting a POST to "/" MAY receive an HTTP status code 307
("Temporary Redirect"). In this case, the location header in the
HTTP response will provide the URL of the appropriate RID
endpoint, and the client may repeat the POST method at the
indicated location.
If RFC 6546 is unsupported, then a request for the "/" resource may
be handled as deemed appropriate by the server.
5.6. HTTP Methods
Servers MAY accept request methods beyond those specified in this
document.
Clients MUST be capable of recognizing and processing any standard
HTTP status code, as defined in Section 5 of [RFC5023].
6. ROLIE Requirements for the Atom Syndication Format
This section describes a number of restrictions of, and extensions
to, the Atom Syndication Format [RFC4287] that define the valid use
of the format in the context of a ROLIE implementation. An
understanding of the Atom Syndication Format specification [RFC4287]
is helpful to understand the requirements in this section.
6.1. Use of the "atom:feed" Element
As described in Section 4.1.1 of [RFC4287], an Atom Feed is an
XML-based document format that describes a list of related
information items. The Atom Feeds provided by a ROLIE service are
listed in the service's Service Document through one or more
"app:collection" elements. Each Feed Document, represented using the
"atom:feed" element, contains a listing of zero or more Entries.
Field, et al. Standards Track [Page 11]
RFC 8322 ROLIE February 2018
When applied to the problem domain of security automation information
sharing, an Atom Feed may be used to represent any meaningful
collection of security automation information resources. Each Entry
in a Feed represents an individual resource (e.g., a specific
checklist, a software vulnerability record). Additional Feeds can be
used to represent other collections of security automation resources.
As discussed in Section 5.1.2, ROLIE defines specialized data
requirements for Feeds containing data related to security
automation. The difference between a ROLIE Feed and a non-ROLIE Feed
can be determined as follows:
ROLIE Feed: For an "atom:feed" to be considered a ROLIE Feed, the
"atom:feed" MUST contain only one child "atom:category" element
with a "scheme" attribute value of
"urn:ietf:params:rolie:category:information-type". This category
MUST have an appropriate "term" attribute value as defined in
Section 7.1.1. This ensures that a given Feed corresponds to a
specific type of security automation information.
Non-ROLIE Feed: For an "atom:feed" to be considered a non-ROLIE
Feed, the "atom:feed" MUST NOT contain an "atom:category" element
with a "scheme" attribute value of
"urn:ietf:params:rolie:category:information-type".
By distinguishing between ROLIE and non-ROLIE Feeds in this way,
implementations supporting ROLIE can host Feeds pertaining to
security automation information alongside Feeds of other non-ROLIE
information within the same AtomPub instance. This is parallel to
the handling of Collections as discussed earlier in this
specification (Section 5.1.2).
Field, et al. Standards Track [Page 12]
RFC 8322 ROLIE February 2018
The following Atom Feed definition represents a stricter definition
of the "atom:feed" element defined in [RFC4287] when used as a
ROLIE Feed. Any element not specified here inherits its definition
and requirements from [RFC4287].
atomFeed =
element atom:feed {
atomCommonAttributes,
(atomAuthor*
& atomCategory+
& atomContributor*
& atomGenerator?
& atomIcon?
& atomId
& atomLink+
& atomLogo?
& atomRights?
& atomSubtitle?
& atomTitle
& atomUpdated
& extensionElement*),
atomEntry*
}
The following subsections contain requirements for a ROLIE Feed.
6.1.1. Use of the "atom:category" Element
An "atom:feed" can contain one or more "atom:category" elements. In
Atom, the naming scheme and the semantic meaning of the terms used to
identify an Atom category are application defined.
The following are additional requirements on the use of the
"atom:category" element when used in a ROLIE Feed:
o All member Entries in the Feed MUST represent security automation
information records of the provided information type category.
o The "atom:feed" MAY include additional "atom:category" elements
using a scheme other than
"urn:ietf:params:rolie:category:information-type". This allows
other category metadata to be included.
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6.1.2. Use of the "atom:link" Element
Link relations defined by the "atom:link" element are used to
represent state transitions using a stateless approach. In Atom, a
type of link relationship can be defined using the "rel" attribute.
A ROLIE Feed MUST contain one or more "atom:link" elements with
rel="service" and an "href" attribute whose value is a URI that
points to an Atom Service Document associated with the Feed. If a
client accesses a Feed without first accessing the service's Service
Document, a link with the "service" relationship provides a means to
discover additional security automation information. The "service"
link relationship is defined in the IANA "Link Relations" registry at
<https://www.iana.org/assignments/link-relations/>.
A Feed can contain an arbitrary number of Entries. In some cases, a
complete Feed may consist of a large number of Entries.
Additionally, as new and updated Entries are ordered at the beginning
of a Feed, a client may only be interested in retrieving the first N
Entries in a Feed to process only the Entries that have changed since
the last retrieval of the Feed. As a practical matter, a large set
of Entries will likely need to be divided into more manageable
portions, or pages. Based on Section 3 of [RFC5005], link elements
SHOULD be included in all Feeds to support paging using the following
link relation types:
o "first" - Indicates that the "href" attribute value of the link
identifies a resource URI for the furthest preceding page of
the Feed.
o "last" - Indicates that the "href" attribute value of the link
identifies a resource URI for the furthest following page of
the Feed.
o "previous" - Indicates that the "href" attribute value of the link
identifies a resource URI for the immediately preceding page of
the Feed.
o "next" - Indicates that the "href" attribute value of the link
identifies a resource URI for the immediately following page of
the Feed.
Field, et al. Standards Track [Page 14]
RFC 8322 ROLIE February 2018
For example:
<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="https://www.w3.org/2005/Atom">
<id>b7f65304-b63b-4246-88e2-c104049c5fd7</id>
<title>Paged Feed</title>
<link rel="self" href="https://example.org/feedA?page=5"/>
<link rel="first" href="https://example.org/feedA?page=1"/>
<link rel="prev" href="https://example.org/feedA?page=4"/>
<link rel="next" href="https://example.org/feedA?page=6"/>
<link rel="last" href="https://example.org/feedA?page=10"/>
<updated>2012-05-04T18:13:51.0Z</updated>
<!-- remainder of the Feed's elements -->
</feed>
Example Paged Feed
A reference to a historical Feed may need to be stable, and/or a Feed
may need to be divided into a series of defined epochs.
Implementations SHOULD support the mechanisms described in Section 4
of [RFC5005] to provide link-based state transitions for maintaining
the archiving of Feeds.
A Feed MAY include additional link relationships not specified in
this document. If a client encounters an unknown link relationship
type, the client MUST ignore the unrecognized link and continue
processing as if the unrecognized link element did not appear. The
definition of new link relations that provide additional state
transition extensions is discussed in Section 7.3.
6.1.3. Use of the "atom:updated" Element
The "atom:updated" element identifies the date and time that a Feed
was last updated.
The "atom:updated" element MUST be populated with the current time at
the instant the Feed was last updated by adding, updating, or
deleting an Entry, or by changing any metadata for the Feed.
Field, et al. Standards Track [Page 15]
RFC 8322 ROLIE February 2018
6.2. Use of the "atom:entry" Element
Each Entry in an Atom Feed, represented by the "atom:entry" element,
describes a single referenced information record, along with
descriptive information about its format, media type, and other
publication metadata. The following "atom:entry" schema definition
represents a stricter representation of the "atom:entry" element
defined in [RFC4287] for use in a ROLIE-based Atom Feed as defined in
Section 6.1.1.
atomEntry =
element atom:entry {
atomCommonAttributes,
(atomAuthor*
& atomCategory*
& atomContent
& atomContributor*
& atomId
& atomLink*
& atomPublished?
& atomRights?
& atomSource?
& atomSummary?
& atomTitle
& atomUpdated
& rolieFormat?
& rolieProperty*
& extensionElement*)
}
The notable changes from [RFC4287] are the addition of "rolieFormat"
and "rolieProperty" elements. Also, the "atomContent" element is
restricted to the atomOutOfLineContent formulation and is now
REQUIRED.
The following subsections contain requirements for Entries in a
ROLIE Feed.
Field, et al. Standards Track [Page 16]
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6.2.1. Use of the "atom:content" Element
An "atom:content" element associates its containing Entry with a
content resource identified by the "src" attribute.
There MUST be exactly one "atom:content" element in the Entry. The
"atom:content" element MUST adhere to this definition, which is a
stricter representation of the "atom:content" element defined in
[RFC4287]:
atomContent =
element atom:content {
atomCommonAttributes,
attribute type { atomMediaType },
attribute src { atomUri },
empty
}
This restricts atomContent in ROLIE to the atomOutOfLineContent
formulation presented in [RFC4287].
The "type" attribute MUST identify the serialization type of the
content -- for example, "application/xml" or "application/json". A
prefixed media type MAY be used to reflect a specific model used with
a given serialization approach (e.g., "application/rdf+xml"). The
"src" attribute MUST be a URI that can be dereferenced to retrieve
the related content data.
6.2.2. Use of the "atom:link" Element
Link relations can be included in an Entry to represent state
transitions to and from the Entry, as well as to provide links to
related information.
If there is a need to provide the same information in different data
models and/or serialization formats, separate Entry instances can be
included in the same Feed or a different Feed. Such an alternate
content representation can be indicated using an "atom:link" having a
"rel" attribute with the value "alternate".
A Feed MAY include additional link relationships not specified in
this document. If a client encounters an unknown link relationship
type, the client MUST ignore the unrecognized link and continue
processing as if the unrecognized link element did not appear. The
definition of new link relations that provide additional state
transition extensions is discussed in Section 7.3.
Field, et al. Standards Track [Page 17]
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6.2.3. Use of the "rolie:format" Element
As mentioned in Sections 1 and 4, a key goal of this specification is
to allow a consumer to review a set of published security automation
information resources and then identify and retrieve any resources of
interest. The format of the data is a key criteria to consider when
deciding what information to retrieve. For a given type of security
automation information, it is expected that a number of different
formats may be used to represent this information. To support this
use case, both the serialization format and the specific data model
expressed in that format must be known by the consumer.
In the Atom Syndication Format, a media type can be defined using the
"type" attribute of the "atom:content" element of an "atom:entry".
The media type can be fully descriptive of the format of the linked
document, such as "application/atom+xml". In some cases, however, a
format-specific media type may not be defined. An example might be
when "application/xml" is used because there is no defined specific
media type for the content. In such a case, the exact data model of
the content cannot be known without first retrieving the content.
In cases where a specific media type does not exist, the
"rolie:format" element is used to describe the data model used to
express the information referenced in the "atom:content" element.
The "rolie:format" element also allows a schema to be identified that
can be used when parsing the content to verify or better understand
the structure of the content.
When it appears, the "rolie:format" element MUST adhere to this
definition:
rolieFormat =
element rolie:format {
atomCommonAttributes,
attribute ns { atomUri },
attribute version { text } ?,
attribute schema-location { atomUri } ?,
attribute schema-type { atomMediaType } ?,
empty
}
The "rolie:format" element MUST provide a "ns" attribute that
identifies the data model of the resource referenced by the
"atom:content" element. For example, the namespace used may be an
XML namespace URI or an identifier that represents a serialized JSON
model. The URI used for the "ns" attribute MUST be absolute. The
resource identified by the URI need not be resolvable.
Field, et al. Standards Track [Page 18]
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The "rolie:format" element MAY provide a "version" attribute that
identifies the version of the format used for the related
"atom:content" element.
The "rolie:format" element MAY provide a "schema-location" attribute,
which is a URI that identifies a schema resource that can be used to
validate the related "atom:content" element.
The "rolie:format" element MAY provide a "schema-type" attribute,
which is a media type (as described in [RFC2045]) identifying the
format of the schema resource identified by the "schema-location"
attribute.
The following nominal example shows how these attributes describe the
format of the content:
<rolie:format ns="urn:ietf:params:xml:ns:iodef-2.0"
version="2.0"
schema-location=
"https://www.iana.org/assignments/xml-registry/schema/iodef-2.0.xsd"
schema-type="text/xml"/>
The previous element provides an indication that the content of the
given Entry is using the Incident Object Description Exchange Format
(IODEF) v2 format.
6.2.4. Use of the "rolie:property" Element
An "atom:category" element provides a way to associate a name/value
pair of categorical information using the "scheme" and "term"
attributes to represent the name and using the "label" attribute to
represent the value. When used in this way, an "atom:category"
allows a specific label to be selected from a finite set of possible
label values that can be used to further classify a given Entry or
Feed. Within ROLIE, there may be a need to associate additional
metadata with an Entry. In such a case, the use of an
"atom:category" is not practical to represent name/value data for
which the allowed values are unbounded. Instead, ROLIE introduces a
new "rolie:property" element that can represent non-categorical
metadata as name/value pairs. Examples include content-specific
identifiers, naming data, and other properties that allow for
unbounded values.
There MAY be zero or more "rolie:property" elements in an
"atom:entry".
Field, et al. Standards Track [Page 19]
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The element MUST adhere to this definition:
rolieProperty =
element rolie:property {
atomCommonAttributes,
attribute name { atomUri },
attribute value { text },
empty
}
The "name" attribute provides a URI that identifies the namespace and
name of the property as a URI.
The "value" attribute is text that provides a value for the property
identified by the "name" attribute.
For example, the nominal element <rolie:property
name="urn:ietf:params:rolie:property:content-id" value="12345"/>
would expose an IODEF ID value contained in a given Entry's content.
The name used in the example also demonstrates the use of a
registered ROLIE property extension, which is described in
Section 7.4.
Implementations MAY use locally defined and namespaced elements in an
Entry in order to provide additional information. Clients that do
not recognize a property with an unregistered "name" attribute MUST
ignore the "rolie:property" element; that is, the client MUST NOT
fail parsing content that contains an unrecognized property.
6.2.5. Requirements for a Standalone Entry
If an Entry is ever shared as a standalone resource, separate from
its containing Feed, then the following additional requirements
apply:
o The Entry MUST have an "atom:link" element with rel="collection"
and href="[URI of the containing Collection]". This allows the
Feed or Feeds of which the Entry is a member to be discovered,
along with the related information the Feed may contain. In the
case where the Entry has multiple containing Feeds, the Entry MUST
have one "atom:link" for each related Feed.
o The Entry MUST declare the information type of the content
resource referenced by the Entry (see Section 7.1.2).
Field, et al. Standards Track [Page 20]
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7. Available Extension Points Provided by ROLIE
This specification does not require particular information types or
data formats; rather, ROLIE is intended to be extended by additional
specifications that define the use of new categories and link
relations. The primary point of extension is through the definition
of new information type category terms. Additional specifications
can register new information type category terms with IANA that serve
as the main characterizing feature of a ROLIE Collection/Feed or
resource/Entry. These additional specifications defining new
information type terms can describe additional requirements for
including specific categories and link relations, as well as the use
of specific data formats supporting a given information type term.
7.1. The Category Extension Point
The "atom:category" element, defined in Section 4.2.2 of [RFC4287],
provides a mechanism to provide additional categorization information
for a content resource in ROLIE. The ability to define new
categories is one of the core extension points provided by Atom. A
Category Document, defined in Section 7 of [RFC5023], provides a
mechanism for an Atom implementation to make discoverable the
"atom:category" terms and associated allowed values.
ROLIE further defines the use of the existing Atom extension category
mechanism by allowing ROLIE-specific category extensions to be
registered with IANA. The
"urn:ietf:params:rolie:category:information-type" category scheme,
which has special meaning for implementations of ROLIE, has been
assigned (see Section 8.3). This allows category scheme namespaces
to be managed in a more consistent way, allowing for greater
interoperability between content producers and consumers.
Any "atom:category" element whose "scheme" attribute uses an
unregistered scheme MUST be considered "Private Use" as defined in
[RFC8126]. Implementations encountering such a category MUST parse
the content without error but MAY otherwise ignore the element.
The use of the "atom:category" element is discussed in the following
subsections.
Field, et al. Standards Track [Page 21]
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7.1.1. General Use of the "atom:category" Element
The "atom:category" element can be used for characterizing a ROLIE
resource. An "atom:category" element has a "term" attribute that
indicates the assigned category value and a "scheme" attribute that
provides an identifier for the category type. The "scheme" provides
a means to describe how a set of category terms should be used and
provides a namespace that can be used to differentiate terms that are
provided by multiple organizations and that have different semantic
meaning.
To further differentiate category types used in ROLIE, an IANA
subregistry has been established for ROLIE protocol parameters to
support the registration of new category "scheme" attribute values by
ROLIE extension specifications. The use of this extension point is
discussed in Section 8.3, using the "name" field with a type
parameter of "category" to indicate a category extension.
7.1.2. Identification of Security Automation Information Types
A ROLIE-specific extension point is provided through the
"atom:category" element's "scheme" attribute value
"urn:ietf:params:rolie:category:information-type". This value is a
Uniform Resource Name (URN) [RFC8141] that is registered with IANA as
described in Section 8.3. When used as the "scheme" attribute in
this way, the "term" attribute is expected to be a registered value
as defined in Section 8.4. Through this mechanism, a given security
automation information type can be used to:
1. identify that an "app:collection" element in a Service Document
points to an Atom Feed that contains Entries pertaining to a
specific type of security automation information (see
Section 5.1.2),
2. identify that an "atom:feed" element in an Atom Feed contains
Entries pertaining to a specific type of security automation
information (see Section 6.1.1), or
3. identify the information type of a standalone resource (see
Section 6.2.5).
Field, et al. Standards Track [Page 22]
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For example, the notional security automation information type
"incident" would be identified as follows:
<atom:category
scheme="urn:ietf:params:rolie:category:information-type"
term="incident"/>
A security automation information type represents a class of
information that represents the same or similar information model
[RFC3444]. Note that this document does not register any information
types but offers the following as examples of potential information
types:
indicator: Computing device- or network-related "observable features
and phenomenon that aid in the forensic or proactive detection of
malicious activity and associated metadata" (from [RFC7970]).
incident: Information pertaining to or derived from security
incidents.
vulnerability reports: Information identifying and describing a
vulnerability in hardware or software.
configuration checklists: Content that can be used to assess the
configuration settings related to installed software.
software tags: Metadata used to identify and characterize
installable software.
This is a short list to inspire new engineering of information type
extensions that support the automation of security processes.
This document does not specify any information types. Instead,
information types in ROLIE are expected to be registered in extension
documents that describe one or more new information types. This
allows the information types used by ROLIE implementations to grow
over time to support new security automation use cases. These
extension documents may also enhance ROLIE Service, Category, Feed,
and Entry Documents by defining link relations, other categories, and
Format data model extensions to address the representational needs of
these specific information types. New information types are added to
ROLIE through registrations to the IANA "ROLIE Information Types"
registry defined in Section 8.4.
Field, et al. Standards Track [Page 23]
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7.2. The "rolie:format" Extension Point
Security automation data pertaining to a given information type may
be expressed using a number of supported formats. As described in
Section 6.2.3, the "rolie:format" element is used to describe the
specific data model used to represent the resource referenced by a
given "atom:entry". The structure provided by the "rolie:format"
element provides a mechanism for extension within the "atom:entry"
model. ROLIE extensions MAY further restrict which data models are
allowed to be used for a given information type.
By declaring the data model used for a given resource, a consumer can
choose to download or ignore the resource, or look for alternate
formats. This saves the consumer from downloading and parsing
resources that the consumer is not interested in or resources
expressed in formats that are not supported by the consumer.
7.3. The Link Relation Extension Point
This document uses several link relations defined in the IANA
"Link Relation Types" registry at
<https://www.iana.org/assignments/link-relations/>. Additional link
relations can be registered in this registry to allow new
relationships to be represented in ROLIE according to Section 4.2.7.2
of [RFC4287]. Based on the preceding reference, if the link relation
is too specific or limited in its intended use, an absolute URI can
be used in lieu of registering a new simple name with IANA.
7.4. The "rolie:property" Extension Point
As discussed previously in Section 6.2.3, many formats contain unique
identifying and characterizing properties that are vital for sharing
information. In order to provide a global reference for these
properties, this document establishes an IANA registry that allows
ROLIE extensions to register named properties using the "name" field
with a type parameter of "property" to indicate a property extension;
see Section 8.3. Implementations SHOULD prefer the use of registered
properties over implementation-specific properties when possible.
ROLIE extensions are expected to register new properties and use
existing properties to provide valuable identifying and
characterizing information for a given information type and/or
format.
Field, et al. Standards Track [Page 24]
RFC 8322 ROLIE February 2018
Any "rolie:property" element whose "name" attribute has
"urn:ietf:params:rolie:property:local" as a prefix MUST be considered
"Private Use" as defined in [RFC8126]. Implementations encountering
such a property MUST parse the content without error but MAY
otherwise ignore the element.
This document also registers a number of general-use properties that
can be used to expose content information in any ROLIE use case. The
following are descriptions of how to use these registered properties:
urn:ietf:params:rolie:property:content-author-name
The "value" attribute of this property is a text representation
indicating the individual or organization that authored the
content referenced by the "src" attribute of the Entry's
"atom:content" element. This author may differ from the
"atom:author" element when the author of the content and the
author of the Entry are different people or entities.
urn:ietf:params:rolie:property:content-id
The "value" attribute of this property is a text representation of
an identifier pertaining to or extracted from the content
referenced by the "src" attribute of the Entry's "atom:content"
element. For example, if the "atom:entry"'s "atom:content"
element links to an IODEF document, the "content-id" value would
be an identifier of that IODEF document.
urn:ietf:params:rolie:property:content-published-date
The "value" attribute of this property is a text representation
indicating the original publication date of the content referenced
by the "src" attribute of the Entry's "atom:content" element.
This date may differ from the published date of the ROLIE Entry
because publication of the content and publication of the ROLIE
Entry represent different events. The date MUST be formatted as
specified in [RFC3339].
urn:ietf:params:rolie:property:content-updated-date
The "value" attribute of this property is a text representation
indicating the date that the content, referenced by the "src"
attribute of the Entry's "atom:content" element, was last updated.
This date may differ from the updated date of the ROLIE Entry
because updates made to the content and to the ROLIE Entry are
different events. The date MUST be formatted as specified in
[RFC3339].
Field, et al. Standards Track [Page 25]
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8. IANA Considerations
This document has a number of IANA considerations, as described in
the following subsections.
8.1. XML Namespaces and Schema URNs
This document uses URNs to describe XML namespaces and XML schemas
conforming to the registry mechanism described in [RFC3688].
ROLIE XML Namespace: The ROLIE namespace (rolie-1.0) has been
registered in the "ns" registry.
URI: urn:ietf:params:xml:ns:rolie-1.0
Registrant Contact: IESG
XML: None. Namespace URIs do not represent an XML specification.
ROLIE XML Schema: The ROLIE schema (rolie-1.0) has been registered
in the "schema" registry.
URI: urn:ietf:params:xml:schema:rolie-1.0
Registrant Contact: IESG
XML: See Appendix A of this document.
8.2. ROLIE URN Sub-namespace
IANA has added an entry to the "IETF URN Sub-namespace for Registered
Protocol Parameter Identifiers" registry located at
<https://www.iana.org/assignments/params/> as per [RFC3553].
The entry is as follows:
Registered Parameter Identifier: rolie
Specification: This document
Repository: ROLIE URN Parameters. See Section 8.3.
Index value: See Section 8.4.
Field, et al. Standards Track [Page 26]
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8.3. ROLIE URN Parameters
A new top-level registry has been created, titled "Resource-Oriented
Lightweight Information Exchange (ROLIE) URN Parameters".
Registration in the "ROLIE URN Parameters" subregistry is via the
Specification Required policy [RFC8126]. Registration requests must
be sent to both the MILE Working Group mailing list (mile@ietf.org)
and IANA. IANA will forward registration requests to the Designated
Expert.
Each entry in this subregistry must record the following fields:
Name: A URN segment that adheres to the pattern {type}:{label}. The
keywords are defined as follows:
{type}: The parameter type. The allowed values are "category"
or "property". "category" denotes a category extension
as discussed in Section 7.1. "property" denotes a
property extension as discussed in Section 7.4.
{label}: A required US-ASCII string that conforms to the URN
syntax requirements (see [RFC8141]). This string must
be unique within the namespace defined by the {type}
keyword. The "local" label for both the "category" and
"property" types has been reserved for private use.
Extension URI: The identifier to use within ROLIE, which is the full
URN using the form "urn:ietf:params:rolie:{name}", where {name} is
the "name" field of this registration.
Reference: A static link to the specification and section where the
definition of the parameter can be found.
Subregistry: An optional field that links to an IANA subregistry for
this parameter. If the {type} is "category", the subregistry must
contain a "name" field whose registered values MUST be US-ASCII.
The list of names are the allowed values of the "term" attribute
in the "atom:category" element (see Section 7.1.2).
Field, et al. Standards Track [Page 27]
RFC 8322 ROLIE February 2018
This repository has the following initial values:
+--------------+------------------------+-------------+-------------+
| Name | Extension URI | Reference | Subregistry |
| | | (This | |
| | | Document) | |
+--------------+------------------------+-------------+-------------+
| category: | urn:ietf:params:rolie: | Section 8.4 | See |
| information- | category: | | Section 8.4 |
| type | information-type | | |
| | | | |
| | | | |
| | | | |
| property: | urn:ietf:params:rolie: | Section 7.4 | None |
| content- | property:content- | | |
| author-name | author-name | | |
| | | | |
| property: | urn:ietf:params:rolie: | Section 7.4 | None |
| content-id | property:content-id | | |
| | | | |
| property: | urn:ietf:params:rolie: | Section 7.4 | None |
| content- | property:content- | | |
| published- | published-date | | |
| date | | | |
| | | | |
| property: | urn:ietf:params:rolie: | Section 7.4 | None |
| content- | property:content- | | |
| updated-date | updated-date | | |
+--------------+------------------------+-------------+-------------+
Field, et al. Standards Track [Page 28]
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8.4. ROLIE Information Types Registry
A new subregistry has been created to store ROLIE information type
values.
Name of Registry: "ROLIE Information Types"
Location of Registry:
<https://www.iana.org/assignments/rolie/>
Fields to record in the registry:
Name: The full name of the security resource information type
as a string from the printable ASCII character set [RFC20] with
individual embedded spaces allowed. This value must be unique
in the context of this table. The ABNF [RFC5234] syntax for
this field is:
1*VCHAR *(SP 1*VCHAR)
Index: An IANA-assigned positive integer that identifies the
registration. The first entry added to this registry uses the
value 1, and this value is incremented for each subsequent
entry added to the registry.
Reference: A list of one or more URIs [RFC3986] from which the
registered specification can be obtained. The registered
specification MUST be readily and publicly available from that
URI. The URI SHOULD be a stable reference.
Allocation Policy: Specification Required, as per [RFC8126]
9. Security Considerations
This document defines a resource-oriented approach for lightweight
information exchange using HTTP over TLS, the Atom Syndication
Format, and AtomPub. As such, implementers must understand the
security considerations described in those specifications. All that
follows is guidance; instructions that are more specific are out of
scope for this document.
To protect the confidentiality of a given resource provided by a
ROLIE implementation, requests for retrieval of the resource need to
be authenticated to prevent unauthorized users from accessing the
resource (see Section 5.4). It can also be useful to log and audit
access to sensitive resources to verify that proper access controls
remain in place over time.
Field, et al. Standards Track [Page 29]
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Access control to information published using ROLIE should use
mechanisms that are appropriate to the sensitivity of the
information. Primitive authentication mechanisms like HTTP Basic
Authentication [RFC7617] are rarely appropriate for sensitive
information. A number of authentication schemes are defined in the
"HTTP Authentication Schemes" registry at
<https://www.iana.org/assignments/http-authschemes/>. Of these, HTTP
Origin-Bound Authentication (HOBA) [RFC7486] and SCRAM-SHA-256
[RFC7804] ("SCRAM" stands for "Salted Challenge Response
Authentication Mechanism") provide improved security properties over
HTTP Basic [RFC7617]and Digest [RFC7616] authentication schemes.
However, sharing communities that are engaged in sensitive
collaborative analysis and/or operational response for indicators and
incidents targeting high-value information systems should adopt a
suitably stronger user authentication solution, such as a risk-based
or multi-factor approach.
Collaborating consortiums may benefit from the adoption of a
federated identity solution, such as those based upon OAuth [RFC6749]
with the JSON Web Token (JWT) [RFC7797], or SAML-core [SAML-core]
("SAML" stands for "Security Assertion Markup Language"), SAML-bind
[SAML-bind], and SAML-prof [SAML-prof] for web-based authentication
and cross-organizational single sign-on. Dependency on a trusted
third-party identity provider implies that appropriate care must be
exercised to sufficiently secure the identity provider. Any attacks
on the federated identity system would present a risk to the
consortium, as a relying party. Potential mitigations include
deployment of a federation-aware identity provider that is under the
control of the information-sharing consortium, with suitably
stringent technical and management controls.
Authorization of resource representations is the responsibility of
the source system, i.e., based on the authenticated user identity
associated with an HTTP(S) request. The required authorization
policies that are to be enforced must therefore be managed by the
security administrators of the source system. Various authorization
architectures would be suitable for this purpose, such as Role-Based
Access Control (RBAC) <https://csrc.nist.gov/projects/
role-based-access-control> and/or Attribute-Based Access Control
(ABAC), as embodied in the eXtensible Access Control Markup Language
(XACML) [XACML]. In particular, implementers adopting XACML may
benefit from the capability to represent their authorization policies
in a standardized, interoperable format. Note that implementers are
free to choose any suitable authorization mechanism that is capable
of fulfilling the policy enforcement requirements relevant to their
consortium and/or organization.
Field, et al. Standards Track [Page 30]
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Additional security requirements such as enforcing message-level
security at the destination system could supplement the security
enforcements performed at the source system; however, these
destination-provided policy enforcements are out of scope for this
specification. Implementers requiring this capability should
consider leveraging, for example, the <RIDPolicy> element in the RID
schema. Refer to Section 9 of [RFC6545] for more information.
Additionally, the underlying serialization approach used in the
representation (e.g., XML, JSON) can offer encryption and message
authentication capabilities. For example, XML Digital Signatures
(XMLDSIG) [RFC3275] for XML, as well as JSON Web Encryption [RFC7516]
and JSON Web Signature [RFC7515] for JSON, can provide such
mechanisms.
When security policies relevant to the source system are to be
enforced at both the source and destination systems, implementers
must take care to avoid unintended interactions of the separately
enforced policies. Potential risks will include unintended denial of
service and/or unintended information leakage. These problems may be
mitigated by avoiding any dependence upon enforcements performed at
the destination system. When distributed enforcement is unavoidable,
the usage of a standard language (e.g., XACML) for the expression of
authorization policies will enable the source and destination systems
to better coordinate and align their respective policy expressions.
A service discovery mechanism is not explicitly specified in this
document, but there are several approaches available for
implementers. When selecting this mechanism, implementations need to
ensure that their choice provides a means for authenticating the
server. DNS SRV records [RFC2782] are a possible solution to the
discovery problem described in Section 5.1.3.
10. Privacy Considerations
The optional "author" field may provide an identification privacy
issue if populated without the author's consent. This information
may become public if posted to a public Feed. When aggregating or
sharing Entries from other Feeds or when programmatically generating
ROLIE Entries from some data source, special care should be taken to
ensure that the author's personal information is not shared without
the author's consent.
When using AtomPub to POST Entries to a Feed, attackers may use
correlating techniques to profile the user. The request time can be
compared to the generated "updated" field of the Entry in order to
build out information about a given user. This correlation attempt
can be mitigated by not using HTTP requests to POST Entries when
profiling is a risk and instead using backend control of the Feeds.
Field, et al. Standards Track [Page 31]
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Adoption of the information-sharing approach described in this
document will enable users to more easily perform correlations across
separate, and potentially unrelated, cybersecurity information
providers. A client may succeed in assembling a data set that would
not have been permitted within the context of the authorization
policies of either provider when considered individually. Thus,
providers may face a risk of an attacker obtaining an access that
constitutes an undetected separation of duties (SOD) violation. It
is important to note that this risk is not unique to this
specification, and a similar potential for abuse exists with any
other cybersecurity information-sharing protocol. However, the wide
availability of tools for HTTP clients and Atom Feed handling implies
that the resources and technical skills required for a successful
exploit may be less than it was previously. This risk can be best
mitigated through appropriate vetting of the client at the time of
account provisioning. In addition, any increase in the risk of this
type of abuse should be offset by the corresponding increase in
effectiveness that this specification affords to the defenders.
Overall, privacy concerns in ROLIE can be mitigated by following
security considerations and by the careful use of the optional
personally identifying elements (e.g., author) provided by Atom
Syndication and ROLIE.
11. References
11.1. Normative References
[RELAX-NG] Clark, J., Ed., "RELAX NG Compact Syntax", November 2002,
<https://www.oasis-open.org/committees/relax-ng/
compact-20021121.html>.
[RFC20] Cerf, V., "ASCII format for network interchange", STD 80,
RFC 20, DOI 10.17487/RFC0020, October 1969,
<https://www.rfc-editor.org/info/rfc20>.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
<https://www.rfc-editor.org/info/rfc2045>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
Field, et al. Standards Track [Page 32]
RFC 8322 ROLIE February 2018
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/info/rfc3339>.
[RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An
IETF URN Sub-namespace for Registered Protocol
Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553,
June 2003, <https://www.rfc-editor.org/info/rfc3553>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC4287] Nottingham, M., Ed., and R. Sayre, Ed., "The Atom
Syndication Format", RFC 4287, DOI 10.17487/RFC4287,
December 2005, <https://www.rfc-editor.org/info/rfc4287>.
[RFC5005] Nottingham, M., "Feed Paging and Archiving", RFC 5005,
DOI 10.17487/RFC5005, September 2007,
<https://www.rfc-editor.org/info/rfc5005>.
[RFC5023] Gregorio, J., Ed., and B. de hOra, Ed., "The Atom
Publishing Protocol", RFC 5023, DOI 10.17487/RFC5023,
October 2007, <https://www.rfc-editor.org/info/rfc5023>.
[RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for
Syntax Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC6546] Trammell, B., "Transport of Real-time Inter-network
Defense (RID) Messages over HTTP/TLS", RFC 6546,
DOI 10.17487/RFC6546, April 2012,
<https://www.rfc-editor.org/info/rfc6546>.
[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, <https://www.rfc-editor.org/info/rfc7525>.
Field, et al. Standards Track [Page 33]
RFC 8322 ROLIE February 2018
[RFC7970] Danyliw, R., "The Incident Object Description Exchange
Format Version 2", RFC 7970, DOI 10.17487/RFC7970,
November 2016, <https://www.rfc-editor.org/info/rfc7970>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in
RFC 2119 Key Words", BCP 14, RFC 8174,
DOI 10.17487/RFC8174, May 2017,
<https://www.rfc-editor.org/info/rfc8174>.
[W3C.REC-xml-names-20091208]
Bray, T., Hollander, D., Layman, A., Tobin, R., and H.
Thompson, "Namespaces in XML 1.0 (Third Edition)", World
Wide Web Consortium Recommendation REC-xml-names-20091208,
December 2009, <https://www.w3.org/TR/2009/
REC-xml-names-20091208>.
11.2. Informative References
[Err3267] RFC Errata, Erratum ID 3267, RFC 6546,
<https://www.rfc-editor.org/errata/eid3267>.
[REST] Fielding, R., "Architectural Styles and the Design of
Network-based Software Architectures", 2000,
<http://www.ics.uci.edu/~fielding/pubs/
dissertation/top.htm>.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
DOI 10.17487/RFC2782, February 2000,
<https://www.rfc-editor.org/info/rfc2782>.
[RFC3275] Eastlake 3rd, D., Reagle, J., and D. Solo, "(Extensible
Markup Language) XML-Signature Syntax and Processing",
RFC 3275, DOI 10.17487/RFC3275, March 2002,
<https://www.rfc-editor.org/info/rfc3275>.
[RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
Information Models and Data Models", RFC 3444,
DOI 10.17487/RFC3444, January 2003,
<https://www.rfc-editor.org/info/rfc3444>.
Field, et al. Standards Track [Page 34]
RFC 8322 ROLIE February 2018
[RFC6545] Moriarty, K., "Real-time Inter-network Defense (RID)",
RFC 6545, DOI 10.17487/RFC6545, April 2012,
<https://www.rfc-editor.org/info/rfc6545>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/info/rfc6749>.
[RFC7486] Farrell, S., Hoffman, P., and M. Thomas, "HTTP
Origin-Bound Authentication (HOBA)", RFC 7486,
DOI 10.17487/RFC7486, March 2015,
<https://www.rfc-editor.org/info/rfc7486>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515,
May 2015, <https://www.rfc-editor.org/info/rfc7515>.
[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<https://www.rfc-editor.org/info/rfc7516>.
[RFC7616] Shekh-Yusef, R., Ed., Ahrens, D., and S. Bremer, "HTTP
Digest Access Authentication", RFC 7616,
DOI 10.17487/RFC7616, September 2015,
<https://www.rfc-editor.org/info/rfc7616>.
[RFC7617] Reschke, J., "The 'Basic' HTTP Authentication Scheme",
RFC 7617, DOI 10.17487/RFC7617, September 2015,
<https://www.rfc-editor.org/info/rfc7617>.
[RFC7797] Jones, M., "JSON Web Signature (JWS) Unencoded Payload
Option", RFC 7797, DOI 10.17487/RFC7797, February 2016,
<https://www.rfc-editor.org/info/rfc7797>.
[RFC7804] Melnikov, A., "Salted Challenge Response HTTP
Authentication Mechanism", RFC 7804, DOI 10.17487/RFC7804,
March 2016, <https://www.rfc-editor.org/info/rfc7804>.
[RFC8141] Saint-Andre, P. and J. Klensin, "Uniform Resource Names
(URNs)", RFC 8141, DOI 10.17487/RFC8141, April 2017,
<https://www.rfc-editor.org/info/rfc8141>.
[SAML-bind]
Cantor, S., Hirsch, F., Kemp, J., Philpott, R., and E.
Maler, "Bindings for the OASIS Security Assertion Markup
Language (SAML) V2.0", OASIS Standard saml-bindings-
2.0-os, March 2005, <http://docs.oasis-open.org/
security/saml/v2.0/saml-bindings-2.0-os.pdf>.
Field, et al. Standards Track [Page 35]
RFC 8322 ROLIE February 2018
[SAML-core]
Cantor, S., Kemp, J., Philpott, R., and E. Maler,
"Assertions and Protocols for the OASIS Security Assertion
Markup Language (SAML) V2.0", OASIS Standard saml-core-
2.0-os, March 2005, <http://docs.oasis-open.org/
security/saml/v2.0/saml-core-2.0-os.pdf>.
[SAML-prof]
Hughes, J., Cantor, S., Hodges, J., Hirsch, F., Mishra,
P., Philpott, R., and E. Maler, "Profiles for the OASIS
Security Assertion Markup Language (SAML) V2.0", OASIS
Standard saml-profiles-2.0-os, March 2005,
<http://docs.oasis-open.org/security/saml/v2.0/
saml-profiles-2.0-os.pdf>.
[TLS-1.3] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", Work in Progress, draft-ietf-tls-tls13-23,
January 2018.
[XACML] Rissanen, E., "eXtensible Access Control Markup Language
(XACML) Version 3.0 Plus Errata 01", July 2017,
<http://docs.oasis-open.org/xacml/3.0/
xacml-3.0-core-spec-en.pdf>.
Field, et al. Standards Track [Page 36]
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Appendix A. RELAX NG Compact Schema for ROLIE
This appendix is informative.
The RELAX NG schema below defines the "rolie:format" element.
# -*- rnc -*-
# RELAX NG Compact Syntax Grammar for the rolie ns
namespace rolie = "urn:ietf:params:xml:ns:rolie-1.0"
# import the ATOM Syndication RELAX NG Compact Syntax Grammar
include "atomsynd.rnc"
# rolie:format
rolieFormat =
element rolie:format {
atomCommonAttributes,
attribute ns { atomUri },
attribute version { text } ?,
attribute schema-location { atomUri } ?,
attribute schema-type { atomMediaType } ?,
empty
}
# rolie:property
rolieProperty =
element rolie:property {
atomCommonAttributes,
attribute name { atomUri },
attribute value { text },
empty
}
Appendix B. Examples of Use
B.1. Service Discovery
This appendix provides a non-normative example of a client doing
service discovery.
An Atom Service Document enables a client to dynamically discover
what Feeds a particular publisher makes available. Thus, a provider
uses an Atom Service Document to enable authorized clients to
determine what specific information the provider makes available to
Field, et al. Standards Track [Page 37]
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the community. The Service Document should be made accessible from
an easily found location, such as a link from the producer's
home page.
A client may format an HTTP GET request to retrieve the Service
Document from the specified location:
GET /rolie/servicedocument
Host: www.example.org
Accept: application/atomsvc+xml
Notice the use of the HTTP Accept: request header, indicating the
MIME type for Atom service discovery. The response to this GET
request will be an XML document that contains information on the
specific Collections that are provided.
Example HTTP GET response:
HTTP/1.1 200 OK
Date: Fri, 24 Aug 2016 17:09:11 GMT
Content-Length: 570
Content-Type: application/atomsvc+xml;charset="utf-8"
<?xml version="1.0" encoding="UTF-8"?>
<service xmlns="https://www.w3.org/2007/app"
xmlns:atom="https://www.w3.org/2005/Atom">
<workspace>
<atom:title type="text">Vulnerabilities</atom:title>
<collection href="https://example.org/provider/vulns">
<atom:title type="text">Vulnerabilities Feed</atom:title>
<categories fixed="yes">
<atom:category
scheme="urn:ietf:params:rolie:category:information-type"
term="vulnerability"/>
</categories>
</collection>
</workspace>
</service>
This simple Service Document example shows that the server provides
one workspace, named "Vulnerabilities". Within that workspace, the
server makes one Collection available.
Field, et al. Standards Track [Page 38]
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A server may also offer a number of different Collections, each
containing different types of security automation information. In
the following example, a number of different Collections are
provided, each with its own category and authorization scope. This
categorization will help the clients to decide which Collections will
meet their needs.
HTTP/1.1 200 OK
Date: Fri, 24 Aug 2016 17:10:11 GMT
Content-Length: 1912
Content-Type: application/atomsvc+xml;charset="utf-8"
<?xml version="1.0" encoding='utf-8'?>
<service xmlns="https://www.w3.org/2007/app"
xmlns:atom="https://www.w3.org/2005/Atom">
<workspace>
<atom:title>Public Security Information Sharing</atom:title>
<collection
href="https://example.org/provider/public/vulns">
<atom:title>Public Vulnerabilities</atom:title>
<atom:link rel="service"
href="https://example.org/rolie/servicedocument"/>
<categories fixed="yes">
<atom:category
scheme="urn:ietf:params:rolie:category:information-type"
term="vulnerability"/>
</categories>
</collection>
</workspace>
<workspace>
<atom:title>Private Consortium Sharing</atom:title>
<collection
href="https://example.org/provider/private/incidents">
<atom:title>Incidents</atom:title>
<atom:link rel="service"
href="https://example.org/rolie/servicedocument"/>
<categories fixed="yes">
<atom:category
scheme="urn:ietf:params:rolie:category:information-type"
term="incident"/>
</categories>
</collection>
</workspace>
</service>
Field, et al. Standards Track [Page 39]
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In this example, the provider is making available a total of two
Collections, organized into two different workspaces. The first
workspace contains a Collection consisting of publicly available
software vulnerabilities. The second workspace provides an incident
Collection for use by a private sharing consortium. An appropriately
authenticated and authorized client may then proceed to make HTTP
requests for these Collections. The publicly provided vulnerability
information may be accessible with or without authentication.
However, users accessing the Collection restricted to authorized
members of a private sharing consortium are expected to authenticate
before access is allowed.
B.2. Feed Retrieval
This appendix provides a non-normative example of a client retrieving
a vulnerability Feed.
Having discovered the available Collections that share security
information, a client who is a member of the general public may be
interested in receiving the Collection of public vulnerabilities,
expressed as Common Vulnerabilities and Exposures (CVEs). The client
may retrieve the Feed for this Collection by performing an HTTP GET
operation on the URL indicated by the Collection's "href" attribute.
Example HTTP GET request for a Feed:
GET /provider/public/vulns
Host: www.example.org
Accept: application/atom+xml
Field, et al. Standards Track [Page 40]
RFC 8322 ROLIE February 2018
The corresponding HTTP response would be an XML document containing
the vulnerability Feed:
Example HTTP GET response for a Feed:
HTTP/1.1 200 OK
Date: Fri, 24 Aug 2016 17:20:11 GMT
Content-Length: 2882
Content-Type: application/atom+xml;charset="utf-8"
<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="https://www.w3.org/2005/Atom"
xmlns:rolie="urn:ietf:params:xml:ns:rolie-1.0"
xml:lang="en-US">
<id>2a7e265a-39bc-43f2-b711-b8fd9264b5c9</id>
<title type="text">
Atom-formatted representation of
a Feed of XML vulnerability documents
</title>
<category
scheme="urn:ietf:params:rolie:category:information-type"
term="vulnerability"/>
<updated>2016-05-04T18:13:51.0Z</updated>
<link rel="self"
href="https://example.org/provider/public/vulns"/>
<link rel="service"
href="https://example.org/rolie/servicedocument"/>
<entry>
<rolie:format ns="urn:ietf:params:xml:ns:exampleformat"/>
<id>dd786dba-88e6-440b-9158-b8fae67ef67c</id>
<title>Sample Vulnerability</title>
<published>2015-08-04T18:13:51.0Z</published>
<updated>2015-08-05T18:13:51.0Z</updated>
<summary>A vulnerability issue identified by CVE-...</summary>
<content type="application/xml"
src="https://example.org/provider/vulns/123456/data"/>
</entry>
<entry>
<!-- ...another entry... -->
</entry>
</feed>
This Feed Document has two Atom Entries, one of which has been
elided. The first Entry illustrates an "atom:entry" element that
provides a summary of essential details about one particular
vulnerability. Based upon this summary information and the provided
Field, et al. Standards Track [Page 41]
RFC 8322 ROLIE February 2018
category information, a client may choose to do an HTTP GET request
on the content "src" attribute to retrieve the full details of the
vulnerability.
B.3. Entry Retrieval
This appendix provides a non-normative example of a client retrieving
a vulnerability as an Atom Entry.
Having retrieved the Feed of interest, the client may then decide,
based on the description and/or category information, that one of the
Entries in the Feed is of further interest. The client may retrieve
this vulnerability Entry by performing an HTTP GET operation on the
URL indicated by the "src" attribute of the "atom:content" element.
Example HTTP GET request for an Entry:
GET /provider/public/vulns/123456
Host: www.example.org
Accept: application/atom+xml;type=entry
The corresponding HTTP response would be an XML document containing
the Atom Entry for the vulnerability record:
Example HTTP GET response for an Entry:
HTTP/1.1 200 OK
Date: Fri, 24 Aug 2016 17:30:11 GMT
Content-Length: 713
Content-Type: application/atom+xml;type=entry;charset="utf-8"
<?xml version="1.0" encoding="UTF-8"?>
<entry xmlns="https://www.w3.org/2005/Atom"
xmlns:rolie="urn:ietf:params:xml:ns:rolie-1.0"
xml:lang="en-US">
<id>f63aafa9-4082-48a3-9ce6-97a2d69d4a9b</id>
<title>Sample Vulnerability</title>
<published>2015-08-04T18:13:51.0Z</published>
<updated>2015-08-05T18:13:51.0Z</updated>
<category
scheme="urn:ietf:params:rolie:category:information-type"
term="vulnerability"/>
<summary>A vulnerability issue identified by CVE-...</summary>
<rolie:format ns="urn:ietf:params:xml:ns:exampleformat"/>
<content type="application/xml"
src="https://example.org/provider/vulns/123456/data">
</content>
</entry>
Field, et al. Standards Track [Page 42]
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The example response above shows an XML document referenced by the
"src" attribute of the "atom:content" element. The client may
retrieve the document using this URL.
Acknowledgements
The authors gratefully acknowledge the valuable contributions of Tom
Maguire, Kathleen Moriarty, and Vijayanand Bharadwaj. These
individuals provided detailed review comments on earlier draft
versions of this document and made many suggestions that have helped
to improve this document.
The authors would also like to thank the MILE Working Group, the SACM
Working Group, and countless other people from both within the IETF
community and outside of it for their excellent review and effort
towards constructing this document.
Authors' Addresses
John P. Field
Pivotal Software, Inc.
625 Avenue of the Americas
New York, New York 10011
United States of America
Phone: (646)792-5770
Email: jfield@pivotal.io
Stephen A. Banghart
National Institute of Standards and Technology
100 Bureau Drive
Gaithersburg, Maryland 20877
United States of America
Phone: (301)975-4288
Email: stephen.banghart@nist.gov
David Waltermire
National Institute of Standards and Technology
100 Bureau Drive
Gaithersburg, Maryland 20877
United States of America
Email: david.waltermire@nist.gov
Field, et al. Standards Track [Page 43]