| MILE Working Group | J. Field |
| Internet-Draft | Pivotal |
| Intended status: Informational | S. Banghart |
| Expires: May 4, 2017 | D. Waltermire |
| NIST | |
| October 31, 2016 |
Resource-Oriented Lightweight Information Exchange
draft-ietf-mile-rolie-05
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 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.
The source for this draft is being maintained on GitHub. Suggested changes should be submitted as pull requests at <https://github.com/CISecurity/ROLIE>. Instructions are on that page as well. Editorial changes can be managed in GitHub, but any substantial issues need to be discussed on the MILE mailing list.
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 May 4, 2017.
Copyright (c) 2016 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.
This document defines a resource-oriented approach to security automation information sharing that follows the REST [REST] architectural style. In this approach, computer security resources are maintained in web-accessible repositories structured as Atom Syndication Format [RFC4287] Feeds. Representations of specific types of security automation information are categorized and organized into indexed Collections which may be requested by the consumer. As the set of resource Collections are forward facing, the consumer may search all available content for which they are authorized to view, and request the information resources which are desired. Through use of granular authentication and access controls, only authorized consumers may be permitted the ability to read or write to a given Feed. This approach is in contrast to, and meant to improve on, the traditional point-to-point messaging system, in which consumers must request individual pieces of information from a server following a triggering event. The point-to-point approach creates a closed system of information sharing that encourages duplication of effort and hinders automated security systems.
The goal of this document is to define a RESTful approach to security information communication with two primary intents: 1) increasing communication and sharing of incident reports, vulnerability assessments, configuration checklists, and other security automation information between providers and consumers; and 2) establishing a standardized communication system to support automated computer security systems.
In order to deal with the great variety in security automation information types and associated resource representations, this specification defines extension points that can be used to add support for new information types and associated resource representations by means of additional supplementary specification documents. This primary document is resource representation agnostic, and defines the core requirements of all implementations. An overview of the extension system is provided in Section 7.Those seeking to provide support for specific security automation information types should refer to the specification for that domain described by the IANA registry found in section 8.4.
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].
Definitions for some of the common computer security-related terminology used in this document can be found in Section 2 of [RFC5070].
The following terms are unqiue to this specification:
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:
Some sections of this specification are illustrated with fragments of a non-normative RELAX NG Compact schema [relax-NG]. However, the text of this specification provides the definition of conformance. Schema for the "http://www.w3.org/2007/app" and "http://www.w3.org/2005/Atom" namespaces appear in RFC5023 appendix B [RFC5023] and RFC4287 appendix B [RFC4287] respectively.
Information sharing is one of the core components of automating security processes. Vulnerabilities, configurations, software identification, security incidents, and patching 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 to sometimes global networks, and the inherent scaling issues of human-in-the-loop sharing become apparent, the need for automation and machine-to-machine communication becomes apparent.
Existing approaches to computer security information sharing often use message exchange patterns that are point-to-point. Sometimes, information that may be useful to share with multiple peers is only made available to peers after they have specifically requested it. Unfortunately, a sharing peer may not know, a priori, what information to request from another peer. Some existing systems provide a mechanism for unsolicited information requests, however, these reports are again sent point-to-point, and must be reviewed for relevance and then prioritized for action by the recipient, introducing additional latency.
In order to adequately combat evolving threats, computer security information resource providers should be able to share selected information proactively. Proactive sharing greatly aids knowledge dissemination, and improves response times and usability by allowing the consumer to choose which information is relevant to its needs.
For example, a security analyst can benefit by having the ability to search a comprehensive collection of attack indicators that have been published by a government agency, or by another member of a sharing consortium. The representation of each indicator may include links to the related resources, enabling an appropriately authenticated and authorized analyst to freely navigate the information space of indicators, incidents, vulnerabilities, and other computer security domain concepts as needed. In this way, an analyst can more effectively utilize the super set of information made publicly available.
Additionally, there is value in maintaining a repository of knowledge that can be queried by a new consumer, allowing this consumer to identify and retrieve any information that is relevant to its needs. In this way, the consumer can gain access to meaningful current and historic information, catching up to the knowledge level of its peers.
Consider the case of an automated endpoint management system attempting to proactively prevent software flaws and mis-configured software from compromising the security of the affected systems. During its full network sweep, the endpoint monitoring system would check each endpoint for outdated, vulnerable, and mis-configured software. This system would benefit from having access to not only the software vendor's list of vulnerabilities and configuration baselines, but also similar information discovered by other security researchers. An advanced system could even give back to this sharing consortium by sharing any relevant information discovered.
These capabilities support a federated collection of information repositories that can be queried and contributed to by an organization, further supporting automated security solutions.
Applying the REST architectural style to the problem domain of security information sharing involves exposing information of any relevant type as simple Web-addressable resources. Each provider maintains their own repository of data, with public and private sections as needed. Any producer or consumer can then discover these repositories, search for relevant Feeds, and pull information from them. By using this approach, an organization can more quickly and easily share relevant data representations with a much larger and potentially more diverse constituency. A consumer may leverage virtually any available HTTP user agent in order to make requests of the service provider. This improved ease of use enables more rapid adoption and broader participation, thereby improving security for everyone.
A key aspect of any RESTful Web service is the ability to provide multiple resource representations. For example, clients may request that a given resource representation be returned as XML, JSON, or in some other format. In order to enable backwards-compatibility and interoperability with existing implementations, the RESTful approach allows the provider to make differing formats available proactively, allowing the consumer to simply select the version that best suits them.
Finally, an important principle of the REST architectural style is the focus on hypermedia as the engine of application state (HATEOAS). Rather than the server maintaining conversational state for each client, the server will instead include a suitable set of hyperlinks in the resource representation that is returned to the client. The included hyperlinks provide the client with a specific set of permitted state transitions. Using these links the client may perform an operation, such as updating or deleting the resource representation. The client may also be provided with hypertext links that can be used to navigate to any related resource. For example, the resource representation for an object may contain links to the related resource(s). In this way, the server remains stateless with respect to a series of client requests.
This section describes a number of restrictions of and extensions to the Atom Publishing Protocol (AtomPub) [RFC5023] that define the use of that protocol 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 Atom Publishing Protocol specification [RFC5023] is helpful to understand the requirements in this section.
As described in RFC5023 section 8 [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 RFC5023 section 4.2 [RFC5023]):
Service
o- Workspace
| |
| o- Collection
| |
| o- IRI, categories, media types
|
o- Workspace
|
o- Collection
|
o- IRI, categories, media types
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 impose any restrictions on the number of Workspaces that may be in a Service Document or the specific Collections to be provided within a given Workspace.
The following restrictions are imposed on the use of the app:workspace element in ROLIE:
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. Atom Feed specific requirements are defined in section 6.1.
The following restrictions are imposed on the use of the app:collection element for ROLIE:
This specification requires that an implementation MUST publish an Atom Service Document that describes the set of security information sharing Collections that are provided by the repository.
The Service Document SHOULD be discoverable via the organization's Web home page or another well-known public resource. An example of this can be found in appendix B.1.
The Service Document SHOULD be located at the standardized location "https://{host:port}/rolie/servicedocument", where {host:port} is the authority portion of the URI. Dereferencing this URI MAY result in a redirect based on a HTTP 3xx status code to direct the client to the actual Service Document. This allows clients to have a well-known location to find a ROLIE service document, while giving implementations flexibility over how the service is deployed.
When deploying a Service Document for use by a closed consortium, the service document MAY also be digitally signed and/or encrypted. For example, consider XML Signature Syntax and Processing [xmldsig] and XML Encryption Syntax and Processing. [xmlenc]
As described in RFC5023 section 7 [RFC5023], a Category Document is an XML-based document format that allows a client to dynamically discover the Categories used within AtomPub Service Documents, and Atom Syndication Feed and Entry documents provided by a publisher. A Category Document consists of one or more app:categories elements that may each contain a number of app:collection elements.
A ROLIE implementation MUST publish an Category Document that describes the set of atom:category elements and associated terms used within the implemented repository.
ROLIE is intended to be handled with TLS. The following requirements have been derived from [RFC7589].
The most recent published version of TLS MUST be supported, and any mandatory-to-implement (MTI) cipher suites in that version MUST be supported as well.
The server MUST support certificate-based client authentication. The implementation MAY use any TLS cipher suite that supports mutual authentication.
During the TLS negotiation, the client MUST carefully examine the certificate presented by the server to determine if it meets the client’s expectations. Particularly, the client MUST check its understanding of the server hostname against the server’s identity as presented in the server Certificate message, in order to prevent man-in-the-middle attacks. Matching is performed according to the rules laid out in the Security Considerations section of [RFC4642].
If the match fails, the client MUST either ask for explicit user confirmation or terminate the connection and indicate the server’s identity is suspect. Additionally, clients MUST verify the binding between the identity of the servers to which they connect and the public keys presented by those servers. Clients SHOULD implement the algorithm in Section 6 of [RFC5280] for general certificate validation, but MAY supplement that algorithm with other validation methods that achieve equivalent levels of verification (such as comparing the server certificate against a local store of already-verified certificates and identity bindings). If the client has external information as to the expected identity of the server, the hostname check MAY be omitted.
The server MUST be capable of verifying the identity of the client with certificate-based authentication according to local policy to ensure that the incoming client request is legitimate before any configuration or state data is sent to or received from the client.
Implementations MUST support user authentication. User authentication MAY be enabled for specific Feeds.
Servers participating in an information sharing consortium and supporting interactive user logins by members of the consortium SHOULD support client authentication via a federated identity scheme (e.g., SAML 2.0).
This document does not mandate the use of any specific user authorization mechanisms. However, service implementers SHOULD provide appropriate authorization checking for all resource accesses, including individual Atom Entries, Atom Feeds, and Atom Service Documents.
The "/" resource MAY be provided for compatibility with existing deployments that are using Transport of Real-time Inter-network Defense (RID) Messages over HTTP/TLS [RFC6546]. If the "/" resource is supported the following behavior MUST be also supported:
If the "/" resource is unsupported, then a request for this resource MUST provide a 404 HTTP status code.
Clients MUST be capable of recognizing and processing any standard HTTP status code, as defined in [RFC5023] Section 5.
This section describes a number of restrictions of and extensions to the Atom Syndication Format [RFC4287] that define the use of that format in the context of a ROLIE-based solution. The normative requirements in this section are generally oriented towards content to be published to a ROLIE repository. An understanding of the Atom Syndication Format specification [RFC4287] is helpful to understand the requirements in this section.
As described in RFC4287 section 4.1.1 [RFC4287], an Atom Feed is an XML-based document format that describes a list of related information items, also known as a Collection. Each Feed document, represented using the atom:feed element, contains a collection of zero or more related information items individually called a "Member Entry" or "Entry".
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 an atom: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.
The following Atom Feed definition represents a stricter definition of the atom:feed element defined in RFC 4287 for use in a ROLIE 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*
}
An atom:feed can be categorized and can contain information from zero or more categories. In Atom the naming scheme and the semantic meaning of the terms used to identify an Atom category are application-defined.
The following restrictions are imposed on the use of the atom:category element when used in an atom:feed:
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 atom:feed MUST contain one or more atom:link elements with rel="service" and href attribute whose value is a IRI that points to an Atom Service Document associated with the atom:feed. When a client is presented with a Feed as its initial view into a repository, 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.
An atom: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. Based on RFC5005 section 3 [RFC5005], link elements SHOULD be included in all Feeds to support paging using the following link relation types:
For example:
<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
<id>b7f65304-b63b-4246-88e2-c104049c5fd7</id>
<title>Paged Feed</title>
<link rel="self" href="http://example.org/feedA?page=5"/>
<link rel="first" href="http://example.org/feedA?page=1"/>
<link rel="prev" href="http://example.org/feedA?page=4"/>
<link rel="next" href="http://example.org/feedA?page=6"/>
<link rel="last" href="http://example.org/feedA?page=10"/>
<updated>2012-05-04T18:13:51.0Z</updated>
<!-- remainder of feed 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 RFC5005 section 4 [RFC5005] to provide link-based state transitions for maintaining archiving of Feeds.
An atom: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.
The atom:updated element MUST be populated with the current time at the instant the Feed representation was last updated by adding, updating, or deleting an Entry; or changing any metadata for the Feed.
Each Entry in an Atom Feed, represented by the atom:entry element, describes a single information record, format, and type combination. 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.
atomEntry =
element atom:entry {
atomCommonAttributes,
(atomAuthor*
& atomCategory*
& atomContent
& atomContributor*
& atomId
& atomLink*
& atomPublished?
& atomRights?
& atomSource?
& atomSummary?
& atomTitle
& atomUpdated
& rolieFormat
& extensionElement*)
}
There MUST be exactly one atomContent element in the Entry. The 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
}
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 an IRI that can be dereferenced to retrieve the related content data.
Link relations can be included in an atom:entry to represent state transitions for the Entry.
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 or a different Feed. Such an alternate content representation can be indicated using an atom:link having a rel attribute with the value "alternate".
An atom: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.
As mentioned earlier, 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.
The rolie:format element is used to describe the data model used to express the information referenced in the atom:content element of an atom:entry. It 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.
There MUST be exactly one rolie:format element in an atom:entry. The 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 value MUST be an absolute or opaque URI. The resource identified by the URI need not be resolvable.
The rolie:format element MAY provide a "version" attribute that identifies the version of the format used for the related atom:content.
The rolie:format element MAY provide a "schema-location" element that is a URI that identifies a schema resource that can be used to validate the related atom:content.
The rolie:format element MAY provide a "schema-type" element, which is a mime type identifying the format of the schema resource identified by the "schema-location" attribute.
If an Entry is ever shared as a standalone resource, separate from its containing Feed, then the following additional requirements apply:
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, link relations, as well as, use of specific data formats supporting a given information type term.
The atom:category element, defined in RFC 4287 section 4.2.2 [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 RFC 5023 section 7 [RFC5023], provides a mechanism for an Atom repository to make discoverable the atom:category terms and allowed values used by a given repository.
ROLIE further defines the use of the existing Atom extension category mechanism by allowing ROLIE specific category extensions to be registered with IANA, and additionally has assigned the "urn:ietf:params:rolie:category:information-type" category scheme that has special meaning for implementations of ROLIE. This allows category scheme namespaces to be managed in a more consistent way, allowing for greater interoperability between content producers and consumers.
Use of the "atom:category" element is discussed in the following subsections.
The atom:category element can be used for characterizing a ROLIE Resource. As discussed earlier in this document, 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 provided by multiple organizations with different semantic meaning.
To further differentiate category types used in ROLIE, an IANA sub-registry has been established for ROLIE protocol parameters to support the registration of new category "scheme" attribute values by ROLIE extension specifications. Use of this extension point is discussed in section 8.3.
A ROLIE specific extension point is provided through the atom:category "scheme" value "urn:ietf:params:rolie:category:information-type". This value is a Uniform Resource Name (URN) [RFC2141] 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 Section 8.4. Through this mechanism a given security automation information type can be used to:
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]. Notional examples of information types include:
This is a short list to inspire new engineering of information type extensions that support the automation of security processes.
This document does not specific 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 Security Resource Information Type registry defined in section 8.4.
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.
This document uses several link relations defined in the IANA Link Relation Types registry. Additional link relations can be registered in this registry to allow new relationships to be represented in ROLIE according to RFC 4287 section 4.2.7.2 [RFC4287]. Based on the preceding reference, if the link relation is too specific or limited in the intended use, an absolute IRI can be used in lieu of registering a new simple name with IANA.
This document has a number of IANA considerations described in the following subsections.
This document uses URNs to describe XML namespaces and XML schemas conforming to a registry mechanism described in [RFC3688].
IANA has added an entry to the "IETF URN Sub-namespace for Registered Protocol Parameter Identifiers" registry located at <http://www.iana.org/assignments/params/params.xml#params-1> as per RFC3553 [RFC3553].
The entry is as follows:
A new top-level registry has been created, entitled "Resource Oriented Lightweight Information Exchange (ROLIE) Parameters". [TO BE REMOVED: This registration should take place at the following location: https://www.iana.org/assignments/rolie]
In this top-level registry, a sub-registry entitled "ROLIE URN Parameters" has been created. Registration in this repository is via the Specification Required policy [RFC5226]. Designated Expert reviews should be routed through the MILE WG mailing list. Failing this, the Designated Expert will be assigned by the IESG.
Each entry in this sub-registry must record the following fields:
This repository has the following initial values:
| Name | Extension IRI | Reference | Sub-Registry |
|---|---|---|---|
| category:information-type | urn:ietf:params:rolie:category:information-type | This document, Section 9.4 | [TO BE REMOVED: This registration should take place at the following location: https://www.iana.org/assignments/rolie/category/information-type] |
A new sub-registry has been created to store ROLIE information type values.
This document defines a resource-oriented approach for lightweight information exchange using HTTP over TLS, the Atom Syndication Format, and the Atom Publishing Protocol. As such, implementers must understand the security considerations described in those specifications. All that follows is guidance, more specific instruction is out of scope for this document and will be located in a dedicated informational document.
All security measures SHOULD be enforced at the source, that is, a provider SHOULD NOT return any Feed content or member Entry content for which the client identity has not been specifically authenticated, authorized, and audited.
The approach described herein is based upon all policy enforcements being implemented at the point when a resource representation is created. As such, producers sharing cyber security information using this specification must take care to authenticate their HTTP clients using a suitably strong user authentication mechanism. Sharing communities that are exchanging information on well-known indicators and incidents for purposes of public education may choose to rely upon HTTP Authentication or similar. 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. In general, trust in the sharing consortium will depend upon the members maintaining adequate user authentication mechanisms.
Collaborating consortiums may benefit from the adoption of a federated identity solution, such as those based upon SAML-core [SAML-core], 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 CSIRT, 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 RBAC and/or ABAC, as embodied in 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.
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, e.g. the <RIDPolicy> element in the RID schema. Refer to RFC6545 section 9 for more information.
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.
Adoption of the information sharing approach described in this document will enable users to more easily perform correlations across separate, and potentially unrelated, cyber security 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 cyber security 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 account provisioning time. 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.
The authors gratefully acknowledge the valuable contributions of Tom Maguire, Kathleen Moriarty, and Vijayanand Bharadwaj. These individuals provided detailed review comments on earlier drafts, and made many suggestions that have helped to improve this document.
| [RFC2141] | Moats, R., "URN Syntax", RFC 2141, DOI 10.17487/RFC2141, May 1997. |
| [RFC3444] | Pras, A. and J. Schoenwaelder, "On the Difference between Information Models and Data Models", RFC 3444, DOI 10.17487/RFC3444, January 2003. |
| [I-D.ietf-mile-rfc5070-bis] | Danyliw, R., "The Incident Object Description Exchange Format v2", Internet-Draft draft-ietf-mile-rfc5070-bis-26, October 2016. |
| [RFC5234] | Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008. |
| [xmldsig] | Bartel, M., Boyer, J., Fox, B., LaMacchia, B. and E. Simon, "XML Signature Syntax and Processing (Second Edition)", June 2008. |
| [xmlenc] | Imamura, T., Dillaway, B. and E. Simon, "XML Encryption Syntax and Processing", December 2002. |
| [XACML] | Rissanen, E., "eXtensible Access Control Markup Language (XACML) Version 3.0", August 2010. |
| [REST] | Fielding, R., "Architectural Styles and the Design of Network-based Software Architectures", 2000. |
This appendix is informative.
The Relax NG schema below defines the rolie:format element.
# -*- rnc -*-
# RELAX NG Compact Syntax Grammar for the rolie:format element
namespace rolie = "urn:ietf:params:xml:ns:rolie-1.0"
namespace atom = "http://www.w3.org/2005/Atom"
# rolie:format
rolieFormat =
element rolie:format {
atom:atomCommonAttributes,
attribute ns { atom:atomURI },
attribute version { text } ?,
attribute schema-location { atom:atomURI } ?,
attribute schema-type { atom:atomMediaType } ?,
empty
}
This section 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 clients or other authorized parties to determine what specific information the provider makes available to the community. While the service document is at a required location, the service document could also be made available at any well known location, such as via 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 Feed Collections that are provided by the provider.
Example HTTP GET response:
HTTP/1.1 200 OK
Date: Fri, 24 Aug 2012 17:09:11 GMT
Content-Length: 570
Content-Type: application/atomsvc+xml;charset="utf-8"
<?xml version="1.0" encoding="UTF-8"?>
<service xmlns="http://www.w3.org/2007/app"
xmlns:atom="http://www.w3.org/2005/Atom">
<workspace>
<atom:title type="text">Vulnerabilities</atom:title>
<collection href="http://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 this server provides one workspace, named "Vunerabilities". Within that workspace, the producer makes one Feed Collection available.
A server may also offer a number of different Feeds, each containing different types of security automation information. In the following example, the Feeds have been categorized. This categorization will help the clients to decide which Feeds will meet their needs.
HTTP/1.1 200 OK
Date: Fri, 24 Aug 2012 17:10:11 GMT
Content-Length: 1912
Content-Type: application/atomsvc+xml;charset="utf-8"
<?xml version="1.0" encoding='utf-8'?>
<service xmlns="http://www.w3.org/2007/app"
xmlns:atom="http://www.w3.org/2005/Atom">
<workspace>
<atom:title>Public Security Information Sharing</atom:title>
<collection
href="http://example.org/provider/public/vulns">
<atom:title>Public Vulnerabilities</atom:title>
<link rel="service"
href="www.example.com/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="http://example.org/provider/private/vulns">
<atom:title>Incidents</atom:title>
<link rel="service"
href="www.example.com/rolie/servicedocument">
<categories fixed="yes">
<atom:category
scheme="urn:ietf:params:rolie:category:information-type"
term="incidents"/>
</categories>
</collection>
</workspace>
</service>
In this example, the provider is making available a total of two Feed Collections, organized into two different workspaces. The first workspace contains a Feed consisting of publicly available software vulnerabilities. The second workspace provides one additional vulnerability Feed, for use by a private sharing consortium. An appropriately authenticated and authorized client may then proceed to make GET requests for one or more of these Feeds. The publicly provided incident information may be accessible with or without authentication. However, users accessing the Feed targeted to the private sharing consortium would be expected to authenticate, and appropriate authorization policies would subsequently be enforced by the Feed provider.
This section provides a non-normative example of a client retrieving an incident Feed.
Having discovered the available security information sharing Feeds, a client who is a member of the general public may be interested in receiving the Feed of public vulnerabilities. The client may retrieve this Feed by performing an HTTP GET operation on the indicated URL.
Example HTTP GET request for a Feed:
GET /provider/vulns Host: www.example.org Accept: application/atom+xml
The corresponding HTTP response would be an XML document containing the incidents Feed:
Example HTTP GET response for a Feed:
HTTP/1.1 200 OK
Date: Fri, 24 Aug 2012 17:20:11 GMT
Content-Length: 2882
Content-Type: application/atom+xml;type=feed;charset="utf-8"
<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom"
xml:lang="en-US">
<id>http://www.example.org/provider/vulns</id>
<title type="text">
Atom formatted representation of
a feed of XML incident documents
</title>
<atom:category
scheme="urn:ietf:params:rolie:category:information-type"
term="vulnerability"/>
<updated>2012-05-04T18:13:51.0Z</updated>
<link rel="self" href="http://example.org/provider/vulns" />
<link rel="service"
href="http://example.org/rolie/servicedocument"/>
<entry>
<rolie:format ns="urn:ietf:params:xml:ns:exampleformat"/>
<id>
http://www.example.org/provider/vulns/123456
</id>
<title>Sample Incident</title>
<published>2014-08-04T18:13:51.0Z</published>
<updated>2014-08-05T18:13:51.0Z</updated>
<summary>A short description of this resource</summary>
<content type="application/xml"
src="http://www.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 completed Entry illustrates an Atom <entry> element that provides a summary of essential details about one particular incident. Based upon this summary information and the provided category information, a client may choose to do an HTTP GET operation to retrieve the full details of the incident. This example exemplifies the benefits a RESTful alternative has to traditional point-to-point messaging systems.
This section provides a non-normative example of a client retrieving an incident 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 incident Entry by performing an HTTP GET operation on the indicated URL.
Example HTTP GET request for an Entry:
GET /provider/vulns/123456 Host: www.example.org Accept: application/atom+xml
The corresponding HTTP response would be an XML document containing the incident:
Example HTTP GET response for an Entry:
HTTP/1.1 200 OK
Date: Fri, 24 Aug 2012 17:30:11 GMT
Content-Length: 4965
Content-Type: application/atom+xml;type=entry;charset="utf-8"
<?xml version="1.0" encoding="UTF-8"?>
<entry>
<id>http://www.example.org/provider/vulns/123456</id>
<title>Sample Incident</title>
<published>2012-08-04T18:13:51.0Z</published>
<updated>2012-08-05T18:13:51.0Z</updated>
<atom:category
scheme="urn:ietf:params:rolie:category:information-type"
term="incident"/>
<summary>A short description of this incident resource</summary>
<rolie:format ns="urn:ietf:params:xml:ns:exampleformat"/>
<content type="application/xml"
src="http://www.example.org/provider/vulns/123456/data">
</content>
</entry>
As can be seen in the example response, above, an XML document is linked to in the attributes of the Atom <content> element. The client may now process the XML document as needed.
Note also that, as described previously, the content of the Atom <category> element is application-defined. The Atom categories have been assigned based on the IANA table content model.
Finally, it should be noted that in order to optimize the client experience, and avoid an additional round trip, a Feed provider may choose to include certain Entry elements inline, as part of the Feed document. That is, an Atom <entry> element within a Feed document may contain arbitrary non-required Atom elements as children. In this case, the client will receive the more explicit information on entries from within the Feed. The decision of whether to include extra Entry elements inline or to include it as a link is a design choice left to the Feed provider (e.g. based upon local environmental factors such as the number of entries contained in a Feed, the available network bandwidth, the available server compute cycles, the expected client usage patterns, etc.).
Changes in draft-ietf-mile-rolie-04 since draft-ietf-mile-rolie-04 version, July 8, 2016 to October 31, 2016
Changes made in draft-ietf-mile-rolie-03 since draft-ietf-mile-rolie-02 version, May 27, 2016 to July 8, 2015
Changes made in draft-ietf-mile-rolie-02 since draft-field-mile-rolie-01 version, December, 2015 to May 27, 2016:
Changes made in draft-ietf-mile-rolie-01 since draft-field-mile-rolie-02 version, August 15, 2013 to December 2, 2015: