RFC 8600
Using Extensible Messaging and Presence Protocol (XMPP) for Security Information Exchange
Pages: 28
Proposed Standard
Proposed Standard
Part 1 of 2 – Pages 1 to 13
Internet Engineering Task Force (IETF) N. Cam-Winget, Ed. Request for Comments: 8600 S. Appala Category: Standards Track S. Pope ISSN: 2070-1721 Cisco Systems P. Saint-Andre Mozilla June 2019 Using Extensible Messaging and Presence Protocol (XMPP) for Security Information ExchangeAbstract
This document describes how to use the Extensible Messaging and Presence Protocol (XMPP) to collect and distribute security incident reports and other security-relevant information between network- connected devices, primarily for the purpose of communication among Computer Security Incident Response Teams and associated entities. To illustrate the principles involved, this document describes such a usage for the Incident Object Description Exchange Format (IODEF). 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/rfc8600.
Copyright Notice Copyright (c) 2019 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Service Discovery . . . . . . . . . . . . . . . . . . . . . . 8 6. Publish-Subscribe . . . . . . . . . . . . . . . . . . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14 8.1. Trust Model . . . . . . . . . . . . . . . . . . . . . . . 14 8.2. Threat Model . . . . . . . . . . . . . . . . . . . . . . 16 8.3. Countermeasures . . . . . . . . . . . . . . . . . . . . . 20 8.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 23 9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 24 10. Operations and Management Considerations . . . . . . . . . . 25 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 11.1. Normative References . . . . . . . . . . . . . . . . . . 25 11.2. Informative References . . . . . . . . . . . . . . . . . 27 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
1. Introduction
This document defines an architecture, i.e., "XMPP-Grid", as a method for using the Extensible Messaging and Presence Protocol (XMPP) [RFC6120] to collect and distribute security incident reports and other security-relevant information among network platforms, endpoints, and any other network-connected device, primarily for the purpose of communication among Computer Security Incident Response Teams and associated entities. In effect, this document specifies an Applicability Statement ([RFC2026], Section 3.2) that defines how to use XMPP for the exchange of security notifications on a controlled- access network among authorized entities. Among other things, XMPP provides a publish-subscribe service [XEP-0060] that acts as a broker, enabling control-plane functions by which entities can discover available information to be published or consumed. Although such information can take the form of any structured data (XML, JSON, etc.), this document illustrates the principles of XMPP-Grid with examples that use the Incident Object Description Exchange Format (IODEF) [RFC7970]. That is, while other security information formats can be shared using XMPP, this document uses IODEF as one such example format that can be published and consumed using XMPP.2. Terminology
This document uses XMPP terminology defined in [RFC6120] and [XEP-0060]. Because the intended audience for this document is those who implement and deploy security reporting systems, mappings are provided for the benefit of XMPP developers and operators. Broker: A specific type of controller containing control-plane functions; as used here, the term refers to an XMPP publish- subscribe service. Broker Flow: A method by which security incident reports and other security-relevant information are published and consumed in a mediated fashion through a Broker. In this flow, the Broker handles authorization of Consumers and Providers to Topics, receives messages from Providers, and delivers published messages to Consumers. Consumer: An entity that contains functions to receive information from other components; as used here, the term refers to an XMPP publish-subscribe Subscriber.
Controller: A component containing control-plane functions that
manage and facilitate information sharing or execute on security
functions; as used here, the term refers to an XMPP server, which
provides core message delivery [RFC6120] used by publish-subscribe
entities.
Node: The XMPP term for a Topic.
Platform: Any entity that connects to the XMPP-Grid in order to
publish or consume security-relevant information.
Provider: An entity that contains functions to provide information
to other components; as used here, the term refers to an XMPP
publish-subscribe Publisher.
Topic: A contextual information channel created on a Broker on which
messages generated by a Provider are propagated in real time to
one or more Consumers. Each Topic is limited to a specific type
and format of security data (e.g., IODEF namespace) and provides
an XMPP interface by which the data can be obtained.
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.
3. Architecture
The following figure illustrates the architecture of XMPP-Grid. +--------------------------------------+ | +--------------------------------------+ | | +--------------------------------------+ | | | | +-| | Platforms | +-| | +--------------------------------------+ / \ / \ / \ / C \ / \ / \ - o - - d - - - ||n||A | a |B | |C ||t|| | t | | | - r - - a - | | \ o / \ / | | \ l / \ / | | /|---------------------|\ | | /|----/ \--------| d |--|\ / / Controller \ ctrl | a | \ \ \ & Broker / plane | t | / \|----\ /--------| a |--|/ \|---------------------|/ | | / \ / \ | | / C \ / \ | | - o - - d - | | ||n||A | a |B | |C ||t|| | t | | | - r - - a - - - \ o / \ / \ / \ l / \ / \ / +------------------------------------+ | |-+ | Platforms | | | | |-+ +------------------------------------+ | | +------------------------------------+ | +------------------------------------+ Figure 1: XMPP-Grid Architecture Platforms connect to the Controller (XMPP server) to authenticate and then establish appropriate authorizations to be a Provider or Consumer of topics of interest at the Broker. The control-plane messaging is established through XMPP and is shown as "A" (control- plane interface) in Figure 1. Authorized Platforms can then share
data either through the Broker (shown as "B" in Figure 1) or, in some cases, directly (shown as "C" in Figure 1). This document focuses primarily on the Broker Flow for information sharing ("direct flow" interactions can be used for specialized purposes, such as bulk data transfer, but methods for doing so are outside the scope of this document).4. Workflow
Implementations of XMPP-Grid adhere to the following workflow: a. A Platform with a source of security data requests connection to the XMPP-Grid via a Controller. b. The Controller authenticates the Platform. c. The Platform establishes authorized privileges (e.g., privilege to publish and/or subscribe to one or more Topics) with a Broker. d. The Platform can publish security incident reports and other security-relevant information to a Topic, subscribe to a Topic, query a Topic, or perform any combination of these operations. e. A Provider unicasts its Topic updates to the Grid in real time through a Broker. The Broker handles replication and distribution of the Topic to Consumers. A Provider can publish the same or different data to multiple Topics. f. Any Platform on the Grid can subscribe to any Topic published to the Grid (as permitted by the authorization policy) and (as Consumers) will then receive a continual, real-time stream of updates from the Topics to which it is subscribed. The general workflow is summarized in the figure below.
+--------------+ +------------+ +---------------+ | IODEF Client | | Controller | | IODEF Service | | (Consumer) | | & Broker | | (Provider) | +--------------+ +------------+ +---------------+ | | | | Establish XMPP | | | Client Session | | | (RFC 6120) | | |--------------------->| | | | Establish XMPP | | | Client Session | | | (RFC 6120) | | |<------------------------| | | Request Topic Creation | | | (XEP-0060) | | |<------------------------| | | Topic Creation Success | | | (XEP-0060) | | |------------------------>| | Request Topic List | | | (XEP-0030) | | |--------------------->| | | Return Topic List | | | (XEP-0030) | | |<---------------------| | | | | | Query Each Topic | | | (XEP-0030) | | |--------------------->| | | Return Topic Data | | | Including Topic Type | | | (XEP-0030) | | |<---------------------| | | | | | Subscribe to IODEF | | | Topic (XEP-0060) | | |--------------------->| | | Subscription Success | | | (XEP-0060) | | |<---------------------| | | | Publish IODEF Incident | | | (XEP-0060) | | Receive IODEF |<------------------------| | Incident (XEP-0060) | | |<---------------------| | | | | Figure 2: IODEF Example Workflow
XMPP-Grid implementations MUST adhere to the mandatory-to-implement and mandatory-to-negotiate features as defined in [RFC6120]. Similarly, implementations MUST implement the publish-subscribe extension [XEP-0060] to facilitate the asynchronous sharing of information. Implementations SHOULD implement Service Discovery as defined in [XEP-0030] to facilitate the means to dynamically discover the available information and namespaces (Topics) to be published or consumed. Care should be taken with implementations if their deployments allow for a large number of Topics. The result set management as defined in [XEP-0059] SHOULD be used to allow the requesting entity to explicitly request Service Discovery result sets to be returned in pages or a limited size, if the discovery results are larger in size. Note that the control plane may optionally also implement [XEP-0203] to facilitate delayed delivery of messages to the connected consumer as described in [XEP-0060]. Since information may be timely and sensitive, capability providers should communicate to the Controller whether its messages can be cached for delayed delivery during configuration; such a function is out of scope for this document. The following sections provide protocol examples for the service discovery and publish-subscribe parts of the workflow.5. Service Discovery
Using the XMPP service discovery extension [XEP-0030], a Controller enables Platforms to discover what information can be consumed through the Broker and at which Topics. Platforms could use [XEP-0059] to restrict the size of the result sets the Controller returns in a Service Discovery response. As an example, the Controller at 'security-grid.example' might provide a Broker at 'broker.security-grid.example', which hosts a number of Topics. A Platform at 'xmpp-grid-client@mile-host.example' would query the Broker about its available Topics by sending an XMPP "disco#items" request to the Broker: <iq type='get' from='xmpp-grid-client@mile-host.example/2EBE702A97D6' to='broker.security-grid.example' id='B3C17F7B-B9EF-4ABA-B08D-805DA9F34626'> <query xmlns='http://jabber.org/protocol/disco#items'/> </iq>
The Broker responds with the Topics it hosts:
<iq type='result'
from='broker.security-grid.example'
to='xmpp-grid-client@mile-host.example/2EBE702A97D6'
id='B3C17F7B-B9EF-4ABA-B08D-805DA9F34626'>
<query xmlns='http://jabber.org/protocol/disco#items'>
<item node='NEA1'
name='Endpoint Posture Information'
jid='broker.security-grid.example'/>
<item node='MILEHost'
name='MILE Host Data'
jid='broker.security-grid.example'/>
</query>
</iq>
In order to determine the exact nature of each Topic (i.e., in order
to find Topics that publish incidents in the IODEF format), a
Platform would send an XMPP "disco#info" request to each Topic:
<iq type='get'
from='xmpp-grid-client@mile-host.example/2EBE702A97D6'
to='broker.security-grid.example'
id='D367D4ED-2795-489C-A83E-EAAFA07A0356'>
<query xmlns='http://jabber.org/protocol/disco#info'
node='MILEHost'/>
</iq>
The Broker responds with the "disco#info" description, which MUST include an XMPP data form [XEP-0004] with a 'pubsub#type' field that specifies the supported namespace (in this example, the IODEF namespace defined in [RFC7970]): <iq type='result' from='broker.security-grid.example' to='xmpp-grid-client@mile-host.example/2EBE702A97D6' id='D367D4ED-2795-489C-A83E-EAAFA07A0356'> <query xmlns='http://jabber.org/protocol/disco#info' node='MILEHost'> <identity category='pubsub' type='leaf'/> <feature var='http://jabber.org/protocol/pubsub'/> <x xmlns='jabber:x:data' type='result'> <field var='FORM_TYPE' type='hidden'> <value>http://jabber.org/protocol/pubsub#meta-data</value> </field> <field var='pubsub#type' label='Payload type' type='text-single'> <value>urn:ietf:params:xml:ns:iodef-2.0</value> </field> </x> </query> </iq> The Platform discovers the Topics by obtaining the Broker's response and obtaining the namespaces returned in the "pubsub#type" field (in the foregoing example, IODEF 2.0).6. Publish-Subscribe
Using the XMPP publish-subscribe extension [XEP-0060], a Consumer subscribes to a Topic, and a Provider publishes information to that Topic, which the Broker then distributes to all subscribed Consumers. First, a Provider would create a Topic as follows: <iq type='set' from='datasource@provider.example/F12C2EFC9BB0' to='broker.security-grid.example' id='A67507DF-2F22-4937-8D30-88D2F7DBA279'> <pubsub xmlns='http://jabber.org/protocol/pubsub'> <create node='MILEHost'/> </pubsub> </iq> Note: The foregoing example is the minimum protocol needed to create a Topic with the default node configuration on the XMPP publish- subscribe service specified in the 'to' address of the creation
request stanza. Depending on security requirements, the Provider might need to request a non-default configuration for the node; see [XEP-0060] for detailed examples. To also help with the Topic configuration, the Provider may also optionally include configuration parameters such as: <configure> <x xmlns='jabber:x:data' type='submit'> <field var='FORM_TYPE' type='hidden'> <value>http://jabber.org/protocol/pubsub#node_config</value> </field> <field var='pubsub#access_model'><value>authorize</value></field> <field var='pubsub#persist_items'><value>1</value></field> <field var='pubsub#send_last_published_item'> <value>never</value> </field> </x> </configure> The above configuration indicates the Topic is configured so that the Broker will a) explicitly approve subscription requests, b) persistently store all messages posted to the Topic, and c) not deliver the most recently published when an entity initially subscribes to the Topic. Please refer to [XEP-0060] for a more detailed description of this configuration and other available configuration options. Unless an error occurs (see [XEP-0060] for various error flows), the Broker responds with success: <iq type='result' from='broker.security-grid.example' to='datasource@provider.example/F12C2EFC9BB0' id='A67507DF-2F22-4937-8D30-88D2F7DBA279'/> Second, a Consumer would subscribe as follows: <iq type='set' from='xmpp-grid-client@mile-host.example/2EBE702A97D6' to='broker.security-grid.example' id='9C6EEE9E-F09A-4418-8D68-3BA6AF852522'> <pubsub xmlns='http://jabber.org/protocol/pubsub'> <subscribe node='MILEHost' jid='xmpp-grid-client@mile-host.example'/> </pubsub> </iq>
Unless an error occurs (see [XEP-0060] for various error flows), the Broker makes an appropriate authorization decision. If access is granted, it responds with success: <iq type='result' from='broker.security-grid.example' to='xmpp-grid-client@mile-host.example/2EBE702A97D6' id='9C6EEE9E-F09A-4418-8D68-3BA6AF852522'> <pubsub xmlns='http://jabber.org/protocol/pubsub'> <subscription node='MILEHost' jid='xmpp-grid-client@mile-host.example' subscription='subscribed'/> </pubsub> </iq> Third, a Provider would publish an incident to the Broker using the MILEHost Topic as follows: <iq type='set' from='datasource@provider.example/F12C2EFC9BB0' to='broker.security-grid.example' id='2A17D283-0DAE-4A6C-85A9-C10B1B40928C'> <pubsub xmlns='http://jabber.org/protocol/pubsub'> <publish node='MILEHost'> <item id='8bh1g27skbga47fh9wk7'> <IODEF-Document version="2.00" xml:lang="en" xmlns="urn:ietf:params:xml:ns:iodef-2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation= "http://www.iana.org/assignments/xml-registry/ schema/iodef-2.0.xsd"> <Incident purpose="reporting" restriction="private"> <IncidentID name="csirt.example.com">492382</IncidentID> <GenerationTime>2015-07-18T09:00:00-05:00</GenerationTime> <Contact type="organization" role="creator"> <Email> <EmailTo>contact@csirt.example.com</EmailTo> </Email> </Contact> </Incident> </IODEF-Document> </item> </publish> </pubsub> </iq>
(The payload in the foregoing example is from [RFC7970]; payloads for additional use cases can be found in [RFC8274].) The Broker would then deliver that incident report to all Consumers who are subscribed to the Topic: <message from='broker.security-grid.example' to='xmpp-grid-client@mile-host.example/2EBE702A97D6' id='37B3921D-4F7F-450F-A589-56119A88BC2E'> <event xmlns='http://jabber.org/protocol/pubsub#event'> <items node='MILEHost'> <item id='iah37s61s964gquqy47aksbx9453ks77'> <IODEF-Document version="2.00" xml:lang="en" xmlns="urn:ietf:params:xml:ns:iodef-2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation= "http://www.iana.org/assignments/xml-registry/ schema/iodef-2.0.xsd"> <Incident purpose="reporting" restriction="private"> <IncidentID name="csirt.example.com">492382</IncidentID> <GenerationTime>2015-07-18T09:00:00-05:00</GenerationTime> <Contact type="organization" role="creator"> <Email> <EmailTo>contact@csirt.example.com</EmailTo> </Email> </Contact> </Incident> </IODEF-Document> </item> </items> </event> </message> Note that [XEP-0060] uses the XMPP "<message />" stanza for delivery of content. To ensure that messages are delivered to the Consumer even if the Consumer is not online at the same time that the Publisher generates the message, an XMPP-Grid Controller MUST support "offline messaging" delivery semantics as specified in [RFC6121], the best practices of which are further explained in [XEP-0160].7. IANA Considerations
This document has no actions for IANA.
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