RFC 6545
Real-time Inter-network Defense (RID)
Internet Engineering Task Force (IETF) K. Moriarty Request for Comments: 6545 EMC Obsoletes: 6045 April 2012 Category: Standards Track ISSN: 2070-1721 Real-time Inter-network Defense (RID)Abstract
Security incidents, such as system compromises, worms, viruses, phishing incidents, and denial of service, typically result in the loss of service, data, and resources both human and system. Service providers and Computer Security Incident Response Teams need to be equipped and ready to assist in communicating and tracing security incidents with tools and procedures in place before the occurrence of an attack. Real-time Inter-network Defense (RID) outlines a proactive inter-network communication method to facilitate sharing incident-handling data while integrating existing detection, tracing, source identification, and mitigation mechanisms for a complete incident-handling solution. Combining these capabilities in a communication system provides a way to achieve higher security levels on networks. Policy guidelines for handling incidents are recommended and can be agreed upon by a consortium using the security recommendations and considerations. This document obsoletes RFC 6045. 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 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6545.
Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.Table of Contents
1. Introduction ....................................................3 1.1. Changes from RFC 6045 ......................................5 1.2. Normative and Informative ..................................6 1.3. Terminology ................................................7 2. Characteristics of Incidents ....................................7 3. Communication between CSIRTs and Service Providers ..............8 3.1. Inter-Service-Provider RID Messaging ......................10 3.2. RID Communication Topology ................................12 4. Message Formats ................................................13 4.1. RID Data Types ............................................13 4.1.1. Boolean ............................................13 4.2. RID Message Types .........................................14 5. IODEF-RID Schema ...............................................15 5.1. RIDPolicy Class ...........................................17 5.1.1. ReportSchema .......................................23 5.2. RequestStatus .............................................26 5.3. IncidentSource ............................................28 5.4. RID Name Spaces ...........................................29 5.5. Encoding ..................................................29 5.6. Including IODEF or Other XML Documents ....................29 5.6.1. Including XML Documents in RID .....................30 6. RID Messages ...................................................31 6.1. Request ...................................................31 6.2. Acknowledgement ...........................................33 6.3. Result ....................................................34 6.4. Report ....................................................36 6.5. Query .....................................................38 7. RID Communication Exchanges ....................................39 7.1. Upstream Trace Communication Flow .........................40 7.1.1. RID TraceRequest Example ...........................43 7.1.2. Acknowledgement Message Example ....................47
7.1.3. Result Message Example .............................47
7.2. Investigation Request Communication Flow ..................50
7.2.1. Investigation Request Example ......................51
7.2.2. Acknowledgement Message Example ....................53
7.3. Report Communication Flow .................................54
7.3.1. Report Example .....................................54
7.4. Query Communication Flow ..................................56
7.4.1. Query Example ......................................57
8. RID Schema Definition ..........................................58
9. Security Requirements ..........................................62
9.1. XML Digital Signatures and Encryption .....................62
9.2. Message Transport .........................................66
9.3. Public Key Infrastructure .................................67
9.3.1. Authentication .....................................68
9.3.2. Multi-Hop Request Authentication ...................69
9.4. Consortiums and Public Key Infrastructures ................70
9.5. Privacy Concerns and System Use Guidelines ................71
9.6. Sharing Profiles and Policies .............................76
10. Security Considerations .......................................77
11. Internationalization Issues ...................................77
12. IANA Considerations ...........................................78
13. Summary .......................................................80
14. References ....................................................80
14.1. Normative References .....................................80
14.2. Informative References ...................................82
Appendix A. Acknowledgements ......................................84
1. Introduction
Organizations require help from other parties to identify incidents,
mitigate malicious activity targeting their computing resources, and
to gain insight into potential threats through the sharing of
information. This coordination might entail working with a service
provider (SP) to filter attack traffic, working with an SP to resolve
a configuration issue that is unintentionally causing problems,
contacting a remote site to take down a bot network, or sharing
watch-lists of known malicious IP addresses in a consortium. The
term "SP" is to be interpreted as any type of service provider or
Computer Security Incident Response Team (CSIRT) that may be involved
in RID communications.
Incident handling involves the detection, reporting, identification,
and mitigation of an incident, whether it be a benign configuration
issue, IT incident, an infraction to a service level agreement (SLA),
system compromise, socially engineered phishing attack, or a denial-
of-service (DoS) attack, etc. When an incident is detected, the
response may include simply filing a report, notification to the
source of the incident, a request to an SP for resolution/mitigation,
or a request to locate the source. One of the more difficult cases is that in which the source of an attack is unknown, requiring the ability to trace the attack traffic iteratively upstream through the network for the possibility of any further actions to take place. In cases when accurate records of an active session between the target or victim system and the source or attacking system are available, the source is easy to identify. Real-time inter-network defense (RID) outlines a proactive inter- network communication method to facilitate sharing incident-handling data while integrating existing detection, tracing, source identification, and mitigation mechanisms for a complete incident handling solution. RID provides a secure method to communicate incident information, enabling the exchange of Incident Object Description and Exchange Format (IODEF) [RFC5070] Extensible Markup Language (XML) documents. RID considers security, policy, and privacy issues related to the exchange of potentially sensitive information, enabling SPs or organizations the options to make appropriate decisions according to their policies. RID includes provisions for confidentiality, integrity, and authentication. The data in RID messages is represented in an XML [XML1.0] document using the IODEF and RID. By following this model, integration with other aspects for incident handling is simplified. Methods are incorporated into the communication system to indicate what actions need to be taken closest to the source in order to halt or mitigate the effects of the incident or attack at hand. RID is intended to provide a method to communicate the relevant information between CSIRTs while being compatible with a variety of existing and possible future detection-tracing and response approaches. Incidents may be extended to include Information Technology (IT) incidents, where RID enables the communication between or within providers for non- security IT incidents. Security and privacy considerations are of high concern since potentially sensitive information may be passed through RID messages. RID messaging takes advantage of XML security, privacy, and policy information set in the RID schema. The RID schema defines communication-specific metadata to support the communication of IODEF documents for exchanging or tracing information regarding incidents. RID messages are encapsulated for transport, which is defined in a separate document [RFC6546]. The authentication, integrity, and authorization features that RID and RID transport offer are used to achieve a necessary level of security. Coordinating with other CSIRTs is not strictly a technical problem. There are numerous procedural, trust, and legal considerations that might prevent an organization from sharing information. RID provides
information and options that can be used by organizations who must then apply their own policies for sharing information. Organizations must develop policies and procedures for the use of the RID protocol and IODEF.1.1. Changes from RFC 6045
This document contains the following changes with respect to its predecessor [RFC6045]: o This document is Standards Track, while [RFC6045] was published as Informational. o This document obsoletes [RFC6045] and moves it to Historic status. o This document refers to the updated RID transport specification [RFC6546], where appropriate. o Edits reflected in this updated version of RID are primarily improvements to the informational descriptions. The descriptions have been updated to clarify that IODEF and RID can be used for all types of incidents and are not limited to network security incidents. The language has been updated to change the focus from attacks to incidents, where appropriate. The term "network provider" has been replaced with the more generic term of "service provider". Several introductory informational sections have been removed as they are not necessary for the implementation of the protocol. The sections include: * 1.3. Attack Types and RID Messaging, * 2. RID Integration with Network Provider Technologies, * 3.1. Integrating Trace Approaches, and * 3.2. Superset of Packet Information for Traces. o An option for a star topology has been included in an informational section to meet current use-case requirements of those who provide reports on incident information. o The schema version was incremented. The schema has changed to include IODEF [RFC5070] enveloped in RID in the RIDPolicy class using the new ReportSchema class, to include one verified erratum, to include additional enumerations in the Justification attribute, to remove the AcrossNationalBoundaries region enumeration, to add the DataWithHandlingRequirements enumeration in TrafficTypes, and to change the name of the RequestAuthorization MsgType to
Acknowledgement. Additional text has been provided to clarify
definitions of enumerated values for some attributes. The
RequestAuthorization name was replaced with Acknowledgement to
more accurately represent the function of that message type. Text
was clarified to note the possible use of this message in response
to Query and Report messages. The attributes were fixed in the
schema to add 'lang' at the RID class level for language support.
o The TraceRequest and Investigation messages have been collapsed
into a single message with the requirement to set the MsgType
according to the functionality required for automation. The
message descriptions were identical with the exception of the
MsgType, which remains an exception depending on the desired
function. Since both of the enumerations for MsgType are each a
Request, 'Investigation' is now 'InvestigationRequest'. Content
may vary within the IODEF document for the type of Request
specified.
o The IncidentQuery message description name and MsgType enumeration
value in the schema have been changed to the more generic name of
'Query'.
o Guidance has been improved to ensure consistent implementations
and use of XML encryption to provide confidentiality based on data
markers, specifically the iodef:restriction attribute in the IODEF
and IODEF-RID schemas. The attribute may also be present in IODEF
extension schemas, where the guidance also applies. Additional
guidance and restrictions have been added for XML requirements.
o All of the normative text from the Security Considerations section
has been moved to a new section, Security Requirements.
o The order in which the RID schema is presented in Section 5 has
been changed to match the order in the IODEF-RID schema.
o Additional text has been provided to explain the content and
interactions between entities in the examples.
o Additional references have been provided to improve
interoperability with stricter guidance on the use of XML digital
signatures and encryption.
1.2. Normative and Informative
Sections 1, 2, 3, and 12 provide helpful background information and
considerations. RID systems participating in a consortium are
REQUIRED to fully implement Sections 4, 5, 6, 7, 8, 9, 10, and 11 to
prevent interoperability concerns.
1.3. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].2. Characteristics of Incidents
An incident may be defined as a benign configuration issue, IT incident, an infraction to a service level agreement (SLA), system compromise, a worm or Trojan infection, or a single- or multiple- source denial-of-service attack. The goal of tracing a security incident may be to identify the source or to find a point on the network as close to the origin of the incident as possible. Incident tracing can be used to identify the source(s) of an attack in order to halt or mitigate the undesired behavior or to correct an identified issue. RID messages can be communicated between entities to report or investigate any type of incident and allow for actions to be taken when the source of the incident or a point closer to the source is known or has been identified. Methods to accomplish mitigation may include remediation of a configuration issue, filtering or rate-limiting the traffic close to the source, or taking the host or network offline. Care must also be taken to ensure that the systems involved in the RID communications are not abused and to use proper analysis in determining if attack traffic is, in fact, attack traffic at each SP involved in the investigation. Investigating security incidents can be a difficult task since attackers go to great lengths to obscure their identity. In the case of a security incident, the true source might be identified through an existing established connection to the attacker's point of origin. However, the attacker may not connect to the compromised system for a long period of time after the initial compromise or may access the system through a series of compromised hosts spread across the network. Other methods of obscuring the source may include targeting the host with the same attack from multiple sources using both valid and spoofed source addresses. This tactic can be used to compromise a machine and leave the difficult task of locating the true origin for the administrators. Attackers use many techniques, which can vary between individuals or even organized groups of attackers. Through analysis, the techniques may be grouped into indicators of compromise to be shared via IODEF and RID, further assisting with the improvement of detection capabilities. Security incidents, including distributed denial-of-service (DDoS) attacks, can be difficult or nearly impossible to trace because of the nature of the attack. Some of the difficulties in investigating attacks include the following: o the incident or attack originates from multiple sources;
o the incident may leverage social-engineering techniques or other
methods to gain access to resources and intellectual property
using what appears to be legitimate access methods such as
outbound web sessions from user systems;
o the attack may include various types of traffic meant to consume
server resources, such as a SYN flood attack without a significant
increase in bandwidth utilization;
o the type of traffic could include valid destination services,
which cannot be blocked since they are essential services to
business, such as DNS servers at an SP or HTTP requests sent to an
organization connected to the Internet;
o the attack may utilize varying types of packets including TCP,
UDP, ICMP, or other IP protocols;
o the attack may be from "zombies" or large botnets, which then
require additional searches to locate a controlling server as the
true origin of the attack;
o the attack may use a very small number of packets from any
particular source, thus making a trace after the fact nearly
impossible;
o the indicators of a compromise may be difficult to detect.
If the source(s) of an incident cannot be determined from IP address
information, it may be possible to trace the traffic based on
characteristics of the incident such as tracing the increased
bandwidth utilization or the type of packets seen by the client. In
the case of packets with spoofed source addresses, it is not a
trivial task to identify the source of an attack.
IODEF, any extensions to IODEF, and RID can be used to detail an
incident, characteristics of the incident (as it evolves), the
incident history, and communications of the incident to facilitate
the resolution and reporting of the incident.
3. Communication between CSIRTs and Service Providers
Expediting the communication between CSIRTs and SPs is essential when
responding to a security-related incident, which may cross network
access points between service providers. As a result of the urgency
involved in this inter-service-provider security incident
communication, there must be an effective system in place to
facilitate the interaction. This communication policy or method
should involve multiple means of communication to avoid a single
point of failure. Email is one way to transfer information about the incident, packet traces, etc. However, email may not be received in a timely fashion or be acted upon with the same urgency as a phone call or other communication mechanism like RID. A technical solution to trace traffic across a single SP may include homegrown or commercial systems for which RID messaging must accommodate the input requirements. The incident-handling system used on the SP's backbone by the CSIRT to coordinate the trace across the single network requires a method to accept, process, and relay RID messages to the system, as well as to wait for responses from the system to continue the RID request process as appropriate. In this scenario, each service provider maintains its own system capable of communicating via RID and integrates with a management station used for monitoring and analysis. An alternative for providers lacking sufficient resources may be to have a neutral third party with access to the provider's network resources who could be used to perform the incident-handling functions. This could be a function of a central organization operating as a CSIRT for countries as a whole or within a consortium that may be able to provide centralized resources. Consortiums could consist of a federation or a group of service providers or CSIRTs that agrees to participate in the RID communication protocol with an agreed-upon policy and communication protocol facilitating the secure transport of IODEF-RID XML documents. Transport for RID messages is specified in [RFC6546]. One goal of RID is to prevent the need to permit access to other networks' equipment. RID provides a standard messaging mechanism to enable the communication of incident-handling information to other providers in a consortium or in neighboring networks. The third party mentioned above may be used in this technical solution to assist in facilitating incident handling and possibly traceback through smaller providers. The RID messaging mechanism may be a logical or physical out-of-band network to ensure that the communication is secure and unaffected by the state of the network under attack. The two management methods would accommodate the needs of larger providers to maintain full management of their network, and the third-party option could be available to smaller providers who lack the necessary human resources to perform incident-handling operations. The first method enables the individual providers to involve (via a notification and alerting system) their network operations staff to authorize the continuance of a trace or other necessary response to a RID communication request through their network.
The network used for the communication should consist of out-of-band or protected channels (direct communication links) or encrypted channels dedicated to the transport of RID messages. The communication links would be direct connections (virtual or physical) between peers who have agreed-upon use and abuse policies through a consortium. Consortiums might be linked through policy comparisons and additional agreements to form a larger web or iterative network of peers that correlates to the traffic paths available over the larger web of networks or is based on regions and logical groups. Contact information, IP addresses of RID systems, and other information must be coordinated between bilateral peers by a consortium and may use existing databases, such as the routing arbiter. The security, configuration, and Confidence rating schemes of the RID messaging peers must be negotiated by peers and must meet certain overall requirements of the fully connected network (Internet, government, education, etc.) through the peering and/or a consortium-based agreement. RID messaging established with clients of an provider may be negotiated in a contract as part of a value-added service or through a service level agreement (SLA). Further discussion is beyond the scope of this document and may be more appropriately handled in peering or service level agreements. Procedures for incident handling need to be established and well known by anyone that may be involved in incident response. The procedures should also contain contact information for internal escalation procedures, as well as for external assistance groups such as a CSIRT, CERT Coordination Center (CERT/CC), Global Information Assurance Certification (GIAC), and the U.S. Federal Bureau of Investigations (FBI) or other assisting government organization in the country of the investigation.3.1. Inter-Service-Provider RID Messaging
RID provides a protocol and format that ensures interoperability between vendors for the implementation of an incident messaging mechanism. The messages should meet several requirements in order to be meaningful as they traverse multiple networks. RID provides the framework necessary for communication between networks involved in the incident handling, possible traceback, and mitigation of a security incident. Several message types described in Section 4.2 are necessary to facilitate the handling of a security incident. The message types include the Report, Query, Request, Acknowledgement, and Result message. The Report message is used when an incident is to be filed on a RID system or associated database, where no further action is required.
A Query message is used to request information on a particular
incident. A Request message with options set to 'TraceRequest' is
used when the source of the traffic may have been spoofed. In that
case, each SP in the upstream path who receives this Request will
issue a trace across the network to determine the upstream source of
the traffic. The Acknowledgement and Result messages are used to
communicate the status and result of a Request. The Request message
with options set to 'InvestigationRequest' may be sent to any party
assisting in an incident investigation. The InvestigationRequest
leverages the bilateral relationships or a consortium's
interconnections to mitigate or stop problematic traffic close to the
source. Routes could determine the fastest path to a known source IP
address in the case of an InvestigationRequest. A Request message
(set to 'TraceRequest' or 'InvestigationRequest') sent between RID
systems to stop traffic at the source through a bordering network
requires the information enumerated below:
1. Enough information to enable the network administrators to make a
decision about the importance of continuing the trace.
2. The incident or IP packet information needed to carry out the
trace or investigation.
3. Contact information of the origin of the RID communication. The
contact information could be provided through the Autonomous
System Number (ASN) [RFC1930] or Network Information Center (NIC)
handle information listed in the Registry for Internet Numbers or
other Internet databases.
4. Network path information to help prevent any routing loops
through the network from perpetuating a trace. If a RID system
receives a Request with MsgType set to 'TraceRequest' that
contains its own information in the path, the trace must cease
and the RID system should generate an alert to inform the network
operations staff that a tracing loop exists.
5. A unique identifier for a single attack. This identifier should
be used to correlate traces to multiple sources in a DDoS attack.
Use of the communication network and the RID protocol must be for
pre-approved, authorized purposes only. It is the responsibility of
each participating party to adhere to guidelines set forth in both a
global use policy established through the peering agreements for each
bilateral peer or agreed-upon consortium guidelines. The purpose of
such policies is to avoid abuse of the system; the policies shall be
developed by a consortium or participating entities. The global
policy may be dependent on the domain it operates under; for example,
a government network or a commercial network such as the Internet
would adhere to different guidelines to address the individual concerns. Privacy issues must be considered in public networks such as the Internet. Privacy issues are discussed in the Security Requirements section, along with other requirements that must be agreed upon by participating entities. RID requests must be legitimate incidents and not used for purposes such as sabotage or censorship. An example of such abuse of the system includes a request to rate-limit legitimate traffic to prevent information from being shared between users on the Internet (restricting access to online versions of papers) or restricting access from a competitor's product in order to sabotage a business. The RID system should be configurable to either require user input or automatically continue traces. This feature enables a network manager to assess the available resources before continuing a Request message set to 'InvestigationRequest' or 'TraceRequest'. If the Confidence rating (provided in IODEF) is low, it may not be in the provider's best interest to continue the Request with options set to 'InvestigationRequest' or 'TraceRequest'. The Confidence ratings must adhere to the specifications for selecting the percentage used to avoid abuse of the system. Requests must be issued by authorized individuals from the initiating CSIRT, set forth in policy guidelines established through peering or a SLA.3.2. RID Communication Topology
The most basic topology for communicating RID systems is a direct connection or a bilateral relationship as illustrated below. ___________ __________ | | | | | RID |__________-------------___________| RID | |_________| | SP Border | |________| ------------- Figure 1: Direct Peer Topology Within the consortium model, several topologies might be agreed upon and used. One would leverage bilateral network peering relationships of the members of the consortium. The peers for RID would match that of routing peers, and the logical network borders would be used. This approach may be necessary for an iterative trace where the source is unknown. The model looks like the above diagram; however, there may be an extensive number of interconnections of bilateral relationships formed. Also within a consortium model, it may be useful to establish an integrated mesh of networks to pass RID messages. This may be beneficial when the source address is known,
and an interconnection may provide a faster route to reach the closest upstream peer to the source of the attack traffic if direct communication between SPs is not possible. An example is illustrated below. _______ _______ _______ | | | | | | __| RID |____-------------____| RID |____-------------____| RID |__ |_____| | SP Border | |_____| | SP Border | |_____| | ------------- ------------- | |_______________________________________________________| Direct connection to network that is not an immediate network peer Figure 2: Mesh Peer Topology By using a fully meshed model in a consortium, broadcasting RID requests would be possible, but not advisable. By broadcasting a request, RID peers that may not have carried the attack traffic on their network would be asked to perform a trace for the potential of decreasing the time in which the true source was identified. As a result, many networks would have utilized unnecessary resources for a Request that may have also been unnecessary. A star topology may be desirable in instances where a peer may be a provider of incident information. This requires trust relationships to be established between the provider of information and each of the consumers of that information. Examples may include country-level CSIRTs or service providers distributing incident information to organizations.4. Message Formats
4.1. RID Data Types
RID is derived from the IODEF data model and inherits all of the data types defined in the IODEF model. One data type is added by RID: BOOLEAN.4.1.1. Boolean
A boolean value is represented by the BOOLEAN data type. The BOOLEAN data type is implemented as "xs:boolean" [XMLschema] in the schema. Note that there are two lexical representations for boolean in [XMLschema]: '1' or 'true' for TRUE and '0' or 'false' or FALSE.
4.2. RID Message Types
The five RID message types described below MUST be implemented. RID messages uses both the IODEF [RFC5070] and RID document, which MUST be encapsulated for transport as specified in [RFC6546]. The messages are generated and received on designated systems for RID communications. Each RID message type, along with an example, is described in the following sections. The IODEF-RID schema is introduced in Section 5 to support the described RID message types. 1. Request. This message type is used when a request ('InvestigationRequest' or 'TraceRequest') is needed. The purpose of the Request message (set to 'InvestigationRequest') is to leverage the existing peer relationships in order to notify the SP closest to the source of the valid traffic of a security- related incident for any necessary actions to be taken. The Request (set to 'TraceRequest') is used when the traffic has to be traced iteratively through networks to find the source by setting the MsgType to 'TraceRequest'. The 'InvestigationRequest' MsgType is used for all other Request messages. 2. Acknowledgement. This message is sent to the initiating RID system from each of the upstream provider's RID systems to provide information on the status of a Request. The Acknowledgement is also used to provide a reason why a Request, Report, or Query was not accepted. 3. Result. The Result message is used to provide a final report and the notification of actions taken for a Request. This message is sent to the initiating CSIRT through the network of RID systems in the path of the trace as notification that the source of the attack was located. 4. Report. This message is used to report a security incident, for which no action is requested. This may be used for the purpose of correlating attack information by CSIRTs, sharing incident information, statistics and trending information, etc. 5. Query. This message is used to request information about an incident or incident type from a trusted system communicating via RID. The response is provided through the Report message. When an application receives a RID message, it must be able to determine the type of message and parse it accordingly. The message type is specified in the RIDPolicy class. The RIDPolicy class may
also be used by the transport protocol to facilitate the communication of security incident data to trace, investigate, query, or report information regarding security incidents.
(page 15 continued on part 2)
