RFC 6045
Real-time Inter-network Defense (RID)
Internet Engineering Task Force (IETF) K. Moriarty Request for Comments: 6045 EMC Category: Informational November 2010 ISSN: 2070-1721 Real-time Inter-network Defense (RID)Abstract
Network 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. Network 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. RID has found use within the international research communities, but has not been widely adopted in other sectors. This publication provides the specification to those communities that have adopted it, and communities currently considering solutions for real-time inter- network defense. The specification may also accelerate development of solutions where different transports or message formats are required by leveraging the data elements and structures specified here.
Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. 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). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see 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/rfc6045. Copyright Notice Copyright (c) 2010 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 ....................................................4 1.1. Normative and Informative ..................................6 1.2. Terminology ................................................6 1.3. Attack Types and RID Messaging .............................6 2. RID Integration with Network Provider Technologies ..............8 3. Characteristics of Attacks ......................................9 3.1. Integrating Trace Approaches ..............................11 3.2. Superset of Packet Information for Traces .................11 4. Communication between Network Providers ........................12 4.1. Inter-Network Provider RID Messaging ......................14 4.2. RID Network Topology ......................................16 4.3. Message Formats ...........................................17 4.3.1. RID Data Types .....................................17 4.3.1.1. Boolean ...................................17 4.3.2. RID Messages and Transport .........................18 4.3.3. IODEF-RID Schema ...................................19 4.3.3.1. RequestStatus Class .......................21 4.3.3.2. IncidentSource Class ......................23 4.3.3.3. RIDPolicy Class ...........................24 4.3.4. RID Namespace ......................................29 4.4. RID Messages ..............................................29 4.4.1. TraceRequest .......................................29 4.4.2. RequestAuthorization ...............................30 4.4.3. Result .............................................31 4.4.4. Investigation Request ..............................33 4.4.5. Report .............................................35 4.4.6. IncidentQuery ......................................36 4.5. RID Communication Exchanges ...............................37 4.5.1. Upstream Trace Communication Flow ..................39 4.5.1.1. RID TraceRequest Example ..................40 4.5.1.2. RequestAuthorization Message Example ......44 4.5.1.3. Result Message Example ....................44 4.5.2. Investigation Request Communication Flow ...........47 4.5.2.1. Investigation Request Example .............48 4.5.2.2. RequestAuthorization Message Example ......50 4.5.3. Report Communication ...............................51 4.5.3.1. Report Example ............................51 4.5.4. IncidentQuery Communication Flow ...................54 4.5.4.1. IncidentQuery Example .....................54 5. RID Schema Definition ..........................................55
6. Security Considerations ........................................60 6.1. Message Transport .........................................62 6.2. Message Delivery Protocol - Integrity and Authentication ..63 6.3. Transport Communication ...................................63 6.4. Authentication of RID Protocol ............................64 6.4.1. Multi-Hop TraceRequest Authentication ..............65 6.5. Consortiums and Public Key Infrastructures ................66 6.6. Privacy Concerns and System Use Guidelines ................67 7. IANA Considerations ............................................72 8. Summary ........................................................72 9. References .....................................................73 9.1. Normative References ......................................73 9.2. Informative References ....................................74 Acknowledgements ..................................................75 Sponsor Information ...............................................751. Introduction
Incident handling involves the detection, reporting, identification, and mitigation of an attack, whether it be a system compromise, socially engineered phishing attack, or a denial-of-service (DoS) attack. When an attack is detected, the response may include simply filing a report, notification to the source of the attack, a request for mitigation, or the 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 victim system and the attacker or source system are available, the source is easy to identify. The problem of tracing incidents becomes more difficult when the source is obscured or spoofed, logs are deleted, and the number of sources is overwhelming. If the source of an attack is known or identified, it may be desirable to request actions be taken to stop or mitigate the effects of the attack. Current approaches to mitigating the effects of security incidents are aimed at identifying and filtering or rate-limiting packets from attackers who seek to hide the origin of their attack by source address spoofing from multiple locations. Measures can be taken at network provider (NP) edge routers providing ingress, egress, and broadcast filtering as a recommended best practice in [RFC2827]. Network providers have devised solutions, in-house or commercial, to trace attacks across their backbone infrastructure to either identify the source on their network or on the next upstream network in the path to the source. Techniques such as collecting packets as traffic traverses the network have been implemented to provide the capability
to trace attack traffic after an incident has occurred. Other methods use packet-marking techniques or flow-based traffic analysis to trace traffic across the network in real time. The single-network trace mechanisms use similar information across the individual networks to trace traffic. Problems may arise when an attempt is made to have a trace continued through the next upstream network since the trace mechanism and management may vary. In the case in which the traffic traverses multiple networks, there is currently no established communication mechanism for continuing the trace. If the next upstream network has been identified, a phone call might be placed to contact the network administrators in an attempt to have them continue the trace. A communication mechanism is needed to facilitate the transfer of information to continue traces accurately and efficiently to upstream networks. The communication mechanism described in this paper, Real-time Inter- network Defense (RID), takes into consideration the information needed by various single-network trace implementations and the requirement for network providers to decide if a TraceRequest should be permitted to continue. The data in RID messages is represented in an Extensible Markup Language (XML) [XML1.0] document using the Incident Object Description Exchange Format (IODEF) and RID. By following this model, integration with other aspects of the network for incident handling is simplified. Finally, 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 attack at hand. RID is intended to provide a method to communicate the relevant information between Computer Security Incident Response Teams (CSIRTs) while being compatible with a variety of existing and possible future detection tracing and response approaches. At this point, RID has found use within the international research communities, but has not been widely adopted in other sectors. This publication provides the specification to those communities that have adopted it, and communities currently considering solutions for real- time inter-network defense. The specification may also accelerate development of solutions where different transports or message formats are required by leveraging the data elements and structures specified here. 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 and privacy policy information set in the RID schema. The RID schema acts as an XML envelope to support the communication of IODEF documents for exchanging or tracing information regarding security incidents. RID messages are encapsulated for transport, which is defined in a
separate document [RFC6046]. The authentication, integrity, and authorization features each layer has to offer are used to achieve a necessary level of security.1.1. Normative and Informative
The XML schema [XMLschema] and transport requirements contained in this document are normative; all other information provided is intended as informative. More specifically, the following sections of this document are intended as informative: Sections 1, 2, and 3; and the sub-sections of 4 including the introduction to 4, 4.1, and 4.2. The following sections of this document are normative: The sub-sections of 4 including 4.3, 4.4, and 4.5; Section 5; and Section 6.1.2. 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].1.3. Attack Types and RID Messaging
RID messaging is intended for use in coordinating incident handling to locate the source of an attack and stop or mitigate the effects of the attack. The attack types include system or network compromises, denial-of-service attacks, or other malicious network traffic. RID is essentially a messaging system coordinating attack detection, tracing mechanisms, and the incident handling responses to locate the source of traffic. If a source address is spoofed, a more detailed trace of a packet (RID TraceRequest) would be required to locate the true source. If the source address is valid, the incident handling may only involve the use of routing information to determine what network provider is closest to the source (RID Investigation request) and can assist with the remediation. The type of RID message used to locate a source is determined by the validity of the source address. RID message types are discussed in Section 4.3. DoS [DoS] attacks are characterized by large amounts of traffic destined for particular Internet locations and can originate from a single or multiple sources. An attack from multiple sources is known as a distributed denial-of-service (DDoS) attack. Because DDoS attacks can originate from multiple sources, tracing such an attack can be extremely difficult or nearly impossible. Many TraceRequests may be required to accomplish the task and may require the use of dedicated network resources to communicate incident handling information to prevent a DoS attack against the RID system and network used for tracing and remediation. Provisions are suggested
to reduce the load and prevent the same trace from occurring twice on a single-network backbone discussed in Section 4 on communication between NPs. The attacks can be launched from systems across the Internet unified in their efforts or by compromised systems enlisted as "zombies" that are controlled by servers, thereby providing anonymity to the controlling server of the attack. This scenario may require multiple RID traces, one to locate the zombies and an additional one to locate the controlling server. DDoS attacks do not necessarily spoof the source of an attack since there are a large number of source addresses, which make it difficult to trace anyway. DDoS attacks can also originate from a single system or a subset of systems that spoof the source address in packet headers in order to mask the identity of the attack source. In this case, an iterative trace through the upstream networks in the path of the attack traffic may be required. RID traces may also be used to locate a system used in an attack to compromise another system. Compromising a system can be accomplished through one of many attack vectors, using various techniques from a remote host or through local privilege escalation attempts. The attack may exploit a system or application level vulnerability that may be the result of a design flaw or a configuration issue. A compromised system, as described above, can be used to later attack other systems. A single RID Investigation request may be used in this case since it is probable that the source address is valid. Identifying the sources of system compromises may be difficult since an attacker may access the compromised system from various sources. The attacker may also take measures to hide their tracks by deleting log files or by accessing the system through a series of compromised hosts. Iterative RID traces may be required for each of the compromised systems used to obscure the source of the attack. If the source address is valid, an Investigation request may be used in lieu of a full RID TraceRequest. Once an attack has been reported, CSIRTs may want to query other CSIRTs if they have detected an attack or simply report that one has taken place. The Report message can be used to file a report without an action taken, and an IncidentQuery can be used to ask if an attack has been seen by another CSIRT. System compromises may result from other security incident types such as worms, Trojans, or viruses. It is often the case that an incident goes unreported even if valid source address information is available because it is difficult to take any action to mitigate or stop the attack. Incident handling is a difficult task for an NP and even at some client locations due to network size and resource limitations.
2. RID Integration with Network Provider Technologies
For the purpose of this document, a network provider (NP) shall be defined as a backbone infrastructure manager of a network. The network provider's Computer Security Incident Response Team shall be referred to as the CSIRT. The backbone may be that of an organization providing network (Internet or private) access to commercial, personal, government, or educational institutions, or the backbone provider of the connected network. The connected network provider is an extension meant to include Intranet and Extranet providers as well as instances such as a business or educational institute's private network. NPs typically manage and monitor their networks through a centralized network management system (NMS). The acronym "NMS" will be used to generically represent management systems on a network used for the management of network resources. An incident handling system (IHS) is used to communicate RID messages and may be integrated with an NMS as well as other components of the network. The components of the network that may be integrated through the RID messaging system include attack or event detection, network tracing, and network devices to stop the effects of an attack. The detection of security incidents may rely on manual reporting, automated intrusion detection tools, and variations in traffic types or levels on a network. Intrusion detection systems (IDSs) may be integrated into the IHS to create IODEF documents or RID messages to facilitate security incident handling. Detection of a security incident is outside the scope of this paper; however, it should be possible to integrate detection methods with RID messaging. RID messaging in an IHS is intended to be flexible in order to accommodate various traceback systems currently in use as well as those that may evolve with technology. RID is intended to communicate the necessary information needed by a trace mechanism to the next upstream NP in the path of a trace. Therefore, a RID message must carry the superset of data required for all tracing systems. If possible, the trace may need to inspect packets to determine a pattern, which could assist reverse path identification. This may be accomplished by inspecting packet header information such as the source and destination IP addresses, ports, and protocol flags to determine if there is a way to distinguish the packets being traced from other packets. A description of the incident along with any available automated trace data should trigger an alert to the NP's CSIRT for further investigation. The various technologies used to trace traffic across a network are described in Section 3.1.
Another area of integration is the ability to mitigate or stop attack traffic once a source has been located. Any automated solution should consider the possible side effects to the network. A change control process or a central point for configuration management might be used to ensure that the security of the network and necessary functionality are maintained and that equipment configuration changes are documented. Automated solutions may depend upon the capabilities and current configuration management solutions on a particular network. The solutions may be based on HTTP/TLS (Transport Layer Security) or an appropriate protocol defined in the transport specification.3. Characteristics of Attacks
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. A security incident may be defined as a system compromise, a worm or Trojan infection, or a single- or multiple- source denial-of-service attack. Incident tracing can be used to identify the source(s) of an attack in order to halt or mitigate the undesired behavior. The communication system, RID, described in this paper can be used to trace any type of security incident and allows for actions to be taken when the source of the attack or a point closer to the source is known or has been identified. The purpose of tracing an attack would be to halt or mitigate the effects of the attack through methods such as filtering or rate-limiting the traffic close to the source or by using methods such as taking the host or network offline. Care must also be taken to ensure that the system is not abused and to use proper analysis in determining if attack traffic is, in fact, attack traffic at each NP along the path of a trace. Tracing 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. Security incidents, including DDoS attacks, can be difficult or nearly impossible to trace because of the nature of the attack. Some of the difficulties in tracing attacks include the following:
o the attack originates from multiple sources;
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 NP 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", 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.
If the source(s) of the attack cannot be determined from IP address
information or tracing the increased bandwidth utilization, it may be
possible to trace the traffic based on the type of packets seen by
the client. In the case of packets with spoofed source addresses, it
is no longer a trivial task to identify the source of an attack. In
the case of an attack using valid source addresses, methods such as
the traceroute utility can be used to fairly accurately identify the
path of the traffic between the source and destination of an attack.
If the true source has been identified, actions should be taken to
halt or mitigate the effects of the attack by reporting the incident
to the NP or the upstream NP closest to the source. In the case of a
spoofed source address, other methods can be used to trace back to
the source of an attack. The methods include packet filtering,
packet hash comparisons, IP marking techniques, ICMP traceback, and
packet flow analysis. As in the case of attack detection, tracing
traffic across a single network is a function that can be used with
RID in order to provide the network with the ability to trace spoofed
traffic to the source, while RID provides all the necessary
information to accommodate the approach used on any single network to
accomplish this task. RID can also be used to report attack traffic
close to the source where the IP address used was determined to be
valid or simply to report that an incident occurred.
3.1. Integrating Trace Approaches
There have been many separate research initiatives to solve the problem of tracing upstream packets to detect the true source of attack traffic. Upstream packet tracing is currently confined to the borders of a network or an NP's network. Traces require access to network equipment and resources, thus potentially limiting a trace to a specific network. Once a trace reaches the boundaries of a network, the network manager or NP adjacent in the upstream trace must be contacted in order to continue the trace. NPs have been working on individual solutions to accomplish upstream tracing within their own network environments. The tracing mechanisms implemented thus far have included proprietary or custom solutions requiring specific information such as IP packet header data, hash values of the attack packets, or marked packets. Hash values are used to compare a packet against a database of packets that have passed through the network as described in "Hash-Based IP Traceback" [HASH-IPtrace]. Other research solutions involve marking packets as explained in "ICMP Traceback Messages" [ICMPtrace], "Practical network support for IP traceback" [NTWK-IPtrace], the IP Flow Information eXport (IPFIX) protocol [RFC3917], and IP marking [IPtrace]. The single-network traceback solutions were considered in developing RID to determine the information needed to accomplish an inter-network trace where different solutions may be in place.3.2. Superset of Packet Information for Traces
In order for network traffic to be traced across a network, an example packet from the attack must be sent along with the TraceRequest or Investigation request. According to the research for hash-based IP traceback, all of the non-changing fields of an IP header along with 8 bytes of payload are required to provide enough information to uniquely trace the path of a packet. The non-changing fields of the packet header and the 8 bytes of payload are the superset of data required by most single-network tracing systems used; limiting the shared data to the superset of the packet header and 8 bytes of payload prevents the need for sharing potentially sensitive information that may be contained in the data portion of a packet. The RecordItem class in the IODEF is used to store a hexadecimal formatted packet including all packet header information plus 8 bytes of payload, or the entire packet contents. The above trace systems do not require a full packet, but it may be useful in some cases, so the option is given to allow a full packet to be included in the data model.
If a subset of a packet is used, the research presented in "Hash- Based IP Traceback" [HASH-IPtrace] provides guidelines to establish a minimum requirement for distinguishing packets. The full packet and content SHOULD be provided, but the minimum requirement MUST be provided. The research from [HASH-IPtrace] found that the first 28 invariant bytes of a packet (masked IP header plus the first 8 bytes of the payload) are sufficient to differentiate almost all non- identical IPv4 packets. RID requires the first 28 invariant bytes of an IPv4 packet in order to perform a trace. RID requires the first 48 invariant bytes for an IPv6 packet in order to distinguish the packet in a trace. Reference [HASH-IPtrace] for additional details. The input mechanism for packets to be traced should be flexible to allow intrusion detection systems or packet sniffers to provide the information. The system creating the RID message should also use the packet information to populate the Incident class information in order to avoid human error and also allow a system administrator to override the automatically populated information.
(page 12 continued on part 2)
