Operational Security Capabilities for IP Network InfrastructureE. Vyncke Internet-Draft Cisco Intended status: Informational B. Donnet Expires: 19 November 2023 J. Iurman Université de Liège 18 May 2023 Attribution of Internet Probes draft-ietf-opsec-probe-attribution-04 Abstract Active measurements at Internet-scale can target either collaborating parties or non-collaborating ones. Sometimes these measurements are viewed as unwelcome or aggressive. This document proposes some simple techniques allowing any party or organization to understand what this unsolicited packet is, what is its purpose, and more importantly who to contact. About This Document This note is to be removed before publishing as an RFC. The latest revision of this draft can be found at https://evyncke.github.io/opsec-probe-attribution/draft-ietf-opsec- probe-attribution.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ietf-opsec-probe- attribution/. Discussion of this document takes place on the Operational Security Capabilities for IP Network Infrastructure Working Group mailing list (mailto:opsec@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/opsec/. Source for this draft and an issue tracker can be found at https://github.com/evyncke/opsec-probe-attribution. Status of This Memo 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 https://datatracker.ietf.org/drafts/current/. Vyncke, et al. Expires 19 November 2023 [Page 1] Internet-Draft Probes Attribution May 2023 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 19 November 2023. Copyright Notice Copyright (c) 2023 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Probe Description . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Probe Description URI . . . . . . . . . . . . . . . . . . 3 2.2. Probe Description File . . . . . . . . . . . . . . . . . 3 2.2.1. Example . . . . . . . . . . . . . . . . . . . . . . . 4 3. Out-of-band Probe Attribution . . . . . . . . . . . . . . . . 4 4. In-band Probe Attribution . . . . . . . . . . . . . . . . . . 5 5. Operational and Technical Considerations . . . . . . . . . . 6 6. Ethical Considerations . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 9.1. Normative References . . . . . . . . . . . . . . . . . . 7 9.2. Informative References . . . . . . . . . . . . . . . . . 8 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction Active measurements at Internet-scale can target either collaborating parties or non-collaborating ones. Such measurements include [LARGE_SCALE] and [RFC7872]. Vyncke, et al. Expires 19 November 2023 [Page 2] Internet-Draft Probes Attribution May 2023 Sending unsolicited probes should obviously be done at a rate low enough to not unduly impact the other parties resources. But even at a low rate, those probes could trigger an alarm that will request some investigation by either the party receiving the probe (i.e., when the probe destination address is one address assigned to the receiving party) or by a third party having some devices where those probes are transiting (e.g., an Internet transit router). This document suggests some simple techniques allowing any party or organization to understand: * what this unsolicited packet is, * what is its purpose, * and more significantly who to contact for further information or to stop the probing. Note: it is expected that only researchers with no bad intentions will use these techniques, although anyone might use them. This is discussed in Section 7. 2. Probe Description 2.1. Probe Description URI This document defines a probe description URI as a URI pointing to either: * a probe description file (see Section 2.2) as defined in Section 8: "https://example.net/.well-known/probing.txt"; * an email address, e.g., "mailto:user@example.net"; * a phone number, e.g., "tel:+1-201-555-0123". 2.2. Probe Description File As defined in Section 8, the probe description file must be made available at "https://example.net/.well-known/probing.txt". The probe description file must follow the format defined in section 4 of [RFC9116] and should contain the following fields defined in section 2 of [RFC9116]: * Canonical * Contact Vyncke, et al. Expires 19 November 2023 [Page 3] Internet-Draft Probes Attribution May 2023 * Expires * Preferred-Languages A new field "Description" should also be included to describe the measurement. To match the format defined in section 4 of [RFC9116], this field must be a one line string. 2.2.1. Example # Canonical URI (if any) Canonical: https://example.net/measurement.txt # Contact address Contact: mailto:user@example.net # Validity Expires: 2023-12-31T18:37:07z # Languages Preferred-Languages: en, es, fr # Probe/Measurement description Description: This is a one-line string description of the measurement, with no line break. 3. Out-of-band Probe Attribution An alternative to URI inclusion is to build a specific URI based on the source address of the probe packet, following [RFC8615]. For example, with a probe source address 2001:db8::dead, the following URI is built: * if the reverse DNS record for 2001:db8::dead exists, e.g., "example.net", then the probe description URI is "https://example.net/.well-known/probing.txt"; * else (or in addition), the probe description URI is "https://[2001:db8::dead]/.well-known/probing.txt". In this case, there might be a certificate verification issue. The built URI must be a reference to the probe description file (see Section 2.2). Vyncke, et al. Expires 19 November 2023 [Page 4] Internet-Draft Probes Attribution May 2023 As an example, the UK National Cyber Security Centre [NCSC] uses a similar attribution. They scan for vulnerabilities across internet- connected systems in the UK and publish information on their scanning ([NCSC_SCAN_INFO]), providing the address of the webpage in reverse DNS. 4. In-band Probe Attribution When the measurement allows for it, a probe description URI should be included in the payload of all probes sent. This could be: * for a [RFC4443] ICMPv6 echo request: in the optional data (see section 4.1 of [RFC4443]); * for a [RFC792] ICMPv4 echo request: in the optional data; * for a [RFC768] UDP datagram: in the data part. Note that if the probe is destined to a listened-to/well-known UDP port, the inclusion of the probe description URI may produce undefined results; * for a [RFC9293] TCP packet with the SYN flag: data is allowed in TCP packets with the SYN flag per section 3.4 of [RFC9293] (2nd paragraph). However, it may change the way the packet is processed, i.e., SYN packets containing data might be discarded; * for a [RFC8200] IPv6 packet with either hop-by-hop or destination options headers, in a PadN option. Indeed, the probe attribution URI can only be added to IPv6 packets in some extension headers used for the probing. However, inserting the probe description URI in PadN options could bias the measurement itself: as per the informational [RFC4942], section 2.1.9.5, it is suggested that a PadN option should only contain 0's and be smaller than 8 octets, thus limiting its use for probe attribution. If a PadN option does not respect the recommendation, it is suggested that one may consider dropping such packets. For example, the Linux Kernel follows these recommendations and discards such packets since its version 3.5; * etc. The probe description URI should start at the first octet of the payload and should be terminated by an octet of 0x00, i.e., it must be null terminated. If the probe description URI cannot be placed at the beginning of the payload, then it should be preceded by an octet of 0x00. Inserting the probe description URI could obviously bias the measurement itself if the probe packet becomes larger than the path MTU. Vyncke, et al. Expires 19 November 2023 [Page 5] Internet-Draft Probes Attribution May 2023 Note: the above techniques produce a valid and legitimate packet for all the nodes forwarding the probe, except maybe for a hop-by-hop options header with a PadN option containing the probe description URI. As for the receiver, it may or may not process the packet, depending on where the probe description URI is included (e.g., TCP SYN flag with the probe description URI included in data, destination options header with a PadN option containing the probe description URI). As a consequence, a response may not be received. The choice of the probe description URI location is important and highly depends on the context, which is why multiple possibilities are proposed in this document. For the record, the in-band probe attribution was used in [I-D.draft-vyncke-v6ops-james]. 5. Operational and Technical Considerations Using either the out-of-band or in-band technique, or even both combined, highly depends on will or context. This section describes the upsides and downsides of each technique, so that probe owners or probe makers can freely decide what works best for their cases. The advantages of using the out-of-band technique are that the probing measurement is not impacted by the probe attribution but also that it is easy to setup, i.e., by running a web server on a probe device to describe the measurements. Unfortunately, there are some disadvantages too. In some cases, using the out-of-band technique might not be possible due to several conditions: the presence of a NAT, too many endpoints to run a web server on, the probe source IP address cannot be known (e.g., RIPE Atlas [RIPE_ATLAS] probes are sent from IP addresses not owned by the probe owner), dynamic source addresses, etc. The advantage of using the in-band technique is to cover the cases where the out-of-band technique is not possible, as listed above. The disadvantage is to potentially bias the measurements, since packets with the Probe Description URI might be discarded depending on the context. Having both the out-of-band and in-band techniques combined also has a big advantage, i.e., it could be used as an indirect means of "authenticating" the Probe Description URI in the in-band probe, thanks to a correlation with the out-of-band technique (e.g., a reverse DNS lookup). While the out-of-band technique alone is less prone to spoofing, the combination with the in-band technique offers a more complete solution. Vyncke, et al. Expires 19 November 2023 [Page 6] Internet-Draft Probes Attribution May 2023 6. Ethical Considerations Executing some measurement experiences over the global Internet obviously require some ethical considerations when transit/ destination non-solicited parties are involved. This document proposes a common way to identity the source and the purpose of active probing in order to reduce the potential burden on the non-solicited parties. But there are other considerations to be taken into account: from the payload content (e.g., is the encoding valid ?) to the transmission rate (see also [IPV6_TOPOLOGY] and [IPV4_TOPOLOGY] for some probing speed impacts). Those considerations are out of scope of this document. 7. Security Considerations While it is expected that only researchers with no bad intentions will use these techniques, they will simplify and shorten the time to identify a probing across the Internet. This information is provided to identify the source and intent of specific probes, but there is no authentication possible for the inline information. As a result, a malevolent actor could provide false information while conducting the probes, so that the action is attributed to a third party. As a consequence, the recipient of this information cannot trust this information without confirmation. If a recipient cannot confirm the information or does not wish to do so, it should treat the flows as if there were no attribution. 8. IANA Considerations The "Well-Known URIs" registry should be updated with the following additional values (using the template from [RFC8615]): * URI suffix: probing.txt * Change controller: IETF * Specification document(s): this document * Status: permanent 9. References 9.1. Normative References Vyncke, et al. Expires 19 November 2023 [Page 7] Internet-Draft Probes Attribution May 2023 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification", STD 89, RFC 4443, DOI 10.17487/RFC4443, March 2006, . [RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI 10.17487/RFC0768, August 1980, . [RFC792] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, DOI 10.17487/RFC0792, September 1981, . [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, . [RFC8615] Nottingham, M., "Well-Known Uniform Resource Identifiers (URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019, . [RFC9116] Foudil, E. and Y. Shafranovich, "A File Format to Aid in Security Vulnerability Disclosure", RFC 9116, DOI 10.17487/RFC9116, April 2022, . [RFC9293] Eddy, W., Ed., "Transmission Control Protocol (TCP)", STD 7, RFC 9293, DOI 10.17487/RFC9293, August 2022, . 9.2. Informative References [I-D.draft-vyncke-v6ops-james] Vyncke, E., Léas, R., and J. Iurman, "Just Another Measurement of Extension header Survivability (JAMES)", Work in Progress, Internet-Draft, draft-vyncke-v6ops- james-03, 9 January 2023, . [IPV4_TOPOLOGY] Beverly, R., "Yarrp'ing the Internet Randomized High-Speed Active Topology Discovery", DOI 10.1145/2987443.2987479, 2016, . Vyncke, et al. Expires 19 November 2023 [Page 8] Internet-Draft Probes Attribution May 2023 [IPV6_TOPOLOGY] Beverly, R., Durairajan, R., Plonka, D., and J. P. Rohrer, "In the IP of the Beholder Strategies for Active IPv6 Topology Discovery", DOI 10.1145/3278532.3278559, 2018, . [LARGE_SCALE] Donnet, B., Raoult, P., Friedman, T., and M. Crovella, "Efficient Algorithms for Large-Scale Topology Discovery", DOI 10.1145/1071690.1064256, 2005, . [NCSC] "The National Cyber Security Centre", n.d., . [NCSC_SCAN_INFO] "NCSC Scanning information", n.d., . [RFC4942] Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/ Co-existence Security Considerations", RFC 4942, DOI 10.17487/RFC4942, September 2007, . [RFC7872] Gont, F., Linkova, J., Chown, T., and W. Liu, "Observations on the Dropping of Packets with IPv6 Extension Headers in the Real World", RFC 7872, DOI 10.17487/RFC7872, June 2016, . [RIPE_ATLAS] "RIPE Atlas", n.d., . Acknowledgments The authors would like to thank Alain Fiocco, Fernando Gont, Ted Hardie, Mehdi Kouhen, and Mark Townsley for helpful discussions as well as Raphael Leas for an early implementation. The authors would also like to gracefully acknowledge useful review and comments received from Jen Linkova, Prapanch Ramamoorthy, Warren Kumari, and Andrew Shaw. Authors' Addresses Vyncke, et al. Expires 19 November 2023 [Page 9] Internet-Draft Probes Attribution May 2023 Éric Vyncke Cisco De Kleetlaan 64 1831 Diegem Belgium Email: evyncke@cisco.com Benoît Donnet Université de Liège Belgium Email: benoit.donnet@uliege.be Justin Iurman Université de Liège Belgium Email: justin.iurman@uliege.be Vyncke, et al. Expires 19 November 2023 [Page 10]