Network Working Group A. Chernyakhovsky Internet-Draft D. McCall Intended status: Informational D. Schinazi Expires: 12 July 2021 Google LLC 8 January 2021 Requirements for a MASQUE Protocol to Proxy IP Traffic draft-ietf-masque-ip-proxy-reqs-01 Abstract There is interest among MASQUE working group participants in designing a protocol that can proxy IP traffic over HTTP. This document describes the set of requirements for such a protocol. Discussion of this work is encouraged to happen on the MASQUE IETF mailing list masque@ietf.org or on the GitHub repository which contains the draft: https://github.com/ietf-wg-masque/draft-ietf- masque-ip-proxy-reqs. Discussion Venues This note is to be removed before publishing as an RFC. Source for this draft and an issue tracker can be found at https://github.com/ietf-wg-masque/draft-ietf-masque-ip-proxy-reqs. 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/. 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 12 July 2021. Chernyakhovsky, et al. Expires 12 July 2021 [Page 1] Internet-Draft IP Proxying Requirements January 2021 Copyright Notice Copyright (c) 2021 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 1.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3 2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Consumer VPN . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Point to Point Connectivity . . . . . . . . . . . . . . . 4 2.3. Point to Network Connectivity . . . . . . . . . . . . . . 4 2.4. Network to Network Connectivity . . . . . . . . . . . . . 4 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. IP Session Establishment . . . . . . . . . . . . . . . . 5 3.2. Proxying of IP packets . . . . . . . . . . . . . . . . . 5 3.3. Maximum Transmission Unit . . . . . . . . . . . . . . . . 5 3.4. IP Assignment . . . . . . . . . . . . . . . . . . . . . . 5 3.5. Route Negotiation . . . . . . . . . . . . . . . . . . . . 5 3.6. Identity . . . . . . . . . . . . . . . . . . . . . . . . 6 3.7. Transport Security . . . . . . . . . . . . . . . . . . . 6 3.8. Flow Control . . . . . . . . . . . . . . . . . . . . . . 6 3.9. Indistinguishability . . . . . . . . . . . . . . . . . . 6 3.10. Support HTTP/2 and HTTP/3 . . . . . . . . . . . . . . . . 6 3.11. Multiplexing . . . . . . . . . . . . . . . . . . . . . . 6 4. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 7 4.1. Load balancing . . . . . . . . . . . . . . . . . . . . . 7 4.2. Authentication . . . . . . . . . . . . . . . . . . . . . 7 4.3. Reliable Transmission of IP Packets . . . . . . . . . . . 7 4.4. Configuration of Congestion and Flow Control . . . . . . 7 4.5. Data Transport Compression . . . . . . . . . . . . . . . 8 5. Non-requirements . . . . . . . . . . . . . . . . . . . . . . 8 5.1. Addressing Architecture . . . . . . . . . . . . . . . . . 8 5.2. Translation . . . . . . . . . . . . . . . . . . . . . . . 8 5.3. IP Packet Extraction . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 Chernyakhovsky, et al. Expires 12 July 2021 [Page 2] Internet-Draft IP Proxying Requirements January 2021 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Normative References . . . . . . . . . . . . . . . . . . . . . 9 Informative References . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction There exist several IETF standards for proxying IP in a way that is authenticated and confidential, such as IKEv2/IPsec [IKEV2]. However, those are distinguishable from common Internet traffic and often blocked. Additionally, large server deployments have expressed interest in using a VPN solution that leverages existing security protocols such as QUIC [QUIC] or TLS [TLS] to avoid adding another protocol to their security posture. This document describes the set of requirements for a protocol that can proxy IP traffic over HTTP. The requirements outlined below are similar to the considerations made in designing the CONNECT-UDP method [CONNECT-UDP], additionally including IP-specific requirements, such as a means of negotiating the routes that should be advertised on either end of the connection. Discussion of this work is encouraged to happen on the MASQUE IETF mailing list masque@ietf.org or on the GitHub repository which contains the draft: https://github.com/ietf-wg-masque/draft-ietf- masque-ip-proxy-reqs. 1.1. Conventions 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. 1.2. Definitions * Data Transport: The mechanism responsible for transmitting IP packets over HTTP. This can involve streams or datagrams. * IP Session: An association between client and server whereby both agree to proxy IP traffic given certain configuration properties. This is similar to a Child Security Association in IKEv2 terminology. An IP Session uses Data Transports to transmit packets. Chernyakhovsky, et al. Expires 12 July 2021 [Page 3] Internet-Draft IP Proxying Requirements January 2021 2. Use Cases There are multiple reasons to deploy an IP proxying protocol. This section discusses some examples of use cases that MUST be supported by the protocol. Note that while the protocol needs to support these use cases, the protocol elements that allow them may be optional. 2.1. Consumer VPN Consumer VPNs refer to network applications that allow a user to hide some properties of their traffic from some network observers. In particular, it can hide the identity of servers the client is connecting to from the client's network provider, and can hide the client's IP address (and derived geographical information) from the servers they are communicating with. Note that this hidden information is now available to the VPN service provider, so is only beneficial for clients who trust the VPN service provider more than other entities. 2.2. Point to Point Connectivity Point-to-point connectivity creates a private, encrypted and authenticated network between two IP addresses. This is useful, for example, with container networking to provide a virtual (overlay) network with addressing separate from the physical transport. An example of this is Wireguard. 2.3. Point to Network Connectivity Point-to-Network connectivity is the more traditional remote-access "VPN" use case, frequently used when a user needs to connect to a different network (such as an enterprise network) for access to resources that are not exposed to the public Internet. 2.4. Network to Network Connectivity Network-to-Network connectivity is also called a site-to-site VPN. Similar to the point-to-network use case, the goal is to connect two networks that are not exposed publicly. The site-to-site aspects make this transparent to the user; the entire networks are connected to each other and route packets transparently without a VPN client installed on the user's device. This style of connectivity can also be used to connect devices that cannot run VPN clients through to the network. Chernyakhovsky, et al. Expires 12 July 2021 [Page 4] Internet-Draft IP Proxying Requirements January 2021 3. Requirements This section lists requirements for a protocol that can proxy IP over an HTTP connection. 3.1. IP Session Establishment The protocol will allow the client to request establishment of an IP Session, along with configuration options and one or more associated Data Transports. The server will have the ability to accept or deny the client's request. 3.2. Proxying of IP packets The protocol will establish Data Transports, which will be able to forward IP packets. The Data Transports MUST be able to forward packets in their unmodified entirety, although extensions may enable the use of modified packet formats (e.g., compression). The protocol will support both IPv6 [IPV6] and IPv4 [IPV4]. 3.3. Maximum Transmission Unit The protocol will allow endpoints to inform each other of the Maximum Transmission Unit (MTU) they are willing to forward. This will allow avoiding IP fragmentation, especially as IPv6 does not allow IP fragmentation by nodes along the path. 3.4. IP Assignment The client will be able to request to be assigned an IP address range, optionally specifying a preferred range. In response to that request, the server will either assign a range of its choosing to the client, or decline the request. For symmetry, the server may request assignment of an IP address range from the client, and the client will either assign a range or decline the request. 3.5. Route Negotiation At any point in an IP Session (not limited to its initial negotiation), the protocol will allow both client and server to inform its peer that it can route a set of IP prefixes. Both endpoints can also request a route to a given prefix, and the peer can choose to provide that route or not. Note that if an endpoint provides its peer with a route, the peer is in no way obligated to route its traffic through the endpoint. Chernyakhovsky, et al. Expires 12 July 2021 [Page 5] Internet-Draft IP Proxying Requirements January 2021 3.6. Identity When negotiating the creation of an IP Session, the protocol will allow both endpoints to exchange an identifier. As examples, the identity could be a user name, an email address, a token, or a fully- qualified domain name. Note that this requirement does not cover authenticating the identifier. 3.7. Transport Security The protocol MUST be run over a protocol that provides mutual authentication, confidentiality and integrity. Using QUIC or TLS would meet this requirement. 3.8. Flow Control The protocol will allow the ability to proxy IP packets without flow control, at least when HTTP/3 is in use. QUIC DATAGRAM frames are not flow controlled and would meet this requirement. The document defining the protocol will provide guidance on how best to use flow control to improve IP Session performance. 3.9. Indistinguishability A passive network observer not participating in the encrypted connection should not be able to distinguish IP proxying from regular encrypted HTTP Web traffic by only observing non-encrypted parts of the traffic. Specifically, any data sent unencrypted (such as headers, or parts of the handshake) should look like the same unencrypted data that would be present for Web traffic. Traffic analysis is out of scope for this requirement. 3.10. Support HTTP/2 and HTTP/3 The IP proxying protocol discussed in this document will run over HTTP. The protocol SHOULD strongly prefer to use HTTP/3 [H3] and SHOULD use the QUIC DATAGRAM frames [DGRAM] when available to improve performance. The protocol SHOULD also support HTTP/2 [H2] as a fallback when UDP is blocked on the network path. Proxying IP over HTTP/2 MAY result in lower performance than over HTTP/3. 3.11. Multiplexing Since recent HTTP versions support concurrently running multiple requests over the same connection, the protocol SHOULD support multiple independent instances of IP proxying over a given HTTP connection. Chernyakhovsky, et al. Expires 12 July 2021 [Page 6] Internet-Draft IP Proxying Requirements January 2021 4. Extensibility The protocol will provide a mechanism by which clients and servers can add extension information to the exchange that establishes the IP Session. If the solution uses an HTTP request and response, this could be accomplished using HTTP headers. Once the IP Session is established, the protocol will provide a mechanism that allows reliably exchanging extension messages in both directions at any point in the lifetime of the IP Session. The subsections below list possible extensions that designers of the protocol will keep in mind to ensure it will be possible to design such extensions. 4.1. Load balancing This extension would allow for load balancing of the traffic sent across the IP Session, such as to another server. This allows the IP proxying mechanisms to scale-out to multiple servers. 4.2. Authentication Since the protocol will offer a way to convey identity, extensions will allow authenticating that identity, from both the client and server, during the establishment of the IP Session. For example, an extension could allow a client to offer an OAuth Access Token [OAUTH] when requesting an IP Session. As another example, another extension could allow an endpoint to demonstrate knowledge of a cryptographic secret. 4.3. Reliable Transmission of IP Packets While it is desirable to transmit IP packets unreliably in most cases, an extension could provide a mechanism to allow forwarding some packets reliably. For example, when using HTTP/3, this can be accomplished by allowing Data Transports to run over both DATAGRAM and STREAM frames. 4.4. Configuration of Congestion and Flow Control An extension will allow exchanging congestion and flow control parameters to improve performance. For example, an extension could disable congestion control for non-retransmitted Data Transports if it knows that the proxied traffic is itself congestion-controlled. Chernyakhovsky, et al. Expires 12 July 2021 [Page 7] Internet-Draft IP Proxying Requirements January 2021 4.5. Data Transport Compression While the core protocol Data Transports will transmit IP packets in their unmodified entirety, an extension can allow compressing these packets. 5. Non-requirements This section discusses topics that are explicitly out of scope for the IP Proxying protocol. These topics MAY be handled by implementers or future extensions. 5.1. Addressing Architecture This document only describes the requirements for a protocol that allows IP proxying. It does not discuss how the IPs assigned are determined, managed, or translated. While these details are important for producing a functional system, they do not need to be handled by the protocol beyond the ability to convey those assignments. Similarly, "ownership" of an IP range is out of scope. If an endpoint communicates to its peer that it can allocate addresses from a range, or route traffic to a range, the peer has no obligation to trust that information. Whether or not to trust this information is left to individual implementations and deployments. 5.2. Translation Some servers may wish to perform Network Address Translation (NAT) or any other modification to packets they forward. Doing so is out of scope for the proxying protocol. In particular, the ability to discover the presence of a NAT, negotiate NAT bindings, or check connectivity through a NAT is explicitly out of scope and left to future extensions. Servers that do not perform NAT will commonly forward packets similarly to how a traditional IP router would, but the specific of that are considered out of scope. In particular, decrementing the Hop Limit (or TTL) field of the IP header is out of scope for MASQUE and expected to be performed by a router behind the MASQUE server, or collocated with it. Chernyakhovsky, et al. Expires 12 July 2021 [Page 8] Internet-Draft IP Proxying Requirements January 2021 5.3. IP Packet Extraction How packets are forwarded between the IP proxying connection and the physical network is out of scope. For example, this can be accomplished on some operating systems using a TUN interface. How this is done is deliberately not specified and will be left to individual implementations. 6. Security Considerations This document only discusses requirements on a protocol that allows IP proxying. That protocol will need to document its security considerations. 7. IANA Considerations This document requests no actions from IANA. Acknowledgments The authors would like to thank participants of the MASQUE working group for their feedback. References Normative References [DGRAM] Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable Datagram Extension to QUIC", Work in Progress, Internet- Draft, draft-ietf-quic-datagram-01, 24 August 2020, . [H2] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext Transfer Protocol Version 2 (HTTP/2)", RFC 7540, DOI 10.17487/RFC7540, May 2015, . [H3] Bishop, M., "Hypertext Transfer Protocol Version 3 (HTTP/3)", Work in Progress, Internet-Draft, draft-ietf- quic-http-33, 15 December 2020, . [IPV4] Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 10.17487/RFC0791, September 1981, . Chernyakhovsky, et al. Expires 12 July 2021 [Page 9] Internet-Draft IP Proxying Requirements January 2021 [IPV6] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, . [QUIC] Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed and Secure Transport", Work in Progress, Internet-Draft, draft-ietf-quic-transport-33, 13 December 2020, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [TLS] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . Informative References [CONNECT-UDP] Schinazi, D., "The CONNECT-UDP HTTP Method", Work in Progress, Internet-Draft, draft-ietf-masque-connect-udp- 03, 5 January 2021, . [IKEV2] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. Kivinen, "Internet Key Exchange Protocol Version 2 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 2014, . [OAUTH] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012, . Authors' Addresses Chernyakhovsky, et al. Expires 12 July 2021 [Page 10] Internet-Draft IP Proxying Requirements January 2021 Alex Chernyakhovsky Google LLC 1600 Amphitheatre Parkway Mountain View, California 94043, United States of America Email: achernya@google.com Dallas McCall Google LLC 1600 Amphitheatre Parkway Mountain View, California 94043, United States of America Email: dallasmccall@google.com David Schinazi Google LLC 1600 Amphitheatre Parkway Mountain View, California 94043, United States of America Email: dschinazi.ietf@gmail.com Chernyakhovsky, et al. Expires 12 July 2021 [Page 11]