Internet DRAFT - draft-schinazi-masque-proxy
draft-schinazi-masque-proxy
Network Working Group D. Schinazi
Internet-Draft Google LLC
Intended status: Informational 28 February 2024
Expires: 31 August 2024
The MASQUE Proxy
draft-schinazi-masque-proxy-02
Abstract
MASQUE (Multiplexed Application Substrate over QUIC Encryption) is a
set of protocols and extensions to HTTP that allow proxying all kinds
of Internet traffic over HTTP. This document defines the concept of
a "MASQUE Proxy", an Internet-accessible node that can relay client
traffic in order to provide privacy guarantees.
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://davidschinazi.github.io/masque-drafts/draft-schinazi-masque-
proxy.html. Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-schinazi-masque-proxy/.
Source for this draft and an issue tracker can be found at
https://github.com/DavidSchinazi/masque-drafts.
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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 31 August 2024.
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Copyright Notice
Copyright (c) 2024 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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Privacy Protections . . . . . . . . . . . . . . . . . . . . . 3
2.1. Protection from Web Servers . . . . . . . . . . . . . . . 3
2.2. Protection from Network Providers . . . . . . . . . . . . 3
2.3. Partitioning . . . . . . . . . . . . . . . . . . . . . . 3
2.4. Obfuscation . . . . . . . . . . . . . . . . . . . . . . . 4
3. Related Technologies . . . . . . . . . . . . . . . . . . . . 4
3.1. OHTTP . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. DoH . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Informative References . . . . . . . . . . . . . . . . . . . 5
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
In the early days of HTTP, requests and responses weren't encrypted.
In order to add features such as caching, HTTP proxies were developed
to parse HTTP requests from clients and forward them on to other HTTP
servers. As SSL/TLS became more common, the CONNECT method was
introduced [CONNECT] to allow proxying SSL/TLS over HTTP. That gave
HTTP the ability to create tunnels that allow proxying any TCP-based
protocol. While non-TCP-based protocols were always prevalent on the
Internet, the large-scale deployment of QUIC [QUIC] meant that TCP no
longer represented the majority of Internet traffic. Simultaneously,
the creation of HTTP/3 [HTTP/3] allowed running HTTP over a non-TCP-
based protocol. In particular, QUIC allows disabling loss recovery
[DGRAM] and that can then be used in HTTP [HTTP-DGRAM]. This
confluence of events created both the possibility and the necessity
for new proxying technologies in HTTP.
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This led to the creation of MASQUE (Multiplexed Application Substrate
over QUIC Encryption). MASQUE allows proxying both UDP
([CONNECT-UDP]) and IP ([CONNECT-IP]) over HTTP. While MASQUE has
uses beyond improving user privacy, its focus and design are best
suited for protecting sensitive information.
2. Privacy Protections
There are currently multiple usage scenarios that can benefit from
using a MASQUE Proxy.
2.1. Protection from Web Servers
Connecting directly to Web servers allows them to access the public
IP address of the user. There are many privacy concerns relating to
user IP addresses [IP-PRIVACY]. Because of these, many user agents
would rather not establish a direct connection to web servers. They
can do that by running their traffic through a MASQUE Proxy. The web
server will only see the IP address of the MASQUE Proxy, not that of
the client.
2.2. Protection from Network Providers
Some users may wish to obfuscate the destination of their network
traffic from their network provider. This prevents network providers
from using data harvested from this network traffic in ways the user
did not intend.
2.3. Partitioning
While routing traffic through a MASQUE proxy reduces the network
provider's ability to observe traffic, that information is transfered
to the proxy operator. This can be suitable for some threat models,
but for the majority of users transferring trust from their network
provider to their proxy (or VPN) provider is not a meaningful
security improvement.
There is a technical solution that allows resolving this issue: it is
possible to nest MASQUE tunnels such that traffic flows through
multiple MASQUE proxies. This has the advantage of partitioning
sensitive information to prevent correlation [PARTITION].
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Though the idea of nested tunnels dates back decades [TODO], MASQUE
now allows running HTTP/3 end-to-end from a user agent to an origin
via multiple nested CONNECT-UDP tunnels. The proxy closest to the
user can see the user's IP address but not the origin, whereas the
other proxy can see the origin without knowing the user's IP address.
If the two proxies are operated by non-colluding entities, this
allows hiding the user's IP address from the origin without the
proxies knowing the user's browsing history.
2.4. Obfuscation
The fact that MASQUE is layered over HTTP makes it much more
resilient to detection. To network observers, the unencrypted bits
in a QUIC connection used for MASQUE are indistinguishable from those
of a regular Web browsing connection. Separately, if paired with a
non-probable HTTP authentication scheme [SIGNATURE-AUTH], any Web
server can also become a MASQUE proxy while remaining
indistinguishable from a regular Web server. It might still be
possible to detect some level of MASQUE usage by analyzing encrypted
traffic patterns, however the cost of performing such an analysis at
scale makes it impractical.
This allows MASQUE to operate on networks that disallow VPNs by using
a combination of protocol detection and blocklists.
3. Related Technologies
This section discusses how MASQUE fits in with other contemporary
privacy-focused IETF protocols.
3.1. OHTTP
Oblivious HTTP [OHTTP] uses a cryptographic primitive [HPKE] that is
more lightweight than TLS [TLS], making it a great fit for
decorrelating HTTP requests. In traditional Web browsing, the user
agent will often make many requests to the same origin (e.g., to load
HTML, style sheets, images, scripts) and those requests are
correlatable since the origin can include identifying query
parameters to join separate requests. In such scenarios, MASQUE is a
better fit since it operates at the granularity of a connection.
However, there are scenarios where a user agent might want to make
non-correlatable requests (e.g., to anonymously report telemetry);
for those, OHTTP provides better efficiency than using MASQUE with a
separate connection per request. While OHTTP and MASQUE are separate
technologies that serve different use cases, they can be colocated on
the same HTTP server that acts as both a MASQUE Proxy and an OHTTP
Relay.
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3.2. DoH
DNS over HTTPS [DoH] allows encrypting DNS traffic by sending it
through an encrypted HTTP connection. Colocating a DoH server with a
MASQUE IP proxy provides better performance than using DNS over port
53 inside the encrypted tunnel.
4. Security Considerations
Implementers of a MASQUE proxy need to review the Security
Considerations of the documents referenced by this one.
5. IANA Considerations
This document has no IANA actions.
6. Informative References
[CONNECT] Khare, R. and S. Lawrence, "Upgrading to TLS Within
HTTP/1.1", RFC 2817, DOI 10.17487/RFC2817, May 2000,
<https://www.rfc-editor.org/rfc/rfc2817>.
[CONNECT-IP]
Pauly, T., Ed., Schinazi, D., Chernyakhovsky, A.,
Kühlewind, M., and M. Westerlund, "Proxying IP in HTTP",
RFC 9484, DOI 10.17487/RFC9484, October 2023,
<https://www.rfc-editor.org/rfc/rfc9484>.
[CONNECT-UDP]
Schinazi, D., "Proxying UDP in HTTP", RFC 9298,
DOI 10.17487/RFC9298, August 2022,
<https://www.rfc-editor.org/rfc/rfc9298>.
[DGRAM] Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable
Datagram Extension to QUIC", RFC 9221,
DOI 10.17487/RFC9221, March 2022,
<https://www.rfc-editor.org/rfc/rfc9221>.
[DoH] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/rfc/rfc8484>.
[HPKE] Barnes, R., Bhargavan, K., Lipp, B., and C. Wood, "Hybrid
Public Key Encryption", RFC 9180, DOI 10.17487/RFC9180,
February 2022, <https://www.rfc-editor.org/rfc/rfc9180>.
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[HTTP-DGRAM]
Schinazi, D. and L. Pardue, "HTTP Datagrams and the
Capsule Protocol", RFC 9297, DOI 10.17487/RFC9297, August
2022, <https://www.rfc-editor.org/rfc/rfc9297>.
[HTTP/3] Bishop, M., Ed., "HTTP/3", RFC 9114, DOI 10.17487/RFC9114,
June 2022, <https://www.rfc-editor.org/rfc/rfc9114>.
[IP-PRIVACY]
Finkel, M., Lassey, B., Iannone, L., and B. Chen, "IP
Address Privacy Considerations", Work in Progress,
Internet-Draft, draft-irtf-pearg-ip-address-privacy-
considerations-01, 23 October 2022,
<https://datatracker.ietf.org/doc/html/draft-irtf-pearg-
ip-address-privacy-considerations-01>.
[OHTTP] Thomson, M. and C. A. Wood, "Oblivious HTTP", RFC 9458,
DOI 10.17487/RFC9458, January 2024,
<https://www.rfc-editor.org/rfc/rfc9458>.
[PARTITION]
Kühlewind, M., Pauly, T., and C. A. Wood, "Partitioning as
an Architecture for Privacy", Work in Progress, Internet-
Draft, draft-iab-privacy-partitioning-05, 11 January 2024,
<https://datatracker.ietf.org/doc/html/draft-iab-privacy-
partitioning-05>.
[QUIC] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/rfc/rfc9000>.
[SIGNATURE-AUTH]
Schinazi, D., Oliver, D., and J. Hoyland, "The Signature
HTTP Authentication Scheme", Work in Progress, Internet-
Draft, draft-ietf-httpbis-unprompted-auth-06, 23 January
2024, <https://datatracker.ietf.org/doc/html/draft-ietf-
httpbis-unprompted-auth-06>.
[TLS] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/rfc/rfc8446>.
[TODO] "find that 20 year old email about using nested CONNECT
tunnels with SSL to improve privacy".
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Acknowledgments
MASQUE was originally inspired directly or indirectly by prior work
from many people. The author would like to thank Nick Harper,
Christian Huitema, Marcus Ihlar, Eric Kinnear, Mirja Kuehlewind,
Brendan Moran, Lucas Pardue, Tommy Pauly, Zaheduzzaman Sarker and Ben
Schwartz for their input.
In particular, the probing resistance component of MASQUE came from a
conversation with Chris A. Wood as we were preparing a draft for an
upcoming Thursday evening BoF.
All of the MASQUE enthusiasts and other contributors to the MASQUE
working group are to thank for the successful standardization of
[HTTP-DGRAM], [CONNECT-UDP], and [CONNECT-IP].
The author would like to express immense gratitude to Christophe A.,
an inspiration and true leader of VPNs.
Author's Address
David Schinazi
Google LLC
1600 Amphitheatre Parkway
Mountain View, CA 94043
United States of America
Email: dschinazi.ietf@gmail.com
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