| Internet-Draft | The MASQUE Proxy | September 2023 |
| Schinazi | Expires 10 March 2024 | [Page] |
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.¶
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.¶
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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.¶
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.¶
There are currently multiple usage scenarios that can benefit from using a MASQUE Proxy.¶
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.¶
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.¶
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].¶
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.¶
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 [UNPROMPTED-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.¶
Implementers of a MASQUE proxy need to review the Security Considerations of the documents referenced by this one.¶
This document has no IANA actions.¶
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.¶