wdiff draft-schinazi-masque-01.txt draft-schinazi-masque-02.txt

Network Working Group D. Schinazi
Internet-Draft Google LLC
Intended status: Experimental July 08, 2019
Expires: 8 January 9, 2020
Expires: 11 July 2020

The MASQUE Protocol
draft-schinazi-masque-01
draft-schinazi-masque-02

Abstract

This document describes MASQUE (Multiplexed Application Substrate
over QUIC Encryption). MASQUE is a mechanism framework that allows co-locating
and obfuscating
concurrently running multiple networking applications behind inside an HTTPS web server.
The currently prevalent use-case is to
HTTP/3 connection. For example, MASQUE can allow running a proxy or VPN
server that is indistinguishable from an HTTPS server QUIC client to any
unauthenticated observer. We do not expect major providers
negotiate proxying capability with an HTTP/3 server, and CDNs
to deploy this behind their main TLS certificate, as they are not
willing to take the risk of getting blocked, as shown when domain
fronting was blocked. An expected subsequently
make use would be for individuals to
enable of this behind their personal websites via easy to configure
open-source software. functionality while concurrently processing HTTP/3
requests and responses.

This document is a straw-man proposal. It does not contain enough
details to implement the protocol, and is currently intended to spark
discussions on the approach it is taking. Discussion of this work is
encouraged to happen on the MASQUE IETF mailing list masque@ietf.org
[1]
(mailto:masque@ietf.org) or on the GitHub repository which contains
the draft: https://github.com/DavidSchinazi/masque-drafts [2].
(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.

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This Internet-Draft will expire on January 9, 11 July 2020.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2
1.1. Conventions and Definitions . . . . . . . . . . . . . . . 3
2. Usage Scenarios . . . . . . . . . . . . . . MASQUE Negotiation . . . . . . . . . 3
2.1. Protection from Network Providers . . . . . . . . . . . . 3
2.2. Protection from Web Servers . . . . . . . . . . . . . . . 4
2.3. Making a Home Server Available . . . . . . . . . . . . . 4
2.4. Onion Routing . . . . . . . . . . . . . . . . . . . . . . 4
3. Requirements . . . MASQUE Applications . . . . . . . . . . . . . . . . . . . . . 4 3
3.1. Invisibility of Usage . . . . . . . . . . . . . . . . . . 4
3.2. Invisibility of the Server . . . . . . . . . . . . . . . 5
3.3. Fallback to HTTP/2 over TLS over TCP . . . . . . . . . . 5
4. Overview of the Mechanism . . . . . . . . . . . . . . . . . . 5
5. Mechanisms the Server Can Advertise to Authenticated Clients 6
5.1. HTTP Proxy . . . . . . . . . . . . . . . . . . . . . . . 6
5.2. 3
3.2. DNS over HTTPS . . . . . . . . . . . . . . . . . . . . . 6
5.3. UDP 4
3.3. QUIC Proxying . . . . . . . . . . . . . . . . . . . . . . 6
5.4. QUIC 4
3.4. UDP Proxying . . . . . . . . . . . . . . . . . . . . . . 6
5.5. 4
3.5. IP Proxying . . . . . . . . . . . . . . . . . . . . . . . 7
5.6. Path MTU Discovery . . . . . . . . . . . . . . . . . . . 7
5.7. 4
3.6. Service Registration . . . . . . . . . . . . . . . . . . 7
6. Operation over HTTP/2 . . . . . . . . . . . . . . . . . . . . 7
7. 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7.1. Traffic Analysis . . . . . . . . . . . . . . . . . . . . 8
7.2. Untrusted Servers . . . . . . . . . . . . . . . . . . . . 8
8. 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. 5
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. 5
6.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. 5
6.2. Informative References . . . . . . . . . . . . . . . . . 10
9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 11
Design Justifications . . . . . . . . . . . . . . . . . . . . . . 11 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13 6

1. Introduction

This document describes MASQUE (Multiplexed Application Substrate
over QUIC Encryption). MASQUE is a mechanism framework that allows co-locating
and obfuscating
concurrently running multiple networking applications behind inside an HTTPS web server.
The currently prevalent use-case is to
HTTP/3 connection (see [HTTP3]). For example, MASQUE can allow running a proxy or VPN
server that is indistinguishable from an HTTPS server
QUIC client to any
unauthenticated observer. We do not expect major providers negotiate proxying capability with an HTTP/3 server,
and CDNs
to deploy this behind their main TLS certificate, as they are not
willing to take the risk of getting blocked, as shown when domain
fronting was blocked. An expected subsequently make use would be for individuals to
enable of this behind their personal websites via easy to configure
open-source software. functionality while concurrently
processing HTTP/3 requests and responses.

MASQUE Negotiation is performed using HTTP mechanisms, but MASQUE
applications can subsequently leverage QUIC [QUIC] features without
using HTTP.

This document is a straw-man proposal. It does not contain enough
details to implement the protocol, and is currently intended to spark
discussions on the approach it is taking. Discussion of this work is
encouraged to happen on the MASQUE IETF mailing list masque@ietf.org
[3]
(mailto:masque@ietf.org) or on the GitHub repository which contains
the draft: https://github.com/DavidSchinazi/masque-drafts [4].

MASQUE leverages the efficient head-of-line blocking prevention
features of the QUIC transport protocol [I-D.ietf-quic-transport]
when MASQUE is used in an HTTP/3 [I-D.ietf-quic-http] server. MASQUE
can also run in an HTTP/2 server [RFC7540] but at a performance cost.
(https://github.com/DavidSchinazi/masque-drafts).

1.1. Conventions and Definitions

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.

2. Usage Scenarios

There are currently multiple usage scenarios that can benefit from
MASQUE.

2.1. Protection from Network Providers

Some users may wish MASQUE Negotiation

In order to obfuscate negotiate the destination use 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.

2.2. Protection from Web Servers

There are many clients who would rather not establish a direct
connection to web servers, for example to avoid location tracking.
The clients can do that MASQUE protocol, the client
starts by running their traffic through sending a MASQUE
server. The web server will only see the IP address of request in the MASQUE
server, not that HTTP data of the client.

2.3. Making a Home Server Available

It is often difficult to connect an HTTP POST
request to a home server. "/.well-known/masque/initial". The IP address
might change over time. Firewalls in the home router or in the
network may block incoming connections. Using a MASQUE server as a
rendez-vous point helps resolve these issues.

2.4. Onion Routing

Routing traffic through a MASQUE server only provides partial
protection against tracking, because the MASQUE server knows the
address of the client. Onion routing as it exists today mitigates
this issue for TCP/TLS. A MASQUE server could allow onion routing
over QUIC.

In this scenario, the client establishes a connection to the MASQUE
server, then through that can use this to another
request specific MASQUE server, etc. This
creates a tree of applications and advertise support for MASQUE servers rooted at the client. QUIC
connections are mapped to a specific branch of the tree.
extensions. The first MASQUE server knows the actual address of the client, but the other
MASQUE servers only know the address of the previous server. To
assure reasonable privacy, the path should include at least 3 MASQUE
servers.

3. Requirements

This section describes the goals and requirements chosen indicates support for the
MASQUE protocol.

3.1. Invisibility of Usage

An authenticated client using MASQUE features appears to observers as
a regular HTTPS client. Observers only see that HTTP/3 or HTTP/2 is
being used over by
sending an encrypted channel. No part of the exchanges
between client HTTP status code 200 response, and server may stick out. Note that traffic analysis
is discussed in Section 7.1.

3.2. Invisibility of the Server

To anyone without private keys, can use the server is indistinguishable from
a regular web server. It is impossible data to send an unauthenticated
probe that
inform the server would reply to differently than if it were a
normal web server.

3.3. Fallback to HTTP/2 over TLS over TCP

When QUIC is blocked, client of which MASQUE can run over TCP and still satisfy
previous requirements. Note that applications are now in this scenario performance may be
negatively impacted.

4. Overview of use, and
various configuration parameters.

Both the Mechanism

The server runs an HTTPS server on port 443, MASQUE negotiation initial request and has a valid TLS
certificate for its domain. The client has a public/private key
pair, and the server maintains response carry a
list of authorized MASQUE clients,
and their public key. (Alternatively, clients can also be
authenticated using a shared secret.) type-length-value fields. The client starts by
establishing type field is a regular HTTPS connection number
corresponding to the server (HTTP/3 over
QUIC or HTTP/2 over TLS 1.3 [RFC8446] over TCP), a MASQUE application, and validates the
server's TLS certificate as it normally would for HTTPS. If
validation fails, the connection is aborted. At this point the
client can send regular unauthenticated HTTP requests to the server.
When it wishes to start MASQUE, the client uses HTTP Transport
Authentication (draft-schinazi-httpbis-transport-auth) to prove its
possession of its associated key. encoded as a QUIC
variable-length integer. The client sends the Transport-
Authentication header alongside an HTTP CONNECT request for "/.well-
known/masque/initial" with the :protocol pseudo-header length field set to
"masque".

When the server receives this CONNECT request, it authenticates represents the
client and if that fails responds with code "405 Method Not Allowed",
making sure its response is length in
bytes of the same value field, encoded as what it would return for any
unexpected CONNECT request. If authentication succeeds, the server
responds with code "101 Switching Protocols", and from then on this
HTTP stream is now dedicated to the MASQUE protocol. That protocol
provides a reliable bidirectional message exchange mechanism, which
is used by QUIC variable-length integer.
The contents of the client and server to negotiate what protocol options
are supported and enabled value field or defined by policy, and client VPN configuration
such as IP addresses. its corresponding
MASQUE application. When using QUIC, this protocol also allows parsing, endpoints to negotiate the use of QUIC extensions, such as support
for the DATAGRAM extension [I-D.pauly-quic-datagram].

Clients MUST NOT attempt to "resume" ignore unknown
MASQUE state similarly to how
TLS sessions can be resumed. Every new QUIC or TLS connection
requires fully authenticating the client and server. QUIC 0-RTT and
TLS early data MUST NOT be used with applications.

3. MASQUE Applications

As soon as they are not forward
secure.

5. Mechanisms the Server Can Advertise to Authenticated Clients

Once a server has authenticated accepted the client's MASQUE CONNECT initial
request, it advertises services that the client may use.

5.1. can advertise support for MASQUE Applications, which will
be multiplexed over this HTTP/3 connection.

3.1. HTTP Proxy

The client can make proxied HTTP requests through the server to other
servers. In practice this will mean using the CONNECT method to
establish a stream over which to run TLS to a different remote
destination. The proxy applies back-pressure to streams in both
directions.

5.2.

3.2. DNS over HTTPS

The client can send DNS queries using DNS over HTTPS (DoH) [RFC8484]
to the MASQUE server.

5.3. UDP Proxying

In order to support WebRTC or QUIC [DOH] to further servers, clients need a
way to relay UDP onwards to a remote server. In practice for most
widely deployed protocols other than DNS, this involves many
datagrams over the same ports. Therefore this mechanism implements
that efficiently: clients can use the
MASQUE protocol stream to
request an UDP association to an IP address and UDP port pair. In
QUIC, the server would reply with a DATAGRAM_ID that the client can
then use to have UDP datagrams sent to this remote server. Datagrams
are then simply transferred between the DATAGRAMs with this ID and
the outer server. There will also be a message on the MASQUE
protocol stream to request shutdown of a UDP association to save
resources when it is no longer needed. When running over TCP, the
client opens a new stream with a CONNECT request to the "masque-udp-
proxy" protocol and then sends datagrams encapsulated inside the
stream with a two-byte length prefix in network byte order. The
target IP and port are sent as part of the URL query. Resetting that
stream instructs the server to release any associates resources.

5.4.

3.3. QUIC Proxying

By leveraging QUIC client connection IDs, a MASQUE server can act as
a QUIC proxy while only using one UDP port. The server informs the
client of a scheme for client connection IDs (for example, random of
a minimum length or vended by the MASQUE server) and then the server
can forward those packets to further web servers.

This mechanism can elide the connection IDs on the link between the
client and MASQUE server by negotiating a mapping between
DATAGRAM_IDs and the tuple (client connection ID, server connection
ID, server IP address, server port).

Compared to UDP proxying, this mode has the advantage of only
requiring one UDP port to be open on the MASQUE server, and can lower
the overhead on the link between client and MASQUE server by
compressing connection IDs.

5.5.

3.4. UDP Proxying

In order to support WebRTC or QUIC to further servers, clients need a
way to relay UDP onwards to a remote server. In practice for most
widely deployed protocols other than DNS, this involves many
datagrams over the same ports. Therefore this mechanism implements
that efficiently: clients can use the MASQUE protocol stream to
request an UDP association to an IP address and UDP port pair. In
QUIC, the server would reply with a DATAGRAM_ID that the client can
then use to have UDP datagrams sent to this remote server. Datagrams
are then simply transferred between the DATAGRAMs with this ID and
the outer server. There will also be a message on the MASQUE
protocol stream to request shutdown of a UDP association to save
resources when it is no longer needed.

3.5. IP Proxying

For the rare cases where the previous mechanisms are not sufficient,
proxying can be performed at the IP layer. This would use a
different DATAGRAM_ID and IP datagrams would be encoded inside it
without framing. Over TCP, a dedicated stream with two byte length
prefix would be used. The server can inspect the IP datagram to look
for the destination address in the IP header.

5.6. Path MTU Discovery

In the main deployment of this mechanism, QUIC will be used between
client and server, and that will most likely be the smallest MTU link
in the path due to QUIC header and authentication tag overhead. The
client is responsible for not sending overly large UDP packets and
notifying the server of the low MTU. Therefore PMTUD is currently
seen as out of scope of this document.

5.7.

3.6. Service Registration

MASQUE can be used to make a home server accessible on the wide area.
The home server authenticates to the MASQUE server and registers a
domain name it wishes to serve. The MASQUE server can then forward
any traffic it receives for that domain name (by inspecting the TLS
Server Name Indication (SNI) extension) to the home server. This
received traffic is not authenticated and it allows non-modified
clients to communicate with the home server without knowing it is not
colocated with the MASQUE server.

To help obfuscate the home server, deployments can use Encrypted
Server Name Indication (ESNI) [I-D.ietf-tls-esni]. [ESNI]. That will require the MASQUE server
sending the cleartext SNI to the home server.

6. Operation over HTTP/2

MASQUE implementations using HTTP/3 MUST support the fallback to
HTTP/2 to avoid incentivizing censors to block HTTP/3 or QUIC. When
running over HTTP/2, MASQUE uses the Extended CONNECT method to
negotiate the use of datagrams over an HTTP/2 stream
[I-D.kinnear-httpbis-http2-transport].

MASQUE implementations SHOULD discover that HTTP/3 is available (as
opposed to only HTTP/2) using the same mechanism as regular HTTP
traffic. This current standardized mechanism for this is HTTP
Alternative Services [RFC7838], but future mechanisms such as
[I-D.schwartz-httpbis-dns-alt-svc] can be used if they become
widespread.

4. Security Considerations

Here be dragons. TODO: slay the dragons.

7.1. Traffic Analysis

While MASQUE ensures that proxied traffic appears similar to regular
HTTP traffic, it doesn't inherently defeat traffic analysis.
However, the fact that MASQUE leverages QUIC allows it to segment
STREAM frames over multiple packets and add PADDING frames to change
the observable characteristics of its encrypted traffic. The exact
details of how to change traffic patterns to defeat traffic analysis
is considered an open research question and is out of scope for this
document.

When multiple MASQUE servers are available, a client can leverage
QUIC connection migration to seamlessly transition its end-to-end
QUIC connections by treating separate MASQUE servers as different
paths. This could afford an additional level of obfuscation in hopes
of rendering traffic analysis less effective.

7.2. Untrusted Servers

As with any proxy or VPN technology, MASQUE hides some of the
client's private information (such as who they are communicating
with) from their network provider by transferring that information to
the MASQUE server. It is paramount that clients only use MASQUE
servers that they trust, as a malicious actor could easily setup a
MASQUE server and advertise it as a privacy solution in hopes of
attracting users to send it their traffic.

5. IANA Considerations

This document will need request IANA to register:

o register the "/.well-known/masque/" "/.well-known/
masque/" URI (expert review)
https://www.iana.org/assignments/well-known-uris/well-known-
uris.xhtml [5]

o The "masque" and "masque-udp-proxy" extended HTTP CONNECT
protocols

We will also need to define the MASQUE control protocol and that https://www.iana.org/assignments/well-
known-uris/well-known-uris.xhtml (https://www.iana.org/assignments/
well-known-uris/well-known-uris.xhtml).

This document will
be likely request IANA to define create a new registries MASQUE Applications
registry which governs a 62-bit space of its own.

9. MASQUE application types.

6. References

9.1.

6.1. Normative References

[I-D.ietf-quic-http]

[HTTP3] Bishop, M., "Hypertext Transfer Protocol Version 3
(HTTP/3)", draft-ietf-quic-http-20 (work Work in progress),
April 2019.

[I-D.ietf-quic-transport] Progress, Internet-Draft, draft-ietf-
quic-http-24, 4 November 2019, <http://www.ietf.org/
internet-drafts/draft-ietf-quic-http-24.txt>.

[QUIC] Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
and Secure Transport", draft-ietf-quic-transport-20 (work Work in progress), April 2019.

[I-D.kinnear-httpbis-http2-transport]
Kinnear, E. and T. Pauly, "Using HTTP/2 as a Transport for
Arbitrary Bytestreams", draft-kinnear-httpbis-
http2-transport-01 (work in progress), March 2019.

[I-D.pauly-quic-datagram]
Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable
Datagram Extension to QUIC", draft-pauly-quic-datagram-03
(work in progress), July 2019. Progress, Internet-Draft,
draft-ietf-quic-transport-24, 3 November 2019,
<http://www.ietf.org/internet-drafts/draft-ietf-quic-
transport-24.txt>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<https://www.rfc-editor.org/info/rfc7540>.

[RFC7838] Nottingham, M., McManus, P., and J. Reschke, "HTTP
Alternative Services", RFC 7838, DOI 10.17487/RFC7838,
April 2016, <https://www.rfc-editor.org/info/rfc7838>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.

[RFC8484]

[DOH] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.

9.2.

6.2. Informative References

[I-D.ietf-httpbis-http2-secondary-certs]
Bishop, M., Sullivan, N., and M. Thomson, "Secondary
Certificate Authentication in HTTP/2", draft-ietf-httpbis-
http2-secondary-certs-04 (work in progress), April 2019.

[I-D.ietf-tls-esni]

[ESNI] Rescorla, E., Oku, K., Sullivan, N., and C. Wood,
"Encrypted Server Name Indication for TLS 1.3", draft-
ietf-tls-esni-03 (work in progress), March 2019.

[I-D.pardue-httpbis-http-network-tunnelling]
Pardue, L., "HTTP-initiated Network Tunnelling (HiNT)",
draft-pardue-httpbis-http-network-tunnelling-01 (work in
progress), October 2018.

[I-D.schwartz-httpbis-dns-alt-svc]
Schwartz, B. and M. Bishop, "Finding HTTP Alternative
Services via the Domain Name Service", draft-schwartz-
httpbis-dns-alt-svc-02 (work in progress), April 2018.

[I-D.schwartz-httpbis-helium]
Schwartz, B., "Hybrid Encapsulation Layer for IP and UDP
Messages (HELIUM)", draft-schwartz-httpbis-helium-00 (work
in progress), June 2018.

[I-D.sullivan-tls-post-handshake-auth]
Sullivan, N., Thomson, M., and M. Bishop, "Post-Handshake
Authentication in TLS", draft-sullivan-tls-post-handshake-
auth-00 (work Work in progress), August 2016.

[RFC8441] McManus, P., "Bootstrapping WebSockets with HTTP/2",
RFC 8441, DOI 10.17487/RFC8441, September 2018,
<https://www.rfc-editor.org/info/rfc8441>.

[RFC8471] Popov, A., Ed., Nystroem, M., Balfanz, D., and J. Hodges,
"The Token Binding Protocol Version 1.0", RFC 8471,
DOI 10.17487/RFC8471, October 2018,
<https://www.rfc-editor.org/info/rfc8471>.

9.3. URIs

[1] mailto:masque@ietf.org

[2] https://github.com/DavidSchinazi/masque-drafts

[3] mailto:masque@ietf.org

[4] https://github.com/DavidSchinazi/masque-drafts

[5] https://www.iana.org/assignments/well-known-uris/well-known-
uris.xhtml
Progress, Internet-Draft, draft-ietf-tls-esni-05, 4
November 2019, <http://www.ietf.org/internet-drafts/draft-
ietf-tls-esni-05.txt>.

Acknowledgments

This proposal was inspired directly or indirectly by prior work from
many people. In particular, this work is related to
[I-D.schwartz-httpbis-helium] and
[I-D.pardue-httpbis-http-network-tunnelling]. The mechanism used to
run the MASQUE protocol over HTTP/2 streams was inspired by
[RFC8441]. Brendan Moran is to thank for the idea of leveraging
connection migration across MASQUE servers. The author would like to thank Christophe A., an inspiration and true
leader of VPNs.

Design Justifications

Using an exported key as a nonce allows us to prevent replay attacks
(since it depends on randomness from both endpoints of the TLS
connection) without requiring the server to send an explicit nonce
before it has authenticated the client. Adding an explicit nonce
mechanism would expose the server as it would need to send these
nonces to clients that have not been authenticated yet.

The rationale for a separate MASQUE protocol stream is to allow
server-initiated messages. If we were to use HTTP semantics, we
would only be able to support the client-initiated request-response
model. We could have used WebSocket for this purpose but that would
have added wire overhead and dependencies without providing useful
features.

There are many other ways to authenticate HTTP, however the
authentication used here needs to work in a single client-initiated
message to meet the requirement of not exposing the server.

The current proposal would also work with TLS 1.2, but in that case
TLS false start and renegotiation must be disabled, and the extended
master secret and renegotiation indication TLS extensions must be
enabled.

If the server or client want to hide that HTTP/2 is used, the client
can set its ALPN to an older version of HTTP and then use the Upgrade
header to upgrade to HTTP/2 inside the TLS encryption.

The client authentication used here is similar to how Token Binding
[RFC8471] operates, but it has very different goals. MASQUE does not
use token binding directly because using token binding requires
sending the token_binding TLS extension in the TLS ClientHello, and
that would stick out compared to a regular TLS connection.

TLS post-handshake authentication
[I-D.sullivan-tls-post-handshake-auth] is not used by this proposal
because that requires sending the "post_handshake_auth" extension in
the TLS ClientHello, and that would stick out from a regular HTTPS
connection.

Client authentication could have benefited from Secondary Certificate
Authentication in HTTP/2 [I-D.ietf-httpbis-http2-secondary-certs],
however that has two downsides: it requires the server advertising
that it supports it in its SETTINGS, and it cannot be sent unprompted
by the client, so the server would have to request authentication.
Both of these would make the server stick out from regular HTTP/2
servers.

MASQUE proposes a new client authentication method (as opposed to
reusing something like HTTP basic authentication) because HTTP
authentication methods are conceptually per-request (they need to be
repeated on each request) whereas the new method is bound to the
underlying connection (be it QUIC or TLS). In particular, this
allows sending QUIC DATAGRAM frames without authenticating every
frame individually. Additionally, HMAC Nick Harper, Christian
Huitema, Marcus Ihlar, Eric Kinnear, Mirja Kuehlewind, Brendan Moran,
Lucas Pardue, Tommy Pauly, Zaheduzzaman Sarker, Ben Schwartz, and asymmetric keying are
preferred to sending a password
Christopher A. Wood for client authentication since they
have a tighter security bound. Going into the design rationale,
HMACs (and signatures) need some data to sign, and to avoid replay
attacks that should be a fresh nonce provided by the remote peer.
Having the server provide an explicit nonce would leak the existence
of the server so we use TLS keying material exporters as they provide
us with a nonce that contains entropy from the server without
requiring explicit communication. their input.

Author's Address

David Schinazi
Google LLC
1600 Amphitheatre Parkway
Mountain View, California 94043 94043,
United States of America

Email: dschinazi.ietf@gmail.com