Internet DRAFT - draft-kuehlewind-masque-quic-substrate
draft-kuehlewind-masque-quic-substrate
Network Working Group M. Kuehlewind
Internet-Draft Z. Sarker
Intended status: Informational Ericsson
Expires: 10 September 2020 T. Fossati
Arm
L. Pardue
Cloudflare
9 March 2020
Use Cases and Requirements for QUIC as a Substrate
draft-kuehlewind-masque-quic-substrate-00
Abstract
In situations where direct connectivity is not available or desired,
proxies in the network are used to forward and potentially translate
traffic. TCP is often used as a proxying or tunneling protocol.
QUIC is a new, emerging transport protocol and there is a similar
expectation that it too will be used as a substrate once it is widely
deployed. Using QUIC instead of TCP in existing scenarios will allow
proxying and tunneling services to maintain the benefits of QUIC
natively, without degrading the performance and security
characteristics. QUIC also opens up new opportunities for these
services to have lower latency and better multistreaming support.
This document summarizes current and future usage scenarios to derive
requirements for QUIC as a substrate and to provide additional
considerations for proxy signaling and control protocol as proposed
by MASQUE.
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 10 September 2020.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Usage Scenarios . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Obfuscation via Tunneling . . . . . . . . . . . . . . . . 3
2.2. Advanced Support of User Agents . . . . . . . . . . . . . 5
2.2.1. Security and Access Policy Enforcement . . . . . . . 6
2.3. Frontend Support for Load Balancing and Migration/
Mobility . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4. IoT Gateways . . . . . . . . . . . . . . . . . . . . . . 7
2.5. Multi-hop Chaining Usage . . . . . . . . . . . . . . . . 8
2.5.1. Considerations for Multiple Encryption . . . . . . . 9
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 9
4. Review of Existing Approaches . . . . . . . . . . . . . . . . 10
5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 11
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Normative References . . . . . . . . . . . . . . . . . . 11
6.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
QUIC is a new transport protocol that was developed with a focus on
optimizing HTTP traffic by supporting multiplexing without head-of-
line-blocking and integrating security directly into the transport.
This tight integration of security allows the transport and security
handshakes to be combined into a single round-trip exchange, after
which both the transport connection and authenticated encryption keys
are ready.
Based on the expectation that QUIC will be widely used for HTTP, it
follows that there will also be a need to enable the use of QUIC for
HTTP proxy services.
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Beyond HTTP, however, QUIC provides a general-purpose transport
protocol that can be used for many other kinds of traffic, whenever
the features provided by QUIC (compared to existing options, like
TCP) are beneficial to the high-layer service. Specifically, QUIC's
ability to multiplex, encrypt data, and migrate between network paths
makes it ideal for solutions that needs to tunnel or proxy traffic.
Existing proxies that are not based on QUIC are often transparent.
That is, they do not require the cooperation of the ultimate
connection endpoints, and are often not visible to one or both of the
endpoints. If QUIC provides the basis for future tunneling and
proxying solutions, it is expected that this relationship will
change. At least one of the endpoints will be aware of the proxy and
explicitly coordinate with it. This allows client hosts to make
explicit decisions about the services they request from proxies (for
example, simple forwarding or more advance, e.g. performance-
optimizing, services), and to do so using a secure communication
channel between themselves and the proxy.
MASQUE [I-D.schinazi-masque] is a proposed framework that allows
running multiple network or application services inside one QUIC
connection to be forwarded to one or more target servers. The end-
to-end traffic between the client and the target server will be
tunnelled in a (outer) QUIC connection between the client and the
MASQUE server. This outer connection can also be used to securely
exchange additional signal or control information between the MASQUE
server and the client.
This document describes some of the use cases for using QUIC for
proxying and tunneling, as proposed by MASQUE, and explains the
protocol impacts and tradeoffs of such deployments.
2. Usage Scenarios
2.1. Obfuscation via Tunneling
Tunnels are used in many scenarios within the core of the network
from a client endpoint to a proxy middlepoint on the way towards the
server. In many cases, when the client explicitly decides to use the
support of a proxy in order to connect to a server, it does so
because a direct connection may be blocked or impaired. This can
either be the case in e.g. enterprise network where traffic is
firewalled and web traffic needs to be routed over an explicitly
provided HTTP proxy, or other reasons for blocking of certain
services e.g. due to censorship, data exfiltration protection, etc.
Tunneling through a proxy server can provide various benefits,
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particularly when using a proxy that has a secure multiplexed channel
like QUIC:
* Obfuscating the traffic patterns of the traffic from the
perspective of observers between the client and the proxy. If the
content of connections to many end servers can be coalesced as one
flow, it becomes increasingly difficult for observers to detect
how many inner connections are being used, or what the content of
those connections are.
* Obfuscating the client's IP address from the perspective of
observers after the proxy, to the end server itself. This allows
the client to reduce information leaked about its actual location,
improving privacy.
* Obfuscating the end server's IP address from the observers between
the client and the proxy, which protects the identity of a private
server's address or circumvents local firewall rules.
In any of these tunneling scenarios, including those deployed today,
the client explicitly decides to make use of a proxy service while it
is usually fully transparent for the server, or even with the
intention to hide the client's identity from the server. This is
explicitly part of the design as these services are targeting an
impaired or otherwise constrained network setup.
Therefore, in this usage scenario the client knows the proxy's
address and explicitly selects to connect to the proxy in order to
instruct the proxy to forward its traffic to a specific target
server. Often the proxy is also preconfigured to "know" the client
and therefore the client needs to authenticate itself (e.g. using
HTTP Transport Authentication [I-D.schinazi-httpbis-transport-auth]).
But even without authentication, at a minimum, the client needs to
communicate directly with the proxy to provide the address of the
target server it wants to connect to, e.g. using HTTP CONNECT, and
potentially other information needed to inform the behaviour of the
proxy.
Usually the server is not aware of the proxy in the middle, so the
proxy needs to re-write the IP address of any traffic inside the
tunnel to ensure that the return traffic is also routed back to the
proxy. This is also often used to conceal the address/location of
the client to the server, e.g. to access local content that would not
be accessible by the client at its current location otherwise.
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2.2. Advanced Support of User Agents
Depending on the traffic that is sent "over" the proxy, it is also
possible that the proxy can perform additional support services if
requested by the client. Today, Performance Enhancing Proxies (PEPs)
usually work transparently by either fully or partially terminating
the transport connection. For many of these support services the
termination is actually not needed and may even be problematic.
However, it is often the only, or at least easiest, solution if no
direct communication with the client is available. Enabling these
services based on an explicit tunnel setup between the client and the
proxy provides such a communication channel and makes it possible to
exchange information in a private and authenticated way.
It is expected that in-network functions are usually provided close
to the client e.g. hosted by the access network provider. Having
this direct relation between the endpoint and the network service is
also necessary in order to discover the service, as the assumption is
that a client knows how to address the proxy service and which
service is offered (besides forwarding). Such a setup is especially
valuable in access networks with challenging link environments such
as satellite or cellular networks. While end-to-end functions need
to be designed to handle all kind of network conditions, direct
support from the network can help to optimize for the specific
characteristics of the access network such as use of link-specific
congestion control or local repair mechanisms.
Further, if not provided by the server directly, a network support
function can also assist the client to adapt or prioritize the
traffic based on user preferences or device characteristics and
capabilities. Again, especially if the access network is
constrained, this can benefit both the network provider to save
resources and the client to receive the desired service quicker or
less impaired. Such a service could even be extended to include
caching or pre-fetching if the necessary trust relationship between
the client and the proxy exists.
Depending on the function requested, the proxy would need to access
or alter the traffic or context which is limiting due to the
necessary trust. Therefore alternative models should be pursued in
most cases. One such model is explicit exchange of information about
the current network state from the proxy to the client. This enables
some services to function by having the end-to-end peers act on or
inject the learned information from the proxy into the end-to-end
connection(s). Thus achieving the benefits without the need to
access the content or some of the traffic metadata directly.
Especially transport layer optimizations do not need access to the
actual user content. Network functions should generally minimize
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dependencies to higher layer characteristics as those may change
frequently.
Similar to previous usage scenario, in this setup the client
explicitly selects the proxy and specifies the requested support
function. Often the server may not need to be aware of it but
depending on the optimization function, server cooperation could be
beneficial as well. Usually though, it is expected that even if the
server is aware, no direct information exchange is needed between the
proxy and the server. Instead, any needed information will be
provided "over" the client and thus, the client and the proxy need a
direct and secured communication channel in order to request and
configure a service and exchange or expose the needed information and
metadata.
2.2.1. Security and Access Policy Enforcement
Some deployment models may wish to enforce security or access
policies on traffic flowing between domains (physical, logical,
administrative, security etc.). To support this, endpoints
coordinate through a gateway that can require information about the
transport layer, application layer and application content. Policy
is generally configured out-of-band, either statically or through
some independent control plane.
In one use case, the enforcement function controls egress traffic; a
client connects to a proxy, typically inside the same domain, in
order to cross the domain boundary. In another use case, the
enforcement function controls ingress traffic; a client connects to a
proxy that controls access to the ultimate destination. This may be
deployed inside the target domain, near it, or further away as a part
of a third-party security service. Clients are usually remote and
diverse, and use connections that have crossed several other domains
(with or without tunnels).
Enforcement functions typically require some form of client
authentication such as username, password, or certificate.
Authentication is enforced at the earliest stage of communication.
Enforcement rules might require access to transport characteristics
of the ultimate endpoints (such as client source IP address). This
might change as traffic moves between domains, whether tunneling is
used or not. Therefore, it can be desirable to encapsulate original
information in form accessible to the enforcement function.
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2.3. Frontend Support for Load Balancing and Migration/Mobility
Application service providers aiming to improve access flexibility
might use proxies in front of their services.
In one usage scenario the client communicates with a reverse proxy
that assists with access to and selection of the content requested.
This proxy that may or may not be under the authority of the service
provider. Today such reverse proxies terminate the connection,
including the security association, and as such appear as the
communication endpoint to the client. Terminating both transport and
security may be problematic if the proxy provider is not under the
direct authority of the actual service provider (e.g. a contracted
third party).
In another usage scenario the client communicates with a frontend
proxy that manages traffic steering to assist with load balancing or
migration for mobility support of server or client. This proxy is
more likely to be located close to the server and under the same
administrative domain, or at least has some trust relationship with
the application service provider. The server may have its own
communication channel with the proxy or tunnel endpoint in order to
provide data that is used for decision making. Meanwhile, the client
is usually not aware of any specifics of the setup behind the
substrate endpoint. However, improving visibility may benefit future
explicit tunneling or proxying approaches.
2.4. IoT Gateways
A number of IoT devices are connected via a low-power wireless
network (e.g., a Bluetooth LE piconet) and need to talk to their
parent cloud service to provide sensor readings or receive firmware
updates.
When end-to-end IP connectivity is not possible or desirable for at
least some of the devices, one or more IP capable nodes in the
piconet can be designated as ad-hoc gateways to forward sensor
traffic to the cloud and vice-versa. In other scenarios, a less
constrained node - sometimes called a "smart gateway" - can provide
the forwarding role permanently. In both cases, the gateway node
routes messages based on client's session identifiers, which need to
be unique among all the active participants so that the gateway can
route unambiguously. The access network attachment is expected to
change over time but the end-to-end communication (especially the
security association) needs to persist for as long as possible.
A strong requirement for these deployments is privacy: data on the
public Internet (i.e., from the gateway to the cloud service) needs
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to be made as opaque as possible to passive observers, possibly
hiding the natural traffic patterns associated with the sensor
network. A mechanism to provide discovery of the proxy node to the
rest of the piconet is also typically necessary.
Today, the above requirements can be met by composing an end-to-end
secure channel (e.g., based on DTLS sessions with client-chosen
connection IDs [I-D.ietf-tls-dtls-connection-id] or application layer
TLS [I-D.friel-tls-atls] from the sensors to the cloud together with
a multiplexed secure tunnel (e.g., using HTTP/2 WebSockets [RFC8441],
or a proprietary shim) from the gateway to the cloud. In the future,
a more homogeneous solution could be provided by QUIC for both the
end-to-end and tunneling services, thus simplifying code dependencies
on the gateway nodes.
2.5. Multi-hop Chaining Usage
Providing a generic approach to use QUIC as a substrate also enables
the combination of multiple of the above use cases. For example,
employing multiple obfuscating proxies in sequence, where the
communication with each proxy is individually secured, can enable
onion-like layered security. Each proxy will only know the address
of the prior hop and after itself, similar as provided by onion
routing in Tor project [TOR].
Further, it would also be possible to chain proxies for different
reasons. A client may select proxying support from its access
network, while a web service provider may utilize a front-end load
balancing proxy to provide end-to-end secure communication with the
applications components servers. Here the proxy and the load
balancer have different tasks. The access network proxy optimizes
the aggregated data transport. The load balancer needs to route
different set of end-to-end protected data that it aggregates. A
third example would be multiple proxies to cooperate and maybe
exchange measurement information in order to optimize the QUIC
connection over a specific segment.
The above examples indicates that a solution likely have to consider
how to establish a security model so that endpoints can selectively
choose what connection related information to share with the
different proxy entities. The possible efficiency should also be
consider and multiple layers of encapsulation should be avoided when
the security model allows for it.
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2.5.1. Considerations for Multiple Encryption
Using QUIC in a multi-hop fashion will generally cause all user data
to be encrypted multiple times, once for each hop. There are two
main reasons to encrypt data multiple times in a multi-hop network:
1. To ensure that no hop can see both the connection metadata of the
client and the server (thus obfuscating IP addresses and other
related data that is visible in cleartext in the transport
protocol headers).
2. To prevent an attacker from being able to correlate data between
different hops to identify a particular flow of data as it passes
through multiple hops.
However, multiple layers of encryption can have a noticeable impact
on the end-to-end latency of data. When a Tor-like approach is used,
each piece of user data will be encrypted N times, where N is the
number of hops. Devices such as IoT devices that may not have
support for cryptographic optimizations, or are constrained in terms
of processing or power usage, could be significantly slowed down due
to the extra overhead or not be able to process such traffic at all.
Since QUIC is an encrypted transport, the content of all packets
after the handshake is opaque to any attacker. Short-header packets,
particularly those that have zero-length Connection IDs, only send
encrypted fields. Thus, for all packets beyond the QUIC handshake,
encrypting packets multiple times through a multi-hop proxy primarily
achieves benefit 2) described above, since benefit 1) is already
achieved by QUIC being forwarded without re-encryption. If a
deployment is more concerned with benefit 1) than benefit 2), it
might be preferable to use a solution that forwards QUIC packets
without re-encrypting once QUIC handshakes are complete.
3. Requirements
To use QUIC as a substrate, it could be beneficial if unreliable
transmission is supported as well as having a way to potentially
influence or disable congestion control if the inner tunnel traffic
is known to be congestion controlled.
Communication between the client and proxy is more likely to be
realized as a separate protocol on top of QUIC or HTTP as e.g.
proposed by MASQUE. However, a QUIC extensibility mechanism could be
used to indicate to the receiver that QUIC is used as a substrate and
potentially additional information about which protocol is used for
communication between these entities. A similar mechanism could be
realized in HTTP instead. In both cases it is important that the
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QUIC connection cannot be identified as a substrate by an observer on
the path.
With QUIC, the use of proxying functions cannot be done
transparently. Instead, proxies needs to be explicitly discoverable.
The simplest form of such discovery could include pre-configuration
or via out-of-band signaling. The proxy could also be discovered
through advertisement when a client is connected to a network (for
example, the Dynamic Host Configuration Protocol). Alternatively,
the client could obtain a white-listed proxy address when making
first contact with the server (CNAME/IPaddress). In both cases the
proxy needs to have a routable address and name.
4. Review of Existing Approaches
As already mentioned, HTTP proxies are usually realized by use of the
HTTP CONNECT method (see Section 4.3.6 of [RFC7231]). This is
commonly used to establish a tunnelled TLS session over a TCP
connection to an origin server identified by a request-target. In
HTTP/1.1, the entire client-to-proxy HTTP connection is converted
into a tunnel. In HTTP/2 (see Section 8.3 of [RFC7540]) and HTTP/3
(see Section 4.2 of [I-D.ietf-quic-http]), a single stream gets
dedicated to a tunnel. Conventional HTTP CONNECT is only specified
to open a TCP connection between proxy and server, even in HTTP/3, so
it enables forwarding based on a split TCP-TCP or QUIC-TCP connection
but unaltered payload traffic. There is no currently-specified HTTP
mechanism to instruct a proxy to create a UDP or IP association to
the server. [HINT] contains a deeper analysis of the problem space
and potential solutions. Of those explored, a good candidate for
MASQUE is the Extended CONNECT method [RFC8441], accepts a
":protocol" pseudo-header that could be used to express an
alternative protocol between proxy and server.
An explicit proxy control protocol is the SOCKS protocol [RFC1928].
Version 6 is currently under standardization
[I-D.olteanu-intarea-socks-6] which provides fast connection
establishment. Use of QUIC could even further improve that.
However, SOCKS provides support to establish forwarding sockets using
a new connection (with a different port). This behavior is visible
to the path and not necessary if the underlying transport is
multiplexing capable, as QUIC is. A SOCKS-like protocol could still
be used for negotiation and authentication between the client and the
proxy. An example proposal for this approach is
[I-D.piraux-quic-tunnel].
In that sense the TCP PROXY protocol could also be seen as a light-
weight version of SOCKS (see
https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt). This
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protocol was never standardized and only provides a limited set of
functionality.
5. Contributors
Magnus Westerlund has contributed two paragraphs on combining
proxies.
Tommy Pauly has contributed text on multiple layers of encryption,
and other edits to the use cases.
6. References
6.1. Normative References
[I-D.schinazi-masque]
Schinazi, D., "The MASQUE Protocol", Work in Progress,
Internet-Draft, draft-schinazi-masque-02, 8 January 2020,
<http://www.ietf.org/internet-drafts/draft-schinazi-
masque-02.txt>.
6.2. Informative References
[HINT] Pardue, L., "HTTP-initiated Network Tunnelling (HiNT)",
Work in Progress, Internet-Draft, draft-pardue-httpbis-
http-network-tunnelling-01, 18 October 2018,
<http://www.ietf.org/internet-drafts/draft-pardue-httpbis-
http-network-tunnelling-01.txt>.
[I-D.friel-tls-atls]
Friel, O., Barnes, R., Pritikin, M., Tschofenig, H., and
M. Baugher, "Application-Layer TLS", Work in Progress,
Internet-Draft, draft-friel-tls-atls-04, 4 November 2019,
<http://www.ietf.org/internet-drafts/draft-friel-tls-atls-
04.txt>.
[I-D.ietf-quic-http]
Bishop, M., "Hypertext Transfer Protocol Version 3
(HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
quic-http-27, 21 February 2020, <http://www.ietf.org/
internet-drafts/draft-ietf-quic-http-27.txt>.
[I-D.ietf-tls-dtls-connection-id]
Rescorla, E., Tschofenig, H., and T. Fossati, "Connection
Identifiers for DTLS 1.2", Work in Progress, Internet-
Draft, draft-ietf-tls-dtls-connection-id-07, 21 October
2019, <http://www.ietf.org/internet-drafts/draft-ietf-tls-
dtls-connection-id-07.txt>.
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[I-D.olteanu-intarea-socks-6]
Olteanu, V. and D. Niculescu, "SOCKS Protocol Version 6",
Work in Progress, Internet-Draft, draft-olteanu-intarea-
socks-6-08, 4 November 2019, <http://www.ietf.org/
internet-drafts/draft-olteanu-intarea-socks-6-08.txt>.
[I-D.piraux-quic-tunnel]
Piraux, M. and O. Bonaventure, "Tunneling Internet
protocols inside QUIC", Work in Progress, Internet-Draft,
draft-piraux-quic-tunnel-00, 4 November 2019,
<http://www.ietf.org/internet-drafts/draft-piraux-quic-
tunnel-00.txt>.
[I-D.schinazi-httpbis-transport-auth]
Schinazi, D., "HTTP Transport Authentication", Work in
Progress, Internet-Draft, draft-schinazi-httpbis-
transport-auth-01, 8 January 2020, <http://www.ietf.org/
internet-drafts/draft-schinazi-httpbis-transport-auth-
01.txt>.
[RFC1928] Leech, M., Ganis, M., Lee, Y., Kuris, R., Koblas, D., and
L. Jones, "SOCKS Protocol Version 5", RFC 1928,
DOI 10.17487/RFC1928, March 1996,
<https://www.rfc-editor.org/info/rfc1928>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
[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>.
[RFC8441] McManus, P., "Bootstrapping WebSockets with HTTP/2",
RFC 8441, DOI 10.17487/RFC8441, September 2018,
<https://www.rfc-editor.org/info/rfc8441>.
[TOR] "TOR Project", 5 June 2019, <https://www.torproject.org/>.
Authors' Addresses
Mirja Kuehlewind
Ericsson
Email: mirja.kuehlewind@ericsson.com
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Zaheduzzaman Sarker
Ericsson
Email: zaheduzzaman.sarker@ericsson.com
Thomas Fossati
Arm
Email: thomas.fossati@arm.com
Lucas Pardue
Cloudflare
Email: lucaspardue.24.7@gmail.com
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