xref: /openssl/README-QUIC.md (revision ada33e98)
1Using OpenSSL with QUIC
2=======================
3
4From OpenSSL 3.2, OpenSSL features support for making QUIC connections as a
5client.
6
7Users interested in using the new QUIC functionality are encouraged to look at
8some of the following resources:
9
10- The new [OpenSSL Guide], which provides introductory guides on the use of TLS,
11  QUIC, and other OpenSSL functionality.
12- The [OpenSSL Guide] incorporates various code samples. The complete source
13  for these can be [found in the source tree under `demos/guide`](./demos/guide/).
14- The [openssl-quic(7) manual page], which provides a basic reference overview
15  of QUIC functionality and how use of QUIC differs from use of TLS with regard
16  to our API.
17- The [Demo-Driven Design (DDD)][DDD] demos, which demonstrate the use of QUIC
18  using simple examples. These can be [found in the source tree under
19  `doc/designs/ddd`].
20- The [demo found in `demos/http3`], which provides an HTTP/3 client example
21  using the nghttp3 HTTP/3 library.
22
23FAQ
24---
25
26### Why would I want to use QUIC, and what functionality does QUIC offer relative to TLS or DTLS?
27
28QUIC is a state-of-the-art secure transport protocol carried over UDP. It can
29serve many of the use cases of SSL/TLS as well as those of DTLS.
30
31QUIC delivers a number of advantages such as support for multiple streams of
32communication; it is the basis for HTTP/3 [RFC 9114]; fast connection
33initiation; and connection migration (enabling a connection to survive IP
34address changes). For a more complete description of what QUIC is and its
35advantages see the [QUIC Introduction] in the [OpenSSL Guide].
36
37For a comprehensive overview of OpenSSL's QUIC implementation, see the
38[openssl-quic(7) manual page].
39
40### How can I use HTTP/3 with OpenSSL?
41
42There are many HTTP/3 implementations in C available. The use of one such HTTP/3
43library with OpenSSL QUIC is demonstrated via the [demo found in `demos/http3`].
44
45### How can I use OpenSSL QUIC in my own application for a different protocol?
46
47The [OpenSSL Guide] provides introductory examples for how to make use of
48OpenSSL QUIC.
49
50The [openssl-quic(7) manual page] and the [Demo-Driven Design (DDD)][DDD] demos
51may also be helpful to illustrate the changes needed if you are trying to adapt
52an existing application.
53
54### How can I test QUIC using `openssl s_client`?
55
56There is basic support for single-stream QUIC using `openssl s_client`:
57
58```shell
59$ openssl s_client -quic -alpn myalpn -connect host:port
60```
61
62In the above example replace `host` with the hostname of the server (e.g.
63`www.example.com`) and `port` with the port for the server (e.g. `443`). Replace
64`myalpn` with the Application Layer Protocol to use (e.g.`h3` represents
65HTTP/3). IANA maintains a standard list of [ALPN ids] that can be used.
66
67This example connects to a QUIC server and opens a single bidirectional stream.
68Data can be passed via stdin/stdout as usual. This allows test usage of QUIC
69using simple TCP/TLS-like usage. Note that OpenSSL has no direct support for
70HTTP/3 so connecting to an HTTP/3 server should be possible but sending an
71HTTP/3 request or receiving any response data is not.
72
73[openssl-quic(7) manual page]: https://www.openssl.org/docs/manmaster/man7/openssl-quic.html
74[OpenSSL Guide]: https://www.openssl.org/docs/manmaster/man7/ossl-guide-introduction.html
75[DDD]: https://github.com/openssl/openssl/tree/master/doc/designs/ddd
76[found in the source tree under `doc/designs/ddd`]: ./doc/designs/ddd/
77[demo found in `demos/http3`]: ./demos/http3/
78[QUIC Introduction]: https://www.openssl.org/docs/manmaster/man7/ossl-guide-quic-introduction.html
79[RFC 9114]: https://tools.ietf.org/html/rfc9114
80[ALPN ids]: https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml#alpn-protocol-ids
81