A QUIC implementation in Java

Kwik is an implementation of the QUIC protocol in Java. Kwik started as client (library) only, but since May 2021 it supports both client and server.

QUIC is a brand-new transport protocol developed by the IETF, which will be the transport layer for the also new HTTP3 protocol. Although necessary for HTTP3, QUIC is more than just the transport protocol for HTTP3: most people consider QUIC as the "next generation TCP". It has similar properties as TCP, e.g. provide a reliable ordered stream, but is better in many ways:

• it can serve multiple streams (concurrently and sequential) over the same QUIC connection
• it does not suffer from the "head of line blocking" problem
• it's encrypted and secured by TLS (not as a separate layer, but embedded in the protocol)
• it requires at most only one network roundtrip to setup the connection (the combination of TCP and TLS needs much more)

If you want to know more about QUIC and are able to understand the dutch language, check out my presentation on Luminis DevCon 2019.

If you're looking for a Java HTTP3 client or server, check out Flupke, which is built on top of Kwik.

Kwik is created and maintained by Peter Doornbosch. The latest greatest can always be found on BitBucket.

Status

The status of the project is different for client and server. For the client role, most QUIC features are implemented. For server role, the essential features necessary for connecting and transfering data in both directions are implemented; see below for more details. For both roles, interoperability is tested with a large number of other implementations, see automated interoperability tests. Due the to fact that most implementations are still in active development, and that some test cases (specifically testing behaviour in the context of packet loss and packet corruption) are non-deterministic, the results of the automatic interoperability test vary with each run, but usually, Kwik is amongst the best w.r.t. the number of successful testcases.

Kwik is still in active development, see git history.

HTTP3 on top of Kwik is supported by Flupke, the Java HTTP3 client.

Kwik supports QUIC v1 (RFC 9000) as well as a few older IETF drafts: draft-32, draft-31, draft-30, and draft-29.

Implemented QUIC features

• version negotation
• handshake based on TLS 1.3
• data exchange over bidirectional and unidirectional streams
• stateless retry
• cipher suites TLS_AES_128_GCM_SHA256 and TLS_CHACHA20_POLY1305_SHA256
• key update

Client only:

• session resumption (see -S and -R options of the sample client)
• connection migration (use the interactive mode of the sample client to try it)
• 0-RTT

Is Kwik ready for production use?

It really depends on your use-case. First of all, as with all open source software, there is no guarantee the software will work, it is provided "as is". Having said that, interoperability with other implementations is heavily tested and ok, so you can assume it works. However, Kwik is not tested in various or extreme networking conditions, so your mileage may vary.
As development focus has been on correctness and features (in that order), performance is not optimal yet.

Kwik does not yet implement all QUIC features. The server does not support session resumption and 0-RTT (the client does) which might make the server less suitable for production use at this moment. In both roles, you cannot set priority on streams, so the division of network capacity over streams cannot be influenced and might not even be fair. When wondering whether limitations would harm your use case: just go ahead and test it! When in doubt, you can always contact the author (see contact details below) for more information or help.

Is Kwik secure?

The TLS library used by Kwik is also "home made". Although all security features are implemented (e.g. certificates are checked as well as the Certificate Verify message that proofs possession of the certificate private key), and only crypto algorithms provided by the JDK are used, it is not security tested nor reviewed by security experts. So if you plan to transfer sensitive data or are afraid of intelligence services trying to spy on you, using Kwik is probably not the best idea.

Usage

Building

To build the project:

• clone the git repository and cd into the directory
• update / get the agent15 (TLS 1.3 library) sources by executing git submodule update --init --recursive
• build with gradle wrapper: ./gradlew build (or gradlew.bat build on Windows).

Gradle will write the output to build/libs.

Client

Kwik is both a library that can be used in any Java application to setup and use a QUIC connection, and a (sample) command line client that can be used to experiment with the QUIC protocol. If you want to use Kwik as a library, consider the various classes in the run package as samples of how to setup and use a QUIC connection with Kwik in Java.

To run the sample client, execute the kwik.sh script or java -jar build/libs/kwik.jar.

Usage of the sample client:

kwik <host>:<port> OR quic <host> <port> OR kwik http[s]://host:port
 -29                            use Quic version IETF_draft_29
 -30                            use Quic version IETF_draft_30
 -31                            use Quic version IETF_draft_31
 -32                            use Quic version IETF_draft_32    
 -A,--alpn <arg>                set alpn (default is hq-xx)
 -c,--connectionTimeout <arg>   connection timeout in seconds
    --chacha20                  use ChaCha20 as only cipher suite     
    --clientCertificate <arg>   certificate (file) for client
                                authentication
    --clientKey <arg>           private key (file) for client certificate
 -h,--help                      show help
 -H,--http <arg>                send HTTP GET request, arg is path, e.g.
                                '/index.html'
 -i,--interactive               start interactive shell
    --initialRtt <arg>          custom initial RTT value (default is 500)
 -k,--keepAlive <arg>           connection keep alive time in seconds
 -l,--log <arg>                 logging options: [pdrcsiRSD]: (p)ackets
                                received/sent, (d)ecrypted bytes, (r)ecovery,
                                (c)ongestion control, (s)tats, (i)nfo, (R)aw
                                bytes, (S)ecrets, (D)ebug; default is "ip", use
                                (n)one to disable
 -L,--logFile <arg>             file to write log message too
    --noCertificateCheck        do not check server certificate
 -O,--output <arg>              write server response to file
 -R,--resumption key <arg>      session ticket file
    --reservedVersion           use reserved version to trigger version
 -S,--storeTickets <arg>        basename of file to store new session tickets
    --saveServerCertificates <arg>   store server certificates in given file
    --secrets <arg>             write secrets to file (Wireshark format)
 -T,--relativeTime              log with time (in seconds) since first packet 
 -v,--version                   show Kwik version
 -v1                            use Quic version 1                                
 -Z,--use0RTT                   use 0-RTT if possible (requires -H and -R)

If you do not provide the --http or the --keepAlive option, the Quic connection will be closed immediately after setup.

Plain Kwik will use HTTP 0.9 for http requests. However, if the flupke-plugin.jar is on the classpath (e.g. when using the kwik.sh script, it will try to load the plugin from the libs directory), it will use Flupke HTTP3 client for the HTTP request.

Server

To run the server, execute java -cp kwik.jar net.luminis.quic.server.Server with the following arguments:

• certificate file
• private key file
• port number
• www directory to serve

This will start the server in retry-mode (see https://quicwg.org/base-drafts/rfc9000.html#name-address-validation-using-re). To run without retry-mode, add the --noRetry flag as first argument.

Adding HTTP/3 Support to the KWIK Server

A plain Kwik server will only provide "HTTP/0.9", which is a very simplified form of HTTP/1, which the QUIC implementors have been using for early testing.

To add HTTP/3 to Kwik,

• Clone the repo Flupke.
• Build the flupke repo cloned above.
• Add the flupke.jar generated to server's class path For e.g. java -cp kwik.jar:flupke.jar net.luminis.quic.server.Server.

Contact

If you have questions about this project, please mail the author (peter dot doornbosch) at luminis dot eu.

Acknowledgements

Thanks to Piet van Dongen for creating the marvellous logo!

License

This program is open source and licensed under LGPL (see the LICENSE.txt and LICENSE-LESSER.txt files in the distribution). This means that you can use this program for anything you like, and that you can embed it as a library in other applications, even commercial ones. If you do so, the author would appreciate if you include a reference to the original.

As of the LGPL license, all modifications and additions to the source code must be published as (L)GPL as well.

If you want to use the source with a different open source license, contact the author.