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110 lines
5.0 KiB
Markdown
110 lines
5.0 KiB
Markdown
# Snowflake
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[](https://travis-ci.org/keroserene/snowflake)
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Pluggable Transport using WebRTC, inspired by Flashproxy.
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<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
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**Table of Contents**
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- [Structure of this Repository](#structure-of-this-repository)
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- [Usage](#usage)
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- [Using Snowflake with Tor](#using-snowflake-with-tor)
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- [Running a Snowflake Proxy](#running-a-snowflake-proxy)
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- [Using the Snowflake Library with Other Applications](#using-the-snowflake-library-with-other-applications)
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- [Test Environment](#test-environment)
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- [FAQ](#faq)
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- [More info and links](#more-info-and-links)
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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### Structure of this Repository
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- `broker/` contains code for the Snowflake broker
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- `doc/` contains Snowflake documentation and manpages
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- `client/` contains the Tor pluggable transport client and client library code
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- `common/` contains generic libraries used by multiple pieces of Snowflake
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- `proxy/` contains code for the Go standalone Snowflake proxy
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- `probetest/` contains code for a NAT probetesting service
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- `server/` contains the Tor pluggable transport server and server library code
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### Usage
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Snowflake is currently deployed as a pluggable transport for Tor.
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#### Using Snowflake with Tor
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To use the Snowflake client with Tor, you will need to add the appropriate `Bridge` and `ClientTransportPlugin` lines to your [torrc](https://2019.www.torproject.org/docs/tor-manual.html.en) file. See the [client README](client) for more information on building and running the Snowflake client.
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#### Running a Snowflake Proxy
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You can contribute to Snowflake by running a Snowflake proxy. We have the option to run a proxy in your browser or as a standalone Go program. See our [community documentation](https://community.torproject.org/relay/setup/snowflake/) for more details.
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#### Using the Snowflake Library with Other Applications
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Snowflake can be used as a Go API, and adheres to the [v2.1 pluggable transports specification](). For more information on using the Snowflake Go library, see the [Snowflake library documentation](doc/using-the-snowflake-library.md).
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### Test Environment
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There is a Docker-based test environment at https://github.com/cohosh/snowbox.
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### FAQ
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**Q: How does it work?**
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In the Tor use-case:
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1. Volunteers visit websites which host the "snowflake" proxy. (just
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like flashproxy)
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2. Tor clients automatically find available browser proxies via the Broker
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(the domain fronted signaling channel).
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3. Tor client and browser proxy establish a WebRTC peer connection.
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4. Proxy connects to some relay.
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5. Tor occurs.
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More detailed information about how clients, snowflake proxies, and the Broker
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fit together on the way...
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**Q: What are the benefits of this PT compared with other PTs?**
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Snowflake combines the advantages of flashproxy and meek. Primarily:
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- It has the convenience of Meek, but can support magnitudes more
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users with negligible CDN costs. (Domain fronting is only used for brief
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signalling / NAT-piercing to setup the P2P WebRTC DataChannels which handle
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the actual traffic.)
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- Arbitrarily high numbers of volunteer proxies are possible like in
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flashproxy, but NATs are no longer a usability barrier - no need for
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manual port forwarding!
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**Q: Why is this called Snowflake?**
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It utilizes the "ICE" negotiation via WebRTC, and also involves a great
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abundance of ephemeral and short-lived (and special!) volunteer proxies...
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### More info and links
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We have more documentation in the [Snowflake wiki](https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/wikis/home) and at https://snowflake.torproject.org/.
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##### -- Android AAR Reproducible Build Setup --
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Using `gomobile` it is possible to build snowflake as shared libraries for all
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the architectures supported by Android. This is in the _.gitlab-ci.yml_, which
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runs in GitLab CI. It is also possible to run this setup in a Virtual Machine
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using [vagrant](https://www.vagrantup.com/). Just run `vagrant up` and it will
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create and provision the VM. `vagrant ssh` to get into the VM to use it as a
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development environment.
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##### uTLS Settings
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Snowflake communicate with broker that serves as signaling server with TLS based domain fronting connection, which may be identified by its usage of Go language TLS stack.
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uTLS is a software library designed to initiate the TLS Client Hello fingerprint of browsers or other popular software's TLS stack to evade censorship based on TLS client hello fingerprint with `-utls-imitate` . You can use `-version` to see a list of supported values.
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Depending on client and server configuration, it may not always work as expected as not all extensions are correctly implemented.
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You can also remove SNI (Server Name Indication) from client hello to evade censorship with `-utls-nosni`, not all servers supports this.
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