meek

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meek is a blocking-resistant pluggable transport for Tor. It encodes a data stream as a sequence of HTTPS requests and responses. Requests are reflected through a hard-to-block third-party web server in order to avoid talking directly to a Tor bridge. HTTPS encryption hides fingerprintable byte patterns in Tor traffic.

https://trac.torproject.org/projects/tor/wiki/doc/meek

The key trick that makes the system work is "domain fronting": communicating with a forbidden domain in a way that makes it look like you are communicating with an allowed domain. It works by putting the allowed domain on the "outside" of a request: in the DNS query and the SNI TLS extension; and the forbidden domain on the "inside": in the Host header of the HTTP request. The trick works with web services that ignore the SNI and handle requests based on the Host header. Google, with its App Engine infrastructure at appspot.com, is one of these services. A client wanting to communicate with a forbidden subdomain of appspot.com while appearing to communicate with www.google.com can run the client plugin program like this: meek-client --url=https://meek-reflect.appspot.com/ --front=www.google.com

The meek-client program by itself has a fingerprintable TLS handshake. To disguise the TLS part of HTTPS connections, meek-client should be run with the --helper option pointing at a browser extension that has been set up separately. How it works is meek-client tells the browser what URL to request, the browser requests it and returns the payload to meek-client. The TLS implementation is that of the browser, so it better blends in with allowed traffic. Browser extensions for Chrome and Firefox are in the chrome and firefox directories.

Here is a summary of the programs that appear in subdirectories.

meek-client: The client transport plugin, run by a censored client.

meek-server: The server transport plugin, run on a Tor relay.

appengine: Reflector web app that runs on Google App Engine. The reflector simply copies requests and responses to an instance of meek-server somewhere. A public instance of the App Engine web app is at https://meek-reflect.appspot.com/.

chrome, firefox: Browser extensions for TLS camouflage.

meek-client-torbrowser: An auxiliary program for the Tor Browser Bundle that runs a copy of Firefox with the browser extension and then configures meek-client to use it as a helper.

terminateprocess-buffer: An auxiliary program used on Windows to assist with cleanup of subprocesses.

latencytest: A test program for App Engine that measures roundtrip times to different destinations.

php: A php reflector similar to the appengine one above. Ideally, it can be run on any platform that supports php. A public instance is at: https://meek-reflect.herokuapp.com/

To the extent possible under law, the authors have dedicated all copyright and related and neighboring rights to this software to the public domain worldwide. This software is distributed without any warranty. See COPYING.