obfs4/

directory
Version: v0.0.0-...-8b1022e Latest Latest
Warning

This package is not in the latest version of its module.

Go to latest
Published: Jun 17, 2016 License: Apache-2.0, BSD-2-Clause, BSD-3-Clause

README

obfs4 - The obfourscator

Yawning Angel (yawning at torproject dot org)

What?

This is a look-like nothing obfuscation protocol that incorporates ideas and concepts from Philipp Winter's ScrambleSuit protocol. The obfs naming was chosen primarily because it was shorter, in terms of protocol ancestery obfs4 is much closer to ScrambleSuit than obfs2/obfs3.

The notable differences between ScrambleSuit and obfs4:

  • The handshake always does a full key exchange (no such thing as a Session Ticket Handshake).
  • The handshake uses the Tor Project's ntor handshake with public keys obfuscated via the Elligator 2 mapping.
  • The link layer encryption uses NaCl secret boxes (Poly1305/XSalsa20).

As an added bonus, obfs4proxy also supports acting as an obfs2/3 client and bridge to ease the transition to the new protocol.

Why not extend ScrambleSuit?

It's my protocol and I'll obfuscate if I want to.

Since a lot of the changes are to the handshaking process, it didn't make sense to extend ScrambleSuit as writing a server implementation that supported both handshake variants without being obscenely slow is non-trivial.

Dependencies

Build time library dependencies are handled by go get automatically but are listed for clarity.

Installation

To build: go get git.torproject.org/pluggable-transports/obfs4.git/obfs4proxy

To install: Copy $GOPATH/bin/obfs4proxy to a permanent location (Eg: /usr/local/bin)

Client side torrc configuration:

ClientTransportPlugin obfs4 exec /usr/local/bin/obfs4proxy

Bridge side torrc configuration:

# Act as a bridge relay.
BridgeRelay 1

# Enable the Extended ORPort
ExtORPort auto

# Use obfs4proxy to provide the obfs4 protocol.
ServerTransportPlugin obfs4 exec /usr/local/bin/obfs4proxy

# (Optional) Listen on the specified address/port for obfs4 connections as
# opposed to picking a port automatically.
#ServerTransportListenAddr obfs4 0.0.0.0:443

Tips and tricks

  • On modern Linux systems it is possible to have obfs4proxy bind to reserved ports (<=1024) even when not running as root by granting the CAP_NET_BIND_SERVICE capability with setcap:

    # setcap 'cap_net_bind_service=+ep' /usr/local/bin/obfs4proxy

  • obfs4proxy can also act as an obfs2 and obfs3 client or server. Adjust the ClientTransportPlugin and ServerTransportPlugin lines in the torrc as appropriate.

  • obfs4proxy can also act as a ScrambleSuit client. Adjust the ClientTransportPlugin line in the torrc as appropriate.

  • The autogenerated obfs4 bridge parameters are placed in DataDir/pt_state/obfs4_state.json. To ease deployment, the client side bridge line is written to DataDir/pt_state/obfs4_bridgeline.txt.

Thanks

  • David Fifield for goptlib.
  • Adam Langley for his Elligator implementation.
  • Philipp Winter for the ScrambleSuit protocol which provided much of the design.

Directories

Path Synopsis
common
csrand
Package csrand implements the math/rand interface over crypto/rand, along with some utility functions for common random number/byte related tasks.
Package csrand implements the math/rand interface over crypto/rand, along with some utility functions for common random number/byte related tasks.
drbg
Package drbg implements a minimalistic DRBG based off SipHash-2-4 in OFB mode.
Package drbg implements a minimalistic DRBG based off SipHash-2-4 in OFB mode.
log
Package log implements a simple set of leveled logging wrappers around the standard log package.
Package log implements a simple set of leveled logging wrappers around the standard log package.
ntor
Package ntor implements the Tor Project's ntor handshake as defined in proposal 216 "Improved circuit-creation key exchange".
Package ntor implements the Tor Project's ntor handshake as defined in proposal 216 "Improved circuit-creation key exchange".
probdist
Package probdist implements a weighted probability distribution suitable for protocol parameterization.
Package probdist implements a weighted probability distribution suitable for protocol parameterization.
replayfilter
Package replayfilter implements a generic replay detection filter with a caller specifiable time-to-live.
Package replayfilter implements a generic replay detection filter with a caller specifiable time-to-live.
socks5
Package socks5 implements a SOCKS 5 server and the required pluggable transport specific extensions.
Package socks5 implements a SOCKS 5 server and the required pluggable transport specific extensions.
uniformdh
Package uniformdh implements the Tor Project's UniformDH key exchange mechanism as defined in the obfs3 protocol specification.
Package uniformdh implements the Tor Project's UniformDH key exchange mechanism as defined in the obfs3 protocol specification.
Go language Tor Pluggable Transport suite.
Go language Tor Pluggable Transport suite.
Package transports provides a interface to query supported pluggable transports.
Package transports provides a interface to query supported pluggable transports.
base
Package base provides the common interface that each supported transport protocol must implement.
Package base provides the common interface that each supported transport protocol must implement.
meeklite
Package meeklite provides an implementation of the Meek circumvention protocol.
Package meeklite provides an implementation of the Meek circumvention protocol.
obfs2
Package obfs2 provides an implementation of the Tor Project's obfs2 obfuscation protocol.
Package obfs2 provides an implementation of the Tor Project's obfs2 obfuscation protocol.
obfs3
Package obfs3 provides an implementation of the Tor Project's obfs3 obfuscation protocol.
Package obfs3 provides an implementation of the Tor Project's obfs3 obfuscation protocol.
obfs4
Package obfs4 provides an implementation of the Tor Project's obfs4 obfuscation protocol.
Package obfs4 provides an implementation of the Tor Project's obfs4 obfuscation protocol.
obfs4/framing
Package framing implements the obfs4 link framing and cryptography.
Package framing implements the obfs4 link framing and cryptography.
scramblesuit
Package scramblesuit provides an implementation of the ScrambleSuit obfuscation protocol.
Package scramblesuit provides an implementation of the ScrambleSuit obfuscation protocol.

Jump to

Keyboard shortcuts

? : This menu
/ : Search site
f or F : Jump to
t or T : Toggle theme light dark auto
y or Y : Canonical URL