snowflake/proxy/snowflake.coffee
2017-03-01 18:51:24 -08:00

263 lines
7.6 KiB
CoffeeScript

###
A Coffeescript WebRTC snowflake proxy
Uses WebRTC from the client, and Websocket to the server.
Assume that the webrtc client plugin is always the offerer, in which case
this proxy must always act as the answerer.
TODO: More documentation
###
# General snowflake proxy constants.
# For websocket-specific constants, see websocket.coffee.
DEFAULT_BROKER = 'snowflake-reg.appspot.com'
DEFAULT_RELAY =
host: 'snowflake.bamsoftware.com'
port: '443'
# Original non-wss relay:
# host: '192.81.135.242'
# port: 9902
COPY_PASTE_ENABLED = false
COOKIE_NAME = "snowflake-allow"
silenceNotifications = false
query = Query.parse(location)
DEBUG = Params.getBool(query, 'debug', false)
COPY_PASTE_ENABLED = Params.getBool(query, 'manual', false)
# Bytes per second. Set to undefined to disable limit.
DEFAULT_RATE_LIMIT = DEFAULT_RATE_LIMIT || undefined
MIN_RATE_LIMIT = 10 * 1024
RATE_LIMIT_HISTORY = 5.0
DEFAULT_BROKER_POLL_INTERVAL = 5.0 * 1000
MAX_NUM_CLIENTS = 1
CONNECTIONS_PER_CLIENT = 1
# TODO: Different ICE servers.
config = {
iceServers: [
{ urls: ['stun:stun.l.google.com:19302'] }
]
}
# Janky state machine
MODE =
INIT: 0
WEBRTC_CONNECTING: 1
WEBRTC_READY: 2
CONFIRMATION_MESSAGE = "You're currently serving a Tor user via Snowflake."
# Minimum viable snowflake for now - just 1 client.
class Snowflake
relayAddr: null
proxyPairs: []
rateLimit: null
state: MODE.INIT
retries: 0
# Prepare the Snowflake with a Broker (to find clients) and optional UI.
constructor: (@broker, @ui) ->
rateLimitBytes = undefined
if 'off' != query['ratelimit']
rateLimitBytes = Params.getByteCount(query, 'ratelimit',
DEFAULT_RATE_LIMIT)
if undefined == rateLimitBytes
@rateLimit = new DummyRateLimit()
else
@rateLimit = new BucketRateLimit(rateLimitBytes * RATE_LIMIT_HISTORY,
RATE_LIMIT_HISTORY)
@retries = 0
# Set the target relay address spec, which is expected to be websocket.
# TODO: Should potentially fetch the target from broker later, or modify
# entirely for the Tor-independent version.
setRelayAddr: (relayAddr) ->
@relayAddr = relayAddr
log 'Using ' + relayAddr.host + ':' + relayAddr.port + ' as Relay.'
log 'Input offer from the snowflake client:' if COPY_PASTE_ENABLED
return true
# Initialize WebRTC PeerConnection, which requires beginning the signalling
# process. If in copy paste mode, the user will need to copy and paste the SDP
# blobs. Otherwise, |pollBroker| automatically arranges signalling.
beginWebRTC: ->
@state = MODE.WEBRTC_CONNECTING
for i in [1..CONNECTIONS_PER_CLIENT]
@makeProxyPair @relayAddr
return if COPY_PASTE_ENABLED
log 'ProxyPair Slots: ' + @proxyPairs.length
log 'Snowflake IDs: ' + (@proxyPairs.map (p) -> p.id).join ' | '
@pollBroker()
# Regularly poll Broker for clients to serve until this snowflake is
# serving at capacity, at which point stop polling.
pollBroker: ->
# Temporary countdown. TODO: Simplify
countdown = (msg, sec) =>
dbg msg
@ui?.setStatus msg + ' (Polling in ' + sec + ' seconds...)'
sec--
if sec >= 0
setTimeout((-> countdown(msg, sec)), 1000)
else
findClients()
# Poll broker for clients.
findClients = =>
pair = @nextAvailableProxyPair()
if !pair
log 'At client capacity.'
# Do nothing until a new proxyPair is available.
return
msg = 'polling for client... '
msg += '[retries: ' + @retries + ']' if @retries > 0
@ui?.setStatus msg
recv = @broker.getClientOffer pair.id
recv.then (desc) =>
@receiveOffer pair, desc
countdown('Serving 1 new client.', DEFAULT_BROKER_POLL_INTERVAL / 1000)
, (err) ->
countdown(err, DEFAULT_BROKER_POLL_INTERVAL / 1000)
@retries++
findClients()
# Returns the first ProxyPair that's available to connect.
nextAvailableProxyPair: ->
return @proxyPairs.find (pp, i, arr) -> return !pp.active
# Receive an SDP offer from some client assigned by the Broker,
# |pair| - an available ProxyPair.
receiveOffer: (pair, desc) =>
console.assert !pair.active
try
offer = JSON.parse desc
dbg 'Received:\n\n' + offer.sdp + '\n'
sdp = new SessionDescription offer
@sendAnswer pair if pair.receiveWebRTCOffer sdp
catch e
log 'ERROR: Unable to receive Offer: ' + e
sendAnswer: (pair) ->
next = (sdp) ->
dbg 'webrtc: Answer ready.'
pair.pc.setLocalDescription sdp
fail = ->
dbg 'webrtc: Failed to create Answer'
pair.pc.createAnswer()
.then next
.catch fail
makeProxyPair: (relay) ->
pair = new ProxyPair relay, @rateLimit
@proxyPairs.push pair
pair.onCleanup = (event) =>
# Delete from the list of active proxy pairs.
@proxyPairs.splice(@proxyPairs.indexOf(pair), 1)
@pollBroker()
pair.begin()
# Stop all proxypairs.
cease: ->
while @proxyPairs.length > 0
@proxyPairs.pop().close()
disable: ->
log 'Disabling Snowflake.'
@cease()
die: ->
log 'Snowflake died.'
@cease()
# Close all existing ProxyPairs and begin finding new clients from scratch.
reset: ->
@cease()
log 'Snowflake resetting...'
@retries = 0
@beginWebRTC()
snowflake = null
# Signalling channel - just tells user to copy paste to the peer.
# When copy-paste mode is not enabled, this is handled automatically by Broker.
Signalling =
send: (msg) ->
log '---- Please copy the below to peer ----\n'
log JSON.stringify msg
log '\n'
receive: (msg) ->
recv = ''
try
recv = JSON.parse msg
catch e
log 'Invalid JSON.'
return
desc = recv['sdp']
if !desc
log 'Invalid SDP.'
return false
pair = snowflake.nextAvailableProxyPair()
if !pair
log 'At client capacity.'
return false
snowflake.receiveOffer pair, msg
# Log to both console and UI if applicable.
# Requires that the snowflake and UI objects are hooked up in order to
# log to console.
log = (msg) ->
console.log 'Snowflake: ' + msg
snowflake?.ui?.log msg
dbg = (msg) -> log msg if DEBUG or snowflake.ui?.debug
snowflakeIsDisabled = ->
cookies = Parse.cookie document.cookie
# Do nothing if snowflake has not been opted in by user.
if cookies[COOKIE_NAME] != '1'
log 'Not opted-in. Please click the badge to change options.'
return true
return false
###
Entry point.
###
init = (isNode) ->
# Hook up to the debug UI if available.
ui = if isNode then null else new UI()
silenceNotifications = Params.getBool(query, 'silent', false)
# Retrieve connectivity information for the Broker and
# initialize Snowflake contexts.
brokerUrl = Params.getString(query, 'broker', DEFAULT_BROKER)
broker = new Broker brokerUrl
snowflake = new Snowflake broker, ui
log '== snowflake proxy =='
if snowflakeIsDisabled()
# Do not activate the proxy if any number of conditions are true.
log 'Currently not active.'
return
# Otherwise, begin setting up WebRTC and acting as a proxy.
log 'Copy-Paste mode detected.' if COPY_PASTE_ENABLED
dbg 'Contacting Broker at ' + broker.url if not COPY_PASTE_ENABLED
relayAddr = Params.getAddress(query, 'relay', DEFAULT_RELAY)
snowflake.setRelayAddr relayAddr
snowflake.beginWebRTC()
# Notification of closing tab with active proxy.
window.onbeforeunload = ->
if !silenceNotifications && MODE.WEBRTC_READY == snowflake.state
return CONFIRMATION_MESSAGE
null
window.onunload = ->
pair.close() for pair in snowflake.proxyPairs
null
window.onload = init.bind null, false