mirror of
https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake.git
synced 2025-10-13 20:11:19 -04:00
81 lines
2.6 KiB
CoffeeScript
81 lines
2.6 KiB
CoffeeScript
###
|
|
Communication with the snowflake broker.
|
|
|
|
Browser snowflakes must register with the broker in order
|
|
to get assigned to clients.
|
|
###
|
|
|
|
STATUS_OK = 200
|
|
STATUS_GONE = 410
|
|
STATUS_GATEWAY_TIMEOUT = 504
|
|
|
|
genSnowflakeID = ->
|
|
Math.random().toString(36).substring(2)
|
|
|
|
# Represents a broker running remotely.
|
|
class Broker
|
|
|
|
clients: 0
|
|
id: null
|
|
|
|
# When interacting with the Broker, snowflake must generate a unique session
|
|
# ID so the Broker can keep track of which signalling channel it's speaking
|
|
# to.
|
|
constructor: (@url) ->
|
|
@clients = 0
|
|
@id = genSnowflakeID()
|
|
log 'Contacting Broker at ' + @url + '\nSnowflake ID: ' + @id
|
|
|
|
# Snowflake registers with the broker using an HTTP POST request, and expects
|
|
# a response from the broker containing some client offer.
|
|
# TODO: Actually support multiple clients.
|
|
getClientOffer: ->
|
|
new Promise (fulfill, reject) =>
|
|
xhr = new XMLHttpRequest()
|
|
try
|
|
xhr.open 'POST', @url + 'proxy'
|
|
xhr.setRequestHeader('X-Session-ID', @id)
|
|
catch err
|
|
###
|
|
An exception happens here when, for example, NoScript allows the domain
|
|
on which the proxy badge runs, but not the domain to which it's trying
|
|
to make the HTTP request. The exception message is like "Component
|
|
returned failure code: 0x805e0006 [nsIXMLHttpRequest.open]" on Firefox.
|
|
###
|
|
log 'Broker: exception while connecting: ' + err.message
|
|
return
|
|
xhr.onreadystatechange = ->
|
|
return if xhr.DONE != xhr.readyState
|
|
switch xhr.status
|
|
when STATUS_OK
|
|
fulfill xhr.responseText # Should contain offer.
|
|
when STATUS_GATEWAY_TIMEOUT
|
|
reject 'Timed out waiting for a client to serve. Retrying...'
|
|
else
|
|
log 'Broker ERROR: Unexpected ' + xhr.status +
|
|
' - ' + xhr.statusText
|
|
xhr.send @id
|
|
log @id + " - polling for client offer..."
|
|
|
|
sendAnswer: (answer) ->
|
|
log @id + ' - Sending answer back to broker...\n'
|
|
log answer.sdp
|
|
xhr = new XMLHttpRequest()
|
|
try
|
|
xhr.open 'POST', @url + 'answer'
|
|
xhr.setRequestHeader('X-Session-ID', @id)
|
|
catch err
|
|
log 'Broker: exception while connecting: ' + err.message
|
|
return
|
|
xhr.onreadystatechange = ->
|
|
return if xhr.DONE != xhr.readyState
|
|
switch xhr.status
|
|
when STATUS_OK
|
|
log 'Broker: Successfully replied with answer.'
|
|
log xhr.responseText
|
|
when STATUS_GONE
|
|
log 'Broker: No longer valid to reply with answer.'
|
|
else
|
|
log 'Broker ERROR: Unexpected ' + xhr.status +
|
|
' - ' + xhr.statusText
|
|
xhr.send JSON.stringify(answer)
|