mirror of
https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake.git
synced 2025-10-13 20:11:19 -04:00
93 lines
3.2 KiB
CoffeeScript
93 lines
3.2 KiB
CoffeeScript
###
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Communication with the snowflake broker.
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Browser snowflakes must register with the broker in order
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to get assigned to clients.
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###
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STATUS_OK = 200
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STATUS_GONE = 410
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STATUS_GATEWAY_TIMEOUT = 504
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MESSAGE_TIMEOUT = 'Timed out waiting for a client offer.'
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MESSAGE_UNEXPECTED = 'Unexpected status.'
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genSnowflakeID = ->
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Math.random().toString(36).substring(2)
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# Represents a broker running remotely.
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class Broker
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clients: 0
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id: null
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# When interacting with the Broker, snowflake must generate a unique session
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# ID so the Broker can keep track of which signalling channel it's speaking
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# to.
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constructor: (@url) ->
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@clients = 0
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@id = genSnowflakeID()
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# Ensure url has the right protocol + trailing slash.
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@url = 'http://' + @url if 0 == @url.indexOf('localhost', 0)
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@url = 'https://' + @url if 0 != @url.indexOf('http', 0)
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@url += '/' if '/' != @url.substr -1
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# Promises some client SDP Offer.
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# Registers this Snowflake with the broker using an HTTP POST request, and
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# waits for a response containing some client offer that the Broker chooses
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# for this proxy..
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# TODO: Actually support multiple clients.
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getClientOffer: =>
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new Promise (fulfill, reject) =>
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xhr = new XMLHttpRequest()
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xhr.onreadystatechange = ->
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return if xhr.DONE != xhr.readyState
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switch xhr.status
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when STATUS_OK
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fulfill xhr.responseText # Should contain offer.
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when STATUS_GATEWAY_TIMEOUT
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reject MESSAGE_TIMEOUT
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else
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log 'Broker ERROR: Unexpected ' + xhr.status +
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' - ' + xhr.statusText
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snowflake.ui.setStatus ' failure. Please refresh.'
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reject MESSAGE_UNEXPECTED
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@_xhr = xhr # Used by spec to fake async Broker interaction
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@_postRequest xhr, 'proxy', @id
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# Assumes getClientOffer happened, and a WebRTC SDP answer has been generated.
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# Sends it back to the broker, which passes it to back to the original client.
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sendAnswer: (answer) ->
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dbg @id + ' - Sending answer back to broker...\n'
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dbg answer.sdp
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xhr = new XMLHttpRequest()
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xhr.onreadystatechange = ->
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return if xhr.DONE != xhr.readyState
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switch xhr.status
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when STATUS_OK
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dbg 'Broker: Successfully replied with answer.'
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dbg xhr.responseText
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when STATUS_GONE
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dbg 'Broker: No longer valid to reply with answer.'
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else
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dbg 'Broker ERROR: Unexpected ' + xhr.status +
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' - ' + xhr.statusText
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snowflake.ui.setStatus ' failure. Please refresh.'
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@_postRequest xhr, 'answer', JSON.stringify(answer)
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# urlSuffix for the broker is different depending on what action
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# is desired.
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_postRequest: (xhr, urlSuffix, payload) =>
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try
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xhr.open 'POST', @url + urlSuffix
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xhr.setRequestHeader('X-Session-ID', @id)
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catch err
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###
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An exception happens here when, for example, NoScript allows the domain
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on which the proxy badge runs, but not the domain to which it's trying
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to make the HTTP xhr. The exception message is like "Component
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returned failure code: 0x805e0006 [nsIXMLHttpRequest.open]" on Firefox.
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###
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log 'Broker: exception while connecting: ' + err.message
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return
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xhr.send payload
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