mirror of
https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake.git
synced 2025-10-13 20:11:19 -04:00
103 lines
2.9 KiB
Go
103 lines
2.9 KiB
Go
// Exchange WebRTC SessionDescriptions over a domain-fronted HTTP
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// signalling channel.
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package main
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import (
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"bytes"
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"io/ioutil"
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"log"
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"net/http"
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"net/url"
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"github.com/keroserene/go-webrtc"
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)
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// RequestInfo encapsulates all the configuration used for a request–response
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// roundtrip, including variables that may come from SOCKS args or from the
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// command line.
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type RequestInfo struct {
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// What to put in the X-Session-ID header - SessionID string
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// The desired potentially filtered URL to request.
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URL *url.URL
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// The Host header to put in the HTTP request (optional and may be
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// different from the host name in URL).
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Host string
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}
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func NewRequestInfo(targetUrl string, front string) *RequestInfo {
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info := new(RequestInfo)
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requestUrl, err := url.Parse(targetUrl)
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if nil != err {
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return nil
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}
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info.URL = requestUrl
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info.Host = front
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return info
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}
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// Meek Signalling Channel.
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type MeekChannel struct {
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info *RequestInfo
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// Used to make all requests.
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transport http.Transport
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}
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func NewMeekChannel(info *RequestInfo) *MeekChannel {
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m := new(MeekChannel)
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// We make a copy of DefaultTransport because we want the default Dial
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// and TLSHandshakeTimeout settings. But we want to disable the default
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// ProxyFromEnvironment setting. Proxy is overridden below if
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// options.ProxyURL is set.
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m.transport = *http.DefaultTransport.(*http.Transport)
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m.transport.Proxy = nil
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m.info = info
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return m
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}
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// Do an HTTP roundtrip using the payload data in buf.
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func (mc *MeekChannel) roundTripHTTP(buf []byte) (*http.Response, error) {
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// Compose an innocent looking request.
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req, err := http.NewRequest("POST", mc.info.Host+"/reg/123", bytes.NewReader(buf))
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if nil != err {
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return nil, err
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}
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// Set actually desired host in the request.
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req.Host = mc.info.URL.String()
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// req.Header.Set("X-Session-Id", m.info.SessionID)
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return mc.transport.RoundTrip(req)
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}
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// Send an SDP offer to the meek facilitator, and wait for an SDP answer from
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// the assigned proxy in the response.
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func (mc *MeekChannel) Negotiate(offer *webrtc.SessionDescription) (
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*webrtc.SessionDescription, error) {
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resp, err := mc.roundTripHTTP([]byte(offer.Serialize()))
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if nil != err {
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return nil, err
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}
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defer resp.Body.Close()
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log.Println("MeekChannel Response: ", resp)
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body, err := ioutil.ReadAll(resp.Body)
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if nil != err {
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return nil, err
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}
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answer := webrtc.DeserializeSessionDescription(string(body))
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return answer, nil
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}
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// Simple interim non-fronting HTTP POST negotiation, to be removed when more
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// general fronting is present.
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func sendOfferHTTP(url string, offer *webrtc.SessionDescription) (*webrtc.SessionDescription, error) {
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resp, err := http.Post(url, "", bytes.NewBuffer([]byte(offer.Serialize())))
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if err != nil {
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return nil, err
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}
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defer resp.Body.Close()
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body, err := ioutil.ReadAll(resp.Body)
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if err != nil {
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return nil, err
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}
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answer := webrtc.DeserializeSessionDescription(string(body))
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return answer, nil
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}
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