mirror of
https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake.git
synced 2025-10-14 05:11:19 -04:00
0f34a7778f
Makes BrokerChannel abstract over a rendezvousMethod. BrokerChannel itself is responsible for keepLocalAddresses and the NAT type state, as well as encoding and decoding client poll messages. rendezvousMethod is only responsible for delivery of encoded messages.
77 lines
2.1 KiB
Go
77 lines
2.1 KiB
Go
package lib
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import (
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"bytes"
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"errors"
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"io"
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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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)
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// httpRendezvous is a rendezvousMethod that communicates with the .../client
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// route of the broker over HTTP or HTTPS, with optional domain fronting.
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type httpRendezvous struct {
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brokerURL *url.URL
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front string // Optional front domain to replace url.Host in requests.
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transport http.RoundTripper // Used to make all requests.
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}
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// newHTTPRendezvous creates a new httpRendezvous that contacts the broker at
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// the given URL, with an optional front domain. transport is the
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// http.RoundTripper used to make all requests.
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func newHTTPRendezvous(broker, front string, transport http.RoundTripper) (*httpRendezvous, error) {
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brokerURL, err := url.Parse(broker)
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if err != nil {
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return nil, err
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}
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return &httpRendezvous{
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brokerURL: brokerURL,
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front: front,
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transport: transport,
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}, nil
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}
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func (r *httpRendezvous) Exchange(encPollReq []byte) ([]byte, error) {
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log.Println("Negotiating via HTTP rendezvous...")
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log.Println("Target URL: ", r.brokerURL.Host)
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log.Println("Front URL: ", r.front)
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// Suffix the path with the broker's client registration handler.
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reqURL := r.brokerURL.ResolveReference(&url.URL{Path: "client"})
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req, err := http.NewRequest("POST", reqURL.String(), bytes.NewReader(encPollReq))
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if err != nil {
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return nil, err
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}
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if r.front != "" {
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// Do domain fronting. Replace the domain in the URL's with the
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// front, and store the original domain the HTTP Host header.
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req.Host = req.URL.Host
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req.URL.Host = r.front
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}
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resp, err := r.transport.RoundTrip(req)
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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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log.Printf("HTTP rendezvous response: %s", resp.Status)
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if resp.StatusCode != http.StatusOK {
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return nil, errors.New(BrokerErrorUnexpected)
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}
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return limitedRead(resp.Body, readLimit)
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}
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func limitedRead(r io.Reader, limit int64) ([]byte, error) {
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p, err := ioutil.ReadAll(&io.LimitedReader{R: r, N: limit + 1})
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if err != nil {
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return p, err
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} else if int64(len(p)) == limit+1 {
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return p[0:limit], io.ErrUnexpectedEOF
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}
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return p, err
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}
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