mirror of
https://github.com/tailscale/tailscale.git
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58 lines
1.9 KiB
Go
58 lines
1.9 KiB
Go
// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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import (
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"bufio"
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"expvar"
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"log"
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"net/http"
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"strings"
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"nhooyr.io/websocket"
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"tailscale.com/derp"
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)
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var counterWebSocketAccepts = expvar.NewInt("derp_websocket_accepts")
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// addWebSocketSupport returns a Handle wrapping base that adds WebSocket server support.
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func addWebSocketSupport(s *derp.Server, base http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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up := strings.ToLower(r.Header.Get("Upgrade"))
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// Very early versions of Tailscale set "Upgrade: WebSocket" but didn't actually
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// speak WebSockets (they still assumed DERP's binary framing). So to distinguish
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// clients that actually want WebSockets, look for an explicit "derp" subprotocol.
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if up != "websocket" || !strings.Contains(r.Header.Get("Sec-Websocket-Protocol"), "derp") {
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base.ServeHTTP(w, r)
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return
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}
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c, err := websocket.Accept(w, r, &websocket.AcceptOptions{
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Subprotocols: []string{"derp"},
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OriginPatterns: []string{"*"},
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// Disable compression because we transmit WireGuard messages that
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// are not compressible.
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// Additionally, Safari has a broken implementation of compression
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// (see https://github.com/nhooyr/websocket/issues/218) that makes
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// enabling it actively harmful.
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CompressionMode: websocket.CompressionDisabled,
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})
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if err != nil {
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log.Printf("websocket.Accept: %v", err)
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return
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}
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defer c.Close(websocket.StatusInternalError, "closing")
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if c.Subprotocol() != "derp" {
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c.Close(websocket.StatusPolicyViolation, "client must speak the derp subprotocol")
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return
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}
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counterWebSocketAccepts.Add(1)
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wc := websocket.NetConn(r.Context(), c, websocket.MessageBinary)
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brw := bufio.NewReadWriter(bufio.NewReader(wc), bufio.NewWriter(wc))
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s.Accept(r.Context(), wc, brw, r.RemoteAddr)
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})
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}
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