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tailscale/cmd/derper/websocket.go

58 lines
1.9 KiB
Go

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