tailscale/ipn/ipnserver/proxyconnect.go

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// 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 ipnserver
import (
"bufio"
"context"
"io"
"net"
"net/http"
"time"
"tailscale.com/logpolicy"
"tailscale.com/types/logger"
)
// handleProxyConnectConn handles a CONNECT request to
// log.tailscale.io (or whatever the configured log server is). This
// is intended for use by the Windows GUI client to log via when an
// exit node is in use, so the logs don't go out via the exit node and
// instead go directly, like tailscaled's. The dialer tried to do that
// in the unprivileged GUI by binding to a specific interface, but the
// "Internet Kill Switch" installed by tailscaled for exit nodes
// precludes that from working and instead the GUI fails to dial out.
// So, go through tailscaled (with a CONNECT request) instead.
func (s *Server) handleProxyConnectConn(ctx context.Context, br *bufio.Reader, c net.Conn, logf logger.Logf) {
defer c.Close()
c.SetReadDeadline(time.Now().Add(5 * time.Second)) // should be long enough to send the HTTP headers
req, err := http.ReadRequest(br)
if err != nil {
logf("ReadRequest: %v", err)
return
}
c.SetReadDeadline(time.Time{})
if req.Method != "CONNECT" {
logf("ReadRequest: unexpected method %q, not CONNECT", req.Method)
return
}
hostPort := req.RequestURI
logHost := logpolicy.LogHost()
allowed := net.JoinHostPort(logHost, "443")
if hostPort != allowed {
logf("invalid CONNECT target %q; want %q", hostPort, allowed)
io.WriteString(c, "HTTP/1.1 403 Forbidden\r\n\r\nBad CONNECT target.\n")
return
}
tr := logpolicy.NewLogtailTransport(logHost)
back, err := tr.DialContext(ctx, "tcp", hostPort)
if err != nil {
logf("error CONNECT dialing %v: %v", hostPort, err)
io.WriteString(c, "HTTP/1.1 502 Fail\r\n\r\nConnect failure.\n")
return
}
defer back.Close()
io.WriteString(c, "HTTP/1.1 200 OK\r\n\r\n")
errc := make(chan error, 2)
go func() {
_, err := io.Copy(c, back)
errc <- err
}()
go func() {
_, err := io.Copy(back, br)
errc <- err
}()
<-errc
}