headscale/noise.go

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package headscale
import (
"encoding/base64"
"net/http"
"github.com/rs/zerolog/log"
"golang.org/x/net/http2"
"golang.org/x/net/http2/h2c"
"tailscale.com/control/controlbase"
"tailscale.com/net/netutil"
)
const (
errWrongConnectionUpgrade = Error("wrong connection upgrade")
errCannotHijack = Error("cannot hijack connection")
errNoiseHandshakeFailed = Error("noise handshake failed")
)
const (
// ts2021UpgradePath is the path that the server listens on for the WebSockets upgrade.
ts2021UpgradePath = "/ts2021"
// upgradeHeader is the value of the Upgrade HTTP header used to
// indicate the Tailscale control protocol.
upgradeHeaderValue = "tailscale-control-protocol"
// handshakeHeaderName is the HTTP request header that can
// optionally contain base64-encoded initial handshake
// payload, to save an RTT.
handshakeHeaderName = "X-Tailscale-Handshake"
)
// NoiseUpgradeHandler is to upgrade the connection and hijack the net.Conn
// in order to use the Noise-based TS2021 protocol. Listens in /ts2021.
func (h *Headscale) NoiseUpgradeHandler(
writer http.ResponseWriter,
req *http.Request,
) {
log.Trace().Caller().Msgf("Noise upgrade handler for client %s", req.RemoteAddr)
// Under normal circumpstances, we should be able to use the controlhttp.AcceptHTTP()
// function to do this - kindly left there by the Tailscale authors for us to use.
// (https://github.com/tailscale/tailscale/blob/main/control/controlhttp/server.go)
//
// When we used to use Gin, we had troubles here as Gin seems to do some
// fun stuff, and not flusing the writer properly.
// So have getNoiseConnection() that is essentially an AcceptHTTP, but in our side.
noiseConn, err := h.getNoiseConnection(writer, req)
if err != nil {
log.Error().Err(err).Msg("noise upgrade failed")
http.Error(writer, err.Error(), http.StatusInternalServerError)
return
}
server := http.Server{}
server.Handler = h2c.NewHandler(h.noiseMux, &http2.Server{})
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err = server.Serve(netutil.NewOneConnListener(noiseConn, nil))
if err != nil {
log.Error().Err(err).Msg("noise server launch failed")
}
}
// getNoiseConnection is basically AcceptHTTP from tailscale
// TODO(juan): Figure out why we need to do this at all.
func (h *Headscale) getNoiseConnection(
writer http.ResponseWriter,
req *http.Request,
) (*controlbase.Conn, error) {
next := req.Header.Get("Upgrade")
if next == "" {
http.Error(writer, errWrongConnectionUpgrade.Error(), http.StatusBadRequest)
return nil, errWrongConnectionUpgrade
}
if next != upgradeHeaderValue {
http.Error(writer, errWrongConnectionUpgrade.Error(), http.StatusBadRequest)
return nil, errWrongConnectionUpgrade
}
initB64 := req.Header.Get(handshakeHeaderName)
if initB64 == "" {
log.Warn().
Caller().
Msg("no handshake header")
http.Error(writer, "missing Tailscale handshake header", http.StatusBadRequest)
return nil, errWrongConnectionUpgrade
}
init, err := base64.StdEncoding.DecodeString(initB64)
if err != nil {
log.Warn().Err(err).Msg("invalid handshake header")
http.Error(writer, "invalid tailscale handshake header", http.StatusBadRequest)
return nil, errWrongConnectionUpgrade
}
hijacker, ok := writer.(http.Hijacker)
if !ok {
log.Error().Caller().Err(err).Msgf("Hijack failed")
http.Error(writer, errCannotHijack.Error(), http.StatusInternalServerError)
return nil, errCannotHijack
}
// This is what changes from the original AcceptHTTP() function.
writer.Header().Set("Upgrade", upgradeHeaderValue)
writer.Header().Set("Connection", "upgrade")
writer.WriteHeader(http.StatusSwitchingProtocols)
// end
netConn, conn, err := hijacker.Hijack()
if err != nil {
log.Error().Caller().Err(err).Msgf("Hijack failed")
http.Error(writer, "HTTP does not support general TCP support", http.StatusInternalServerError)
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return nil, errCannotHijack
}
if err := conn.Flush(); err != nil {
netConn.Close()
return nil, errCannotHijack
}
netConn = netutil.NewDrainBufConn(netConn, conn.Reader)
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noiseConn, err := controlbase.Server(req.Context(), netConn, *h.noisePrivateKey, init)
if err != nil {
netConn.Close()
return nil, errNoiseHandshakeFailed
}
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return noiseConn, nil
}