control/controlhttp: package to get a controlbase.Conn over HTTP(S).

Updates #3488

Signed-off-by: David Anderson <danderson@tailscale.com>
pull/3759/head
David Anderson 3 years ago committed by Dave Anderson
parent d5a7eabcd0
commit 96f008cf87

@ -0,0 +1,242 @@
// 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 controlhttp implements the Tailscale 2021 control protocol
// base transport over HTTP.
//
// This tunnels the protocol in control/controlbase over HTTP with a
// variety of compatibility fallbacks for handling picky or deep
// inspecting proxies.
//
// In the happy path, a client makes a single cleartext HTTP request
// to the server, the server responds with 101 Switching Protocols,
// and the control base protocol takes place over plain TCP.
//
// In the compatibility path, the client does the above over HTTPS,
// resulting in double encryption (once for the control transport, and
// once for the outer TLS layer).
package controlhttp
import (
"context"
"crypto/tls"
"encoding/base64"
"errors"
"fmt"
"io"
"log"
"net"
"net/http"
"net/http/httptrace"
"net/url"
"tailscale.com/control/controlbase"
"tailscale.com/net/dnscache"
"tailscale.com/net/dnsfallback"
"tailscale.com/net/netns"
"tailscale.com/net/tlsdial"
"tailscale.com/net/tshttpproxy"
"tailscale.com/types/key"
)
// upgradeHeader is the value of the Upgrade HTTP header used to
// indicate the Tailscale control protocol.
const (
upgradeHeaderValue = "tailscale-control-protocol"
handshakeHeaderName = "X-Tailscale-Handshake"
)
// Dial connects to the HTTP server at addr, requests to switch to the
// Tailscale control protocol, and returns an established control
// protocol connection.
//
// If Dial fails to connect using addr, it also tries to tunnel over
// TLS to <addr's host>:443 as a compatibility fallback.
func Dial(ctx context.Context, addr string, machineKey key.MachinePrivate, controlKey key.MachinePublic) (*controlbase.Conn, error) {
host, port, err := net.SplitHostPort(addr)
if err != nil {
return nil, err
}
a := &dialParams{
ctx: ctx,
host: host,
httpPort: port,
httpsPort: "443",
machineKey: machineKey,
controlKey: controlKey,
proxyFunc: tshttpproxy.ProxyFromEnvironment,
}
return a.dial()
}
type dialParams struct {
ctx context.Context
host string
httpPort string
httpsPort string
machineKey key.MachinePrivate
controlKey key.MachinePublic
proxyFunc func(*http.Request) (*url.URL, error) // or nil
// For tests only
insecureTLS bool
}
func (a *dialParams) dial() (*controlbase.Conn, error) {
init, cont, err := controlbase.ClientDeferred(a.machineKey, a.controlKey)
if err != nil {
return nil, err
}
u := &url.URL{
Scheme: "http",
Host: net.JoinHostPort(a.host, a.httpPort),
Path: "/switch",
}
conn, httpErr := a.tryURL(u, init)
if httpErr == nil {
ret, err := cont(a.ctx, conn)
if err != nil {
conn.Close()
return nil, err
}
return ret, nil
}
// Connecting over plain HTTP failed, assume it's an HTTP proxy
// being difficult and see if we can get through over HTTPS.
u.Scheme = "https"
u.Host = net.JoinHostPort(a.host, a.httpsPort)
init, cont, err = controlbase.ClientDeferred(a.machineKey, a.controlKey)
if err != nil {
return nil, err
}
conn, tlsErr := a.tryURL(u, init)
if tlsErr == nil {
ret, err := cont(a.ctx, conn)
if err != nil {
conn.Close()
return nil, err
}
return ret, nil
}
return nil, fmt.Errorf("all connection attempts failed (HTTP: %v, HTTPS: %v)", httpErr, tlsErr)
}
func (a *dialParams) tryURL(u *url.URL, init []byte) (net.Conn, error) {
dns := &dnscache.Resolver{
Forward: dnscache.Get().Forward,
LookupIPFallback: dnsfallback.Lookup,
UseLastGood: true,
}
dialer := netns.NewDialer(log.Printf)
tr := http.DefaultTransport.(*http.Transport).Clone()
defer tr.CloseIdleConnections()
tr.Proxy = a.proxyFunc
tshttpproxy.SetTransportGetProxyConnectHeader(tr)
tr.DialContext = dnscache.Dialer(dialer.DialContext, dns)
// Disable HTTP2, since h2 can't do protocol switching.
tr.TLSClientConfig.NextProtos = []string{}
tr.TLSNextProto = map[string]func(string, *tls.Conn) http.RoundTripper{}
tr.TLSClientConfig = tlsdial.Config(a.host, tr.TLSClientConfig)
if a.insecureTLS {
tr.TLSClientConfig.InsecureSkipVerify = true
tr.TLSClientConfig.VerifyConnection = nil
}
tr.DialTLSContext = dnscache.TLSDialer(dialer.DialContext, dns, tr.TLSClientConfig)
tr.DisableCompression = true
// (mis)use httptrace to extract the underlying net.Conn from the
// transport. We make exactly 1 request using this transport, so
// there will be exactly 1 GotConn call. Additionally, the
// transport handles 101 Switching Protocols correctly, such that
// the Conn will not be reused or kept alive by the transport once
// the response has been handed back from RoundTrip.
//
// In theory, the machinery of net/http should make it such that
// the trace callback happens-before we get the response, but
// there's no promise of that. So, to make sure, we use a buffered
// channel as a synchronization step to avoid data races.
//
// Note that even though we're able to extract a net.Conn via this
// mechanism, we must still keep using the eventual resp.Body to
// read from, because it includes a buffer we can't get rid of. If
// the server never sends any data after sending the HTTP
// response, we could get away with it, but violating this
// assumption leads to very mysterious transport errors (lockups,
// unexpected EOFs...), and we're bound to forget someday and
// introduce a protocol optimization at a higher level that starts
// eagerly transmitting from the server.
connCh := make(chan net.Conn, 1)
trace := httptrace.ClientTrace{
GotConn: func(info httptrace.GotConnInfo) {
connCh <- info.Conn
},
}
ctx := httptrace.WithClientTrace(a.ctx, &trace)
req := &http.Request{
Method: "POST",
URL: u,
Header: http.Header{
"Upgrade": []string{upgradeHeaderValue},
"Connection": []string{"upgrade"},
handshakeHeaderName: []string{base64.StdEncoding.EncodeToString(init)},
},
}
req = req.WithContext(ctx)
resp, err := tr.RoundTrip(req)
if err != nil {
return nil, err
}
if resp.StatusCode != http.StatusSwitchingProtocols {
return nil, fmt.Errorf("unexpected HTTP response: %s", resp.Status)
}
// From here on, the underlying net.Conn is ours to use, but there
// is still a read buffer attached to it within resp.Body. So, we
// must direct I/O through resp.Body, but we can still use the
// underlying net.Conn for stuff like deadlines.
var switchedConn net.Conn
select {
case switchedConn = <-connCh:
default:
}
if switchedConn == nil {
resp.Body.Close()
return nil, fmt.Errorf("httptrace didn't provide a connection")
}
if next := resp.Header.Get("Upgrade"); next != upgradeHeaderValue {
resp.Body.Close()
return nil, fmt.Errorf("server switched to unexpected protocol %q", next)
}
rwc, ok := resp.Body.(io.ReadWriteCloser)
if !ok {
resp.Body.Close()
return nil, errors.New("http Transport did not provide a writable body")
}
return &wrappedConn{switchedConn, rwc}, nil
}
type wrappedConn struct {
net.Conn
rwc io.ReadWriteCloser
}
func (w *wrappedConn) Read(bs []byte) (int, error) {
return w.rwc.Read(bs)
}
func (w *wrappedConn) Write(bs []byte) (int, error) {
return w.rwc.Write(bs)
}
func (w *wrappedConn) Close() error {
return w.rwc.Close()
}

@ -0,0 +1,398 @@
// 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 controlhttp
import (
"context"
"crypto/tls"
"fmt"
"io"
"log"
"net"
"net/http"
"net/http/httputil"
"net/url"
"strconv"
"sync"
"testing"
"tailscale.com/control/controlbase"
"tailscale.com/net/socks5"
"tailscale.com/types/key"
)
func TestControlHTTP(t *testing.T) {
tests := []struct {
name string
proxy proxy
}{
// direct connection
{
name: "no_proxy",
proxy: nil,
},
// SOCKS5
{
name: "socks5",
proxy: &socksProxy{},
},
// HTTP->HTTP
{
name: "http_to_http",
proxy: &httpProxy{
useTLS: false,
allowConnect: false,
allowHTTP: true,
},
},
// HTTP->HTTPS
{
name: "http_to_https",
proxy: &httpProxy{
useTLS: false,
allowConnect: true,
allowHTTP: false,
},
},
// HTTP->any (will pick HTTP)
{
name: "http_to_any",
proxy: &httpProxy{
useTLS: false,
allowConnect: true,
allowHTTP: true,
},
},
// HTTPS->HTTP
{
name: "https_to_http",
proxy: &httpProxy{
useTLS: true,
allowConnect: false,
allowHTTP: true,
},
},
// HTTPS->HTTPS
{
name: "https_to_https",
proxy: &httpProxy{
useTLS: true,
allowConnect: true,
allowHTTP: false,
},
},
// HTTPS->any (will pick HTTP)
{
name: "https_to_any",
proxy: &httpProxy{
useTLS: true,
allowConnect: true,
allowHTTP: true,
},
},
}
for _, test := range tests {
t.Run(test.name, func(t *testing.T) {
testControlHTTP(t, test.proxy)
})
}
}
func testControlHTTP(t *testing.T, proxy proxy) {
client, server := key.NewMachine(), key.NewMachine()
sch := make(chan serverResult, 1)
handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
conn, err := AcceptHTTP(context.Background(), w, r, server)
if err != nil {
log.Print(err)
}
res := serverResult{
err: err,
}
if conn != nil {
res.clientAddr = conn.RemoteAddr().String()
res.version = conn.ProtocolVersion()
res.peer = conn.Peer()
res.conn = conn
}
sch <- res
})
httpLn, err := net.Listen("tcp", "127.0.0.1:0")
if err != nil {
t.Fatalf("HTTP listen: %v", err)
}
httpsLn, err := net.Listen("tcp", "127.0.0.1:0")
if err != nil {
t.Fatalf("HTTPS listen: %v", err)
}
httpServer := &http.Server{Handler: handler}
go httpServer.Serve(httpLn)
defer httpServer.Close()
httpsServer := &http.Server{
Handler: handler,
TLSConfig: tlsConfig(t),
}
go httpsServer.ServeTLS(httpsLn, "", "")
defer httpsServer.Close()
//ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
//defer cancel()
a := dialParams{
ctx: context.Background(), //ctx,
host: "localhost",
httpPort: strconv.Itoa(httpLn.Addr().(*net.TCPAddr).Port),
httpsPort: strconv.Itoa(httpsLn.Addr().(*net.TCPAddr).Port),
machineKey: client,
controlKey: server.Public(),
insecureTLS: true,
}
if proxy != nil {
proxyEnv := proxy.Start(t)
defer proxy.Close()
proxyURL, err := url.Parse(proxyEnv)
if err != nil {
t.Fatal(err)
}
a.proxyFunc = func(*http.Request) (*url.URL, error) {
return proxyURL, nil
}
} else {
a.proxyFunc = func(*http.Request) (*url.URL, error) {
return nil, nil
}
}
conn, err := a.dial()
if err != nil {
t.Fatalf("dialing controlhttp: %v", err)
}
defer conn.Close()
si := <-sch
if si.conn != nil {
defer si.conn.Close()
}
if si.err != nil {
t.Fatalf("controlhttp server got error: %v", err)
}
if clientVersion := conn.ProtocolVersion(); si.version != clientVersion {
t.Fatalf("client and server don't agree on protocol version: %d vs %d", clientVersion, si.version)
}
if si.peer != client.Public() {
t.Fatalf("server got peer pubkey %s, want %s", si.peer, client.Public())
}
if spub := conn.Peer(); spub != server.Public() {
t.Fatalf("client got peer pubkey %s, want %s", spub, server.Public())
}
if proxy != nil && !proxy.ConnIsFromProxy(si.clientAddr) {
t.Fatalf("client connected from %s, which isn't the proxy", si.clientAddr)
}
}
type serverResult struct {
err error
clientAddr string
version int
peer key.MachinePublic
conn *controlbase.Conn
}
type proxy interface {
Start(*testing.T) string
Close()
ConnIsFromProxy(string) bool
}
type socksProxy struct {
sync.Mutex
proxy socks5.Server
ln net.Listener
clientConnAddrs map[string]bool // addrs of the local end of outgoing conns from proxy
}
func (s *socksProxy) Start(t *testing.T) (url string) {
t.Helper()
s.Lock()
defer s.Unlock()
ln, err := net.Listen("tcp", "127.0.0.1:0")
if err != nil {
t.Fatalf("listening for SOCKS server: %v", err)
}
s.ln = ln
s.clientConnAddrs = map[string]bool{}
s.proxy.Logf = t.Logf
s.proxy.Dialer = s.dialAndRecord
go s.proxy.Serve(ln)
return fmt.Sprintf("socks5://%s", ln.Addr().String())
}
func (s *socksProxy) Close() {
s.Lock()
defer s.Unlock()
s.ln.Close()
}
func (s *socksProxy) dialAndRecord(ctx context.Context, network, addr string) (net.Conn, error) {
var d net.Dialer
conn, err := d.DialContext(ctx, network, addr)
if err != nil {
return nil, err
}
s.Lock()
defer s.Unlock()
s.clientConnAddrs[conn.LocalAddr().String()] = true
return conn, nil
}
func (s *socksProxy) ConnIsFromProxy(addr string) bool {
s.Lock()
defer s.Unlock()
return s.clientConnAddrs[addr]
}
type httpProxy struct {
useTLS bool // take incoming connections over TLS
allowConnect bool // allow CONNECT for TLS
allowHTTP bool // allow plain HTTP proxying
sync.Mutex
ln net.Listener
rp httputil.ReverseProxy
s http.Server
clientConnAddrs map[string]bool // addrs of the local end of outgoing conns from proxy
}
func (h *httpProxy) Start(t *testing.T) (url string) {
t.Helper()
h.Lock()
defer h.Unlock()
ln, err := net.Listen("tcp", "127.0.0.1:0")
if err != nil {
t.Fatalf("listening for HTTP proxy: %v", err)
}
h.ln = ln
h.rp = httputil.ReverseProxy{
Director: func(*http.Request) {},
Transport: &http.Transport{
DialContext: h.dialAndRecord,
TLSClientConfig: &tls.Config{
InsecureSkipVerify: true,
},
TLSNextProto: map[string]func(string, *tls.Conn) http.RoundTripper{},
},
}
h.clientConnAddrs = map[string]bool{}
h.s.Handler = h
if h.useTLS {
h.s.TLSConfig = tlsConfig(t)
go h.s.ServeTLS(h.ln, "", "")
return fmt.Sprintf("https://%s", ln.Addr().String())
} else {
go h.s.Serve(h.ln)
return fmt.Sprintf("http://%s", ln.Addr().String())
}
}
func (h *httpProxy) Close() {
h.Lock()
defer h.Unlock()
h.s.Close()
}
func (h *httpProxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
if r.Method != "CONNECT" {
if !h.allowHTTP {
http.Error(w, "http proxy not allowed", 500)
return
}
h.rp.ServeHTTP(w, r)
return
}
if !h.allowConnect {
http.Error(w, "connect not allowed", 500)
return
}
dst := r.RequestURI
c, err := h.dialAndRecord(context.Background(), "tcp", dst)
if err != nil {
http.Error(w, err.Error(), 500)
return
}
defer c.Close()
cc, ccbuf, err := w.(http.Hijacker).Hijack()
if err != nil {
http.Error(w, err.Error(), 500)
return
}
defer cc.Close()
io.WriteString(cc, "HTTP/1.1 200 OK\r\n\r\n")
errc := make(chan error, 1)
go func() {
_, err := io.Copy(cc, c)
errc <- err
}()
go func() {
_, err := io.Copy(c, ccbuf)
errc <- err
}()
<-errc
}
func (h *httpProxy) dialAndRecord(ctx context.Context, network, addr string) (net.Conn, error) {
var d net.Dialer
conn, err := d.DialContext(ctx, network, addr)
if err != nil {
return nil, err
}
h.Lock()
defer h.Unlock()
h.clientConnAddrs[conn.LocalAddr().String()] = true
return conn, nil
}
func (h *httpProxy) ConnIsFromProxy(addr string) bool {
h.Lock()
defer h.Unlock()
return h.clientConnAddrs[addr]
}
func tlsConfig(t *testing.T) *tls.Config {
// Cert and key taken from the example code in the crypto/tls
// package.
certPem := []byte(`-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----`)
keyPem := []byte(`-----BEGIN EC PRIVATE KEY-----
MHcCAQEEIIrYSSNQFaA2Hwf1duRSxKtLYX5CB04fSeQ6tF1aY/PuoAoGCCqGSM49
AwEHoUQDQgAEPR3tU2Fta9ktY+6P9G0cWO+0kETA6SFs38GecTyudlHz6xvCdz8q
EKTcWGekdmdDPsHloRNtsiCa697B2O9IFA==
-----END EC PRIVATE KEY-----`)
cert, err := tls.X509KeyPair(certPem, keyPem)
if err != nil {
t.Fatal(err)
}
return &tls.Config{
Certificates: []tls.Certificate{cert},
}
}

@ -0,0 +1,95 @@
// 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 controlhttp
import (
"bufio"
"context"
"encoding/base64"
"errors"
"fmt"
"net"
"net/http"
"tailscale.com/control/controlbase"
"tailscale.com/types/key"
)
// AcceptHTTP upgrades the HTTP request given by w and r into a
// Tailscale control protocol base transport connection.
//
// AcceptHTTP always writes an HTTP response to w. The caller must not
// attempt their own response after calling AcceptHTTP.
func AcceptHTTP(ctx context.Context, w http.ResponseWriter, r *http.Request, private key.MachinePrivate) (*controlbase.Conn, error) {
next := r.Header.Get("Upgrade")
if next == "" {
http.Error(w, "missing next protocol", http.StatusBadRequest)
return nil, errors.New("no next protocol in HTTP request")
}
if next != upgradeHeaderValue {
http.Error(w, "unknown next protocol", http.StatusBadRequest)
return nil, fmt.Errorf("client requested unhandled next protocol %q", next)
}
initB64 := r.Header.Get(handshakeHeaderName)
if initB64 == "" {
http.Error(w, "missing Tailscale handshake header", http.StatusBadRequest)
return nil, errors.New("no tailscale handshake header in HTTP request")
}
init, err := base64.StdEncoding.DecodeString(initB64)
if err != nil {
http.Error(w, "invalid tailscale handshake header", http.StatusBadRequest)
return nil, fmt.Errorf("decoding base64 handshake header: %v", err)
}
hijacker, ok := w.(http.Hijacker)
if !ok {
http.Error(w, "make request over HTTP/1", http.StatusBadRequest)
return nil, errors.New("can't hijack client connection")
}
w.Header().Set("Upgrade", upgradeHeaderValue)
w.Header().Set("Connection", "upgrade")
w.WriteHeader(http.StatusSwitchingProtocols)
conn, brw, err := hijacker.Hijack()
if err != nil {
return nil, fmt.Errorf("hijacking client connection: %w", err)
}
if err := brw.Flush(); err != nil {
conn.Close()
return nil, fmt.Errorf("flushing hijacked HTTP buffer: %w", err)
}
if brw.Reader.Buffered() > 0 {
conn = &drainBufConn{conn, brw.Reader}
}
nc, err := controlbase.Server(ctx, conn, private, init)
if err != nil {
conn.Close()
return nil, fmt.Errorf("noise handshake failed: %w", err)
}
return nc, nil
}
// drainBufConn is a net.Conn with an initial bunch of bytes in a
// bufio.Reader. Read drains the bufio.Reader until empty, then passes
// through subsequent reads to the Conn directly.
type drainBufConn struct {
net.Conn
r *bufio.Reader
}
func (b *drainBufConn) Read(bs []byte) (int, error) {
if b.r == nil {
return b.Conn.Read(bs)
}
n, err := b.r.Read(bs)
if b.r.Buffered() == 0 {
b.r = nil
}
return n, err
}
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