ipn/{ipnlocal,localapi}: add localapi handler to dial/proxy file PUTs

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscaled/depaware.txt

@@ -163,7 +163,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         golang.org/x/crypto/salsa20/salsa                            from golang.org/x/crypto/nacl/box+
         golang.org/x/net/bpf                                         from github.com/mdlayher/netlink+
         golang.org/x/net/dns/dnsmessage                              from net+
-        golang.org/x/net/http/httpguts                               from net/http
+        golang.org/x/net/http/httpguts                               from net/http+
         golang.org/x/net/http/httpproxy                              from net/http
         golang.org/x/net/http2/hpack                                 from net/http
         golang.org/x/net/idna                                        from golang.org/x/net/http/httpguts+
@@ -247,7 +247,8 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         net                                                          from crypto/tls+
         net/http                                                     from expvar+
         net/http/httptrace                                           from github.com/tcnksm/go-httpstat+
-        net/http/internal                                            from net/http
+        net/http/httputil                                            from tailscale.com/ipn/localapi
+        net/http/internal                                            from net/http+
         net/http/pprof                                               from tailscale.com/cmd/tailscaled
         net/textproto                                                from golang.org/x/net/http/httpguts+
         net/url                                                      from crypto/x509+

ipn/ipnlocal/local.go

@@ -19,6 +19,7 @@ import (
 	"strings"
 	"sync"
 	"sync/atomic"
+	"syscall"
 	"time"
 
 	"inet.af/netaddr"
@@ -2155,3 +2156,16 @@ func (b *LocalBackend) CheckIPForwarding() error {
 	}
 	return nil
 }
+
+// peerDialControlFunc is non-nil on platforms that require a way to
+// bind to dial out to other peers.
+var peerDialControlFunc func(*LocalBackend) func(network, address string, c syscall.RawConn) error
+
+// PeerDialControlFunc returns a net.Dialer.Control func (possibly nil) to use to
+// dial other Tailscale peers from the current environment.
+func (b *LocalBackend) PeerDialControlFunc() func(network, address string, c syscall.RawConn) error {
+	if peerDialControlFunc != nil {
+		return peerDialControlFunc(b)
+	}
+	return nil
+}

ipn/ipnlocal/peerapi_macios_ext.go

@@ -7,6 +7,7 @@
 package ipnlocal
 
 import (
+	"errors"
 	"fmt"
 	"log"
 	"net"
@@ -20,6 +21,7 @@ import (
 
 func init() {
 	initListenConfig = initListenConfigNetworkExtension
+	peerDialControlFunc = peerDialControlFuncNetworkExtension
 }
 
 // initListenConfigNetworkExtension configures nc for listening on IP
@@ -33,16 +35,7 @@ func initListenConfigNetworkExtension(nc *net.ListenConfig, ip netaddr.IP, st *i
 	nc.Control = func(network, address string, c syscall.RawConn) error {
 		var sockErr error
 		err := c.Control(func(fd uintptr) {
-
-			v6 := strings.Contains(address, "]:") || strings.HasSuffix(network, "6") // hacky test for v6
-			proto := unix.IPPROTO_IP
-			opt := unix.IP_BOUND_IF
-			if v6 {
-				proto = unix.IPPROTO_IPV6
-				opt = unix.IPV6_BOUND_IF
-			}
-
-			sockErr = unix.SetsockoptInt(int(fd), proto, opt, tunIf.Index)
+			sockErr = bindIf(fd, network, address, tunIf.Index)
 			log.Printf("peerapi: bind(%q, %q) on index %v = %v", network, address, tunIf.Index, sockErr)
 		})
 		if err != nil {
@@ -52,3 +45,40 @@ func initListenConfigNetworkExtension(nc *net.ListenConfig, ip netaddr.IP, st *i
 	}
 	return nil
 }
+
+func bindIf(fd uintptr, network, address string, ifIndex int) error {
+	v6 := strings.Contains(address, "]:") || strings.HasSuffix(network, "6") // hacky test for v6
+	proto := unix.IPPROTO_IP
+	opt := unix.IP_BOUND_IF
+	if v6 {
+		proto = unix.IPPROTO_IPV6
+		opt = unix.IPV6_BOUND_IF
+	}
+	return unix.SetsockoptInt(int(fd), proto, opt, ifIndex)
+}
+
+func peerDialControlFuncNetworkExtension(b *LocalBackend) func(network, address string, c syscall.RawConn) error {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	st := b.prevIfState
+	pas := b.peerAPIServer
+	index := -1
+	if st != nil && pas != nil && pas.tunName != "" {
+		if tunIf, ok := st.Interface[pas.tunName]; ok {
+			index = tunIf.Index
+		}
+	}
+	return func(network, address string, c syscall.RawConn) error {
+		if index == -1 {
+			return errors.New("failed to find TUN interface to bind to")
+		}
+		var sockErr error
+		err := c.Control(func(fd uintptr) {
+			sockErr = bindIf(fd, network, address, index)
+		})
+		if err != nil {
+			return err
+		}
+		return sockErr
+	}
+}

ipn/localapi/localapi.go

@@ -11,12 +11,15 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
+	"net/http/httputil"
 	"net/url"
 	"reflect"
 	"runtime"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"inet.af/netaddr"
@@ -73,6 +76,10 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		h.serveFiles(w, r)
 		return
 	}
+	if strings.HasPrefix(r.URL.Path, "/localapi/v0/file-put/") {
+		h.serveFilePut(w, r)
+		return
+	}
 	switch r.URL.Path {
 	case "/localapi/v0/whois":
 		h.serveWhoIs(w, r)
@@ -243,14 +250,85 @@ func (h *Handler) serveFileTargets(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "want GET to list targets", 400)
 		return
 	}
-	wfs, err := h.b.FileTargets()
+	fts, err := h.b.FileTargets()
 	if err != nil {
 		http.Error(w, err.Error(), 500)
 		return
 	}
-	makeNonNil(&wfs)
+	makeNonNil(&fts)
 	w.Header().Set("Content-Type", "application/json")
-	json.NewEncoder(w).Encode(wfs)
+	json.NewEncoder(w).Encode(fts)
+}
+
+func (h *Handler) serveFilePut(w http.ResponseWriter, r *http.Request) {
+	if !h.PermitWrite {
+		http.Error(w, "file access denied", http.StatusForbidden)
+		return
+	}
+	if r.Method != "PUT" {
+		http.Error(w, "want PUT to put file", 400)
+		return
+	}
+	fts, err := h.b.FileTargets()
+	if err != nil {
+		http.Error(w, err.Error(), 500)
+		return
+	}
+
+	upath := strings.TrimPrefix(r.URL.EscapedPath(), "/localapi/v0/file-put/")
+	slash := strings.Index(upath, "/")
+	if slash == -1 {
+		http.Error(w, "bogus URL", 400)
+		return
+	}
+	stableID, filenameEscaped := tailcfg.StableNodeID(upath[:slash]), upath[slash+1:]
+
+	var ft *ipnlocal.FileTarget
+	for _, x := range fts {
+		if x.Node.StableID == stableID {
+			ft = x
+			break
+		}
+	}
+	if ft == nil {
+		http.Error(w, "node not found", 404)
+		return
+	}
+	dstURL, err := url.Parse(ft.PeerAPIURL)
+	if err != nil {
+		http.Error(w, "bogus peer URL", 500)
+		return
+	}
+	outReq, err := http.NewRequestWithContext(r.Context(), "PUT", "http://peer/v0/put/"+filenameEscaped, r.Body)
+	if err != nil {
+		http.Error(w, "bogus outreq", 500)
+		return
+	}
+	outReq.ContentLength = r.ContentLength
+
+	rp := httputil.NewSingleHostReverseProxy(dstURL)
+	rp.Transport = getDialPeerTransport(h.b)
+	rp.ServeHTTP(w, outReq)
+}
+
+var dialPeerTransportOnce struct {
+	sync.Once
+	v *http.Transport
+}
+
+func getDialPeerTransport(b *ipnlocal.LocalBackend) *http.Transport {
+	dialPeerTransportOnce.Do(func() {
+		t := http.DefaultTransport.(*http.Transport).Clone()
+		t.Dial = nil //lint:ignore SA1019 yes I know I'm setting it to nil defensively
+		dialer := net.Dialer{
+			Timeout:   30 * time.Second,
+			KeepAlive: 30 * time.Second,
+			Control:   b.PeerDialControlFunc(),
+		}
+		t.DialContext = dialer.DialContext
+		dialPeerTransportOnce.v = t
+	})
+	return dialPeerTransportOnce.v
 }
 
 func defBool(a string, def bool) bool {