[client] Replace the eBPF WireGuard proxy with loopback endpoint addressing (#7316)

client/iface/wgproxy/loopback/proxy_privileged_test.go

@@ -0,0 +1,196 @@
+//go:build linux && !android && privileged
+
+package loopback
+
+import (
+	"context"
+	"net"
+	"strconv"
+	"testing"
+	"time"
+)
+
+const testWGPort = 51862
+
+// relayEnd stands in for a relayed connection: the proxy writes what it read
+// from WireGuard into it, and the test reads it back out here.
+func relayEnd(t *testing.T) (proxySide net.Conn, testSide *net.UDPConn) {
+	t.Helper()
+
+	testSide, err := net.ListenUDP("udp", &net.UDPAddr{IP: net.ParseIP("127.0.0.1")})
+	if err != nil {
+		t.Fatalf("relay listener: %v", err)
+	}
+	t.Cleanup(func() {
+		if err := testSide.Close(); err != nil {
+			t.Logf("close relay listener: %v", err)
+		}
+	})
+
+	proxySide, err = net.Dial("udp", testSide.LocalAddr().String())
+	if err != nil {
+		t.Fatalf("relay conn: %v", err)
+	}
+	t.Cleanup(func() {
+		if err := proxySide.Close(); err != nil {
+			t.Logf("close relay conn: %v", err)
+		}
+	})
+
+	return proxySide, testSide
+}
+
+// TestProxyDemuxesByDestinationAddress is the core of the design: one socket
+// serves every peer, and the destination address decides which relayed
+// connection a WireGuard packet belongs to.
+func TestProxyDemuxesByDestinationAddress(t *testing.T) {
+	proxy := NewProxy(testWGPort, 1280)
+	if err := proxy.Listen(); err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	defer func() {
+		if err := proxy.Free(); err != nil {
+			t.Errorf("free proxy: %v", err)
+		}
+	}()
+
+	const peers = 3
+	endpoints := make([]*net.UDPAddr, 0, peers)
+	readers := make([]*net.UDPConn, 0, peers)
+	for i := 0; i < peers; i++ {
+		proxySide, testSide := relayEnd(t)
+		endpoint, _, err := proxy.AddRelayedConn(proxySide)
+		if err != nil {
+			t.Fatalf("add relayed conn %d: %v", i, err)
+		}
+		if endpoint.Port != proxy.proxyPort {
+			t.Errorf("peer %d endpoint port = %d, want the shared proxy port %d", i, endpoint.Port, proxy.proxyPort)
+		}
+		endpoints = append(endpoints, endpoint)
+		readers = append(readers, testSide)
+	}
+
+	// every peer must have its own address, otherwise they are indistinguishable
+	seen := make(map[string]bool, peers)
+	for i, endpoint := range endpoints {
+		if seen[endpoint.IP.String()] {
+			t.Fatalf("peer %d reuses endpoint address %s", i, endpoint.IP)
+		}
+		seen[endpoint.IP.String()] = true
+	}
+
+	wgSock, err := net.ListenUDP("udp", &net.UDPAddr{IP: net.ParseIP("127.0.0.1")})
+	if err != nil {
+		t.Fatalf("wg socket: %v", err)
+	}
+	defer func() {
+		if err := wgSock.Close(); err != nil {
+			t.Logf("close wg socket: %v", err)
+		}
+	}()
+
+	for i, endpoint := range endpoints {
+		payload := []byte{byte(i), 'p', 'k', 't'}
+		if _, err := wgSock.WriteTo(payload, endpoint); err != nil {
+			t.Fatalf("write to peer %d endpoint %s: %v", i, endpoint, err)
+		}
+
+		buf := make([]byte, 1500)
+		if err := readers[i].SetReadDeadline(time.Now().Add(2 * time.Second)); err != nil {
+			t.Fatalf("set read deadline: %v", err)
+		}
+		n, _, err := readers[i].ReadFrom(buf)
+		if err != nil {
+			t.Fatalf("peer %d did not receive its packet: %v", i, err)
+		}
+		if string(buf[:n]) != string(payload) {
+			t.Errorf("peer %d got %q, want %q", i, buf[:n], payload)
+		}
+
+		// no other peer may see it
+		for j, other := range readers {
+			if j == i {
+				continue
+			}
+			if err := other.SetReadDeadline(time.Now().Add(100 * time.Millisecond)); err != nil {
+				t.Fatalf("set read deadline: %v", err)
+			}
+			if _, _, err := other.ReadFrom(buf); err == nil {
+				t.Errorf("packet for peer %d also delivered to peer %d", i, j)
+			}
+		}
+	}
+}
+
+// TestProxyDropsPacketsOutsideTheRange guards the wildcard bind: anything that
+// is not addressed to a handed-out endpoint must not reach a relayed peer.
+func TestProxyDropsPacketsOutsideTheRange(t *testing.T) {
+	proxy := NewProxy(testWGPort+1, 1280)
+	if err := proxy.Listen(); err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	defer func() {
+		if err := proxy.Free(); err != nil {
+			t.Errorf("free proxy: %v", err)
+		}
+	}()
+
+	proxySide, testSide := relayEnd(t)
+	if _, _, err := proxy.AddRelayedConn(proxySide); err != nil {
+		t.Fatalf("add relayed conn: %v", err)
+	}
+
+	sender, err := net.Dial("udp", net.JoinHostPort("127.0.0.1", strconv.Itoa(proxy.proxyPort)))
+	if err != nil {
+		t.Fatalf("sender: %v", err)
+	}
+	defer func() {
+		if err := sender.Close(); err != nil {
+			t.Logf("close sender: %v", err)
+		}
+	}()
+
+	if _, err := sender.Write([]byte("stray")); err != nil {
+		t.Fatalf("write stray packet: %v", err)
+	}
+
+	buf := make([]byte, 1500)
+	if err := testSide.SetReadDeadline(time.Now().Add(500 * time.Millisecond)); err != nil {
+		t.Fatalf("set read deadline: %v", err)
+	}
+	if _, _, err := testSide.ReadFrom(buf); err == nil {
+		t.Error("packet addressed to 127.0.0.1 was forwarded to a relayed peer")
+	}
+}
+
+// A wrapper that is closed before it starts forwarding still has to give its
+// endpoint address back, otherwise the range leaks an address per attempt.
+func TestClosingBeforeWorkReleasesTheAddress(t *testing.T) {
+	proxy := NewProxy(testWGPort+2, 1280)
+	if err := proxy.Listen(); err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	defer func() {
+		if err := proxy.Free(); err != nil {
+			t.Errorf("free proxy: %v", err)
+		}
+	}()
+
+	proxySide, _ := relayEnd(t)
+	wrapper := NewProxyWrapper(proxy)
+	if err := wrapper.AddRelayedConn(context.Background(), nil, proxySide); err != nil {
+		t.Fatalf("add relayed conn: %v", err)
+	}
+
+	if got := len(proxy.relayedConnStore); got != 1 {
+		t.Fatalf("store holds %d entries after adding one conn, want 1", got)
+	}
+
+	if err := wrapper.CloseConn(); err != nil {
+		t.Fatalf("close conn: %v", err)
+	}
+
+	if got := len(proxy.relayedConnStore); got != 0 {
+		t.Errorf("store holds %d entries after close, want 0", got)
+	}
+}