fix(tunnel/tor): keep tunneldir clean (#300)

* fix(tunnel/tor): keep tunneldir clean

This diff ensures that we don't keep the log file growing and
we also remove the temporary files created by the library we
are currently using for running tor from golang.

Part of https://github.com/ooni/probe/issues/985

* fix(session.go): tell use we're using a tunnel

internal/engine/session.go

@@ -168,6 +168,8 @@ func NewSession(ctx context.Context, config SessionConfig) (*Session, error) {
 	if proxyURL != nil {
 		switch proxyURL.Scheme {
 		case "psiphon", "tor", "fake":
+			config.Logger.Infof(
+				"starting '%s' tunnel; please be patient...", proxyURL.Scheme)
 			tunnel, err := tunnel.Start(ctx, &tunnel.Config{
 				Name:      proxyURL.Scheme,
 				Session:   &sessionTunnelEarlySession{},
@@ -178,6 +180,7 @@ func NewSession(ctx context.Context, config SessionConfig) (*Session, error) {
 			if err != nil {
 				return nil, err
 			}
+			config.Logger.Infof("tunnel '%s' running...", proxyURL.Scheme)
 			sess.tunnel = tunnel
 			proxyURL = tunnel.SOCKS5ProxyURL()
 		}

internal/engine/tunnel/tor.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"net/url"
+	"os"
 	"path/filepath"
 	"strings"
 	"time"
@@ -45,9 +46,6 @@ func (tt *torTunnel) Stop() {
 	tt.instance.Close()
 }
 
-// TODO(bassosimone): the current design is such that we have a bunch of
-// torrc-$number and a growing tor.log file inside of stateDir.
-
 // ErrTorUnableToGetSOCKSProxyAddress indicates that we could not
 // get the SOCKS proxy address via the control port.
 var ErrTorUnableToGetSOCKSProxyAddress = errors.New(
@@ -70,6 +68,7 @@ func torStart(ctx context.Context, config *Config) (Tunnel, error) {
 	}
 	stateDir := filepath.Join(config.TunnelDir, "tor")
 	logfile := filepath.Join(stateDir, "tor.log")
+	maybeCleanupTunnelDir(stateDir, logfile)
 	extraArgs := append([]string{}, config.TorArgs...)
 	extraArgs = append(extraArgs, "Log")
 	extraArgs = append(extraArgs, "notice stderr")
@@ -112,3 +111,19 @@ func torStart(ctx context.Context, config *Config) (Tunnel, error) {
 		proxy:         &url.URL{Scheme: "socks5", Host: proxyAddress},
 	}, nil
 }
+
+// maybeCleanupTunnelDir removes stale files inside
+// of the tunnel directory.
+func maybeCleanupTunnelDir(dir, logfile string) {
+	os.Remove(logfile)
+	removeWithGlob(filepath.Join(dir, "torrc-*"))
+	removeWithGlob(filepath.Join(dir, "control-port-*"))
+}
+
+// removeWithGlob globs and removes files.
+func removeWithGlob(pattern string) {
+	files, _ := filepath.Glob(pattern)
+	for _, file := range files {
+		os.Remove(file)
+	}
+}

internal/engine/tunnel/tor_test.go

@@ -3,7 +3,12 @@ package tunnel
 import (
 	"context"
 	"errors"
+	"fmt"
+	"io/ioutil"
 	"net/url"
+	"os"
+	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/cretz/bine/control"
@@ -226,3 +231,53 @@ func TestTorUnsupportedProxy(t *testing.T) {
 		t.Fatal("expected nil tunnel here")
 	}
 }
+
+func TestMaybeCleanupTunnelDir(t *testing.T) {
+	fakeTunDir := filepath.Join("testdata", "fake-tun-dir")
+	if err := os.RemoveAll(fakeTunDir); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.MkdirAll(fakeTunDir, 0700); err != nil {
+		t.Fatal(err)
+	}
+	fakeData := []byte("deadbeef\n")
+	logfile := filepath.Join(fakeTunDir, "tor.log")
+	if err := ioutil.WriteFile(logfile, fakeData, 0600); err != nil {
+		t.Fatal(err)
+	}
+	for idx := 0; idx < 3; idx++ {
+		filename := filepath.Join(fakeTunDir, fmt.Sprintf("torrc-%d", idx))
+		if err := ioutil.WriteFile(filename, fakeData, 0600); err != nil {
+			t.Fatal(err)
+		}
+		filename = filepath.Join(fakeTunDir, fmt.Sprintf("control-port-%d", idx))
+		if err := ioutil.WriteFile(filename, fakeData, 0600); err != nil {
+			t.Fatal(err)
+		}
+		filename = filepath.Join(fakeTunDir, fmt.Sprintf("antani-%d", idx))
+		if err := ioutil.WriteFile(filename, fakeData, 0600); err != nil {
+			t.Fatal(err)
+		}
+	}
+	files, err := filepath.Glob(filepath.Join(fakeTunDir, "*"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(files) != 10 {
+		t.Fatal("unexpected number of files")
+	}
+	maybeCleanupTunnelDir(fakeTunDir, logfile)
+	files, err = filepath.Glob(filepath.Join(fakeTunDir, "*"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(files) != 3 {
+		t.Fatal("unexpected number of files")
+	}
+	expectPrefix := filepath.Join(fakeTunDir, "antani-")
+	for _, file := range files {
+		if !strings.HasPrefix(file, expectPrefix) {
+			t.Fatal("unexpected file name: ", file)
+		}
+	}
+}