GODT-1917: gRPC service should use random port.

WIP: bridge-gui wait and parse gRPC service config fie.

internal/frontend/grpc/config.go

@@ -0,0 +1,65 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+package grpc
+
+import (
+	"encoding/json"
+	"os"
+)
+
+// config is a structure containing the service configuration data that are exchanged by the gRPC server and client.
+type config struct {
+	Port  int    `json:"port"`
+	Cert  string `json:"cert"`  // coming soon
+	Token string `json:"token"` // coming soon
+}
+
+// save saves a gRPC service configuration to file.
+func (s *config) save(path string) error {
+	// Another process may be waiting for this file to be available. In order to prevent this process to open
+	// the file while we are writing in it, we write it with a temp file name, then rename it.
+	tempPath := path + "_"
+	if err := s._save(tempPath); err != nil {
+		return err
+	}
+
+	return os.Rename(tempPath, path)
+}
+
+func (s *config) _save(path string) error {
+	f, err := os.Create(path) //nolint:errcheck,gosec
+	if err != nil {
+		return err
+	}
+
+	defer func() { _ = f.Close() }()
+
+	return json.NewEncoder(f).Encode(s)
+}
+
+// load loads a gRPC service configuration from file.
+func (s *config) load(path string) error {
+	f, err := os.Open(path) //nolint:errcheck,gosec
+	if err != nil {
+		return err
+	}
+
+	defer func() { _ = f.Close() }()
+
+	return json.NewDecoder(f).Decode(s)
+}

internal/frontend/grpc/config_test.go

@@ -0,0 +1,55 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+package grpc
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+const (
+	dummyPort    = 12
+	dummyCert    = "A dummy cert"
+	dummyToken   = "A dummy token"
+	tempFileName = "test.json"
+)
+
+func TestConfig(t *testing.T) {
+	conf1 := config{
+		Port:  dummyPort,
+		Cert:  dummyCert,
+		Token: dummyToken,
+	}
+
+	// Read-back test
+	tempDir := t.TempDir()
+	tempFilePath := filepath.Join(tempDir, tempFileName)
+	require.NoError(t, conf1.save(tempFilePath))
+
+	conf2 := config{}
+	require.NoError(t, conf2.load(tempFilePath))
+	require.Equal(t, conf1, conf2)
+
+	// failure to load
+	require.Error(t, conf2.load(tempFilePath+"_"))
+
+	// failure to save
+	require.Error(t, conf2.save(filepath.Join(tempDir, "non/existing/folder", tempFileName)))
+}

internal/frontend/grpc/service.go

@@ -22,7 +22,9 @@ package grpc
 import (
 	"context"
 	cryptotls "crypto/tls"
+	"fmt"
 	"net"
+	"path/filepath"
 	"strings"
 	"sync"
 	"time"
@@ -31,6 +33,7 @@ import (
 	"github.com/ProtonMail/proton-bridge/v2/internal/config/settings"
 	"github.com/ProtonMail/proton-bridge/v2/internal/events"
 	"github.com/ProtonMail/proton-bridge/v2/internal/frontend/types"
+	"github.com/ProtonMail/proton-bridge/v2/internal/locations"
 	"github.com/ProtonMail/proton-bridge/v2/internal/updater"
 	"github.com/ProtonMail/proton-bridge/v2/internal/users"
 	"github.com/ProtonMail/proton-bridge/v2/pkg/keychain"
@@ -43,6 +46,10 @@ import (
 	"google.golang.org/protobuf/types/known/emptypb"
 )
 
+const (
+	serviceConfigFileName = "grpcServiceConfig.json"
+)
+
 // Service is the RPC service struct.
 type Service struct { // nolint:structcheck
 	UnimplementedBridgeServer
@@ -68,6 +75,7 @@ type Service struct { // nolint:structcheck
 	initializing       sync.WaitGroup
 	initializationDone sync.Once
 	firstTimeAutostart sync.Once
+	locations          *locations.Locations
 }
 
 // NewService returns a new instance of the service.
@@ -78,6 +86,7 @@ func NewService(
 	updater types.Updater,
 	bridge types.Bridger,
 	restarter types.Restarter,
+	locations *locations.Locations,
 ) *Service {
 	s := Service{
 		UnimplementedBridgeServer: UnimplementedBridgeServer{},
@@ -92,6 +101,7 @@ func NewService(
 		initializing:       sync.WaitGroup{},
 		initializationDone: sync.Once{},
 		firstTimeAutostart: sync.Once{},
+		locations:          locations,
 	}
 
 	// Initializing.Done is only called sync.Once. Please keep the increment
@@ -111,12 +121,18 @@ func NewService(
 
 	RegisterBridgeServer(s.grpcServer, &s)
 
-	s.listener, err = net.Listen("tcp", "127.0.0.1:9292") // Port should be configurable from the command-line.
+	s.listener, err = net.Listen("tcp", "127.0.0.1:0") // Port 0 means that the port is randomly picked by the system.
+
 	if err != nil {
-		s.log.WithError(err).Error("could not create listener")
-		panic(err)
+		s.log.WithError(err).Panic("could not create listener")
 	}
 
+	if err := s.saveGRPCServerConfigFile(); err != nil {
+		s.log.WithError(err).Panic("could not write gRPC service configuration file")
+	}
+
+	s.log.Info("gRPC server listening at ", s.listener.Addr())
+
 	return &s
 }
 
@@ -387,3 +403,19 @@ func (s *Service) installUpdate() {
 
 	_ = s.SendEvent(NewUpdateSilentRestartNeededEvent())
 }
+
+func (s *Service) saveGRPCServerConfigFile() error {
+	address, ok := s.listener.Addr().(*net.TCPAddr)
+	if !ok {
+		return fmt.Errorf("could not retrieve gRPC service listener address")
+	}
+
+	sc := config{Port: address.Port}
+
+	settingsPath, err := s.locations.ProvideSettingsPath()
+	if err != nil {
+		return err
+	}
+
+	return sc.save(filepath.Join(settingsPath, serviceConfigFileName))
+}