We build too many walls and not enough bridges

internal/imap/server.go

@@ -0,0 +1,188 @@
+// Copyright (c) 2020 Proton Technologies AG
+//
+// This file is part of ProtonMail Bridge.
+//
+// ProtonMail 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.
+//
+// ProtonMail 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 ProtonMail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package imap
+
+import (
+	"crypto/tls"
+	"fmt"
+	"io"
+	"strings"
+	"time"
+
+	imapid "github.com/ProtonMail/go-imap-id"
+	"github.com/ProtonMail/proton-bridge/internal/bridge"
+	"github.com/ProtonMail/proton-bridge/internal/events"
+	"github.com/ProtonMail/proton-bridge/internal/imap/uidplus"
+	"github.com/ProtonMail/proton-bridge/pkg/listener"
+	"github.com/emersion/go-imap"
+	imapappendlimit "github.com/emersion/go-imap-appendlimit"
+	imapidle "github.com/emersion/go-imap-idle"
+	imapquota "github.com/emersion/go-imap-quota"
+	imapspecialuse "github.com/emersion/go-imap-specialuse"
+	imapserver "github.com/emersion/go-imap/server"
+	"github.com/emersion/go-sasl"
+	"github.com/sirupsen/logrus"
+)
+
+type imapServer struct {
+	server        *imapserver.Server
+	eventListener listener.Listener
+}
+
+// NewIMAPServer constructs a new IMAP server configured with the given options.
+func NewIMAPServer(debugClient, debugServer bool, port int, tls *tls.Config, imapBackend *imapBackend, eventListener listener.Listener) *imapServer { //nolint[golint]
+	s := imapserver.New(imapBackend)
+	s.Addr = fmt.Sprintf("%v:%v", bridge.Host, port)
+	s.TLSConfig = tls
+	s.AllowInsecureAuth = true
+	s.ErrorLog = newServerErrorLogger("server-imap")
+	s.AutoLogout = 30 * time.Minute
+
+	if debugClient || debugServer {
+		var localDebug, remoteDebug imap.WriterWithFields
+		if debugClient {
+			remoteDebug = &logWithFields{log: log.WithField("pkg", "imap/client"), fields: logrus.Fields{}}
+		}
+		if debugServer {
+			localDebug = &logWithFields{log: log.WithField("pkg", "imap/server"), fields: logrus.Fields{}}
+		}
+		s.Debug = imap.NewDebugWithFields(localDebug, remoteDebug)
+	}
+
+	serverID := imapid.ID{
+		imapid.FieldName:       "ProtonMail",
+		imapid.FieldVendor:     "Proton Technologies AG",
+		imapid.FieldSupportURL: "https://protonmail.com/support",
+	}
+
+	s.EnableAuth(sasl.Login, func(conn imapserver.Conn) sasl.Server {
+		conn.Server().ForEachConn(func(candidate imapserver.Conn) {
+			if id, ok := candidate.(imapid.Conn); ok {
+				if conn.Context() == candidate.Context() {
+					imapBackend.setLastMailClient(id.ID())
+					return
+				}
+			}
+		})
+
+		return sasl.NewLoginServer(func(address, password string) error {
+			user, err := conn.Server().Backend.Login(address, password)
+			if err != nil {
+				return err
+			}
+
+			ctx := conn.Context()
+			ctx.State = imap.AuthenticatedState
+			ctx.User = user
+			return nil
+		})
+	})
+
+	s.Enable(
+		imapidle.NewExtension(),
+		//imapmove.NewExtension(), // extension is not fully implemented: if UIDPLUS exists it MUST return COPYUID and EXPUNGE continuous responses
+		imapspecialuse.NewExtension(),
+		imapid.NewExtension(serverID),
+		imapquota.NewExtension(),
+		imapappendlimit.NewExtension(),
+		uidplus.NewExtension(),
+	)
+
+	return &imapServer{
+		server:        s,
+		eventListener: eventListener,
+	}
+}
+
+// Starts the server.
+func (s *imapServer) ListenAndServe() {
+	go s.monitorDisconnectedUsers()
+
+	log.Info("IMAP server listening at ", s.server.Addr)
+	err := s.server.ListenAndServe()
+	if err != nil {
+		s.eventListener.Emit(events.ErrorEvent, "IMAP failed: "+err.Error())
+		log.Error("IMAP failed: ", err)
+		return
+	}
+	defer s.server.Close() //nolint[errcheck]
+
+	log.Info("IMAP server stopped")
+}
+
+// Stops the server.
+func (s *imapServer) Close() {
+	_ = s.server.Close()
+}
+
+func (s *imapServer) monitorDisconnectedUsers() {
+	ch := make(chan string)
+	s.eventListener.Add(events.CloseConnectionEvent, ch)
+
+	for address := range ch {
+		address := address
+		log.Info("Disconnecting all open IMAP connections for ", address)
+		disconnectUser := func(conn imapserver.Conn) {
+			connUser := conn.Context().User
+			if connUser != nil && strings.EqualFold(connUser.Username(), address) {
+				_ = conn.Close()
+			}
+		}
+		s.server.ForEachConn(disconnectUser)
+	}
+}
+
+// logWithFields is used for debuging with additional field.
+type logWithFields struct {
+	log    *logrus.Entry
+	fields logrus.Fields
+}
+
+func (lf *logWithFields) Writer() io.Writer {
+	w := lf.log.WithFields(lf.fields).WriterLevel(logrus.DebugLevel)
+	lf.fields = logrus.Fields{}
+	return w
+}
+
+func (lf *logWithFields) SetField(key, value string) {
+	lf.fields[key] = value
+}
+
+// serverErrorLogger implements go-imap/logger interface.
+type serverErrorLogger struct {
+	tag string
+}
+
+func newServerErrorLogger(tag string) *serverErrorLogger {
+	return &serverErrorLogger{tag}
+}
+
+func (s *serverErrorLogger) CheckErrorForReport(serverErr string) {
+}
+
+func (s *serverErrorLogger) Printf(format string, args ...interface{}) {
+	err := fmt.Sprintf(format, args...)
+	s.CheckErrorForReport(err)
+	log.WithField("pkg", s.tag).Error(err)
+}
+
+func (s *serverErrorLogger) Println(args ...interface{}) {
+	err := fmt.Sprintln(args...)
+	s.CheckErrorForReport(err)
+	log.WithField("pkg", s.tag).Error(err)
+}