move SFTPGo package to the internal folder

SFTPGo is a daemon and command line tool, not a library.

The public API are provided by the SDK

Signed-off-by: Nicola Murino <nicola.murino@gmail.com>

internal/sftpd/subsystem.go

@@ -0,0 +1,87 @@
+// Copyright (C) 2019-2022  Nicola Murino
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published
+// by the Free Software Foundation, version 3.
+//
+// This program 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 Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package sftpd
+
+import (
+	"io"
+	"net"
+
+	"github.com/pkg/sftp"
+
+	"github.com/drakkan/sftpgo/v2/internal/common"
+	"github.com/drakkan/sftpgo/v2/internal/dataprovider"
+	"github.com/drakkan/sftpgo/v2/internal/logger"
+)
+
+type subsystemChannel struct {
+	reader io.Reader
+	writer io.Writer
+}
+
+func (s *subsystemChannel) Read(p []byte) (int, error) {
+	return s.reader.Read(p)
+}
+
+func (s *subsystemChannel) Write(p []byte) (int, error) {
+	return s.writer.Write(p)
+}
+
+func (s *subsystemChannel) Close() error {
+	return nil
+}
+
+func newSubsystemChannel(reader io.Reader, writer io.Writer) *subsystemChannel {
+	return &subsystemChannel{
+		reader: reader,
+		writer: writer,
+	}
+}
+
+// ServeSubSystemConnection handles a connection as SSH subsystem
+func ServeSubSystemConnection(user *dataprovider.User, connectionID string, reader io.Reader, writer io.Writer) error {
+	err := user.CheckFsRoot(connectionID)
+	if err != nil {
+		errClose := user.CloseFs()
+		logger.Warn(logSender, connectionID, "unable to check fs root: %v close fs error: %v", err, errClose)
+		return err
+	}
+
+	connection := &Connection{
+		BaseConnection: common.NewBaseConnection(connectionID, common.ProtocolSFTP, "", "", *user),
+		ClientVersion:  "",
+		RemoteAddr:     &net.IPAddr{},
+		LocalAddr:      &net.IPAddr{},
+		channel:        newSubsystemChannel(reader, writer),
+	}
+	err = common.Connections.Add(connection)
+	if err != nil {
+		errClose := user.CloseFs()
+		logger.Warn(logSender, connectionID, "unable to add connection: %v close fs error: %v", err, errClose)
+		return err
+	}
+	defer common.Connections.Remove(connection.GetID())
+
+	dataprovider.UpdateLastLogin(user)
+	sftp.SetSFTPExtensions(sftpExtensions...) //nolint:errcheck
+	server := sftp.NewRequestServer(connection.channel, sftp.Handlers{
+		FileGet:  connection,
+		FilePut:  connection,
+		FileCmd:  connection,
+		FileList: connection,
+	}, sftp.WithRSAllocator())
+
+	defer server.Close()
+	return server.Serve()
+}