SSH Backup Storage Support (#107)

* SSH Client implemented

* Private key auth implemented
Code refactoring

* Refactoring

* Passphrase renamed to IdentityPassphrase
Default private key location changed to .ssh/id

cmd/backup/script.go

@@ -7,8 +7,11 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"github.com/pkg/sftp"
+	"golang.org/x/crypto/ssh"
 	"io"
 	"io/fs"
+	"io/ioutil"
 	"net/http"
 	"os"
 	"path"
@@ -39,6 +42,8 @@ type script struct {
 	cli          *client.Client
 	minioClient  *minio.Client
 	webdavClient *gowebdav.Client
+	sshClient    *ssh.Client
+	sftpClient   *sftp.Client
 	logger       *logrus.Logger
 	sender       *router.ServiceRouter
 	template     *template.Template
@@ -159,6 +164,57 @@ func newScript() (*script, error) {
 		}
 	}
 
+	if s.c.SSHHostName != "" {
+		var authMethods []ssh.AuthMethod
+
+		if s.c.SSHPassword != "" {
+			authMethods = append(authMethods, ssh.Password(s.c.SSHPassword))
+		}
+
+		if _, err := os.Stat(s.c.SSHIdentityFile); err == nil {
+			key, err := ioutil.ReadFile(s.c.SSHIdentityFile)
+			if err != nil {
+				return nil, errors.New("newScript: error reading the private key")
+			}
+
+			var signer ssh.Signer
+			if s.c.SSHIdentityPassphrase != "" {
+				signer, err = ssh.ParsePrivateKeyWithPassphrase(key, []byte(s.c.SSHIdentityPassphrase))
+				if err != nil {
+					return nil, errors.New("newScript: error parsing the encrypted private key")
+				}
+				authMethods = append(authMethods, ssh.PublicKeys(signer))
+			} else {
+				signer, err = ssh.ParsePrivateKey(key)
+				if err != nil {
+					return nil, errors.New("newScript: error parsing the private key")
+				}
+				authMethods = append(authMethods, ssh.PublicKeys(signer))
+			}
+		}
+
+		sshClientConfig := &ssh.ClientConfig{
+			User:            s.c.SSHUser,
+			Auth:            authMethods,
+			HostKeyCallback: ssh.InsecureIgnoreHostKey(),
+		}
+		sshClient, err := ssh.Dial("tcp", fmt.Sprintf("%s:%s", s.c.SSHHostName, s.c.SSHPort), sshClientConfig)
+		s.sshClient = sshClient
+		if err != nil {
+			return nil, fmt.Errorf("newScript: error creating ssh client: %w", err)
+		}
+		_, _, err = s.sshClient.SendRequest("keepalive", false, nil)
+		if err != nil {
+			return nil, err
+		}
+
+		sftpClient, err := sftp.NewClient(sshClient)
+		s.sftpClient = sftpClient
+		if err != nil {
+			return nil, fmt.Errorf("newScript: error creating sftp client: %w", err)
+		}
+	}
+
 	if s.c.EmailNotificationRecipient != "" {
 		emailURL := fmt.Sprintf(
 			"smtp://%s:%s@%s:%d/?from=%s&to=%s",
@@ -512,6 +568,52 @@ func (s *script) copyBackup() error {
 		s.logger.Infof("Uploaded a copy of backup `%s` to WebDAV-URL '%s' at path '%s'.", s.file, s.c.WebdavUrl, s.c.WebdavPath)
 	}
 
+	if s.sshClient != nil {
+		source, err := os.Open(s.file)
+		if err != nil {
+			return fmt.Errorf("copyBackup: error reading the file to be uploaded: %w", err)
+		}
+		defer source.Close()
+
+		destination, err := s.sftpClient.Create(filepath.Join(s.c.SSHRemotePath, name))
+		if err != nil {
+			return fmt.Errorf("copyBackup: error creating file on SSH storage: %w", err)
+		}
+		defer destination.Close()
+
+		chunk := make([]byte, 1000000)
+		for {
+			num, err := source.Read(chunk)
+			if err == io.EOF {
+				tot, err := destination.Write(chunk[:num])
+				if err != nil {
+					return fmt.Errorf("copyBackup: error uploading the file to SSH storage: %w", err)
+				}
+
+				if tot != len(chunk[:num]) {
+					return fmt.Errorf("sshClient: failed to write stream")
+				}
+
+				break
+			}
+
+			if err != nil {
+				return fmt.Errorf("copyBackup: error uploading the file to SSH storage: %w", err)
+			}
+
+			tot, err := destination.Write(chunk[:num])
+			if err != nil {
+				return fmt.Errorf("copyBackup: error uploading the file to SSH storage: %w", err)
+			}
+
+			if tot != len(chunk[:num]) {
+				return fmt.Errorf("sshClient: failed to write stream")
+			}
+		}
+
+		s.logger.Infof("Uploaded a copy of backup `%s` to SSH storage '%s' at path '%s'.", s.file, s.c.SSHHostName, s.c.SSHRemotePath)
+	}
+
 	if _, err := os.Stat(s.c.BackupArchive); !os.IsNotExist(err) {
 		if err := copyFile(s.file, path.Join(s.c.BackupArchive, name)); err != nil {
 			return fmt.Errorf("copyBackup: error copying file to local archive: %w", err)
@@ -645,6 +747,37 @@ func (s *script) pruneBackups() error {
 		})
 	}
 
+	if s.sshClient != nil {
+		candidates, err := s.sftpClient.ReadDir(s.c.SSHRemotePath)
+		if err != nil {
+			return fmt.Errorf("pruneBackups: error reading directory from SSH storage: %w", err)
+		}
+
+		var matches []string
+		for _, candidate := range candidates {
+			if !strings.HasPrefix(candidate.Name(), s.c.BackupPruningPrefix) {
+				continue
+			}
+			if candidate.ModTime().Before(deadline) {
+				matches = append(matches, candidate.Name())
+			}
+		}
+
+		s.stats.Storages.SSH = StorageStats{
+			Total:  uint(len(candidates)),
+			Pruned: uint(len(matches)),
+		}
+
+		doPrune(len(matches), len(candidates), "SSH backup(s)", func() error {
+			for _, match := range matches {
+				if err := s.sftpClient.Remove(filepath.Join(s.c.SSHRemotePath, match)); err != nil {
+					return fmt.Errorf("pruneBackups: error removing file from SSH storage: %w", err)
+				}
+			}
+			return nil
+		})
+	}
+
 	if _, err := os.Stat(s.c.BackupArchive); !os.IsNotExist(err) {
 		globPattern := path.Join(
 			s.c.BackupArchive,