S3: add support for serving virtual folders

inside the same bucket each user can be assigned to a virtual folder.
This is similar to a chroot directory for local filesystem

README.md

@@ -419,8 +419,13 @@ The HTTP request has a 15 seconds timeout.
 
 ## S3 Compabible Object Storage backends
 
-Each user can be mapped with an S3-Compatible bucket, this way the mapped bucket is exposed over SFTP/SCP.
+Each user can be mapped with an S3-Compatible bucket or a bucket virtual folder, this way the mapped bucket/virtual folder is exposed over SFTP/SCP.
-SFTPGo uses multipart uploads and parallel downloads for storing and retrieving files from S3 and automatically try to create the mapped bucket if it does not exists.
+
+Specifying a different `key_prefix` you can assign different virtual folders of the same bucket to different users. This is similar to a chroot directory for local filesystem. The virtual folder identified by `key_prefix` does not need to be pre-created.
+
+SFTPGo uses multipart uploads and parallel downloads for storing and retrieving files from S3.
+
+SFTPGo tries to automatically create the mapped bucket if it does not exists but it's a better idea to pre-create the bucket and to assign to it the wanted options such as automatic encryption and authorizations.
 
 Some SFTP commands doesn't work over S3:
 
@@ -465,6 +470,7 @@ Flags:
       --s3-access-secret string
       --s3-bucket string
       --s3-endpoint string
+      --s3-key-prefix string      Allows to restrict access to the virtual folder identified by this prefix and its contents
       --s3-region string
       --s3-storage-class string
   -s, --sftpd-port int            0 means a random non privileged port
@@ -522,6 +528,7 @@ For each account the following properties can be configured:
 - `s3_access_secret`, required for S3 filesystem. It is stored encrypted (AES-256-GCM)
 - `s3_endpoint`, specifies s3 endpoint (server) different from AWS
 - `s3_storage_class`
+- `s3_key_prefix`, allows to restrict access to the virtual folder identified by this prefix and its contents
 
 These properties are stored inside the data provider.
 

cmd/portable.go

@@ -28,6 +28,7 @@ var (
 	portableS3AccessSecret       string
 	portableS3Endpoint           string
 	portableS3StorageClass       string
+	portableS3KeyPrefix          string
 	portableCmd                  = &cobra.Command{
 		Use:   "portable",
 		Short: "Serve a single directory",
@@ -70,6 +71,7 @@ Please take a look at the usage below to customize the serving parameters`,
 							AccessSecret: portableS3AccessSecret,
 							Endpoint:     portableS3Endpoint,
 							StorageClass: portableS3StorageClass,
+							KeyPrefix:    portableS3KeyPrefix,
 						},
 					},
 				},
@@ -105,5 +107,7 @@ func init() {
 	portableCmd.Flags().StringVar(&portableS3AccessSecret, "s3-access-secret", "", "")
 	portableCmd.Flags().StringVar(&portableS3Endpoint, "s3-endpoint", "", "")
 	portableCmd.Flags().StringVar(&portableS3StorageClass, "s3-storage-class", "", "")
+	portableCmd.Flags().StringVar(&portableS3KeyPrefix, "s3-key-prefix", "", "Allows to restrict access to the virtual folder "+
+		"identified by this prefix and its contents")
 	rootCmd.AddCommand(portableCmd)
 }

dataprovider/dataprovider.go

@@ -413,19 +413,19 @@ func buildUserHomeDir(user *User) {
 
 func validatePermissions(user *User) error {
 	if len(user.Permissions) == 0 {
-		return &ValidationError{err: "Please grant some permissions to this user"}
+		return &ValidationError{err: "please grant some permissions to this user"}
 	}
 	permissions := make(map[string][]string)
 	if _, ok := user.Permissions["/"]; !ok {
-		return &ValidationError{err: fmt.Sprintf("Permissions for the root dir \"/\" must be set")}
+		return &ValidationError{err: fmt.Sprintf("permissions for the root dir \"/\" must be set")}
 	}
 	for dir, perms := range user.Permissions {
 		if len(perms) == 0 {
-			return &ValidationError{err: fmt.Sprintf("No permissions granted for the directory: %#v", dir)}
+			return &ValidationError{err: fmt.Sprintf("no permissions granted for the directory: %#v", dir)}
 		}
 		for _, p := range perms {
 			if !utils.IsStringInSlice(p, ValidPerms) {
-				return &ValidationError{err: fmt.Sprintf("Invalid permission: %#v", p)}
+				return &ValidationError{err: fmt.Sprintf("invalid permission: %#v", p)}
 			}
 		}
 		cleanedDir := filepath.ToSlash(path.Clean(dir))
@@ -433,7 +433,7 @@ func validatePermissions(user *User) error {
 			cleanedDir = strings.TrimSuffix(cleanedDir, "/")
 		}
 		if !path.IsAbs(cleanedDir) {
-			return &ValidationError{err: fmt.Sprintf("Cannot set permissions for non absolute path: %#v", dir)}
+			return &ValidationError{err: fmt.Sprintf("cannot set permissions for non absolute path: %#v", dir)}
 		}
 		if utils.IsStringInSlice(PermAny, perms) {
 			permissions[cleanedDir] = []string{PermAny}
@@ -452,7 +452,7 @@ func validatePublicKeys(user *User) error {
 	for i, k := range user.PublicKeys {
 		_, _, _, _, err := ssh.ParseAuthorizedKey([]byte(k))
 		if err != nil {
-			return &ValidationError{err: fmt.Sprintf("Could not parse key nr. %d: %s", i, err)}
+			return &ValidationError{err: fmt.Sprintf("could not parse key nr. %d: %s", i, err)}
 		}
 	}
 	return nil
@@ -468,13 +468,13 @@ func validateFilters(user *User) error {
 	for _, IPMask := range user.Filters.DeniedIP {
 		_, _, err := net.ParseCIDR(IPMask)
 		if err != nil {
-			return &ValidationError{err: fmt.Sprintf("Could not parse denied IP/Mask %#v : %v", IPMask, err)}
+			return &ValidationError{err: fmt.Sprintf("could not parse denied IP/Mask %#v : %v", IPMask, err)}
 		}
 	}
 	for _, IPMask := range user.Filters.AllowedIP {
 		_, _, err := net.ParseCIDR(IPMask)
 		if err != nil {
-			return &ValidationError{err: fmt.Sprintf("Could not parse allowed IP/Mask %#v : %v", IPMask, err)}
+			return &ValidationError{err: fmt.Sprintf("could not parse allowed IP/Mask %#v : %v", IPMask, err)}
 		}
 	}
 	return nil
@@ -484,13 +484,13 @@ func validateFilesystemConfig(user *User) error {
 	if user.FsConfig.Provider == 1 {
 		err := vfs.ValidateS3FsConfig(&user.FsConfig.S3Config)
 		if err != nil {
-			return &ValidationError{err: fmt.Sprintf("Could not validate s3config: %v", err)}
+			return &ValidationError{err: fmt.Sprintf("could not validate s3config: %v", err)}
 		}
 		vals := strings.Split(user.FsConfig.S3Config.AccessSecret, "$")
 		if !strings.HasPrefix(user.FsConfig.S3Config.AccessSecret, "$aes$") || len(vals) != 4 {
 			accessSecret, err := utils.EncryptData(user.FsConfig.S3Config.AccessSecret)
 			if err != nil {
-				return &ValidationError{err: fmt.Sprintf("Could encrypt s3 access secret: %v", err)}
+				return &ValidationError{err: fmt.Sprintf("could not encrypt s3 access secret: %v", err)}
 			}
 			user.FsConfig.S3Config.AccessSecret = accessSecret
 		}
@@ -504,10 +504,10 @@ func validateFilesystemConfig(user *User) error {
 func validateUser(user *User) error {
 	buildUserHomeDir(user)
 	if len(user.Username) == 0 || len(user.HomeDir) == 0 {
-		return &ValidationError{err: "Mandatory parameters missing"}
+		return &ValidationError{err: "mandatory parameters missing"}
 	}
 	if len(user.Password) == 0 && len(user.PublicKeys) == 0 {
-		return &ValidationError{err: "Please set a password or at least a public_key"}
+		return &ValidationError{err: "please set a password or at least a public_key"}
 	}
 	if !filepath.IsAbs(user.HomeDir) {
 		return &ValidationError{err: fmt.Sprintf("home_dir must be an absolute path, actual value: %v", user.HomeDir)}

dataprovider/user.go

@@ -408,6 +408,7 @@ func (u *User) getACopy() User {
 			AccessSecret: u.FsConfig.S3Config.AccessSecret,
 			Endpoint:     u.FsConfig.S3Config.Endpoint,
 			StorageClass: u.FsConfig.S3Config.StorageClass,
+			KeyPrefix:    u.FsConfig.S3Config.KeyPrefix,
 		},
 	}
 

httpd/api_utils.go

@@ -435,6 +435,10 @@ func compareUserFsConfig(expected *dataprovider.User, actual *dataprovider.User)
 	if expected.FsConfig.S3Config.StorageClass != actual.FsConfig.S3Config.StorageClass {
 		return errors.New("S3 storage class mismatch")
 	}
+	if expected.FsConfig.S3Config.KeyPrefix != actual.FsConfig.S3Config.KeyPrefix &&
+		expected.FsConfig.S3Config.KeyPrefix+"/" != actual.FsConfig.S3Config.KeyPrefix {
+		return errors.New("S3 key prefix mismatch")
+	}
 	return nil
 }
 

httpd/httpd_test.go

@@ -250,6 +250,17 @@ func TestAddUserInvalidFsConfig(t *testing.T) {
 	if err != nil {
 		t.Errorf("unexpected error adding user with invalid fs config: %v", err)
 	}
+	u.FsConfig.S3Config.Bucket = "test"
+	u.FsConfig.S3Config.Region = "eu-west-1"
+	u.FsConfig.S3Config.AccessKey = "access-key"
+	u.FsConfig.S3Config.AccessSecret = "access-secret"
+	u.FsConfig.S3Config.Endpoint = "http://127.0.0.1:9000/path?a=b"
+	u.FsConfig.S3Config.StorageClass = "Standard"
+	u.FsConfig.S3Config.KeyPrefix = "/somedir/subdir/"
+	_, _, err = httpd.AddUser(u, http.StatusBadRequest)
+	if err != nil {
+		t.Errorf("unexpected error adding user with invalid fs config: %v", err)
+	}
 }
 
 func TestUserPublicKey(t *testing.T) {
@@ -341,6 +352,7 @@ func TestUserS3Config(t *testing.T) {
 	user.FsConfig.S3Config.Region = "us-east-1"
 	user.FsConfig.S3Config.AccessKey = "Server-Access-Key1"
 	user.FsConfig.S3Config.Endpoint = "http://localhost:9000"
+	user.FsConfig.S3Config.KeyPrefix = "somedir/subdir"
 	user, _, err = httpd.UpdateUser(user, http.StatusOK)
 	if err != nil {
 		t.Errorf("unable to update user: %v", err)
@@ -1467,6 +1479,7 @@ func TestWebUserS3Mock(t *testing.T) {
 	user.FsConfig.S3Config.AccessSecret = "access-secret"
 	user.FsConfig.S3Config.Endpoint = "http://127.0.0.1:9000/path?a=b"
 	user.FsConfig.S3Config.StorageClass = "Standard"
+	user.FsConfig.S3Config.KeyPrefix = "somedir/subdir/"
 	form := make(url.Values)
 	form.Set("username", user.Username)
 	form.Set("home_dir", user.HomeDir)
@@ -1490,6 +1503,7 @@ func TestWebUserS3Mock(t *testing.T) {
 	form.Set("s3_access_secret", user.FsConfig.S3Config.AccessSecret)
 	form.Set("s3_storage_class", user.FsConfig.S3Config.StorageClass)
 	form.Set("s3_endpoint", user.FsConfig.S3Config.Endpoint)
+	form.Set("s3_key_prefix", user.FsConfig.S3Config.KeyPrefix)
 	req, _ = http.NewRequest(http.MethodPost, webUserPath+"/"+strconv.FormatInt(user.ID, 10), strings.NewReader(form.Encode()))
 	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
 	rr = executeRequest(req)
@@ -1530,6 +1544,9 @@ func TestWebUserS3Mock(t *testing.T) {
 	if updateUser.FsConfig.S3Config.Endpoint != user.FsConfig.S3Config.Endpoint {
 		t.Error("s3 endpoint mismatch")
 	}
+	if updateUser.FsConfig.S3Config.KeyPrefix != user.FsConfig.S3Config.KeyPrefix {
+		t.Error("s3 key prefix mismatch")
+	}
 	req, _ = http.NewRequest(http.MethodDelete, userPath+"/"+strconv.FormatInt(user.ID, 10), nil)
 	rr = executeRequest(req)
 	checkResponseCode(t, http.StatusOK, rr.Code)

httpd/internal_test.go

@@ -274,6 +274,12 @@ func TestCompareUserFsConfig(t *testing.T) {
 	if err == nil {
 		t.Errorf("S3 storage class does not match")
 	}
+	expected.FsConfig.S3Config.StorageClass = ""
+	expected.FsConfig.S3Config.KeyPrefix = "somedir/subdir"
+	err = compareUserFsConfig(expected, actual)
+	if err == nil {
+		t.Errorf("S3 key prefix does not match")
+	}
 }
 
 func TestApiCallsWithBadURL(t *testing.T) {

httpd/schema/openapi.yaml

@@ -732,6 +732,10 @@ components:
           description: optional endpoint
         storage_class:
           type: string
+        key_prefix:
+          type: string
+          description: key_prefix is similar to a chroot directory for a local filesystem. If specified the SFTP user will only see contents that starts with this prefix and so you can restrict access to a specific virtual folder. The prefix, if not empty, must not start with "/" and must end with "/". If empty the whole bucket contents will be available
+          example: folder/subfolder/
       required:
         - bucket
         - region

httpd/web.go

@@ -238,6 +238,7 @@ func getFsConfigFromUserPostFields(r *http.Request) dataprovider.Filesystem {
 		fs.S3Config.AccessSecret = r.Form.Get("s3_access_secret")
 		fs.S3Config.Endpoint = r.Form.Get("s3_endpoint")
 		fs.S3Config.StorageClass = r.Form.Get("s3_storage_class")
+		fs.S3Config.KeyPrefix = r.Form.Get("s3_key_prefix")
 	}
 	return fs
 }

scripts/README.md

@@ -44,7 +44,7 @@ Let's see a sample usage for each REST API.
 Command:
 
 ```
-python sftpgo_api_cli.py add-user test_username --password "test_pwd" --home-dir="/tmp/test_home_dir" --uid 33 --gid 1000 --max-sessions 2 --quota-size 0 --quota-files 3 --permissions "list" "download" "upload" "delete" "rename" "create_dirs" "overwrite" --subdirs-permissions "/dir1:list,download" "/dir2:*" --upload-bandwidth 100 --download-bandwidth 60 --status 0 --expiration-date 2019-01-01 --allowed-ip "192.168.1.1/32" --fs S3 --s3-bucket test --s3-region eu-west-1 --s3-access-key accesskey --s3-access-secret secret --s3-endpoint "http://127.0.0.1:9000" --s3-storage-class Standard
+python sftpgo_api_cli.py add-user test_username --password "test_pwd" --home-dir="/tmp/test_home_dir" --uid 33 --gid 1000 --max-sessions 2 --quota-size 0 --quota-files 3 --permissions "list" "download" "upload" "delete" "rename" "create_dirs" "overwrite" --subdirs-permissions "/dir1:list,download" "/dir2:*" --upload-bandwidth 100 --download-bandwidth 60 --status 0 --expiration-date 2019-01-01 --allowed-ip "192.168.1.1/32" --fs S3 --s3-bucket test --s3-region eu-west-1 --s3-access-key accesskey --s3-access-secret secret --s3-endpoint "http://127.0.0.1:9000" --s3-storage-class Standard --s3-key-prefix "vfolder/"
 ```
 
 Output:
@@ -60,6 +60,7 @@ Output:
       "access_secret": "$aes$6c088ba12b0b261247c8cf331c46d9260b8e58002957d89ad1c0495e3af665cd0227",
       "bucket": "test",
       "endpoint": "http://127.0.0.1:9000",
+      "key_prefix": "vfolder/",
       "region": "eu-west-1",
       "storage_class": "Standard"
     }

scripts/sftpgo_api_cli.py

@@ -73,7 +73,8 @@ class SFTPGoApiRequests:
 	def buildUserObject(self, user_id=0, username="", password="", public_keys=[], home_dir="", uid=0, gid=0,
 					max_sessions=0, quota_size=0, quota_files=0, permissions={}, upload_bandwidth=0, download_bandwidth=0,
 					status=1, expiration_date=0, allowed_ip=[], denied_ip=[], fs_provider='local', s3_bucket='',
-					s3_region='', s3_access_key='', s3_access_secret='', s3_endpoint='', s3_storage_class=''):
+					s3_region='', s3_access_key='', s3_access_secret='', s3_endpoint='', s3_storage_class='',
+					s3_key_prefix=''):
 		user = {"id":user_id, "username":username, "uid":uid, "gid":gid,
 			"max_sessions":max_sessions, "quota_size":quota_size, "quota_files":quota_files,
 			"upload_bandwidth":upload_bandwidth, "download_bandwidth":download_bandwidth,
@@ -92,7 +93,8 @@ class SFTPGoApiRequests:
 		if allowed_ip or denied_ip:
 			user.update({"filters":self.buildFilters(allowed_ip, denied_ip)})
 		user.update({"filesystem":self.buildFsConfig(fs_provider, s3_bucket, s3_region, s3_access_key,
-														s3_access_secret, s3_endpoint, s3_storage_class)})
+														s3_access_secret, s3_endpoint, s3_storage_class,
+														s3_key_prefix)})
 		return user
 
 	def buildPermissions(self, root_perms, subdirs_perms):
@@ -127,11 +129,12 @@ class SFTPGoApiRequests:
 		return filters
 
 	def buildFsConfig(self, fs_provider, s3_bucket, s3_region, s3_access_key, s3_access_secret, s3_endpoint,
-					s3_storage_class):
+					s3_storage_class, s3_key_prefix):
 		fs_config = {'provider':0}
 		if fs_provider == 'S3':
 			s3config = {'bucket':s3_bucket, 'region':s3_region, 'access_key':s3_access_key, 'access_secret':
-					s3_access_secret, 'endpoint':s3_endpoint, 'storage_class':s3_storage_class}
+					s3_access_secret, 'endpoint':s3_endpoint, 'storage_class':s3_storage_class, 'key_prefix':
+					s3_key_prefix}
 			fs_config.update({'provider':1, 's3config':s3config})
 		return fs_config
 
@@ -147,22 +150,23 @@ class SFTPGoApiRequests:
 	def addUser(self, username="", password="", public_keys="", home_dir="", uid=0, gid=0, max_sessions=0, quota_size=0,
 			quota_files=0, perms=[], upload_bandwidth=0, download_bandwidth=0, status=1, expiration_date=0,
 			subdirs_permissions=[], allowed_ip=[], denied_ip=[], fs_provider='local', s3_bucket='', s3_region='',
-			s3_access_key='', s3_access_secret='', s3_endpoint='', s3_storage_class=''):
+			s3_access_key='', s3_access_secret='', s3_endpoint='', s3_storage_class='', s3_key_prefix=''):
 		u = self.buildUserObject(0, username, password, public_keys, home_dir, uid, gid, max_sessions,
 			quota_size, quota_files, self.buildPermissions(perms, subdirs_permissions), upload_bandwidth, download_bandwidth,
 			status, expiration_date, allowed_ip, denied_ip, fs_provider, s3_bucket, s3_region,
-			s3_access_key, s3_access_secret, s3_endpoint, s3_storage_class)
+			s3_access_key, s3_access_secret, s3_endpoint, s3_storage_class, s3_key_prefix)
 		r = requests.post(self.userPath, json=u, auth=self.auth, verify=self.verify)
 		self.printResponse(r)
 
 	def updateUser(self, user_id, username="", password="", public_keys="", home_dir="", uid=0, gid=0, max_sessions=0,
 				quota_size=0, quota_files=0, perms=[], upload_bandwidth=0, download_bandwidth=0, status=1,
 				expiration_date=0, subdirs_permissions=[], allowed_ip=[], denied_ip=[], fs_provider='local',
-				s3_bucket='', s3_region='', s3_access_key='', s3_access_secret='', s3_endpoint='', s3_storage_class=''):
+				s3_bucket='', s3_region='', s3_access_key='', s3_access_secret='', s3_endpoint='', s3_storage_class='',
+				s3_key_prefix=''):
 		u = self.buildUserObject(user_id, username, password, public_keys, home_dir, uid, gid, max_sessions,
 			quota_size, quota_files, self.buildPermissions(perms, subdirs_permissions), upload_bandwidth, download_bandwidth,
 			status, expiration_date, allowed_ip, denied_ip, fs_provider, s3_bucket, s3_region, s3_access_key,
-			s3_access_secret, s3_endpoint, s3_storage_class)
+			s3_access_secret, s3_endpoint, s3_storage_class, s3_key_prefix)
 		r = requests.put(urlparse.urljoin(self.userPath, "user/" + str(user_id)), json=u, auth=self.auth, verify=self.verify)
 		self.printResponse(r)
 
@@ -419,6 +423,9 @@ def addCommonUserArguments(parser):
 	parser.add_argument('--fs', type=str, default='local', choices=['local', 'S3'],
 					help='Filesystem provider. Default: %(default)s')
 	parser.add_argument('--s3-bucket', type=str, default='', help='Default: %(default)s')
+	parser.add_argument('--s3-key-prefix', type=str, default='', help='Virtual root directory. If non empty only this ' +
+					'directory and its contents will be available. Cannot start with "/". For example "folder/subfolder/".' +
+					' Default: %(default)s')
 	parser.add_argument('--s3-region', type=str, default='', help='Default: %(default)s')
 	parser.add_argument('--s3-access-key', type=str, default='', help='Default: %(default)s')
 	parser.add_argument('--s3-access-secret', type=str, default='', help='Default: %(default)s')
@@ -527,13 +534,14 @@ if __name__ == '__main__':
 				args.quota_size, args.quota_files, args.permissions, args.upload_bandwidth, args.download_bandwidth,
 				args.status, getDatetimeAsMillisSinceEpoch(args.expiration_date), args.subdirs_permissions, args.allowed_ip,
 				args.denied_ip, args.fs, args.s3_bucket, args.s3_region, args.s3_access_key, args.s3_access_secret,
-				args.s3_endpoint, args.s3_storage_class)
+				args.s3_endpoint, args.s3_storage_class, args.s3_key_prefix)
 	elif args.command == 'update-user':
 		api.updateUser(args.id, args.username, args.password, args.public_keys, args.home_dir, args.uid, args.gid,
 					args.max_sessions, args.quota_size, args.quota_files, args.permissions, args.upload_bandwidth,
 					args.download_bandwidth, args.status, getDatetimeAsMillisSinceEpoch(args.expiration_date),
 					args.subdirs_permissions, args.allowed_ip, args.denied_ip, args.fs, args.s3_bucket, args.s3_region,
-					args.s3_access_key, args.s3_access_secret, args.s3_endpoint, args.s3_storage_class)
+					args.s3_access_key, args.s3_access_secret, args.s3_endpoint, args.s3_storage_class,
+					args.s3_key_prefix)
 	elif args.command == 'delete-user':
 		api.deleteUser(args.id)
 	elif args.command == 'get-users':

sftpd/handler.go

@@ -302,7 +302,7 @@ func (c Connection) handleSFTPSetstat(filePath string, request *sftp.Request) er
 }
 
 func (c Connection) handleSFTPRename(sourcePath string, targetPath string, request *sftp.Request) error {
-	if c.fs.GetRelativePath(sourcePath, c.User.GetHomeDir()) == "/" {
+	if c.fs.GetRelativePath(sourcePath) == "/" {
 		c.Log(logger.LevelWarn, logSender, "renaming root dir is not allowed")
 		return sftp.ErrSSHFxPermissionDenied
 	}
@@ -319,7 +319,7 @@ func (c Connection) handleSFTPRename(sourcePath string, targetPath string, reque
 }
 
 func (c Connection) handleSFTPRmdir(dirPath string, request *sftp.Request) error {
-	if c.fs.GetRelativePath(dirPath, c.User.GetHomeDir()) == "/" {
+	if c.fs.GetRelativePath(dirPath) == "/" {
 		c.Log(logger.LevelWarn, logSender, "removing root dir is not allowed")
 		return sftp.ErrSSHFxPermissionDenied
 	}
@@ -348,7 +348,7 @@ func (c Connection) handleSFTPRmdir(dirPath string, request *sftp.Request) error
 }
 
 func (c Connection) handleSFTPSymlink(sourcePath string, targetPath string, request *sftp.Request) error {
-	if c.fs.GetRelativePath(sourcePath, c.User.GetHomeDir()) == "/" {
+	if c.fs.GetRelativePath(sourcePath) == "/" {
 		c.Log(logger.LevelWarn, logSender, "symlinking root dir is not allowed")
 		return sftp.ErrSSHFxPermissionDenied
 	}

sftpd/scp.go

@@ -325,7 +325,7 @@ func (c *scpCommand) handleRecursiveDownload(dirPath string, stat os.FileInfo) e
 		}
 		var dirs []string
 		for _, file := range files {
-			filePath := c.connection.fs.GetRelativePath(c.connection.fs.Join(dirPath, file.Name()), c.connection.User.GetHomeDir())
+			filePath := c.connection.fs.GetRelativePath(c.connection.fs.Join(dirPath, file.Name()))
 			if file.Mode().IsRegular() || file.Mode()&os.ModeSymlink == os.ModeSymlink {
 				err = c.handleDownload(filePath)
 				if err != nil {

sftpd/sftpd.go

@@ -307,7 +307,7 @@ func GetConnectionsStats() []ConnectionStatus {
 					StartTime:     utils.GetTimeAsMsSinceEpoch(t.start),
 					Size:          size,
 					LastActivity:  utils.GetTimeAsMsSinceEpoch(t.lastActivity),
-					Path:          c.fs.GetRelativePath(t.path, c.User.GetHomeDir()),
+					Path:          c.fs.GetRelativePath(t.path),
 				}
 				conn.Transfers = append(conn.Transfers, connTransfer)
 			}

sftpd/sftpd_test.go

@@ -2904,58 +2904,119 @@ func TestRootDirCommands(t *testing.T) {
 
 func TestRelativePaths(t *testing.T) {
 	user := getTestUser(true)
-	path := filepath.Join(user.HomeDir, "/")
+	var path, rel string
-	fs := vfs.NewOsFs("", user.GetHomeDir())
+	filesystems := []vfs.Fs{vfs.NewOsFs("", user.GetHomeDir())}
-	rel := fs.GetRelativePath(path, user.GetHomeDir())
+	s3config := vfs.S3FsConfig{
+		KeyPrefix: strings.TrimPrefix(user.GetHomeDir(), "/") + "/",
+	}
+	s3fs, _ := vfs.NewS3Fs("", user.GetHomeDir(), s3config)
+	filesystems = append(filesystems, s3fs)
+	for _, fs := range filesystems {
+		path = filepath.Join(user.HomeDir, "/")
+		rel = fs.GetRelativePath(path)
 		if rel != "/" {
 			t.Errorf("Unexpected relative path: %v", rel)
 		}
 		path = filepath.Join(user.HomeDir, "//")
-	rel = fs.GetRelativePath(path, user.GetHomeDir())
+		rel = fs.GetRelativePath(path)
 		if rel != "/" {
 			t.Errorf("Unexpected relative path: %v", rel)
 		}
 		path = filepath.Join(user.HomeDir, "../..")
-	rel = fs.GetRelativePath(path, user.GetHomeDir())
+		rel = fs.GetRelativePath(path)
 		if rel != "/" {
-		t.Errorf("Unexpected relative path: %v", rel)
+			t.Errorf("Unexpected relative path: %v path: %v", rel, path)
 		}
 		path = filepath.Join(user.HomeDir, "../../../../../")
-	rel = fs.GetRelativePath(path, user.GetHomeDir())
+		rel = fs.GetRelativePath(path)
 		if rel != "/" {
 			t.Errorf("Unexpected relative path: %v", rel)
 		}
 		path = filepath.Join(user.HomeDir, "/..")
-	rel = fs.GetRelativePath(path, user.GetHomeDir())
+		rel = fs.GetRelativePath(path)
 		if rel != "/" {
-		t.Errorf("Unexpected relative path: %v", rel)
+			t.Errorf("Unexpected relative path: %v path: %v", rel, path)
 		}
 		path = filepath.Join(user.HomeDir, "/../../../..")
-	rel = fs.GetRelativePath(path, user.GetHomeDir())
+		rel = fs.GetRelativePath(path)
 		if rel != "/" {
 			t.Errorf("Unexpected relative path: %v", rel)
 		}
 		path = filepath.Join(user.HomeDir, "")
-	rel = fs.GetRelativePath(path, user.GetHomeDir())
+		rel = fs.GetRelativePath(path)
 		if rel != "/" {
 			t.Errorf("Unexpected relative path: %v", rel)
 		}
 		path = filepath.Join(user.HomeDir, ".")
-	rel = fs.GetRelativePath(path, user.GetHomeDir())
+		rel = fs.GetRelativePath(path)
 		if rel != "/" {
 			t.Errorf("Unexpected relative path: %v", rel)
 		}
 		path = filepath.Join(user.HomeDir, "somedir")
-	rel = fs.GetRelativePath(path, user.GetHomeDir())
+		rel = fs.GetRelativePath(path)
 		if rel != "/somedir" {
 			t.Errorf("Unexpected relative path: %v", rel)
 		}
 		path = filepath.Join(user.HomeDir, "/somedir/subdir")
-	rel = fs.GetRelativePath(path, user.GetHomeDir())
+		rel = fs.GetRelativePath(path)
 		if rel != "/somedir/subdir" {
 			t.Errorf("Unexpected relative path: %v", rel)
 		}
 	}
+}
+
+func TestResolvePaths(t *testing.T) {
+	user := getTestUser(true)
+	var path, resolved string
+	var err error
+	filesystems := []vfs.Fs{vfs.NewOsFs("", user.GetHomeDir())}
+	s3config := vfs.S3FsConfig{
+		KeyPrefix: strings.TrimPrefix(user.GetHomeDir(), "/") + "/",
+	}
+	os.MkdirAll(user.GetHomeDir(), 0777)
+	s3fs, _ := vfs.NewS3Fs("", user.GetHomeDir(), s3config)
+	filesystems = append(filesystems, s3fs)
+	for _, fs := range filesystems {
+		path = "/"
+		resolved, _ = fs.ResolvePath(filepath.ToSlash(path))
+		if resolved != fs.Join(user.GetHomeDir(), "/") {
+			t.Errorf("Unexpected resolved path: %v for: %v, fs: %v", resolved, path, fs.Name())
+		}
+		path = "."
+		resolved, _ = fs.ResolvePath(filepath.ToSlash(path))
+		if resolved != fs.Join(user.GetHomeDir(), "/") {
+			t.Errorf("Unexpected resolved path: %v for: %v, fs: %v", resolved, path, fs.Name())
+		}
+		path = "test/sub"
+		resolved, _ = fs.ResolvePath(filepath.ToSlash(path))
+		if resolved != fs.Join(user.GetHomeDir(), "/test/sub") {
+			t.Errorf("Unexpected resolved path: %v for: %v, fs: %v", resolved, path, fs.Name())
+		}
+		path = "../test/sub"
+		resolved, err = fs.ResolvePath(filepath.ToSlash(path))
+		if fs.Name() == "osfs" {
+			if err == nil {
+				t.Errorf("Unexpected resolved path: %v for: %v, fs: %v", resolved, path, fs.Name())
+			}
+		} else {
+			if resolved != fs.Join(user.GetHomeDir(), "/test/sub") && err == nil {
+				t.Errorf("Unexpected resolved path: %v for: %v, fs: %v", resolved, path, fs.Name())
+			}
+		}
+		path = "../../../test/../sub"
+		resolved, err = fs.ResolvePath(filepath.ToSlash(path))
+		if fs.Name() == "osfs" {
+			if err == nil {
+				t.Errorf("Unexpected resolved path: %v for: %v, fs: %v", resolved, path, fs.Name())
+			}
+		} else {
+			if resolved != fs.Join(user.GetHomeDir(), "/sub") && err == nil {
+				t.Errorf("Unexpected resolved path: %v for: %v, fs: %v", resolved, path, fs.Name())
+			}
+		}
+	}
+	os.RemoveAll(user.GetHomeDir())
+}
 
 func TestUserPerms(t *testing.T) {
 	user := getTestUser(true)

templates/user.html

@@ -243,6 +243,17 @@
         </div>
     </div>
 
+    <div class="form-group row">
+        <label for="idS3KeyPrefix" class="col-sm-2 col-form-label">S3 Key Prefix</label>
+        <div class="col-sm-10">
+            <input type="text" class="form-control" id="idS3KeyPrefix" name="s3_key_prefix" placeholder=""
+                value="{{.User.FsConfig.S3Config.KeyPrefix}}" maxlength="255" aria-describedby="S3KeyPrefixHelpBlock">
+            <small id="S3KeyPrefixHelpBlock" class="form-text text-muted">
+                Similar to a chroot for local filesystem. Cannot start with "/". Example: "somedir/subdir/".
+            </small>
+        </div>
+    </div>
+
     <input type="hidden" name="expiration_date" id="hidden_start_datetime" value="">
     <button type="submit" class="btn btn-primary float-right mt-3 mb-5 px-5 px-3">Submit</button>
 </form>

vfs/osfs.go

@@ -180,8 +180,8 @@ func (OsFs) GetAtomicUploadPath(name string) string {
 
 // GetRelativePath returns the path for a file relative to the user's home dir.
 // This is the path as seen by SFTP users
-func (OsFs) GetRelativePath(name, rootPath string) string {
+func (fs OsFs) GetRelativePath(name string) string {
-	rel, err := filepath.Rel(rootPath, filepath.Clean(name))
+	rel, err := filepath.Rel(fs.rootDir, filepath.Clean(name))
 	if err != nil {
 		return ""
 	}

vfs/s3fs.go

@@ -23,6 +23,13 @@ import (
 // S3FsConfig defines the configuration for S3fs
 type S3FsConfig struct {
 	Bucket string `json:"bucket,omitempty"`
+	// KeyPrefix is similar to a chroot directory for local filesystem.
+	// If specified the SFTP user will only see contents that starts with
+	// this prefix and so you can restrict access to a specific virtual
+	// folder. The prefix, if not empty, must not start with "/" and must
+	// end with "/".
+	//If empty the whole bucket contents will be available
+	KeyPrefix    string `json:"key_prefix,omitempty"`
 	Region       string `json:"region,omitempty"`
 	AccessKey    string `json:"access_key,omitempty"`
 	AccessSecret string `json:"access_secret,omitempty"`
@@ -95,6 +102,9 @@ func (fs S3Fs) Stat(name string) (os.FileInfo, error) {
 		}
 		return NewS3FileInfo(name, true, 0, time.Time{}), nil
 	}
+	if "/"+fs.config.KeyPrefix == name+"/" {
+		return NewS3FileInfo(name, true, 0, time.Time{}), nil
+	}
 	prefix := path.Dir(name)
 	if prefix == "/" || prefix == "." {
 		prefix = ""
@@ -403,7 +413,7 @@ func (fs S3Fs) ScanRootDirContents() (int, int64, error) {
 	defer cancelFn()
 	err := fs.svc.ListObjectsV2PagesWithContext(ctx, &s3.ListObjectsV2Input{
 		Bucket: aws.String(fs.config.Bucket),
-		Prefix: aws.String(""),
+		Prefix: aws.String(fs.config.KeyPrefix),
 	}, func(page *s3.ListObjectsV2Output, lastPage bool) bool {
 		for _, fileObject := range page.Contents {
 			numFiles++
@@ -423,14 +433,20 @@ func (S3Fs) GetAtomicUploadPath(name string) string {
 
 // GetRelativePath returns the path for a file relative to the user's home dir.
 // This is the path as seen by SFTP users
-func (S3Fs) GetRelativePath(name, rootPath string) string {
+func (fs S3Fs) GetRelativePath(name string) string {
-	rel := name
+	rel := path.Clean(name)
-	if name == "." {
+	if rel == "." {
 		rel = ""
 	}
 	if !strings.HasPrefix(rel, "/") {
 		return "/" + rel
 	}
+	if len(fs.config.KeyPrefix) > 0 {
+		if !strings.HasPrefix(rel, "/"+fs.config.KeyPrefix) {
+			rel = "/"
+		}
+		rel = path.Clean("/" + strings.TrimPrefix(rel, "/"+fs.config.KeyPrefix))
+	}
 	return rel
 }
 
@@ -441,7 +457,10 @@ func (S3Fs) Join(elem ...string) string {
 
 // ResolvePath returns the matching filesystem path for the specified sftp path
 func (fs S3Fs) ResolvePath(sftpPath string) (string, error) {
-	return sftpPath, nil
+	if !path.IsAbs(sftpPath) {
+		sftpPath = path.Clean("/" + sftpPath)
+	}
+	return fs.Join("/", fs.config.KeyPrefix, sftpPath), nil
 }
 
 func (fs *S3Fs) resolve(name *string, prefix string) (string, bool) {

vfs/vfs.go

@@ -4,7 +4,9 @@ package vfs
 import (
 	"errors"
 	"os"
+	"path"
 	"runtime"
+	"strings"
 	"time"
 
 	"github.com/drakkan/sftpgo/logger"
@@ -36,7 +38,7 @@ type Fs interface {
 	IsPermission(err error) bool
 	ScanRootDirContents() (int, int64, error)
 	GetAtomicUploadPath(name string) string
-	GetRelativePath(name, rootPath string) string
+	GetRelativePath(name string) string
 	Join(elem ...string) string
 }
 
@@ -80,6 +82,15 @@ func ValidateS3FsConfig(config *S3FsConfig) error {
 	if len(config.AccessSecret) == 0 {
 		return errors.New("access_secret cannot be empty")
 	}
+	if len(config.KeyPrefix) > 0 {
+		if strings.HasPrefix(config.KeyPrefix, "/") {
+			return errors.New("key_prefix cannot start with /")
+		}
+		config.KeyPrefix = path.Clean(config.KeyPrefix)
+		if !strings.HasSuffix(config.KeyPrefix, "/") {
+			config.KeyPrefix += "/"
+		}
+	}
 	return nil
 }