storage: Directory selection form and validator

Directory selection allows to:
- select from default directory
- select from available Samba shares
- specify subdirectory
- insert custom directory

- directory validator checks: path exists, is directory, is readable, is writable
- samba: action script: include share path in share list
- create freedombox-share group inside users module  instead of samba module

Closes #1703

Signed-off-by: Veiko Aasa <veiko17@disroot.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

actions/samba

@@ -163,9 +163,10 @@ def _get_shares():
     config = configparser.ConfigParser()
     config.read_string(output.decode())
     for name in config.sections():
-        mount_point = _get_mount_point(config[name]['path'])
+        path = config[name]['path']
+        mount_point = _get_mount_point(path)
         mount_point = os.path.normpath(mount_point)
-        shares.append(dict(name=name, mount_point=mount_point))
+        shares.append(dict(name=name, mount_point=mount_point, path=path))
 
     return shares
 

actions/storage

@@ -21,6 +21,7 @@ Configuration helper for disks manager.
 
 import argparse
 import json
+import os
 import re
 import subprocess
 import sys
@@ -51,6 +52,14 @@ def parse_arguments():
     subparsers.add_parser('usage-info',
                           help='Get information about disk space usage')
 
+    subparser = subparsers.add_parser('validate-directory',
+                                      help='Validate a directory')
+    subparser.add_argument('--path', help='Path of the directory',
+                           required=True)
+    subparser.add_argument('--check-writable', required=False, default=False,
+                           action='store_true',
+                           help='Check that the directory is writable')
+
     subparsers.required = True
     return parser.parse_args()
 
@@ -316,6 +325,19 @@ def subcommand_usage_info(_):
     subprocess.run(command, check=True)
 
 
+def subcommand_validate_directory(arguments):
+    """Validate a directory"""
+    directory = arguments.path
+    if not os.path.exists(directory):
+        print('ValidationError: 1')
+    if not os.path.isdir(directory):
+        print('ValidationError: 2')
+    if not os.access(directory, os.R_OK):
+        print('ValidationError: 3')
+    if arguments.check_writable and not os.access(directory, os.W_OK):
+        print('ValidationError: 4')
+
+
 def main():
     """Parse arguments and perform all duties."""
     arguments = parse_arguments()

plinth/modules/samba/__init__.py

@@ -28,7 +28,7 @@ from plinth import action_utils, actions
 from plinth import app as app_module
 from plinth import frontpage, menu
 from plinth.daemon import Daemon
-from plinth.modules.users import create_group, register_group
+from plinth.modules.users import register_group
 from plinth.modules.firewall.components import Firewall
 from plinth.utils import format_lazy
 
@@ -106,7 +106,6 @@ def init():
 def setup(helper, old_version=None):
     """Install and configure the module."""
     helper.install(managed_packages)
-    create_group('freedombox-share')
     helper.call('post', actions.superuser_run, 'samba', ['setup'])
     helper.call('post', app.enable)
 

plinth/modules/storage/forms.py

@@ -0,0 +1,161 @@
+#
+# This file is part of FreedomBox.
+#
+# 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, either version 3 of the
+# License, or (at your option) any later version.
+#
+# 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 <http://www.gnu.org/licenses/>.
+#
+"""
+Forms for directory selection.
+"""
+
+import json
+import os
+
+from django import forms
+from django.core.exceptions import ValidationError
+from django.utils.translation import ugettext_lazy as _
+
+from plinth import actions, module_loader
+from plinth.forms import AppForm
+from plinth.modules import storage
+
+
+def get_available_samba_shares():
+    """Get available samba shares."""
+    available_shares = []
+    if is_module_enabled('samba'):
+        samba_shares = json.loads(
+            actions.superuser_run('samba', ['get-shares']))
+        if samba_shares:
+            disks = storage.get_disks()
+            for share in samba_shares:
+                for disk in disks:
+                    if share['mount_point'] == disk['mount_point']:
+                        available_shares.append(share)
+                        break
+    return available_shares
+
+
+def is_module_enabled(name):
+    """Check whether a module is enabled."""
+    if name in module_loader.loaded_modules:
+        module = module_loader.loaded_modules['samba']
+        if module.setup_helper.get_state(
+        ) != 'needs-setup' and module.app.is_enabled():
+            return True
+
+    return False
+
+
+class DirectoryValidator:
+    username = None
+    check_writable = False
+    add_user_to_share_group = False
+    service_to_restart = None
+
+    def __init__(self, username=None, check_writable=None):
+        if username is not None:
+            self.username = username
+        if check_writable is not None:
+            self.check_writable = check_writable
+
+    def __call__(self, value):
+        """Validate a directory."""
+        if not value.startswith('/'):
+            raise ValidationError(_('Invalid directory name.'), 'invalid')
+
+        command = ['validate-directory', '--path', value]
+        if self.check_writable:
+            command.append('--check-writable')
+
+        if self.username:
+            output = actions.run_as_user('storage', command,
+                                         become_user=self.username)
+        else:
+            output = actions.run('storage', command)
+
+        if 'ValidationError' in output:
+            error_nr = int(output.strip().split()[1])
+            if error_nr == 1:
+                raise ValidationError(
+                    _('Directory does not exist.'), 'invalid')
+            elif error_nr == 2:
+                raise ValidationError(_('Path is not a directory.'), 'invalid')
+            elif error_nr == 3:
+                raise ValidationError(
+                    _('Directory is not readable by the user.'), 'invalid')
+            elif error_nr == 4:
+                raise ValidationError(
+                    _('Directory is not writable by the user.'), 'invalid')
+
+
+class DirectorySelectForm(AppForm):
+    """Directory selection form."""
+    storage_dir = forms.ChoiceField(choices=[], label=_('Directory'),
+                                    required=True)
+    storage_subdir = forms.CharField(
+        label=_('Subdirectory (optional)'), required=False)
+
+    def __init__(self, title=None, default='/', validator=DirectoryValidator,
+                 *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        if title:
+            self.fields['storage_dir'].label = title
+        self.validator = validator
+        self.default = os.path.normpath(default)
+        self.set_form_data()
+
+    def clean(self):
+        """Clean and validate form data."""
+        if self.cleaned_data['is_enabled'] or not self.initial['is_enabled']:
+            storage_dir = self.cleaned_data['storage_dir']
+            storage_subdir = self.cleaned_data['storage_subdir']
+            if storage_dir != '/':
+                storage_subdir = storage_subdir.lstrip('/')
+            storage_path = os.path.realpath(
+                os.path.join(storage_dir, storage_subdir))
+            if self.validator:
+                self.validator(storage_path)
+            self.cleaned_data.update({'storage_path': storage_path})
+
+    def get_initial(self, choices):
+        """Get initial form data."""
+        initial_selection = ()
+        subdir = ''
+        storage_path = self.initial['storage_path']
+        for choice in choices:
+            if storage_path.startswith(choice[0]):
+                initial_selection = choice
+                subdir = storage_path.split(choice[0], 1)[1].strip('/')
+                if choice[0] == '/':
+                    subdir = '/' + subdir
+                break
+        return (initial_selection, subdir)
+
+    def set_form_data(self):
+        """Set initial form data."""
+        choices = []
+        if self.default:
+            choices = choices + [(self.default, '{0}: {1}'.format(
+                _('Default'), self.default))]
+        available_shares = get_available_samba_shares()
+        for share in available_shares:
+            choices = choices + [(share['path'], '{0} ({1}): {2}'.format(
+                _('Samba share'), share['name'], share['path']))]
+        choices = choices + [('/', _('Other directory (specify below)'))]
+
+        initial_value, subdir = self.get_initial(choices)
+
+        self.fields['storage_dir'].choices = choices
+        self.initial['storage_dir'] = initial_value
+        self.initial['storage_subdir'] = subdir

plinth/modules/users/__init__.py

@@ -18,6 +18,7 @@
 FreedomBox app to manage users.
 """
 
+import grp
 import subprocess
 
 from django.utils.translation import ugettext_lazy as _
@@ -27,7 +28,7 @@ from plinth import app as app_module
 from plinth import cfg, menu
 from plinth.utils import format_lazy
 
-version = 2
+version = 3
 
 is_essential = True
 
@@ -92,6 +93,7 @@ def setup(helper, old_version=None):
     if not old_version:
         helper.call('post', actions.superuser_run, 'users', ['first-setup'])
     helper.call('post', actions.superuser_run, 'users', ['setup'])
+    create_group('freedombox-share')
 
 
 def diagnose():
@@ -148,3 +150,16 @@ def get_last_admin_user():
         return admin_users[0]
 
     return None
+
+
+def add_user_to_share_group(username, service=None):
+    """Add user to the freedombox-share group."""
+    try:
+        group_members = grp.getgrnam('freedombox-share').gr_mem
+    except KeyError:
+        group_members = []
+    if username not in group_members:
+        actions.superuser_run(
+            'users', ['add-user-to-group', username, 'freedombox-share'])
+        if service:
+            action_utils.service_restart(service)