backups: Fix incomplete download archives

- Downloaded archives can't be fully extracted as tar.gz is incomplete at the
  end and corrupt. This is due to complete gzip streaming implementation that is
  does not flush the final bytes of gzip stream. Remove custom implementation
  and get gzipped stream directly from borg.

- Fix mimetype for .tar.gz to application/gzip.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

actions/backups

@@ -174,7 +174,8 @@ def _extract(archive_path, destination, locations=None, env=None):
 
 def subcommand_export_tar(arguments):
     """Export archive contents as tar stream on stdout."""
-    run(['borg', 'export-tar', arguments.path, '-'], arguments=arguments)
+    run(['borg', 'export-tar', arguments.path, '-', '--tar-filter=gzip'],
+        arguments=arguments)
 
 
 def _read_archive_file(archive, filepath, env=None):

plinth/modules/backups/repository.py

@@ -29,8 +29,7 @@ from plinth import actions
 from plinth.errors import ActionError
 
 from . import api, network_storage, _backup_handler, ROOT_REPOSITORY_NAME, \
-        ROOT_REPOSITORY_UUID, ROOT_REPOSITORY, restore_archive_handler, \
-        zipstream
+        ROOT_REPOSITORY_UUID, ROOT_REPOSITORY, restore_archive_handler
 from .errors import BorgError, BorgRepositoryDoesNotExistError, SshfsError
 
 logger = logging.getLogger(__name__)
@@ -141,11 +140,11 @@ class BorgRepository():
     def create_repository(self):
         self.run(['init', '--path', self.repo_path, '--encryption', 'none'])
 
-    def get_zipstream(self, archive_name):
+    def get_download_stream(self, archive_name):
         args = ['export-tar', '--path', self._get_archive_path(archive_name)]
         args += self._get_encryption_arguments(self.credentials)
         proc = self._run('backups', args, run_in_background=True)
-        return zipstream.ZipStream(proc.stdout, 'readline')
+        return proc.stdout
 
     def get_archive(self, name):
         for archive in self.list_archives():

plinth/modules/backups/views.py

@@ -239,7 +239,8 @@ class DownloadArchiveView(View):
         filename = '%s.tar.gz' % name
 
         response = StreamingHttpResponse(
-            repository.get_zipstream(name), content_type='application/x-gzip')
+            repository.get_download_stream(name),
+            content_type='application/gzip')
         response['Content-Disposition'] = 'attachment; filename="%s"' % \
             filename
         return response

plinth/modules/backups/zipstream.py

@@ -1,47 +0,0 @@
-#
-# 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/>.
-#
-
-import gzip
-from io import BytesIO
-
-
-class ZipStream(object):
-    """Zip a stream that yields binary data"""
-
-    def __init__(self, stream, get_chunk_method):
-        """
-        - stream: the input stream
-        - get_chunk_method: name of the method to get a chunk of the stream
-        """
-        self.stream = stream
-        self.buffer = BytesIO()
-        self.zipfile = gzip.GzipFile(mode='wb', fileobj=self.buffer)
-        self.get_chunk = getattr(self.stream, get_chunk_method)
-
-    def __next__(self):
-        line = self.get_chunk()
-        if not len(line):
-            raise StopIteration
-        self.zipfile.write(line)
-        self.zipfile.flush()
-        zipped = self.buffer.getvalue()
-        self.buffer.truncate(0)
-        self.buffer.seek(0)
-        return zipped
-
-    def __iter__(self):
-        return self