# Copyright 2018-2021 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import contextlib
import logging
import os
import shutil
from typing import IO, TYPE_CHECKING, Any, Callable, Optional, Sequence
import attr
from twisted.internet.defer import Deferred
from twisted.internet.interfaces import IConsumer
from twisted.protocols.basic import FileSender
from synapse.api.errors import NotFoundError
from synapse.logging.context import defer_to_thread, make_deferred_yieldable
from synapse.util import Clock
from synapse.util.file_consumer import BackgroundFileConsumer
from ._base import FileInfo, Responder
from .filepath import MediaFilePaths
if TYPE_CHECKING:
from synapse.server import HomeServer
from .storage_provider import StorageProviderWrapper
logger = logging.getLogger(__name__)
class MediaStorage:
"""Responsible for storing/fetching files from local sources.
Args:
hs
local_media_directory: Base path where we store media on disk
filepaths
storage_providers: List of StorageProvider that are used to fetch and store files.
"""
def __init__(
self,
hs: "HomeServer",
local_media_directory: str,
filepaths: MediaFilePaths,
storage_providers: Sequence["StorageProviderWrapper"],
):
self.hs = hs
self.reactor = hs.get_reactor()
self.local_media_directory = local_media_directory
self.filepaths = filepaths
self.storage_providers = storage_providers
self.spam_checker = hs.get_spam_checker()
self.clock = hs.get_clock()
async def store_file(self, source: IO, file_info: FileInfo) -> str:
"""Write `source` to the on disk media store, and also any other
configured storage providers
Args:
source: A file like object that should be written
file_info: Info about the file to store
Returns:
the file path written to in the primary media store
"""
with self.store_into_file(file_info) as (f, fname, finish_cb):
# Write to the main repository
await self.write_to_file(source, f)
await finish_cb()
return fname
async def write_to_file(self, source: IO, output: IO):
"""Asynchronously write the `source` to `output`."""
await defer_to_thread(self.reactor, _write_file_synchronously, source, output)
@contextlib.contextmanager
def store_into_file(self, file_info: FileInfo):
"""Context manager used to get a file like object to write into, as
described by file_info.
Actually yields a 3-tuple (file, fname, finish_cb), where file is a file
like object that can be written to, fname is the absolute path of file
on disk, and finish_cb is a function that returns an awaitable.
fname can be used to read the contents from after upload, e.g. to
generate thumbnails.
finish_cb must be called and waited on after the file has been
successfully been written to. Should not be called if there was an
error.
Args:
file_info: Info about the file to store
Example:
with media_storage.store_into_file(info) as (f, fname, finish_cb):
# .. write into f ...
await finish_cb()
"""
path = self._file_info_to_path(file_info)
fname = os.path.join(self.local_media_directory, path)
dirname = os.path.dirname(fname)
if not os.path.exists(dirname):
os.makedirs(dirname)
finished_called = [False]
try:
with open(fname, "wb") as f:
async def finish():
# Ensure that all writes have been flushed and close the
# file.
f.flush()
f.close()
spam = await self.spam_checker.check_media_file_for_spam(
ReadableFileWrapper(self.clock, fname), file_info
)
if spam:
logger.info("Blocking media due to spam checker")
# Note that we'll delete the stored media, due to the
# try/except below. The media also won't be stored in
# the DB.
raise SpamMediaException()
for provider in self.storage_providers:
await provider.store_file(path, file_info)
finished_called[0] = True
yield f, fname, finish
except Exception as e:
try:
os.remove(fname)
except Exception:
pass
raise e from None
if not finished_called:
raise Exception("Finished callback not called")
async def fetch_media(self, file_info: FileInfo) -> Optional[Responder]:
"""Attempts to fetch media described by file_info from the local cache
and configured storage providers.
Args:
file_info
Returns:
Returns a Responder if the file was found, otherwise None.
"""
paths = [self._file_info_to_path(file_info)]
# fallback for remote thumbnails with no method in the filename
if file_info.thumbnail and file_info.server_name:
paths.append(
self.filepaths.remote_media_thumbnail_rel_legacy(
server_name=file_info.server_name,
file_id=file_info.file_id,
width=file_info.thumbnail_width,
height=file_info.thumbnail_height,
content_type=file_info.thumbnail_type,
)
)
for path in paths:
local_path = os.path.join(self.local_media_directory, path)
if os.path.exists(local_path):
logger.debug("responding with local file %s", local_path)
return FileResponder(open(local_path, "rb"))
logger.debug("local file %s did not exist", local_path)
for provider in self.storage_providers:
for path in paths:
res: Any = await provider.fetch(path, file_info)
if res:
logger.debug("Streaming %s from %s", path, provider)
return res
logger.debug("%s not found on %s", path, provider)
return None
async def ensure_media_is_in_local_cache(self, file_info: FileInfo) -> str:
"""Ensures that the given file is in the local cache. Attempts to
download it from storage providers if it isn't.
Args:
file_info
Returns:
Full path to local file
"""
path = self._file_info_to_path(file_info)
local_path = os.path.join(self.local_media_directory, path)
if os.path.exists(local_path):
return local_path
# Fallback for paths without method names
# Should be removed in the future
if file_info.thumbnail and file_info.server_name:
legacy_path = self.filepaths.remote_media_thumbnail_rel_legacy(
server_name=file_info.server_name,
file_id=file_info.file_id,
width=file_info.thumbnail_width,
height=file_info.thumbnail_height,
content_type=file_info.thumbnail_type,
)
legacy_local_path = os.path.join(self.local_media_directory, legacy_path)
if os.path.exists(legacy_local_path):
return legacy_local_path
dirname = os.path.dirname(local_path)
if not os.path.exists(dirname):
os.makedirs(dirname)
for provider in self.storage_providers:
res: Any = await provider.fetch(path, file_info)
if res:
with res:
consumer = BackgroundFileConsumer(
open(local_path, "wb"), self.reactor
)
await res.write_to_consumer(consumer)
await consumer.wait()
return local_path
raise NotFoundError()
def _file_info_to_path(self, file_info: FileInfo) -> str:
"""Converts file_info into a relative path.
The path is suitable for storing files under a directory, e.g. used to
store files on local FS under the base media repository directory.
"""
if file_info.url_cache:
if file_info.thumbnail:
return self.filepaths.url_cache_thumbnail_rel(
media_id=file_info.file_id,
width=file_info.thumbnail_width,
height=file_info.thumbnail_height,
content_type=file_info.thumbnail_type,
method=file_info.thumbnail_method,
)
return self.filepaths.url_cache_filepath_rel(file_info.file_id)
if file_info.server_name:
if file_info.thumbnail:
return self.filepaths.remote_media_thumbnail_rel(
server_name=file_info.server_name,
file_id=file_info.file_id,
width=file_info.thumbnail_width,
height=file_info.thumbnail_height,
content_type=file_info.thumbnail_type,
method=file_info.thumbnail_method,
)
return self.filepaths.remote_media_filepath_rel(
file_info.server_name, file_info.file_id
)
if file_info.thumbnail:
return self.filepaths.local_media_thumbnail_rel(
media_id=file_info.file_id,
width=file_info.thumbnail_width,
height=file_info.thumbnail_height,
content_type=file_info.thumbnail_type,
method=file_info.thumbnail_method,
)
return self.filepaths.local_media_filepath_rel(file_info.file_id)
def _write_file_synchronously(source: IO, dest: IO) -> None:
"""Write `source` to the file like `dest` synchronously. Should be called
from a thread.
Args:
source: A file like object that's to be written
dest: A file like object to be written to
"""
source.seek(0) # Ensure we read from the start of the file
shutil.copyfileobj(source, dest)
class FileResponder(Responder):
"""Wraps an open file that can be sent to a request.
Args:
open_file: A file like object to be streamed ot the client,
is closed when finished streaming.
"""
def __init__(self, open_file: IO):
self.open_file = open_file
def write_to_consumer(self, consumer: IConsumer) -> Deferred:
return make_deferred_yieldable(
FileSender().beginFileTransfer(self.open_file, consumer)
)
def __exit__(self, exc_type, exc_val, exc_tb):
self.open_file.close()
class SpamMediaException(NotFoundError):
"""The media was blocked by a spam checker, so we simply 404 the request (in
the same way as if it was quarantined).
"""
@attr.s(slots=True)
class ReadableFileWrapper:
"""Wrapper that allows reading a file in chunks, yielding to the reactor,
and writing to a callback.
This is simplified `FileSender` that takes an IO object rather than an
`IConsumer`.
"""
CHUNK_SIZE = 2 ** 14
clock = attr.ib(type=Clock)
path = attr.ib(type=str)
async def write_chunks_to(self, callback: Callable[[bytes], None]):
"""Reads the file in chunks and calls the callback with each chunk."""
with open(self.path, "rb") as file:
while True:
chunk = file.read(self.CHUNK_SIZE)
if not chunk:
break
callback(chunk)
# We yield to the reactor by sleeping for 0 seconds.
await self.clock.sleep(0)