fetch remote downloads for _matrix/client/v1/media/download over federation download endpoint

synapse/federation/federation_client.py

@@ -1871,6 +1871,26 @@ class FederationClient(FederationBase):
 
         return filtered_statuses, filtered_failures
 
+    async def federation_download_media(
+        self,
+        destination: str,
+        media_id: str,
+        output_stream: BinaryIO,
+        max_size: int,
+        max_timeout_ms: int,
+        download_ratelimiter: Ratelimiter,
+        ip_address: str,
+    ) -> Tuple[int, Dict[bytes, List[bytes]], bytes]:
+        return await self.transport_layer.federation_download_media(
+            destination,
+            media_id,
+            output_stream=output_stream,
+            max_size=max_size,
+            max_timeout_ms=max_timeout_ms,
+            download_ratelimiter=download_ratelimiter,
+            ip_address=ip_address,
+        )
+
     async def download_media(
         self,
         destination: str,

synapse/federation/transport/client.py

@@ -824,7 +824,6 @@ class TransportLayerClient:
         ip_address: str,
     ) -> Tuple[int, Dict[bytes, List[bytes]]]:
         path = f"/_matrix/media/r0/download/{destination}/{media_id}"
-
         return await self.client.get_file(
             destination,
             path,
@@ -852,7 +851,6 @@ class TransportLayerClient:
         ip_address: str,
     ) -> Tuple[int, Dict[bytes, List[bytes]]]:
         path = f"/_matrix/media/v3/download/{destination}/{media_id}"
-
         return await self.client.get_file(
             destination,
             path,
@@ -873,6 +871,29 @@ class TransportLayerClient:
             ip_address=ip_address,
         )
 
+    async def federation_download_media(
+        self,
+        destination: str,
+        media_id: str,
+        output_stream: BinaryIO,
+        max_size: int,
+        max_timeout_ms: int,
+        download_ratelimiter: Ratelimiter,
+        ip_address: str,
+    ) -> Tuple[int, Dict[bytes, List[bytes]], bytes]:
+        path = f"/_matrix/federation/v1/media/download/{media_id}"
+        return await self.client.federation_get_file(
+            destination,
+            path,
+            output_stream=output_stream,
+            max_size=max_size,
+            args={
+                "timeout_ms": str(max_timeout_ms),
+            },
+            download_ratelimiter=download_ratelimiter,
+            ip_address=ip_address,
+        )
+
 
 def _create_path(federation_prefix: str, path: str, *args: str) -> str:
     """

synapse/http/matrixfederationclient.py

@@ -75,9 +75,11 @@ from synapse.http.client import (
     BlocklistingAgentWrapper,
     BodyExceededMaxSize,
     ByteWriteable,
+    SimpleHttpClient,
     _make_scheduler,
     encode_query_args,
     read_body_with_max_size,
+    read_multipart_response,
 )
 from synapse.http.connectproxyclient import BearerProxyCredentials
 from synapse.http.federation.matrix_federation_agent import MatrixFederationAgent
@@ -466,6 +468,12 @@ class MatrixFederationHttpClient:
 
         self._sleeper = AwakenableSleeper(self.reactor)
 
+        self._simple_http_client = SimpleHttpClient(
+            hs,
+            ip_blocklist=hs.config.server.federation_ip_range_blocklist,
+            use_proxy=True,
+        )
+
     def wake_destination(self, destination: str) -> None:
         """Called when the remote server may have come back online."""
 
@@ -1553,6 +1561,176 @@ class MatrixFederationHttpClient:
         )
         return length, headers
 
+    async def federation_get_file(
+        self,
+        destination: str,
+        path: str,
+        output_stream: BinaryIO,
+        download_ratelimiter: Ratelimiter,
+        ip_address: str,
+        max_size: int,
+        args: Optional[QueryParams] = None,
+        retry_on_dns_fail: bool = True,
+        ignore_backoff: bool = False,
+    ) -> Tuple[int, Dict[bytes, List[bytes]], bytes]:
+        """GETs a file from a given homeserver over the federation /download endpoint
+        Args:
+            destination: The remote server to send the HTTP request to.
+            path: The HTTP path to GET.
+            output_stream: File to write the response body to.
+            download_ratelimiter: a ratelimiter to limit remote media downloads, keyed to
+                requester IP
+            ip_address: IP address of the requester
+            max_size: maximum allowable size in bytes of the file
+            args: Optional dictionary used to create the query string.
+            ignore_backoff: true to ignore the historical backoff data
+                and try the request anyway.
+
+        Returns:
+            Resolves to an (int, dict, bytes) tuple of
+            the file length, a dict of the response headers, and the file json
+
+        Raises:
+            HttpResponseException: If we get an HTTP response code >= 300
+                (except 429).
+            NotRetryingDestination: If we are not yet ready to retry this
+                server.
+            FederationDeniedError: If this destination is not on our
+                federation whitelist
+            RequestSendFailed: If there were problems connecting to the
+                remote, due to e.g. DNS failures, connection timeouts etc.
+            SynapseError: If the requested file exceeds ratelimits
+        """
+        request = MatrixFederationRequest(
+            method="GET", destination=destination, path=path, query=args
+        )
+
+        # check for a minimum balance of 1MiB in ratelimiter before initiating request
+        send_req, _ = await download_ratelimiter.can_do_action(
+            requester=None, key=ip_address, n_actions=1048576, update=False
+        )
+
+        if not send_req:
+            msg = "Requested file size exceeds ratelimits"
+            logger.warning(
+                "{%s} [%s] %s",
+                request.txn_id,
+                request.destination,
+                msg,
+            )
+            raise SynapseError(HTTPStatus.TOO_MANY_REQUESTS, msg, Codes.LIMIT_EXCEEDED)
+
+        response = await self._send_request(
+            request,
+            retry_on_dns_fail=retry_on_dns_fail,
+            ignore_backoff=ignore_backoff,
+        )
+
+        headers = dict(response.headers.getAllRawHeaders())
+
+        expected_size = response.length
+        # if we don't get an expected length then use the max length
+        if expected_size == UNKNOWN_LENGTH:
+            expected_size = max_size
+            logger.debug(
+                f"File size unknown, assuming file is max allowable size: {max_size}"
+            )
+
+        read_body, _ = await download_ratelimiter.can_do_action(
+            requester=None,
+            key=ip_address,
+            n_actions=expected_size,
+        )
+        if not read_body:
+            msg = "Requested file size exceeds ratelimits"
+            logger.warning(
+                "{%s} [%s] %s",
+                request.txn_id,
+                request.destination,
+                msg,
+            )
+            raise SynapseError(HTTPStatus.TOO_MANY_REQUESTS, msg, Codes.LIMIT_EXCEEDED)
+
+        # this should be a multipart/mixed response with the boundary string in the header
+        raw_content_type = headers.get(b"Content-Type")
+        assert raw_content_type is not None
+        content_type = raw_content_type[0].decode("UTF-8")
+        boundary = content_type.split("boundary=")[1]
+
+        try:
+            # add a byte of headroom to max size as function errs at >=
+            deferred = read_multipart_response(
+                response, output_stream, boundary, expected_size + 1
+            )
+            deferred.addTimeout(self.default_timeout_seconds, self.reactor)
+        except BodyExceededMaxSize:
+            msg = "Requested file is too large > %r bytes" % (expected_size,)
+            logger.warning(
+                "{%s} [%s] %s",
+                request.txn_id,
+                request.destination,
+                msg,
+            )
+            raise SynapseError(HTTPStatus.BAD_GATEWAY, msg, Codes.TOO_LARGE)
+        except defer.TimeoutError as e:
+            logger.warning(
+                "{%s} [%s] Timed out reading response - %s %s",
+                request.txn_id,
+                request.destination,
+                request.method,
+                request.uri.decode("ascii"),
+            )
+            raise RequestSendFailed(e, can_retry=True) from e
+        except ResponseFailed as e:
+            logger.warning(
+                "{%s} [%s] Failed to read response - %s %s",
+                request.txn_id,
+                request.destination,
+                request.method,
+                request.uri.decode("ascii"),
+            )
+            raise RequestSendFailed(e, can_retry=True) from e
+        except Exception as e:
+            logger.warning(
+                "{%s} [%s] Error reading response: %s",
+                request.txn_id,
+                request.destination,
+                e,
+            )
+            raise
+
+        multipart_response = await make_deferred_yieldable(deferred)
+        if not multipart_response.url:
+            assert multipart_response.length is not None
+            length = multipart_response.length
+            headers[b"Content-Type"] = [multipart_response.content_type]
+            headers[b"Content-Disposition"] = [multipart_response.disposition]
+
+        # the response contained a redirect url to download the file from
+        else:
+            str_url = multipart_response.url.decode("utf-8")
+            logger.info(
+                "{%s} [%s] File download redirected, now downloading from: %s",
+                request.txn_id,
+                request.destination,
+                str_url,
+            )
+            length, headers, _, _ = await self._simple_http_client.get_file(
+                str_url, output_stream, expected_size
+            )
+
+        logger.info(
+            "{%s} [%s] Completed: %d %s [%d bytes] %s %s",
+            request.txn_id,
+            request.destination,
+            response.code,
+            response.phrase.decode("ascii", errors="replace"),
+            length,
+            request.method,
+            request.uri.decode("ascii"),
+        )
+        return length, headers, multipart_response.json
+
 
 def _flatten_response_never_received(e: BaseException) -> str:
     if hasattr(e, "reasons"):

synapse/media/media_repository.py

@@ -480,6 +480,7 @@ class MediaRepository:
         name: Optional[str],
         max_timeout_ms: int,
         ip_address: str,
+        use_federation_endpoint: bool,
     ) -> None:
         """Respond to requests for remote media.
 
@@ -492,6 +493,8 @@ class MediaRepository:
             max_timeout_ms: the maximum number of milliseconds to wait for the
                 media to be uploaded.
             ip_address: the IP address of the requester
+            use_federation_endpoint: whether to request the remote media over the new
+                federation `/download` endpoint
 
         Returns:
             Resolves once a response has successfully been written to request
@@ -522,6 +525,7 @@ class MediaRepository:
                 max_timeout_ms,
                 self.download_ratelimiter,
                 ip_address,
+                use_federation_endpoint,
             )
 
         # We deliberately stream the file outside the lock
@@ -569,6 +573,7 @@ class MediaRepository:
                 max_timeout_ms,
                 self.download_ratelimiter,
                 ip_address,
+                False,
             )
 
         # Ensure we actually use the responder so that it releases resources
@@ -585,6 +590,7 @@ class MediaRepository:
         max_timeout_ms: int,
         download_ratelimiter: Ratelimiter,
         ip_address: str,
+        use_federation_endpoint: bool,
     ) -> Tuple[Optional[Responder], RemoteMedia]:
         """Looks for media in local cache, if not there then attempt to
         download from remote server.
@@ -598,6 +604,8 @@ class MediaRepository:
             download_ratelimiter: a ratelimiter limiting remote media downloads, keyed to
                 requester IP.
             ip_address: the IP address of the requester
+            use_federation_endpoint: whether to request the remote media over the new federation
+            /download endpoint
 
         Returns:
             A tuple of responder and the media info of the file.
@@ -628,18 +636,45 @@ class MediaRepository:
 
         # Failed to find the file anywhere, lets download it.
 
-        try:
+        if not use_federation_endpoint:
-            media_info = await self._download_remote_file(
+            try:
-                server_name, media_id, max_timeout_ms, download_ratelimiter, ip_address
+                media_info = await self._download_remote_file(
-            )
+                    server_name,
-        except SynapseError:
+                    media_id,
-            raise
+                    max_timeout_ms,
-        except Exception as e:
+                    download_ratelimiter,
-            # An exception may be because we downloaded media in another
+                    ip_address,
-            # process, so let's check if we magically have the media.
+                )
-            media_info = await self.store.get_cached_remote_media(server_name, media_id)
+            except SynapseError:
-            if not media_info:
+                raise
-                raise e
+            except Exception as e:
+                # An exception may be because we downloaded media in another
+                # process, so let's check if we magically have the media.
+                media_info = await self.store.get_cached_remote_media(
+                    server_name, media_id
+                )
+                if not media_info:
+                    raise e
+
+        else:
+            try:
+                media_info = await self._federation_download_remote_file(
+                    server_name,
+                    media_id,
+                    max_timeout_ms,
+                    download_ratelimiter,
+                    ip_address,
+                )
+            except SynapseError:
+                raise
+            except Exception as e:
+                # An exception may be because we downloaded media in another
+                # process, so let's check if we magically have the media.
+                media_info = await self.store.get_cached_remote_media(
+                    server_name, media_id
+                )
+                if not media_info:
+                    raise e
 
         file_id = media_info.filesystem_id
         if not media_info.media_type:
@@ -775,6 +810,123 @@ class MediaRepository:
             quarantined_by=None,
         )
 
+    async def _federation_download_remote_file(
+        self,
+        server_name: str,
+        media_id: str,
+        max_timeout_ms: int,
+        download_ratelimiter: Ratelimiter,
+        ip_address: str,
+    ) -> RemoteMedia:
+        """Attempt to download the remote file from the given server name,
+        using the given file_id as the local id and downloading over federation v1 download
+        endpoint
+
+        Args:
+            server_name: Originating server
+            media_id: The media ID of the content (as defined by the
+                remote server). This is different than the file_id, which is
+                locally generated.
+            max_timeout_ms: the maximum number of milliseconds to wait for the
+                media to be uploaded.
+            download_ratelimiter: a ratelimiter limiting remote media downloads, keyed to
+                requester IP
+            ip_address: the IP address of the requester
+
+        Returns:
+            The media info of the file.
+        """
+
+        file_id = random_string(24)
+
+        file_info = FileInfo(server_name=server_name, file_id=file_id)
+
+        async with self.media_storage.store_into_file(file_info) as (f, fname):
+            try:
+                length, headers, json = await self.client.federation_download_media(
+                    server_name,
+                    media_id,
+                    output_stream=f,
+                    max_size=self.max_upload_size,
+                    max_timeout_ms=max_timeout_ms,
+                    download_ratelimiter=download_ratelimiter,
+                    ip_address=ip_address,
+                )
+            except RequestSendFailed as e:
+                logger.warning(
+                    "Request failed fetching remote media %s/%s: %r",
+                    server_name,
+                    media_id,
+                    e,
+                )
+                raise SynapseError(502, "Failed to fetch remote media")
+
+            except HttpResponseException as e:
+                logger.warning(
+                    "HTTP error fetching remote media %s/%s: %s",
+                    server_name,
+                    media_id,
+                    e.response,
+                )
+                if e.code == twisted.web.http.NOT_FOUND:
+                    raise e.to_synapse_error()
+                raise SynapseError(502, "Failed to fetch remote media")
+
+            except SynapseError:
+                logger.warning(
+                    "Failed to fetch remote media %s/%s", server_name, media_id
+                )
+                raise
+            except NotRetryingDestination:
+                logger.warning("Not retrying destination %r", server_name)
+                raise SynapseError(502, "Failed to fetch remote media")
+            except Exception:
+                logger.exception(
+                    "Failed to fetch remote media %s/%s", server_name, media_id
+                )
+                raise SynapseError(502, "Failed to fetch remote media")
+
+            if b"Content-Type" in headers:
+                media_type = headers[b"Content-Type"][0].decode("ascii")
+            else:
+                media_type = "application/octet-stream"
+            upload_name = get_filename_from_headers(headers)
+            time_now_ms = self.clock.time_msec()
+
+            # Multiple remote media download requests can race (when using
+            # multiple media repos), so this may throw a violation constraint
+            # exception. If it does we'll delete the newly downloaded file from
+            # disk (as we're in the ctx manager).
+            #
+            # However: we've already called `finish()` so we may have also
+            # written to the storage providers. This is preferable to the
+            # alternative where we call `finish()` *after* this, where we could
+            # end up having an entry in the DB but fail to write the files to
+            # the storage providers.
+            await self.store.store_cached_remote_media(
+                origin=server_name,
+                media_id=media_id,
+                media_type=media_type,
+                time_now_ms=time_now_ms,
+                upload_name=upload_name,
+                media_length=length,
+                filesystem_id=file_id,
+            )
+
+        logger.info("Stored remote media in file %r", fname)
+
+        return RemoteMedia(
+            media_origin=server_name,
+            media_id=media_id,
+            media_type=media_type,
+            media_length=length,
+            upload_name=upload_name,
+            created_ts=time_now_ms,
+            filesystem_id=file_id,
+            last_access_ts=time_now_ms,
+            quarantined_by=None,
+        )
+
     def _get_thumbnail_requirements(
         self, media_type: str
     ) -> Tuple[ThumbnailRequirement, ...]:

synapse/rest/media/download_resource.py

@@ -105,4 +105,5 @@ class DownloadResource(RestServlet):
                 file_name,
                 max_timeout_ms,
                 ip_address,
+                False,
             )