forked-synapse/synapse/rest/client/media.py

#
# This file is licensed under the Affero General Public License (AGPL) version 3.
#
# Copyright 2020 The Matrix.org Foundation C.I.C.
# Copyright 2015, 2016 OpenMarket Ltd
# Copyright (C) 2024 New Vector, Ltd
#
# 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.
#
# See the GNU Affero General Public License for more details:
# <https://www.gnu.org/licenses/agpl-3.0.html>.
#
# Originally licensed under the Apache License, Version 2.0:
# <http://www.apache.org/licenses/LICENSE-2.0>.
#
# [This file includes modifications made by New Vector Limited]
#
#

import logging
import re

from synapse.http.server import (
    HttpServer,
    respond_with_json,
    respond_with_json_bytes,
    set_corp_headers,
    set_cors_headers,
)
from synapse.http.servlet import RestServlet, parse_integer, parse_string
from synapse.http.site import SynapseRequest
from synapse.media._base import (
    DEFAULT_MAX_TIMEOUT_MS,
    MAXIMUM_ALLOWED_MAX_TIMEOUT_MS,
    respond_404,
)
from synapse.media.media_repository import MediaRepository
from synapse.media.media_storage import MediaStorage
from synapse.media.thumbnailer import ThumbnailProvider
from synapse.server import HomeServer
from synapse.util.stringutils import parse_and_validate_server_name

logger = logging.getLogger(__name__)


class UnstablePreviewURLServlet(RestServlet):
    """
    Same as `GET /_matrix/media/r0/preview_url`, this endpoint provides a generic preview API
    for URLs which outputs Open Graph (https://ogp.me/) responses (with some Matrix
    specific additions).

    This does have trade-offs compared to other designs:

    * Pros:
      * Simple and flexible; can be used by any clients at any point
    * Cons:
      * If each homeserver provides one of these independently, all the homeservers in a
        room may needlessly DoS the target URI
      * The URL metadata must be stored somewhere, rather than just using Matrix
        itself to store the media.
      * Matrix cannot be used to distribute the metadata between homeservers.
    """

    PATTERNS = [
        re.compile(r"^/_matrix/client/unstable/org.matrix.msc3916/media/preview_url$")
    ]

    def __init__(
        self,
        hs: "HomeServer",
        media_repo: "MediaRepository",
        media_storage: MediaStorage,
    ):
        super().__init__()

        self.auth = hs.get_auth()
        self.clock = hs.get_clock()
        self.media_repo = media_repo
        self.media_storage = media_storage
        assert self.media_repo.url_previewer is not None
        self.url_previewer = self.media_repo.url_previewer

    async def on_GET(self, request: SynapseRequest) -> None:
        requester = await self.auth.get_user_by_req(request)
        url = parse_string(request, "url", required=True)
        ts = parse_integer(request, "ts")
        if ts is None:
            ts = self.clock.time_msec()

        og = await self.url_previewer.preview(url, requester.user, ts)
        respond_with_json_bytes(request, 200, og, send_cors=True)


class UnstableMediaConfigResource(RestServlet):
    PATTERNS = [
        re.compile(r"^/_matrix/client/unstable/org.matrix.msc3916/media/config$")
    ]

    def __init__(self, hs: "HomeServer"):
        super().__init__()
        config = hs.config
        self.clock = hs.get_clock()
        self.auth = hs.get_auth()
        self.limits_dict = {"m.upload.size": config.media.max_upload_size}

    async def on_GET(self, request: SynapseRequest) -> None:
        await self.auth.get_user_by_req(request)
        respond_with_json(request, 200, self.limits_dict, send_cors=True)


class UnstableThumbnailResource(RestServlet):
    PATTERNS = [
        re.compile(
            "/_matrix/client/unstable/org.matrix.msc3916/media/thumbnail/(?P<server_name>[^/]*)/(?P<media_id>[^/]*)$"
        )
    ]

    def __init__(
        self,
        hs: "HomeServer",
        media_repo: "MediaRepository",
        media_storage: MediaStorage,
    ):
        super().__init__()

        self.store = hs.get_datastores().main
        self.media_repo = media_repo
        self.media_storage = media_storage
        self.dynamic_thumbnails = hs.config.media.dynamic_thumbnails
        self._is_mine_server_name = hs.is_mine_server_name
        self._server_name = hs.hostname
        self.prevent_media_downloads_from = hs.config.media.prevent_media_downloads_from
        self.thumbnailer = ThumbnailProvider(hs, media_repo, media_storage)
        self.auth = hs.get_auth()

    async def on_GET(
        self, request: SynapseRequest, server_name: str, media_id: str
    ) -> None:
        # Validate the server name, raising if invalid
        parse_and_validate_server_name(server_name)
        await self.auth.get_user_by_req(request)

        set_cors_headers(request)
        set_corp_headers(request)
        width = parse_integer(request, "width", required=True)
        height = parse_integer(request, "height", required=True)
        method = parse_string(request, "method", "scale")
        # TODO Parse the Accept header to get an prioritised list of thumbnail types.
        m_type = "image/png"
        max_timeout_ms = parse_integer(
            request, "timeout_ms", default=DEFAULT_MAX_TIMEOUT_MS
        )
        max_timeout_ms = min(max_timeout_ms, MAXIMUM_ALLOWED_MAX_TIMEOUT_MS)

        if self._is_mine_server_name(server_name):
            if self.dynamic_thumbnails:
                await self.thumbnailer.select_or_generate_local_thumbnail(
                    request, media_id, width, height, method, m_type, max_timeout_ms
                )
            else:
                await self.thumbnailer.respond_local_thumbnail(
                    request, media_id, width, height, method, m_type, max_timeout_ms
                )
            self.media_repo.mark_recently_accessed(None, media_id)
        else:
            # Don't let users download media from configured domains, even if it
            # is already downloaded. This is Trust & Safety tooling to make some
            # media inaccessible to local users.
            # See `prevent_media_downloads_from` config docs for more info.
            if server_name in self.prevent_media_downloads_from:
                respond_404(request)
                return

            ip_address = request.getClientAddress().host
            remote_resp_function = (
                self.thumbnailer.select_or_generate_remote_thumbnail
                if self.dynamic_thumbnails
                else self.thumbnailer.respond_remote_thumbnail
            )
            await remote_resp_function(
                request,
                server_name,
                media_id,
                width,
                height,
                method,
                m_type,
                max_timeout_ms,
                ip_address,
            )
            self.media_repo.mark_recently_accessed(server_name, media_id)


def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
    if hs.config.experimental.msc3916_authenticated_media_enabled:
        media_repo = hs.get_media_repository()
        if hs.config.media.url_preview_enabled:
            UnstablePreviewURLServlet(
                hs, media_repo, media_repo.media_storage
            ).register(http_server)
        UnstableMediaConfigResource(hs).register(http_server)
        UnstableThumbnailResource(hs, media_repo, media_repo.media_storage).register(
            http_server
        )