# -*- coding: utf-8 -*- # Copyright 2016 OpenMarket Ltd # # 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 cgi import datetime import errno import fnmatch import itertools import logging import os import re import shutil import sys import traceback import simplejson as json from six.moves import urllib_parse as urlparse from six import string_types from twisted.web.server import NOT_DONE_YET from twisted.internet import defer from twisted.web.resource import Resource from ._base import FileInfo from synapse.api.errors import ( SynapseError, Codes, ) from synapse.util.logcontext import make_deferred_yieldable, run_in_background from synapse.util.stringutils import random_string from synapse.util.caches.expiringcache import ExpiringCache from synapse.http.client import SpiderHttpClient from synapse.http.server import ( respond_with_json_bytes, respond_with_json, wrap_json_request_handler, ) from synapse.util.async import ObservableDeferred from synapse.util.stringutils import is_ascii logger = logging.getLogger(__name__) class PreviewUrlResource(Resource): isLeaf = True def __init__(self, hs, media_repo, media_storage): Resource.__init__(self) self.auth = hs.get_auth() self.clock = hs.get_clock() self.filepaths = media_repo.filepaths self.max_spider_size = hs.config.max_spider_size self.server_name = hs.hostname self.store = hs.get_datastore() self.client = SpiderHttpClient(hs) self.media_repo = media_repo self.primary_base_path = media_repo.primary_base_path self.media_storage = media_storage self.url_preview_url_blacklist = hs.config.url_preview_url_blacklist # memory cache mapping urls to an ObservableDeferred returning # JSON-encoded OG metadata self._cache = ExpiringCache( cache_name="url_previews", clock=self.clock, # don't spider URLs more often than once an hour expiry_ms=60 * 60 * 1000, ) self._cache.start() self._cleaner_loop = self.clock.looping_call( self._expire_url_cache_data, 10 * 1000 ) def render_OPTIONS(self, request): return respond_with_json(request, 200, {}, send_cors=True) def render_GET(self, request): self._async_render_GET(request) return NOT_DONE_YET @wrap_json_request_handler @defer.inlineCallbacks def _async_render_GET(self, request): # XXX: if get_user_by_req fails, what should we do in an async render? requester = yield self.auth.get_user_by_req(request) url = request.args.get("url")[0] if "ts" in request.args: ts = int(request.args.get("ts")[0]) else: ts = self.clock.time_msec() # XXX: we could move this into _do_preview if we wanted. url_tuple = urlparse.urlsplit(url) for entry in self.url_preview_url_blacklist: match = True for attrib in entry: pattern = entry[attrib] value = getattr(url_tuple, attrib) logger.debug(( "Matching attrib '%s' with value '%s' against" " pattern '%s'" ) % (attrib, value, pattern)) if value is None: match = False continue if pattern.startswith('^'): if not re.match(pattern, getattr(url_tuple, attrib)): match = False continue else: if not fnmatch.fnmatch(getattr(url_tuple, attrib), pattern): match = False continue if match: logger.warn( "URL %s blocked by url_blacklist entry %s", url, entry ) raise SynapseError( 403, "URL blocked by url pattern blacklist entry", Codes.UNKNOWN ) # the in-memory cache: # * ensures that only one request is active at a time # * takes load off the DB for the thundering herds # * also caches any failures (unlike the DB) so we don't keep # requesting the same endpoint observable = self._cache.get(url) if not observable: download = run_in_background( self._do_preview, url, requester.user, ts, ) observable = ObservableDeferred( download, consumeErrors=True ) self._cache[url] = observable else: logger.info("Returning cached response") og = yield make_deferred_yieldable(observable.observe()) respond_with_json_bytes(request, 200, og, send_cors=True) @defer.inlineCallbacks def _do_preview(self, url, user, ts): """Check the db, and download the URL and build a preview Args: url (str): user (str): ts (int): Returns: Deferred[str]: json-encoded og data """ # check the URL cache in the DB (which will also provide us with # historical previews, if we have any) cache_result = yield self.store.get_url_cache(url, ts) if ( cache_result and cache_result["expires_ts"] > ts and cache_result["response_code"] / 100 == 2 ): defer.returnValue(cache_result["og"]) return media_info = yield self._download_url(url, user) logger.debug("got media_info of '%s'" % media_info) if _is_media(media_info['media_type']): file_id = media_info['filesystem_id'] dims = yield self.media_repo._generate_thumbnails( None, file_id, file_id, media_info["media_type"], url_cache=True, ) og = { "og:description": media_info['download_name'], "og:image": "mxc://%s/%s" % ( self.server_name, media_info['filesystem_id'] ), "og:image:type": media_info['media_type'], "matrix:image:size": media_info['media_length'], } if dims: og["og:image:width"] = dims['width'] og["og:image:height"] = dims['height'] else: logger.warn("Couldn't get dims for %s" % url) # define our OG response for this media elif _is_html(media_info['media_type']): # TODO: somehow stop a big HTML tree from exploding synapse's RAM file = open(media_info['filename']) body = file.read() file.close() # clobber the encoding from the content-type, or default to utf-8 # XXX: this overrides any or XML charset headers in the body # which may pose problems, but so far seems to work okay. match = re.match(r'.*; *charset=(.*?)(;|$)', media_info['media_type'], re.I) encoding = match.group(1) if match else "utf-8" og = decode_and_calc_og(body, media_info['uri'], encoding) # pre-cache the image for posterity # FIXME: it might be cleaner to use the same flow as the main /preview_url # request itself and benefit from the same caching etc. But for now we # just rely on the caching on the master request to speed things up. if 'og:image' in og and og['og:image']: image_info = yield self._download_url( _rebase_url(og['og:image'], media_info['uri']), user ) if _is_media(image_info['media_type']): # TODO: make sure we don't choke on white-on-transparent images file_id = image_info['filesystem_id'] dims = yield self.media_repo._generate_thumbnails( None, file_id, file_id, image_info["media_type"], url_cache=True, ) if dims: og["og:image:width"] = dims['width'] og["og:image:height"] = dims['height'] else: logger.warn("Couldn't get dims for %s" % og["og:image"]) og["og:image"] = "mxc://%s/%s" % ( self.server_name, image_info['filesystem_id'] ) og["og:image:type"] = image_info['media_type'] og["matrix:image:size"] = image_info['media_length'] else: del og["og:image"] else: logger.warn("Failed to find any OG data in %s", url) og = {} logger.debug("Calculated OG for %s as %s" % (url, og)) jsonog = json.dumps(og) # store OG in history-aware DB cache yield self.store.store_url_cache( url, media_info["response_code"], media_info["etag"], media_info["expires"] + media_info["created_ts"], jsonog, media_info["filesystem_id"], media_info["created_ts"], ) defer.returnValue(jsonog) @defer.inlineCallbacks def _download_url(self, url, user): # TODO: we should probably honour robots.txt... except in practice # we're most likely being explicitly triggered by a human rather than a # bot, so are we really a robot? file_id = datetime.date.today().isoformat() + '_' + random_string(16) file_info = FileInfo( server_name=None, file_id=file_id, url_cache=True, ) with self.media_storage.store_into_file(file_info) as (f, fname, finish): try: logger.debug("Trying to get url '%s'" % url) length, headers, uri, code = yield self.client.get_file( url, output_stream=f, max_size=self.max_spider_size, ) except Exception as e: # FIXME: pass through 404s and other error messages nicely logger.warn("Error downloading %s: %r", url, e) raise SynapseError( 500, "Failed to download content: %s" % ( traceback.format_exception_only(sys.exc_type, e), ), Codes.UNKNOWN, ) yield finish() try: if "Content-Type" in headers: media_type = headers["Content-Type"][0] else: media_type = "application/octet-stream" time_now_ms = self.clock.time_msec() content_disposition = headers.get("Content-Disposition", None) if content_disposition: _, params = cgi.parse_header(content_disposition[0],) download_name = None # First check if there is a valid UTF-8 filename download_name_utf8 = params.get("filename*", None) if download_name_utf8: if download_name_utf8.lower().startswith("utf-8''"): download_name = download_name_utf8[7:] # If there isn't check for an ascii name. if not download_name: download_name_ascii = params.get("filename", None) if download_name_ascii and is_ascii(download_name_ascii): download_name = download_name_ascii if download_name: download_name = urlparse.unquote(download_name) try: download_name = download_name.decode("utf-8") except UnicodeDecodeError: download_name = None else: download_name = None yield self.store.store_local_media( media_id=file_id, media_type=media_type, time_now_ms=self.clock.time_msec(), upload_name=download_name, media_length=length, user_id=user, url_cache=url, ) except Exception as e: logger.error("Error handling downloaded %s: %r", url, e) # TODO: we really ought to delete the downloaded file in this # case, since we won't have recorded it in the db, and will # therefore not expire it. raise defer.returnValue({ "media_type": media_type, "media_length": length, "download_name": download_name, "created_ts": time_now_ms, "filesystem_id": file_id, "filename": fname, "uri": uri, "response_code": code, # FIXME: we should calculate a proper expiration based on the # Cache-Control and Expire headers. But for now, assume 1 hour. "expires": 60 * 60 * 1000, "etag": headers["ETag"][0] if "ETag" in headers else None, }) @defer.inlineCallbacks def _expire_url_cache_data(self): """Clean up expired url cache content, media and thumbnails. """ # TODO: Delete from backup media store now = self.clock.time_msec() logger.info("Running url preview cache expiry") if not (yield self.store.has_completed_background_updates()): logger.info("Still running DB updates; skipping expiry") return # First we delete expired url cache entries media_ids = yield self.store.get_expired_url_cache(now) removed_media = [] for media_id in media_ids: fname = self.filepaths.url_cache_filepath(media_id) try: os.remove(fname) except OSError as e: # If the path doesn't exist, meh if e.errno != errno.ENOENT: logger.warn("Failed to remove media: %r: %s", media_id, e) continue removed_media.append(media_id) try: dirs = self.filepaths.url_cache_filepath_dirs_to_delete(media_id) for dir in dirs: os.rmdir(dir) except Exception: pass yield self.store.delete_url_cache(removed_media) if removed_media: logger.info("Deleted %d entries from url cache", len(removed_media)) # Now we delete old images associated with the url cache. # These may be cached for a bit on the client (i.e., they # may have a room open with a preview url thing open). # So we wait a couple of days before deleting, just in case. expire_before = now - 2 * 24 * 60 * 60 * 1000 media_ids = yield self.store.get_url_cache_media_before(expire_before) removed_media = [] for media_id in media_ids: fname = self.filepaths.url_cache_filepath(media_id) try: os.remove(fname) except OSError as e: # If the path doesn't exist, meh if e.errno != errno.ENOENT: logger.warn("Failed to remove media: %r: %s", media_id, e) continue try: dirs = self.filepaths.url_cache_filepath_dirs_to_delete(media_id) for dir in dirs: os.rmdir(dir) except Exception: pass thumbnail_dir = self.filepaths.url_cache_thumbnail_directory(media_id) try: shutil.rmtree(thumbnail_dir) except OSError as e: # If the path doesn't exist, meh if e.errno != errno.ENOENT: logger.warn("Failed to remove media: %r: %s", media_id, e) continue removed_media.append(media_id) try: dirs = self.filepaths.url_cache_thumbnail_dirs_to_delete(media_id) for dir in dirs: os.rmdir(dir) except Exception: pass yield self.store.delete_url_cache_media(removed_media) logger.info("Deleted %d media from url cache", len(removed_media)) def decode_and_calc_og(body, media_uri, request_encoding=None): from lxml import etree try: parser = etree.HTMLParser(recover=True, encoding=request_encoding) tree = etree.fromstring(body, parser) og = _calc_og(tree, media_uri) except UnicodeDecodeError: # blindly try decoding the body as utf-8, which seems to fix # the charset mismatches on https://google.com parser = etree.HTMLParser(recover=True, encoding=request_encoding) tree = etree.fromstring(body.decode('utf-8', 'ignore'), parser) og = _calc_og(tree, media_uri) return og def _calc_og(tree, media_uri): # suck our tree into lxml and define our OG response. # if we see any image URLs in the OG response, then spider them # (although the client could choose to do this by asking for previews of those # URLs to avoid DoSing the server) # "og:type" : "video", # "og:url" : "https://www.youtube.com/watch?v=LXDBoHyjmtw", # "og:site_name" : "YouTube", # "og:video:type" : "application/x-shockwave-flash", # "og:description" : "Fun stuff happening here", # "og:title" : "RemoteJam - Matrix team hack for Disrupt Europe Hackathon", # "og:image" : "https://i.ytimg.com/vi/LXDBoHyjmtw/maxresdefault.jpg", # "og:video:url" : "http://www.youtube.com/v/LXDBoHyjmtw?version=3&autohide=1", # "og:video:width" : "1280" # "og:video:height" : "720", # "og:video:secure_url": "https://www.youtube.com/v/LXDBoHyjmtw?version=3", og = {} for tag in tree.xpath("//*/meta[starts-with(@property, 'og:')]"): if 'content' in tag.attrib: og[tag.attrib['property']] = tag.attrib['content'] # TODO: grab article: meta tags too, e.g.: # "article:publisher" : "https://www.facebook.com/thethudonline" /> # "article:author" content="https://www.facebook.com/thethudonline" /> # "article:tag" content="baby" /> # "article:section" content="Breaking News" /> # "article:published_time" content="2016-03-31T19:58:24+00:00" /> # "article:modified_time" content="2016-04-01T18:31:53+00:00" /> if 'og:title' not in og: # do some basic spidering of the HTML title = tree.xpath("(//title)[1] | (//h1)[1] | (//h2)[1] | (//h3)[1]") if title and title[0].text is not None: og['og:title'] = title[0].text.strip() else: og['og:title'] = None if 'og:image' not in og: # TODO: extract a favicon failing all else meta_image = tree.xpath( "//*/meta[translate(@itemprop, 'IMAGE', 'image')='image']/@content" ) if meta_image: og['og:image'] = _rebase_url(meta_image[0], media_uri) else: # TODO: consider inlined CSS styles as well as width & height attribs images = tree.xpath("//img[@src][number(@width)>10][number(@height)>10]") images = sorted(images, key=lambda i: ( -1 * float(i.attrib['width']) * float(i.attrib['height']) )) if not images: images = tree.xpath("//img[@src]") if images: og['og:image'] = images[0].attrib['src'] if 'og:description' not in og: meta_description = tree.xpath( "//*/meta" "[translate(@name, 'DESCRIPTION', 'description')='description']" "/@content") if meta_description: og['og:description'] = meta_description[0] else: # grab any text nodes which are inside the tag... # unless they are within an HTML5 semantic markup tag... #
,