# -*- 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 datetime import errno import fnmatch import itertools import logging import os import re import shutil import sys import traceback import six from six import string_types from six.moves import urllib_parse as urlparse from canonicaljson import json from twisted.internet import defer from twisted.web.resource import Resource from twisted.web.server import NOT_DONE_YET from synapse.api.errors import Codes, SynapseError from synapse.http.client import SpiderHttpClient from synapse.http.server import ( respond_with_json, respond_with_json_bytes, wrap_json_request_handler, ) from synapse.http.servlet import parse_integer, parse_string from synapse.metrics.background_process_metrics import run_as_background_process from synapse.rest.media.v1._base import get_filename_from_headers from synapse.util.async_helpers import ObservableDeferred from synapse.util.caches.expiringcache import ExpiringCache from synapse.util.logcontext import make_deferred_yieldable, run_in_background from synapse.util.stringutils import random_string from ._base import FileInfo logger = logging.getLogger(__name__) _charset_match = re.compile(br"<\s*meta[^>]*charset\s*=\s*([a-z0-9-]+)", flags=re.I) _content_type_match = re.compile(r'.*; *charset="?(.*?)"?(;|$)', flags=re.I) 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._cleaner_loop = self.clock.looping_call( self._start_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 = parse_string(request, "url") if b"ts" in request.args: ts = parse_integer(request, "ts") 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 ): # It may be stored as text in the database, not as bytes (such as # PostgreSQL). If so, encode it back before handing it on. og = cache_result["og"] if isinstance(og, six.text_type): og = og.encode('utf8') defer.returnValue(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 with open(media_info['filename'], 'rb') as file: body = file.read() encoding = None # Let's try and figure out if it has an encoding set in a meta tag. # Limit it to the first 1kb, since it ought to be in the meta tags # at the top. match = _charset_match.search(body[:1000]) # If we find a match, it should take precedence over the # Content-Type header, so set it here. if match: encoding = match.group(1).decode('ascii') # If we don't find a match, we'll look at the HTTP Content-Type, and # if that doesn't exist, we'll fall back to UTF-8. if not encoding: match = _content_type_match.match( media_info['media_type'] ) 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).encode('utf8') # 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_info()[0], e), ), Codes.UNKNOWN, ) yield finish() try: if b"Content-Type" in headers: media_type = headers[b"Content-Type"][0].decode('ascii') else: media_type = "application/octet-stream" time_now_ms = self.clock.time_msec() download_name = get_filename_from_headers(headers) 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, }) def _start_expire_url_cache_data(self): return run_as_background_process( "expire_url_cache_data", self._expire_url_cache_data, ) @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... #
,