diff --git a/README.rst b/README.rst index 6136e0c1fe..02e7c61d1e 100644 --- a/README.rst +++ b/README.rst @@ -104,7 +104,7 @@ Installing prerequisites on Ubuntu or Debian:: sudo apt-get install build-essential python2.7-dev libffi-dev \ python-pip python-setuptools sqlite3 \ - libssl-dev python-virtualenv libjpeg-dev + libssl-dev python-virtualenv libjpeg-dev libxslt1-dev Installing prerequisites on ArchLinux:: @@ -557,6 +557,23 @@ as the primary means of identity and E2E encryption is not complete. As such, we are running a single identity server (https://matrix.org) at the current time. + +URL Previews +============ + +Synapse 0.15.0 introduces an experimental new API for previewing URLs at +/_matrix/media/r0/preview_url. This is disabled by default. To turn it on +you must enable the `url_preview_enabled: True` config parameter and explicitly +specify the IP ranges that Synapse is not allowed to spider for previewing in +the `url_preview_ip_range_blacklist` configuration parameter. This is critical +from a security perspective to stop arbitrary Matrix users spidering 'internal' +URLs on your network. At the very least we recommend that your loopback and +RFC1918 IP addresses are blacklisted. + +This also requires the optional lxml and netaddr python dependencies to be +installed. + + Password reset ============== diff --git a/UPGRADE.rst b/UPGRADE.rst index 4f08cbb96a..699f04c2c2 100644 --- a/UPGRADE.rst +++ b/UPGRADE.rst @@ -30,6 +30,14 @@ running: python synapse/python_dependencies.py | xargs -n1 pip install +Upgrading to v0.15.0 +==================== + +If you want to use the new URL previewing API (/_matrix/media/r0/preview_url) +then you have to explicitly enable it in the config and update your dependencies +dependencies. See README.rst for details. + + Upgrading to v0.11.0 ==================== diff --git a/docs/url_previews.rst b/docs/url_previews.rst new file mode 100644 index 0000000000..634d9d907f --- /dev/null +++ b/docs/url_previews.rst @@ -0,0 +1,74 @@ +URL Previews +============ + +Design notes on a URL previewing service for Matrix: + +Options are: + + 1. Have an AS which listens for URLs, downloads them, and inserts an event that describes their metadata. + * Pros: + * Decouples the implementation entirely from Synapse. + * Uses existing Matrix events & content repo to store the metadata. + * Cons: + * Which AS should provide this service for a room, and why should you trust it? + * Doesn't work well with E2E; you'd have to cut the AS into every room + * the AS would end up subscribing to every room anyway. + + 2. Have a generic preview API (nothing to do with Matrix) that provides a previewing service: + * Pros: + * Simple and flexible; can be used by any clients at any point + * Cons: + * If each HS provides one of these independently, all the HSes in a room may needlessly DoS the target URI + * We need somewhere to store the URL metadata rather than just using Matrix itself + * We can't piggyback on matrix to distribute the metadata between HSes. + + 3. Make the synapse of the sending user responsible for spidering the URL and inserting an event asynchronously which describes the metadata. + * Pros: + * Works transparently for all clients + * Piggy-backs nicely on using Matrix for distributing the metadata. + * No confusion as to which AS + * Cons: + * Doesn't work with E2E + * We might want to decouple the implementation of the spider from the HS, given spider behaviour can be quite complicated and evolve much more rapidly than the HS. It's more like a bot than a core part of the server. + + 4. Make the sending client use the preview API and insert the event itself when successful. + * Pros: + * Works well with E2E + * No custom server functionality + * Lets the client customise the preview that they send (like on FB) + * Cons: + * Entirely specific to the sending client, whereas it'd be nice if /any/ URL was correctly previewed if clients support it. + + 5. Have the option of specifying a shared (centralised) previewing service used by a room, to avoid all the different HSes in the room DoSing the target. + +Best solution is probably a combination of both 2 and 4. + * Sending clients do their best to create and send a preview at the point of sending the message, perhaps delaying the message until the preview is computed? (This also lets the user validate the preview before sending) + * Receiving clients have the option of going and creating their own preview if one doesn't arrive soon enough (or if the original sender didn't create one) + +This is a bit magical though in that the preview could come from two entirely different sources - the sending HS or your local one. However, this can always be exposed to users: "Generate your own URL previews if none are available?" + +This is tantamount also to senders calculating their own thumbnails for sending in advance of the main content - we are trusting the sender not to lie about the content in the thumbnail. Whereas currently thumbnails are calculated by the receiving homeserver to avoid this attack. + +However, this kind of phishing attack does exist whether we let senders pick their thumbnails or not, in that a malicious sender can send normal text messages around the attachment claiming it to be legitimate. We could rely on (future) reputation/abuse management to punish users who phish (be it with bogus metadata or bogus descriptions). Bogus metadata is particularly bad though, especially if it's avoidable. + +As a first cut, let's do #2 and have the receiver hit the API to calculate its own previews (as it does currently for image thumbnails). We can then extend/optimise this to option 4 as a special extra if needed. + +API +--- + +GET /_matrix/media/r0/preview_url?url=http://wherever.com +200 OK +{ + "og:type" : "article" + "og:url" : "https://twitter.com/matrixdotorg/status/684074366691356672" + "og:title" : "Matrix on Twitter" + "og:image" : "https://pbs.twimg.com/profile_images/500400952029888512/yI0qtFi7_400x400.png" + "og:description" : "“Synapse 0.12 is out! Lots of polishing, performance & bugfixes: /sync API, /r0 prefix, fulltext search, 3PID invites https://t.co/5alhXLLEGP”" + "og:site_name" : "Twitter" +} + +* Downloads the URL + * If HTML, just stores it in RAM and parses it for OG meta tags + * Download any media OG meta tags to the media repo, and refer to them in the OG via mxc:// URIs. + * If a media filetype we know we can thumbnail: store it on disk, and hand it to the thumbnailer. Generate OG meta tags from the thumbnailer contents. + * Otherwise, don't bother downloading further. diff --git a/synapse/config/repository.py b/synapse/config/repository.py index 2e96c09013..49922c6d03 100644 --- a/synapse/config/repository.py +++ b/synapse/config/repository.py @@ -16,6 +16,8 @@ from ._base import Config from collections import namedtuple +import sys + ThumbnailRequirement = namedtuple( "ThumbnailRequirement", ["width", "height", "method", "media_type"] ) @@ -23,7 +25,7 @@ ThumbnailRequirement = namedtuple( def parse_thumbnail_requirements(thumbnail_sizes): """ Takes a list of dictionaries with "width", "height", and "method" keys - and creates a map from image media types to the thumbnail size, thumnailing + and creates a map from image media types to the thumbnail size, thumbnailing method, and thumbnail media type to precalculate Args: @@ -53,12 +55,25 @@ class ContentRepositoryConfig(Config): def read_config(self, config): self.max_upload_size = self.parse_size(config["max_upload_size"]) self.max_image_pixels = self.parse_size(config["max_image_pixels"]) + self.max_spider_size = self.parse_size(config["max_spider_size"]) self.media_store_path = self.ensure_directory(config["media_store_path"]) self.uploads_path = self.ensure_directory(config["uploads_path"]) self.dynamic_thumbnails = config["dynamic_thumbnails"] self.thumbnail_requirements = parse_thumbnail_requirements( config["thumbnail_sizes"] ) + self.url_preview_enabled = config["url_preview_enabled"] + if self.url_preview_enabled: + try: + from netaddr import IPSet + if "url_preview_ip_range_blacklist" in config: + self.url_preview_ip_range_blacklist = IPSet( + config["url_preview_ip_range_blacklist"] + ) + if "url_preview_url_blacklist" in config: + self.url_preview_url_blacklist = config["url_preview_url_blacklist"] + except ImportError: + sys.stderr.write("\nmissing netaddr dep - disabling preview_url API\n") def default_config(self, **kwargs): media_store = self.default_path("media_store") @@ -80,7 +95,7 @@ class ContentRepositoryConfig(Config): # the resolution requested by the client. If true then whenever # a new resolution is requested by the client the server will # generate a new thumbnail. If false the server will pick a thumbnail - # from a precalcualted list. + # from a precalculated list. dynamic_thumbnails: false # List of thumbnail to precalculate when an image is uploaded. @@ -100,4 +115,62 @@ class ContentRepositoryConfig(Config): - width: 800 height: 600 method: scale + + # Is the preview URL API enabled? If enabled, you *must* specify + # an explicit url_preview_ip_range_blacklist of IPs that the spider is + # denied from accessing. + url_preview_enabled: False + + # List of IP address CIDR ranges that the URL preview spider is denied + # from accessing. There are no defaults: you must explicitly + # specify a list for URL previewing to work. You should specify any + # internal services in your network that you do not want synapse to try + # to connect to, otherwise anyone in any Matrix room could cause your + # synapse to issue arbitrary GET requests to your internal services, + # causing serious security issues. + # + # url_preview_ip_range_blacklist: + # - '127.0.0.0/8' + # - '10.0.0.0/8' + # - '172.16.0.0/12' + # - '192.168.0.0/16' + + # Optional list of URL matches that the URL preview spider is + # denied from accessing. You should use url_preview_ip_range_blacklist + # in preference to this, otherwise someone could define a public DNS + # entry that points to a private IP address and circumvent the blacklist. + # This is more useful if you know there is an entire shape of URL that + # you know that will never want synapse to try to spider. + # + # Each list entry is a dictionary of url component attributes as returned + # by urlparse.urlsplit as applied to the absolute form of the URL. See + # https://docs.python.org/2/library/urlparse.html#urlparse.urlsplit + # The values of the dictionary are treated as an filename match pattern + # applied to that component of URLs, unless they start with a ^ in which + # case they are treated as a regular expression match. If all the + # specified component matches for a given list item succeed, the URL is + # blacklisted. + # + # url_preview_url_blacklist: + # # blacklist any URL with a username in its URI + # - username: '*' + # + # # blacklist all *.google.com URLs + # - netloc: 'google.com' + # - netloc: '*.google.com' + # + # # blacklist all plain HTTP URLs + # - scheme: 'http' + # + # # blacklist http(s)://www.acme.com/foo + # - netloc: 'www.acme.com' + # path: '/foo' + # + # # blacklist any URL with a literal IPv4 address + # - netloc: '^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$' + + # The largest allowed URL preview spidering size in bytes + max_spider_size: "10M" + + """ % locals() diff --git a/synapse/http/client.py b/synapse/http/client.py index cbd45b2bbe..6c89b20984 100644 --- a/synapse/http/client.py +++ b/synapse/http/client.py @@ -15,17 +15,24 @@ from OpenSSL import SSL from OpenSSL.SSL import VERIFY_NONE -from synapse.api.errors import CodeMessageException +from synapse.api.errors import ( + CodeMessageException, SynapseError, Codes, +) from synapse.util.logcontext import preserve_context_over_fn import synapse.metrics +from synapse.http.endpoint import SpiderEndpoint from canonicaljson import encode_canonical_json -from twisted.internet import defer, reactor, ssl +from twisted.internet import defer, reactor, ssl, protocol +from twisted.internet.endpoints import SSL4ClientEndpoint, TCP4ClientEndpoint from twisted.web.client import ( - Agent, readBody, FileBodyProducer, PartialDownloadError, + BrowserLikeRedirectAgent, ContentDecoderAgent, GzipDecoder, Agent, + readBody, FileBodyProducer, PartialDownloadError, ) +from twisted.web.http import PotentialDataLoss from twisted.web.http_headers import Headers +from twisted.web._newclient import ResponseDone from StringIO import StringIO @@ -238,6 +245,107 @@ class SimpleHttpClient(object): else: raise CodeMessageException(response.code, body) + # XXX: FIXME: This is horribly copy-pasted from matrixfederationclient. + # The two should be factored out. + + @defer.inlineCallbacks + def get_file(self, url, output_stream, max_size=None): + """GETs a file from a given URL + Args: + url (str): The URL to GET + output_stream (file): File to write the response body to. + Returns: + A (int,dict,string,int) tuple of the file length, dict of the response + headers, absolute URI of the response and HTTP response code. + """ + + response = yield self.request( + "GET", + url.encode("ascii"), + headers=Headers({ + b"User-Agent": [self.user_agent], + }) + ) + + headers = dict(response.headers.getAllRawHeaders()) + + if 'Content-Length' in headers and headers['Content-Length'] > max_size: + logger.warn("Requested URL is too large > %r bytes" % (self.max_size,)) + raise SynapseError( + 502, + "Requested file is too large > %r bytes" % (self.max_size,), + Codes.TOO_LARGE, + ) + + if response.code > 299: + logger.warn("Got %d when downloading %s" % (response.code, url)) + raise SynapseError( + 502, + "Got error %d" % (response.code,), + Codes.UNKNOWN, + ) + + # TODO: if our Content-Type is HTML or something, just read the first + # N bytes into RAM rather than saving it all to disk only to read it + # straight back in again + + try: + length = yield preserve_context_over_fn( + _readBodyToFile, + response, output_stream, max_size + ) + except Exception as e: + logger.exception("Failed to download body") + raise SynapseError( + 502, + ("Failed to download remote body: %s" % e), + Codes.UNKNOWN, + ) + + defer.returnValue((length, headers, response.request.absoluteURI, response.code)) + + +# XXX: FIXME: This is horribly copy-pasted from matrixfederationclient. +# The two should be factored out. + +class _ReadBodyToFileProtocol(protocol.Protocol): + def __init__(self, stream, deferred, max_size): + self.stream = stream + self.deferred = deferred + self.length = 0 + self.max_size = max_size + + def dataReceived(self, data): + self.stream.write(data) + self.length += len(data) + if self.max_size is not None and self.length >= self.max_size: + self.deferred.errback(SynapseError( + 502, + "Requested file is too large > %r bytes" % (self.max_size,), + Codes.TOO_LARGE, + )) + self.deferred = defer.Deferred() + self.transport.loseConnection() + + def connectionLost(self, reason): + if reason.check(ResponseDone): + self.deferred.callback(self.length) + elif reason.check(PotentialDataLoss): + # stolen from https://github.com/twisted/treq/pull/49/files + # http://twistedmatrix.com/trac/ticket/4840 + self.deferred.callback(self.length) + else: + self.deferred.errback(reason) + + +# XXX: FIXME: This is horribly copy-pasted from matrixfederationclient. +# The two should be factored out. + +def _readBodyToFile(response, stream, max_size): + d = defer.Deferred() + response.deliverBody(_ReadBodyToFileProtocol(stream, d, max_size)) + return d + class CaptchaServerHttpClient(SimpleHttpClient): """ @@ -269,6 +377,59 @@ class CaptchaServerHttpClient(SimpleHttpClient): defer.returnValue(e.response) +class SpiderEndpointFactory(object): + def __init__(self, hs): + self.blacklist = hs.config.url_preview_ip_range_blacklist + self.policyForHTTPS = hs.get_http_client_context_factory() + + def endpointForURI(self, uri): + logger.info("Getting endpoint for %s", uri.toBytes()) + if uri.scheme == "http": + return SpiderEndpoint( + reactor, uri.host, uri.port, self.blacklist, + endpoint=TCP4ClientEndpoint, + endpoint_kw_args={ + 'timeout': 15 + }, + ) + elif uri.scheme == "https": + tlsPolicy = self.policyForHTTPS.creatorForNetloc(uri.host, uri.port) + return SpiderEndpoint( + reactor, uri.host, uri.port, self.blacklist, + endpoint=SSL4ClientEndpoint, + endpoint_kw_args={ + 'sslContextFactory': tlsPolicy, + 'timeout': 15 + }, + ) + else: + logger.warn("Can't get endpoint for unrecognised scheme %s", uri.scheme) + + +class SpiderHttpClient(SimpleHttpClient): + """ + Separate HTTP client for spidering arbitrary URLs. + Special in that it follows retries and has a UA that looks + like a browser. + + used by the preview_url endpoint in the content repo. + """ + def __init__(self, hs): + SimpleHttpClient.__init__(self, hs) + # clobber the base class's agent and UA: + self.agent = ContentDecoderAgent( + BrowserLikeRedirectAgent( + Agent.usingEndpointFactory( + reactor, + SpiderEndpointFactory(hs) + ) + ), [('gzip', GzipDecoder)] + ) + # We could look like Chrome: + # self.user_agent = ("Mozilla/5.0 (%s) (KHTML, like Gecko) + # Chrome Safari" % hs.version_string) + + def encode_urlencode_args(args): return {k: encode_urlencode_arg(v) for k, v in args.items()} diff --git a/synapse/http/endpoint.py b/synapse/http/endpoint.py index bc28a2959a..a456dc19da 100644 --- a/synapse/http/endpoint.py +++ b/synapse/http/endpoint.py @@ -75,6 +75,37 @@ def matrix_federation_endpoint(reactor, destination, ssl_context_factory=None, return transport_endpoint(reactor, domain, port, **endpoint_kw_args) +class SpiderEndpoint(object): + """An endpoint which refuses to connect to blacklisted IP addresses + Implements twisted.internet.interfaces.IStreamClientEndpoint. + """ + def __init__(self, reactor, host, port, blacklist, + endpoint=TCP4ClientEndpoint, endpoint_kw_args={}): + self.reactor = reactor + self.host = host + self.port = port + self.blacklist = blacklist + self.endpoint = endpoint + self.endpoint_kw_args = endpoint_kw_args + + @defer.inlineCallbacks + def connect(self, protocolFactory): + address = yield self.reactor.resolve(self.host) + + from netaddr import IPAddress + if IPAddress(address) in self.blacklist: + raise ConnectError( + "Refusing to spider blacklisted IP address %s" % address + ) + + logger.info("Connecting to %s:%s", address, self.port) + endpoint = self.endpoint( + self.reactor, address, self.port, **self.endpoint_kw_args + ) + connection = yield endpoint.connect(protocolFactory) + defer.returnValue(connection) + + class SRVClientEndpoint(object): """An endpoint which looks up SRV records for a service. Cycles through the list of servers starting with each call to connect @@ -120,7 +151,7 @@ class SRVClientEndpoint(object): return self.default_server else: raise ConnectError( - "Not server available for %s", self.service_name + "Not server available for %s" % self.service_name ) min_priority = self.servers[0].priority @@ -174,7 +205,7 @@ def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE, clock=t and answers[0].type == dns.SRV and answers[0].payload and answers[0].payload.target == dns.Name('.')): - raise ConnectError("Service %s unavailable", service_name) + raise ConnectError("Service %s unavailable" % service_name) for answer in answers: if answer.type != dns.SRV or not answer.payload: diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py index cf1414b4db..1adbdd9421 100644 --- a/synapse/python_dependencies.py +++ b/synapse/python_dependencies.py @@ -41,7 +41,11 @@ REQUIREMENTS = { CONDITIONAL_REQUIREMENTS = { "web_client": { "matrix_angular_sdk>=0.6.8": ["syweb>=0.6.8"], - } + }, + "preview_url": { + "lxml>=3.6.0": ["lxml"], + "netaddr>=0.7.18": ["netaddr"], + }, } diff --git a/synapse/rest/media/v1/base_resource.py b/synapse/rest/media/v1/base_resource.py index 58ef91c0b8..2b1938dc8e 100644 --- a/synapse/rest/media/v1/base_resource.py +++ b/synapse/rest/media/v1/base_resource.py @@ -72,6 +72,7 @@ class BaseMediaResource(Resource): self.store = hs.get_datastore() self.max_upload_size = hs.config.max_upload_size self.max_image_pixels = hs.config.max_image_pixels + self.max_spider_size = hs.config.max_spider_size self.filepaths = filepaths self.version_string = hs.version_string self.downloads = {} diff --git a/synapse/rest/media/v1/media_repository.py b/synapse/rest/media/v1/media_repository.py index 7dfb027dd1..97b7e84af9 100644 --- a/synapse/rest/media/v1/media_repository.py +++ b/synapse/rest/media/v1/media_repository.py @@ -17,6 +17,7 @@ from .upload_resource import UploadResource from .download_resource import DownloadResource from .thumbnail_resource import ThumbnailResource from .identicon_resource import IdenticonResource +from .preview_url_resource import PreviewUrlResource from .filepath import MediaFilePaths from twisted.web.resource import Resource @@ -78,3 +79,9 @@ class MediaRepositoryResource(Resource): self.putChild("download", DownloadResource(hs, filepaths)) self.putChild("thumbnail", ThumbnailResource(hs, filepaths)) self.putChild("identicon", IdenticonResource()) + if hs.config.url_preview_enabled: + try: + self.putChild("preview_url", PreviewUrlResource(hs, filepaths)) + except Exception as e: + logger.warn("Failed to mount preview_url") + logger.exception(e) diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py new file mode 100644 index 0000000000..8464fc0176 --- /dev/null +++ b/synapse/rest/media/v1/preview_url_resource.py @@ -0,0 +1,462 @@ +# -*- 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. + +from .base_resource import BaseMediaResource + +from twisted.web.server import NOT_DONE_YET +from twisted.internet import defer +from urlparse import urlparse, urlsplit, urlunparse + +from synapse.api.errors import ( + SynapseError, Codes, +) +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 ( + request_handler, respond_with_json_bytes +) +from synapse.util.async import ObservableDeferred +from synapse.util.stringutils import is_ascii + +import os +import re +import fnmatch +import cgi +import ujson as json + +import logging +logger = logging.getLogger(__name__) + +try: + from lxml import html +except ImportError: + pass + + +class PreviewUrlResource(BaseMediaResource): + isLeaf = True + + def __init__(self, hs, filepaths): + try: + if html: + pass + except: + raise RuntimeError("Disabling PreviewUrlResource as lxml not available") + + if not hasattr(hs.config, "url_preview_ip_range_blacklist"): + logger.warn( + "For security, you must specify an explicit target IP address " + "blacklist in url_preview_ip_range_blacklist for url previewing " + "to work" + ) + raise RuntimeError( + "Disabling PreviewUrlResource as " + "url_preview_ip_range_blacklist not specified" + ) + + BaseMediaResource.__init__(self, hs, filepaths) + self.client = SpiderHttpClient(hs) + if hasattr(hs.config, "url_preview_url_blacklist"): + self.url_preview_url_blacklist = hs.config.url_preview_url_blacklist + + # simple memory cache mapping urls to 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.downloads = {} + + def render_GET(self, request): + self._async_render_GET(request) + return NOT_DONE_YET + + @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() + + # impose the URL pattern blacklist + if hasattr(self, "url_preview_url_blacklist"): + url_tuple = 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 + ) + + # first check the memory cache - good to handle all the clients on this + # HS thundering away to preview the same URL at the same time. + og = self.cache.get(url) + if og: + respond_with_json_bytes(request, 200, json.dumps(og), send_cors=True) + return + + # then 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["download_ts"] + cache_result["expires"] > ts and + cache_result["response_code"] / 100 == 2 + ): + respond_with_json_bytes( + request, 200, cache_result["og"].encode('utf-8'), + send_cors=True + ) + return + + # Ensure only one download for a given URL is active at a time + download = self.downloads.get(url) + if download is None: + download = self._download_url(url, requester.user) + download = ObservableDeferred( + download, + consumeErrors=True + ) + self.downloads[url] = download + + @download.addBoth + def callback(media_info): + del self.downloads[url] + return media_info + media_info = yield download.observe() + + # FIXME: we should probably update our cache now anyway, so that + # even if the OG calculation raises, we don't keep hammering on the + # remote server. For now, leave it uncached to aid debugging OG + # calculation problems + + logger.debug("got media_info of '%s'" % media_info) + + if self._is_media(media_info['media_type']): + dims = yield self._generate_local_thumbnails( + media_info['filesystem_id'], media_info + ) + + 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 self._is_html(media_info['media_type']): + # TODO: somehow stop a big HTML tree from exploding synapse's RAM + + try: + tree = html.parse(media_info['filename']) + og = yield self._calc_og(tree, media_info, requester) + except UnicodeDecodeError: + # XXX: evil evil bodge + # Empirically, sites like google.com mix Latin-1 and utf-8 + # encodings in the same page. The rogue Latin-1 characters + # cause lxml to choke with a UnicodeDecodeError, so if we + # see this we go and do a manual decode of the HTML before + # handing it to lxml as utf-8 encoding, counter-intuitively, + # which seems to make it happier... + file = open(media_info['filename']) + body = file.read() + file.close() + tree = html.fromstring(body.decode('utf-8', 'ignore')) + og = yield self._calc_og(tree, media_info, requester) + + else: + logger.warn("Failed to find any OG data in %s", url) + og = {} + + logger.debug("Calculated OG for %s as %s" % (url, og)) + + # store OG in ephemeral in-memory cache + self.cache[url] = 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"], + json.dumps(og), + media_info["filesystem_id"], + media_info["created_ts"], + ) + + respond_with_json_bytes(request, 200, json.dumps(og), send_cors=True) + + + @defer.inlineCallbacks + def _calc_og(self, tree, media_info, requester): + # 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:')]"): + 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]") + og['og:title'] = title[0].text.strip() if title else 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'] = self._rebase_url(meta_image[0], media_info['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 * int(i.attrib['width']) * int(i.attrib['height']) + )) + if not images: + images = tree.xpath("//img[@src]") + if images: + og['og:image'] = images[0].attrib['src'] + + # 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( + self._rebase_url(og['og:image'], media_info['uri']), requester.user + ) + + if self._is_media(image_info['media_type']): + # TODO: make sure we don't choke on white-on-transparent images + dims = yield self._generate_local_thumbnails( + image_info['filesystem_id'], image_info + ) + 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"] + + 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... + #
,