diff --git a/synapse/rest/media/v1/media_repository.py b/synapse/rest/media/v1/media_repository.py
index 7dfb027dd1..8f3491b91c 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 +79,5 @@ class MediaRepositoryResource(Resource):
self.putChild("download", DownloadResource(hs, filepaths))
self.putChild("thumbnail", ThumbnailResource(hs, filepaths))
self.putChild("identicon", IdenticonResource())
+ self.putChild("preview_url", PreviewUrlResource(hs, filepaths))
+
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..fb8ab3096f
--- /dev/null
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -0,0 +1,164 @@
+# 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 twisted.web.resource import Resource
+from lxml import html
+from synapse.http.client import SimpleHttpClient
+from synapse.http.server import respond_with_json_bytes
+from simplejson import json
+
+import logging
+logger = logging.getLogger(__name__)
+
+class PreviewUrlResource(Resource):
+ isLeaf = True
+
+ def __init__(self, hs, filepaths):
+ Resource.__init__(self)
+ self.client = SimpleHttpClient(hs)
+ self.filepaths = filepaths
+ self.max_spider_size = hs.config.max_spider_size
+ self.server_name = hs.hostname
+ self.clock = hs.get_clock()
+
+ def render_GET(self, request):
+ self._async_render_GET(request)
+ return NOT_DONE_YET
+
+ @request_handler
+ @defer.inlineCallbacks
+ def _async_render_GET(self, request):
+ url = request.args.get("url")
+
+ try:
+ # TODO: keep track of whether there's an ongoing request for this preview
+ # and block and return their details if there is one.
+
+ media_info = self._download_url(url)
+ except:
+ os.remove(fname)
+ raise
+
+ if self._is_media(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,
+ "og:image:width" : dims.width,
+ "og:image:height" : dims.height,
+ }
+
+ # define our OG response for this media
+ elif self._is_html(media_type):
+ tree = html.parse(media_info.filename)
+
+ # suck it up into lxml and define our OG response.
+ # if we see any 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" : "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"
+
+ og = {}
+ for tag in tree.xpath("//*/meta[starts-with(@property, 'og:')]"):
+ og[tag.attrib['property']] = tag.attrib['content']
+
+ # TODO: store our OG details in a cache (and expire them when stale)
+ # TODO: delete the content to stop diskfilling, as we only ever cared about its OG
+
+ respond_with_json_bytes(request, 200, json.dumps(og), send_cors=True)
+
+ def _download_url(url):
+ requester = yield self.auth.get_user_by_req(request)
+
+ # XXX: horrible duplication with base_resource's _download_remote_file()
+ file_id = random_string(24)
+
+ fname = self.filepaths.local_media_filepath(file_id)
+ self._makedirs(fname)
+
+ try:
+ with open(fname, "wb") as f:
+ length, headers = yield self.client.get_file(
+ url, output_stream=f, max_size=self.max_spider_size,
+ )
+ media_type = headers["Content-Type"][0]
+ 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=fname,
+ media_type=media_type,
+ time_now_ms=self.clock.time_msec(),
+ upload_name=download_name,
+ media_length=length,
+ user_id=requester.user,
+ )
+
+ except:
+ os.remove(fname)
+ raise
+
+ return {
+ "media_type": media_type,
+ "media_length": length,
+ "download_name": download_name,
+ "created_ts": time_now_ms,
+ "filesystem_id": file_id,
+ "filename": fname,
+ }
+
+
+ def _is_media(content_type):
+ if content_type.lower().startswith("image/"):
+ return True
+
+ def _is_html(content_type):
+ content_type = content_type.lower()
+ if content_type == "text/html" or
+ content_type.startswith("application/xhtml"):
+ return True
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