diff --git a/synapse/rest/media/v1/oembed.py b/synapse/rest/media/v1/oembed.py
index e04671fb95..6d7e1f9064 100644
--- a/synapse/rest/media/v1/oembed.py
+++ b/synapse/rest/media/v1/oembed.py
@@ -96,6 +96,32 @@ class OEmbedProvider:
# No match.
return None
+ def autodiscover_from_html(self, tree: "etree.Element") -> Optional[str]:
+ """
+ Search an HTML document for oEmbed autodiscovery information.
+
+ Args:
+ tree: The parsed HTML body.
+
+ Returns:
+ The URL to use for oEmbed information, or None if no URL was found.
+ """
+ # Search for link elements with the proper rel and type attributes.
+ for tag in tree.xpath(
+ "//link[@rel='alternate'][@type='application/json+oembed']"
+ ):
+ if "href" in tag.attrib:
+ return tag.attrib["href"]
+
+ # Some providers (e.g. Flickr) use alternative instead of alternate.
+ for tag in tree.xpath(
+ "//link[@rel='alternative'][@type='application/json+oembed']"
+ ):
+ if "href" in tag.attrib:
+ return tag.attrib["href"]
+
+ return None
+
def parse_oembed_response(self, url: str, raw_body: bytes) -> OEmbedResult:
"""
Parse the oEmbed response into an Open Graph response.
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 044f44a397..1fe0fc8aa9 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -22,7 +22,7 @@ import re
import shutil
import sys
import traceback
-from typing import TYPE_CHECKING, Dict, Generator, Iterable, Optional, Union
+from typing import TYPE_CHECKING, Dict, Generator, Iterable, Optional, Tuple, Union
from urllib import parse as urlparse
import attr
@@ -296,22 +296,32 @@ class PreviewUrlResource(DirectServeJsonResource):
body = file.read()
encoding = get_html_media_encoding(body, media_info.media_type)
- og = decode_and_calc_og(body, media_info.uri, encoding)
-
- await self._precache_image_url(user, media_info, og)
-
- elif oembed_url and _is_json(media_info.media_type):
- # Handle an oEmbed response.
- with open(media_info.filename, "rb") as file:
- body = file.read()
-
- oembed_response = self._oembed.parse_oembed_response(url, body)
- og = oembed_response.open_graph_result
-
- # Use the cache age from the oEmbed result, instead of the HTTP response.
- if oembed_response.cache_age is not None:
- expiration_ms = oembed_response.cache_age
+ tree = decode_body(body, encoding)
+ if tree is not None:
+ # Check if this HTML document points to oEmbed information and
+ # defer to that.
+ oembed_url = self._oembed.autodiscover_from_html(tree)
+ og = {}
+ if oembed_url:
+ oembed_info = await self._download_url(oembed_url, user)
+ og, expiration_ms = await self._handle_oembed_response(
+ url, oembed_info, expiration_ms
+ )
+
+ # If there was no oEmbed URL (or oEmbed parsing failed), attempt
+ # to generate the Open Graph information from the HTML.
+ if not oembed_url or not og:
+ og = _calc_og(tree, media_info.uri)
+
+ await self._precache_image_url(user, media_info, og)
+ else:
+ og = {}
+ elif oembed_url:
+ # Handle the oEmbed information.
+ og, expiration_ms = await self._handle_oembed_response(
+ url, media_info, expiration_ms
+ )
await self._precache_image_url(user, media_info, og)
else:
@@ -479,6 +489,39 @@ class PreviewUrlResource(DirectServeJsonResource):
else:
del og["og:image"]
+ async def _handle_oembed_response(
+ self, url: str, media_info: MediaInfo, expiration_ms: int
+ ) -> Tuple[JsonDict, int]:
+ """
+ Parse the downloaded oEmbed info.
+
+ Args:
+ url: The URL which is being previewed (not the one which was
+ requested).
+ media_info: The media being previewed.
+ expiration_ms: The length of time, in milliseconds, the media is valid for.
+
+ Returns:
+ A tuple of:
+ The Open Graph dictionary, if the oEmbed info can be parsed.
+ The (possibly updated) length of time, in milliseconds, the media is valid for.
+ """
+ # If JSON was not returned, there's nothing to do.
+ if not _is_json(media_info.media_type):
+ return {}, expiration_ms
+
+ with open(media_info.filename, "rb") as file:
+ body = file.read()
+
+ oembed_response = self._oembed.parse_oembed_response(url, body)
+ open_graph_result = oembed_response.open_graph_result
+
+ # Use the cache age from the oEmbed result, if one was given.
+ if open_graph_result and oembed_response.cache_age is not None:
+ expiration_ms = oembed_response.cache_age
+
+ return open_graph_result, expiration_ms
+
def _start_expire_url_cache_data(self) -> Deferred:
return run_as_background_process(
"expire_url_cache_data", self._expire_url_cache_data
@@ -631,26 +674,22 @@ def get_html_media_encoding(body: bytes, content_type: str) -> str:
return "utf-8"
-def decode_and_calc_og(
- body: bytes, media_uri: str, request_encoding: Optional[str] = None
-) -> JsonDict:
+def decode_body(
+ body: bytes, request_encoding: Optional[str] = None
+) -> Optional["etree.Element"]:
"""
- Calculate metadata for an HTML document.
-
- This uses lxml to parse the HTML document into the OG response. If errors
- occur during processing of the document, an empty response is returned.
+ This uses lxml to parse the HTML document.
Args:
body: The HTML document, as bytes.
- media_url: The URI used to download the body.
request_encoding: The character encoding of the body, as a string.
Returns:
- The OG response as a dictionary.
+ The parsed HTML body, or None if an error occurred during processed.
"""
# If there's no body, nothing useful is going to be found.
if not body:
- return {}
+ return None
from lxml import etree
@@ -662,25 +701,22 @@ def decode_and_calc_og(
parser = etree.HTMLParser(recover=True, encoding="utf-8")
except Exception as e:
logger.warning("Unable to create HTML parser: %s" % (e,))
- return {}
-
- def _attempt_calc_og(body_attempt: Union[bytes, str]) -> Dict[str, Optional[str]]:
- # Attempt to parse the body. If this fails, log and return no metadata.
- tree = etree.fromstring(body_attempt, parser)
-
- # The data was successfully parsed, but no tree was found.
- if tree is None:
- return {}
+ return None
- return _calc_og(tree, media_uri)
+ def _attempt_decode_body(
+ body_attempt: Union[bytes, str]
+ ) -> Optional["etree.Element"]:
+ # Attempt to parse the body. Returns None if the body was successfully
+ # parsed, but no tree was found.
+ return etree.fromstring(body_attempt, parser)
# Attempt to parse the body. If this fails, log and return no metadata.
try:
- return _attempt_calc_og(body)
+ return _attempt_decode_body(body)
except UnicodeDecodeError:
# blindly try decoding the body as utf-8, which seems to fix
# the charset mismatches on https://google.com
- return _attempt_calc_og(body.decode("utf-8", "ignore"))
+ return _attempt_decode_body(body.decode("utf-8", "ignore"))
def _calc_og(tree: "etree.Element", media_uri: str) -> Dict[str, Optional[str]]:
|
