diff options
Diffstat (limited to 'synapse/rest')
| -rw-r--r-- | synapse/rest/media/v1/preview_url_resource.py | 80 |
1 files changed, 39 insertions, 41 deletions
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py index 5bddd21ef1..7ee91a0c05 100644 --- a/synapse/rest/media/v1/preview_url_resource.py +++ b/synapse/rest/media/v1/preview_url_resource.py @@ -295,8 +295,7 @@ class PreviewUrlResource(DirectServeJsonResource): with open(media_info.filename, "rb") as file: body = file.read() - encoding = get_html_media_encoding(body, media_info.media_type) - tree = decode_body(body, encoding) + tree = decode_body(body, media_info.uri, media_info.media_type) if tree is not None: # Check if this HTML document points to oEmbed information and # defer to that. @@ -632,16 +631,19 @@ class PreviewUrlResource(DirectServeJsonResource): logger.debug("No media removed from url cache") -def get_html_media_encoding(body: bytes, content_type: str) -> str: +def get_html_media_encodings(body: bytes, content_type: Optional[str]) -> Iterable[str]: """ - Get the encoding of the body based on the (presumably) HTML body or media_type. + Get potential encoding of the body based on the (presumably) HTML body or the content-type header. The precedence used for finding a character encoding is: - 1. meta tag with a charset declared. + 1. <meta> tag with a charset declared. 2. The XML document's character encoding attribute. 3. The Content-Type header. - 4. Fallback to UTF-8. + 4. Fallback to utf-8. + 5. Fallback to windows-1252. + + This roughly follows the algorithm used by BeautifulSoup's bs4.dammit.EncodingDetector. Args: body: The HTML document, as bytes. @@ -653,36 +655,39 @@ def get_html_media_encoding(body: bytes, content_type: str) -> str: # Limit searches to the first 1kb, since it ought to be at the top. body_start = body[:1024] - # Let's try and figure out if it has an encoding set in a meta tag. + # Check if it has an encoding set in a meta tag. match = _charset_match.search(body_start) if match: - return match.group(1).decode("ascii") + yield match.group(1).decode("ascii") # TODO Support <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> - # If we didn't find a match, see if it an XML document with an encoding. + # Check if it has an XML document with an encoding. match = _xml_encoding_match.match(body_start) if match: - return match.group(1).decode("ascii") + yield 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. - content_match = _content_type_match.match(content_type) - if content_match: - return content_match.group(1) + # Check the HTTP Content-Type header for a character set. + if content_type: + content_match = _content_type_match.match(content_type) + if content_match: + yield content_match.group(1) - return "utf-8" + # Finally, fallback to UTF-8, then windows-1252. + yield "utf-8" + yield "windows-1252" def decode_body( - body: bytes, request_encoding: Optional[str] = None + body: bytes, uri: str, content_type: Optional[str] = None ) -> Optional["etree.Element"]: """ This uses lxml to parse the HTML document. Args: body: The HTML document, as bytes. - request_encoding: The character encoding of the body, as a string. + uri: The URI used to download the body. + content_type: The Content-Type header. Returns: The parsed HTML body, or None if an error occurred during processed. @@ -691,32 +696,25 @@ def decode_body( if not body: return None + for encoding in get_html_media_encodings(body, content_type): + try: + body_str = body.decode(encoding) + except Exception: + pass + else: + break + else: + logger.warning("Unable to decode HTML body for %s", uri) + return None + from lxml import etree - # Create an HTML parser. If this fails, log and return no metadata. - try: - parser = etree.HTMLParser(recover=True, encoding=request_encoding) - except LookupError: - # blindly consider the encoding as utf-8. - parser = etree.HTMLParser(recover=True, encoding="utf-8") - except Exception as e: - logger.warning("Unable to create HTML parser: %s" % (e,)) - return None + # Create an HTML parser. + parser = etree.HTMLParser(recover=True, encoding="utf-8") - 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_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_decode_body(body.decode("utf-8", "ignore")) + # Attempt to parse the body. Returns None if the body was successfully + # parsed, but no tree was found. + return etree.fromstring(body_str, parser) def _calc_og(tree: "etree.Element", media_uri: str) -> Dict[str, Optional[str]]: |