diff options
| -rw-r--r-- | changelog.d/9164.bugfix | 1 | ||||
| -rw-r--r-- | synapse/rest/media/v1/preview_url_resource.py | 44 | ||||
| -rw-r--r-- | tests/test_preview.py | 29 |
3 files changed, 64 insertions, 10 deletions
diff --git a/changelog.d/9164.bugfix b/changelog.d/9164.bugfix new file mode 100644 index 0000000000..1c54a256c1 --- /dev/null +++ b/changelog.d/9164.bugfix @@ -0,0 +1 @@ +Fix a long-standing bug where an internal server error was raised when attempting to preview an HTML document in an unknown character encoding. diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py index a632099167..bf3be653aa 100644 --- a/synapse/rest/media/v1/preview_url_resource.py +++ b/synapse/rest/media/v1/preview_url_resource.py @@ -386,7 +386,7 @@ class PreviewUrlResource(DirectServeJsonResource): """ Check whether the URL should be downloaded as oEmbed content instead. - Params: + Args: url: The URL to check. Returns: @@ -403,7 +403,7 @@ class PreviewUrlResource(DirectServeJsonResource): """ Request content from an oEmbed endpoint. - Params: + Args: endpoint: The oEmbed API endpoint. url: The URL to pass to the API. @@ -692,27 +692,51 @@ class PreviewUrlResource(DirectServeJsonResource): def decode_and_calc_og( body: bytes, media_uri: str, request_encoding: Optional[str] = None ) -> Dict[str, Optional[str]]: + """ + 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. + + 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. + """ # If there's no body, nothing useful is going to be found. if not body: return {} 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) - tree = etree.fromstring(body, parser) - og = _calc_og(tree, media_uri) + 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 {} + + 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) + return _calc_og(tree, media_uri) + + # Attempt to parse the body. If this fails, log and return no metadata. + try: + return _attempt_calc_og(body) 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 + return _attempt_calc_og(body.decode("utf-8", "ignore")) -def _calc_og(tree, media_uri: str) -> Dict[str, Optional[str]]: +def _calc_og(tree: "etree.Element", media_uri: str) -> Dict[str, Optional[str]]: # suck our tree into lxml and define our OG response. # if we see any image URLs in the OG response, then spider them diff --git a/tests/test_preview.py b/tests/test_preview.py index c19facc1cb..0c6cbbd921 100644 --- a/tests/test_preview.py +++ b/tests/test_preview.py @@ -261,3 +261,32 @@ class PreviewUrlTestCase(unittest.TestCase): html = "" og = decode_and_calc_og(html, "http://example.com/test.html") self.assertEqual(og, {}) + + def test_invalid_encoding(self): + """An invalid character encoding should be ignored and treated as UTF-8, if possible.""" + html = """ + <html> + <head><title>Foo</title></head> + <body> + Some text. + </body> + </html> + """ + og = decode_and_calc_og( + html, "http://example.com/test.html", "invalid-encoding" + ) + self.assertEqual(og, {"og:title": "Foo", "og:description": "Some text."}) + + def test_invalid_encoding2(self): + """A body which doesn't match the sent character encoding.""" + # Note that this contains an invalid UTF-8 sequence in the title. + html = b""" + <html> + <head><title>\xff\xff Foo</title></head> + <body> + Some text. + </body> + </html> + """ + og = decode_and_calc_og(html, "http://example.com/test.html") + self.assertEqual(og, {"og:title": "ÿÿ Foo", "og:description": "Some text."}) |