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Support oEmbed for media previews. (#7920) 

Fixes previews of Twitter URLs by using their oEmbed endpoint to grab content.
This commit is contained in:
Patrick Cloke 2020-07-27 07:50:44 -04:00 committed by GitHub
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commit 3fc8fdd150
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3 changed files with 355 additions and 53 deletions
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1
changelog.d/7920.feature Normal file
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@ -0,0 +1 @@
Support oEmbed for media previews.

265
synapse/rest/media/v1/preview_url_resource.py
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@ -26,6 +26,7 @@ import traceback
from typing import Dict, Optional
from urllib import parse as urlparse
import attr
from canonicaljson import json
from twisted.internet import defer
@ -56,6 +57,65 @@ _content_type_match = re.compile(r'.*; *charset="?(.*?)"?(;|$)', flags=re.I)
OG_TAG_NAME_MAXLEN = 50
OG_TAG_VALUE_MAXLEN = 1000
ONE_HOUR = 60 * 60 * 1000
# A map of globs to API endpoints.
_oembed_globs = {
# Twitter.
"https://publish.twitter.com/oembed": [
"https://twitter.com/*/status/*",
"https://*.twitter.com/*/status/*",
"https://twitter.com/*/moments/*",
"https://*.twitter.com/*/moments/*",
# Include the HTTP versions too.
"http://twitter.com/*/status/*",
"http://*.twitter.com/*/status/*",
"http://twitter.com/*/moments/*",
"http://*.twitter.com/*/moments/*",
],
}
# Convert the globs to regular expressions.
_oembed_patterns = {}
for endpoint, globs in _oembed_globs.items():
for glob in globs:
# Convert the glob into a sane regular expression to match against. The
# rules followed will be slightly different for the domain portion vs.
# the rest.
#
# 1. The scheme must be one of HTTP / HTTPS (and have no globs).
# 2. The domain can have globs, but we limit it to characters that can
# reasonably be a domain part.
# TODO: This does not attempt to handle Unicode domain names.
# 3. Other parts allow a glob to be any one, or more, characters.
results = urlparse.urlparse(glob)
# Ensure the scheme does not have wildcards (and is a sane scheme).
if results.scheme not in {"http", "https"}:
raise ValueError("Insecure oEmbed glob scheme: %s" % (results.scheme,))
pattern = urlparse.urlunparse(
[
results.scheme,
re.escape(results.netloc).replace("\\*", "[a-zA-Z0-9_-]+"),
]
+ [re.escape(part).replace("\\*", ".+") for part in results[2:]]
)
_oembed_patterns[re.compile(pattern)] = endpoint
@attr.s
class OEmbedResult:
# Either HTML content or URL must be provided.
html = attr.ib(type=Optional[str])
url = attr.ib(type=Optional[str])
title = attr.ib(type=Optional[str])
# Number of seconds to cache the content.
cache_age = attr.ib(type=int)
class OEmbedError(Exception):
"""An error occurred processing the oEmbed object."""
class PreviewUrlResource(DirectServeJsonResource):
isLeaf = True
@ -99,7 +159,7 @@ class PreviewUrlResource(DirectServeJsonResource):
cache_name="url_previews",
clock=self.clock,
# don't spider URLs more often than once an hour
expiry_ms=60 * 60 * 1000,
expiry_ms=ONE_HOUR,
)
if self._worker_run_media_background_jobs:
@ -310,6 +370,87 @@ class PreviewUrlResource(DirectServeJsonResource):
return jsonog.encode("utf8")
def _get_oembed_url(self, url: str) -> Optional[str]:
"""
Check whether the URL should be downloaded as oEmbed content instead.
Params:
url: The URL to check.
Returns:
A URL to use instead or None if the original URL should be used.
"""
for url_pattern, endpoint in _oembed_patterns.items():
if url_pattern.fullmatch(url):
return endpoint
# No match.
return None
async def _get_oembed_content(self, endpoint: str, url: str) -> OEmbedResult:
"""
Request content from an oEmbed endpoint.
Params:
endpoint: The oEmbed API endpoint.
url: The URL to pass to the API.
Returns:
An object representing the metadata returned.
Raises:
OEmbedError if fetching or parsing of the oEmbed information fails.
"""
try:
logger.debug("Trying to get oEmbed content for url '%s'", url)
result = await self.client.get_json(
endpoint,
# TODO Specify max height / width.
# Note that only the JSON format is supported.
args={"url": url},
)
# Ensure there's a version of 1.0.
if result.get("version") != "1.0":
raise OEmbedError("Invalid version: %s" % (result.get("version"),))
oembed_type = result.get("type")
# Ensure the cache age is None or an int.
cache_age = result.get("cache_age")
if cache_age:
cache_age = int(cache_age)
oembed_result = OEmbedResult(None, None, result.get("title"), cache_age)
# HTML content.
if oembed_type == "rich":
oembed_result.html = result.get("html")
return oembed_result
if oembed_type == "photo":
oembed_result.url = result.get("url")
return oembed_result
# TODO Handle link and video types.
if "thumbnail_url" in result:
oembed_result.url = result.get("thumbnail_url")
return oembed_result
raise OEmbedError("Incompatible oEmbed information.")
except OEmbedError as e:
# Trap OEmbedErrors first so we can directly re-raise them.
logger.warning("Error parsing oEmbed metadata from %s: %r", url, e)
raise
except Exception as e:
# Trap any exception and let the code follow as usual.
# FIXME: pass through 404s and other error messages nicely
logger.warning("Error downloading oEmbed metadata from %s: %r", url, e)
raise OEmbedError() from e
async def _download_url(self, url, user):
# TODO: we should probably honour robots.txt... except in practice
# we're most likely being explicitly triggered by a human rather than a
@ -319,54 +460,90 @@ class PreviewUrlResource(DirectServeJsonResource):
file_info = FileInfo(server_name=None, file_id=file_id, url_cache=True)
with self.media_storage.store_into_file(file_info) as (f, fname, finish):
# If this URL can be accessed via oEmbed, use that instead.
url_to_download = url
oembed_url = self._get_oembed_url(url)
if oembed_url:
# The result might be a new URL to download, or it might be HTML content.
try:
logger.debug("Trying to get preview for url '%s'", url)
length, headers, uri, code = await self.client.get_file(
url,
output_stream=f,
max_size=self.max_spider_size,
headers={"Accept-Language": self.url_preview_accept_language},
)
except SynapseError:
# Pass SynapseErrors through directly, so that the servlet
# handler will return a SynapseError to the client instead of
# blank data or a 500.
raise
except DNSLookupError:
# DNS lookup returned no results
# Note: This will also be the case if one of the resolved IP
# addresses is blacklisted
raise SynapseError(
502,
"DNS resolution failure during URL preview generation",
Codes.UNKNOWN,
)
except Exception as e:
# FIXME: pass through 404s and other error messages nicely
logger.warning("Error downloading %s: %r", url, e)
oembed_result = await self._get_oembed_content(oembed_url, url)
if oembed_result.url:
url_to_download = oembed_result.url
elif oembed_result.html:
url_to_download = None
except OEmbedError:
# If an error occurs, try doing a normal preview.
pass
raise SynapseError(
500,
"Failed to download content: %s"
% (traceback.format_exception_only(sys.exc_info()[0], e),),
Codes.UNKNOWN,
)
await finish()
if url_to_download:
with self.media_storage.store_into_file(file_info) as (f, fname, finish):
try:
logger.debug("Trying to get preview for url '%s'", url_to_download)
length, headers, uri, code = await self.client.get_file(
url_to_download,
output_stream=f,
max_size=self.max_spider_size,
headers={"Accept-Language": self.url_preview_accept_language},
)
except SynapseError:
# Pass SynapseErrors through directly, so that the servlet
# handler will return a SynapseError to the client instead of
# blank data or a 500.
raise
except DNSLookupError:
# DNS lookup returned no results
# Note: This will also be the case if one of the resolved IP
# addresses is blacklisted
raise SynapseError(
502,
"DNS resolution failure during URL preview generation",
Codes.UNKNOWN,
)
except Exception as e:
# FIXME: pass through 404s and other error messages nicely
logger.warning("Error downloading %s: %r", url_to_download, e)
raise SynapseError(
500,
"Failed to download content: %s"
% (traceback.format_exception_only(sys.exc_info()[0], e),),
Codes.UNKNOWN,
)
await finish()
if b"Content-Type" in headers:
media_type = headers[b"Content-Type"][0].decode("ascii")
else:
media_type = "application/octet-stream"
download_name = get_filename_from_headers(headers)
# FIXME: we should calculate a proper expiration based on the
# Cache-Control and Expire headers. But for now, assume 1 hour.
expires = ONE_HOUR
etag = headers["ETag"][0] if "ETag" in headers else None
else:
html_bytes = oembed_result.html.encode("utf-8") # type: ignore
with self.media_storage.store_into_file(file_info) as (f, fname, finish):
f.write(html_bytes)
await finish()
media_type = "text/html"
download_name = oembed_result.title
length = len(html_bytes)
# If a specific cache age was not given, assume 1 hour.
expires = oembed_result.cache_age or ONE_HOUR
uri = oembed_url
code = 200
etag = None
try:
if b"Content-Type" in headers:
media_type = headers[b"Content-Type"][0].decode("ascii")
else:
media_type = "application/octet-stream"
time_now_ms = self.clock.time_msec()
download_name = get_filename_from_headers(headers)
await self.store.store_local_media(
media_id=file_id,
media_type=media_type,
time_now_ms=self.clock.time_msec(),
time_now_ms=time_now_ms,
upload_name=download_name,
media_length=length,
user_id=user,
@ -389,10 +566,8 @@ class PreviewUrlResource(DirectServeJsonResource):
"filename": fname,
"uri": uri,
"response_code": code,
# FIXME: we should calculate a proper expiration based on the
# Cache-Control and Expire headers. But for now, assume 1 hour.
"expires": 60 * 60 * 1000,
"etag": headers["ETag"][0] if "ETag" in headers else None,
"expires": expires,
"etag": etag,
}
def _start_expire_url_cache_data(self):
@ -449,7 +624,7 @@ class PreviewUrlResource(DirectServeJsonResource):
# These may be cached for a bit on the client (i.e., they
# may have a room open with a preview url thing open).
# So we wait a couple of days before deleting, just in case.
expire_before = now - 2 * 24 * 60 * 60 * 1000
expire_before = now - 2 * 24 * ONE_HOUR
media_ids = await self.store.get_url_cache_media_before(expire_before)
removed_media = []

142
tests/rest/media/v1/test_url_preview.py
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@ -12,8 +12,11 @@
# 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.
import json
import os
import re
from mock import patch
import attr
@ -131,7 +134,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
self.reactor.nameResolver = Resolver()
def test_cache_returns_correct_type(self):
self.lookups["matrix.org"] = [(IPv4Address, "8.8.8.8")]
self.lookups["matrix.org"] = [(IPv4Address, "10.1.2.3")]
request, channel = self.make_request(
"GET", "url_preview?url=http://matrix.org", shorthand=False
@ -187,7 +190,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
)
def test_non_ascii_preview_httpequiv(self):
self.lookups["matrix.org"] = [(IPv4Address, "8.8.8.8")]
self.lookups["matrix.org"] = [(IPv4Address, "10.1.2.3")]
end_content = (
b"<html><head>"
@ -221,7 +224,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
self.assertEqual(channel.json_body["og:title"], "\u0434\u043a\u0430")
def test_non_ascii_preview_content_type(self):
self.lookups["matrix.org"] = [(IPv4Address, "8.8.8.8")]
self.lookups["matrix.org"] = [(IPv4Address, "10.1.2.3")]
end_content = (
b"<html><head>"
@ -254,7 +257,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
self.assertEqual(channel.json_body["og:title"], "\u0434\u043a\u0430")
def test_overlong_title(self):
self.lookups["matrix.org"] = [(IPv4Address, "8.8.8.8")]
self.lookups["matrix.org"] = [(IPv4Address, "10.1.2.3")]
end_content = (
b"<html><head>"
@ -292,7 +295,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
"""
IP addresses can be previewed directly.
"""
self.lookups["example.com"] = [(IPv4Address, "8.8.8.8")]
self.lookups["example.com"] = [(IPv4Address, "10.1.2.3")]
request, channel = self.make_request(
"GET", "url_preview?url=http://example.com", shorthand=False
@ -439,7 +442,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
# Hardcode the URL resolving to the IP we want.
self.lookups["example.com"] = [
(IPv4Address, "1.1.1.2"),
(IPv4Address, "8.8.8.8"),
(IPv4Address, "10.1.2.3"),
]
request, channel = self.make_request(
@ -518,7 +521,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
"""
Accept-Language header is sent to the remote server
"""
self.lookups["example.com"] = [(IPv4Address, "8.8.8.8")]
self.lookups["example.com"] = [(IPv4Address, "10.1.2.3")]
# Build and make a request to the server
request, channel = self.make_request(
@ -562,3 +565,126 @@ class URLPreviewTests(unittest.HomeserverTestCase):
),
server.data,
)
def test_oembed_photo(self):
"""Test an oEmbed endpoint which returns a 'photo' type which redirects the preview to a new URL."""
# Route the HTTP version to an HTTP endpoint so that the tests work.
with patch.dict(
"synapse.rest.media.v1.preview_url_resource._oembed_patterns",
{
re.compile(
r"http://twitter\.com/.+/status/.+"
): "http://publish.twitter.com/oembed",
},
clear=True,
):
self.lookups["publish.twitter.com"] = [(IPv4Address, "10.1.2.3")]
self.lookups["cdn.twitter.com"] = [(IPv4Address, "10.1.2.3")]
result = {
"version": "1.0",
"type": "photo",
"url": "http://cdn.twitter.com/matrixdotorg",
}
oembed_content = json.dumps(result).encode("utf-8")
end_content = (
b"<html><head>"
b"<title>Some Title</title>"
b'<meta property="og:description" content="hi" />'
b"</head></html>"
)
request, channel = self.make_request(
"GET",
"url_preview?url=http://twitter.com/matrixdotorg/status/12345",
shorthand=False,
)
request.render(self.preview_url)
self.pump()
client = self.reactor.tcpClients[0][2].buildProtocol(None)
server = AccumulatingProtocol()
server.makeConnection(FakeTransport(client, self.reactor))
client.makeConnection(FakeTransport(server, self.reactor))
client.dataReceived(
(
b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
b'Content-Type: application/json; charset="utf8"\r\n\r\n'
)
% (len(oembed_content),)
+ oembed_content
)
self.pump()
client = self.reactor.tcpClients[1][2].buildProtocol(None)
server = AccumulatingProtocol()
server.makeConnection(FakeTransport(client, self.reactor))
client.makeConnection(FakeTransport(server, self.reactor))
client.dataReceived(
(
b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
b'Content-Type: text/html; charset="utf8"\r\n\r\n'
)
% (len(end_content),)
+ end_content
)
self.pump()
self.assertEqual(channel.code, 200)
self.assertEqual(
channel.json_body, {"og:title": "Some Title", "og:description": "hi"}
)
def test_oembed_rich(self):
"""Test an oEmbed endpoint which returns HTML content via the 'rich' type."""
# Route the HTTP version to an HTTP endpoint so that the tests work.
with patch.dict(
"synapse.rest.media.v1.preview_url_resource._oembed_patterns",
{
re.compile(
r"http://twitter\.com/.+/status/.+"
): "http://publish.twitter.com/oembed",
},
clear=True,
):
self.lookups["publish.twitter.com"] = [(IPv4Address, "10.1.2.3")]
result = {
"version": "1.0",
"type": "rich",
"html": "<div>Content Preview</div>",
}
end_content = json.dumps(result).encode("utf-8")
request, channel = self.make_request(
"GET",
"url_preview?url=http://twitter.com/matrixdotorg/status/12345",
shorthand=False,
)
request.render(self.preview_url)
self.pump()
client = self.reactor.tcpClients[0][2].buildProtocol(None)
server = AccumulatingProtocol()
server.makeConnection(FakeTransport(client, self.reactor))
client.makeConnection(FakeTransport(server, self.reactor))
client.dataReceived(
(
b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
b'Content-Type: application/json; charset="utf8"\r\n\r\n'
)
% (len(end_content),)
+ end_content
)
self.pump()
self.assertEqual(channel.code, 200)
self.assertEqual(
channel.json_body,
{"og:title": None, "og:description": "Content Preview"},
)