mirror of
https://git.anonymousland.org/anonymousland/synapse.git
synced 2025-07-30 15:38:33 -04:00
Support rendering previews with data: URLs in them (#11767)
Images which are data URLs will no longer break URL previews and will properly be "downloaded" and thumbnailed.
This commit is contained in:
Patrick Cloke
GitHub
parent
c3040dd5cc
commit
807efd26ae
6 changed files with 299 additions and 74 deletions
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@ -21,8 +21,9 @@ import re
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import shutil
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import sys
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import traceback
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from typing import TYPE_CHECKING, Iterable, Optional, Tuple
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from typing import TYPE_CHECKING, BinaryIO, Iterable, Optional, Tuple
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from urllib import parse as urlparse
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from urllib.request import urlopen
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import attr
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@ -70,6 +71,17 @@ ONE_DAY = 24 * ONE_HOUR
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IMAGE_CACHE_EXPIRY_MS = 2 * ONE_DAY
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@attr.s(slots=True, frozen=True, auto_attribs=True)
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class DownloadResult:
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length: int
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uri: str
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response_code: int
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media_type: str
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download_name: Optional[str]
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expires: int
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etag: Optional[str]
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@attr.s(slots=True, frozen=True, auto_attribs=True)
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class MediaInfo:
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"""
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@ -256,7 +268,7 @@ class PreviewUrlResource(DirectServeJsonResource):
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if oembed_url:
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url_to_download = oembed_url
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media_info = await self._download_url(url_to_download, user)
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media_info = await self._handle_url(url_to_download, user)
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logger.debug("got media_info of '%s'", media_info)
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@ -297,7 +309,9 @@ class PreviewUrlResource(DirectServeJsonResource):
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oembed_url = self._oembed.autodiscover_from_html(tree)
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og_from_oembed: JsonDict = {}
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if oembed_url:
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oembed_info = await self._download_url(oembed_url, user)
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oembed_info = await self._handle_url(
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oembed_url, user, allow_data_urls=True
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)
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(
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og_from_oembed,
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author_name,
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@ -367,7 +381,135 @@ class PreviewUrlResource(DirectServeJsonResource):
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return jsonog.encode("utf8")
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async def _download_url(self, url: str, user: UserID) -> MediaInfo:
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async def _download_url(self, url: str, output_stream: BinaryIO) -> DownloadResult:
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"""
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Fetches a remote URL and parses the headers.
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Args:
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url: The URL to fetch.
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output_stream: The stream to write the content to.
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Returns:
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A tuple of:
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Media length, URL downloaded, the HTTP response code,
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the media type, the downloaded file name, the number of
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milliseconds the result is valid for, the etag header.
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"""
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try:
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logger.debug("Trying to get preview for url '%s'", url)
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length, headers, uri, code = await self.client.get_file(
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url,
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output_stream=output_stream,
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max_size=self.max_spider_size,
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headers={"Accept-Language": self.url_preview_accept_language},
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)
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except SynapseError:
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# Pass SynapseErrors through directly, so that the servlet
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# handler will return a SynapseError to the client instead of
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# blank data or a 500.
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raise
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except DNSLookupError:
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# DNS lookup returned no results
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# Note: This will also be the case if one of the resolved IP
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# addresses is blacklisted
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raise SynapseError(
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502,
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"DNS resolution failure during URL preview generation",
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Codes.UNKNOWN,
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)
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except Exception as e:
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# FIXME: pass through 404s and other error messages nicely
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logger.warning("Error downloading %s: %r", url, e)
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raise SynapseError(
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500,
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"Failed to download content: %s"
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% (traceback.format_exception_only(sys.exc_info()[0], e),),
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Codes.UNKNOWN,
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)
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if b"Content-Type" in headers:
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media_type = headers[b"Content-Type"][0].decode("ascii")
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else:
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media_type = "application/octet-stream"
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download_name = get_filename_from_headers(headers)
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# FIXME: we should calculate a proper expiration based on the
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# Cache-Control and Expire headers. But for now, assume 1 hour.
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expires = ONE_HOUR
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etag = headers[b"ETag"][0].decode("ascii") if b"ETag" in headers else None
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return DownloadResult(
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length, uri, code, media_type, download_name, expires, etag
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)
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async def _parse_data_url(
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self, url: str, output_stream: BinaryIO
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) -> DownloadResult:
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"""
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Parses a data: URL.
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Args:
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url: The URL to parse.
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output_stream: The stream to write the content to.
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Returns:
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A tuple of:
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Media length, URL downloaded, the HTTP response code,
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the media type, the downloaded file name, the number of
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milliseconds the result is valid for, the etag header.
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"""
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try:
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logger.debug("Trying to parse data url '%s'", url)
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with urlopen(url) as url_info:
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# TODO Can this be more efficient.
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output_stream.write(url_info.read())
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except Exception as e:
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logger.warning("Error parsing data: URL %s: %r", url, e)
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raise SynapseError(
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500,
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"Failed to parse data URL: %s"
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% (traceback.format_exception_only(sys.exc_info()[0], e),),
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Codes.UNKNOWN,
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)
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return DownloadResult(
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# Read back the length that has been written.
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length=output_stream.tell(),
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uri=url,
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# If it was parsed, consider this a 200 OK.
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response_code=200,
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# urlopen shoves the media-type from the data URL into the content type
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# header object.
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media_type=url_info.headers.get_content_type(),
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# Some features are not supported by data: URLs.
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download_name=None,
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expires=ONE_HOUR,
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etag=None,
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)
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async def _handle_url(
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self, url: str, user: UserID, allow_data_urls: bool = False
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) -> MediaInfo:
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"""
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Fetches content from a URL and parses the result to generate a MediaInfo.
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It uses the media storage provider to persist the fetched content and
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stores the mapping into the database.
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Args:
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url: The URL to fetch.
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user: The user who ahs requested this URL.
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allow_data_urls: True if data URLs should be allowed.
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Returns:
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A MediaInfo object describing the fetched content.
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"""
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# TODO: we should probably honour robots.txt... except in practice
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# we're most likely being explicitly triggered by a human rather than a
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# bot, so are we really a robot?
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@ -377,61 +519,27 @@ class PreviewUrlResource(DirectServeJsonResource):
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file_info = FileInfo(server_name=None, file_id=file_id, url_cache=True)
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with self.media_storage.store_into_file(file_info) as (f, fname, finish):
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try:
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logger.debug("Trying to get preview for url '%s'", url)
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length, headers, uri, code = await self.client.get_file(
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url,
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output_stream=f,
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max_size=self.max_spider_size,
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headers={"Accept-Language": self.url_preview_accept_language},
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)
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except SynapseError:
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# Pass SynapseErrors through directly, so that the servlet
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# handler will return a SynapseError to the client instead of
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# blank data or a 500.
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raise
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except DNSLookupError:
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# DNS lookup returned no results
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# Note: This will also be the case if one of the resolved IP
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# addresses is blacklisted
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raise SynapseError(
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502,
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"DNS resolution failure during URL preview generation",
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Codes.UNKNOWN,
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)
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except Exception as e:
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# FIXME: pass through 404s and other error messages nicely
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logger.warning("Error downloading %s: %r", url, e)
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if url.startswith("data:"):
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if not allow_data_urls:
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raise SynapseError(
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500, "Previewing of data: URLs is forbidden", Codes.UNKNOWN
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)
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raise SynapseError(
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500,
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"Failed to download content: %s"
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% (traceback.format_exception_only(sys.exc_info()[0], e),),
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Codes.UNKNOWN,
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)
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await finish()
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if b"Content-Type" in headers:
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media_type = headers[b"Content-Type"][0].decode("ascii")
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download_result = await self._parse_data_url(url, f)
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else:
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media_type = "application/octet-stream"
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download_result = await self._download_url(url, f)
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download_name = get_filename_from_headers(headers)
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# FIXME: we should calculate a proper expiration based on the
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# Cache-Control and Expire headers. But for now, assume 1 hour.
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expires = ONE_HOUR
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etag = headers[b"ETag"][0].decode("ascii") if b"ETag" in headers else None
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await finish()
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try:
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time_now_ms = self.clock.time_msec()
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await self.store.store_local_media(
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media_id=file_id,
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media_type=media_type,
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media_type=download_result.media_type,
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time_now_ms=time_now_ms,
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upload_name=download_name,
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media_length=length,
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upload_name=download_result.download_name,
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media_length=download_result.length,
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user_id=user,
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url_cache=url,
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)
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@ -444,16 +552,16 @@ class PreviewUrlResource(DirectServeJsonResource):
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raise
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return MediaInfo(
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media_type=media_type,
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media_length=length,
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download_name=download_name,
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media_type=download_result.media_type,
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media_length=download_result.length,
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download_name=download_result.download_name,
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created_ts_ms=time_now_ms,
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filesystem_id=file_id,
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filename=fname,
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uri=uri,
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response_code=code,
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expires=expires,
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etag=etag,
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uri=download_result.uri,
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response_code=download_result.response_code,
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expires=download_result.expires,
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etag=download_result.etag,
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)
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async def _precache_image_url(
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@ -474,8 +582,8 @@ class PreviewUrlResource(DirectServeJsonResource):
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# FIXME: it might be cleaner to use the same flow as the main /preview_url
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# request itself and benefit from the same caching etc. But for now we
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# just rely on the caching on the master request to speed things up.
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image_info = await self._download_url(
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rebase_url(og["og:image"], media_info.uri), user
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image_info = await self._handle_url(
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rebase_url(og["og:image"], media_info.uri), user, allow_data_urls=True
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)
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if _is_media(image_info.media_type):
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