# Copyright 2014-2016 OpenMarket Ltd # Copyright 2019-2021 The Matrix.org Foundation C.I.C. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # 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 logging import os import urllib from types import TracebackType from typing import Awaitable, Dict, Generator, List, Optional, Tuple, Type import attr from twisted.internet.interfaces import IConsumer from twisted.protocols.basic import FileSender from twisted.web.server import Request from synapse.api.errors import Codes, SynapseError, cs_error from synapse.http.server import finish_request, respond_with_json from synapse.http.site import SynapseRequest from synapse.logging.context import make_deferred_yieldable from synapse.util.stringutils import is_ascii, parse_and_validate_server_name logger = logging.getLogger(__name__) # list all text content types that will have the charset default to UTF-8 when # none is given TEXT_CONTENT_TYPES = [ "text/css", "text/csv", "text/html", "text/calendar", "text/plain", "text/javascript", "application/json", "application/ld+json", "application/rtf", "image/svg+xml", "text/xml", ] def parse_media_id(request: Request) -> Tuple[str, str, Optional[str]]: """Parses the server name, media ID and optional file name from the request URI Also performs some rough validation on the server name. Args: request: The `Request`. Returns: A tuple containing the parsed server name, media ID and optional file name. Raises: SynapseError(404): if parsing or validation fail for any reason """ try: # The type on postpath seems incorrect in Twisted 21.2.0. postpath: List[bytes] = request.postpath # type: ignore assert postpath # This allows users to append e.g. /test.png to the URL. Useful for # clients that parse the URL to see content type. server_name_bytes, media_id_bytes = postpath[:2] server_name = server_name_bytes.decode("utf-8") media_id = media_id_bytes.decode("utf8") # Validate the server name, raising if invalid parse_and_validate_server_name(server_name) file_name = None if len(postpath) > 2: try: file_name = urllib.parse.unquote(postpath[-1].decode("utf-8")) except UnicodeDecodeError: pass return server_name, media_id, file_name except Exception: raise SynapseError( 404, "Invalid media id token %r" % (request.postpath,), Codes.UNKNOWN ) def respond_404(request: SynapseRequest) -> None: respond_with_json( request, 404, cs_error("Not found %r" % (request.postpath,), code=Codes.NOT_FOUND), send_cors=True, ) async def respond_with_file( request: SynapseRequest, media_type: str, file_path: str, file_size: Optional[int] = None, upload_name: Optional[str] = None, ) -> None: logger.debug("Responding with %r", file_path) if os.path.isfile(file_path): if file_size is None: stat = os.stat(file_path) file_size = stat.st_size add_file_headers(request, media_type, file_size, upload_name) with open(file_path, "rb") as f: await make_deferred_yieldable(FileSender().beginFileTransfer(f, request)) finish_request(request) else: respond_404(request) def add_file_headers( request: Request, media_type: str, file_size: Optional[int], upload_name: Optional[str], ) -> None: """Adds the correct response headers in preparation for responding with the media. Args: request media_type: The media/content type. file_size: Size in bytes of the media, if known. upload_name: The name of the requested file, if any. """ def _quote(x: str) -> str: return urllib.parse.quote(x.encode("utf-8")) # Default to a UTF-8 charset for text content types. # ex, uses UTF-8 for 'text/css' but not 'text/css; charset=UTF-16' if media_type.lower() in TEXT_CONTENT_TYPES: content_type = media_type + "; charset=UTF-8" else: content_type = media_type request.setHeader(b"Content-Type", content_type.encode("UTF-8")) if upload_name: # RFC6266 section 4.1 [1] defines both `filename` and `filename*`. # # `filename` is defined to be a `value`, which is defined by RFC2616 # section 3.6 [2] to be a `token` or a `quoted-string`, where a `token` # is (essentially) a single US-ASCII word, and a `quoted-string` is a # US-ASCII string surrounded by double-quotes, using backslash as an # escape character. Note that %-encoding is *not* permitted. # # `filename*` is defined to be an `ext-value`, which is defined in # RFC5987 section 3.2.1 [3] to be `charset "'" [ language ] "'" value-chars`, # where `value-chars` is essentially a %-encoded string in the given charset. # # [1]: https://tools.ietf.org/html/rfc6266#section-4.1 # [2]: https://tools.ietf.org/html/rfc2616#section-3.6 # [3]: https://tools.ietf.org/html/rfc5987#section-3.2.1 # We avoid the quoted-string version of `filename`, because (a) synapse didn't # correctly interpret those as of 0.99.2 and (b) they are a bit of a pain and we # may as well just do the filename* version. if _can_encode_filename_as_token(upload_name): disposition = "inline; filename=%s" % (upload_name,) else: disposition = "inline; filename*=utf-8''%s" % (_quote(upload_name),) request.setHeader(b"Content-Disposition", disposition.encode("ascii")) # cache for at least a day. # XXX: we might want to turn this off for data we don't want to # recommend caching as it's sensitive or private - or at least # select private. don't bother setting Expires as all our # clients are smart enough to be happy with Cache-Control request.setHeader(b"Cache-Control", b"public,max-age=86400,s-maxage=86400") if file_size is not None: request.setHeader(b"Content-Length", b"%d" % (file_size,)) # Tell web crawlers to not index, archive, or follow links in media. This # should help to prevent things in the media repo from showing up in web # search results. request.setHeader(b"X-Robots-Tag", "noindex, nofollow, noarchive, noimageindex") # separators as defined in RFC2616. SP and HT are handled separately. # see _can_encode_filename_as_token. _FILENAME_SEPARATOR_CHARS = { "(", ")", "<", ">", "@", ",", ";", ":", "\\", '"', "/", "[", "]", "?", "=", "{", "}", } def _can_encode_filename_as_token(x: str) -> bool: for c in x: # from RFC2616: # # token = 1*<any CHAR except CTLs or separators> # # separators = "(" | ")" | "<" | ">" | "@" # | "," | ";" | ":" | "\" | <"> # | "/" | "[" | "]" | "?" | "=" # | "{" | "}" | SP | HT # # CHAR = <any US-ASCII character (octets 0 - 127)> # # CTL = <any US-ASCII control character # (octets 0 - 31) and DEL (127)> # if ord(c) >= 127 or ord(c) <= 32 or c in _FILENAME_SEPARATOR_CHARS: return False return True async def respond_with_responder( request: SynapseRequest, responder: "Optional[Responder]", media_type: str, file_size: Optional[int], upload_name: Optional[str] = None, ) -> None: """Responds to the request with given responder. If responder is None then returns 404. Args: request responder media_type: The media/content type. file_size: Size in bytes of the media. If not known it should be None upload_name: The name of the requested file, if any. """ if not responder: respond_404(request) return # If we have a responder we *must* use it as a context manager. with responder: if request._disconnected: logger.warning( "Not sending response to request %s, already disconnected.", request ) return logger.debug("Responding to media request with responder %s", responder) add_file_headers(request, media_type, file_size, upload_name) try: await responder.write_to_consumer(request) except Exception as e: # The majority of the time this will be due to the client having gone # away. Unfortunately, Twisted simply throws a generic exception at us # in that case. logger.warning("Failed to write to consumer: %s %s", type(e), e) # Unregister the producer, if it has one, so Twisted doesn't complain if request.producer: request.unregisterProducer() finish_request(request) class Responder: """Represents a response that can be streamed to the requester. Responder is a context manager which *must* be used, so that any resources held can be cleaned up. """ def write_to_consumer(self, consumer: IConsumer) -> Awaitable: """Stream response into consumer Args: consumer: The consumer to stream into. Returns: Resolves once the response has finished being written """ def __enter__(self) -> None: pass def __exit__( self, exc_type: Optional[Type[BaseException]], exc_val: Optional[BaseException], exc_tb: Optional[TracebackType], ) -> None: pass @attr.s(slots=True, frozen=True, auto_attribs=True) class ThumbnailInfo: """Details about a generated thumbnail.""" width: int height: int method: str # Content type of thumbnail, e.g. image/png type: str # The size of the media file, in bytes. length: Optional[int] = None @attr.s(slots=True, frozen=True, auto_attribs=True) class FileInfo: """Details about a requested/uploaded file.""" # The server name where the media originated from, or None if local. server_name: Optional[str] # The local ID of the file. For local files this is the same as the media_id file_id: str # If the file is for the url preview cache url_cache: bool = False # Whether the file is a thumbnail or not. thumbnail: Optional[ThumbnailInfo] = None # The below properties exist to maintain compatibility with third-party modules. @property def thumbnail_width(self) -> Optional[int]: if not self.thumbnail: return None return self.thumbnail.width @property def thumbnail_height(self) -> Optional[int]: if not self.thumbnail: return None return self.thumbnail.height @property def thumbnail_method(self) -> Optional[str]: if not self.thumbnail: return None return self.thumbnail.method @property def thumbnail_type(self) -> Optional[str]: if not self.thumbnail: return None return self.thumbnail.type @property def thumbnail_length(self) -> Optional[int]: if not self.thumbnail: return None return self.thumbnail.length def get_filename_from_headers(headers: Dict[bytes, List[bytes]]) -> Optional[str]: """ Get the filename of the downloaded file by inspecting the Content-Disposition HTTP header. Args: headers: The HTTP request headers. Returns: The filename, or None. """ content_disposition = headers.get(b"Content-Disposition", [b""]) # No header, bail out. if not content_disposition[0]: return None _, params = _parse_header(content_disposition[0]) upload_name = None # First check if there is a valid UTF-8 filename upload_name_utf8 = params.get(b"filename*", None) if upload_name_utf8: if upload_name_utf8.lower().startswith(b"utf-8''"): upload_name_utf8 = upload_name_utf8[7:] # We have a filename*= section. This MUST be ASCII, and any UTF-8 # bytes are %-quoted. try: # Once it is decoded, we can then unquote the %-encoded # parts strictly into a unicode string. upload_name = urllib.parse.unquote( upload_name_utf8.decode("ascii"), errors="strict" ) except UnicodeDecodeError: # Incorrect UTF-8. pass # If there isn't check for an ascii name. if not upload_name: upload_name_ascii = params.get(b"filename", None) if upload_name_ascii and is_ascii(upload_name_ascii): upload_name = upload_name_ascii.decode("ascii") # This may be None here, indicating we did not find a matching name. return upload_name def _parse_header(line: bytes) -> Tuple[bytes, Dict[bytes, bytes]]: """Parse a Content-type like header. Cargo-culted from `cgi`, but works on bytes rather than strings. Args: line: header to be parsed Returns: The main content-type, followed by the parameter dictionary """ parts = _parseparam(b";" + line) key = next(parts) pdict = {} for p in parts: i = p.find(b"=") if i >= 0: name = p[:i].strip().lower() value = p[i + 1 :].strip() # strip double-quotes if len(value) >= 2 and value[0:1] == value[-1:] == b'"': value = value[1:-1] value = value.replace(b"\\\\", b"\\").replace(b'\\"', b'"') pdict[name] = value return key, pdict def _parseparam(s: bytes) -> Generator[bytes, None, None]: """Generator which splits the input on ;, respecting double-quoted sequences Cargo-culted from `cgi`, but works on bytes rather than strings. Args: s: header to be parsed Returns: The split input """ while s[:1] == b";": s = s[1:] # look for the next ; end = s.find(b";") # if there is an odd number of " marks between here and the next ;, skip to the # next ; instead while end > 0 and (s.count(b'"', 0, end) - s.count(b'\\"', 0, end)) % 2: end = s.find(b";", end + 1) if end < 0: end = len(s) f = s[:end] yield f.strip() s = s[end:]