1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
|
# Copyright 2014-2016 OpenMarket Ltd
# Copyright 2018 New Vector Ltd
#
# 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 abc
import collections
import html
import logging
import types
import urllib
from http import HTTPStatus
from inspect import isawaitable
from typing import (
TYPE_CHECKING,
Any,
Awaitable,
Callable,
Dict,
Iterable,
Iterator,
List,
Optional,
Pattern,
Tuple,
Union,
)
import jinja2
from canonicaljson import encode_canonical_json
from typing_extensions import Protocol
from zope.interface import implementer
from twisted.internet import defer, interfaces
from twisted.python import failure
from twisted.web import resource
from twisted.web.server import NOT_DONE_YET, Request
from twisted.web.static import File
from twisted.web.util import redirectTo
from synapse.api.errors import (
CodeMessageException,
Codes,
RedirectException,
SynapseError,
UnrecognizedRequestError,
)
from synapse.http.site import SynapseRequest
from synapse.logging.context import defer_to_thread, preserve_fn, run_in_background
from synapse.logging.opentracing import trace_servlet
from synapse.util import json_encoder
from synapse.util.caches import intern_dict
from synapse.util.iterutils import chunk_seq
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
HTML_ERROR_TEMPLATE = """<!DOCTYPE html>
<html lang=en>
<head>
<meta charset="utf-8">
<title>Error {code}</title>
</head>
<body>
<p>{msg}</p>
</body>
</html>
"""
def return_json_error(f: failure.Failure, request: SynapseRequest) -> None:
"""Sends a JSON error response to clients."""
if f.check(SynapseError):
# mypy doesn't understand that f.check asserts the type.
exc: SynapseError = f.value # type: ignore
error_code = exc.code
error_dict = exc.error_dict()
logger.info("%s SynapseError: %s - %s", request, error_code, exc.msg)
else:
error_code = 500
error_dict = {"error": "Internal server error", "errcode": Codes.UNKNOWN}
logger.error(
"Failed handle request via %r: %r",
request.request_metrics.name,
request,
exc_info=(f.type, f.value, f.getTracebackObject()), # type: ignore[arg-type]
)
# Only respond with an error response if we haven't already started writing,
# otherwise lets just kill the connection
if request.startedWriting:
if request.transport:
try:
request.transport.abortConnection()
except Exception:
# abortConnection throws if the connection is already closed
pass
else:
respond_with_json(
request,
error_code,
error_dict,
send_cors=True,
)
def return_html_error(
f: failure.Failure,
request: Request,
error_template: Union[str, jinja2.Template],
) -> None:
"""Sends an HTML error page corresponding to the given failure.
Handles RedirectException and other CodeMessageExceptions (such as SynapseError)
Args:
f: the error to report
request: the failing request
error_template: the HTML template. Can be either a string (with `{code}`,
`{msg}` placeholders), or a jinja2 template
"""
if f.check(CodeMessageException):
# mypy doesn't understand that f.check asserts the type.
cme: CodeMessageException = f.value # type: ignore
code = cme.code
msg = cme.msg
if isinstance(cme, RedirectException):
logger.info("%s redirect to %s", request, cme.location)
request.setHeader(b"location", cme.location)
request.cookies.extend(cme.cookies)
elif isinstance(cme, SynapseError):
logger.info("%s SynapseError: %s - %s", request, code, msg)
else:
logger.error(
"Failed handle request %r",
request,
exc_info=(f.type, f.value, f.getTracebackObject()), # type: ignore[arg-type]
)
else:
code = HTTPStatus.INTERNAL_SERVER_ERROR
msg = "Internal server error"
logger.error(
"Failed handle request %r",
request,
exc_info=(f.type, f.value, f.getTracebackObject()), # type: ignore[arg-type]
)
if isinstance(error_template, str):
body = error_template.format(code=code, msg=html.escape(msg))
else:
body = error_template.render(code=code, msg=msg)
respond_with_html(request, code, body)
def wrap_async_request_handler(h):
"""Wraps an async request handler so that it calls request.processing.
This helps ensure that work done by the request handler after the request is completed
is correctly recorded against the request metrics/logs.
The handler method must have a signature of "handle_foo(self, request)",
where "request" must be a SynapseRequest.
The handler may return a deferred, in which case the completion of the request isn't
logged until the deferred completes.
"""
async def wrapped_async_request_handler(self, request):
with request.processing():
await h(self, request)
# we need to preserve_fn here, because the synchronous render method won't yield for
# us (obviously)
return preserve_fn(wrapped_async_request_handler)
# Type of a callback method for processing requests
# it is actually called with a SynapseRequest and a kwargs dict for the params,
# but I can't figure out how to represent that.
ServletCallback = Callable[
..., Union[None, Awaitable[None], Tuple[int, Any], Awaitable[Tuple[int, Any]]]
]
class HttpServer(Protocol):
"""Interface for registering callbacks on a HTTP server"""
def register_paths(
self,
method: str,
path_patterns: Iterable[Pattern],
callback: ServletCallback,
servlet_classname: str,
) -> None:
"""Register a callback that gets fired if we receive a http request
with the given method for a path that matches the given regex.
If the regex contains groups these gets passed to the callback via
an unpacked tuple.
Args:
method: The HTTP method to listen to.
path_patterns: The regex used to match requests.
callback: The function to fire if we receive a matched
request. The first argument will be the request object and
subsequent arguments will be any matched groups from the regex.
This should return either tuple of (code, response), or None.
servlet_classname (str): The name of the handler to be used in prometheus
and opentracing logs.
"""
pass
class _AsyncResource(resource.Resource, metaclass=abc.ABCMeta):
"""Base class for resources that have async handlers.
Sub classes can either implement `_async_render_<METHOD>` to handle
requests by method, or override `_async_render` to handle all requests.
Args:
extract_context: Whether to attempt to extract the opentracing
context from the request the servlet is handling.
"""
def __init__(self, extract_context=False):
super().__init__()
self._extract_context = extract_context
def render(self, request):
"""This gets called by twisted every time someone sends us a request."""
defer.ensureDeferred(self._async_render_wrapper(request))
return NOT_DONE_YET
@wrap_async_request_handler
async def _async_render_wrapper(self, request: SynapseRequest):
"""This is a wrapper that delegates to `_async_render` and handles
exceptions, return values, metrics, etc.
"""
try:
request.request_metrics.name = self.__class__.__name__
with trace_servlet(request, self._extract_context):
callback_return = await self._async_render(request)
if callback_return is not None:
code, response = callback_return
self._send_response(request, code, response)
except Exception:
# failure.Failure() fishes the original Failure out
# of our stack, and thus gives us a sensible stack
# trace.
f = failure.Failure()
self._send_error_response(f, request)
async def _async_render(self, request: Request):
"""Delegates to `_async_render_<METHOD>` methods, or returns a 400 if
no appropriate method exists. Can be overridden in sub classes for
different routing.
"""
# Treat HEAD requests as GET requests.
request_method = request.method.decode("ascii")
if request_method == "HEAD":
request_method = "GET"
method_handler = getattr(self, "_async_render_%s" % (request_method,), None)
if method_handler:
raw_callback_return = method_handler(request)
# Is it synchronous? We'll allow this for now.
if isawaitable(raw_callback_return):
callback_return = await raw_callback_return
else:
callback_return = raw_callback_return # type: ignore
return callback_return
_unrecognised_request_handler(request)
@abc.abstractmethod
def _send_response(
self,
request: SynapseRequest,
code: int,
response_object: Any,
) -> None:
raise NotImplementedError()
@abc.abstractmethod
def _send_error_response(
self,
f: failure.Failure,
request: SynapseRequest,
) -> None:
raise NotImplementedError()
class DirectServeJsonResource(_AsyncResource):
"""A resource that will call `self._async_on_<METHOD>` on new requests,
formatting responses and errors as JSON.
"""
def __init__(self, canonical_json=False, extract_context=False):
super().__init__(extract_context)
self.canonical_json = canonical_json
def _send_response(
self,
request: SynapseRequest,
code: int,
response_object: Any,
):
"""Implements _AsyncResource._send_response"""
# TODO: Only enable CORS for the requests that need it.
respond_with_json(
request,
code,
response_object,
send_cors=True,
canonical_json=self.canonical_json,
)
def _send_error_response(
self,
f: failure.Failure,
request: SynapseRequest,
) -> None:
"""Implements _AsyncResource._send_error_response"""
return_json_error(f, request)
_PathEntry = collections.namedtuple(
"_PathEntry", ["pattern", "callback", "servlet_classname"]
)
class JsonResource(DirectServeJsonResource):
"""This implements the HttpServer interface and provides JSON support for
Resources.
Register callbacks via register_paths()
Callbacks can return a tuple of status code and a dict in which case the
the dict will automatically be sent to the client as a JSON object.
The JsonResource is primarily intended for returning JSON, but callbacks
may send something other than JSON, they may do so by using the methods
on the request object and instead returning None.
"""
isLeaf = True
def __init__(self, hs: "HomeServer", canonical_json=True, extract_context=False):
super().__init__(canonical_json, extract_context)
self.clock = hs.get_clock()
self.path_regexs: Dict[bytes, List[_PathEntry]] = {}
self.hs = hs
def register_paths(self, method, path_patterns, callback, servlet_classname):
"""
Registers a request handler against a regular expression. Later request URLs are
checked against these regular expressions in order to identify an appropriate
handler for that request.
Args:
method (str): GET, POST etc
path_patterns (Iterable[str]): A list of regular expressions to which
the request URLs are compared.
callback (function): The handler for the request. Usually a Servlet
servlet_classname (str): The name of the handler to be used in prometheus
and opentracing logs.
"""
method = method.encode("utf-8") # method is bytes on py3
for path_pattern in path_patterns:
logger.debug("Registering for %s %s", method, path_pattern.pattern)
self.path_regexs.setdefault(method, []).append(
_PathEntry(path_pattern, callback, servlet_classname)
)
def _get_handler_for_request(
self, request: SynapseRequest
) -> Tuple[ServletCallback, str, Dict[str, str]]:
"""Finds a callback method to handle the given request.
Returns:
A tuple of the callback to use, the name of the servlet, and the
key word arguments to pass to the callback
"""
# At this point the path must be bytes.
request_path_bytes: bytes = request.path # type: ignore
request_path = request_path_bytes.decode("ascii")
# Treat HEAD requests as GET requests.
request_method = request.method
if request_method == b"HEAD":
request_method = b"GET"
# Loop through all the registered callbacks to check if the method
# and path regex match
for path_entry in self.path_regexs.get(request_method, []):
m = path_entry.pattern.match(request_path)
if m:
# We found a match!
return path_entry.callback, path_entry.servlet_classname, m.groupdict()
# Huh. No one wanted to handle that? Fiiiiiine. Send 400.
return _unrecognised_request_handler, "unrecognised_request_handler", {}
async def _async_render(self, request):
callback, servlet_classname, group_dict = self._get_handler_for_request(request)
# Make sure we have an appropriate name for this handler in prometheus
# (rather than the default of JsonResource).
request.request_metrics.name = servlet_classname
# Now trigger the callback. If it returns a response, we send it
# here. If it throws an exception, that is handled by the wrapper
# installed by @request_handler.
kwargs = intern_dict(
{
name: urllib.parse.unquote(value) if value else value
for name, value in group_dict.items()
}
)
raw_callback_return = callback(request, **kwargs)
# Is it synchronous? We'll allow this for now.
if isinstance(raw_callback_return, (defer.Deferred, types.CoroutineType)):
callback_return = await raw_callback_return
else:
callback_return = raw_callback_return # type: ignore
return callback_return
class DirectServeHtmlResource(_AsyncResource):
"""A resource that will call `self._async_on_<METHOD>` on new requests,
formatting responses and errors as HTML.
"""
# The error template to use for this resource
ERROR_TEMPLATE = HTML_ERROR_TEMPLATE
def _send_response(
self,
request: SynapseRequest,
code: int,
response_object: Any,
):
"""Implements _AsyncResource._send_response"""
# We expect to get bytes for us to write
assert isinstance(response_object, bytes)
html_bytes = response_object
respond_with_html_bytes(request, 200, html_bytes)
def _send_error_response(
self,
f: failure.Failure,
request: SynapseRequest,
) -> None:
"""Implements _AsyncResource._send_error_response"""
return_html_error(f, request, self.ERROR_TEMPLATE)
class StaticResource(File):
"""
A resource that represents a plain non-interpreted file or directory.
Differs from the File resource by adding clickjacking protection.
"""
def render_GET(self, request: Request):
set_clickjacking_protection_headers(request)
return super().render_GET(request)
def _unrecognised_request_handler(request):
"""Request handler for unrecognised requests
This is a request handler suitable for return from
_get_handler_for_request. It actually just raises an
UnrecognizedRequestError.
Args:
request (twisted.web.http.Request):
"""
raise UnrecognizedRequestError()
class RootRedirect(resource.Resource):
"""Redirects the root '/' path to another path."""
def __init__(self, path):
resource.Resource.__init__(self)
self.url = path
def render_GET(self, request):
return redirectTo(self.url.encode("ascii"), request)
def getChild(self, name, request):
if len(name) == 0:
return self # select ourselves as the child to render
return resource.Resource.getChild(self, name, request)
class OptionsResource(resource.Resource):
"""Responds to OPTION requests for itself and all children."""
def render_OPTIONS(self, request):
request.setResponseCode(204)
request.setHeader(b"Content-Length", b"0")
set_cors_headers(request)
return b""
def getChildWithDefault(self, path, request):
if request.method == b"OPTIONS":
return self # select ourselves as the child to render
return resource.Resource.getChildWithDefault(self, path, request)
class RootOptionsRedirectResource(OptionsResource, RootRedirect):
pass
@implementer(interfaces.IPushProducer)
class _ByteProducer:
"""
Iteratively write bytes to the request.
"""
# The minimum number of bytes for each chunk. Note that the last chunk will
# usually be smaller than this.
min_chunk_size = 1024
def __init__(
self,
request: Request,
iterator: Iterator[bytes],
):
self._request: Optional[Request] = request
self._iterator = iterator
self._paused = False
try:
self._request.registerProducer(self, True)
except AttributeError as e:
# Calling self._request.registerProducer might raise an AttributeError since
# the underlying Twisted code calls self._request.channel.registerProducer,
# however self._request.channel will be None if the connection was lost.
logger.info("Connection disconnected before response was written: %r", e)
# We drop our references to data we'll not use.
self._request = None
self._iterator = iter(())
else:
# Start producing if `registerProducer` was successful
self.resumeProducing()
def _send_data(self, data: List[bytes]) -> None:
"""
Send a list of bytes as a chunk of a response.
"""
if not data or not self._request:
return
self._request.write(b"".join(data))
def pauseProducing(self) -> None:
self._paused = True
def resumeProducing(self) -> None:
# We've stopped producing in the meantime (note that this might be
# re-entrant after calling write).
if not self._request:
return
self._paused = False
# Write until there's backpressure telling us to stop.
while not self._paused:
# Get the next chunk and write it to the request.
#
# The output of the JSON encoder is buffered and coalesced until
# min_chunk_size is reached. This is because JSON encoders produce
# very small output per iteration and the Request object converts
# each call to write() to a separate chunk. Without this there would
# be an explosion in bytes written (e.g. b"{" becoming "1\r\n{\r\n").
#
# Note that buffer stores a list of bytes (instead of appending to
# bytes) to hopefully avoid many allocations.
buffer = []
buffered_bytes = 0
while buffered_bytes < self.min_chunk_size:
try:
data = next(self._iterator)
buffer.append(data)
buffered_bytes += len(data)
except StopIteration:
# The entire JSON object has been serialized, write any
# remaining data, finalize the producer and the request, and
# clean-up any references.
self._send_data(buffer)
self._request.unregisterProducer()
self._request.finish()
self.stopProducing()
return
self._send_data(buffer)
def stopProducing(self) -> None:
# Clear a circular reference.
self._request = None
def _encode_json_bytes(json_object: Any) -> bytes:
"""
Encode an object into JSON. Returns an iterator of bytes.
"""
return json_encoder.encode(json_object).encode("utf-8")
def respond_with_json(
request: SynapseRequest,
code: int,
json_object: Any,
send_cors: bool = False,
canonical_json: bool = True,
):
"""Sends encoded JSON in response to the given request.
Args:
request: The http request to respond to.
code: The HTTP response code.
json_object: The object to serialize to JSON.
send_cors: Whether to send Cross-Origin Resource Sharing headers
https://fetch.spec.whatwg.org/#http-cors-protocol
canonical_json: Whether to use the canonicaljson algorithm when encoding
the JSON bytes.
Returns:
twisted.web.server.NOT_DONE_YET if the request is still active.
"""
# could alternatively use request.notifyFinish() and flip a flag when
# the Deferred fires, but since the flag is RIGHT THERE it seems like
# a waste.
if request._disconnected:
logger.warning(
"Not sending response to request %s, already disconnected.", request
)
return None
if canonical_json:
encoder = encode_canonical_json
else:
encoder = _encode_json_bytes
request.setResponseCode(code)
request.setHeader(b"Content-Type", b"application/json")
request.setHeader(b"Cache-Control", b"no-cache, no-store, must-revalidate")
if send_cors:
set_cors_headers(request)
run_in_background(
_async_write_json_to_request_in_thread, request, encoder, json_object
)
return NOT_DONE_YET
def respond_with_json_bytes(
request: Request,
code: int,
json_bytes: bytes,
send_cors: bool = False,
):
"""Sends encoded JSON in response to the given request.
Args:
request: The http request to respond to.
code: The HTTP response code.
json_bytes: The json bytes to use as the response body.
send_cors: Whether to send Cross-Origin Resource Sharing headers
https://fetch.spec.whatwg.org/#http-cors-protocol
Returns:
twisted.web.server.NOT_DONE_YET if the request is still active.
"""
if request._disconnected:
logger.warning(
"Not sending response to request %s, already disconnected.", request
)
return
request.setResponseCode(code)
request.setHeader(b"Content-Type", b"application/json")
request.setHeader(b"Content-Length", b"%d" % (len(json_bytes),))
request.setHeader(b"Cache-Control", b"no-cache, no-store, must-revalidate")
if send_cors:
set_cors_headers(request)
_write_bytes_to_request(request, json_bytes)
return NOT_DONE_YET
async def _async_write_json_to_request_in_thread(
request: SynapseRequest,
json_encoder: Callable[[Any], bytes],
json_object: Any,
):
"""Encodes the given JSON object on a thread and then writes it to the
request.
This is done so that encoding large JSON objects doesn't block the reactor
thread.
Note: We don't use JsonEncoder.iterencode here as that falls back to the
Python implementation (rather than the C backend), which is *much* more
expensive.
"""
json_str = await defer_to_thread(request.reactor, json_encoder, json_object)
_write_bytes_to_request(request, json_str)
def _write_bytes_to_request(request: Request, bytes_to_write: bytes) -> None:
"""Writes the bytes to the request using an appropriate producer.
Note: This should be used instead of `Request.write` to correctly handle
large response bodies.
"""
# The problem with dumping all of the response into the `Request` object at
# once (via `Request.write`) is that doing so starts the timeout for the
# next request to be received: so if it takes longer than 60s to stream back
# the response to the client, the client never gets it.
#
# The correct solution is to use a Producer; then the timeout is only
# started once all of the content is sent over the TCP connection.
# To make sure we don't write all of the bytes at once we split it up into
# chunks.
chunk_size = 4096
bytes_generator = chunk_seq(bytes_to_write, chunk_size)
# We use a `_ByteProducer` here rather than `NoRangeStaticProducer` as the
# unit tests can't cope with being given a pull producer.
_ByteProducer(request, bytes_generator)
def set_cors_headers(request: Request):
"""Set the CORS headers so that javascript running in a web browsers can
use this API
Args:
request: The http request to add CORS to.
"""
request.setHeader(b"Access-Control-Allow-Origin", b"*")
request.setHeader(
b"Access-Control-Allow-Methods", b"GET, HEAD, POST, PUT, DELETE, OPTIONS"
)
request.setHeader(
b"Access-Control-Allow-Headers",
b"X-Requested-With, Content-Type, Authorization, Date",
)
def respond_with_html(request: Request, code: int, html: str):
"""
Wraps `respond_with_html_bytes` by first encoding HTML from a str to UTF-8 bytes.
"""
respond_with_html_bytes(request, code, html.encode("utf-8"))
def respond_with_html_bytes(request: Request, code: int, html_bytes: bytes):
"""
Sends HTML (encoded as UTF-8 bytes) as the response to the given request.
Note that this adds clickjacking protection headers and finishes the request.
Args:
request: The http request to respond to.
code: The HTTP response code.
html_bytes: The HTML bytes to use as the response body.
"""
# could alternatively use request.notifyFinish() and flip a flag when
# the Deferred fires, but since the flag is RIGHT THERE it seems like
# a waste.
if request._disconnected:
logger.warning(
"Not sending response to request %s, already disconnected.", request
)
return
request.setResponseCode(code)
request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
request.setHeader(b"Content-Length", b"%d" % (len(html_bytes),))
# Ensure this content cannot be embedded.
set_clickjacking_protection_headers(request)
request.write(html_bytes)
finish_request(request)
def set_clickjacking_protection_headers(request: Request):
"""
Set headers to guard against clickjacking of embedded content.
This sets the X-Frame-Options and Content-Security-Policy headers which instructs
browsers to not allow the HTML of the response to be embedded onto another
page.
Args:
request: The http request to add the headers to.
"""
request.setHeader(b"X-Frame-Options", b"DENY")
request.setHeader(b"Content-Security-Policy", b"frame-ancestors 'none';")
def respond_with_redirect(request: Request, url: bytes) -> None:
"""Write a 302 response to the request, if it is still alive."""
logger.debug("Redirect to %s", url.decode("utf-8"))
request.redirect(url)
finish_request(request)
def finish_request(request: Request):
"""Finish writing the response to the request.
Twisted throws a RuntimeException if the connection closed before the
response was written but doesn't provide a convenient or reliable way to
determine if the connection was closed. So we catch and log the RuntimeException
You might think that ``request.notifyFinish`` could be used to tell if the
request was finished. However the deferred it returns won't fire if the
connection was already closed, meaning we'd have to have called the method
right at the start of the request. By the time we want to write the response
it will already be too late.
"""
try:
request.finish()
except RuntimeError as e:
logger.info("Connection disconnected before response was written: %r", e)
|
