/
rtcdtlstransport.py
699 lines (595 loc) · 22.6 KB
/
rtcdtlstransport.py
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
import asyncio
import binascii
import datetime
import enum
import logging
import os
import traceback
from dataclasses import dataclass, field
from typing import Any, Dict, List, Optional, Set, Type, TypeVar
import pylibsrtp
from cryptography import x509
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import ec
from OpenSSL import SSL, crypto
from pyee.asyncio import AsyncIOEventEmitter
from pylibsrtp import Policy, Session
from . import clock, rtp
from .rtcicetransport import RTCIceTransport
from .rtcrtpparameters import RTCRtpReceiveParameters, RTCRtpSendParameters
from .rtp import (
AnyRtcpPacket,
RtcpByePacket,
RtcpPacket,
RtcpPsfbPacket,
RtcpRrPacket,
RtcpRtpfbPacket,
RtcpSrPacket,
RtpPacket,
is_rtcp,
)
from .stats import RTCStatsReport, RTCTransportStats
CERTIFICATE_T = TypeVar("CERTIFICATE_T", bound="RTCCertificate")
logger = logging.getLogger(__name__)
@dataclass(frozen=True)
class SRTPProtectionProfile:
libsrtp_profile: int
openssl_profile: bytes
key_length: int
salt_length: int
def get_key_and_salt(self, src, idx: int) -> bytes:
key_start = idx * self.key_length
salt_start = 2 * self.key_length + idx * self.salt_length
return (
src[key_start : key_start + self.key_length]
+ src[salt_start : salt_start + self.salt_length]
)
SRTP_AEAD_AES_256_GCM = SRTPProtectionProfile(
libsrtp_profile=Policy.SRTP_PROFILE_AEAD_AES_256_GCM,
openssl_profile=b"SRTP_AEAD_AES_256_GCM",
key_length=32,
salt_length=12,
)
SRTP_AEAD_AES_128_GCM = SRTPProtectionProfile(
libsrtp_profile=Policy.SRTP_PROFILE_AEAD_AES_128_GCM,
openssl_profile=b"SRTP_AEAD_AES_128_GCM",
key_length=16,
salt_length=12,
)
SRTP_AES128_CM_SHA1_80 = SRTPProtectionProfile(
libsrtp_profile=Policy.SRTP_PROFILE_AES128_CM_SHA1_80,
openssl_profile=b"SRTP_AES128_CM_SHA1_80",
key_length=16,
salt_length=14,
)
# AES-GCM may not be available depending on how libsrtp2 was built.
SRTP_PROFILES: List[SRTPProtectionProfile] = []
for srtp_profile in [
SRTP_AEAD_AES_256_GCM,
SRTP_AEAD_AES_128_GCM,
SRTP_AES128_CM_SHA1_80,
]:
try:
Policy(srtp_profile=srtp_profile.libsrtp_profile)
except pylibsrtp.Error: # pragma: no cover
pass
else:
SRTP_PROFILES.append(srtp_profile)
def certificate_digest(x509: crypto.X509) -> str:
return x509.digest("SHA256").decode("ascii")
def generate_certificate(key: ec.EllipticCurvePrivateKey) -> x509.Certificate:
name = x509.Name(
[
x509.NameAttribute(
x509.NameOID.COMMON_NAME,
binascii.hexlify(os.urandom(16)).decode("ascii"),
)
]
)
now = datetime.datetime.now(tz=datetime.timezone.utc)
builder = (
x509.CertificateBuilder()
.subject_name(name)
.issuer_name(name)
.public_key(key.public_key())
.serial_number(x509.random_serial_number())
.not_valid_before(now - datetime.timedelta(days=1))
.not_valid_after(now + datetime.timedelta(days=30))
)
return builder.sign(key, hashes.SHA256(), default_backend())
class State(enum.Enum):
NEW = 0
CONNECTING = 1
CONNECTED = 2
CLOSED = 3
FAILED = 4
@dataclass
class RTCDtlsFingerprint:
"""
The :class:`RTCDtlsFingerprint` dictionary includes the hash function
algorithm and certificate fingerprint.
"""
algorithm: str
"The hash function name, for instance `'sha-256'`."
value: str
"The fingerprint value."
class RTCCertificate:
"""
The :class:`RTCCertificate` interface enables the certificates used by an
:class:`RTCDtlsTransport`.
To generate a certificate and the corresponding private key use
:func:`generateCertificate`.
"""
def __init__(self, key: crypto.PKey, cert: crypto.X509) -> None:
self._key = key
self._cert = cert
@property
def expires(self) -> datetime.datetime:
"""
The date and time after which the certificate will be considered invalid.
"""
return self._cert.to_cryptography().not_valid_after_utc
def getFingerprints(self) -> List[RTCDtlsFingerprint]:
"""
Returns the list of certificate fingerprints, one of which is computed
with the digest algorithm used in the certificate signature.
"""
return [
RTCDtlsFingerprint(
algorithm="sha-256",
value=certificate_digest(self._cert),
)
]
@classmethod
def generateCertificate(cls: Type[CERTIFICATE_T]) -> CERTIFICATE_T:
"""
Create and return an X.509 certificate and corresponding private key.
:rtype: RTCCertificate
"""
key = ec.generate_private_key(ec.SECP256R1(), default_backend())
cert = generate_certificate(key)
return cls(
key=crypto.PKey.from_cryptography_key(key),
cert=crypto.X509.from_cryptography(cert),
)
def _create_ssl_context(
self, srtp_profiles: List[SRTPProtectionProfile]
) -> SSL.Context:
ctx = SSL.Context(SSL.DTLS_METHOD)
ctx.set_verify(
SSL.VERIFY_PEER | SSL.VERIFY_FAIL_IF_NO_PEER_CERT, lambda *args: 1
)
ctx.use_certificate(self._cert)
ctx.use_privatekey(self._key)
ctx.set_cipher_list(
b"ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA"
)
ctx.set_tlsext_use_srtp(b":".join(x.openssl_profile for x in srtp_profiles))
return ctx
@dataclass
class RTCDtlsParameters:
"""
The :class:`RTCDtlsParameters` dictionary includes information relating to
DTLS configuration.
"""
fingerprints: List[RTCDtlsFingerprint] = field(default_factory=list)
"List of :class:`RTCDtlsFingerprint`, one fingerprint for each certificate."
role: str = "auto"
"The DTLS role, with a default of auto."
class RtpRouter:
"""
Router to associate RTP/RTCP packets with streams.
https://tools.ietf.org/html/draft-ietf-mmusic-sdp-bundle-negotiation-53
"""
def __init__(self) -> None:
self.receivers: Set = set()
self.senders: Dict[int, Any] = {}
self.mid_table: Dict[str, Any] = {}
self.ssrc_table: Dict[int, Any] = {}
self.payload_type_table: Dict[int, Set] = {}
def register_receiver(
self,
receiver,
ssrcs: List[int],
payload_types: List[int],
mid: Optional[str] = None,
):
self.receivers.add(receiver)
if mid is not None:
self.mid_table[mid] = receiver
for ssrc in ssrcs:
self.ssrc_table[ssrc] = receiver
for payload_type in payload_types:
if payload_type not in self.payload_type_table:
self.payload_type_table[payload_type] = set()
self.payload_type_table[payload_type].add(receiver)
def register_sender(self, sender, ssrc: int) -> None:
self.senders[ssrc] = sender
def route_rtcp(self, packet: AnyRtcpPacket) -> Set:
recipients = set()
def add_recipient(recipient) -> None:
if recipient is not None:
recipients.add(recipient)
# route to RTP receiver
if isinstance(packet, RtcpSrPacket):
add_recipient(self.ssrc_table.get(packet.ssrc))
elif isinstance(packet, RtcpByePacket):
for source in packet.sources:
add_recipient(self.ssrc_table.get(source))
# route to RTP sender
if isinstance(packet, (RtcpRrPacket, RtcpSrPacket)):
for report in packet.reports:
add_recipient(self.senders.get(report.ssrc))
elif isinstance(packet, (RtcpPsfbPacket, RtcpRtpfbPacket)):
add_recipient(self.senders.get(packet.media_ssrc))
# for REMB packets, media_ssrc is always 0, we need to look into the FCI
if isinstance(packet, RtcpPsfbPacket) and packet.fmt == rtp.RTCP_PSFB_APP:
try:
for ssrc in rtp.unpack_remb_fci(packet.fci)[1]:
add_recipient(self.senders.get(ssrc))
except ValueError:
pass
return recipients
def route_rtp(self, packet: RtpPacket) -> Optional[Any]:
ssrc_receiver = self.ssrc_table.get(packet.ssrc)
pt_receivers = self.payload_type_table.get(packet.payload_type, set())
# the SSRC and payload type are known and match
if ssrc_receiver is not None and ssrc_receiver in pt_receivers:
return ssrc_receiver
# the SSRC is unknown but the payload type matches, update the SSRC table
if ssrc_receiver is None and len(pt_receivers) == 1:
pt_receiver = list(pt_receivers)[0]
self.ssrc_table[packet.ssrc] = pt_receiver
return pt_receiver
# discard the packet
return None
def unregister_receiver(self, receiver) -> None:
self.receivers.discard(receiver)
self.__discard(self.mid_table, receiver)
self.__discard(self.ssrc_table, receiver)
for pt, receivers in self.payload_type_table.items():
receivers.discard(receiver)
def unregister_sender(self, sender) -> None:
self.__discard(self.senders, sender)
def __discard(self, d: Dict, value: Any) -> None:
for k, v in list(d.items()):
if v == value:
d.pop(k)
class RTCDtlsTransport(AsyncIOEventEmitter):
"""
The :class:`RTCDtlsTransport` object includes information relating to
Datagram Transport Layer Security (DTLS) transport.
:param transport: An :class:`RTCIceTransport`.
:param certificates: A list of :class:`RTCCertificate` (only one is allowed
currently).
"""
def __init__(
self, transport: RTCIceTransport, certificates: List[RTCCertificate]
) -> None:
assert len(certificates) == 1
certificate = certificates[0]
super().__init__()
self.encrypted = False
self._data_receiver = None
self._role = "auto"
self._rtp_header_extensions_map = rtp.HeaderExtensionsMap()
self._rtp_router = RtpRouter()
self._state = State.NEW
self._stats_id = "transport_" + str(id(self))
self._task: Optional[asyncio.Future[None]] = None
self._transport = transport
# counters
self.__rx_bytes = 0
self.__rx_packets = 0
self.__tx_bytes = 0
self.__tx_packets = 0
# SRTP
self._rx_srtp: Session = None
self._tx_srtp: Session = None
# SSL
self._srtp_profiles = SRTP_PROFILES
self._ssl: Optional[SSL.Connection] = None
self.__local_certificate = certificate
@property
def state(self) -> str:
"""
The current state of the DTLS transport.
One of `'new'`, `'connecting'`, `'connected'`, `'closed'` or `'failed'`.
"""
return str(self._state)[6:].lower()
@property
def transport(self):
"""
The associated :class:`RTCIceTransport` instance.
"""
return self._transport
def getLocalParameters(self) -> RTCDtlsParameters:
"""
Get the local parameters of the DTLS transport.
:rtype: :class:`RTCDtlsParameters`
"""
return RTCDtlsParameters(
fingerprints=self.__local_certificate.getFingerprints()
)
async def start(self, remoteParameters: RTCDtlsParameters) -> None:
"""
Start DTLS transport negotiation with the parameters of the remote
DTLS transport.
:param remoteParameters: An :class:`RTCDtlsParameters`.
"""
assert self._state == State.NEW
assert len(remoteParameters.fingerprints)
# For WebRTC, the DTLS role is explicitly determined as part of the
# offer / answer exchange.
#
# For ORTC however, we determine the DTLS role based on the ICE role.
if self._role == "auto":
if self.transport.role == "controlling":
self._set_role("server")
else:
self._set_role("client")
# Initialise SSL.
self._ssl = SSL.Connection(
self.__local_certificate._create_ssl_context(
srtp_profiles=self._srtp_profiles
)
)
if self._role == "server":
self._ssl.set_accept_state()
else:
self._ssl.set_connect_state()
self._set_state(State.CONNECTING)
try:
while not self.encrypted:
try:
self._ssl.do_handshake()
except SSL.WantReadError:
await self._write_ssl()
await self._recv_next()
except SSL.Error as exc:
self.__log_debug("x DTLS handshake failed (error %s)", exc)
self._set_state(State.FAILED)
return
else:
self.encrypted = True
except ConnectionError:
self.__log_debug("x DTLS handshake failed (connection error)")
self._set_state(State.FAILED)
return
# check remote fingerprint
x509 = self._ssl.get_peer_certificate()
remote_fingerprint = certificate_digest(x509)
fingerprint_is_valid = False
for f in remoteParameters.fingerprints:
if (
f.algorithm.lower() == "sha-256"
and f.value.lower() == remote_fingerprint.lower()
):
fingerprint_is_valid = True
break
if not fingerprint_is_valid:
self.__log_debug("x DTLS handshake failed (fingerprint mismatch)")
self._set_state(State.FAILED)
return
# generate keying material
openssl_profile = self._ssl.get_selected_srtp_profile()
for srtp_profile in self._srtp_profiles:
if srtp_profile.openssl_profile == openssl_profile:
self.__log_debug(
"x DTLS handshake negotiated %s",
srtp_profile.openssl_profile.decode(),
)
break
else:
self.__log_debug("x DTLS handshake failed (no SRTP profile negotiated)")
self._set_state(State.FAILED)
return
view = self._ssl.export_keying_material(
b"EXTRACTOR-dtls_srtp",
2 * (srtp_profile.key_length + srtp_profile.salt_length),
)
if self._role == "server":
srtp_tx_key = srtp_profile.get_key_and_salt(view, 1)
srtp_rx_key = srtp_profile.get_key_and_salt(view, 0)
else:
srtp_tx_key = srtp_profile.get_key_and_salt(view, 0)
srtp_rx_key = srtp_profile.get_key_and_salt(view, 1)
rx_policy = Policy(
key=srtp_rx_key,
ssrc_type=Policy.SSRC_ANY_INBOUND,
srtp_profile=srtp_profile.libsrtp_profile,
)
rx_policy.allow_repeat_tx = True
rx_policy.window_size = 1024
self._rx_srtp = Session(rx_policy)
tx_policy = Policy(
key=srtp_tx_key,
ssrc_type=Policy.SSRC_ANY_OUTBOUND,
srtp_profile=srtp_profile.libsrtp_profile,
)
tx_policy.allow_repeat_tx = True
tx_policy.window_size = 1024
self._tx_srtp = Session(tx_policy)
# start data pump
self.__log_debug("- DTLS handshake complete")
self._set_state(State.CONNECTED)
self._task = asyncio.ensure_future(self.__run())
async def stop(self) -> None:
"""
Stop and close the DTLS transport.
"""
if self._task is not None:
self._task.cancel()
self._task = None
if self._ssl and self._state in [State.CONNECTING, State.CONNECTED]:
try:
self._ssl.shutdown()
except SSL.Error:
pass
try:
await self._write_ssl()
except ConnectionError:
pass
self.__log_debug("- DTLS shutdown complete")
async def __run(self) -> None:
try:
while True:
await self._recv_next()
except ConnectionError:
for receiver in self._rtp_router.receivers:
receiver._handle_disconnect()
except Exception as exc:
if not isinstance(exc, asyncio.CancelledError):
self.__log_warning(traceback.format_exc())
raise exc
finally:
self._set_state(State.CLOSED)
def _get_stats(self) -> RTCStatsReport:
report = RTCStatsReport()
report.add(
RTCTransportStats(
# RTCStats
timestamp=clock.current_datetime(),
type="transport",
id=self._stats_id,
# RTCTransportStats,
packetsSent=self.__tx_packets,
packetsReceived=self.__rx_packets,
bytesSent=self.__tx_bytes,
bytesReceived=self.__rx_bytes,
iceRole=self.transport.role,
dtlsState=self.state,
)
)
return report
async def _handle_rtcp_data(self, data: bytes) -> None:
try:
packets = RtcpPacket.parse(data)
except ValueError as exc:
self.__log_debug("x RTCP parsing failed: %s", exc)
return
for packet in packets:
# route RTCP packet
for recipient in self._rtp_router.route_rtcp(packet):
await recipient._handle_rtcp_packet(packet)
async def _handle_rtp_data(self, data: bytes, arrival_time_ms: int) -> None:
try:
packet = RtpPacket.parse(data, self._rtp_header_extensions_map)
except ValueError as exc:
self.__log_debug("x RTP parsing failed: %s", exc)
return
# route RTP packet
receiver = self._rtp_router.route_rtp(packet)
if receiver is not None:
await receiver._handle_rtp_packet(packet, arrival_time_ms=arrival_time_ms)
async def _recv_next(self) -> None:
# get timeout
timeout = None
if not self.encrypted:
timeout = self._ssl.DTLSv1_get_timeout()
# receive next datagram
if timeout is not None:
try:
data = await asyncio.wait_for(self.transport._recv(), timeout=timeout)
except asyncio.TimeoutError:
self.__log_debug("x DTLS handling timeout")
self._ssl.DTLSv1_handle_timeout()
await self._write_ssl()
return
else:
data = await self.transport._recv()
self.__rx_bytes += len(data)
self.__rx_packets += 1
first_byte = data[0]
if first_byte > 19 and first_byte < 64:
# DTLS
self._ssl.bio_write(data)
try:
data = self._ssl.recv(1500)
except SSL.ZeroReturnError:
data = None
except SSL.Error:
data = b""
await self._write_ssl()
if data is None:
self.__log_debug("- DTLS shutdown by remote party")
raise ConnectionError
elif data and self._data_receiver:
await self._data_receiver._handle_data(data)
elif first_byte > 127 and first_byte < 192 and self._rx_srtp:
# SRTP / SRTCP
arrival_time_ms = clock.current_ms()
try:
if is_rtcp(data):
data = self._rx_srtp.unprotect_rtcp(data)
await self._handle_rtcp_data(data)
else:
data = self._rx_srtp.unprotect(data)
await self._handle_rtp_data(data, arrival_time_ms=arrival_time_ms)
except pylibsrtp.Error as exc:
self.__log_debug("x SRTP unprotect failed: %s", exc)
def _register_data_receiver(self, receiver) -> None:
assert self._data_receiver is None
self._data_receiver = receiver
def _register_rtp_receiver(
self, receiver, parameters: RTCRtpReceiveParameters
) -> None:
ssrcs = set()
for encoding in parameters.encodings:
ssrcs.add(encoding.ssrc)
self._rtp_header_extensions_map.configure(parameters)
self._rtp_router.register_receiver(
receiver,
ssrcs=list(ssrcs),
payload_types=[codec.payloadType for codec in parameters.codecs],
mid=parameters.muxId,
)
def _register_rtp_sender(self, sender, parameters: RTCRtpSendParameters) -> None:
self._rtp_header_extensions_map.configure(parameters)
self._rtp_router.register_sender(sender, ssrc=sender._ssrc)
async def _send_data(self, data: bytes) -> None:
if self._state != State.CONNECTED:
raise ConnectionError("Cannot send encrypted data, not connected")
self._ssl.send(data)
await self._write_ssl()
async def _send_rtp(self, data: bytes) -> None:
if self._state != State.CONNECTED:
raise ConnectionError("Cannot send encrypted RTP, not connected")
if is_rtcp(data):
data = self._tx_srtp.protect_rtcp(data)
else:
data = self._tx_srtp.protect(data)
await self.transport._send(data)
self.__tx_bytes += len(data)
self.__tx_packets += 1
def _set_role(self, role: str) -> None:
self._role = role
def _set_state(self, state: State) -> None:
if state != self._state:
self.__log_debug("- %s -> %s", self._state, state)
self._state = state
self.emit("statechange")
def _unregister_data_receiver(self, receiver) -> None:
if self._data_receiver == receiver:
self._data_receiver = None
def _unregister_rtp_receiver(self, receiver) -> None:
self._rtp_router.unregister_receiver(receiver)
def _unregister_rtp_sender(self, sender) -> None:
self._rtp_router.unregister_sender(sender)
async def _write_ssl(self) -> None:
"""
Flush outgoing data which OpenSSL put in our BIO to the transport.
"""
try:
data = self._ssl.bio_read(1500)
except SSL.Error:
data = b""
if data:
await self.transport._send(data)
self.__tx_bytes += len(data)
self.__tx_packets += 1
def __log_debug(self, msg: str, *args) -> None:
logger.debug(f"RTCDtlsTransport(%s) {msg}", self._role, *args)
def __log_warning(self, msg: str, *args) -> None:
logger.warning(f"RTCDtlsTransport(%s) {msg}", self._role, *args)