forked from project-chip/connectedhomeip
-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathCASESession.cpp
2312 lines (1873 loc) · 97.6 KB
/
CASESession.cpp
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
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/*
*
* Copyright (c) 2021-2022 Project CHIP Authors
* All rights reserved.
*
* 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.
*/
/**
* @file
* This file implements the the CHIP CASE Session object that provides
* APIs for constructing a secure session using a certificate from the device's
* operational credentials.
*
*/
#include <protocols/secure_channel/CASESession.h>
#include <atomic>
#include <inttypes.h>
#include <memory>
#include <string.h>
#include <lib/core/CHIPEncoding.h>
#include <lib/core/CHIPSafeCasts.h>
#include <lib/support/CHIPMem.h>
#include <lib/support/CodeUtils.h>
#include <lib/support/SafeInt.h>
#include <lib/support/ScopedBuffer.h>
#include <lib/support/TypeTraits.h>
#include <messaging/SessionParameters.h>
#include <platform/PlatformManager.h>
#include <protocols/Protocols.h>
#include <protocols/secure_channel/CASEDestinationId.h>
#include <protocols/secure_channel/PairingSession.h>
#include <protocols/secure_channel/SessionResumptionStorage.h>
#include <protocols/secure_channel/StatusReport.h>
#include <system/SystemClock.h>
#include <system/TLVPacketBufferBackingStore.h>
#include <tracing/macros.h>
#include <transport/SessionManager.h>
namespace {
enum
{
kTag_TBEData_SenderNOC = 1,
kTag_TBEData_SenderICAC = 2,
kTag_TBEData_Signature = 3,
kTag_TBEData_ResumptionID = 4,
};
enum
{
kTag_TBSData_SenderNOC = 1,
kTag_TBSData_SenderICAC = 2,
kTag_TBSData_SenderPubKey = 3,
kTag_TBSData_ReceiverPubKey = 4,
};
enum
{
kTag_Sigma1_InitiatorRandom = 1,
kTag_Sigma1_InitiatorSessionId = 2,
kTag_Sigma1_DestinationId = 3,
kTag_Sigma1_InitiatorEphPubKey = 4,
kTag_Sigma1_InitiatorMRPParams = 5,
kTag_Sigma1_ResumptionID = 6,
kTag_Sigma1_InitiatorResumeMIC = 7,
};
enum
{
kTag_Sigma2_ResponderRandom = 1,
kTag_Sigma2_ResponderSessionId = 2,
kTag_Sigma2_ResponderEphPubKey = 3,
kTag_Sigma2_Encrypted2 = 4,
kTag_Sigma2_ResponderMRPParams = 5,
};
enum
{
kTag_Sigma3_Encrypted3 = 1,
};
} // namespace
namespace chip {
using namespace Crypto;
using namespace Credentials;
using namespace Messaging;
using namespace Encoding;
using namespace Protocols::SecureChannel;
constexpr uint8_t kKDFSR2Info[] = { 0x53, 0x69, 0x67, 0x6d, 0x61, 0x32 };
constexpr uint8_t kKDFSR3Info[] = { 0x53, 0x69, 0x67, 0x6d, 0x61, 0x33 };
constexpr uint8_t kKDFS1RKeyInfo[] = { 0x53, 0x69, 0x67, 0x6d, 0x61, 0x31, 0x5f, 0x52, 0x65, 0x73, 0x75, 0x6d, 0x65 };
constexpr uint8_t kKDFS2RKeyInfo[] = { 0x53, 0x69, 0x67, 0x6d, 0x61, 0x32, 0x5f, 0x52, 0x65, 0x73, 0x75, 0x6d, 0x65 };
constexpr uint8_t kResume1MIC_Nonce[] =
/* "NCASE_SigmaS1" */ { 0x4e, 0x43, 0x41, 0x53, 0x45, 0x5f, 0x53, 0x69, 0x67, 0x6d, 0x61, 0x53, 0x31 };
constexpr uint8_t kResume2MIC_Nonce[] =
/* "NCASE_SigmaS2" */ { 0x4e, 0x43, 0x41, 0x53, 0x45, 0x5f, 0x53, 0x69, 0x67, 0x6d, 0x61, 0x53, 0x32 };
constexpr uint8_t kTBEData2_Nonce[] =
/* "NCASE_Sigma2N" */ { 0x4e, 0x43, 0x41, 0x53, 0x45, 0x5f, 0x53, 0x69, 0x67, 0x6d, 0x61, 0x32, 0x4e };
constexpr uint8_t kTBEData3_Nonce[] =
/* "NCASE_Sigma3N" */ { 0x4e, 0x43, 0x41, 0x53, 0x45, 0x5f, 0x53, 0x69, 0x67, 0x6d, 0x61, 0x33, 0x4e };
constexpr size_t kTBEDataNonceLength = sizeof(kTBEData2_Nonce);
static_assert(sizeof(kTBEData2_Nonce) == sizeof(kTBEData3_Nonce), "TBEData2_Nonce and TBEData3_Nonce must be same size");
// Amounts of time to allow for server-side processing of messages.
//
// These timeout values only allow for the server-side processing and assume that any transport-specific
// latency will be added to them.
//
// The session establishment fails if the response is not received within the resulting timeout window,
// which accounts for both transport latency and the server-side latency.
static constexpr ExchangeContext::Timeout kExpectedLowProcessingTime = System::Clock::Seconds16(2);
static constexpr ExchangeContext::Timeout kExpectedSigma1ProcessingTime = kExpectedLowProcessingTime;
static constexpr ExchangeContext::Timeout kExpectedHighProcessingTime = System::Clock::Seconds16(30);
// Helper for managing a session's outstanding work.
// Holds work data which is provided to a scheduled work callback (standalone),
// then (if not canceled) to a scheduled after work callback (on the session).
template <class DATA>
class CASESession::WorkHelper
{
public:
// Work callback, processed in the background via `PlatformManager::ScheduleBackgroundWork`.
// This is a non-member function which does not use the associated session.
// The return value is passed to the after work callback (called afterward).
// Set `cancel` to true if calling the after work callback is not necessary.
typedef CHIP_ERROR (*WorkCallback)(DATA & data, bool & cancel);
// After work callback, processed in the main Matter task via `PlatformManager::ScheduleWork`.
// This is a member function to be called on the associated session after the work callback.
// The `status` value is the result of the work callback (called beforehand), or the status of
// queueing the after work callback back to the Matter thread, if the work callback succeeds
// but queueing fails.
//
// When this callback is called asynchronously (i.e. via ScheduleWork), the helper guarantees
// that it will keep itself (and hence `data`) alive until the callback completes.
typedef CHIP_ERROR (CASESession::*AfterWorkCallback)(DATA & data, CHIP_ERROR status);
public:
// Create a work helper using the specified session, work callback, after work callback, and data (template arg).
// Lifetime is managed by sharing between the caller (typically the session) and the helper itself (while work is scheduled).
static Platform::SharedPtr<WorkHelper> Create(CASESession & session, WorkCallback workCallback,
AfterWorkCallback afterWorkCallback)
{
struct EnableShared : public WorkHelper
{
EnableShared(CASESession & session, WorkCallback workCallback, AfterWorkCallback afterWorkCallback) :
WorkHelper(session, workCallback, afterWorkCallback)
{}
};
auto ptr = Platform::MakeShared<EnableShared>(session, workCallback, afterWorkCallback);
if (ptr)
{
ptr->mWeakPtr = ptr; // used by `ScheduleWork`
}
return ptr;
}
// Do the work immediately.
// No scheduling, no outstanding work, no shared lifetime management.
//
// The caller must guarantee that it keeps the helper alive across this call, most likely by
// holding a reference to it on the stack.
CHIP_ERROR DoWork()
{
// Ensure that this function is being called from main Matter thread
assertChipStackLockedByCurrentThread();
VerifyOrReturnError(mSession && mWorkCallback && mAfterWorkCallback, CHIP_ERROR_INCORRECT_STATE);
auto * helper = this;
bool cancel = false;
helper->mStatus = helper->mWorkCallback(helper->mData, cancel);
if (!cancel)
{
helper->mStatus = (helper->mSession->*(helper->mAfterWorkCallback))(helper->mData, helper->mStatus);
}
return helper->mStatus;
}
// Schedule the work for later execution.
// If lifetime is managed, the helper shares management while work is outstanding.
CHIP_ERROR ScheduleWork()
{
VerifyOrReturnError(mSession && mWorkCallback && mAfterWorkCallback, CHIP_ERROR_INCORRECT_STATE);
// Hold strong ptr while work is outstanding
mStrongPtr = mWeakPtr.lock(); // set in `Create`
auto status = DeviceLayer::PlatformMgr().ScheduleBackgroundWork(WorkHandler, reinterpret_cast<intptr_t>(this));
if (status != CHIP_NO_ERROR)
{
// Release strong ptr since scheduling failed.
mStrongPtr.reset();
}
return status;
}
// Cancel the work, by clearing the associated session.
void CancelWork() { mSession.store(nullptr); }
bool IsCancelled() const { return mSession.load() == nullptr; }
// This API returns true when background thread fails to schedule the AfterWorkCallback
bool UnableToScheduleAfterWorkCallback() { return mScheduleAfterWorkFailed.load(); }
// Do after work immediately.
// No scheduling, no outstanding work, no shared lifetime management.
void DoAfterWork()
{
VerifyOrDie(UnableToScheduleAfterWorkCallback());
AfterWorkHandler(reinterpret_cast<intptr_t>(this));
}
private:
// Create a work helper using the specified session, work callback, after work callback, and data (template arg).
// Lifetime is not managed, see `Create` for that option.
WorkHelper(CASESession & session, WorkCallback workCallback, AfterWorkCallback afterWorkCallback) :
mSession(&session), mWorkCallback(workCallback), mAfterWorkCallback(afterWorkCallback)
{}
// Handler for the work callback.
static void WorkHandler(intptr_t arg)
{
auto * helper = reinterpret_cast<WorkHelper *>(arg);
// Hold strong ptr while work is handled
auto strongPtr(std::move(helper->mStrongPtr));
VerifyOrReturn(!helper->IsCancelled());
bool cancel = false;
// Execute callback in background thread; data must be OK with this
helper->mStatus = helper->mWorkCallback(helper->mData, cancel);
VerifyOrReturn(!cancel && !helper->IsCancelled());
// Hold strong ptr to ourselves while work is outstanding
helper->mStrongPtr.swap(strongPtr);
auto status = DeviceLayer::PlatformMgr().ScheduleWork(AfterWorkHandler, reinterpret_cast<intptr_t>(helper));
if (status != CHIP_NO_ERROR)
{
ChipLogError(SecureChannel, "Failed to Schedule the AfterWorkCallback on foreground thread: %" CHIP_ERROR_FORMAT,
status.Format());
// We failed to schedule after work callback, so setting mScheduleAfterWorkFailed flag to true
// This can be checked from foreground thread and after work callback can be retried
helper->mStatus = status;
// Release strong ptr to self since scheduling failed, because nothing guarantees
// that AfterWorkHandler will get called at this point to release the reference,
// and we don't want to leak. That said, we want to ensure that "helper" stays
// alive through the end of this function (so we can set mScheduleAfterWorkFailed
// on it), but also want to avoid racing on the single SharedPtr instance in
// helper->mStrongPtr. That means we need to not touch helper->mStrongPtr after
// writing to mScheduleAfterWorkFailed.
//
// The simplest way to do this is to move the reference in helper->mStrongPtr to
// our stack, where it outlives all our accesses to "helper".
strongPtr.swap(helper->mStrongPtr);
// helper and any of its state should not be touched after storing mScheduleAfterWorkFailed.
helper->mScheduleAfterWorkFailed.store(true);
}
}
// Handler for the after work callback.
static void AfterWorkHandler(intptr_t arg)
{
// Ensure that this function is being called from main Matter thread
assertChipStackLockedByCurrentThread();
auto * helper = reinterpret_cast<WorkHelper *>(arg);
// Hold strong ptr while work is handled, and ensure that helper->mStrongPtr does not keep
// holding a reference.
auto strongPtr(std::move(helper->mStrongPtr));
if (!strongPtr)
{
// This can happen if scheduling AfterWorkHandler failed. Just grab a strong ref
// to handler directly, to fulfill our API contract of holding a strong reference
// across the after-work callback. At this point, we are guaranteed that the
// background thread is not touching the helper anymore.
strongPtr = helper->mWeakPtr.lock();
}
if (auto * session = helper->mSession.load())
{
// Execute callback in Matter thread; session should be OK with this
(session->*(helper->mAfterWorkCallback))(helper->mData, helper->mStatus);
}
}
private:
// Lifetime management: `ScheduleWork` sets `mStrongPtr` from `mWeakPtr`.
Platform::WeakPtr<WorkHelper> mWeakPtr;
// Lifetime management: `ScheduleWork` sets `mStrongPtr` from `mWeakPtr`.
Platform::SharedPtr<WorkHelper> mStrongPtr;
// Associated session, cleared by `CancelWork`.
std::atomic<CASESession *> mSession;
// Work callback, called by `WorkHandler`.
WorkCallback mWorkCallback;
// After work callback, called by `AfterWorkHandler`.
AfterWorkCallback mAfterWorkCallback;
// Return value of `mWorkCallback`, passed to `mAfterWorkCallback`.
CHIP_ERROR mStatus;
// If background thread fails to schedule AfterWorkCallback then this flag is set to true
// and CASEServer then can check this one and run the AfterWorkCallback for us.
//
// When this happens, the write to this boolean _must_ be the last code that touches this
// object on the background thread. After that, the Matter thread owns the object.
std::atomic<bool> mScheduleAfterWorkFailed{ false };
public:
// Data passed to `mWorkCallback` and `mAfterWorkCallback`.
DATA mData;
};
struct CASESession::SendSigma3Data
{
FabricIndex fabricIndex;
// Use one or the other
const FabricTable * fabricTable;
const Crypto::OperationalKeystore * keystore;
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R3_Signed;
size_t msg_r3_signed_len;
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R3_Encrypted;
size_t msg_r3_encrypted_len;
chip::Platform::ScopedMemoryBuffer<uint8_t> icacBuf;
MutableByteSpan icaCert;
chip::Platform::ScopedMemoryBuffer<uint8_t> nocBuf;
MutableByteSpan nocCert;
P256ECDSASignature tbsData3Signature;
};
struct CASESession::HandleSigma3Data
{
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R3_Signed;
size_t msg_r3_signed_len;
ByteSpan initiatorNOC;
ByteSpan initiatorICAC;
uint8_t rootCertBuf[kMaxCHIPCertLength];
ByteSpan fabricRCAC;
P256ECDSASignature tbsData3Signature;
FabricId fabricId;
NodeId initiatorNodeId;
ValidationContext validContext;
};
CASESession::~CASESession()
{
// Let's clear out any security state stored in the object, before destroying it.
Clear();
}
void CASESession::OnSessionReleased()
{
// Call into our super-class before we clear our state.
PairingSession::OnSessionReleased();
Clear();
}
void CASESession::Clear()
{
MATTER_TRACE_SCOPE("Clear", "CASESession");
// Cancel any outstanding work.
if (mSendSigma3Helper)
{
mSendSigma3Helper->CancelWork();
mSendSigma3Helper.reset();
}
if (mHandleSigma3Helper)
{
mHandleSigma3Helper->CancelWork();
mHandleSigma3Helper.reset();
}
// This function zeroes out and resets the memory used by the object.
// It's done so that no security related information will be leaked.
mCommissioningHash.Clear();
PairingSession::Clear();
mState = State::kInitialized;
Crypto::ClearSecretData(mIPK);
if (mFabricsTable != nullptr)
{
mFabricsTable->RemoveFabricDelegate(this);
mFabricsTable->ReleaseEphemeralKeypair(mEphemeralKey);
mEphemeralKey = nullptr;
}
mLocalNodeId = kUndefinedNodeId;
mPeerNodeId = kUndefinedNodeId;
mFabricsTable = nullptr;
mFabricIndex = kUndefinedFabricIndex;
}
void CASESession::InvalidateIfPendingEstablishmentOnFabric(FabricIndex fabricIndex)
{
if (mFabricIndex != fabricIndex)
{
return;
}
if (!IsSessionEstablishmentInProgress())
{
return;
}
AbortPendingEstablish(CHIP_ERROR_CANCELLED);
}
CHIP_ERROR CASESession::Init(SessionManager & sessionManager, Credentials::CertificateValidityPolicy * policy,
SessionEstablishmentDelegate * delegate, const ScopedNodeId & sessionEvictionHint)
{
MATTER_TRACE_SCOPE("Init", "CASESession");
VerifyOrReturnError(delegate != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
VerifyOrReturnError(mGroupDataProvider != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
VerifyOrReturnError(sessionManager.GetSessionKeystore() != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
Clear();
ReturnErrorOnFailure(mCommissioningHash.Begin());
mDelegate = delegate;
ReturnErrorOnFailure(AllocateSecureSession(sessionManager, sessionEvictionHint));
mValidContext.Reset();
mValidContext.mRequiredKeyUsages.Set(KeyUsageFlags::kDigitalSignature);
mValidContext.mRequiredKeyPurposes.Set(KeyPurposeFlags::kServerAuth);
mValidContext.mValidityPolicy = policy;
return CHIP_NO_ERROR;
}
CHIP_ERROR
CASESession::PrepareForSessionEstablishment(SessionManager & sessionManager, FabricTable * fabricTable,
SessionResumptionStorage * sessionResumptionStorage,
Credentials::CertificateValidityPolicy * policy,
SessionEstablishmentDelegate * delegate, const ScopedNodeId & previouslyEstablishedPeer,
Optional<ReliableMessageProtocolConfig> mrpLocalConfig)
{
MATTER_TRACE_SCOPE("PrepareForSessionEstablishment", "CASESession");
// Below VerifyOrReturnError is not SuccessOrExit since we only want to goto `exit:` after
// Init has been successfully called.
VerifyOrReturnError(fabricTable != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
ReturnErrorOnFailure(Init(sessionManager, policy, delegate, previouslyEstablishedPeer));
CHIP_ERROR err = CHIP_NO_ERROR;
SuccessOrExit(err = fabricTable->AddFabricDelegate(this));
mFabricsTable = fabricTable;
mRole = CryptoContext::SessionRole::kResponder;
mSessionResumptionStorage = sessionResumptionStorage;
mLocalMRPConfig = MakeOptional(mrpLocalConfig.ValueOr(GetDefaultMRPConfig()));
ChipLogDetail(SecureChannel, "Allocated SecureSession (%p) - waiting for Sigma1 msg",
mSecureSessionHolder.Get().Value()->AsSecureSession());
exit:
if (err != CHIP_NO_ERROR)
{
Clear();
}
return err;
}
CHIP_ERROR CASESession::EstablishSession(SessionManager & sessionManager, FabricTable * fabricTable, ScopedNodeId peerScopedNodeId,
ExchangeContext * exchangeCtxt, SessionResumptionStorage * sessionResumptionStorage,
Credentials::CertificateValidityPolicy * policy, SessionEstablishmentDelegate * delegate,
Optional<ReliableMessageProtocolConfig> mrpLocalConfig)
{
MATTER_TRACE_SCOPE("EstablishSession", "CASESession");
CHIP_ERROR err = CHIP_NO_ERROR;
// Return early on error here, as we have not initialized any state yet
ReturnErrorCodeIf(exchangeCtxt == nullptr, CHIP_ERROR_INVALID_ARGUMENT);
ReturnErrorCodeIf(fabricTable == nullptr, CHIP_ERROR_INVALID_ARGUMENT);
// Use FabricTable directly to avoid situation of dangling index from stale FabricInfo
// until we factor-out any FabricInfo direct usage.
ReturnErrorCodeIf(peerScopedNodeId.GetFabricIndex() == kUndefinedFabricIndex, CHIP_ERROR_INVALID_ARGUMENT);
const auto * fabricInfo = fabricTable->FindFabricWithIndex(peerScopedNodeId.GetFabricIndex());
ReturnErrorCodeIf(fabricInfo == nullptr, CHIP_ERROR_INVALID_ARGUMENT);
err = Init(sessionManager, policy, delegate, peerScopedNodeId);
mRole = CryptoContext::SessionRole::kInitiator;
// We are setting the exchange context specifically before checking for error.
// This is to make sure the exchange will get closed if Init() returned an error.
mExchangeCtxt.Emplace(*exchangeCtxt);
// From here onwards, let's go to exit on error, as some state might have already
// been initialized
SuccessOrExit(err);
SuccessOrExit(err = fabricTable->AddFabricDelegate(this));
mFabricsTable = fabricTable;
mFabricIndex = fabricInfo->GetFabricIndex();
mSessionResumptionStorage = sessionResumptionStorage;
mLocalMRPConfig = MakeOptional(mrpLocalConfig.ValueOr(GetDefaultMRPConfig()));
mExchangeCtxt.Value()->UseSuggestedResponseTimeout(kExpectedSigma1ProcessingTime);
mPeerNodeId = peerScopedNodeId.GetNodeId();
mLocalNodeId = fabricInfo->GetNodeId();
ChipLogProgress(SecureChannel, "Initiating session on local FabricIndex %u from 0x" ChipLogFormatX64 " -> 0x" ChipLogFormatX64,
static_cast<unsigned>(mFabricIndex), ChipLogValueX64(mLocalNodeId), ChipLogValueX64(mPeerNodeId));
err = SendSigma1();
SuccessOrExit(err);
exit:
if (err != CHIP_NO_ERROR)
{
Clear();
}
return err;
}
void CASESession::OnResponseTimeout(ExchangeContext * ec)
{
MATTER_TRACE_SCOPE("OnResponseTimeout", "CASESession");
VerifyOrReturn(ec != nullptr, ChipLogError(SecureChannel, "CASESession::OnResponseTimeout was called by null exchange"));
VerifyOrReturn(mExchangeCtxt.HasValue() && (&mExchangeCtxt.Value().Get() == ec),
ChipLogError(SecureChannel, "CASESession::OnResponseTimeout exchange doesn't match"));
ChipLogError(SecureChannel,
"CASESession timed out while waiting for a response from peer " ChipLogFormatScopedNodeId ". Current state was %u",
ChipLogValueScopedNodeId(ScopedNodeId(mPeerNodeId, mFabricIndex)), to_underlying(mState));
MATTER_TRACE_COUNTER("CASETimeout");
// Discard the exchange so that Clear() doesn't try aborting it. The
// exchange will handle that.
DiscardExchange();
AbortPendingEstablish(CHIP_ERROR_TIMEOUT);
}
void CASESession::AbortPendingEstablish(CHIP_ERROR err)
{
MATTER_TRACE_SCOPE("AbortPendingEstablish", "CASESession");
// This needs to come before Clear() which will reset mState.
SessionEstablishmentStage state = MapCASEStateToSessionEstablishmentStage(mState);
Clear();
// Do this last in case the delegate frees us.
NotifySessionEstablishmentError(err, state);
}
CHIP_ERROR CASESession::DeriveSecureSession(CryptoContext & session) const
{
switch (mState)
{
case State::kFinished: {
std::array<uint8_t, sizeof(mIPK) + kSHA256_Hash_Length> msg_salt;
{
Encoding::LittleEndian::BufferWriter bbuf(msg_salt);
bbuf.Put(mIPK, sizeof(mIPK));
bbuf.Put(mMessageDigest, sizeof(mMessageDigest));
VerifyOrReturnError(bbuf.Fit(), CHIP_ERROR_BUFFER_TOO_SMALL);
}
ReturnErrorOnFailure(session.InitFromSecret(*mSessionManager->GetSessionKeystore(), mSharedSecret.Span(),
ByteSpan(msg_salt), CryptoContext::SessionInfoType::kSessionEstablishment,
mRole));
return CHIP_NO_ERROR;
}
case State::kFinishedViaResume: {
std::array<uint8_t, sizeof(mInitiatorRandom) + decltype(mResumeResumptionId)().size()> msg_salt;
{
Encoding::LittleEndian::BufferWriter bbuf(msg_salt);
bbuf.Put(mInitiatorRandom, sizeof(mInitiatorRandom));
bbuf.Put(mResumeResumptionId.data(), mResumeResumptionId.size());
VerifyOrReturnError(bbuf.Fit(), CHIP_ERROR_BUFFER_TOO_SMALL);
}
ReturnErrorOnFailure(session.InitFromSecret(*mSessionManager->GetSessionKeystore(), mSharedSecret.Span(),
ByteSpan(msg_salt), CryptoContext::SessionInfoType::kSessionResumption, mRole));
return CHIP_NO_ERROR;
}
default:
return CHIP_ERROR_INCORRECT_STATE;
}
}
CHIP_ERROR CASESession::RecoverInitiatorIpk()
{
Credentials::GroupDataProvider::KeySet ipkKeySet;
CHIP_ERROR err = mGroupDataProvider->GetIpkKeySet(mFabricIndex, ipkKeySet);
if (err != CHIP_NO_ERROR)
{
ChipLogError(SecureChannel, "Failed to obtain IPK for initiating: %" CHIP_ERROR_FORMAT, err.Format());
return err;
}
if ((ipkKeySet.num_keys_used == 0) || (ipkKeySet.num_keys_used > Credentials::GroupDataProvider::KeySet::kEpochKeysMax))
{
ChipLogError(SecureChannel, "Found invalid IPK keyset for initiator.");
return CHIP_ERROR_INTERNAL;
}
// For the generation of the Destination Identifier,
// the originator SHALL use the operational group key with the second oldest
// EpochStartTime, if one exists, otherwise it SHALL use the single operational
// group key available. The EpochStartTime are already ordered
size_t ipkIndex = (ipkKeySet.num_keys_used > 1) ? ((ipkKeySet.num_keys_used - 1) - 1) : 0;
memcpy(&mIPK[0], ipkKeySet.epoch_keys[ipkIndex].key, sizeof(mIPK));
// Leaving this logging code for debug, but this cannot be enabled at runtime
// since it leaks private security material.
#if 0
ChipLogProgress(SecureChannel, "RecoverInitiatorIpk: GroupDataProvider %p, Got IPK for FabricIndex %u", mGroupDataProvider,
static_cast<unsigned>(mFabricIndex));
ChipLogByteSpan(SecureChannel, ByteSpan(mIPK));
#endif
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::SendSigma1()
{
MATTER_TRACE_SCOPE("SendSigma1", "CASESession");
size_t data_len = TLV::EstimateStructOverhead(kSigmaParamRandomNumberSize, // initiatorRandom
sizeof(uint16_t), // initiatorSessionId,
kSHA256_Hash_Length, // destinationId
kP256_PublicKey_Length, // InitiatorEphPubKey,
SessionParameters::kEstimatedTLVSize, // initiatorSessionParams
SessionResumptionStorage::kResumptionIdSize, CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES);
System::PacketBufferTLVWriter tlvWriter;
System::PacketBufferHandle msg_R1;
TLV::TLVType outerContainerType = TLV::kTLVType_NotSpecified;
uint8_t destinationIdentifier[kSHA256_Hash_Length] = { 0 };
// Lookup fabric info.
const auto * fabricInfo = mFabricsTable->FindFabricWithIndex(mFabricIndex);
ReturnErrorCodeIf(fabricInfo == nullptr, CHIP_ERROR_INCORRECT_STATE);
// Validate that we have a session ID allocated.
VerifyOrReturnError(GetLocalSessionId().HasValue(), CHIP_ERROR_INCORRECT_STATE);
// Generate an ephemeral keypair
mEphemeralKey = mFabricsTable->AllocateEphemeralKeypairForCASE();
VerifyOrReturnError(mEphemeralKey != nullptr, CHIP_ERROR_NO_MEMORY);
ReturnErrorOnFailure(mEphemeralKey->Initialize(ECPKeyTarget::ECDH));
// Fill in the random value
ReturnErrorOnFailure(DRBG_get_bytes(mInitiatorRandom, sizeof(mInitiatorRandom)));
// Construct Sigma1 Msg
msg_R1 = System::PacketBufferHandle::New(data_len);
VerifyOrReturnError(!msg_R1.IsNull(), CHIP_ERROR_NO_MEMORY);
tlvWriter.Init(std::move(msg_R1));
ReturnErrorOnFailure(tlvWriter.StartContainer(TLV::AnonymousTag(), TLV::kTLVType_Structure, outerContainerType));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(1), ByteSpan(mInitiatorRandom)));
// Retrieve Session Identifier
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(2), GetLocalSessionId().Value()));
// Generate a Destination Identifier based on the node we are attempting to reach
{
// Obtain originator IPK matching the fabric where we are trying to open a session. mIPK
// will be properly set thereafter.
ReturnErrorOnFailure(RecoverInitiatorIpk());
FabricId fabricId = fabricInfo->GetFabricId();
Crypto::P256PublicKey rootPubKey;
ReturnErrorOnFailure(mFabricsTable->FetchRootPubkey(mFabricIndex, rootPubKey));
Credentials::P256PublicKeySpan rootPubKeySpan{ rootPubKey.ConstBytes() };
MutableByteSpan destinationIdSpan(destinationIdentifier);
ReturnErrorOnFailure(GenerateCaseDestinationId(ByteSpan(mIPK), ByteSpan(mInitiatorRandom), rootPubKeySpan, fabricId,
mPeerNodeId, destinationIdSpan));
}
ReturnErrorOnFailure(tlvWriter.PutBytes(TLV::ContextTag(3), destinationIdentifier, sizeof(destinationIdentifier)));
ReturnErrorOnFailure(
tlvWriter.PutBytes(TLV::ContextTag(4), mEphemeralKey->Pubkey(), static_cast<uint32_t>(mEphemeralKey->Pubkey().Length())));
VerifyOrReturnError(mLocalMRPConfig.HasValue(), CHIP_ERROR_INCORRECT_STATE);
ReturnErrorOnFailure(EncodeSessionParameters(TLV::ContextTag(5), mLocalMRPConfig.Value(), tlvWriter));
// Try to find persistent session, and resume it.
bool resuming = false;
if (mSessionResumptionStorage != nullptr)
{
CHIP_ERROR err = mSessionResumptionStorage->FindByScopedNodeId(fabricInfo->GetScopedNodeIdForNode(mPeerNodeId),
mResumeResumptionId, mSharedSecret, mPeerCATs);
if (err == CHIP_NO_ERROR)
{
// Found valid resumption state, try to resume the session.
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(6), mResumeResumptionId));
uint8_t initiatorResume1MIC[CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES];
MutableByteSpan resumeMICSpan(initiatorResume1MIC);
ReturnErrorOnFailure(GenerateSigmaResumeMIC(ByteSpan(mInitiatorRandom), ByteSpan(mResumeResumptionId),
ByteSpan(kKDFS1RKeyInfo), ByteSpan(kResume1MIC_Nonce), resumeMICSpan));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(7), resumeMICSpan));
resuming = true;
}
}
ReturnErrorOnFailure(tlvWriter.EndContainer(outerContainerType));
ReturnErrorOnFailure(tlvWriter.Finalize(&msg_R1));
ReturnErrorOnFailure(mCommissioningHash.AddData(ByteSpan{ msg_R1->Start(), msg_R1->DataLength() }));
// Call delegate to send the msg to peer
ReturnErrorOnFailure(mExchangeCtxt.Value()->SendMessage(Protocols::SecureChannel::MsgType::CASE_Sigma1, std::move(msg_R1),
SendFlags(SendMessageFlags::kExpectResponse)));
mState = resuming ? State::kSentSigma1Resume : State::kSentSigma1;
ChipLogProgress(SecureChannel, "Sent Sigma1 msg");
mDelegate->OnSessionEstablishmentStarted();
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::HandleSigma1_and_SendSigma2(System::PacketBufferHandle && msg)
{
MATTER_TRACE_SCOPE("HandleSigma1_and_SendSigma2", "CASESession");
ReturnErrorOnFailure(HandleSigma1(std::move(msg)));
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::FindLocalNodeFromDestinationId(const ByteSpan & destinationId, const ByteSpan & initiatorRandom)
{
MATTER_TRACE_SCOPE("FindLocalNodeFromDestinationId", "CASESession");
VerifyOrReturnError(mFabricsTable != nullptr, CHIP_ERROR_INCORRECT_STATE);
bool found = false;
for (const FabricInfo & fabricInfo : *mFabricsTable)
{
// Basic data for candidate fabric, used to compute candidate destination identifiers
FabricId fabricId = fabricInfo.GetFabricId();
NodeId nodeId = fabricInfo.GetNodeId();
Crypto::P256PublicKey rootPubKey;
ReturnErrorOnFailure(mFabricsTable->FetchRootPubkey(fabricInfo.GetFabricIndex(), rootPubKey));
Credentials::P256PublicKeySpan rootPubKeySpan{ rootPubKey.ConstBytes() };
// Get IPK operational group key set for current candidate fabric
GroupDataProvider::KeySet ipkKeySet;
CHIP_ERROR err = mGroupDataProvider->GetIpkKeySet(fabricInfo.GetFabricIndex(), ipkKeySet);
if ((err != CHIP_NO_ERROR) ||
((ipkKeySet.num_keys_used == 0) || (ipkKeySet.num_keys_used > Credentials::GroupDataProvider::KeySet::kEpochKeysMax)))
{
continue;
}
// Try every IPK candidate we have for a match
for (size_t keyIdx = 0; keyIdx < ipkKeySet.num_keys_used; ++keyIdx)
{
uint8_t candidateDestinationId[kSHA256_Hash_Length];
MutableByteSpan candidateDestinationIdSpan(candidateDestinationId);
ByteSpan candidateIpkSpan(ipkKeySet.epoch_keys[keyIdx].key);
err = GenerateCaseDestinationId(ByteSpan(candidateIpkSpan), ByteSpan(initiatorRandom), rootPubKeySpan, fabricId, nodeId,
candidateDestinationIdSpan);
if ((err == CHIP_NO_ERROR) && (candidateDestinationIdSpan.data_equal(destinationId)))
{
// Found a match, stop working, cache IPK, update local fabric context
found = true;
MutableByteSpan ipkSpan(mIPK);
CopySpanToMutableSpan(candidateIpkSpan, ipkSpan);
mFabricIndex = fabricInfo.GetFabricIndex();
mLocalNodeId = nodeId;
break;
}
}
if (found)
{
break;
}
}
return found ? CHIP_NO_ERROR : CHIP_ERROR_KEY_NOT_FOUND;
}
CHIP_ERROR CASESession::TryResumeSession(SessionResumptionStorage::ConstResumptionIdView resumptionId, ByteSpan resume1MIC,
ByteSpan initiatorRandom)
{
MATTER_TRACE_SCOPE("TryResumeSession", "CASESession");
VerifyOrReturnError(mSessionResumptionStorage != nullptr, CHIP_ERROR_INCORRECT_STATE);
VerifyOrReturnError(mFabricsTable != nullptr, CHIP_ERROR_INCORRECT_STATE);
SessionResumptionStorage::ConstResumptionIdView resumptionIdSpan(resumptionId);
ScopedNodeId node;
ReturnErrorOnFailure(mSessionResumptionStorage->FindByResumptionId(resumptionIdSpan, node, mSharedSecret, mPeerCATs));
// Cross check resume1MIC with the shared secret
ReturnErrorOnFailure(
ValidateSigmaResumeMIC(resume1MIC, initiatorRandom, resumptionId, ByteSpan(kKDFS1RKeyInfo), ByteSpan(kResume1MIC_Nonce)));
const auto * fabricInfo = mFabricsTable->FindFabricWithIndex(node.GetFabricIndex());
VerifyOrReturnError(fabricInfo != nullptr, CHIP_ERROR_INCORRECT_STATE);
mFabricIndex = node.GetFabricIndex();
mPeerNodeId = node.GetNodeId();
mLocalNodeId = fabricInfo->GetNodeId();
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::HandleSigma1(System::PacketBufferHandle && msg)
{
MATTER_TRACE_SCOPE("HandleSigma1", "CASESession");
CHIP_ERROR err = CHIP_NO_ERROR;
System::PacketBufferTLVReader tlvReader;
uint16_t initiatorSessionId;
ByteSpan destinationIdentifier;
ByteSpan initiatorRandom;
ChipLogProgress(SecureChannel, "Received Sigma1 msg");
MATTER_TRACE_COUNTER("Sigma1");
bool sessionResumptionRequested = false;
ByteSpan resumptionId;
ByteSpan resume1MIC;
ByteSpan initiatorPubKey;
SuccessOrExit(err = mCommissioningHash.AddData(ByteSpan{ msg->Start(), msg->DataLength() }));
tlvReader.Init(std::move(msg));
SuccessOrExit(err = ParseSigma1(tlvReader, initiatorRandom, initiatorSessionId, destinationIdentifier, initiatorPubKey,
sessionResumptionRequested, resumptionId, resume1MIC));
ChipLogDetail(SecureChannel, "Peer assigned session key ID %d", initiatorSessionId);
SetPeerSessionId(initiatorSessionId);
VerifyOrExit(mFabricsTable != nullptr, err = CHIP_ERROR_INCORRECT_STATE);
if (sessionResumptionRequested && resumptionId.size() == SessionResumptionStorage::kResumptionIdSize &&
CHIP_NO_ERROR ==
TryResumeSession(SessionResumptionStorage::ConstResumptionIdView(resumptionId.data()), resume1MIC, initiatorRandom))
{
std::copy(initiatorRandom.begin(), initiatorRandom.end(), mInitiatorRandom);
std::copy(resumptionId.begin(), resumptionId.end(), mResumeResumptionId.begin());
// Send Sigma2Resume message to the initiator
SuccessOrExit(err = SendSigma2Resume());
mDelegate->OnSessionEstablishmentStarted();
// Early returning here, since we have sent Sigma2Resume, and no further processing is needed for the Sigma1 message
return CHIP_NO_ERROR;
}
// Attempt to match the initiator's desired destination based on local fabric table.
err = FindLocalNodeFromDestinationId(destinationIdentifier, initiatorRandom);
if (err == CHIP_NO_ERROR)
{
ChipLogProgress(SecureChannel, "CASE matched destination ID: fabricIndex %u, NodeID 0x" ChipLogFormatX64,
static_cast<unsigned>(mFabricIndex), ChipLogValueX64(mLocalNodeId));
// Side-effect of FindLocalNodeFromDestinationId success was that mFabricIndex/mLocalNodeId are now
// set to the local fabric and associated NodeId that was targeted by the initiator.
}
else
{
ChipLogError(SecureChannel, "CASE failed to match destination ID with local fabrics");
ChipLogByteSpan(SecureChannel, destinationIdentifier);
}
SuccessOrExit(err);
// ParseSigma1 ensures that:
// mRemotePubKey.Length() == initiatorPubKey.size() == kP256_PublicKey_Length.
memcpy(mRemotePubKey.Bytes(), initiatorPubKey.data(), mRemotePubKey.Length());
SuccessOrExit(err = SendSigma2());
mDelegate->OnSessionEstablishmentStarted();
exit:
if (err == CHIP_ERROR_KEY_NOT_FOUND)
{
SendStatusReport(mExchangeCtxt, kProtocolCodeNoSharedRoot);
mState = State::kInitialized;
}
else if (err != CHIP_NO_ERROR)
{
SendStatusReport(mExchangeCtxt, kProtocolCodeInvalidParam);
mState = State::kInitialized;
}
return err;
}
CHIP_ERROR CASESession::SendSigma2Resume()
{
MATTER_TRACE_SCOPE("SendSigma2Resume", "CASESession");
size_t max_sigma2_resume_data_len =
TLV::EstimateStructOverhead(SessionResumptionStorage::kResumptionIdSize, CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES,
sizeof(uint16_t), SessionParameters::kEstimatedTLVSize);
System::PacketBufferTLVWriter tlvWriter;
System::PacketBufferHandle msg_R2_resume;
TLV::TLVType outerContainerType = TLV::kTLVType_NotSpecified;
// Validate that we have a session ID allocated.
VerifyOrReturnError(GetLocalSessionId().HasValue(), CHIP_ERROR_INCORRECT_STATE);
msg_R2_resume = System::PacketBufferHandle::New(max_sigma2_resume_data_len);
VerifyOrReturnError(!msg_R2_resume.IsNull(), CHIP_ERROR_NO_MEMORY);
tlvWriter.Init(std::move(msg_R2_resume));
// Generate a new resumption ID
ReturnErrorOnFailure(DRBG_get_bytes(mNewResumptionId.data(), mNewResumptionId.size()));
ReturnErrorOnFailure(tlvWriter.StartContainer(TLV::AnonymousTag(), TLV::kTLVType_Structure, outerContainerType));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(1), mNewResumptionId));
uint8_t sigma2ResumeMIC[CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES];
MutableByteSpan resumeMICSpan(sigma2ResumeMIC);
ReturnErrorOnFailure(GenerateSigmaResumeMIC(ByteSpan(mInitiatorRandom), mNewResumptionId, ByteSpan(kKDFS2RKeyInfo),
ByteSpan(kResume2MIC_Nonce), resumeMICSpan));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(2), resumeMICSpan));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(3), GetLocalSessionId().Value()));
VerifyOrReturnError(mLocalMRPConfig.HasValue(), CHIP_ERROR_INCORRECT_STATE);
ReturnErrorOnFailure(EncodeSessionParameters(TLV::ContextTag(4), mLocalMRPConfig.Value(), tlvWriter));
ReturnErrorOnFailure(tlvWriter.EndContainer(outerContainerType));
ReturnErrorOnFailure(tlvWriter.Finalize(&msg_R2_resume));
// Call delegate to send the msg to peer
ReturnErrorOnFailure(mExchangeCtxt.Value()->SendMessage(Protocols::SecureChannel::MsgType::CASE_Sigma2Resume,
std::move(msg_R2_resume),
SendFlags(SendMessageFlags::kExpectResponse)));
mState = State::kSentSigma2Resume;
ChipLogDetail(SecureChannel, "Sent Sigma2Resume msg");
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::SendSigma2()
{
MATTER_TRACE_SCOPE("SendSigma2", "CASESession");
VerifyOrReturnError(GetLocalSessionId().HasValue(), CHIP_ERROR_INCORRECT_STATE);
VerifyOrReturnError(mFabricsTable != nullptr, CHIP_ERROR_INCORRECT_STATE);
chip::Platform::ScopedMemoryBuffer<uint8_t> icacBuf;
VerifyOrReturnError(icacBuf.Alloc(kMaxCHIPCertLength), CHIP_ERROR_NO_MEMORY);
chip::Platform::ScopedMemoryBuffer<uint8_t> nocBuf;
VerifyOrReturnError(nocBuf.Alloc(kMaxCHIPCertLength), CHIP_ERROR_NO_MEMORY);
MutableByteSpan icaCert{ icacBuf.Get(), kMaxCHIPCertLength };
ReturnErrorOnFailure(mFabricsTable->FetchICACert(mFabricIndex, icaCert));
MutableByteSpan nocCert{ nocBuf.Get(), kMaxCHIPCertLength };
ReturnErrorOnFailure(mFabricsTable->FetchNOCCert(mFabricIndex, nocCert));
// Fill in the random value
uint8_t msg_rand[kSigmaParamRandomNumberSize];
ReturnErrorOnFailure(DRBG_get_bytes(&msg_rand[0], sizeof(msg_rand)));
// Generate an ephemeral keypair